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91.
Objective To study on the role of thymus transplantation for heart allograft in rats. Methods Vascularized heart-thymus combined transplantation was performed with microsurgical technique. Graft survival, histopathology,
level of IL-2, IL-4 and its mRNA expression in serum and cardiac grafts were investigated. Results Heart-thymus combined transplantation achieved effect in the prolongation of cardiac graft survival with short-term administration
of cyclosporine. Conclusions Vascularized thymus transplantation induced immune tolerance in thymectomized rats. 相似文献
92.
随着国内外SMS业务的巨大成功,移动消息类业务的市场潜力初步显露,并逐步呈现了SMS与EMS、UMS、MMS、IM等多种不同标准的消息类业务互相竞争的局面。通过对移动消息业业务发展历史的回顾,在对SMS的成功要素与UMS、MMS业务对比分析基础上,探讨了移动消息类业务发展演进趋势。 相似文献
93.
Qiang Wang Yi Shen Ye Zhang Jian Qiu Zhang 《IEEE transactions on instrumentation and measurement》2003,52(4):1041-1047
Hyperspectral image fusion is a key technique of hyperspectral data processing. In recent years, many fusion methods have been proposed, but there is little work concerning evaluation of the performances of different image fusion methods. In this paper, a method called quantitative correlation analysis (QCA) is proposed, which provides a quantitative measure of the information transferred by an image fusion technique into the output image. Using the proposed method, the performances of different image fusion methods can be compared and analyzed directly based on the images of before and after performing the fusion. The correlation information entropy, based on the developed QCA, is also proposed and testified by numerical simulations. Typical hyperspectral data are applied to the proposed method. The results show that the method is effective, and its conclusions agree with the classification results in applications. 相似文献
94.
We address the problem of computing fundamental performance bounds for estimation of object boundaries from noisy measurements in inverse problems, when the boundaries are parameterized by a finite number of unknown variables. Our model applies to multiple unknown objects, each with its own unknown gray level, or color, and boundary parameterization, on an arbitrary known background. While such fundamental bounds on the performance of shape estimation algorithms can in principle be derived from the Cramer-Rao lower bounds, very few results have been reported due to the difficulty of computing the derivatives of a functional with respect to shape deformation. We provide a general formula for computing Cramer-Rao lower bounds in inverse problems where the observations are related to the object by a general linear transform, followed by a possibly nonlinear and noisy measurement system. As an illustration, we derive explicit formulas for computed tomography, Fourier imaging, and deconvolution problems. The bounds reveal that highly accurate parametric reconstructions are possible in these examples, using severely limited and noisy data. 相似文献
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我国矿用牙轮钻头同世界先进水平相比有较大差距,大力开展矿用牙轮钻头CAD/CAM/CAE工作,促进学科交叉融合,是摆脱落后局面,参与全球性竞争的一项重要任务。 相似文献
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Distributed Rule-Regulated Spectrum Sharing 总被引:2,自引:0,他引:2
Lili Cao Haitao Zheng 《Selected Areas in Communications, IEEE Journal on》2008,26(1):130-145
Dynamic spectrum access is a promising technique to use spectrum efficiently. Without being restricted to any prefixed spectrum bands, nodes choose operating spectrum on-demand. Such flexibility, however, makes efficient and fair spectrum access in large-scale networks a great challenge. Prior work in this area focused on explicit coordination where nodes communicate with peers to modify local spectrum allocation, and may heavily stress the communication resource. In this paper, we introduce a distributed spectrum management architecture where nodes share spectrum resource fairly by making independent actions following spectrum rules. We present five spectrum rules to regulate node behavior and maximize system fairness and spectrum utilization, and analyze the associated complexity and overhead. We show analytically and experimentally that the proposed rule-based approach achieves similar performance with the explicit coordination approach, while significantly reducing communication cost. 相似文献