61 research outputs found
2010 Seventh International Conference on Information Technology: New Generations
No full textIsaac Macwan (with Hassan Bajwa, Vignesh Veerapandian, and Xinghao Chen) is a contributing author, VHDL Implementation of High-Performance and Dynamically Configures Multi-port Cache Memory, pp. 1212-1216.https://digitalcommons.fairfield.edu/engineering-books/1057/thumbnail.jp
How the planning, engineering and politics of transportation established, preserves and perpetuates the automobile city
No full textThesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning; and, (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis. Page [167] blank.Includes bibliographical references (p. 161-166).The last eight decades of urban transportation planning and engineering in the United States have been dominated by the hegemony of the automobile. Auto-oriented planning of the transportation and land use system has had a profound impact on the built environment both in greenfield developments and neighborhoods that predated the auto. The pedestrian quality of cities has been eroded by the automobile, and urban renewal in the United States erased many neighborhoods strongly oriented around walking and transit use. Equally pervasive as the auto itself is the place for the car in the institutional cultures and practices involved in shaping the city. The shortcomings of mobility-oriented transportation planning have been well critiqued, even from the very early days of Interstate building. In recent decades there has been a flurry of interest in articulating sustainable transportation policies to provide multi-modal accessibility and to consider the interactions between transportation, land use, and other policy realms such as health, energy, environment and equity. The current impending crisis of aging and ailing highway structures in the United States presents a momentous opportunity to reassess the need and purpose of such infrastructure, and to rebuild, reconceptualize, or remove it in a matter more consistent with current policy goals and planning processes - rather than the ones in place when initially built. Despite the interest, need and opportunity to reconceptualize aging infrastructure in America to support a more sustainable reshaping of land use and activity patterns, the potential to do so is heavily impaired by a transportation planning process that is still dominated by the tools, methods and assumptions, political biases, procedural failures, and instilled human behaviors of the first highway-building era. The McGrath Highway in Somerville, MA is used as a case study to discuss how persistence of 1950s technical, procedural and political dysfunctions threaten to undermine this opportunity. Short-term actions and strategies to avoid this impending fate are suggested for McGrath Highway with applicability to a wider national context of similar opportunities.by Vignesh Krishnamurthy.S.M.in TransportationM.C.P
In-Situ Infrared Spectroscopic Studies of Palladium Thin Films during CO2 Electro-Reduction
No full textAn exponential growth in CO2 concentration over the past few decades has led to an accelerated impact of climate change on planet earth. In a bid to curb these emissions, people across the globe are slowly transitioning towards renewable energy sources with battery technology aiding this growth. Given that battery technology is still in its nascent stage, the “Electrochemical reduction of CO2” could be a viable solution supporting it without decelerating the momentum gained towards renewable development. Although plausible, the direct reduction of CO2 to liquid fuels entails huge energy expenditure thus requiring the implementation of catalysts. Unique in its ability, palladium reversibly reduces CO2 to formic acid making it an interesting candidate for the reduction reaction. In addition to the production of formic acid, palladium is also know to produce carbon monoxide (CO) which completely deactivates the surface preventing further reactions from occurring. Thus the aim of the current study is focused on analysing the electrochemical reduction of CO2 on palladium thin films using surface enhanced infrared absorption spectroscopy to better understand the deactivation mechanisms of CO on the palladium thin film. The smoothness of the as- sputtered 15 nm palladium thin film with a RMS roughness of 0.511 nm and partially coalesced islands were ascertained, thus requiring surface activation to introduce the enhancement mechanism. Experimental analysis of CO2 reduction on the palladium thin film was performed to unearth significant insights through the combination of electrochemical analysis techniques with surface enhanced infrared absorption spectroscopy. Results obtained through implementation of these methodologies provided substantial information not only on the influence of the palladium-hydrogen system on the electrochemical reduction of CO2 but also on the impact of alkali metal cations on the palladium-hydrogen system and the CO2 reduction reaction over the sputtered palladium thin film. CO formation, accumulation and desorption coupled with hydrogen evolution and desorption were some of the few avenues that were enumerated upon during the experimental investigation. The identity of CO chemisorbed on the palladium thin film along with bicarbonate direct/ indirect reduction to form CO was confirmed through the utilization of N2 saturated C13 NaHCO3 solution. In addition to the analysis of the reduction reaction, emphasis on the oxidation of CO was also provided suggesting the formation of dense CO structures with the existence of strong CO dipole – dipole coupling on the palladium surface. Materials Science and Engineerin
Stability of excitons in double quantum well: Through electron and holes transmission probabilities
No full textEffect of non-parabolicity and confinement potential on exciton binding energy in a quantum well
No full textWAAM Martensitic Stainless Steel: Process Optimization & Resulting Weld Geometrical Characterization
No full textWire Arc Additive Manufacturing (WAAM), one of the Additive Manufacturing (AM) deposition methods which employs the basic principles of Gas Metal Arc Welding (GMAW) welding technique was used to show that it is possible to build moulds for ceramic products using AISI 420 stainless steel due to its characteristics such as corrosion resistance, machinability, hardness and dimensional stability. The WAAM process also is efficient in terms of its deposition rate, reduced material wastage and high surface quality.To investigate the feasibility of AM of AISI 420 stainless steel using WAAM, Response Surface Methodology (RSM - a predictive technique) was used to navigate within the input parameter range for process optimization. Bead-on-plate welding experiments were performed with a MIG welding robot on a structural steel (S355J2) as the substrate. In the tested range according to RSM analyses, the optimum weld condition was 261 A (Current), 29 V (Volts) and 0.59 m/min S (Travel Speed) with preheating at 200°C. However, this condition was found to be unsuitable for AM due to its low deposition speed, non - uniform building surface morphology and inter-run porosities when overlapping welds were deposited. Further analyses on the metallurgy of the WAAM AISI 420 stainless steel through Scanning Electron Microscope (SEM) revealed that the weld metal consisted of a martensite matrix and delta-ferrite at the grain boundaries. The Vickers Hardness of the weld metal was 514HV.To achieve WAAM feasibility using AISI 420 stainless steel, modified RSM method was performed by expanding the input parameters and visually inspecting the bead for its shape, size and quality. The experiment adopted was called the Ramping Procedure wherein a single resulting weld bead can represent many input parameter combinations. The optimum condition for the input parameters were identified to be 200 A (Current), 18.5 V (Volts) and 1.00 m/min S (Travel Speed). With the optimal processing conditions, rectangular blocks or walls were modelled and designed in the Autodesk Powermill software and built to evaluate the feasibility of WAAM AISI 420 stainless steel. Samples were built without preheating and no surface defects and cracking were observed. Microstructural and hardness studies were then performed. Results show that the as-welded weld metal consisted of delta-ferrite present in a martensite matrix. The hardness of the weld metal was 623 HV. The WAAM optimization procedure for AISI 420 stainless steel that has not been explored for AM processes due to its high sensitivity to welding thermal cycles that can lead to cracking. In this study, it has been successfully demonstrated that crack free AISI 420 stainless steel can be deposited with WAAM
Life Cycle Assessment (LCA) analysis of thin film Silicon-based HyET solar cells
No full textGiven the rising research of thin film solar cells in recent years, flexible technology has been proven to be more light weight and cost effective. As photovoltaics is increasingly becoming the front runner in sustainable energy production, concerns over the associated impacts of solar modules throughout their life cycle are also increasing. This study quantifies the environmental impacts through LCA analysis for Roll-to-Roll (R2R) production process of thin film flexible silicon-based solar modules manufactured by a Dutch company HyET in The Netherlands.This study considers three product lines over a life cycle demarcated into its manufacturing, encapsulation and installation. The three product lines (cases) are as follows.1. Single junction a-Si with 7% efficiency.2. a-Si/nc-Si tandem cell with 10% efficiency3. a-Si/nc-Si tandem cell with 12% efficiencyThe installation phase considers a rooftop setup of capacity of 2.1 kWp with Balance of System (BoS) components.LCA analysis is carried out on Simapro 9.1.0.11 following the guidelines and the framework of International Organization for Standardization ISO14044. The outcome of LCA analysis is measured in terms of Global Warming Potential (GWP), Primary Energy Demand (PED) and Energy Pay Back Time (EPBT). Ecoinvent 3.5 is used as the primary database for these analyses to select the inventory. GWP is assessed using the CML-IA baseline method while PED is assessed using Cumulative energy demand v1.11 method. Sensitivity analysis is done by changing the location of production and up-scaling capacity. The installation stage is observed to contribute the highest GWP and also has the highest PED on account of BoS components. The LCA analysis has demonstrated similar trends of GWP, PED for all three product lines. EPBT on the other hand, is longer for 10% tandem cell on account of relatively larger module area as compared to 12% tandem cell and also the relatively higher energy consumption as compared to the single junction cell. The choice of substrate material is seen to impact the assessment indicators significantly. Flexible glass is observed to be the optimal choice for large-scale production. The choice of encapsulant material also affects the indicators demonstrably. Sensitivity analysis shows a positive impact on the indicators through up-scaling, while the location is not established as a significant factor sufficiently under considered assumptions.This project describes about the Life Cycle Assessment analysis of thin film Silicon-based HyET solar cells and their comparison to different substrate technologiesElectrical Engineering | Sustainable Energy Technolog
Design with data: Practising exploratory inquiring on data visualisation
No full textIntending to implement a data-enabled design approach to use this data in their creative design process, Ford established a research collaboration with the faculty of Industrial Design Engineering at the Delft University of Technology. As part of the collaboration, several lines of research were carried out, like data strategy, data visualisation, and early prototyping in the form of graduation projects. In one such work, Mellado Cruz (2021) identified that exploratory inquiring as a means to derive insights from data visualisations has great potential in supporting the creative design process. With her empirical studies, she could generate theoretical knowledge about this process; however, bridging work was needed to convert this knowledge into a practical and actionable outcome.In this project, I address the research question, "How can exploratory inquiring on data visualisation be operationalised in the Ford design team to support their creative design process? ". I begin the process with a phase of immersion into theory and context- using published literature about exploratory data analysis,data visualisation, creativity, and design theory to obtain theoretical understanding and the thesis reports of past graduation projects. At the end of this phase, I identify three potential opportunities that can aid in implementing exploratory inquiring in Ford design teams. One of the opportunities- to conceptualise exploratory inquiring as a collaborative design method- was identified as the most feasible in terms of the scope of the project, practical and desirable for the Ford design teams. A preliminary concept method was developed based on the learnings from the literature in line with this direction. This was iteratively prototyped, tested and refined for three cycles in the design iterations phase. The version at the end of the third cycle was used to create the final deliverable- a toolkit consisting of an information booklet that helps in circulating the procedural knowledge of the method within the team to create awareness and canvasses that support the execution of the method. In the last parts of this report, I provide recommendations for future studies to tackle the limitations I faced in this project and possibly inspire new works in the area of data-enabled design.Strategic Product Desig
LVDC for buildings in the Netherlands: Technical and commercial potentials from DC Office Lab
No full textCurrent energy concerns like growing energy demand, the desire for a clean environment and energy conservation started thrusting the society towards distributed renewable electricity generation (DG) technologies. These technologies such as PV solar, Fuel Cells (FC) and urban wind produce Direct Current (DC). The electronic equipment such as laptops, PCs, communication systems, LED lighting, batteries, Electric Vehicles (EV) and Fuel Cell Electric Vehicles (FCEV) also operate in DC. But the present-day electricity distribution system is based on Alternating Current (AC). From this conventional system, the conversion losses can be substantial when DC generation and DC loads are operated. For which, several (DC/AC – AC/DC) conversion steps are required. These conversion losses can be mitigated by removing the intermediate conversion steps and distributing DC power to the DC loads directly. For which, the main aim of the thesis focuses on the technical and commercial potential of Low Voltage DC (LVDC) grids for buildings in the Netherlands. DC office is a small office building at The Green Village (TGV) in TU Delft where a 350 Vdc LVDC system is installed for experimental purposes. The experiments are carried out using both LVDC and LVAC grids in DC Office project. The obtained experimental data are randomized using Matlab to create a year-long load profile. The results are used for discussing the LVDC technical potential in terms of overall efficiency and energy savings. From these results cost-savings are calculated. Along with this, usage of copper and aluminum as electrical conductor in buildings and its investment cost-savings are discussed. For the commercial potential of LVDC grids for buildings in the Netherlands, the Function of Innovation Systems (FIS) approach is used to identify the corresponding LVDC stakeholders, research, pilot projects, rules and regulations and policies for development. For the technical potential, there are three different cases formulated for analysis. They are ACTube case, DCLED case and ACLED case. In the experiments, tubelights are used in the ACTube case and LEDs are used in the DCLED case, in-order to neglect the energy savings obtained from LED technology, ACLED case is assumed. The overall efficiency of the LVDC grid (DCLED case) is 94.82% and the LVAC grid (ACTube case) is 88.16% and the LVAC grid (ACLED case) is 88.67%. From all these cases, the LVDC grid is around 6.5% more efficient than LVAC grid in small buildings similar to the DC Office. The energy savings obtained by LVDC grid replacing LVAC grid (ACTube) is 2013 kWh/year, and if tubelights in AC are replaced with LEDs in AC, then 1854 kWh/year is estimated to be saved. The cost-savings are calculated from the energy savings obtained by replacing LVAC grid (ACTube case) with LVDC grid (DCLED case). Considering the total lifetime of the LVDC system as 12 years, the cost savings obtained are € 221.43/year achieving payback in 6 years. For the commercial potential, using seven functions of FIS it is identified that there are several stakeholders interested in LVDC projects and are responsible for pilot projects. The government also is implementing the new NPR 9090 as the rules and guidelines for LVDC grid installations in buildings. It is also identified that people have positive acceptance of the LVDC grid in their houses. But the knowledge sharing about LVDC among the society is currently lacking. Moreover, the AC electricity distributors are interested in shifting towards the DC micro grid distribution.DC Office LabThe Green VillageElectrical Engineering | Sustainable Energy Technolog
On the computation of probabilities and eigenvalues for random and non-random matrices
No full textThesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from PDF version of thesis.Includes bibliographical references (p. 43-44).Can you imagine doing hundreds of millions of operations on non-integers and not obtaining a single round-off error? For n < 12, the algorithm used in this thesis does exactly that. We took advantage of a floating point property that we have not seen used before. If only we had quad precision we could have gone even further and extended the algorithm without round-off error for higher values of 'n'. The problem in question concerns whether the eigenvalues are real or complex. The eigenvalues of an n-by-n real random matrix whose elements are independent random variables with standard normal are examined. An exact expression to determine the probability Pn,k that exactly k eigenvalues are real are derived in [1]. This expression was used to compute the probabilities Pn,k, but the computation was achieved only up to n = 9. For higher values of n, the symbolic expressions generated during the course of an algorithm to compute an exact probability as expressed in Mathematica code requires large amounts of memory. In this thesis, we target development of a more efficient algorithm. The symbolic algorithm implemented in Mathematica is converted into an equivalent numerical version and is implemented using MATLAB. After implementing the serial code in MATLAB, the code is parallelized using a client-server parallel computing platform named Star-p. This modified code implementation along with superior hardware in terms of better processor speeds and larger memory, has enabled the probability evaluation for all values of k up to n= 11, and for certain k values for n = 12 and 13.(cont.) An expression for the expected number of real eigenvalues En=o kpn,k is obtained in paper [2]. Results relating the rational and irrational parts of the summations n =o kpn,ki, En k=0 (Pk n,k and En= - n,k 0 k)Pn,k are conjectured. Three eigenvalue algorithms, the block Davidson, the block KrylovSchur and the Locally optimal Block Pre-conditioned Conjugate Gradient Method (LOBPCG) are analyzed and their performance on different types of matrices are studied. The performance of the algorithms as a function of the parameters , block size, number of blocks and the type of preconditioner is also examined in this thesis. The block Krylov Schur Algorithm for the matrices which are used for the experiments have proved to much superior to the others in terms of computation time. Also its been more efficient in finding eigenvalues for matrices representing grids with Neumann boundary conditions which have at least one zero eigenvalue. There exists one optimal combination of block size and number of blocks at which the time for eigenvalue computation is minimum. These parameters have different effects for different cases. The block Davidson algorithm has also been incorporated with the locking mechanism and this implementation is found to be much superior to its counterpart without the locking mechanism for matrices which have at least one zero eigenvalue.by Vignesh Peruvamba Sundaresh.S.M
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