In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stre...In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.展开更多
Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state ...Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.展开更多
目的探讨人外周血早期中性粒细胞-淋巴细胞比值(neutrophil to lymphocyte ratio,NLR)、血小板-淋巴细胞比值(platelet to lymphocyte ratio,PLR)和中性粒细胞-淋巴细胞和血小板比值(neutrophils to lymphocytes and platelets ratio,N/...目的探讨人外周血早期中性粒细胞-淋巴细胞比值(neutrophil to lymphocyte ratio,NLR)、血小板-淋巴细胞比值(platelet to lymphocyte ratio,PLR)和中性粒细胞-淋巴细胞和血小板比值(neutrophils to lymphocytes and platelets ratio,N/LP)在重度创伤性颅脑损伤(severe traumatic brain injury,sTBI)患者早期结果中的预测价值。方法回顾性分析2014年6月-2016年12月中国医科大学第七临床学院神经外科收治的95例sTBI患者的临床资料。比较预后良好组(n=36)和预后不良组(n=59)患者的早期NLR、PLR和N/LP差异,分析影响预后相关危险因素并绘制森林图,采用多因素logsitic回归确定独立危险因素并构建临床预测模型;绘制出受试者工作特征曲线(receiver operating characteristic curve,ROC),分析并比较NLR、PLR和N/LP单独或联合其他指标构建出的不同临床预测模型的差异。结果sTBI预后良好组和预后不良组早期NLR、PLR和N/LP比较,差异均有统计学意义(P<0.05);多因素logsitic回归分析提示,年龄、入院格拉斯哥昏迷评分(Glasgow coma scale,GCS)、NLR、PLR和N/LP是影响sTBI患者早期结果的独立危险因素,差异有统计学意义(P<0.05)。根据多因素logstic回归分析构建出19个临床预后预测模型,其中NLR+PLR+N/LP及其联合指标(年龄和GCS)模型曲线下面积(area under curve,AUC)均高于同组其他模型,分别为0.912、0.935、0.933和0.954;Age+GCS+NLR+PLR+N/LP预测模型在所有组别中AUC最大,表明该模型预测患者预后的价值最高。结论NLR、PLR和N/LP的升高与sTBI不良预后相关;早期NLR、PLR及N/LP联合年龄和GCS评分在sTBI早期结果预测中具有重要价值。展开更多
基金The research work was financially supported by the National Natural Scientice Foundation of China(Grant No.10142001)by the Shandong Provincial Natural Scientice Foundation(Grant No.Y2006F46)
文摘In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.
基金This project is supported by Science and Technology Developing Foundation of Tianjin Higher Education (No.20030703).
文摘Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.
文摘目的探讨人外周血早期中性粒细胞-淋巴细胞比值(neutrophil to lymphocyte ratio,NLR)、血小板-淋巴细胞比值(platelet to lymphocyte ratio,PLR)和中性粒细胞-淋巴细胞和血小板比值(neutrophils to lymphocytes and platelets ratio,N/LP)在重度创伤性颅脑损伤(severe traumatic brain injury,sTBI)患者早期结果中的预测价值。方法回顾性分析2014年6月-2016年12月中国医科大学第七临床学院神经外科收治的95例sTBI患者的临床资料。比较预后良好组(n=36)和预后不良组(n=59)患者的早期NLR、PLR和N/LP差异,分析影响预后相关危险因素并绘制森林图,采用多因素logsitic回归确定独立危险因素并构建临床预测模型;绘制出受试者工作特征曲线(receiver operating characteristic curve,ROC),分析并比较NLR、PLR和N/LP单独或联合其他指标构建出的不同临床预测模型的差异。结果sTBI预后良好组和预后不良组早期NLR、PLR和N/LP比较,差异均有统计学意义(P<0.05);多因素logsitic回归分析提示,年龄、入院格拉斯哥昏迷评分(Glasgow coma scale,GCS)、NLR、PLR和N/LP是影响sTBI患者早期结果的独立危险因素,差异有统计学意义(P<0.05)。根据多因素logstic回归分析构建出19个临床预后预测模型,其中NLR+PLR+N/LP及其联合指标(年龄和GCS)模型曲线下面积(area under curve,AUC)均高于同组其他模型,分别为0.912、0.935、0.933和0.954;Age+GCS+NLR+PLR+N/LP预测模型在所有组别中AUC最大,表明该模型预测患者预后的价值最高。结论NLR、PLR和N/LP的升高与sTBI不良预后相关;早期NLR、PLR及N/LP联合年龄和GCS评分在sTBI早期结果预测中具有重要价值。
