The effect of nonlinearities on the dynamic response of a large shuttle payload

The STS Centaur was designed to be a high energy upper stage for use with the Space Shuttle. Two versions were designed under development when the program was cancelled. The first version, designated G-prime, was for planetary missions. The second version, designated G, was to place spacecraft in geosynchronous orbit. As a part of the STS Centaur finite-element model verification effort, test articles of both versions were subjected to a series of static tests. In addition the Centaur G-prime test article was subjected to a series of dynamic tests including a modal survey. Both the static and dynamic tests showed that nonlinearities existed in the Centaur and its support system. The support system included flight-like latches. The nonlinearities were particularly apparent in tests that loaded the forward support structure of the Centaur. These test results were used to aid in the development of two improved finite-element models. The first was a linear model, while the second contained nonlinear elements at the boundaries. Results from both models were compared with the transient response obtained from a step-relaxation or twang test. The linear model was able to accurately match the low frequency response found in the test data. However, only the nonlinear model was able to match higher frequency response that was present in some of the test data. In addition the nonlinear model was able to predict other nonlinear behavior such as the dynamic jump that occurs in systems with nonlinear stiffness

EPID 7133 - Epidemiologic Research Methods I

This course will focus on epidemiologic methods - primarily methods used in observational studies, cohort studies, case-control studies and randomized controlled trials. With respect to cohort studies, topics covered include cohort identification, ascertainment of exposure status, follow-up of cohort members, measuring outcomes, sources of bias and interpretational issues. Case-control topics include issues around defining cases and controls, control of confounding, and sources of bias/systematic error. Topics around randomized trials include randomization procedures, defining and assembling treatment/intervention arms, selecting study subjects and approaches to data collection. Other topics covered in this course include surveillance and ecologic studies. Pros and cons of all study designs will be discussed, in part through readings of published papers. Fundamentals of data analysis will also be addressed, but a detailed discussion is reserved for Epidemiology Research II

EPID 9431 – Mental Health Epidemiology

This course will explore factors that determine the frequency and distribution of mental health problems in populations. Strategies for mental health intervention will also be discussed

EPID 7134 – Epidemiologic Methods II

This course provides instruction and hands-on experience in the analysis and interpretation of data from epidemiologic studies. Topics to be covered include epidemiology research questions that can be addressed by cross-sectional, case-control and cohort studies; the rationale underlying the major techniques used to analyze data from these studies; the conditions under which these methods are appropriate and their relative advantages and disadvantages. Attention will be given to how interactions, confounders and nonlinear relationships among variables can be addressed along with interpretation of statistical software output from epidemiologic studies employing these designs and analytical methods

EPID 8230 – Observational Study Design and Analysis

This course will focus on the design and conduct of observational research designs including cohort, case-control and cross-sectional approaches. This course will provide instruction related to issues specific to observational research approaches. Students will develop and present detailed study plans for each research approach

EPID 8130 - Field Methods in Epidemiology

This course addresses practical aspects of management and implementation of research studies and will focus on the conduct of research consistent with the scientific method. Topics include planning study activities, questionnaire design and implementation, and operations research

EPID 8230 – Observational Study Design and Analysis

This course will focus on the design and conduct of observational research designs including cohort, case-control and cross-sectional approaches. This course will provide instruction related to issues specific to observational research approaches. Students will develop and present detailed study plans for each research approach

A Comparison of Functionally Divergent Forms of the Purine Biosynthesis Enzyme PurE.

Purines are the basic building block for essential biomolecules such as DNA, RNA, NADH, CoA, and several essential vitamin cofactors. Most organisms have the ability to synthesize purines through the de novo purine biosynthesis pathway

EPID 7134 - Epidemiologic Methods II

This course provides instruction and hands-on experience in the analysis and interpretation of data from epidemiologic studies. Topics to be covered include epidemiology research questions that can be addressed by case-control and cohort studies, the rationale underlying the major techniques used to analyze data from case-control and cohort studies, the conditions under which these methods are appropriate and their relative advantages and disadvantages. Attention will be given to how interactions, confounders and nonlinear relationships among variables can be addressed along with interpretation of statistical software output from epidemiologic studies employing these designs and analytical methods

EPID 8130 - Field Methods in Epidemiology

This course addresses practical aspects of management and implementation of research studies and will focus on the conduct of research consistent with the scientific method. Topics include planning study activities, questionnaire design and implementation, and operations research