Study on the analogy feedback active soft edge noise barrier

It is feasible to enhance the effect of reduction of the noise barrier on low frequency noise using the active control system. On the basis of the forerunners’ research, an analogy feedback active control system that is easy to be carried out was arranged on the top of a noise barrier to form an analogy feedback active soft edge noise barrier in order to enhance the effect of reduction of the noise barrier on low frequency noise. Through a preliminary experimental study, this method was proved to be feasible and the following preliminary conclusions on the arrangement of active control systems were made: (1) when control sources were arranged in a single row, the control effect was determined by the density of arrangement: the higher the density, the better the control effect; (2) with the same density of arrangement, the control effect of the double row arrangement was better than that of the single row arrangement; (3) with the same number of control sources, the single row arrangement had better control effect than the double row arrangement.     

四子孔径光学合成孔径成像系统空间排布性能分析

对三种空间排布结构的四子孔径光学合成孔径成像系统性能进行了分析.根据避免有效频率信息丢失的原则,分别计算了三种结构各自对应的空间排布限制条件.在此基础上得到了三种结构的有效频率覆盖范围和等效孔径.结果表明,当频率覆盖范围要求比较高时,只能选择三臂结构;当环形均匀结构和三臂结构具有相同的有效频率覆盖范围时,按照抑制次峰的选择标准,三臂结构要优于环形均匀结构;当环形优化结构和三臂结构具有相同的有效频率覆盖范围时,环形优化结构的点扩展函数次峰要明显大于三臂结构,而且环形优化结构的光学传递函数缺乏三臂结构的对称特性.     

Effects of array arrangements in nano-patterned thin film media

In this work, the effect of different arrays arrangements on the magnetic behaviour of patterned thin film media is simulated. The modeled films consist of 80×80 cobalt grains of uniform diameter (20 nm) distributed into two different array arrangement: hexagonal (triangular) or square arrays. In addition to that, for each array arrangement, two cases of anisotropy orientations, random and textured films are considered. For both array arrangements and media orientations, hysteresis loops at different array separation (d) were simulated. Predictions show that for closely packed films, the shearing effects on the magnetization loop are much larger for the square array arrangement than the hexagonal one. According to these predictions, the bit switching field distribution in interacting 2D systems is much narrower for the hexagonal array arrangement. This result could be very important for high-density magnetic recording where a narrow bit switching field distribution is required.     

基于虚云纹原理的数字相移形貌影栅云纹仿真系统

在阐述形貌影栅云纹法的虚云纹原理的基础上,利用计算机模拟了各种光场中的全场仿真影栅云纹图,结合相移技术创建了以精确解答为基准的数字相移形貌影栅云纹仿真系统,并且讨论了点照射—点观测光场设置下使用相移法必然会引入系统初始误差的普遍现象。通过对点照射—点观测光场中参数差异所带来不同的系统初始误差进行分析和评估,得到了降低这种光场系统误差所应遵循的准则。这些新的工作对规范、合理设计数字形貌影栅云纹仪实验系统和对特殊的光场设置进行误差分析将有所帮助,进一步对研究工作的前期准备具有启发和指导作用。     

Non-collinear magnetic moments of seven-atom Cr, Mn and Fe clusters

The non-collinearity of magnetic moments of pentagonal bipyramid Cr₇, Mn₇ and Fe₇ clusters is discussed. The magnetic moments are calculated by the discrete variational non-collinear spin-density functional method. For the Cr₇ cluster, a coplanar magnetic arrangement appears at the large interatomic distance. With decreasing the interatomic distance, the coplanar arrangement changes to the parallel arrangement with a small absolute magnetic moment. For the Mn₇ cluster, the magnetic arrangement changes from coplanar to antiparallel with decreasing the interatomic distance. Also for the Fe₇ cluster, some coplanar magnetic moments appear at the interatomic distance of 2.23 ?. In these coplanar magnetic arrangements, the magnetic moment at the basal site of the pentagon rotates with a step of 144 degrees for the Cr₇ clusters and 72 degrees for the Mn₇ and Fe₇ clusters. Received 30 November 2000     

Slow-fast coincidence system for a fast neutron time-of-flight spectrometer

The authors describe the arrangement of a slow-fast coincidence system for a fast neutron time-of-flight spectrometer. In the “fast” section of the instrument a fast differential coincidence circuit is used. Compared with the original arrangement [1] the circuit permits a higher system stability to be achieved. In the concluding part of the paper results are given of measurements on neutrons from the Li⁷(d, n) Be⁸ reaction.     

First stages of the deposition of bismuth on copper examined by LEED: II. The (111) substrate

Three ordered overlayer structures are observed after evaporation for different times onto the (111) substrate. They are interpreted as monolayers with different densities: I, adsorption in sites of high coordination; II, a dense pseudo-square arrangement of bismuth atoms; III, a compact hexagonal arrangement. Structure III is only observed at high coverage and above 245°C. A reversible transformation occurs between II and III for a limited range of coverage. When they exist alone both structures II and III show melting type transitions. A schematic surface phase diagram is established.     

Analysis of a 69.3° Vicinal HAGB in Pure Titanium

A transmission electron microscopy study and geometric analysis has been performed on a vicinal 69.3° high angle grain boundary in pure Ti which exhibits a characteristic dislocation arrangement. The dislocation configuration was modelled using the usual CSL/DSC/O-lattice approach and the predicted arrangement required to accommodate the deviation from a 37 three-dimensional CSL matched well with the arrangement observed experimentally. It was, however, also shown that an identical arrangement would be required to accommodate the deviation from a 37 two-dimensional CSL. Thus the analysis of such boundaries does not constitute a good test to distinguish between the two- and three-dimensional models of the low-energy reference structures adopted high-angle grain boundaries.     

Second-harmonic generation from ellipsoidal silver nanoparticles embedded in silica glass

Second-harmonic generation of uniformly oriented, ellipsoidal silver nanoparticles in a glass matrix was observed and investigated as a function of incidence angle, light polarization, and spatial arrangement of the particles. The results can be explained by the symmetry of the spatial nanoparticle arrangement and by resonance enhancement that is due to the localized surface plasmons of the particles. Second-harmonic enhancement is observed only in sufficiently thin layers (deltakl < pi); on a sample with two separate layers, strong modulation owing to quasi-phase matching is obtained.     

Scanning tunneling microscopy study of pinning-induced vortex lattice distortion in ion-irradiated NbSe2

We observe vortex pinning in 2.2 GeV Au-ion irradiated NbSe₂ by scanning tunneling microscopy (STM) at 3K. The ion irradiation generates columnar defects which act as pinning sites. At various external magnetic fields the vortex arrangement is clearly resolved but shows strong distortion. The location of individual defects is extracted from STM data and compared to the vortex arrangement.     

A dispersionless Michelson interferometer for the characterization of attosecond pulses

A novel application of a free-standing transmission grating as a beam splitter in a Michelson-type interferometer is described. The arrangement can operate in the XUV and soft X-ray spectral region and, therefore, it is well suited for the characterization of attosecond pulses. Using ray-tracing codes, we have analyzed three different setups in which spherical mirrors are employed in conjunction with the transmission grating and have investigated in detail their dispersive characteristics. It is shown that such an arrangement can be made to exhibit group-delay dispersion of ∼1 as² while it provides two co-propagating and converging beams. Received: 12 October 2001 / Revised version: 17 December 2001 / Published online: 7 February 2002     

Should Epstein strip arrangement be changed?

The paper describes effect of texture on the anisotropy of magnetic properties and shows that an Epstein strip arrangement including strips cut in a direction 45° to the rolling direction gives property values that are closer to the average values than the traditional RD+TD arrangement.     

Encryption of color images using MSVD in DCST domain

In this paper, a new image encryption and decryption algorithm based on Multiresolution Singular Value Decomposition (MSVD) and Discrete Cosine Stockwell Transform (DCST) is proposed. An original image is first transformed in DCST domain and then decomposed into four subbands using MSVD, all the four subbands are further decomposed into four subimages according to their indexing and masked by the parameters generated by MSVD. We have used number of bands of DCST, arrangement of MSVD subbands, arrangement of various subimages obtained from MSVD subbands, values and arrangement of a 4×4 matrix generated by MSVD and the arrangement of masked subimages as encryption and decryption keys. To ensure the correct decryption of encrypted image, it is indeed necessary to have correct knowledge of all keys in correct order along with their exact values. If all the keys are correct but a single key is wrong even though it would be almost impossible to guess the original image. The efficiency of proposed algorithm is evaluated by comparing it with some recent published works and it is evident from the experimental results and analysis that the proposed algorithm can transmit the images more securely and efficiently over the network.     

Structure and non-collinear magnetism of iron linear chains

Atomic structures and non-collinear magnetic moments are calculated by the first principle molecular dynamics for Fe₅ and Fe₆ linear chains with several fixed and free chain-lengths. The dimerization appears in the optimized atomic structures of all the chains. For the Fe₅, the magnetic arrangement is parallel for a large chain-length and changes to non-collinear with decreasing the chain-length. For the Fe₆, the magnetic arrangement is antiparallel in a unit of dimer for a small chain-length and changes to non-collinear with increasing the chain-length. These magnetic behaviors are simulated by a simple J₁-J₂ Heisenberg model.     

Self-Assembly of Chiral Nematic Liquid Crystalline Phases of AgNR@SiO2@Cysteine@CsPbBr3 Hybrid Nanorods with Plasmon-Dependent Photoluminescence

The direct synthesis of a chiral nematic liquid crystalline phase of AgNR@SiO₂@cysteine@CsPbBr₃ hybrid nanorods (HNRs) is reported. The circular dichroism spectra can be divided into three components: (1) the interband absorption–enhanced optical activity of structural arrangement of cysteine (cys) molecules, 200–320 nm, (2) the chiral nematic liquid crystalline arrangement of the Ag nanorods (AgNRs), 350–450 nm, and (3) the exciton adsorption edge of the perovskite, 500–550 nm. The polarizing optical microscope images indicate that the chiroptical response of perovskite arises from chiral nematic crystalline arrangement rather than cys-induced electronic coupling between a chiral ligand and otherwise achiral perovskite quantum dots (QDs). The luminescent intensity of CsPbBr₃ QDs in AgNR@SiO₂@cys@CsPbBr₃ HNRs is boosted 87-fold due to the local surface plasmon resonance field enhancement effect. Furthermore, the high-performance green light emitting diode is constructed employing AgNR@SiO₂@cys@CsPbBr₃ complexes, which exhibit excellent luminescent properties. This work contributes insights into structure–property relationships and this strategy promisingly provides guidance for the other inorganic chiral semiconductor suprastructures.     

Hexagonal arrangement of phospholipids in bilayer membranes

The phospholipid membrane plays a key role in myriad biological processes and phenomena, and the arrangement structure of membrane determines its function. However, the molecular arrangement structure of phospholipids in cell membranes is difficult to detect experimentally. On the basis of molecular dynamic simulations both in a non-destructive way and at native environment, we observed and confirmed that the phospholipids self-assemble to a hexagonal arrangement structure under physiological conditions. The underlying mechanism was revealed to be that there are hexagonal arrangement regions with a lower free energy around each lipid molecule. The findings potentially advance the understanding of biological functions of phospholipid bilayers.     

Experimental Investigation of the Effect of Flow Arrangements on the Performance of a Micro-Channel Heat Sink

Abstract

An experimental study is carried out to investigate the effect of entrance and exit conditions that prevail due to different flow arrangements on the thermal performance of a copper micro-channel heat sink. Three flow arrangements—U-type, S-type, and P-type—were considered for the analysis with a test piece having inlet and outlet plenum dimensions of 10 mm × 30 mm × 2.5 mm with an array of parallel micro-channels having an individual width of 330 μm and a uniform channel depth of 2.5 mm. Performance evaluations for different flow conditions at inlet and outlet plenums were made by maintaining constant heat supply at 125 W, 225 W, and 375 W with varying Reynolds number ranging from 224 to 1,121. Nusselt number and pressure drop were computed by measuring temperature difference and pressure drop across the inlet and outlet plenum for various test combinations. Maximum heat transfer was observed for the U-type flow arrangement, followed by the P-type and S-type; maximum pressure drop was noted for the S-type flow arrangement, followed by the U-type and P-type arrangements for a constant Reynolds number. A detailed analysis of the experimental results indicate that from a pressure drop point of view, the P-type flow arrangement is preferred, whereas from the heat transfer point of view, the U-type is found to be a better option.     

永磁体 N-N 相对式排列提升旋转式高温超导磁通泵开路电压的仿真研究

旋转式高温超导磁通泵可以无接触地向超导线圈中注入直流电, 在超导磁体充电方面具有独特的优势.在本文中, 我们基于 H-A 方程耦合建立了一个磁通泵二维有限元模型, 分别模拟了三块永磁体、 五块永磁体在不同的排列方式下对磁通泵开路电压的影响. 与正常的 N 极向下的排列方式相比, N-N 相对式排列改进后能够提升磁通泵的开路电压; 改进式 Halbach 排列对开路电压几乎没有影响. 在50 Hz 的旋转频率下, 永磁体 N-N 相对式排列使开路电压提升13% . 这是由于永磁体 N-N 相对式排列后, 磁通将会被挤压, 从而产生有多个峰值的磁感应强度分布, 使等效电压波形从不对称的四重峰变为多重峰. 最后, 对永磁体宽度进行了参数化扫描来分析永磁体尺寸对开路电压的影响. 通过优化磁体结构设计, 可以控制磁感应强度分布, 提升磁通泵的开路电压, 为提升实验装置的输出性能提供一种新颖的设计方向.     

A new method for rapid realization of the high-resolution extended-range holographic image-deblurring filter

The filter is photographically realized for its amplitude by two sandwiched components of combined extended-dynamic-range slope γ=1, and for its phase by a high-spatial-frequency range hologram recorded through them in a “triple-diffraction” arrangement.