Despite appropriate design of girder under bending and shear,the deflection of long steel girders usually exceeds the allowable range,and therefore the structural designers encounter challenges in this regard.Consider...Despite appropriate design of girder under bending and shear,the deflection of long steel girders usually exceeds the allowable range,and therefore the structural designers encounter challenges in this regard.Considering significant features of the cables,namely,low weight,small cross section,and high tensile strength,they are used in this research so as to control the deflection of long girder bridges,rather than increasing their heights.In this study,theoretical relations are developed to calculate the increase in pre-tensioning force of V-shaped steel cables under external loading as well as the deflection of steel girder bridges with V-shaped cables and different support conditions.To verify the theoretical relations,the steel girder bridge is modeled in the finite element ABAQUS software with different support conditions without cable and with V-shaped cables.The obtained results show that the theoretical relations can appropriately predict the deflection of girder bridge with V-shaped cables and different support conditions.In this study,the effects of the distance from support on the deflection of mid span are studied in both simply supported and fixed supported girder bridge so as to obtain the appropriate distance from support causing the minimum deflection.展开更多
Hypersonic vehicles, which flight at Mach numbers greater than 5, will serve as a more convenient and efficient transport tool than present subsonic airplanes for long-distance jour- neys in future. Typically, it only...Hypersonic vehicles, which flight at Mach numbers greater than 5, will serve as a more convenient and efficient transport tool than present subsonic airplanes for long-distance jour- neys in future. Typically, it only takes a couple of hours from Beijing to New York at hypersonic speed. Recent interest in these vehicles has grown intensively, and various types of in- novative designs have been proposed and studied. Despite entering the age of hypersonic flight, there still exist many problems to resolve [1-4]. How to design an advanced aero- dynamic configuration is one of them [5].展开更多
This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varyi...This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varying dike conditions. To address concerns related to intense whirls and concentrated flow around the dike head, comparative analysis was performed in terms of flow structures and energy reduction around I-shaped and T-shaped dikes with two ratios of wing length (lw) to dike length (ld) (lw/ld = 1.41 and 2.43). The T-shaped dike wings were equipped with diverse designs: angled footing, delta vane, and streamlined tapered, resulting in elevated backwater in front of the dike, reduced velocity, and enhanced energy reduction. The findings indicated that elongating the wing reciprocally affected the depth-averaged velocity (at the dike head and near the adjacent dike bank), concurrently impacting flow deflection, backwater rise, and energy reduction rate. The T-shaped dike, specifically with an angled footing (lw/ld = 2.43), yielded optimal outcomes. These included significant reductions in maximum energy (46%), tip velocity (98%), and dike adjacent bank velocity (90%), as well as significant flow deflection towards the mainstream, outperforming the I-shaped impermeable dike. The proposed solutions exhibit efficacy in mitigating rapid deterioration during floods, securing both the dike head and the neighboring bank to avert failures in high-energy flow.展开更多
This paper represents the performance analysis of the different shapes of antenna balun and feeding techniques for step constant tapered slot antenna. This work also addresses the benefits of antenna balun (circular a...This paper represents the performance analysis of the different shapes of antenna balun and feeding techniques for step constant tapered slot antenna. This work also addresses the benefits of antenna balun (circular and rectangular) along with two types of feeding techniques (Microstrip line L-shape and Microstrip line I-shape). The performance of the antenna for each technique is thoroughly investigated using Computer Simulation Technology (CST) Microwave Studio software simulation under the resonant frequency of 5.9 GHz. Results demonstrate that the proposed model is an effective tool for improving antenna performance. Moreover, an extensive comparison has been carried out between the two different shapes, with and without antenna balun and between two feeding techniques focusing on return losses, gain, directivity, and voltage standing wave ratio (VSWR).展开更多
This study is primarily aimed at creating three machine learning models:artificial neural net_(w)ork(ANN),random forest(RF),and k-nearest neighbour(KNN),so as to predict the crippling load(CL)of I-shaped steel columns...This study is primarily aimed at creating three machine learning models:artificial neural net_(w)ork(ANN),random forest(RF),and k-nearest neighbour(KNN),so as to predict the crippling load(CL)of I-shaped steel columns.Five input parameters,namely length of column(L),width of flange(bf),flange thickness(t_(f)),web thickness(t_(w))and height of column(H),are used to compute the crippling load(CL).A range of performance indicators,including the coefficient of determination(R_(2)),variance account factor(VAF),a-10 index,root mean square error(RMSE),mean absolute error(MAE)and mean absolute deviation(MAD),are used to assess the effectiveness of the established machine learning models.The results show that all of the three ML(machine learning)models can accurately predict the crippling load,but the performance of ANN is superior:it delivers the highest value of R_(2)=0.998 and the lowest value of RMSE=0.008 in the training phase,as well as the highest value of R_(2)=0.996 and the smaller value of RMSE=0.012 in the testing phase.Additional methods,including rank analysis,reliability analysis,regression plot,Taylor diagram and error matrix plot,are employed to assess the models’performance.The reliability index(β)of the models is calculated by using the first-order second moment(FOSM)technique,and the result is compared with the actual value.Additionally,sensitivity analysis is performed to check the impact of the input variables on the output(CL),finding that bf has the greatest impact on the crippling load,followed by t_(f),t_(w),H and L,in that order.This study demonstrates that ML techniques are useful for developing a reliable numerical tool for measuring the crippling load of I-shaped steel columns.It is found that the proposed techniques can also be used to predict other kinds of failures as well as different kinds of perforated columns.展开更多
文摘Despite appropriate design of girder under bending and shear,the deflection of long steel girders usually exceeds the allowable range,and therefore the structural designers encounter challenges in this regard.Considering significant features of the cables,namely,low weight,small cross section,and high tensile strength,they are used in this research so as to control the deflection of long girder bridges,rather than increasing their heights.In this study,theoretical relations are developed to calculate the increase in pre-tensioning force of V-shaped steel cables under external loading as well as the deflection of steel girder bridges with V-shaped cables and different support conditions.To verify the theoretical relations,the steel girder bridge is modeled in the finite element ABAQUS software with different support conditions without cable and with V-shaped cables.The obtained results show that the theoretical relations can appropriately predict the deflection of girder bridge with V-shaped cables and different support conditions.In this study,the effects of the distance from support on the deflection of mid span are studied in both simply supported and fixed supported girder bridge so as to obtain the appropriate distance from support causing the minimum deflection.
基金supported by the National Natural Science Foundation of China(Grant Nos.11372324,and 11572333)the State Key Laboratory of High Temperature Gas Dynamics,Institute of Mechanics,Chinese Academy of Sciences(Grant Nos.LHD2017TC01,LHD2017MS04,and LHD2017QN03)
文摘Hypersonic vehicles, which flight at Mach numbers greater than 5, will serve as a more convenient and efficient transport tool than present subsonic airplanes for long-distance jour- neys in future. Typically, it only takes a couple of hours from Beijing to New York at hypersonic speed. Recent interest in these vehicles has grown intensively, and various types of in- novative designs have been proposed and studied. Despite entering the age of hypersonic flight, there still exist many problems to resolve [1-4]. How to design an advanced aero- dynamic configuration is one of them [5].
文摘This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varying dike conditions. To address concerns related to intense whirls and concentrated flow around the dike head, comparative analysis was performed in terms of flow structures and energy reduction around I-shaped and T-shaped dikes with two ratios of wing length (lw) to dike length (ld) (lw/ld = 1.41 and 2.43). The T-shaped dike wings were equipped with diverse designs: angled footing, delta vane, and streamlined tapered, resulting in elevated backwater in front of the dike, reduced velocity, and enhanced energy reduction. The findings indicated that elongating the wing reciprocally affected the depth-averaged velocity (at the dike head and near the adjacent dike bank), concurrently impacting flow deflection, backwater rise, and energy reduction rate. The T-shaped dike, specifically with an angled footing (lw/ld = 2.43), yielded optimal outcomes. These included significant reductions in maximum energy (46%), tip velocity (98%), and dike adjacent bank velocity (90%), as well as significant flow deflection towards the mainstream, outperforming the I-shaped impermeable dike. The proposed solutions exhibit efficacy in mitigating rapid deterioration during floods, securing both the dike head and the neighboring bank to avert failures in high-energy flow.
文摘This paper represents the performance analysis of the different shapes of antenna balun and feeding techniques for step constant tapered slot antenna. This work also addresses the benefits of antenna balun (circular and rectangular) along with two types of feeding techniques (Microstrip line L-shape and Microstrip line I-shape). The performance of the antenna for each technique is thoroughly investigated using Computer Simulation Technology (CST) Microwave Studio software simulation under the resonant frequency of 5.9 GHz. Results demonstrate that the proposed model is an effective tool for improving antenna performance. Moreover, an extensive comparison has been carried out between the two different shapes, with and without antenna balun and between two feeding techniques focusing on return losses, gain, directivity, and voltage standing wave ratio (VSWR).
文摘This study is primarily aimed at creating three machine learning models:artificial neural net_(w)ork(ANN),random forest(RF),and k-nearest neighbour(KNN),so as to predict the crippling load(CL)of I-shaped steel columns.Five input parameters,namely length of column(L),width of flange(bf),flange thickness(t_(f)),web thickness(t_(w))and height of column(H),are used to compute the crippling load(CL).A range of performance indicators,including the coefficient of determination(R_(2)),variance account factor(VAF),a-10 index,root mean square error(RMSE),mean absolute error(MAE)and mean absolute deviation(MAD),are used to assess the effectiveness of the established machine learning models.The results show that all of the three ML(machine learning)models can accurately predict the crippling load,but the performance of ANN is superior:it delivers the highest value of R_(2)=0.998 and the lowest value of RMSE=0.008 in the training phase,as well as the highest value of R_(2)=0.996 and the smaller value of RMSE=0.012 in the testing phase.Additional methods,including rank analysis,reliability analysis,regression plot,Taylor diagram and error matrix plot,are employed to assess the models’performance.The reliability index(β)of the models is calculated by using the first-order second moment(FOSM)technique,and the result is compared with the actual value.Additionally,sensitivity analysis is performed to check the impact of the input variables on the output(CL),finding that bf has the greatest impact on the crippling load,followed by t_(f),t_(w),H and L,in that order.This study demonstrates that ML techniques are useful for developing a reliable numerical tool for measuring the crippling load of I-shaped steel columns.It is found that the proposed techniques can also be used to predict other kinds of failures as well as different kinds of perforated columns.
