The quality of the continuous rigid-frame railway bridge is related to the safety of train operation,so it is necessary to test its stiffness,strength,and other indicators.Static load test is a common technique for br...The quality of the continuous rigid-frame railway bridge is related to the safety of train operation,so it is necessary to test its stiffness,strength,and other indicators.Static load test is a common technique for bridge inspection.This article summarizes the purpose of the static load test for a continuous rigid-frame railway bridge,including the required equipment,operation methods,etc.,and lists examples to analyze the operation process and precautions of static load test,hoping to provide reference information for relevant personnel.展开更多
Highway bridges are an important part of the transportation industry and can promote social economic construction and development.In actual operation,highway bridges are often damaged due to overload and natural facto...Highway bridges are an important part of the transportation industry and can promote social economic construction and development.In actual operation,highway bridges are often damaged due to overload and natural factors,which tend to affect the safety and shorten the service life of these bridges.Assessing the overall state and performance of highway bridges is therefore a key element.Static load test,which is a type of sustainable detection experiment,has many advantages,including low cost,high efficiency,and high accuracy.In this paper,the bridge structure is analyzed through the application of theoretical calculations and relevant comparisons,so as to judge the operating state of the bridge.展开更多
Resilience to psychological stress is defined as adaption to challenging life experiences and not the absence of adverse life events.Determinants of resilience include personality traits,genetic/epigenetic modificatio...Resilience to psychological stress is defined as adaption to challenging life experiences and not the absence of adverse life events.Determinants of resilience include personality traits,genetic/epigenetic modifications of genes involved in the stress response,cognitive and behavioral flexibility,secure attachment with a caregiver,social and community support systems,nutrition and exercise,and alignment of circadian rhythm to the natural light/dark cycle.Therefore,resilience is a dynamic and flexible process that continually evolves by the intersection of different domains in human’s life;biological,social,and psychological.The objective of this minireview is to summarize the existing knowledge about the multitude factors and molecular alterations that result from resilience to stress response.Given the multiple contributing factors in building resilience,we set out a goal to identify which factors were most supportive of a causal role by the current literature.We focused on resilience-related molecular alterations resulting from mind-body homeostasis in connection with psychosocial and environmental factors.We conclude that there is no one causal factor that differentiates a resilient person from a vulnerable one.Instead,building resilience requires an intricate network of positive experiences and a healthy lifestyle that contribute to a balanced mind-body connection.Therefore,a holistic approach must be adopted in future research on stress response to address the multiple elements that promote resilience and prevent illnesses and psychopathology related to stress allostatic load.展开更多
Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the...Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism. The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant. Some new load cells, test procedure, and construction technology were adopted based on the applications to different deep foundations, which could enlarge the application scopes of bi-directional loading test. A new type of bi-directional loading test for pipe pile was conducted, in which the load cell was installed and loaded after the pipe pile with special connector has been set up. Unlike the conventional bi-directional loading test, the load cell can be reused and shows an evident economic benefit.展开更多
The retained coal in the end slope of an open-pit mine can be mined by the highwall mining techniques.However,the instability mechanism of the reserved rib pillar under dynamic loads of mining haul trucks and static l...The retained coal in the end slope of an open-pit mine can be mined by the highwall mining techniques.However,the instability mechanism of the reserved rib pillar under dynamic loads of mining haul trucks and static loads of the overlying strata is not clear,which restricts the safe and efcient application of highwall mining.In this study,the load-bearing model of the rib pillar in highwall mining was established,the cusp catastrophe theory and the safety coefcient of the rib pillar were considered,and the criterion equations of the rib pillar stability were proposed.Based on the limit equilibrium theory,the limit stress of the rib pillar was analyzed,and the calculation equations of plastic zone width of the rib pillar in highwall mining were obtained.Based on the Winkler foundation beam theory,the elastic foundation beam model composed of the rib pillar and roof under the highwall mining was established,and the calculation equations for the compression of the rib pillar under dynamic and static loads were developed.The results showed that with the increase of the rib pillar width,the total compression of the rib pillar under dynamic and static loads decreases nonlinearly,and the compression of the rib pillar caused by static loads of the overlying strata and trucks has a decisive role.Numerical simulation and theoretical calculation were also performed in this study.In the numerical simulation,the coal seam with a buried depth of 122 m and a thickness of 3 m is mined by highwall mining techniques.According to the established rib pillar instability model of the highwall mining system,it is found that when the mining opening width is 3 m,the reasonable width of the rib pillar is at least 1.3 m,and the safety factor of the rib pillar is 1.3.The numerical simulation results are in good agreement with the results of theoretical calculation,which verifes the feasibility of the theoretical analysis of the rib pillar stability.This research provides a reference for the stability analysis of rib pillars under highwall mining.展开更多
Crack initiation and subcritical crack growth in glass sheet and SIC bar specimen under static loading were investigated to study the failure process. It has been demonstrated that the lifetime process of brittle mate...Crack initiation and subcritical crack growth in glass sheet and SIC bar specimen under static loading were investigated to study the failure process. It has been demonstrated that the lifetime process of brittle materials involves three possible forms of crack growth: subcritical crack growth, partly subcritical crack growth and instantaneous fracture without subcritical crack growth. Curves of ν-K obtained in step-by-step static fatigue tests and in constant loading rate tests showed different trends for borosilicate glass sheet. α-SiC that is generally considered immune to mechanical fatigue effect and environmental attack was also tested under static loading and the lifetime was measured. The results showed that the threshold load to damage effect was over 80% of the initial strength for the SiC.展开更多
The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating ci...The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.展开更多
Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance ...Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial,axial and overturning moment loadings.The relation between the negative axial clearance and the contact force distribution is analyzed.The static load-carrying capacity curves are established,and the effects of the changes in negative axial clearance,curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed.The results show that,with the increase in the absolute value of negative clearance,the maximum contact load decreases first and then increases.The clearance values in the range of 0.2 mme0 mm have little effect on the static load-carrying capacity of bearing.With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle,the static load capacity of bearing decreases.展开更多
As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundati...As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.展开更多
One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-sta...One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.展开更多
In this paper, the axisymmetric nonlinear free vibration problems of cylindrically orthoiropic shallow thin spherical and conical shells under uniformly distributed static loads are studied by using MWR and Lindstedt-...In this paper, the axisymmetric nonlinear free vibration problems of cylindrically orthoiropic shallow thin spherical and conical shells under uniformly distributed static loads are studied by using MWR and Lindstedt-Poincare perturbation method. from which, the characteristic relation between frequency ratio and amplitude is obtsained.The effects of static loads, geometric and material parameters on vibrational behavior of shells are also展开更多
Large-scale parallelization of molecular dynamics simulations is facing challenges which seriously affect the simulation efficiency,among which the load imbalance problem is the most critical.In this paper,we propose,...Large-scale parallelization of molecular dynamics simulations is facing challenges which seriously affect the simulation efficiency,among which the load imbalance problem is the most critical.In this paper,we propose,a new molecular dynamics static load balancing method(MDSLB).By analyzing the characteristics of the short-range force of molecular dynamics programs running in parallel,we divide the short-range force into three kinds of force models,and then package the computations of each force model into many tiny computational units called"cell loads",which provide the basic data structures for our load balancing method.In MDSLB,the spatial region is separated into sub-regions called"local domains",and the cell loads of each local domain are allocated to every processor in turn.Compared with the dynamic load balancing method,MDSLB can guarantee load balance by executing the algorithm only once at program startup without migrating the loads dynamically.We implement MDSLB in OpenFOAM software and test it on TianHe-1A supercomputer with 16 to 512 processors.Experimental results show that MDSLB can save 34%–64%time for the load imbalanced cases.展开更多
According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrop...According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrophe model was analyzed. The analysis results indicate that the furcation collection where catastrophe may take place is not only decided by mechanical system itself but also relates to exterior loading, which is different from the results obtained under mono-static loading where the bifurcation collection is only determined by mechanics of the system itself and has nothing to do with exterior loading. In addition, the corresponding 1D coupled static-dynamic loading experiment is designed to verify the analysis results of catastrophe model. The test is done with Instron 1342 electro-servo controlled testing system, in which medium strain rate is caused by monotony rising dynamic load. The parameters are obtained combining theoretical model with experiment. The experimental and theoretical curves of critical dynamic load vs static load are rather coincided, thus the new model is proved to be correct.展开更多
This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads.By applying the numerical simulation software-RFPA2D,we have done numerical experiment about the si...This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads.By applying the numerical simulation software-RFPA2D,we have done numerical experiment about the siltstone's crushing effect by dynamic load on single cutter head without confining pressure,dynamic load on single cutter head with confining pressure 10MPa and different dual-cutter heads spacing by combined dynamic and static loads with confining pressure 10MPa.Experimental results show that the confining pressure can obviously affect the rock fragmentation effect.Combined dynamic and static loads can greatly improve the rock fragmentation effect.There exists an optimal spacing of dual-cutter head that can make the rock fragmentation achieve the desired effect.Through analyzing the acoustic emission accumulative energy and quantity,the authors make a conclusion that the optimum spacing is 30 mm.展开更多
Introduction: Allostatic load (AL) index proposes indicators for the functioning of the main potentially stress-affected systems. Sex differences in stress response and stress-related diseases susceptibility have been...Introduction: Allostatic load (AL) index proposes indicators for the functioning of the main potentially stress-affected systems. Sex differences in stress response and stress-related diseases susceptibility have been described for the general population. In this observational study we describe the effects of sex and age on AL variables, in a cohort of patients with general anxiety disorders and neuroticism treated with alprazolam during 12 weeks, before and after treatment. Methods: Patients with general (DSM IV) anxiety disorders with >6 in Hamilton scale, AL (>1 Crimmins and Seeman AL modified criteria) and neuroticism >18 (NEO-FFI inventory), were included. All patients completed psychiatric assessment, AL index determination before (−1 week) and after 12 weeks of treatment with alprazolam (0.25 - 1 mg/t.i.d). Allostatic load parameters comprised cardiovascular, metabolic and inflammatory variables. Univariate analysis (two-way ANOVA), Student’s t-test (related variables) and Pearson correlations were determined. Results: Fifty-four patients, 35 females (48.6 ± 11.7 years) and 19 males (44.2 ± 12.8 years) with general anxiety disorder were included;28 patients with Conclusions: In this preliminary analysis we described sex and age differences in psychiatry aspects and AL indexes in patients with general anxiety disorders in the short-term treatment with alprazolam. These considerations remark the need of pondering sex and age differences during the use of drugs for protracted periods.展开更多
An eight-channel force loading system is presented, which adopts position control system and forcecontrol system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligentPID algo...An eight-channel force loading system is presented, which adopts position control system and forcecontrol system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligentPID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlledcylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to展开更多
Seismic method is usually used for elastic parametric estimation.This is why this method presents dynamic parameters of Earth.Frequency seismic range changes greatly from geodynamic modelling time.Now we have opportun...Seismic method is usually used for elastic parametric estimation.This is why this method presents dynamic parameters of Earth.Frequency seismic range changes greatly from geodynamic modelling time.Now we have opportunity to use geodesy result for some years for elastic parameters estimation.Static solution from elastic theory may be used for the interpretation of long term results.It presents static elastic parameter.The inverse problem for different types of vertical surface loading on one year period is calculated.Two cases of loading with maximal and minimal area are presented.Results are determined by space geodesy and leveling methods.Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from2000 km to 3000 km.Pressure-displacement coefficients(PDC) can be achieved by three years observation(0.997 mm/mbar for NVSK GPS station).It is used for elastic module study of geology medium with maximum thickness up to 600 km.In the context of elastic model,the modulus of rigidity is estimated to be 113 GPa.Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle.Smaller size of surface loading-local loading is seasonal variation of water reservoir.Annual vertical changes were obtained by leveling near the dam of the reservoir.PDC ratio was 1.15 mm/bar for these places.In elastic theory,the Young modulus E = 80 GPa(Poisson ratio = 0.25,the modulus of rigidity = 32 GPa) was calculated by sixteen years of leveling measurements.This result can effectively be represented for upper crust.Our results were checked by solution for coseismic displacement of ChyiaAltai earthquake(Sep.27,2003,M = 7.3).Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10%level.展开更多
Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is su...Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is suitable for parallel computing. In this paper, a static load balance parallel method is presented by combining Message Passing Interface (MPI) with Adaptively Modified CBFM (AMCBFM). In this method, the object geometry is partitioned into distinct blocks, and the serial number of blocks is sent to related nodes according to a certain rule. Every node only needs to calculate the information on local blocks. The obtained results confirm the accuracy and efficiency of the proposed method in speeding up solving large electrical scale problems.展开更多
Purpose: Anxiety disorders are frequently associated with chronic stress with possible cognitive consequences. The aim of this study was to determine the verbal fluency performance in a cohort of patients with anxiety...Purpose: Anxiety disorders are frequently associated with chronic stress with possible cognitive consequences. The aim of this study was to determine the verbal fluency performance in a cohort of patients with anxiety disorders and allostatic load, treated with alprazolam during 12 weeks. Methods: Patients with GAD (general anxiety disorders, DSM IV), with >6 in Hamilton Anxiety Rating Scale (HAM-A), neuroticism > 18 (NEO-FFI inventory), and normal Mini-Mental State Examination were included. Clinical and Psychiatric examination, Allostatic Load Index and cognitive assessment were analyzed before and after 12 weeks of treatment. The phonemic and semantic verbal fluency tests were determined in all patients. The scoring for each fluency task was determined by counting the number of correct words. The total score from each semantic and phonemic verbal task was analyzed comparing the individual score with normal data controlled by age and sex. Patients with scores > ?2 standard deviation (SD) from normative data were considered impaired. Results: Fifty-four patients completed the semantic verbal fluency test before treatment and fifty patients completed after treatment. According to the z-scores before treatment 7 patients of 54 (12.9%) had verbal fluency impairments. After treatment none patients showed semantic verbal fluency deficits but 3 patients of 50 (6%) showed phonemic impairments. Impaired group was significantly associated with an older age before treatment (p = 0.033) and with a similar tendency but not significant (p = 0.09) after treatment (Student t test). Conclusion: In this study older age factor was associated with verbal fluency impairment in GAD patients. Stratified treatments analyzing age and sex factors, including allostatic load measurements and cognitive assessments may be useful tools to determine the effectiveness and the safety of psychopharmacological treatments.展开更多
Spiral springs have a wide range of applications in various fields.As a result of the complexity of friction,few theoretical analyses of spring belts under static loading have been carried out.Considering the piecewis...Spiral springs have a wide range of applications in various fields.As a result of the complexity of friction,few theoretical analyses of spring belts under static loading have been carried out.Considering the piecewise smooth property of the whole contact area,a simplified static model of spiral springs under loading is established in this paper.Besides,three main stress and friction distribution areas of the spring belt are proposed,namely,internal,transitional,and external regions.Since the outermost side of the spring is not subject to any pressure,a recursive method is adopted from the outside to the inside.The model provides the parameter conditions,i.e.,the internal and external forces are independent or dependent.Therefore,the case that the whole contact region of the spring belt has one subregion,two subregions,and three subregions is obtained.The model gives a theoretical basis for the parameter optimization of spiral springs.展开更多
文摘The quality of the continuous rigid-frame railway bridge is related to the safety of train operation,so it is necessary to test its stiffness,strength,and other indicators.Static load test is a common technique for bridge inspection.This article summarizes the purpose of the static load test for a continuous rigid-frame railway bridge,including the required equipment,operation methods,etc.,and lists examples to analyze the operation process and precautions of static load test,hoping to provide reference information for relevant personnel.
文摘Highway bridges are an important part of the transportation industry and can promote social economic construction and development.In actual operation,highway bridges are often damaged due to overload and natural factors,which tend to affect the safety and shorten the service life of these bridges.Assessing the overall state and performance of highway bridges is therefore a key element.Static load test,which is a type of sustainable detection experiment,has many advantages,including low cost,high efficiency,and high accuracy.In this paper,the bridge structure is analyzed through the application of theoretical calculations and relevant comparisons,so as to judge the operating state of the bridge.
文摘Resilience to psychological stress is defined as adaption to challenging life experiences and not the absence of adverse life events.Determinants of resilience include personality traits,genetic/epigenetic modifications of genes involved in the stress response,cognitive and behavioral flexibility,secure attachment with a caregiver,social and community support systems,nutrition and exercise,and alignment of circadian rhythm to the natural light/dark cycle.Therefore,resilience is a dynamic and flexible process that continually evolves by the intersection of different domains in human’s life;biological,social,and psychological.The objective of this minireview is to summarize the existing knowledge about the multitude factors and molecular alterations that result from resilience to stress response.Given the multiple contributing factors in building resilience,we set out a goal to identify which factors were most supportive of a causal role by the current literature.We focused on resilience-related molecular alterations resulting from mind-body homeostasis in connection with psychosocial and environmental factors.We conclude that there is no one causal factor that differentiates a resilient person from a vulnerable one.Instead,building resilience requires an intricate network of positive experiences and a healthy lifestyle that contribute to a balanced mind-body connection.Therefore,a holistic approach must be adopted in future research on stress response to address the multiple elements that promote resilience and prevent illnesses and psychopathology related to stress allostatic load.
基金Supported by the National Natural Science Foundation of China (50908048)the Priority Academic Program Development (PAPD) Project of JiangsuHigher Education Institutions
文摘Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism. The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant. Some new load cells, test procedure, and construction technology were adopted based on the applications to different deep foundations, which could enlarge the application scopes of bi-directional loading test. A new type of bi-directional loading test for pipe pile was conducted, in which the load cell was installed and loaded after the pipe pile with special connector has been set up. Unlike the conventional bi-directional loading test, the load cell can be reused and shows an evident economic benefit.
基金fnancially supported by National Natural Science Foundation of China(Grant No.51974295).
文摘The retained coal in the end slope of an open-pit mine can be mined by the highwall mining techniques.However,the instability mechanism of the reserved rib pillar under dynamic loads of mining haul trucks and static loads of the overlying strata is not clear,which restricts the safe and efcient application of highwall mining.In this study,the load-bearing model of the rib pillar in highwall mining was established,the cusp catastrophe theory and the safety coefcient of the rib pillar were considered,and the criterion equations of the rib pillar stability were proposed.Based on the limit equilibrium theory,the limit stress of the rib pillar was analyzed,and the calculation equations of plastic zone width of the rib pillar in highwall mining were obtained.Based on the Winkler foundation beam theory,the elastic foundation beam model composed of the rib pillar and roof under the highwall mining was established,and the calculation equations for the compression of the rib pillar under dynamic and static loads were developed.The results showed that with the increase of the rib pillar width,the total compression of the rib pillar under dynamic and static loads decreases nonlinearly,and the compression of the rib pillar caused by static loads of the overlying strata and trucks has a decisive role.Numerical simulation and theoretical calculation were also performed in this study.In the numerical simulation,the coal seam with a buried depth of 122 m and a thickness of 3 m is mined by highwall mining techniques.According to the established rib pillar instability model of the highwall mining system,it is found that when the mining opening width is 3 m,the reasonable width of the rib pillar is at least 1.3 m,and the safety factor of the rib pillar is 1.3.The numerical simulation results are in good agreement with the results of theoretical calculation,which verifes the feasibility of the theoretical analysis of the rib pillar stability.This research provides a reference for the stability analysis of rib pillars under highwall mining.
基金This work was supported by the National Natural Science Foundation of China(No.59872035 and No.59902227)the Science Foundation of Beijing(2002019).
文摘Crack initiation and subcritical crack growth in glass sheet and SIC bar specimen under static loading were investigated to study the failure process. It has been demonstrated that the lifetime process of brittle materials involves three possible forms of crack growth: subcritical crack growth, partly subcritical crack growth and instantaneous fracture without subcritical crack growth. Curves of ν-K obtained in step-by-step static fatigue tests and in constant loading rate tests showed different trends for borosilicate glass sheet. α-SiC that is generally considered immune to mechanical fatigue effect and environmental attack was also tested under static loading and the lifetime was measured. The results showed that the threshold load to damage effect was over 80% of the initial strength for the SiC.
基金Supported by National Natural Science Foundation of China(Grant No11472239)Hebei Provincial Natural Science Foundation of China(Grant No.A2015203023)Key Project of Science and Technology Research of Higher Education of Hebei Province of China(Grant No.ZD20131055)
文摘The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.
基金supported by NSFC(51105131)Excellent Youth Foundation of Henan Scientific Committee(124100510002)Creative Talent Foundation in University of Henan Province(2011HASTIT016)
文摘Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial,axial and overturning moment loadings.The relation between the negative axial clearance and the contact force distribution is analyzed.The static load-carrying capacity curves are established,and the effects of the changes in negative axial clearance,curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed.The results show that,with the increase in the absolute value of negative clearance,the maximum contact load decreases first and then increases.The clearance values in the range of 0.2 mme0 mm have little effect on the static load-carrying capacity of bearing.With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle,the static load capacity of bearing decreases.
文摘As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.
基金supported by the National Natural Science Foundation of China(U1134201)partly supported by the National High Technology Research and Development Program of China(0912JJ0104-DL00-H-HZ-001-20100105)
文摘One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.
文摘In this paper, the axisymmetric nonlinear free vibration problems of cylindrically orthoiropic shallow thin spherical and conical shells under uniformly distributed static loads are studied by using MWR and Lindstedt-Poincare perturbation method. from which, the characteristic relation between frequency ratio and amplitude is obtsained.The effects of static loads, geometric and material parameters on vibrational behavior of shells are also
基金Project supported by the National Natural Science Foundation of China (Grant Nos.61303071 and 61120106005)the Natural Science Fund from the Guangzhou Science and Information Technology Bureau (Grant No.134200026)
文摘Large-scale parallelization of molecular dynamics simulations is facing challenges which seriously affect the simulation efficiency,among which the load imbalance problem is the most critical.In this paper,we propose,a new molecular dynamics static load balancing method(MDSLB).By analyzing the characteristics of the short-range force of molecular dynamics programs running in parallel,we divide the short-range force into three kinds of force models,and then package the computations of each force model into many tiny computational units called"cell loads",which provide the basic data structures for our load balancing method.In MDSLB,the spatial region is separated into sub-regions called"local domains",and the cell loads of each local domain are allocated to every processor in turn.Compared with the dynamic load balancing method,MDSLB can guarantee load balance by executing the algorithm only once at program startup without migrating the loads dynamically.We implement MDSLB in OpenFOAM software and test it on TianHe-1A supercomputer with 16 to 512 processors.Experimental results show that MDSLB can save 34%–64%time for the load imbalanced cases.
基金Project(50490272 ,50490274 ,10472134) supported by the Natural Science Foundation of China project(2005038250)supported by the China Postdoctoral Foundation
文摘According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrophe model was analyzed. The analysis results indicate that the furcation collection where catastrophe may take place is not only decided by mechanical system itself but also relates to exterior loading, which is different from the results obtained under mono-static loading where the bifurcation collection is only determined by mechanics of the system itself and has nothing to do with exterior loading. In addition, the corresponding 1D coupled static-dynamic loading experiment is designed to verify the analysis results of catastrophe model. The test is done with Instron 1342 electro-servo controlled testing system, in which medium strain rate is caused by monotony rising dynamic load. The parameters are obtained combining theoretical model with experiment. The experimental and theoretical curves of critical dynamic load vs static load are rather coincided, thus the new model is proved to be correct.
基金National Science Foundation of China (No.50974059No.50934006)
文摘This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads.By applying the numerical simulation software-RFPA2D,we have done numerical experiment about the siltstone's crushing effect by dynamic load on single cutter head without confining pressure,dynamic load on single cutter head with confining pressure 10MPa and different dual-cutter heads spacing by combined dynamic and static loads with confining pressure 10MPa.Experimental results show that the confining pressure can obviously affect the rock fragmentation effect.Combined dynamic and static loads can greatly improve the rock fragmentation effect.There exists an optimal spacing of dual-cutter head that can make the rock fragmentation achieve the desired effect.Through analyzing the acoustic emission accumulative energy and quantity,the authors make a conclusion that the optimum spacing is 30 mm.
文摘Introduction: Allostatic load (AL) index proposes indicators for the functioning of the main potentially stress-affected systems. Sex differences in stress response and stress-related diseases susceptibility have been described for the general population. In this observational study we describe the effects of sex and age on AL variables, in a cohort of patients with general anxiety disorders and neuroticism treated with alprazolam during 12 weeks, before and after treatment. Methods: Patients with general (DSM IV) anxiety disorders with >6 in Hamilton scale, AL (>1 Crimmins and Seeman AL modified criteria) and neuroticism >18 (NEO-FFI inventory), were included. All patients completed psychiatric assessment, AL index determination before (−1 week) and after 12 weeks of treatment with alprazolam (0.25 - 1 mg/t.i.d). Allostatic load parameters comprised cardiovascular, metabolic and inflammatory variables. Univariate analysis (two-way ANOVA), Student’s t-test (related variables) and Pearson correlations were determined. Results: Fifty-four patients, 35 females (48.6 ± 11.7 years) and 19 males (44.2 ± 12.8 years) with general anxiety disorder were included;28 patients with Conclusions: In this preliminary analysis we described sex and age differences in psychiatry aspects and AL indexes in patients with general anxiety disorders in the short-term treatment with alprazolam. These considerations remark the need of pondering sex and age differences during the use of drugs for protracted periods.
文摘An eight-channel force loading system is presented, which adopts position control system and forcecontrol system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligentPID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlledcylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to
文摘Seismic method is usually used for elastic parametric estimation.This is why this method presents dynamic parameters of Earth.Frequency seismic range changes greatly from geodynamic modelling time.Now we have opportunity to use geodesy result for some years for elastic parameters estimation.Static solution from elastic theory may be used for the interpretation of long term results.It presents static elastic parameter.The inverse problem for different types of vertical surface loading on one year period is calculated.Two cases of loading with maximal and minimal area are presented.Results are determined by space geodesy and leveling methods.Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from2000 km to 3000 km.Pressure-displacement coefficients(PDC) can be achieved by three years observation(0.997 mm/mbar for NVSK GPS station).It is used for elastic module study of geology medium with maximum thickness up to 600 km.In the context of elastic model,the modulus of rigidity is estimated to be 113 GPa.Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle.Smaller size of surface loading-local loading is seasonal variation of water reservoir.Annual vertical changes were obtained by leveling near the dam of the reservoir.PDC ratio was 1.15 mm/bar for these places.In elastic theory,the Young modulus E = 80 GPa(Poisson ratio = 0.25,the modulus of rigidity = 32 GPa) was calculated by sixteen years of leveling measurements.This result can effectively be represented for upper crust.Our results were checked by solution for coseismic displacement of ChyiaAltai earthquake(Sep.27,2003,M = 7.3).Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10%level.
文摘Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is suitable for parallel computing. In this paper, a static load balance parallel method is presented by combining Message Passing Interface (MPI) with Adaptively Modified CBFM (AMCBFM). In this method, the object geometry is partitioned into distinct blocks, and the serial number of blocks is sent to related nodes according to a certain rule. Every node only needs to calculate the information on local blocks. The obtained results confirm the accuracy and efficiency of the proposed method in speeding up solving large electrical scale problems.
文摘Purpose: Anxiety disorders are frequently associated with chronic stress with possible cognitive consequences. The aim of this study was to determine the verbal fluency performance in a cohort of patients with anxiety disorders and allostatic load, treated with alprazolam during 12 weeks. Methods: Patients with GAD (general anxiety disorders, DSM IV), with >6 in Hamilton Anxiety Rating Scale (HAM-A), neuroticism > 18 (NEO-FFI inventory), and normal Mini-Mental State Examination were included. Clinical and Psychiatric examination, Allostatic Load Index and cognitive assessment were analyzed before and after 12 weeks of treatment. The phonemic and semantic verbal fluency tests were determined in all patients. The scoring for each fluency task was determined by counting the number of correct words. The total score from each semantic and phonemic verbal task was analyzed comparing the individual score with normal data controlled by age and sex. Patients with scores > ?2 standard deviation (SD) from normative data were considered impaired. Results: Fifty-four patients completed the semantic verbal fluency test before treatment and fifty patients completed after treatment. According to the z-scores before treatment 7 patients of 54 (12.9%) had verbal fluency impairments. After treatment none patients showed semantic verbal fluency deficits but 3 patients of 50 (6%) showed phonemic impairments. Impaired group was significantly associated with an older age before treatment (p = 0.033) and with a similar tendency but not significant (p = 0.09) after treatment (Student t test). Conclusion: In this study older age factor was associated with verbal fluency impairment in GAD patients. Stratified treatments analyzing age and sex factors, including allostatic load measurements and cognitive assessments may be useful tools to determine the effectiveness and the safety of psychopharmacological treatments.
基金the National Natural Science Foundation of China(No.11972055)the National Defense Science and Technology Fund in the Technical Field of the Foundation Strengthening Plan(No.2020-JCJQ-JJ-009)the Civil Aerospace Pre-research Project(No.D020206)。
文摘Spiral springs have a wide range of applications in various fields.As a result of the complexity of friction,few theoretical analyses of spring belts under static loading have been carried out.Considering the piecewise smooth property of the whole contact area,a simplified static model of spiral springs under loading is established in this paper.Besides,three main stress and friction distribution areas of the spring belt are proposed,namely,internal,transitional,and external regions.Since the outermost side of the spring is not subject to any pressure,a recursive method is adopted from the outside to the inside.The model provides the parameter conditions,i.e.,the internal and external forces are independent or dependent.Therefore,the case that the whole contact region of the spring belt has one subregion,two subregions,and three subregions is obtained.The model gives a theoretical basis for the parameter optimization of spiral springs.
