Using Model-Based Systems Engineering To Provide Artifacts for NASA Project Life-Cycle and Technical Reviews

The ability of systems engineers to use model-based systems engineering (MBSE) to generate self-consistent, up-to-date systems engineering products for project life-cycle and technical reviews is an important aspect for the continued and accelerated acceptance of MBSE. Currently, many review products are generated using labor-intensive, error-prone approaches based on documents, spreadsheets, and chart sets; a promised benefit of MBSE is that users will experience reductions in inconsistencies and errors. This work examines features of SysML that can be used to generate systems engineering products. Model elements, relationships, tables, and diagrams are identified for a large number of the typical systems engineering artifacts. A SysML system model can contain and generate most systems engineering products to a significant extent and this paper provides a guide on how to use MBSE to generate products for project life-cycle and technical reviews. The use of MBSE can reduce the schedule impact usually experienced for review preparation, as in many cases the review products can be auto-generated directly from the system model. These approaches are useful to systems engineers, project managers, review board members, and other key project stakeholders

Ground measurements of shock-wave pressure for fighter airplanes flying at very low altitudes and comments on associated response phenomena

Ground measurements of shock wave pressure for fighter aircraft at very low altitude

Low-noise fan exit guide vanes

Low-noise fan exit guide vanes are disclosed. According to the present invention a fan exit guide vane has an outer shell substantially shaped as an airfoil and defining an interior cavity. A porous portion of the outer shell allows communication between the fluctuations in the air passing over the guide vane and the interior cavity. At least one acoustically resonant chamber is located within the interior cavity. The resonant chamber is in communication with the porous portion of the outer perimeter. The resonant chamber is configured to reduce the noise generated at a predetermined frequency. In various preferred embodiments, there is a plurality of acoustically resonant chambers located within the interior cavity. The resonant chambers can be separated by one or more partitions within the interior cavity. In these embodiments, the resonant chambers can be configured to reduce the noise generated over a range of predetermined frequencies

The AMSC mobile satellite system

The American Mobile Satellite Consortium (AMSC) Mobile Satellite Service (MSS) system is described. AMSC will use three multi-beam satellites to provide L-band MSS coverage to the United States, Canada and Mexico. The AMSC MSS system will have several noteworthy features, including a priority assignment processor that will ensure preemptive access to emergency services, a flexible SCPC channel scheme that will support a wide diversity of services, enlarged system capacity through frequency and orbit reuse, and high effective satellite transmitted power. Each AMSC satellite will make use of 14 MHz (bi-directional) of L-band spectrum. The Ku-band will be used for feeder links

Mobile satellite service in the United States

Mobile satellite service (MSS) has been under development in the United States for more than two decades. The service will soon be provided on a commercial basis by a consortium of eight U.S. companies called the American Mobile Satellite Consortium (AMSC). AMSC will build a three-satellite MSS system that will offer superior performance, reliability and cost effectiveness for organizations requiring mobile communications across the U.S. The development and operation of MSS in North America is being coordinated with Telesat Canada and Mexico. AMSC expects NASA to provide launch services in exchange for capacity on the first AMSC satellite for MSAT-X activities and for government demonstrations

The structure and mechanistic impact of carbon deposits in dehydrogenation reactions

The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes is widely studied as a route to the formation of alkenes and di-alkenes, important precursor molecules for synthetic rubbers, plastics and a variety of other products [1-4]. Recent studies have focused on the non-oxidative DH of butane over alumina-supported vanadia catalysts [5-7]. In the present work, we provide a detailed understanding of both the role and structure of coke deposited on VOx/Al2O3 during reaction. A range of characterisation techniques have been employed including the first application of terahertz time domain spectroscopy (THz-TDS) to the study of coke. Complementary THz-TDS characterisation of carbonaceous materials including carbon nanofibres (CNFs) has also been conducted

The role and structure of carbonaceous materials in dehydrogenation reactions

The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes is widely studied as a route to the formation of alkenes and di-alkenes, important precursor molecules for synthetic rubbers, plastics and a variety of other products [1,2]. Recent studies have focused on the non-oxidative DH of butane over alumina-supported vanadia catalysts [3-5]. In the present work, we provide a detailed understanding of both the role and structure of coke deposited on VOx/Al2O3 during reaction. A range of characterisation techniques have been employed including the first application of terahertz time domain spectroscopy (THz-TDS) to the study of coke. Complementary THz-TDS characterisation of carbonaceous materials including carbon nanofibres (CNFs) has also been conducted. For such materials THz-TDS spectra can be correlated with their catalytic performance in the oxidative dehydrogenation of ethylbenzene to form styrene

Exploring the uptake and use of electronic cigarettes provided to smokers accessing homeless centres: a four-centre cluster feasibility trial

Background: Smoking prevalence is extremely high in adults experiencing homelessness, and there is little evidence regarding which cessation interventions work best. This study explored the feasibility of providing free electronic cigarette starter kits to smokers accessing homeless centres in the UK. / Objectives: Seven key objectives were examined to inform a future trial: (1) assess willingness of smokers to participate in the study to estimate recruitment rates; (2) assess participant retention in the intervention and control arms; (3) examine the perceived value of the intervention, facilitators of and barriers to engagement, and influence of local context; (4) assess service providers’ capacity to support the study and the type of information and training required; (5) assess the potential efficacy of supplying free electronic cigarette starter kits; (6) explore the feasibility of collecting data on contacts with health-care services as an input to a main economic evaluation; and (7) estimate the cost of providing the intervention and usual care. / Design: A prospective cohort four-centre pragmatic cluster feasibility study with embedded qualitative process evaluation. / Setting: Four homeless centres. Two residential units in London, England. One day centre in Northampton, England. One day centre in Edinburgh, Scotland. / Intervention: In the intervention arm, a single refillable electronic cigarette was provided together with e-liquid, which was provided once per week for 4 weeks (choice of three flavours: fruit, menthol or tobacco; two nicotine strengths: 12 or 18 mg/ml). There was written information on electronic cigarette use and support. In the usual-care arm, written information on quitting smoking (adapted from NHS Choices) and signposting to the local stop smoking service were provided. / Results: Fifty-two per cent of eligible participants invited to take part in the study were successfully recruited (56% in the electronic cigarette arm; 50.5% in the usual-care arm; total n = 80). Retention rates were 75%, 63% and 59% at 4, 12 and 24 weeks, respectively. The qualitative component found that perceived value of the intervention was high. Barriers were participants’ personal difficulties and cannabis use. Facilitators were participants’ desire to change, free electronic cigarettes and social dynamics. Staff capacity to support the study was generally good. Carbon monoxide-validated sustained abstinence rates at 24 weeks were 6.25% (3/48) in the electronic cigarette arm compared with 0% (0/32) in the usual-care arm (intention to treat). Almost all participants present at follow-up visits completed measures needed for input into an economic evaluation, although information about staff time to support usual care could not be gathered. The cost of providing the electronic cigarette intervention was estimated at £114.42 per person. An estimated cost could not be calculated for usual care. / Limitations: Clusters could not be fully randomised because of a lack of centre readiness. The originally specified recruitment target was not achieved and recruitment was particularly difficult in residential centres. Blinding was not possible for the measurement of outcomes. Staff time supporting usual care could not be collected. / Conclusions: The study was associated with reasonable recruitment and retention rates and promising acceptability in the electronic cigarette arm. Data required for full cost-effectiveness evaluation in the electronic cigarette arm could be collected, but some data were not available in the usual-care arm. / Future work: Future research should focus on several key issues to help design optimal studies and interventions with this population, including which types of centres the intervention works best in, how best to retain participants in the study, how to help staff to deliver the intervention, and how best to record staff treatment time given the demands on their time. / Trial registration: Current Controlled Trials ISRCTN14140672; the protocol was registered as researchregistry4346. / Funding: This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 9, No. 7. See the NIHR Journals Library website for further project information

Bridging Time Scales in Cellular Decision Making with a Stochastic Bistable Switch

Cellular transformations which involve a significant phenotypical change of the cell's state use bistable biochemical switches as underlying decision systems. In this work, we aim at linking cellular decisions taking place on a time scale of years to decades with the biochemical dynamics in signal transduction and gene regulation, occuring on a time scale of minutes to hours. We show that a stochastic bistable switch forms a viable biochemical mechanism to implement decision processes on long time scales. As a case study, the mechanism is applied to model the initiation of follicle growth in mammalian ovaries, where the physiological time scale of follicle pool depletion is on the order of the organism's lifespan. We construct a simple mathematical model for this process based on experimental evidence for the involved genetic mechanisms. Despite the underlying stochasticity, the proposed mechanism turns out to yield reliable behavior in large populations of cells subject to the considered decision process. Our model explains how the physiological time constant may emerge from the intrinsic stochasticity of the underlying gene regulatory network. Apart from ovarian follicles, the proposed mechanism may also be of relevance for other physiological systems where cells take binary decisions over a long time scale.Comment: 14 pages, 4 figure