共查询到20条相似文献,搜索用时 15 毫秒
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《Signal Processing, IEEE Transactions on》2005,53(9):3488-3502
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. 相似文献
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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... 相似文献
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USB在单光子计数种子活性快速检测仪中的应用 总被引:5,自引:0,他引:5
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。 相似文献
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激光全息干涉在三维温度场可视化中的应用 总被引:3,自引:0,他引:3
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。 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(3):1204-1217
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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。 相似文献
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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. 相似文献
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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。 相似文献
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浅析3D显示技术在LED显示屏上的应用 总被引:2,自引:1,他引:1
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。 相似文献
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连续移动三维瞬态激光熔池温度场数值模拟 总被引:30,自引:6,他引:30
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。 相似文献
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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. 相似文献
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联合检测技术在第三代移动通信中的应用 总被引:4,自引:0,他引:4
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. 相似文献
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S. F. Busch M. Weidenbach M. Fey F. Schäfer T. Probst M. Koch 《Journal of Infrared, Millimeter and Terahertz Waves》2014,35(12):993-997
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. 相似文献
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Salim Ben?Chaabane Mounir Sayadi Farhat Fnaiech Eric Brassart Franck Betin 《Circuits, Systems, and Signal Processing》2011,30(1):55-71
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. 相似文献
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《Microwave Theory and Techniques》2002,50(4):1165-1172
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 相似文献