Design and Construction of a Step Etching Instrument

An instrument was designed and constructed to perform a sequential etch of an oxidized silicon wafer by periodically lowering the wafer deeper into an etch bath. The unit will step the wafer at four different time intervals 15, 30, 45 and 60 seconds. Either five or ten steps can be done at one time. The unit is primarily designed for the etching of silicon dioxide in a Buffered Oxide Etch

Master of Science

thesisThere has been much research on how to get unmanned aerial vehicles (UAVs) to perch on many different types of surfaces and objects, including flat surfaces, ramps, tree branches, power lines, etc. Many of these surfaces are static and it is easy to detect falls using inertial sensors such as accelerometers or gyroscopes. However, some perches, such as tree branches and power lines, are not static. When the UAV is perched on these perches, it will move with them, making the detection of falls from such a perch much more difficult than simply trying to sense motion. This thesis proposes two methods for fall detection of a UAV perched on such a dynamic perch. Computer vision is used on a feed from a camera mounted on the bottom of the UAV. Optical flow is used in conjunction with a filter that segments the perch in the image from the background to estimate the relative motion between the UAV and the perch. If the motion exceeds certain bounds, the UAV is considered falling. The second method tries to find the instantaneous center of rotation (ICR) of the UAV utilizing accelerometers and a gyroscope mounted to the UAV frame. Two methods are proposed to do this, one based on integrating the accelerometers to find the velocity at a point, the other finds the distance between the ICR and three points on the rigid frame of the UAV. The ICR estimates from these two methods are compared to an ICR estimate derived from data from an external Vicon motion capture system. The estimated ICR is then compared to the ICR of the perch that the UAV has perched on, if the two diverge enough, the perch is considered to be falling. The proposed methods were tested experimentally by placing a test quadrotor fitted with the appropriate sensors on three different test perches: a painted PVC pipe, a PVC pipe with a swirl pattern on it, and a tree branch. The quadrotor and perch are then actuated in three different tests. The first test has the quadrotor rotating about the perch while the perch is static. The second test has the quadrotor swinging on the perch without slipping. In the final test, the swing perch angle is increased until the quadrotor falls off. Each of the 9 tests is performed 5 times. Accelerometer, gyroscope, and vision data are gathered during these tests and analyzed using the methods described in this thesis. These experiments show that the vision method works fairly well, and that the ICR method works to a degree, but there is more work to be done in that area

Magmatic Intrusions into the Sulfur-Rich Carmel Formation on the Colorado Plateau, USA: Implications for the Mars 2020 Mission

We report on basaltic dikes in the Colorado Plateau, which crosscut sulfate bearing sediments and compare this to Martian basalts and basaltic sediments in contact with sulfate mineralizations

An overview of Viscosity Solutions of Path-Dependent PDEs

This paper provides an overview of the recently developed notion of viscosity solutions of path-dependent partial di erential equations. We start by a quick review of the Crandall- Ishii notion of viscosity solutions, so as to motivate the relevance of our de nition in the path-dependent case. We focus on the wellposedness theory of such equations. In partic- ular, we provide a simple presentation of the current existence and uniqueness arguments in the semilinear case. We also review the stability property of this notion of solutions, in- cluding the adaptation of the Barles-Souganidis monotonic scheme approximation method. Our results rely crucially on the theory of optimal stopping under nonlinear expectation. In the dominated case, we provide a self-contained presentation of all required results. The fully nonlinear case is more involved and is addressed in [12]

A new representation for non--local operators and path integrals

We derive an alternative representation for the relativistic non--local kinetic energy operator and we apply it to solve the relativistic Salpeter equation using the variational sinc collocation method. Our representation is analytical and does not depend on an expansion in terms of local operators. We have used the relativistic harmonic oscillator problem to test our formula and we have found that arbitrarily precise results are obtained, simply increasing the number of grid points. More difficult problems have also been considered, observing in all cases the convergence of the numerical results. Using these results we have also derived a new representation for the quantum mechanical Green's function and for the corresponding path integral. We have tested this representation for a free particle in a box, recovering the exact result after taking the proper limits, and we have also found that the application of the Feynman--Kac formula to our Green's function yields the correct ground state energy. Our path integral representation allows to treat hamiltonians containing non--local operators and it could provide to the community a new tool to deal with such class of problems.Comment: 9 pages ; 1 figure ; refs added ; title modifie

Alteration and Oxidiation of an Olivine Lamprophyre Dike from Southern Utah, USA: An Analog for Mars

We report on oxidized basaltic dike intrusions on the Colorado Plateau as analog for Martian basalt oxidation

Recurrent violent injury: magnitude, risk factors, and opportunities for intervention from a statewide analysis.

INTRODUCTION: Although preventing recurrent violent injury is an important component of a public health approach to interpersonal violence and a common focus of violence intervention programs, the true incidence of recurrent violent injury is unknown. Prior studies have reported recurrence rates from 0.8% to 44%, and risk factors for recurrence are not well established. METHODS: We used a statewide, all-payer database to perform a retrospective cohort study of emergency department visits for injury due to interpersonal violence in Florida, following up patients injured in 2010 for recurrence through 2012. We assessed risk factors for recurrence with multivariable logistic regression and estimated time to recurrence with the Kaplan-Meier method. We tabulated hospital charges and costs for index and recurrent visits. RESULTS: Of 53 908 patients presenting for violent injury in 2010, 11.1% had a recurrent violent injury during the study period. Trauma centers treated 31.8%, including 55.9% of severe injuries. Among recurrers, 58.9% went to a different hospital for their second injury. Low income, homelessness, Medicaid or uninsurance, and black race were associated with increased odds of recurrence. Patients with visits for mental and behavioral health and unintentional injury also had increased odds of recurrence. Index injuries accounted for $105 million in costs, and recurrent injuries accounted for another$25.3 million. CONCLUSIONS: Recurrent violent injury is a common and costly phenomenon, and effective violence prevention programs are needed. Prevention must include the nontrauma centers where many patients seek care

A Predictive Model for Human-Unmanned Vehicle Systems : Final Report

Advances in automation are making it possible for a single operator to control multiple unmanned vehicles (UVs). This capability is desirable in order to reduce the operational costs of human-UV systems (HUVS), extend human capabilities, and improve system effectiveness. However, the high complexity of these systems introduces many significant challenges to system designers. To help understand and overcome these challenges, high-fidelity computational models of the HUVS must be developed. These models should have two capabilities. First, they must be able to describe the behavior of the various entities in the team, including both the human operator and the UVs in the team. Second, these models must have the ability to predict how changes in the HUVS and its mission will alter the performance characteristics of the system. In this report, we describe our work toward developing such a model. Via user studies, we show that our model has the ability to describe the behavior of a HUVS consisting of a single human operator and multiple independent UVs with homogeneous capabilities. We also evaluate the model’s ability to predict how changes in the team size, the human-UV interface, the UV’s autonomy levels, and operator strategies affect the system’s performance.Prepared for MIT Lincoln Laborator