Upper bound analysis of slope stability with nonlinear failure criterion based on strength reduction technique

Based on the upper bound limit analysis theorem and the shear strength reduction technique, the equation for expressing critical limit-equilibrium state was employed to define the safety factor of a given slope and its corresponding critical failure mechanism by means of the kinematical approach of limit analysis theory. The nonlinear shear strength parameters were treated as variable parameters and a kinematically admissible failure mechanism was considered for calculation schemes. The iterative optimization method was adopted to obtain the safety factors. Case study and comparative analysis show that solutions presented here agree with available predictions when nonlinear criterion reduces to linear criterion, and the validity of present method could be illuminated. From the numerical results, it can also be seen that nonlinear parameter rn, slope foot gradient ,β, height of slope H, slope top gradient a and soil bulk density γ have significant effects on the safety factor of the slope.

Development and validation of a predictive model for acute-onchronic liver failure after transjugular intrahepatic portosystemic shunt

BACKGROUND Transjugular intrahepatic portosystemic shunt(TIPS)is a cause of acute-onchronic liver failure(ACLF).AIM To investigate the risk factors of ACLF within 1 year after TIPS in patients with cirrhosis and construct a prediction model.METHODS In total,379 patients with decompensated cirrhosis treated with TIPS at Nanjing Drum Tower Hospital from 2017 to 2020 were selected as the training cohort,and 123 patients from Nanfang Hospital were included in the external validation cohort.Univariate and multivariate logistic regression analyses were performed to identify independent predictors.The prediction model was established based on the Akaike information criterion.Internal and external validation were conducted to assess the performance of the model.RESULTS Age and total bilirubin(TBil)were independent risk factors for the incidence of ACLF within 1 year after TIPS.We developed a prediction model comprising age,TBil,and serum sodium,which demonstrated good discrimination and calibration in both the training cohort and the external validation cohort.CONCLUSION Age and TBil are independent risk factors for the incidence of ACLF within 1 year after TIPS in patients with decompensated cirrhosis.Our model showed satisfying predictive value.

Inverse Estimation on Trigger Factors of Simultaneous Slope Failures with Purification of Training Data Sets

This paper presents an procedure for purifying training data sets （i.e., past occurrences of slope failures） for inverse estimation on unobserved trigger factors of ＂different types of simultaneous slope failures＂. Due to difficulties in pixel-by-pixel observations of trigger factors, as one of the measures, the authors had proposed an inverse analysis algorithm on trigger factors based on SEM （structural equation modeling）. Through a measurement equation, the trigger factor is inversely estimated, and a TFI （trigger factor influence） map can be also produced. As a subsequence subject, a purification procedure of training data set should be constructed to improve the accuracy of TFI map which depends on the representativeness of given training data sets of different types of slope failures. The proposed procedure resamples the matched pixels between original groups of past slope failures （i.e., surface slope failures, deep-seated slope failures, landslides） and classified three groups by K-means clustering for all pixels corresponding to those slope failures. For all cases of three types of slope failures, the improvement of success rates with respect to resampled training data sets was confirmed. As a final outcome, the differences between TFI maps produced by using original and resampled training data sets, respectively, are delineated on a DIF map （difference map） which is useful for analyzing trigger factor influence in terms of ＂risky- and safe-side assessment＂ sub-areas with respect to ＂different types of simultaneous slope failures＂.

Serum uric acid as an index of impaired renal function in congestive heart failure

Background Hyperuricemia is frequently present in patients with heart failure. Many pathological conditions, such as tissue ischemia, renal function impairment, cardiac function impairment, metabolic syndrome, and inflammatory status, may impact uric acid （UA） metabolism. This study was to assess their potential relations to UA metabolism in heart failure. Methods We retrospectively assessed clinical charac- teristics, echocardiological, renal, metabolic and inflammatory variables selected on the basis of previous evidence of their involvement in cardiovascular diseases and UA metabolism in a large cohort of randomly selected adults with congestive heart failure （n = 553）. By clustering of indices, those variables were explored using factor analysis. Results In factor analysis, serum uric acid （SUA） formed part of a principal cluster of renal functional variables which included serum creatinine （SCr） and blood urea nitrogen （BUN）. Univariate correlation coefficients between variables of patients with congestive heart failure showed that the strongest correlations for SUA were with BUN （r = 0.48, P 〈 0.001） and SCr （r = 0.47, P 〈 0.001）. Conclusions There was an inverse relationship between SUA levels and measures of renal function in patients with congestive heart failure. The strong correlation between SUA and SCr and BUN levels suggests that elevated SUA concentrations reflect an impairment of renal function in heart failure.

Determination and stability analysis of ultimate open-pit slope under geomechanical uncertainty

In open-pit mines,pit slope as one of the important parameters affects the mine economy and total minable reserve,and it is also affected by different uncertainties which arising from many sources.One of the most critical sources of uncertainty effects on the pit slope design is rock mass geomechanical properties.By comparing the probability of failure resulted from deterministic procedure and probabilistic one,this paper investigated the effects of aforesaid uncertainties on open-pit slope stability in metal mines.In this way,to reduce the effect of variance,it implemented Latin Hypercube Sampling(LHS)technique.Furthermore,a hypothesis test was exerted to compare the effects on two cases in Middle East.Subsequently,the investigation approved high influence of geomechanical uncertainties on overall pit steepness and stability in both iron and copper mines,though on the first case the effects were just over.

Preoperative risk factor analysis in orthotopic liver transplantation with pretransplant artificial liver support therapy

AIM： To assess the value of pre-transplant artificial liver support in reducing the pre-operative risk factors relating to early mortality after orthotopic liver transplantation （OLT）. METHODS： Fifty adult patients with various stages and various etiologies undergoing OLT procedures were treated with molecular adsorbent recycling system （MARS） as preoperative liver support therapy. The study included two parts, the first one is to evaluate the medical effectiveness of single MARS treatment with some clinical and laboratory parameters, which were supposed to be the therapeutical pre-transplant risk factors, the second part is to study the patients undergoing OLT using the regression analysis on preoperative risk factors relating to early mortality （30 d） after OLT. RESULTS： In the 50 patients, the statistically significant improvement in the biochemical parameters was observed （pre-treatment and post-treatment）. Eight patients avoided the scheduled Ltx due to significant relief of clinical condition or recovery of failing liver function, 8 patients died, 34 patients were successfully bridged to Ltx, the immediate outcome of this 34 patients within 30d observation was： 28 kept alive and 6 patients died. CONCLUSION： Pre-operative SOFA, level of creatinine, INR, TNF-α, IL-10 are the main preoperative risk factors that cause early death after operation, MARS treatment before transplantion can relieve these factors significantly.

Relationship between critical seismic acceleration coefficient and static factor of safety of 3D slopes

Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.

Improving the Reliability of a Domestic Refrigerator Compressor Subjected to Repetitive Loading

As a reliability quantitative specification, parametric accelerated life testing was used to assess the reliability of a newly designed compressor of a commercial refrigerator subjected to repetitive stresses. A generalized life-stress failure model and new sample size equation with a new load concept were derived starting with the basic refrigeration cycle. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly evaluate the expected lifetime. The design of this testing should help an engineer uncover the design parameters affecting reliability during the design process of the compressor system. Consequently, it should help companies improve product reliability and avoid recalls due to the product failures in the field. A newly designed compressor in a commercial refrigerator was used as a test case.

考虑水力效应的裂缝边坡稳定性非线性能耗分析

现有考虑水力效应的裂缝边坡稳定性分析大多基于线性破坏准则,而岩土体破坏往往呈现非线性特征,因此开展水力效应影响下的裂缝边坡稳定性非线性极限上限分析具有重要意义。基于极限分析上限定理及强度折减技术,结合“外切线法”非线性破坏准则,构建坡顶含竖直裂缝的边坡对数螺旋线破坏模式,根据虚功原理推导出裂缝边坡安全系数解析式,通过MATLAB优化计算,结合边坡工程实例探讨了典型因素对裂缝边坡稳定性、临界裂缝及滑动面位置的影响规律。研究结果表明:随着地下水位h的持续上升,边坡安全系数不断降低,临界裂缝深度逐渐增大且临界裂缝位置逐渐向坡顶缘偏移;非线性系数m明显影响边坡的稳定性,边坡安全系数随着非线性系数的增大显著减小,采用线性破坏准则会高估地下水位变化对边坡稳定性的影响;随着非线性系数的增大,临界裂缝深度随之增大,临界裂缝位置距离坡顶缘越来越远,滑坡体体积逐渐增大;裂缝与坡顶缘距离l m随着非线性系数m的增大而增大(当m增大0.2时,l m增大约1 m),且随着裂缝与坡顶缘距离的增大,边坡安全系数无明显变化,临界裂缝深度先逐渐减小后趋于稳定。

新疆生产建设兵团2016—2022年肺结核患者不良转归列线图预测模型的构建与验证

目的:构建新疆生产建设兵团(以下简称“兵团”)2016—2022年肺结核患者不良转归的列线图预测模型,评价模型的预测效果和应用价值。方法:回顾性分析兵团2016—2022年肺结核患者的治疗转归情况。通过单因素log-rank检验及多因素Cox回归分析筛选变量并构建肺结核患者不良转归的预测模型,采用列线图对预测模型进行展示。采用区分度、校准度以及临床效益性评价模型的预测能力,采用Boostrap(B=1000)自抽样验证法对模型进行内部验证。结果:2016—2022年兵团肺结核患者不良转归率为5.07%(405/7993)。多因素Cox回归分析结果显示,少数民族(HR=1.382,95%CI:1.106~1.725),年龄在30~60岁(HR=1.535,95%CI:1.097~2.148)、>60岁(HR=2.895,95%CI:2.088~4.013),合并糖尿病患者(HR=1.753,95%CI:1.255~2.450),复治(HR=1.846,95%CI:1.400~2.434),现地址类型为本省其他地区(HR=1.430,95%CI:1.129~1.810)、外省(HR=1.596,95%CI:1.186~2.147),无基层管理(HR=1.385,95%CI:1.132~1.694),现管理地区为南疆(HR=1.276,95%CI:1.017~1.600)是影响肺结核患者治疗转归的危险因素。据此构建兵团肺结核患者发生不良转归的列线图预测模型,模型的受试者工作特征曲线下面积为0.697(95%CI:0.633~0.761),校正曲线与理想曲线总体走势较为一致。结论:本研究构建的列线图预测模型具有良好的预测价值,能够帮助临床决策者快速识别患者中高危人群并且进行个性化管理,及时规避风险从而提高患者的治疗成功率。

重型颅脑损伤患者胃肠功能衰竭风险预测模型的建立

目的建立重型颅脑损伤(sTBI)患者胃肠功能衰竭风险预测模型,并进行验证。方法选择2019年1月至2023年3月达州市中西医结合医院神经外科接诊的147例sTBI患者资料进行分析。收集可能影响sTBI患者胃肠功能衰竭的相关因素,根据急性胃肠道损伤(AGI)分级将患者分为胃肠功能衰竭组与非胃肠功能衰竭组,以LASSO筛选出潜在影响因素后行多因素Logistic回归分析,根据多因素分析结果建立列线图模型并进行验证。结果本研究模型组102例sTBI患者中共有33例(32.35%)出现胃肠功能衰竭,多因素Logistic回归分析结果显示:机械通气情况、休克、通便措施、肺部感染情况、血钠、人肠脂肪酸结合蛋白(iFABP)、D-乳酸及二胺氧化酶(DAO)为sTBI患者胃肠功能衰竭的独立性影响因素(P<0.05)。ROC分析显示模型组曲线下面积(AUC)为0.942,95%CI为0.896~0.988;验证组AUC为0.908,95%CI为0.849~0.966。校准曲线结果显示,预测曲线与标准曲线基本拟合。决策曲线分析结果显示,当列线图模型预测sTBI患者胃肠功能衰竭风险的概率阈值为0.10~0.90时,患者的净收益率大于0。结论sTBI患者胃肠功能衰竭主要受机械通气情况、休克、通便措施等相关因素的影响,本研究基于上述因素建立的列线图预测模型用于预测sTBI患者胃肠功能衰竭具有较高的准确度与区分度。

多级边坡地震稳定性拟静力极限上限分析

基于极限分析上限定理,结合非线性Mohr-Coulomb破坏准则,运用地震拟静力分析方法,构建三级边坡在地震效应影响下对数螺旋线破坏极限分析模型,并推导出边坡安全系数计算方程。通过MATLAB编程计算,采用序列二次规划方法优化求解,分析了地震效应下多种因素对多级边坡稳定性的影响。研究结果表明,边坡坡角和台阶宽度是影响地震作用下多级边坡稳定性的重要因素,为提高地震区域的边坡稳定性,应合理设置边坡台阶宽度并放缓坡角;地震效应对边坡稳定性的影响在非线性条件下更符合工程实际,非线性系数m的增加将降低边坡稳定性;水平地震效应明显影响边坡稳定性,随着水平地震系数kh的增大,边坡安全系数FS显著减小,且减小速率逐渐加快;同时当地震效应比例系数λ越大,即竖向地震作用越大时,边坡在水平和竖向地震效应作用下更易失稳。因此,进行多级边坡工程设计时有必要同时考虑水平地震效应和竖向地震效应。

三相电压型VIENNA整流器建模及稳定性分析

基于电动汽车直流充电桩的VIENNA型前级整流电路,提出采用小信号方法对VIENNA整流器进行建模。该方法首先通过采用局部线性化技术和状态空间平均法推导dq0坐标系下VIENNA整流器的数学模型,得出相关传递函数矩阵,即VIENNA整流器小信号线性化模型,进而用于控制器的设计;然后,采用频域法分别对电压环、电流环进行设计,利用频域法及根轨迹曲线详细分析各项参数对系统的影响,并利用曲线拟合的方式给出了系统稳定域随各项参数变化的曲线;最后,在实验中验证所提方法的正确性。

中医疗法对慢性心力衰竭患者利尿剂抵抗的影响

目的探讨中医疗法对慢性心力衰竭患者利尿剂抵抗的影响,为该病患者利尿剂抵抗的预防及诊疗提供参考。方法回顾性收集2020年1月—2022年12月在上海市浦东新区光明中医医院住院的慢性心力衰竭患者资料,将患者分为发生利尿剂抵抗组和未发生利尿剂抵抗组,比较2组一般资料、中医治疗情况,采用Lasso回归和Logistic回归分析中医疗法预防利尿剂抵抗的效果及影响因素。结果符合入组标准慢性心力衰竭患者419例,其中发生利尿剂抵抗组154例,未发生利尿剂抵抗组265例,2组均使用中西医标准治疗。2组患者使用中药涂擦、耳针疗法、灸法、手指点穴、穴位敷贴、中药包熨烫和中医定向透药疗法的比例差异均有统计学意义(P均<0.05),应用耳穴压丸、推拿和中药塌渍疗法的比例差异均无统计学意义(P均>0.05)。Logistic回归(模型3)分析结果显示,中药涂擦(OR=0.608,95%CI:0.377~0.979)、耳针疗法(OR=0.458,95%CI:0.268~0.782)、灸法疗法(OR=0.621,95%CI:0.403~0.956)、手指点穴疗法(OR=0.624,95%CI:0.405~0.962)、穴位敷贴疗法(OR=0.612,95%CI:0.399~0.938)、中药包熨烫疗法(OR=0.599,95%CI:0.373~0.961)和中医定向透药疗法(OR=0.552,95%CI:0.349~0.873)是利尿剂抵抗发生的保护因素,与模型1和模型2结果一致。结论中医疗法能够有效预防慢性心力衰竭患者利尿剂抵抗的发生,应积极发挥中医优势,为慢性心力衰竭的临床研究提供循证医学证据。

心力衰竭患者营养不良危险因素的Meta分析

目的:通过Meta分析探讨心力衰竭患者营养不良的危险因素。方法:计算机检索PubMed、Embase、Web of Science、Cochrane Library、CINAHL、MEDLINE、维普期刊数据库、万方数据库、中国知网以及中国生物医学文献数据库,检索时限为建库至2023年7月,采用RevMan 5.4软件进行Meta分析。结果:共纳入17篇文献,纳入样本量累计5883例,其中营养不良患者2591例(45.3%),共包含12项危险因素,1项保护因素,Meta分析结果显示,年龄增长、无配偶、月收入<3000元、NYHA分级为Ⅲ级及以上、吸烟、水肿、合并慢性阻塞型肺疾病、合并糖尿病、BNP值或NT-ProBNP值增高、血红蛋白含量降低、血清总蛋白<60 g/L为心力衰竭患者营养不良的危险因素(P<0.05),服用ACEI/ARB为心力衰竭患者营养不良的保护因素(P<0.05)。结论:心力衰竭患者营养不良的危险因素较多,护理人员可依据上述的危险因素,识别易发生营养不良的患者,尽早进行营养支持,改善患者预后,提高其生活质量。

温压耦合作用下锚固界面变形失效机理

深部地层高地温、高地应力环境使巷道围岩树脂锚固支护结构稳定性降低,围岩变形有效控制问题亟待解决。因此,研究温度与压力耦合作用下锚杆杆体-树脂锚固剂界面变形破坏机理十分必要。首先,根据两淮矿区深部支护工程现状并结合室内不同温度环境下拉拔试验结果,发现高地温环境下树脂锚固体变形破坏加剧;进一步分析锚固体受拉拔荷载作用轴向、径向破坏模式,将第一锚固界面破坏分为弹性围岩-剪切-滑移型、未贯穿-剪胀滑移破坏及贯穿-剪胀滑移破坏等3种模式。其次,基于弹塑力学分析受围岩应力作用锚固界面不同破坏类型的界面受力状态,考虑高温环境下树脂锚固剂层力学强度弱化,建立温度-围岩应力耦合作用的第一界面失效破坏力学计算模型;分析围岩应力、环境温度及弹性模量比等因素变化对第一界面锚固性能影响的规律,发现第一界面极限轴向荷载随温度升高而降低,围岩处于裂隙发育或裂隙贯穿状态时,围岩应力对第一锚固界面剪切破坏影响程度较未产生裂隙时大幅度增高。最后,结合室内拉拔试验数据对比验证所推导计算方程式的合理性。研究可为深部巷道围岩稳定性控制及锚固支护参数设计提供理论依据。

基于HFACS的核电厂调试人因事件分析

核电厂调试是电厂运行的前一阶段,旨在验证全厂设备符合运行要求。人因失效会严重影响调试的安全可靠性,对调试人因事件进行分析可帮助识别诱发人因失效的潜在因素,从而为调试安全质量管理提供指导。基于领域专家判断,修改并建立针对调试的人因分析与分类系统(HFACS),并由5位领域专家应用该系统对127起人因事件进行分析编码。研究所获频率统计结果与核电厂运行事件分析结果的对比表明,调试和运行作为两种不同的电厂阶段,在监督管理、失误类型上存在共性,在组织影响、不安全行为的前提条件及人员违规上存在差异。通过相关性分析,研究识别出与人因失效具有显著关联的若干因素,调试作业的管理可通过控制这些因素来减少人因失效的发生。

老年心力衰竭病人衰弱危险因素的Meta分析

目的:通过Meta分析明确老年心力衰竭病人衰弱的危险因素,为后期老年心力衰竭病人衰弱的干预提供科学依据。方法:系统检索PubMed、CINAHL、Web of Science、the Cochrane Library、中国知网、万方数据知识服务平台、维普网,纳入关于老年心力衰竭病人衰弱危险因素的研究,检索时间限定为建库至2023年2月28日。由2名系统评价研究员严格按照纳入和排除标准独立筛选文献、评价纳入研究的偏倚风险以及提取数据资料,由第三方对研究分歧进行判断,采用RevMan 5.3软件进行Meta分析。结果:最终纳入16篇文献,其中1篇病例对照研究,15篇横断面研究。心力衰竭病人合计3 622例,其中衰弱病人2 401例,涉及影响因素10个。Meta分析结果显示,老年心力衰竭病人衰弱发生率为63%[95%CI(0.53,0.73),P<0.001],老年心力衰竭病人衰弱的危险因素为年龄[OR=1.14,95%CI(1.04,1.25),P<0.01]、心功能分级[OR=2.70,95%CI(1.57,4.64),P<0.01]、多重用药[OR=2.40,95%CI(1.42,4.04),P<0.01]、左心房内径[OR=2.05,95%CI(1.91,2.20),P<0.01]。敏感性分析显示,血肌酐、射血分数、共病指数及血红蛋白在两种模型下合并效应量有变化,存在发表偏倚。结论:老年心力衰竭病人的衰弱发生率较高,影响因素较多。应针对衰弱相关危险因素进行早期评估与干预,以减少衰弱对心力衰竭病人的不良影响,提高心力衰竭病人生活质量。

美国在1979年伊斯兰革命中的情报失误及其启示

[研究目的]研究1979年伊斯兰革命过程中美国情报工作的失误表现与成因能够为中国在对外事务研判和情报分析等方面提供更多借鉴和参考。[研究方法]主要使用文献分析法对美国相关外交档案展开梳理,从情报周期的各个阶段展开分析,系统梳理事前威胁研判、情报搜集和情报分析、情报分发等多个环节的失误成因和内在的逻辑关系。[研究结论]美国在这次伊朗国内政局变动中存在情报失误的情况,启示我们应提升战略情报预警能力,及时研判风险等级,情报消费者也应该注重保持中立,不断优化情报分发机制,才能避免类似失误。

钢渣磨细粉对沥青胶浆及混合料性能的影响

为探究钢渣磨细粉(SSFP)对沥青胶浆及其混合料性能的影响,使用粒径小于5 mm的钢渣制备SSFP。以石灰岩矿粉(LP)作为对照,对不同粉胶比(F/A)下SSFP沥青胶浆的性能进行了分析和评价,并探究了SSFP对沥青混合料性能的影响。结果表明:相较于LP,SSFP对沥青胶浆及混合料的高、低温及疲劳性能均有所提升,其中低温性能提升幅度最大,SSFP沥青胶浆的蠕变劲度模量提升了190.57%,SSFP沥青混合料的低温弯曲破坏应变提升了9.93%;增大F/A可提升沥青胶浆的高温性能,但会损伤其疲劳性能和低温性能;SSFP应用于沥青混合料中具备较强的可行性和推广价值。