Analysis of the effects of the global financial crisis on the Turkish economy, using hierarchical methods

We have analyzed the topology of 50 important Turkish companies for the period 2006-2010 using the concept of hierarchical methods (the minimal spanning tree (MST) and hierarchical tree (HT)). We investigated the statistical reliability of links between companies in the MST by using the bootstrap technique. We also used the average linkage cluster analysis (ALCA) technique to observe the cluster structures much better. The MST and HT are known as useful tools to perceive and detect global structure, taxonomy, and hierarchy in financial data. We obtained four clusters of companies according to their proximity. We also observed that the Banks and Holdings cluster always forms in the centre of the MSTs for the periods 2006-2007, 2008, and 2009-2010. The clusters match nicely with their common production activities or their strong interrelationship. The effects of the Automobile sector increased after the global financial crisis due to the temporary incentives provided by the Turkish government. We find that Turkish companies were not very affected by the global financial crisis.     

The web of connections between tourism companies: Structure and dynamics

Tourism destination networks are amongst the most complex dynamical systems, involving a myriad of human-made and natural resources. In this work we report a complex network-based systematic analysis of the Elba (Italy) tourism destination network, including the characterization of its structure in terms of several traditional measurements, the investigation of its modularity, as well as its comprehensive study in terms of the recently reported superedges approach. In particular, structural (the number of paths of distinct lengths between pairs of nodes, as well as the number of reachable companies) and dynamical features (transition probabilities and the inward/outward activations and accessibilities) are measured and analyzed, leading to a series of important findings related to the interactions between tourism companies. Among the several reported results, it is shown that the type and size of the companies influence strongly their respective activations and accessibilities, while their geographical position does not seem to matter. It is also shown that the Elba tourism network is largely fragmented and heterogeneous, so that it could benefit from increased integration.     

Correlations,hierarchies and networks of the world’s automotive companies

We investigate, within the scope of econophysics, the correlations, hierarchies and networks of the world’s automotive companies over the 2003–2010 period by using the concept of a minimal spanning tree (MST) and hierarchical tree (HT). We derive a hierarchical organization and construct the MSTs and HTs for the 2003–2010 period and illustrate how the MSTs and their associated HTs developed over time. These periods are divided into two subperiods, such as 2003–2006 and 2007–2010, in order to test various time-windows and understand the temporal evolution of the correlation structure over time. We perform the bootstrap techniques to investigate a value of the statistical reliability to the links of the MSTs. We also use average linkage cluster analysis (ALCA) to observe the cluster structure more clearly in HTs. From the structural topologies of these trees, we identify different clusters of companies according to their geographical proximity and economic ties. Our results show that some companies are more important within the network, due to a tighter connection with other companies. We also find that these important companies play a predominant role in the world’s automotive industry.     

Investigation of major international and Turkish companies via hierarchical methods and bootstrap approach

We present a study, within the scope of econophysics, of the hierarchical structure of 98 among the largest international companies including 18 among the largest Turkish companies, namely Banks, Automobile, Software-hardware, Telecommunication Services, Energy and the Oil-Gas sectors, viewed as a network of interacting companies. We analyze the daily time series data of the Boerse-Frankfurt and Istanbul Stock Exchange. We examine the topological properties among the companies over the period 2006–2010 by using the concept of hierarchical structure methods (the minimal spanning tree (MST) and the hierarchical tree (HT)). The period is divided into three subperiods, namely 2006–2007, 2008 which was the year of global economic crisis, and 2009–2010, in order to test various time-windows and observe temporal evolution. We carry out bootstrap analyses to associate the value of statistical reliability to the links of the MSTs and HTs. We also use average linkage clustering analysis (ALCA) in order to better observe the cluster structure. From these studies, we find that the interactions among the Banks/Energy sectors and the other sectors were reduced after the global economic crisis; hence the effects of the Banks and Energy sectors on the correlations of all companies were decreased. Telecommunication Services were also greatly affected by the crisis. We also observed that the Automobile and Banks sectors, including Turkish companies as well as some companies from the USA, Japan and Germany were strongly correlated with each other in all periods.     

The network of scientific collaborations within the European framework programme

We use the emergent field of complex networks to analyze the network of scientific collaborations between entities (universities, research organizations, industry related companies,…) which collaborate in the context of the so-called framework programme. We demonstrate here that it is a scale-free network with an accelerated growth, which implies that the creation of new collaborations is encouraged. Moreover, these collaborations possess hierarchical modularity. Likewise, we find that the information flow depends on the size of the participants but not on geographical constraints.     

基于SPIHT的图像加密与压缩关联算法

为了研究图像压缩与加密同步进行问题, 本文提出了一种在变换域下的图像加密与压缩关联算法在该算法中, 加密过程发生在小波变换与SPIHT编码之间它充分利用了离散小波变换和基于层次树的集合划分(set partitioning in hierarchical trees, SPIHT)编码属性, 扩散过程被限制在单个子带内部. 此外, 混淆过程保留了SPIHT编码中两个最重要的位和符号位, 它包含了图像的重要信息. 实验结果表明, 算法具有良好的安全性、图像重构视觉质量以及很高的加/解密速度.     

Vertex centrality as a measure of information flow in Italian Corporate Board Networks

The aim of this article is to investigate the governance models of companies listed on the Italian Stock Exchange by using a network approach, which describes the interlinks between boards of directors. Following mainstream literature, I construct a weighted graph representing the listed companies (vertices) and their relationships (weighted edges), the Corporate Board Network; I then apply three different vertex centrality measures: degree, betweenness and flow betweenness. What emerges from the network construction and by applying the degree centrality is a structure with a large number of connections but not particularly dense, where the presence of a small number of highly connected nodes (hubs) is evident.Then I focus on betweenness and flow betweenness; indeed I expect that these centrality measures may give a representation of the intensity of the relationship between companies, capturing the volume of information flowing from one vertex to another. Finally, I investigate the possible scale-free structure of the network.     

Ni~(2 )∶CsMgCl_3晶体的光谱精细结构、零场分裂参量及Jahn-Teller效应

应用不可约张量理论构造了三角对称晶场中3d2/3d8态离子的45阶可完全对角化的微扰哈密顿矩阵,研究了CsNiCl3单晶掺入Cs MgCl3晶体后光谱精细结构、晶体结构、零场分裂参量、Jahn-Teller效应以及自旋单重态对Ni2 离子基态能级的影响,理论与实验相符合.研究了自旋-自旋耦合作用和Trees修正对Ni2 :Cs MgCl3晶体的光谱精细结构和零场分裂参量的影响,发现有五种机理会影响零场分裂参量:(1)自旋-轨道耦合机理;(2)自旋-自旋耦合机理;(3)自旋-轨道与自旋-自旋联合耦合机理;(4)自旋-轨道与Trees修正联合耦合机理,(5)自旋-自旋作用与Trees联合耦合机理.其中自旋-轨道耦合机理是最主要的,其它几种机理也是不可忽略的.     

Ni2+：CsMgCl3晶体的光谱精细结构、零场分裂参量及Jahn-Teller效应

应用不可约张量理论构造了三角对称晶场中3d2/3d8态离子的45阶可完全对角化的微扰哈密顿矩阵,研究了CsNiCl3单晶掺入CsMgCl3晶体后光谱精细结构、晶体结构、零场分裂参量、Jahn-Teller效应以及自旋单重态对Ni2+离子基态能级的影响,理论与实验相符合.研究了自旋-自旋耦合作用和Trees修正对Ni2+:CsMgCl3晶体的光谱精细结构和零场分裂参量的影响,发现有五种机理会影响零场分裂参量:(1)自旋-轨道耦合机理;(2)自旋-自旋耦合机理;(3)自旋-轨道与自旋-自旋联合耦合机理;(4)自旋-轨道与Trees修正联合耦合机理,(5)自旋-自旋作用与Trees联合耦合机理.其中自旋-轨道耦合机理是最主要的,其它几种机理也是不可忽略的.     

Statistical physics analysis of the computational complexity of solving random satisfiability problems using backtrack algorithms

The computational complexity of solving random 3-Satisfiability (3-SAT) problems is investigated using statistical physics concepts and techniques related to phase transitions, growth processes and (real-space) renormalization flows. 3-SAT is a representative example of hard computational tasks; it consists in knowing whether a set of αN randomly drawn logical constraints involving N Boolean variables can be satisfied altogether or not. Widely used solving procedures, as the Davis-Putnam-Loveland-Logemann (DPLL) algorithm, perform a systematic search for a solution, through a sequence of trials and errors represented by a search tree. The size of the search tree accounts for the computational complexity, i.e. the amount of computational efforts, required to achieve resolution. In the present study, we identify, using theory and numerical experiments, easy (size of the search tree scaling polynomially with N) and hard (exponential scaling) regimes as a function of the ratio α of constraints per variable. The typical complexity is explicitly calculated in the different regimes, in very good agreement with numerical simulations. Our theoretical approach is based on the analysis of the growth of the branches in the search tree under the operation of DPLL. On each branch, the initial 3-SAT problem is dynamically turned into a more generic 2+p-SAT problem, where p and 1 - p are the fractions of constraints involving three and two variables respectively. The growth of each branch is monitored by the dynamical evolution of α and p and is represented by a trajectory in the static phase diagram of the random 2+p-SAT problem. Depending on whether or not the trajectories cross the boundary between satisfiable and unsatisfiable phases, single branches or full trees are generated by DPLL, resulting in easy or hard resolutions. Our picture for the origin of complexity can be applied to other computational problems solved by branch and bound algorithms. Received 10 March 2001     

基于小波变换的干涉图压缩算法

在研究小波变换和分层树集合分割排序算法的基础上,将小波图像压缩技术应用于干涉图的压缩.根据小波分解系数矩阵中高频子图像上数据接近于零,信息主要表现部分在低频子图像上,以及干涉图数据中主要信息集中在零光程差附近的特征,将干涉图一行数据拆开并按对角Z型排列存储为矩阵形式,再进行小波压缩.结果表明,此改进能提高压缩性能.     

基于改进支持向量机算法的退耕地树种信息提取

树种间的光谱差异分析及分类算法的改进是利用遥感影像提取树种信息的难点,也是提高退耕地树种信息提取精度的关键.文章采用TM影像,通过不同树种光谱信息的差异分析,筛选出区分树种信息的光谱指标,并采用改进的支持向量机算法对退耕还林地不同树种信息进行了提取.结果表明,该研究算法提取的平均精度为81.7%,较传统支持向量机算法提...     

Optimally discriminant moments for speckle detection in real B-scan images

The paper presents and evaluates a speckle detection method for B-scan images. This is a fully automatic method and does not require information about the sensor parameters, which is often missing in retrospective studies.The characterization and posterior detection of speckle noise in ultrasound (US) has been regarded as an important research topic in US imaging, for improving signal-to-noise ratio by removing speckle noise and for exploiting speckle correlation information. Most of the existing methods require either manual intervention, the need to know sensor parameters or are based on statistical models which often do not generalize well to B-scans of different imaging areas. The proposed method aims to overcome those limitations.The main novelty of this work is to show that speckle detection can be improved based on finding optimally discriminant low order speckle statistics. In addition, and in contrast with other approaches the presented method is fully automatic and can be efficiently implemented to B-scan images.The method detects speckle patches using an ellipsoid discriminant function which classifies patches based on features extracted from optimally discriminant low order moments of the uncompressed intensity B-scan information. In addition, if the uncompressed signal is not available, we propose and evaluate a method for the estimation of this factor.The computation of low order moments using an optimality criteria, the decompression factor estimation and other key aspects of the method are quantitatively evaluated using both simulated and real (phantom and in vivo) data. Speckle detection results are obtained using again phantom and in vivo studies which show the validity of our approach. In addition, speckle probability images (SPI) are presented which provide valuable information about the distribution of speckle and non-speckle areas in an image.The presented evaluation and results show the effectiveness of our approach. In particular, the need for using discriminant analysis to determine the optimal discriminant power of the statistical moments and that this optimal value strongly depends on the characteristics and imaged tissues in the B-scan data.     

Femtosecond Laser-Induced Breakdown Spectroscopy for Detection of Trace Elements in Sophora Leaves

Sophora leaves from several areas in Beijing are analysed by femtosecond laser-induced breakdown spectroscopy （femto-LIBS）. Although the used spectral detection system is not time-resolved, the spectral lines of trace mineral elements are detected and analysed. It is proven that the femto-LIBS can be an efficient method to detect mineral trace elements contained in tree leaves which is a biomonitor for atmospheric pollution assessment or botanic studies. An interesting case of correlation between trace elements detected in tree leaves and the pollution of the concerned area is presented, for the first time to our knowledge.     

Near-Field Optical Transfer Function for Far-Field Super-Resolution Imaging

The far-field superlens based on surface plasmon polaritons （SPP） has shown great application potential, but it is difficult and time-consuming to reconstruct the far-field image. We derive a near-field optical transfer function （NOTF） of a silver slab and analyse its validity so that accurate information of nano-seale object in the near-field can be computed rapidly. The NOTF is helpful not only for analysing the super-resolution imaging process in far-field, but also for providing a track to describe the transmission of optical information from near-field to far-field by using the optical transfer functions theorv only.     

Nanotechnology,voluntary oversight,and corporate social performance: does company size matter?

In this article, we examine voluntary oversight programs for nanotechnology in the context of corporate social performance (CSP) in order to better understand the drivers, barriers, and forms of company participation in such programs. At the theoretical level, we use the management framework of CSP to understand the voluntary behavior of companies. At the empirical level, we investigate nanotech industry participation in the Environmental Protection Agency’s Nanoscale Materials Stewardship Program (NMSP) as an example of CSP, in order to examine the effects of company characteristics on CSP outcomes. The analysis demonstrates that, on the average, older and larger companies for which nanotech is one of the many business activities demonstrate greater CSP as judged by company actions, declarations, and self-evaluations. Such companies tended to submit more of the requested information to the NMSP, including specific information about health and safety, and to claim fewer of the submitted items as confidential business information. They were also more likely to have on-line statements of generic and nano-specific corporate social responsibility principles, policies, and achievements. The article suggests a need to encourage smaller and younger companies to participate in voluntary oversight programs for nanotechnology and presents options for better design of these programs.     

The role of power law nonlinearity in the discrete nonlinear Schrödinger equation on the formation of stationary localized states in the Cayley tree

We study the formation of stationary localized states using the discrete nonlinear Schr?dinger equation in a Cayley tree with connectivity K. Two cases, namely, a dimeric power law nonlinear impurity and a fully nonlinear system are considered. We introduce a transformation which reduces the Cayley tree into an one dimensional chain with a bond defect. The hopping matrix element between the impurity sites is reduced by . The transformed system is also shown to yield tight binding Green's function of the Cayley tree. The dimeric ansatz is used to find the reduced Hamiltonian of the system. Stationary localized states are found from the fixed point equations of the Hamiltonian of the reduced dynamical system. We discuss the existence of different kinds of localized states. We have also analyzed the formation of localized states in one dimensional system with a bond defect and nonlinearity which does not correspond to a Cayley tree. Stability of the states is discussed and stability diagram is presented for few cases. In all cases the total phase diagram for localized states have been presented. Received: 18 September 1997 / Revised: 31 October and 17 november 1997 / Accepted: 19 November 1997