Factors influencing pedestrians＇ speed were investigated. They included types of pedes- trian facilities, the accompanying numbers, gender, age, purpose of trips and surrounding pedestri- ans. The data mining techniq...Factors influencing pedestrians＇ speed were investigated. They included types of pedes- trian facilities, the accompanying numbers, gender, age, purpose of trips and surrounding pedestri- ans. The data mining technique of statistical package for the social science （SPSS） was used to filter and analyze the data of pedestrians＇ speed under different conditions. The differences among influ- encing factors on pedestrians＇ speed was investigated by comparing the diagrams generated by SPSS. Through comprehensive analysis, including quantitative and qualitative analysis, a pedestrian＇ s speed was influenced significantly by the facilities, bis surrounding pedestrians and his own person- ality.展开更多
In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owin...In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owing to the overheating that results from excessive exposure to solar irradiance.This conclusion has been formulated based on a mathematical model,which in turn is based on the assumption that the PV module temperature can be calculated using an empirical relation of this temperature to ambient temperature,available solar irradiance,and nominal operation cell temperature(NOCT).To support this conclusion,it is claimed that the mathematical model is validated experimentally.However,this assumption is vague and widely used in the literature.The objective of the present work is to reevaluate the above-mentioned assumption and to discuss the results deriving from it.It is shown experimentally in the present work that the above-mentioned assumption overestimates the PV module temperature.At a solar irradiance of 900 W/m2,ambient temperature of 25℃,and wind speed of 5 m/s,the measured PV module temperature is lower than the value calculated based on the mentioned assumption by 29.26%.展开更多
基金Supported by the National Natural Science Foundation of China (60674012)Beijing Jiaotong University Research Fund(2007RC039)
文摘Factors influencing pedestrians＇ speed were investigated. They included types of pedes- trian facilities, the accompanying numbers, gender, age, purpose of trips and surrounding pedestri- ans. The data mining technique of statistical package for the social science （SPSS） was used to filter and analyze the data of pedestrians＇ speed under different conditions. The differences among influ- encing factors on pedestrians＇ speed was investigated by comparing the diagrams generated by SPSS. Through comprehensive analysis, including quantitative and qualitative analysis, a pedestrian＇ s speed was influenced significantly by the facilities, bis surrounding pedestrians and his own person- ality.
文摘In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owing to the overheating that results from excessive exposure to solar irradiance.This conclusion has been formulated based on a mathematical model,which in turn is based on the assumption that the PV module temperature can be calculated using an empirical relation of this temperature to ambient temperature,available solar irradiance,and nominal operation cell temperature(NOCT).To support this conclusion,it is claimed that the mathematical model is validated experimentally.However,this assumption is vague and widely used in the literature.The objective of the present work is to reevaluate the above-mentioned assumption and to discuss the results deriving from it.It is shown experimentally in the present work that the above-mentioned assumption overestimates the PV module temperature.At a solar irradiance of 900 W/m2,ambient temperature of 25℃,and wind speed of 5 m/s,the measured PV module temperature is lower than the value calculated based on the mentioned assumption by 29.26%.
