Simulating study of the interaction between the propulsion and flight control systems of a subsonic lift fan VTOL

The possibility of interactions between the propulsion and flight control systems of a three-fan subsonic VTOL aircraft was studied using nonreal time simulation. Time histories of critical internal engine parameters were obtained and possible deleterious effects of engine dynamics on flight control were identified and analyzed. No deleterious effects, with the exception of the effects of the fan actuator deadband, were found. A method of alleviating these effects through feedback of the actuator output to the flight controller was developed

Direct investment: a doubtful alternative to international debt

The paper considers a model in which private foreign investors make direct long-lived capital investments in a small developing country that is subject to stochastic shocks to production. Depending upon the preferences of the host country, we find that expropriation can occur because of either desperation or opportunism. We show that under reasonable assumptions, increased investment makes expropriation less likely to occur and that the level of investment chosen by atomistic foreign investors may be nonoptimal.International finance ; Developing countries

Green building literacy: a framework for advancing green building education

Curriculum design; Environmental literacy; Green building education; Green building literacy; Next generation science standards; Science literacyBackground: Despite the increasing square footage of green buildings worldwide, green building expertise remains largely in the domain of building industry professionals. However, the performance of and advocacy for green buildings would benefit from a green building literate general public. Green building education is an expanding frontier for STEM education and can create opportunities to integrate science and environmental literacies into the study of everyday environments. Few resources exist, however, to help STEM educators incorporate green building themes into the science classroom. The work here developed educational tools for connecting green buildings and science education through a multi-step process. An interdisciplinary literature review yielded a series of frameworks that were improved through two focus groups with science and environmental educators and built environment professionals. Results: The result of this process is a toolbox of conceptual frameworks for educators interested in using a systems-based approach to teach about green buildings as sites for complex interactions between human activity and Earth systems. The work here first leverages the broad definition of environmental literacy (knowledge, skills, affect, and behavior) to advance a working definition for "green building literacy." Next, major domains of green building knowledge are developed and linked to the Next Generation Science Standards. Conclusions: Green building literacy has been an ill-defined term and green building themes have not been rigorously connected to science and environmental education. The work here provides a foundation for promoting green building literacy through K-12 STEM education. The educational tools developed through this process can be used as a starting point for lesson planning to catalyze green building education in a variety of formal and informal settings. c2019, The Author(s).Includes bibliographical references

Sensing of Fluctuating Nanoscale Magnetic Fields Using NV Centres in Diamond

New magnetometry techniques based on Nitrogen-Vacancy (NV) defects in diamond allow for the imaging of static (DC) and oscillatory (AC) nanoscopic magnetic systems. However, these techniques require accurate knowledge and control of the sample dynamics, and are thus limited in their ability to image fields arising from rapidly fluctuating (FC) environments. We show here that FC fields place restrictions on the DC field sensitivity of an NV qubit magnetometer, and that by probing the dephasing rate of the qubit in a magnetic FC environment, we are able to measure fluctuation rates and RMS field strengths that would be otherwise inaccessible with the use of DC and AC magnetometry techniques. FC sensitivities are shown to be comparable to those of AC fields, whilst requiring no additional experimental overheads or control over the sample.Comment: 5 pages, 4 figure

Propulsion system mathematical model for a lift/cruise fan V/STOL aircraft

A propulsion system mathematical model is documented that allows calculation of internal engine parameters during transient operation. A non-realtime digital computer simulation of the model is presented. It is used to investigate thrust response and modulation requirements as well as the impact of duty cycle on engine life and design criteria. Comparison of simulation results with steady-state cycle deck calculations showed good agreement. The model was developed for a specific 3-fan subsonic V/STOL aircraft application, but it can be adapted for use with any similar lift/cruise V/STOL configuration

Combining community-based research and local knowledge to confront asthma and subsistence-fishing hazards in Greenpoint/Williamsburg, Brooklyn, New York.

Activists in the environmental justice movement are challenging expert-driven scientific research by taking the research process into their own hands and speaking for themselves by defining, analyzing, and prescribing solutions for the environmental health hazards confronting communities of the poor and people of color. I highlight the work of El Puente and The Watchperson Project--two community-based organizations in the Greenpoint/Williamsburg neighborhood in Brooklyn, New York, that have engaged in community-based participatory research (CBPR) to address asthma and risks from subsistence-fish diets. The CBPR process aims to engage community members as equal partners alongside scientists in problem definition, information collection, and data analysis--all geared toward locally relevant action for social change. In the first case I highlight how El Puente has organized residents to conduct a series of asthma health surveys and tapped into local knowledge of the Latino population to understand potential asthma triggers and to devise culturally relevant health interventions. In a second case I follow The Watchperson Project and their work surveying subsistence anglers and note how the community-gathered information contributed key data inputs for the U.S. Environmental Protection Agency Cumulative Exposure Project in the neighborhood. In each case I review the processes each organization used to conduct CBPR, some of their findings, and the local knowledge they gathered, all of which were crucial for understanding and addressing local environmental health issues. I conclude with some observations about the benefits and limits of CBPR for helping scientists and communities pursue environmental justice

A Survey of Information Sources Used for Progress Decisions about Medical Students

Although many medical schools have adopted a variety of methods to assess student competency, the extent to which these innovations have changed how decisions about student progress are made is not clear. This paper describes a survey of 126 accredited allopathic U.S. medical schools to determine which information sources are used for decisions related to medical student progress and graduation. Respondents were asked to indicate up to three information sources used for seven specific decisions about student progress. The results indicate that multiple choice questions (MCQs) and faculty ratings remain the most frequently used information sources. Clinical skills education in the pre-clinical curriculum is the area with the broadest use of assessments for progress decisions. Several explanations are suggested for the primacy of MCQs and faculty ratings in student decisions, including familiarity for faculty and students, ease of implementation and the resources required for the adoption of other assessment strategies

Algebraic properties of generalized Rijndael-like ciphers

We provide conditions under which the set of Rijndael functions considered as permutations of the state space and based on operations of the finite field \GF (p^k) ($p\geq 2$ a prime number) is not closed under functional composition. These conditions justify using a sequential multiple encryption to strengthen the AES (Rijndael block cipher with specific block sizes) in case AES became practically insecure. In Sparr and Wernsdorf (2008), R. Sparr and R. Wernsdorf provided conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (2^k) is equal to the alternating group on the state space. In this paper we provide conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (p^k) ($p\geq 2$) is equal to the symmetric group or the alternating group on the state space.Comment: 22 pages; Prelim0

Smoothly-varying hopping rates in driven flow with exclusion

We consider the one-dimensional totally asymmetric simple exclusion process (TASEP) with position-dependent hopping rates. The problem is solved,in a mean field/adiabatic approximation, for a general (smooth) form of spatial rate variation. Numerical simulations of systems with hopping rates varying linearly against position (constant rate gradient), for both periodic and open boundary conditions, provide detailed confirmation of theoretical predictions, concerning steady-state average density profiles and currents, as well as open-system phase boundaries, to excellent numerical accuracy.Comment: RevTeX 4.1, 14 pages, 9 figures (published version

Microchannel heat transfer with slip flow and wall effects

Cataloged from PDF version of article.Analysis is presented for conjugate heat transfer in a parallel-plate microchannel. Axial conduction in the fluid and in the adjacent wall is included. The fluid is a constant property gas with a slip-flow velocity distribution. The microchannel is heated by a small region on the channel wall. The analytic solution is given in the form of integrals by the method of Green's functions. Quadrature is used to obtain numerical results for the temperature and heat transfer coefficient on the heated region for various Peclet number, Knudsen number, and wall materials. A region downstream of the heater is also explored. These results have application in the optimal design of small-scale heat transfer devices for biomedical applications, electronic cooling, and advanced fuel cells