End-to-End Congestion Control Schemes: Utility Functions, Random Losses and ECN Marks

We present a framework for designing end-to-end congestion control schemes in a network where each user may have a different utility function and may experience noncongestion-related losses. We first show that there exists an additive-increase-multiplicative-decrease scheme using only end-to-end measurable losses such that a socially optimal solution can be reached. We incorporate round-trip delay in this model, and show that one can generalize observations regarding TCP-type congestion avoidance to more general window flow control schemes. We then consider explicit congestion notification (ECN) as an alternate mechanism (instead of losses) for signaling congestion and show that ECN marking levels can be designed to nearly eliminate losses in the network by choosing the marking level independently for each node in the network. While the ECN marking level at each node may depend on the number of flows through the node, the appropriate marking level can be estimated using only aggregate flow measurements, i.e., per-flow measurements are not required

An Adaptive Virtual Queue (AVQ) Algorithm for Active Queue Management

Virtual queue-based marking schemes have been recently proposed for Active Queue Management (AQM) in Internet routers. We consider a particular scheme, which we call the Adaptive Virtual Queue (AVQ), and study its following properties: its stability in the presence of feedback delays, its ability to maintain small queue lengths, and its robustness in the presence of extremely short flows (the so-called web mice). Using a linearized model of the system dynamics, we present a simple rule to design the parameters of the AVQ algorithm. We then compare its performance through simulation with several well-known AQM schemes such as RED, REM, Proportional Integral (PI) controller, and a nonadaptive virtual queue algorithm. With a view toward implementation, we show that AVQ can be implemented as a simple token bucket using only a few lines of code

Simulation of air breakdown mechanism using different electrodes

Rapid growth in power sector of nation has given the opportunity to power engineers to protect the power equipment for reliable operation during their operating life. It has been seen from the several studies conducted by power engineers that one of the main problem in high voltage power (HV) equipment is the degradation of insulation i.e., quality of insulation of power equipment. As the high voltage power equipments are mainly subjected with spark over voltage causes by the lighting strokes, switching action, a protective device is used for determine the safe clearance required for proper insulation level. The sphere gaps are commonly used for measurements of peak values of high voltages and have been adopted by IEC and IEEE as a calibration device. Generally, the standard sphere gaps are widely used for protective device in electrical power equipments. The sphere gaps are filled up with insulating medium such as liquid insulation (transformer oil), and gas insulation (SF6, N2, CO2, CCl2F2 etc.) in HV power equipments. Normally, air medium is widely used as an insulating medium in different electrical power equipments as its breakdown strength is 30kV/cm. Therefore electrical breakdown characteristic of small air gap under the different applied voltage has its great significance for the design consideration of various air insulated HV equipment. In addition, the effect of breakdown voltage on different insulation like lamiflex, leatheroid, plywood, craft paper, and polyester fiber has also been studied. To observe the effect on insulation due to breakdown mechanism, the insulation samples are collected both before and after breakdown voltage test and analysis has been done with the help of Scanning electron microscope (SEM). To simulate the air breakdown voltage with and without the insulation barrier has been studied experimentally in high voltage laboratory, a standard diameter of 25 cm spheres are used for measurement of air breakdown voltages and electric field of the high voltage equipments. The above experiment is conducted at the normal temperature and pressure. The simulation of such air breakdown voltage has been carried out in the COMSOL environment. Finally, the experimental result has been compared with theoretical, and simulation results.

Exploring User-Provided Connectivity - A Simple Model

The advent of cheap and ubiquitous wireless access has introduced a number of new connectivity paradigms. This paper investigates one of them, user-provided connectivity or UPC. In contrast to traditional infrastructure-based connectivity, e.g., connectivity through the up-front build-out of expensive base-stations, UPC realizes connectivity organically as users join and expand its coverage. The low(er) deployment cost this affords is one of its main attractions. Conversely, the disadvantages of connectivity sharing and a high barrier-to-entry from low initial penetration create strong disincentives to its adoption. The paper’s contributions are in formulating and solving a simple model that captures key aspects of UPC adoption, and in articulating guidelines to make it successful. For analytical tractability, the model is arguably simplistic, but the robustness of its findings is demonstrated numerically across a wide range of more general (and more realistic) configuration

Effect of Volume Fraction and Fiber Distribution on Stress Transfer in a Stochastic Framework of Continuous Fiber Composite: A Micromechanical Study

In fiber Reinforced Composites (FRC) fiber breakage is a common phenomenon resulting in stress concentration. This high stress gets transfer in the vicinity of the breakage which is quantified by Stress Transfer Coefficient (STC). In this paper, an attempt is made to check the effect of fiber volume fraction and the distribution of the fibers on STC and ineffective length. The fiber volume fraction is changed considering three cases: 1) by changing the number of fibers, 2) by changing the dimension of the Represntative Volume Element (RVE) and 3) by changing the fiber radius. Cases with change in dimension of RVE and change in fiber radius, periodic and semi-random arrangents of fibers are considered. From the analysis of 200 RVE's for each volume fraction in random and semi-random arrangements, it is observed that the distribution of STC does not follow any standard distribution, even if the fiber arrangement follows the normal distribution. The fiber cross-sectional dimension plays a critical role in regaining the broken fiber strength. The periodic arrangement of fibers can be said to be beneficial over the random arrangement considering the stress transfer from the broken fiber

Flows on Graphs with Random Capacities

We investigate flows on graphs whose links have random capacities. For binary trees we derive the probability distribution for the maximal flow from the root to a leaf, and show that for infinite trees it vanishes beyond a certain threshold that depends on the distribution of capacities. We then examine the maximal total flux from the root to the leaves. Our methods generalize to simple graphs with loops, e.g., to hierarchical lattices and to complete graphs.Comment: 8 pages, 6 figure

Synthesis and Characterization of Nonaqueous Deposited Nanocrystalline Cds Film

A nanocrystallineCdS film can be deposited by chemical bath deposition using non aqueous medium. XRD analysis confirms the crystalline structure of CdS (002) with 34 nm crystallite size. The as deposited films are stoichiometric in nature with Cd and S atomic % ratio equal to 1.0. The field emission scanning electron miceoscope and atomic force microscopy studies revels a densely packed non porous granular deposit with RMS value of roughness equal to 92nm. The band gap of the film is measures by spectroscopy and it is observed to 2.40 eV which is good agreement with the reported result. The photoluminescence prominent peak of the CdS film is observed to be 392 nm

IR2Vec: LLVM IR based Scalable Program Embeddings

We propose IR2Vec, a Concise and Scalable encoding infrastructure to represent programs as a distributed embedding in continuous space. This distributed embedding is obtained by combining representation learning methods with flow information to capture the syntax as well as the semantics of the input programs. As our infrastructure is based on the Intermediate Representation (IR) of the source code, obtained embeddings are both language and machine independent. The entities of the IR are modeled as relationships, and their representations are learned to form a seed embedding vocabulary. Using this infrastructure, we propose two incremental encodings:Symbolic and Flow-Aware. Symbolic encodings are obtained from the seed embedding vocabulary, and Flow-Aware encodings are obtained by augmenting the Symbolic encodings with the flow information. We show the effectiveness of our methodology on two optimization tasks (Heterogeneous device mapping and Thread coarsening). Our way of representing the programs enables us to use non-sequential models resulting in orders of magnitude of faster training time. Both the encodings generated by IR2Vec outperform the existing methods in both the tasks, even while using simple machine learning models. In particular, our results improve or match the state-of-the-art speedup in 11/14 benchmark-suites in the device mapping task across two platforms and 53/68 benchmarks in the Thread coarsening task across four different platforms. When compared to the other methods, our embeddings are more scalable, is non-data-hungry, and has betterOut-Of-Vocabulary (OOV) characteristics.Comment: Accepted in ACM TAC