A numerical study of the effects of wind tunnel wall proximity on an airfoil model

A procedure was developed for modeling wind tunnel flows using computational fluid dynamics. Using this method, a numerical study was undertaken to explore the effects of solid wind tunnel wall proximity and Reynolds number on a two-dimensional airfoil model at low speed. Wind tunnel walls are located at varying wind tunnel height to airfoil chord ratios and the results are compared with freestream flow in the absence of wind tunnel walls. Discrepancies between the constrained and unconstrained flows can be attributed to the presence of the walls. Results are for a Mach Number of 0.25 at angles of attack through stall. A typical wind tunnel Reynolds number of 1,200,000 and full-scale flight Reynolds number of 6,000,000 were investigated. At this low Mach number, wind tunnel wall corrections to Mach number and angle of attack are supported. Reynolds number effects are seen to be a consideration in wind tunnel testing and wall interference correction methods. An unstructured grid Navier-Stokes code is used with a Baldwin-Lomax turbulence model. The numerical method is described since unstructured flow solvers present several difficulties and fundamental differences from structured grid codes, especially in the area of turbulence modeling and grid generation

Multi-Target Tracking in Distributed Sensor Networks using Particle PHD Filters

Multi-target tracking is an important problem in civilian and military applications. This paper investigates multi-target tracking in distributed sensor networks. Data association, which arises particularly in multi-object scenarios, can be tackled by various solutions. We consider sequential Monte Carlo implementations of the Probability Hypothesis Density (PHD) filter based on random finite sets. This approach circumvents the data association issue by jointly estimating all targets in the region of interest. To this end, we develop the Diffusion Particle PHD Filter (D-PPHDF) as well as a centralized version, called the Multi-Sensor Particle PHD Filter (MS-PPHDF). Their performance is evaluated in terms of the Optimal Subpattern Assignment (OSPA) metric, benchmarked against a distributed extension of the Posterior Cram\'er-Rao Lower Bound (PCRLB), and compared to the performance of an existing distributed PHD Particle Filter. Furthermore, the robustness of the proposed tracking algorithms against outliers and their performance with respect to different amounts of clutter is investigated.Comment: 27 pages, 6 figure

On the problem of modeling for parameter identification in distributed structures

Structures are often characterized by parameters, such as mass and stiffness, that are spatially distributed. Parameter identification of distributed structures is subject to many of the difficulties involved in the modeling problem, and the choice of the model can greatly affect the results of the parameter identification process. Analogously to control spillover in the control of distributed-parameter systems, identification spillover is shown to exist as well and its effect is to degrade the parameter estimates. Moreover, as in modeling by the Rayleigh-Ritz method, it is shown that, for a Rayleigh-Ritz type identification algorithm, an inclusion principle exists in the identification of distributed-parameter systems as well, so that the identified natural frequencies approach the actual natural frequencies monotonically from above

Cross-middleware Interoperability in Distributed Concurrent Engineering

Secure, distributed collaboration between different organizations is a key challenge in Grid computing today. The GDCD project has produced a Grid-based demonstrator Virtual Collaborative Facility (VCF) for the European Space Agency. The purpose of this work is to show the potential of Grid technology to support fully distributed concurrent design, while addressing practical considerations including network security, interoperability, and integration of legacy applications. The VCF allows domain engineers to use the concurrent design methodology in a distributed fashion to perform studies for future space missions. To demonstrate the interoperability and integration capabilities of Grid computing in concurrent design, we developed prototype VCF components based on ESA’s current Excel-based Concurrent Design Facility (a non-distributed environment), using a STEP-compliant database that stores design parameters. The database was exposed as a secure GRIA 5.1 Grid service, whilst a .NET/WSE3.0-based library was developed to enable secure communication between the Excel client and STEP database

An Empirical Microeconomic Study of the Entrepreneur

Entrepreneurs are an important segment of the economy, particularly in terms of economic development (Baumol, et al. 2007). However, the study of entrepreneurs and how they create firms is still an open question (Venkataraman 1998). In part, this question remains open as a result of the academic discussion about various definitions of entrepreneur and the identification of these individuals under each definition. This dissertation uses the Panel Survey of Entrepreneurial Dynamics (PSED) to study two questions about nascent entrepreneurs. The first question is about the identity of these nascent entrepreneurs and if they differ from the self-employed. The second question examines what happens to these nascent entrepreneurs over their periods of firm formation, where they may either successfully begin an operating firm or choose to quit the effort at firm formation. For the first question, a probability model of the decision to become an entrepreneur is analyzed. It is found that the self-employed are, in fact, a different group than nascent entrepreneurs, although there are similarities. The differences between these groups dominate the similarities. The differences support the contention of entrepreneurship researchers, such as Aldrich (1990), that researching only the self-employed as entrepreneurs introduces selection bias in the study of entrepreneurship. For the second question, a competing risks hazard model is used to estimate the effects of ability, optimism, resources, and management strategy on two possible outcomes for the nascent entrepreneur - successfully creating an operating firm or deciding instead to quit the effort. It is found that the nascent entrepreneur's ability, access to resources, and management strategy significantly affect the nascent entrepreneur's chances of getting a firm operational. However, only the self-employment status of the nascent entrepreneur has a significant effect on a nascent entrepreneur's decision to quit the effort of firm formation

Low-Income Households\u27 Perceived Obstacles and Reactions in Obtaining Affordable Housing

Low-income affordable housing remains an issue for the town on Martha\u27s Vineyard where this study was conducted, in which an estimated 54% of low-/moderate-income households spend more than 50% of monthly income on housing. Using Schneider and Ingram\u27s work regarding the social construction of target populations as the foundation, the purpose of this qualitative research was to assess how the perceived social standing and political power contributed to determining the benefits and burdens allocated to the town\u27s low-income households. Data for this study consisted of 14 individual semistructured interviews with members of low-income households who were seeking or in affordable housing. The research concentrated on the obstacles and reactions the low-income households experienced in the quest for affordable housing. Data were coded and analyzed using a value coding procedure followed by thematic analysis. Three themes emerged from the research: a perception by the participants of not being valued in the community and a lack of attention by town leadership to their affordable housing struggles; a self-reliance to find affordable housing; and coping strategies by renting bedrooms with shared kitchen and living areas or resorting to a 9-month lease and being displaced during the summer tourist season. The research illuminated the low-income community\u27s housing experiences and perceptions, thereby helping town leaders to form housing policy and make fiscal decisions. The implications for positive social change include recommendations to town leadership to examine incentivizing homeowners to offer affordable rentals, investigating congregate housing solutions, and developing multifamily affordable housing for the town\u27s low-income households

Factors influencing teacher use of computer aided learning

Education teachers who attended an intensive training course in Computer Aided Learning (CAL) were surveyed to determine their subsequent use of computers in the classroom, what factors were influential in their computer use, and the reasons for taking the training course. Teachers reported an increase of computer use after the training course. Several factors were related to their computer use including available resources, administrator support, educational levels, teacher belief in computer effectiveness, teacher competence in CAL, and available budget money. Personal interest in CAL was ranked highest for why they attended the course with administrator request being ranked the lowest. Computer use increases when teachers are motivated and receive adequate training in CAL

Comments on the September 29, 2014 FSB Consultative Document, ‘Cross-Border Recognition of Resolution Action’

This CIGI Paper No. 51 was released on December 3, 2014 by the Centre for International Governance Innovation (CIGI) as a response to the Financial Stability Board’s (FSB) Consultative Document, “Cross-Border Recognition of Resolution Action.” Principally authored by CIGI Senior Fellow Steven L. Schwarcz (who works with the think tank’s International Law Research Program), the Paper comments on the policy measures proposed by the FSB, an international body that monitors and makes recommendations about the global financial system, to address the cross-border legal uncertainties of troubled systemically important financial firms. In that context, the Paper explains why a statutory approach is more effective than a contractual approach at removing obstacles in cross-border resolutions of those firms, and thus a better method to achieve financial stability. The Paper also recommends that the FSB establish a working group on statutory mechanisms for the cross-border resolution of financial firms