自动转换开关电器,即ATSE(Automatic Transfer Switching Equipment),是主要适用于交流50Hz、不超过1000V的紧急供电系统,用于两路电源切换,在转换电源期间不中断向负载供电的低压电器产品。作为目前在建筑电气工程设计经常采用的配电...自动转换开关电器,即ATSE(Automatic Transfer Switching Equipment),是主要适用于交流50Hz、不超过1000V的紧急供电系统,用于两路电源切换,在转换电源期间不中断向负载供电的低压电器产品。作为目前在建筑电气工程设计经常采用的配电设备之一,ATSE的设计与选用直接关系到整个配电系统的可靠性和安全性。展开更多
15-day old seedlings of wheat and rape were grown in a series of solutions with different concentrations of KNO3 for a definite period of time. The changes in NO3- concentration of the solutions were determined by the...15-day old seedlings of wheat and rape were grown in a series of solutions with different concentrations of KNO3 for a definite period of time. The changes in NO3- concentration of the solutions were determined by the double ion-selective electrode method, and then the amount of NO3- taken up by the plants was estimated and values of Km and Imax of the Michealis-Menten equation were calculated. Results show that both the method and conditions of determination affected the values of Km and Imax. For example, the Km value was appreciably reduced when the volume of culture solution was increased or when the duration of nutrient uptake was shortened; the Km value obtained with short-term depletion method was higher than that obtained with long-term one. Similar Variations were found for the values of Imax. There was a considerable difference in the characteristics of uptake kinetics between wheat and rape when determined under the same conditions of determination. The isotherm of NO3- uptake by wheat could be separated into saturated and unsaturated parts, and when the concentration of NO3- exceeded 180 uuuuuuuuuuuuM, the relationship between the rate of NO3- uptake and NO3- concentration tended to be linear. However, the isotherm of NO3- uptake by rape was found to fit the Michealis-Menten equation and no linear relationship could be found.展开更多
Performance characteristics data of solar photovoltaic （PV） cell/module are conventionally obtained under standard testing conditions. In the present work, the performance of PV modules under extreme temperatures an...Performance characteristics data of solar photovoltaic （PV） cell/module are conventionally obtained under standard testing conditions. In the present work, the performance of PV modules under extreme temperatures and insolations experienced in State of Qatar was utilized to aid presenting a simplified characterization approach for the special case of arid environmental conditions. The chosen model was the well-known single diode model with both series and parallel resistors for greater accuracy. The modeling technique was validated by comparing the numerically calculated electrical characteristics with experimentally obtained data using two approaches： a single indoor fixed monocrystalline PV module inside a solar simulation chamber which physically simulated different weather scenarios by changing irradiation intensities and temperature, and a set of outdoor fixed polycrystalline PV modules. The result of the indoor experiment was presented in form of performance curves, and the outdoor experiment results in a monthly accumulated power production chart format. Both illustration types showed acceptable tolerance.展开更多
文摘自动转换开关电器,即ATSE(Automatic Transfer Switching Equipment),是主要适用于交流50Hz、不超过1000V的紧急供电系统,用于两路电源切换,在转换电源期间不中断向负载供电的低压电器产品。作为目前在建筑电气工程设计经常采用的配电设备之一,ATSE的设计与选用直接关系到整个配电系统的可靠性和安全性。
文摘15-day old seedlings of wheat and rape were grown in a series of solutions with different concentrations of KNO3 for a definite period of time. The changes in NO3- concentration of the solutions were determined by the double ion-selective electrode method, and then the amount of NO3- taken up by the plants was estimated and values of Km and Imax of the Michealis-Menten equation were calculated. Results show that both the method and conditions of determination affected the values of Km and Imax. For example, the Km value was appreciably reduced when the volume of culture solution was increased or when the duration of nutrient uptake was shortened; the Km value obtained with short-term depletion method was higher than that obtained with long-term one. Similar Variations were found for the values of Imax. There was a considerable difference in the characteristics of uptake kinetics between wheat and rape when determined under the same conditions of determination. The isotherm of NO3- uptake by wheat could be separated into saturated and unsaturated parts, and when the concentration of NO3- exceeded 180 uuuuuuuuuuuuM, the relationship between the rate of NO3- uptake and NO3- concentration tended to be linear. However, the isotherm of NO3- uptake by rape was found to fit the Michealis-Menten equation and no linear relationship could be found.
文摘Performance characteristics data of solar photovoltaic （PV） cell/module are conventionally obtained under standard testing conditions. In the present work, the performance of PV modules under extreme temperatures and insolations experienced in State of Qatar was utilized to aid presenting a simplified characterization approach for the special case of arid environmental conditions. The chosen model was the well-known single diode model with both series and parallel resistors for greater accuracy. The modeling technique was validated by comparing the numerically calculated electrical characteristics with experimentally obtained data using two approaches： a single indoor fixed monocrystalline PV module inside a solar simulation chamber which physically simulated different weather scenarios by changing irradiation intensities and temperature, and a set of outdoor fixed polycrystalline PV modules. The result of the indoor experiment was presented in form of performance curves, and the outdoor experiment results in a monthly accumulated power production chart format. Both illustration types showed acceptable tolerance.
