The damage and even failure of hard brittle rocks has been the most important challenge facing the safety of construction of deep engineering works,so the key to solving this problem is the recognition of the strength...The damage and even failure of hard brittle rocks has been the most important challenge facing the safety of construction of deep engineering works,so the key to solving this problem is the recognition of the strength characteristics and description of the mechanical behavior of hard brittle rocks.Therefore,in view of this problem,in this study,we first analyzed the strength and mechanical response characteristics revealed in tests of,and site excavation in,hard brittle rocks.Second,by analyzing rock-strength envelopes on meridional and deviatoric planes,the generalized polyaxial strain energy(GPSE)strength criterion was applied.This allows description of the effects of the minimum principal stress,intermediate principal stress,hydrostatic pressure,and Lode’s angle of stress on the strength of hard rocks.By establishing evolutionary relationships of strength parameters and dilation parameters with plastic volumetric strain in rock failure,we established an elasto-plastic mechanical constitutive model for hard brittle rocks based on the GPSE criterion.In addition,through use of the failure approach index theory and the dilatancy safety factor,an evaluation index for degree of damage considering dilatant effects of rocks was proposed.Finally,the constitutive model established in this study and the proposed evaluation index were integrated into the numerical simulation method to simulate triaxial tests on rocks and numerical simulation of deformation and fracture of the rocks surrounding the deep-buried auxiliary tunnels in China’s Jinping II Hydropower Station.In this way,the reasonableness of the model and the index was verified.The strength theory and the constitutive model established in this research are applicable to the analysis of high-stress deformation and fracture of hard brittle rock masses,which supports the theoretical work related to deep engineering operations.展开更多
There is considerable safety potential in ensuring that motorists respect the speed limits. High speeds increase the number and severity of accidents. Technological development over the last 20 years has enabled the d...There is considerable safety potential in ensuring that motorists respect the speed limits. High speeds increase the number and severity of accidents. Technological development over the last 20 years has enabled the development of systems that allow automatic speed control. The first generation of automatic speed control was point-based, but in recent years a potentially more effective alternative automatic speed control method has been introduced. This method is based upon records of drivers’ average travel speed over selected sections of the road and is normally called average speed control or section control. This article discusses the different methods for automatic speed control and presents an evaluation of the safety effects of average speed control, documented through changes in speed levels and accidents before and after the implementation of average speed control at selected sites in the UK. The study demonstrates that the introduction of average speed control results in statistically significant and substantial reductions both in speed and in number of accidents. The evaluation indicates that average speed control has a higher safety effect than point-based automatic speed control.展开更多
Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves...Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves accuracy.However,the performance of the CMFs derived from the EB method has never been fully investigated.This study aims to examine the accuracy of CMFs estimated with the EB method.Artificial realistic data(ARD)and real crash data are used to evaluate the CMFs.The results indicate that:1)The CMFs derived from the EB before-after method are nearly the same as the true values.2)The estimated CMF standard errors do not reflect the true values.The estimation remains at the same level regardless of the pre-assumed CMF standard error.The EB before-after study is not sensitive to the variation of CMF among sites.3)The analyses with real-world traffic and crash data with a dummy treatment indicate that the EB method tends to underestimate the standard error of the CMF.Safety researchers should recognize that the CMF variance may be biased when evaluating safety effectiveness by the EB method.It is necessary to revisit the algorithm for estimating CMF variance with the EB method.展开更多
The influence of gas drainage on float coal spontaneous combustion in the work face with ＂U＂ style ventilation was studied. Numerical simulation was used to compare the mutative law of steady flow and density field ...The influence of gas drainage on float coal spontaneous combustion in the work face with ＂U＂ style ventilation was studied. Numerical simulation was used to compare the mutative law of steady flow and density field in the gob area under different drainage conditions by solving the equation set, including mass, momentum, and component transition. Consequently, the sequence of drainage effect and safety was obtained. The result manifests that the more effective the drainage pattern is, the easier float coal spontaneous combustion is caused due to air being guided into the depth of the gob area when the drainage position is arranged in the gas accumulation area. If the widened scope of oxidation zone exceeds the upper limit of the work face advancing speed, nitrogen injection should be applied to decrease the probability of spontaneous combustion. Then, the pipe laying drainage in the upper angle is most economical and safe compared with other drainage patterns when only the situation of gas accumulation is controlled in the upper angle. Finally, drainage pressure must not be too great. Otherwise the drainage density will decrease even if hazard is caused by back flow possibly happening in the return outlet when the drainage position is arranged near the work face.展开更多
BACKGROUND Appendectomy is the procedure of choice for the treatment of acute appendicitis.However,surgery may not be appropriate for patients with coexisting severe illness or comorbidities such as acute pancreatitis...BACKGROUND Appendectomy is the procedure of choice for the treatment of acute appendicitis.However,surgery may not be appropriate for patients with coexisting severe illness or comorbidities such as acute pancreatitis(AP).Endoscopic retrograde appendicitis treatment(ERAT)may be a novel alternative to surgery for treating such patients where existing medical therapies have failed.CASE SUMMARY We report 2 cases of moderately severe AP who developed acute uncomplicated appendicitis during their hospital stay and did not respond to traditional medical therapy.One patient had moderately severe AP due to hyperlipidemia,while the other patient had a gallstone induced by moderately severe AP.Neither patient was fit to undergo an appendectomy procedure because of the concurrent AP.Therefore,the alternative and minimally invasive ERAT was considered.After written informed consent was collected from the patients,the ERAT procedure was performed.Both patients exhibited fast postoperative recovery after ERAT with minimal surgical trauma.CONCLUSION ERAT is a safe and effective minimally invasive endoscopic procedure for acute appendicitis in patients with coexistent AP.展开更多
The role of drug-eluting stent （DES）, which prevents acute or subacute recoil and elutes drugs to prevent smooth muscle cell proliferation, is temporary and limited within a few weeks after its implantation. Beyond ...The role of drug-eluting stent （DES）, which prevents acute or subacute recoil and elutes drugs to prevent smooth muscle cell proliferation, is temporary and limited within a few weeks after its implantation. Beyond that, there is no utility or advantages but only limitations just like foreign materials in patients＇ body. All of these problems can be solved with the use of fully bioabsorbable stent （BAS）,展开更多
An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, clo...An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.展开更多
Biodegradable metals are promising candidates for bone defect repair.With an evidence-based approach,this study investigated and analyzed the performance and degradation properties of biodegradable metals in animal mo...Biodegradable metals are promising candidates for bone defect repair.With an evidence-based approach,this study investigated and analyzed the performance and degradation properties of biodegradable metals in animal models for bone defect repair to explore their potential clinical translation.Animal studies on bone defect repair with biodegradable metals in comparison with other traditional biomaterials were reviewed.Data was carefully collected after identification of population,intervention,comparison,outcome,and study design(PICOS),and following the inclusion criteria of biodegradable metals in animal studies.30 publications on pure Mg,Mg alloys,pure Zn and Zn alloys were finally included after extraction from a collected database of 2543 publications.A qualitative systematic review and a quantitative meta-analysis were performed.Given the heterogeneity in animal model,anatomical site and critical size defect(CSD),biodegradable metals exhibited mixed effects on bone defect repair and degradation in animal studies in comparison with traditional non-degradable metals,biodegradable polymers,bioceramics,and autogenous bone grafts.The results indicated that there were limitations in the experimental design of the included studies,and quality of the evidence presented by the studies was very low.To enhance clinical translation of biodegradable metals,evidence-based research with data validity is needed.Future studies should adopt standardized experimental protocols in investigating the effects of biodegradable metals on bone defect repair with animal models.展开更多
Based on the published animal studies,we systematically evaluated the outcomes of various materials for rotator cuff repair in animal models and the potentials of their clinical translation.74 animal studies were fina...Based on the published animal studies,we systematically evaluated the outcomes of various materials for rotator cuff repair in animal models and the potentials of their clinical translation.74 animal studies were finally included,of which naturally derived biomaterials were applied the most widely(50.0%),rats were the most commonly used animal model(47.0%),and autologous tissue demonstrated the best outcomes in all animal models.The biomechanical properties of naturally derived biomaterials(maximum failure load:WMD 18.68[95%CI 7.71-29.66];P=0.001,and stiffness:WMD 1.30[95%CI 0.01-2.60];P=0.048)was statistically significant in the rabbit model.The rabbit model showed better outcomes even though the injury was severer compared with the rat model.展开更多
Regulatory science for medical devices aims to develop new tools,standards and approaches to assess the safety,effectiveness,quality and performance of medical devices.In the field of biomaterials,hernia mesh is a cla...Regulatory science for medical devices aims to develop new tools,standards and approaches to assess the safety,effectiveness,quality and performance of medical devices.In the field of biomaterials,hernia mesh is a class of implants that have been successfully translated to clinical applications.With a focus on hernia mesh and its regulatory science system,this paper collected and reviewed information on hernia mesh products and biomaterials in both Chinese and American markets.The current development of regulatory science for hernia mesh,including its regulations,standards,guidance documents and classification,and the scientific evaluation of its safety and effectiveness was first reported.Then the research prospect of regulatory science for hernia mesh was discussed.New methods for the preclinical animal study and new tools for the evaluation of the safety and effectiveness of hernia mesh,such as computational modeling,big data platform and evidence-based research,were assessed.By taking the regulatory science of hernia mesh as a case study,this review provided a research basis for developing a regulatory science system of implantable medical devices,furthering the systematic evaluation of the safety and effectiveness of medical devices for better regulatory decision-making.This was the first article reviewing the regulatory science of hernia mesh and biomaterial-based implants.It also proposed and explained the concepts of evidence-based regulatory science and technical review for the first time.展开更多
基金The work was supported by the National Key Research and Development Project of China(Grant No.2016 YFC 0401804)the Key projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)+1 种基金the National Natural Science Foundation of China(Grant Nos.51539002 and 51779018)It was also supported by the Basic Research Fund for Central Research Institutes of Public Causes(CKSF 2017054/YT).
文摘The damage and even failure of hard brittle rocks has been the most important challenge facing the safety of construction of deep engineering works,so the key to solving this problem is the recognition of the strength characteristics and description of the mechanical behavior of hard brittle rocks.Therefore,in view of this problem,in this study,we first analyzed the strength and mechanical response characteristics revealed in tests of,and site excavation in,hard brittle rocks.Second,by analyzing rock-strength envelopes on meridional and deviatoric planes,the generalized polyaxial strain energy(GPSE)strength criterion was applied.This allows description of the effects of the minimum principal stress,intermediate principal stress,hydrostatic pressure,and Lode’s angle of stress on the strength of hard rocks.By establishing evolutionary relationships of strength parameters and dilation parameters with plastic volumetric strain in rock failure,we established an elasto-plastic mechanical constitutive model for hard brittle rocks based on the GPSE criterion.In addition,through use of the failure approach index theory and the dilatancy safety factor,an evaluation index for degree of damage considering dilatant effects of rocks was proposed.Finally,the constitutive model established in this study and the proposed evaluation index were integrated into the numerical simulation method to simulate triaxial tests on rocks and numerical simulation of deformation and fracture of the rocks surrounding the deep-buried auxiliary tunnels in China’s Jinping II Hydropower Station.In this way,the reasonableness of the model and the index was verified.The strength theory and the constitutive model established in this research are applicable to the analysis of high-stress deformation and fracture of hard brittle rock masses,which supports the theoretical work related to deep engineering operations.
文摘There is considerable safety potential in ensuring that motorists respect the speed limits. High speeds increase the number and severity of accidents. Technological development over the last 20 years has enabled the development of systems that allow automatic speed control. The first generation of automatic speed control was point-based, but in recent years a potentially more effective alternative automatic speed control method has been introduced. This method is based upon records of drivers’ average travel speed over selected sections of the road and is normally called average speed control or section control. This article discusses the different methods for automatic speed control and presents an evaluation of the safety effects of average speed control, documented through changes in speed levels and accidents before and after the implementation of average speed control at selected sites in the UK. The study demonstrates that the introduction of average speed control results in statistically significant and substantial reductions both in speed and in number of accidents. The evaluation indicates that average speed control has a higher safety effect than point-based automatic speed control.
基金Project(51978082)supported by the National Natural Science Foundation of ChinaProject(19B022)supported by the Outstanding Youth Foundation of Hunan Education Department,ChinaProject(2019QJCZ056)supported by the Young Teacher Development Foundation of Changsha University of Science&Technology,China。
文摘Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves accuracy.However,the performance of the CMFs derived from the EB method has never been fully investigated.This study aims to examine the accuracy of CMFs estimated with the EB method.Artificial realistic data(ARD)and real crash data are used to evaluate the CMFs.The results indicate that:1)The CMFs derived from the EB before-after method are nearly the same as the true values.2)The estimated CMF standard errors do not reflect the true values.The estimation remains at the same level regardless of the pre-assumed CMF standard error.The EB before-after study is not sensitive to the variation of CMF among sites.3)The analyses with real-world traffic and crash data with a dummy treatment indicate that the EB method tends to underestimate the standard error of the CMF.Safety researchers should recognize that the CMF variance may be biased when evaluating safety effectiveness by the EB method.It is necessary to revisit the algorithm for estimating CMF variance with the EB method.
基金Supported by the National Natural Science Foundation of China （51074168） the Specialized Fund for the Basic Research Operating Expenses Program of Central College（2010QZ03）
文摘The influence of gas drainage on float coal spontaneous combustion in the work face with ＂U＂ style ventilation was studied. Numerical simulation was used to compare the mutative law of steady flow and density field in the gob area under different drainage conditions by solving the equation set, including mass, momentum, and component transition. Consequently, the sequence of drainage effect and safety was obtained. The result manifests that the more effective the drainage pattern is, the easier float coal spontaneous combustion is caused due to air being guided into the depth of the gob area when the drainage position is arranged in the gas accumulation area. If the widened scope of oxidation zone exceeds the upper limit of the work face advancing speed, nitrogen injection should be applied to decrease the probability of spontaneous combustion. Then, the pipe laying drainage in the upper angle is most economical and safe compared with other drainage patterns when only the situation of gas accumulation is controlled in the upper angle. Finally, drainage pressure must not be too great. Otherwise the drainage density will decrease even if hazard is caused by back flow possibly happening in the return outlet when the drainage position is arranged near the work face.
文摘BACKGROUND Appendectomy is the procedure of choice for the treatment of acute appendicitis.However,surgery may not be appropriate for patients with coexisting severe illness or comorbidities such as acute pancreatitis(AP).Endoscopic retrograde appendicitis treatment(ERAT)may be a novel alternative to surgery for treating such patients where existing medical therapies have failed.CASE SUMMARY We report 2 cases of moderately severe AP who developed acute uncomplicated appendicitis during their hospital stay and did not respond to traditional medical therapy.One patient had moderately severe AP due to hyperlipidemia,while the other patient had a gallstone induced by moderately severe AP.Neither patient was fit to undergo an appendectomy procedure because of the concurrent AP.Therefore,the alternative and minimally invasive ERAT was considered.After written informed consent was collected from the patients,the ERAT procedure was performed.Both patients exhibited fast postoperative recovery after ERAT with minimal surgical trauma.CONCLUSION ERAT is a safe and effective minimally invasive endoscopic procedure for acute appendicitis in patients with coexistent AP.
文摘The role of drug-eluting stent （DES）, which prevents acute or subacute recoil and elutes drugs to prevent smooth muscle cell proliferation, is temporary and limited within a few weeks after its implantation. Beyond that, there is no utility or advantages but only limitations just like foreign materials in patients＇ body. All of these problems can be solved with the use of fully bioabsorbable stent （BAS）,
基金Project(51274250)supported by the National Natural Science Foundation of ChinaProject(2012BAK09B02-05)supported by the National Key Technology R&D Program during the 12th Five-year Plan of China
文摘An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.
文摘Biodegradable metals are promising candidates for bone defect repair.With an evidence-based approach,this study investigated and analyzed the performance and degradation properties of biodegradable metals in animal models for bone defect repair to explore their potential clinical translation.Animal studies on bone defect repair with biodegradable metals in comparison with other traditional biomaterials were reviewed.Data was carefully collected after identification of population,intervention,comparison,outcome,and study design(PICOS),and following the inclusion criteria of biodegradable metals in animal studies.30 publications on pure Mg,Mg alloys,pure Zn and Zn alloys were finally included after extraction from a collected database of 2543 publications.A qualitative systematic review and a quantitative meta-analysis were performed.Given the heterogeneity in animal model,anatomical site and critical size defect(CSD),biodegradable metals exhibited mixed effects on bone defect repair and degradation in animal studies in comparison with traditional non-degradable metals,biodegradable polymers,bioceramics,and autogenous bone grafts.The results indicated that there were limitations in the experimental design of the included studies,and quality of the evidence presented by the studies was very low.To enhance clinical translation of biodegradable metals,evidence-based research with data validity is needed.Future studies should adopt standardized experimental protocols in investigating the effects of biodegradable metals on bone defect repair with animal models.
基金supported by the Natural Science Foundation of China(Number:81873184)the National Innovation and Entrepreneurship Training Program for Undergraduate(No.202110730235).
文摘Based on the published animal studies,we systematically evaluated the outcomes of various materials for rotator cuff repair in animal models and the potentials of their clinical translation.74 animal studies were finally included,of which naturally derived biomaterials were applied the most widely(50.0%),rats were the most commonly used animal model(47.0%),and autologous tissue demonstrated the best outcomes in all animal models.The biomechanical properties of naturally derived biomaterials(maximum failure load:WMD 18.68[95%CI 7.71-29.66];P=0.001,and stiffness:WMD 1.30[95%CI 0.01-2.60];P=0.048)was statistically significant in the rabbit model.The rabbit model showed better outcomes even though the injury was severer compared with the rat model.
基金The authors thank the financial support from National Natural Science Foundation of China(51973018)National Natural Science Foundation of China(51773018)Beijing Municipal Science and Technology Commission Projects(No.Z191100002019017).
文摘Regulatory science for medical devices aims to develop new tools,standards and approaches to assess the safety,effectiveness,quality and performance of medical devices.In the field of biomaterials,hernia mesh is a class of implants that have been successfully translated to clinical applications.With a focus on hernia mesh and its regulatory science system,this paper collected and reviewed information on hernia mesh products and biomaterials in both Chinese and American markets.The current development of regulatory science for hernia mesh,including its regulations,standards,guidance documents and classification,and the scientific evaluation of its safety and effectiveness was first reported.Then the research prospect of regulatory science for hernia mesh was discussed.New methods for the preclinical animal study and new tools for the evaluation of the safety and effectiveness of hernia mesh,such as computational modeling,big data platform and evidence-based research,were assessed.By taking the regulatory science of hernia mesh as a case study,this review provided a research basis for developing a regulatory science system of implantable medical devices,furthering the systematic evaluation of the safety and effectiveness of medical devices for better regulatory decision-making.This was the first article reviewing the regulatory science of hernia mesh and biomaterial-based implants.It also proposed and explained the concepts of evidence-based regulatory science and technical review for the first time.
