[目的]采用决策试用和评估实验室分析法(Decision Making And Trial Evaluation Laboratory, DEMATEL)对新冠疫情常态化防控期间医院感染风险因素进行分析。[方法]成立研究小组,采取5M1E理论和专家咨询法对文献研究获得的新冠疫情常态...[目的]采用决策试用和评估实验室分析法(Decision Making And Trial Evaluation Laboratory, DEMATEL)对新冠疫情常态化防控期间医院感染风险因素进行分析。[方法]成立研究小组,采取5M1E理论和专家咨询法对文献研究获得的新冠疫情常态化防控期间医院感染风险因素进行分析,构建风险因素的直接影响矩阵,再通过DEMATEL方法对因素间关系进行计算。[结果]研究获得医院感染风险因素27项,通过DEMATEL方法识别出12个原因因素和15个结果因素,影响因素中有8个因素的原因度和中心度均较高,对体系的影响力最大,是整个系统中的驱动要素,分别为人力配置、培训考核、感控理念、感控标准、一体防控、监督机制、绩效考核、科研教学。[结论]DEMATEL方法可作为分析新冠疫情常态化防控期间医院感染风险因素及制定改进措施的有效方法。展开更多
To analyze the feasibility of application of composite material as the insulating material, it is necessary to have knowledge of some of its mechanical properties. An insulating material may suffer from the most diffe...To analyze the feasibility of application of composite material as the insulating material, it is necessary to have knowledge of some of its mechanical properties. An insulating material may suffer from the most different efforts, but the major applications suggest mechanical bending and compression tests because the insulation can be applied on roofs of homes, liners similar to, in the form of plates. Thus, the product is continually flexed. When the material is used on a floor, it suffers constant compressions over its use. For tests performed in this study, we used the ASTM D695-96 for compression, an example of literature. Using such a standard test, specimens were produced for compression test, with specimens made of cylindrical shapes, respecting the condition that the height of the specimen corresponds to twice the diameter of the base. Polyurethane castor without charge vermiculite and mass loads of 10%, 15% and 20% matrix： four specimens for each type of material were produced. The composites were tested in a universal testing machine at a speed of 2 mm/s. The results are average values of four test samples, and initially show the behavior of castor oil polyurethane during the compression test, which is detailed in the stress versus strain curve. The achieved results are promising, and detailed in this paper.展开更多
Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical...Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical test system of arch,research is made on the failure mechanism and mechanical properties of CC arch.Then,a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity;a calculation formula is deduced for the internal force of the arch;an analysis is made on the influence of different factors on the internal force of the arch;and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity.With numerical calculation and laboratory experiment,the ultimate bearing capacity and internal force distribution is analyzed for CC arches.The research results show that:1)CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability;2)The key damage position of the arch is the two sides;3)Theoretical analysis,numerical calculation and laboratory experiment have good consistency in the internal force distribution,bearing capacity,and deformation and failure modes of the arch.All of that verifies the correctness of the theoretical calculation.Based on the above results,a field experiment is carried out in Liangjia Mine.Compared with the U-shaped steel arch support,CC arch support is more effective in surrounding rock deformation control.The research results can provide a basis for the design of CC arch support in underground engineering.展开更多
Determining the optimal timing is the core of preventive maintenance. Highway agencies always face with the challenge of determining optimal timing for preventive maintenance, particularly in China where there are no ...Determining the optimal timing is the core of preventive maintenance. Highway agencies always face with the challenge of determining optimal timing for preventive maintenance, particularly in China where there are no condition indicators designed for determining adequate timing for applying preventive maintenance and little literature relating to the development of pavement performance. This work presented the indicators, including crack ratio （Rc）, rutting depth （DR）, international roughness index （IIR） and sideway force coefficient （CsF） to determine the adequate timing for preventive maintenance in China. The proper ranges of each indicator to apply to preventive maintenance were then recommended. They are 0.28%-1.4% for Rc, 10-15 mm for DR, 1.97-3.5 for lrR, 40--50 for CSF. Based on pavement condition survey data collected on the test roads in Hebei Province, China, on the application of slurry seal at different timings, the pavement performance was established and the adequate timings for applying slurry seal was studied. Based on benefit-cost analysis, it is suggested that the fourth year is the optimal timing for applying slurry seal based on the condition in China. A framework is established to determine the adequate timings of applying other preventive maintenance methods.展开更多
The collapsibility of loess, which can be effectively eliminated by the dynamic compaction, does great harm to the safety of constructions. The effect of the dynamic compaction is evaluated through the contrast and an...The collapsibility of loess, which can be effectively eliminated by the dynamic compaction, does great harm to the safety of constructions. The effect of the dynamic compaction is evaluated through the contrast and analysis of the physical and mechanical properties of the collapsible loess before and after dynamic compacting. The compacting effect can be divided into three phases along the depth, and the most effective improved depth is from 3 to 8 m.展开更多
In this paper,the soil-pile system of O-cell test of pile is simplified as an axi-symmetric problem.By using aggregation of quadrilateral isoparametric elements to simulate pile and soil,setting Goodman's elements...In this paper,the soil-pile system of O-cell test of pile is simplified as an axi-symmetric problem.By using aggregation of quadrilateral isoparametric elements to simulate pile and soil,setting Goodman's elements between pile and soils,a method of numerical simulation analysis on O-cell test of pile is presented with the consideration of nonlinear mechanical behavior of soils and pile-soil interface.The method is applied to the analysis of a case of O-cell test of pile.The load-displacement curves and axial force curves of upper pile and lower pile obtained from the O-cell test of pile are fitted,and parameters of the mechanical model of soils and interface are determined.Analysis results validate that the numerical simulation analysis method put forward in this paper is applicable.Furthermore,the interaction and influence of upper pile and lower pile in the O-cell test are also studied with the method.The result shows that if load box is located in a soil layer with fine mechanical behavior,the interaction of upper pile and lower pile in O-cell test can be ignored generally.展开更多
While Colleague English Tests (CET) have promoted the college English teaching, they have also led to the extension of test-oriented education and hindered students' capability in communication. To examine the val...While Colleague English Tests (CET) have promoted the college English teaching, they have also led to the extension of test-oriented education and hindered students' capability in communication. To examine the validity of CET Band Four, resumed tests were carried out in sampled students of Grade 2001 one year after they took CET-4 in December, 2002. The control class was examined with the original paper of CET-4 2002, while the treatment class was tested with the same paper in which the multiple-choice questions were all changed into the subjective ones. The test scores were processed by statistical analysis. The results showed that although there was no significant difference between the two classes in CET-4 scores, there was significant difference between them in their experimental test scores. The scores of the treatment class were significantly lower than that of the control class, which proves that CET cannot objectively reflect students' capability in communication, and thus its validity is low. To eliminate the negative backwash effect of CET, suggestions are put forward that CET be devised as a criterion-referenced test, frequency of the test be reduced, subjective questions be increased, and commercialization of the test be avoided.展开更多
文摘[目的]采用决策试用和评估实验室分析法(Decision Making And Trial Evaluation Laboratory, DEMATEL)对新冠疫情常态化防控期间医院感染风险因素进行分析。[方法]成立研究小组,采取5M1E理论和专家咨询法对文献研究获得的新冠疫情常态化防控期间医院感染风险因素进行分析,构建风险因素的直接影响矩阵,再通过DEMATEL方法对因素间关系进行计算。[结果]研究获得医院感染风险因素27项,通过DEMATEL方法识别出12个原因因素和15个结果因素,影响因素中有8个因素的原因度和中心度均较高,对体系的影响力最大,是整个系统中的驱动要素,分别为人力配置、培训考核、感控理念、感控标准、一体防控、监督机制、绩效考核、科研教学。[结论]DEMATEL方法可作为分析新冠疫情常态化防控期间医院感染风险因素及制定改进措施的有效方法。
文摘To analyze the feasibility of application of composite material as the insulating material, it is necessary to have knowledge of some of its mechanical properties. An insulating material may suffer from the most different efforts, but the major applications suggest mechanical bending and compression tests because the insulation can be applied on roofs of homes, liners similar to, in the form of plates. Thus, the product is continually flexed. When the material is used on a floor, it suffers constant compressions over its use. For tests performed in this study, we used the ASTM D695-96 for compression, an example of literature. Using such a standard test, specimens were produced for compression test, with specimens made of cylindrical shapes, respecting the condition that the height of the specimen corresponds to twice the diameter of the base. Polyurethane castor without charge vermiculite and mass loads of 10%, 15% and 20% matrix： four specimens for each type of material were produced. The composites were tested in a universal testing machine at a speed of 2 mm/s. The results are average values of four test samples, and initially show the behavior of castor oil polyurethane during the compression test, which is detailed in the stress versus strain curve. The achieved results are promising, and detailed in this paper.
基金Projects(51674154,51704125,51874188) supported by the National Natural Science Foundation of ChinaProjects(2017T100116,2017T100491,2016M590150,2016M602144) supported by the China Postdoctoral Science Foundation+2 种基金Projects(2017GGX30101,2018GGX109001,ZR2017QEE013) supported by the Natural Science Foundation of Shandong Province,ChinaProject(SKLCRSM18KF012) supported by the State Key Laboratory of Coal Resources and Safe Mining,ChinaProject(2018WLJH76) supported by the Young Scholars Program of Shandong University,China
文摘Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical test system of arch,research is made on the failure mechanism and mechanical properties of CC arch.Then,a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity;a calculation formula is deduced for the internal force of the arch;an analysis is made on the influence of different factors on the internal force of the arch;and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity.With numerical calculation and laboratory experiment,the ultimate bearing capacity and internal force distribution is analyzed for CC arches.The research results show that:1)CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability;2)The key damage position of the arch is the two sides;3)Theoretical analysis,numerical calculation and laboratory experiment have good consistency in the internal force distribution,bearing capacity,and deformation and failure modes of the arch.All of that verifies the correctness of the theoretical calculation.Based on the above results,a field experiment is carried out in Liangjia Mine.Compared with the U-shaped steel arch support,CC arch support is more effective in surrounding rock deformation control.The research results can provide a basis for the design of CC arch support in underground engineering.
基金Project(IRT1050) supported by Program for Changjiang Scholars and Innovative Research Team in University, ChinaProject (2009318000027) supported by Ministry of Transport of ChinaProject(CHD2011TD002) supported by the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University, China
文摘Determining the optimal timing is the core of preventive maintenance. Highway agencies always face with the challenge of determining optimal timing for preventive maintenance, particularly in China where there are no condition indicators designed for determining adequate timing for applying preventive maintenance and little literature relating to the development of pavement performance. This work presented the indicators, including crack ratio （Rc）, rutting depth （DR）, international roughness index （IIR） and sideway force coefficient （CsF） to determine the adequate timing for preventive maintenance in China. The proper ranges of each indicator to apply to preventive maintenance were then recommended. They are 0.28%-1.4% for Rc, 10-15 mm for DR, 1.97-3.5 for lrR, 40--50 for CSF. Based on pavement condition survey data collected on the test roads in Hebei Province, China, on the application of slurry seal at different timings, the pavement performance was established and the adequate timings for applying slurry seal was studied. Based on benefit-cost analysis, it is suggested that the fourth year is the optimal timing for applying slurry seal based on the condition in China. A framework is established to determine the adequate timings of applying other preventive maintenance methods.
基金Acknowledgement The authors of this paper thank the financial support from National Natural Science Foundation of China through project No.50478096.
文摘The collapsibility of loess, which can be effectively eliminated by the dynamic compaction, does great harm to the safety of constructions. The effect of the dynamic compaction is evaluated through the contrast and analysis of the physical and mechanical properties of the collapsible loess before and after dynamic compacting. The compacting effect can be divided into three phases along the depth, and the most effective improved depth is from 3 to 8 m.
文摘In this paper,the soil-pile system of O-cell test of pile is simplified as an axi-symmetric problem.By using aggregation of quadrilateral isoparametric elements to simulate pile and soil,setting Goodman's elements between pile and soils,a method of numerical simulation analysis on O-cell test of pile is presented with the consideration of nonlinear mechanical behavior of soils and pile-soil interface.The method is applied to the analysis of a case of O-cell test of pile.The load-displacement curves and axial force curves of upper pile and lower pile obtained from the O-cell test of pile are fitted,and parameters of the mechanical model of soils and interface are determined.Analysis results validate that the numerical simulation analysis method put forward in this paper is applicable.Furthermore,the interaction and influence of upper pile and lower pile in the O-cell test are also studied with the method.The result shows that if load box is located in a soil layer with fine mechanical behavior,the interaction of upper pile and lower pile in O-cell test can be ignored generally.
基金This article is a product of the research programsponsored by Beijing Education Committee .
文摘While Colleague English Tests (CET) have promoted the college English teaching, they have also led to the extension of test-oriented education and hindered students' capability in communication. To examine the validity of CET Band Four, resumed tests were carried out in sampled students of Grade 2001 one year after they took CET-4 in December, 2002. The control class was examined with the original paper of CET-4 2002, while the treatment class was tested with the same paper in which the multiple-choice questions were all changed into the subjective ones. The test scores were processed by statistical analysis. The results showed that although there was no significant difference between the two classes in CET-4 scores, there was significant difference between them in their experimental test scores. The scores of the treatment class were significantly lower than that of the control class, which proves that CET cannot objectively reflect students' capability in communication, and thus its validity is low. To eliminate the negative backwash effect of CET, suggestions are put forward that CET be devised as a criterion-referenced test, frequency of the test be reduced, subjective questions be increased, and commercialization of the test be avoided.
