3,578 research outputs found

    Viability study of sailing propulsion combined with a conventional system

    Full text link
    For many years now, sails have been used as a propulsion system. At present, they are restricted to recreational/sport crafts since the appearance of the first steam vessels in the beginning of the 19 th century. But in the last years, due to the increase of fuel price and the pollution of the environment, it is being studied the possibility to introduce again the sail as a propulsive method combined with other conventional systems. In this paper, it is studied the viability of using a sail as a propellant with other conventional systems of propulsion. After considering the concept of apparent wind, the range of use of this complementary propulsion is presented. The calculation methodology, the numerical simulations and the wind inputs from a specific route are also included

    Dark matter, extra-terrestrial gamma-rays and the MSSM: a viability study

    Full text link
    We fit the γ\gamma-ray excess from the galactic centre (GC) in terms of parameters of the minimal supersymmetric standard model (MSSM). Consistency with other γ\gamma-ray observation, such as those from dwarf spheroidal galaxies, is also ensured, in addition to the constraints from direct dark matter search. Furthermore, we expect the contribution to the relic density from the MSSM dark mater candidate, namely, the lightest neutralino, should not go below the stipulated value; otherwise it will amount to going beyond the MSSM by including some additional dark matter source. After a detailed scan of the parameter space in terms of four representative types of particle spectra, we identify the ones that are best fit to the observed data. However, these two are somewhat unsatisfactory in terms of χmin2\chi^2_{min} as well as pp-values. In some case(s), the unacceptability of low-χmin2\chi^2_{min} regions due to direct search constraint is responsible for this. In others, the observed shape of the γ\gamma-ray spectrum makes the fits unsatisfactory. The imposed lower limit on relic density, too, has a role to play all along. On the whole, the conclusion is that the MSSM is not a very satisfactory fit for the GC γ\gamma-ray compounded with other cosmological observations and direct search limits.Comment: 40 pages, 16 figures: figures corrected, typos corrected, matches with version published in JCA

    NBA Expansion and Relocation: A Viability Study of Various Cities

    Get PDF
    An examination of possible expansion or relocation sites for the NBA is undertaken using a two-equation system requiring two-stage probit least squares to estimate. The location model forecasts the best cities for an NBA team based on the underlying characteristics of current NBA teams. The results suggest that Louisville, San Diego, Baltimore, St. Louis, and Norfolk appear to be the most promising candidates for relocation or expansion.basketball; NBA; franchise location; probit; regression; econometrics; two-stage

    A viability study for SOFC combined heat and power Energy systems for buildings

    Get PDF
    The main objective of this work is to develop a software tool to perform an techno-economic feasibility analysis of cogeneration systems for electricity and heat production, based on fuel cell technology (FC-CHP). The software tool should provide useful information to the decision makers. Moreover, the developed software will be applied to specific case studies to obtain the main indicators of the economic viability of the system. A FC-CHP system is a technology with potential to change the current paradigm, which consists in obtaining electricity from the power grid and, separately, heat through gas boilers. The method developed in this study allows to carry out a viability analysis over a specific time horizon, based on technical and economic parameters, to size the FC-CHP system and to adapt the calculations to the market conditions of each case study. It is important to consider the market conditions, because the previous works found in the literature remark that the viability of the FC-CHP technology depends on specific factors that vary by country and region. Local economic factors include government policies to support new technologies of distributed generation, that is, generation of electricity at or near where it will be used. Another local factor is the difference in prices between natural gas and electricity ("spark spread"), and the expected evolution of these prices. From the environmental point of view, the composition of the country's power generation mix has influence on the emissions reduction using FC-CHP. The pattern of thermal and electrical energy demand of each specific case also influence, and the relative amount of each one (heat-to-power ratio). The method developed requires a source of energy consumption data, which can be real or simulated. Special attention has been paid to see the impact of few consumption data in the results. A correction has to be made in the results for those situations when only the aggregate monthly or weekly consumption is available for analysis. From heat and electricity consumption data, a Matlab/Simulink model is used to calculate the amount of fuel needed so that the SOFC-CHP system can meet the demand, the amount of thermal energy that should be provided by an additional system (a conventional condensing boiler), as well as the electrical energy to be imported or exported from the electricity grid. The annual results are extrapolated to a time horizon of 10 years, to validate the economic viability of the project. Different operation modes (disconnected or connected to power grid) and operation strategies (heat-driven, power-driven, maximum-driven) of the SOFC-CHP system are analyzed in buildings of the Universitat Politècnica de Catalunya with varied heat-to-power 4 Memòria ratios, to determine the strategy that best suits each case. The results show that the high initial investment is one of the main obstacles to obtain a return on the investment in a reasonable time. However, the cogeneration system is economically viable in some of the studied cases, especially if the building has a heat to power ratio greater than one. The evolution of energy prices also greatly influences in the viability of the project. As for the operation strategies, those following maximum demand and those following electricity demand offer better results than the strategy that follows the thermal demand, because the former cases use the fuel cell throughout the year and can take more advantage of cogeneration

    Organic agriculture program viability study

    Get PDF
    A survey was conducted to determine the viability of offering an organic agriculture program and classes at Western Iowa Tech Community College

    A Viability Study of Photovoltaic Systems

    Get PDF
    Concerns over climate change and other environmental problems highlight a need for a shift toclean and renewable energy. The main objective of this study is to investigate the viability ofphotovoltaic electricity in the southeastern region of the United States. To achieve this goal, twocase studies were conducted involving a large retail store and a recreation center. Historical datarelated to weather conditions, solar energy and power demand were investigated and as a resultgrid-connected photovoltaic systems were designed to provide green energy for these facilities.Several engineering factors that went into the design process as well as economic andenvironmental considerations were thoroughly discussed in this paper. The engineering analysisdeals with factors such as solar radiation, shade evaluations, array orientation, module stringsizing, and estimating energy production. Although a PV system does not emit any pollutionduring operation, manufacturing its various components involve a substantial amount of energy.Thus, the environmental study presented here takes into consideration the energy payback periodin addition to the pollution offsets of the PV system. The economic analysis utilizes capitalbudgeting techniques to determine the net present value and internal rate of return based onestimated cash flows over the expected lifetime of the PV system. Furthermore, the marketanalysis takes into consideration the various assumptions related to the cost and performance ofPV systems such as inverter lifespan, future inverter cost, and module degradation. Theseassumptions, along with the expected trend in the electricity price market, were incorporated intothe cash flow estimates

    Viability study of automobile shredder residue as fuel

    Get PDF
    Car Fluff samples collected from a shredding plant in Italy were classified based on particle size, and three different size fractions were obtained in this way. A comparison between these size fractions and the original light fluff was made from two different points of view: (i) the properties of each size fraction as a fuel were evaluated and (ii) the pollutants evolved when each size fraction was subjected to combustion were studied. The aim was to establish which size fraction would be the most suitable for the purposes of energy recovery. The light fluff analyzed contained up to 50 wt.% fines (particle size < 20 mm). However, its low calorific value and high emissions of polychlorinated dioxins and furans (PCDD/Fs), generated during combustion, make the fines fraction inappropriate for energy recovery, and therefore, landfilling would be the best option. The 50–100 mm fraction exhibited a high calorific value and low PCDD/F emissions were generated when the sample was combusted, making it the most suitable fraction for use as refuse-derived fuel (RDF). Results obtained suggest that removing fines from the original ASR sample would lead to a material product that is more suitable for use as RDF.Support for this work was provided by the Spanish MEC, research project CTQ2008-05520 and by the Valencian Community Government with the research projects Prometeo/2009/043/FEDER

    Clinical Viability Study of Preattentive Visual Search Glaucoma

    Get PDF
    Background/Aim: Previous research has shown that several clinical conditions cause increased pre-attentive visual search (PAVS) times, implying reduced parallel search capabilities in glaucoma, DLB dementia and Parkinson’s disease. The purpose of the research reported here was two-fold • To examine for the first time the effect of a number of variables on PAVS performance including optical blur, age, retinal eccentricity and perceptual learning. Such investigations are designed to elucidate the nature of best clinical practise and to determine whether the test remains viable in the presence of such potentially confounding variables. • To analyse the efficiency of PAVS in cases of established glaucoma: glaucoma suspects and age –matched normals. Such an investigation is designed to determine the differential diagnostic capacity of the current test and to provide diagnostic cut-off performance indices to facilitate clinical categorisation of patients Methods: Suitably configured flicker, motion displacement and orientation pop-out stimuli were presented to subjects on a computer monitor. The subjects’ task was to accurately locate the pop-out target from among 120 distractors on either left or right of the monitor as rapidly as possible. PAVS performance was determined through analysis of the speed of accurate target location and its relation to the individuals’ complex (non-preattentive) reaction time. Results: The current test remains largely resistant to the sensory degradation effects of optical blur and retinal eccentricity. Only the orientation task requires a reasonable level of visual acuity (better than 6/18). The perceptual learning effect is minimal, therefore little practice is required prior to clinical application of the test. The sensory and motor effects of age are rendered negligible through the development of a measure of perceptual search ability. The test therefore remains clinically robust. In relation to glaucomatous neuropathy, the test yields consistently high sensitivity and specificity for each task and thus appears to provide a suitable means of glaucoma detection. Conclusions: All investigations thus far indicate that, at the very least, the test provides a simple, rapid and accurate means of screening for the effects of glaucomatous optic neuropathy. Its capacity to differentiate glaucoma from suspects suggests its diagnostic ability extends beyond that achieved by conventional perimetry. Longitudinal analysis should confirm whether this is true

    NBA Expansion and Relocation: A Viability Study of Various Cities

    Get PDF
    An examination of possible expansion or relocation sites for the NBA is undertaken using a two-equation system requiring two-stage probit least squares to estimate. The location model forecasts the best cities for an NBA team based on the underlying characteristics of current NBA teams. The results suggest that Louisville, San Diego, Baltimore, St. Louis, and Norfolk appear to be the most promising candidates for relocation or expansion

    Characterization and Biocompatibility Study of Nematic and Cholesteryl Liquid Crystals.

    Get PDF
    noIntensive research in bio-engineering has been conducted in the search for flexible biomaterials that could support cell growth and cells attachment. Flexible synthetic materials that support cell growth without the aid of synthetic extracellular matrix proteins are still rare. Cholesteryl liquid crystal containing cholesteryl moieties may have suitable biological affinity. Human keratinocytes (HaCat) were cultured with a nematic liquid crystal and three cholesteryl liquid crystals of different formulation. Subsequently, the trypan blue dye exclusion assay was used to determine cell viability in the liquid crystals. The two classes of liquid crystal were characterized by Differential Scanning Calorimeter (DSC) and polarizing microscope (POM) to understand the nature of the interface material. The cell viability study in medium containing liquid crystals verified that liquid crystals had no effects on cell viability. However, only the surface of cholesteryl liquid crystal has shown affinity to HaCat cells. In addition, cells continued to proliferate in the presence of liquid crystals without a change of medium for eight days. No sign of exothermic and endothermic activities at 370C were observed from the DSC test results for the three samples. Biological and mechanical test result of the cholesteryl liquid crystals has shown that cholesteryl liquid crystals are non toxic and support cell attachment without extracellular matrix protein at very low elasticity
    • …
    corecore