检索结果-南通市图书馆

Flight strategy optimization for high-altitude long-endurance solar-powered aircraft based on Gauss pseudo-spectral method

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2019年第10期32卷 2286-2298页

作者： Shaoqi WANG Dongli MA Muqing YANG Liang ZHANG Guanxiong LI School of Aeronautic Science and Engineering Beihang University

solar-powered aircraft have attracted great attention owing to their potential for longendurance flight and wide application prospects.Due to the particularity of energy system,flight strategy optimization is a significant way to enhance the flight performance for solar-powered aircraft.In this study,a flight strategy optimization model for high-altitude long-endurance solar-powered aircraft was proposed.This model consists of three-dimensional kinematic model,aerodynamic model,energy collection model,energy store model and energy loss model.To solve the nonlinear optimal control problem with process constraints and terminal constraints,Gauss pseudo-spectral method was employed to discretize the state equations and constraint equations.Then a typical mission flying from given initial point to given final point within a time interval was considered.Results indicate that proper changes of the attitude angle contribute to increasing the energy gained by photovoltaic cells.Utilization of gravitational potential energy can partly take the role of battery pack.Integrating these two measures,the optimized flight strategy can improve the final state of charge compared with current constant-altitude constant-velocity strategy.The optimized strategy brings more profits on condition of lower sunlight intensity and shorter daytime.

关键词： Battery pack Flight strategy optimization Gauss pseudo-spectral method Photovoltaic cell solar-powered aircraft

Study on cyclic characteristics of the solar-powered adsorption cooling system

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第6期52卷 1551-1562页

作者： JingYi Wu Sheng Li YanFei Hu Institute of Refrigeration and Cryogenics Shanghai Jiao Tong University Shanghai 200240 China

According to the typical variable heat source of solar energy and the unsteady adsorption process of adsorption chiller,the research of cyclic transient characteristics of the solar-powered adsorption cooling system is presented in this work.A mathematic model of the whole system including the model of adsorption chiller,which reveals the transient operation process of the solar-powered adsorption cooling system,is developed and verified by experimental data.On the basis of the simulated results,the transient characteristics and the overall performance of the system,not only in the traditional open cycle mode but also in closed cycle mode,are both analyzed theoretically.Furthermore,the influence of parameters matching of components configuration and operation process on the cyclic characteristics of the system,such as the solar collector area,the water tank capacity and the chiller startup temperature,are discussed.The research in this work may play a very important role in optimizing the system cyclic process and improving the system adaptability especially under the condition of variable heat source.

关键词： solar-powered cooling system adsorption chiller unsteady state cyclic characteristics

Biologging is suspect to cause corneal opacity in two populations of wild living Northern Bald Ibises (Geronticus eremita)

在线全文

学校读者我要写书评

暂无评论

Avian Research 2020年第4期11卷 412-420页

作者： Johannes Fritz Barbara Eberhard Corinna Esterer Bernhard Goenner Daniela Trobe Markus Unsoeld Bernhard Voelkl Helena Wehner Alexandra Scope Waldrappteam LIFE Northern Bald Ibis6162 MuttersAustria Department of Behavioural and Cognitive Biology University of ViennaViennaAustria Veterinary University Vienna ViennaAustria University of Bern Vetsuisse FacultyBernSwitzerland Bavarian State Collection of Zoology MunichGermany

Background:In this paper,we present evidence that biologging is strongly correlated with eye irritation,with sometimes severely impairing effects.A migratory population of the Northern Bald Ibis(Geronticus eremita,NBI)is reintroduced in Europe,in course of a LIFE+project.Since 2014,all individuals have been equipped with GPS-devices.Remote monitoring allows the implementation of focussed measures against major mortality causes.Methods:Initially all birds carried battery-powered devices,fixed on the lower back of the birds.Since 2016 an increasing amount of birds has been equipped with solar-powered devices,fixed on the upper back,the more sunexposed position.In 2016,we observed opacity in the cornea of one eye(unilateral corneal opacity;UCO)during a regular health monitoring for the first time.Results:By 2018,a total of 25 birds were affected by UCO,with varying intensity up to blindness.Clinical examination of the birds revealed no clear cause for the symptoms.However,only birds carrying a device on the upper back were affected(2017 up to 70%of this group).In contrast,none of the birds carrying devices on the lower back ever showed UCO symptoms.This unexpected relationship between tagging and UCO was discovered in 2017.After we took countermeasures by removing the device or repositioning it on the lower back,we observed an immediate reduction of the incidence rate without any new cases reported since January 2019.NBI roost with their head on the back,one eye closely placed to the device if it was positioned on the upper back.Thus,we conclude that the most parsimonious explanation for the symptomatology is either a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the GSM module of the device or a repetitive slight mechanical irritation of the corneal surface.Concrete evidence is missing so far.Meanwhile,cases of UCO were found in another NBI population.Conclusion:Our observations indicate that further research in the fast-growing field of biologging is urgently needed.T

关键词： Blindness Electromagnetic radiation Endangered bird species Eye opacity GPS-devices Mechanical irritation Reintroduction solar-powered

Optimization of Desiccant Absorption System Using a Genetic Algorithm

在线全文

学校读者我要写书评

暂无评论

Journal of Software Engineering and Applications 2011年第9期4卷 527-533页

作者： Ayman A. Aly 不详

Optimization of the open absorption desiccant cooling system has been carried out in the present work. A finite difference method is used to simulate the combined heat and mass transfer processes that occur in the liquid desiccant regenerator which uses calcium chloride (CaCl2) solution as the working desiccant. The source of input heat is assumed to be the total radiation incident on a tilted surface. The system of equations is solved using the Matlab-Simulink platform. The effect of the important parameters, namely the regenerator length, desiccant solution flow rate and concentration, and air flow rates, on the performance of the system is investigated. In order to optimize the system performance, a genetic algorithm technique has been applied. The system coefficient of performance COP has been maximized for different design parameters. It has been found that the maximum values of COP could be obtained for different combinations of regenerator length solution flow rate and air flow rate. Therefore, it is essential to select the design parameters for each ambient condition to maximize the performance of the system.

关键词： Genetic Algorithm Modeling Optimization solar-powered Desiccant