About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials...About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials Science.The college has its Chemistry program ranking ESI Top 6%o worldwide,and Materials Science program ranking 589th in the world since2023.The college has led publications appearing in journals such as Nat.Catal.,Nat.Commun.,Sci.Adv.,J.Am.Chem.Soc.,Angew.Chem.展开更多
About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials...About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials Science.The collegehas its Chemistry program ranking ESI Top 6‰ worldwide,and Materials Scienceprogram ranking 589th in the world since 2023.展开更多
This study examines the influence of window size and ventilation strategies on the IAQ(indoor air quality)of public toilets in elementary schools within Dhaka City.Maintaining adequate IAQ in school toilets is crucial...This study examines the influence of window size and ventilation strategies on the IAQ(indoor air quality)of public toilets in elementary schools within Dhaka City.Maintaining adequate IAQ in school toilets is crucial,as poor air quality can pose significant health risks,including respiratory issues,discomfort,and increased susceptibility to infectious diseases.Moreover,substandard IAQ can lead to unpleasant odors and poor sanitation,negatively impacting students’overall well-being and learning environment.The research evaluates key IAQ indicators,including carbon dioxide(CO_(2))and sulfur dioxide(SO_(2))concentrations,humidity,and temperature,to determine the effectiveness of various ventilation setups.The study employs comparative analysis by varying window sizes and ventilation strategies,such as natural ventilation with different window opening percentages.Findings reveal that toilets with larger window areas and higher opening percentages achieve significantly improved natural ventilation,resulting in reduced levels of CO_(2)and SO_(2),lower humidity,and more stable temperatures.These improvements contribute to creating a more hygienic and comfortable environment.The results underscore the critical role of window design and placement in enhancing ventilation efficiency and minimizing pollutant buildup in public toilets.Based on these insights,the study provides actionable recommendations for optimizing window dimensions,placement,and ventilation strategies in the design of school toilets and facilities.By implementing these design improvements,schools can significantly enhance toilets sanitation,improve health outcomes for students,and create a more conducive learning environment.The findings offer practical solutions for addressing IAQ challenges in window design for architects and designers.展开更多
Rock mass damage at great depths near underground openings is often of a zonal character.However,the classical elastoplastic theory fails to explain sufficiently all properties of zonal failure structures.A new non-Eu...Rock mass damage at great depths near underground openings is often of a zonal character.However,the classical elastoplastic theory fails to explain sufficiently all properties of zonal failure structures.A new non-Euclidean mathematical model for highly-stressed rock mass was developed based on the principles of mechanics of defected material and non-equilibrium thermodynamics.Methods were developed to determine model parameters that provide satisfactory correspondence between the experimental findings concerning faulted zonal structures near openings at great depths and mathematical calculations.The mechanism of this phenomenon was discovered which consisted in a periodical character of stresses in the surrounding rock mass and development of tensile macrocracks at zones of maximal tangential stresses.Main relationships between the cracking zone width and rock mass strength were established.展开更多
In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings o...In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings of−600 m level in Coal Mine“6.13”,Democratic People's Republic of Korea.The displacement components used for back analysis are the crown settlement and sidewalls convergence monitored at the end of the openings excavation,and the final closures predicted by GVM.The non-linear relation between displacements and back analysis parameters was obtained by artificial neural network(ANN)and Burger-creep viscoplastic(CVISC)model of FLAC3D.Then,the optimal parameters were determined for rock mass surrounding tunnel by genetic algorithm(GA)with both groups of measured displacements at the end of the final excavation and closures predicted by GVM.The maximum absolute error(MAE)and standard deviation(Std)between calculated displacements by numerical simulation with back analysis parameters and in situ ones were less than 6 and 2 mm,respectively.Therefore,it was found that the proposed method could be successfully applied to determining design parameters and stability for tunnels and underground cavities,as well as mine openings and stopes.展开更多
Framed structures are usually infilled with masonry walls. They may cause a significant increase in both stiffness and strength, reducing the deformation demand and increasing the energy dissipation capacity of the sy...Framed structures are usually infilled with masonry walls. They may cause a significant increase in both stiffness and strength, reducing the deformation demand and increasing the energy dissipation capacity of the system. On the other hand, irregular arrangements of the masonry panels may lead to the concentration of damage in some regions, with negative effects; for example soft story mechanisms and shear failures in short columns. Therefore, the presence ofinfill walls should not be neglected, especially in regions of moderate and high seismicity. To this aim, simple models are available for solid infills walls, such as the diagonal no-tension strut model, while infilled frames with openings have not been adequately investigated. In this study, the effect of openings on the strength and stiffness of infilled frames is investigated by means of about 150 experimental and numerical tests. The main parameters involved are identified and a simple model to take into account the openings in the infills is developed and compared with other models proposed by different researchers. The model, which is based on the use of strength and stiffness reduction factors, takes into account the opening dimensions and presence of reinforcing elements around the opening. An example of an application of the proposed reduction factors is also presented.展开更多
Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath...Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath steel beams leading to uneconomic floor heights. The most adopted solution for this issue is the use of steel beam web openings to provide the required space for services. These openings could lead to a significant decrease of the beam load carrying capacity depending on the adopted openings shape, size and location. These aspects motivated the present study based on FE simulations calibrated against numerical and test results. The results accuracy enabled a comprehensive parametric analysis of beams with web openings to be made focused on the profile size, web opening location, among others. The study also investigated the efficiency of longitudinal stiffeners welded at the opening region and benefits of using an adequate edge concordance radius in beams with rectangular and square openings. The obtained results showed the need of using welded longitudinal stiffeners in order to increase the beams ultimate load carrying capacity. This adoption can double or even triple the ultimate load of beams with rectangular and square opening heights equal to 0.75 H, respectively.展开更多
Rockburst,earthquake and blasting cause some dynamic loads on rock support and rock reinforcement system.Elements of rock support and rock reinforcement are generally made of steel bar or cables,which are resistant ag...Rockburst,earthquake and blasting cause some dynamic loads on rock support and rock reinforcement system.Elements of rock support and rock reinforcement are generally made of steel bar or cables,which are resistant against corrosion.These support elements may be subjected to vibrations induced by turbines,vehicle traffic and long-term corrosion in addition to dynamic loading caused by earthquake,rockburst and blasting.In this study,some theoretical,numerical and experimental studies are conducted on rockbolts and rock anchors under shaking and impulsive loading.Then the outcomes of these studies are presented and their practical implications are discussed accordingly.展开更多
Two dimensional,reinforced concrete building frames built on raft foundation and having infill wall panels with openings in them are analysed using the direct stiffness method.Beams and columns are modelled by beam co...Two dimensional,reinforced concrete building frames built on raft foundation and having infill wall panels with openings in them are analysed using the direct stiffness method.Beams and columns are modelled by beam column elements.Wall panels are modelled by plane stress finite elements.The raft foundation is modelled by uniaxial finite elements.The soil is modelled as half space model.Openings in wall panels are introduced by using fictitious beams between real floor beams. A computer program is written to carry out the static analysis and do the necessary comparison to show the effect of openings on the structural behavior.展开更多
A brief introduction is made for the Numerical Manifold Method and its analysing process in rock mechanics. Some aspects of the manifold method are improved in implementing process according to the practice of excavat...A brief introduction is made for the Numerical Manifold Method and its analysing process in rock mechanics. Some aspects of the manifold method are improved in implementing process according to the practice of excavating underground openings. Corresponding formulas are given and a computer program of the Numerical Manifold Method has been completed in this paper.展开更多
A linear three dimensional finite element (FE) study has been carried out to examine the structural response of a prestressed concrete (PSC) inner containment (IC) dome of reactor building (double containment system) ...A linear three dimensional finite element (FE) study has been carried out to examine the structural response of a prestressed concrete (PSC) inner containment (IC) dome of reactor building (double containment system) of a typical Indian Nuclear Power Plant, having large steam generator (SG) openings with due emphasis on the local behaviour of the steel-concrete interfaces at the SG openings, due to initial prestress transfer. The predominant thrust of the study has been placed on the objective of predicting the possibilities of separation at the steel-concrete interface zones adjacent to the embedded plates (EPs) of the SG openings. Two types of modeling and analysis have been made to study the overall and local behaviour of the structure. Prestressing ducts, passive reinforcements and EPs have been included in the models in certain ways. For the FE analysis, the interface zone has been modeled using interface elements, the properties of which were derived from the results of past experiments conducted on steel plate-concrete inter-face specimens. The FE analysis results have been compared with the results of the past two FE analytical studies on the linear behaviour of the same PSC IC dome. Important observations have been made regarding dome deformation and stresses throughout the structure with special emphasis on the local behaviour of steel-concrete interfaces at and around the SG openings.展开更多
The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and func...The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and functional degradation. The Tinguá Biological Reserve-RJ comprises approximately 26,000 hectares of well-preserved Atlantic Forest, but it is subject to impacts caused by two canopy openings along oil pipelines. Comparisons were made between pipeline edges and forest interiors to evaluate edge effects on the structure and dynamics of those tree communities. Tree densities were higher along forest edges, apparently increasing over time. Tree basal areas, on the other hand, have decreased along edges due to higher mortality rates. Linear canopy opening edges showed higher densities of small trees, while the interior had more very large trees, indicating changes in successional processes and community structural patterns due to edge effects.展开更多
Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex var...Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex variable function, a series' of conformal mapping functions are obtained from different cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And, the general expressions for the equations of a cylindrical shell, including the solutions of stress concentrations meeting the boundary conditions of the large openings' edges, are given in the mapping plane. Furthermore, by applying the orthogonal function expansion technique, the problem can be summarized into the solution of infinite algebraic equation series. Finally, numerical results are obtained for stress concentration factors at the cutout's edge with various opening's ratios and different loading conditions. This new method, at the same time, gives a possibility to the research of cylindrical shells with large non-circular openings or with nozzles.展开更多
The aero engine turbine rotors are under strong centrifugal load and the highest thermal load.The ventilation openings on the rotors are inevitable,because air flow need to pass through them to cool the temperatures d...The aero engine turbine rotors are under strong centrifugal load and the highest thermal load.The ventilation openings on the rotors are inevitable,because air flow need to pass through them to cool the temperatures down and keep the air pressure balanced in internal aero engine.The ventilation openings will lead to stress concentration effect.In this paper,the stress concentration factor of elliptical opening on rotating disc is deduced by superposition method.How to define the optimal location and shape of the elliptical opening on rotating disc to decrease the stress concentration effect has been investigated specifically.The reliability and accuracy of the theoretical deviation process is verified by Finite Element Method(FEM).The process of how to obtain the optimal location of the elliptical ventilation opening with particular shape on turbine sealing disc is described as an engineering application case.The investigation provides sufficient theoretical support for optimal location and shape definition of elliptical ventilation opening on aero engine rotors with stress concentration effect by pure mechanics consideration.展开更多
Stress concentrations about thin cylindrical shells with small openings are reconsidered front a nerv angle. There is a sort of special internal relation between theoretical solutions about cylindrical shells,vith lar...Stress concentrations about thin cylindrical shells with small openings are reconsidered front a nerv angle. There is a sort of special internal relation between theoretical solutions about cylindrical shells,vith large openings and one,with small openings. Using this relation, the extent of applying the theory about small openings to engineering practice is estimated again, thus an idea of how to use this theory and a nerv appraisal of the application of theoretical solutions about cylindrical shells with small openings to engineering practice are given.展开更多
About us:The Clige of Cemistry and Materials Engineering(CME)in Wenzhou University(Zhejing Province,China)is looking for postdoctoral candidates(up to 25) specialized in Chemistry Chemical Engineering and Materials Se...About us:The Clige of Cemistry and Materials Engineering(CME)in Wenzhou University(Zhejing Province,China)is looking for postdoctoral candidates(up to 25) specialized in Chemistry Chemical Engineering and Materials Secence. The college has is Chemistry program ranking ESI Top 6‰ worldwide.展开更多
When service ducts and cables are required to pass through the structural beams,it is a common practical solution to use composite beams with rectangular or circular openings.The fire safety standards in many countrie...When service ducts and cables are required to pass through the structural beams,it is a common practical solution to use composite beams with rectangular or circular openings.The fire safety standards in many countries have recommended design methods for composite beams without openings,while the design method for composite beams with web openings is not addressed yet.Due to the complicated distribution of temperature and stress around the openings in the web of the steel beam,extra complexity has been introduced in determination of the structural capability of the beam and the failure mode in fire.These failure modes generally occur at lower limiting temperatures than the solid beam with same size.It is recognized that the thickness of a reactive coating required to provide a given fire resistance to a composite beam with web openings is affected by the beam’s web thickness,opening configuration,the degree of the beam asymmetry and the structural utilization factor,as well as the nature of the proprietary fire protection itself.Therefore it is necessary that such beams are structurally evaluated taking into account all possible modes of structural failure under both ambient and fire conditions.It is also necessary for additional thermal data to be measured around the web openings and on the web posts from fire tests.The additional thermal data will be used in conjunction with a structural model to determine limiting temperatures of beams with web openings.Steel Construction Institute(SCI)has produced a structural analysis model referenced as report RT1356,which divides a composite beam with web openings into different stress blocks,and then analyses the global bending,vertical shear,local Vierendeel bending,web-post buckling etc.The Association for Specialist Fire Protection(ASFP)recommended the test protocol in the Yellow Book,to determine the temperature distribution around the openings and web post.This paper will discuss a series of fire tests having been carried out in the laboratory of EXOVA Warringtonfire to establish temperature distribution in composite beams with web openings.Test result shows that the distribution of temperature is product specific and strongly affected by opening configuration and opening distance.EXOVA Warringtonfire has also developed a sophisticated calculator,ThermCalc,for analyzing temperature and structural following the method presented in RT1356.Using ThermCalc,parametric study has been carried out,and the effect of load utilization factor,opening size,opening distance,slab depth,decking configuration etc.was investigated.展开更多
The shear wall with and without openings that served as a structural element or/and partition wall was utilized in a low-cost housing for the low-income people in Indonesia. The houses,however,should be withstoodfrom ...The shear wall with and without openings that served as a structural element or/and partition wall was utilized in a low-cost housing for the low-income people in Indonesia. The houses,however,should be withstoodfrom earthquake inertial force, so there must be no casualties when disaster struck. The alternative types of composite structure made of wood and cement based building materials needed to meet with the high demand for earthquake-resistant houses in Indonesia. In order to understand the mechanism of earthquake resisting performance of shear wall, we needs to investigate behavior of shear wallsnot only for cyclic static but alsofor dynamic loading. In this study, theseries of full-scale experiment on timber frame shear walls with and without openings,compose of Laminated Veneer Lumber (LVL) engineered wood (Paraserianthes Falcatariaand Hevea Brasiliensis) and sheathed by Fiber Cement Board (FCB), was carried out.By analyzing testing result using theoretical approaches, we intended to predict static initial stiffness and yielding strength as well as basic dynamic properties shear walls. For static behavior, good agreements were obtain from comparison between experiment and theoretical prediction based on mechanical model. While, for dynamic behavior, agreement was not sufficient due tothe effect of bending and rocking of actual test specimens. The information obtain by this study will be useful for practical engineers or structural designers to design the high performance earthquake resisting timber houses with a low construction cost.展开更多
The nucleophilic ring opening reaction of propargyl epoxides by amines based on a silver catalyst is presented, The reaction takes place under mild conditions and features a high regioselectivity to provide an effecti...The nucleophilic ring opening reaction of propargyl epoxides by amines based on a silver catalyst is presented, The reaction takes place under mild conditions and features a high regioselectivity to provide an effective method for the synthesis of 2-amino homopropargyl alcohols in moderate to high yields,展开更多
In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixi...In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixing of the coolant. The communication of the outer strap affects the hydraulic force exerted by the spacer grid of the fuel assembly which could induce fuel assembly bow. In present study, in order to understand the influencing factors of hydraulic force exerted by the spacer grid, outer straps with various flow opening design features, different location and size are investigated by a commercially CFD （computational fluid dynamics） code, ANSYS CFX 12.1. Three dimensional rod bundles including the outer strap without and with different openings are modelled for simulation. The analysis results show that the openings on the spacer grid outer strap can reduce the lateral hydraulic loadings perpendicular to the centerline of the fuel rods exerted by the spacer grids obviously because of the pressures inside and outside the spacer grids being balanced. Besides, influences of the opening design features on the hydraulic force, resistance characteristics and lateral flow factor are investigated in details.展开更多
文摘About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials Science.The college has its Chemistry program ranking ESI Top 6%o worldwide,and Materials Science program ranking 589th in the world since2023.The college has led publications appearing in journals such as Nat.Catal.,Nat.Commun.,Sci.Adv.,J.Am.Chem.Soc.,Angew.Chem.
文摘About us:The College of Chemistry and Materials Engineering(CME)in Wenzhou University(Zhejiang Province,China)is looking for postdoctoral candidates(up to 25)specialized in Chemistry,Chemical Engineering and Materials Science.The collegehas its Chemistry program ranking ESI Top 6‰ worldwide,and Materials Scienceprogram ranking 589th in the world since 2023.
文摘This study examines the influence of window size and ventilation strategies on the IAQ(indoor air quality)of public toilets in elementary schools within Dhaka City.Maintaining adequate IAQ in school toilets is crucial,as poor air quality can pose significant health risks,including respiratory issues,discomfort,and increased susceptibility to infectious diseases.Moreover,substandard IAQ can lead to unpleasant odors and poor sanitation,negatively impacting students’overall well-being and learning environment.The research evaluates key IAQ indicators,including carbon dioxide(CO_(2))and sulfur dioxide(SO_(2))concentrations,humidity,and temperature,to determine the effectiveness of various ventilation setups.The study employs comparative analysis by varying window sizes and ventilation strategies,such as natural ventilation with different window opening percentages.Findings reveal that toilets with larger window areas and higher opening percentages achieve significantly improved natural ventilation,resulting in reduced levels of CO_(2)and SO_(2),lower humidity,and more stable temperatures.These improvements contribute to creating a more hygienic and comfortable environment.The results underscore the critical role of window design and placement in enhancing ventilation efficiency and minimizing pollutant buildup in public toilets.Based on these insights,the study provides actionable recommendations for optimizing window dimensions,placement,and ventilation strategies in the design of school toilets and facilities.By implementing these design improvements,schools can significantly enhance toilets sanitation,improve health outcomes for students,and create a more conducive learning environment.The findings offer practical solutions for addressing IAQ challenges in window design for architects and designers.
基金supported by grants No.13-06-0113m_a from“Scientific Fund”of Far Eastern Federal UniversityNo.5.2535.2014K from the Ministry of Education and Science of the Russian Federation
文摘Rock mass damage at great depths near underground openings is often of a zonal character.However,the classical elastoplastic theory fails to explain sufficiently all properties of zonal failure structures.A new non-Euclidean mathematical model for highly-stressed rock mass was developed based on the principles of mechanics of defected material and non-equilibrium thermodynamics.Methods were developed to determine model parameters that provide satisfactory correspondence between the experimental findings concerning faulted zonal structures near openings at great depths and mathematical calculations.The mechanism of this phenomenon was discovered which consisted in a periodical character of stresses in the surrounding rock mass and development of tensile macrocracks at zones of maximal tangential stresses.Main relationships between the cracking zone width and rock mass strength were established.
基金Project(32-41)supported by the National Science and Technical Development Foundation of DPR of Korea。
文摘In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings of−600 m level in Coal Mine“6.13”,Democratic People's Republic of Korea.The displacement components used for back analysis are the crown settlement and sidewalls convergence monitored at the end of the openings excavation,and the final closures predicted by GVM.The non-linear relation between displacements and back analysis parameters was obtained by artificial neural network(ANN)and Burger-creep viscoplastic(CVISC)model of FLAC3D.Then,the optimal parameters were determined for rock mass surrounding tunnel by genetic algorithm(GA)with both groups of measured displacements at the end of the final excavation and closures predicted by GVM.The maximum absolute error(MAE)and standard deviation(Std)between calculated displacements by numerical simulation with back analysis parameters and in situ ones were less than 6 and 2 mm,respectively.Therefore,it was found that the proposed method could be successfully applied to determining design parameters and stability for tunnels and underground cavities,as well as mine openings and stopes.
基金The financial support of the Ministry of the Instruction, University and Research of Italy (MIUR)
文摘Framed structures are usually infilled with masonry walls. They may cause a significant increase in both stiffness and strength, reducing the deformation demand and increasing the energy dissipation capacity of the system. On the other hand, irregular arrangements of the masonry panels may lead to the concentration of damage in some regions, with negative effects; for example soft story mechanisms and shear failures in short columns. Therefore, the presence ofinfill walls should not be neglected, especially in regions of moderate and high seismicity. To this aim, simple models are available for solid infills walls, such as the diagonal no-tension strut model, while infilled frames with openings have not been adequately investigated. In this study, the effect of openings on the strength and stiffness of infilled frames is investigated by means of about 150 experimental and numerical tests. The main parameters involved are identified and a simple model to take into account the openings in the infills is developed and compared with other models proposed by different researchers. The model, which is based on the use of strength and stiffness reduction factors, takes into account the opening dimensions and presence of reinforcing elements around the opening. An example of an application of the proposed reduction factors is also presented.
文摘Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath steel beams leading to uneconomic floor heights. The most adopted solution for this issue is the use of steel beam web openings to provide the required space for services. These openings could lead to a significant decrease of the beam load carrying capacity depending on the adopted openings shape, size and location. These aspects motivated the present study based on FE simulations calibrated against numerical and test results. The results accuracy enabled a comprehensive parametric analysis of beams with web openings to be made focused on the profile size, web opening location, among others. The study also investigated the efficiency of longitudinal stiffeners welded at the opening region and benefits of using an adequate edge concordance radius in beams with rectangular and square openings. The obtained results showed the need of using welded longitudinal stiffeners in order to increase the beams ultimate load carrying capacity. This adoption can double or even triple the ultimate load of beams with rectangular and square opening heights equal to 0.75 H, respectively.
文摘Rockburst,earthquake and blasting cause some dynamic loads on rock support and rock reinforcement system.Elements of rock support and rock reinforcement are generally made of steel bar or cables,which are resistant against corrosion.These support elements may be subjected to vibrations induced by turbines,vehicle traffic and long-term corrosion in addition to dynamic loading caused by earthquake,rockburst and blasting.In this study,some theoretical,numerical and experimental studies are conducted on rockbolts and rock anchors under shaking and impulsive loading.Then the outcomes of these studies are presented and their practical implications are discussed accordingly.
文摘Two dimensional,reinforced concrete building frames built on raft foundation and having infill wall panels with openings in them are analysed using the direct stiffness method.Beams and columns are modelled by beam column elements.Wall panels are modelled by plane stress finite elements.The raft foundation is modelled by uniaxial finite elements.The soil is modelled as half space model.Openings in wall panels are introduced by using fictitious beams between real floor beams. A computer program is written to carry out the static analysis and do the necessary comparison to show the effect of openings on the structural behavior.
文摘A brief introduction is made for the Numerical Manifold Method and its analysing process in rock mechanics. Some aspects of the manifold method are improved in implementing process according to the practice of excavating underground openings. Corresponding formulas are given and a computer program of the Numerical Manifold Method has been completed in this paper.
文摘A linear three dimensional finite element (FE) study has been carried out to examine the structural response of a prestressed concrete (PSC) inner containment (IC) dome of reactor building (double containment system) of a typical Indian Nuclear Power Plant, having large steam generator (SG) openings with due emphasis on the local behaviour of the steel-concrete interfaces at the SG openings, due to initial prestress transfer. The predominant thrust of the study has been placed on the objective of predicting the possibilities of separation at the steel-concrete interface zones adjacent to the embedded plates (EPs) of the SG openings. Two types of modeling and analysis have been made to study the overall and local behaviour of the structure. Prestressing ducts, passive reinforcements and EPs have been included in the models in certain ways. For the FE analysis, the interface zone has been modeled using interface elements, the properties of which were derived from the results of past experiments conducted on steel plate-concrete inter-face specimens. The FE analysis results have been compared with the results of the past two FE analytical studies on the linear behaviour of the same PSC IC dome. Important observations have been made regarding dome deformation and stresses throughout the structure with special emphasis on the local behaviour of steel-concrete interfaces at and around the SG openings.
文摘The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and functional degradation. The Tinguá Biological Reserve-RJ comprises approximately 26,000 hectares of well-preserved Atlantic Forest, but it is subject to impacts caused by two canopy openings along oil pipelines. Comparisons were made between pipeline edges and forest interiors to evaluate edge effects on the structure and dynamics of those tree communities. Tree densities were higher along forest edges, apparently increasing over time. Tree basal areas, on the other hand, have decreased along edges due to higher mortality rates. Linear canopy opening edges showed higher densities of small trees, while the interior had more very large trees, indicating changes in successional processes and community structural patterns due to edge effects.
文摘Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex variable function, a series' of conformal mapping functions are obtained from different cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And, the general expressions for the equations of a cylindrical shell, including the solutions of stress concentrations meeting the boundary conditions of the large openings' edges, are given in the mapping plane. Furthermore, by applying the orthogonal function expansion technique, the problem can be summarized into the solution of infinite algebraic equation series. Finally, numerical results are obtained for stress concentration factors at the cutout's edge with various opening's ratios and different loading conditions. This new method, at the same time, gives a possibility to the research of cylindrical shells with large non-circular openings or with nozzles.
文摘The aero engine turbine rotors are under strong centrifugal load and the highest thermal load.The ventilation openings on the rotors are inevitable,because air flow need to pass through them to cool the temperatures down and keep the air pressure balanced in internal aero engine.The ventilation openings will lead to stress concentration effect.In this paper,the stress concentration factor of elliptical opening on rotating disc is deduced by superposition method.How to define the optimal location and shape of the elliptical opening on rotating disc to decrease the stress concentration effect has been investigated specifically.The reliability and accuracy of the theoretical deviation process is verified by Finite Element Method(FEM).The process of how to obtain the optimal location of the elliptical ventilation opening with particular shape on turbine sealing disc is described as an engineering application case.The investigation provides sufficient theoretical support for optimal location and shape definition of elliptical ventilation opening on aero engine rotors with stress concentration effect by pure mechanics consideration.
文摘Stress concentrations about thin cylindrical shells with small openings are reconsidered front a nerv angle. There is a sort of special internal relation between theoretical solutions about cylindrical shells,vith large openings and one,with small openings. Using this relation, the extent of applying the theory about small openings to engineering practice is estimated again, thus an idea of how to use this theory and a nerv appraisal of the application of theoretical solutions about cylindrical shells with small openings to engineering practice are given.
文摘About us:The Clige of Cemistry and Materials Engineering(CME)in Wenzhou University(Zhejing Province,China)is looking for postdoctoral candidates(up to 25) specialized in Chemistry Chemical Engineering and Materials Secence. The college has is Chemistry program ranking ESI Top 6‰ worldwide.
文摘When service ducts and cables are required to pass through the structural beams,it is a common practical solution to use composite beams with rectangular or circular openings.The fire safety standards in many countries have recommended design methods for composite beams without openings,while the design method for composite beams with web openings is not addressed yet.Due to the complicated distribution of temperature and stress around the openings in the web of the steel beam,extra complexity has been introduced in determination of the structural capability of the beam and the failure mode in fire.These failure modes generally occur at lower limiting temperatures than the solid beam with same size.It is recognized that the thickness of a reactive coating required to provide a given fire resistance to a composite beam with web openings is affected by the beam’s web thickness,opening configuration,the degree of the beam asymmetry and the structural utilization factor,as well as the nature of the proprietary fire protection itself.Therefore it is necessary that such beams are structurally evaluated taking into account all possible modes of structural failure under both ambient and fire conditions.It is also necessary for additional thermal data to be measured around the web openings and on the web posts from fire tests.The additional thermal data will be used in conjunction with a structural model to determine limiting temperatures of beams with web openings.Steel Construction Institute(SCI)has produced a structural analysis model referenced as report RT1356,which divides a composite beam with web openings into different stress blocks,and then analyses the global bending,vertical shear,local Vierendeel bending,web-post buckling etc.The Association for Specialist Fire Protection(ASFP)recommended the test protocol in the Yellow Book,to determine the temperature distribution around the openings and web post.This paper will discuss a series of fire tests having been carried out in the laboratory of EXOVA Warringtonfire to establish temperature distribution in composite beams with web openings.Test result shows that the distribution of temperature is product specific and strongly affected by opening configuration and opening distance.EXOVA Warringtonfire has also developed a sophisticated calculator,ThermCalc,for analyzing temperature and structural following the method presented in RT1356.Using ThermCalc,parametric study has been carried out,and the effect of load utilization factor,opening size,opening distance,slab depth,decking configuration etc.was investigated.
文摘The shear wall with and without openings that served as a structural element or/and partition wall was utilized in a low-cost housing for the low-income people in Indonesia. The houses,however,should be withstoodfrom earthquake inertial force, so there must be no casualties when disaster struck. The alternative types of composite structure made of wood and cement based building materials needed to meet with the high demand for earthquake-resistant houses in Indonesia. In order to understand the mechanism of earthquake resisting performance of shear wall, we needs to investigate behavior of shear wallsnot only for cyclic static but alsofor dynamic loading. In this study, theseries of full-scale experiment on timber frame shear walls with and without openings,compose of Laminated Veneer Lumber (LVL) engineered wood (Paraserianthes Falcatariaand Hevea Brasiliensis) and sheathed by Fiber Cement Board (FCB), was carried out.By analyzing testing result using theoretical approaches, we intended to predict static initial stiffness and yielding strength as well as basic dynamic properties shear walls. For static behavior, good agreements were obtain from comparison between experiment and theoretical prediction based on mechanical model. While, for dynamic behavior, agreement was not sufficient due tothe effect of bending and rocking of actual test specimens. The information obtain by this study will be useful for practical engineers or structural designers to design the high performance earthquake resisting timber houses with a low construction cost.
基金the National Natural Science Foundation of China(No. 21302095)Research Fund for the Doctoral Program of Higher Education of China(No. 20133221120003)+2 种基金Jiangsu Provincial NSFC(Nos. BK20130945, BK20130924)Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP)Nanjing Tech University for financial support
文摘The nucleophilic ring opening reaction of propargyl epoxides by amines based on a silver catalyst is presented, The reaction takes place under mild conditions and features a high regioselectivity to provide an effective method for the synthesis of 2-amino homopropargyl alcohols in moderate to high yields,
文摘In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixing of the coolant. The communication of the outer strap affects the hydraulic force exerted by the spacer grid of the fuel assembly which could induce fuel assembly bow. In present study, in order to understand the influencing factors of hydraulic force exerted by the spacer grid, outer straps with various flow opening design features, different location and size are investigated by a commercially CFD （computational fluid dynamics） code, ANSYS CFX 12.1. Three dimensional rod bundles including the outer strap without and with different openings are modelled for simulation. The analysis results show that the openings on the spacer grid outer strap can reduce the lateral hydraulic loadings perpendicular to the centerline of the fuel rods exerted by the spacer grids obviously because of the pressures inside and outside the spacer grids being balanced. Besides, influences of the opening design features on the hydraulic force, resistance characteristics and lateral flow factor are investigated in details.
