Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals tha...Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.展开更多
A silicon pressure sensor is one of the very first MEMS components appearing in the microsystem area.The market for the MEMS pressure sensor is rapidly growing due to consumer electronic applications in recent years. ...A silicon pressure sensor is one of the very first MEMS components appearing in the microsystem area.The market for the MEMS pressure sensor is rapidly growing due to consumer electronic applications in recent years. Requirements of the pressure sensors with low cost, low power consumption and high accuracy drive one to develop a novel technology. This paper first overviews the historical development of the absolute pressure sensor briefly. It then reviews the state of the art technology for fabricating crystalline silicon membranes over sealed cavities by using the silicon migration technology in detail. By using only one lithographic step, the membranes defined in lateral and vertical dimensions can be realized by the technology. Finally, applications of MEMS through using the silicon migration technology are summarized.展开更多
研究黏性土中桩土界面的抗剪强度及其参数受超孔隙水压力影响的规律,对工程实践具有重要意义。利用自制的大型恒刚度直剪仪,完成了一系列不同界面粗糙度、不同试样含水率和不同剪切速率试验条件下的直剪试验,分析了在不同试验条件下超...研究黏性土中桩土界面的抗剪强度及其参数受超孔隙水压力影响的规律,对工程实践具有重要意义。利用自制的大型恒刚度直剪仪,完成了一系列不同界面粗糙度、不同试样含水率和不同剪切速率试验条件下的直剪试验,分析了在不同试验条件下超孔隙水压力变化规律,进而得到考虑超孔隙水压力的桩土界面抗剪强度及其参数的变化规律。研究结果表明:随着界面粗糙度等级提高,桩土界面超孔隙水压力减小,桩土界面抗剪强度、有效黏聚力和有效摩擦系数增加;随着含水率的增加,桩土界面超孔隙水压力增加,桩土界面抗剪强度降低,含水率对桩土界面抗剪强度的影响主要是改变了桩土界面的黏聚力,黏聚力先增大后减小,对摩擦系数的影响较小;特定试验条件下,随着剪切速率的增加,桩土界面超孔隙水压力增加,桩土界面抗剪强度降低,桩土界面黏聚力先增大后又减小,变化幅度不超过2 k Pa,对摩擦系数的影响较小。因此,桩土界面抗剪强度及其参数是界面粗糙度、试样含水率和剪切速率变化引起超孔隙水压力变化共同影响的结果,试验结果可供相关工程设计参考。展开更多
为了消除环境温度对硅压阻式传感器输出的影响,大幅提升硅压阻式传感器的测量精度,将传感器芯片与热源和测温原件封装在一起,通过控制加热的方式使传感器工作在恒定50℃的环境中,对传感器进行线性标定和测试。结果显示:在-45~45℃环境下...为了消除环境温度对硅压阻式传感器输出的影响,大幅提升硅压阻式传感器的测量精度,将传感器芯片与热源和测温原件封装在一起,通过控制加热的方式使传感器工作在恒定50℃的环境中,对传感器进行线性标定和测试。结果显示:在-45~45℃环境下,600~1 100 h Pa量程内气压传感器的测量误差小于0.3 h Pa。展开更多
基金This work was partly financially supported by NEDO.
文摘Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.
基金Project supported by the National Major Science&Technology Program of China(No.2011ZX02507-001)
文摘A silicon pressure sensor is one of the very first MEMS components appearing in the microsystem area.The market for the MEMS pressure sensor is rapidly growing due to consumer electronic applications in recent years. Requirements of the pressure sensors with low cost, low power consumption and high accuracy drive one to develop a novel technology. This paper first overviews the historical development of the absolute pressure sensor briefly. It then reviews the state of the art technology for fabricating crystalline silicon membranes over sealed cavities by using the silicon migration technology in detail. By using only one lithographic step, the membranes defined in lateral and vertical dimensions can be realized by the technology. Finally, applications of MEMS through using the silicon migration technology are summarized.
文摘研究黏性土中桩土界面的抗剪强度及其参数受超孔隙水压力影响的规律,对工程实践具有重要意义。利用自制的大型恒刚度直剪仪,完成了一系列不同界面粗糙度、不同试样含水率和不同剪切速率试验条件下的直剪试验,分析了在不同试验条件下超孔隙水压力变化规律,进而得到考虑超孔隙水压力的桩土界面抗剪强度及其参数的变化规律。研究结果表明:随着界面粗糙度等级提高,桩土界面超孔隙水压力减小,桩土界面抗剪强度、有效黏聚力和有效摩擦系数增加;随着含水率的增加,桩土界面超孔隙水压力增加,桩土界面抗剪强度降低,含水率对桩土界面抗剪强度的影响主要是改变了桩土界面的黏聚力,黏聚力先增大后减小,对摩擦系数的影响较小;特定试验条件下,随着剪切速率的增加,桩土界面超孔隙水压力增加,桩土界面抗剪强度降低,桩土界面黏聚力先增大后又减小,变化幅度不超过2 k Pa,对摩擦系数的影响较小。因此,桩土界面抗剪强度及其参数是界面粗糙度、试样含水率和剪切速率变化引起超孔隙水压力变化共同影响的结果,试验结果可供相关工程设计参考。
文摘为了消除环境温度对硅压阻式传感器输出的影响,大幅提升硅压阻式传感器的测量精度,将传感器芯片与热源和测温原件封装在一起,通过控制加热的方式使传感器工作在恒定50℃的环境中,对传感器进行线性标定和测试。结果显示:在-45~45℃环境下,600~1 100 h Pa量程内气压传感器的测量误差小于0.3 h Pa。
