Recent advances in van der Waals(vdW) ferroelectrics have sparked the development of related heterostructures with non-volatile and field-tunable functionalities. In vdW ferroelectric heterojunctions, the interfacial ...Recent advances in van der Waals(vdW) ferroelectrics have sparked the development of related heterostructures with non-volatile and field-tunable functionalities. In vdW ferroelectric heterojunctions, the interfacial electrical characteristics play a crucial role in determining their performance and functionality. In this study,we explore the interfacial polarization coupling in two-dimensional(2D) ferroelectric heterojunctions by fabricating a graphene/h-BN/CuInP_(2)S_(6)/α-In_(2)Se_(3)/Au ferroelectric field-effect transistor. By varying the gate electric field, the CuInP_(2)S_(6)/α-In_(2)Se_(3) heterojunction displays distinct interfacial polarization coupling states, resulting in significantly different electrical transport behaviors. Under strong gate electric fields, the migration of Cu ions further enhances the interfacial polarization effect, enabling continuous tuning of both the polarization state and carrier concentration in α-In_(2)Se_(3). Our findings offer valuable insights for the development of novel multifunctional devices based on 2D ferroelectric materials.展开更多
The disk-pad brake used in automobile is divided i nt o two parts: the disk, geometrically axisymmetric, and the pad, of which the geo metry is three-dimensional. In the course of braking, all parameters of the pro ce...The disk-pad brake used in automobile is divided i nt o two parts: the disk, geometrically axisymmetric, and the pad, of which the geo metry is three-dimensional. In the course of braking, all parameters of the pro cesses (velocity, load, temperature, physicomechanical and tribological characte ristics of materials of the couple, and conditions of contacts) vary with the ti me. Considerable evidence has show that the contact temperature is an integral f actor reflecting the specific power friction influence at the combined effect of load, speed, friction coefficient, thermo physical and durability properties of materials of a frictional couple. Furthermore, the physic mechanical state of t he interface of the disk and pads is determined not only by the contact temperat ure but also by the nonstationary temperature field. Using the two-dimensional model for thermal analysis implies that the contact conditions and frictiona l heat flux transfer are independent of θ. This may lead to false thermal elast ic distortions and unrealistic contact conditions. An analytical model is presen ted in this paper for the determination of contact temperature distribution on t he working surface of a brake. To consider the effects of the moving heat source (the pad) with relative sliding speed variation, a transient finite element tec hnique is used to characterize the temperature fields of the solid rotor with ap propriate thermal boundary conditions. And the transient heat conduction problem can be solved as a nominal 3-D transient heat transfer problem with an immovab le heat source. Numerical results shows that the operating characteristics of th e brake exert an essentially influence on the surface temperature distribution a nd the maximal contact temperature. The temperature field presents a noaxisymmet ric characteristic (a function of θ) and proves to be strongly localized and po ssesses a sharp gradient in both axial and radial directions.展开更多
近年来,绿色BIM(building information modeling)受到美国等发达国家建设领域的广泛关注与重视,多数运用绿色BIM技术的建筑工程项目也获得了能够有效兼顾可持续性与经济性的良好效果。尽管绿色BIM实践中仍存在诸多问题,但绿色BIM已成为...近年来,绿色BIM(building information modeling)受到美国等发达国家建设领域的广泛关注与重视,多数运用绿色BIM技术的建筑工程项目也获得了能够有效兼顾可持续性与经济性的良好效果。尽管绿色BIM实践中仍存在诸多问题,但绿色BIM已成为建设领域未来发展的必然趋势。笔者基于绿色BIM在美国的应用现状对其在中国建设领域的影响进行了初步分析,分析认为,相较于美国的绿色BIM,中国的绿色BIM起步较晚,技术上也存在巨大差距,在发展过程中,应充分借鉴绿色BIM在美国的成熟实践经验,并结合中国建设领域的特点,形成符合中国国情的绿色BIM操作流程、重视绿色BIM在不同类型建筑工程项目中的运用、重视建筑材料及可再生能源的选择和使用、加强BIM软件及相关技术本土化和政府投入,以有效推动绿色建筑发展、实现节能减排目标。展开更多
基金supported by the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-049)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)the Fundamental Research Funds for the Central Universities(Grant No.WK3510000013)。
文摘Recent advances in van der Waals(vdW) ferroelectrics have sparked the development of related heterostructures with non-volatile and field-tunable functionalities. In vdW ferroelectric heterojunctions, the interfacial electrical characteristics play a crucial role in determining their performance and functionality. In this study,we explore the interfacial polarization coupling in two-dimensional(2D) ferroelectric heterojunctions by fabricating a graphene/h-BN/CuInP_(2)S_(6)/α-In_(2)Se_(3)/Au ferroelectric field-effect transistor. By varying the gate electric field, the CuInP_(2)S_(6)/α-In_(2)Se_(3) heterojunction displays distinct interfacial polarization coupling states, resulting in significantly different electrical transport behaviors. Under strong gate electric fields, the migration of Cu ions further enhances the interfacial polarization effect, enabling continuous tuning of both the polarization state and carrier concentration in α-In_(2)Se_(3). Our findings offer valuable insights for the development of novel multifunctional devices based on 2D ferroelectric materials.
文摘The disk-pad brake used in automobile is divided i nt o two parts: the disk, geometrically axisymmetric, and the pad, of which the geo metry is three-dimensional. In the course of braking, all parameters of the pro cesses (velocity, load, temperature, physicomechanical and tribological characte ristics of materials of the couple, and conditions of contacts) vary with the ti me. Considerable evidence has show that the contact temperature is an integral f actor reflecting the specific power friction influence at the combined effect of load, speed, friction coefficient, thermo physical and durability properties of materials of a frictional couple. Furthermore, the physic mechanical state of t he interface of the disk and pads is determined not only by the contact temperat ure but also by the nonstationary temperature field. Using the two-dimensional model for thermal analysis implies that the contact conditions and frictiona l heat flux transfer are independent of θ. This may lead to false thermal elast ic distortions and unrealistic contact conditions. An analytical model is presen ted in this paper for the determination of contact temperature distribution on t he working surface of a brake. To consider the effects of the moving heat source (the pad) with relative sliding speed variation, a transient finite element tec hnique is used to characterize the temperature fields of the solid rotor with ap propriate thermal boundary conditions. And the transient heat conduction problem can be solved as a nominal 3-D transient heat transfer problem with an immovab le heat source. Numerical results shows that the operating characteristics of th e brake exert an essentially influence on the surface temperature distribution a nd the maximal contact temperature. The temperature field presents a noaxisymmet ric characteristic (a function of θ) and proves to be strongly localized and po ssesses a sharp gradient in both axial and radial directions.
文摘近年来,绿色BIM(building information modeling)受到美国等发达国家建设领域的广泛关注与重视,多数运用绿色BIM技术的建筑工程项目也获得了能够有效兼顾可持续性与经济性的良好效果。尽管绿色BIM实践中仍存在诸多问题,但绿色BIM已成为建设领域未来发展的必然趋势。笔者基于绿色BIM在美国的应用现状对其在中国建设领域的影响进行了初步分析,分析认为,相较于美国的绿色BIM,中国的绿色BIM起步较晚,技术上也存在巨大差距,在发展过程中,应充分借鉴绿色BIM在美国的成熟实践经验,并结合中国建设领域的特点,形成符合中国国情的绿色BIM操作流程、重视绿色BIM在不同类型建筑工程项目中的运用、重视建筑材料及可再生能源的选择和使用、加强BIM软件及相关技术本土化和政府投入,以有效推动绿色建筑发展、实现节能减排目标。
