16904687
What signals do packet-pair dispersions carry?
Although packet-pair probing has been used as one of the primary mechanisms to measure bottleneck capacity, cross-traffic intensity, and available bandwidth of end-to-end Internet paths, there is still no conclusive answer as to what information about the path is contained in the output packet-pair dispersions and how it is encoded. In this paper, we address this issue by deriving closed-form expression of packet-pair dispersion in the context of a single-hop path and general bursty cross-traffic arrival. Under the assumptions of cross-traffic stationarity and ASTA sampling, we examine the statistical properties of the information encoded in inter-packet spacings and derive the asymptotic average of the output packet-pair dispersions as a closed-form function of the input dispersion. We show that this result is different from what was obtained in prior work using fluid cross-traffic models and that this discrepancy has a significant impact on the accuracy of packet-pair bandwidth estimation.
353647
On Estimating Tight-Link Bandwidth Characteristics over Multi-Hop Paths
In this paper, we explore multi-hop bandwidth estimation assuming arbitrary cross-traffic at each node and develop a new probing method called Envelope that can asymptotically estimate not only the available bandwidth but also the raw capacity of the tight link. Envelope is based on a multi-link recursive extension of unbiased single-hop estimators proposed in the past (e.g., [14]) and a variation of the packet-cartouche technique [6]. Through extensive simulations, we evaluate Envelope in various network settings and cross-traffic conditions and find that it can measure tight-link bandwidth characteristics with accuracy that significantly surpasses that of the existing methods. We also find that Envelope can measure non-tight links in certain path and cross-traffic configurations.
35018228
Service-Level Management of Adaptive Distributed Network Applications
The paper is on generic service-level management tools that enable the reconfiguration of a distributed network application whenever there are resource-level changes or failures in the underlying network sub-systems. A network service is provided to client applications through a protocol module, with the latter exercising network infrastructure resources in a manner to meet the client requirements. Client requests for a network service instantiate the underlying protocol module with parameters specified at the service interface level, along with a prescription of critical properties to be enforced therein. At run-time, a management module may automatically monitor the service compliance to client-prescribed requirements, and notify the client whenever a service quality degradation is detected. The paper proposes a ‘function’-based model of service provisioning to realize our management approach. In this model, a service prescription conforms to generic interface templates based on an enumeration of the service attributes visible to clients, and how these attributes logically relate to one another in composing a client-level quality expectation. Our management model is independent of the specifics of problem-domain, which simplifies the development of distributed adaptive applications through a ‘software reuse’ of the management module. The paper presents the case study of an application: CDN, to demonstrate the usefulness of our model.
8305231
Packet-pair bandwidth estimation: stochastic analysis of a single congested node
We examine the problem of estimating the capacity of bottleneck links and available bandwidth of end-to-end paths under non-negligible cross-traffic conditions. We present a simple stochastic analysis of the problem in the context of a single congested node and derive several results that allow the construction of asymptotically-accurate bandwidth estimators. We first develop a generic queuing model of an Internet router and solve the estimation problem assuming renewal cross-traffic at the bottleneck link. Noticing that the renewal assumption on Internet flows is too strong, we investigate an alternative filtering solution that asymptotically converges to the desired values of the bottleneck capacity and available bandwidth under arbitrary (including non-stationary) cross-traffic. This is one of the first methods that simultaneously estimates both types of bandwidth and is provably accurate. We finish the paper by discussing the impossibility of a similar estimator for paths with two or more congested routers.
1211146
Multi-hop probing asymptotics in available bandwidth estimation: stochastic analysis
This paper analyzes the asymptotic behavior of packet-train probing over a multi-hop network path P carrying arbitrarily routed bursty cross-traffic flows. We examine the statistical mean of the packet-train output dispersions and its relationship to the input dispersion. We call this relationship the response curve of path P. We show that the real response curve Z is tightly lower-bounded by its multi-hop fluid counterpart F, obtained when every cross-traffic flow on P is hypothetically replaced with a constant-rate fluid flow of the same average intensity and routing pattern. The real curve Z asymptotically approaches its fluid counterpart F as probing packet size or packet train length increases. Most existing measurement techniques are based upon the single-hop fluid curve S associated with the bottleneck link in P. We note that the curve S coincides with F in a certain large-dispersion input range, but falls below F in the remaining small-dispersion input ranges. As an implication of these findings, we show that bursty cross-traffic in multi-hop paths causes negative bias (asymptotic underestimation) to most existing techniques. This bias can be mitigated by reducing the deviation of Z from S using large packet size or long packet-trains. However, the bias is not completely removable for the techniques that use the portion of S that falls below F.
15500512
Real-time simulation of physically based on-surface flow
Although many papers have been published in the field of fluid simulation, little attention has been paid to on-surface flow involving wetting and stain transportation as well as erosion and deposition phenomena. In this paper, we introduce nonzero divergence in the mass equation of Navier–Stokes equations to simulate water penetration from on-surface flow into substrate material. Also, the volume of fluid method is adopted to track the free surface. With a computation of the actual amount of absorbed water we render the wetting effects with fully dry and fully wet texture images simultaneously. Using our model, the on-surface flow that accompanies water absorption can be simulated realistically in real time with OpenGL preview rendering. Experimental results illustrate that our model can be widely applied to solve various problems related to on-surface flow.
1984219
Incorporation of input glitches into power macromodeling
Previous research on power macromodeling has always assumed glitch-free input signals. However, in an actual operating environment, the input signals of a circuit can contain glitches, which are generated by the previous stage of circuitry. In this paper, we investigate the impact of input glitches on the power dissipation of a circuit. Specifically, we show that the frequency and average duration of input glitches are two important factors affecting the overall power consumption. Input glitches can also increase output glitching by a surprisingly large amount. We present a simple yet effective analytical power macromodeling approach incorporating the effects of input glitching. In experiments with ISCAS-85 benchmark circuits, the average error of the proposed technique is 4.44%.
39271056
A hybrid representation of environment models in image-based real time walkthrough
In this paper, a hybrid representation of environment models using a combination of points and polygons is proposed. Through the model, a real time walkthrough of a complex environment can be achieved. We start from multiple depth reference images and classify the pixels of images into two categories, corresponding respectively to planar and non-planar surfaces in 3D space, then all the redundant points are removed by a comparison algorithm of sampling rate. For pixels corresponding to nonplanar surfaces, the point representation is maintained, and a local reconstruction and resampling process is employed to re-sample a set of points that distribute more uniformly on the surfaces. The re-sampled points are organized by an OBB-tree according to their space coordinates and a multiresolution structure is built to improve the rendering efficiency. For pixels corresponding to planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to texture maps. Under this hybrid representation, texture mapping and point-based rendering are employed to render the novel views, to take full advantage of the acceleration utility of graphics hardware. The algorithm demonstrates the combined advantages of approaches in traditional computer graphics and PBR/IBR, texture mapping for plane surfaces and point-based rendering for high detail surfaces and shapes.
2422545
Probe-level measurement error improves accuracy in detecting differential gene expression
MOTIVATION
Finding differentially expressed genes is a fundamental objective of a microarray experiment. Numerous methods have been proposed to perform this task. Existing methods are based on point estimates of gene expression level obtained from each microarray experiment. This approach discards potentially useful information about measurement error that can be obtained from an appropriate probe-level analysis. Probabilistic probe-level models can be used to measure gene expression and also provide a level of uncertainty in this measurement. This probe-level measurement error provides useful information which can help in the identification of differentially expressed genes.


RESULTS
We propose a Bayesian method to include probe-level measurement error into the detection of differentially expressed genes from replicated experiments. A variational approximation is used for efficient parameter estimation. We compare this approximation with MAP and MCMC parameter estimation in terms of computational efficiency and accuracy. The method is used to calculate the probability of positive log-ratio (PPLR) of expression levels between conditions. Using the measurements from a recently developed Affymetrix probe-level model, multi-mgMOS, we test PPLR on a spike-in dataset and a mouse time-course dataset. Results show that the inclusion of probe-level measurement error improves accuracy in detecting differential gene expression.


AVAILABILITY
The MAP approximation and variational inference described in this paper have been implemented in an R package pplr. The MCMC method is implemented in Matlab. Both software are available from http://umber.sbs.man.ac.uk/resources/puma.
7988049
Word Sense Disambiguation for Cross-Language Information Retrieval
We have developed a word sense disambiguation algorithm, following Cheng and Wilensky (1997), to disambiguate among WordNet synsets. This algorithm is to be used in a cross-language information retrieval system, CINDOR, which indexes queries and documents in a language-neutral concept representation based on WordNet synsets. Our goal is to improve retrieval precision through word sense disambiguation. An evaluation against human disambiguation judgements suggests promise for our approach.