国际未来直线对撞机(ILC)阻尼环Lattice设计

为了使国际未来直线对撞机达到高的亮度, 对撞机的阻尼环必须要有很小的自然发射度. 同时, 阻尼环要有很大的接收度来接受来自正电子注入系统的大能散、大发射度的正电子束团. 对于磁聚焦结构的设计来说, 同时达到以上要求是一件很有挑战性的工作. 为了降低ILC阻尼环的造价采用修正的FODO结构设计了可以满足ILC要求的阻尼环备用Lattice, 并使四极磁铁的数量比起ILC阻尼环BCD设计减少了一半.     

Cross section of inelastic polarized neutron scattering by superconducting rings

A general expression for the cross section of inelastic magnetic scattering of cold polarized neutrons by superconducting rings has been derived. In this scattering process, the metastable superconducting current changes via quantum jumps corresponding to a decrease in the number of fluxoids in the superconducting ring by one or several units and the change in the energy of the ring is transferred to the kinetic energy of the scattered neutron. For rings from type-II superconductors with a thickness smaller than the field penetration depth but larger than the electron mean free path, the cross sections of inelastic scattering with neutron spin flip have been obtained for the first time. The possibility of increasing the cross section of neutron scattering by a system of rings has been discussed.     

A novel method of flat YBCO rings development for shield-type superconducting fault current limiters fabrication

The application of flat superconductor rings has been investigated in the structure of inductive shield-type high temperature superconducting fault current limiters, HT_c-SFCL. A laboratory scale inductive shield-type HT_c-SFCL has been designed and fabricated using flat superconductor rings. The fabrication process has been fully presented. YBCO powder has been used for the fabrication of superconductor rings. This fabrication process, being quite innovative, is introduced completely. The method of the trapped field measurement has been used for the critical current density measurement of the fabricated superconductor rings. The device with nominal current of 2 A was tested in a 30 V circuit. The SFCL successfully limited the fault currents of up to 10 times the nominal current to an approximately fixed value of 3 A. The voltage-current characteristic of the fabricated prototype has also been obtained and has shown compatibility with the fault current limitation results.     

Thin-film sensing using circular split-ring resonators at mm-wave frequencies

In this paper, we investigate a thin-film sensing approach using split-ring resonators. The sensitivity based on tuned magnetic resonance has been demonstrated using three methods: by depositing the film in the gap, under the rings as an intermediate layer and on the rings as an overlayer. The numerical simulations and experimental results are presented. In addition, the advantages and the limitations of each approach are discussed. Moreover, the sensitivity of the circular rings are compared with that of the square rings.     

介观金属双环系统中的持续电流和量子能谱

基于电荷的不连续性,对处于外磁场中的介观双环系统进行量子化.假设系统在电荷表象中具有变换的对称性,通过求解电流和Hamilton算符的本征值方程,给出介观金属环互感系统中的量子电流和能谱关系;分析和研究了介观金属环中量子电流和能谱的性质.结果表明,持续电流和量子能谱不仅与外磁场、介观双环参数有关,而且还明显地依赖于电荷的量子化性质.     

Interaction of scandium and titanium atoms with a carbon surface containing five- and seven-membered rings

The use of carbon nanotubes coated by atoms of transition metals to store molecular hydrogen is associated with the problem of the aggregation of these atoms, which leads to the formation of metal clusters. The quantum-chemical simulation of cluster models of the carbon surface of a graphene type with scandium and titanium atoms has been performed. It has been shown that the presence of five- and seven-membered rings, in addition to six-membered rings, in these structures makes it possible to strongly suppress the processes of the migration of metal atoms over the surface, preventing their clustering.     

Study of local density of electron states in InGaAs/GaAs quantum rings by combined STM/AFM

The electronic structure of self-assembled InGaAs/GaAs(001) quantum rings grown by atmospheric pressure metal-organic vapor phase epitaxy has been investigated by combined scanning tunneling/atomic force microscopy (STM/AFM) in ultrahigh vacuum (UHV) for the first time. The current images and the tunnel spectra of contact of Pt-coated Si AFM probe to the quantum ring heterostructure surface revealing the spatial distribution of the local density of states and the electron size quantization spectra in the quantum rings have been obtained.     

On graphene melting

Dynamics of disordering of graphene upon heating has been studied by computer simulation. The mechanism governing the formation of seeds for a three-dimensional grid of entangled carbon chains into which graphene is transformed upon melting has been analyzed in detail. It has been shown that the emergence of these seeds is preceded by the disruption of several interatomic bonds, accompanied with the formation of large rings or groups of adjacent rings and the formation of penta- and heptagons of their C–C bonds. The results of this work on the whole agree with the Lindemann–Lozovik criterion. The melting temperature is estimated as T_m ~ 5100 K.     

Raman Scattering by Plasma Oscillations in Quantum Rings

Resonant Raman scattering in quantum rings with a sufficiently large number of conduction electrons has been studied. The cross section for Raman scattering accompanied by the excitation of a one-dimensional plasmon in a ring has been determined in the self-consistent field approximation.     

Embedded-ring migration on graphene zigzag edge

Reaction pathways are presented for hydrogen-mediated isomerization of a zigzag graphene edge containing a five-member carbon ring surrounded by six-member rings. A new reaction sequence in which this embedded five-member ring moves, or migrates, through the edge has been identified. The elementary steps of the pathways were analyzed using density functional theory (DFT). Rate coefficients were obtained by classical transition state theory utilizing the DFT energies, frequencies, and geometries. The results indicate that this new reaction sequence is competitive with the other important zigzag edge reactions allowing embedded five-member rings to move freely within a zigzag edge. The embedded rings have slight thermodynamic preference for the interior of the edge over the corner for large substrates.     

Full diagonalization of the EKS model on small rings

Summary A numerical symmetry-aided study of the supersymmetric Hubbard model of Essler, Korepin and Schoutens on small rings is presented. The complete spectrum has been determined for rings up to seven sites, allowing a thorough discussion of the physical features of the zero- as well as finite-temperature states of the model.     

Spatial mode cleaning in radically asymmetric strongly focused laser beams

We demonstrate that a femtosecond laser pulse strongly focused in air can produce a highly symmetric damage pattern on glass. This damage pattern contains a series of near-perfect radial rings, with diameters much larger than the predicted focal spot diameter. These rings disappear when the experiment is conducted in vacuum, indicating atmospheric involvement. Surprisingly, the shape and size of the rings seem to be nearly independent of the shape of the generating laser beam, showing dramatic spatial mode cleaning. A “half moon” initial laser mode created by obscuring one side of the round beam produces rings of similar quality to those obtained with the unclipped beam. While spatial mode cleaning has previously been reported in filaments, this is the most dramatic demonstration of the effect that we are aware of. We argue that the effect is due primarily to ionization, in contrast to studies in longer filaments that attribute it to self-focusing.     

一种阶梯结构的色散平坦光子晶体光纤的研究

以多极法理论为基础,提出了一种阶梯结构的光子晶体光纤.通过改变其内四层的三个结构参量(内两层孔孔径,外两层孔孔径和孔间距),实现色散绝对值在1.1～1.8μm的波段内变化仅为0.05～2 ps/(km·nm)的平坦甚至超平坦的特性.在此情况下对其有效模场面积进行数值模拟,充分展示了达到色散平坦和超平坦时,相对于传统光子晶体光纤,此种结构的光纤对芯区内光场的局域能力有很大程度的增强,其有效模场面积可仅为传统光子晶体光纤的1/30.最后,经过大量的数值计算和理论分析,归纳出若要此种阶梯结构的光纤在1.1～1.8μm的波段内达到色散平坦甚至超平坦特性的设计依据.     

用振动光谱的频率参数研究分子结构的构象变化 Ⅰ．芳香酯液晶分子的研究

通过振动光谱的频率参数，结合构象与键级的关系，观测了芳香酯液晶分子（一种高分子液晶模型化合物）在相态变化过程中的构象结构变化。认为这种液晶化合物在由晶态到液晶态的变化过程中是从酯基与苯环呈相互垂直状态到酯基与Ａ环是共平面状态而与Ｂ环不共平面即垂直的状态。     

等温退火对辐照诱发的非晶TiNiCu合金微观组织结构的影响

 TiNiCu记忆合金在美国Argonne国家实验室IVEM Tandem National Facility加速器产生的400keV Xe+离子辐照到0.4dpa时发生非晶化转变。通过电子显微镜研究了非晶化的TiNiCu合金的回复和再结晶过程。退火加热的速度是10℃/min。在280℃时非晶环附近出现电子衍射斑点以及明场像中出现少量析出相，表明回复和再结晶开始。退火到550℃出现多晶环，650℃时有片状马氏体变体生成，750℃时有很锐利的多晶环出现，表明再结晶过程基本完成。经标定再结晶晶粒仍然是TiNiCu记忆合金。再结晶组织与辐照前TiNiCu 合金的显微组织相比有较大差异。     

DTPA双芳酰胺钆配合物作为肝胆磁共振成象造影剂

对三种DTPA双芳酰胺钆配合物用作肝胆磁共振成象造影剂进行了研究.配合物的亲脂性通过正辛醇-水分配比进行表征,结果表明实验值与理论值有很好的线性关系.蛋白结合实验表明亲脂性较强的配合物具有较强的蛋白结合能力.家兔的活体磁共振成象表明,将芳香环引入配合物中可以实现肝细胞对配合物的特异性摄取.     

The Incidence of Strain on the Quenching of the Vibrationally Induced Intensity of the Secondary Transition of the Benzene Chromophore: A New Explanation

It has been assumed for a long time that strain, induced by rings fused to the benzene chromophore, limits the amplitude of vibrational motions, and then decreases the intensity of the vibrationally induced part of the secondary transition. That assumption has been grounded on the well known RAPOPORT and SMOLENSKY's work.^1–2     

International Linear Collider damping ring lattice design with two wiggler sections

The International Linear Collider (ILC), which is based on super-conducting RF acceleration technology, requires the damping rings to provide beams with extremely small equilibrium emittance, and large acceptance to ensure good injection efficiency for high-emittance, and high-energy spread beam from the positron source. In order to reduce the cost for ILC damping rings, an alternative lattice which is different from the baseline configuration design has been designed with modified FODO arc cells, and the total quadrupole number has been reduced by half. At the same time, to decrease the total cost involved in constructing access shafts needed to supply power, cryogenics etc. for the wigglers and other systems, the number of wiggler sections is decreased from 8 to 4, and further to 2. This new lattice has been optimized to have a good dynamic aperture. This alternative ILC damping ring lattice design will reduce the cost largely as compared with the baseline design.     

A new type of reconstruction on the InSb(1̄1̄1̄) surface determined by grazing incidence X-ray diffraction

The (3×3) reconstruction of the InSb(1̄1̄1̄) surface has been investigated by grazing incidence X-ray diffraction and scanning tunneling microscopy. The structure is characterized by 6-atom rings on top of a slightly buckled InSb top double layer. Two types of rings have been found, an elliptic ring consisting of 4 In and 2 Sb atoms and a trigonal ring with 3 In and 3 Sb atoms. The bond angles and lengths are consistent with the concept of rehybridization and depolarization which explains the reconstructions of the (111) and (110) surfaces.     

羟基卟啉衍生物LB膜的紫外可见光谱表征

研究了两种具有两条脂链的羟基卟啉在气液界面上的成膜性能及其ＬＢ膜。ＵＶ－Ｖｉｓ光谱表明,两种卟啉在ＬＢ膜中的聚集态不同,卟啉环上脂链和羟基呈对称了代时形成Ｊ－聚体,呈同侧取代时形成氢键聚集体。利用偏振ＵＶ－Ｖｉｓ吸收谱测定了ＬＢ膜中卟啉环的取向。结果表明,侧链和羟基的相对位置对环的取向没有影响,但影响膜中平均分子截面积的大小和环间的距离,因而影响膜中分子的聚集态。