Online Steiner Tree with Deletions

In the online Steiner tree problem, the input is a set of vertices that appear one-by-one, and we have to maintain a Steiner tree on the current set of vertices. The cost of the tree is the total length of edges in the tree, and we want this cost to be close to the cost of the optimal Steiner tree at all points in time. If we are allowed to only add edges, a tight bound of $\Theta(\log n)$ on the competitiveness is known. Recently it was shown that if we can add one new edge and make one edge swap upon every vertex arrival, we can maintain a constant-competitive tree online. But what if the set of vertices sees both additions and deletions? Again, we would like to obtain a low-cost Steiner tree with as few edge changes as possible. The original paper of Imase and Waxman had also considered this model, and it gave a greedy algorithm that maintained a constant-competitive tree online, and made at most $O(n^{3/2})$ edge changes for the first $n$ requests. In this paper give the following two results. Our first result is an online algorithm that maintains a Steiner tree only under deletions: we start off with a set of vertices, and at each time one of the vertices is removed from this set: our Steiner tree no longer has to span this vertex. We give an algorithm that changes only a constant number of edges upon each request, and maintains a constant-competitive tree at all times. Our algorithm uses the primal-dual framework and a global charging argument to carefully make these constant number of changes. We then study the natural greedy algorithm proposed by Imase and Waxman that maintains a constant-competitive Steiner tree in the fully-dynamic model (where each request either adds or deletes a vertex). Our second result shows that this algorithm makes only a constant number of changes per request in an amortized sense.Comment: An extended abstract appears in the SODA 2014 conferenc

Low power VCO-based analog-to-digital conversion

textThis dissertation presents novel two stage ADC architecture with a VCO based second stage. With the scaling of the supply voltages in modern CMOS process it is difficult to design high gain operational amplifiers needed for traditional voltage domain two-stage analog to digital converters. However time resolution continues to improve with the advancement in CMOS technology making VCO-based ADC more attractive. The nonlinearity in voltage-to-frequency transfer function is the biggest challenge in design of VCO based ADC. The hybrid approach used in this work uses a voltage domain first stage to determine the most significant bits and uses a VCO based second stage to quantize the small residue obtained from first stage. The architecture relaxes the gain requirement on the the first stage opamp and also relaxes the linearity requirements on the second stage VCO. The prototype ADC built in 65nm CMOS process achieves 63.7dB SNDR in 10MHz bandwidth while only consuming 1.1mW of power. The performance of the prototype chip is comparable to the state-of-art in terms of figure-of-merit but this new architecture uses significantly less circuit area.Electrical and Computer Engineerin

TRANSMISSION LOSS OF CYLINDRICAL MUFFLER WITH DIFFERENT LENGTH TO DIAMETER RATIO BY USING TWO LOAD METHOD AND SIMULATION TOOL

This paper shows the details of measurement of the acoustical transmission loss of single expansion chamber muffler with various lengths to diameter ratios of cylindrical chamber muffler. A muffler is an important noise control element for reduction of machinery exhaust noise, fan noise, and other noise sources involving the flow of gases. Mufflers are typically arranged along the exhaust pipe as the part of the exhaust system of an internal combustion engine to reduce its noise. Firstly simulation tool results (Comsol) are compared with experimentally then results are observed with various expansion ratio

A new method for solving linear multi-objective transportation problems with fuzzy parameters

AbstractThere are several methods in the literature for solving transportation problems by representing the parameters as normal fuzzy numbers. Chiang [J. Chiang, The optimal solution of the transportation problem with fuzzy demand and fuzzy product, J. Inform. Sci. Eng. 21 (2005) 439–451] pointed out that it is better to represent the parameters as (λ,ρ) interval-valued fuzzy numbers instead of normal fuzzy numbers and proposed a method to find the optimal solution of single objective transportation problems by representing the availability and demand as (λ,ρ) interval-valued fuzzy numbers. In this paper, the shortcomings of the existing method are pointed out and to overcome these shortcomings, a new method is proposed to find solution of a linear multi-objective transportation problem by representing all the parameters as (λ,ρ) interval-valued fuzzy numbers. To illustrate the proposed method a numerical example is solved. The advantages of the proposed method over existing method are also discussed

Role of Brownian motion on the thermal conductivity enhancement of nanofluids

This study involves Brownian dynamics simulations of a real nanofluid system in which the interparticle potential is determined based on Debye length and surface interaction of the fluid and the solid. This paper shows that Brownian motion can increase the thermal conductivity of the nanofluid by 6% primarily due to random walk motion and not only through diffusion. This increase is limited by the maximum concentration for each particle size and is below that predicted by the effective medium theory. Beyond the maximum limit, particle aggregates begin to form. Brownian motion contribution stays as a constant beyond a certain particle diameter

Improved Performance of Stability and Turbine Response of Hydro Power Plant System by Fuzzy Logic

In this Research work, simulation model of typical canal kind small hydro-electric power plant developed through model inter-connection of assorted equipments of plant into consideration during MATLAB/SIMULINK based mostly package surroundings. Varied elements of tiny electricity plant, governor, semi-Kaplan turbine and open channel. Synchronous exciter, generators are being thought about below modeling and simulation. Aim is to check its behavior throughout transient condition. Victimization simulated model sweetening through Fuzzy logic controller are done to scale back oscillations, peak overshoot and peak undershoot throughout transient amount and additionally to enhance steady state response this invalidator prices and safety conditions, in choosing simplest alternatives within early phase of design and to see devices. Using fuzzy logic, the turbine response max overshoot is 0.25 and stabilizes at 0.36. Whereas using PID the turbine response max overshoot is 0.38 and stabilizes at 0.8. Without any controllers the max overshoot is 0.39 and stabilizes at 0.9. DOI: 10.17762/ijritcc2321-8169.150614

Simulation of Cylindrical Resonator with Spiral Neck and Straight Neck to Attenuate the Low Frequency Noise of Muffler

This paper is concentrated for improving the transmission loss and reduces the low frequency noise level by development of Helmholtz Resonator within a limited space. The modified Helmholtz resonator, i.e. cylindrical resonator with spiral neck is used to occupy the small space. Introduction of spiral neck instead of straight neck with cylindrical cavity reduces the space of resonator. For first cut-off frequency (resonance frequency) the volume of resonator is fixed, so with the help of spiral neck its length increases, volume increases and its curvature effect is also helpful in the reduction of noise. The finite element analysis tool Comsol multiphysics is used to validate the result. The results shows interesting factor that resonator not only attenuate a particular low frequency noise as well it increases transmission loss with spiral neck. Helmholtz resonator with a spiral neck can achieve high sound reduction within a small space at low frequency

Dynamic Event Driven Fault Diagnosis for Distributed Networks

The occurrence of faults is a common feature in most networks and addressing this issue is an important aspect of network maintenance. In this project, we take up the problem of detecting faults in general arbitrary networks. The networks that we have considered for the implementation of our algorithm are general arbitrary networks; where every node in the network has a minimum of two neighbors. Various types of faults occur in such networks. This algorithm is applicable to hard faults. While doing so, we have assumed our own set of well-defined assumptions which will be followed during the implementation phase of the algorithm. The approach taken to diagnose the system brings about a system level diagnosis and consists of two phases. Each of phases has its own complexity and constraints. In this algorithm we follow the principle of periodic testing that occurs after a certain fixed period has passed. During each such period the tester node performs a test on a fault free node and then determines whether the node it has tested is faulty or fault free. This is a brief abstraction of the first phase also known as the ”Test Phase”