An iterative algorithm for signal reconstruction from bispectrum

The author presents a procedure to reconstruct a (minimum or nonminimum phase) discrete-time signal from its bispectrum. The algorithm is iterative and based on using the method of projections onto convex sets (POCS) in an inner product space in which the vector space consists of real sequences, and vector addition, is defined in terms of the convolution operation. Prior information, such as an energy bound on the signal, can be incorporated into this algorithm. An algorithm that employs energy information was found to produce better results in simulation than one that ignores energy constraints     

Bit-serial window partitioning algorithm for stack filtering

The authors introduce a new bit-serial algorithm for stack filtering, designated as the bit-serial window partitioning algorithm. It is shown that the proposed algorithm can achieve very important savings over the conventional bit-serial binary-tree search algorithm, in terms of the computational speed. This improved efficiency is obtained by evaluating the Boolean function at thresholds corresponding to the sample values within the filter window, and by taking advantage of the ordering information associated with the threshold sequences     

A reconstruction algorithm from truncated projections

A new tomographic reconstruction method is proposed which permits the reconstruction of a region of interest within a slice from partially truncated scanning data. This method utilizes two types of source data, namely a series of truncated projections and the outline of the object's cross section. The principle of this algorithm is to estimate the outside area of truncation in one projection from the projection data of the other viewing angles and the outline data of the object. The above estimation is accomplished by following two repeated procedures: 1) the modification of the calculated projection data compared each time with the already measured projection data of the truncated area, and 2) the modification of the reconstructed image compared also each time with the shape of the object. Computer simulation shows the convergence of the results obtained by this algorithm thus verifying its validity, and a reconstructed image after iterative processes exhibits good quality.     

On a trie partitioning algorithm for power-efficient TCAMs

Internet routers conduct routing table (RT) lookup based on the destination IP address of the incoming packet to decide which output port to forward the packet. Ternary content-addressible memories (TCAM) uses parallelism to achieve lookup in a single cycle. One of the major drawbacks of TCAM is its high-power consumption. Trie-based architecture has been proposed to reduce TCAM power consumption. The idea is to use an index TCAM to select one of many data TCAM blocks for lookup. However, power reduction is limited by the size of the index TCAM, which is always enabled for search. In this paper we develop a simple but effective trie-partitioning algorithm to reduce the index TCAM size, which achieves better reduction in power consumption, and at the same time guarantees full TCAM space utilization. We compared our algorithm (LogSplit) with PostOrderSplit (IEEE INFOCOM, 2003). For two real-world RTs (AADS and PAIX), the size of the index TCAM generated by LogSplit is 55–70% of that generated by PostOrderSplit; the largest power reduction factor of LogSplit is 41 for AADS and 68 for PAIX, while the largest power reduction factor of PostOrderSplit is 33 for AADS and 52 for PAIX. The improvement is even more significant in the worst case: the size of the index TCAM generated by LogSplit is 18–30% of that generated by PostOrderSplit for IPv4, and less than 1% of that generated by PostOrderSplit for IPv6; the largest power reduction factor of LogSplit is 173 for both IPv4 and IPv6, while the largest power reduction factor of PostOrderSplit is only 82 for IPv4 and 41 for IPv6. Copyright © 2007 John Wiley & Sons, Ltd.     

Three-dimensional surface reconstruction from multistatic SAR images

This paper discusses reconstruction of three-dimensional surfaces from multiple bistatic synthetic aperture radar (SAR) images. Techniques for surface reconstruction from multiple monostatic SAR images already exist, including interferometric processing and stereo SAR. We generalize these methods to obtain algorithms for bistatic interferometric SAR and bistatic stereo SAR. We also propose a framework for predicting the performance of our multistatic stereo SAR algorithm, and, from this framework, we suggest a metric for use in planning strategic deployment of multistatic assets.     

A partitioning algorithm for technoiogy-mapped designs onsingle-chip emulation systems

Reconfigurable single-chip emulation systems were proposed as an alternative to multichip emulation systems. Because they cannot be emulated on a single chip at once, large designs are sliced into partitions that are downloaded and executed sequentially on the same reconfigurable emulation chip. In this paper, we address the problem of partitioning a design on a reconfigurable single-chip emulator under resource constraints. First, we extract an acyclic flow graph of the design to be emulated. Then, we model the problem as an integer linear programming problem (IP) based on the acyclic flow graph of the design where the structure of the assignment and precedence constraints produce a tight formulation. To partition a design, our algorithm uses two distinct steps with different objectives. In the first step, we minimize the number of cycles needed to schedule every look-up table (LUT) in the circuit. Then flip-flops (FFs) are inserted into the appropriate cycles of the schedule in the second step. Experiments are conducted on small- and medium-size circuits from the MCNC Partitioning93 benchmark suite. The obtained results show that our algorithm produces optimal partitioning schedules     

一种改进的压缩感知重构算法研究

主要研究重构算法的贪婪算法中的正交匹配追踪算法,并提出了基于正交匹配追踪算法的改进算法,对图像进行列变换后,再对原图像进行行变换,然后综合两幅图像的优点,重构出原图像.仿真结果表明这种改进的算法能够有效地提高重构效果.     

A method for brain 3D surface reconstruction from MR images

Due to the encephalic tissues are highly irregular, three-dimensional （3D） modeling of brain always leads to compli- cated computing. In this paper, we explore an efficient method for brain surface reconstruction from magnetic reso- nance （MR） images of head, which is helpful to surgery planning and tumor localization. A heuristic algorithm is pro- posed foi＂ surface triangle mesh generation with preserved features, and the diagonal length is regarded as the heuristic information to optimize the shape of triangle. The experimental results show that our approach not only reduces the computational complexity, but also completes 3D visualization with good quality.     

Graph partitioning algorithm for opportunistic routing in large-scale wireless network

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Analog computation structure for surface reconstruction

A novel analog computation structure for real-time surface reconstruction is proposed. The structure is derived based on the variational principle that minimizes an energy functional for computing a smooth surface to interpolate an initial representation consisting of surface values at sparsely distributed locations. An unified and general approach to solve the ill-posed reconstruction problem from the viewpoint of functional analysis is proposed. The desired surface is modelled as a linear combination of a set of basis functions. A resistive network whose connections is a function of the basis functions is then constructed to calculate the weighting coefficients for the linear combination. With this network, the known surface values at those sparse points are applied to the network as the voltage sources. The desired coefficients are then obtained as the voltage values at the nodes of the network. This characteristic makes the proposed computation structure suitable for real-time surface reconstruction.     

A distributed access algorithm for cellular radio systems withchannel partitioning

Previous results in distributed power control and distributed channel access have demonstrated the possibility of high-capacity cellular radio networks without central control. However, these distributed algorithms may not converge completely in practical systems where the rate of channel variation (due to mobility, handoff, or interfering users entering or leaving the channel) approaches the rate at which power levels can be accurately measured and adjusted. We propose a new channel partitioning technique in which both dynamically allocated and fixed assignment channels are employed. This technique enables rapid distributed access that is inherently fair. Simulation results indicate that it is robust in responding to user mobility and handoff while yielding significant capacity gains over traditional fixed assignment systems     

分布式压缩感知联合重构算法

分布式压缩感知是用尽可能少线性测量值来表示一个联合稀疏信号。分布式压缩感知联合重构算法是以信号集中的某个信号为边信息,根据信号集中信号之间的相关关系来重构信号的算法。为了解决已有重构算法的复杂性以及减少重构算法所需的测量值数,提出了两种新的分布式压缩感知联合重构算法。对提出的两种新算法在信号和图像处理上进行了实验,验证了其可行性与先进性。结果表示,这两种联合重建算法在获取相同的图像质量时需要测量值更少。     

A super-resolution reconstruction algorithm for hyperspectral images

The spatial resolution of a hyperspectral image is often coarse because of the limitations of the imaging hardware. Super-resolution reconstruction (SRR) is a promising signal post-processing technique for hyperspectral image resolution enhancement. This paper proposes a maximum a posteriori (MAP) based multi-frame super-resolution algorithm for hyperspectral images. Principal component analysis (PCA) is utilized in both parts of the proposed algorithm: motion estimation and image reconstruction. A simultaneous motion estimation method with the first few principal components, which contain most of the information of a hyperspectral image, is proposed to reduce computational load and improve motion field accuracy. In the image reconstruction part, different image resolution enhancement techniques are applied to different groups of components, to reduce computational load and simultaneously remove noise. The proposed algorithm is tested on both synthetic images and real image sequences. The experimental results and comparative analyses verify the effectiveness of this algorithm.     

基于两层模糊划分的在策略时间差分算法

针对传统的基于查询表或函数逼近的Q值迭代算法在处理连续空间问题时收敛速度慢、且不易求解连续行为策略的问题,提出了一种基于两层模糊划分的在策略时间差分算法——DFP-OPTD,并从理论上分析其收敛性。算法中第一层模糊划分作用于状态空间,第二层模糊划分作用于动作空间,并结合两层模糊划分计算出Q值函数。根据所得的Q值函数,使用梯度下降方法更新模糊规则中的后件参数。将DFP-OPTD应用于经典强化学习问题中,实验结果表明,该算法有较好的收敛性能,且可以求解连续行为策略。     

激光共焦扫描显微镜中一种新的三维重构算法

由序列断层图像恢复出目标物体的三维图像是激光共焦扫描显微镜(LCSM)系统的重要组成部分。根据精细物体表面的特点,提出了一种新的基于物体表面的三维重构算法,并应用在LCSM系统中,得到了较好的结果。     

基于波段指数的高光谱影像波段选择算法

为了去除高光谱影像的数据冗余,提高高光谱影像处理的精度和效率,提出了一种基于波段指数的高光谱影像波段选择算法。采用小波变换对高光谱图像数据进行去噪处理,依据联合偏度-峰度指数将波段进行分组,再根据波段指数的大小确定相对较小指数的波段,并将其作为冗余波段进行去除,从而得到最小波段集。结果表明,利用该波段集和全波段所选的端元是一致的,在不影响端元提取的前提下,最大程度地去除了冗余波段,而且该波段集与全波段的分类精度较接近。该算法在波段选择过程中具有可行性与有效性,为降低高光谱影像维数提供了一种帮助。     

Recursive total least squares algorithm for image reconstruction from noisy,undersampled frames

It is shown how the efficient recursive total least squares algorithm recently developed by C.E. Davila [3] for real data can be applied to image reconstruction from noisy, undersampled multiframes when the displacement of each frame relative to a reference frame is not accurately known. To do this, the complex-valued image data in the wavenumber domain is transformed into an equivalent real data problem to which Davila's algorithm is successfully applied. Two detailed illustrative examples are provided in support of the procedure. Similar reconstruction in the presence of blur as well as noise is currently under investigation.     

Conjugate-gradient algorithm with edge-preserving regularizationfor image reconstruction from Ipswich data for mystery objects

This paper presents some evidence of the effectiveness of adding edge preserving (EP) regularization to the conjugate radient (CG) method, in reconstructing the shape and permittivity profile of dielectric objects. Without any a priori information, our CG algorithm is also still efficient, and succeeded in reconstructing two mystery targets. As the two targets are now known, we hope we can greatly enhance the reconstruction quality by choosing better values for the calibration factors, and by applying our EP regularization to these data     

Hybrid evolutionary partitioning algorithm for heat transfer enhancement in VLSI circuits

In this paper, a new approach to improving the heat transfer in integrated circuits (ICs) is presented. It is based on improving the thermal conductivity of ICs by increasing the number of their external connections up to the level determined by the packaging standard. In order to attain this goal, a new hybrid evolutionary partitioning algorithm (HEPA) for circuits partitioning is introduced. The computations carried out for the chosen benchmarks show that HEPA is able to reach optimal solutions in the case of bipartitioning problem, and almost optimal in the case of k-way partitioning (k>2). The presented approach is especially dedicated for a flip chip interconnect technology which is used in contemporary ICs.     

A modified-set partitioning in hierarchical trees algorithm for real-time image compression

Among all algorithms based on wavelet transform and zerotree quantization, Said and Pearlman’s set partitioning in hierarchical trees (SPIHT) algorithm is well known for its simplicity and efficiency. SPIHT’s high memory requirement is a major drawback to hardware implementation. In this study, we present a modification of SPIHT named modified SPIHT (MSPIHT), which requires less execution time at a low bit rate and less working memory than SPIHT. The MSPIHT coding algorithm is modified with the use of one list to store the coordinates of wavelet coefficients instead of three lists of SPIHT; defines two terms, number of error bits and absolute zerotree; and merges the sorting pass and the refinement pass together as one scan pass. Comparison of MSPIHT with SPIHT on different test image shows that MSPIHT reduces execution time at most 7 times for coding a 512 × 512 grayscale image; reduces execution time at most 11 times at a low bit rate; saves at least 0.5625 MB of memory; and reduces minor peak signal-to noise ratio (PSNR) values, thereby making it highly promising for real-time and memory limited mobile communications. Published in Russian in Radiotekhnika i Elektronika, 2008, Vol. 53, No. 6 pp. 676–685. The text was submitted by the authors in English.