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Electrical Engineering and Computer Sciences - Master's degree
Mostrando recursos 1 - 20 de 4.725
Hybrid intensity and time-of-flight signal processing techniques for intelligent distance sensors - Hiromi, Itariu
With the advent of "smart" consumer electronics, distance sensing is an increasingly important field in optical sensing. A novel approach to active infrared(IR) 1D distance sensing is proposed, employing both intensity and time-of-flight information. Conventional intensity based sensors lack in distance accuracy, and conventional time-of- flight sensors suffer from crosstalk and backscatter issues. The purpose of this work is to explore the solution space to these issues that hybrid intensity/time-of-flight systems enable, and to investigate their characteristics. Optical behavior of time-of-flight and intensity of an active IR system is analyzed, and a comprehensive reflection model is created. This model is...
Of intent and action : implementing personality traits for storytelling through concept patterns - Song, Susan S. (Susan Shuchen)
Personality traits such as "kind," "aggressive," and "brave" are integral to storytelling because they impart succinct descriptors of character personalities. Authors apply traits to characters, readers infer characters' traits from the narrative, and readers learn the meaning of new traits. For instance, a reader can learn the personality trait "vindictive" from Alexandre Dumas's novel The Count of Monte Cristo and then use this trait to predict or explain a character's behavior. The reader can also infer that a character from this novel, such as Edmond Dantes, is "vindictive" without needing Dumas to explicitly describe the character with this trait. With...
A stacked full-bridge microinverter topology for photovoltaic applications - Yogeswaran, Kesavan
Previous work has been done to develop a microinverter for solar photovoltaic applications consisting of a high-frequency series resonant inverter and transformer section connected to a a cycloconverter that modulates the resonant current into a single-phase 240 VRMS utility line. This thesis presents a new stacked full-bridge topology that improves upon the previous high-frequency inverter section. By utilizing new operating modes to reduce the reliance on frequency control and allowing for the use of lower blocking voltage transistors, the operating frequency range of the HF inverter is reduced and efficiency is increased, especially at low output powers and lower portions...
Design and testing of a roadside traffic threat alerting mechanism - Powale, Pallavi
Every year, law enforcement officials, emergency personnel, and other workers stopped in traffic outside their vehicles are struck by inattentive drivers. Until now, most efforts to prevent these types of accidents have been geared toward making these at-risk parties more conspicuous to oncoming motorists. In contrast, this work proposes an alerting mechanism designed specifically to induce defensive behavior on the part of the at-risk officers (or other roadside personnel), once a hazardous situation has been detected. The immediate objective of this research was to produce an effective alarm prototype for a high noise, low-light operation environment such as a dimly...
StorySpace : spatial semantic comparison of narrative - Puncel, Michael L
It is well known that humans are far more adept than computers at identifying similarities between stories. Humans are able to communicate values and event patterns back and forth through these narratives. Parents communicate through the telling of "The Tortoise and the Hare" that hard work and determination can often trump talent, and that hubris can lead to one's downfall. It would be quite useful to develop a computational technique to apply this type of analysis to a story to relate to more generic cases. In this paper, I demonstrate the beginnings of a technique called Spatial Semantic Analysis of...
Fab trees for designing complex 3D printable materials - Wang, Ye, M. Eng. Massachusetts Institute of Technology
With more 3D printable materials being invented, 3D printers nowadays could replicate not only geometries, but also appearance and physical properties. On the software side, the tight coupling between geometry and material specification, and the lack of tools in specifying materials volumetrically, however, hinder the full usage of the multi-material capability of 3D printers. The heavy dependency on traditional modeling software also makes casual users, who are becoming one of the most important user groups, unwelcome in this rising area. This thesis aims to solve the above problems by proposing fab trees for creating and combining procedural material specifications defined...
Doppler channel emulation of high-bandwidth signals - Colosimo, Joseph William
The Airborne Networks Group at MIT Lincoln Laboratory has funded the construction of a channel emulator capable of applying, in real-time, environmental models to communications equipment in order to test the robustness of new wireless communications algorithms in development. Specific design goals for the new emulator included support for higher bandwidth capabilities than commercial channel emulators and the creation of a flexible framework for future implementation of more complex channel models. Following construction of the emulator's framework, a module capable of applying Doppler shifting to the input signal was created and tested using DVB-S2 satellite modems. Testing not only verified...
Algorithms for 3D time-of-flight imaging - Mei, Jonathan (Jonathan B.)
This thesis describes the design and implementation of two novel frameworks and processing schemes for 3D imaging based on time-of- flight (TOF) principles. The first is a low power, low hardware complexity technique based on parametric signal processing for orienting and localizing simple planar scenes. The second is an improved method for simultaneously performing phase unwrapping and denoising for sinusoidal amplitude modulated continuous wave ToF cameras using multiple frequencies. The first application uses several unfocused photodetectors with high time resolution to estimate information about features in the scene. Because the time profiles of the responses for each sensor are parametric...
Ecology and evolution simulation and quest design for an educational massive multiplayer online game - Zhang, Mark (Mark A.)
In this design-based research project, I developed two simulations to be used as student tools in a massively multiplayer online game targeted at STEM education, the Radix Endeavor. I designed both the underlying agent-based model as well as the user interface for each simulation, and furthermore designed quests for my simulations for the purposes of playtesting. My final ecological prototype is able to authentically model fairly complex food webs of six or more organisms, and my final evolutionary prototype can handle complex fitness relationships between the individual traits of a single population and various environmental factors. In my thesis, I...
Assessing intrusiveness of smartphone apps - Zhang, Fan, M. Eng. Massachusetts Institute of Technology
We tackle the challenge of improving transparency for smartphone apps by focusing on the intrusiveness component of assessing privacy risk. Specifically, we develop a framework for qualitatively assessing and quantitatively measuring the intrusiveness of apps based on their data access behavior. This framework has two essential components: 1) the Privacy Fingerprint, a concise yet holistic visual that captures the data access patterns unique to each app, including which types and under which privacy-relevant usage contexts sensitive data are collected, and 2) an Intrusiveness Score that numerically measures each app's level of intrusiveness, based on real data accesses gathered from empirical...
Reduced traces and JITing in Church - Wu, Jeff (Jeffrey K.)
Church is a Turing-complete probabilistic programming language, designed for inference. By allowing for easy description and manipulation of distributions, it allows one to describe classical Al models in compact ways, providing a language for very rich expression. However, for inference in Bayes nets, Hidden Markov Models, and topic models, the very settings for which probabilistic programming languages like Church were designed for, researchers typically instead write special cased algorithms in regular programming languages to maximize performance. In this paper, we argue that an extremely general language can still support very fast inference. We first introduce the theoretical aspects of our...
GPSZip : semantic representation and compression system for GPS using coresets - Wu, Cathy, M. Eng. Massachusetts Institute of Technology
We present a semantic approach for compressing mobile sensor data and focus on GPS streams. Unlike popular text-compression methods, our approach takes advantage of the fact that agents (robotic, personal, or vehicular) perform tasks in a physical space, and the resulting sensor stream usually contains repeated observations of the same locations, actions, or scenes. We model this sensor stream as a Markov process with unobserved states, and our goal is to compute the Hidden Markov Model (HMM) that maximizes the likelihood estimation (MLE) of generating the stream. Our semantic representation and compression system comprises of two main parts: 1) trajectory...
A controllable laser projector for diverting traffic - Wu, Brian Xiuken
For this Master's thesis, I designed and implemented a combined laser and controller system that can receive and convert commands from a computer into useful laser projections. In the last 10 years, on average, one police officer, who is conducting a vehicle stop or directing traffic, is struck and killed by an oncoming vehicle per month in the United States. Most of these instances occur at night. Current literature proposes that for some drivers, especially those who are fatigued, the combination of bright, rapidly flashing emergency lighting causes them to drive closer to a emergency vehicle rather than away from...
A material segmentation and classification system - Wong, Jennifer L
In this thesis, I developed a material segmentation and classification system that takes in images of an object and identifies the material composition of the object's surface. The 3D surface is first segmented into regions that likely contain the same material, using color as a heuristic measure. The material classification of each region is then based on the cosine lobe model. The cosine lobe model is our adopted reflectance model, which allows for a simple approximation of a material's reflectance properties, which then serves as the material's unique signature.
Optimizations in stream programming for multimedia applications - Wong, Eric, M. Eng. Massachusetts Institute of Technology
Multimedia applications are the most dominant workload in desktop and mobile computing. Such applications regularly process continuous sequences of data and can be naturally represented under the stream programming domain to take take advantage of domain-specific optimizations. Exploiting characteristics specific to multimedia programs can provide further significant impact on performance for this class of programs. This thesis identifies many multimedia applications that maintain induction variable state, which directly inhibits data parallelism for the program. We demonstrates it is essential to recognize and parallelize filters with induction variable state to enable scalable parallelization. We eliminate such state by introducing a new...
Competitive algorithms for online matching and vertex cover problems - Wong, Chiu Wai, M. Eng. Massachusetts Institute of Technology
The past decade has witnessed an explosion of research on the online bipartite matching problem. Surprisingly, its dual problem, online bipartite vertex cover, has never been explicitly studied before. One of the motivation for studying this problem is that it significantly generalizes the classical ski rental problem. An instance of such problems specifies a bipartite graph G = (L, R, E) whose left vertices L are offline and right vertices arrive online one at a time. An algorithm must maintain a valid vertex cover from which no vertex can ever be removed. The objective is to minimize the size of...
A ballistic transport model for HEMTs and III-V MOSFETs - Warnock, Shireen M
As silicon MOSFETs keep scaling down in size, the continued improvement on their logic performance is threated by their fundamental physical limits. With silicon approaching these limits, MOSFETs designed with III-V semiconductors have emerged as promising candidates to replace them. The low-effective mass of various III-V materials such as InGaAs and InAs allow both faster and more power efficient performance. One of the key challenges, particularly as devices continue to shrink, is to understand the important of non-idealities in FET structures. High-electron mobility transistors, or HEMTs, are III-V Quantum-Well FETs that we can use to explore many issues of relevance...