A Unidirectional Open–Close Mechanism of Metal‐Ion‐Driven Molecular Hinges with Adjustable Amplitude

A basic requirement for each molecular system that is supposed to perform work is a synchronized and unidirectional movement. Unidirectionality can be achieved by a change of configuration or conformation that is controllable by external stimulation. Molecular hinges based on a bipyridine unit work unidirectionally and are able to reach an amplitude of motion that amounts to about 180°. To analyze if it is possible to adjust the height of the unidirectional amplitude of motion, three planar chiral molecular hinge systems with a 2,2′‐bipyridine unit as functional element were designed and stimulated with various divalent metal ions in different solvents. The configurations of the hinges were determined by DFT calculations using B3LYP and the 6‐31G* basis set and experimentally verified by 2D NMR NOESY spectra. Circular dichroism (CD) and UV spectroscopy were used to study the properties of the hinges by the addition of metal ions (primarily Zn²⁺ and Hg²⁺) in dichloromethane and methanol. The choice of metal ions and solvents determines whether or not and how far the hinges are closed. Furthermore, a drastic change in the height of the amplitude of motion can be reached by modifying the position of the bipyridine unit in the hinge. Amplitude values from 45 up to 190° were obtained from quantum mechanical calculations. This control of the amplitude of motion can in the future be used for more complex switching processes of molecular machines.     

Exact solution procedures for the balanced unidirectional cyclic layout problem

In this paper, we consider the balanced unidirectional cyclic layout problem (BUCLP) arising in the determination of workstation locations around a closed loop conveyor system, in the allocation of cutting tools on the sites around a turret, in the positioning of stations around a unidirectional single loop AGV path. BUCLP is known to be NP-Complete. One important property of this problem is the balanced material flow assumption where the material flow is conserved at every workstation. We first develop a branch-and-bound procedure by using the special material flow property of the problem. Then, we propose a dynamic programming algorithm, which provides optimum solutions for instances with up to 20 workstations due to memory limitations. The branch and bound procedure can solve problems with up to 50 workstations.     

Reconfigurable metamaterial for asymmetric and symmetric elastic wave absorption based on exceptional point in resonant bandgap

Elastic wave absorption at subwavelength scale is of significance in many engineering applications. Non-Hermitian metamaterials show the ability in high-efficiency wave absorption. However, the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability. Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits, to achieve as...     

Method of primers in calculating the probability of destruction of a unidirectional composite material in tension

A method of primers is elaborated which allows one to calculate the distribution function of durability of a composite material in tension in the reinforcement direction. Integral and differential equations for calculating the probabilities of formation of primers and destruction of a material caused by their formation are presented. Distribution functions of material strength for the parameter of Weibull distribution of fiber strength on the interval 2.1 ≤ β _f ≤ 50.1 are calculated. From the functions, the average values and root-mean-square deviations of material strength are found. The results obtained agree well with calculations by using the structural-imitation simulation. The distribution functions of material strength with a high precision are approximated by the three-parameter Weibull distributions. The distribution parameters are approximated by the linear functions of ln (β_f). __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 823–838, November–December, 2007.     

Deformation behavior and strength of unidirectional carbon fiber laminates

The elastic deformation behavior and the load-carrying capacity of unidirectional carbon fiber laminates under static loading at room and cryogenic (down to 77 K) temperatures are investigated. The possible ways of predicting their elastic and strength characteristics proceeding from the volume content and mechanical parameters of fibers and matrix are analyzed. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 583–598, September–October, 2006.     

可用于拓宽光波单向传输带宽的光子晶体异质结构界面

基于光波单向传输的全光二极管在集成光通信、全光网络和光信息处理中有重要应用.基于方向带隙失配设计的光子晶体异质结构可实现光波单向传输,但正向透射率较低,带宽较窄.基于对光子晶体异质界面倾斜角度的研究,根据界面全反射条件,利用可集成材料硅和二氧化硅设计了一种空气孔型二维光子晶体异质结构.异质结构界面两侧的光子晶体对1550 nm波长附近的TE模光波在Γ-X方向均呈导带,避免了方向带隙失配.研究发现当异质界面满足全反射条件时,由于光子晶体的自准直效应,较宽波段的正向光波得以高效传播,而反向光波在界面由于全反射而被禁止传播.光子晶体异质结构界面的全反射效应打破了方向带隙对光波单向传输的限制,使得反向光波在光子晶体中为导带时同样可实现近零透射率,从而拓宽了光波单向传输的波长范围.基于全反射界面的光子晶体异质结构经过优化后,其正向透射率达0.64,透射对比度为0.97,单向传输带宽可达553 nm.     

正N边形柱的隐身条件的严格推导及其隐身特性验证

基于坐标变换理论,提出并推导了正N边形柱的隐身条件,并得到了相应隐身罩材料本构参数张量的通解表达式. 根据导出的本构参数张量,利用电磁仿真软件分别对N取不同值时的三个典型算例进行仿真验证. 仿真结果证实了所得到的本构参数张量的正确性. 考虑到损耗对于隐身效果的影响分析,这些分析结果为隐身物理机理的进一步理解,以及降低对称度隐身罩的设计奠定了理论基础. 关键词： 坐标变换 非均匀各向异性介质 本构参数张量 隐身     

Development of a surface acoustic wave wireless and passive temperature sensor incorporating reflective delay line

based on optimal design on the core element of the sensor,a wireless and passive surface acoustic wave(SAW)temperature sensor integrated with ID Tag was presented.A reflective delay line,which consists of a transducer and eight reflectors on YZ LiNbO3 substrate.Was fabricated as the sensor element,in which,three reflectors were used for temperature sensing,and the other five were for the ID Tag using phase encoding.Single phase unidirectional transducers(SPUDTs)and shorted grating were used to structure the sAW device,leading to excellent signal to noise ratio(SNR).The performance of the SAW device was simulated by the coupling of modes(COM)prior to fabrication.Using the network analyzer,the response in time domain of the fabricated 434 MHz SAW sensor was characterized,the measured S11 agrees well with the simulated one,sharp reflection peaks,high signal/noise,and low spurious noise between the reflection peaks were observed.Using the radar system based on FSCW as the reader unit.the developed SAW temperature sensors were evaluated wirelessly.Excellent1 inearity and good resolution of士1℃ were observed.     

Time-dependent scalar Beltrami-Hertz potentials in free space

We have solved the Beltrami-Maxwell equations for free space in terms of time-dependent scalar functions, the so-called scalar Beltrami-Hertz potentials. The two Beltrami fields have been represented in terms of scalar Beltrami-Hertz potentials. While the method is formulated for general sources, it is at its most powerful when the impressed source current densities are unidirectional: each Beltrami field, a complex-valued vector, can then be derived from a single scalar Beltrami-Hertz potential. We have calculated the corresponding scalar Green function explicity and given closed-form solutions for dipolar sources. Finally, the connection between the Beltrami-Maxwell formalism and conventional electromagnetic theory has been re-affirmed.     

非晶态铁基合金退火样品的偏移回线

报道了非晶态铁基合金(Fe_65.9Cr_11.6Si_7.5B₁₅和Fe₆₀Co_5.9Cr_11.6Si_7.5B₁₅)退火样品的回线偏移现象.研究了偏移回线与测量磁场H_m,温度T和时间t的关系.基于退火产生的硬磁颗粒与剩余非晶软磁母体之间的静磁相互作用机制,利用等效的单向各向异性模型可以很好地分 关键词： 铁基非晶合金 偏移回线 单向各向异性