Spatial-resolution enhancement in computed tomography

We propose an approach that combines an asymmetric fan-beam configuration and a new reconstruction algorithm to enhancing spatial resolution in computed tomography (CT). The asymmetric configuration can be achieved by changing the center of rotation (COR) from the conventional symmetric configuration. It does not, however, require new detectors and X-ray source nor alter the relative geometry between the detector and the X-ray source. By effectively reducing the distance of the COR to the X-ray source, the asymmetric configuration can increase the effective sampling density in projection data without reducing the size of the field of view (FOV). The proposed algorithm, on the other hand, can reconstruct images directly from data acquired with this asymmetric configuration. We performed numerical studies to demonstrate and validate the proposed acquisition/reconstruction approach. Results in these studies confirm that the proposed approach can lead to enhanced spatial resolution in reconstructed images. The proposed acquisition/reconstruction approach may find applications in micro-CT and industrial CT in which the CORs may be changed.     

Optimal base-station locations in two-tiered wireless sensor networks

We consider generic two-tiered wireless sensor networks (WSNs) consisting of sensor clusters deployed around strategic locations, and base-stations (BSs) whose locations are relatively flexible. Within a sensor cluster, there are many small sensor nodes (SNs) that capture, encode, and transmit relevant information from a designated area, and there is at least one application node (AN) that receives raw data from these SNs, creates a comprehensive local-view, and forwards the composite bit-stream toward a BS. This paper focuses on the topology control process for ANs and BSs, which constitute the upper tier of two-tiered WSNs. Since heterogeneous ANs are battery-powered and energy-constrained, their node lifetime directly affects the network lifetime of WSNs. By proposing algorithmic approaches to locate BSs optimally, we can maximize the topological network lifetime of WSNs deterministically, even when the initial energy provisioning for ANs is no longer always proportional to their average bit-stream rate. The obtained optimal BS locations are under different lifetime definitions according to the mission criticality of WSNs. By studying intrinsic properties of WSNs, we establish the upper and lower bounds of maximal topological lifetime, which enable a quick assessment of energy provisioning feasibility and topology control necessity. Numerical results are given to demonstrate the efficacy and optimality of the proposed topology control approaches designed for maximizing network lifetime of WSNs.     

特种加工线切割机床智能渐进式走丝控制方案及控制器硬件电路设计

针对特种加工设备中走丝线切割机床升级改造需求大,成本高的问题,提出了一种低成本的设备改造方案。在不增加硬件投资的前提下,提出了精粗加工渐进使用电极丝的改造方案,并设计出智能渐进走丝控制器的硬件电路原理图和PCB板。通过与相关厂家的合作改造表明,该智能渐进走丝控制方案和硬件电路能够最大限度的降低改造成本,并能提升机床的加工精度、表面光洁度和加工的一致性。     

云计算在电信行业的应用研究

云计算被认为是继微型计算机、互联网后的第三次IT革命,是IT技术发展的大势所趋。本文结合云计算的特点,介绍了云计算的技术体系架构,提出了云计算的适用性,分析了电信行业IT系统的现状,进一步给出了云计算的应用和实施建议。     

Half-conductive coupling interconnection technology for digitaltransmission between CMOS chips

This paper describes how to use half-conductive coupling (HC-coupling) to obtain digital interconnections between two flip-chip standard CMOS integrated circuits. For process simplicity, the HC-layer can be unpatterned and the CMOS chips do not require any post-processing steps. Measurements of a complete HC-coupling, digital communication link show reliable operation up to 100 Mb/s channel speed. The two flipped prototype CMOS chips were fabricated in 0.8-μm, 5-V CMOS. The I/O pads' pitch was 150 μm     

A First Principles Study of Ferroelectricity and Magnetism Coexisting in Fe-Doped K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>

First-principles calculations were performed to investigate the coexistence of ferroelectricity and magnetism in Fe-doped tetragonal K_0.5Na_0.5NbO₃ (KNN) with different Fe concentrations. It was found that all three systems can possess both magnetism and ferroelectricity, and the magnetism becomes stronger with an increase in the concentration of Fe. The magnetic properties are due to ferromagnetism of Fe, and the Fe-Nb and Fe-O bonds induce magnetic moments on Nb and O atoms. Ferroelectricity comes from the hybridization of Nb and O, as in the case of pure KNN. The predicted results provide insight into the origin of the induced magnetic moments and an approach for obtaining multiferroic materials.     

智能复合材料光纤传感层的研究

光纤自诊断系统是智能复合材料结构的重要组成部分。但是 ,将光纤传感器阵列埋入复合材料是实现智能复合材料的一个难题。解决这一问题的方法是将光纤传感器集成在一起形成一个模块化的便于埋入复合材料中的光纤传感层。本文探讨两种使用聚酰亚胺制作传感层的方法。一种是把光纤传感器阵列埋入聚酰亚胺薄膜中 ;另一种是用作为光学材料的含氟聚酰亚胺制作矩形 (道沟 )光波导和光传感器。后一种方法制作的传感器模块集成度高、可靠性好 ,是值得注意的发展方向。     

Anti-aliasing weighting functions for single-slice helical CT

Spatially variant longitudinal aliasing plagues most volumes reconstructed from single-slice helical computed tomography data, and its presence can degrade resolution and distort image structures. We have recently developed a Fourier-based approach to longitudinal interpolation in helical computed tomography that can, for scans performed at pitch 1 or lower, essentially eliminate this longitudinal aliasing by exploiting a generalization of the Whittaker-Shannon sampling theorem whose conditions are satisfied by the interlaced pairs of direct and complementary longitudinal samples. However, the algorithm is computationally intensive and cannot be pipelined. In this paper, we address this shortcoming by deriving two spatial-domain, projection-data weighting functions that approximate the application of the Fourier-based approach, and preserve its aliasing suppression properties to some degree, while allowing for a pipelined implementation. The first approach, which we call simply 180AA, for anti-aliasing, is a direct spatial-domain approximation of the 180FT approach. The second approach, which we call 180BSP, is based on an approximate generalized interpolation approach making use of B-splines. Studies of aliasing and resolution properties in reconstructions from simulated data indicate that while the 180AA and 180BSP approaches do not perfectly replicate the favorable aliasing suppression and resolution properties of the 180FT approach, they do represent an improvement over the clinically standard 180LI approach on these fronts.     

基于ARM7的太阳能控制器的设计与现实

本文阐述了太阳能光伏电池的工作原理以及伏安特性,提供了一套完善的太阳能控制器电路.该电路采用了目前最流行的ARM芯片为控制核心,来实时监控光伏两端电压、蓄电池两端电压以及充电电流和放电电流.从而控制整个电路的工作状态.