An efficient non-iterative algorithm to estimate the apparent diffusion coefficient of water molecules in the magnetic resonance diffusion imaging experiments

Many studies have shown that the magnetic resonance signal decay with an extend range of diffusion weighting(b-factor)is a bi-exponential attenuation in the diffusion-weighted magnetic resonance imaging experiments in vivo.Based on this feature and the two-compartmental model,we propose a twice-linear-fitting(TLF)algorithm to estimate the apparent diffusion coefficient(ADC)of the water molecules instead of the commonly used iterative Levenberg–Marquardt(LM)method.The TLF algorithm consists of two liner fitting steps to estimate the fast and the slow apparent diffusion coefficients and their sizes,respectively.It is unnecessary to guess the initial values in the whole fitting process.The time consumption of the TLF algorithm is much less than that of the iterative LM method.Moreover,the TLF algorithm may avoid the extraneous solutions,which often deteriorates the results of the LM method.Compared with the iterative fitting method,the TLF algorithm is a reliable and timeefficient approach to estimate the ADC of water molecules in vivo in magnetic resonance diffusion-weighted imaging experiments.     

CCD成像模型及仿真系统研究

针对光学遥感CCD(Charge-Coupled Device)的成像过程,研究CCD成像的数学建模及仿真问题.基于CCD成像原理,探讨了模型建立中的一些关键问题,并按照CCD信号处理流程设计了一套完整的CCD成像模型,采用Matlab/Simulink平台设计实现了该仿真系统.仿真验证试验表明,该系统较好的仿真了CCD成像过程,仿真结果准确度、可信度较高.     

美发剂对人体健康的影响

当今社会，美发已经成为了一种潮流，这其中染发剂、烫发剂功不可没．但是，不可否认的是，美发剂在满足人们爱美心理的同时，也在吞噬着人们的健康，它就象一个隐形杀手在威胁着人们的生命．本文主要阐述了染发剂、烫发剂的种类和化学成分，染发剂、烫发剂的作用机理及美发剂对人体健康的影响．     

3D virtual reconstruction of the Pleistocene cheetah skull from the Tangshan, Nanjing, China

The development of computer tomography and image processing has made it possible to establish virtual 3D reconstruction and non-invasive dissection of fossil specimens. We used these methods to reconstruct a virtual 3D skull of a Pleistocene cheetah skull from the Tuozi cave, Tangshan, Nanjing, and virtually dissected it for anatomic studies, and measured the volumes of different parts of the endocranium. The endocranium of the cheetah skull has showed that its frontal sinus is beehive-like, the frontal lobe of cerebra is relatively large but the temporal lobe is relatively small, its cerebral sulcus and gyrus are more complicated than those of the domestic cat, similar to those of the domestic dog, but simpler than those of giant panda, pig, cattle and horse. The technology of virtual 3D reconstruction and non-invasive dissection of fossil specimens can extend the morphological study from the exterior to the interior, and it can also help to study fragile specimens and virtually backup rare and precious specimens.     

基于智能Agent的复合学习方法

从实例学习和事例推理的关系出发,分析了专家经验累积的过程,指出传统知识获取瓶颈的根源.在此基础上,借助agent理论,提出了一种从专家分析实例学习和事例推理的有机结合模型,给出了专家知识获取的基本框架.构成此框架的各归纳学习agent在专家的协助下,可通过加强学习机制相互促进.     

二维目标的微波成像新方法

首先从体等效原理出发，得到一个积分方程组，该方程组将目标的介电常数与目标内总场及接收点上的散射场联系起来。随后，对该方程组求变分，寻求散射场对目标介电参数的梯度方向，得到反演方程。文中列举了几个典型反演实例，考察了方法的收敛速度、运行时间及对复杂目标的适应能力等因素，所得结果相当令人满意，为了尽量与实际探测接近，文中还讨论了方法抗随机噪声的能力，模拟表明，该方法具有相当强的抗噪声性能。     

Functional magnetic resonance imaging of amphetamine craving

The aim of this study is to identify the brain activity associated with amphetamine craving for understanding the neurobiology of addiction by watching pictures of happy, sad or amphetamine. Brain activity was measured in 12 amphetamine addicts and 12 healthy subjects by fMRI while the subjects watched pictures designed to elicit happy feelings, sad feelings, or the desire to use amphetamine. The result demonstrated that amphetamine cues led to abnormally high cingulate and low frontal lobe activation in amphetamine addicts, who showed abnormalities in affect-related brain activation.     

油田水处理中使用絮凝剂的研究与探讨

通过对絮凝剂在油田水处理中使用的研究,分析探讨了絮凝剂的净化反应机理、絮凝剂的类型及应用、以及它在油田水处理方面的重要作用,并且针对目前油田所使用的絮凝剂的主要性能和发挥絮凝剂在油田水处理方面的作用进行了深入的研究探讨。     

电子商务中软件代理人特点分析

分析软件代理人在电子商务中应具有的特有的角色特点,并用这些特点对软件代理人进行了分类,提出三种不同层次的代理人,以及代理人组织的概念和特点。并探讨了当前电子商务中软件代理人开发的最有前景的三个领域。