Asymptotic behavior of solutions for the one-dimensional drift-diffusion model in the quarter plane

In this paper, we study the classical drift-diffusion model arising from the semiconductor device simulation, which is the simplest macroscopic model describing the dynamics of the electron and the hole. We prove the global existence of strong solutions for the initial boundary value problem in the quarter plane. In particular, we show that in large time, these solutions tend to the nonlinear diffusion wave which is different from the steady state, at an algebraic time-decay rate. As far as we know, this is the first result about the nonlinear diffusion wave phenomena of the solutions for the one-dimensional drift-diffusion model in the quarter plane.     

重尾环境下二维风险模型在有限时间内的破产概率

在保险风险和金融风险为重尾分布的条件下,得到了二维风险模型两种破产概率的精确估计以及另外一个破产概率的上下界.作为应用,最后给出了累积折扣值停止损失保费的一个近似结果.     

Synthetic GPI as a candidate anti-toxic vaccine in a model of malaria

The malaria parasite Plasmodium falciparum infects 5-10% of the world's population and kills two million people annually. Fatalities are thought to result in part from pathological reactions initiated by a malarial toxin. Glycosylphosphatidylinositol (GPI) originating from the parasite has the properties predicted of a toxin; however, a requirement for toxins in general and GPI in particular in malarial pathogenesis and fatality remains unproven. As anti-toxic vaccines can be highly effective public health tools, we sought to determine whether anti-GPI vaccination could prevent pathology and fatalities in the Plasmodium berghei/rodent model of severe malaria. The P. falciparum GPI glycan of the sequence NH(2)-CH(2)-CH(2)-PO(4)-(Man alpha 1-2)6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH(2)alpha 1-6myo-inositol-1,2-cyclic-phosphate was chemically synthesized, conjugated to carriers, and used to immunize mice. Recipients were substantially protected against malarial acidosis, pulmonary oedema, cerebral syndrome and fatality. Anti-GPI antibodies neutralized pro-inflammatory activity by P. falciparum in vitro. Thus, we show that GPI is a significant pro-inflammatory endotoxin of parasitic origin, and that several disease parameters in malarious mice are toxin-dependent. GPI may contribute to pathogenesis and fatalities in humans. Synthetic GPI is therefore a prototype carbohydrate anti-toxic vaccine against malaria.     

An incipient 3(10) helix in Piv-Pro-Pro-Ala-NHMe as a model for peptide folding

The molecular mechanism of helix nucleation in peptides and proteins is not yet understood and the question of whether sharp turns in the polypeptide backbone serve as nuclei for protein folding has evoked controversy. A recent study of the conformation of a tetrapeptide containing the stereochemically constrained residue alpha-aminoisobutyric acid, both in solution and the solid state, yielded a structure consisting of two consecutive beta-turns, leading to an incipient 3(10) helical conformation. :This led us to speculate that specific tri- and tetrapeptide sequences may indeed provide a helical twist to the amino-terminal segment of helical regions in proteins and provide a nucleation site for further propagation. The transformation from a 3(10) helical structure to an alpha-helix should be facile and requires only small changes in the phi and psi conformational angles and a rearrangement of the hydrogen bonding pattern. If such a mechanism is involved then it should be possible to isolate an incipient 3(10) helical conformation in a tripeptide amide or tetrapeptide sequence, based purely on the driving force derived from short-range interactions. We have synthesised and studied the model peptide pivaloyl-Pro-Pro-Ala-NHMe (compound I) and provide here spectroscopic evidence for a 3(10) helical conformation in compound I.     

时变风中Spar平台系泊系统的耦合动力分析

在中国南海东部百年一遇的台风海况下,考虑不同风载荷的计算方式,对某Classic-Spar平台及其系泊缆索的动力响应作了时域非线性数值模拟.首先将平台频域水动力结果变换到时域;然后运用非线性有限元方法计算张紧式系泊缆索的动张力特性;最后运用四阶龙格-库塔法在时间域内计算平台及其系泊系统的非线性耦合运动方程.分析结果表明:在时变风的作用下,平台运动不仅会偏离平衡位置,而且由于时变风的特征频率通常在Spar平台水平面运动的自振频率附近,因此相对于稳态风,考虑时变风的影响将会激起平台大幅度的水平面慢漂运动响应,从而诱发很大的系自张力.     

贮灰场防尘措施的风洞试验研究

针对燃煤电厂贮灰场运行过程中普遍存在粉煤灰二次扬尘的污染问题,进行了利用石灰粉、膨润土悬液和水玻璃、聚丙烯酰胺溶液制成的各种悬液或溶液,喷撒在灰面上的多种防尘措施的风洞试验。试验表明,配制的几种悬液可以形成保护薄壳,能够有效地减缓水分蒸发,延长了二次起尘灰面形成的运行期;能够抵御较强风力的吹蚀,且可以重复喷洒,成本低廉,具有良好的环境效益。     

摇摆状态下TFE/NMP降膜吸收试验研究

建立了摇摆振动单管吸收试验台，对具有新型工质对TFE／NMP吸收式制冷系统中的核心部件——吸收器在不同溶液体积流量、摇摆振动频率和幅度条件下进行降膜吸收试验．通过对试验数据的处理和分析可以看出，在渔船常见的摇摆振动条件下，降膜吸收器的热、质传递优于静态下的情形，且适当提高摇摆频率或减小摇摆幅度亦有利于降膜吸收效果的改善．     

ALE有限元法解二维自由面流体大晃动问题

从Navier-Stokes方程和连续性方程出发,在ALE描述下,用四边形单元对所求区域加以划分;并借助于Galerkin加权余量法导出相应的有限元方程组,在有限元计算中速度和压力均采用四节点线性插值函数;通过二维自由面流体大晃动问题实例的计算,给出相应的计算结果,阐明了该方法的优越性和局限性。     

Numerical study of threshold gain behavior for a THz random laser in a two-dimensional active disordered medium with a three-level atomic system

By numerically solving Maxwell’s equations and rate equations in a two-dimensional (2D) active random media made of ruby grains with a three-level atomic system, the threshold gain behavior for a THz random laser is investigated. The spectral intensity variation with the pumping rate is calculated for both the transverse magnetic (TM) field and the transverse electric (TE) field. The computed results show that THz random lasing could occur in a 2D disordered medium for both the TM and TE cases. Further analysis reveals that the THz lasing threshold for TM fields is lower than that for TE fields.     

污染环境中具有阶段结构的种群模型的生存分析

研究了污染环境对具有阶段结构的种群模型的影响,考虑到新生个体的出生对种群体内毒素的影响,以及死亡的种群个体将毒素带回环境.主要运用比较定理,给出了种群一致持续生存,弱持续生存和绝灭的判据.     

污染环境中具有阶段结构的种群模型的生存分析

研究了污染环境对具有阶段结构的种群模型的影响,考虑到新生个体的出生对种群体内毒素的影响,以及死亡的种群个体将毒素带回环境。主要运用比较定理,给出了种群一致持续生存,弱持续生存和绝灭的判据。     

毛细管中考虑动态效应的二相不混溶流体模型

给出了毛细管中基于Navier—Stokes方程、加入了广义Navier边界条件以及动态毛管压强的不相溶二相流的流动模型．     

段长在汉语语音识别系统后处理阶段的应用

针对传统的隐含马尔可夫模型(hidden Markov model,HMM)存在的缺陷,该文提出了一种在识别的后处理阶段使用段长模型的方法,并应用在基于HMM的汉语识别系统上。该方法利用归一化的段长模型对识别系统的解码结果重新打分,比较前后两次算出的分数从而选出更可靠的识别结果。实验表明,通过该方法将段长模型应用在识别过程中,可以显著提高识别系统的性能,大量减少识别结果中的插入错误。数据显示,该方法使识别系统的音节错误率下降了大约10%,识别系统最终的插入错误和删除错误都低于1%。     

初生空化数的计算模型

从“气核惯性失稳导致空化”这一观点出发,提出了应用于数值模拟的初生空化判别标准及其数学模型,采用Ｍｏｎｔｅ－Ｃａｒｌｏ方法模拟空化现象中的各种随机因素,在可靠度的意义下将气核空化初生与流场空化初生联系起来．以黄河小浪底工程消能泄洪洞为例,对三级串联孔板的初生空化数作了计算．     

低速风洞大振幅升沉振动加速度导数测量装置的设计

为了研究飞行器在纵向大迎角状态下的动态失速现象，设计了一套用于低速风洞的升沉振动测量装置，本装置采用强迫振动方法，利用偏心滑块机构将转动变为直线运动，可测量出由模型升沉振动加速度产生的导数利用此导数值可将组合动导数分离，为准确预测飞行器飞行特性提供可靠的保证，此装置的特点是振动幅值大，天平测量精度高，试验数据可靠。     

跳-扩散模型下一类房产期权模型及计算分析

假设房产价格服从跳-扩散模型,研究分期付款看涨房产期权的定价问题.以北京西奥中心写字楼以租代售的实例为背景,在Black-Scholes框架下建立了实物期权定价的偏微分方程模型,推导出相应的二叉树格式离散模型,并进行数值模拟和参数分析,结果表明该模型较扩散模型更接近实际市场.     

立体足迹造型与识别系统技术及在法庭诉讼中的证据作用

传统的“经验型”足迹鉴定由痕迹技术人员手工操作、定性分析,主观性强。立体足迹造型与识别系统的处理过程和识别结果与足迹专家检验过程吻合,识别精度高,可以对犯罪嫌疑人与作案人足迹的相似性做出形、数、图、谱相结合的科学结论,经得起法庭质证的“检验”．从而发挥了足迹鉴定结论的证据作用。     

港口内靠码头系泊船波浪力时域模型

为进行港口内靠码头系泊船波浪力的时域计算,提出了一种耦合数值方法。用包含船体的矩形柱面将整个港口区域划分为船体表面与柱面所围区域(内域)和柱面与整个港口边界面所围区域(外域)。内域流动由三维NavierStokes(NS)方程控制,通过VOF方法数值求解和描述其自由表面;外域流动由二维浅水波模型——改进的Boussinesq方程控制,应用有限差分三对角矩阵算法(TDMA)快速求解。内域解和外域解通过速度/压力和波面连续的匹配边界条件联系起来。应用所建立的NS/Boussinesq耦合模式同步和高效率地获得了港内波浪变形、系泊船附近三维流场、船表面波压力分布和波浪荷载。     

大型凹陷斜坡区倒灌式成藏模式—以三肇凹陷扶杨油层为例

利用300条地震剖面、672口测井曲线、6口井岩心对松辽盆地三肇凹陷扶杨油层断层特征及运动期次、储层沉积特征进行了综合研究,结合探井试油和试验区动态资料分析认为,T2断层受控于基底断层具有平面密集成带、剖面"似花状"组合特征,且油气成藏期活动的油源断层多为断层密集带边界断层.沉积微相研究表明三肇凹陷南部扶杨油层为西南保康沉积体系而非多物源交汇区,属于典型的河控浅水缓坡三角洲沉积体系,即主要储层为分流河道砂体,且主要含油目的层扶Ⅰ油层组为向上逐渐退积的演化序列.明水组末期青一段源岩达到生油高峰,油气在超压作用下沿开启的油源断层下排,首先充注断层上升盘一侧河道砂体,即断层密集带两侧上升盘为油气运聚富集区,而断层密集带内多为地堑式组合,不利于油气聚集,在成藏模式指导下刻画出47个有利圈闭,预测新增石油地质储量0.5亿t.