转子极数对无刷双馈电机耦合能力的影响

针对目前无刷双馈电机(BDFM)两套不同极数定子绕组之间,耦合能力弱而导致该类型电机功率密度低及性能指标差的问题,以结构简单易于制造的普通凸极磁阻转子BDFM为例,研究了转子极数对电机耦合能力的影响。基于绕组函数理论,对BDFM进行了电感参数计算;通过分析电感参数,研究了极数、相同转子极数而不同定子绕组的极数配合和多极凸极磁阻转子对其耦合的影响。研究表明:合适的转子极数和极数配合可以改进BDFM的耦合能力,进而提高其功率密度,改善其性能指标。

典型反应性合金冲击释能量及耦合毁伤能力对比

反应性合金是一种高密度超钝感的新型含能材料,在高速撞击下可释放大量化学能,具有与动能耦合毁伤目标的潜力。通过弹道枪驱动非晶合金类、传统合金类和高熵合金类反应性合金样品,以1500 m/s速度撞击准密闭容器和间隔靶。对比分析了3种样品冲击释能行为和对间隔靶耦合毁伤能力的差异。结果显示:反应性合金样品在高速侵彻靶板后形成的燃烧碎片云对间隔靶兼具动能和化学能毁伤能力;化学能释放效率与样品的静态抗压强度正相关;由于样品所携带的化学能和动能随着燃烧碎片云运动,释放在靶后不同空间处,故对间隔靶的毁伤能力与其总携带能量无关;化学能对耦合毁伤能力的贡献程度主要取决于释能效率。

风险-能力耦合:精准扶贫中的分配正义研究

以分配正义为方法论策略,从风险分配正义和能力正义两个进路分别探讨顶梁柱公益保险项目对贫困户贫困风险的消除和转移作用及对其可行能力的提升作用,并采用准实验法对比了实验组和对照组在两种作用上的区别,最终将二者进行了理论意义上的统一,建构出“风险-能力耦合”策略框架。这一框架在避免贫困的恶性循环、实现“风险转移-能力提升”的良性循环方面作用显著。在精准扶贫的攻坚阶段,面对“最难啃的硬骨头”,“风险-能力耦合”的扶贫将成为解决这一痛点和难点的有效策略。

湖南省生态-经济系统耦合发展探析

从系统论视角出发,剖析了湖南省生态-经济系统内部诸要素及其结构特征,构建评价指标体系;运用定量评价模型,对区域系统的耦合状态进行了分析。结果表明:1996—2006年湖南省综合支撑能力呈对数型上升,而综合消耗水平呈指数型上升,二者演化速度具有非同步性,耦合度呈快速上升趋势,年均增长4.89度;从2008年起将进入过度开发时期,虽然湖南省资源较丰富,但远未具备过度开发型的物质条件;湖南省进入过度开发时期的原因是,在经济增长方式仍然非常落后和产业结构未得到有效调整的情况下,一味突出出口导向型经济,从而导致综合消耗水平发展快速增长。

定子电励磁无刷同步电机藕合能力研究

采用转子磁场调制作用进行间接耦合,定子上嵌有两套不同极数绕组,机电能量转换的效果就越好,转子"极数转换器"的作用越强。本文采用有限元的方法,确定最优转子的结构和参数,分析不同参数对电机性能的影响,对电极进行特性仿真,解决参数的计算问题。转子结构和参数的选取是提高电机运行性能和效率的关键。

强磁场条件下气体超声波流量计PCB板建模仿真分析

针对强电磁干扰环境下,多声道气体超声波流量计印制电路板(PCB)的超声波回波信号处理电路与时序电路电磁兼容性问题进行研究,研究了强电磁脉冲场强值对耦合电流的影响,建立了外部强电磁干扰源等效模型,并结合三维电磁场仿真软件(CST)来模拟外部强电磁干扰环境下,通过观察关键敏感电路的不同的电流端口来研究不同电磁干扰源强度下对PCB关键敏感电路电磁耦合的影响,根据强电磁干扰源的大小与流量计PCB板的关键敏感电路感应电压值的线性关系,确认关键敏感电路可受干扰强电磁场的最大辐射阈值,提出了PCB板上关键敏感电路电磁敏感度建模仿真方法,据此总结相关规律,提出优化对应PCB关键敏感电路的相应设计,进行前后仿真分析对比,关键敏感电路耦合电流显著减少,证明了多声道气体超声波流量计在强电磁干扰环境下的抗耦合干扰能力得到显著提高。

深槽式凸极转子无刷双馈电机的电磁设计

对传统的普通凸极转子进行优化设计,研究了凸极长度和宽度对转子耦合能力的影响,确定最优尺寸方案。为了提高电机性能,对优化后的普通凸极转子进行结构改进,增加深槽,得到了深槽式凸极转子无刷双馈电机,并对新增深槽的宽度和深度对转子耦合能力的影响进行了分析,确定深槽最优尺寸,短路导电条被嵌入到深槽中,谐波磁通流通轨迹得到更好的限定,转子的磁耦合作用得到进一步提升。利用Ansoft有限元分析软件计算得到了磁力线分布和气隙的各次谐波磁通百分比,研究比较了优化前与优化后的转子磁耦合作用。

Numerical studies of effect of tool sizes and pin shapes on friction stir welding of AA2024-T3 alloy

Coupled thermo-mechanical model was used to investigate the effects of the pin diameter, the shoulder diameter and the in conical angle on the heat generations, the material deformations and the energy histories in friction stir welding（FSW） of AA2024-T3 alloy. Results indicate that the shoulder-plate contact area takes more important contribution to the heat generation than the pin-plate contact area. The increase of the shoulder diameter or the decrease of the pin diameter can lead to the increase of the welding temperature in FSW, but the change of shoulder size is more important. Compared to the cases in FSW of AA6061-T6, the input power is obviously increased in FSW of AA2024-T3 and the ratio of the plastic dissipation to the friction dissipation becomes decreased.

中国高铁的集成创新为何能够成功

中国从上世纪90年代下半期开始自主研发以中华之星为代表的高速列车,并在短短的12年里走过从吸收消化再创新,系统集成创新到原始创新的道路。改革开放以来中国有很多产业实施市场换技术的战略,为什么只有高铁取得了突出的成绩?这不仅是技术攻关,更是一次资源分配和制度创新,特别是以项目为契机,充分发挥政策的导向和指引作用,大力促进产学研深度融合,注重科研院校在重大项目立项、论证、攻关等核心环节的作用,这些经验都对其它重大项目攻关有着重大的借鉴作用。

THE STRUCTURE DESIGN AND THE DYNAMIC ANALYSIS OF THE MAGNETIZATION MECHANISM OF THE COLLECTOR OF MACHINING WASTE

This paper presents the structural design and dynamic analysis of the magnetic field of the collector of machining wastes. From the viewpoint of energy the magnetic coupled force exerted on machining wastes by the nonuniform magnetic field of a permanent magnet has been discussed. The difficult problem that machining wastes attracted by a permanent magnet above the iron base platform has been solved.

Application of the generalized quasi-complementary energy principle to the fluid-solid coupling problem

The fluid-solid coupling theory, an interdisciplinary science between hydrodynamics and solid mechanics, is an important tool for response analysis and direct design of structures in naval architecture and ocean engineering. By applying the corresponding relations between generalized forces and generalized displacements, convolutions were performed between the basic equations of elasto-dynamics in the primary space and corresponding virtual quantities. The results were integrated and then added algebraically. In light of the fact that body forces and surface forces are both follower forces, the generalized quasi-complementary energy principle with two kinds of variables for an initial value problem is established in non-conservative systems. Using the generalized quasi-complementary energy principle to deal with the fluid-solid coupling problem and to analyze the dynamic response of structures, a method for using two kinds of variables simultaneously for calculation of force and displacement was derived.

A new measurement method of crack propagation rate for brittle rock under THMC coupling condition

A new electrical method of conductive carbon-film(with waterproof and anticorrosion ability)was proposed to continuously measure crack propagation rate of brittle rock under THMC coupling condition.A self-designed coupling testing system was used to conduct THMC coupling fracture tests of the pre-cracked red sandstone specimens(where the temperature is only changed)by this new electrical method of conductive carbon-film.Calculation results obtained by the energy method coincide well with the test results.And the higher the temperature is,the earlier the crack is initiated and the larger the crack propagation rate and accelerated velocity are,which can prove the validity of the new electrical method.This new electrical method has advantages of continuously measuring crack propagation rate over the conventional electrical,optical and acoustic methods,and can provide important basis for safety assessment and cracking-arrest design of deep rock mass engineering.

Main properties of ultra-high performance fiber reinforced cement composites under couple effect of load and environment

This study aims to reveal the mechanism that how the content of steel fibers and strength grades affect the macro performance of the ultra-high performance fiber reinforced cementitious composite （UHPFRCC） and to study the UHPFRCC durability under the combined effect of loads and environments. Three types of high and ultra-high performance fiber reinforced cement composites with different strength grades （100, 150, 200 MPa） and different steel fiber volume fractions （0%, 1%, 2%, 3%） are prepared. The main properties of mechanical performance and short-term durability are studied. A preloading frame is designed to apply a four- point load external flexural stress with a stress selection ratio of 0.5 for UHPFRCC150 specimens. The results show that the growth in strength grade with a proper content of steel fiber greatly increases the strength and toughness of the HPFRCC and the UHPFRCC while decreasing the dry-shrinkage ratio. For the loaded specimens, the existence of steel fiber can reduce the negative influence of tensile stress on the Cl- penetration resistance of the UHPFRCC in addition to improving its ability to resist the freeze-thaw damage.

Microstructure and mechanical properties of friction stir processed TA5 alloy

Ultra-fine grained TA5 titanium alloy was fabricated by friction stir processing(FSP).Temperature distribution and material flow were simulated by the coupled Euler−Lagrange(CEL)method.The microstructure and mechanical properties of TA5 alloy were characterized by optical and scanning electron microscope,Vickers hardness,and tensile tests.The processed alloy was composed of ultra-fine grained and equiaxed grains due to dynamic recrystallization.The microstructure recrystallized through grain boundary rotation and dislocation accumulation.The grain size reached the minimum on the advancing side of the stir zone with the highest grain misorientation.Ultimate tensile strength was promoted to over 830 MPa after FSP at a rotating speed of 200 r/min,whereas elongation varied a little.The specimens all fractured on the retreating side of the stir zone and smaller dimples were depicted from the fracture morphologies of FSP specimens.

A new apparatus for investigating stress,deformation and seepage coupling properties of rock fractures

A true triaxial apparatus which is composed of three units was presented.The apparatus allows for investigations on deformation and seepage behaviors of a single rock fracture subjected to lateral stress and normal stress.The first unit has three jacks which can apply loads independently in three orthogonal directions.The second unit is used to supply water inflow,control seepage pressure and measure flow velocity in real time.The third unit is for measuring the normal deformation of rock fractures.Some tests for investigating the normal deformation and seepage behaviors of rock fractures subjected to normal and lateral loads on hard granite specimens with an artificial persistent fracture,were introduced.The results show that both the normal deformation and the hydraulic conductivity are influenced not only by the normal stress but also by the lateral stress.It is also shown that the aperture and the hydraulic conductivity decrease with the increasing normal stress but increase with the increasing lateral stress and both the aperture and the hydraulic conductivity obey exponential relationships with the normal stress and the lateral stress.

New analytical solution for the analysis and design of permanent magnet thrust bearings

On the basis of the current sheet model, a new analytical solution for permanent magnet （PM） bearings is developed. Compared with analytical methods based on the coupling energy model and the magnetic dipole model, the proposed one is more physically intuitive and convenient for engineering designers. According to the analytical model, the thrust characteristics of a novel PM thrust bearing is studied and verified by finite element analysis （FEA）. In the proposed thrust bearing configuration, the rotor is composed of stacked PM tings with alternative axial magnetization directions, and the stator with alternative radial magnetization directions while copper rings are used to separate adjacent PM rings. A prototype PM thrust bearing with the proposed configuration is designed and fabricated. The performances of the PM thrust beating are experimentally validated. It is shown that the calculation accuracy of the presented analytical solution is satisfying.

Comparison of Synchronization Ability of Four Types of Regular Coupled Networks

We investigate the synchronization ability of four types of regular coupled networks. By introducing the proper error variables and Lyapunov functions, we turn the stability of synchronization manifold into that of null solution of error equations, further, into the negative definiteness of some symmetric matrices, thus we get the sufficient synchronization stability conditions. To test the valid of the results, we take the Chua's circuit as an example. Although the theoretical synchronization thresholds appear to be very conservative, they provide new insights about the influence of topology and scale of networks on synchronization, and that the theoretical results and our numerical simulations are consistent.

Cu2O-Au Nanocomposites with Novel Structures and Remarkable Chemisorption Capacity and Photocatalytic Activity

The decomposition of Cull nanoparticles in aqueous solution has been successfully developed as a novel method for the preparation of Cu2O nanoparticles. In particular, we found that the decomposition of Cull nanoparticles in aqueous solution could be catalyzed by Au colloids, forming CU2O-Au nanocomposites. The composition and structure of the resulting Cu2O-Au nanocomposites have been characterized in detail by inductively coupled plasma atomic emission spectroscopy, powder X-ray diffraction, N2 adsorption-desorption isotherms, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Their visible-light-driven photocatalytic activity toward various dye molecules has also been investigated. Depending on the Au：Cu ratio, Cu20-Au nanocomposites exhibit different novel nanostructures including a beautiful flower-like nanostructure that consists of polycrystalline Cu2O, amorphous Cu2O and Au colloids. We propose that the rapidly-generated bubbles of H2 during the course of the catalytic decomposition reaction drive the simultaneously-formed Cu2O to form amorphous curved thin foils and might also act as a template to assemble curved thin foils of amorphous Cu2O, polycrystalline Cu2O and Au colloids into uniform nanostructures. A Cu2O-Au nanocomposite with a Cu：Au ratio of 40 exhibits remarkable chemisorption capacity and visible-light-driven photocatalytic activity towards methyl orange and acid orange 7 and is a promising chemisorption-photocatalysis integrated catalyst. The catalytic decomposition of the metal hydride might open up a new approach for the fabrication of other metal/metal oxide nanocomposites with novel nanostructures and properties.

Simulation of Unsteady State Performance of a Secondary Air System by the 1D-3D-Structure Coupled Method

This paper describes the calculation method for unsteady state conditions in the secondary air systems in gas turbines. The 1D-3D-Structure coupled method was applied. A 1D code was used to model the standard components that have typical geometric characteristics. Their flow and heat transfer were described by empirical correlations based on experimental data or CFD calculations. A 3D code was used to model the non-standard components that cannot be described by typical geometric languages, while a finite element analysis was carried out to compute the structural deformation and heat conduction at certain important positions. These codes were coupled through their interfaces. Thus, the changes in heat transfer and structure and their interactions caused by exterior disturbances can be reflected. The results of the coupling method in an unsteady state showed an apparent deviation from the existing data, while the results in the steady state were highly consistent with the existing data. The difference in the results in the unsteady state was caused primarily by structural deformation that cannot be predicted by the 1D method. Thus, in order to obtain the unsteady state performance of a secondary air system more accurately and efficiently, the 1D-3D-Structure coupled method should be used.