Effect of smoking on the risk of gastrointestinal cancer after cholecystectomy: A national population-based cohort study

BACKGROUND The role of smoking in the incidence of colorectal cancer(CRC)or gastric cancer(GC)in populations undergoing cholecystectomy has not been investigated.AIM To evaluate the effect of smoking on CRC or GC development in cholecystectomy patients.METHODS A total of 174874 patients who underwent cholecystectomy between January 1,2010 and December 31,2017 were identified using the Korean National Health Insurance Service claims database.These patients were matched 1:1 with mem-bers of a healthy population according to age and sex.CRC or GC risk after cholecystectomy and the association between smoking and CRC or GC risk in cholecystectomy patients were evaluated using adjusted hazard ratios(HRs)and 95%CIs.RESULTS The risks of CRC(adjusted HR:1.15;95%CI:1.06-1.25;P=0.0013)and GC(adjusted HR:1.11;95%CI:1.01-1.22;P=0.0027)were significantly higher in cholecystectomy patients.In the population who underwent cholecystectomy,both CRC and GC risk were higher in those who had smoked compared to those who had never smoked.For both cancers,the risk tended to increase in the order of non-smokers,ex-smokers,and current smokers.In addition,a positive correlation was observed between the amount of smoking and the risks of both CRC and GC.CONCLUSION Careful follow-up and screening should be performed,focusing on the increased risk of gastrointestinal cancer in the cholecystectomy group,particularly considering the individual smoking habits.

Optimal Insurance with Background Risk under the Ambiguity and Belief Heterogeneity Structure

In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.

Understanding Dependent Competing Risks： A Simulation Study to Illustrate the Relationship Between Cause-Specific Hazard and Marginal Hazard

In the analysis of competing risk data, the observed effect of a covariate can be obtained via a Fine and Gray sub-distribution hazard ratio. Sometimes, it is also desirable to obtain the virtual effect of a covariate as if the competing risks were non-existent. Under the latent failure time scenario, when the event of interest and the competing risk event are independent, the cause-specific hazard ratio obtained from the Cox model where the competing events are censored represents the ratio of the marginal hazards and can be interpreted as the virtual effect of the covariate. However, when the two events are not independent, the cause-specific hazard ratio is not the ratio of the marginal hazards as the ratio depends not only on the marginal hazards but also on the correlation between the competing risk and the event of interest. Using simulation, we investigated the degree to which the cause-specific hazard ratio changes relative to the marginal hazard with this correlation. It was found that the discrepancy between the cause-specific hazard ratio and the theoretical marginal hazard ratio increased as the proportion of competing risk events and the correlation between the events increased （〉0.2）. Depending on the direction of the correlation, the cause-specific hazard ratio can over- or under-estimate the marginal hazard ratio. Using real-life datasets, we show how these results can be used to make inferences on the virtual effects.

Biomechanical Considerations in the Unruptured Cerebral Aneurysm Study (UCAS Japan): Rupture Risk and True Stress of Wall

When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.

The Cox Proportional Hazard Regression Model Vis-à-Vis ITN-Factor Impact on Mortality Due to Malaria

This study has provided a starting point for defining and working with Cox models in respect of multivariate modeling. In medical researches, there may be situations, where several risk factors potentially affect patient prognosis, howbeit, only one or two might predict patient’s predicament. In seeking to find out which of the risk factors contribute the most to the survival times of patients, there was the need for researchers to adjust the covariates to realize their impact on survival times of patients. Aside the multivariate nature of the covariates, some covariates might be categorical while others might be quantitative. Again, there might be cases where researchers need a model that has the capability of extending survival analysis methods to assessing simultaneously the effect of several risk factors on survival times. This study unveiled the Cox model as a robust technique which could accomplish the aforementioned cases. An investigation meant to evaluate the ITN-factor vis-à-vis its contribution towards death due to Malaria was exemplified with the Cox model. Data were taken from hospitals in Ghana. In doing so, we assessed hospital in-patients who reported cases of malaria (origin state) to time until death or censoring (destination stage) as a result of predictive factors (exposure to the malaria parasites) and some socioeconomic variables. We purposefully used Cox models to quantify the effect of the ITN-factor in the presence of other risk factors to obtain some measures of effect that could describe the relationship between the exposure variable and time until death adjusting for other variables. PH assumption holds for all three covariates. Sex of patient was insignificant to deaths due to malaria. Age of patient and user status were both significant. The magnitude of the coefficient (0.384) of ITN user status depicts its high contribution to the variation in the dependent variable.

动静组合加载条件下煤体失稳破坏能量阈值判定方法及工程应用

以某矿7305工作面地质及开采条件为研究背景,通过研究动静组合加载条件下煤体失稳破坏过程吸收能对煤体破裂的影响规律,提出利用吸收能比率ξ表征煤体存储能量的能力,进而确定动静载作用下煤体失稳破坏能量阈值,并利用该值提出了煤体冲击危险等级评价新方法,并在7305工作面进行工程现场验证,对比7305工作面CT反演监测结果,发现利用煤体失稳破坏能量阈值对7305工作面冲击危险区进行划分,效果较好,判定结果较为吻合。

月度防控视角下韩江下游城镇地质灾害危险性评价

华南山区地质环境条件复杂,地质灾害频发,亟需开展区域地质灾害危险性评价,解决“地质灾害最可能发生月度及相应易发区在哪里”的问题,以针对性地分级、分阶段部署相应防控措施,有效降低地质灾害可能造成的损失。以韩江下游广东省梅州市留隍镇为例,选取坡度、坡形、高程、工程地质岩组、土层厚度、距断裂距离、植被NDVI值与用地类型共8个评价指标,通过灾害频率比(FR)模型对指标分级赋值;采用灰色关联度法计算指标权重,结合信息量模型完成研究区地质灾害易发性评价,并通过ROC曲线对结果进行验证;在易发性评价的基础上,将月度作为最小时间评价尺度,以历史发灾记录最大月均降雨量作为激发极值优化降雨假设模型,计算1~12月地质灾害发生概率,并完成各月度地质灾害危险性评价及分区。结果表明:①总体上,留隍镇地质灾害共划分为低易发区、中易发区、高易发区、极高易发区4类易发区,各区面积占比分别为58.60%,22.99%,13.39%,5.02%,经ROC曲线检验评价精度达到0.81,表明评价结果客观有效。②月度地质灾害危险性评价结果显示,5~8月留隍镇地质灾害发生概率最大,建议将其作为全年重点防御时段;且集中分布于留隍镇北部、中部及南部,建议将上述区域作为重点防御区。研究成果可为研究区域年内不同月度地灾防控工作安排及防控措施动态调整提供参考。

青海省湟水流域潜在地质灾害识别与易发性评价

[目的]明确青海省湟水流域地质灾害空间分布特征与规律,为该地区防灾减灾提供数据支撑与科学依据。[方法]通过小基线子集干涉测量(small baseline subset interferometric synthetic aperture radar,SBAS-InSAR)技术识别地质灾害点,结合地形因素、地质因素、环境因素、气象因素、人类活动因素进行灾害空间分布规律分析,建立逻辑回归(logistic regression,LR)—频率比(frequency response,FR)模型并检验,利用返回概率值进行易发性评价。[结果]①湟水流域所分布的潜在地质灾害以滑坡、崩塌为主,多种类型潜在地质灾害并生。滑坡与不稳定斜坡通常发育于坡度较缓的山坡上,通常伴有大量张拉与剪切裂缝,尤其在雨季发育明显,对山体下方交通、居民安全构成威胁。发育于河谷两岸的滑坡与不稳定斜坡还可能阻塞河流,形成堰塞湖,进一步加剧灾害风险。崩塌多发育在岩石结构较为疏松或风化严重的陡峭山壁,因地质脆弱,加之降雨等自然因素刺激,易使山体土块、岩石块下落,对下方的居民区和交通线路构成威胁。②研究区2425—3650 m高程区间的地质灾害分布较多,东北向为地质灾害易发坡向;地质灾害易发性随归一化植被指数(normalized digital vegetation index,NDVI)增加而降低,随坡度、地形起伏度、日降水量增加而升高,随距断层距离增加而减少。③湟水流域高易发区及较高易发区,面积约5937.60 km 2,占研究区总面积约38.78%,主要集中在湟水流域南、北边缘地区,湟中、大通、海晏交界处,以及建筑区周边边坡上。④对评价结果进行检验,模型预测性能受试者特征曲线(receiver operating characteristic curve,ROC曲线)线下面积(area under curve,AUC)为0.787,易发区由高至低FR逐级减小,与实际灾害点的分布具有良好的一致性。⑤断层核密度为湟水流域地质灾害发育的主控因子,坡向、地形起伏度、道路核密度次之,剖面曲率对地质灾害发育影响最小。[结论]①利用SBAS-InSAR技术能有效识别湟水流域潜在地质灾害,LR-FR模型获得的易发性评价结果可靠。②湟水流域地质灾害易发区的分布具有明显的空间差异性,主要分布在海拔较高、植被覆盖率较低、降雨量较大、距离断层近的地区,断层核密度为地质灾害易发性的主控因子。③湟水流域的地质灾害具有多发性、突发性和高风险性的特点,给当地居民生活、区域经济发展及生态环境带来了严重的影响。因此,对其进行监测、预警和防治工作显得尤为重要。

Expression patterns of cluster of differentiation 147 impact the prognosis of hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)has very low overall survival.According to global cancer statistics,approximately 905677 new cases were reported in 2020,with at least 830180 of them being fatal.Cluster of differentiation 147(CD147)is a novel,transmembrane glycoprotein that is expressed in a wide variety of tumor cells and plays an important role in various stages of tumor development.Based on the reports described previously,we theorize that CD147 may be used as a novel biological indicator to predict the prognosis of HCC.To study this possibility,expression profiles of CD147 and corresponding clinical data from The Cancer Genome Atlas(TCGA)and Gene Expression Omnibus(GEO)databases were analyzed,and a hazard ratio(HR)was established.AIM To explore the pattern of CD147 expression and its applicability in the prognosis of HCC.To establish HRs and probability points for predicting the prognosis of HCC by correlating CD147 expression with clinical characteristics.To determine if CD147 can be a reliable biomarker in HCC prognosis.METHODS The CD147 expression profile in HCC and corresponding clinical data were obtained from TCGA database.The expression patterns of CD147 were then validated by analyzing data from the GEO database.In addition,CD147 immunohistochemistry in HCC was obtained from the Human Protein Atlas.CD147 expression patterns and clinical characteristics in the prognosis of HCC were analyzed by accessing the UALCAN web resource.Accuracy,sensitivity,and specificity of the CD147 expression profile in predictive prognosis were determined by the time-dependent receiver operating characteristic(ROC)curves.Kaplan-Meier curves were plotted to estimate the HR of survival in HCC.Univariate and multivariate Cox regression proportional hazards analyses of CD147 expression levels and clinical characteristics as prognostic factors of HCC were performed.Nomograms were used to establish probability points and predict prognosis.RESULTS Data from TCGA and GEO databases revealed that CD147 was significantly overexpressed in HCC(P=1.624×10^(-12) and P=1.2×10^(-5),respectively).The expression of CD147 and prognosis of HCC were significantly correlated with the clinical characteristics of HCC as per the data from the UALCAN web resource(P<0.05).Kaplan-Meier analysis of CD147 expression in HCC revealed that the high expression groups showed poor prognosis and an HR of survival>1[log-rank test,P=0.000542,HR(in high expression group):1.856,95%confidence interval(CI):1.308 to 2.636].ROC curves were plotted to analyze the 1-year,3-year,and 5-year survival rates.The area under the ROC curve values were 0.675(95%CI:0.611 to 0.740),0.623(95%CI:0.555 to 0.692),and 0.664(95%CI:0.582 to 9.745),respectively.Univariate Cox analysis of CD147 expression and clinical characteristics of HCC and multivariate Cox analysis of CD147 patterns and pathological tumor-node-metastasis stage showed significant differences(univariate Cox,P=0.00013,HR:1.424,95%CI:1.884 to 1.707 and P=0.00066,HR:1.376,95%CI:1.145 to 1.654,respectively;multivariate Cox,P=0.00578,HR:1.507,95%CI:1.126 to 2.018 and P=0.00336,HR:1.443,95%CI:1.129 to 1.844,respectively).Nomograms were plotted to establish the probability points and predict prognosis.The total points ranged from 0 to 180,and the C-index value was 0.673(95%CI:0.600 to 1.000,P<0.01).CONCLUSION Overexpression of CD147 was correlated with poor prognosis in HCC.The CD147 expression profile combined with clinical characteristics can reliably predict the prognosis of HCC.CD147 can serve as a biomarker to predict the prognosis of HCC.

A Systematic Review and Meta-Analysis of Randomized Control Trials to Check Role of Non-Steroidal Anti-inflammatory Drugs as Protective Factor in Alzheimer Disease Subjects

Background: Alzheimer’s disease is the major neurodegenerative disease, affecting more than two third cases of dementia in the world. NSAIDs are widely used anti-inflammatory analgesic agents representing 7.7% of worldwide prescriptions of which 90% are in patients over 65 years old. Based on mixed findings observed by different RCTs, a systematic review and meta-analysis were conducted to develop a better understanding of the protective role of Non-steroidal anti-inflammatory drugs (NSAIDs) in AD. Methods: Database search was Pubmed, WebScience, and Embase. RCTs investigating the effect of NSAIDs on AD or test scores assessing cognitive function in people without AD at baseline were included. Three indicators were MMSE Score, ADAS-cog score, and CDR-sob. 10 studies were included in the present Meta-analysis. Results: For the ADAS-cog score, the pooled effect size was -0.31 with 95% CI -0.06 to 0.02, which was statistically significant (p = 0.03). MMSE score difference, the pooled effect size was -0.06 with 95% CI -0.22 to 0.10, which was statistically insignificant (p-value = 0.47). For the MMSE average score, the pooled effect size was -0.002 with 95% CI -0.03 to 0.07, which was statistically insignificant (p-value = 0.87). For the CDR-sob score difference, the pooled effect size calculated using the random effect model was -0.06 with 95% CI -0.39 to 0.05 which was statistically insignificant (p = 0.14). For CDR-sob average score, the pooled effect size calculated using the random effect model was 0.21 with 95% CI -0.09 to 0.51, which was statistically insignificant (p-value = 0.17). Conclusion: Present Meta-analysis shows that NSAIDs in general are not effective in the treatment of AD. They also have no protective effect against the development of AD on their sustained use.

Meta-analysis of outcomes from drug-eluting stent implantation in infrapopliteal arteries

BACKGROUND Percutaneous drug-eluting stent implantation(DESI)is an emerging and promising treatment modality for infrapopliteal artery diseases(IPADs).This systematic review and meta-analysis summarizes and quantitatively analyzes the outcomes of DESI in IPADs considering the hazard ratio(HR),which is a more accurate and appropriate outcome measure than the more commonly used relative risk and odds ratio.AIM To explore the superiority of drug-eluting stents(DESs)vs traditional treatment modalities for IPADs.METHODS The following postoperative indicators were the outcomes of interest:All-cause death(ACD)-free survival,major amputation(MA)-free survival,target lesion revascularization(TLR)-free survival,adverse event(AE)-free survival,and primary patency(PP)survival.The outcome measures were then compared according to their respective HRs with 95%confidence intervals(CIs).The participants were human IPAD patients who underwent treatments for infrapopliteal lesions.DESI was set as the intervention arm,and traditional percutaneous transluminal angioplasty(PTA)with or without bare metal stent implantation(BMSI)was set as the control arm.A systematic search in the Excerpta Medica Database(Embase),PubMed,Web of Science,and Cochrane Library was performed on November 29,2022.All controlled studies published in English with sufficient data on outcomes of interest for extraction or conversion were included.When studies did not directly report the HRs but gave a corresponding survival curve,we utilized Engauge Digitizer software and standard formulas to convert the information and derive HRs.Then,meta-analyses were conducted using a random-effects model.RESULTS Five randomized controlled trials and three cohort studies involving 2639 participants were included.The ACDfree and MA-free survival HR values for DESI were not statistically significant from those of the control treatment(P>0.05);however,the HR values for TLR-free,AE-free,and PP-survival differed significantly[2.65(95%CI:1.56-4.50),1.57(95%CI:1.23-2.01),and 5.67(95%CI:3.56-9.03),respectively].CONCLUSION Compared with traditional treatment modalities(i.e.,PTA with or without BMSI),DESI for IPADs is superior in avoiding TLR and AEs and maintaining PP but shows no superiority or inferiority in avoiding ACD and MA.

川藏交通廊道崩滑灾害分布及其危险性评价

川藏交通廊道雅安到林芝段位于青藏高原东南部,沿线地质条件复杂、河流切割强烈、地质环境脆弱、新构造运动活跃,具有山高谷深、坡体稳定性差等特点,是我国崩滑灾害最发育、危害最严重的地区之一。为了保障廊道内相关工程的顺利建设和后期安全运营,本文以线路两侧一级分水岭为界,通过遥感解译和野外调查,获得川藏交通廊道雅安—林芝段崩滑灾害共4509处,在此基础上,选取高程、坡度、坡向、工程地质岩组、断裂、水系、公路、地震动峰值加速度、降雨共9个因子分析了灾害的空间分布规律及发育特征,建立了频率比法与逻辑回归方法耦合模型,并运用到高原山区重大交通廊道崩滑灾害危险性评价中。研究结果表明:(1)廊道沿线各县区段的崩滑灾害面密度在空间上总体呈从西向东递减的趋势。(2)有利于灾害发生的条件分别是:高程1~4 km,坡度大于20°,S、SW和W坡向,较软弱、较坚硬和坚硬岩组,距断裂6.4 km范围内,距水系3.2 km范围内,距公路800 m范围内,地震动峰值加速度0.20g,年均降雨量大于1100 mm。(3)将研究区危险性等级划分为极低危险(18.64%)、低危险(26.18%)、中等危险(24.75%)、高危险(19.82%)、极高危险(10.61%)5级,其中:极高危险区与高危险区主要分布在断裂附近和坡度较陡的区域。(4)耦合模型的AUC值达到了0.737,优于单一的频率比模型的0.712,表明耦合模型的评价结果具有更高的精度。该研究可为川藏交通廊道雅安到林芝段相关工程的规划、建设和未来运营过程中的防灾减灾工作提供重要参考。

基于贝叶斯Cox回归模型分析耐多药肺结核患者死亡的影响因素

目的:耐多药肺结核(multidrug-resistant tuberculosis,MDR-TB)具有较高的病死率,一直以来都是全球结核病防控工作的难点之一。分析MDR-TB患者不良结局的影响因素有助于改善MDR-TB患者的程序化管理,优化MDR-TB的治疗策略。在分析随访数据时,Cox比例风险回归模型是一种重要的多因素分析方法,但其存在较大的应用局限性,如难以处理样本量小等实际问题对模型的影响。基于此,本研究分别采用贝叶斯Cox回归模型和常规Cox回归模型,分析MDR-TB患者在抗结核治疗期间死亡的影响因素,并比较这2种方法在应用中的差异。方法:数据资料来自2017年11月1日至2021年3月31日在兰州市肺科医院接受治疗的388例MDR-TB患者。采用生存分析方法分析MDR-TB患者在治疗期间的死亡情况及其影响因素。分别构建常规Cox回归模型和贝叶斯Cox回归模型来估计MDR-TB患者死亡影响因素的风险比(hazard ratio,HR)及其95%置信区间(95%confidence interval,95%CI),模型的参数估计可靠性通过各自变量的参数标准差和HR值的95%CI来判断,参数标准差和95%CI范围越小,模型的估计结果越可靠。结果:纳入研究的388例MDR-TB患者的生存时间为10.18(4.26,18.13)个月,最长生存时间为31.90个月。观察期间共有12例因肺结核死亡,病死率为3.1%,死亡患者的生存时间为4.78(2.63,6.93)个月。50%的死亡患者出现在抗结核治疗的前5个月,最后一个死亡患者出现在治疗的第13个月。常规Cox回归模型分析结果显示:有合并症的患者死亡风险约为无合并症者的6.96倍(HR=6.96,95%CI 2.00~24.24;P=0.002);接受定期随访患者的死亡风险比未接受定期随访患者降低约81%(HR=0.19,95%CI 0.05~0.77;P=0.020)。贝叶斯Cox回归模型中,各参数的迭代历史图和BGR图(Blue/Green/Red plot)均提示模型的收敛效果良好,其参数估计结果显示:首次痰培养结果阳性的患者死亡风险低于阴性患者(HR=0.33,95%CI 0.08~0.87);相对于无合并症患者,有合并症患者的死亡风险提高了约6.80倍(HR=7.80,95%CI 1.90~21.91);与未接受定期随访者相比,接受定期随访的患者死亡风险降低了90%(HR=0.10,95%CI 0.01~0.30)。2个模型的结果比较显示:贝叶斯Cox模型中除接受定期随访参数的标准差(贝叶斯模型为0.77;常规模型为0.72)和肺部空洞参数的标准差(贝叶斯模型为0.73;常规模型为0.73)不小于常规模型外,其他参数的标准差和对应HR的95%CI均明显小于常规模型。结论:抗结核治疗的第1年是MDR-TB患者死亡的高风险期。合并症是影响MDR-TB患者死亡的主要危险因素,而首次痰培养阳性、接受定期随访的患者死亡风险更小。在样本量较小且结局发生率较低的数据中贝叶斯Cox回归模型的参数估计较常规Cox模型更可靠。

基于频率比模型和随机森林模型耦合的地质灾害易发性评价

目前利用机器学习进行易发性评价时,非地质灾害单元通常是在研究区范围内随机选取,会导致部分非地质灾害单元落在潜在地质灾害单元之上,造成模型评价结果偏差,所以非地质灾害单元的有效选取成为当前易发性评价的难点问题。以浙江省长兴县李家巷镇为研究区,选取高程、坡度、坡向、剖面曲率、岩组、距水系距离、距断层距离、归一化植被指数和土地利用这9个环境因子作为评价指标,利用频率比模型(frequency radio,FR)进行非地质灾害单元的选取,然后选用随机森林模型(random forest,RF)进行地质灾害易发性评价,并与未经有效筛选非地质灾害单元的RF模型结果进行对比分析。结果表明,与RF模型相比,FR-RF模型的特异性(Specificity)提升了9.51%,说明对非地质灾害单元的预测能力显著提升,同时敏感性(Recall)提升了13.71%,说明对地质灾害单元的预测性能也大幅提升,受试者工作特征曲线下的面积(area under curve,AUC)和准确率(Accuracy)分别提高了6%、11.66%,模型整体性能及预测能力得到改进;地质灾害极高和高易发区主要分布于存在碎屑岩和坡度较大的区域,总面积为7.35 km 2,相较于RF模型结果,面积增加了25.98%,而极低和低易发区面积减少了16.7%;坡度、工程岩组是该研究区地质灾害的主控因素,相对重要性占比分别为37.7%和28.0%。

三种升温模式下钢构件火灾危险性分析

为了研究变电站中可能出现的标准火灾、电力火灾和碳氢火灾三种火灾模式对无防火保护钢构件的影响,首先使用自制的耐火实验炉对三种火灾升温模式下不同厚度钢板达到临界温度的时间进行了实验分析;然后采用ABAQUS软件对实验结果进行了模拟复现,并对不同升温模式下钢构件达到临界温度的时间与钢构件荷载比的关系进行了数值模拟。结果表明:标准火灾升温模式下钢构件达到临界温度的时间为16~23 min,电力火灾、碳氢火灾升温模式下钢构件达到临界温度的时间为2~6 min,电力火灾和碳氢火灾升温模式下钢构件达到临界温度的时间相对标准火灾升温模式有急剧缩短,平均缩短幅度超60%,最大幅度达86.3%;数值模拟结果显示电力火灾、碳氢火灾升温模式下钢构件荷载比大于0.70时其达到临界温度的时间均低于6 min,钢结构稳定性失效的危险性较大,且钢构件的荷载比越大其到达临界温度的时间越短,两者之间具有较强的线性关系。该研究结果对多种火灾升温模式下钢构件的防火保护设计具有一定的参考价值。

基于连续因子和非连续因子的山区崩滑流易发性研究

以祁连山东段北坡为研究区,基于区内390个崩滑流点,选择坡度、坡向、水流强度指数、道路、土地利用、断层等评价因子,结合因子剔除方法,应用改进频率比(连续因子计算)和证据权法(非连续因子计算)进行易发性评价,并用密度法和ROC曲线验证评价结果精度.结果表明,评价因子的筛选对易发性结果极为重要;不同因子组合下两种方法的易发性结果曲线下面积值均高于0.80;极低-低易发等级面积约占80%,高-极高易发等级面积约占6.5%,高-极高易发等级中崩滑流灾害点数量均超过64%,亟需加强区内地质灾害潜在风险转移研究.

蓝田县滑坡灾害易发性区划与评价

为了减少滑坡等地质灾害造成的人员伤亡和财产损失,对滑坡灾害易发性进行区划与评价。采用频率比法和加权信息量法,以地处秦岭北麓关中平原东南部的蓝田县为研究对象,选取高程、坡度、坡向、平面曲率、植被指数、地层岩性、距道路距离及距断层距离等作为滑坡的评价因子,并通过受试者工作特征(Receiver Operating Characteristic, ROC)曲线和密度法对上述两种方法的评价结果进行分析。结果表明,加权信息量法的评价结果优于频率比法,蓝田县的滑坡主要分布在高程500~1 000 m,坡度10°~20°,偏南坡向,曲率在-2~2范围内白鹿黄土塬沿边坡地和骊山黄土丘陵地区。随着归一化植被指数的增大和距断层距离减小,滑坡灾害的数量逐渐增多,滑坡中高易发区主要分布在西北部人为活动密集的地区。

涂装中面涂水性废溶剂回收利用效益分析

在水性3C2B喷涂工艺下,中涂、色漆机器人生产喷涂过程中需频繁调用设定好的清洗程序,产生大量水性危废,危废处理成本高。通过引入基于浓度检测技术的膜分离工艺设备,处理机器人清洗排放的水性废液,实现了溶剂、水的回收再利用和减排。

生存分析资料进行Meta分析时所需主要结局指标的换算方法

生存资料的Meta分析越来越多,但是大部分原始文献并没有全面报告实际死亡数(O)、理论死亡数(E)、风险比(HR)及其方差(V),本文总结了O-E、HR和V等指标的多种转换公式。希望研究者能够灵活应用这些公式计算生存资料Meta分析的必备指标,并采用HR进行生存资料的Meta分析。

中国老年人的躯体功能对死亡风险的影响

健康受到生理的、心理的以及社会的多种因素的综合影响。在世界人口老龄化日趋严峻的背景下,研究老年人特别是研究老年人口众多的中国老年人的健康状况和死亡风险及其影响因素具有重要的现实意义。通过分析全国老年人口健康状况调查(CLHLS)2002-2011年纵向数据,建立Cox等比例风险模型,研究发现了中国老年人的躯体功能对死亡风险有显著的影响,ADL、IADL和LOA/LOM好的老年人比差的老年人的死亡风险分别低了25%、18%和5%;另外,慢性病、性别、年龄、民族、城乡与区域、职业地位和主要收入来源、活动参与和生病照料者也对死亡风险有显著的影响。