In this paper the operation of a three level H-bridge converter as well as its parallel operations is analyzed and simulated on the computer. Based on the simulation results the operating behavior between （a） a thre...In this paper the operation of a three level H-bridge converter as well as its parallel operations is analyzed and simulated on the computer. Based on the simulation results the operating behavior between （a） a three level H-bridge neutral point clamped convener, （b） a three level back-to-back H-bridge neutral point clamped convener, （c） two three level H-bridge neutral point clamped converters parallel connected is being compared. From the simulation results it is obvious that in the first two cases the ripples, the distortion in primary and secondary winding currents, and the power factor are quite satisfactory and almost identical to each other. In the third case as compared with the first two, it is observed that current harmonics with higher amplitude appear in the primary winding of the transformer.展开更多
In this paper, experimental investigations are presented to assess the performance variations in a single cylinder spark ignited engine when run with three different gasoline-alcohol blends： （88% gasoline-12% methan...In this paper, experimental investigations are presented to assess the performance variations in a single cylinder spark ignited engine when run with three different gasoline-alcohol blends： （88% gasoline-12% methanol, 88% gasoline-12% ethanol and 88% gasoline-6% methanol-6% ethanol）. Additional tests are carried out with the basic gasoline fuel for comparison analysis and performance assessment. Engine performance is investigated under a variety of engine operating conditions. The results are presented in the domain of engine speed. In particular, the brake power of the engine is shown to be slightly increased. The brake thermal efficiency showed an increase compared with the basic gasoline engine. Similarly, it is shown that brake specific fuel consumption is enhanced compared with basic gasoline engine. The exhaust gas temperature showed a decrease compared with gasoline fuel which is preferable to reduce emissions. The alcohol additives are strongly recommended to enhance performance, increasing the mileage and reducing the emissions.展开更多
There is a need for determinations of soil organic carbon (SOC) and inorganic carbon (SIC) due to increasing interest in soil carbon sequestration. Two sets of soil samples were collected separately from the Yanqi Bas...There is a need for determinations of soil organic carbon (SOC) and inorganic carbon (SIC) due to increasing interest in soil carbon sequestration. Two sets of soil samples were collected separately from the Yanqi Basin of northwest China to evaluate loss-on-ignition (LOI) method for estimating SOC and SIC in arid soils through determining SOC using an element analyzer, a modified Walkley-Black method and a LOI method with combustion at 375℃ for 17 h and determining SIC using a pressure calcimeter method and a LOI procedure estimated by a weight loss between 375 to 800℃. Our results indicated that the Walkley-Black method provided 99%recovery of SOC for the arid soils tested. There were strong linear relationships(r > 0.93, P < 0.001) for both SOC and SIC between the traditional method and the LOI technique. One set of soil samples was used to develop relationships between LOI and SOC(by the Walkley-Black method), and between LOI and SIC(by the pressure calcimeter method), and the other set of soil samples was used to evaluate the derived equations by comparing predicted SOC and SIC with measured values. The mean absolute errors were small for both SOC (1.7 g C kg-1) and SIC(1.22 g C kg-1), demonstrating that the LOI method was reliable and could provide accurate estimates of SOC and SIC for arid soils.展开更多
文摘In this paper the operation of a three level H-bridge converter as well as its parallel operations is analyzed and simulated on the computer. Based on the simulation results the operating behavior between （a） a three level H-bridge neutral point clamped convener, （b） a three level back-to-back H-bridge neutral point clamped convener, （c） two three level H-bridge neutral point clamped converters parallel connected is being compared. From the simulation results it is obvious that in the first two cases the ripples, the distortion in primary and secondary winding currents, and the power factor are quite satisfactory and almost identical to each other. In the third case as compared with the first two, it is observed that current harmonics with higher amplitude appear in the primary winding of the transformer.
文摘In this paper, experimental investigations are presented to assess the performance variations in a single cylinder spark ignited engine when run with three different gasoline-alcohol blends： （88% gasoline-12% methanol, 88% gasoline-12% ethanol and 88% gasoline-6% methanol-6% ethanol）. Additional tests are carried out with the basic gasoline fuel for comparison analysis and performance assessment. Engine performance is investigated under a variety of engine operating conditions. The results are presented in the domain of engine speed. In particular, the brake power of the engine is shown to be slightly increased. The brake thermal efficiency showed an increase compared with the basic gasoline engine. Similarly, it is shown that brake specific fuel consumption is enhanced compared with basic gasoline engine. The exhaust gas temperature showed a decrease compared with gasoline fuel which is preferable to reduce emissions. The alcohol additives are strongly recommended to enhance performance, increasing the mileage and reducing the emissions.
基金Supported by the "Hundred Talents Program" of the Chinese Academy of Sciences
文摘There is a need for determinations of soil organic carbon (SOC) and inorganic carbon (SIC) due to increasing interest in soil carbon sequestration. Two sets of soil samples were collected separately from the Yanqi Basin of northwest China to evaluate loss-on-ignition (LOI) method for estimating SOC and SIC in arid soils through determining SOC using an element analyzer, a modified Walkley-Black method and a LOI method with combustion at 375℃ for 17 h and determining SIC using a pressure calcimeter method and a LOI procedure estimated by a weight loss between 375 to 800℃. Our results indicated that the Walkley-Black method provided 99%recovery of SOC for the arid soils tested. There were strong linear relationships(r > 0.93, P < 0.001) for both SOC and SIC between the traditional method and the LOI technique. One set of soil samples was used to develop relationships between LOI and SOC(by the Walkley-Black method), and between LOI and SIC(by the pressure calcimeter method), and the other set of soil samples was used to evaluate the derived equations by comparing predicted SOC and SIC with measured values. The mean absolute errors were small for both SOC (1.7 g C kg-1) and SIC(1.22 g C kg-1), demonstrating that the LOI method was reliable and could provide accurate estimates of SOC and SIC for arid soils.
