Simulation research on monomer agglomeration of nonmetallic inclusions in steel with a diffusion limited aggregation model

The monomer agglomeration of nonmetallic inclusions was simulated with a diffusion limited aggregation （DLA） model of the fractal theory. The simulation study with a random two-dimensional diffusion was carried out. The results indicate that the DLA model can be used for the simulation of agglomeration behavior of the cluster-type inclusions. The morphology of clusters was observed with SEM and compared with the simulated agglomerates. The modelling procedure of the DLA model is applicable for the agglomeration process. The uncertainty of agglomeration process and the persuasive average agglomerative ratio was analyzed. The factors about the agglomerative ratio with the collision path distance and the size of particles or seed were discussed. The adherence of the nonmetallic inclusions on the dam, the weir and the walls of a tundish, and the absorption of inclusions by stopper or nozzle were also discussed.

The height-width ratio limited value for rubber bearing isolated structure computed by uniform design method

Rubber isolation is the most mature control technology in practical application, and is widely used by short rigid buildings. However, many high isolation buildings have been built around the world in recent years, which do not follow the existing criterions and codes. Many researchers began to research the special problems caused by larger height-width ratio isolation structures. The overturning effect of high height-width ratio structures with rubber bearing is firstly studied. Considering the main factors, such as the height-width ratio of structures, type of site, the designed basic acceleration of ground motion and the decouple factor in horizon, computing experiment is defined with the Uniform Design Method, which is also known as designing isolation structure. The forces of the bearing under edge of structures based on the position of the rubber bearing are calculated. The result indicates that the rubber bearings will lose its functionality under very high tension and compressing force of earthquake motion in horizon and vertical, when the height-width ratio is over a certain value. Thus, based on the calculation result of isolation structures defined in the uniform design method, regression analysis is conducted, and also the rubber edge force regression formula are gotten, which has higher correlation and smaller standard deviation. This formula can be used to roughly calculate whether the pull force occurs at the edge of the building. By the edge bearings of isolation structure minimum force formula, the height-width ratio limited value of the isolation structure is deducted when rubber bearing has minimum force of zero.

Likelihood Ratio and Strong Limit Theorems for the Discrete Random Variable

This in virtue of the notion of likelihood ratio and the tool of moment generating function, the limit properties of the sequences of random discrete random variables are studied, and a class of strong deviation theorems which represented by inequalities between random variables and their expectation are obtained. As a result, we obtain some strong deviation theorems for Poisson distribution and binomial distribution.

Confidence limit calculation for antidotal potency ratio derived from lethal dose 50

AIM:To describe confidence interval calculation for antidotal potency ratios using bootstrap method.METHODS:We can easily adapt the nonparametric bootstrap method which was invented by Efron to construct confidence intervals in such situations like this.The bootstrap method is a resampling method in which the bootstrap samples are obtained by resampling from the original sample.RESULTS:The described confidence interval calculation using bootstrap method does not require the sampling distribution antidotal potency ratio.This can serve as a substantial help for toxicologists,who are directed to employ the Dixon up-and-down method with the application of lower number of animals to determine lethal dose 50 values for characterizing the investigated toxic molecules and eventually for characterizing the antidotal protections by the test antidotal systems.CONCLUSION:The described method can serve as a useful tool in various other applications.Simplicity ofthe method makes it easier to do the calculation using most of the programming software packages.

Bifurcation and Limit Cycle of a Ratio-dependent Predator-prey, System with Refuge on Prey

Influences of prey refuge on the dynamics of a predator-prey model with ratio-dependent functional response are investigated. The local and global stability of positive equilibrium of the system are considered. Theoretical analysis indicates that constant refuge leads to the system undergo supercritical Hopf bifurcation twice with the birth rate of prey species changing continuously.

California Bearing Ratio for Cohesive Soils from Quasi Static Cone Tests

The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R2 = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.

光伏发电系统容配比与功率限值整定方法

为在保证系统可靠运行的前提下实现光伏发电系统发电量最大化,提出一种以光伏发电系统度电成本为目标的容配比与变功率限值整定方法,分析容配比和变功率限值对光伏逆变器可靠性以及系统发电量的影响规律,建立考虑功率器件寿命的光伏发电系统容配比与功率限值参数优化整定模型,并利用启发式算法进行模型求解。最后,不同纬度地区的算例分析结果验证所提整定方法的有效性。

考虑硬化历史的圆筒形件二次拉深极限拉深比的解析模型

以圆筒形件二次拉深成形为例,基于主应力法和板料弯曲理论,考虑材料硬化历史、壁厚比t_(min)/t_(max)、凹模圆角半径和摩擦因数的影响,建立了一种预测圆筒形件二次拉深极限拉深比的解析模型,并对SUS304不锈钢板料进行了拉深试验验证。结果表明:解析模型的预测值与试验结果吻合较好;考虑硬化历史的解析模型与未考虑硬化历史的模型相比二次拉深极限拉深比相差约10%;摩擦因数、凹模圆角半径对二次拉深极限拉深比有显著影响,摩擦因数越大,二次拉深极限拉深比越小;凹模圆角半径越大,二次拉深极限拉深比越大。

不同性能水平下600 MPa级高强钢筋混凝土柱位移角限值研究

基于性能抗震设计思想的600 MPa级高强钢筋混凝土柱位移角限值研究,对于推广高强钢筋混凝土柱的应用至关重要。通过17根HTRB630高强钢筋混凝土柱试件和3根HRB400钢筋混凝土柱试件的拟静力试验研究了其抗震性能。与HRB400钢筋混凝土柱相比,HTRB630高强钢筋混凝土柱的滞回曲线的形状没有发生明显改变,试件具有较好的承载能力和延性。将基于Kunnath损伤模型计算的损伤指数与试验中测量的损伤指数范围进行了比较,结果表明,Kunnath损伤模型可以准确计算HTRB630高强钢筋混凝土柱的损伤指标。根据HTRB630高强钢筋混凝土柱的破坏特点,以屈服点、峰值点和极限点作为高强钢筋混凝土柱的性能水平控制点。基于性能抗震设计的思想,将600 MPa级高强钢筋混凝土柱的性能水平划分为5个性能水平,即正常使用、暂时使用、修复后使用、生命安全和接近倒塌性能水平。结合参考文献中600 MPa级高强钢筋混凝土柱的试验数据,对65个600 MPa级高强钢筋混凝土柱各特征点的位移角进行了相对频率统计分析,得到了600 MPa级高强钢筋混凝土柱在暂时使用、修复后使用和接近倒塌3个性能水平下具有超过90%安全保证率的位移角限值分别为1/150、1/80和1/60。

复合空间索对大跨度铁路悬索桥横向刚度影响的研究

为提升大跨度铁路悬索桥的横向刚度,提出一种由主、副斜拉索组成的复合空间索结构。然后,基于材料有效利用率和静力分析,对复合空间索的直径、主斜拉索在加劲梁和地表的锚点位置、副斜拉索的数量等参数进行了优化。最后,采用风-车-桥耦合振动分析法,基于行车性能得到了桥梁横向挠跨比限值,分析了主、副斜拉索对横向挠跨比限值提升率的影响。结果表明:基于材料有效利用率,主斜拉索与加劲梁的锚点位置宜设在1/4主跨附近,且主斜拉索的地表锚点、加劲梁锚点与桥塔的垂直距离相等时最优,每组复合空间索中副斜拉索设置1根即可;在复合空间索的最优布置形式下,桥梁横向挠跨比可降低14.18%,横向挠跨比限值可提升16.79%。

轴压荷载下装配式SCCT剪力墙钢板屈曲行为研究

为探究装配式SCCT剪力墙钢板屈曲机制及钢板屈曲对墙体轴压承载性能的影响,建立了考虑钢材初始缺陷的装配式SCCT剪力墙非线性数值分析模型,对模型受力机理及钢板临界屈曲应力进行了分析,并根据参数分析结果提出了钢板临界屈曲应力计算方法。结果表明:墙体承载力主要由管内混凝土承担,各部件间协同工作,应力及变形传递性能良好;当管外混凝土厚度大于20 mm、钢材初始缺陷低于1/1000时,二者对钢板临界屈曲应力影响可忽略不计;对于Q235和Q355常用钢,要求钢板不发生弹性屈曲的距厚比限值分别为44.9、36.6。

带T形钢翼缘的核心钢管混凝土组合柱轴压比限值研究

为了充分发挥带T形钢翼缘的核心钢管混凝土组合柱(T-CFST柱)的变形性能,保证柱在地震作用下能满足延性需求,通过理论推导和数值模拟,对T-CFST柱的延性和轴压比限值进行研究。基于大小偏心受压界限破坏建立了T-CFST柱的标准轴压比和设计轴压比计算公式,同时基于ABAQUS软件建立了T-CFST柱的精细化有限元模型,在验证有限元模型准确性的基础上,研究了高轴压比下不同影响因素对组合柱延性的影响,建议了不同含钢率、型钢强度、混凝土强度下组合柱的设计轴压比限值。结果表明:T-CFST柱延性随混凝土强度降低、截面含钢率降低、型钢强度提高、体积配箍率提高而提高;即使在较大轴压比时,柱的延性依然较好,T-CFST柱的轴压比限值在计算的基础上有所提高。

红黏土动剪切模量比与阻尼比概率分布特征研究

为探讨红黏土的动力学参数特征,揭示动剪切模量比与阻尼比在典型剪应变条件下的概率分布规律,本文以广西红黏土为研究对象,通过收集整理321组动力特性试验基础数据,给出了广西红黏土在典型剪应变条件下动剪切模量比与阻尼比随剪应变的试验推荐关系曲线,分析了不同概率水准条件下动剪切模量比和阻尼比的不确定性分布形态,并利用Boltzmann曲线给出了不同概率水准下动剪切模量比与阻尼比的上下限值及拟合公式。通过与前人给出的常规土类研究结果进行对比,初步揭示了红黏土动力特性与深度和剪应变的关系规律。研究表明:红黏土动剪切模量比、阻尼比在八组典型剪应变条件的上下限值随超越概率的变化呈现一定的规律,在数学形式上均满足Boltzmann方程。当剪应变在1×10^(-4)~1×10^(-3)时,动剪切模量比与阻尼比离散程度均达到最大。在同一剪应变条件下,随着超越概率的增大,红黏土动剪切模量比与阻尼比上下限之间的差距显著增大。

电网频率校正控制方法在高比例新能源电网的适应性

新能源出力由自然禀赋决定,在电力平衡约束下的高比例新能源电网运行方式调整范围逐渐增加,传统固定策略的频率校正控制方法失配风险不断提高。建立典型系统,给出了研究频率校正控制的电网运行场景域描述方法,计算了频率校正控制系统任一轮次适应的电网运行场景域。提出将控制量可整定的范围作为评价任一轮次适应性的指标,使用多个轮次的最小可整定范围评价频率校正控制系统的适应性。利用实际电网参数建立分析模型,计算频率校正控制系统适应的极限新能源接入比例。传统频率校正控制方法难以适应新能源比例高的场景,亟需新型控制方法。

2195铝锂合金贮箱球底充液拉深成形起皱缺陷演变规律数值模拟研究

为满足登月着陆器舱体高可靠性、轻量化制造需求,提出贮箱球底充液拉深成形方法。对于直径3350 mm的2195铝锂合金箱底,相对2219和5A06铝合金,材料塑性差,成形易开裂失效,且整底成形厚径比仅为2.5‰,易起皱失稳。针对上述问题,建立了整底充液拉深成形仿真模型,进行不同液室压力、压边力条件下的数值模拟,讨论整底充液拉深成形变形规律,分析整底成形缺陷形式及控制方法,优化整底充液拉深液室压力加载路径,获得球底壁厚分布规律。结果表明:拉深行程达0.24H(H为零件最终高度)时,球底悬空区域为典型的压缩应力状态,产生了沿母线方向的起皱缺陷环向均布12个,拉深行程0.79H时,环向起皱数量倍增;引入液室压力后使悬空区由压缩应力状态转变为拉伸应力状态,从而避免了悬空区起皱缺陷的发生;压边力和液室压力对悬空区应力状态影响显著,随着压边力增大,球底壁厚减薄趋势增大,而随着液室压力的增大,球底壁厚减薄趋势减弱;球底拉深试验对初始壁厚9.5 mm板材,采用2.5×107 N压边力、8 MPa液室压力加载路径时,壁厚最大减薄率为7.4%,壁厚分布均匀,无起皱缺陷。

计数抽样检验程序在检验检测机构质量管理中的应用

检验检测机构通过建立并运行质量管理体系,以实现组织设定的质量目标。检测报告合格率是检验检测机构质量目标测量的重要内容。计数抽样检验程序GB/T 2828系列标准广泛应用于检验生产方最终产品、零部件和原材料、在制品、库存品、维修操作、数据或记录等的质量。本文旨在探讨检验检测机构引入计数检验抽样的程序对质量目标进行测量和监视的必要性、可行性以及技术路径,并提供应用实例。

垃圾量有限预知下环卫车在线调度策略

目前,垃圾清运是环保工作重点关注的问题之一,一般垃圾清运成本占总垃圾处理成本的60%~80%,所以以成本最小化为目标的环卫车调度问题就成为热点问题。现有对该问题的研究大部分都是基于静态需求,最后计算出环卫车调度的离线最优。因此,将需求动态变化的特征纳入考虑范围,提出了在垃圾量有限预知的情况下城市环卫车在线调度的诱导策略和组合优化策略,同时证明了两个策略不同情况下的竞争比。最后通过实例比较策略的执行效果,得出了该实例的最优在线调度策略为诱导策略。

基于不同茎叶比的仙鹤草配方颗粒研究

目的:建立一个仙鹤草配方颗粒指标性含量数据筛选的方法。方法:基于仙鹤草茎、叶在黄酮类与鞣花酸的含量差异,以仙鹤草标准汤剂中茎叶比例为横坐标、黄酮/鞣花酸含量比为纵坐标建立仙鹤草标准汤剂所用饮片茎叶比例预测模型,并结合仙鹤草药材自然环境生长状况下茎/叶比例对数据进行筛选,确定入选用于仙鹤草配方颗粒指标性含量制定的仙鹤草标准汤剂参照数据。结果:通过对数据的筛选,确定了仙鹤草标准汤剂槲皮苷的含量范围为1.33~2.47 mg/g,鞣花酸的含量范围为1.35~2.50 mg/g。结论:建立的黄酮/鞣花酸含量比的方法可预测仙鹤草配方颗粒所用饮片的茎叶比例,利用茎/叶比例对仙鹤草标准汤剂指标性含量数据进行筛选,所得范围较筛选前明显缩窄,以此制定的指标性含量限度范围可有效地保证生产的中药配方颗粒与临床所用饮片的一致性。

某388m超高层建筑的侧移刚度与整体稳定性分析

通过某带伸臂桁架和环带桁架加强层的边筒-周边框架体系超高层结构工程设计实例,讨论了高层建筑结构侧移刚度和整体稳定性分析方法。指出在计算结构侧移刚度时应考虑楼板面内有限刚度、地下室结构构件变形、混凝土抗侧向力结构构件开裂刚度折减及二阶效应,从而得到更准确的结构侧移变形和最低阶整体屈曲荷载因子。提出了利用弯矩-曲率分析方法,并根据构件实际受力状态,迭代计算混凝土抗侧向力结构构件的开裂刚度折减系数。比较了中国、欧盟及美国规范关于整体稳定性分析的计算方法,提出在进行整体稳定性分析时,应考虑各种不利因素,从而准确评估二阶效应。讨论了高层建筑在正常使用极限状态下层间位移角限值的取值,并介绍了美国规范对层间位移角的计算方法和限值的建议。详细论述了当前中国规程中关于侧移刚度分析的不足并提出建议,以期为相关类似工程设计提供参考。

新型高聚物固化剂稳定土路用性能试验研究

为研究高分子聚合物固化剂对水泥石灰土强度和耐久性的影响,以醋酸乙烯酯-乙烯共聚乳液、纯丙乳液、硅丙乳液、聚乙二醇、纳米二氧化硅(n-SiO2)、木质素磺酸钙、十二烷基苯磺酸钠、KH-550等为原料,制备了一种高分子聚物土壤固化剂V。通过7 d无侧限抗压强度试验确定固化剂与水泥、石灰的最适宜配比,并对固化剂稳定土进行水稳定试验、冻融试验、劈裂试验,分析稳定土路用性能。结果表明:当固化剂掺量为0.1%,水泥掺量为5%,石灰掺量为3%时,试件7 d无侧限抗压强度最高,为5.46 MPa。养护28 d后,试件水稳定系数、抗冻指标和劈裂强度分别为89.66%、83.7%、0.77 MPa。通过数据对比可知,固化剂对水泥石灰土各性能有明显提升。