How Should Life Support Be Modeled and Simulated?

Why do most space life support research groups build and investigate large models for systems simulation? The need for them seems accepted, but are we asking the right questions and solving the real problems? The modeling results leave many questions unanswered. How then should space life support be modeled and simulated? Life support system research and development uses modeling and simulation to study dynamic behavior as part of systems engineering and analysis. It is used to size material flows and buffers and plan contingent operations. A DoD sponsored study used the systems engineering approach to define a set of best practices for modeling and simulation. These best practices describe a systems engineering process of developing and validating requirements, defining and analyzing the model concept, and designing and testing the model. Other general principles for modeling and simulation are presented. Some specific additional advice includes performing a static analysis before developing a dynamic simulation, applying the mass and energy conservation laws, modeling on the appropriate system level, using simplified subsystem representations, designing the model to solve a specific problem, and testing the model on several different problems. Modeling and simulation is necessary in life support design but many problems are outside its scope

The Impact of Socioeconomic Factors on Selected Practices by Small Livestock Producers in Florida

Socioeconomic factors could affect the practices of small livestock producers who produce and sell locally or regionally. Yet, there is limited research on the issue in the Southeastern U.S., for example, Florida. Thus, this study assessed the impact of socioeconomic factors on practices of small livestock producers in Florida. The data were obtained from a sample of seventy producers from several counties in Florida, and were analyzed using descriptive statistics and logistic regression analysis. The results showed that a majority practiced rotational grazing; did not test soil regularly; had parasite problems; did not use veterinary services, and practiced record keeping. Further, the binary logistic regression analyses showed that selected socioeconomic factors had statistically significant effects on selected practices. For instance, gender had a statistically significant effect on soil testing; household income had a statistically significant effect on parasite problem; gender had a statistically significant effect on the use of veterinary services; and farming status, race/ethnicity, education, and household income had statistically significant effects on record keeping. The findings suggest that socioeconomic factors may be important in producers adopting practices. Keywords: Socioeconomic Factors, Selected Practices, Farm Practices, Small Livestock Producers, Small Producer

Drug-Testing: Some Fundamental Conceptual and Juristic Problems

Discussions about the use or abuse of drugs or of drug-testing are usually charged with a high degree of emotiveness and subjectivity. By the same token, additionally, writings on the subject of drug testing often pose peculiar problems of analysis and objectivity. The purpose of this article is to explore and analyze some fundamental conceptual legal problems germane to a consideration of the legality of drug-testing in a democratic society which practices the rule of law and which places a high premium, in its normative scheme, on the principle of individual or personal liberty. The justification for this exercise lies primarily in the fact that in contemporary American society drug-testing is not only a reality, but raises issues both of immense legal complexity and practical significance. This article approaches the subject from five perspectives. The first is that of constructing a factual substratum for the conceptual legal issues to be addressed. The second is that of identifying and isolating the critical issues for determination raised by the facts. The third is an analytical examination of those issues by reference to certain conceptual or juristic criteria. The fourth is to predict, by way of rationalization of existing legal principles, the probable judicial approach of the courts in resolving the issue of the legality of drug-testing if confronted with the task of pronouncing upon it. The fifth is to inquire whether judges can validly and legitimately apply juristic principles postulated by legal scientists to complex moral and social issues of the day

Design and manufacture of a chain driven motor shaft for Formula Electric applications

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (page 23).This document describes the design, manufacture, and testing of a motor shaft assembly that is a subcomponent of the drivetrain system in a Formula Electric racecar. The design covers detailed analysis of the bearing, sprocket, shaft, pins, and spacer created to meet a set of functional requirements. The process of determining these requirements is also covered, along with a set of best practices for thoughtful design in general. An initial phase of testing is covered as well, from the design of the testing apparatus to the execution of a torsional test on the shaft. With limited data, conclusions are hard to draw with certainty, but initial results seem to indicate that the shaft performs as expected. The intent of this document is to serve as an example of the level of detail and thoroughness that is expected when designing racecar components. To that end, this document should provide a number of unique examples of how specific problems were modeled and addressed in the design. It should also serve as a template for future documentation of such design efforts.by Jack J. Wanderman.S.B

Towards a robust parallel solver for large-scale industrial flow simulations

In this work a CFD analysis is done on incompressible viscous flows using Finite Volume schemes implemented in the open-source software OpenFOAM. The objective of this study is twofold: to gain experience with the software and to define a set of best practices when running large-scale cases in OpenFOAM using parallel architectures. The first objective is obtained by testing three academic benchmarks, namely the lid- driven cavity, the flow over a backward facing step, and flow past a circular cylinder. The validation of these results is made by contrasting them to the data available in the literature. The second objective was fulfilled by studying two large-scale industrial problems, laminar flow inside an S-bend and turbulent external flow around a car. For the latter, the DriveAer geometry has been used. The analysis of these high- performance computing studies has been defined in terms of the relative efficiency and speed up for the two problems. The studied cases have been scaled up until 84 CPUs for the S-bend, and until 224 CPUs for the vehicle geometry. Furthermore, the performance of three partitioners, namely the simple, hierarchical, and scotch decomposers have been evaluated