782 research outputs found

    An Exploratory Study of Forces and Frictions affecting Large-Scale Model-Driven Development

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    In this paper, we investigate model-driven engineering, reporting on an exploratory case-study conducted at a large automotive company. The study consisted of interviews with 20 engineers and managers working in different roles. We found that, in the context of a large organization, contextual forces dominate the cognitive issues of using model-driven technology. The four forces we identified that are likely independent of the particular abstractions chosen as the basis of software development are the need for diffing in software product lines, the needs for problem-specific languages and types, the need for live modeling in exploratory activities, and the need for point-to-point traceability between artifacts. We also identified triggers of accidental complexity, which we refer to as points of friction introduced by languages and tools. Examples of the friction points identified are insufficient support for model diffing, point-to-point traceability, and model changes at runtime.Comment: To appear in proceedings of MODELS 2012, LNCS Springe

    Differences between the Grab Start and Track Start in Collegiate Swimmers

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    International Journal of Exercise Science 10(4): 515-521, 2017. The purpose of this investigation was to determine which foot stance, the track start (TS) or the grab start (GS), is most beneficial for competitive swimmers. Seven male and eight female collegiate swimmers participated in this study. The average participant age was 20.1 ± 1.13 years while the average years of competitive swimming experience was 10.8 ± 3.36 years. Participants performed three TS and three GS stances consecutively. Distance markers were placed on the side of the pool to determine where each swimmer entered the water. Video analysis was used to determine the following factors: start phase time, flight phase time, flight distance, horizontal entrance velocity, and entrance angle. Prior to participating in the study, swimmers completed a brief survey regarding age and competitive swimming experience, and researchers measured each participant’s height and weight. A paired sample T-test was used to determine significant differences between the GS and TS. The results indicated that the TS foot stance resulted in a shorter start phase time (0.76 ± 0.07 s vs. 0.88 ± 0.10 s; P \u3c 0.001), a shorter flight phase time (0.81 ± 0.08 vs. 0.95 ± 0.07; P \u3c 0.001), and a greater horizontal entrance velocity (3.56 ± 0.51 m/s vs. 3.10 ± 0.41 m/s; P \u3c 0.001). The GS allowed swimmers to travel further in the air (2.96 ± 0.43 m vs. 2.88 ± 0.41 m; P = 0.013). The TS entrance angle was significantly shallower than the GS entrance angle (36.98 ± 3.17° vs. 38.53 ± 3.81°; P = 0.004). Based on the results, the TS foot stance provides swimmers with the greatest advantage

    Non-invasive voiding assessment in conscious mice

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    OBJECTIVE: To review available options of assessing murine bladder function and to evaluate a non-invasive technique suitable for long-term recording. METHODS: We reviewed previously described methods to record rodent bladder function. We used modified metabolic cages to capture novel recording tracings of mouse micturition. We evaluated our method in a pilot study with female mice undergoing partial bladder outlet obstruction or sham operation, respectively; half of the partial obstruction and sham group received treatment with an S6K-inhibitor, targeting the mTOR pathway, which is known to be implicated in bladder response to obstruction. RESULTS: Our non-invasive method using continuous urine weight recording reliably detected changes in murine bladder function resulting from partial bladder outlet obstruction or treatment with S6K-inhibitor. We found obstruction as well as treatment with S6K-inhibitor to correlate with a hyperactive voiding pattern. CONCLUSIONS: While invasive methods to assess murine bladder function largely disturb bladder histology and intrinsically render post-cystometry gene expression analysis of questionable value, continuous urine weight recording is a reliable, inexpensive, and critically non-invasive method to assess murine bladder function, suitable for a long-term application

    The mathematical theory of resonant transducers in a spherical gravity wave antenna

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    The rigoruos mathematical theory of the coupling and response of a spherical gravitational wave detector endowed with a set of resonant transducers is presented and developed. A perturbative series in ascending powers of the square root of the ratio of the resonator to the sphere mass is seen to be the key to the solution of the problem. General layouts of arbitrary numbers of transducers can be assessed, and a specific proposal (PHC), alternative to the highly symmetric TIGA of Merkowitz and Johnson, is described in detail. Frequency spectra of the coupled system are seen to be theoretically recovered in full agreement with experimental determinations.Comment: 31 pages, 7 figures, LaTeX2e, \usepackage{graphicx,deleq

    Bacterial iron-oxide nanowires from biofilm waste as a new adsorbent for the removal of arsenic from water

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    Biofilm, generated by the bacteria in the groundwater pumping system pipelines of the Salt Interception Scheme on the River Murray in South Australia is discarded as a waste material accumulated after periodic cleaning of the pipes. Structural and chemical composition characterizations confirm that this waste material is composed of amorphous twisted iron-oxide nanowires (ION), generated by bacteria, and they have a unique structure and properties. The adsorption performance of these iron-oxide nanowires for arsenic removal from water was evaluated to define their adsorption capacity for As(III) and As(V) and kinetics. Obtained results demonstrate considerable adsorption properties of this waste biological material and suggest its promising application as a new and low-cost adsorbent for water treatment.Ivan Andjelkovic, Sara Azari, Mason Erkelens, Peter Forward, Martin F. Lambert and Dusan Losi

    A novel interplanetary communications relay

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    A case study of a potential Earth-Mars interplanetary communications relay, designed to ensure continuous communications, is detailed. The relay makes use of orbits based on artificial equilibrium points via the application of continuous low thrust, which allows a spacecraft to hover above the orbital plane of Mars and thus ensure communications when the planet is occulted with respect to the Earth. The artificial equilibria of two different low-thrust propulsion technologies are considered: solar electric propulsion, and a solar sail/solar electric propulsion hybrid. In the latter case it is shown that the combination of sail and solar electric propulsion may prove advantageous, but only under specific circumstances of the relay architecture suggested. The study takes into account factors such as the spacecraft's power requirements and communications band utilized to determine the mission and system architecture. A detailed contingency analysis is considered for recovering the relay after increasing periods of spacecraft motor failure, and combined with a consideration for how best to deploy the relay spacecraft to maximise propellant reserves and mission duration

    A comparison of the epidemiology of ice hockey injuries between male and female youth in Canada

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    BACKGROUND: Hockey is played by youth across Canada, and its popularity has increased dramatically among females in the past decade. Despite this, there has been little epidemiological research comparing the injury patterns of young female and male hockey players. OBJECTIVE: To describe and compare injuries sustained by female and male youth hockey players using the Canadian Hospitals Injury Reporting and Prevention Program database. METHODS: In the present cross-sectional, retrospective comparison study, the Canadian Hospitals Injury Reporting and Prevention Program database was used to identify all hockey-related injuries sustained by children seven to 17.5 years of age over a 15-year period (January 1995 to December 2009). Exclusion criteria included paid professional players and children with injuries sustained while playing road hockey. RESULTS: Inclusion criteria were met by 33,233 children (2637 [7.9%] females and 30,596 [92.1%] males). Compared with males, females reported proportionately more soft tissue injuries (39.8% versus 32.6%; P\u3c0.01) and sprains/strains (21.1% versus 17.6%; P\u3c0.01). Males experienced more fractures (27.1% versus 18.2%; P\u3c0.01) and were most often injured through body checking (42.8% versus 25.7%; P\u3c0.01). Females showed a trend toward increased concussion with age, and were most often injured through collisions (28.6% versus 24.6%; P\u3c0.01). CONCLUSION: Compared with males, female hockey players sustained proportionately more soft tissue injures and sprains/strains, and showed a trend toward concussions in late adolecence. Males experienced more fractures, shoulder injuries and injuries due to body checking. Further research is required to identify risk factors for injury in female youth hockey players and to target injury prevention

    Formation of antihydrogen in antiproton - positron collision

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    A quantum mechanical approach is proposed for the formation of antihydrogen in the ground and excited states (2s, 2p) via the mechanism of three body recombination (TBR) inside a trapped plasma of anti proton and positron or in the collision between the two beams of them. Variations of the differential (DCS) as well as the total (TCS) formation cross sections are studied as a function of the incident energies of both the active and the spectator positrons. Significantly large cross sections are found at very low incident energies in the TBR process as compared to other processes leading to antihydrogen. The present formation cross section decreases with increasing positron energy (temperature) but no simple power law could be predicted for it covering the entire energy range, corroborating the experimental findings qualitatively. The formation cross sections are found to be much higher for unequal energies of the two positrons than for equal energies, as expected physically.Comment: 14 pages, 13 figure
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