The aim of this paper is to get the decomposition of distributional derivatives of functions with bounded variation in the framework of Carnot-Caratheodory spaces (C-C spaces in brievity) in which the vector fields ar...The aim of this paper is to get the decomposition of distributional derivatives of functions with bounded variation in the framework of Carnot-Caratheodory spaces (C-C spaces in brievity) in which the vector fields are of Carnot type. For this purpose the approximate continuity of BV functions is discussed first, then approximate differentials of L1 functions are defined in the case that vector fields are of Carnot type and finally the decomposition Xu = (?)u ·Ln + X2 u is proved, where u ∈ BVx(?) and (Ω)u denotes the approximate differential of u.展开更多
海上风力发电-高压直流输电HVDC(high voltage direct current)系统是风力发电及其功率传输技术的发展方向。文中分析了电压型精简矩阵变换器RMC(reduced matrix converter)的双极性电压空间矢量调制BV-SVM(bipolar voltage space vecto...海上风力发电-高压直流输电HVDC(high voltage direct current)系统是风力发电及其功率传输技术的发展方向。文中分析了电压型精简矩阵变换器RMC(reduced matrix converter)的双极性电压空间矢量调制BV-SVM(bipolar voltage space vector pulse-width modulation)策略,提出了基于RMC的直驱海上风电-高压直流输电系统控制策略以及基于有功功率指令修正的RMC换流器功率协调控制策略。在正常情况下实现了最大风能跟踪MPPT(maximum power point tracking)控制、直流稳压以及并网有功/无功功率解耦控制;在电网电压跌落时实现了HVDC系统海上-岸上换流器协调控制,保持HVDC系统有功功率传输平衡,提高了风电机组的低电压穿越LVRT(low-voltage ride-through)能力。仿真结果验证了所提控制策略的正确性和可行性。展开更多
Hepatolithiasis(HL)is a common and serious disease with high incidence in Southeast Asian countries(1),especially in Southwest China,South China,and Southeast coastal areas of China.Based on the pathological character...Hepatolithiasis(HL)is a common and serious disease with high incidence in Southeast Asian countries(1),especially in Southwest China,South China,and Southeast coastal areas of China.Based on the pathological characteristics of the segmented stone distribution and atrophy of the hepatic parenchyma,resection of the atrophied liver involving the diseased bile duct is the most effective and common surgical treatment for HL.As proposed by Shindoh et al.,hepatobiliary surgeons have used anatomic liver resection(AR)for hepatocellular carcinoma(HCC),which involves complete resection of the anatomic area supplied by the portal vein of the Glissonean branch(2).However,factors such as changes in bile fluid dynamics,stone compression,and chronic inflammation associated with HL lead to portal vein and hepatic artery stenosis and occlusion in some diseased areas,resulting in the diseased bile duct and hepatic vein(HV)becoming significant characteristic anatomical structures.In such cases,the effect and success rate of indocyanine green fluorescence staining are poor for navigation during HL surgery.Digital imaging techniques such as 3D visualization,3D printing,and artificial intelligence can facilitate preoperative evaluation but not accurate evaluation of all real anatomical structures and guidance of the transection plane.In such patients with HL,the lack of effective intrahepatic anatomic landmarks used during AR results in residual stones and diseased bile ducts and recurrence of stones.This necessitates repeated surgeries and affects postoperative recovery and patients’quality of life.Therefore,to allow for standardized and more accurate hepatectomy for HL and provide a theoretical basis for formulating corresponding treatment norms,we proposed and applied hepatectomy guided by the bile duct and HV(H-BV),that is by using the diseased bile duct tree and HV as anatomic landmarks.展开更多
In this paper, we study the problem of boundary layer for nonstationary flows of viscous incompressible fluids. There are some open problems in the field of boundary layer. The method used here is mainly based on a tr...In this paper, we study the problem of boundary layer for nonstationary flows of viscous incompressible fluids. There are some open problems in the field of boundary layer. The method used here is mainly based on a transformation which reduces the boundary layer system to an initial-boundary value problem for a single quasilinear parabolic equation. We prove the existence of weak solutions to the modified nonstationary boundary layer system. Moreover, the stability and uniqueness of weak solutions are discussed.展开更多
文摘The aim of this paper is to get the decomposition of distributional derivatives of functions with bounded variation in the framework of Carnot-Caratheodory spaces (C-C spaces in brievity) in which the vector fields are of Carnot type. For this purpose the approximate continuity of BV functions is discussed first, then approximate differentials of L1 functions are defined in the case that vector fields are of Carnot type and finally the decomposition Xu = (?)u ·Ln + X2 u is proved, where u ∈ BVx(?) and (Ω)u denotes the approximate differential of u.
文摘海上风力发电-高压直流输电HVDC(high voltage direct current)系统是风力发电及其功率传输技术的发展方向。文中分析了电压型精简矩阵变换器RMC(reduced matrix converter)的双极性电压空间矢量调制BV-SVM(bipolar voltage space vector pulse-width modulation)策略,提出了基于RMC的直驱海上风电-高压直流输电系统控制策略以及基于有功功率指令修正的RMC换流器功率协调控制策略。在正常情况下实现了最大风能跟踪MPPT(maximum power point tracking)控制、直流稳压以及并网有功/无功功率解耦控制;在电网电压跌落时实现了HVDC系统海上-岸上换流器协调控制,保持HVDC系统有功功率传输平衡,提高了风电机组的低电压穿越LVRT(low-voltage ride-through)能力。仿真结果验证了所提控制策略的正确性和可行性。
文摘Hepatolithiasis(HL)is a common and serious disease with high incidence in Southeast Asian countries(1),especially in Southwest China,South China,and Southeast coastal areas of China.Based on the pathological characteristics of the segmented stone distribution and atrophy of the hepatic parenchyma,resection of the atrophied liver involving the diseased bile duct is the most effective and common surgical treatment for HL.As proposed by Shindoh et al.,hepatobiliary surgeons have used anatomic liver resection(AR)for hepatocellular carcinoma(HCC),which involves complete resection of the anatomic area supplied by the portal vein of the Glissonean branch(2).However,factors such as changes in bile fluid dynamics,stone compression,and chronic inflammation associated with HL lead to portal vein and hepatic artery stenosis and occlusion in some diseased areas,resulting in the diseased bile duct and hepatic vein(HV)becoming significant characteristic anatomical structures.In such cases,the effect and success rate of indocyanine green fluorescence staining are poor for navigation during HL surgery.Digital imaging techniques such as 3D visualization,3D printing,and artificial intelligence can facilitate preoperative evaluation but not accurate evaluation of all real anatomical structures and guidance of the transection plane.In such patients with HL,the lack of effective intrahepatic anatomic landmarks used during AR results in residual stones and diseased bile ducts and recurrence of stones.This necessitates repeated surgeries and affects postoperative recovery and patients’quality of life.Therefore,to allow for standardized and more accurate hepatectomy for HL and provide a theoretical basis for formulating corresponding treatment norms,we proposed and applied hepatectomy guided by the bile duct and HV(H-BV),that is by using the diseased bile duct tree and HV as anatomic landmarks.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 10131050).
文摘In this paper, we study the problem of boundary layer for nonstationary flows of viscous incompressible fluids. There are some open problems in the field of boundary layer. The method used here is mainly based on a transformation which reduces the boundary layer system to an initial-boundary value problem for a single quasilinear parabolic equation. We prove the existence of weak solutions to the modified nonstationary boundary layer system. Moreover, the stability and uniqueness of weak solutions are discussed.
