Cable-driven parallel robots(CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several adv...Cable-driven parallel robots(CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several advantages, including larger workspaces, higher payload-to-weight ratio and lower manufacturing costs rather than rigid-link robots. In this paper, the history of the development of CDPRs is introduced and several successful latest application cases of CDPRs are presented. The theory development of CDPRs is introduced focusing on design, performance analysis and control theory. Research on CDPRs gains wide attention and is highly motivated by the modern engineering demand for large load capacity and workspace. A number of exciting advances in CDPRs are summarized in this paper since it is proposed in the 1980 s, which points to a fruitful future both in theory and application. In order to meet the increasing requirements of robot in different areas, future steps foresee more in-depth research and extension applications of CDPRs including intelligent control, composite materials, integrated and reconfigurable design.展开更多
Hydrological models are very useful tools for evaluating water resources, and the hydroclimatic hazards associated with the water cycle. However, their calibration and validation require the use of performance criteri...Hydrological models are very useful tools for evaluating water resources, and the hydroclimatic hazards associated with the water cycle. However, their calibration and validation require the use of performance criteria which choice is not straightforward. This paper aims to evaluate the influence of the performance criteria on water balance components and water extremes using two global rainfall-runoff models (HBV and GR4J) over the Ouémé watershed at the Bonou and Savè outlets. Three (3) Efficacy criteria (Nash, coefficient of determination, and KGE) were considered for calibration and validation. The results show that the Nash criterion provides a good assessment of the simulation of the different parts of the hydrograph. KGE is better for simulating peak flows and water balance elements than other efficiency criteria. This study could serve as a basis for the choice of performance criteria in hydrological modelling.展开更多
In this paper, we present a novel approach to model user request patterns in the World Wide Web. Instead of focusing on the user traffic for web pages, we capture the user interaction at the object level of the web pa...In this paper, we present a novel approach to model user request patterns in the World Wide Web. Instead of focusing on the user traffic for web pages, we capture the user interaction at the object level of the web pages. Our framework model consists of three sub-models: one for user file access, one for web pages, and one for storage servers. Web pages are assumed to consist of different types and sizes of objects, which are characterized using several categories: articles, media, and mosaics. The model is implemented with a discrete event simulation and then used to investigate the performance of our system over a variety of parameters in our model. Our performance measure of choice is mean response time and by varying the composition of web pages through our categories, we find that our framework model is able to capture a wide range of conditions that serve as a basis for generating a variety of user request patterns. In addition, we are able to establish a set of parameters that can be used as base cases. One of the goals of this research is for the framework model to be general enough that the parameters can be varied such that it can serve as input for investigating other distributed applications that require the generation of user request access patterns.展开更多
The Pan-Eurasian Experiment Modelling Platform(PEEX-MP)is one of the key blocks of the PEEX Research Programme.The PEEX MP has more than 30 models and is directed towards seamless envir-onmental prediction.The main fo...The Pan-Eurasian Experiment Modelling Platform(PEEX-MP)is one of the key blocks of the PEEX Research Programme.The PEEX MP has more than 30 models and is directed towards seamless envir-onmental prediction.The main focus area is the Arctic-boreal regions and China.The models used in PEEX-MP cover several main components of the Earth’s system,such as the atmosphere,hydrosphere,pedosphere and biosphere,and resolve the physicalchemicalbiological processes at different spatial and temporal scales and resolutions.This paper introduces and discusses PEEX MP multi-scale modelling concept for the Earth system,online integrated,forward/inverse,and socioeconomical modelling,and other approaches with a particular focus on applications in the PEEX geographical domain.The employed high-performance com-puting facilities,capabilities,and PEEX dataflow for modelling results are described.Several virtual research platforms(PEEXView,Virtual Research Environment,Web-based Atlas)for handling PEEX modelling and observational results are introduced.The over-all approach allows us to understand better physical-chemicalbiological processes,Earth’s system interactions and feedbacks and to provide valuable information for assessment studies on evaluating risks,impact,consequences,etc.for population,envir-onment and climate in the PEEX domain.This work was also one of the last projects of Prof.Sergej Zilitinkevich,who passed away on 15 February 2021.Since the finalization took time,the paper was actually submitted in 2023 and we could not argue that the final paper text was agreed with him.展开更多
Wind energy has emerged as a promising renewable energy source and wind turbine technology has developed rapidly in recent years.Improved wind turbine performance depends heavily on the design and optimization of wind...Wind energy has emerged as a promising renewable energy source and wind turbine technology has developed rapidly in recent years.Improved wind turbine performance depends heavily on the design and optimization of wind blades.This work offers a critical evaluation of the state of the art in the field of numerical modelling and simulation analysis,which have become crucial for the design and optimization of wind blades.The evaluation of the literature includes considerable research on the application of numerical methods for the structural and aerodynamic performance of wind blades under various operating situations,as well as for analysis and optimization of wind blades.The article illustrates how numerical techniques can be used to analyse wind blade performance and maximize design efficiency.The study of blade performance under various wind conditions has also been made possible through the use of simulation analysis,thus enhancing the efficiency and dependability of wind turbines.Improvements in wind turbine efficiency and dependability,and ultimately the move towards a more sustainable energy future,will be greatly helpful for the development of numerical modelling and simulation techniques.展开更多
China Energy’s National Institute of Clean-and-Low-Carbon Energy(NICE)is developing a Power Plant Smart Management(PPSM)platform that employs digital-twin technology to undertake techno-economic modelling analysis on...China Energy’s National Institute of Clean-and-Low-Carbon Energy(NICE)is developing a Power Plant Smart Management(PPSM)platform that employs digital-twin technology to undertake techno-economic modelling analysis on China Energy’s existing coal-fired power-plant units and explore cost-effective solutions to improve those plant units’thermal efficiencies and operating performance.This paper presents a case study of PPSM on a 320-MWe coal-fired thermal power-plant unit,demonstrating how the digital-twin technology was employed to explore and analyse optimization solutions.Various optimization solutions and their cost-effectiveness were assessed using the digital-twin-modelling analysis;the results indicated the optimization solutions are expected to improve the plant unit’s operating efficiency and reduce its current electricity-generation coal consumption by up to 3.5 g/kWh standard coal equivalent(sce),worth annual fuel-cost savings of approximately 4 million RMB for a single unit or 8 million RMB for the two identical 320-MWe units that the power plant currently operates.The digital twin was also employed to assess the power-plant unit’s operating economics during both summer and winter.In summer,when the unit operates in electricity-generation-only mode,the unit’s operating thermal efficiency could drop by up to 6%points following the grid demand of load changes from 100%maximum continuous rating(MCR)down to 30% MCR,resulting in an~45 RMB/MWh increase of electricity-generation cost.In winter,when the unit operates in combined heat and power(CHP)cogeneration mode,for the same boiler load,the CHP operation increases the plant unit’s operating profit with increasing district-heating duty,although the relative profit gain from the CHP cogeneration could start to decrease when the district-heating steam-extraction flow increases to a certain point that varies depending on the market prices of heat and electricity,while the fuel cost was found to be equivalent to~50% of the unit’s total CHP income co展开更多
The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g ...The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g for specific scientific experiments.MAIS is mainly composed of a stator and a floater,and payloads are mounted on the floater.Sensing relative motion with respect to the stator fixed on the spacecraft,the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators.This isolation results in a high-level microgravity environment.Before MAIS was launched into space,its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight.This article first presents an overview of the MAIS’s hardware system,particularly system structure,measurement sensors,and control actuators.Its system dynamics,state estimation,and control laws are then discussed,followed by the results of computer simulation and engineering tests,including the test of the six-degree-of-freedom motion by aircraft parabolic flight.Simulation and test results verify the accuracy of the control strategy design,effectiveness of the control algorithms,and performance of the entire control system,paving the way for operation of MAIS in space.This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices.These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.展开更多
Fast high-precision patient-specific vascular tissue and geometric structure reconstruction is an essential task for vascular tissue engineering and computer-aided minimally invasive vascular disease diagnosis and sur...Fast high-precision patient-specific vascular tissue and geometric structure reconstruction is an essential task for vascular tissue engineering and computer-aided minimally invasive vascular disease diagnosis and surgery.In this paper,we present an effective vascular geometry reconstruction technique by representing a highly complicated geometric structure of a vascular system as an implicit function.By implicit geometric modelling,we are able to reduce the complexity and level of difficulty of this geometric reconstruction task and turn it into a parallel process of reconstructing a set of simple short tubular-like vascular sections,thanks to the easy-blending nature of implicit geometries on combining implicitly modelled geometric forms.The basic idea behind our technique is to consider this extremely difficult task as a process of team exploration of an unknown environment like a cave.Based on this idea,we developed a parallel vascular modelling technique,called Skeleton Marching,for fast vascular geometric reconstruction.With the proposed technique,we first extract the vascular skeleton system from a given volumetric medical image.A set of sub-regions of a volumetric image containing a vascular segment is then identified by marching along the extracted skeleton tree.A localised segmentation method is then applied to each of these sub-image blocks to extract a point cloud from the surface of the short simple blood vessel segment contained in the image block.These small point clouds are then fitted with a set of implicit surfaces in a parallel manner.A high-precision geometric vascular tree is then reconstructed by blending together these simple tubular-shaped implicit surfaces using the shape-preserving blending operations.Experimental results show the time required for reconstructing a vascular system can be greatly reduced by the proposed parallel technique.展开更多
This paper deals with the evaluation of the Coefficient of Performance (COP) of solar adsorption refrigeration. In the literature, simulation models to predict the thermal behaviour and the coefficient of performance ...This paper deals with the evaluation of the Coefficient of Performance (COP) of solar adsorption refrigeration. In the literature, simulation models to predict the thermal behaviour and the coefficient of performance of these systems are uncommon. This is why we suggest a model to simulate the operation of the machine in a typical hot and dry climate of the city of Ouagadougou. The objective is to provide a model for calculating the COP from the measurement of the ambient temperature and the irradiation of a given site. Starting from mathematical modelling, a resolution and simulation were made with COMSOL software based on the Dubinin-Astakhov adsorption model, the heat transfer balance equations, and the Linear Driving Force (LDF) model to describe the thermal behaviour of the system. A one-week measurement sequence on the adsorption solar refrigerator at the Albert Schweitzer Ecological Centre (CEAS) validated the numerical results. The measurement shows that for the days with high sunshine, the temperature of the reaction medium reaches 110°C, and the pressure reaches 500 mbar. This leads to a production of cold that allows it to reach the temperature of -5°C at the evaporator. Under these conditions, the COP is worth 14%. These results are obtained both by numerical simulation using the COMSOL 5.1 software and after a measurement session on the solar refrigerator available to the CEAS. We obtained an experimental and theoretical coefficient of performance varying between 9% and 14% with a difference of between 0% and 3%. We conclude that our model is suitable to estimate the COP of any device based on its thermal properties, the ambient temperature and the irradiation of a given site.展开更多
The two-phase thermosyphon loop is an efficient solution for space cooling. This paper presents the simulation results of numerical studies on the heat transfer and thermal performance of a two-phase thermosiphon loop...The two-phase thermosyphon loop is an efficient solution for space cooling. This paper presents the simulation results of numerical studies on the heat transfer and thermal performance of a two-phase thermosiphon loop for passive air-conditioning of a house. The fluid considered in this study is methanol, which is compatible with copper and is environmentally friendly. These numerical results show that the temperature at the evaporator wall drops from 23<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C to 13<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and increases at the condenser. The solar flux density has a strong influence on the condenser temperature. The mass flow rates and masses at the evaporator and condenser increase with temperature. The variation of evaporating and condensing temperature affects the performance of the system. For a constant evaporating and condensing temperature of 2<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and 29<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, the COP is 0.77 and 0.84 respectively. With these results, the use of the two-phase thermosyphon loop in air conditioning is possible to obtain a thermal comfort of the occupants acceptable by the standards but with a large exchange surface of the evaporator.展开更多
The paper investigates the long-term seismic behaviour of an underground reinforced concrete(RC)metro tunnel in Santiago,Chile,considering the combined effects of chloride-induced corrosion and cumulative,low-amplitud...The paper investigates the long-term seismic behaviour of an underground reinforced concrete(RC)metro tunnel in Santiago,Chile,considering the combined effects of chloride-induced corrosion and cumulative,low-amplitude seismic shaking on the structure’s performance.The soil-tunnel response is evaluated with the aid of transient,nonlinear finite element analysis using a two-dimensional(2D)plane strain numerical model that adopts advanced nonlinear models for the simulation of soil and concrete plasticity and the dynamic stiffness behaviour.The effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and strength.The study illustrates the influence of ageing and repeated seismic shaking on lining deformation,crack development,and the modal characteristics of the intact and degrading systems.The results indicate that multiple lowamplitude events drive the non-degrading RC tunnel beyond its elastic regime without significant structural response consequences.A noticeable impact of corrosion deterioration on the structure’s seismic performance is revealed,increasing with the number and intensity of earthquake events.Two different tunnel embedment depths are comparatively assessed.The analyses demonstrate larger coseismic section convergence in the case of the deeper tunnel,yet a less pronounced effect of ageing and successive seismic loading compared to the shallow section,which is evident in the RC lining cracks at the end of shaking.展开更多
In this research, we have projected and carried out a novel fishbone network that shows better performance in the term of minimizing the packet delay with respect to sink speed. Previous study implies that sector angl...In this research, we have projected and carried out a novel fishbone network that shows better performance in the term of minimizing the packet delay with respect to sink speed. Previous study implies that sector angle affects greatly on designing fishbone network. Finite Set of nodes arranges to sense the physical condition of any system is called wireless sensor. Our designed fishbone network can be potentially applied for a wireless sensing system to formulate a whole network. The network is a novel design which has been finalized by comparing sector angle. Analysis takes place by varying packet delay according to sink speed. Future analysis takes place for Quality of Service (QoS) and Quality of Experience (QoE). Latency of Packet and its size is the measurement criteria of any network or service is called Quality of Service (QoS). On the other hand the user experience of using the designed network is called Quality of Experience (QoE). Our designed network has been analyzed in TCP Tracer to find out the latency or packet delay for different users. The user data has been shorted and equated among them for latency with different no of packets. Our proposed spiral fishbone network shows better QoS and QoE. In future more nodes can be added to design extended fishbone network for wireless.展开更多
Decision making is one of the important activities of the managerial problems. Scientific methodology for quantitative techniques is an essential tool in the contemporary decision making protocols. In this paper an at...Decision making is one of the important activities of the managerial problems. Scientific methodology for quantitative techniques is an essential tool in the contemporary decision making protocols. In this paper an attempt is made to develop a stochastic model on manager’s performance appraisal. Managerial choice among the available options for decision making is formulated to obtain the stochastic process, to derive the model and to obtain statistical measures. Numerical illustrations are provided for understanding the managerial performance and its evaluation. This study is useful to assess the abilities of an employee by his/her employer. Development of Desktop automations to this study will open a wide spectrum of dynamic Decision Support Systems.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51605126,51575150,91748109)
文摘Cable-driven parallel robots(CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several advantages, including larger workspaces, higher payload-to-weight ratio and lower manufacturing costs rather than rigid-link robots. In this paper, the history of the development of CDPRs is introduced and several successful latest application cases of CDPRs are presented. The theory development of CDPRs is introduced focusing on design, performance analysis and control theory. Research on CDPRs gains wide attention and is highly motivated by the modern engineering demand for large load capacity and workspace. A number of exciting advances in CDPRs are summarized in this paper since it is proposed in the 1980 s, which points to a fruitful future both in theory and application. In order to meet the increasing requirements of robot in different areas, future steps foresee more in-depth research and extension applications of CDPRs including intelligent control, composite materials, integrated and reconfigurable design.
文摘Hydrological models are very useful tools for evaluating water resources, and the hydroclimatic hazards associated with the water cycle. However, their calibration and validation require the use of performance criteria which choice is not straightforward. This paper aims to evaluate the influence of the performance criteria on water balance components and water extremes using two global rainfall-runoff models (HBV and GR4J) over the Ouémé watershed at the Bonou and Savè outlets. Three (3) Efficacy criteria (Nash, coefficient of determination, and KGE) were considered for calibration and validation. The results show that the Nash criterion provides a good assessment of the simulation of the different parts of the hydrograph. KGE is better for simulating peak flows and water balance elements than other efficiency criteria. This study could serve as a basis for the choice of performance criteria in hydrological modelling.
文摘In this paper, we present a novel approach to model user request patterns in the World Wide Web. Instead of focusing on the user traffic for web pages, we capture the user interaction at the object level of the web pages. Our framework model consists of three sub-models: one for user file access, one for web pages, and one for storage servers. Web pages are assumed to consist of different types and sizes of objects, which are characterized using several categories: articles, media, and mosaics. The model is implemented with a discrete event simulation and then used to investigate the performance of our system over a variety of parameters in our model. Our performance measure of choice is mean response time and by varying the composition of web pages through our categories, we find that our framework model is able to capture a wide range of conditions that serve as a basis for generating a variety of user request patterns. In addition, we are able to establish a set of parameters that can be used as base cases. One of the goals of this research is for the framework model to be general enough that the parameters can be varied such that it can serve as input for investigating other distributed applications that require the generation of user request access patterns.
基金the last projects of Prof.Sergej Zilitinkevich(1936-2021)The financial support was/is provided through multiple projects related to the Pan-Eurasian EXperiment(PEEX)programme including Academy of Finland projects-ClimEco(grant#314798/799)+6 种基金ACCC(grant#337549)HEATCOST(grant#334798)European Union’s Horizon 2020 Programme projects-iCUPE under ERA-PLANET(grant#689443),INTAROS(grant#727890),EXHAUSTION(grant#820655),CRiceS(grant#101003826),RI-URBANS(grant#101036245)Horizon Europe project FOCI(grant#101056783)Erasmus+Programme projects-ECOIMPACT(grant#561975-EPP-1-2015-1-FI-EPPKA2-CBHE-JP),ClimEd(grant#619285-EPP-1-2020-1-FIEPPKA2-CBHE-JP)The Norwegian Research Council INTPART educational and networking project(322317/H30):URban Sustainability in Action:Multi-disciplinary Approach through Jointly Organized Research schoolsand the EEA project(Contract No.2020TO01000219):Turbulent-resolving urban modelling of air quality and thermal comfort(TURBAN).
文摘The Pan-Eurasian Experiment Modelling Platform(PEEX-MP)is one of the key blocks of the PEEX Research Programme.The PEEX MP has more than 30 models and is directed towards seamless envir-onmental prediction.The main focus area is the Arctic-boreal regions and China.The models used in PEEX-MP cover several main components of the Earth’s system,such as the atmosphere,hydrosphere,pedosphere and biosphere,and resolve the physicalchemicalbiological processes at different spatial and temporal scales and resolutions.This paper introduces and discusses PEEX MP multi-scale modelling concept for the Earth system,online integrated,forward/inverse,and socioeconomical modelling,and other approaches with a particular focus on applications in the PEEX geographical domain.The employed high-performance com-puting facilities,capabilities,and PEEX dataflow for modelling results are described.Several virtual research platforms(PEEXView,Virtual Research Environment,Web-based Atlas)for handling PEEX modelling and observational results are introduced.The over-all approach allows us to understand better physical-chemicalbiological processes,Earth’s system interactions and feedbacks and to provide valuable information for assessment studies on evaluating risks,impact,consequences,etc.for population,envir-onment and climate in the PEEX domain.This work was also one of the last projects of Prof.Sergej Zilitinkevich,who passed away on 15 February 2021.Since the finalization took time,the paper was actually submitted in 2023 and we could not argue that the final paper text was agreed with him.
基金funded by the National Key Research and Development Program of China(No.2020YFC1910000).
文摘Wind energy has emerged as a promising renewable energy source and wind turbine technology has developed rapidly in recent years.Improved wind turbine performance depends heavily on the design and optimization of wind blades.This work offers a critical evaluation of the state of the art in the field of numerical modelling and simulation analysis,which have become crucial for the design and optimization of wind blades.The evaluation of the literature includes considerable research on the application of numerical methods for the structural and aerodynamic performance of wind blades under various operating situations,as well as for analysis and optimization of wind blades.The article illustrates how numerical techniques can be used to analyse wind blade performance and maximize design efficiency.The study of blade performance under various wind conditions has also been made possible through the use of simulation analysis,thus enhancing the efficiency and dependability of wind turbines.Improvements in wind turbine efficiency and dependability,and ultimately the move towards a more sustainable energy future,will be greatly helpful for the development of numerical modelling and simulation techniques.
文摘China Energy’s National Institute of Clean-and-Low-Carbon Energy(NICE)is developing a Power Plant Smart Management(PPSM)platform that employs digital-twin technology to undertake techno-economic modelling analysis on China Energy’s existing coal-fired power-plant units and explore cost-effective solutions to improve those plant units’thermal efficiencies and operating performance.This paper presents a case study of PPSM on a 320-MWe coal-fired thermal power-plant unit,demonstrating how the digital-twin technology was employed to explore and analyse optimization solutions.Various optimization solutions and their cost-effectiveness were assessed using the digital-twin-modelling analysis;the results indicated the optimization solutions are expected to improve the plant unit’s operating efficiency and reduce its current electricity-generation coal consumption by up to 3.5 g/kWh standard coal equivalent(sce),worth annual fuel-cost savings of approximately 4 million RMB for a single unit or 8 million RMB for the two identical 320-MWe units that the power plant currently operates.The digital twin was also employed to assess the power-plant unit’s operating economics during both summer and winter.In summer,when the unit operates in electricity-generation-only mode,the unit’s operating thermal efficiency could drop by up to 6%points following the grid demand of load changes from 100%maximum continuous rating(MCR)down to 30% MCR,resulting in an~45 RMB/MWh increase of electricity-generation cost.In winter,when the unit operates in combined heat and power(CHP)cogeneration mode,for the same boiler load,the CHP operation increases the plant unit’s operating profit with increasing district-heating duty,although the relative profit gain from the CHP cogeneration could start to decrease when the district-heating steam-extraction flow increases to a certain point that varies depending on the market prices of heat and electricity,while the fuel cost was found to be equivalent to~50% of the unit’s total CHP income co
基金The authors gratefully acknowledge DLR for providing us the opportunity to attend the 27th parabolic flight campaign and Novespace for the support for the test of MAIS by the Airbus A310 ZERO-GThe authors would also like to thank Weijia Ren,Xiaoru Sang,Shimeng Lv,Peng Yang,Yu-e Gao,Lingcai Song,Mengxi Yu,Boqi Kang,Yanlin Zhou,and Anping Wang,who have contributed significantly to the MAIS project.
文摘The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g for specific scientific experiments.MAIS is mainly composed of a stator and a floater,and payloads are mounted on the floater.Sensing relative motion with respect to the stator fixed on the spacecraft,the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators.This isolation results in a high-level microgravity environment.Before MAIS was launched into space,its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight.This article first presents an overview of the MAIS’s hardware system,particularly system structure,measurement sensors,and control actuators.Its system dynamics,state estimation,and control laws are then discussed,followed by the results of computer simulation and engineering tests,including the test of the six-degree-of-freedom motion by aircraft parabolic flight.Simulation and test results verify the accuracy of the control strategy design,effectiveness of the control algorithms,and performance of the entire control system,paving the way for operation of MAIS in space.This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices.These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.
基金partly supported by National Natural Science Foundation of China (No. 61502402)the Fundamental Research Funds for the Central Universities (No. 20720180073)
文摘Fast high-precision patient-specific vascular tissue and geometric structure reconstruction is an essential task for vascular tissue engineering and computer-aided minimally invasive vascular disease diagnosis and surgery.In this paper,we present an effective vascular geometry reconstruction technique by representing a highly complicated geometric structure of a vascular system as an implicit function.By implicit geometric modelling,we are able to reduce the complexity and level of difficulty of this geometric reconstruction task and turn it into a parallel process of reconstructing a set of simple short tubular-like vascular sections,thanks to the easy-blending nature of implicit geometries on combining implicitly modelled geometric forms.The basic idea behind our technique is to consider this extremely difficult task as a process of team exploration of an unknown environment like a cave.Based on this idea,we developed a parallel vascular modelling technique,called Skeleton Marching,for fast vascular geometric reconstruction.With the proposed technique,we first extract the vascular skeleton system from a given volumetric medical image.A set of sub-regions of a volumetric image containing a vascular segment is then identified by marching along the extracted skeleton tree.A localised segmentation method is then applied to each of these sub-image blocks to extract a point cloud from the surface of the short simple blood vessel segment contained in the image block.These small point clouds are then fitted with a set of implicit surfaces in a parallel manner.A high-precision geometric vascular tree is then reconstructed by blending together these simple tubular-shaped implicit surfaces using the shape-preserving blending operations.Experimental results show the time required for reconstructing a vascular system can be greatly reduced by the proposed parallel technique.
文摘This paper deals with the evaluation of the Coefficient of Performance (COP) of solar adsorption refrigeration. In the literature, simulation models to predict the thermal behaviour and the coefficient of performance of these systems are uncommon. This is why we suggest a model to simulate the operation of the machine in a typical hot and dry climate of the city of Ouagadougou. The objective is to provide a model for calculating the COP from the measurement of the ambient temperature and the irradiation of a given site. Starting from mathematical modelling, a resolution and simulation were made with COMSOL software based on the Dubinin-Astakhov adsorption model, the heat transfer balance equations, and the Linear Driving Force (LDF) model to describe the thermal behaviour of the system. A one-week measurement sequence on the adsorption solar refrigerator at the Albert Schweitzer Ecological Centre (CEAS) validated the numerical results. The measurement shows that for the days with high sunshine, the temperature of the reaction medium reaches 110°C, and the pressure reaches 500 mbar. This leads to a production of cold that allows it to reach the temperature of -5°C at the evaporator. Under these conditions, the COP is worth 14%. These results are obtained both by numerical simulation using the COMSOL 5.1 software and after a measurement session on the solar refrigerator available to the CEAS. We obtained an experimental and theoretical coefficient of performance varying between 9% and 14% with a difference of between 0% and 3%. We conclude that our model is suitable to estimate the COP of any device based on its thermal properties, the ambient temperature and the irradiation of a given site.
文摘The two-phase thermosyphon loop is an efficient solution for space cooling. This paper presents the simulation results of numerical studies on the heat transfer and thermal performance of a two-phase thermosiphon loop for passive air-conditioning of a house. The fluid considered in this study is methanol, which is compatible with copper and is environmentally friendly. These numerical results show that the temperature at the evaporator wall drops from 23<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C to 13<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and increases at the condenser. The solar flux density has a strong influence on the condenser temperature. The mass flow rates and masses at the evaporator and condenser increase with temperature. The variation of evaporating and condensing temperature affects the performance of the system. For a constant evaporating and condensing temperature of 2<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and 29<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, the COP is 0.77 and 0.84 respectively. With these results, the use of the two-phase thermosyphon loop in air conditioning is possible to obtain a thermal comfort of the occupants acceptable by the standards but with a large exchange surface of the evaporator.
基金supported by the Newton Fund:EPSRC,UK&CONICYT,Chile(EPSRC Grant No.EP/N03435X/1)the Extending Shaking Tunnel Vision project funded jointly by the Global Challenge Research Fund(GCRF)and the Higher Education Funding Council for England(HEFCE)under account number 95541229,both led by the University of Leeds.
文摘The paper investigates the long-term seismic behaviour of an underground reinforced concrete(RC)metro tunnel in Santiago,Chile,considering the combined effects of chloride-induced corrosion and cumulative,low-amplitude seismic shaking on the structure’s performance.The soil-tunnel response is evaluated with the aid of transient,nonlinear finite element analysis using a two-dimensional(2D)plane strain numerical model that adopts advanced nonlinear models for the simulation of soil and concrete plasticity and the dynamic stiffness behaviour.The effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and strength.The study illustrates the influence of ageing and repeated seismic shaking on lining deformation,crack development,and the modal characteristics of the intact and degrading systems.The results indicate that multiple lowamplitude events drive the non-degrading RC tunnel beyond its elastic regime without significant structural response consequences.A noticeable impact of corrosion deterioration on the structure’s seismic performance is revealed,increasing with the number and intensity of earthquake events.Two different tunnel embedment depths are comparatively assessed.The analyses demonstrate larger coseismic section convergence in the case of the deeper tunnel,yet a less pronounced effect of ageing and successive seismic loading compared to the shallow section,which is evident in the RC lining cracks at the end of shaking.
文摘In this research, we have projected and carried out a novel fishbone network that shows better performance in the term of minimizing the packet delay with respect to sink speed. Previous study implies that sector angle affects greatly on designing fishbone network. Finite Set of nodes arranges to sense the physical condition of any system is called wireless sensor. Our designed fishbone network can be potentially applied for a wireless sensing system to formulate a whole network. The network is a novel design which has been finalized by comparing sector angle. Analysis takes place by varying packet delay according to sink speed. Future analysis takes place for Quality of Service (QoS) and Quality of Experience (QoE). Latency of Packet and its size is the measurement criteria of any network or service is called Quality of Service (QoS). On the other hand the user experience of using the designed network is called Quality of Experience (QoE). Our designed network has been analyzed in TCP Tracer to find out the latency or packet delay for different users. The user data has been shorted and equated among them for latency with different no of packets. Our proposed spiral fishbone network shows better QoS and QoE. In future more nodes can be added to design extended fishbone network for wireless.
文摘Decision making is one of the important activities of the managerial problems. Scientific methodology for quantitative techniques is an essential tool in the contemporary decision making protocols. In this paper an attempt is made to develop a stochastic model on manager’s performance appraisal. Managerial choice among the available options for decision making is formulated to obtain the stochastic process, to derive the model and to obtain statistical measures. Numerical illustrations are provided for understanding the managerial performance and its evaluation. This study is useful to assess the abilities of an employee by his/her employer. Development of Desktop automations to this study will open a wide spectrum of dynamic Decision Support Systems.
