GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, i...GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, including deeply etched, bevel, and stepped-mesas terminal structures, to suppress electric field crowding effects at the device and junction edges. Deeply-etched mesa terminal yields a breakdown voltage of 1205 V, i.e., 89% of the ideal voltage. The bevel-mesa terminal achieves about 89% of the ideal breakdown voltage, while the step-mesa terminal is less effective in mitigating electric field crowding, at about 32% of the ideal voltage. This work can provide an important reference for the design of high-power, high-voltage GaN-based P-i-N power devices, finding a terminal protection structure suitable for GaNPiN diodes to further enhance the breakdown performance of the device and to unleash the full potential of GaN semiconductor materials.展开更多
西南印度洋中脊(Southwest Indian Ridge,SWIR)热液区具有潜在发育的大规模硫化物矿床,当前正在开展SWIR硫化物矿产资源评价。测量分析硫化物和不同围岩的声速等物性特征是硫化物近底地震勘探资料处理和解释的基础。该文对西南印度洋中...西南印度洋中脊(Southwest Indian Ridge,SWIR)热液区具有潜在发育的大规模硫化物矿床,当前正在开展SWIR硫化物矿产资源评价。测量分析硫化物和不同围岩的声速等物性特征是硫化物近底地震勘探资料处理和解释的基础。该文对西南印度洋中脊热液区的硫化物和围岩等样品进行了系统的物性测量,结合岩石物性(包括密度、孔隙度、P波速度)与矿物组成,深入分析了西南印度洋中脊热液区岩石声速变化特性及其影响因素。结果表明,SWIR热液区围岩的P波速度受到岩石骨架矿物、孔隙和围压的影响。由于岩石孔隙度总体偏小,对P波速度的影响并不显著,但围压的增加使岩石微裂缝和孔隙逐渐闭合,P波速度呈非线性指数变化。蚀变作用导致了矿物成分改变,是影响围岩声速的最关键因素。单一物性参数测量结果可能存在多解性,联合波速、密度、磁性和电性等多物性参数测量有利于岩性区分。该研究成果有助于识别硫化物和围岩,为我国西南印度洋合同区多金属硫化物地震勘探工作提供重要支撑。展开更多
The mixed spin P-fields(MSP for short) theory sets up a geometric platform to relate Gromov-Witten invariants of the quintic three-fold and Fan-Jarvis-Ruan-Witten invariants of the quintic polynomial in five variables...The mixed spin P-fields(MSP for short) theory sets up a geometric platform to relate Gromov-Witten invariants of the quintic three-fold and Fan-Jarvis-Ruan-Witten invariants of the quintic polynomial in five variables. It starts with Wittens vision and the P-fields treatment of GW invariants and FJRW invariants. Then it briefly discusses the master space technique and its application to the set-up of the MSP moduli. Some key results in MSP theory are explained and some examples are provided.展开更多
This paper unfolds and reviews the theory of abstract algebra, field extensions and discusses various kinds of field extensions. Field extensions are said to be algebraic or transcendental. We pay much attention to al...This paper unfolds and reviews the theory of abstract algebra, field extensions and discusses various kinds of field extensions. Field extensions are said to be algebraic or transcendental. We pay much attention to algebraic extensions. Finally, we construct finite extensions of Q and finite extensions of the function field over finite field F<sub>p </sub>using the notion of field completion, analogous to field extensions. With the study of field extensions, considering any polynomial with coefficients in the field, we can find the roots of the polynomial, and with the notion of algebraically closed fields, we have one field, F, where we can find the roots of any polynomial with coefficients in F.展开更多
文摘GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, including deeply etched, bevel, and stepped-mesas terminal structures, to suppress electric field crowding effects at the device and junction edges. Deeply-etched mesa terminal yields a breakdown voltage of 1205 V, i.e., 89% of the ideal voltage. The bevel-mesa terminal achieves about 89% of the ideal breakdown voltage, while the step-mesa terminal is less effective in mitigating electric field crowding, at about 32% of the ideal voltage. This work can provide an important reference for the design of high-power, high-voltage GaN-based P-i-N power devices, finding a terminal protection structure suitable for GaNPiN diodes to further enhance the breakdown performance of the device and to unleash the full potential of GaN semiconductor materials.
文摘西南印度洋中脊(Southwest Indian Ridge,SWIR)热液区具有潜在发育的大规模硫化物矿床,当前正在开展SWIR硫化物矿产资源评价。测量分析硫化物和不同围岩的声速等物性特征是硫化物近底地震勘探资料处理和解释的基础。该文对西南印度洋中脊热液区的硫化物和围岩等样品进行了系统的物性测量,结合岩石物性(包括密度、孔隙度、P波速度)与矿物组成,深入分析了西南印度洋中脊热液区岩石声速变化特性及其影响因素。结果表明,SWIR热液区围岩的P波速度受到岩石骨架矿物、孔隙和围压的影响。由于岩石孔隙度总体偏小,对P波速度的影响并不显著,但围压的增加使岩石微裂缝和孔隙逐渐闭合,P波速度呈非线性指数变化。蚀变作用导致了矿物成分改变,是影响围岩声速的最关键因素。单一物性参数测量结果可能存在多解性,联合波速、密度、磁性和电性等多物性参数测量有利于岩性区分。该研究成果有助于识别硫化物和围岩,为我国西南印度洋合同区多金属硫化物地震勘探工作提供重要支撑。
基金supported by Hong Kong General Research Fund(Nos.600711,6301515,602512)the National Science Foundation(Nos.NSF-1104553,DMS-1159156,DMS-1206667,DMS-1159416)
文摘The mixed spin P-fields(MSP for short) theory sets up a geometric platform to relate Gromov-Witten invariants of the quintic three-fold and Fan-Jarvis-Ruan-Witten invariants of the quintic polynomial in five variables. It starts with Wittens vision and the P-fields treatment of GW invariants and FJRW invariants. Then it briefly discusses the master space technique and its application to the set-up of the MSP moduli. Some key results in MSP theory are explained and some examples are provided.
文摘This paper unfolds and reviews the theory of abstract algebra, field extensions and discusses various kinds of field extensions. Field extensions are said to be algebraic or transcendental. We pay much attention to algebraic extensions. Finally, we construct finite extensions of Q and finite extensions of the function field over finite field F<sub>p </sub>using the notion of field completion, analogous to field extensions. With the study of field extensions, considering any polynomial with coefficients in the field, we can find the roots of the polynomial, and with the notion of algebraically closed fields, we have one field, F, where we can find the roots of any polynomial with coefficients in F.
