Near-equiatomic NiTi shape memory alloys are known to exhibit Lüders-type deformation associated with a stress-induced transformation.Many studies have been conducted in the past mainly focusing on the macroscopi...Near-equiatomic NiTi shape memory alloys are known to exhibit Lüders-type deformation associated with a stress-induced transformation.Many studies have been conducted in the past mainly focusing on the macroscopic characteristics of the phenomenon and some theories have been proposed in the literature to explain its mechanisms,but some aspects of this phenomenon are still unclear,particularly at the microscopic scale.This study investigated the local strain evolution during the initiation and propagation of Lüders band in a pseudoelastic NiTi alloy during tensile deformation by means of digital image correlation(DIC)analysis.Based on the evidence collected,distinct stages of Lüders band formation and propagation are defined and the corresponding local strain rates are obtained.These local strain rates are much higher than the global strain rate of the testing,giving insight to the mechanism of this phenomenon.展开更多
In this study,the high-strength pipe steel,i.e.X80,was heated at 260℃for half an hour followed by air cooling for thermal simulation of pipe coating process.During the uniaxial loading of the specified tension sample...In this study,the high-strength pipe steel,i.e.X80,was heated at 260℃for half an hour followed by air cooling for thermal simulation of pipe coating process.During the uniaxial loading of the specified tension samples,the migration behaviour of Lüders bands and the re-distribution of stress after strain ageing heat treatment were investigated using digital image correlation.Digital image correlation was adopted to characterise the local axial and shear strain fields of samples that were extracted from different locations across the wall thickness of the high-strength pipe steel,and electron backscatter diffraction was used to compare the evolution of crystallographic texture among these locations.Other characterisation methods regarding microstructure and mechanical properties were conducted meanwhile,including optical microscopy,scanning electron microscopy and X-ray diffraction to accurately define the detailed performances that strain ageing,i.e.being heated to 260℃for half an hour,has led to.The obtained results show that the Lüders band-related microstructure,dislocation density,lattice constant and texture vary at the different locations across the wall thickness and influence the fi nal mechanical properties of the selected high-strength pipe steel.展开更多
Editor's note: We are sorry that because of the over-crowded space in our last issue, we are delayed in presenting the second part of the report delivered by the CAS President Lu Yongxiang at the 2002 working conf...Editor's note: We are sorry that because of the over-crowded space in our last issue, we are delayed in presenting the second part of the report delivered by the CAS President Lu Yongxiang at the 2002 working conference of CAS. The report appears in two installments in this and the 1st issue of this volume.展开更多
Addition of Fe B C and Fe Mo B C m aster alloy pow ders to Fe Mo B Csintered steels can ac tivate the sintering process by liquid phase sintering . The for m ation of liquid ( α- Fe + ( Fe , Mo...Addition of Fe B C and Fe Mo B C m aster alloy pow ders to Fe Mo B Csintered steels can ac tivate the sintering process by liquid phase sintering . The for m ation of liquid ( α- Fe + ( Fe , Mo) 2 B+ Fe3( B, C) → L) i m proves m echanical properties of the steels , and ultim ate tensilestrengths of 684 774 M Pa , i m pact energy of 47 ±7 Jand elongation of 2 5 ±0 9 were ob tained . Optim u m a mount of liquid phase exists , and alarge a mount of liquid phase will re sult in the form ation of continuous netw ork of liquid phase that is detrim ental to strength andelongation .展开更多
Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hca...Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .展开更多
We investigate the cross-sectional buckling of multi-concentric tubular nanomaterials, which are called multiwalled carbon nanotubes (MWNTs), using an analysis based on thin-shell theory. MWNTs under hydrostatic press...We investigate the cross-sectional buckling of multi-concentric tubular nanomaterials, which are called multiwalled carbon nanotubes (MWNTs), using an analysis based on thin-shell theory. MWNTs under hydrostatic pressure experience radial buckling. As a result of this, different buckling modes are obtained depending on the inter-tube separation d as well as the number of constituent tubes N and the innermost tube diameter. All of the buckling modes are classified into two deformation phases. In the first phase, which corresponds to an elliptic deformation, the radial stiffness increases rapidly with increasing N. In contrast, the second phase yields wavy, corrugated structures along the circumference for which the radial stiffness declines with increasing N. The hard-to-soft phase transition in radial buckling is a direct consequence of the core-shell structure of MWNTs. Special attention is devoted to how the variation in d affects the critical tube number Nc, which separates the two deformation phases observed in N -walled nanotubes, i.e., the elliptic phase for N Nc. We demonstrate that a larger d tends to result in a smaller Nc, which is attributed to the primary role of the interatomic forces between concentric tubes in the hard-to-soft transition during the radial buckling of MWNTs.展开更多
Exceptional room-temperature plastic deformability has been recently uncovered in a series of two-dimensional(2D)van der Waals(vdW)crystals,adding a new facet to these materials alongside the rich physical properties....Exceptional room-temperature plastic deformability has been recently uncovered in a series of two-dimensional(2D)van der Waals(vdW)crystals,adding a new facet to these materials alongside the rich physical properties.Although several mechanisms have been proposed to interpret the deformation of specific materials,a deep and systematic understanding is still missing to rationalize and compare the deformability for a variety of vdW materials.In this work,focusing on typical hexagonal vdW crystals such as graphite,h-BN,transition metal dichalcogenides(TMDCs),and IIIA-VIA compounds,the deformation parameters(slip barrier energy,cleavage energy,elastic modulus)and bond features are calculated,and their correlations are systematically studied.Noticeably,there is a strong positive relation between cross-layer slip/cleavage energy,in-plane modulus,and the intralayer bond strength.The IIIA-VIA compounds(GaS,GaSe,InSe)are predicted to show a larger deformability factor,probably due to their weaker and softer chemical bonds.Moreover,it is anticipated that the deformability can be further modulated by constructing superlattice structures.These findings will facilitate the understanding and development of a variety of deformable 2D inorganic semiconductors as both few-layers and bulks.展开更多
随着清洁可再生能源的不断发展,利用洋流能为水下微型无线传感器提供电能已成为研究热点。水下涡激振动能量俘获系统是一种在浅海低流速条件下利用涡激振动效应俘获洋流能的发电装置。本文将非线性恢复力、单向轴承及齿轮齿条机构与振...随着清洁可再生能源的不断发展,利用洋流能为水下微型无线传感器提供电能已成为研究热点。水下涡激振动能量俘获系统是一种在浅海低流速条件下利用涡激振动效应俘获洋流能的发电装置。本文将非线性恢复力、单向轴承及齿轮齿条机构与振动钝体结合,提出一种新型基于洋流能的涡激振动能量俘获系统。采用Van der Pol方程描述流体和钝体间的耦合效应,建立系统流-固-电耦合动力学方程。对系统进行稳定性分析,得到系统在单稳、双稳及三稳态情况下的参数数值范围,将3种稳态下系统的振幅比进行对比,发现系统处于三稳态时具有较强的发电优势。借助数值仿真,通过钝体振动的时域图、相图、分岔图及庞加莱截面详细研究流体参数(水流流速)和结构参数(质量比和阻尼比)对系统位移响应的影响,并分析单向轴承对传动轴转速的影响。分析质量比和阻尼比对发电功率的影响。结果表明,三稳态系统拥有非常丰富的非线性动力学行为,出现混沌运动、多周期运动及准周期运动,阻尼比的变化主要影响发电功率的峰值,而质量比的变化主要影响涡激振动的共振区间范围。展开更多
We aim to systematically review challenges imposed by emerging distributed energy resources(DERs)to model in two basic distribution management system(DMS)online applications—power flow and short-circuit analysis,as w...We aim to systematically review challenges imposed by emerging distributed energy resources(DERs)to model in two basic distribution management system(DMS)online applications—power flow and short-circuit analysis,as well as to offer a systematic review of potential solutions.In the last decade,electronically coupled DERs became increasingly popular.DERs can employ a wide range of control strategies for power,current,or voltage control,in both normal and faulted conditions.Therefore,DERs cannot be modeled with the traditional PQ(load or generator bus)or PV(generator bus)bus types used for modeling synchronous and induction machines in online power flow calculations.Moreover,since fault currents of DERs are limited to predefined maximal values,electronically coupled DERs cannot be represented with traditional voltage source behind impedance models for online short-circuit calculation(SCC).However,most of the DMS software packages still use the traditional models to represent all DER types,including those that are electronically coupled.This paper shows that there will be large calculation errors in such practice,which make the system model an inadequate representation of the system.This will lead to serious errors in the management,control,and operation of distribution systems.Nonetheless,potential solutions to the challenges are systematically reviewed.Finally,the calculation results on a distribution test system with all DER types are used to prove the claim.展开更多
Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers....Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers.It has been extensively studied in various systems,including parallel nanowires,double quantum wells,and double-layer graphene.Here,we report the observation of Coulomb drag in a novel system consisting of two graphene layers separated laterally by a 30 nm gap within the material plane,exhibiting behavior distinct from that in vertical graphene heterostructures.Our experiments reveal pronounced negative drag resistances under an out-of-plane magnetic field at the quantum Hall edges,reaching a maximum when the carrier densities in both graphene layers are tuned to the charge neutrality point via gate voltages.Our work establish two separate and spatially closed quantum Hall edge modes as a new platform to explore electronic interaction physics between one dimensional systems.展开更多
The second order diffraction forces on a floating semicircular cylinder and a submerged circular cylinder are calculated using the method of Lighthill(ref.3). The first order potential is obtained by the multipole exp...The second order diffraction forces on a floating semicircular cylinder and a submerged circular cylinder are calculated using the method of Lighthill(ref.3). The first order potential is obtained by the multipole expansion and numerical results are provided.展开更多
Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics...Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.展开更多
If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate...If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate sound wave towards surronding water. It has been revealed by previous investigations that the amplitude of backscattering sound appears to be minimum at the eigenfrequencies of the underwater metallic cylinders because of the destructive interference between reradiated wave of the eigenvibration and the geometrical reflected wave from surface of the cylinders. In this paper, a new phenomenon has been revealed. The amplitude of backscattering sound appears to be maximum at the eigenfrequencies of a cylinder made from nonmetallic material in which the velocity of elastic transverse wave is less than the sound velocity in water.展开更多
China's efforts to build a harmonious world begin with establishing peaceful borders with its neighbors China's recent contribution to the world of international relations is the promotion of "building a ...China's efforts to build a harmonious world begin with establishing peaceful borders with its neighbors China's recent contribution to the world of international relations is the promotion of "building a harmonious world together," put forward by President Hu Jintao at the 60th anniversary of the UN in September 2005. As the core of the country's peaceful foreign policy in the new era, this approach has been well received and widely discussed in the international community. Meanwhile, Chinese foreign pol...展开更多
The fundamentals of cohesive powder consolidation and flow behaviour using a reasonable combination of particle and continuum mechanics are explained. By means of the model 搒tiff particles with soft contacts? the inf...The fundamentals of cohesive powder consolidation and flow behaviour using a reasonable combination of particle and continuum mechanics are explained. By means of the model 搒tiff particles with soft contacts? the influ-ence of elastic-plastic repulsion in particle contacts is demonstrated. With this as the physical basis, the stationary yield locus, instantaneous yield loci and consolidation loci, flow function and compression function are presented. The flow properties of a very cohesive titania nanopowder (dS=200 nm) are shown. These models are used to evaluate shear cell test results as constitutive functions for computer aided apparatus design for reliable powder flow.展开更多
Helsmoortel-Van der Aa综合征(HVDAS)是一种罕见的神经发育障碍性疾病,主要由活性依赖性神经保护蛋白(ADNP)基因突变引起,是最常见的孤独症谱系障碍(ASD)单基因病因之一。本文分析2024年就诊于海口市妇幼保健院的1例患儿,男,3岁10个月...Helsmoortel-Van der Aa综合征(HVDAS)是一种罕见的神经发育障碍性疾病,主要由活性依赖性神经保护蛋白(ADNP)基因突变引起,是最常见的孤独症谱系障碍(ASD)单基因病因之一。本文分析2024年就诊于海口市妇幼保健院的1例患儿,男,3岁10个月,因“运动、语言发育迟缓2年余,社交障碍1年余”入院,检查发现患儿存在孤独症谱系障碍、全面发育迟缓、特殊面容、矮小、脑积水等临床表现,基因检测发现患儿携带ADNP基因杂合突变{NM_001282531.3(ADNP):c.2189(exon6)delG[p.(Arg730Glnfs3)]},其父母及妹妹均未携带该突变。总结临床资料并结合文献复习,ADNP基因在染色质重塑和神经发育障碍中发挥重要作用,ADNP基因突变可累及多系统。此例HVDAS具有典型临床表现,并拓宽了脑积水的表型谱,为此类基因变异的遗传咨询以及临床医师的早期识别提供了参考依据。展开更多
基金financial support from the Australian Research Council in grants DP180101744 and DP180101955support from the US National Science Foundation under Grant DMR-1923929。
文摘Near-equiatomic NiTi shape memory alloys are known to exhibit Lüders-type deformation associated with a stress-induced transformation.Many studies have been conducted in the past mainly focusing on the macroscopic characteristics of the phenomenon and some theories have been proposed in the literature to explain its mechanisms,but some aspects of this phenomenon are still unclear,particularly at the microscopic scale.This study investigated the local strain evolution during the initiation and propagation of Lüders band in a pseudoelastic NiTi alloy during tensile deformation by means of digital image correlation(DIC)analysis.Based on the evidence collected,distinct stages of Lüders band formation and propagation are defined and the corresponding local strain rates are obtained.These local strain rates are much higher than the global strain rate of the testing,giving insight to the mechanism of this phenomenon.
基金financially supported by the BAJC(Baosteel-Australia Joint Research and Development Centre)Project。
文摘In this study,the high-strength pipe steel,i.e.X80,was heated at 260℃for half an hour followed by air cooling for thermal simulation of pipe coating process.During the uniaxial loading of the specified tension samples,the migration behaviour of Lüders bands and the re-distribution of stress after strain ageing heat treatment were investigated using digital image correlation.Digital image correlation was adopted to characterise the local axial and shear strain fields of samples that were extracted from different locations across the wall thickness of the high-strength pipe steel,and electron backscatter diffraction was used to compare the evolution of crystallographic texture among these locations.Other characterisation methods regarding microstructure and mechanical properties were conducted meanwhile,including optical microscopy,scanning electron microscopy and X-ray diffraction to accurately define the detailed performances that strain ageing,i.e.being heated to 260℃for half an hour,has led to.The obtained results show that the Lüders band-related microstructure,dislocation density,lattice constant and texture vary at the different locations across the wall thickness and influence the fi nal mechanical properties of the selected high-strength pipe steel.
文摘Editor's note: We are sorry that because of the over-crowded space in our last issue, we are delayed in presenting the second part of the report delivered by the CAS President Lu Yongxiang at the 2002 working conference of CAS. The report appears in two installments in this and the 1st issue of this volume.
文摘Addition of Fe B C and Fe Mo B C m aster alloy pow ders to Fe Mo B Csintered steels can ac tivate the sintering process by liquid phase sintering . The for m ation of liquid ( α- Fe + ( Fe , Mo) 2 B+ Fe3( B, C) → L) i m proves m echanical properties of the steels , and ultim ate tensilestrengths of 684 774 M Pa , i m pact energy of 47 ±7 Jand elongation of 2 5 ±0 9 were ob tained . Optim u m a mount of liquid phase exists , and alarge a mount of liquid phase will re sult in the form ation of continuous netw ork of liquid phase that is detrim ental to strength andelongation .
文摘Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .
文摘We investigate the cross-sectional buckling of multi-concentric tubular nanomaterials, which are called multiwalled carbon nanotubes (MWNTs), using an analysis based on thin-shell theory. MWNTs under hydrostatic pressure experience radial buckling. As a result of this, different buckling modes are obtained depending on the inter-tube separation d as well as the number of constituent tubes N and the innermost tube diameter. All of the buckling modes are classified into two deformation phases. In the first phase, which corresponds to an elliptic deformation, the radial stiffness increases rapidly with increasing N. In contrast, the second phase yields wavy, corrugated structures along the circumference for which the radial stiffness declines with increasing N. The hard-to-soft phase transition in radial buckling is a direct consequence of the core-shell structure of MWNTs. Special attention is devoted to how the variation in d affects the critical tube number Nc, which separates the two deformation phases observed in N -walled nanotubes, i.e., the elliptic phase for N Nc. We demonstrate that a larger d tends to result in a smaller Nc, which is attributed to the primary role of the interatomic forces between concentric tubes in the hard-to-soft transition during the radial buckling of MWNTs.
基金supported by the National Natural Science Foundation of China(T2122013,52373292,52232010)the China Postdoctoral Science Foundation(BX20230222).
文摘Exceptional room-temperature plastic deformability has been recently uncovered in a series of two-dimensional(2D)van der Waals(vdW)crystals,adding a new facet to these materials alongside the rich physical properties.Although several mechanisms have been proposed to interpret the deformation of specific materials,a deep and systematic understanding is still missing to rationalize and compare the deformability for a variety of vdW materials.In this work,focusing on typical hexagonal vdW crystals such as graphite,h-BN,transition metal dichalcogenides(TMDCs),and IIIA-VIA compounds,the deformation parameters(slip barrier energy,cleavage energy,elastic modulus)and bond features are calculated,and their correlations are systematically studied.Noticeably,there is a strong positive relation between cross-layer slip/cleavage energy,in-plane modulus,and the intralayer bond strength.The IIIA-VIA compounds(GaS,GaSe,InSe)are predicted to show a larger deformability factor,probably due to their weaker and softer chemical bonds.Moreover,it is anticipated that the deformability can be further modulated by constructing superlattice structures.These findings will facilitate the understanding and development of a variety of deformable 2D inorganic semiconductors as both few-layers and bulks.
文摘随着清洁可再生能源的不断发展,利用洋流能为水下微型无线传感器提供电能已成为研究热点。水下涡激振动能量俘获系统是一种在浅海低流速条件下利用涡激振动效应俘获洋流能的发电装置。本文将非线性恢复力、单向轴承及齿轮齿条机构与振动钝体结合,提出一种新型基于洋流能的涡激振动能量俘获系统。采用Van der Pol方程描述流体和钝体间的耦合效应,建立系统流-固-电耦合动力学方程。对系统进行稳定性分析,得到系统在单稳、双稳及三稳态情况下的参数数值范围,将3种稳态下系统的振幅比进行对比,发现系统处于三稳态时具有较强的发电优势。借助数值仿真,通过钝体振动的时域图、相图、分岔图及庞加莱截面详细研究流体参数(水流流速)和结构参数(质量比和阻尼比)对系统位移响应的影响,并分析单向轴承对传动轴转速的影响。分析质量比和阻尼比对发电功率的影响。结果表明,三稳态系统拥有非常丰富的非线性动力学行为,出现混沌运动、多周期运动及准周期运动,阻尼比的变化主要影响发电功率的峰值,而质量比的变化主要影响涡激振动的共振区间范围。
基金the Ministry of Education and Science of the Republic of Serbia for its support to this research through the ProjectⅢ-42004.
文摘We aim to systematically review challenges imposed by emerging distributed energy resources(DERs)to model in two basic distribution management system(DMS)online applications—power flow and short-circuit analysis,as well as to offer a systematic review of potential solutions.In the last decade,electronically coupled DERs became increasingly popular.DERs can employ a wide range of control strategies for power,current,or voltage control,in both normal and faulted conditions.Therefore,DERs cannot be modeled with the traditional PQ(load or generator bus)or PV(generator bus)bus types used for modeling synchronous and induction machines in online power flow calculations.Moreover,since fault currents of DERs are limited to predefined maximal values,electronically coupled DERs cannot be represented with traditional voltage source behind impedance models for online short-circuit calculation(SCC).However,most of the DMS software packages still use the traditional models to represent all DER types,including those that are electronically coupled.This paper shows that there will be large calculation errors in such practice,which make the system model an inadequate representation of the system.This will lead to serious errors in the management,control,and operation of distribution systems.Nonetheless,potential solutions to the challenges are systematically reviewed.Finally,the calculation results on a distribution test system with all DER types are used to prove the claim.
基金support from the National Key Projects for Research and Development of China(Grant Nos.2022YFA1204700,2021YFA1400400)National Natural Science Foundation of China(Grant No.12525403)+3 种基金Natural Science Foundation of Jiangsu Province(Grant Nos.BK20220066,BK20233001)Program for Innovative Talents and Entrepreneur in Jiangsu(Grant No.JSSCTD202101)support from the JSPS KAKENHI(Grant Numbers 21H05233 and 23H02052)World Premier International Research Center Initiative(WPI),MEXT,Japan.
文摘Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers.It has been extensively studied in various systems,including parallel nanowires,double quantum wells,and double-layer graphene.Here,we report the observation of Coulomb drag in a novel system consisting of two graphene layers separated laterally by a 30 nm gap within the material plane,exhibiting behavior distinct from that in vertical graphene heterostructures.Our experiments reveal pronounced negative drag resistances under an out-of-plane magnetic field at the quantum Hall edges,reaching a maximum when the carrier densities in both graphene layers are tuned to the charge neutrality point via gate voltages.Our work establish two separate and spatially closed quantum Hall edge modes as a new platform to explore electronic interaction physics between one dimensional systems.
文摘The second order diffraction forces on a floating semicircular cylinder and a submerged circular cylinder are calculated using the method of Lighthill(ref.3). The first order potential is obtained by the multipole expansion and numerical results are provided.
基金supported by National Natural Science Foundation of China(61921002 and 92163204)。
文摘Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.
基金The project was supported by the National Science Foundation
文摘If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate sound wave towards surronding water. It has been revealed by previous investigations that the amplitude of backscattering sound appears to be minimum at the eigenfrequencies of the underwater metallic cylinders because of the destructive interference between reradiated wave of the eigenvibration and the geometrical reflected wave from surface of the cylinders. In this paper, a new phenomenon has been revealed. The amplitude of backscattering sound appears to be maximum at the eigenfrequencies of a cylinder made from nonmetallic material in which the velocity of elastic transverse wave is less than the sound velocity in water.
文摘China's efforts to build a harmonious world begin with establishing peaceful borders with its neighbors China's recent contribution to the world of international relations is the promotion of "building a harmonious world together," put forward by President Hu Jintao at the 60th anniversary of the UN in September 2005. As the core of the country's peaceful foreign policy in the new era, this approach has been well received and widely discussed in the international community. Meanwhile, Chinese foreign pol...
文摘The fundamentals of cohesive powder consolidation and flow behaviour using a reasonable combination of particle and continuum mechanics are explained. By means of the model 搒tiff particles with soft contacts? the influ-ence of elastic-plastic repulsion in particle contacts is demonstrated. With this as the physical basis, the stationary yield locus, instantaneous yield loci and consolidation loci, flow function and compression function are presented. The flow properties of a very cohesive titania nanopowder (dS=200 nm) are shown. These models are used to evaluate shear cell test results as constitutive functions for computer aided apparatus design for reliable powder flow.
文摘Helsmoortel-Van der Aa综合征(HVDAS)是一种罕见的神经发育障碍性疾病,主要由活性依赖性神经保护蛋白(ADNP)基因突变引起,是最常见的孤独症谱系障碍(ASD)单基因病因之一。本文分析2024年就诊于海口市妇幼保健院的1例患儿,男,3岁10个月,因“运动、语言发育迟缓2年余,社交障碍1年余”入院,检查发现患儿存在孤独症谱系障碍、全面发育迟缓、特殊面容、矮小、脑积水等临床表现,基因检测发现患儿携带ADNP基因杂合突变{NM_001282531.3(ADNP):c.2189(exon6)delG[p.(Arg730Glnfs3)]},其父母及妹妹均未携带该突变。总结临床资料并结合文献复习,ADNP基因在染色质重塑和神经发育障碍中发挥重要作用,ADNP基因突变可累及多系统。此例HVDAS具有典型临床表现,并拓宽了脑积水的表型谱,为此类基因变异的遗传咨询以及临床医师的早期识别提供了参考依据。
