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Posted on April 25, 2020 by Nitin Prakash
Whatever you background, Clojure is almost guaranteed to affect
the way you think about programming.
- Eli Bendersky

I’ve been meaning to start a series on Clojure for quite a while now. I started exploring functional programming around June, 2019 and stumbled upon this language. I sure had my doubts on how impactful it might be. However, I was quite shocked with the pleasant development experience. The elegant integration with emacs and the joy of using REPL are all something that keeps me enganged in exploring clojure more and more everyday. I can keep going but first, let’s dig into the background of Clojure so that we don’t get lost right at the beginning.

A language that doesn't affect the way you think about programming,
is not worth knowing.

- Alan Perlis

### What is clojure?

• A functional programming language.
• A complied language. Yet dynamic in nature i.e., clojure features are also supported at runtime.
• Values built-in data structure philosphy. That is, it provides built-in support for map, vector, hash-map, list etc.
• Provides persitent data structures that essentially focuses on immutability and multi-threading.
• Shares code as data philosphy with a macro system.

For those of you who know, it’s a LISP! Don’t get confused now. Being a lisp does not mean it can’t be used to build production ready softwares. It’s fairly important to understand that clojure comes with a lot of features alongside being a lisp.

Having said that, clojure provides a very powerful support for interfaces. These interfaces are called protocols and discourages thinking in terms of classes with inheritance. It supports multiple dispatch functions as well. Clojure also provides a great support for concurrency and parallelism in multiple ways.

### Code as data

Let’s consider the follwing block of code. By the looks of it, anyone can say that it takes two arguments, x and y and returns the addition of the two.

(defn add
[x y]
(+ x y))

Hold your horses. Let’s take a close look and try to understand the way it can be interpreted. In the above code,

• x and y are symbols. A symbol is basically an object representing a name. These are first class names in Clojure.
• [x y] is a vector containing the symbols.
• (+ x y) is a linked list data structure containing two symbols x and y.

From the above, I want to infer that when we talk about any piece of clojure code, * We talk about a code that will execute. * We think of it as a data structure consisting of vectors, maps, intergers, strings etc.

In computer programming, this is called Homoiconicity. Clojure is said to be homoiconic. In simple terms, it is said to share code as data philosphy. Code forms are data structures and data structures can be thought of as forms and executed as code.

We’ll look at some basic terms before diving deep into web programming.

### Functions

Creating and using functions, and creating functions that use functions, is what Clojure programers do. Clojure has a number of ways to create a function. I’ll give an overview on some of them.

(def print-string
(fn [] "That's cute. What else clojure is capable of?"))
=> #'user/print-string

(print-string)
=> "That's cute. What else clojure is capable of?"

def is used declare a variable. fn creates a simple function object. It can be stored in a var, passed to functions etc. defn is a macro that makes defining functions a little bit simpler. The above can be written as:

user> (defn print-string
[]
"That's cute. What else clojure is capable of?")
=> #'user/print-string

user> (print-string)
=> "That's cute. What else clojure is capable of?"

We can also overload arity in a single function, self-reference it.

user> (defn sum
([x] x)
([x y] (+ x y))
([x y z] (+ x y z)))
=> #'user/sum

user> (sum 1)
1
user> (sum 1 2)
3
user> (sum 1 2 4)
7

### REPL

This stands for Read-Eval-Print-Loop. The REPL reads in text through the reader and further transforms it into a Clojure data structure. We can imagine REPL as our playground where we can test running code or even try out new ideas.

The reason it is such a fantastic feature is because of the feedback loop which tremendously enhances development cycle. This kind of feature is not available for most languages. We’ll see the power of REPL in further sections. You can also read more about REPL here.

### Pure functions

These are functions that will always produce the same result for a given input. These cannot have any observable side effects and don’t depend on any kind of outside state, other than that which was given as arguments to the function. The result of such functions don’t change during the execution of the program or between executions of the program, as the dependency on outside state can lead to changes in the result of the function.

Side effects are observed application state change outside a function

user> (defn product
[x y] (* x y))
=> #'user/sum

user> (product 1 2)
2

The above function product will always result the same for a fixed x and y. Even the examples above where we discussed multi arity were pure functions.

But,

user> (def principal 1000)
=> #'user/amount

user> (defn interest
[time rate] (/ (* principal time rate) 100))
=> #'user/interest

user> (interest 10 5)
=> 50000

The above function interest is not a pure function as it depends on a variable principal. If it changed, interest would produce a different result for the same time and rate. These are called impure functions.

### Keywords

According to Clojure documentation, keywords can be described as symbols that evaluate to themeselves.

user> :foobar
=> :foobar

user> (keyword? :foorbar)
=> true

user> (keyword 100)
=> nil

Don’t worry about the functioning of keyword? right now. You can perhaps go through cheatsheet that has various built-in functions listed categorically. What I would like you to understand is that keywords provide a very fast equality test. And also these are the keys of a hashmap in clojure.

user> (def sample-map {:a 1 :b 2})
=> #'user/sample-map

user> sample-map
=> {:a 1, :b 2}

user> (:a sample-map)
=> 1

### Collections and Sequences

There a lot of operations over collections and sequences provided by clojure. But before diving into those operation, we need to understand the difference between a sequence abstraction and a collection abstraction.

Every sequence is a collection, but not every collection is a sequence.

The collection abstraction is closely related to the sequence abstraction. All of Clojure’s core data structures — vectors, maps, lists and sets — take part in both abstractions. The main difference is that sequence is about operating on the individual element that is expected to be accessed in linear fashion whereas collection is more about the overall data structure.

user.core> (def foo '[1 2 3 4])
=> #'user/foo
user.core> foo
=> [1 2 3 4]

;; An individual element can't be empty.
;; Only the whole data structure can be emtpty.
;; Therefore, when we talk about collections we
;; are more so referring to the data structure as whole
user.core> (empty? foo)
=> false

### Starting a simple project

This section focuses on generating an outline for a simple clojure project (not for web programming). We will use Leiningen as our tool to automate any sort of clojure project throughout the series. There are others such as boot but we will focus on lein.

To generate a project skeleton, a simple lein command can do the trick:

lein new app clojure-first

This should genetate a structure as follows:

├── CHANGELOG.md
├── doc
│   └── intro.md
├── project.clj
├── resources
├── src
│   └── clojure_first
│       └── core.clj
├── target
└── test
└── clojure_first
└── core_test.clj

To run the project,

lein run

This command successfully runs because there is a -main function in src/clojure_first/core.clj which is the entry point for the app. Remove that and you might end up setting your hair on fire. Well, to ensure that doesn’t happend we depend on lein.

To try out repl, you can run

lein repl

### Conclusion

In this post we figured out:

1. What is clojure?
2. Clojure philosphy.
3. Basic terms related to clojure.
4. Starting a simple clojure project.

I’m not going to debate on what editor you should and should not use. But I highly recommend one of the follwing:

1. Emacs + cider
2. IntelliJ + Cursive

Both of the above are the most used development environment for clojure. I personally use spacemacs (an emacs flavour) for clojure development.

In the next post we’ll setup a web project and try to understand it’s working.


text:
### 统计代写|金融统计代写Financial Statistics代考|GRA6518

statistics-lab™ 为您的留学生涯保驾护航 在代写金融统计Financial Statistics方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写金融统计Financial Statistics代写方面经验极为丰富，各种代写金融统计Financial Statistics相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• Advanced Probability Theory 高等概率论
• Advanced Mathematical Statistics 高等数理统计学
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 统计代写|金融统计代写Financial Statistics代考|High Frequency Data

In this section we further elaborate on high frequency data and introduce the series that will be analyzed later. High frequency data are very important in the financial environment, mainly because there exist large movements in short intervals of time. This aspect represents an interesting opportunity for trading. Furthermore, it is well known that volatilities in different frequencies have significant cross-correlation. We can even say that coarse volatility predicts fine volatility better than the inverse, as shown in Dacorogna et al. (2001).

As an example, take the tick by tick foreign exchange (FX) time series Euro-Dollar, from January First 1999 to December 31, 2002. Returns are calculated using bid and ask prices, as
$$r_{t}=\ln \left(\left(p_{t}^{b i d}+p_{t}^{a s k}\right) / 2\right)-\ln \left(\left(p_{t-1}^{b i d}+p_{t-1}^{a s k}\right) / 2\right)$$
We discard Saturdays and Sundays, and we replace holidays with the means of the last ten observations of the returns for each respective hour and day. After cleaning the data (see Dacorogna et al. (2001), for details) we will consider equally spaced returns, with sampling interval $\Delta t=15 \mathrm{~min}$. This seems to be adequate, as many studies indicate.

Figure 2 shows Euro-Dollar returns calculated as above. The length of this time series is 95,317 . The figure shows that the absolute returns present a seasonal pattern. This is due to the fact that physical time does not follow, necessarily, the same pattern as the business time. This is a typical behavior of a financial time series and we will use a seasonal adjustment procedure similar to that of Martens et al. (2002). However, we will use absolute returns instead of squared returns; that is, we will compute the seasunal patturn as
$$S_{d_{,}, h}=\frac{1}{s} \sum_{j=1}^{s} \mid\left(r_{d_{t}, j, t} \mid,\right.$$
where $r_{d, s, t}$ is the return in the weekday $d$, week $s$ and hour $h$, and $s$ is the number of weeks from the beginning of the series. Therefore, $S_{d, N}, N_{t}$ is the rolling window mean of the absolute returns with the beginning fixed.

In Figure 3 we have the autocorrelation function of these returns and of squared returns. The seasonality pattern is no longer present.

FX data has some distinct characteristics, mainly because they are produced twenty four hours a day, seven days a week. In particular, Euro-Dollar is the most liquid FX in the world. However, there are periods where the activity is greater or smaller, causing seasonal patterns to occur, as seen above.
Let us analyze some facts about these returns that we will denote simply by rt. We can see in Figure 4 the histogram fitted with a non-parametric density kernel estimate, using unbiased cross-validation method to estimate the bandwidth. It shows fat tails and high kurtosis, namely, 121 , while its skewness coefficient is $-0.079$, showing almost symmetry. A normality test (Jarque-Bera) rejects the hypothesis that these returns are normal.

## 统计代写|金融统计代写Financial Statistics代考|Introduction and Motivation

A financial asset is referred to as a “safe haven” asset if it provides hedging benefits during periods of market turbulence. In other words, during periods of market stress, “safe haven” assets are supposed to be uncorrelated, or negatively correlated, with large markets slumps experienced by more traditional financial assets (typically stock or bond prices).

The financial literature identifies various asset classes exhibiting “safe haven” features: gold and other precious metals, the exchange rates of some key international currencies against the US dollar, oil and other important agricultural commodities, and US long-term government bonds.

This paper contributes to the existing literature focusing on some of the most representative “safe haven” assets, namely gold, the Swiss Franc/US dollar exchange rate, and oil. The main motivation behind this choice is twofold.

First, empirical research on these assets have attracted major attention in recent years, both from academia and from institutional investors. Second, there are some weaknesses in the applied literature that need to be addressed.

The hedging properties of gold and its monetary role as a store of value are widely documented. Jaffe $(1989)$ and Chua et al. (1990) find that gold yields significant portfolio diversification benefits. Moreover, the “safe haven” properties of gold in volatile market conditions are widely documented: See, among others, Baur and McDermott (2010), Hood and Malik (2013), Reboredo (2013), and Ciner et al. (2013).
The popular views of gold as a store of value and a “safe haven” asset are well described in Baur and McDermott (2010). As reported by these authors, the 17 th Century British Mercantilist Sir William Petty described gold as “wealth at all times and all places” (Petty 1690). This popular perception of gold spreads over centuries, reinforced by its historic links to money, and even today gold is described as “ant attractive each way bet” against risks of financial losses or inflation (Economist 2005, 2009).

Turning to the role of the Swiss Franc as a “safe haven” asset, Ranaldo and Söderlind (2010) documented that the Swiss currency yields substantial hedging benefits against a decrease in US stock prices and an increase in forex volatility. These findings corroborate earlier results (Kugler and Weder 2004; Campbell et al. 2010). More recent research documented that increased risk aversion after the 2008 global financial turmoil strengthened the “safe haven” role of the Swiss currency (Tamakoshi and Hamori 2014).

## 统计代写|金融统计代写Financial Statistics代考|A Multivariate Garch Model of Asset Returns

This section employs a well-known approach belonging to the class of Multivariate Garch estimators, namely Engle (2002) Dynamic Conditional Correlation model, in order to compute time-varying conditional correlations between asset returns. The first sub-section provides a short outline of this econometric framework. The latter sub-section presents parameters estimates and analyzes pair-wise correlation patterns between asset returns.
3.1. Engle (2002) Dynamic Conditional Correlation Model
Let $r_{t}=\left(r_{1 t}, \ldots, r_{n t}\right)$ represent a $(n \times 1)$ vector of financial assets returns at time (t). Moreover, let $\varepsilon_{t}$ $=\left(\varepsilon_{1 t}, \ldots, \varepsilon_{n t}\right)$ be a $(n \times 1)$ vector of error terms obtained from an estimated system of mean equations for these return series.

Engle (2002) proposes the following decomposition for the conditional variance-covariance matrix of asset returns:
$$H_{t}=D_{t} R_{t} D_{t}$$
where $D_{t}$ is a $(n \times n)$ diagonal matrix of time-varying standard deviations from univariate Garch models, and $R_{t}$ is a $(n \times n)$ time-varying correlation matrix of asset returns $\left(\rho_{i j}, t\right)$.

The conditional variance-covariance matrix $\left(\mathrm{H}{t}\right)$ displayed in equation [1] is estimated in two steps. In the first step, univariate Garch $(1,1)$ models are applied to mean returns equations, thus obtaining conditional variance estimates for each financial asset ( $\sigma{i t}^{2} ;$ for $\left.i=1,2, \ldots ., n\right)$, namely:
$$\sigma_{i t}^{2}=\sigma_{U i t}^{2}\left(1-\lambda_{1 i}-\lambda_{2 i}\right)+\lambda_{1 i} \sigma_{i, t-1}^{2}+\lambda_{2 i} \varepsilon_{i, t-1}^{2}$$

where $\sigma^{2}$ uit is the unconditional variance of the $i$ th asset return, $\lambda_{1 i}$ is the volatility persistence parameter, and $\lambda_{2 i}$ is the parameter capturing the influence of past errors on the conditional variance.
In the second step, the residuals vector obtained from the mean equations system $\left(\varepsilon_{t}\right)$ is divided by the corresponding estimated standard deviations, thus obtaining standardized residuals (i.e., $u_{i t}=$ $\varepsilon_{i t} / \sqrt{\sigma_{i, t}^{2}}$ for $\left.\mathrm{i}=1,2, \ldots ., n\right)$, which are subsequently used to estimate the parameters governing the time-varying correlation matrix.

More specifically, the dynamic conditional correlation matrix of asset returns may be expressed as:
$$Q_{t}=\left(1-\delta_{1}-\delta_{2}\right) \overline{\mathrm{Q}}+\delta_{1} Q_{t-1}+\delta_{2}\left(u_{t-1} u_{t-1}^{\prime}\right)$$
where $\overline{\mathrm{Q}}=\mathrm{E}\left[u_{t} u_{t}^{\prime}\right]$ is the $(n \times n)$ unconditional covariance matrix of standardized residuals, and $\delta_{1}$ and $\delta_{2}$ are parameters (capturing, respectively, the persistence in correlation dynamics and the impact of past shocks on current conditional correlations).

## 统计代写|金融统计代写Financial Statistics代考|High Frequency Data

$$r_{t}=\ln \left(\left(p_{t}^{b i d}+p_{t}^{a s k}\right) / 2\right)-\ln \left(\left(p_{t-1}^{\text {bid }}+p_{t-1}^{a s k}\right) / 2\right)$$

$$S_{d, h}=\frac{1}{s} \sum_{j=1}^{s} \mid\left(r_{d_{t}, j, t} \mid\right.$$

## 统计代写|金融统计代写Financial Statistics代考|Introduction and Motivation

Baur 和 McDermott (2010) 很好地描述了黄金作为价值储存和”避风港”盗产的流行观点。正如这些作者所报道的那样， 17 世纪的英国重商主义者威廉·㑉蒂爵士将黄金描述为“随时随地的财富”(佩蒂 1690 年)。这种对黄金的普遍看法传播 了几个世纪，并因其与货币的历史联系而得到加强，即使在今天，黄金也被描述为“对金融损失或通货膨胀风险进行”单向 押注” (Economist 2005, 2009)。

## 统计代写|金融统计代写Financial Statistics代考|A Multivariate Garch Model of Asset Returns

3.1。Engle (2002) 动态条件相关模型

Engle (2002) 对资产收益的条件方差-协方差矩阵提出了以下分解:
$$H_{t}=D_{t} R_{t} D_{t}$$

$$\sigma_{i t}^{2}=\sigma_{U i t}^{2}\left(1-\lambda_{1 i}-\lambda_{2 i}\right)+\lambda_{1 i} \sigma_{i, t-1}^{2}+\lambda_{2 i} \varepsilon_{i, t-1}^{2}$$

$$Q_{t}=\left(1-\delta_{1}-\delta_{2}\right) \overline{\mathrm{Q}}+\delta_{1} Q_{t-1}+\delta_{2}\left(u_{t-1} u_{t-1}^{\prime}\right)$$

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

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The Arithmetic and Geometry of Algebraic Cycles

Edited by: B. Brent Gordon University of Oklahoma, Norman, OK
James D. Lewis University of Alberta, Edmonton, AB, Canada
Stefan Müller-Stach Universität Essen, Essen, Germany
Shuji Saito Tokyo Institute of Technology, Oh-Okayama, Meguro-ku, Japan
Noriko Yui Queen’s University, Kingston, ON, Canada
A co-publication of the AMS and Centre de Recherches Mathématiques
Available Formats:
Softcover ISBN: 978-0-8218-1954-8
Product Code: CRMP/24
432 pp
List Price: $136.00 MAA Member Price:$122.40
AMS Member Price: $108.80 Electronic ISBN: 978-1-4704-3938-5 Product Code: CRMP/24.E 432 pp List Price:$128.00
MAA Member Price: $115.20 AMS Member Price:$102.40
Bundle Print and Electronic Formats and Save!
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List Price: $204.00 MAA Member Price:$183.60
AMS Member Price: $163.20 Click above image for expanded view The Arithmetic and Geometry of Algebraic Cycles Edited by: B. Brent Gordon University of Oklahoma, Norman, OK James D. Lewis University of Alberta, Edmonton, AB, Canada Stefan Müller-Stach Universität Essen, Essen, Germany Shuji Saito Tokyo Institute of Technology, Oh-Okayama, Meguro-ku, Japan Noriko Yui Queen’s University, Kingston, ON, Canada A co-publication of the AMS and Centre de Recherches Mathématiques Available Formats:  Softcover ISBN: 978-0-8218-1954-8 Product Code: CRMP/24 432 pp  List Price:$136.00 MAA Member Price: $122.40 AMS Member Price:$108.80
 Electronic ISBN: 978-1-4704-3938-5 Product Code: CRMP/24.E 432 pp
 List Price: $128.00 MAA Member Price:$115.20 AMS Member Price: $102.40 Bundle Print and Electronic Formats and Save! This product is available for purchase as a bundle. Purchasing as a bundle enables you to save on the electronic version. List Price:$204.00
MAA Member Price: $183.60 AMS Member Price:$163.20
• Book Details

CRM Proceedings & Lecture Notes
Volume: 242000
MSC: Primary 11; 14;

The NATO ASI/CRM Summer School at Banff offered a unique, full, and in-depth account of the topic, ranging from introductory courses by leading experts to discussions of the latest developments by all participants. The papers have been organized into three categories: cohomological methods; Chow groups and motives; and arithmetic methods.

As a subfield of algebraic geometry, the theory of algebraic cycles has gone through various interactions with algebraic $K$-theory, Hodge theory, arithmetic algebraic geometry, number theory, and topology. These interactions have led to developments such as a description of Chow groups in terms of algebraic $K$-theory, the application of the Merkurjev-Suslin theorem to the arithmetic Abel-Jacobi mapping, progress on the celebrated conjectures of Hodge, and of Tate, which compute cycles class groups respectively in terms of Hodge theory or as the invariants of a Galois group action on étale cohomology, the conjectures of Bloch and Beilinson, which explain the zero or pole of the $L$-function of a variety and interpret the leading non-zero coefficient of its Taylor expansion at a critical point, in terms of arithmetic and geometric invariant of the variety and its cycle class groups.

The immense recent progress in the theory of algebraic cycles is based on its many interactions with several other areas of mathematics. This conference was the first to focus on both arithmetic and geometric aspects of algebraic cycles. It brought together leading experts to speak from their various points of view. A unique opportunity was created to explore and view the depth and the breadth of the subject. This volume presents the intriguing results.

Graduate students and research mathematicians interested in algebraic cycles.

• Cohomological Methods
• Filtrations on the cohomology of abelian varieties
• Building mixed Hodge structures
• The Atiyah-Chern character yields the semiregularity map as well as the infinitesimal Abel-Jacobi map
• Regulators and characteristic classes of flat bundles
• Height pairings asymptotics and Bott-Chern forms
• Logarithmic Hodge structures and classifying spaces
• Chow Groups and Motives
• Motives and algebraic de Rham cohomology
• Hermitian vector bundles and characteristic classes
• The mixed motive of a projective variety
• Bloch’s conjecture and the $K$-theory of projective surfaces
• From Jacobians to one-motives: Exposition of a conjecture of Deligne
• Motives, algebraic cycles and Hodge theory
• Arithmetic methods
• Picard-Fuchs uniformization: Modularity of the mirror map and mirror-moonshine
• Hilbert modular varieties in positive characteristic
• On the Néron-Severi groups of some $K$3 surfaces
• Torsion zero-cycles and the Abel-Jacobi map over the real numbers
• A remark on the Griffiths groups of certain product varieties
• $p$-adic Abel-Jacobi maps and $p$-adic heights
• Crystalline fundamental groups and $p$-adic Hodge theory
• Thompson series, and the mirror maps of pencils of $K$3 surfaces
• Request Review Copy
Volume: 242000
MSC: Primary 11; 14;

The NATO ASI/CRM Summer School at Banff offered a unique, full, and in-depth account of the topic, ranging from introductory courses by leading experts to discussions of the latest developments by all participants. The papers have been organized into three categories: cohomological methods; Chow groups and motives; and arithmetic methods.

As a subfield of algebraic geometry, the theory of algebraic cycles has gone through various interactions with algebraic $K$-theory, Hodge theory, arithmetic algebraic geometry, number theory, and topology. These interactions have led to developments such as a description of Chow groups in terms of algebraic $K$-theory, the application of the Merkurjev-Suslin theorem to the arithmetic Abel-Jacobi mapping, progress on the celebrated conjectures of Hodge, and of Tate, which compute cycles class groups respectively in terms of Hodge theory or as the invariants of a Galois group action on étale cohomology, the conjectures of Bloch and Beilinson, which explain the zero or pole of the $L$-function of a variety and interpret the leading non-zero coefficient of its Taylor expansion at a critical point, in terms of arithmetic and geometric invariant of the variety and its cycle class groups.

The immense recent progress in the theory of algebraic cycles is based on its many interactions with several other areas of mathematics. This conference was the first to focus on both arithmetic and geometric aspects of algebraic cycles. It brought together leading experts to speak from their various points of view. A unique opportunity was created to explore and view the depth and the breadth of the subject. This volume presents the intriguing results.

Graduate students and research mathematicians interested in algebraic cycles.

• Cohomological Methods
• Filtrations on the cohomology of abelian varieties
• Building mixed Hodge structures
• The Atiyah-Chern character yields the semiregularity map as well as the infinitesimal Abel-Jacobi map
• Regulators and characteristic classes of flat bundles
• Height pairings asymptotics and Bott-Chern forms
• Logarithmic Hodge structures and classifying spaces
• Chow Groups and Motives
• Motives and algebraic de Rham cohomology
• Hermitian vector bundles and characteristic classes
• The mixed motive of a projective variety
• Bloch’s conjecture and the $K$-theory of projective surfaces
• From Jacobians to one-motives: Exposition of a conjecture of Deligne
• Motives, algebraic cycles and Hodge theory
• Arithmetic methods
• Picard-Fuchs uniformization: Modularity of the mirror map and mirror-moonshine
• Hilbert modular varieties in positive characteristic
• On the Néron-Severi groups of some $K$3 surfaces
• Torsion zero-cycles and the Abel-Jacobi map over the real numbers
• A remark on the Griffiths groups of certain product varieties
• $p$-adic Abel-Jacobi maps and $p$-adic heights
• Crystalline fundamental groups and $p$-adic Hodge theory
• Thompson series, and the mirror maps of pencils of $K$3 surfaces
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# 电子工程代写|数据管理和数据系统代写Data Management and Data Systems代考|DATA5001

## 电子工程代写|数据管理和数据系统代写Data Management and Data Systems代考|Materials and Methodology

The used scene of Hyperion hyperspectral remote sensing image have contiguous 242 narrow bands in the range of $0.4-2.5 \mu \mathrm{m}$ with capability of spatial and spectral resolutions such as $30 \mathrm{~m}$ and $10 \mathrm{~nm}$, respectively, with narrow swath coverage of $7.5 \times 100 \mathrm{~km}$ including high radiometric accuracy of 12 bit quantization $[1,5,11$, $1214]$

The AVIRIS-NG hyperspectral remote sensing data have 425 narrow contiguous bands in spectral region of VNIR and SWIR ranging from $0.38$ to $2.51 \mu \mathrm{m}$ of electromagnetic spectrum. The spatial and spectral resolutions are $8.1 \mathrm{~m}$ and $5 \mathrm{~nm}$, respectively $[2,6,9,16]$. The adopted methodology for mineral identification is divided into three parts such as pre-image processing, extraction of mineral spectra, and validation. The stage of prefield-image processing contains de-striping, bad band removal, and atmospheric correction. The second stage related to extraction of mineral spectra through image. Third stage involves in matching of image-extracted spectra and measured spectra of minerals through USGS mineral library spectra and with field samples spectra. There are 155 bands and 390 bands were found suitable for mineral identification and extraction of spectra by Hyperion and AVIRIS-NG hyperspectral image, respectively (Fig. 2).

## 电子工程代写|数据管理和数据系统代写Data Management and Data Systems代考|Result and Discussion

The comparative analysis of extracted spectra of talc mineral by Hyperion hyperspectral remote sensing image of Chabhadiya area of Jahajpur, Bhilwara, Rajasthan shows diagnostic absorption features at $2.31 \mu \mathrm{m}$ due to $\mathrm{Mg}-\mathrm{OH}[3,5,12,21]$. Absorptions present at $1.4$ and $1.9 \mu \mathrm{m}$ due to $\mathrm{OH}$ and $\mathrm{HOH}$ overtones. There is some minor absorption also presents between $2.0$ and $2.2 \mu \mathrm{m}$. In spectral range of $0.4-2.5 \mu \mathrm{m}$, some major absorption such as at $0.45 \mu \mathrm{m}$ due to $\mathrm{Fe}^{3+}$ and at $0.9 \mu \mathrm{m}, 1.1 \mu \mathrm{m}$ due to $\mathrm{O}{2}$ and $\mathrm{H}{2} \mathrm{O}$ also identified in VNIR region of EMR. The Hyperion image spectra showing deep absorption at $0.85-0.95 \mu \mathrm{m}$ which is indication of the presence of hematite [24] and showing normal absorption at near $0.456 \mu \mathrm{m}$ [10]. The spectral analysis of AVIRIS-NG extracted talc mineral spectra shows diagnostic absorption at $2.31 \mu \mathrm{m}$ with doublet $2.29 \mu \mathrm{m}$ due to $\mathrm{Mg}-\mathrm{OH}$, and $1.4$ and $1.9$ due to overtones of $\mathrm{OH}$ and $\mathrm{HOH}$. At near $1.4-1.5 \mu \mathrm{m}$ and $2.0 \mu \mathrm{m}$ shows maximum variation in absorption due to $\mathrm{O}{2}$ and $\mathrm{CO}{2}$ which is not present in the Hyperion image. Absorption at $0.47$ and $0.6 \mu \mathrm{m}$ indicating the presence of $\mathrm{Fe}^{3+}$, (Hematite) and lesser deep absorption at $0.9 \mu \mathrm{m}$ which is unavailable in Hyperion image. Various minor absorptions are also present minutely compared to minor absorption features of Hyperion image. The shape and reflectance value are also differentiating the characteristics and properties of both spectra. The subtle changes and subtle variation in shape, reflectance, and absorption can be observed very minutely in AVIRIS-NG than the Hyperion image. The spectroscopic spectra of talc field samples also validating the potential and capability of identification of talc and hematite with absorption at $2.31 \mu \mathrm{m}$ with doublet at $2.28 \mu \mathrm{m}$ with overtones of $\mathrm{OH}$ and $\mathrm{HOH}$ at $1.4$ and $1.9 \mu \mathrm{m}$ and $\mathrm{Fe}^{3+}$ presence identified at absorptions at near $0.56$ and $0.9 \mu \mathrm{m}$, respectively. The shape, absorption, reflectance, and depth of image spectra of Hyperion and AVIRIS-NG in correlation of spectroscopic result of field sample spectra including comparison with USGS talc minerals spectra shows the most accurate and acute capability and performance of AVIRIS-NG hyperspectral images. The USGS talc mineral library spectra show complete matching of identified and measured spectra of talc through Hyperion, AVIRIS-NG, and spectroscopic field sample spectra (Fig. 3).

## 电子工程代写|数据管理和数据系统代写Data Management and Data Systems代考|Materials and Methodology

Hyperion 高光谱遥感影像所用场景有 242 个连续窄带，范围为0.4−2.5米米具有空间和光谱分辨率的能力，例如30 米和10 n米，分别具有窄幅覆盖7.5×100 ķ米包括 12 位量化的高辐射精度[1,5,11, 1214]

AVIRIS-NG 高光谱遥感数据在 VNIR 和 SWIR 的光谱区域有 425 个窄的连续波段，范围从0.38至2.51米米的电磁频谱。空间和光谱分辨率为8.1 米和5 n米， 分别[2,6,9,16]. 所采用的矿物鉴定方法分为图像前处理、矿物光谱提取和验证三个部分。前场图像处理阶段包括去条纹、去除坏带和大气校正。第二阶段涉及通过图像提取矿物光谱。第三阶段涉及通过USGS矿物库光谱和现场样品光谱匹配图像提取光谱和矿物测量光谱。Hyperion和AVIRIS-NG高光谱图像分别发现155个波段和390个波段适合矿物识别和光谱提取（图2）。

## 电子工程代写|数据管理和数据系统代写Data Management and Data Systems代考|Result and Discussion

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## LOG#048. Thomas precession.

LORENTZ TRANSFORMATIONS IN NON-STANDARD FORM Let me begin this post with an uncommon representation of Lorentz transformations in terms of “uncommon matrices”. A Lorentz transformation can be written symbolically, as we have seen before, as the set of linear transformations … Continue reading


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An undrained triaxial compression strength test was conducted on clayey silt soils and the following test results are obatined.
$\sigma_{3}kN/m^{2}$ 17 44 56
$\sigma_{1}kN/m^{2}$ 157 204 225
$U kN/m^{2}$ 12 20 22

Draw the associated Mohr's circles and determine the values of the shear parameters considering the (a) total stress and (b) effective stresses.

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Total Stress

• For a solution with total stresses, draw Mohr circles C 1  ,C 2  and C 3  for each of the specimens using the corresponding principal stresses σ 1  and σ 3  .
• Draw a Mohr envelope tangent to these circles as shown in Fig.Now from the figure Hence,
• C=48kN/m^2 ; phi = 15°.

Effective Stress Parameters

• The effective principal stresses may be found by subtracting the pore pressures u from the total principal stresses as given below.

• As before draw Mohr circles C'1 ,C'2 and C'3 for each of the specimens as shown in Fig.

• C'=46kN/m^2 and Phi'=20°.


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hosppeds
April 2015, VOLUME5 /ISSUE 4

# Variability of Intensive Care Management for Children With Bronchiolitis

1. Heather C. Pierce, MD1,
2. Jonathan M. Mansbach, MD, MPH2,
3. Erin S. Fisher, MD1,
4. Charles G. Macias, MD, MPH3,
5. Brian M. Pate, MD4,
6. Pedro A. Piedra, MD5,
7. Ashley F. Sullivan, MS, MPH6,
8. Janice A. Espinola, MPH6 and
9. Carlos A. Camargo Jr, MD, DrPH6
1. 1Department of Pediatrics, Rady Children’s Hospital, University of California, San Diego, California;
2. 2Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts;
3. 3Department of Pediatrics, Section of Emergency Medicine, Texas Children’s Hospital, Baylor College of Medicine, Houston, Texas;
4. 4Department of Pediatrics, Children’s Mercy Hospital, Kansas City, Missouri;
5. 5Departments of Molecular Virology and Microbiology, and Pediatrics, Baylor College of Medicine, Houston, Texas; and
6. 6Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
1. Address correspondence to Heather C. Pierce, MD, Department of Pediatrics, Division of Pediatric Hospital Medicine, Rady Children’s Hospital, University of California, San Diego, 3030 Children’s Way, Suite 213, San Diego, CA 92123. E-mail: hpierce{at}rchsd.org

## Abstract

Objective: To determine the extent of variability in testing and treatment of children with bronchiolitis requiring intensive care.

Methods: This prospective, multicenter observational study included 16 academic children’s hospitals across the United States during the 2007 to 2010 fall and winter seasons. The study included children <2 years old hospitalized with bronchiolitis who required admission to the ICU and/or continuous positive airway pressure (CPAP) within 24 hours of admission. Among the 2207 enrolled patients with bronchiolitis, 342 children met inclusion criteria. Clinical data and nasopharyngeal aspirates were collected.

Results: Respiratory distress severity scores and intraclass correlation coefficients were calculated. The study patients’ median age was 2.6 months, and 59% were male. Across the 16 sites, the median respiratory distress severity score was 5.1 (interquartile range: 4.5–5.4; P < .001). The median value of the percentages for all sites using CPAP was 15% (range: 3%–100%), intubation was 26% (range: 0%–100%), and high-flow nasal cannula (HFNC) was 24% (range: 0%–94%). Adjusting for site-specific random effects (as well as children’s demographic characteristics and severity of bronchiolitis), the intraclass correlation coefficient for CPAP and/or intubation was 21% (95% confidence interval: 8–44); for HFNC, it was 44.7% (95% confidence interval: 24–67).

Conclusions: In this multicenter study of children requiring intensive care for bronchiolitis, we identified substantial institutional variability in testing and treatment, including use of CPAP, intubation, and HFNC. These differences were not explained by between-site differences in patient characteristics, including severity of illness. Further research is needed to identify best practices for intensive care interventions for this major cause of pediatric hospitalization.

• continuous positive airway pressure
• high-flow nasal cannula
• institutional variability
• intraclass correlation coefficient
• intubation
• respiratory distress

Bronchiolitis is the leading cause of hospitalization in infants, with ∼125 000 to 150 000 hospitalizations each year in the United States.1,2 Despite the prevalence of this disease, the management of children with bronchiolitis varies widely, both within and between institutions.35 In 2006, the American Academy of Pediatrics recommended supportive care only for bronchiolitis6; there is no conclusive evidence for routine use of bronchodilators,7 systemic corticosteroids,8,9 or chest radiographs (CXRs).10,11 Since publication of these recommendations, subsequent studies indicate a decreased use of steroids, bronchodilators, and radiography, as well as reduced viral antigen testing and resource utilization.1215

However, the American Academy of Pediatrics consensus statement did not provide recommendations for the 10% to 16% of hospitalized children who require intensive care.1,16 Although Willson et al5 found that the threshold for intubation with bronchiolitis varied widely across 10 hospitals, they did not examine other respiratory modalities used in critically ill patients such as continuous positive airway pressure (CPAP) or high-flow nasal cannula (HFNC). Since the study by Willson et al was published, small prospective studies of between 12 and 29 children,1719 as well as 2 larger retrospective studies,20,21 found that both CPAP and HFNC improved respiratory rates, oxygenation, and work of breathing in children with severe bronchiolitis. Unfortunately, current data to identify a subgroup that confers the greatest benefit are not available,16,22 nor is there a consensus on objective measures to guide escalation of therapy. Management may be provider or institution driven, making comparisons across institutions a critical component in identifying areas needing further investigation. From 2000 to 2009, only 2% of hospitalized bronchiolitis patients required mechanical ventilation (noninvasive and invasive); however, these children accounted for 18% of the total annual costs.23 Decreasing unnecessary variation and utilization of these costly interventions will thus have the largest impact on the expense of caring for children with severe bronchiolitis.

Numerous studies have attempted to describe the predictors of ICU admission or severe disease.2427 However, there are no multicenter studies specifically examining the variability in critical care management and treatment across different institutions. Data on site-to-site variability will aid in focusing research efforts toward development of evidence-based guidelines, thereby increasing patient safety and reducing cost. The focus of the present study was to examine variability in intensive care management among 16 large urban US medical centers for children hospitalized with bronchiolitis.

## METHODS

### Study Design

This prospective, multicenter cohort study was conducted for 3 consecutive years during the 2007–2010 winter seasons, as part of the Multicenter Airway Research Collaboration (MARC), a program of the Emergency Medicine Network (EMNet) (www.emnet-usa.org). For reference, detailed methods have been described previously.27 Inclusion criteria consisted of an attending physician’s diagnosis of bronchiolitis, age <2 years, and parental informed consent. The exclusion criteria were previous enrollment and transfer to a participating hospital >48 hours after the original admission time. Because we aimed to enroll 20% of our total sample from the ICU, the ward and ICU enrollments were therefore separate. Once the site reached its target enrollment for each month, enrollment stopped until the beginning of the next month.

### Data Collection

Investigators conducted a structured interview assessing children’s demographic characteristics, medical and environmental history, duration of symptoms, and details of the acute illness. Details regarding birth history and any comorbid conditions were collected. Comorbid conditions included review of respiratory, cardiac, neurologic, gastrointestinal, and immunologic diseases. Preadmission evaluation (clinic or emergency department) and daily hospital clinical data, including respiratory rates with trends, assessment of retractions, oxygen saturation with trends, medical management, and disposition, were obtained by chart review. These data were manually reviewed at the EMNet coordinating center; site investigators were queried about any missing data, and discrepancies were identified.

To examine the variability in ICU care, ICU cases were defined as any patient admitted to the ICU and/or having received an ICU intervention (ie, CPAP and/or intubation) on their first inpatient day. Isolating this early ICU population allowed us to focus on a group of patients of great interest to treating clinicians. This group of patients was more likely to be clinically similar to each other and different from those who were initially treated in the ward and then later declined after a day of being hospitalized. Thus, these patients represented a more homogeneous subset of children, allowing better assessment of management variability according to sites. To evaluate bronchiolitis severity among children receiving early intensive care, a modified respiratory distress severity score (RDSS) was calculated by using 4 assessments made during the preadmission visit: respiratory rate, presence of wheezing (yes or no), air entry (normal, mild, or moderate/severe difficulty), and retractions (none, mild, or moderate/severe).28 Each component was scored 0, 1, or 2, with the exception of wheeze, which was scored either 0 (no wheeze) or 2 (wheeze). These scores were summed for a total score between 0 and 8 (with 8 indicating the most severe distress).

### Statistical Analyses

All analyses were performed by using Stata version 11.2 (Stata Corp, College Station, TX). Data are presented as proportions with 95% confidence intervals (CIs), medians with interquartile ranges, or means with 95% CIs. When 1 of the RDSS components was missing, the Stata impute command was used to calculate the RDSS. Children missing data for >1 RDSS component were not assigned an RDSS. To assess ICU care variability, the association between study site and other factors was examined by using the χ2 test, Fisher’s exact test, analysis of variance, and the Kruskal-Wallis test, where applicable. All P values were 2-tailed, with P < .05 considered statistically significant.

The variability of test utilization and management interventions were quantified between sites (while assessing the effect of each child’s characteristics) by creating 2 multilevel mixed effects logistic regression models for each test and treatment of interest and then calculating each model’s corresponding intraclass correlation coefficient (ICC). The first models created for each test and management outcomes of interest accounted for random site effects but did not adjust for patient-level characteristics. The second set of complete models accounted for random site effects while simultaneously adjusting for patient-level characteristics (ie, age, gender, race, insurance provider, median household income according to zip code, RDSS, apnea). Therefore, the ICCs derived from our first models specifying only random site effects represent the proportion of the total treatment variation that is attributable to the site-level differences without adjusting for patient-level characteristics. The ICCs from our complete adjusted models represent the proportion of the total treatment variation that is attributable to the site-level differences after accounting for differences in patient-level characteristics. Comparing both models, the contribution of patient characteristics to the total outcome variation seen according to site would be reflected in a corresponding decrease in the adjusted ICC. ICC values are presented as proportions, with a possible range of 0% to 100%, which is interpreted as none (ie, 0%) up to all (ie, 100%) of the observed outcome variability being due to between-site differences.

## RESULTS

Among the 2207 enrolled subjects, 2104 (95%) had full disposition data. Of these 2104 children, 342 (16%) required ICU admission or CPAP and/or intubation within 24 hours of hospitalization. Individual sites contributed from 3 to 42 patients per site over the entire 3-year study period, with a mean and median of 21 patients per site. Demographic data, medical history, and clinical presentation are shown in Table 1. Among all children receiving early intensive care, the mean age was 2.6 months (95% CI: 1.2–7.3); 59% were male, 66% were white, and 35% were Hispanic. Most children were publicly insured (58%). Preterm infants comprised 29% of the study population; this finding did not differ by site (P = .61). Comorbid conditions and apnea at preadmission were present in 21% and 20% of all children, respectively, and were marginally associated with site (comorbid conditions, P = .06; apnea, P = .08). RDSS values were imputed for 36 patients; 31 patients did not have RDSS values imputed because they were missing ≥2 RDSS components. When comparing the imputed RDSS variable versus the nonimputed RDSS variable (calculated from children with complete data), the overall mean RDSS was unchanged, and there was no material difference observed in the mean RDSS by site (data not shown). Thus, all RDSS results include the imputed values. The mean RDSS was 4.9 and ranged from 3.2 to 6.3 across the 16 study sites. Median length of stay in the ICU ranged from 2 to 6 days. No deaths occurred in this patient cohort.

TABLE 1

Demographic Characteristics, Medical History, and Clinical Presentation of Children With Bronchiolitis Receiving Intensive Care

Comparing data aggregated according to site, testing was common, with >75% of children having a complete blood cell count (CBC) and CXR performed at 14 and 13 sites, respectively. An intravenous line was placed in 93% of children. Regarding treatments, median use of inpatient corticosteroids across the sites was 33% (range: 19%–100%), and median use of inpatient antibiotics across sites was 64% (range: 33%–100%). Comparing preadmission use versus inpatient use of corticosteroids and antibiotics demonstrated an overall increase of 15% and 17%, respectively. Details of testing and treatments are shown in Table 2. Use of respiratory supportive therapies varied considerably according to site. The median use of CPAP alone was 15%, whereas the overall and median use of intubation was 26% (Figs 1 and 2, respectively). The median use of CPAP and/or intubation was 34% (range: 7%–100%). Median use of HFNC across sites was 24% (range: 0%–94%) (Fig 3).

TABLE 2

Diagnostic Tests and Treatments Administered to Children With Bronchiolitis Receiving Intensive Care

FIGURE 1

Proportion of bronchiolitis patients according to site who received CPAP within 24 hours of admission.

FIGURE 2

Proportion of patients with bronchiolitis according to site who were intubated within 24 hours of admission.

FIGURE 3

Proportion of patients with bronchiolitis according to site who received HFNC within 24 hours of admission.

Children who received the following treatments had higher mean RDSS values: bronchodilators (5.2 vs 4.4; P = .01), corticosteroids (5.4 vs 4.6; P = .003), and HFNC (5.4 vs 4.7; P = .004). However, CPAP/intubation was not associated with RDSS (P = .33). ICC values assessing intersite variation with and without adjustment for patient-level characteristics are presented in Table 3. Adjusting for children’s characteristics had no material effect on the ICC (24%) for checking a CBC. ICC for bronchodilator use in both models showed no significant variation according to site. ICCs for inpatient corticosteroid and antibiotic use were consistently <1%, demonstrating almost no variation by site. In contrast, the ICC of the CPAP/intubation model with site-specific random effects remained high, even after adjusting for children’s demographic characteristics and bronchiolitis severity (21.3% vs 20.9%). Examining CPAP and intubation separately revealed site variation as well (Figs 1 and 2), with ICCs of 27.9% and 14.8%, respectively, in the models only adjusted for site effects. When adjusting for patient characteristics, the ICC for CPAP changed minimally, whereas the ICC for intubation exhibited a modest decrease (7.2%). These data demonstrate substantial site variability in the use of CPAP and/or intubation that is not explained by differences in patient-level characteristics. Use of HFNC had the highest ICC that was sustained even after adjustment for children’s characteristics and severity (42.5% vs 44.7%) (Fig 3). Given that 1 site contributed only 3 patients to the study, the ICC variability analyses were repeated by excluding this outlier site, but results did not materially change (data not shown).

TABLE 3

ICC Assessing Between-Site Variability in the Use of Tests and Treatments Given to Children With Bronchiolitis Who Received Intensive Care, With and Without Adjustment For Children’s Characteristics

## DISCUSSION

In this multicenter, prospective study of bronchiolitis patients requiring intensive care, we found substantial institution-level variation in diagnostic testing and, more importantly, in the use of CPAP, intubation, and HFNC. The variation in care between sites persisted even after controlling for multiple factors, including demographic characteristics, medical history, and disease severity. Our data strongly suggest the need for further research to develop evidence-based guidelines that improve clinical outcomes while decreasing unnecessary resource utilization.

Based on national data, Hasegawa et al23 reported a 21% increase (1.9% to 2.3%) in use of mechanical ventilation between 2000 and 2009 for bronchiolitis. Given the total volume of >325 000 patients hospitalized with bronchiolitis reported in this study, a 21% increase is of great importance. Notably, the authors did not distinguish between invasive ventilation (ie, intubation) and noninvasive ventilation (ie, CPAP). Considering our overall rates of CPAP (21%) and HFNC (33%) across 16 sites, we subjectively believe this trend is largely reflective of increased use of noninvasive ventilation (NIV). These distinctions are particularly important given that 2 single-site studies concluded that increasing NIV over time led to decreasing rates of intubation.29,30

Overall, the evidence demonstrating the effectiveness of CPAP and HFNC for bronchiolitis is limited. Although CPAP trials have shown promising results with decreases in respiratory distress,17,18,20 a comprehensive review of CPAP for bronchiolitis was inconclusive due to the low quality of the evidence.31 Evidence for HFNC is also limited, with a retrospective single-site study comparing children before and after introduction of HFNC in the ICU demonstrating a decreased rate of both intubation and ICU length of stay.21 A prospective study of 21 children showed increased pharyngeal pressures that resulted in reduced respiratory effort.19 Two systemic reviews suggest that HFNC is well tolerated, but there was insufficient evidence to determine its effectiveness.32,33 Given that HFNC is not superior to positive pressure ventilation, clinical indications require further clarification.33

Our data reflect the lack of guidelines for physicians regarding initiation or escalation of CPAP or HFNC. Specific characteristics of children most likely to benefit from either modality are also unknown. For bronchiolitis, studies have attempted to validate objective respiratory scoring systems for research and early clinical practice.34,35 However, a respiratory severity scoring system has not been validated against end points relevant to critical care, which would be useful for guiding escalation decisions.36 Similar findings have been reported regarding variability in critical care treatment of severe asthma exacerbations; namely, a lack of high-quality research and need for objective respiratory scoring relevant to the critically ill. Overall, our data highlight the need for further examination of mechanical ventilation (eg, CPAP, intubation) and HFNC in bronchiolitis to identify indications, objective escalation criteria, and safety profiles.

When solid data to provide guidance are lacking, variability in care ensues, as demonstrated by our findings from16 different US sites. This variability persisted with minimal change in the ICC even after controlling for age, demographic characteristics, and severity of illness (including apnea). Although CPAP and HFNC require special equipment and properly trained staff, which may differ substantially between institutions, this availability cannot fully explain the differences across large academic medical centers. We recognize that the use of CPAP or HFNC for bronchiolitis may have been initiated (or discontinued) at specific sites during our study period, which potentially affects subsequent intubation rates. This change in practice can lead to varying utilization, reflecting clinician experience and familiarity with use of these interventions specific to this disease. This finding further supports the lack of consensus regarding proper use of these modalities in this early ICU population. Our data suggest that clinicians across 16 institutions, when faced with similar clinical presentations, chose different respiratory supportive modalities specifically in the setting of acute respiratory decompensation within 24 hours.

From 2000 to 2009, national hospital charges for children with bronchiolitis increased 30% from $1.34 billion to$1.75 billion, despite decreased hospitalizations.23 Mortality rates have also decreased over the past decade. Children with risk factors including prematurity, very low birth weight, or comorbid conditions are more likely to be admitted to the ICU16,3739 and represent a higher percentage of bronchiolitis admissions in recent national trends.23 It is unclear if these risk factors contribute to earlier and more frequent use of NIV at specific sites or if better outcomes are seen in this population with NIV. It is also unclear if there is a causal relationship between increased use of NIV and decreased mortality rates. In the present study, there were no significant differences in prematurity, age, or comorbid conditions across sites to fully explain the variability in use of different methods of mechanical ventilation. Reducing variability by using quality improvement methods has been effective for the care of noncritically ill children with bronchiolitis1215,40 and could be successfully used in the critical population as well.

Although the majority of the costs of caring for patients with severe bronchiolitis resided with mechanical ventilation, variability in care was also evident in diagnostic testing. There are no clear indications for obtaining a CBC for bronchiolitis.41 Some clinicians may argue that critically ill children require more testing, but it is worth mentioning this variability because it is also possible some tests add to unnecessary charges and blood draws.42 In the present study, there was a clear discrepancy between sites ordering a CBC, with a range of 39% to 100% not explained by age. Although infants aged <2 months routinely have more extensive evaluation for fever, median age was consistent across sites. CXRs were also obtained in most children in this study, with substantial between-site variation. Although previous research questions the necessity and cost-effectiveness of CXRs in bronchiolitis,10,11,43 other data suggest this uncertainty applies to children with mild or moderate distress and oxygen saturations >92%,11 which may not represent the present cohort. CXRs must be individually considered for those not following a standard course10,44 and are also typically obtained after intubation. Despite this consideration, our data show similar percentages of comorbid conditions at each site and minimal change in adjusted ICC, indicating that patient characteristics or severity of respiratory distress does not fully explain this variability.

In this severely ill population, the median use of corticosteroids at each site almost doubled from the preadmission visit to the inpatient setting (18% vs 33%). A similar pattern was seen for antibiotics, with use increasing from 47% at preadmission to 64% at the inpatient period. These increases are notable given the lack of indication for either treatment in bronchiolitis. Although there is no clear guidance regarding the use of corticosteroids, including for intubated children with respiratory syncytial virus bronchiolitis,45 15 of 16 sites reported increased use comparing inpatient with preadmission rates. Our study included children aged up to 2 years, which could overlap with cases of undiagnosed reactive airway disease, but our early intensive care cohort comprised almost entirely infants (overall mean age: 2.6 months). Furthermore, despite the low risk of bacterial coinfections and previous studies encouraging decreased utilization of antibiotics,46,47 14 of the 16 sites reported higher inpatient antibiotic use. One study of 23 infants did suggest that early empirical antibiotics may be justified in this population presenting with respiratory failure because of a higher risk of concomitant bacterial pneumonia.48 Corticosteroid and antibiotic use did not exhibit site-specific ICC variation, indicating increased use was not attributed to specific sites but rather most sites increased utilization in a potentially decompensating patient. Similarly, a review of ICU management for pediatric asthma showed increased use of medications not routinely recommended and with little supportive evidence.36 We speculate that in the face of limited guidance on outcomes in this population, sites justifiably may try other medications, including corticosteroids and antibiotics, in an attempt to treat severely ill children showing signs of rapid respiratory decline.

Our study has several potential limitations. Although we focused on common clinical elements, tests, and treatments, the study sites were large urban medical centers and the results may not be generalizable to community hospitals. In addition, indications for initiating antibiotics vary, particularly in more acutely ill patients with rapid decline and concern for secondary infection. Comorbid conditions were likewise included and may have influenced certain treatment decisions, but they were present in a similar percentage at each site. Imputation of the RDSS was required for only 36 observations and was performed when only 1 component of the RDSS was missing. Sensitivity analyses suggest this imputation did not introduce significant bias. The exact timing of the RDSS may not have coincided with sudden rapid decline leading to escalation in respiratory support but was within 24 hours. For this reason, the ICC was calculated, which includes several factors rather than the RDSS alone, for clearer comparisons between institutions. Lastly, criteria for ICU admission or transfer out of the ICU differ across institutions and by site-specific resources. As a result, the severity of respiratory distress may not have been the reason for ICU admission or transfer to a lower level of care, which would affect meaningful interpretation of ICU length of stay. However, this study provides a valuable snapshot of intensive care resource utilization for a large number of infants at 16 sites across the United States.

## CONCLUSIONS

In this multicenter, multiyear prospective study of children with bronchiolitis requiring ICU-level care within 24 hours of admission, we found substantial between-site variability in utilization of CPAP, intubation, and HFNC that was not explained by differences in severity of illness or patient characteristics. There is overall increasing use of these respiratory supportive modalities in the setting of decreasing mortality but rising costs of bronchiolitis hospitalization. Considering the impact of increasing costs in this common pediatric illness, further research is needed to generate evidence that can better provide guidance to clinicians and thereby reduce between-site variability. The ultimate goal of such guidelines would be to improve clinical outcomes while decreasing unnecessary resource utilization.

## Acknowledgments

The authors thank the Multicenter Airway Research Collaboration-30 investigators for their ongoing dedication to bronchiolitis research: Besh Barcega, MD, Loma Linda Medical Center; John Cheng, MD, and Carlos Delgado, MD, Children’s Healthcare of Atlanta; Haitham Haddad, MD, Rainbow Babies & Children’s Hospital; Frank LoVecchio, MD, Maricopa Medical Center; Eugene Mowad, MD, Akron Children’s Hospital; Mark Riederer, MD, and Paul Hain, MD, Monroe Carell Jr Children’s Hospital at Vanderbilt; M. Jason Sanders, MD, Children’s Memorial Hermann Hospital; Alan Schroeder, MD, Santa Clara Valley Medical Center; Nikhil Shah, MD, and Dorothy Damore, MD, New York Presbyterian Hospital–Cornell; Michelle Stevenson, MD, MS, Kosair Children’s Hospital; Stephen Teach, MD, MPH, Children’s National Medical Center; and Lisa Zaoutis, MD, Children’s Hospital of Philadelphia.

## Footnotes

• FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

• FUNDING: Supported by the National Institutes of Health (grants U01 AI-67693 and K23 AI-77801). Funded by the National Institutes of Health (NIH).

• POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

• The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Allergy and Infectious Diseases or the National Institutes of Health. The funding institutions had no role in study design, collection, analysis, or interpretation of data; the writing of the report; or the decision to submit for publication.

CBC
complete blood cell count
CI
confidence interval
CXR
CPAP
continuous positive airway pressure
HFNC
high-flow nasal cannula
ICC
intraclass correlation coefficient
NIV
noninvasive ventilation
RDSS
respiratory distress severity score

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text:
Revision history [back]

Application Development Tutorial - Archetype Version

I am trying to follow the Application Development Tutorial, here: https://wiki.opendaylight.org/view/ControllerCoreFunctionalityTutorials:ApplicationDevelopment_Tutorial

The project was created after the opendaylight-startup-archetype, as described in the tutorial:

mvn archetype:generate -DarchetypeGroupId=org.opendaylight.controller \
-DarchetypeArtifactId=opendaylight-startup-archetype \
-DarchetypeVersion=1.2.0-SNAPSHOT \
-DarchetypeRepository=http://nexus.opendaylight.org/content/repositories/opendaylight.snapshot/ \
-DarchetypeCatalog=http://nexus.opendaylight.org/content/repositories/opendaylight.snapshot/archetype-catalog.xml

The HelloProvider class (at impl/src/main/java/org/opendaylight/hello/impl/HelloProvider.java), however, doesn't correspond to what is described in the tutorial.

The tutorial version, for example, has:

@Override
public void onSessionInitiated(ProviderContext session) {
LOG.info("HelloProvider Session Initiated");
}

While mine has:

/**
* Method called when the blueprint container is created.
*/
public void init() {
LOG.info("HelloProvider Session Initiated");
}

Aside for other differences. I checked the archetype source code here and it really doesn't match what's described at the tutorial.

Am I missing anything, or did the 1.2.0-SNAPSHOT version of the archetype really changed? According to the answer for this question, it seems that it has something to do to OpenDaylight using Blueprint, and that I should use a different version of the archetype. What are the implicantions of this change?


text:
## Mathematics

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text:
## Journal of the Mathematical Society of Japan

### An explicit dimension formula for Siegel cusp forms with respect to the non-split symplectic groups

Hidetaka KITAYAMA

#### Abstract

We give an explicit dimension formula for the spaces of vector valued Siegel cusp forms of degree two with respect to a certain kind of arithmetic subgroups of the non-split Q-forms of Sp(2,R).

#### Article information

Source
J. Math. Soc. Japan, Volume 63, Number 4 (2011), 1263-1310.

Dates
First available in Project Euclid: 27 October 2011

Permanent link to this document
https://projecteuclid.org/euclid.jmsj/1319721141

Digital Object Identifier
doi:10.2969/jmsj/06341263

Mathematical Reviews number (MathSciNet)
MR2855813

Zentralblatt MATH identifier
1267.11054

#### Citation

KITAYAMA, Hidetaka. An explicit dimension formula for Siegel cusp forms with respect to the non-split symplectic groups. J. Math. Soc. Japan 63 (2011), no. 4, 1263--1310. doi:10.2969/jmsj/06341263. https://projecteuclid.org/euclid.jmsj/1319721141

#### References

• H. Aoki and T. Ibukiyama, Simple graded rings of Siegel modular forms, differential operators and Borcherds products, Internat. J. Math., 16 (2005), 249–279.
• T. Arakawa, Automorphic forms on quaternion unitary group of degree 2 (in Japanese), Master thesis, University of Tokyo, 1975.
• T. Arakawa, The dimension of the space of cusp forms on the Siegel upper half plane of degree two related to a quaternion unitary group, J. Math. Soc. Japan, 33 (1981), 125–145.
• K. Hashimoto, On Brandt matrices associated with the positive definite quaternion Hermitian forms, J. Fac. Sci. Univ. Tokyo Sect. IA Math., 27 (1980), 227–245.
• K. Hashimoto, The dimension of the spaces of cusp forms on Siegel upper half plane of degree two I, J. Fac. Sci. Univ. Tokyo Sect. IA Math., 30 (1983), 403–488.
• K. Hashimoto, The dimension of the spaces of cusp forms on Siegel upper half plane of degree two II, The $\mathbf{Q}$-rank one case, Math. Ann., 266 (1984), 539–559.
• K. Hashimoto and T. Ibukiyama, On class numbers of positive definite binary quaternion hermitian forms, J. Fac. Sci. Univ. Tokyo Sect. IA Math., 27 (1980), 549–601.
• K. Hashimoto and T. Ibukiyama, On class numbers of positive definite binary quaternion hermitian forms (II), J. Fac. Sci. Univ. Tokyo Sect. IA Math., 28 (1982), 695–699.
• K. Hashimoto and T. Ibukiyama, On class numbers of positive definite binary quaternion hermitian forms (III), J. Fac. Sci. Univ. Tokyo Sect. IA Math., 30 (1983), 393–401.
• K. Hashimoto and T. Ibukiyama, On relations of dimensions of automorphic forms of $Sp(2,\bR)$ and its compact twist $Sp(2)$ (II), Automorphic forms and number theory, Adv. Stud. Pure Math., 7 (1985), 31–102.
• Y. Hirai, On Eisenstein series on quaternion unitary groups of degree 2, J. Math. Soc. Japan, 51 (1999), 93–128.
• T. Ibukiyama, On symplectic Euler factors of genus two, J. Fac. Sci. Univ. Tokyo Sect. IA Math., 30 (1984), 587–614.
• T. Ibukiyama, On relations of dimensions of automorphic forms of $Sp(2,\mathbf{R})$ and its compact twist $Sp(2)$ (I), Automorphic forms and number theory, Adv. Stud. Pure Math., 7 (1985), 7–30.
• T. Ibukiyama, On differential operators on automorphic forms and invariant pluri-harmonic polynomials, Comment. Math. Univ. St. Pauli, 48 (1999), 103–118.
• T. Ibukiyama, Paramodular forms and compact twist, In: Automorphic Forms on $GSp(4)$, Proceedings of the 9th Autumn Workshop on Number Theory, (ed. M.Furusawa), 2007, pp.,37–48.
• T. Ibukiyama, Dimension formulas of Siegel modular forms of weight 3 and supersingular abelian surfaces, Proceedings of the 4-th Spring Conference, 2007, pp.,39–60.
• R. P. Langlands, The dimension of spaces of automorphic forms, Amer. J. Math., 85 (1963), 99–125.
• Y. Morita, An explicit formula for the dimension of spaces of Siegel modular forms of degree two, J. Fac. Sci. Univ. Tokyo Sect. IA Math., 21 (1974), 167–248.
• V. Platonov and A. Rapinchuk, Algebraic groups and number theory, Academic Press, 1994.
• G. Shimura, Arithmetic of alternating forms and quaternion hermitian forms, J. Math. Soc. Japan, 15 (1963), 33–65.
• S. Wakatsuki, Dimension formulas for spaces of vector valued Siegel cusp forms of degree two, to appear in J. Number Theory.


text:
Takeshi Torii

## Power operations and the generalized Chern character

video: comming soon.
abstract:
We have defined a generalization of the Chern character as a multiplicative natural transformation from the $$(n+1)$$st Morava $$E$$-theory to a certain extension of the $$n$$th Morava $$E$$-theory, which we call the generalized Chern character. On the other hand, we have power operations in Morava $$E$$-theory, since it is an $$E_{\infty}$$-ring spectrum. In this talk I will discuss the relationship between power operations in different Morava $$E$$-theories through the generalized Chern character.


text:
Magma - Maple Programming Help

Home : Support : Online Help : Mathematics : Algebra : Magma : Magma/Rank

Magma

 Rank
 compute the (lexicographic) rank of a magma represented by its Cayley table

 Calling Sequence Rank( m )

Parameters

 m - Array representing the Cayley table of a finite magma

Description

 • The Rank command returns the lexicographic rank of the magma represented by the Cayley table m.

Examples

 > $\mathrm{with}\left(\mathrm{Magma}\right):$
 > $m≔⟨⟨⟨1|2|3⟩,⟨2|3|1⟩,⟨3|1|2⟩⟩⟩$
 ${m}{≔}\left[\begin{array}{ccc}{1}& {2}& {3}\\ {2}& {3}& {1}\\ {3}& {1}& {2}\end{array}\right]$ (1)
 > $\mathrm{Rank}\left(m\right)$
 ${4070}$ (2)
 > $m≔⟨⟨⟨1|2|3⟩,⟨2|3|3⟩,⟨3|1|2⟩⟩⟩$
 ${m}{≔}\left[\begin{array}{ccc}{1}& {2}& {3}\\ {2}& {3}& {3}\\ {3}& {1}& {2}\end{array}\right]$ (3)
 > $\mathrm{Rank}\left(m\right)$
 ${4124}$ (4)

Compatibility

 • The Magma[Rank] command was introduced in Maple 15.


text:
Finding a graph-theoretic representation of expressions in Boole's algebra

I just read "Boole's Algebra Isn't Boolean Algebra" by Theodore Halperin (behind a paywall here). I don't have a strong background in abstract algebra, so, frankly, the paper is a bit over my head but the gist of it is as follows: the algebra developed by Boole in the 19th century has some strange properties. Boole interprets every term in an expression as representing a set and restricts the domain of valid expressions on the basis of relationships between the underlying sets. In particular, he asserts that the expression $x + y$ is valid iff $x$ and $y$ represent disjoint sets, and $x - y$ is valid iff the intersection of $x$ and $y$ is nonempty. He also defines an operation $w = \frac x y$ such that $w$ has many solutions. Halperin goes to great lengths to construct a commutative ring that satisfies Boole's constraints.

I think that there might be a nice, intuitive, graph-theoretic interpretation of Boole's algebra where we can say something like "Given a complex expression in Boole's algebra, $\Phi = \{\phi_1, \phi_2\, \dots, \phi_n\}$, we can construct a (di)graph $G$ such that $\Phi$ is valid if and only if $G$ has some property $P$."

For example, to test if $X + Y$ is valid, we could do something like the following:

Let $G$ be a graph. Let $V(G) = X \cup Y \cup \{v_X, v_Y\}$, i.e. make a vertex for every element of the underlying set, plus a vertex for each term in the expression. Then define

$$E(G) = \{uv_X \mid u \in X \} \cup \{uv_Y \mid u \in Y \}$$

and let $\partial(G)$ be the set of all valid bonds formed by subsets of $V(G)$. It follows that $X + Y$ is valid if and only if $|\partial(G)| = 2$.

From there, I'm not sure how to go about forming graphs for complex expressions like $\frac {y(x + z)} {z^2 + 1}$ by composing simpler graphs. I imagine that there is literature about representing Boolean algebra on graphs, but I haven't been able to find it.

Does anyone have an elegant interpretation? Or a pointer to relevant literature that might get me started?

EDIT: I can't find the article for free anywhere, but wikipedia touches on the issues:

In places, Boole talks of terms being interpreted by sets, but he also recognises terms that cannot always be so interpreted, such as the term 2AB...Such terms he classes uninterpretable terms...uninterpretable terms cannot be the ultimate result of equational manipulations from meaningful starting formulae.

Halperin's paper shows that his algebra is isomorphic to "a commutative ring with unit having no additive or multiplicative nilpotents." I think, for that reason, that it will require heavier machinery to represent than normal Boolean logic operations.

• You may want to check reductions from SAT to graph problems; they routinely use gadgets that encode satisfiability into graphs. – Raphael Apr 24 '14 at 20:43
• havent read article & it would be nice if the info were somewhere open. however, sketch of answer: presumably everything boole talked about is convertible to the standard basis of AND,OR,NOT functionally complete circuits. – vzn Apr 25 '14 at 14:59
• Boole's algebra doesn't obey "1 + 1 = 1", he says that 1 + 1 is undefined. I can't think of how I would encode a test for whether or not x and y are disjoint in a circuit. – Patrick Collins Apr 25 '14 at 19:01
• @vzn I edited with some more info to make the issues clearer. Circuits might work but it's definitely not trivial. – Patrick Collins Apr 25 '14 at 19:15
• ok not totally sure this is answerable (interpretable terms seems a crux: is question somehow asking to interpret uninterpretable terms? also where do they come from? etc) but sounds more like a tcs.se question, try flagging for mod attn after a wk or so of no answer – vzn Apr 25 '14 at 20:23

Those papers present the idea that a boolean function can be represented as a hypercube in which the vertices represent combinations of truth values. That is, rather than construct a graph with a vertex for each boolean variable X, Y etc, construct a graph where one vertex represents the tuple <X=0,Y=0>, one represents <X=0,Y=1> etc.


text:
Functions Practice Test
Chapter
Chapter 2
Section
Functions Practice Test
Solutions 19 Videos

Describe the reflection that transforms f(x) to g(x).

Q1

The graph of f(x) is transformed to obtain the graph of g(x) = 4f(3x + 21) - 15. Describe the horizontal translation that occurs.

Q2

Describe, in the appropriate order, the transformations that must be applied to the graph of f(x) to obtain the graph of g(x) = 5f(x - 9) + 7.

Q3

State the restrictions on X in the expression \displaystyle \frac{(x + 7)(x -1)}{(x -4)(x + 7)} .

Q4

If a function is defined by a set of points, then the inverse can be found by

A. reflecting the points in the y-axis

B. interchanging the x- and y-coordinates

C. reflecting the points in the origin

D. taking the reciprocal of each coordinate

Q5

Are \displaystyle \frac{6x^2 -27x - 105}{x - 7}  and \displaystyle (x + 3)(x + 10)-(x+ 3)(x+ 5)  equivalent expressions? Justify your answer.

Q6

Sketch the inverse of given f(x).

Q7

Simplify the expression and state any restrictions.

\displaystyle \frac{x - 8}{x + 7} \times \frac{x+ 15}{x^2 + 12x -45}

Q8a

Simplify the expression and state any restrictions.

\displaystyle \frac{x^2 +12x + 20}{x + 5} \div \frac{x^2 + 7x - 30}{x + 10}

Q8b

Simplify the expression and state any restrictions.

\displaystyle \frac{x + 3}{x - 7} - \frac{x+ 9}{x -2}

Q8c

Simplify the expression and state any restrictions.

\displaystyle \frac{x+ 8}{x + 3} + \frac{x - 6}{x^2 + 9x + 18}

Q8d

a) Given the function g(x) = 4(3x+ 6)^2 + 9, identify the base function as one of f(x) = x, f(x) = x^2,

f(x) = \sqrt{x}, and f(x) = \frac{1}{x}.

b) Describe, in the appropriate order. the transformations that must be applied to the base function f(X) to obtain the transformed function g(X].

c) Sketch the graphs of f(x) and g(x).

d) State the domain and range of the functions.

Q9

a) Given the function \displaystyle g(x) = \frac{1}{5}\sqrt{2(x- 8)}-3 , identify the base function as one of f(x) = x, f(x) = x^2, f(x) = \sqrt{x}, and f(x) = \frac{1}{x}.

b) Describe, in the appropriate order, the transformations that must be applied to the base function f(X] to obtain the transformed function g[X].

c) Sketch the graphs of f(x) and g(x).

d) State the domain and range of the functions.

Q10

Given the function g(x) = \frac{2}{0.5x} + 5, identify the base function as one of f(x) = x, f(x) = x^2, f(x) = \sqrt{x}, and f(x) = \frac{1}{x}.

b) Describe, in the appropriate order, the transformations that must be applied to the base function f(x) to obtain the transformed function g(x).

c) Sketch the graphs of f(x) and g(x).

d) State the domain and range of the functions.

Q11

For each function,

• i) determine f^{-1}(x)
• ii) graph f(x) and its inverse
• iii) determine whether the inverse of f(x) is a function

\displaystyle f(x) = 3x + 8

Q12a

For each function,

• i) determine f^{-1}(x)
• ii) graph f(x) and its inverse
• iii) determine whether the inverse of f(x) is a function

\displaystyle f(x) = 6(x - 9)^2 + 8

Q12b

A small skateboard company is trying to determine the best price for its boards. When the boards are priced at $80, 120 are sold in a month. After doing some research, the company finds that each increase of$5 will result in selling 15 fewer boards.

a) Write an equation to represent the revenue, R, in dollars, as a function of x, the number of $5 increases. b) State the domain and range of the revenue function. c) Determine the inverse of the revenue function. What does this equation represent in the context of the question? State the domain and range of the inverse. d) Determine the number of$5 increases for a revenue of \$8100.

Q13

A small plane is travelling between Windsor and Pele’e Island (a distance of approximately 60 km) and is directly affected by the prevailing winds. Thus, the actual speed of the plane with respect to the ground is the speed of the plane (160 km/h) plus or minus the wind speed, w.

a) Develop a simplified equation for the total time it takes to make a round trip if the wind speed is w. State the domain and range and any restrictions on this relationship.

b) Graph your relationship from part a).

c) The pilot thinks that if he has a strong headwind on the way out, then he will be able to make up any lost time on the way back when he has a tailwind. Determine if he is correct.

In Canada, fuel efficiency, l, for cars is stated in litres per 100 km. In the United States, fuel efficiency, m, is stated in miles per gallon (mpg). The formula m = 235/l can be used to convert from the Canadian system to the United States system.
b) In Canada, cars that have better fuel efficiency have a lower value for 8. Is the same true for m? Justify your response.


text:
Chemistry (4th Edition)

$N_2$ and $H_2$ will decrease their concentrations, and $NH_3$ will increase its concentration.
1. Write the equilibrium constant expression: - The exponent of each concentration is equal to its balance coefficient. $$K_c = \frac{[Products]}{[Reactants]} = \frac{[ NH_3 ]^{ 2 }}{[ N_2 ][ H_2 ]^{ 3 }}$$ 2. At equilibrium, these are the concentrations of each compound: $[ N_2 ] = 0.60 \space M - x$ $[ H_2 ] = 0.76 \space M - 3x$ $[ NH_3 ] = 0.48 \space M+ 2x$ $$1.2 = \frac{(0.48 + 2x)^2}{(0.60 - x)(0.76-3x)^3}$$ Real solutions: x = 0.0144 and x = 1.027 1.027 cannot be the correct value, because if so: $[N_2] = 0.60 -1.027 =$ Negative number. So: x = 0.0144 $[ N_2 ] = 0.60 \space M - 0.0144 = 0.59 M$ $[ H_2 ] = 0.76 \space M - 3(0.0144) = 0.72 M$ $[ NH_3 ] = 0.48 \space M+ 2(0.0144) = 0.051 M$


text:
# How to resolve collision between a dynamic AABB and static AABB?

I wanted to ask, how do I resolve collision between 2 cubes - in my case I want to push a moving / dynamic cube (used for the player) out of another static cube (used for the floor or objects in the scene)?

I tried various things, but in the end I don't know how to make the dynamic cube stay smoothly on top of the floor or not able to go through other objects (everything AABB vs AABB for now).

Below are the most important snippets to understand my problem better.

From PhysicsEngine.cpp

IntersectData intersectData =
m_objects[i]->getCollider().intersect(
m_objects[j]->getCollider());

// if they intersect, reverse movement to have solid box collisions.
if(intersectData.getDoesIntersect())
{
// revert movement (later push?) collision response.
glm::vec3 diff = m_objects[i]->getPosition() - m_objects[j]->getPosition();
glm::vec3 sep = glm::normalize(intersectData.getDirection()) * diff;
// std::cout << "Separation between: " << m_objects[i]->

// if testCollisionResponse - push back.
if (m_objects[i]->testCollisionResponse)
{
m_objects[i]->setPosition(m_objects[i]->getPosition() + sep);
// m_objects[i]->setVelocity(glm::vec3(0.0));
// m_objects[i]->testGravity = false;
// m_objects[i]->testGravity = false;
}
else if (m_objects[j]->testCollisionResponse)
{
m_objects[j]->setPosition(m_objects[j]->getPosition() - sep);
// m_objects[j]->setVelocity(glm::vec3(0.0));
// m_objects[j]->testGravity = false;
}
}

AABB.cpp

uGE::IntersectData uGE::AABB::intersectAABB(const AABB& other) const

{ glm::vec3 distances1 = other.getMinExtents() - m_maxExtents;

// test the other way around.
glm::vec3 distances2 = m_minExtents - other.getMaxExtents();

// pick the biggest values between the vectors on each axis.
glm::vec3 distancesOnEachAxis = glm::max(distances1, distances2);

float maxDistance = distancesOnEachAxis[0];
for (int i = 0; i < 3; i++)
{
if (distancesOnEachAxis[i] > maxDistance)
{
maxDistance = distancesOnEachAxis[i];
}
}

return uGE::IntersectData(maxDistance < 0, distancesOnEachAxis);

}

IntersectData.hpp

class IntersectData

{ public: IntersectData(const bool doesIntersect, const glm::vec3 direction) : m_doesIntersect(doesIntersect), m_direction(direction) {}

inline bool getDoesIntersect() const { return m_doesIntersect; }
inline float getDistance() const { return glm::length(m_direction); }
inline const glm::vec3 getDirection() const { return m_direction; }

private: const bool m_doesIntersect; const glm::vec3 m_direction; };

These are the project files (if you want to see more): https://github.com/BigThinker/CPPGame/blob/master/uGE/uGE/Physics/PhysicsEngine.cpp

All the best, Aldo

I think you may need to look further than simple collision detection to make this happen. Due to the discrete nature of a simulation such as this, it's hard to achieve a smooth "flooring" of one object onto a surface as it will constantly collide, then be adjusted, then collide, then be adjusted again.

One approach in projects I've used in the past is to manage this via a set of different phyics "states" which an object could be in. Examples might be: Grounded, Airbourne etc.

In this way, you run a different set of phyics rules depending on the state your object is currently in, and use hitbox detection differently in each, and to help transition between the two.

For example, imagine the case of a player character who appears in midair, above the floor. THe inital state is set to Airbourne and the physics system applies gravity to the character to start them falling.

Eventually, the AABB hitbox detection system detects a collision between the player physics hitbox and the floor hitbox. At this point the physics state transitions to Grounded and the position is adjusted to ensure there is no collision (as you discuss).

Now, the physics system knows the player is grounded, so can use different techniques to track the floor, rather than relying on the hitbox. Depending on your game, you might have a defined "floor" plane which you can query the height of at the current location. You might be able to ray-cast downwards (a short distance) to ensure you are still near the ground, and then transition back to 'Airbourne' when not.

There are many approaches to this, but the principal is that simple hitboxes are probably not sufficient for "smoothly" adhering one object to another where movement is possible. Use them to detect collisions, and use that information to inform transitions in your physics system to control character movement.

• Thanks a ton for your input. I think that this approach would work well in my case, and I'm going to try and implement this. – BigThinker Feb 28 '15 at 3:27
• Very glad if my answer was useful to your situation! – xan Mar 2 '15 at 9:23

Optional approach: I read through Game Physics Engine Development by Ian Millington to find out that before he resolves the impulse (velocity) and interpenetration, he removes the change in velocity by gravity like so:

// resting contact implementation.
// what is the velocity due to acceleration only?
glm::vec3 velocityDueAcc = particle[0]->getAcceleration();

// separation velocity due to acceleration (i.e. gravity)
// contact normal is the normalized vector between 2 objects's positions.
// duration is the frame duration (delta time).
float sepVelocityDueAcc = glm::dot(velocityDueAcc, contactNormal) * duration;

// if there's separation velocity from acceleration,
// remove it from the new separation velocity.
// (turn back the movement from y acceleration before resolving v and p).
if (sepVelocityDueAcc < 0)
{
newSepVelocity += restitution * sepVelocityDueAcc;

// make sure there wasn't removed more than there
// was to remove.
if (newSepVelocity < 0) newSepVelocity = 0;
}
// ...
// use newSepVelocity to resolve velocity.

Kind of an ad hoc approach to solving this problem, but it's working well so far.