Affine-permutation invariance of 2-D shapes.

Shapes provide a rich set of clues on the identity and topological properties of an object. In many imaging environments, however, the same object appears to have different shapes due to distortions such as translation, rotation, reflection, scaling, or skewing. Further, the order by which the object's feature points are scanned changes, i.e., the order of the pixels may be permuted. Relating two-dimensional shapes of the same object distorted by different affine and permutation transformations is a challenge. We introduce a shape invariant that we refer to as the intrinsic shape of an object and describe an algorithm, BLAISER, to recover it. The intrinsic shape is invariant to affine-permutation distortions. It is a uniquely defined representative of the equivalence class of all affine-permutation distortions of the same object. BLAISER computes the intrinsic shape from any arbitrarily affine-permutation distorted image of the object, without prior knowledge regarding the distortions or the undistorted shape of the object. The critical step of BLAISER is the determination of the shape orientation and we provide a detailed discussion on this topic. The operations of BLAISER are based on low-order moments of the input shape and, thus, robust to error and noise. Examples illustrate the performance of the algorithm.     

Turbo encoding and decoding of Reed-Solomon codes through binary decomposition and self-concatenation

This paper presents a two-stage turbo-coding scheme for Reed-Solomon (RS) codes through binary decomposition and self-concatenation. In this scheme, the binary image of an RS code over GF(2/sup m/) is first decomposed into a set of binary component codes with relatively small trellis complexities. Then the RS code is formatted as a self-concatenated code with itself as the outer code and the binary component codes as the inner codes in a turbo-coding arrangement. In decoding, the inner codes are decoded with turbo decoding and the outer code is decoded with either an algebraic decoding algorithm or a reliability-based decoding algorithm. The outer and inner decoders interact during each decoding iteration. For RS codes of lengths up to 255, the proposed two-stage coding scheme is practically implementable and provides a significant coding gain over conventional algebraic and reliability-based decoding algorithms.     

毫米级氟化钙盘腔的加工与测试

回音壁模式(Whispering Gallery Mode,WGM)的光学谐振腔作为光学研究的重要工具具有广泛的应用前景。以超纯单晶氟化钙为材料加工了直径为5 mm,厚度为1 mm的CaF2盘型腔,并用化学机械抛光法对其进行了光学抛光,得到了粗糙度为纳米级别的CaF2盘型腔。搭建盘腔与锥形光纤的耦合测试平台测试所加工盘型腔的光学性能,测得在波长为1 550 nm时所加工的盘型腔的品质因数为2.1106。对CaF2盘型腔损耗机制进行了理论分析,提出了提高CaF2盘型腔品质因数的方法。     

长波GaAs QWIP二维周期光栅的耦合效率研究

在量子阱红外探测器(QWIP)上制备光栅的目的是对垂直入射的红外辐射进行有效的耦合.为了研究光栅的光耦合性能,基于模式扩展理论,详细计算长波(14.7 μm)QWIP二维周期矩形光栅的耦合效率.计算结果表明,光栅周期D=4.7 μm,栅孔深度h=1.45μm,d(栅孔)/D=0.707时,光栅的耦合效率达到最大.并且从几何光学的考虑出发,对计算结果进行了验证和分析.还讨论了二维周期光栅衍射光场的分布情况.     

Decomposition of magnetoencephalographic data into components corresponding to deep and superficial sources

We extend the signal space separation (SSS) method to decompose multichannel magnetoencephalographic (MEG) data into regions of interest inside the head. It has been shown that the SSS method can transform MEG data into a signal component generated by neurobiological sources and a noise component generated by external sources outside the head. In this paper, we show that the signal component obtained by the SSS method can be further decomposed by a simple operation into signals originating from deep and superficial sources within the brain. This is achieved by using a scheme that exploits the beamspace methodology that relies on a linear transformation that maximizes the power of the source space of interest. The efficiency and accuracy of the algorithm are demonstrated by experiments utilizing both simulated and real MEG data.     

Formation of absolute PBG of 2D square lattice by changing the shapes and orientations of rods

In this paper, the effects of shapes and orientations of rods on absolute PBGs in 2D square lattice are studied. By replacing round rods with square rods, which sides are along with the direction of elementary lattices vectors, the absolute PBGs in 2D square lattice with wave vector in periodic plane and off periodic plane have been studied and then through changing the square rods orientation, the changing of the width and position of PBG has been obtained.     

阳极氧化制备硅基TiO_2纳米管阵列及形貌表征

TiO_2纳米管因其具有独特的结构优势和优异的物理化学性质,受到了广泛的关注与研究。然而,TiO_2纳米管阵列(NTA)的制备主要以钛片为基底,很难与硅的微加工工艺相兼容,制约了其在微型电子设备中的应用。为将TiO_2纳米管阵列与硅衬底结合,首先以磁控溅射方法在硅基底上沉积一层金属钛薄膜,通过阳极氧化法制备硅基TiO_2纳米管阵列。采用扫描电子显微镜(SEM)分别探究了阳极氧化过程中外加电压、电解液组成、阳极氧化时间对纳米管形貌的影响,并得到了优化的实验参数。实验发现:50 V恒压条件下,在含有质量分数0.5%氟化铵的乙二醇电解液中对金属钛薄膜进行阳极氧化,成功制备出直径约110 nm、高2.00μm的TiO_2纳米管阵列。高比表面积的TiO_2纳米管可根据需要负载不同的物质材料,应用于传感器、药物传输、超级电容器等领域,极大拓展了其在微电子器件方面的应用。     

An investigation into the use of iteration methods for the analysis of axially symmetric and sheet beam electrode shapes with an emitting surface

The techniques for analyzing an axially symmetric or two-dimensional electrode system with an emitting surface have been studied with a computer program. The program is very easy to use and performs in one pass the steps which have usually previously been followed on analog and digital devices separately. The program alternately solves Poisson's equation by a relaxation technique, traces trajectories, recomputes the space-charge distribution and again performs a relaxation process. This procedure continues until satisfactory convergence has been achieved. The ease of use of the computer program has allowed the investigation of different methods of speeding up the convergence. The results are illustrated with two specific examples.     

TiO2薄膜的热处理晶化及形貌研究

对Si(111)和Si(100)衬底上用化学气相沉积法制成的TiO2薄膜进行了不同温度的热处理，并用原子力显微镜对处理后薄膜的形貌变化进行了观察。X－射线衍射分析表明形貌变化过程即晶化过程。晶化物相为金红石。晶化程度（或形貌变化程度）与热处理的温度有次数（或热处理时间）有关。Si(111)衬底上TiO2晶化形貌为杂乱分布的柱状、板状，定向不好；而Si(100）衬底上TiO2晶化形貌为定向较好的四方柱状或板状，这是因为Si(100)与金红石（001）都属四方对称结构，两相结构在此方向上容易匹配的结果。在相同热处理条件下，Si(111)衬底比Si(100)衬底上TiO2晶化程度高，说明非定向附生的晶化作用比定向附生的晶化作用容易实现。     

部分相干平顶光束的M2因子、模分解及合成

推导出以模式间相互独立的厄米高斯光束为基底的部分相干平顶光束的模系数和M2因子的解析式,对部分相干平顶光束的模分解及合成进行了研究.研究结果表明,随着光束阶数M及表征光束相干性的参数w0/ν0的增加,基模的份额减小,M2因子增大.采用模式间相互独立的厄米高斯光束叠加的方法合成部分相干平顶光束的光强矩形分布与光束M2因子二者无法同时兼顾,即若要求空间分布非常接近矩形,则光束的M2因子较大,若要求光束的M2因子较小,则只能降低对光强矩形分布的要求.在实际工作中,可以通过选择恰当的基底基模高斯光束的束腰尺寸以及控制各模式的光功率,由模式间相互独立的厄米高斯光束合成部分相干平顶光束.     

Assessment of the 3-d reconstruction and high-resolution geometrical modeling of the human skeletal trunk from 2-D radiographic images

This paper presents an in vivo validation of a method for the three-dimensional (3-D) high-resolution modeling of the human spine, rib cage, and pelvis for the study of spinal deformities. The method uses an adaptation of a standard close-range photogrammetry method called direct linear transformation to reconstruct the 3-D coordinates of anatomical landmarks from three radiographic images of the subject's trunk. It then deforms in 3-D 1-mm-resolution anatomical primitives (reference bones) obtained by serial computed tomography-scan reconstruction of a dry specimen. The free-form deformation is calculated using dual kriging equations. In vivo validation of this method on 40 scoliotic vertebrae gives an overall accuracy of 3.3 +/- 3.8 mm, making it an adequate tool for clinical studies and mechanical analysis purposes.     

Identification of geometrical shapes in paintings and its application to demonstrate the foundations of geometry in 1650 B.C.

In this paper, an original general methodology is introduced to establish whether a handmade shape corresponds to a given geometrical prototype. Using this methodology, one can decide if an artist had the intention of drawing a specific mathematical prototype or not. This analysis is applied to the 1650 B.C. wall paintings from the prehistoric settlement on Thera, and inferences of great archaeological and historical importance are made. In particular, strong evidence is obtained suggesting that the spirals depicted on the wall paintings correspond to linear (Archimedes) spirals, certain shapes correspond to canonical 48-gon and 32-gon, while other shapes correspond to parts of ellipses. It seems that the presented wall paintings constitute the earliest archaeological findings on which these geometrical patterns appear with such remarkable accuracy.     

Image decomposition via the combination of sparse representations and a variational approach.

The separation of image content into semantic parts plays a vital role in applications such as compression, enhancement, restoration, and more. In recent years, several pioneering works suggested such a separation be based on variational formulation and others using independent component analysis and sparsity. This paper presents a novel method for separating images into texture and piecewise smooth (cartoon) parts, exploiting both the variational and the sparsity mechanisms. The method combines the basis pursuit denoising (BPDN) algorithm and the total-variation (TV) regularization scheme. The basic idea presented in this paper is the use of two appropriate dictionaries, one for the representation of textures and the other for the natural scene parts assumed to be piecewise smooth. Both dictionaries are chosen such that they lead to sparse representations over one type of image-content (either texture or piecewise smooth). The use of the BPDN with the two amalgamed dictionaries leads to the desired separation, along with noise removal as a by-product. As the need to choose proper dictionaries is generally hard, a TV regularization is employed to better direct the separation process and reduce ringing artifacts. We present a highly efficient numerical scheme to solve the combined optimization problem posed by our model and to show several experimental results that validate the algorithm's performance.     

Terminal-centric view of software. reconfigurable system architecture and enabling components and technologies

Reconfigurable radio in Europe is rapidly gaining momentum and becoming a key enabler for realizing the vision of being optimally connected anywhere, anytime. At the center of this exciting technology is the reconfigurable terminal that will move across different radio access networks, adapting at every instant to an optimum mode of operation. This will require coordinated reconfiguration management support from both the terminal and the network, but the terminal will inherit a significant part of this intelligence. This article focuses on a novel reconfigurable terminal architecture that advances the state of the art and encompasses the overall protocol stack from the physical to application layer in IP-based radio access networks. The proposed architecture is composed of a terminal reconfiguration management part and enabling middleware technologies like the complementary Distributed Processing Environment and agent platforms, flexible protocol stacks that can flexibly be interchanged to support different wireless technologies and associated mechanisms, and finally, object-oriented reconfigurable RF and baseband components. The work presented in this article is conducted in the context of the IST projects SCOUT (www.ist-scout.org) and TRUST (www4.in.tum.de/-scout/trust webpage/spl I.bar/src/ trust frameset.html) of the European 5th Framework Program.     

A model for investigating the introduction of digital techniques based on a decomposition into elementary networks: methodology and first results

This paper concerns the definition of general rules for planning and decision making in the digitalization of a long distance telecommunications network. It is shown that, under some hypotheses, a network built around a transit centre may be decomposed into elementary triangular networks for which traffic routing and circuit routing are treated at the same time. In the proposed method the evolution in time of the existing network is optimized by minimizing the discounted cost and taking into account modularity constraints. In particular, using simple examples, the dependence of the transit threshold on the immediate environment is studied. Finally we show how the model may be used for setting up a network configurator.