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611.
对渤、黄海14个主要海湾的原始验潮记录进行了分析,从中筛选出水位变化幅度大于或等于50cm的54个假潮个例,着重分析了伴随假潮过程的天气形势,把可能引发假潮的天气形势归纳为4种基本类型。分析结果显示:绝大多数(92%)引发假潮的天气个例都与锋面活动有关;所有个例中低层大气基本上都是弱静力稳定,且都具有较强的垂直风速切变。根据观测事实和稳定度理论分析认为,低层大气的弱静力稳定层结构以及由垂直风速切变引起的剪切不稳定性,是假潮气象学成因的一种必要条件和物理机制。 相似文献
612.
Fuzzy Optimum Model of Semi-Structural Decision for Lectotype Optimization of Offshore Platforms 总被引:8,自引:0,他引:8
In the process of concept design of offshore platforms, it is necessary to select the best from feasible alternatives through comparison and filter. The criterion set, used to evaluate and select the satisfying alternative, consists of many qualitative and quantitative factors. Therefore, the selection is a problem of multicriteria and semi- structural decision- making. Different from traditional methods in semi- structural decision- making, a new framework and methodology is presented in this paper for evaluation of offshore platform alternatives. First, the criterion set is established for the evaluation of alternatives. Next, the approach is studied to construct the relative membership degree matrix, in which both qualitative and quantitative factors are consistent with the uniform calculating standard. And then a new weight-assessing method is developed for calculation of the weights based on the relative membership degree matrix. Finally, a multi-hierarchy fuzzy optimum model is adopted to select t 相似文献
613.
Measurement of 224Ra, 226Ra and 228Ra in seawater using Mn-fiber adsorption-γ spectrum method 总被引:2,自引:1,他引:2
I~IOXThe half-lives of natural radioactive nuclides "'Ra, 226Ra and 228Ra are 3. 66 d, 5. 76 a,1600 a respectively, hence, the marine process with various time scales can be researched by taking these nuclides as tracers. Because these nuclides can be determined by measuring them or theirdaughters' a,g, y-rays, they have been applied extensively in oceanography research. Huang(1996), Huang et al. (1996 a,b) and Chen (1996) have given reviews on it.Since the contents of "'Ra, 226Ra and 228… 相似文献
614.
The incompressible viscous uniform and shear flow past a circular cylinder is studied. The two-dimensional Navier-Stokes equations are solved by a finite element method. The governing equations are discretized by a weighted residual method in space. The stable three-step scheme is applied to the momentum equations in the time integration. The numerical model is firstly applied to the computation of the lid-driven cavity flow for its validation. The computed results agree well with the measured data and other numerical results. Then, it is used to simulate the viscous uniform and shear flow over a circular cylinder for Reynolds numbers from lO0 to lO00. The transient time interval before the vortex shedding occurs is shortened considerably by introduction of artificial perturbation. The computed Strouhal number, drag and lift coefficients agree well with the experimental data. The computation shows that the finite element model can be successfully applied to the viscous flow problem. 相似文献
615.
珠江口东南近海海区污损生物研究 总被引:4,自引:2,他引:4
为研究珠江口东南近海海区污损生物状况,于1986年5月至1987年6月,在香港东南约114和160km,水深为95和113m处布设了两个生物浮标站,并对距香港约172km,水深为115m处的Marex水文气象浮标上的污损生物群落进行调查.此次调查共采集和鉴定出污损生物78种,其中在浸海只有3个月的试板上,主要有柄蔓足类、水螅和藻类,优势种是细板条茗荷、茗荷和直杯螅.至于浸海时间达6~12个月的浮标(包括沉标)及锚链系统,其上还有相当数量的多种双壳类软体动物、无柄蔓足类和苔藓动物等硬性污损生物附着.在种类垂直分布方面,污损生物群落组成随深度发生明显变化. 相似文献
616.
The effects of different lateral confinement stress on the fatigue behavior of and cumulative damage to plain concrete are investigated experimentally. Eighty 100 mm x 100 mm x 100 mm specimens of ordinary strength concrete are tested under constant- or variable-amplitude fatigue loading and lateral confinement pressure in two orthogonal directions. A fatigue equation is developed by modifying the classical Aas-Jakobsen S-N equation for taking into account the effect of the confined stress on fatigue strength of plain concrete. The results of variable-amplitude fatigue tests indicate that the linear damage theory proposed by Palmgren and Miner is unreasonable in the biaxial stress state. A nonlinear cumulative damage model that could model the effects of the magnitude and sequence of variable-amplitude fatigue loading and lateral confinement pressure is proposed on the basis of the evolution laws of the residual strains in the longitudinal direction during fatigue tests. The residual fatigue life predic 相似文献
617.
Temperature data at different layers of the past 45 years were studied and we found adiploe mode in the thermocline layer (DMT): anomalously cold sea temperature off the coast of Sumatra and warm sea temperature in the western Indian Ocean. First, we analyzed the temperature and the temperature anomaly (TA) along the equatorial Indian Ocean in different layers. This shows that stronger cold and warm TA signals appeared at subsurface than at the surface in the tropical Indian O-cean. This result shows that there may be a strong dipole mode pattern in the subsurface tropical Indian Ocean. Secondly we used Empirical Orthogonal Functions (EOF) to analyze the TA at thermocline layer. The first EOF pattern was a dipole mode pattern. Finally we analyzed the correlations between DMT and surface tropical dipole mode (SDM), DMT and Nino 3 SSTA, etc. and these correlations are strong. 相似文献
618.
麻痹性贝毒(Paralytic Shellfish Poisoning,PSP)毒素由石房蛤毒素(saxitoxin,STX)及其衍生物组成,目前己发现20余种,在赤潮研究、分子生物学和神经生物学基础研究、医药、军事防化等方面都有应用潜力[其结构、类型和应用见本集刊王云峰等(2003)“麻痹性贝毒毒素的应用研究进展”一文]。由于PSP毒素的稀有来源和国际社会对STX交易的禁止,限制了国内PSP毒素应用及研究的全面深入展开,因此本文作者对PSP毒素进行了制备,并采用不同方法对制备的PSP毒素进行了研究。
PSP毒素能够选择性地可逆抑制可兴奋膜的电压依赖钠离子通道的开放,从而阻止神经冲动的发生和传导,使神经、肌肉丧失兴奋性(Frace et al.,1986;Penzotti et al.,1998)。本文利用神经束膜下记录和全细胞膜片钳技术,报道了从塔玛亚历山大藻(Alexandrium tamarense)中提取的PSP粗毒素对小鼠运动神经末梢膜电流和NG108-15细胞钠离子通道的作用研究结果,并与STX标准毒素的作用结果进行了比较。
NG108-15细胞是由小鼠神经母细胞瘤和大鼠胶质细胞瘤融合的杂交细胞,经分化剂分化后,显示诸+L1196如兴奋性、合成和释放乙酰胆碱、与培养肌细胞形成突触联系等多种神经细胞的基本特性(Hamprcht,1977)和Na+、K+、Ca2+等多种离子通道,已作为神经细胞模型被广泛应用于分析药物对离子通道作用的研究(Enomoto et al.,1992; Docherty et al.,1992;Shi et al.,1993;Hu et al.,1997a;Hu et al.,1997b);发育出具有Na+内流支持的锋电位(Hamprecht,1977),该电位是分析作用于膜钠离子通道药物的好材料。 相似文献
619.
620.
The effect of the cone spacing of a conieal structure on the ice force is studied by model experiments. The ice force reduction coefficient presented in this paper expresses the relationship between the ice force and the arrangement of cones. The experiments prove that the mode of the ice failure before the boundary of upward-downward bending cone (UDBC) is crushing. A conclusion can also be drawn from the experiments that the ice force on the boundary of UDBC is by far less than that on a vertical pile with the same diameter. Moreover, the ice force frequencies on upright and inve-rted cones are obtained under the field condition of the platform JZ20-2, respectively. The results show that the alterna-tion of the ice force on UDBC can hardly induce resonance of platform JZ20-2. 相似文献