A novel backlight unit for volume-holographic optical elements-based time-multiplexed three-dimensional displays

In volume-holographic optical elements (VHOEs)-based time-sequential three-dimensional (3-D) displays, two reference beams generated from a backlight unit (BLU) illuminate VHOEs, and from which object beams satisfying the Brag condition are then diffracted. These beams form a pair of alternating light fields for stereo 3-D view. Since this system operates based on diffraction optics, its performance highly depends on the degrees of collimation and uniformity of the reference beams. Thus, a new BLU system to generate uniformly-collimated reference beams for the VHOEs-based 3-D display is proposed by combined use of a light-guide-plate (LGP) grooved with an array of angle-variant flat-top prisms, and two LED light sources attached with reflection-type beam collimators. Simulation results with LightTools 7.1 show that the average full-width at half maximum (FWHM), backshift ratio and intensity uniformity of the LGP output beam of the proposed system have been significantly reduced down to 2.8° and 0.4%, and increased up to 90.9%, respectively, from the values of 51.8°, 26.5% and 24.5% of the conventional system. They represent 18.5-, 66.3- and 3.7-fold improvements of those values in the proposed system, respectively. These successful results confirm the feasibility of the proposed system in the practical VHOEs-based 3-D display.     

Possible evidence for the observation of noncompact (nonbaryonic) gravitational microlenses (“neutralino stars”)

The microlensing of distant stars by noncompact objects such as neutralino stars is considered. Recently, Gurevich and Zybin considered the objects as microlenses. Using a nonsingular density distribution, we analyze microlensing by noncompact objects. We obtain analytic solutions to the gravitational-lens equation and an analytic expression for the amplification factor of the gravitational lens. We show that, on the basis of a model of microlensing by noncompact objects, it is possible to interpret microlensing-event candidates having two typical maxima of light curves which are usually interpreted as binary microlenses.     

基于支撑矢量机的天体光谱自动分类方法

天体光谱自动识别系统的主要目标是对天体进行分类和参数测量。文章提出一种新的基于支撑矢量机的非活动天体与活动天体的自动分类方法。在信噪比低的时候 ,由于红移值未知使得噪声与发射谱线难于辨别 ,因此不能单纯依靠寻找发射谱线来确定是否为活动天体。据此 ,在低噪声情况下对非活动天体与活动天体的区分成为难点。本方法结合主分量分析法和支撑矢量机 ,能够对红移值未知的活动天体与非活动天体比较有效地进行自动光谱分类 ,对天文界的大型巡天计划中的海量观测数据自动处理有比较重要的应用价值。     

Three-dimensional Fourier Fringe Analysis

Over the years two-dimensional Fourier Fringe Analysis (2D-FFA) has demonstrated both its capability and its relative robustness in analysing fringe patterns within a short time-frame from static objects. Nowadays, there is an increasing demand to measure dynamic objects. Today 2D-FFA is seen as a fast and flexible method of processing fringe patterns for dynamic objects. But it is still inherently a 2D approach, i.e. it deals with three-dimensional data (video sequences) on an individual 2D frame-by-frame basis. In this paper, a novel three-dimensional Fourier Fringe Analysis (3D-FFA) algorithm is proposed to demodulate fringe pattern sequences taken from dynamic objects. This technique processes the stack of fringe patterns as a single 3D volume, not as a set of individual 2D frames that are each processed in isolation. The proposed algorithm has been evaluated on both computer simulated and real dynamic objects. Results show that the proposed technique is able to demodulate fringe pattern volumes successfully.     

Multiple helical scans and the reconstruction of over FOV-sized objects in cone-beam CT

In cone-beam computed tomography(CBCT),there are often cases where the size of the specimen is larger than the field of view(FOV)(referred to as over FOV-sized(OFS)).To acquire the complete projection data for OFS objects,some scan modes have been developed for long objects and short but over-wide objects.However,these modes still cannot meet the requirements for both longitudinally long and transversely wide objects.In this paper,we propose a multiple helical scan mode and a corresponding reconstruction algorithm for both longitudinally long and transversely wide objects.The simulation results show that our model can deal with the problem and that the results are acceptable,while the OFS object is twice as long compared with the FOV in the same latitude.     

Simultaneous use of amplitude and phase to improve the validation process in a joint transform correlator

We present an alternative technique to enhance the discrimination performance in a JTC architecture, employed as a validation procedure. We define as complex objects those amplitude objects bonded to random phase masks. When using complex objects as reference inputs in a JTC optical validation system, correlation peak intensity and correlation peak shape become simultaneous key parameters to increase the discrimination ability of the system. Simulation results, comparing amplitude-only objects versus complex objects as inputs to the system, reveal the validity of our approach and show the sensitivity of the JTC architecture to the additional phase structures.     

Exotic branes in string theory

Besides the familiar D-branes, string theory contains a vast number of other non-perturbative objects. While a complete classification is lacking, many of these objects are related to each other through various dualities. Codimension two objects play a special role, because their charges are no longer additive but are instead expressed in terms of holonomies of scalar fields, which is given by an element of the relevant duality group. In this paper we present a detailed exposition of these “exotic” objects, the charges they carry, and their connection to non-geometric compactifications. Despite the name “exotic branes”, these objects are in fact ubiquitous in string theory, as they can automatically appear when describing bound states of conventional branes, and as such may be of particular importance in describing the microscopic degrees of freedom of black holes.     

Locating the position of objects in non-line-of-sight based on time delay estimation

Non-line-of-sight imaging detection is to detect hidden objects by indirect light and intermediary surface(diffuser).It has very important significance in indirect access to an object or dangerous object detection, such as medical treatment and rescue. An approach to locating the positions of hidden objects is proposed based on time delay estimation. The time delays between the received signals and the source signal can be obtained by correlation analysis, and then the positions of hidden objects will be located. Compared with earlier systems and methods, the proposed approach has some modifications and provides significant improvements, such as quick data acquisition, simple system structure and low cost, and can locate the positions of hidden objects as well: this technology lays a good foundation for developing a practical system that can be used in real applications.     

Transfer characteristics of rectangular phase gratings in interference microscopy

In this Letter, the transfer characteristics of rectangular periodic phase objects are studied. It turns out that there are significant differences compared to amplitude objects. The imaging of an amplitude object can be understood as a linear process, whereas phase objects behave nonlinearly. It is shown that under certain conditions the correct shape of a rectangular phase grating can be obtained by an interference microscope as long as the first order diffraction component passes the optical imaging system. This result is in a good agreement with experimental observations and computer simulation results.     

非朗伯体红外测温计算研究

根据红外辐射理论和红外热像仪的测温原理,建立了红外热像仪测温的通用数学模型;基于物体表面法向发射率的特点,简化了热像仪测温的数学模型,得到了红外热像仪测温的计算公式。通过相关实验,验证了在一定的温度范围内,物体的发射率和反射率之和基本保持不变这一结论。物体的发射率与反射率之和a与物体种类、表面状况及物体温度有关。物体与朗伯体越接近,a越大,其值越接近于1;物体表面状况偏离朗伯体越远,表面越光滑,越小。实验表明,若物体接近朗伯体,则可将其视为朗伯体,无需进行实际物体修正;对于非朗伯体(特别是表面光滑且发射率较低的物体),需要对其红外测温进行修正,否则将增大测温误差,甚至偏离其真实温度很远。该研究表明,通过修正,可以对非朗伯体进行红外测温。     

Generalized Rule Induction Based on Immune Algorithm

A generalized rule induction mechanism, immune algorithm, for knowledge bases is building an inheritance hierarchy of classes based on the content of their knowledge objects. This hierarchy facilitates group-related processing tasks such as answering set queries, discriminating between objects, finding similarities among objects, etc. Building this hierarchy is a difficult task for knowledge engineers. Conceptual induction may be used to automate or assist engineers in the creation of such a classification structure. This paper introduces a new conceptual rule induction method, which addresses the problem of clustering large amounts of structured objects. The conditions under which the method is applicable are discussed.     

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.     

光电反馈式静电悬浮与静电悬浮力测定

本文提出光电反馈式静电悬浮的新方法,简要讨论静电悬浮的原理、装置及其光电反馈控制过程.采用铝片和CD光盘作为悬浮体,测定了不同静电电压和不同悬浮间距时的静电悬浮力,揭示了它们之间的相互关系.结果显示这两种悬浮体均可获得足够的静电悬浮力,证明了静电悬浮的可行性.静电悬浮方法的显着特点是既适用于导电体与非导电体的悬浮,又适用于磁性体与非磁性体的悬浮,克服了传统磁悬浮技术仅适用于磁性体的局限性,可广泛应用于精密元器件的悬浮与非接触无损操作.     

Object based dual watermarking for video authentication

Video cameras have been widely installed in public facilities for the surveillance applications. So, video authentication has becoming increasingly attractive. This paper presents a dual watermarking for video authentication based on moving objects. For each frame, the frame index, as a watermark is first embedded into the moving objects of the corresponding frame using a reversible watermarking method, aiming to detect the temporal tampering. Then the principle content and the details of the moving objects combined with the authentication code, as the other watermark, are embedded into the frame for spatial tampering location and recovery. Specially, a synthesized frame method is proposed for lossless recovery of moving objects and effective extraction of frame index. Statistical analysis and experiment results show that the proposed method can locate spatial, temporal and spatio-temporal tampering accurately. The spatial tampered regions can be recovered approximately and the moving objects can be restored completely when the tampered area is limited.     

Generalized Rule Induction Based on Immune Algorithm

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基于Logistic回归模型的Blazar天体的分类

从文献中收集了205个Blazar天体,包括142个BL Lac天体和63个平谱射电类星体(FSRQs).对这些天体的类别与它们的红移、射电5 GHz辐射流量、光学V波段流量、1 keV处X射线流量、X射线光子谱指数进行了相关性和Logistic回归分析.结果表明,对Blazar天体分类产生主要影响的因素是红移、射电5 GHz辐射流量和X射线光子谱指数,综合应用这三个物理量判别Blazar天体的分类的准确率可达到91.2%,得到的分类方程具有良好的预测效果,可以作为Blazar天体分类的一个重要的判据.而光学V波段流量和1 keV处X射线流量不能区分开BL Lac天体和FSRQs,它们与Blazar天体分类没有相关性.本文结果支持将BL Lac天体和FSRQs归为Blazar天体,不同类别的Blazar天体之间能通过一种演化序列相联系. 关键词： Logistic 分类 Blazar天体     

Some objects formed in the interaction of electrical discharges with metals and polymers

An experimental approach is developed for producing autonomous objects reminiscent of ball lightning by the charging of an activated base made of materials such as polymers and metals with an energetic metastable plasma. Methods of obtaining these autonomous objects and some of their properties are described. It is found that as the energy-deposition parameters are increased, these objects increasingly resemble ball lightning. An attempt is made to indicate the specific forms of the charging and to give a brief phenomenological treatment of the processes responsible for the observed effects. Zh. Tekh. Fiz. 67, 19–28 (March 1997)     

Hardening by softening in a flow of chainlike self-driven objects

A two-dimensional square lattice system, on which flexible, chainlike, self-driven objects move randomly but are drifted to a same direction, causing a unidirectional net flow, is investigated by numerical simulations. It is shown that the objects exhibit a freezing transition from a smoothly flowing state to a completely jammed state, in which the objects become immobile and cannot move anymore. Comparison with the flow of rigid objects shows that this complete jamming (hardening) results from the flexibility (softening) of each self-driven object. This is the first report of the freezing transition of a free transport system (without obstacles) where the net flow is not multidirectional (as in the case of opposing flows or crossing flows) but unidirectional.     

Design and simulation of a high resolution active imaging technique utilizing Fresnel telescopy

A new technique for high resolution active laser imaging of space objects is demonstrated. The technique, referred as Fresnel telescopy, is a variant of Fourier telescopy, which additionally uses Fresnel zone plates to scan objects. The design scheme of a compact schematic of transmitting and receiving system for Fresnel telescopy is proposed. We provide simulations results for imaging of a photograph of satellite to illustrate and clarify the proposed idea. The technique is found to have substantial practical value and offers significant practical benefit for high resolution imaging of objects in the field of military applications.     

基于单层感知器的彩色图像目标提取方法

针对复杂背号下的彩色图像的目标提取,提出了一种基于单层感知器的目标提取方法。通过建立以颜色分量为输入、阈值型函数为输出的单层感知器网络并训练得到最适权重,实现彩色图像的目标与背景分离。与现有主流目标提取算法进行对比实验,结果表明,该方法能够更加准确、有效地分离目标和背景,且方法适用范围广,实现简单。