目的慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)合并呼吸衰竭是老年人常见病和多发病,严重影响老年人生活质量及生命健康。本研究分析老年COPD合并呼吸衰竭的相关危险因素,为临床预防及治疗提供依据。方法选择2016-...目的慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)合并呼吸衰竭是老年人常见病和多发病,严重影响老年人生活质量及生命健康。本研究分析老年COPD合并呼吸衰竭的相关危险因素,为临床预防及治疗提供依据。方法选择2016-03-15-2018-04-30广饶县大码头中心卫生院接收的84例COPD合并呼吸衰竭老年患者作为病例组,同时选取84例单纯COPD老年患者作为对照组。分析两组患者一般资料、肺功能指标、动脉血气指标以及降钙素原水平差异,采用多因素Logistic回归分析,明确COPD合并呼吸衰竭的影响因素。结果两组患者年龄(t=1.793,P=0.075)、体质量指数(t=0.240,P=0.811)和吸烟(χ2=2.885,P=0.089)比较,差异无统计学意义;病例组病程≥10年61例(72.62%),高于对照组的48例(57.14)%,差异有统计学意义,χ2=4.415,P=0.036。病例组动脉血氧分压(arterial oxygen partial pressure,PaO2)水平为(53.77±4.98)mm Hg,低于对照组的(64.10±4.58)mm Hg,t=13.981,P<0.001;病例组第1秒用力呼气容积(forced expiratory volume in the first second,FEV1)水平为(2.16±0.12)L,低于对照组的(2.67±0.18)L,t=21.073,P<0.001;病例组二氧化碳分压(partial pressure of carbon dioxide,PaCO2)水平为(55.48±5.37)mm Hg,高于对照组的(46.94±3.04)mm Hg,t=12.671,P<0.001;病例组降钙素原(procalcitionin,PCT)水平为(0.76±0.13)ng/mL,高于对照组的(0.57±0.09)ng/mL,t=11.208,P<0.001;病例组第1秒钟用力呼气容积占预计值百分比(forced expiratory volume%of predicted value in the first second,FEV1/FVC)为(58.24±2.62)%,与对照组的(58.56±2.11)%差异无统计学意义,t=0.616,P=0.539;病例组pH值为7.36±0.14,与对照组的7.35±0.12比较差异无统计学意义,t=0.351,P=0.726。Logistic多元回归分析结果显示,病程长(OR=1.989,95%CI为1.043~3.793,P=0.037)、PaCO2水平高(OR=0.643,95%CI为0.561~0.737,P<0.001)和PCT水平高(OR=0.980,95%CI为0.974~0.986,P<0.001)是影响老年COPD患者合并呼吸衰竭的独立危展开更多
A combination of experimental measurements and numerical analysis was utilized to study the low-velocity impact damage of domestic carbon fiber-reinforced composites(CFRCs).The results indicated that the low-velocity ...A combination of experimental measurements and numerical analysis was utilized to study the low-velocity impact damage of domestic carbon fiber-reinforced composites(CFRCs).The results indicated that the low-velocity impact damage induced pits and longitudinal cracks on the front side,oblique cracks and delaminationin on the back side.The pit depth increased with the increasing impact energy.It was demonstrated that the numerical analysis strain history curve was similar to the experimentally measured strain history curve,which verified the accuracy of numerical analysis in which the Hashin failure criterion was used.The work provides basic data and theoretical basis for the promotion and application of the domestic carbon fiber,and demonstrates the feasibility of replacing imported carbon fibers with domestic carbon fibers.展开更多
The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening. An experimental study on the hysteretic characteristics of prestressed co...The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening. An experimental study on the hysteretic characteristics of prestressed concrete frame beams under different loading histories was performed to explore the influence of load history on energy dissipation and failure characteristics of the member. Based on the test results, the failure of the beam is defined, and the relationship between the failure moment under cyclic load and from the skeleton curve is formulated. Finally, based on displacement and energy dissipation, a model for prestressed concrete beam damage-failure evaluation is developed. In this model, the effect of deformation level, cumulative dissipated energy, and loading history on prestressed concrete beam damage-failure is incorporated, thus it is applicable to stochastic earthquake forces.展开更多
Vibration failure of piping is a serious problem and a matter of concern for safety and reliability of plant operations. Fatigue is the main cause of such failures. Due to the complexity of the phenomenon no closed fo...Vibration failure of piping is a serious problem and a matter of concern for safety and reliability of plant operations. Fatigue is the main cause of such failures. Due to the complexity of the phenomenon no closed form design solutions are available. In our study an analytical technique based on the theory of vibrations in the time domain has been presented. Using the inverse theory, the problem has been reduced to a system of Volterra Integral equations to be solved simultaneously at every time step. The solution of the inverse problem may be used in the conventional method to calculate stresses and end reactions which are important from the perspective of engineering design and condition monitoring. The method is robust, simple and can be easily adopted by practicing engineers.展开更多
The recent proliferation of wind turbines has revealed problems in their vulnerability under different site conditions, as evidenced by recent collapses of wind towers after severe actions. Analyses of structures subj...The recent proliferation of wind turbines has revealed problems in their vulnerability under different site conditions, as evidenced by recent collapses of wind towers after severe actions. Analyses of structures subjected to variable actions can be conducted through several methods with different accuracy levels. Nonlinear dynamics is the most reliable among such methods. This study develops a numerical procedure to obtain approximate solutions for rigid-plastic responses of structures subjected to base harmonic pulses. The procedure's model is applied to a wind turbine tower subjected to inertial forces generated by harmonic ground acceleration, and failure is assumed to depend on the formation of shear hinges. The proposed approach provides an efficient representation of the post-elastic behavior of the structure, has a low computational cost and high effectiveness, and uses a limited number of mechanical parameters.展开更多
文摘目的慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)合并呼吸衰竭是老年人常见病和多发病,严重影响老年人生活质量及生命健康。本研究分析老年COPD合并呼吸衰竭的相关危险因素,为临床预防及治疗提供依据。方法选择2016-03-15-2018-04-30广饶县大码头中心卫生院接收的84例COPD合并呼吸衰竭老年患者作为病例组,同时选取84例单纯COPD老年患者作为对照组。分析两组患者一般资料、肺功能指标、动脉血气指标以及降钙素原水平差异,采用多因素Logistic回归分析,明确COPD合并呼吸衰竭的影响因素。结果两组患者年龄(t=1.793,P=0.075)、体质量指数(t=0.240,P=0.811)和吸烟(χ2=2.885,P=0.089)比较,差异无统计学意义;病例组病程≥10年61例(72.62%),高于对照组的48例(57.14)%,差异有统计学意义,χ2=4.415,P=0.036。病例组动脉血氧分压(arterial oxygen partial pressure,PaO2)水平为(53.77±4.98)mm Hg,低于对照组的(64.10±4.58)mm Hg,t=13.981,P<0.001;病例组第1秒用力呼气容积(forced expiratory volume in the first second,FEV1)水平为(2.16±0.12)L,低于对照组的(2.67±0.18)L,t=21.073,P<0.001;病例组二氧化碳分压(partial pressure of carbon dioxide,PaCO2)水平为(55.48±5.37)mm Hg,高于对照组的(46.94±3.04)mm Hg,t=12.671,P<0.001;病例组降钙素原(procalcitionin,PCT)水平为(0.76±0.13)ng/mL,高于对照组的(0.57±0.09)ng/mL,t=11.208,P<0.001;病例组第1秒钟用力呼气容积占预计值百分比(forced expiratory volume%of predicted value in the first second,FEV1/FVC)为(58.24±2.62)%,与对照组的(58.56±2.11)%差异无统计学意义,t=0.616,P=0.539;病例组pH值为7.36±0.14,与对照组的7.35±0.12比较差异无统计学意义,t=0.351,P=0.726。Logistic多元回归分析结果显示,病程长(OR=1.989,95%CI为1.043~3.793,P=0.037)、PaCO2水平高(OR=0.643,95%CI为0.561~0.737,P<0.001)和PCT水平高(OR=0.980,95%CI为0.974~0.986,P<0.001)是影响老年COPD患者合并呼吸衰竭的独立危
基金Funded by the Fundamental Research Funds for the Central Universities(No.2018IB001)and the National High-tech Research and Development Program of China(863 Program)(No.2013AA031306)。
文摘A combination of experimental measurements and numerical analysis was utilized to study the low-velocity impact damage of domestic carbon fiber-reinforced composites(CFRCs).The results indicated that the low-velocity impact damage induced pits and longitudinal cracks on the front side,oblique cracks and delaminationin on the back side.The pit depth increased with the increasing impact energy.It was demonstrated that the numerical analysis strain history curve was similar to the experimentally measured strain history curve,which verified the accuracy of numerical analysis in which the Hashin failure criterion was used.The work provides basic data and theoretical basis for the promotion and application of the domestic carbon fiber,and demonstrates the feasibility of replacing imported carbon fibers with domestic carbon fibers.
基金Science Foundation of Jiangsu Province for the scholar abroad Under Grant No. SJ200325
文摘The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening. An experimental study on the hysteretic characteristics of prestressed concrete frame beams under different loading histories was performed to explore the influence of load history on energy dissipation and failure characteristics of the member. Based on the test results, the failure of the beam is defined, and the relationship between the failure moment under cyclic load and from the skeleton curve is formulated. Finally, based on displacement and energy dissipation, a model for prestressed concrete beam damage-failure evaluation is developed. In this model, the effect of deformation level, cumulative dissipated energy, and loading history on prestressed concrete beam damage-failure is incorporated, thus it is applicable to stochastic earthquake forces.
文摘Vibration failure of piping is a serious problem and a matter of concern for safety and reliability of plant operations. Fatigue is the main cause of such failures. Due to the complexity of the phenomenon no closed form design solutions are available. In our study an analytical technique based on the theory of vibrations in the time domain has been presented. Using the inverse theory, the problem has been reduced to a system of Volterra Integral equations to be solved simultaneously at every time step. The solution of the inverse problem may be used in the conventional method to calculate stresses and end reactions which are important from the perspective of engineering design and condition monitoring. The method is robust, simple and can be easily adopted by practicing engineers.
文摘The recent proliferation of wind turbines has revealed problems in their vulnerability under different site conditions, as evidenced by recent collapses of wind towers after severe actions. Analyses of structures subjected to variable actions can be conducted through several methods with different accuracy levels. Nonlinear dynamics is the most reliable among such methods. This study develops a numerical procedure to obtain approximate solutions for rigid-plastic responses of structures subjected to base harmonic pulses. The procedure's model is applied to a wind turbine tower subjected to inertial forces generated by harmonic ground acceleration, and failure is assumed to depend on the formation of shear hinges. The proposed approach provides an efficient representation of the post-elastic behavior of the structure, has a low computational cost and high effectiveness, and uses a limited number of mechanical parameters.
