The roundabouts are widely used in China,some of which have central islands as scenic spots.The crosswalks connecting to the central islands,normally full of pedestrians,have negative impact on roundabout capability a...The roundabouts are widely used in China,some of which have central islands as scenic spots.The crosswalks connecting to the central islands,normally full of pedestrians,have negative impact on roundabout capability and pedestrian safety.Therefore,this study proposes a fuzzy cellular automata(FCA)model to explore the safety and efficiency impacts of pedestrian-vehicle conflicts at a two-lane roundabout.To reason the decision-making process of individual drivers before crosswalks,membership functions in the fuzzy inference system were calibrated with field data conducted in Changsha,China.Using specific indicators of efficiency and safety performance,it was shown that circulating vehicles can move smoothly in low traffic flow,but the roundabout system is prone to the traffic congestion if traffic flow reaches to a certain level.Also,the high yielding rate of drivers has a negative impact on the traffic efficiency but can improve pedestrian safety.Furthermore,a pedestrian restriction measure was deduced for the roundabout crosswalk from the FCA model and national guideline of setting traffic lights.展开更多
Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeli...Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeling is given for AC energy-saving control and effectiveness optimization is made. To facilitate the implement of the control and energy saving, priorities have been assigned to the major control steps based on logical reasoning. Forward-looking tree modeling based on FDES has been simplified to help further optimization, and a simple and concrete example has been put forward illustrating energy-saving control in AC system.展开更多
Results of a research about statistical reasoning that six high school teachers developed in a computer environment are presented in this article. A sequence of three activities with the support of software Fathom was...Results of a research about statistical reasoning that six high school teachers developed in a computer environment are presented in this article. A sequence of three activities with the support of software Fathom was presented to the teachers in a course to investigate about the reasoning that teachers develop about the data analysis, particularly about the distribution concept, that involves important concepts such as averages, variability and graphics representations. The design of the activities was planned so that the teachers analyzed quantitative variables separately first, and later made an analysis of a qualitative variable versus a quantitative variable with the objective of establishing comparisons between distributions and use concepts as averages, variability, shape and outliers. The instructions in each activity indicated to the teachers to use all the resources of the software that were necessary to make the complete analysis and respond to certain questions that pretended to capture the type of representations they used to answer. The results indicate that despite the abundance of representations provided by the software, teachers focu,; on the calculation of averages to describe and compare distributions, rather than on the important properties of data such as variability, ：shape and outliers. Many teachers were able to build interesting graphs reflecting important properties of the data, but cannot use them 1：o support data analysis. Hence, it is necessary to extend the teachers＇ understanding on data analysis so they can take advantage of the cognitive potential that computer tools to offer.展开更多
The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlat...The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlations(DCS)and deterministic total enthalpy correlations(DCH).These correlations should be modeled to close the system of equations.In this paper,the distribution of DC in a transonic centrifugal compressor is presented,and its relative importance is revealed.The assumption made by Adamczyk that the pure unsteady fluctuation is significantly smaller than the spatial fluctuation is verified at the impeller-diffuser interface.The decomposition of DCH is also discussed to determine its two different physical mechanisms.Finally,the transport equations in terms of DCS in cylindrical coordinates are derived,and the terms are evaluated to determine the ones that are necessary to model.All these analyses significantly contribute to our model development for DC in centrifugal compressors.展开更多
基金Project(2020YFB1600400)supported by the National Key Research and Development Program of ChinaProject(2019JJ50837)supported by the Natural Science Foundation of Hunan Province,ChinaProject(71801227)supported by the National Natural Science Foundation of China。
文摘The roundabouts are widely used in China,some of which have central islands as scenic spots.The crosswalks connecting to the central islands,normally full of pedestrians,have negative impact on roundabout capability and pedestrian safety.Therefore,this study proposes a fuzzy cellular automata(FCA)model to explore the safety and efficiency impacts of pedestrian-vehicle conflicts at a two-lane roundabout.To reason the decision-making process of individual drivers before crosswalks,membership functions in the fuzzy inference system were calibrated with field data conducted in Changsha,China.Using specific indicators of efficiency and safety performance,it was shown that circulating vehicles can move smoothly in low traffic flow,but the roundabout system is prone to the traffic congestion if traffic flow reaches to a certain level.Also,the high yielding rate of drivers has a negative impact on the traffic efficiency but can improve pedestrian safety.Furthermore,a pedestrian restriction measure was deduced for the roundabout crosswalk from the FCA model and national guideline of setting traffic lights.
基金PhD Programs Foundation of Ministry of Education of China( No.20060255006)Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (No.706024)
文摘Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeling is given for AC energy-saving control and effectiveness optimization is made. To facilitate the implement of the control and energy saving, priorities have been assigned to the major control steps based on logical reasoning. Forward-looking tree modeling based on FDES has been simplified to help further optimization, and a simple and concrete example has been put forward illustrating energy-saving control in AC system.
文摘Results of a research about statistical reasoning that six high school teachers developed in a computer environment are presented in this article. A sequence of three activities with the support of software Fathom was presented to the teachers in a course to investigate about the reasoning that teachers develop about the data analysis, particularly about the distribution concept, that involves important concepts such as averages, variability and graphics representations. The design of the activities was planned so that the teachers analyzed quantitative variables separately first, and later made an analysis of a qualitative variable versus a quantitative variable with the objective of establishing comparisons between distributions and use concepts as averages, variability, shape and outliers. The instructions in each activity indicated to the teachers to use all the resources of the software that were necessary to make the complete analysis and respond to certain questions that pretended to capture the type of representations they used to answer. The results indicate that despite the abundance of representations provided by the software, teachers focu,; on the calculation of averages to describe and compare distributions, rather than on the important properties of data such as variability, ：shape and outliers. Many teachers were able to build interesting graphs reflecting important properties of the data, but cannot use them 1：o support data analysis. Hence, it is necessary to extend the teachers＇ understanding on data analysis so they can take advantage of the cognitive potential that computer tools to offer.
基金supported by the National Natural Science Foundation of China(Grant Nos.51376001,51006006,51420105008 and 51376014)the National Basic Research Program of China("973"Project)(Grant Nos.2012CB720205,2014CB046405)+2 种基金the Aeronautical Science Foundation of China(Grant No.2012ZB51014)the Beijing Higher Education Young Elite Teacher Projectthe Fundamental Research Funds for the Central Universities
文摘The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlations(DCS)and deterministic total enthalpy correlations(DCH).These correlations should be modeled to close the system of equations.In this paper,the distribution of DC in a transonic centrifugal compressor is presented,and its relative importance is revealed.The assumption made by Adamczyk that the pure unsteady fluctuation is significantly smaller than the spatial fluctuation is verified at the impeller-diffuser interface.The decomposition of DCH is also discussed to determine its two different physical mechanisms.Finally,the transport equations in terms of DCS in cylindrical coordinates are derived,and the terms are evaluated to determine the ones that are necessary to model.All these analyses significantly contribute to our model development for DC in centrifugal compressors.
