Pigmy and giant dipole states in stable and unstable oxygen isotopes

We have studied dipole states of oxygen isotopes in large scale shell model calculations. The calculated photoreaction cross sections in ¹⁶O, ¹⁷O and ¹⁸O give reasonable agreement with experimental observations both in the low energy region below ?ω=15 MeV and in the high energy giant resonance region (15 MeV < ?ω ≤ 30 MeV). We found that the transition strength below dipole giant resonance (?ω ≤ 15 MeV) exhausts about 10% of the classical Thomas-Reiche-Kuhn sum rule and more than 40% of the cluster sum rule in heavier oxygen isotopes than ¹⁷O. The predicted Pigmy strengths in ²⁰O and ²²O are also confirmed by recent Coulomb excitation experiment at GSI.     

Multilevel detonation cell structures in methane-air mixtures

High-resolution numerical simulations of two-dimensional detonations in a methane-air mixture with extremely high activation energy show the formation of multiple levels of cellular structures caused by the propagation of triple-shock configurations. Two main types of these configurations were observed based on the structure of transverse waves behind the leading edge of the detonation. Collisions were observed between two triple-shock configurations with attached transverse detonations, two triple-shock configurations with inert transverse waves, and one of each of these types. These collisions give rise to the formation of highly irregular, and, in some cases incomplete, cells. Smoke foils obtained from detonation of a near-stoichiometric mixture of natural gas and air show similar results. Estimates of the width of the experimental cells qualitatively match those inferred from the calculations.     

Diverse magnetism in stable and metastable structures of CrTe

In this paper, we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations. By considering the electronic correlation effect, we predicted the ground-state structure of CrTe to be NiAs-type (space group P6₃/mmc) structure at ambient pressure, consistent with the experimental observation. Moreover, we found two extra meta-stable Cmcaand R\overline{3}m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure. The Cmcastructure is a layered antiferromagnetic metal. The cleaved energy of a single layer is 0.464 J/m² , indicating the possible synthesis of CrTe monolayer. The R\overline{3}m structure is a ferromagnetic half-metal. When external pressure is applied, the ground-state structure of CrTe transitions from P63/mmc structure to R\overline{3}m structure at a pressure of 34 GPa, then to R\overline{3}m structure at 42 GPa. We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.     

Fabrication of structures with tunable morphologies and sizes by soft molding

This paper presents a simple and versatile patterning method to fabricate polymer patterns with different morphologies and sizes by utilizing soft molding. When a patterned elastomeric stamp was placed on the polymer solution dropped on the substrate, the polymer solution will fill into the grooves of the stamp under capillary force. Through the modulation of the polymer concentration, it is possible to produce highly regular and reproducible polymer patterns with tunable morphologies and sizes using the same microscopic patterned mold. The gained polymer patterns can be further transferred to produce second-generation stamps.     

On the construction of stable and unstable manifolds of two-dimensional invertible maps

An equation is proposed for describing stable and unstable manifolds for a wide class of two-dimensional invertible maps. Several branches of the stable and unstable manifolds of the dissipative mapx _n+1 =1–a|x _n |+bz _n ,z _n+1 =x _n are constructed explicitly. The limiting case when the strange attractor disappears is discussed.     

Formation of mesoscopically organized phase structures in polymer mixtures

Mesomorphic phase structures in blends of sulfonic acid-terminated poly(ethylene glycol) (sPEG) and tertiary amino-terminated poly(2-ethylhexyl methacrylate) (aP2EHMA) were investigated by small angle X-ray scattering technique. SAXS results suggest the blends form lamellar morphology regardless of the blend composition between 30 and 70 wt% in sPEG. The blend containing 50 wt% of sPEG forms the highest ordered lamellar morphology and variation of the composition causes distortion of the ordered morphology. Due to the dissociating and reconstructing natures of the non-covalent bond between the sPEG and aP2EHMA, the lamellar morphology is maintained with the variation of the composition.     

Mean-field and RPA approaches to stable and unstable nuclei with semi-realistic interactions

We have developed semi-realistic NN interactions by modifying the M3Y interaction that was derived from the G -matrix. The modification has been made so that the saturation and the spin-orbit splittings should be reproduced. After viewing nuclear-matter properties, the semi-realistic M3Y-P5 interaction, which includes realistic tensor channels, is applied to finite nuclei in the mean-field and the random-phase approximations. In comparison with the results with widely used phenomenological interactions, we find that notable interaction dependence could remain in several Landau-Migdal parameters in the nuclear matter, in the N -dependence of proton single-particle levels in the Sn isotopes, and in the M1 strength distribution in ²⁰⁸Pb . Having microscopic origin in part, the semi-realistic interaction describes all these properties to reasonable accuracy. We confirm that the tensor force plays a crucial role in the single-particle levels and in the M1 distribution. Applying the semi-realistic interaction, we give prediction for a ground-state property of ⁶⁰Ca , for the magic nature of N = 32 and 34 in the neutron-rich region, and for the property of the first excited state of ²⁴O .     

New method for calculating stable and unstable periodic orbits of one-dimensional maps

A new iterative method of calculating periodic orbits of one-dimensional maps is presented, based on a lemma of Metropolis, Stein and Stein, with accelerated convergence based on Feigenbaum's scaling hypothesis. We are able to calculate global bifurcation diagrams, including unstable branches.     

Formation of stable structures from damage elements

Failure is described as the evolution of a kinetic system, and the conditions are considered for the formation of a stable structure arising from damage elements. A parabolic-type equation system describes the kinetics and is constructed on the basis of interaction between damage elements of two types, which are identified as local excited states interacting in accordance with the rules of formal chemical kinetics. The solutions staisfy the general laws of solid-state failure.Translated from Izvestiya Vyssikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 46–49, July, 1987.     

Thermodynamically stable fractal-like domain structures in magnetic films

A fractal-like structure of the domain boundaries was revealed in “overcritical” uniaxial Permalloy magnetic films. The fractal dimension of domain boundaries at the film surfaces was determined as a function of the film thickness. It is shown that the phase transition between the two possible types of fractal-like structures is accompanied by a jump in fractal dimension.

     

Coherent structures and entropy in constrained, modulationally unstable, nonintegrable systems

Many studies have shown that nonintegrable systems with modulational instabilities constrained by more than one conservation law exhibit universal long time behavior involving large coherent structures in a sea of small fluctuations. We show how this behavior can be explained in detail by simple thermodynamic arguments.     

Au-Pd与Au-Pt合金团簇稳定结构对比

由贵金属元素组成的合金团簇在光、电、磁和催化等领域吸引了广泛的研究兴趣.本文基于多体Gupta势函数采用内核构建的自适应免疫优化算法优化了Au-Pd和Au-Pt团簇最稳定结构.研究结果显示98原子Au-Pd与Au-Pt团簇均包含面心立方结构、十面体、二十面体和Leary四面体结构,但是两者的构型分布上存在着差异.键数变化分析结果显示Au原子分布趋势接近.此外,147原子Au-Pd和AuPt团簇均为完整二十面体结构.序列参数分析显示均形成核层结构.     

Spontaneous processes and stable structures in some three-phase cellular fluids

Cellular fluids are systems consisting of a collection of fluid cells surrounded by thin liquid films. In this study, systems composed of two different kinds of cells (i.e., filled with fluids A and B) immersed in a third fluid phase (a liquid C) have been examined. The object of the study is a collection of polyhedra of fluid B separated by a thin film of liquid C (a host B/C network), modified by the insertion of small droplets/bubbles of fluid A. Interfacial tensions acting along the A-C and B-C interfaces are assumed to be the only driving forces determining the structure of the resulting mixed system. Different configurations of mixed A/B/C systems, formed by the insertion of A singlets or doublets into the nodes, edges, films and interior parts of cells of the B/C network have been analyzed in terms of the interfacial energy of the system. The possibility of spontaneous migration of cells A through the B/C network and the possible final cell arrangements have been examined.     

Phase visualization in the study of cellular structures by confocal microscopy

It is experimentally shown that recording of the axial hologram, along with the confocal image, expands the possibilities of studying biological structures. Specifically, this approach makes it possible to visualize the phase of object wave without significant changes in the confocal microscope design and using standard methods for image processing.     

Investigation of an unstable diffusion process in isothermal three-component gaseous mixtures under steady conditions

The diffusional transport of a ternary gaseous mixture of helium, Freon-12, and argon is studied under isothermal conditions by a steady-flow method. The experiments were done at atmospheric pressure and a temperature of 298 K. The data are compared with the theory. It is shown that the mass transfer of the components is influenced by convective flows. Zh. Tekh. Fiz. 69, 5–9 (July 1999)     

基于流动显示的压缩拐角流动结构定量研究

在Ma = 3.0的超声速风洞中, 采用NPLS技术对上游边界层为层流的25° 压缩拐角进行了流动显示实验, 获得了压缩拐角的精细流动结构, 边界层、剪切层和激波等结构清晰可见. 基于流动显示数据, 采用间歇性、空间相关性和分形分析对流动结构进行了定量研究, 计算了边界层和分离区的间歇因子分布, 获取了边界层中拟序结构和结构角的大小, 给出了边界层分形维数的分布, 并与Ringuette和Bookey等的实验结果进行比较, 阐述了压缩拐角流动结构的定量特征.     

混合流体Rayleigh-Benard行波对流中的缺陷结构

通过流体力学基本方程的数值模拟,研究了含有缺陷的行波对流的动力学特性. 当分离比Ψ＝－06时,随着相对瑞利数r逐渐增加,系统由局部行波对流过渡到含有缺陷的行波对流,然后缺陷消失过渡到无缺陷的行波对流. 对于不同分离比的研究表明,缺陷出现的周期随着分离比减小而迅速增加,随着r增加而增加. 在负的小分离比时的增加速率大于大分离比时的增加速率. 缺陷存在区间Δr随着分离比绝对值减小很快变小, 并且当Ψ＝－011时缺陷消失,没有发现含有缺陷的行波对流. 当r大于Δr的上限时,系统过渡到无缺陷的行波对流.可是,当r小于Δr的下限时,不同的分离比Ψ值,对应不同的行波对流斑图. 这说明分离比明显地影响着各斑图形成及它们之间的转换,斑图之间的转换是很复杂的. 关键词： Rayleigh-Benard对流 缺陷 混合流体 行波