First and second order non-equilibrium phase transition and evidence for non-extensive Tsallis statistics in Earth’s magnetosphere

In this paper strong evidence is provided for significant far from equilibrium phase transition processes in the Earth’s magnetosphere as revealed by the nonlinear analysis of in situ observations. These results constitute the solid base for the solution of the durable controversy about the chaotic or non-chaotic character of the magnetospheric dynamics. During the last two decades the concept of low dimensional chaos was supported by theoretical and experimental methods by our group in Thrace and others scientists, as an explicative paradigm of the magnetospheric dynamics including substorm processes. In parallel, the concept of self-organized criticality (SOC) and space-time intermittency was introduced as new and opposing to low dimensional chaos concepts for modeling the magnetospheric dynamics. Novel results concerning the nonlinear analysis of in situ space plasma data (magnetic-electric field, energetic particles and bulk plasma flow time series) obtained by the Geotail spacecraft presented in this paper for the first time reveal the following: (a) Coexistence of SOC and chaos states in the magnetospheric system and global phase transition from one state to the other during substorms. (b) Strong intermittent turbulent character of the magnetospheric system at the SOC or the low dimensional chaos states. (c) Clear indications for non-extensivity and q-Gaussian statistics during periods of low dimensional and chaotic dynamics of the magnetosphere. (d) Low dimensional and nonlinear space plasma dynamics in the day side magnetopause and bow shock dynamics. The dual character of the magnetospheric dynamics including low dimensional chaotic (coherent) and high dimensional turbulent states, as supported in this paper, is in agreement and verifies previous theoretical and experimental studies.     

Probing solar system objects at infrared wavelengths

Two recent investigations of solar system objects are described as examples of the application of high spectral resolving power and of combined temporal-spatial power spectral analysis to planetary problems. The detection and characterization of water vapor in comets Halley and Wilson (19861) by airborne infrared observations is used to illustrate the extraction of physico-chemical information from doppler-limited spectra. Time series analysis of thermal emission from the atmosphere of Jupiter is used to illustrate the extraction of dynamical information from two dimensional photometric measurements.     

浅海波导中目标散射的边界元方法

提出了一种计算三维散射体在声速剖面随深度变化、距离无关浅海波导中散射声场的数值方法波导边界元方法。当散射体不十分靠近波导界面因而边界多次散射可以忽略时,在边界元计算中可以用自由场格林函数近似波导格林函数。应用镜像法和球波函数加法定理推导了理想波导中球体散射声场的解析解,用来验证波导边界元方法的计算精度,证明该数值方法是准确的。对浅海波导中水下潜器散射声场数值模拟的结果表明,浅海波导海面、海底界面反射、声速剖面等对目标散射声场的幅值和方向性都有很大的影响。      

3D Reconstruction of Large-Depth Objects Using Fresnel Diffraction of a Ronchi Grating and Simultaneous Recording of Reference and Object Fringes

We propose an active triangulation based range-finding system that, besides its simplicity, has two advantages over similar existing systems. First, the system can acquire range data for large-depth objects since it generates an illumination pattern with large-depth of focus using Fresnel diffraction from a Ronchi grating projected over the entire object surface. Secondly, the system does not need preliminary recording of reference fringes since it displays simultaneously, on a single image, both reference and object deformed fringes. This system offers other properties: it is mechanically simple, uses everyday optical components, is low cost, can be operated via a PC and uses relatively simple image analysis software. Three dimensional reconstructions are illustrated for various objects having 10 cm maximum depth variations. The depth accuracy (typically 0.5 mm for an object located at 350 mm from the camera) is comparable with other systems, but a certain compromise has to be accepted in acquisition time (typically 1 minute). This system can find applications in research laboratories as a tool to provide range data with relatively good depth accuracy.     

基于岩石重构图像的核磁共振响应模拟

能够反映孔隙介质内部真实复杂结构的CT图像经常被用于模拟研究中并能取得较好的结果. 但是,在很多情况下缺少三维CT图像或者其分辨率受限,此时,更易于获取的二维薄片图像被用于构建三维的孔隙结构图像. 假定孔隙介质各向同性,基于二维图像,使用多点统计方法可以构建岩石的三维孔隙结构. 基于数字图像,采用随机游走方法模拟得到核磁共振响应,然后由模拟得到的回波串反演得到T₂分布. 研究表明,岩石重构图像中的模拟结果与CT图像中的模拟结果有较好的一致性. 基于数字图像的核磁共振响应模拟为分析不同孔隙结构的核磁共振响应提供了便利,同时,模拟结果也为验证孔隙结构的重构效果提供了依据.     

基于等效电流源的分层媒质目标反演研究

针对分层媒质目标反演问题, 提出了一种基于等效电流源的目标重建方法. 该方法首先利用散射数据重建辐射电流源, 然后将等效电流源的求解转化为最优化问题来处理, 通过共轭梯度方法搜索得到全局最优解, 进而实现对目标的反演, 该方法充分挖掘了散射数据所包含的信息, 缩小了解的搜索空间维度, 具有求解效率高的优点. 深入研究了频率、 采样间隔、 采样长度、 噪声水平以及背景估计对反演结果的影响, 并对上述结果做了理论分析. 仿真结果表明, 该方法能够较好地实现分层媒质目标的反演, 可以应用于穿墙成像、地质勘探等领域. 关键词： 电磁散射 分层媒质 等效电流源     

Three Dimensionality of the Recognized Visual Space of Illumination Proved by Hidden Illumination

We hypothesized that the recognized visual space of illumination (RVSI) was constructed in our brain when we grasped the state of illumination of a space. The importance about the RVSI is that it is three dimensional and is valid not only at the surfaces of the existing objects in the space, but also for the entire portion in the space where no objects exist. With this property of RVSI we are able to predict the appearance of an object surface in terms of lightness as well as of color when the object shifts from one place to the other in the space. The three dimensionality of the RVSI is proved by giving a hidden illumination within a space and by asking a subject to judge the lightness or color of a test patch placed in the area of the hidden illumination. In spite of the additional light on the test patch the subject did not recognize that the light was added but simply felt that the surface was made of a higher lightness or colored by transferring the light into an increase of the reflectance factor of the test patch. The results can be interpreted if we assume that a same RVSI exists throughout the entire space including the area of the hidden illumination.     

Active microwave radiometry and its applications

Summary In microwave bands, attenuation and reflectivity of objects are usually determined by locating the objects between two antennas, connected to a generator and a detector. If a narrowband signal is used, the radiators and an object should be adequately separated as otherwise so-called near field exists around the radiators; due to interfering wave fronts, space is filled by interference maxima and minima that prevent a reasonable measurement from being done.The described method employs wideband noise instead of a narrowband or CW (continuous wave) signal. Therefore a radiometer is used as detector and a noise generator as source.By creating a random field in the space between radiators, interesting phenomena have been observed which can find also a practical use even though no ready-to-use theory apparently exists to describe such phenomena.     

目标与传输介质多功能红外实验系统环境模拟设备的研制

作者研制了一套目标与传输介质红外试验用空中环境模拟设备,该设备提供冷背景、热真空、太阳辐射模拟、特殊介质注入等多种环境模拟功能。文中详细论述了其设计思想、主要结构、性能指标和必要的设计计算,给出了设备的试验结果。     

光照光谱功率分布的估计和颜色分割

提出了应用有限维线性模型和双色反射模型和双色反射模型抽表示而物体颜色的本征特性的方法，首先估计出光照的光谱功率分布，再获取物体的表面光谱反射率，从而得到和光照与几何条件无关的归一化偏差光谱反射率，它仅反映物体的表面反射特性，可作为颜色分割和识别的可靠特征。     

空间点目标光谱探测与特征识别研究进展

光学观测是空间目标识别的重要手段,由于探测距离远,视场中的空间目标多呈现为非分辨的点目标。相比于传统的定轨测量和光度测量,光谱探测提供了波长维的可分辨信息,极大的提升了目标表面材质判别能力,并为目标状态反演提供了更可靠的依据,极具应用潜力。介绍了近年来国内外学者在空间点目标光谱探测及特征识别方面的典型研究进展,依据主要研究方法,分为多通道测光探测、高光谱探测、实验室光谱特性测量、目标特性建模仿真四个方向。其中,多通道测光获得了低光谱分辨率的测量数据,是常用的广域空间目标分类判别手段;高光谱探测研究反射能量在波长维的精细分布,有助于反演重点目标的材质组成;实验室光谱特性测量可在受控条件下模拟目标探测的物理过程,提供材质光谱特性数据库;目标特性建模仿真则对物理属性抽象特征化,研究目标光谱变化过程。通过分析国内外研究成果,总结当前研究的能力与不足,提出几点研究思路,为后续研究开展提供参考。     

线指数特征空间内恒星光谱离群数据挖掘与分析

大规模光谱巡天将产生海量的光谱数据,为搜寻一些奇异甚至于未知类型的光谱提供了机会,对这些特殊天体的研究有助于揭示宇宙的演变规律和生命起源,巡天数据的离群数据挖掘有助于这些特殊的光谱的发现。利用线指数对光谱数据进行降维能够在尽可能多的保留光谱物理特征的同时,有效解决高维光谱数据聚类分析中运算复杂度较高的问题。提出了基于线指数特征的海量恒星光谱离群数据挖掘及分析的方法,以恒星光谱的Lick线指数作为光谱数据的特征,利用聚类搜寻离群数据的方法在海量光谱巡天数据搜寻离群数据,以此为基础并给出线指数特征空间内离群光谱数据的分析方法。实验结果证明：(1)以线指数作为光谱的特征值能快速的完成对高维光谱数据的离群数据挖掘,可以解决高维光谱数据运算复杂度高的问题;(2)该方法是在聚类结果上进行的离群数据挖掘,能够有效的挖掘出数量较少的发射线恒星、晚M型恒星、极贫金属星、缺失数据光谱等数据;(3)线指数特征空间的离群数据挖掘可以得到线指数特征空间内特殊恒星的发现规则。本文所提出的基于线指数特征的离群数据挖掘及分析方法可以应用到巡天数据的相关研究中。     

一维自旋1/2电子系统的单杂质散射研究

应用高斯波泛函方法，研究了单个局域杂质对一维自旋1/2传导电子的散射问题．研究结果表明，双粒子散射与单粒子散射具有同样的重要性．由于这两种散射机制相互竞争，形成了拉亭格液体中电荷密度波和自旋密度波的各自的重整化质量．随着这些质量的消失，在参量空间中出现了相界，在不同相区中系统呈现不同的动力学行为 关键词：     

On the Energy Spectrum of Yang–Mills Instantons over Asymptotically Locally Flat Spaces

In this paper we prove that over an asymptotically locally flat (ALF) Riemannian four-manifold the energy of an “admissible” SU(2) Yang–Mills instanton is always integer. This result sharpens the previously known energy identity for such Yang–Mills instantons over ALF geometries. Furthermore we demonstrate that this statement continues to hold for the larger gauge group U(2). Finally we make the observation that there might be a natural relationship between 4 dimensional Yang–Mills theory over an ALF space and 2 dimensional conformal field theory. This would provide a further support for the existence of a similar correspondence investigated by several authors recently.     

High order weighted essentially non-oscillatory WENO-Z schemes for hyperbolic conservation laws

In [10], the authors have designed a new fifth order WENO finite-difference scheme by adding a higher order smoothness indicator which is obtained as a simple and inexpensive linear combination of the already existing low order smoothness indicators. Moreover, this new scheme, dubbed as WENO-Z, has a CPU cost which is equivalent to the one of the classical WENO-JS [2], and smaller than that of the mapped WENO-M, [5], since it involves no mapping of the nonlinear weights. In this article, we take a closer look at Taylor expansions of the Lagrangian polynomials of the WENO substencils and the related inherited symmetries of the classical lower order smoothness indicators to obtain a general formula for the higher order smoothness indicators that allows the extension of the WENO-Z scheme to all (odd) orders of accuracy. We further investigate the improved accuracy of the WENO-Z schemes at critical points of smooth solutions as well as their distinct numerical features as a result of the new sets of nonlinear weights and we show that regarding the numerical dissipation WENO-Z occupies an intermediary position between WENO-JS and WENO-M. Some standard numerical experiments such as the one dimensional Riemann initial values problems for the Euler equations and the Mach 3 shock density-wave interaction and the two dimensional double-Mach shock reflection problems are presented.     

Positivity of energy in five dimensional classical unified field theories, II

Five dimensional classical unified field theories as well as Yang-Mills theory with gauge group U(1), are described in terms of a Lorentzian five dimensional space V₅ with metric tensor γβ which admits a space-like Killing vector ζ. It is assumed that: (1) V₅ has the topology of V₄ x S¹, S¹ is a circle and V₄ is a four dimensional Lorentzian space that is asymptotically flat and (2) the Einstein tensor Γ_β of V₅ satisfies Γ_β Uυ^{β 0} where U and υ are future oriented time-like vectors with γ_βυζ^β = 0. The spinor approach of Witten [4], Nester [3] and Moreschi and Sparling [5] is used to show that the conserved five dimensional energymomentum vector P = ifΓ_β = 0 then V₅ must admit a time-like Killing vector. Lichnerowicz's results [1] then imply that V₅ must be flat. A lower bound for P⁴ (the mass) similar to that found by Gibbons and Hull [6] is obtained.     

Geometry of financial markets—Towards information theory model of markets

Most parameters used to describe states and dynamics of financial market depend on proportions of the appropriate variables rather than on their actual values. Therefore, projective geometry seems to be the correct language to describe the theater of financial activities. We suppose that the objects of interest of agents, called here baskets, form a vector space over the reals. A portfolio is defined as an equivalence class of baskets containing assets in the same proportions. Therefore portfolios form a projective space. Cross ratios, being invariants of projective maps, form key structures in the proposed model. Quotation with respect to an asset Ξ (i.e. in units of Ξ) is given by linear maps. Among various types of metrics that have financial interpretation, the min-max metric on the space of quotations can be introduced. This metric has an interesting interpretation in terms of rates of return. It can be generalized so that to incorporate a new numerical parameter (called temperature) that describes agent's lack of knowledge about the state of the market. In a dual way, a metric on the space of market quotation is defined. In addition, one can define an interesting metric structure on the space of portfolios/quotation that is invariant with respect to hyperbolic (Lorentz) symmetries of the space of portfolios. The introduced formalism opens new interesting and possibly fruitful fields of research.     

Testing and Analysis of the Structure of Transmitting Media or Objects with Registration of the Field Structure in the Image Plane

A solution to the phase problem in optics is considered within the context of the registration and analysis of the amplitude–phase structure of optical nonuniformities in stationary transmitting media or in investigated objects. To solve the problem, the object or the medium is tested by radiation with a known structure. For a certain selected direction of testing, the structural change due to the interaction with the object is registered. To obtain information on the amplitudes and phases of the testing light field, an original development of the modulationspectral method put forward by the authors is used. To solve the problem, the intensity distribution is detected in the image plane both for an unmodulated field and for that subjected to an additional twodimensional modulation specially formed in the plane of spatial frequencies. The modulation should provide a visualization of the phase information contained in the light field. The intensity distributions obtained make it possible to determine the twodimensional structure of the testing field at the output of the medium or the object. In the proposed variant of the method, the testing field should not be affected in the investigated plane. The interpretation of the results is easier, since it is the image that is registered. The two intensity distributions can be registered simultaneously, provided the light beam is divided into two channels after the optical system. It is significant that the method requires no iteration procedures in solving the problem. This allows one to expect speedingup of the processing of the information and analyzing it in almost real time. Two variants of optical schemes are considered in the paper. The first one deals with media or objects with a modulation effect described by multiplication by a complex function characterizing the effect. In the second case, the effect of the object leads to redistribution of the radiation in the investigated plane and is described by the operation of convolution of the testing signal and the function characterizing the effect.     

Multidimensional Polyhedral Gamut Representation of Reflective Objects and Calculation of Metamer Ensembles

The spectral reflectance of most reflective objects, such as natural objects and color hardcopy, is relatively smooth and can be approximated by several principal components with high accuracy. Although the subspace spanned by those principal components represents a space in which reflective objects exist, it does not provide the limit of the object distribution or the gamut. In this paper we propose to represent the gamut of reflective objects as a convex polyhedron in the subspace spanned by several principal components. The concept of the polyhedral gamut representation based on the spectral reflectance database and its application to the calculation of metamer ensembles are described. The color-mismatch volume caused by different illuminant and/or observer for a metamer ensemble is also calculated and compared with the theoretical ones.