金属柱壳在爆炸加载断裂中的单旋现象

系列实验结果表明,在较强的滑移爆轰加载下,许多金属材料的旋转柱壳会呈现一种奇特的单旋剪切失稳破坏模式———受驱动壳壁结构上众多剪切滑移带及断口取向一致化,在45°和135°两族剪切带中,出现一族占优的现象。通过高速分幅和X光照相对剪切裂纹在壳壁内、外表的生成发展图像的记录和碎片样品回收,结合过程应力分析,对微剪切断裂发展过程中环向和纵向关联的可能机制进行了分析讨论,但疑点仍较多。在分析柱壳的高应变率失稳行为时,对于与加载条件及几何构形紧密耦合的材料动载剪切强度、各向异性性质所扮演的角色需要进一步认识。剪切断裂的单旋与聚能罩内层无破坏的射流整体旋转现象表现方式和程度虽有差异,但可能有着共同本质,值得深入探索。

狄拉克方程的单旋量解法以及由此引起的认识上的差异

把狄拉克方程分解成了两个单旋量的联立方程组 .指出现行的自旋理论仅考虑了其中的一个方程 ,是以一个单旋量代替双旋量来描述状态而建立起来的 .笔者在认同现行自旋理论可以作为狄拉克方程的一种求解方法 ,因而同意其中的某些提法外 ,对于其主要的物理观念 :微观粒子存在着独立于现实的位形空间之外的一个自旋空间 ,在这个自旋空间内禀着角动量S和磁矩 μs;这个自旋理论是相对论性量子力学导出的必然结论等等看法予以否定 .笔者认为 ,只有同时考虑两个单旋量的方程 ,同时计及两个单旋量 ,才能准确地描述状态 ,从而正确地描述客观规律 .

三维单旋导向挡板鼓泡流化床内气固流动的CPFD模拟

单旋导向挡板是一种广泛应用于流化床反应器中的横向内构件,研究其对鼓泡流化床内气固流动的影响具有重要意义。采用计算颗粒流体力学(CPFD)方法耦合Igci曳力模型研究带有两层单旋导向挡板的鼓泡流化床内的三维气固流动,并与空筒鼓泡流化床作对比。首先将轴向和径向时均固含率分布的模拟结果和实验数据进行对比,验证了该计算方法的可靠性;随后考察了单旋导向挡板对鼓泡流化床内气泡平均当量直径沿床高的分布以及气体停留时间分布的影响,计算结果表明,单旋导向挡板对大气泡具有一定的破碎作用,在挡板影响区域内气泡平均当量直径变小。同时,有、无挡板流化床内的气体停留时间分布曲线与其数学特征基本一致,表明单旋导向挡板的存在对鼓泡流化床内的气体返混没有明显影响。

单旋翼涵道风扇式无人直升机的钟摆现象与控制

单旋翼涵道风扇式无人直升机,采用轴对称的基本布局。其机体绕旋翼桨毂的钟摆现象为对称变悬点二维摆,且具有非线性、强耦合、高阶次、不稳定等特性。对于此钟摆现象,采用拉格朗日方程建立其多自由度模型、并在平衡态进行解耦和线性化。然后,设计线性二次最优控制器,使机体的摆动能在任何干扰下都稳定在平衡态。

不锈钢单旋体管生产工艺及孔型设计

介绍了不锈钢单旋体管的用途及质量要求 ,重点阐述了变形锥长度只有 80

表面加工塑性层对金属柱壳剪切带自组织单旋起始的影响

在外爆加载金属柱壳高速坍塌过程中,发生塑性变形失稳形成的剪切带具有高度的自组织特征,甚至出现剪切带排列的单旋现象—剪切带在顺时针和逆时针两个方向呈现一个方向占优的现象.柱壳在坍塌时,最大剪切应力位于柱壳内表面,剪切带的形核及扩展行为受内表面材料介观状态的影响显著.本文通过选材和控制柱壳加工工艺,获得了内表面具有不同厚度塑性层的20钢柱壳,采用厚壁圆筒实验技术,研究了表面加工塑性层对金属柱壳绝热剪切带自组织单旋现象起始的影响规律及其物理机制.研究结果表明,金属柱壳内表面加工塑性层显著改变了试样剪切带的起始条件,沿顺时针或逆时针方向排列的剪切带形核数量在总剪切带数量中所占比例取决于表面加工塑性层的厚度和晶粒取向,具有单一晶粒拉伸方向的较厚塑性层样品更容易形成单向螺旋剪切带结构.在相同变形条件下,随着塑性层厚度增加,剪切带平均形核速率和扩展速率增大,剪切带平均间距减小.结果可为理解金属柱壳在高速塌陷过程中绝热剪切带占优取向现象提供有价值的参考.

概率波和非概率波

对于把克莱因-戈尔登方程当作是玻色子的方程的看法提出异议,认为它是所有微观粒子均要满足的方程,但它却不能成为任何一类粒子的波动方程.提出了克-戈方程中包含着概率和非概率两类波的概念,认为概率波还要遵从一个对时和空都是一阶导数的方程,这才是粒子的波动方程.不同种类粒子性质的不同则体现在他们概率波类型的不同上.

First-Principles Study on Switching Performance and Spin Filtering Efficiency of Dimethyldihydropyrene/Cyclophanediene Single-Molecule Devices with Zigzag Graphene Nanoribbon Electrodes

Moleculardeviceswith highswitchingperformance and/or the perfect spin filtering effect have always been the pursuit with the development of molecular electronics.Hereb,yusingthe 2001.0V nonequilibrium.Green's function method in combination with the density functionaltheory,the switching performance and spin filtering properties of dimethyldihydropyrene(DHP)/cyclophanediene(CPD)photoswitchable molecule connected by carbon atomic chains(CACs)to two zigzag graphene nanoribbon electrodes have been theoretically investigated.The results show that DHP is more conductive than CPD and therefore an evident switching effect is demonstrated,and the switching ratio(RON/OFF)can reach 4.5×103.It is further revealed that the RoON/OF of DHP/CPD closely depends on the length of CACs.More specifically,the RoN/OFF values of DHP/CPD with odd-numbered CACs are larger than those with even-numbered CACs.More interestingly,a high or even perfect spin filtering effect can be obtained in these investigated DHP/CPD single-molecule devices.Our study is helpful for future design of single-molecule switches and spin filters and provides a way to optimize their performance by means of varying the length of bridging CACs.

某型无人直升机扭振现象的建模与仿真

单旋翼涵道风扇式无人直升机的两个发动机,通过由减速器及传动轴等组成的传动系统驱动旋翼及风扇,这些部分联系在一起形成了一个机械扭振系统。针对此现象,采用拉格朗日方程建立了扭振系统的数学模型,进而得出了整个系统数学模型的状态方程。并进行了数字仿真,再现了外场试验的扭振现象。

Effects of Supplementary Pollination by Single-rotor Agricultural Unmanned Aerial Vehicle in Hybrid Rice Seed Production

In 2012-2015, under the conditions of different natural wind speeds, the single-rotor agricultural unmanned aerial vehicle was used for the supplementary pollination during seed production of 10 hybrid combinations with big parental row ratios in the hybrid rice seed production bases of Hunan, Hainan and Guangdong Province, and the pollination effects were studied through the investigation of pollen density in the field, outcrossing seeding rate of female parent and seed production yield. The results showed that under the parental row ratio of 6：（40-60）, the seed setting rate and yields of the supplementary pollination by single-rotor agricultural UAV could reach and even higher than those of artificial pollination, indicating the single-rotor agricultural UAV could be used in supplementary pollination for hybdd rice seed production, which could promote the whole-process mechanization of seed production.

Influence of spiral crystal selector on crystal orientation of single crystal superalloy

To increase efficiency and improve performance, reducing cost and emissions, advanced single crystal Ni-based superalloys are required in aerospace propulsion and power generating gas turbines. With the development of alloy, significant improvements in casting techniques have been achieved by introducing the directionally solidified （DS） casting process followed by single crystal （SX） technique. The deviation of preferred orientation of single crystal superalloys is one of the most important defects in casting. In directional solidification equipment with high temperature gradient, single crystal specimens of DZ417G alloy were prepared successfully by the modified Bridgeman method with spiral grain selector. The orientation was investigated by means of X-ray diffraction （XRD） and electron backscattered diffraction （EBSD）.The results show that the crystal selector with a smaller angle can effectively reduce the deviation of preferred orientation.

Effects of Rotational Isomerism and Bond Length Alternation on Optical Spectra of FTC Chromophore in Solution

Rotational isomerism effects on the optical spectra of a push-pull nonlinear optical chro-mophore 2-dicyanomethylen-3-cyano-4-f2-[E-（4-N,N-di（2-acetoxyethyl）-amino）-phenylene-（3,4-dibutyl）-thien-5]-E-vinylg-5,5-dimethyl-2,5-dihydrofuran （FTC） in a few solvents have been studied using the time-dependent density functional theory in combination with the polarizable continuum model. It is shown that the maximum absorption peaks of the ro-tamers have difference of nearly 30 nm both in vacuum and in solutions. The population of the rotamers changes a lot in different solvents. Based on the geometries optimized by Hartree-Fock method, the Maxwell-Boltzmann averaged absorption has been calculated and the maximum absorption peak is in good agreement with experiment. It indicates that the bond length alternation can have an important effect on the optical spectra.

Adaptive filter for a miniature MEMS based attitude and heading reference system

An extended Kalman filter with adaptive gain was used to build a miniature attitude and heading reference system based on a stochastie model. The adaptive filter has six states with a time variable transition matrix. When the system is in the non-acceleration mode, the accelerometer measurements of the gravity and the compass measurements of the heading have observability and yield good eslimates of the states. When the system is in the high dynamic mode and the bias has converged to an aceurate estimate, the attitude caleulation will be maintained for a long interval of time. The adaptive filter tunes its gain automatically based on the system dynamics sensed by the accelerometers to yield optimal performance,

π-Electron-Assisted Relaxation of Spin Excited States in Cobalt Phthalocyanine Molecules on Au（111） Surface

We present our investigation on the spin relaxation of cobalt phthalocyanine （CoPc） films on Au（111） （CoPc/Au（111）） surface using scanning tunneling microscopy and spectroscopy. The spin relaxation time derived from the linewidth of spin-flip inelastic electron tunneling spectroscopy is quantitatively analyzed according to the Korringa-like formula. We find that although this regime of the spin relaxation time calculation by just considering the exchange interaction between itinerant conduction electrons and localized d-shells （s-d exchange interaction） can successfully reproduce the experimental value of the adsorbed magnetic atom, it fails in our case of CoPc/Au（111）. Instead, we can obtain the relaxation time that is in good agreement with the experimental result by considering the fact that the 7c electrons in CoPc molecules are spin polarized, where the spin polarized 7c electrons extended at the Pc macrocycle may also scatter the conduction electrons in addition to the localized d spins. Our analyses indicate that the scattering by the π electrons provides an efficient spin relaxation channel in addition to the s-d interaction and thus leads to much short relaxation time in such a kind of molecular system on a metal substrate.

Effect of moving baffle on average velocity and mixing of binary particles in rotating drums

Adding a moving baffle to the drum is a new way to enhance the motion and mixing of particles in rotating drums.To obtain its influence on binary particles,horizontal rotating drums provided with a moving baffle were investigated by discrete element method(DEM).AtΩ=15 r/min,increasing the length of moving baffle can increase the fluctuation amplitude of average particle velocity.AtΩ=60 r/min,the influence of the moving baffle on the average velocity fluctuation tends to be more random.At both rotational speeds,the moving baffle causes the average particle velocity to fluctuate more sharply.The moving baffle can enhance particle mixing.AtΩ=15 r/min,the moving baffle with length ofδ=1/3 can best enhance particle mixing.However,atΩ=60 r/min,only the moving baffle with a specific length(δ=1/4)can enhance mixing.This basic research has a positive reference value for the application of the moving baffle in industry.

Effects of directional solidification parameters and crystal selector on microstructure of single crystal of Ni-base superalloys

The single crystal of nickel-base super alloy is widely used for making turbine blades.The microstructure of the alloy,especially the deviation of preferred orientation of single crystal,possesses the most important effects on the mechanical properties of the blades.In this study,the single crystal ingot and blade of DZ417G alloy are prepared by means of the spiral crystal selector as well as the directional solidification method,and the effect of the parameters(i.e.,the shape of samples,the withdrawal rate)and the structure of the spiral crystal selector on the formation of single crystal and the crystal orientation are investigated.This method can prepare not only the single crystal ingot with simple shape but also the single crystal blades with the complex shape,the simple with rod-shape can form the single crystal easily with a relatively fast withdrawal rate,but the blade with complex shape requires much slower withdrawal rate to form single crystal.The length of the crystal selector almost has no effect on the crystal orientation.However,the angle of selector plays an obvious role on the orientation;the selector with a smaller angle can effectively reduce the deviation of preferred orientation;the appropriate angle of selector to obtain optimal orientation is found to be around30°and the deviation of preferred orientation is about30°for this selector.

Analytical solution for electromagnetic scattering from a sphere of uniaxial left-handed material

Based on the analytical solution of electromagnetic scattering by a uniaxial anisotropic sphere in the spectral domain, an analytical solution to the electromagnetic scattering by a uniaxial left-handed materials (LHMs) sphere is obtained in terms of spherical vector wave functions in a uniaxial anisotropic LHM medium. The expression of the analytical solution contains only some one-dimensional integral which can be calculated easily. Numerical results show that Mie series of plane wave scattering by an isotropic LHM sphere is a special case of the present method. Some numerical results of electromagnetic scattering of a uniaxial anisotropic sphere by a plane wave are given.

Lyase Activities of Heterologous CpcS and CpcT for Phycocyanin Holo-β-subunit from Arthrospira platensis in Escherichia coli

Arthrospira platensis is an economically important cyanobacterium; and it has been used widely in food and pharmaceutical industries. The phycocyanin(PC) from A. platensis is extremely valuable in medicine and molecular biology due to its antioxidation and anti-tumoring activity and applicability as fluorescence protein tag. In present study, two recombinant plasmids, one contained the phycocyanobilin(PCB)-producing genes(hox1 and pcyA) while the other contained the phycobiliprotein gene(cpcB) and the lyase gene(either cpcS/U or cpcT), were constructed and synchronically transferred into E. coli in order to test the the activities of relevant lyases for catalysing PCB addition to CpcB during synthesizing fluorescent PC holo-β-subunit(β-PC) of A. platensis. As was evidenced by the fluorescence emitted at a peak specific for PC, CpcB was successfully synthesized in E. coli, to which co-expressed PCBs attached though at a relatively low efficiency. The results showed that the attachment of PCBs to CpcB were carried out mainly by co-expressed CpcS/U but CpcB also showed some autocatalytic activity. Currently, no CpcT activity was detected in this E. coli expression system. Further studies will be conducted to improve the efficiency of fluorescent PC synthesis in E. coli.

Singlet-Triplet Transitions of a Poeschl-Teller Quantum Dot

We study the energy spectra of a two-dimensional two-electron quantum dot （QD） with P6schl-Tefler confining potential under the influence of perpendicular homogeneous magnetic field. Calculations are made by using the method of numerical diagonalization of Hamiltonian matrix within the effectlve-mass approximation. A ground-state behavior （spin singlet-triplet transitions） as a function of the strength of a magnetic field is found. We find that the dot radius R of a Poeschl-Teller potential is important for the ground-state transition and the feature of ground-state for a Poeschl Teller QD and a parabolic QD is similar when R is larger. The larger the well depth, the higher the magnetic field for the singlet-triplet transition of the ground-state of two interacting electrons in a Poesehl-Teller QD.

Spin Parity Effect on Magnetic Relaxation by Quantum Tunneling in Nanomagnets

Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe8 system, while the prediction for odd resonance awaits the experimental verification.