基于流场的爆炸分裂效果模拟

通过分析冲击波气流的运动特点,对Navier-Stokes方程进行合理简化。根据简化后的方程所反映出的气流速度变化规律,提出描述冲击波气流运动的扩散模型。基于该模型所定义的流场,对碎片的运动进行控制,实现对冲击波作用下物体碎片飞散效果的模拟。实验结果表明,该方法具有较强的真实感,能够满足实时性要求。     

DNA片段拼接中的预归并重复序列屏蔽方法

针对DNA片段拼接中的重复序列识别及屏蔽问题,提出一种预归并重复序列屏蔽方法。在片段拼接前通过扫描子串标识出可能存在重叠关系的shotgun片段,利用子串归并该相关片段,标识出重复序列的位置信息,达到屏蔽的目的。计算机模拟分析表明,该方法识别重复序列的错误率低,通过预归并有效缩减了shotgun集合的规模,降低了拼接时的计算复杂度。     

Robust Cardiac Function Assessment in 4D PC‐MRI Data of the Aorta and Pulmonary Artery

Four‐dimensional phase‐contrast magnetic resonance imaging (4D PC‐MRI) allows the non‐invasive acquisition of time‐resolved, 3D blood flow information. Stroke volumes (SVs) and regurgitation fractions (RFs) are two of the main measures to assess the cardiac function and severity of valvular pathologies. The flow rates in forward and backward direction through a plane above the aortic or pulmonary valve are required for their quantification. Unfortunately, the calculations are highly sensitive towards the plane's angulation since orthogonally passing flow is considered. This often leads to physiologically implausible results. In this work, a robust quantification method is introduced to overcome this problem. Collaborating radiologists and cardiologists were carefully observed while estimating SVs and RFs in various healthy volunteer and patient 4D PC‐MRI data sets with conventional quantification methods, that is, using a single plane above the valve that is freely movable along the centerline. By default it is aligned perpendicular to the vessel's centerline, but free angulation (rotation) is possible. This facilitated the automation of their approach which, in turn, allows to derive statistical information about the plane angulation sensitivity. Moreover, the experts expect a continuous decrease of the blood flow volume along the vessel course. Conventional methods are often unable to produce this behaviour. Thus, we present a procedure to fit a monotonous function that ensures such physiologically plausible results. In addition, this technique was adapted for the usage in branching vessels such as the pulmonary artery. The performed informal evaluation shows the capability of our method to support diagnosis; a parameter evaluation confirms the robustness. Vortex flow was identified as one of the main causes for quantification uncertainties.     

直升机尾桨试验台拖动与计算机监控系统的应用

根据尾桨试验台拖动系统的特点及技术要求,采用S7-300 PLC作为中央控制器,Pll工控机作为监控计算机,SIMOVERT MD工程型变频器作为DP从站,构成了一个基于PROFIBUS-DP现场总线的控制网络.     

Iron enhances generation of fibrin fibers in human blood: Implications for pathogenesis of stroke

Stroke is associated with the intracerebral formation of fibrin clots which may lead to irreversible brain damage. Thrombolytic therapies employ a variety of natural and/or recombinant plasminogen activators to initiate fibrinolytic degradation of cerebral thrombi. However, such therapies when installed beyond 4‐ to 6‐h window, may fail to achieve the expected outcome. This is due to the hydroxyl radical‐induced modification of fibrin(ogen) molecules rendering them refractory to fibrinolytic degradation, but no cause of the increased free radical generation in stroke was offered. Here, we show by means of electron microscopy that iron ions added to human blood dramatically enhances fibrin fibers formation with thrombin, and significantly delays fibrinolysis during spontaneous clotting of native blood. Iron ions caused the appearance dense matted fibrin deposits, similar, if not identical, to those observed in plasma of patients with stroke. These results may explain a known relationship between thrombotic diseases and the increased body concentrations of free iron and/or hemoglobin derivatives. We conclude that any action resulting in the inhibition of hemostatic abnormalities, as well as in the reduction of body free iron and scavenging of hydroxyl radicals (e.g., by polyphenols) can potentially prevent pathological reactions associated with consequences of stroke. Microsc. Res. Tech. 75:1185–1190, 2012. © 2012 Wiley Periodicals, Inc.     

藏文自动分词中未登录词处理方法研究

藏文中后接成份出现频率较高,分词中未登录词的后缀单切现象会影响分词的正确率,为此,采用词(语素)+缀归并的方法,将藏文后接成份与前一词(语素)归并为一个切分单位输出。针对藏文中大量人名、地名、单位名等未登录词在分词时出现的碎片切分现象,使用分词碎片整合方法,将多次出现的词条碎片整合为一个切分单位输出。实验结果表明,2种方法能提高藏文自动分词的识别正确率。     

基于甲骨文字形动态描述库的甲骨文输入方法

该文分析了目前常用的甲骨文字在编码和输入方面的问题和不足,给出了一种甲骨文字形动态描述的方法。该方法在现代汉字的编码和书写规范基础上,使用有向笔段和笔元对甲骨文进行描述,用扩展的编码区域和外部描述字形库相结合的方式,解决了甲骨文字特别是异体字和没有识别的甲骨文字的输入和输出问题。     

BitTorrent类型P2P系统模型研究与性能分析

对BitTorrent（BT）类型的P2P系统进行了建模与性能分析。详细地分析了系统中的peer行为。考虑到文件片段对系统的影响，建立了peer模型和seed模型以及文件片段模型、感兴趣与阻塞模型、peer选择模型等。对peer在BT子系统中对邻居peer的感兴趣概率、被邻居peer阻塞的概率以及选择上传peer的概率进行了分析。应用这个模型对peer的上传行为发生的概率与BT子系统peer总数的关系进行了分析, 结果表明, 上传行为发生的概率随着BT子系统peer总数的增加而减少。     

基于笔划宽度提取的手写体汉字归一化方法

手写体汉字书写变形是手写体汉字识别预处理阶段的重要问题之一。为了有效地改善手写体汉字变形并识别手写体汉字,提出了手写体汉字笔划宽度提取,以及基于提取出的笔划宽度的手写体汉字归一化的方法。用上述方法在计算机上进行仿真实验,实验结果表明,手写体汉字归一化的方法既能保证原手写体汉字的形状结构特征不变,并可有效地改善手写体汉字变形差异。     

传统避雷针保护对信息防雷的危害

根据传统避雷针的保护方法和信息防雷的要求，结合工程雷击实例，剖析传统的避雷针保护对信息防雷的危害，并提出信息时代应用避雷针保护应遵循的原则，以确保信息设备的雷电安全。