Digital Commons Network^™

Enhanced Diagnostic Accuracy Of Mammograms On A Mobile Device, Sharanya Padmanabhan

Open Access Theses

With the death of a woman every 13 minutes in the US, and one every minute worldwide, due to breast cancer, the need for early detection cannot be overstated. Mammography is a boon for both early detection and screening of breast tumors. It is an imaging system that uses low dose (9mrem) x-rays for examining the breasts, by the electrons reflected from the tissues (thermoelectric effect). However, there are 20% false positives and 10% false negatives in current practice. Hence, there is a critical need for enhancing the accuracy of these mammograms. Towards this, this thesis was aimed at enhancing …

Performance-On-Demand Mems (Podmems): Electrical Control Of Effective Mass, Damping, And Stiffness, Shehrin Sayed

Open Access Theses

We propose the use of electrostatic force feedback to control the stiffness, damping, or mass of MEMS. If feedback forces are proportional to sensed displacement, velocity, or acceleration of a MEMS proof mass, then feedback can be used to increase or decrease the apparent stiffness, damping, and or mass of the MEMS. Such feedback can be used to compensate for process variations, packaging stress, thermal drift, viscous damping, etc. Prior efforts by others include position or velocity based feedback for modifying frequency, bandwidth, quality factor, or sensitivity of resonators. We present a means of quantitative control of stiffness, damping, and …

Finfet Device Optimization At 15nm For Near-Threshold Operation, Jolene Singh

Open Access Theses

Much of the current research in the electronic industry focuses on reducing power consumption of digital circuits. Towards the same many attempts are being made to reduce the operating voltage of the circuits. It has been shown through device and circuit analysis that a circuit consumes minimum energy when operated near threshold voltage. In this thesis I vary device parameters and study their effects on energy consumption and delay of the device for the two regions of operation - superthreshold and near-threshold, using LUTs of IV and CV characteristics, verilogA and hSpice. Finally, device parameters are obtained for an optimum …

Modulation Of Cell-Matrix Interaction For Cryopreservation Of Engineered Tissue, Angela Christine Seawright

Open Access Theses

Long term preservation of functional engineered tissues can significantly advance tissue engineering industry and regenerative medicine. Several preservation techniques have been proposed and investigated for this purpose, and cryopreservation is a leading candidate. While tissues are cryopreserved, ice forms in both the extracellular and intracellular spaces and causes freezing-induced spatiotemporal deformation of the tissue. During this process the cells undergo dehydration by the freezing-induced osmotic pressure difference and mechanical deformation, transmitted through cell-extracellular matrix adhesions. However, the significance and interaction of these cellular level transport and mechanics processes are not well understood. Therefore, this study aims to establish mechanistic understanding …

Modeling Tools For Conformal Orthotic Devices, Steven David Riddle

Open Access Theses

The purpose of this thesis is to advance the design of conformal orthotic devices through the development of two modeling tools to address knowledge gaps in the field.

The field of human orthotics has been continually troubled by identifying successful methods of harnessing devices to the body. Past orthotics have utilized a rigid framework with minimal degrees of freedom (DOFs) driven by hard actuators attached to the body at select anchor points. Many devices design the structure and anchor points such that they reduce the degrees of freedom of a targeted joint, limiting the user's mobility and often causing the …

Effects Of Blood Flow On The Heating Of Cardiac Stents Due To Radio Frequency Fields, Nate Ian Elder

Open Access Theses

A safety concern during MRI scans with implanted medical devices is heating induced by the incident RF field. This research was performed to better understand the heating of cardiac stents during MRI. Heating of cardiac stents tends to occur at their ends. The temperature rise will be affected by blood flow through the lumen of the stent. In this work, an experiment was performed to simulate heating of a cardiac stent in the presence of blood flow during exposure to the electric field induced by a 64 MHz magnetic field, which corresponds to MRI at 1.5 T. The test procedure …

Autonomous Orientation And Geolocation Via Celestial Objects, Cheng Liu

Open Access Theses

Based on a hemispherical sensor geometry, a novel celestial navigation system is developed to use celestial objects to determine the absolute location and orientation information without the aid of satellites via two different approaches.

The first approach employs a hemispherical arrangement of light intensity sensors to determine the vector to the dominant light source. We present the sensing system to measure the sun vector via least squares method and achieve the application of a low-cost, small-sized solar compass. The system is shown to work well under ideal conditions but is susceptible to noise and uncertainties in some situations.

The second …

Vibrational Photoacoustic Tomography: Deep Tissue Imaging With Biomarker Sensitivity, Rui Li

Open Access Theses

As a molecular and functional imaging modality, photoacoustic imaging has been applied to animals or human organs such as breast, brain and skin. Till now, the contrast mechanism of photoacoustic imaging is mainly based on electronic absorption in visible and near infrared region. Inherent molecular vibration offers a contrast mechanism for chemical imaging in a label free manner. In vibrational microscopy based on either infrared absorption or Raman scattering, the imaging depth is limited to the ballistic photon mean free path, which is a few hundred microns in a biological sample. Owing to much weaker acoustic scattering in tissues as …

Time Domain Simulation Of Novel Photovoltaic Materials, Haejun Chung

Open Access Theses

Thin-film silicon-based solar cells have operated far from the Shockley- Queisser limit in all experiments to date. Novel light-trapping structures, however, may help address this limitation. Finite-difference time domain simulation methods offer the potential to accurately determine the light-trapping potential of arbitrary dielectric structures, but suffer from materials modeling problems. In this thesis, existing dispersion models for novel photovoltaic materials will be reviewed, and a novel dispersion model, known as the quadratic complex rational function (QCRF), will be proposed. It has the advantage of accurately fitting experimental semiconductor dielectric values over a wide bandwidth in a numerically stable fashion. Applying …

The Design And Evaluation Of A 5.8 Ghz Laptop-Based Radar System, Kevin Chi-Ming Teng

Open Access Theses

This project involves design and analysis of a 5.8 GHz laptop-based radar system. The radar system measures Doppler, ranging and forming Synthetic Aperture Radar (SAR) images utilizing Matlab software provided from MIT Open Courseware and performs data acquisition and signal processing. The main purpose of this work is to bring new perspective to the existing radar project by increasing the ISM band frequency from 2.4 GHz to 5.8 GHz and to carry out a series of experiments on the implementation of the radar kit. Demonstrating the radar at higher operating frequency is capable of providing accurate data results in Doppler, …

Quantum Computing With Steady State Spin Currents, Brian Matthew Sutton

Open Access Theses

Many approaches to quantum computing use spatially confined qubits in the presence of dynamic fields to perform computation. These approaches are contrasted with proposals using mobile qubits in the presence of static fields. In this thesis, steady state quantum computing using mobile electrons is explored using numerical modeling. Firstly, a foundational introduction to the case of spatially confined qubits embodied via quantum dots is provided. A collection of universal gates implemented with dynamic fields is described using simulations. These gates are combined to implement a five-qubit Grover search to provide further insight on the time-dependent field approach. Secondly, the quantum …

Detection Of Brain Abnormalities In Football Players Through Diffusion Weighted Imaging, Allan Emilio Diaz Gaez

Open Access Theses

Depression and cognitive impairment are commonly found in retired football players. Although they receive high magnitude hits to the head, the majority of the hits are sub-concussive, resulting in no clinical symptoms. Recent work using functional magnetic resonance (fMRI) and neurocognitive testing confirms that blows, causing changes in brain function, might not necessarily result in clinical diagnosis of concussion. Furthermore, cognitive deficiency in football players may be attributed to repetitive sub-concussive blows to the head. Diffusion weighted imaging (DWI) has previously been utilized to detect white matter (WM) abnormalities in mild traumatic brain injury (mTBI) patients, including those who have …

Potential For Electrical Power Generation Using Forest Wood Biomass In Rural Areas Of Catalonia, Arnau Gonzalez

Open Access Theses

Biomass is a renewable energy source that has been used for many years. However, its usage as an electricity source in Spain is not well developed due to many causes, among which highlights the lack of knowledge about the available technical potential. This research sought to close this gap assessing the technical potential for electricity generation using forest wood biomass in rural areas of Catalonia. The study characterizes the amount and type of biomass available in Catalonian forests that can be used to produce electricity without going beyond the capacity of regeneration of the forest, as well as the state-of-the-art …

The Perceptual Salience Of Amplitude Modulated Cortical Stimulation: Peak Equivalence Or Rms Equivalence?, Oliver Brian Regele

Open Access Theses

Intracortical microstimulation (ICMS) is a method of electrically stimulating the primary motor, visual, somatosensory and auditory cortices in the brain. The goal is to replace deficient sensory function in cases such as deafness, blindness and paralysis. However these neural prosthetics have not made the full transition to clinical trials due to a lack of sufficient investigation into the optimal stimulation waveforms. Sinusoidally amplitude modulated (SAM) signals have been shown to be important to sensory systems, yet have not been fully explored as a stimulation waveform for stimulating cortical tissue.

This work represents an investigation into the detection characteristics of electrical …