This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(S...This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.展开更多
Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical proper...Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.展开更多
The Sargent dividing wall column can implement four products separation sequences in one column based on Fully Thermally Coupled Distillation Column. The initial design parameters are required for the design optimizat...The Sargent dividing wall column can implement four products separation sequences in one column based on Fully Thermally Coupled Distillation Column. The initial design parameters are required for the design optimization or dynamic control of the Sargent dividing wall column, and in order to make the rigorous simulation of the Sargent dividing wall column more conducive to convergence, a ten column model for complex Sargent column is established in this paper,and the shortcut design method of this model is proposed. The internal minimum vapor and liquid flow are obtained by the Underwood equations and the mass balance method and the V-min method. The separation for a 4-component shortcut mixture of pentane, hexane, heptane and octane was considered, while the initial values of design parameters and the ratio of vapor-liquid distribution of each column were calculated by using the shortcut design method of a ten column model. And by comparing the shortcut calculations with rigorous simulation results, the practicality and reliability of shortcut calculations were verified. The reason for energy saving was analyzed based on back-mixing. A virtual heat exchanger is proposed to make the Sargent dividing wall column more energy efficient.展开更多
The column bioleaching of copper flotation tailings was comparatively investigated using layered heap construction method(LM),agglomerate heap construction method(AM),and pellets-sintering heap construction method(PM)...The column bioleaching of copper flotation tailings was comparatively investigated using layered heap construction method(LM),agglomerate heap construction method(AM),and pellets-sintering heap construction method(PM).The bacterial communities of free,attached,weakly-attached,and strongly-attached microbes in the later bioleaching stage were investigated.In AM group,the addition of lump sulphide ore resulted in the low leachate pH,high ferric iron concentration,and rapid microbial adsorption,which obtained the maximum copper extraction(60.1%)compared with LM(54.6%)and PM(43.9%)groups.The relative abundance of dominant genera and microbial communities of different microbiota underwent changes in three heap construction methods.The alpha-diversity indexes of attached,weakly-attached,and strongly-attached microbes were different,while no significant change was observed in free bacteria.The variation of whole bacterial community was significantly associated with solution pH,total iron,and ferric iron concentrations.Pearson correlation analysis and partial least square path model both indicated that attached bacteria made larger contribution to the copper extraction of tailings.展开更多
MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The result...MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The results show that the appropriate range of LiMn 2O 4 grain size was 60-160 meshes and the concentration of leaching solution HCl was 0.1 mol·L -1.The adsorption capacity Q of λ-MnO 2 for lithium increased with the increase of pH and changed markedly at pH 6.0-10.0.It was 3.80mmol/g at pH 12.0.The distribution coefficients K d of Li + and Na + were 3.406×10 4 and 2.300 respectively,and the separation coefficient α Li Na was 1.481×10 4 at pH 6.5.As a result,λ-MnO 2 is a high performance ion-sieve material for lithium ion.展开更多
The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory sy...The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called ＂perfectibility＂ parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.展开更多
In order to investigate the calculation methods on crack resistance capacity of connection composed of cross shaped steel encased ultra high strength concrete(CSSEUHSC)columns and steel encased concrete(SEC)beams unde...In order to investigate the calculation methods on crack resistance capacity of connection composed of cross shaped steel encased ultra high strength concrete(CSSEUHSC)columns and steel encased concrete(SEC)beams under cycle loads,six interior connection specimens were tested in the laboratory.A discussion on the crack resistance capacity was presented.Calculation methods of crack resistance capacity were deduced based on the experimental case and calculation results were in good agreement with the experimental results.The research results indicated that parameters of connection composed of CSSEUHSC columns and SEC beams with better crack resistance performance may be referred for engineering application.展开更多
Concrete filled steel tube structures have gained booming development in recent decades, especially in China. Simplified methods have been proposed in design codes, such as the Eurocode 4 (EC4) and the China engineeri...Concrete filled steel tube structures have gained booming development in recent decades, especially in China. Simplified methods have been proposed in design codes, such as the Eurocode 4 (EC4) and the China engineering and construction specification (CECS). In EC4, the confinement effect is reasonably related to slenderness and load eccentricity. The CECS method is much straight forward in that the slenderness ratio and load eccentricity are treated as independent reduction factors. To make use of the advantages of both the CECS and the EC4 methods, the CECS method is modified to consider the confinement effect associated with slenderness and load eccentricity. It is shown that the proposed method can predict well the ultimate load capacity of circular section concrete filled steel tube columns.展开更多
Nicotine and cotinine in hair are good biomarkers for assessing long-term exposure to smoking. However, analytical devices such as GC/MS are associated with high cost and are not widely used. HPLC/UV is used widely in...Nicotine and cotinine in hair are good biomarkers for assessing long-term exposure to smoking. However, analytical devices such as GC/MS are associated with high cost and are not widely used. HPLC/UV is used widely in laboratories, but is unsuitable for measurement of minor constituents, except when using the column-switching method. Thus, we aimed to establish a simple, inexpensive and sensitive method based on HPLC/UV with column switching for measuring nicotine and cotinine in hair. First, we compared the presence and absence of a column selection unit. We then measured amounts of nicotine and cotinine in hair samples collected from the general population, and compared both the corresponding levels and the detection limits with those in previous studies. Finally, initial and running costs of HPLC/UV were compared with other analytical methods. As one of the results, the areas of nicotine and cotinine measured by HPLC/UV with column-switching method were 12.9 and 16.9 times greater, respectively, than those without the column-switching method. The amount of nicotine and cotinine in hair was significantly correlated to number of cigarettes smoked per day (r = 0.228, p = 0.040). In addition, the HPLC/UV method showed similar sensitivity and detection limit (nicotine, 0.10 ng/mg;cotinine, 0.08 ng/mg) as reported in previous studies. The cost of the HPLC/UV method is lower than that of other analytical methods. We were able to establish a low-cost method with good sensitivity for measuring nicotine and cotinine in hair. The HPLC/UV with a column-switching method will be useful as a first step in screening surveys in order to better understand the effects of smoking exposure.展开更多
In the Chenggong tunnel of Kunming, aiming at the engineering of shallow buried and strongly expanded surrounding rock, the construction method of three steps plus central columns is introduced. The soil of Chenggong ...In the Chenggong tunnel of Kunming, aiming at the engineering of shallow buried and strongly expanded surrounding rock, the construction method of three steps plus central columns is introduced. The soil of Chenggong Tunnel is tested in laboratory to determine its expansibility. The traditional three-step method and three-step plus center pillar method are compared and analyzed by using MIDAS-GTS. Finally, the deformation of surrounding rock after the construction of three-step plus center pillar method is obtained through on-site monitoring. The results show that: 1) The free expansion rate, montmorillonite content and cation exchange capacity of Chenggong tunnel soil are determined, and the expansive parameters are obtained. 2) Through numerical simulation, it is concluded that under the condition of strong expansive soil and weak surrounding rock, the settlement of vault and two sides caused by the traditional step method are both larger than that of the three steps plus center pillar method. This new improved method can effectively reduce the disturbance to surrounding rock and significantly reduce the settlement of vault;3) The data of vault settlement and displacement of two sides of the tunnel after the construction of the three-step plus center pillar method are obtained by on-site monitoring, and are simulated and analyzed by using MIDAS-GTS software. The relative error value of vault settlement obtained by the two methods is 1%, which indicates that MIDAS-GTS has good simulation effect on the stress state and deformation state of the tunnel, and further indicates that this method is very practical for the case of small convergence of side walls and large vault settlement.展开更多
In this paper, we prove the local and Supcrlinear convergence theorem of the column-updating method for n>2. This is an oped problem for the convergene theory of the column-updating method given by Martinez in the ...In this paper, we prove the local and Supcrlinear convergence theorem of the column-updating method for n>2. This is an oped problem for the convergene theory of the column-updating method given by Martinez in the Intcrnational Conference of the NATO-ASI (Italy, 1994).展开更多
Airport disruptions often pose challenges in assigning aircraft to gates,resulting in infeasible planned schedules.In particular,a large number of transfer passengers miss their connections in the context of disruptio...Airport disruptions often pose challenges in assigning aircraft to gates,resulting in infeasible planned schedules.In particular,a large number of transfer passengers miss their connections in the context of disruptions,which cause huge economic losses to airlines and serious passengers’dissatisfaction.This paper proposes a set-partitioning-based model to optimize Aircraft-Gate Reassignment with Transfer Passenger Connections(AGRP-TPC),which incorporates flexible gate-swap and aircraft-delay operations to mitigate the overall impact of disruptions.To efficiently solve the model,we introduce the concepts of additive-transfer and nonstop-transfer to handle passenger connections,and develop a Hierarchical Column-and-Row Generation(HCRG)approach guided by airport terminal space attribute.The column generation and row generation procedures solve iteratively until no new variables and constraints are generated.In addition,a follow-on strategy and a diving heuristic are designed to efficiently obtain high-quality solutions.We evaluate the proposed approach using various instances from a major Chinese international airport.Computational results demonstrate that our approach outperforms the comparison algorithms and produces good solutions within the time limit.Detailed results indicate that our approach effectively reduces overall losses in aircraft-gate reassignment following disruptions,and it can serve as an auxiliary decision-making tool for airport operators and airlines.展开更多
The utilization of high-strength steel bars(HSSB)within concrete structures demonstrates significant advantages in material conservation and mechanical performance enhancement.Nevertheless,existing design codes exhibi...The utilization of high-strength steel bars(HSSB)within concrete structures demonstrates significant advantages in material conservation and mechanical performance enhancement.Nevertheless,existing design codes exhibit limitations in addressing the distinct statistical characteristics of HSSB,particularly regarding strength design parameters.For instance,GB50010-2010 fails to specify design strength values for reinforcement exceeding 600 MPa,creating technical barriers for advancing HSSB implementation.This study systematically investigates the reliability of eccentric compression concrete columns reinforced with 600 MPa-grade HSSB through high-order moment method analysis.Material partial factors were calibrated against target reliability indices prescribed by GB50068-2018,incorporating critical variables including live-to-dead load ratios,design methodologies,and service conditions.The findings show that the value of k significantly affects the calibration of material partial factors,impacting the reliability of bearing capacity.Considering various k values and target reliability indices,it is recommended that the material partialfactorbe setat1.15,implyingthatthedesignstrengthfor600MPahigh-strengthsteelbars shouldbe considered as 522 MPa.For safety levels I and II,load adjustment factors of 1.1 and 0.9,respectively,may be applied.展开更多
目的:运用网状Meta分析评估不同免疫吸附柱治疗类风湿关节炎的有效性与安全性,为临床诊治提供循证依据。方法:计算机检索维普、万方、中国知网、PubMed、CBM、CochraneLibrary、Web of Science等数据库,检索公开发表的免疫吸附柱治疗类...目的:运用网状Meta分析评估不同免疫吸附柱治疗类风湿关节炎的有效性与安全性,为临床诊治提供循证依据。方法:计算机检索维普、万方、中国知网、PubMed、CBM、CochraneLibrary、Web of Science等数据库,检索公开发表的免疫吸附柱治疗类风湿关节炎的研究,检索时限至2024年8月。采用Cochrane 5.4手册对纳入的随机对照试验进行质量评价,采用纽卡斯尔-渥太华量表(NOS)对回顾性队列研究进行质量评价。运用R4.1.1软件进行贝叶斯网状Meta分析。结果:最终纳入13篇研究,总样本量891例,共有4种免疫吸附柱。网状Meta分析结果表明,降低C-反应蛋白前3名排序:HA280型吸附柱+常规西药>PH-350型吸附柱+常规西药>A蛋白吸附柱;降低红细胞沉降率前3名排序:白细胞吸附柱>HA280型吸附柱+常规西药>PH-350型吸附柱+常规西药;降低关节肿胀计数前3名排序:白细胞吸附柱>A蛋白吸附柱+常规西药>PH-350型吸附柱+常规西药;降低关节压痛计数前3名排序:白细胞吸附柱>A蛋白吸附柱+常规西药>PH-350型吸附柱+常规西药;降低患者对疾病活动性评分前3名排序:PH-350型吸附柱+常规西药>白细胞吸附柱>A蛋白吸附柱;降低目测类比评分前3名排序:PH-350型吸附柱+常规西药>A蛋白吸附柱>白细胞吸附柱;降低医师对疾病活动性评分前3名排序:PH-350型吸附柱+常规西药>白细胞吸附柱>常规西药。结论:基于纳入的13篇文献证据表明,在降低C-反应蛋白方面,HA280型吸附柱联合常规西药作为首选;在降低红细胞沉降率、关节肿胀计数、关节压痛计数方面,白细胞吸附柱作为首选;在降低患者对疾病活动性评分、医师对疾病活动性评分及目测类比评分方面,PH-350型吸附柱联合常规西药作为首选,在临床中可根据患者的具体情况合理选择不同的免疫吸附柱。展开更多
文摘This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.
基金Foundation of Key Laboratory of Coast Civil Structure Safety (Tianjin University),Ministry of EducationChinese Program for New Century Excellent Talents in University+1 种基金Seed Foundation of Tianjin UniversitySeed Foundation of Xinjiang University
文摘Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.
基金supported by the High-level Talents Program of Hebei Province (A 2017002032)
文摘The Sargent dividing wall column can implement four products separation sequences in one column based on Fully Thermally Coupled Distillation Column. The initial design parameters are required for the design optimization or dynamic control of the Sargent dividing wall column, and in order to make the rigorous simulation of the Sargent dividing wall column more conducive to convergence, a ten column model for complex Sargent column is established in this paper,and the shortcut design method of this model is proposed. The internal minimum vapor and liquid flow are obtained by the Underwood equations and the mass balance method and the V-min method. The separation for a 4-component shortcut mixture of pentane, hexane, heptane and octane was considered, while the initial values of design parameters and the ratio of vapor-liquid distribution of each column were calculated by using the shortcut design method of a ten column model. And by comparing the shortcut calculations with rigorous simulation results, the practicality and reliability of shortcut calculations were verified. The reason for energy saving was analyzed based on back-mixing. A virtual heat exchanger is proposed to make the Sargent dividing wall column more energy efficient.
基金financial supports from the National Key R&D Program of China(No.2018YFC1801804)the Shandong Provincial Natural Science Foundation,China(Nos.ZR2020QD120 and ZR2018LD001)Project of Introducing and Cultivating Young Talent in the Universities of Shandong Province,China(No.QC2019YY144)。
文摘The column bioleaching of copper flotation tailings was comparatively investigated using layered heap construction method(LM),agglomerate heap construction method(AM),and pellets-sintering heap construction method(PM).The bacterial communities of free,attached,weakly-attached,and strongly-attached microbes in the later bioleaching stage were investigated.In AM group,the addition of lump sulphide ore resulted in the low leachate pH,high ferric iron concentration,and rapid microbial adsorption,which obtained the maximum copper extraction(60.1%)compared with LM(54.6%)and PM(43.9%)groups.The relative abundance of dominant genera and microbial communities of different microbiota underwent changes in three heap construction methods.The alpha-diversity indexes of attached,weakly-attached,and strongly-attached microbes were different,while no significant change was observed in free bacteria.The variation of whole bacterial community was significantly associated with solution pH,total iron,and ferric iron concentrations.Pearson correlation analysis and partial least square path model both indicated that attached bacteria made larger contribution to the copper extraction of tailings.
基金theNationalNaturalScienceFoundationofChi na (No .5 9972 0 2 7)theNaturalScienceFoundationofHubeiProvince (No .2 0 0 2AB0 74) )
文摘MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The results show that the appropriate range of LiMn 2O 4 grain size was 60-160 meshes and the concentration of leaching solution HCl was 0.1 mol·L -1.The adsorption capacity Q of λ-MnO 2 for lithium increased with the increase of pH and changed markedly at pH 6.0-10.0.It was 3.80mmol/g at pH 12.0.The distribution coefficients K d of Li + and Na + were 3.406×10 4 and 2.300 respectively,and the separation coefficient α Li Na was 1.481×10 4 at pH 6.5.As a result,λ-MnO 2 is a high performance ion-sieve material for lithium ion.
文摘The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called ＂perfectibility＂ parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.
基金supported by National Natural Science Foundation of China(Nos.51168034,50878037)China Postdoctoral Science Foundation(No.20100471445)Open Foundation of State Key Laboratory of Coastal and Offshore Engineering(No.LP1015)
文摘In order to investigate the calculation methods on crack resistance capacity of connection composed of cross shaped steel encased ultra high strength concrete(CSSEUHSC)columns and steel encased concrete(SEC)beams under cycle loads,six interior connection specimens were tested in the laboratory.A discussion on the crack resistance capacity was presented.Calculation methods of crack resistance capacity were deduced based on the experimental case and calculation results were in good agreement with the experimental results.The research results indicated that parameters of connection composed of CSSEUHSC columns and SEC beams with better crack resistance performance may be referred for engineering application.
文摘Concrete filled steel tube structures have gained booming development in recent decades, especially in China. Simplified methods have been proposed in design codes, such as the Eurocode 4 (EC4) and the China engineering and construction specification (CECS). In EC4, the confinement effect is reasonably related to slenderness and load eccentricity. The CECS method is much straight forward in that the slenderness ratio and load eccentricity are treated as independent reduction factors. To make use of the advantages of both the CECS and the EC4 methods, the CECS method is modified to consider the confinement effect associated with slenderness and load eccentricity. It is shown that the proposed method can predict well the ultimate load capacity of circular section concrete filled steel tube columns.
文摘Nicotine and cotinine in hair are good biomarkers for assessing long-term exposure to smoking. However, analytical devices such as GC/MS are associated with high cost and are not widely used. HPLC/UV is used widely in laboratories, but is unsuitable for measurement of minor constituents, except when using the column-switching method. Thus, we aimed to establish a simple, inexpensive and sensitive method based on HPLC/UV with column switching for measuring nicotine and cotinine in hair. First, we compared the presence and absence of a column selection unit. We then measured amounts of nicotine and cotinine in hair samples collected from the general population, and compared both the corresponding levels and the detection limits with those in previous studies. Finally, initial and running costs of HPLC/UV were compared with other analytical methods. As one of the results, the areas of nicotine and cotinine measured by HPLC/UV with column-switching method were 12.9 and 16.9 times greater, respectively, than those without the column-switching method. The amount of nicotine and cotinine in hair was significantly correlated to number of cigarettes smoked per day (r = 0.228, p = 0.040). In addition, the HPLC/UV method showed similar sensitivity and detection limit (nicotine, 0.10 ng/mg;cotinine, 0.08 ng/mg) as reported in previous studies. The cost of the HPLC/UV method is lower than that of other analytical methods. We were able to establish a low-cost method with good sensitivity for measuring nicotine and cotinine in hair. The HPLC/UV with a column-switching method will be useful as a first step in screening surveys in order to better understand the effects of smoking exposure.
文摘In the Chenggong tunnel of Kunming, aiming at the engineering of shallow buried and strongly expanded surrounding rock, the construction method of three steps plus central columns is introduced. The soil of Chenggong Tunnel is tested in laboratory to determine its expansibility. The traditional three-step method and three-step plus center pillar method are compared and analyzed by using MIDAS-GTS. Finally, the deformation of surrounding rock after the construction of three-step plus center pillar method is obtained through on-site monitoring. The results show that: 1) The free expansion rate, montmorillonite content and cation exchange capacity of Chenggong tunnel soil are determined, and the expansive parameters are obtained. 2) Through numerical simulation, it is concluded that under the condition of strong expansive soil and weak surrounding rock, the settlement of vault and two sides caused by the traditional step method are both larger than that of the three steps plus center pillar method. This new improved method can effectively reduce the disturbance to surrounding rock and significantly reduce the settlement of vault;3) The data of vault settlement and displacement of two sides of the tunnel after the construction of the three-step plus center pillar method are obtained by on-site monitoring, and are simulated and analyzed by using MIDAS-GTS software. The relative error value of vault settlement obtained by the two methods is 1%, which indicates that MIDAS-GTS has good simulation effect on the stress state and deformation state of the tunnel, and further indicates that this method is very practical for the case of small convergence of side walls and large vault settlement.
文摘In this paper, we prove the local and Supcrlinear convergence theorem of the column-updating method for n>2. This is an oped problem for the convergene theory of the column-updating method given by Martinez in the Intcrnational Conference of the NATO-ASI (Italy, 1994).
基金supported by the National Natural Science Foundation of China(No.U2333218).
文摘Airport disruptions often pose challenges in assigning aircraft to gates,resulting in infeasible planned schedules.In particular,a large number of transfer passengers miss their connections in the context of disruptions,which cause huge economic losses to airlines and serious passengers’dissatisfaction.This paper proposes a set-partitioning-based model to optimize Aircraft-Gate Reassignment with Transfer Passenger Connections(AGRP-TPC),which incorporates flexible gate-swap and aircraft-delay operations to mitigate the overall impact of disruptions.To efficiently solve the model,we introduce the concepts of additive-transfer and nonstop-transfer to handle passenger connections,and develop a Hierarchical Column-and-Row Generation(HCRG)approach guided by airport terminal space attribute.The column generation and row generation procedures solve iteratively until no new variables and constraints are generated.In addition,a follow-on strategy and a diving heuristic are designed to efficiently obtain high-quality solutions.We evaluate the proposed approach using various instances from a major Chinese international airport.Computational results demonstrate that our approach outperforms the comparison algorithms and produces good solutions within the time limit.Detailed results indicate that our approach effectively reduces overall losses in aircraft-gate reassignment following disruptions,and it can serve as an auxiliary decision-making tool for airport operators and airlines.
基金supported by grants from the Natural Science Foundation of Fujian Province(Grant No.2022J05184).
文摘The utilization of high-strength steel bars(HSSB)within concrete structures demonstrates significant advantages in material conservation and mechanical performance enhancement.Nevertheless,existing design codes exhibit limitations in addressing the distinct statistical characteristics of HSSB,particularly regarding strength design parameters.For instance,GB50010-2010 fails to specify design strength values for reinforcement exceeding 600 MPa,creating technical barriers for advancing HSSB implementation.This study systematically investigates the reliability of eccentric compression concrete columns reinforced with 600 MPa-grade HSSB through high-order moment method analysis.Material partial factors were calibrated against target reliability indices prescribed by GB50068-2018,incorporating critical variables including live-to-dead load ratios,design methodologies,and service conditions.The findings show that the value of k significantly affects the calibration of material partial factors,impacting the reliability of bearing capacity.Considering various k values and target reliability indices,it is recommended that the material partialfactorbe setat1.15,implyingthatthedesignstrengthfor600MPahigh-strengthsteelbars shouldbe considered as 522 MPa.For safety levels I and II,load adjustment factors of 1.1 and 0.9,respectively,may be applied.
文摘目的:运用网状Meta分析评估不同免疫吸附柱治疗类风湿关节炎的有效性与安全性,为临床诊治提供循证依据。方法:计算机检索维普、万方、中国知网、PubMed、CBM、CochraneLibrary、Web of Science等数据库,检索公开发表的免疫吸附柱治疗类风湿关节炎的研究,检索时限至2024年8月。采用Cochrane 5.4手册对纳入的随机对照试验进行质量评价,采用纽卡斯尔-渥太华量表(NOS)对回顾性队列研究进行质量评价。运用R4.1.1软件进行贝叶斯网状Meta分析。结果:最终纳入13篇研究,总样本量891例,共有4种免疫吸附柱。网状Meta分析结果表明,降低C-反应蛋白前3名排序:HA280型吸附柱+常规西药>PH-350型吸附柱+常规西药>A蛋白吸附柱;降低红细胞沉降率前3名排序:白细胞吸附柱>HA280型吸附柱+常规西药>PH-350型吸附柱+常规西药;降低关节肿胀计数前3名排序:白细胞吸附柱>A蛋白吸附柱+常规西药>PH-350型吸附柱+常规西药;降低关节压痛计数前3名排序:白细胞吸附柱>A蛋白吸附柱+常规西药>PH-350型吸附柱+常规西药;降低患者对疾病活动性评分前3名排序:PH-350型吸附柱+常规西药>白细胞吸附柱>A蛋白吸附柱;降低目测类比评分前3名排序:PH-350型吸附柱+常规西药>A蛋白吸附柱>白细胞吸附柱;降低医师对疾病活动性评分前3名排序:PH-350型吸附柱+常规西药>白细胞吸附柱>常规西药。结论:基于纳入的13篇文献证据表明,在降低C-反应蛋白方面,HA280型吸附柱联合常规西药作为首选;在降低红细胞沉降率、关节肿胀计数、关节压痛计数方面,白细胞吸附柱作为首选;在降低患者对疾病活动性评分、医师对疾病活动性评分及目测类比评分方面,PH-350型吸附柱联合常规西药作为首选,在临床中可根据患者的具体情况合理选择不同的免疫吸附柱。
