高寒区高混凝土坝关键技术难题与解决途径

随着小湾、锦屏一级等300 m级特高混凝土坝的陆续建成,我国混凝土筑坝技术水平迈入了世界先进行列。相对而言,高寒区混凝土筑坝技术是我国坝工技术的短板,世界上高寒区混凝土坝也出现了较多严重事故。未来,我国即将在高寒地区建设QBT、叶巴滩等特高混凝土坝,面临挑战。为此,基于典型工程的统计数据分析了我国高寒区的气象、水文特点,结合当前混凝土坝的技术进展评述,提出了高寒区混凝土筑坝亟待攻克的诸如高强高抗冻高抗裂大坝混凝土的制备与施工质量控制、混凝土坝施工运行全过程防裂、大坝表面耐久防护与安全监控三大关键难题,阐明了其中的关键科学问题、技术难题、总体技术路线和近期要研究的主要问题,为实现高寒区高混凝土坝高质量建设与长期安全运行指明了技术路径,可为相关研究提供参考。     

精密光栅位移传感器的若干信号处理问题研究

光栅传感器是一类精密传感器 ,在直线位移或角位移的测量中有广泛的应用。但在工业应用中 ,除各种电磁干扰外 ,还有微小机械振动产生的干扰以及温度误差等 ,使测量精度大大下降。本文提出了在后续处理电路和信号处理方法上解决这一问题 ,提高传感器精度、分辨率和抗干扰能力的综合方法 ,如分频、温度补偿、定时器飞读和计数脉冲确认机制等。在实际使用中发现 ,应用这些方法的测量系统的稳定性、抗干扰能力和精度等指标都得到提高。     

心墙坝浸润线简化计算方法

通过理论分析和数值计算,在考虑坝体与防渗墙的相对渗透系数关系的基础上,提出了估算心墙坝坝体浸润线的一种简化计算方法,给出了浸润线位置的拟合公式。以白鸭山水库大坝为例,将该简化方法与有限元法的计算结果进行对比,表明该简化方法合理、可行。这一简化计算方法可大大减少中小型水库大坝在进行除险加固方案比选时的计算工作量。     

管道网系的系統分析

对于不可压縮流体在一条串联管路上流动的計算,伯努利方程的应用是十分广泛而有效的。但对于具有支路网絡管道体系中流体輸送的問題,还比較缺少一套系統的分析原理和方法。 在本文中,将一般导管阻力的計算公式: 改写成对体积流量线性元件的形式:幷且引入了“全路”的槪念,即得到一組线性方程式,可以用来描写复杂管路体系的一般流动問题。把此方程組用矩陣形式表达出来,不但使列写方程組的过程中有一套明确而简便的规则可循,不易出错,而且还能便于运用电子计算机解方程组。     

在线人工阅卷平台的研究与设计

结合实际工作需求,通过对一些常用考试试题答题、传统人工阅卷方式以及以往人工阅卷系统进行研究、比较和分析,并且适应市场上常见的考试内容开发一套统一的、高安全性、收缩性强的在线人工阅卷平台,来解决计算机“无纸化”考试的多样化阅卷问题.根据实际项目需求对在线人工阅卷的整体功能需求、系统需求和环境需求进行深入探讨,分析和总结人工阅卷的核心功能组件,同时对系统平台的开放性、稳定性、可靠性、安全性等提出更高的要求.     

长江干流朱沱站- 大通站基流变化特征

基流是河川径流中相对稳定的径流组成部分, 基流分割在水资源、水环境和水安全的管理研究中都有着重要 的应用。为了探究沿长江干流的基流变化特征, 使用递归数字滤波法对长江干流7 个水文站进行基流分割研究。 结果表明, 各站基流指数在01 768~ 01 798 之间。对朱沱站- 大通站区间基流量贡献最大的区间是宜昌站- 螺山 站, 其次是朱沱站- 寸滩站, 最小的是万县站- 宜昌站。2000 年前后, 长江干流基流量出现明显的衰减变化。基流 量衰减最大的是宜昌站( 衰减率为81 82%) , 其次为万县站( 衰减率为81 79%) 。     

基于ABAQUS 的南水北调高填方边坡稳定性分析

利用大型有限元软件 ABAQUS 建立了高填方渠段某一断面的二维有限元数值模型,根据有限元强度折减法的基本原理以及土体特性,对高填方渠道边坡的稳定性进行了分析,再利用有限元强度折减法的失稳判定依据确定了合理可行的边坡稳定安全系数。结果证明,有限元强度折减法所获得的临界滑动面结果与极限平衡法的结果几乎一致。可见,以特征点的位移突变性和塑性区的贯通性来分析边坡的临界破坏可以减少误差并得到合理唯一的边坡安全系数,因此是合理可行的。     

Airway responses in healthy and asthmatic subjects following exposure to low ambient air temperature

Agonist-activated Ca2+ entry is important in many biological responses such as secretion and cell growth(1,2). In nonexcitable cells which have no voltage-operated Ca2+ channels (VOCC), agonist-receptor interaction can trigger Ca2+ entry across the plasmalemma via several entry pathways(1-3) (Fig 1): (A) channels which are intrinsic structures of the receptor (receptor-operated channels), (B) channels which are coupled to receptors via a G-protein (G-protein-operated channels), (C) channels which are activated by some second messengers (second-messenger-operated channels), and (D) channels which open upon intracellular nonmitochondrial Ca2+ store depletion (Ca2+ release-activated channels) resulting from inositol 1, 4, 5-trisphosphate-induced Ca2+ release or inhibition of Ca2+ re-uptake (see next section). Ca2+ entry via the 4th type of channel, also known as "capacitative Ca2+ entry" (CCE)[4], has aroused much interest in the past decade because of its intriguing nature as retrograde signalling. In this brief review, we present the evidence for and the possible biochemical processes involved in CCE. We also discuss the use of 2 novel Ca2+ entry blockers: tetrandrine and SK&F 96365. Emphasis will be put on the human leukemic HL-60 cell line, a popular cell system for intracellular Ca2+ homeostasis studies and also a model the signal transduction of which we have been investigating during the past few years.     

Cytokines as adjuvants for ruminant vaccines

Successful vaccination against any potential pathogen is critically dependent on inducing an appropriate immune response. The pivotal role of cytokines in the immune response to vaccination suggests that non-protective responses or responses that exacerbate disease subsequent to infectious challenge may be the result of limiting or preferential production of one or a number of these mediators. This suggests that the use of recombinant cytokines as vaccine adjuvants may offer a mechanism whereby the magnitude and phenotype of the immune response to vaccination can be specifically modified. In mice, recombinant cytokines have been used extensively as therapeutics, while studies describing vaccine adjuvant activity are more limited. Recombinant (r) interleukin (IL)-1, IL-2 and interferon (IFN) gamma have been used primarily to enhance humoral responses with enhanced protection assessed where appropriate. Cytokine adjuvant studies in ruminants have been restricted to recombinant ovine (rov) and bovine (rbov) IL-1 and IL-2. In sheep, their application has been optimised with respect to dose, route of delivery and formulation, for induction of humoral and cell mediated immunity (DTH and cytotoxicity) to the model protein antigen (Ag) avidin. The level of adjuvant activity of IL-1 in particular compares favourably to that of a variety of other traditional and new chemical adjuvants and detailed analysis has indicated no adverse local or systemic side-effects. Recent studies in our laboratory demonstrating the effectiveness of rovIL-1 as an adjuvant in single and multi-component bacterial toxoid vaccines, and studies from other laboratories demonstrating the application of rbovIL-1 as an adjuvant for the response in cattle to live attenuated viral vaccines, suggest that rIL-1 may become the adjuvant of choice for diseases where protection is mediated by high levels of circulating antibody (Ab). With respect to helminth parasites, IL-1 may prove useful as a component of vaccines based on "hidden Ags" which rely on induction of Ab. Based on analysis in mouse models of helminth infection, other cytokines such as IL-4 and IL-10 may be appropriate for vaccines based on induction of mechanisms involved in natural immunity.