14916260
Spurious modulation on current-mode controlled DC/DC converters: an explanation for intermittent chaotic operation
We explain the mechanism that causes "intermittent" instability and chaos in a current-mode controlled switching converter. The circuit model used to study the phenomenon incorporates a coupling process through which a spurious signal is coupled to the current sensing and ramp compensation circuitry, resulting in a modulation of the compensation slope which causes the system to become unstable intermittently. We describe a way to find the parameter boundaries where intermittent chaotic operation emerges.
7975007
Optimum design of very low distortion class E power amplifiers
In this paper, the optimum design of a class E power amplifier with resonant tank being symmetrically driven by two class E circuits is studied. The optimally designed symmetrical class E circuit has extremely low harmonic distortion, and the load matching network (if required) is non-critical and can be designed with ease. Practical steady-state design equations are derived and graphically presented. Experimental circuits are constructed for distortion evaluation.
28398925
Object Assisted Video Coding for Video Conferencing System
An object-based video coding for video conferencing system is proposed. There are two main processes: segmentation process and face detection process. The segmentation process is used to segment each frame of a video sequence into two non-overlapping regions, namely foreground and background. A novel face detection technique based on chrominance and the contour of the segmented region is applied to the foreground region. Smaller quantization step is used for the facial region to improve viewer's perception while a larger quantization step is used for the background to compensate the coding efficiency. The remaining regions are kept in normal coding quality to prevent degradation of important information other than the facial regio.
18516994
Fast analytical approach to finding steady-state waveforms for power electronics circuits using orthogonal polynomial basis functions
This paper describes a general analytical procedure for steady-state waveform analysis of power electronics circuits using orthogonal polynomials. The proposed method exploits the time-domain piecewise property of power electronics circuits as well as the orthogonality of certain polynomials in order to maximize the accuracy and computational efficiency. This new analytical approach can provide a fast means to obtain improved and more robust solutions of steady-state waveforms of power electronics circuits
8528863
Stability Analysis of RED Gateway with Multiple TCP Reno Connections
It has been observed that a bottleneck random early detection (RED) gateway becomes oscillatory when regulating a flow in multiple TCP connections. The stability boundary of the TCP-RED system depends on various network parameters, making the adjustment of the RED gateway a difficult task. Based on a fluid-flow model, analytical conditions were formulated that describe the stable boundary of the RED gateway depending on the number of TCP Reno connections. The proposed model accurately generates a stability boundary surface in a four dimensional space, which facilitates the adjustment of parameters for stable operation of the RED gateway. The accuracy of the analytical results has been verified using the ns-2 network simulations.
46438966
76-Space analysis of grey matter diffusivity: Methods and applications
Diffusion Weighted Imaging (DWI) and Diffusion Tensor Imaging (DTI) are widely used in the study and diagnosis of neurological diseases involving the White Matter (WM). However, many neurological and neurodegenerative diseases (e.g., Alzheimer's disease and Creutzfeldt-Jakob disease) are generally considered to involve the Grey Matter (GM). Investigation of GM diffusivity of normal aging and pathological brains has both scientific significance and clinical applications. Most of previous research reports on quantification of GM diffusivity were based on the manually labeled Region of Interests (ROI) analysis of specific neuroanatomic regions. The well-known drawbacks of ROI analysis include inter-rater variations, irreproducible results, tediousness, and requirement of a priori definition of interested regions. In this paper, we present a new framework of automated 76-space analysis of GM diffusivity using DWI/DTI. The framework will be evaluated using clinical data, and applied for study of normal brain, Creutzfeldt-Jakob disease and Schizophrenia.
16395036
A Distributed Approach to Musical Composition
Current techniques for automated composition use a single algorithm, focusing on one aspect of musical generation. In our system we make use of several algorithms, distributed using an agent oriented middleware, with each specialising on a separate aspect of composition. This paper describes the architecture and algorithms behind this system, with a focus on the agent framework used for implementation. We show early results which encourage a future application of this framework in automated music composition and analysis.
15946756
Movement-based interactive dance performance
Movement-based interactive dance has recently attracted great interest in the performing arts. While utilizing motion capture technology, the goal of this project was to design the necessary real-time motion analysis engine, staging, and communication systems for the completion of a movement-based interactive multimedia dance performance. The movement analysis engine measured the correlation of dance movement between three people wearing similar sets of retro-reflective markers in a motion capture volume. This analysis provided the framework for the creation of an interactive dance piece, Lucidity, which will be described in detail. Staging such a work also presented additional challenges. These challenges and our proposed solutions will be discussed. We conclude with a description of the final work and a summary of our future research objectives.
21918881
End system multicast: an architectural infrastructure and topological optimization
Although IP multicast has been proposed and investigated for years, there are major problems inherent in the IP multicasting technique, e.g. difficulty to scale up the system, difficulty in allocating a globally unique multicast address, complexity in supporting higher level features such as reliable data transfer and congestion/flow control, more importantly, difficulty to deploy on the current Internet infrastructure due to necessity to change many core routers. Recently, end-system multicast (ESM) has been proposed as an alternative solution so that multicasting services can be quickly deployed. In this paper, we consider the'architectural' and 'optimization' issues on designing an ESM-tree. Specifically, we present a distributed algorithm on how to create and maintain an ESM-tree. We propose a distributed algorithm to perform tree optimization (TO) so that an ESM-tree can dynamically adapt to the changing network condition (e.g. drop in transfer bandwidth) so that the nodes within an ESM-tree can receive data more efficiently. The distributed algorithm has the important theoretical properties that at all times, a tree topology can be maintained and any node joining, leaving, as well as any TO operation will not 'partition' the underlying ESM-tree. Therefore, our work can be used to provide an efficient architectural infrastructure for ESM services. We have implemented a prototype ESM system and carried out experiments to illustrate the effectiveness and the performance gains of our ESM optimization protocol.
1799321
Design patterns for games
Designing a two-person game involves identifying the game model to compute the best moves, the user interface (the "view") to play the game, and the controller to coordinate the model and the view. A crucial task is to represent the algorithms used in their highest abstract forms. This can prove to be a difficult and subtle endeavor. It is made easier however by the use of good object-oriented (OO) design principles to help maintain a high level abstract viewpoint during the design process. The state pattern is used to represent the game board and is coupled with the visitor pattern to provide state-dependent, variant behaviors. The min-max algorithm and its variants are implemented as the strategy pattern, which allows flexible and extensible computational capability. Careful analysis is performed to properly abstract the interactions between the model and the view. The command design pattern is used to provide callback services between the model and the view. Leading students through this design process enables them to learn algorithms and architectures that easily scale to full-sized applications.