基于Monte Carlo模拟的软土基坑隆起分析

基于圆弧滑动模型确定的安全系数,将基坑隆起破坏的不利事件划分为5种情况,利用Monte Carlo模拟确定不利事件发生概率,提出了考虑基坑隆起破坏引起的不利事件发生概率及经济损失的风险评估模型。将所提方法应用于福州地铁2号线某基坑工程中,结果表明,当围护结构插入比小于1.2时,加固对基坑隆起破坏损失期望减小效果显著;当围护结构插入比大于1.2时,加固对基坑隆起破坏损失期望减小效果一般;当插入比小于0.8时,基坑隆起破坏的损失期望等级属于"严重";当插入比介于0.8～1.2时,基坑隆起破坏的损失期望等级属于"需要考虑";当插入比大于1.2时,基坑隆起破坏的损失期望等级属于"可忽略"。     

倾斜无粘性土场地浅埋管道竖向隆起破坏研究（英文）

目的:研究斜坡内浅埋管道隆起破坏时滑裂面与场地倾角的关系以及倾斜场地土体隆起抗力的变化规律。创新点:推导出无粘性土场地中管道隆起破坏滑裂面倾角解析计算式。方法:利用莫尔圆极点法分析倾斜场地土体的应力状态,基于Rankine土压力理论、摩尔库伦强度准则和极限平衡条件,解析求解倾斜场地管道隆起时两侧的滑裂角,并推导相应的土体隆起抗力峰值计算式。结论:1.倾斜场地管道两边的滑裂面呈非对称破坏模式,滑裂面整体向坡脚方向偏转,且地表变形影响范围大于水平条件。2.管道埋深比(H/D)一定时,滑裂面偏转程度随场地倾斜程度的增大而增大;场地倾角一定时,滑裂角偏转程度随H/D的增大而减小;当H/D4时,可以忽略场地倾角的影响。3.当H/D1时,隆起抗力峰值随场地倾斜程度的增大而减小。4.现有的油气输运管道设计规范中,均未考虑场地倾斜的影响,且管线最小埋设深度仅0.5 m,存在安全隐患。     

深厚软弱地层坑内土体加固对支护结构变形的影响

为分析基坑内侧土体加固对支护结构水平位移的影响规律,将加固体及未加固土体视为复合土体,以弹性地基梁法为基础建立支挡结构的杆系有限元模型,结合工程实例计算分析土体加固参数对支护结构水平位移的影响。结果表明,支护结构水平位移随加固深度的增加而减小,且存在临界深度。当加固体的水泥掺量在0～15%范围内增加或置换率在0～0.5范围内增加,支护结构水平位移显著减小,加固效果显著;当水泥掺量大于15%或置换率大于0.5,支护结构水平位移变化较小,加固效能降低。     

玻璃纤维布加固的钢筋混凝土梁试验研究与抗弯承载力计算

对9根玻璃纤维布加固的钢筋混凝土梁和3根对比梁进行了抗弯性能试验研究. 试验中考虑了配筋率、加固量、剪跨比与混凝土强度等级4个参数. 试验结果表明, 经玻璃纤维布加固的钢筋混凝土梁抗弯承载力有显著提高; 混凝土强度、配筋率、加固量对极限荷载有显著影响; 剪跨比对加固梁的破坏形态有影响. 根据不同的破坏模式, 提出了抗弯承载力计算方法.     

无支撑两级基坑支护结构变形影响因素分析

为探究无支撑多级支护结构的不同设计参数对基坑变形的影响,以一个无支撑两级支护的粉质黏土深基坑为例,利用FLAC3D软件建立数值模型,并基于正交试验通过极差、方差分析,就两级支护间距、开挖比以及两级支护结构长度对支护结构位移的影响进行研究。主要结论如下:采用无支撑两级支护结构的粉质黏土深基坑,两级支护结构的顶部最大位移受两级支护间距和开挖比影响的敏感度较高两级支护结构位移之间存在“叠加作用”、“牵引作用”的相互影响,但当两级支护间距不小于总开挖深度的0.5倍时,相互影响不显著当两级支护间距不小于总开挖深度的0.5倍,且开挖比为0.8~1.3时,两级支护结构的顶部最大位移比较接近,且不超过规范的一级基坑下限控制值,处于最合理的工作状态。     

求随机变量期望的四种方法

<正>期望是随机变量的重要的特征数字.已知期望,便掌握了这个随机变量的平均水平,也就大体上掌握了它取值的概率规律.求期望的常用方法有直接运用定义、运用期望性质、分解事件、整体考虑等.下面举例说明.     

如何理解概率与风险判断的关系

<正>概率是高中数学的重要模块之一.在现实生活中,我们可以接触到许多与概率有关的事件,风险判断就是其中一个典型的例子.运用概率知识可以帮助我们进行正确的风险判断,进而把损失控制在最小范围内,实现收益的增长.通过对高中数学的学习,我们了解到概率是指对某一随机事件发生的可能性大小的衡量,一般情况下,我们用0-1范围的数值对随机事件发生的可能性大小的进行度量;当概率值越接近于0时,说明该事件发生的可能     

概率与方程联姻趣题解析

对简单的概率（试验涉及一种因素,如抽取一次等）计算问题,可以利用简单枚举法求随机事件发生的概率：当随机事件含有两个因素时,可以利用列表法计算某种情况发生的概率;当随机事件含有两个以上因素时,往往利用画树形图法求某种情况发生的概率．概率与方程联姻,     

概率浅说(一)

全日制六年制重点中学高中三年级安排了“概率”教学二十课时,为了帮助读者教好这一新增内容,本刊约请了人民教育出版社编辑高尚华作《概率浅说》讲座.共分三讲:第一讲随机事件;用频率定义概率;概率的古典定义;事件的关系与运算.第二讲概率的基本性质;概率的几何意义;条件概率与独立性;全概率公式.第三讲独立试验序列;离散型随机变量及其分布列;离散型随机变量的数学期望与方差.全文内容丰富,通俗易懂,且配有足够的例题及习题(附答案供教师教学时参考).     

概率

[知识要点]1.　　　　称为必然事件;　　　　不可能事件;　　　　称为不确定事件.2.某一事件发生的可能性大小称为这个事件发生的概率.必然事件发生的概率为1,记作P(必然事件)=1;不可能事件发生的概率为0,记作P(不可能事件)=0;如果A为不确定事件,那么0相似文献   

某地铁车站深基坑开挖地连墙水平位移分析

现场监测难以预测基坑和围护结构后期变形规律。采用MIDAS/GTS NX对某地铁车站深基坑开挖及支护全过程进行数值模拟,探寻深基坑开挖引起的地连墙水平位移变化规律,并对比现场监测数据验证数据模拟的可靠性。研究结果表明:随着基坑的开挖,地连墙不同深度下的水平位移变化呈现出内凸的规律,开挖完成时模拟最大水平位移值约为11.6 mm,现场监测最大值约为13.9 mm,最大水平位移位于开挖面附近;改变地连墙厚度及嵌固深度后发现,地连墙厚度及嵌固深度的增大可减小地连墙深层水平位移,但对地连墙顶部水平位移影响较小。研究成果可为深基坑开挖对周边环境影响的分析及类似工程施工方案的优化提供参考。     

Effects of flipped classrooms integrated with MOOCs and game-based learning on the learning motivation and outcomes of students from different backgrounds

ABSTRACT

This study aimed to investigate the effect of flipped classrooms integrated with massive open online courses (MOOCs) and game-based learning on the learning motivation and learning outcomes of students from different backgrounds (in terms of gender, grade, self-confidence indicators in mathematics, and roles played in the game-based learning process). Surveys and a semi-structured open questionnaire were used for data collection, including a basic information questionnaire (to understand the participants’ backgrounds), a questionnaire on learning motivation (the Motivated Strategies for Learning Questionnaire, MSLQ), a test of learning achievements in mathematics, and a semi-structured open-ended questionnaire (to understand the learners’ feelings). Quantitative analysis results showed that flipped classrooms integrated with MOOCs and game-based learning can enhance students’ learning motivation and outcomes. Specifically, compared with students with high self-confidence in learning mathematics, students with low and medium levels of self-confidence showed significantly greater improvement in overall learning motivation. Significantly more enhancements were found for the expectation component of “soldiers” (students with relatively lower learning achievements) than for “generals” (students with higher learning achievements). Furthermore, students in the eighth grade showed significantly greater progress in academic performance than did students in the seventh grade.     

Recovery of extinction responding in rats following discontinuation of reinforcement of alternative behavior: A test of two explanations

One procedure which has been used to supplement extinction in order to produce faster and more complete response suppression is to provide reinforcement for some alternative response which is incompatible with the response undergoing extinction. When reinforcement for the alternative behavior is discontinued, however, substantial recovery of the original response has often been observed. The present set of experiments demonstrated that such recovery is best accounted for by a “response prevention” hypothesis rather than by a “discriminative cue” hypothesis. High-frequency reinforcement of alternative behavior during the first half of an extinction phase seems similar in effect to procedures which physically prevent rats from emitting the response programmed for extinction.     

冲抓成孔灌注桩悬臂围护形式深基坑支护技术

本文介绍了有较厚砂砾层且地下水位较高的地基中，冲抓成孔灌注桩悬臂围护形式深基坑支护的设计分析方法、降水措施、施工技术要求及对周边环境的保护。     

依沙佐米治疗难治性/复发性多发性骨髓瘤临床试验效果的Meta分析

目的:评价依沙佐米治疗难治性/复发性多发性骨髓瘤(RRMM)的疗效及安全性。方法:计算机检索依沙佐米治疗RRMM的临床试验,手工检索纳入查询到的所有文献,提取数据后,使用R软件3.5.0进行Meta分析。结果:共纳入8篇文献,包括1096例RRMM患者,含依沙佐米三联方案的疗效优于单联方案或双联方案,以依沙佐米联合来那度胺和地塞米松(IRD)方案疗效最佳;IRD方案腹泻,恶心,皮疹,血小板减少,呕吐,腹泻≥3级,低血压≥3级,恶心≥3级高于来那度胺和地塞米松(RD)方案,而失眠,贫血≥3级低于RD方案,差异有统计学意义(P<0.05)。结论:含依沙佐米三联方案治疗RRMM的疗效较依沙佐米单联方案或二联方案显著。IRD方案疗效最佳,其不良反应较RD方案增多。     

Test research on influence of draft on towing behaviors of 3-bucket foundation platform

To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.     

Partial reinforcement in autoshaping with pigeons

The acquisition, maintenance, and extinction of autoshaped responding in pigeons were studied under partial and continuous reinforcement. Five values of probability of reinforcement, ranging from .1 to 1.0, were combined factorially with five values of intertrial interval ranging from 15 to 250 sec for different groups. The number of trials required before autoshaped responding emerged varied inversely with the duration of the intertriai interval and probability of reinforcment, but partial reinforcement did not increase the number of reinforcers before acquisition. During maintained training, partial reinforcement increased the overall rate of responding. A temporal gradient of accelerated responding over the trial duration emerged during maintenance training for partial reinforcement groups, and was evident for all groups in extinction. Partial reinforcement groups responded more than continuous reinforcement groups over an equivalent number of trials in extinction. However, this partial-reinforcment extinction effect disappeared when examined in terms of the omission of “expected” reinforcers.     

RECALL AND PRINTED‐WORD RECOGNITION OF RECENTLY‐TAUGHT EMOTIONALLY CHARGED WORDS AS COMPARED TO RECENTLY‐TAUGHT NEUTRAL WORDS

This study is an experimental test of the hypothesis that “emotionally charged” words will result in greater learning as measured by tests of “recall” and “printed‐word recognition” than words that are judged to be emotionally “neutral”.

Ten third‐grade subjects were pre‐tested on “printed‐word recognition” of ten words judged by two clinical psychologists to be “emotionally charged” and similarly pre‐tested on ten words judged to be emotionally “neutral.” After equal exposure to both “neutral” and “emotionally charged” words on four successive teaching days, subjects were post‐tested for “recall” and “printed‐word recognition” five days after the last teaching session.

The results strongly indicate for both the “recall” and “printed‐word recognition” that there is a significantly greater retention of the “emotionally charged” words over the “neutral” words. Despite the fact that a significantly greater number of “neutral” words was recognized in print at the outset of the study, the final performance level for “printed‐word recognition” for both the “emotionally charged” and “neutral” words is identical.

The major implications of the results obtained in this study is that the content of reading materials and the methods for teaching them must be revised so that reading deals with events, ideas, and feelings which are emotionally significant to the child, A personally relevant reading program will not only facilitate the task of learning to read, but will capture and explore the feelings and emotions of each child, as well.     

Memory interval distribution effects in pigeons

Pigeons were trained with two concurrent delayed conditional discriminations that involved different distributions of memory intervals, namely 1 and 5 sec in the “short” and 5 and 10 sec in the “long” distribution. Memory for the initial stimulus was much better after 5 sec in the short distribution than in the long one. The memory functions between the intervals within each distribution were essentially flat. These findings were replicated in a second study that involved differential outcomes; this procedure enhanced memory generally within trials so that memory intervals of 1, 9, and 19 sec could be used, with 9 sec serving as the common memory interval. The findings are interpreted on the basis of the subject’s expectation of the likely duration of the upcoming memory interval and the associated delay of reinforcement.