共查询到20条相似文献，搜索用时 15 毫秒
1.
In order to analyze seepage feature and seepage failure mechanisms of seawall under flood infiltration, a numerical model for saturated-unsaturated and unsteady seepage flow analysis considering soil permeability variation with seepage failure process was established. And the corresponding finite element computation program was made. Numerical simulation of flood seepage for typical section of real seawall was carried out by use of the program. The computed results were compared with the measured results of field test, which shows good agreement. Based on the numerical simulation results, it can be seen that flood seepage of seawall is a saturated-unsaturated and unsteady seepage flow process and seepage failure of seawall is caused by long time flood infiltration under large seepage gradient. Therefore, upon the flood infiltration, seepage failure of the seawall is a very complicated process, which involves soil permeability variation with seepage failure process and saturated-unsaturated/unsteady seepage flow. It is questionable to use the steady seepage analysis method to simulate seepage failure process of seawall. 相似文献
2.
This paper studies the seepage of coal samples under the influence of each single factor, the axial stress, confining pressure, gas pressure, and temperature by experiments. It uses Ansys12.0 to numerically simulate the law of coalbed methane seepage, coal deformation, pore pressure, the distribution of flow field under the influence of each single field and multi-field coupled. The numerical simulation show that the result of numerical simulation of gas seepage law in the coal under each single fields is basically the same as the experimental result. The curve of gas seepage and average effective stress under the condition of multi-field coupled is negative exponential relationship. Stress influenced the deformation of the specimen is greater than the seepage field. The axial stress on the deformation of the specimen is greater than confining presses The influence on the flow field by confining pressure is greater than axial stress, the influence of axial stress on the pore pressure is greater than confining pressure, pore-pressure under the action of multi-field is bigger than pro-pressure under each single field. To study the seepage law of coalbed methane, it should consider the influence of gas-solid-heat at the same time. 相似文献
3.
流固耦合的多元结构深厚覆盖层透水地基的力学特性 总被引：3，自引：0，他引：3
深厚覆盖层多元结构坝基在渗流过程中各土层力学差异明显,分析时关注的具体问题也不尽相同,需要深入研究。基于比奥固结理论,考虑土体的非线性流变以及土体固结变形过程中孔隙度、渗透系数、弹性模量及泊松比的变化;借助ADINA流固耦合模块来模拟西藏达嘎水电站坝基渗流场与应力场耦合过程,分析各层力学特性及相互作用。研究表明,透水性较强的表层土体是渗流主要通道,也是渗流进出区和沉降变形体现区,应在上游采取措施提高其压缩模量,下游区域增设反滤层和排水设施;坝基中的粉细砂层是坝基沉降的主要原因,对坝基沉降起主导作用,同时应注意其液化特性对坝基的不利影响;坝基中的承压含水土层对下游上部结构产生向上顶托力,若位置较深,则破坏性较小;坝基深部土层对整个坝基的渗流破坏影响较小,但对沉降和渗流量的影响不可忽视;表层砂卵砾石层和粉细砂层的渗透系数相差较小时,土层间不会发生接触冲刷。此外,还发现坝基孔隙水压力在快速衰减阶段被消散,期间土体固结较快。垂直防渗墙能有效降低渗透坡降和渗流量,将坝基沉降变形控制在防渗墙上游区域,但上游坝基变形对防渗墙产生较大的水平推力,应加大防渗墙尺寸或者采用辅助渗控措施。 相似文献
4.
A non-linear circuit model of photodiode built according to the working principle of self-scanned photodiode array image sensor is presented for improving the property of the sensor. Through the analysis of the non_linear circuit model,we get the state equations, and the equations are resolved with Runge_Kutta algorithm. The Runge_Kutta algorithm is realized in C language, and the numeric result of the circuit is obtained. The analysis of the numeric result of the model shows that the non_linear performance of the sensor can be improved by reducing the capcitor of the PN junction and the dynamic performance of the image sensor can be enhanced by paralleling capacitor C M , and all the analysis is consistent with the real measurement results of the sensor. The circuit model of photodiode is improved over previous model. 相似文献
5.
基于极限平衡理论,以砂土边坡为研究对象,推导了渗流和地震存在时拟静力法和拟动力法边坡安全系数的计算表达式。通过程序求解,与已有算例对比表明,计算结果基本一致,验证了2种方法解析式的合理性。参数分析表明,水位越高,边坡失稳越严重,水力梯度与安全系数基本为线性关系。渗流方向向下时,稳定性随水力梯度的增加而增大;渗流方向向上时,变化规律相反。水平地震加速度系数对稳定性的影响剧烈,竖向地震加速度系数对稳定性影响较小,简化计算可以忽略不计。最终得出拟静力法的解析式,简单、实用,而拟动力法则可以更为全面地考察砂土边坡稳定性随时间变化的特点。 相似文献
6.
The influence of initial internal structure of coal sample on gas flow characteristic 总被引：1，自引：0，他引：1
Three kinds of coal samples with different components are chosen as study objects.Density calculation and SEM are adopted to study their internal structures,and a self made triaxial gas seepage instrument is used to study their internal gas flow characteristics.The results show that internal structures of coal samples made of different particle size coal powders under identical external conditions are various,and nonlinearity is presented on the influence caused by fabric.Gas flow characteristic is complex in complete stress strain process,generally it firstly increases and then decreases,initial gas flow velocity is lower than the one after the failure of coal sample,and obvious hysteretic nature of gas flow characteristic is showed.The influence of gas flow characteristic caused by initial internal structure of coal sample is nonlinear and the stress sensitivity is high on the influence of gas flow characteristic caused by initial internal structure.The more complex the initial internal structure of the coal sample is,the lower the axial tress sensitivity is,and the higher the confining pressure sensitivity is. 相似文献
7.
Analysis and numerical simulation of fluid-structure coupling of gas drainage from boreholes 总被引：2，自引：0，他引：2
Gas drainage from boreholes is main method of utilization and management of Chinese coal seam gas. As the exploitation depth increases, stress field and other factors on the impact of gas seepage are increasingly apparent. Based on the basis of a series of assumptions of coal seam gas, porosity and permeability equations are described by considering stress, coal seam gas pressure change on the coal produced by deformation of the skeleton. The fluid-structure coupling equations are derived by using the basic theorem of porous media flow and the fluid structure coupling theory. The gas seepage field is simulated and analyzed by using multi-physics coupling analysis software. The effect of gas pressure distribution, different burial depths and different drilling parameters (drainage negative pressure, drilling radius) on gas seepage field is obtained. Analysis of simulation results can provide theoretical guidance for on-site gas drainage. 相似文献
8.
There is no universal method of finding the analytic solutions to transmission lines discribed by partial differential equations,so many researchers are studying and developing transmission line theories.Computing steady-state solutions of uniform transmission lines is one part of the study.The paper introduces another method of computing sinsoidal steady-state solutions of lossy uniform transmission lines.First,the complex expressions of voltage and current with zero initial state are obtained from the complex frequency-domain model of lossy uniform tansmission lines.The network functions,which are the ratios of voltage and current's image functions to the excitation's image function,can be found from the complex expressions.Sinusoidal steady-state solutions can be obtained by using the relation between network function and system's frequency characteristic.Finally,the method is demonstrated to be effective by an example. 相似文献
9.
本文利用在河南种植的72个小麦品种面包烘烤品质指标的试验资料,借助于灰色关联分析法,对11种高分子量麦谷蛋白亚基进行了综合评估.结果表明:等权关联度与加权关联度分析结果基本吻合;Glu-1D5+10亚基对小麦烘烤品质的贡献最大;各亚基的关联度排序与其实际烘焙功能相一致.同时认为,采用多个品质指标的综合评估结果制定HMW麦谷蛋白亚基的评分系统,可能比用单一指标制定的评分方法更可靠. 相似文献
10.
The Matrine and Oxymatirne are two kinds of alkaloid, and have many kinds of pharmacological functions. In recent years, their anti-tumor mechanism has been paid more attention. This article is a summarization of the research progress of Matrine and Oxymatirne in the anti-tumor mechanism. Now people have found out that the Matrine and Oxymatirne can restrain the multiplication of tumor cells via restrainning the synthesizatinon of DNA and the enzyme activity and effectting the normal cycle, and they also can restrain the transfer of the tumour via controlling the expression of the genes, and induce the death of the tumour cell and induce the tumour cell to differentiate into the common cell via controlling the expression of the genes and effecting the telomerase activity. 相似文献
11.
超级稻花后强、弱势粒灌浆相关蛋白质表达的差异 总被引：2，自引：0，他引：2
为进一步揭示水稻强、弱势粒灌浆差异的机理,以2个超级稻品种两优培九(两系杂交籼稻)和淮稻9号(粳稻)为材料,通过双向电泳观察花后强、弱势粒灌浆相关蛋白质表达的差异并对差异蛋白进行质谱分析。结果表明,弱势粒花后3~15 d的灌浆速率和最终粒重均显著低小于强势粒。花后3 d、8 d和15 d弱势粒中蛋白质表达的点少于强势粒,花后25 d则弱势粒多于强势粒。花后强、弱势粒间差异蛋白质表达量在2倍以上的点有类似变化趋势。选择有显著差异的27个蛋白点进行质谱分析,其中14个点的功能得到鉴定。这些蛋白质分别参与籽粒的淀粉合成、蛋白合成、光合作用、能量代谢、环境适应以及细胞信号转导等。说明强、弱势粒间多种灌浆相关蛋白质表达的差异是其灌浆和粒重差异的重要原因。 相似文献
12.
Taking raw coal samples collected from the wangying colliery in Fuxin basin as the research object, the experiment of coalbed methane seepage law is conducted by the triaxial osmoscope and the relationship between effective stress and coal permeability is presented. The experiment results indicate that the coal permeability is of stress sensitivity and tended to decline in exponent with the increment of effective stress, which is consistent with the former research results. The seepage flow curves from experiments demonstrate the nonlinear characteristics under different confining pressures and moisture contents, and it accurately reflecte the effect of coal body deformation on the coalbed methane seepage flow in the experimental process. Therefore considering the influence of effective stress on the coal body deformation, a new motion equation for the nonlinear percolation characteristic of coalbed methane is established. Moreover, the motion equation is correlated well with the experimental data, and the fitting correlation coefficients are above 99.6%. 相似文献
13.
Yu Chuxin Xian Xuefu Tan Xueshu 《保鲜与加工》1989,(5):1-10
This paper analyzes comprehensively the present approaches about the flow theory and governing equation of the gas seepage in China from the equations of the gas flow continuity, motion, state ane content. The viewpoint is put forward in the paper that the gas amount taking part in seepage flow is only a part of the whole gas content. The governing equation, of gas seepage flow in coal seams is set up on condition that procedures of adsorption and desorption are convertible completely. 相似文献
14.
The voltage instability of power system often occurs when the active power on one or more weak branches exceeds its transfer capability. A preventive control model for static voltage stability is proposed using the active power transfer capability of weak branches as static voltage stability constraints. A local line based voltage stability index is used to determine the critical contingencies, weak branches and transfer capability of each weak branch. A static security analysis method, which is based on DC power flow equations, is used to establish the non linear active power flow expressions on weak branches following each critical contingency. The active power constraints on weak branches can be obtained from the active power flow expressions and transfer capabilities of weak branches. A quadratic optimal model for preventive control including the proposed active power constraints on weak branches is presented. The simulation results for IEEEE14 bus system and IEEE118 bus system demonstrate the correctness and effectiveness of the proposed preventive control model. 相似文献
15.
16.
甘蓝型油菜油酸脱氢酶基因(fad2)多个拷贝的发现及分析 总被引：5，自引：0，他引：5
以甘蓝型油菜湘油15为材料, 随机挑选56个来自基因组的fad2基因克隆、47个来自幼苗整株的fad2基因cDNA克隆和9个授粉27 d后种子中fad2 cDNA克隆进行双向测序。基因组中56个fad2序列的碱基同源性为91.0%~99.9%, 从中得到11个差异序列, 即11个不同的fad2基因拷贝。将其翻译成氨基酸序列发现, 6个拷贝在编码区中出现多个终止密码子, 另外5个的同源性为90.60%~99.74%, 与47个来自幼苗整株的fad2基因cDNA序列进行比较, 发现fad2基因没有内含子。从种子中的9个fad2 cDNA克隆序列中找到2个有差异的cDNA, 它们的编码区中没有终止密码子, 说明在种子中有多个fad2基因表达。基因组中的11个拷贝根据同源性可分成两组, 命名为fad2I和fad2II。RT-PCR分析发现在授粉27 d的种子中fad2I有较强表达, fad2II没有表达; 但在叶片中两者都有表达。 相似文献
17.
M-Band scale similarity transform (MST) is introduced and its properities are investigated. MST has relation to approximation order. One can increase approximation of M-band multiscaling functions with help of MST. 相似文献
18.
实验设计了四种直径和三种剂量12个组合的胶体金（CG）对小白鼠进行注射处理；采用MTT法、放射性免疫法、LDH短程释放法，测定了T、B淋巴细胞增殖活性及其腹腔巨嗜细胞活性，外周血血清和脾脏淋巴细胞诱导白介素2含量和脾脏NK细胞活性，结果表明：不同直径和剂量的CG对机体有不同程度的影响，其中直径15nm、10nmCG的0.3mL和0.2mL剂量组不仅对T、B淋巴细胞增殖活性和血清中IL-2含量有显著促进，也可显著提高腹腔巨噬细胞活性及脾脏NK细胞杀伤活性，0.1mL剂量组虽有提高但不显著；直径5nm、20nm各个剂量组效果的波动较大，中、高剂量组对四项指标起促进作用但不显著，低剂量组则没有促进作用。证明了15nm和10nm中高剂量的胶体金可显著提高小鼠机体特异性和非特异性细胞免疫功能。 相似文献
19.
广州市城市森林生态系统服务功能价值评估 总被引：5，自引：0，他引：5
为了全面系统地了解城市森林的服务功能,客观科学地评价城市森林生态系统服务功能价值。在大量调查数据的基础上,运用实际市场、替代（隐含）市场和假想（模拟）市场评估技术,估算了广州市城市森林生态系统14类服务功能价值。结果表明：2009年,广州市城市森林生态系统服务功能总价值4417157×104元/年,其中直接经济价值122155×104元/年,间接经济价值4209833×104元/年,间接经济是直接经济价值的35.16倍;把森林生态系统服务功能价值分为经济效益、生态效益和社会效益3个部分,经济效益（122155×104元/年）、生态效益（3546983×104元/年）和社会效益（748019×104元/年）分别占总服务价值2.77%、80.30%和16.93%;14类服务功能价值大小的顺序是：调节小气候＞释放O2＞游憩休闲＞文化教育＞林副产品＞社会就业＞CO2固定＞养分积累＞改良土壤＞生物多样性＞涵养水源＞土壤保持＞净化空气＞促进科技进步。在城市森林服务功能评价中,城市森林调节小气候、释放O2、提供游憩休闲的服务价值处于十分重要的地位。 相似文献
20.
张福娟 《农产品加工．学刊》2012,(11):202-204
探讨了食品专业课程多媒体教学与传统教学的优势与不足。结合教学实践,分析了食品专业课程多媒体教学和传统教学的优势互补,最大限度地发挥2种教学方法的综合功能,取得较好的教学效果。食品专业课程的教学,应交叉使用多媒体教学方法和传统教学方法,充分发挥2种教学方法的优势,充分结合起来,汲取二者的优点,克服二者的缺点。 相似文献