Limit equilibrium analysis for stability of soil nailed slope and optimum design of soil nailing parameters

Reinforcement of slopes using soil nailing can effectively improve slope stability, and it has been widely used in upgrading cut slopes. Based on the assumptions of stresses on the slip surface, a new method for analyzing the stability of a slope reinforced with soil nails was established in the limit equilibrium theory framework, by considering that slope sliding occurs owing to shear failure of the slip surface, which subjects to Mohr–Coulomb(M–C) strength criterion. Meanwhile, in order to easily analyze the stability of a soil nailed slope in actual engineering and facilitate optimum design of parameters for soil nailing, factor of safety(FOS) contour curve charts were drawn on the basis of the established linear proportional relationship between the spacing of soil nails and slope height, and the length of soil nails and slope height. Then, by analyzing and verifying the results obtained from classic examples, some conclusions can be got as follows: 1) The results obtained from the current method are close to those obtained from the traditional limit equilibrium methods, and the current method can provide a strict solution for the slope FOS as it satisfies all the static equilibrium conditions of a sliding body, thus confirming the feasibility of the current method; 2) The slope FOS contour curve charts can be used not only to reliably analyze the stability of a soil nailed slope, but also to design optimally the parameters of soil nailing for the slope with a certain safety requirement.

A Study on the Stability Analysis and Optimum Design for Journal Bearings

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Optimum line reclosing time for the enhancement of interconnected power system stability

Automatic line reclosing schemes used in an extra-high-voltage power system is an economical and effective means to maintain transient stability. A novel method is proposed in the paper to adaptively optimize the automatic line reclosing time after a transient fault for enhancement of interconnected power system transient stability. Both the study on the transient energy over network and the structure-preserving multi-machines power system model illustrate that the excessive convergence of potential energy on the lines with a certain cutset deteriorate power system stability, and therefore, an optimum line reclosing strategy can be established by minimizing the change in transient potential energy distribution across a cutset lines in the vicinity of the faulty line as an optimization target, and the optimal reclosure time is set to the time of minimum line phase angle difference. Without any pre-determined knowledge, the method is adaptive to various power system operation modes and fault conditions, and easy to implement because only a limited number of data measured at one location on a tie-line linking sub-networks are required. Simulations have been performed with the OMIB(One Machine and Infinite Bus System) and a real inter-connected power system to verify the applicability of the method proposed.

APPROACH FOR LAYOUT OPTIMIZATION OF TRUSS STRUCTURES WITH DISCRETE VARIABLES UNDER DYNAMIC STRESS, DISPLACEMENT AND STABILITY CONSTRAINTS

A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static method, the mathematical model of structure optimization under dynamic stress, dynamic displacement and dynamic stability constraints were transformed into one subjected to static stress, displacement and stability constraints. The optimization procedures include two levels, i.e., the topology optimization and the shape optimization. In each level, the comprehensive algorithm was used and the relative difference quotients of two kinds of variables were used to search the optimum solution. A comparison between the optimum results of model with stability constraints and the optimum results of model without stability constraint was given. And that shows the stability constraints have a great effect on the optimum solutions.

A micro-kinetic model of enhanced foam stability under artificial seismic wave

To get a deeper understanding on the synergistic enhancement effect of low frequency artificial seismic wave on foam stability,a micro-kinetic model of enhanced foam stability under low frequency artificial seismic wave is established based on a vertical liquid film drainage model and elastic wave theory.The model is solved by non-dimensional transformation of the high order partial differential equations and a compound solution of implicit and explicit differences and is verified to be accurate.The foam film thickness,surfactant concentration distribution and drainage velocity under the action of low frequency artificial seismic wave are quantitatively analyzed.The research shows that low-frequency vibration can reduce the difference between the maximum and minimum concentrations of surfactant in the foam liquid film at the later stage of drainage,enhance the effect of Marangoni effect,and improve the stability of the foam liquid film.When the vibration frequency is close to the natural frequency of the foam liquid film,the vibration effect is the best,and the best vibration frequency is about 50 Hz.The higher the vibration acceleration,the faster the recovery rate of surfactant concentration in the foam liquid film is.The higher the vibration acceleration,the stronger the ability of Marangoni effect to delay the drainage of foam liquid film and the better the foam stability is.It is not the higher the vibration acceleration,the better.The best vibration acceleration is about 0.5 times of gravity acceleration.Reasonable vibration parameters would greatly enhance the effect of Marangoni effect.The smaller the initial concentration of surfactant,the better the vibration works in enhancing Marangoni effect.

A Simple and Effective Test Method of the Emulsion Stability

An innovational test method was developed on the basis of redefinition of the emulsion stability. The stability was characterized by relative volume percentage of disperse phase demulsified thoroughly from the top part and the bottom part of an emulsion sample, each weighting the same amount, after being settled for a given time at constant temperature. Three series of emulsions were prepared and tested successfully, which were emulsions of paraffin oil and water stabilized with polyoxyethylene lauryl ether series (AEO3 and AEO9) at various HLBs, and emulsions of rapeseed oil and water stablized with sorbitan monoleate (Span80) and each of polyoxyethylene (20) sorbitan carboxylic esters (Tween20, Tween40, Tween60, Tween80 and Tween85) at different HLBs. It proved that this method is especially workable while the boundaries are opaque in a wide range of HLBs and is capable of offering an accurate optimum HLB.

Optimization of Slope Angle and Its Seismic Stability: A Case Study for the Proposed Open Pit Coalmine in Phulbari,NW Bangladesh

The present study reflects upon the results of substantial program of two-dimensional Finite Element Method(FEM) numerical analyses of the open pit that links to slope angle optimization associated with the safety factor of the pit slope of a coal mine in Bangladesh. In the present analyses, two types of models have been presented. The first model estimates safety factor without seismic effect on the overall pit slope of the model; the second model incorporates safety factor with seismic stability of the model. The calculated optimum slope angle of the first model is 31owith a rational safety factor of 1.51,prior to the seismic effect. However, the value is reduced to 0.93, 0.82, and 0.72, after we applies the seismic effect in the second model with M6, M6.5, and M7, respectively. Finally, our modeling results emphasize that for the case of the proposed Phulbari coalmine, there is extremely high prospect for causing massive slope failure along the optimum pit slope angle with 31oif the mine area felt seismic shaking,like the Sikkim(in northern India) earthquake with M6.9 on September 18, 2011.

Stability analysis of underground engineering based on multidisciplinary design optimization

Aiming at characteristics of underground engineering,analyzed the feasibility of Multidisciplinary Design Optimization (MDO) used in underground engineering,and put forward a modularization-based MDO method and the idea of MDO to resolve problems in stability analysis,proving the validity and feasibility of using MDO in underground engi- neering.Characteristics of uncertainty,complexity and nonlinear become bottle-neck to carry on underground engineering stability analysis by MDO.Therefore,the application of MDO in underground engineering stability analysis is still at a stage of exploration,which need some deep research.

基于疫苗接种的SEIHRVI传染病模型分析与最优控制

为研究疫苗接种对控制传染病的影响,建立了具有标准发生率的传染病模型。通过推导得出模型的基本再生数,给出地方病平衡点的存在条件。借助构造Lyapunov函数证明了平衡点的全局稳定性。应用Pontryagin最大值原理分析了最优控制问题,得出最优控制策略。结果表明:提高疫苗接种率和效力能有效控制疾病传播;注意自我保护,及时接种以及重视治疗一定程度上可减小疾病爆发的规模。

Optimum Design of Highway Excavation Slope Angle: Evidence from Dawu Section of Jingzhu Highway

The optimum design of the highway excavation slope angle is one of the most important problems to the highway construction and to the slope improvement. The Dawu Section of Jingzhu (Beijing Zhuhai) Highway is taken as an example to illustrate the study method for excavation slope angle design. The analysis of the engineering condition from different angles with different factors shows that the stability of the slope is calculated by using residual pushing force and the Sarma method. Then the sensitive analysis of the slope stability is conducted by using residual pushing force method. Finally, the optimum angle of design is presented on the precondition of ensuring the whole stability of slope and the economic reasonability. The study results show that the most sensitive factors are the shear strength parameter and the seismic force, and that the optimum excavation slope angle is 60°.

用于电致变色技术的氧化钨薄膜最佳厚度的探索

WO_(3)薄膜在小直流电压作用下,通过阳离子的嵌入/脱出可以在深蓝色和透明态之间进行可逆变色.注入离子的迁移路程(即薄膜厚度)对WO_(3)电致变色性能和循环稳定性有极大影响.因此,本文采用直流反应磁控溅射制备WO_(3)薄膜,通过控制溅射时间制备得到200 nm、500 nm、800 nm、1100 nm、1400 nm 5种厚度的薄膜样品,分别测试其初始态和1000圈CV循环后的电荷储量、调制率、响应时间及记忆时间,探究用于电致变色技术的WO_(3)薄膜的最佳厚度.结果表明,800 nm厚度的WO_(3)薄膜表现出的电致变色性能和循环稳定性明显优于其他厚度,在1000圈循环后电荷储量下降了25.1%,在波长550 nm处调制率衰减了1.59%,24 h静置后透过率增加了11.73%.该研究可为WO_(3)薄膜的产业化应用提供更为精确的理论指导.

水泥稳定火山岩碎石体积及力学性能研究

为实现火山岩集料在沥青路面基层的资源化利用,设计基于火山岩的水泥稳定碎石,通过试验对比火山岩水泥稳定碎石与传统石灰岩水泥稳定碎石的体积(最佳含水率、最大干密度)和力学特性(无侧限抗压强度)。结果表明,相比石灰岩集料,火山岩集料密度相对较小、强度和抗磨耗性能较低而吸水率相对较大;相同条件下,水泥稳定火山岩碎石相比水泥稳定石灰岩碎石的最佳含水率相对较高,而最大干密度整体降低约16.5%;相比石灰岩水稳碎石,火山岩水稳碎石在相同条件下的强度明显较低,为满足4.5 MPa强度设计要求,火山岩水稳碎石需在石灰岩水稳碎石基础上增加约1%水泥用量。

发酵核桃乳的稳定剂复配配方优化及香气成分分析

本文以脱皮核桃仁为原料,经发酵工艺制备发酵核桃乳,以羧甲基纤维素钠添加量、果胶添加量、结冷胶添加量为考察因素,以发酵核桃乳的稳定性指数、感官评分为评价指标,通过单因素实验和正交试验对发酵核桃乳的各稳定剂单体的添加量进行优化,同时通过顶空固相微萃取(headspace solid phase microextraction,HSSPME)和气相色谱质谱(gas chromatography-mass spectrometry,GC-MS)联用技术对核桃乳发酵前后的香气成分及含量变化进行分析。结果表明:发酵核桃乳的稳定剂优化组合是羧甲基纤维素钠添加量2.5‰、果胶添加量1.1‰、结冷胶添加量0.3‰,此条件下产品的稳定性指数为1.1,感官评分为94.5分,产品稳定性较好,口感酸甜可口;醛类、酮类、醇类物质在发酵后出现较大变化,核桃乳发酵后香气品质得到显著提升。

受媒体报道和治疗影响的传染病模型的最优控制分析

首先,建立了一个具有治疗措施和媒体报道的传染病模型,证明了无病平衡点的全局稳定性,分析了地方病平衡点的存在性及其局部稳定性,并给出了疾病的持久性.其次,为了减少感染者的数量并降低媒体报道和治疗过程中的经济成本,建立了传染病最优控制模型,利用最优控制理论分析了使经济成本最低且感染者人数最少的最优控制方法.最后,通过数值模拟分析了最优控制措施对疾病传播的影响.研究结果表明,对传染病只采取单一的控制措施是远远不够的,多种控制措施相结合才是抑制传染病流行的最佳策略.

基于流浸膏物料性质的中药口服液体制剂剂型设计与优化关键技术研究

中药口服液体制剂具有显效迅速、服用方便等优点,但仍存在有效成分损失、澄明度降低和特殊患群(儿童)口服顺应性差的共性瓶颈问题。中药提取物流浸膏作为口服液体制剂生产过程的中间体,其部分性质很大程度上决定口服液体制剂的性质。该文构建中药流浸膏物料性质表征体系,挖掘出与制剂性质密切相关的物料性质:溶解性、酸碱性和味道,在此基础上,建立基于溶解性能的中药口服液体制剂有效性提升技术、基于酸碱性的稳定性提高技术以及基于味道性能的中药口服液体制剂口感改善技术,从而提升产品的内在品质。总结基于流浸膏物料性质的中药口服液体制剂剂型设计与优化技术的研究思路,以期为中药口服液体制剂的研究开发提供理论指导和技术支撑。

基于ADP的状态约束互联非线性系统的分散镇定

针对一类含有常数型状态约束的互联非线性系统,提出一种基于自适应动态规划(adaptive dynamic programming,ADP)的分散镇定方法.引入边界函数对原系统进行坐标变换,将状态约束系统转化为无约束系统.对转化后的系统构造独立子系统和改进的代价函数,将鲁棒分散镇定问题转化为最优调节问题.构建局部评判神经网络并采用策略迭代算法求解哈密顿-雅可比-贝尔曼(Hamilton-Jacobi-Bellman,HJB)方程,进而得到近似最优镇定律.通过李雅普诺夫稳定性理论证明了本文所提方法可使闭环互联系统和局部评判神经网络估计误差动态最终一致有界.数值仿真结果验证了所提出分散镇定方法的有效性.

某海上油田砂岩地层井壁稳定研究及应用

本文应用构造地质力学方法研究了该区域地应力的相对大小和大致方位,并应用井壁崩落椭圆法最终确定了该区块的最大地应力方向,从井壁稳定的力学机理出发,分析定向井井周应力分布规律,对坍塌压力、破裂压力随井斜、方位的分布规律进行了计算分析。

振动击实方法在水泥稳定级配碎石施工控制中的应用

本文结合云南省某高速公路项目建设过程中使用振动击实方法进行水泥稳定级配的配合比设计与施工控制中。对级配碎石的级配控制、最佳含水量、拌和加水量的控制,以达到最佳的施工效果。通过与重型击实方法的对比,使用振动击实方法可以更好选择材料级配并降低水泥剂量。但振动击实所确定的最佳含水量往往是理论状态的含水量,可以根据天气情况和运距适当调整含水量,以达到较好的和易性满足施工要求。

发酵菠萝酒的风味及其稳定性研究

以海南菠萝为原料,分别采用酿酒酵母和法国经典酵母在不同加糖量的条件下发酵制备菠萝酒,研究了发酵菠萝酒的感官指标,通过GC-MS方法研究了它们的香气成分;同时,研究其在室温、低温(4℃)和光照条件下的稳定性。结果表明对于当加糖量为0.10 g/g菠萝肉时,发酵所得的菠萝酒的风味最佳,酒度最高,低温保藏最佳。

果汁酸性奶冻的研制

主要介绍了一种果汁酸性奶冻的生产配方,结果发现:当CMC、卡拉胶、黄原胶与魔芋胶以3∶2∶1·2∶1·8比例复配,添加量为8‰时,可以有效改善果汁酸性奶冻的稳定性及口感。当蔗糖用量为6%,AK糖用量为0·02%时,采用柠檬酸∶乳酸∶酒石酸=1∶1∶1将产品pH调整到4·1时,产品口感爽滑,酸甜适中,有良好的咀嚼性。