Minimally Redundant 2-D Array Designs for 3-D Medical Ultrasound Imaging

In real-time ultrasonic 3-D imaging, in addition to difficulties in fabricating and interconnecting 2-D transducer arrays with hundreds of elements, there are also challenges in acquiring and processing data from a large number of ultrasound channels. The coarray (spatial convolution of the transmit and receive arrays) can be used to find efficient array designs that capture all of the spatial frequency content (a transmit–receive element combination corresponds to a spatial frequency) with a reduced number of active channels and firing events. Eliminating the redundancies in the transmit–receive element combinations and firing events reduces the overall system complexity and improves the frame rate. Here we explore four reduced redundancy 2-D array configurations for miniature 3-D ultrasonic imaging systems. Our approach is based on 1) coarray design with reduced redundancy using different subsets of linear arrays constituting the 2-D transducer array, and 2) 3-D scanning using fan-beams (narrow in one dimension and broad in the other dimension) generated by the transmit linear arrays. We form the overall array response through coherent summation of the individual responses of each transmit–receive array pairs. We present theoretical and simulated point spread functions of the array configurations along with quantitative comparison in terms of the front-end complexity and image quality.      

A 3-D Spectral-Element Time-Domain Method for Electromagnetic Simulation

A spectral-element time-domain (SETD) method is proposed to solve 3-D transient electromagnetic problems based on Gauss-Lobatto-Legendre polynomials. It has the advantages of spectral accuracy and block-diagonal mass matrix. With the inexpensive inversion of the block-diagonal mass matrix, the proposed method requires only a trivial sparse matrix-vector product at each time step, thus significantly reducing CPU time and memory requirement. Galerkin's method is used for spatial discretization, and a fourth-order Runge-Kutta scheme is employed for the time integration. The perfectly matched layer (PML) is employed to truncate the boundary in unbounded problems. The pseudospectral time-domain method is used to simplify the treatment of the PML inside the proposed SETD method. Numerical examples are shown to verify the efficiency and the spectral accuracy with the order of basis functions     

A Hybrid SIM-SEM Method for 3-D Electromagnetic Scattering Problems

A new method combining the spectral integral method and spectral element method (SIM-SEM) is proposed to simulate 3-D electromagnetic scattering from inhomogeneous objects. In this hybrid technique (a special case of the finite element boundary integral (FEM-BI) combination), the SEM with the mixed-order curl conforming vector Gauss-Lobatto-Legendre (GLL) basis functions are used to represent the interior electric field with high accuracy, while the SIM on a cuboid surface is used as an exact radiation boundary condition. The Toeplitz property of the SIM matrix is utilized to reduce the memory and CPU time costs in an iterative solver by using the fast Fourier transform algorithm. Unlike the traditional FEM-BI combination where the BI portion usually dominates the computational complexity, the computational costs are much lower in the SIM-SEM method. Numerical results verify the accuracy and capability of this method, confirming that the SIM-SEM method is a good alternative for solving scattering problems from inhomogeneous objects.      

A 3-D Discontinuous Spectral Element Time-Domain Method for Maxwell's Equations

A discontinuous spectral element time-domain method is proposed to analyze transient electromagnetic properties of general 3-D structures. This method is advantageous in that its mass matrices are block-diagonal due to the Gauss-Lobatto-Legendre polynomials, and it allows different orders of basis functions for each subdomain. The Riemann solver is employed in the boundary integral terms to communicate fields between adjacent subdomains. Perfectly matched layers are utilized to truncate the computational domain. Galerkin method is used for spatial discretization, and a fourth-order Runge-Kutta scheme is employed for the time integration. The validity of the proposed approach is demonstrated through several numerical examples of initial value problems and scattering problems.     

基于改进三维后向投影的多圈圆迹SAR相干三维成像方法

圆迹SAR(CSAR)因其特殊曲线运动轨迹而具备3维成像能力.单圈CSAR理论上可以获得距离方位平面亚波长级的分辨率,但是高程向分辨率却很低.同时,利用后向投影(BP)算法进行CSAR 3维成像的算法复杂度高,成像效率低.该文提出一种基于改进3维后向投影的多圈CSAR相干3维成像方法,针对现有成像算法时间复杂度高的问题,提出一种构造几何插值核的CSAR改进3维后向投影算法,可将3维插值操作转化为1维插值操作和距离向量搜索操作,通过多圈CSAR改进3维后向投影成像结果相干积累的方式得到最终3维图像.该文所提方法可有效解决单圈CSAR 3维成像高程向分辨率低的问题,改善3维成像细节,同时能够大幅降低CSAR 3维成像时间.仿真圆锥目标和美国空军实验室GOTCHA数据3维成像结果验证了该文所提方法的有效性.     

A 3-D Radial Point Interpolation Method for Meshless Time-Domain Modeling

In this paper, the radial point interpolation method, one of the meshless numerical techniques that has recently emerged in the area of computational electromagnetics, is extended to three dimensions for time-domain electromagnetic modeling. Its capabilities of conformal and multiscale modeling of arbitrary geometries over conventional grid-based numerical techniques are numerically validated and evaluated. A general approach to determining the numerical stability condition of the method is described. Consequently, this study presents another possible approach to automatic meshing of complex structures and an adaptive scheme for numerical solution refinements.      

2—D Fourier Transform Method for Optical Measurement of 3—D Surface

A emthod of 2-D Fourier transform used in 3-D surface profilometry is proposed,analyzed and compared with 1-D Fourier transform method in theory and practical measuring result.It was proved that the 2-D Fourier transform method has more advantages over 1-D Fourier transform methodd in biggest crook-rate limits,accuracy and sensitivity of measuring.Styudy on measuring object surface details with large crook-rate changing accurately used new higher-power index low-pass filter of spatial frequency domain.A new method of automatic produced reference grating image and error-correcting is proposed.One undeform row of deform grating image is used to extend a complete reference grating image,and some error-correcting method is used to process the result to get accurate surface shape and the deflection of reference surface normal line deviated from the axle of camera.By this new method,one deform rectangle grating image is only used to get the 3-D shape accurately.     

A 3-D Spectral Integral Method (SIM) for Surface Integral Equations

An efficient 3-D spectral integral method (SIM) has been proposed to speed up the method of moments (MOM) calculation of induced currents on a cuboid. This method utilizes the Toeplitz structure in the impedance matrix and the fast Fourier transform to accelerate the MOM solution. It reduces the memory and CPU time per iteration from $O(N^2)$ in the MOM to $O(N^{1.5})$ and $O(N^{1.5}log N)$, respectively. Thus, the SIM can be also used as an efficient radiation boundary condition for the finite element method. Numerical results confirm the effectiveness of this method.      

A Nonspurious 3-D Vector Discontinuous Galerkin Finite-Element Time-Domain Method

We propose a nonspurious vector discontinuous Galerkin finite-element time-domain (DG-FETD) method for 3-D electromagnetic simulation. To facilitate the implementation of numerical fluxes for domain decomposition, we construct the DG-FETD scheme based on the first-order Maxwell's equations with variables ${bf E}$ and ${bf H}$. The LT/QN and the CT/LN edge elements are employed to represent ${bf E}$ and ${bf H}$, respectively (or vice versa), to suppress spurious modes, and the Riemann solver is utilized as the numerical flux to correct fields on the interfaces between adjacent subdomains. Numerical experiments show the nonspurious property of the proposed method.      

A versatile controller for 3-D machining

A controller that produces sculptured surfaces from a small input without postprocessing is presented. It generates straight lines, circular arcs, and algebraic and trigonometric curves in any plane or combinations of such forms to produce complex lines and surfaces for machining applications. The controller is very versatile and can reduce programming costs by orders of magnitude     

Concise Current Source Implementation for Efficient 3-D ADI-FDTD Method

A concise current source implementation is presented for the unconditionally stable 3-D alternating direction implicit finite-difference time-domain (ADI-FDTD) method. Unlike the conventional implicit symmetric source scheme applied in both updating procedures, the new implementation involves implicit current formulation in the first procedure only. Note however that the resultant accuracy does not deteriorate but remains to be identical as before. This is achieved using our recent efficient algorithm for the 3-D ADI-FDTD method. Moreover, the current formulations applied in both procedures therein are simplified, along with further reduction of the floating point operations count for the main iterations. Analytical validation of the equivalence among conventional implicit symmetric source scheme and our efficient algorithms with alternative current implementations are discussed. Numerical results provide closer scrutiny of the asymmetry errors, which may still exist even with symmetric source.     

A Design Method for 3-D FIR Cone-Shaped Filters Based on the McClellan Transformation

This paper presents an efficient technique for designing three-dimensional (3-D) finite-impusle-response (FIR) digital filters having cone-shaped magnitude response. The McClellan transformation method is used as basis of the design. The new approach proposes a closed form solution for the transform coefficients of the mapping function. A simultaneous determination of the 1-D cutoff frequency of the prototype filter is also considered. The newly obtained relations for the transform parameters are very simple and depend on the angle of inclination of the cone. Additionally, the analytical expressions for the impulse response coefficients of the transformation subfilter are also derived. The behavior of the transformation function is examined, followed by several detailed examples with different input specifications of designed 3-D cone filters.      

A 3-D Enlarged Cell Technique (ECT) for the Conformal FDTD Method

In this paper, we present an enlarged cell technique (ECT) to avoid the time step reduction encountered in the conformal finite-difference time-domain (CFDTD) method due to small irregular cells truncated by metallic boundaries. We focus our efforts on the discussion of the accuracy and stability of the ECT and its comparison with other conformal methods, especially the one called the uniformly stable conformal (USC) method. We also provide a simplified ECT, which is much easier to implement. In the ECT, a stability criterion is first constructed to identify instable irregular cells, i.e., those having so small an area to cause instability. Those instable cells are then enlarged into their adjacent cells to obtain a large, stable area. Careful treatment is performed on the communication between the intruding and intruded cells in terms of electromotive force by keeping the total electromotive force conservative. This technique is verified by several 3-D numerical experiments. Results show that the ECT is second-order accurate and numerically stable at the regular Courant time step limit.     

A Semantics-based Translation Method for Automated Verification of SystemC TLM Designs

SystemC has become a de-facto standard language for SoC and ASIP designs. The verification of implementation with SystemC is the key to guarantee the correctness of designs and prevent the errors from propagating to the lower levels. In this project, we attempt translate SystemC programs to formal models and use existing model checkers to implement the verification. The method we proposed is based on a semantic translation method which translates sequential execution statements described as software character to parallel execution ones which are more closely with the implementation of hardware. This kind of conversion is inevitable to verify hardware designs but is overlooked in related works. The main contribution of this work is a translation method which can preserve the semantic consistency while building SMV model for SystemC design. We present the translation rules and implement a prototype tool which supports a subset of SystemC to demonstrate the effectiveness of our method.     

A Waveform Diversity Method for Optimizing 3-D Power Depositions Generated by Ultrasound Phased Arrays

A waveform-diversity-based approach for 3-D tumor heating is compared to spot scanning for hyperthermia applications. The waveform diversity method determines the excitation signals applied to the phased array elements and produces a beam pattern that closely matches the desired power distribution. The optimization algorithm solves the covariance matrix of the excitation signals through semidefinite programming subject to a series of quadratic cost functions and constraints on the control points. A numerical example simulates a 1444-element spherical-section phased array that delivers heat to a 3-cm-diameter spherical tumor located 12 cm from the array aperture, and the results show that waveform diversity combined with mode scanning increases the heated volume within the tumor while simultaneously decreasing normal tissue heating. Whereas standard single focus and multiple focus methods are often associated with unwanted intervening tissue heating, the waveform diversity method combined with mode scanning shifts energy away from intervening tissues where hotspots otherwise accumulate to improve temperature localization in deep-seated tumors.      

Low-Impedance Tungsten Microelectrode for Recording from Sensory Ganglia

A low-impedance (0-3-3.0 M? at 1.0 kHz) reliable tungsten microelectrode has been developed. The electrode is easily reproducible, and single electrodes have been successfully used in repeated recordings from sensory ganglia.     

基于距离像位相编码的三维物体识别

本文分析了距离像的相位傅立叶变换的原理和特征,研究了生成三维物体定向图的方法,通过计算机模拟实验分析了距离像的相位傅立叶变换用于三维物体识别和定向的性能.生成一种大间隔角度旋转得到的三维物体定向图,通过计算机模拟实验证实能准确的定位物体小角度的旋转方向,表明这种方法具有相当高的物体定向精度.     

Unconditionally Stable LOD–FDTD Method for 3-D Maxwell's Equations

This letter presents an unconditionally stable locally 1-D finite-difference time-domain (LOD-FDTD) method for 3-D Maxwell's equations. The method does not exhibit the second-order noncommutativity error and its second-order temporal accuracy is ascertained via numerical justification. The method also involves simpler updating procedures and facilitates exploitation of parallel and/or reduced output processing. This leads to its higher computation efficiency than the alternating direction implicit and split-step FDTD methods     

3-D nFPGA: A Reconfigurable Architecture for 3-D CMOS/Nanomaterial Hybrid Digital Circuits

In this paper, we introduce a novel reconfigurable architecture, named 3D field-programmable gate array (3D nFPGA), which utilizes 3D integration techniques and new nanoscale materials synergistically. The proposed architecture is based on CMOS nanohybrid techniques that incorporate nanomaterials such as carbon nanotube bundles and nanowire crossbars into CMOS fabrication process. This architecture also has built-in features for fault tolerance and heat alleviation. Using unique features of FPGAs and a novel 3D stacking method enabled by the application of nanomaterials, 3D nFPGA obtains a 4x footprint reduction comparing to the traditional CMOS-based 2D FPGAs. With a customized design automation flow, we evaluate the performance and power of 3D nFPGA driven by the 20 largest MCNC benchmarks. Results demonstrate that 3D nFPGA is able to provide a performance gain of 2.6 x with a small power overhead comparing to the traditional 2D FPGA architecture.     

Efficient Algorithm for the Unconditionally Stable 3-D ADI–FDTD Method

This letter presents a new efficient algorithm for the unconditionally stable three-dimensional alternating direction implicit finite-difference time-domain (3-D ADI-FDTD) method. The algorithm involves updating equations whose right-hand sides are much simpler and more concise than those in the conventional implementation. This leads to substantial reduction in the number of arithmetic operations required for their computations. To take full advantage of the efficiency gain, efforts are made as well to maintain or reduce other computation costs in for-looping and solving tridiagonal systems. Certain field array reuse is also exploited which reduces the memory space and the memory indexing overhead