期刊文献+
共找到434篇文章
< 1 2 22 >
每页显示 20 50 100
Baryon Magnetic Moment in the Scalar Strong Interaction Hadron Theory
1
作者 F. C. Hoh 《Journal of Modern Physics》 2014年第11期995-1000,共6页
The magnetic moments of the baryon octet are derived from a first principle’s theory, the scalar strong interaction hadron theory, and are in approximate agreement with data. It is conjectured that this agreement may... The magnetic moments of the baryon octet are derived from a first principle’s theory, the scalar strong interaction hadron theory, and are in approximate agreement with data. It is conjectured that this agreement may be improved by including the “spin-orbit coupling” term not evaluated here. 展开更多
关键词 BARYON Magnetic moment First Principle’s theory Internal COORDINATES
下载PDF
Cooperative game theory-based steering law design of a CMG system
2
作者 HUA Bing NI Rui +2 位作者 ZHENG Mohong WU Yunhua CHEN Zhiming 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2023年第1期185-196,共12页
Spacecraft require a large-angle manoeuvre when performing agile manoeuvring tasks, therefore a control moment gyroscope(CMG) is employed to provide a strong moment.However, the control of the CMG system easily falls ... Spacecraft require a large-angle manoeuvre when performing agile manoeuvring tasks, therefore a control moment gyroscope(CMG) is employed to provide a strong moment.However, the control of the CMG system easily falls into singularity, which renders the actuator unable to output the required moment. To solve the singularity problem of CMGs, the control law design of a CMG system based on a cooperative game is proposed. First, the cooperative game model is constructed according to the quadratic programming problem, and the cooperative strategy is constructed. When the strategy falls into singularity, the weighting coefficient is introduced to carry out the strategy game to achieve the optimal strategy. In theory, it is proven that the cooperative game manipulation law of the CMG system converges, the sum of the CMG frame angular velocities is minimized, the energy consumption is small, and there is no output torque error. Then, the CMG group system is simulated.When the CMG system is near the singular point, it can quickly escape the singularity. When the CMG system falls into the singularity, it can also escape the singularity. Considering the optimization of angular momentum and energy consumption, the feasibility of the CMG system steering law based on a cooperative game is proven. 展开更多
关键词 control moment gyroscopes(CMG) cooperative game theory steering laws
下载PDF
基于密度泛函理论对团簇CrPS_(4)的光谱分析 被引量:2
3
作者 方志刚 刘立娥 +3 位作者 吴庭慧 宋静丽 原琳 魏代霞 《贵州师范大学学报(自然科学版)》 CAS 北大核心 2024年第3期1-8,共8页
为快速、高效得到物质的谱图数据,利用计算化学方法,根据拓扑学原理,利用密度泛函理论,对团簇CrPS_(4)10种优化构型的红外光谱、拉曼光谱、偶极矩以及极化率进行了分析,并利用构型2^((4))的理论红外谱图与前人所得实际光谱图进行了对比... 为快速、高效得到物质的谱图数据,利用计算化学方法,根据拓扑学原理,利用密度泛函理论,对团簇CrPS_(4)10种优化构型的红外光谱、拉曼光谱、偶极矩以及极化率进行了分析,并利用构型2^((4))的理论红外谱图与前人所得实际光谱图进行了对比。结果显示:CrPS_(4)红外光谱的波峰大致分布在300~700 cm^(-1)范围内,拉曼光谱的波峰范围主要分布在200~700 cm^(-1)范围内;团簇CrPS_(4)振动形式为伸缩振动时,其对入射光的吸收强度较大;在频率较低的波段,CrPS_(4)更易发生红外吸收,在频率较高的波段,更易发生拉曼散射;总偶极矩的排列顺序为2^((2))>6^((4))>4^((2))>3^((2))>3^((4))>4^((4))>1^((2))>2^((4))>5^((4))>1^((4)),偶极矩越大,红外活性越强;极化率大小关系满足5^((4))<1^((4))<6^((4))<4^((4))<3^((4))<1^((2))<2^((4))<2^((2))<3^((2))<4^((2)),极化率越大,拉曼活性越强;所有构型的3大主轴中,XX轴的极化率均大于YY轴与ZZ轴;构型2^((4))的理论光谱图与实际结果对比发现,两者光谱图波峰频率基本吻合,实验与理论分析互为补充。 展开更多
关键词 光谱 密度泛函理论 红外光谱 拉曼光谱 极化率 偶极矩
下载PDF
基于弯矩修正法的浅水区海底直铺管道允许悬跨长度计算
4
作者 付长静 王锦国 赵天龙 《计算力学学报》 CAS CSCD 北大核心 2024年第3期588-592,共5页
海底管道悬空问题是管道工程建设中经常遇到的重要问题,当管道的悬跨长度达到一定值时,管道较容易失稳,而悬空油气管道失稳破坏导致的后果往往非常严重,因此需要对悬空的海底管道进行定期的维护和处理,但由于海上作业难度大,针对悬空管... 海底管道悬空问题是管道工程建设中经常遇到的重要问题,当管道的悬跨长度达到一定值时,管道较容易失稳,而悬空油气管道失稳破坏导致的后果往往非常严重,因此需要对悬空的海底管道进行定期的维护和处理,但由于海上作业难度大,针对悬空管道的治理成本非常高,因此可考虑对处于悬空但在安全允许悬空范围内的管道暂时不进行加固,此时就需要计算管道的允许悬跨长度,为管道的治理提供依据。由于我国油田大多建设在近海地区,因此在考虑管道的悬空问题时需考虑浅水区波浪的特点。本文考虑浅水区波浪的非线性影响,推导得到浅水区波浪场内任意一水质点的水平流速和竖向流速计算公式,并根据该公式和Morison方程,进一步建立了管道悬跨水动力载荷的表达式,最后基于弯矩修正法,提出浅水区平铺海底管道允许悬跨长度计算公式。根据工程实例,结合本文研究,计算得到该工程所在海区平铺管道允许悬跨长度。 展开更多
关键词 浅水波浪理论 弯矩修正法 海底管道 悬跨长度
下载PDF
某海域极端环境下15万吨级FPSO波浪荷载数值研究
5
作者 刘中柏 高宁波 +1 位作者 唐鑫彤 徐业峻 《装备环境工程》 CAS 2024年第4期109-115,共7页
目的评估在役15万吨级FPSO在某海域百年一遇极端波浪作用下典型横剖面的水动力特性,进而得到FPSO的极值荷载,作为FPSO返坞改造的关键控制参数。方法基于国产自主三维频域线性势流软件COMPASS-WALCS,建立15万吨级FPSO湿表面网格模型,根... 目的评估在役15万吨级FPSO在某海域百年一遇极端波浪作用下典型横剖面的水动力特性,进而得到FPSO的极值荷载,作为FPSO返坞改造的关键控制参数。方法基于国产自主三维频域线性势流软件COMPASS-WALCS,建立15万吨级FPSO湿表面网格模型,根据三维绕射-辐射理论,计算湿表面上的水动力荷载,将每个绕射单元上的水动压力直接映射到结构模型上进行计算。采用谱分析方法对百年一遇海况进行分析,得到短期运动极值响应。对响应幅值算子(RAO)和波能谱密度进行谱分析,得到极端波浪下的响应谱,进而得到浮体运动和波浪荷载短期预报各种统计值,利用统计方法求得短期响应的最大值。结果计算了船中部Fr143横剖面的载荷极值,即垂向弯矩、垂向剪力、剖面型心加速度等,发现船舶迎浪时弯矩值最大,随着浪向角增大,弯矩值逐渐减小,剖面垂向剪力则随着浪向角增大逐渐增大。结论FPSO在极端波浪作用下,其大迎浪角条件下荷载更加危险,需要给予格外关注。 展开更多
关键词 浮式生产储卸油装置 势流理论 极端波浪 响应幅值算子 水平弯矩 加速度
下载PDF
最优组合赋权在航空发动机性能评估中的应用
6
作者 冯正兴 张青 卢堂宝 《机械设计与制造》 北大核心 2024年第3期224-228,共5页
为了提高航空发动机机队性能评估的可信度和科学性,提出一种结合改进TOPSIS和最优组合赋权的综合性能评估方法。首先利用单一主、客观赋权法计算各评价指标的权重,再通过基于矩估计理论的最优组合赋权模型得到评价指标的最优组合权重。... 为了提高航空发动机机队性能评估的可信度和科学性,提出一种结合改进TOPSIS和最优组合赋权的综合性能评估方法。首先利用单一主、客观赋权法计算各评价指标的权重,再通过基于矩估计理论的最优组合赋权模型得到评价指标的最优组合权重。基于此权重值,利用余弦相似理论和虚拟负理想解对TOPSIS方法进行改进,得到更为合理的相对贴近度对发动机性能进行评估。以某公司PW4056发动机机队为例进行验证,结果表明所提出的新方法能够有效地评估发动机的性能水平,具有很好的工程应用价值。 展开更多
关键词 航空发动机机队 矩估计理论 最优组合赋权 改进TOPSIS 性能评估
下载PDF
重子磁矩的协变手征有效理论研究
7
作者 周海峰 杨继锋 《华东师范大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第3期12-26,共15页
在SU(3)协变手征有效理论框架下,使用扩展的极小减除(extended minimal subtraction,EMS)方案,计算了至次领头阶(next-to-leading order,NLO)的重子质量和重子磁矩的一圈图修正贡献,并使用实验数据与PACS-CS格点数据组的数据对解析结果... 在SU(3)协变手征有效理论框架下,使用扩展的极小减除(extended minimal subtraction,EMS)方案,计算了至次领头阶(next-to-leading order,NLO)的重子质量和重子磁矩的一圈图修正贡献,并使用实验数据与PACS-CS格点数据组的数据对解析结果进行了数值拟合.结果表明,在NLO重子质量和重子磁矩的修正贡献中,EMS方案可以给出不错的理论结果和数值拟合的结果;该结果相较于重重子方法和红外正规化方法的结果更加优秀,并且与EOMS(extended-on-mass-shell)方案的结果相近. 展开更多
关键词 手征有效场论 扩展的极小减除方案 重子质量 重子磁矩 数值拟合
下载PDF
Non-Uniform Pion Tetrahedron Aether and Electron Tetrahedron Model
8
作者 Rami Rom 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第2期810-824,共15页
We propose that the QCD vacuum pion tetrahedron condensate density vary in space and drops to extremely low values in the Kennan, Barger and Cowie (KBC) void in analogy to earth’s atmospheric density drop with elevat... We propose that the QCD vacuum pion tetrahedron condensate density vary in space and drops to extremely low values in the Kennan, Barger and Cowie (KBC) void in analogy to earth’s atmospheric density drop with elevation from earth. We propose a formula for the gravitation acceleration based on the non-uniform pion tetrahedron condensate. Gravity may be due to the underlying microscopic attraction between quarks and antiquarks, which are part of the vacuum pion tetrahedron condensate. We propose an electron tetrahedron model, where electrons are comprised of tetraquark tetrahedrons, and . The quarks determine the negative electron charge and the or quarks determine the electron two spin states. The electron tetrahedron may perform a high frequency quark exchange reactions with the pion tetrahedron condensate by tunneling through the condensation gap creating a delocalized electron cloud with a fixed spin. The pion tetrahedron may act as a QCD glue bonding electron pairs in atoms and molecules and protons to neutrons in the nuclei. Conservation of valence quarks and antiquarks is proposed. 展开更多
关键词 Standard Model (SM) QCD Vacuum Condensate Electric Dipole moment (EDM) KBC Void ANTIMATTER MOND theory Aether
下载PDF
进油节流调速回路速度精度的可靠性灵敏度分析
9
作者 谷建国 杨俊彦 +2 位作者 张圣东 游世辉 石晓磷 《机床与液压》 北大核心 2024年第6期52-57,共6页
为提升机床产品的工作精度,以进油节流调速回路为研究对象,开展速度精度可靠性及灵敏度的研究。对进油节流调速回路的速度负载特性进行系统分析,推导出液压缸活塞的运动速度;采用随机摄动理论、四阶矩技术建立进油节流调速回路的速度可... 为提升机床产品的工作精度,以进油节流调速回路为研究对象,开展速度精度可靠性及灵敏度的研究。对进油节流调速回路的速度负载特性进行系统分析,推导出液压缸活塞的运动速度;采用随机摄动理论、四阶矩技术建立进油节流调速回路的速度可靠性分析模型;最后通过可靠性灵敏度分析,确定影响运动精度的敏感参数。研究结果表明:节流阀的阀口开度对速度精度可靠性影响最大,因此在设计中应降低设计值并严格控制公差值。 展开更多
关键词 节流调速回路 速度精度 随机摄动理论 四阶矩技术 可靠性灵敏度分析
下载PDF
重大改建船的原船重量重心分布推算
10
作者 谢琴 吴林峰 +1 位作者 施明波 刘在良 《中国修船》 2024年第3期43-46,共4页
文章以“海州湾之星”改建船为例,演算了如何在没有初始重量重心分布的情况下,利用静力学原理推算原船重量重心分布的方法,并利用该方法得到原船空船重量重心分布,核算了改建后船舶的总纵强度,并取得船级社的认可,可为同行提供借鉴。
关键词 空船重量重心分布 总纵强度 空心梁理论 剪力弯矩图
下载PDF
Ordered Rate Constitutive Theories for Non-Classical Thermoviscoelastic Fluids with Internal Rotation Rates 被引量:1
11
作者 K. S. Surana S. W. Long J. N. Reddy 《Applied Mathematics》 2018年第8期907-939,共33页
The paper presents constitutive theories for non-classical thermoviscoelastic fluids with dissipation and memory using a thermodynamic framework based on entirety of velocity gradient tensor. Thus, the conservation an... The paper presents constitutive theories for non-classical thermoviscoelastic fluids with dissipation and memory using a thermodynamic framework based on entirety of velocity gradient tensor. Thus, the conservation and the balance laws used in this work incorporate symmetric as well as antisymmetric part of the velocity gradient tensor. The constitutive theories derived here hold in coand contra-variant bases as well as in Jaumann rates and are derived using convected time derivatives of Green’s and Almansi strain tensors as well as the Cauchy stress tensor and its convected time derivatives in appropriate bases. The constitutive theories are presented in the absence as well as in the presence of the balance of moment of moments as balance law. It is shown that the dissipation mechanism and the fading memory in such fluids are due to stress rates as well as moment rates and their conjugates. The material coefficients are derived for the general forms of the constitutive theories based on integrity. Simplified linear (or quasi-linear) forms of the constitutive theories are also presented. Maxwell, Oldroyd-B and Giesekus constitutive models for non-classical thermoviscoelastic fluids are derived and are compared with those derived based on classical continuum mechanics. Both, compressible and incompressible thermoviscoelastic fluids are considered. 展开更多
关键词 RATE CONSTITUTIVE Theories Non-Classical Thermofluids With Memory Convected Time Derivatives Internal Rotation Gradient TENSOR Generators and INVARIANTS CAUCHY moment TENSOR
下载PDF
Caring Science in Nursing.coming of Age in:Theory-Practice-Research 被引量:15
12
作者 Jean Watson 《护理学杂志(综合版)》 CSCD 2014年第1期1-3,共3页
Jean Watson(华生)博士通过探究护理的哲学与科学根基,比较自然科学之医学典范与人文科学之护理典范的差异,以"Caring"为护理核心本质,发展了关怀科学(Caring Science)。本论著中Watson博士概述了关怀科学的理论根基——整体... Jean Watson(华生)博士通过探究护理的哲学与科学根基,比较自然科学之医学典范与人文科学之护理典范的差异,以"Caring"为护理核心本质,发展了关怀科学(Caring Science)。本论著中Watson博士概述了关怀科学的理论根基——整体论(Unitary Ontology),及其伦理归属(Ethic of Belonging);介绍了人文关怀的10大要素(Caritas Processes);阐述了人际间关怀时刻(Transpersonal Caring Moment)的内涵以及护理人员实现人性关怀的方法学(CaritasHeart TM Methodology)。最后,Watson博士提出了关怀科学在护理实践应用的指导方针。希望此论著对我国护理工作者认识和实践人文关怀有所裨益! 展开更多
关键词 临床护理 护理方法 护理学 护士
下载PDF
The moment-method form of Pocklington's integral equation above ground
13
作者 江滨浩 刘永坦 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2000年第3期14-18,共5页
Pocklington’s integral equation is presented for analysis of current distributions on wire antenna above ground. Sommerfeld type integrals, the kernel functions of the integral equation, can be approximately expresse... Pocklington’s integral equation is presented for analysis of current distributions on wire antenna above ground. Sommerfeld type integrals, the kernel functions of the integral equation, can be approximately expressed as the elementary functions using the Fresnel plane wave reflection coefficients method; and the Pocklington’s integral equation will be rearranged into a linear equation with solution easily obtained by using the method of moments, when the sinusoidal sub domain expansion is chosen to express the current distributions. 展开更多
关键词 electromagnetic theory Pocklington’s INTEGRAL EQUATION METHOD of momentS sommerfeld type INTEGRALS
下载PDF
Effects of charge on the structures and spin moments of Nil3 cluster
14
作者 谢尊 马庆敏 +2 位作者 王静 刘英 李有成 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第12期3637-3641,共5页
The structural stability and magnetic properties of the icosahedral Ni13, Ni13^+1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximatio... The structural stability and magnetic properties of the icosahedral Ni13, Ni13^+1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximations for the exchange-correlation energy. The calculated results show that the ground states of neutral and charged clusters all favour a D3d structure, a distorted icosahedron, due to the Jahn-Teller effect. The radial distortions caused by doping one electron and by doping one hole are opposite to each other. Doping one electron will result in a 1/2 decrease and doping one hole will result in a 1/2 increase of the total spin. Both increasing interatomic spacing and decreasing coordination will lead to an enhancement of the spin magnetic moments for Nil3 clusters. 展开更多
关键词 density functional theory Jahn-Teller distortion stable structures spin magnetic moments
下载PDF
The effect of a permanent dipole moment on the polar molecule cavity quantum electrodynamics
15
作者 赵晶云 秦立国 +2 位作者 蔡勋明 林强 王中阳 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第4期127-136,共10页
A dressed-state perturbation theory beyond the rotating wave approximation (RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field.... A dressed-state perturbation theory beyond the rotating wave approximation (RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments (PDM) and the counter-rotating wave term (CRT) can be shown separately. The validity of these explicit results is discussed by comparison with the direct numerical simulation. Compared to the CRT coupling, PDM results in the coupling of more dressed states and the energy shift is proportional to the square of the normalized permanent dipole difference, and a greater Bloch-Siegert shift can be produced in the giant dipole molecule cavity QED. In addition, our method can also be extended to the solution of the two-level atom Rabi model Hamiltonian beyond the RWA. 展开更多
关键词 dressed-state perturbation theory permanent dipole moment counter-rotating wave term Bloch-Siegert shift
下载PDF
Rate Constitutive Theories of Orders n and 1n for Internal Polar Non-Classical Thermofluids without Memory
16
作者 Karan S. Surana Stephen W. Long J. N. Reddy 《Applied Mathematics》 2016年第16期2033-2077,共45页
In recent papers, Surana et al. presented internal polar non-classical Continuum theory in which velocity gradient tensor in its entirety was incorporated in the conservation and balance laws. Thus, this theory incorp... In recent papers, Surana et al. presented internal polar non-classical Continuum theory in which velocity gradient tensor in its entirety was incorporated in the conservation and balance laws. Thus, this theory incorporated symmetric part of the velocity gradient tensor (as done in classical theories) as well as skew symmetric part representing varying internal rotation rates between material points which when resisted by deforming continua result in dissipation (and/or storage) of mechanical work. This physics referred as internal polar physics is neglected in classical continuum theories but can be quite significant for some materials. In another recent paper Surana et al. presented ordered rate constitutive theories for internal polar non-classical fluent continua without memory derived using deviatoric Cauchy stress tensor and conjugate strain rate tensors of up to orders n and Cauchy moment tensor and its conjugate symmetric part of the first convected derivative of the rotation gradient tensor. In this constitutive theory higher order convected derivatives of the symmetric part of the rotation gradient tensor are assumed not to contribute to dissipation. Secondly, the skew symmetric part of the velocity gradient tensor is used as rotation rates to determine rate of rotation gradient tensor. This is an approximation to true convected time derivatives of the rotation gradient tensor. The resulting constitutive theory: (1) is incomplete as it neglects the second and higher order convected time derivatives of the symmetric part of the rotation gradient tensor;(2) first convected derivative of the symmetric part of the rotation gradient tensor as used by Surana et al. is only approximate;(3) has inconsistent treatment of dissipation due to Cauchy moment tensor when compared with the dissipation mechanism due to deviatoric part of symmetric Cauchy stress tensor in which convected time derivatives of up to order n are considered in the theory. The purpose of this paper is to present ordered rate constitutive theories for deviatoric Cauchy strain tensor, moment tensor and heat vector for thermofluids without memory in which convected time derivatives of strain tensors up to order n are conjugate with the Cauchy stress tensor and the convected time derivatives of the symmetric part of the rotation gradient tensor up to orders 1n are conjugate with the moment tensor. Conservation and balance laws are used to determine the choice of dependent variables in the constitutive theories: Helmholtz free energy density Φ, entropy density η, Cauchy stress tensor, moment tensor and heat vector. Stress tensor is decomposed into symmetric and skew symmetric parts and the symmetric part of the stress tensor and the moment tensor are further decomposed into equilibrium and deviatoric tensors. It is established through conjugate pairs in entropy inequality that the constitutive theories only need to be derived for symmetric stress tensor, moment tensor and heat vector. Density in the current configuration, convected time derivatives of the strain tensor up to order n, convected time derivatives of the symmetric part of the rotation gradient tensor up to orders 1n, temperature gradient tensor and temperature are considered as argument tensors of all dependent variables in the constitutive theories based on entropy inequality and principle of equipresence. The constitutive theories are derived in contravariant and covariant bases as well as using Jaumann rates. The nth and 1nth order rate constitutive theories for internal polar non-classical thermofluids without memory are specialized for n = 1 and 1n = 1 to demonstrate fundamental differences in the constitutive theories presented here and those used presently for classical thermofluids without memory and those published by Surana et al. for internal polar non-classical incompressible thermofluids. 展开更多
关键词 Rate Constitutive Theories Non-Classical Thermofluids Without Memory Convected Time Derivatives Internal Rotation Gradient Tensor Generators and Invariants Cauchy moment Tensor
下载PDF
涡扇叶片在机测量自适应采样方法 被引量:1
17
作者 高峰 潘子月 +3 位作者 张旭涛 李艳 张东亚 魏晓庆 《计算机集成制造系统》 EI CSCD 北大核心 2023年第3期843-851,共9页
涡扇叶片的加工和检测精度直接影响到涡扇的结构强度和气动性能。为提高叶片的在机测量精度和效率,提出一种基于弯矩理论的自适应曲面采样方法,以解决叶片曲面在前缘和后缘位置处曲率急剧变化以及轮廓面的全局采样问题。根据曲面的几何... 涡扇叶片的加工和检测精度直接影响到涡扇的结构强度和气动性能。为提高叶片的在机测量精度和效率,提出一种基于弯矩理论的自适应曲面采样方法,以解决叶片曲面在前缘和后缘位置处曲率急剧变化以及轮廓面的全局采样问题。根据曲面的几何特征变化,自适应确定检测点的分布密度和数量。仿真和在机测量实验验证了该方法的有效性和可行性。通过与双向等参数法、改进的分区等参数法和Hammersley序列法的采样结果对比表明,基于弯矩理论的自适应采样方法实现了对采样点位置及数量的微细精准调整,采样误差小,重构表面精度高,满足在机测量对时间和精度的要求。 展开更多
关键词 涡扇叶片 非均匀有理B样条 曲面建模 弯矩理论 自适应采样
下载PDF
椭圆封头与筒体过渡段应力分布
18
作者 刘红姣 刘喆 +1 位作者 唐柳华 林雪慧 《机械设计》 CSCD 北大核心 2023年第8期42-49,共8页
在中低压容器常规设计中,对椭圆封头与筒体过渡段的边缘应力一般不予计算,只在结构上进行局部处理。为了探究边缘应力对椭圆封头及筒体过渡段的影响,文中针对5种不同直径的椭圆封头,采用ABAQUS有限元分析软件和有矩理论,对比研究了封头... 在中低压容器常规设计中,对椭圆封头与筒体过渡段的边缘应力一般不予计算,只在结构上进行局部处理。为了探究边缘应力对椭圆封头及筒体过渡段的影响,文中针对5种不同直径的椭圆封头,采用ABAQUS有限元分析软件和有矩理论,对比研究了封头过渡段内外壁面应力的变化规律,同时采用有矩理论研究了封头过渡段内外壁面边缘应力的影响范围及最大值出现的位置。结果表明:5种不同直径封头直边段内外壁面存在大小相等、方向相反的边缘应力,内外壁面最大径向边缘应力与筒体薄膜应力相当,最大值至连接处的距离远大于椭圆形封头标准规定的直边高度,直径越大,距离越远。封头标准GB/T 25198—2010中规定直边高度处径向应力超出筒体薄膜应力的44%~61%。直边段与筒体薄膜应力相当的横截面距连接处0~15 mm,与直径关系不大。研究结果可对中低压容器的设计制造和安全运行起到一定的指导作用,为封头标准的修订提供参考依据。 展开更多
关键词 椭圆封头 直边高度 有限元分析 有矩理论 边缘应力
下载PDF
基于放宽静稳定度空空导弹重定向研究
19
作者 李斌 郭正玉 《航空兵器》 CSCD 北大核心 2023年第6期37-43,共7页
采用放宽静稳定度设计,利用空空导弹静不稳定性产生的气动力矩,设计了空空导弹重定向使用流程,提出了空空导弹完成重定向的运动学标志。根据细长体理论和粘性横流理论分析了空空导弹重定向过程中的气动力和力矩,认为无控细长旋成体无法... 采用放宽静稳定度设计,利用空空导弹静不稳定性产生的气动力矩,设计了空空导弹重定向使用流程,提出了空空导弹完成重定向的运动学标志。根据细长体理论和粘性横流理论分析了空空导弹重定向过程中的气动力和力矩,认为无控细长旋成体无法满足本文提出的完成重定向的运动学标志,必须增加气动舵面或直接力等控制方式。以大长细比鸭式舵身的简单组合体为研究对象,采用工程理论方法获取0°~180°攻角范围内气动特性,并计算了重定向过程中空空导弹轨迹和姿态。结果表明,本文提出的基于放宽静稳定度的重定向技术能够在1.15 s内实现空空导弹安全、快速、稳定的重定向。最后,分析了空空导弹重定向过程中应该注意的关键设计问题。 展开更多
关键词 空空导弹 放宽静稳定度 重定向 细长体理论 粘性横流理论 大攻角 俯仰力矩
下载PDF
团簇Mo_(2)S_(4)的磁学性质与偶极矩研究
20
作者 方志刚 吴庭慧 +3 位作者 王倩 刘立娥 宋静丽 魏代霞 《江西师范大学学报(自然科学版)》 CAS 北大核心 2023年第4期405-411,共7页
为分析团簇Mo_(2)S_(4)的磁学性质与极性强弱,运用Gaussian09程序对所设计的团簇Mo_(2)S_(4)模型在B3LYP/lanl2dz水平下进行优化计算,得到了10种优化构型.因为单重态构型核外无成单电子,所以该文仅对三重态构型的磁学性质展开讨论.对成... 为分析团簇Mo_(2)S_(4)的磁学性质与极性强弱,运用Gaussian09程序对所设计的团簇Mo_(2)S_(4)模型在B3LYP/lanl2dz水平下进行优化计算,得到了10种优化构型.因为单重态构型核外无成单电子,所以该文仅对三重态构型的磁学性质展开讨论.对成单电子数、磁矩、自旋布居数、电子自旋密度差图和偶极矩等数据进行研究.研究结果表明:团簇Mo_(2)S_(4)具有较好的磁学性能,金属原子Mo对团簇Mo_(2)S_(4)的磁性起主要作用;在多数优化构型的d轨道中,α电子是团簇Mo_(2)S_(4)磁性的主要贡献者;团簇Mo_(2)S_(4)的构型1(3)、2(3)的α电子剩余较多,而构型3(3)、4(3)、5(3)的α电子、β电子均有部分剩余,自旋密度差均是在金属原子Mo上.构型4(1)的偶极矩最小,极性最弱;构型5(1)的偶极矩最大,极性最强;各构型的极性由大到小顺序为5(1)>2(1)>3(3)>5(3)>1(3)>1(1)>2(3)>3(1)>4(3)>4(1). 展开更多
关键词 量子化学 团簇Mo_(2)S_(4) 磁学性质 密度泛函理论 偶极矩
下载PDF
上一页 1 2 22 下一页 到第
使用帮助 返回顶部