214 research outputs found
Agile and robust resource management in CSMA wireless networks:
No full textWith the recent push towards wireless broadband, and user migration towards mobile devices, it has become imperative for wireless networks to support higher network capacity, increased battery life, and greater mobility. While a combination of both local- and wide-area wireless technologies will be needed to meet these requirements, we believe that carrier-sense multiple-access (CSMA) wireless networks, if designed well, can play an important role in the future. Traditional CSMA wireless networks, which form the basis for today's ubiquitous wireless LAN technology--IEEE 802.11 or WiFi, cannot satisfy the stated requirements mainly because they lack efficient resource management (or resource parameter adaptation) techniques. Several fundamental characteristics of these networks, and practical implementation challenges, also limit the applicability of solutions from other domains. Taken together, these considerations force us to fundamentally re-think the design of resource parameter adaptation for CSMA wireless networks.
In this dissertation, we first identify that, to satisfy the requirements, resource management techniques for CSMA wireless networks should possess two fundamental, but conflicting properties, agility, and robustness. Briefly, to provide increased bandwidth to mobile users, agile solutions are required that exploit opportunities for improved performance; at the same time, solutions cannot afford to compromise on link robustness. In addition, we realize that striking this trade-off effectively calls for different solutions in indoor and outdoor environments. To prove these hypotheses, we present the design and implementation of two resource management frameworks, Symphony and Sonata, for indoor and outdoor environments respectively. Indoors, Symphony increases network capacity and battery life for mobile clients by addressing the classical problem of joint, per-link, transmit power control and rate adaptation. For improved robustness, Symphony uses novel mechanisms based on measuring the expected transmission time (ETT), and the utility of RTS/CTS frames, while relying on a learning approach to converge quickly to the right resource parameter choice. Outdoors, the Sonata framework introduces a novel and fundamental tradeoff between directionality and base station diversity for uplink transmissions. Using a new location-based approach for improved parameter convergence, Sonata is able strike the agility-robustness tradeoff effectively.
Together, these frameworks prove that, achieving the right balance between agility and robustness can enable CSMA wireless networks to transition to the wireless broadband era.Ph.D.Includes bibliographical references (p. 96-106)by Kishore Ramachandra
Behavioral Subtyping in Object-Oriented Languages
Get PDFdata types, modules, packages; F.3.1 [Logics and Meanings of Programs] Specifying and Verifying and Reasoning about Programs --- logics of programs, pre- and post-conditions, theory A version of this technical report is published as the author's doctoral dissertation. c fl Copyright 1997 by Krishna Kishore Dhara All rights reserved. Department of Computer Science 226 Atanasoff Hall Iowa State University Ames, Iowa 50011-1040, USA ii TABLE OF CONTENTS 1. INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1.1 Problem : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 1.1.1 Reasoning problem and behavioral subtyping : : : : : : : : : : 2 1.1.2 Aliasing and behavioral subtyping : : : : : : : : : : : : : : : : 4 1.2 Overview of the solutions : : : : : : : : : : : : : : : : : : : : : : : : : 6 1.2.1 Different notions of behavioral subtyping : : : : : : : : : : : : 6 1.2.2 Semantic conditions : : : : : : : : : : : : : : : : : : : : : : : : 7 1.2.3 "..
The structure of lobbying and protection in U.S. agriculture
Get PDFThe author surveys the empirical literature on the political economy of agricultural protection. He uses a detailed data set of agricultural Political Action Committee (PAC) contributions over five U.S. congressional election cycles over the 1991-2000 period to investigate the relationship between lobbying spending and agricultural protection. A detailed graphical analysis of campaign contributions by the agricultural PACs indicates that although there are very many PACs, in most sectors the majority of contributions are made by very few PACs. Econometric analysis reveals that lobbying spending by agricultural PACs is positively associated with the use of nontariff barriers and specific tariffs by the United States. There is a strong association between the average U.S. tariff on goods that benefit from U.S. export subsidies and lobbying spending. And there is no association between agricultural protection and trade measures such as import penetration and the export-to-output ratio.Economic Theory&Research,Politics and Government,Agricultural Knowledge&Information Systems,Wetlands,ICT Policy and Strategies
A non-redundant role of complement protein C1q in normal and adverse pregnancy
Get PDFAvailability of data and materials: Not applicable.Copyright © The Author(s) 2022. Complement component 1q (C1q) is the recognition molecule of the classical pathway of the complement system that can bind to an array of closely spaced antigen-bound immunoglobulin G (IgG) and IgM antibodies. In addition to its involvement in defence against a range of pathogens and clearance of apoptotic and necrotic cells, C1q has also been implicated in immune and non-immune homeostasis. C1q is locally produced by immune cells such as monocytes, macrophages, and dendritic cells. C1q is also synthesized by decidual endothelial cells, thus acting as a link between decidual cells and trophoblasts, as well as contributing to the remodelling of spiral arteries. Furthermore, C1q is produced by the extravillous trophoblasts (EVTs) invading the decidua. As a pro-angiogenic molecule, C1q is also important for normal placentation processes as it favors the active angiogenesis in the developing decidua. These observations have been validated by C1q gene knock-out mice which showed pre-eclampsia (PE)-like symptoms, characterized by hypertension, proteinuria, glomerular endotheliosis, and increased soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio, and increased oxidative stress. The role of C1q in normal and adverse human pregnancy is being studied extensively due to its absence or low level as a likely precipitating factor for the development of PE.Funding: Not applicable
Artists’ Moving Image: South Asian Trajectories
No full textA special South Asia-focused journal edition of the journal, 'Moving Image Review and Art Journal'. The edition includes eight articles, features, reviews and interviews as well as a contextual preface by the editors, Lucia King and Rashmi Sawhney. Trajectories of film history and the practices of 'artists' moving image' makers from South Asia are traced and critiqued, including the significant impact of documentary film experimentation from the 1960s to the present. Author contributors are: Nancy Adajania, Avijit Mukul Kishore, Adnan Madani, Shai Heredia, Nicole Wolf, Kaushik Bhamik, Lucia King and Rashmi Sawhney
The Effects of Endogenous Protection on the Economic Landscape
Get PDFThe author studies the impact of political economy variables on the spatial distribution of industry. The political game between a single lobby and a partial opportunistic incumbent may alter the economic landscape of a small economy. The trade policy endogenously determined becomes the channel to understand how the players’ behaviour impacts on the long run spatial distribution of industry. When the rest of the world is a free trader and the spending share of an economy is relatively small, the marginal change in the trade policy has a relevant impact on the industry share. Amazingly, if a small economy is characterised by a government that is not very much concerned about general welfare and there is a lobby of few capital owners that play actively, the possible outcome will be a relocation of industry that favours such an economy. Capital owners might make capital flow to look for protection. Political variables may act as a dispersion force.
Inspection and evaluation of dry fibers in thick composites
Get PDFThis paper presents the investigation of dry fibers in thick composites. Dry fibers can be defined as lack of epoxy in localized regions. These local regions act as potential defects in thick composites under compressive loads and act as an initiation point for defects such as matrix cracking and delamination. Detection and characterization of dryness in glass/epoxy composites, with thickness greater than one inch, is presented in this paper. One inch samples with dry fibers were fabricated and tested. Detection is carried out with the help of air coupled ultrasonics in both through transmission and singled sided inspection. To characterize the amount of epoxy, time of flight data was correlated with density and fiber volume fraction. Based on the observations a technique was developed for characterization of dryness.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This proceeding appeared in Dayal, Vinay, Sunil Kishore Chakrapani, and Daniel Barnard. "Inspection and evaluation of dry fibers in thick composites." In AIP Conference Proceedings, vol. 1511, no. 1, pp. 1036-1042. American Institute of Physics, 2013, and may be found at
DOI: 10.1063/1.4789157.
Copyright 2013 American Institute of Physics.
Posted with permission
Detection of in-plane fiber waviness in composite laminates using guided Lamb modes
Get PDFThis paper presents the study of Lamb wave interaction with in-plane fiber waviness in thin composite laminates. Previous studies show that a reduction in stiffness of the laminate occurs due to in-plane waviness. Aspect ratio and shear angles were used to define severity of waviness. Air coupled ultrasonic transducers were used to generate the fundamental anti-symmetric mode (A0), which was used in this study. A reduction in velocity of the A0 mode was observed when it interacts with in-plane waviness. To confirm the findings, dispersion curves were plotted for straight fiber zone and waviness zone. Experimental B-Scans of wavy laminate were used to evaluate the velocity change. Conclusions were made based on the correlation between experimentally and analytically observed velocities.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This proceeding appeared in Chakrapani, Sunil Kishore, Daniel Barnard, and Vinay Dayal. "Detection of in-plane fiber waviness in composite laminates using guided Lamb modes." In AIP Conference Proceedings, vol. 1581, no. 1, pp. 1134-1140. American Institute of Physics, 2014, and may be found at
DOI: 10.1063/1.4864948.
Copyright 2014 AIP Publishing LLC.
Posted with permission
Inspection of spar-core bond in helicopter rotor blades using finite element analysis
Get PDFThis work focuses on inspection of spar-core bond of a helicopter rotor blade using finite element analysis. Structures which have high density, high stiffness cores can be very difficult to inspect due to various mode conversions. FEM was used to capture these mode conversions effectively. The structure consists of a thin spar section followed by a spar-core half space and another thin spar section. A Lamb wave excited in the spar section can mode convert into a Rayleigh wave in the spar-core section due to the coupling of the core material. This in turn mode converts back into a Lamb wave upon interacting with the next spar section. This work focuses solely on capturing the mode conversions between Rayleigh and Lamb modes at different discontinuities in the geometry.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This proceeding appeared in Chakrapani, Sunil Kishore, Daniel J. Barnard, and Vinay Dayal. "Inspection of spar-core bond in helicopter rotor blades using finite element analysis." In AIP Conference Proceedings, vol. 1650, no. 1, pp. 1766-1773. American Institute of Physics, 2015, and may be found at
DOI: 10.1063/1.4914800.
Copyright 2015 AIP Publishing LLC.
Posted with permission
Rayleigh wave interaction and mode conversion in a delamination
Get PDFThe interaction of Rayleigh waves with a delamination in a fiber reinforced composite plate was analyzed in the present work. Rayleigh waves interacting with delamination, mode convert into Lamb waves in the delamination zone. These guided Lamb modes have the capability to mode convert back into Rayleigh modes when they interact with the edge of the delamination. Unidirectional glass/epoxy laminate with delamination of known size was fabricated and tested using air-coupled ultrasonics. Finite element models were developed to understand the various mode conversions. Experimental and numerical A-Scans, mode velocities were used to identify each mode. A good correlation between experimental and numerical results was observed.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This proceeding appeared in Chakrapani, Sunil Kishore, Vinay Dayal, and Jamie Dunt. "Rayleigh wave interaction and mode conversion in a delamination." In AIP Conference Proceedings, vol. 1581, no. 1, pp. 690-696. American Institute of Physics, 2014, and may be found at
DOI: 10.1063/1.4864887.
Copyright 2014 AIP Publishing LLC.
Posted with permission
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