Synthesis, physicochemical characterization and crystallographic twinning of Li2ZnSnS4

Li₂ZnSnS₄ is a new diamond-like semiconductor, which is of interest as a host structure for the creation of potentially interesting electronic, magnetic and photovoltaic materials. The compound was synthesized via traditional high-temperature solid-state methods and was predicted to adopt a wurtz-stannite structure with all atoms possessing tetrahedral environments. Initial analysis of single-crystal X-ray diffraction data indicated crystallographic disorder that upon closer examination violated basic chemical principles. The structure was subsequently re-evaluated and the apparent “disorder” problem was found to be the result of pseudo-merohedral twinning. The crystal structure was finally solved in the monoclinic space group Pn, which resulted in a chemically reasonable model. The refinement converged with R1=1.68% (for all data). Additional characterization of the sample, including diffuse reflectance, thermal analysis and second harmonic generation measurements, was also performed.     

酸性溶液中Rh电极上CO孪生吸附态的FTIRS研究

采用现场多步ＦＴＩＲ光谱技术结合ＣＯ吸附分子探针方法，研究了Ｒｈ电极表面分子过程，在电化学处理后的光滑Ｒｈ电极表面上首次检测到两种ＣＯ孪生吸附态及其随电位变化过程，使用电位循环扫描方法改变Ｒｈ电极表面状态，在０．０５ｍｏｌ／Ｌ，Ｈ２ＳＯ４酸性溶液中，取取－０．２７５至２．４Ｖ电位区间和１．５Ｖ／ｓ扫描速率对Ｒｈ电极进行循环扫描处理２ｍｉｎ处理后的Ｒｈ电极表面积累一层氧化物，ＣＯ以孪生态吸附于表面Ｒ     

-contingent epiderivatives in reflexive spaces

In this paper we introduce a notion of the τ^w-contingent epiderivative of a set-valued map by considering the weak topology in the image space. We establish a chain rule formula for families of τ^w-contingent and contingent epiderivatives. When the image space is reflexive and the ordering cone a half-space, we give conditions for the existence of the family of τ^w-contingent epiderivatives of a stable set-valued map; moreover we obtain an interesting formula that connects this family with the contingent epiderivative of an associated scalar set-valued map. Finally we apply the previous results in order to establish optimality conditions for a set-valued optimization problem via epiderivatives with respect to half-spaces associated with the ordering cone. In particular we provide a scalarization method for computing these conditions in reflexive spaces.     

Proving total dual integrality with cross-free families—A general framework

We present a theorem stating that certain classes of linear programming problems have integer optimal (primal and dual) solutions. The theorem includes as special cases earlier results of Johnson, Edmonds and Giles, Frank, Hoffman and Schwartz, Gröflin and Hoffman, and Lawler and Martel. The proof method consists of deriving total dual integrality for the corresponding system of linear inequalities from the total unimodularity of certain ‘cross-free’ subsystems. The scheme presented here differs from the one proposed earlier by Grishuhin in that Grishuhin requires the total unimodularity of cross-free subsystems in the axioms, whereas here this follows from easier verifiable axioms.     

Endpoint theory for set-valued nonlinear asymptotic contractions with respect to generalized pseudodistances in uniform spaces

In uniform spaces, inspired by ideas of Banach, Tarafdar and Yuan, we introduce the concepts of generalized pseudodistances and generalized gauge maps, for set-valued dynamic systems we define various nonlinear asymptotic contractions and contractions with respect to these pseudodistances and gauges, provide conditions on the iterates of these set-valued dynamic systems and present a method which is useful for establishing conditions guaranteeing the existence and uniqueness of endpoints (stationary points) of these set-valued dynamic systems and conditions that each generalized sequence of iterations (in particular, each dynamic process) converges and the limit of a generalized sequence of iterations is an endpoint. The definitions, the results and the method are new for set-valued dynamic systems in uniform, locally convex and metric spaces and even for single-valued maps. The paper includes a number of various examples which show a fundamental difference between our results and those existing in the literature.     

On solving the multi-period single-sourcing problem under uncertainty

We present a framework for solving the strategic problem of assigning retailers to facilities in a multi-period single-sourcing product environment under uncertainty in the demand from the retailers and the cost of production, inventory holding, backlogging and distribution of the product. By considering a splitting variable mathematical representation of the Deterministic Equivalent Model, we specialize the so-called Branch-and-Fix Coordination algorithmic framework. It exploits the structure of the model and, specifically, the non-anticipativity constraints for the assignment variables. The algorithm uses the Twin Node Family (TNF) concept. Our procedure is specifically designed for coordinating the selection of the branching TNF and the branching S3 set, such that the non-anticipativity constraints are satisfied. Some computational experience is reported. D. Romero Morales: The work of this author was supported in part by the National Science Foundation under Grant No. DMI-0355533 The work of the first three authors has been partially supported by the grants TIC2003-05982-C05-05 and SEC2002-00112 from MCyT, Spain     

亚强非局域介质中的超高斯空间光孤子族研究

研究了亚强非局域介质中超高斯光束的传播特性.运用变分法,对任意实对称响应函数泰勒级数展开取至四阶,得到了1+1维亚强非局域非线性介质中光束传输的超高斯光束的近似分析解.分析结果表明：束宽解是椭圆雅可比双周期函数,相移、空间啁啾以及临界输入功率都正比于超高斯光束的阶数.提出了超高斯空间光孤子族模型和准方波形空间光孤子的实现可能性.     

The complexity of social groups and social systems described by graph structures

This paper presents methodology which permits the complete ranking of nondirected graphs (NDG's) on an attribute labelled ‘complexity.’ The technique applies to both small and large systems as might arise in studies of group or organization behavior. The methodology extends to cover the complexity of directed graphs (DG's) and permits the detailed specification of individual and group behavior.For the NDG an abstract automaton representing the participants' interaction or communications function is sited at each node. Each automaton is constructed so its internal complexity is sufficient to realize the minimal social action (e.g. transmission of a rumor and the path followed by the rumor) within the framework of the NDG. It is shown that the complexity of each node automaton depends upon the order of the graph, the degree of the node and the longest path parameter of the graph. The combined complexity of node automata constitutes the complexity of the NDG. The complexity of a DG is specified as a composition of complexities computed for the associated NDG and logical devices which produce the observed behavior. Illustrative examples pertaining to the committee-subcommittee problem and to organizational structures are presented.     

Separation of vibration fringe data from rotating object fringes using pulsed ESPI

In industrial and other types of non-controlled environments, an unbalanced rotating object may present characteristic out-of-plane vibration amplitude at a specific frequency. For this type of cases and as a first step towards a complete evaluation, it is only desired to visualize the effect of the vibration on the rotating object, or vice versa, for instance to achieve object balancing. Real time optical non-intrusive measurement techniques such as pulsed electronic speckle pattern interferometry (ESPI), are well suited to study this rotating-vibrating object. The advantage offered by ESPI is that real-time fringe data is qualitatively analyzed while being observed on a TV monitor. The present paper proposes a qualitative method, based on pulsed ESPI, to separate rotation fringes from fringes solely related to vibration. The method relies on a high precision scheme that synchronizes and fixes an object point during rotation, without the use of an optomechanical object derotator.