To investigate the dynamic response problem of the double medium formed by the adherence of sprayed concrete and surrounding rock in the tunnel,a split Hopkinson pressure bar of 75 mm in diameter was adopted at the ag...To investigate the dynamic response problem of the double medium formed by the adherence of sprayed concrete and surrounding rock in the tunnel,a split Hopkinson pressure bar of 75 mm in diameter was adopted at the ages of 3,7 and 10 d.Experimental results showed that dynamic compressive strength and dynamic increase factors(DIF)of the combined bodies increase with the strain rate.With the growth of strain rate,the critical strain of the combined bodies first increases,then deceases.Furthermore,the combined bodies of 3 d reveal the plastic property and brittle property for 7 d and 10 d when the strain rate is over 80/s.The failure characteristic of the sprayed concrete changes from tearing strain damage to crushing damage as the growth of strain rate,and the failure characteristic of rock presents the tensile failure mode as demonstrated by the scanning electron microscope(SEM).展开更多
To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the...To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.展开更多
Introduction Splenic cysts are rare in pediatric surgery.They can be classified as'true'cysts or pseudocysts on the basis of the presence or absence of an epithelial lining.Congenital cysts represent 10% of sp...Introduction Splenic cysts are rare in pediatric surgery.They can be classified as'true'cysts or pseudocysts on the basis of the presence or absence of an epithelial lining.Congenital cysts represent 10% of splenic cysts, most of which are epidermoid lesions.Splenectomy was initially the surgical treatment employed due to size,risk of operative compli-展开更多
The objective of this study was to analyze the efficacy of combined drug therapy for elderly patients with coronary heart disease and hypertension.66 elderly patients with coronary heart disease and hypertension were ...The objective of this study was to analyze the efficacy of combined drug therapy for elderly patients with coronary heart disease and hypertension.66 elderly patients with coronary heart disease and hypertension were enrolled from December 2016 to November 2017.They were randomly divided into two groups,33 patients in each group.Patients in the experimental group received nifedipine.In combination with enalapril,patients enrolled in the control group received nifedipine monotherapy.Compared with the control group,the total effective rate,serum nitric oxide(NO)after treatment,C-reactive protein(CRP)after treatment,homocysteine(HCY)after treatment,and blood pressure after treatment were significantly improved(P<0.05).There were no significant differences in serum NO,pre-treatment CRP,pre-treatment HCY,pre-treatment blood pressure,and adverse reactions during treatment between the two groups(P>0.05).The elderly patients with coronary heart disease and hypertension are treated with nifedipine and enalapril.展开更多
To the Editor:The main cause for failed complex coronary lesions especially chronic total occlusion(CTO)revascularization is the inability of device delivery due to the lack of adequate guide support or the failure of...To the Editor:The main cause for failed complex coronary lesions especially chronic total occlusion(CTO)revascularization is the inability of device delivery due to the lack of adequate guide support or the failure of guidewire manipulation,such as unsuccessful externalization of the retrograde guidewire and incapable reentry into the true lumen.Some devices and techniques have been used to deal with these problems,and the guide catheter extension system(GCES)is one of the effective solutions.展开更多
基金Supported by the National Key Research Program(2017YFC0804200)the National Key Basic Research Program(2016YFC0600903)the National Natural Science Foundation of China(51274204)
文摘To investigate the dynamic response problem of the double medium formed by the adherence of sprayed concrete and surrounding rock in the tunnel,a split Hopkinson pressure bar of 75 mm in diameter was adopted at the ages of 3,7 and 10 d.Experimental results showed that dynamic compressive strength and dynamic increase factors(DIF)of the combined bodies increase with the strain rate.With the growth of strain rate,the critical strain of the combined bodies first increases,then deceases.Furthermore,the combined bodies of 3 d reveal the plastic property and brittle property for 7 d and 10 d when the strain rate is over 80/s.The failure characteristic of the sprayed concrete changes from tearing strain damage to crushing damage as the growth of strain rate,and the failure characteristic of rock presents the tensile failure mode as demonstrated by the scanning electron microscope(SEM).
文摘To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.
文摘Introduction Splenic cysts are rare in pediatric surgery.They can be classified as'true'cysts or pseudocysts on the basis of the presence or absence of an epithelial lining.Congenital cysts represent 10% of splenic cysts, most of which are epidermoid lesions.Splenectomy was initially the surgical treatment employed due to size,risk of operative compli-
文摘The objective of this study was to analyze the efficacy of combined drug therapy for elderly patients with coronary heart disease and hypertension.66 elderly patients with coronary heart disease and hypertension were enrolled from December 2016 to November 2017.They were randomly divided into two groups,33 patients in each group.Patients in the experimental group received nifedipine.In combination with enalapril,patients enrolled in the control group received nifedipine monotherapy.Compared with the control group,the total effective rate,serum nitric oxide(NO)after treatment,C-reactive protein(CRP)after treatment,homocysteine(HCY)after treatment,and blood pressure after treatment were significantly improved(P<0.05).There were no significant differences in serum NO,pre-treatment CRP,pre-treatment HCY,pre-treatment blood pressure,and adverse reactions during treatment between the two groups(P>0.05).The elderly patients with coronary heart disease and hypertension are treated with nifedipine and enalapril.
基金supported by a grant from the Key Project of Medical Science Research in Hebei Province(No.20130001)
文摘To the Editor:The main cause for failed complex coronary lesions especially chronic total occlusion(CTO)revascularization is the inability of device delivery due to the lack of adequate guide support or the failure of guidewire manipulation,such as unsuccessful externalization of the retrograde guidewire and incapable reentry into the true lumen.Some devices and techniques have been used to deal with these problems,and the guide catheter extension system(GCES)is one of the effective solutions.
