180 research outputs found
Review of the book Critiquing Brahmanism: A collection of essays, by K. Murali (Ajith)
No full textDr. Devin Zane Shaw (Douglas College) reviews the book Critiquing Brahmanism: A collection of essays, by K. Murali (Ajith) (2020).Final article published
Performance Analysis of Process Parameters on Machining Titanium (Ti-6Al-4V) Alloy Using Abrasive Water Jet Machining Process
Full text linkAbstractOwing to its light weight and corrosive resistant, Titanium (Ti-6Al-4V) alloy is mainly utilized in fabricating medical device applications. Since it has high strength, it is very difficult to machine alloy using conventional machining. In the present study, an endeavor has been made to machine titanium alloy using AWJM process. Since the process involves with less heat affect zone and higher material removal, it is possible to enhance machinability of workpiece. It has attempted to find the influence of process parameters on surface roughness and topography for enhancing the process. It has been observed that the abrasive flow rate and standoff distance has the most significant role on determining surface quality
Performance evaluation of transmit diversity techniques in the CDMA 2000 standard
Full text linkThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 123).This thesis evaluates the performance of two forward-link transmit diversity techniques in the CDMA2000 standard: Space-Time Spreading (STS) and Phase-Sweep Transmit Diversity (PSTD). For each technique, the evaluation consists of conducting 9.6 kbps Markov calls in the field and measuring the mean forward-link fundamental-channel (F-FCH) transmit power required to achieve a 1% frame error-rate (FER) at the mobile receiver. The required transmit power is used to compute an estimate of cell capacity as measured by the number of supported users, assuming a fixed total transmit power at the base station. It is observed that enabling STS increases capacity by up to 80% if all mobiles support STS, but capacity is reduced by up to 20% when fewer than 35% of the mobiles support the technique. The capacity loss results from interference of the diversity-antenna signal on mobiles that do not support STS; such interference causes an F-FCH transmit power increase of up to 1.5 dB in multipath Rayleigh-faded channels, as observed in lab experiments. PSTD, which does not require mobile-specific support, was found to improve cell capacity by 12% according to the field experiments.by Murali S. Vajapeyam.M.Eng
Towards low temperature sintering methods for dye sensitized solar cells
No full textAccess to economically viable renewable energy sources is essential for the development of a globally sustainable society. Solar energy has a large potential to satisfy the future need for renewable energy sources. Dye sensitized solar cells are a third generation of photovoltaic technologies with the potential for low cost environmentally safe energy production. Commercialization of this technology requires that dye sensitized solar cells with higher efficiencies can be fabricated on flexible substrates. The commonly used material for the anode in a Dye Sensitized Solar Cell consists of titanium dioxide nanoparticles covered with a layer of light sensitizing dye. For efficient electron transport throughout the nanoparticle network, good particle interconnections are necessary. For low temperature processing these interconnections can be achieved through a hydrothermal process. The focus of this research is to understand at a fundamental level this reaction-based sintering process. A titanium alkoxide precursor was mixed with commercial titania nanoparticles and coated on a transparent conductive oxide substrate. The product of the hydrolysis and condensation of the alkoxide served to connect the nanoparticles thus improving the electrical conduction of the titania electrode; this was confirmed by solar cell testing and electrochemical impedance spectroscopy. To further understand the formation of interconnections during reactive sintering, a model system based on inert silica particles was investigated. Titanium alkoxide precursor was mixed with commercial silica particles and reacted. Three different types of silica particles were used: each with a different morphology. The silica-titania multilayers/powders were characterized using SEM, XRD and BET. The efficiency of DSSCs is higher when larger non-porous silica particles are used and thin nanocrystalline titania is coated on this superstructure. This gave insight into the locations where the reactive liquid finally goes as these reactions are carried out. As a further extension of this study, thin layers of this same kind of silica-titania composite were obtained by spin coating a titanium alkoxide sol mixed with monosized 500nm silica particles. SEM was used to examine the morphology of the contact/neck formation. Image analysis was done to quantify the effect of key process parameters on the average neck width at 2-particle contact points. The use of image analysis to study mixed oxide sub-monolayers in this way is the first of its kind. These observational tools and the model system approach developed in this research could be applied to many systems that are of interest for optical and mechanical applications.Ph.D.Includes bibliographical referencesIncludes vitaby Sukanya Mural
Atomically thin solid-state nanopore field-effect transistors for single-molecule sensing
No full textSubmission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-12-01The student, Nagendra Bala Murali Athreya, accepted the attached license on 2021-10-29 at 15:20.The student, Nagendra Bala Murali Athreya, submitted this Dissertation for approval on 2021-10-29 at 15:35.This Dissertation was approved for publication on 2021-11-03 at 14:21.DSpace SAF Submission Ingestion Package generated from Vireo submission #17179 on 2022-04-29 at 16:09:22Made available in DSpace on 2022-04-29T21:58:19Z (GMT). No. of bitstreams: 4
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Previous issue date: 2021-11-03Embargo set by: Seth Robbins for item 123417
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Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimitedSolid-state nanopores have emerged as promising replacement candidates for single-molecule sensing over biological nanopores due to their chemical and mechanical robustness. In this context, two-dimensional solid-state materials such as graphene and MoS2 have gained much interest for ultra-fast and reliable sensing because of their atom size thickness that anticipates excellent spatial resolution and their electrical responsivity that enables sensing in-plane electron current modulated by the molecule translocating through the pore, simultaneously with ionic blockade current. This dissertation focuses on the development and implementation of a comprehensive computational model for atomically thin solid-state nanopore FETs applied toward single bio-molecule sensing. The developed software pipeline combines all-atom molecular dynamics simulations with electron transport modeling in semiconducting 2D membranes and statistical signal processing to analyze the detailed interaction between biomolecules and solid-state nanopore membranes. Various scalable FET architectures are explored in efforts to improve the sensor signal quality and bio-molecule detection capabilities. The validation of the device designs and methodology is illustrated with some of the important biomedical applications such as DNA sensing, epigenetic detection of DNA methylation, and identification of single-stranded breaks in dsDNA
Bringing NoCs to 65nm
Full text linkVery deep submicron process technologies are ideal application fields for NoCs, which offer a promising solution to the scalability problem. This article sheds light on the benefits and challenges of Noc-Based interconnect design in nanometer CMOS. The author present experimental results from fully working 65-NM Noc Designs and a detailed scalability analysis.LSI1ES
A VLA–GMRT Look At 11 Powerful Fr II Quasars
No full textWe present results from 1.4 and 5 GHz observations at matched resolution with the Karl G. Jansky Very Large Array (VLA) of 11 powerful 3C FR II quasars. We examine the 11 quasars along with a sample of 13 narrow-line FR II radio galaxies and find that radio-loud unification largely holds but environmental effects cannot be ignored. The radio core prominence, largest linear size, and axial ratio parameter values indicate that quasars are at relatively smaller angles compared to the radio galaxies and thus probe orientation. Lack of correlation between statistical orientation indicators such as misalignment angle and radio core prominence, and larger lobe distortions in quasars compared to radio galaxies suggest that intrinsic/environment effects are also at play. Some of 150 MHz observations with the TGSS–GMRT reveal peculiar lobe morphologies in these FR II sources, suggesting complex past lives and possibly restarted AGN activity. Using the total 150 MHz flux density we estimate the time-averaged jet kinetic power in these sources and this ranges from (1–38) × 10⁻⁴⁵ erg s⁻¹, with 3C 470 having the highest jet kinetic power. © 2018 The Author(s).Erik Jonsson School of Engineering and Computer Scienc
Software distributed shared memory over virtual interface architecture: implementation and performance
No full textIn this paper, we describe an implementation of a software Distributed Shared Memory (DSM) over Virtual Interface Architecture (VIA) for a Linux-based cluster of PCs and evaluate its performance. VIA is a user-level memory-mapped communication model that provides zero-copy communication and low-overhead by excluding the operating system kernel from the communication path. To our best knowledge, our implementation is the first software DSM protocol on VIA. The DSM protocol we have implemented on VIA is Home-based Lazy Release Consistency (HLRC) that previous studies have shown to exhibit good scalability by reducing the number of messages and memory overhead compared to the homeless counterpart. The experimental results obtained on seven Splash-2 applications show that VIA can be successfully used to support software shared memory on clusters of PCs. The paper is accompanied by a source-code distribution of the software DSM protocol for Linux/VIA clusters.Technical report DCS-TR-41
Three essays in sustainable operations management with implications for the triple bottom line
Full text linkWe are in a state of overshoot; the human population today consumes natural resources at a rate that exceeds what the planet can sustainably provide in the long term (Meadows et al., 2004). Two key causes of this overshoot are the overconsumption of natural resources, and the reluctance or inability of society to remedy this overconsumption through the appropriate use and deployment of technology and management practices. In this light, the work contained in this dissertation is intended to explore potential solutions that operations management can provide to mitigate the impact of these two causes of overshoot. Therefore, in the spirit of the Triple Bottom Line (3BL) framework for sustainability, we evaluate environmental and social, along with the economic implications of strategic and operational decisions in the contexts of natural resource management and green product development in this dissertation.
Freshwater is an invaluable resource to all life on earth. Groundwater reservoirs, an important source of freshwater, are drying up across the United States and the globe, creating a severe mismatch in the supply and demand of freshwater. Two new management paradigms have cropped up in recent years to remedy this mismatch: water trading and privatization. The first essay in this dissertation explores the impact of these paradigms on groundwater management and the ensuing 3BL implications.
Voluntary green product development has emerged as a viable alternative to the traditional 'command and control' approach for environmental regulation. The second essay in this chapter addresses a producer's problem of labeling its product to communicate its environmental attributes that are otherwise invisible to consumers. The key objectives of this essay are to identify the efficacy of external ecolabeling agencies and the role of producer credibility in stimulating green product development and its resulting benefits from a 3BL perspective.
The final essay in this dissertation explores the phenomenon of pre-competitive collaboration between firms in the context of green product development. In it, we identify the motivation for and the 3BL implications of horizontal R&D collaboration between competing supply chains as well as vertical collaboration within a supply chain through cost-sharing.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-08-01The student, - Karthik Murali, accepted the attached license on 2015-07-14 at 22:49.The student, - Karthik Murali, submitted this Dissertation for approval on 2015-07-15 at 00:41.This Dissertation was approved for publication on 2015-07-15 at 11:02.DSpace SAF Submission Ingestion Package generated from Vireo submission #8469 on 2015-09-29 at 15:06:13Made available in DSpace on 2015-09-29T21:08:08Z (GMT). No. of bitstreams: 2
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Studies on the cytochrome bd-type oxygen reductase superfamily and the discovery of a novel nitric oxide reductase
Full text linkRespiration is the process by which an organism utilizes the reducing equivalents (electrons) produced during catabolism to create an electrochemical potential across the cellular membrane, which can then be expended to produce ATP. Living organisms, bacteria and archaea in particular have discovered numerous ways to respire using highly conserved enzyme superfamilies whose members can couple the free energy released during redox reactions to the creation of proton motive force. Combined with biochemical studies, the evolution of these superfamilies deduced from bioinformatics is very informative about the structural and functional features that are most useful to conserve energy by the creation of proton motive force. This work investigates two important enzyme superfamilies whose members are responsible for virtually all aerobic respiration on the planet– the bd-type oxygen reductase superfamily and the heme-copper oxidoreductase superfamily.
The bd-type oxygen reductases are present in bacteria and archaea and catalyze the 4-electron reduction of oxygen to water. Electrons from membrane bound quinols first reduce a low spin heme b from which they are transferred to a di-heme active site where where oxygen is reduced to water. Energy is conserved by the transfer of protons from the cytoplasm to the active site which is located near the periplasmic surface. E. coli has two bd-type quinol oxidases, called cytochrome bd-I and cytochrome bd-II. It had previously been shown that cytochrome bd-I generates a proton motive force, but work from another group claimed that this was not the case for bd-II. As part of this work, it was demonstrated that bd-II functions identically to bd-I and generates a membrane voltage.
In a second project dealing with the cytochrome bd superfamily, genomic sequence analysis of cytochrome bd revealed a subfamily of distinct enzymes present in archaea. One of these archael cytochrome bds, was heterologously expressed in Escherichia coli, purified and characterized. This enzyme was shown to have three hemes b instead of two hemes b and one heme d, as is typical of enzymes of this superfamily. The enzyme is highly active, using ubiquinol as substrate. This is the first example in which a member of the cytochrome bd superfamily lacking heme d has been isolated and characterized. A third project involving the importance of a glutamic acid residue in the active site of Escherichia coli cytochrome bd has also been discussed.
The heme-copper oxidoreductase (HCO) superfamily contains many proton pumping oxygen reductases as well as several subfamilies of nitric oxide reductases (NORs) which convert nitric oxide to nitrous oxide. These NORs perform different chemistry than the HCOs but have a very similar protein structure and a similar active site. Significantly, the active site of purified NORs contain a Fe atom instead of the copper in the oxygen redutases. Using bioinformatics methods, a distinct new clade of NORs was identified that was previously not recognized. These enzymes have been assumed reduce nitric oxide and were thus named eNORs. One member of this clade is encoded in the genome of Rhodothermus marinus, a thermophilic bacteroidete.
Rhodothermus marinus was shown to possess a nitric oxide reductase by measuring the accumulation of nitrous oxide in the containers in which the bacteria is grown on nitrate. Then the enzyme was purified and characterized and confirmed to be a nitric oxide reductase. This confirms for the first time a large group of enzymes, previously not identified, that participate in denitrification in many prokaryotes.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Ranjani Murali, accepted the attached license on 2016-04-16 at 14:40.The student, Ranjani Murali, submitted this Dissertation for approval on 2016-04-16 at 14:55.This Dissertation was approved for publication on 2016-04-18 at 16:10.DSpace SAF Submission Ingestion Package generated from Vireo submission #9267 on 2016-07-07 at 14:16:57Made available in DSpace on 2016-07-07T21:17:33Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-04-18Embargo set by: Seth Robbins for item 93266
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