Joint Detection-Estimation of Brain Activity in Functional MRI: A Multichannel Deconvolution Solution

Analysis of functional magnetic resonance imaging (fMRI) data focuses essentially on two questions: first, a detection problem that studies which parts of the brain are activated by a given stimulus and, second, an estimation problem that investigates the temporal dynamic of the brain response during activations. Up to now, these questions have been addressed independently. However, the activated areas need to be known prior to the analysis of the temporal dynamic of the response. Similarly, a typical shape of the response has to be assumed a priori for detection purpose. This situation motivates the need for new methods in neuroimaging data analysis that are able to go beyond this unsatisfactory tradeoff. The present paper raises a novel detection-estimation approach to perform these two tasks simultaneously in region-based analysis. In the Bayesian framework, the detection of brain activity is achieved using a mixture of two Gaussian distributions as a prior model on the “neural” response levels, whereas the hemodynamic impulse response is constrained to be smooth enough in the time domain with a Gaussian prior. All parameters of interest, as well as hyperparameters, are estimated from the posterior distribution using Gibbs sampling and posterior mean estimates. Results obtained both on simulated and real fMRI data demonstrate first that our approach can segregate activated and nonactivated voxels in a given region of interest (ROI) and, second, that it can provide spatial activation maps without any assumption on the exact shape of the Hemodynamic Response Function (HRF), in contrast to standard model-based analysis.     

Estimation of Distribution Algorithm for Joint Resource Management in D2D Communication

Wireless Personal Communications - Device to device (D2D) communication technique is one of the established means to enhance data rate in next generation wireless systems. Use of same resource of...     

USB在单光子计数种子活性快速检测仪中的应用

研制了一种超微弱发光单光子计数种子活性快速检测仪（FSAA），该仪器利用单光子计数手段，能够灵敏、直接并有对照性检测种子的超微弱化学发光（TUCL），获得种子的活力信息，该检测仪可以区分老化程度相差1季的水稻种子的超弱发光。本系统利用Cypress公司的EZ-USB AN2131Q芯片实现了单片数据采集和控制。介绍了通用串行总线（USB）的特点及其在数据采集过程中的优点。     

激光全息干涉在三维温度场可视化中的应用

介绍了实时激光全息干涉技术应用于三维温度场可视化的原理、实验装置与光路系统、实验结果等。通过实验成功地实现了3 种条件下三维温度场的可视化,定性地获得了溶液加热后内部温度的变化规律,并观测到溶液受热的初始阶段存在随时间迁移的“蘑菇”形干涉条纹。     

Novel Scheme for Joint Estimation of SNR, Doppler, and Carrier Frequency Offset in Double-Selective Wireless Channels

As receiver performance will be degraded by carrier frequency offset (CFO), Doppler shift, and low signal-to-noise ratio (SNR), a novel estimator that jointly considers CFO, Doppler shift, and SNR is proposed in this paper. The proposed algorithm uses the Fourier transform (FT) to calculate the power spectral density of time-varying channels through channel estimates. Then, a new periodogram technique is utilized to estimate CFO, Doppler shift, and SNR together. Unlike conventional methods in sinusoid estimation, which rely on the peak-value search of a periodogram, this paper exploits the hypothesis test to address the random frequency modulation of time-varying channels. Furthermore, to optimize estimation performance, a theoretical analysis is also provided on the influences of some key parameters, e.g., the length of the signal processed with fast FT , the amplitude threshold value, the SNR dynamic range, and the velocity dynamic range. Correspondingly, the appropriate key parameters are chosen according to this analysis and are validated by simulations. The results are consistent with our analysis and present high accuracy over a wide range of velocities and SNRs.      

3D教室信息管理系统的研发方案研究

通过对三维教室的信息管理系统研发条件和内容的深入分析，得知了研发过程中需要的先进技术如3DMax、JQuery和SSH等。最后给出了基于3DMax、JQuery和SSH等技术的三维教室信息管理系统的研发思路。     

基于统计特征的3D人脸识别生物模板保护方案

生物模板的安全是生物识别系统安全的一个重要因素,传统的生物识别系统直接存储生物模板的方式导致一系列的安全和隐私问题,成为阻碍生物识别技术发展与推广的瓶颈.基于统计特性提取特征是人脸识别中一项较为成熟的技术,本文针对此类生物模板,提出了一种合适的模板保护方案,该方案的核心思想是利用密码学中的Hash函数实现模板与待测特征信息之间的匹配,通过选取特征向量中的主要成分、量化和纠错码等方法解决生物信息模糊性和Hash函数敏感性之间的矛盾.通过对方案的安全分析和在3D人脸识别中的仿真实验,验证了方案的安全性和可行性.     

三坐标雷达阵地标校研究

分析了Ｐ波段相扫比幅测高三坐标雷达的测试结果。探讨了环境对雷达测量的影响。介绍了一种利用民航测量结果进行阵地校标的开发工具，它是提高雷达对环境适应性的一种行之有效的方法。     

浅析3D显示技术在LED显示屏上的应用

文章介绍了4种3D显示技术应用到LED显示屏的原理以及应用方法,并分析了每种方法应用的优缺点,分析了采用分时技术的LED显示屏能够较好地显示3D图像,且性价比高。     

连续移动三维瞬态激光熔池温度场数值模拟

详细介绍了在ANSYS软件平台上,建立连续移动三维瞬态激光熔池温度场计算模型的方法,计算模型中考虑了材料表面温度对激光吸收率的影响及材料相变过程对激光熔池温度场的影响。系统分析了连续移动三维激光熔池温度场随时间的变化规律。通过该计算模型,可以掌握激光加工过程中连续移动激光熔池的加热和冷却规律。计算结果表明,当激光沿45#钢基板表面由一端向另一端沿直线扫描时,由于热传导的作用,激光熔池温度随时间增加而升高,同时连续移动熔池表面温度最高点不在激光束中心,而是稍稍偏后于激光束中心。在相同激光工艺参数下,计算熔池横截面尺寸与实验所测熔池横截面尺寸相吻合,表明所建立的连续移动熔池温度场计算模型是正确和可靠的。     

Application of the Joint Fast Walsh Hadamard-Inverse Fast Fourier Transform in a LDPC Coded OFDM Wireless Communication System: Performance and Complexity Analysis

An efficient low complexity T transform which combines the Walsh Hadamard Transform and Discrete Fourier Transform (DFT) into a single fast orthonormal unitary transform is considered for the application in low density parity check coded orthogonal frequency division multiplexing (LDPC-OFDM) across additive white Gaussian noise channel model and multipath fading channel models. The T-transform is developed through the sparse matrices factorization method using Kronecker product scheme. T-transform based COFDM system, which is capable of reducing peak to average power ratio (PAPR) of the transmitted symbols and improving the bit error rate (BER) performance at a reasonable reduced complexity. Several signaling formats such as Quadrature phase shift keying and 16- ary Quadrature amplitude modulation (16-QAM) are considered. A T COFDM system is described which could provide an alternative to DFT-COFDM system, and is therefore a better alternative to balance the transform complexity, PAPR reduction and system performance. Simulation results are used to examine and compare the complexity, PAR and the BER performance of T-OFDM system and DFT-OFDM system. Numerical results show that the T-COFDM system outperforms the DFT-COFDM based in the multipath channel models.     

联合检测技术在第三代移动通信中的应用

传统的直接序列扩频-码分多址通信系统(DS-CDMA)中,多址干扰(MAI)的存在制约了系统的性能和容量.一个较好的解决办法是联合检测技术,联合检测技术也成为第三代移动通信系统的关键技术之一.本文研究了几种主要的联合检测技术的原理、复杂度,并基于TD-SCDMA上行链路中用MATLAB仿真比较了各种算法的性能,并以ZF-BLE算法为基准,分析了智能天线对联合检测技术的改善.     

Optical Properties of 3D Printable Plastics in the THz Regime and their Application for 3D Printed THz Optics

We characterize the terahertz (THz) properties of several materials which can be used for fused material deposition 3D printing. We identify Polystyrene as a material which shows a promising compromise between printability and THz transparency. Furthermore, printed THz lenses are presented and characterized.     

A New Method for the Estimation of Mass Functions in?the?Dempster�CShafer��s Evidence Theory: Application to Colour Image Segmentation

In this paper, the problem of colour image segmentation is addressed using the Dempster–Shafer (DS) theory. Examples are provided showing that this theory is able to take into account a large variety of special situations that occur and which are not well solved using classical approaches. Modelling both uncertainty and imprecision, and computing the conflict between images and introducing a priori information are the main features of this theory. Consequently, the performance of such a segmentation scheme is largely conditioned by the appropriate estimation of mass functions in the DS evidence theory. In this paper, a new method of automatically determining the mass function for colour-image segmentation problems is presented. The mass function of each pixel is determined by applying possibilistic c-means (PCM) clustering to the grey levels of the three primitive colours. A reliability criterion, associated with each pixel and the mass functions of its neighbouring pixels, is used into a fuzzy based reasoning system in order to decide on the appropriate segmentation. Experimental segmentation results on medical and textured colour images highlight the effectiveness of the proposed method.     

相干信号联合波达角-频率估计的 一种新型预处理方法

本文有效地将一维中的前向/后向空间平滑技术扩展到二维中的时-空阵列数据矩阵,提出了一种用于相干信号联合波达角-频率估计的新型预处理方法.本文详细地分析了如何构造前向/后向平滑时-空阵列数据矩阵,导出了确保信号波达角-频率参数可分辨应满足的条件.与仅利用前向空间平滑的现有预处理方法不同,本文的预处理方法同时利用前向和后向空间平滑,因而提高了阵元的利用率,使联合波达角-频率估计的性能明显提高.     

D3.js在建筑热舒适评价中的应用研究

从建筑热舒适评价可视化需求出发,提出了一种基于D3.js类库的热舒适评价可视化方案。该方案绘制了不同标准下的热舒适模型,并实现了相关参数评价的可视化,可以使建筑设计者更加直观地看到设计参数是否满足热环境中舒适度的问题。     

Application of the SSOR preconditioned CG algorithm to the vectorFEM for 3D full-wave analysis of electromagnetic-field boundary-valueproblems

The symmetric successive overrelaxation (SSOR) preconditioning scheme is applied to the conjugate-gradient (CG) method for solving a large system of linear equations resulting from the use of edge-based finite-element method (FEM). For this scheme, there is no additional computing time required to construct the preconditioning matrix and it contains more global information of the coefficient matrix when compared with those of the banded-matrix preconditioning scheme. The efficient implementation of this preconditioned CG (PCG) algorithm is described in details for complex coefficient matrix. With SSOR as the preconditioner and its efficient implementation in the CG algorithm, this PCG approach can reach convergence in five times CPU time shorter than CG for several typical structures. By comparison with other preconditioned techniques, these results demonstrate that SSOR preconditioning strategy is especially effective for CG iterative method when an edge FEM is applied to solve large-scale time-harmonic electromagnetic-field problems     

三维可视化技术在断层解释中的应用

在油田开发中,复杂构造区块的解释难度不断加大,三维可视化技术成为了研究地质构造的重要手段,本文以相干体为着眼点,利用多角度立体空间可视化解释技术,在三维空间对复杂断层进行精细解释,复杂断层在三维可视化技术的作用下,变的易于观察和认识,为日后的储层预测等工作奠定了基础。