The accurate estimation of fracture geometry parameters and the characterization of rock mass structure are two important topics in the geological disposal system of high-level radioactive waste(HLW).The Beishan area,...The accurate estimation of fracture geometry parameters and the characterization of rock mass structure are two important topics in the geological disposal system of high-level radioactive waste(HLW).The Beishan area,as the current preselected area for China’s HLW disposal,has three subareas considered to be the key survey area at the stage of site selection.In this paper,a comprehensive survey method conducted on the outcrop is developed to estimate fracture geometry parameters.Results show that fracture occurrence obeys a Fisher distribution,fracture trace length obeys a normal distribution,and the distribution of spacing obeys a negative exponential distribution.An evaluation index,Rock Mass Structure Rating(RMSR),is proposed to characterize rock mass structure for the three subareas.The results show that the Xinchang area is more suitable to act as China’s HLW disposal repository site.At the same time,the index can also be applied to characterize surface rock mass structure and rock mass integrity at the site selection phase of HLW disposal.展开更多
Geometry parameters of optical fiber are crucial in evaluating the quality of the optical fiber.Near⁃field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters.To dist...Geometry parameters of optical fiber are crucial in evaluating the quality of the optical fiber.Near⁃field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters.To distinguish the boundary between fiber core and cladding,it is necessary to illuminate the fiber.The end face of the core is a bright spot with unclear edge,so the true edge of the core and the cladding cannot be accurately judged.A method is proposed in this paper to measure the geometry parameters of optical fiber by Bessel function fitting.Theoretically,the solution to the electromagnetic vector of mode field satisfies Bessel function,and the boundary between the core and the cladding can be precisely extracted by Bessel function fitting.Edges of the fiber were fitted by elliptical curves,and the geometry parameters of the fibers could be calculated.Results show that the maximum deviations of the diameters and the average differences of the fibers were decreased under normal and abnormal conditions respectively.The proposed method is an efficient way to obtain edge data and can improve the accuracy and stability of geometry parameters of optical fibers.展开更多
Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is deve...To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is developed to identify the geometric parameters.The study utilizes a common precast element for highway bridges as the research subject.First,edge feature points of the bridge component section are extracted from images of the precast component cross-sections by combining the Canny operator with mathematical morphology.Subsequently,a deep learning model is developed to identify the geometric parameters of the precast components using the extracted edge coordinates from the images as input and the predefined control parameters of the bridge section as output.A dataset is generated by varying the control parameters and noise levels for model training.Finally,field measurements are conducted to validate the accuracy of the developed method.The results indicate that the developed method effectively identifies the geometric parameters of bridge precast components,with an error rate maintained within 5%.展开更多
The bubble deformation processes were reported when gas was injected into polyme r melt flow field in another paper, the experiments showed that the deformation was severely affected by the volume of the bubble, and ...The bubble deformation processes were reported when gas was injected into polyme r melt flow field in another paper, the experiments showed that the deformation was severely affected by the volume of the bubble, and in turn, for the different bubbles, several different deformation processes were presented d uring their movement along the flow channel. In addition, we could find that the magnitude of the bubble volume was dependent upon the pressure difference of th e gas injection pressure and the melt pressure. In this paper, more experimental conditions were changed to investigate the parameters relevant to the detachmen t of bubbles from the injection nozzle. The experimental results show that the p ressure difference, the melt flow velocity as well as the melt pressure were all critical for the parameters, such as the bubble detachment time, the maximum bu bble diameters and the magnitude of the bubble volume. The morphology changes of bubble were very large when the flow field was abruptly changed, and the situat ions were more complicated.展开更多
This paper develops a model that only requires two sets of small-size rock specimens with the ratio of the structural geometry parameter maximum to minimum ae,max:ae,min≥3:1 to determine the rock fracture and strengt...This paper develops a model that only requires two sets of small-size rock specimens with the ratio of the structural geometry parameter maximum to minimum ae,max:ae,min≥3:1 to determine the rock fracture and strength parameters without size effect and predict the actual structural performance of rock.Regardless of three-point-bending,four-point-bending,or a combination of the above two specimen types,fracture toughness KICand tensile strength ftof rock were determined using only two sets of specimens with ae,max:ae,min≥3:1.The values KICand ftwere consistent with those determined using multiple sets of specimens.The full structural failure curve constructed by two sets of small-size specimens with ae,max:ae,min≥3:1 can accurately predict large-size specimens fracture failure,and±10%upper and lower limits of the curve can encompass the test results of large-size specimens.The peak load prediction curve was constructed by two sets of specimens with ae,max:ae,min≥3:1,and±15%upper and lower limits of the peak load prediction curve can cover the small-size specimen tests data.The model and method proposed in this paper require only two sets of small-size specimens,and their selection is unaffected by the specimen type,geometry,and initial crack length.展开更多
Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate ...Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.展开更多
The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with πh11/2×γh11/2^-1.The energy spect...The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with πh11/2×γh11/2^-1.The energy spectra,electromagnetic transition probabilities B（M1） and B（E2）,angular momenta,and K-distributions are studied.It is demonstrated that the chirality still remains not only in the yrast and yrare bands,but also in the two higher excited bands whenγ deviates from 30°.The chiral geometry relies significantly on γ,and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands.展开更多
The natural convective heat transfer coefficient(hn,c)of the human body is a critical parameter for developing a comprehensive mathematical model of human thermal regulation.As age-dependent personalized thermal comfo...The natural convective heat transfer coefficient(hn,c)of the human body is a critical parameter for developing a comprehensive mathematical model of human thermal regulation.As age-dependent personalized thermal comfort models advance,the hn,c for children and adolescents need increased attention.This study analyzed the hn,c of 36 human models across six age groups using a numerical simulation method validated by experimental data from the thermal manikin.Our results indicate that hn,c on the human body surface decreases progressively with age.The average hn,c of children and adolescents was higher than those of adults(18-70 yr)by 11.66%(4-6 yr),9.23%(7-10 yr),6.67%(11-12 yr),3.89%(13-15 yr),and 1.67%(16-17 yr).The distribution of hn,c across the human body surface is non-uniform,with the highest values observed on the face,hands,feet,and inner arm regions near the torso.For the upper limbs(hands,forearms,upper arms),lower limbs(feet,thighs,calves),and trunk(chest,back,pelvis),hn,c generally decreased with increasing height level.Body segment length directly influences boundary layer development,exhibiting an inverse relationship with hn,c.Based on geometric dimension analysis,a prediction model for local hn,c was developed,incorporating temperature differences and characteristic dimensions.These findings offer a reference for selecting hn,c in developing personalized thermal comfort models.展开更多
基金supported by the National Key Research and Development Program of China,under grant No.2018YFC1504903the Chongqing Natural Science Foundation,under grant No.cstc2020jcyj-msxm X0743 and cstc 2020jcyj-bsh0142+3 种基金the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,under grant No.Z019018China postdoctoral science foundation Grant No.2019M662918 and 2020M673152Regional Joint Fund for Basic and Applied Basic Research Fund of Guangdong Province,No.2019A1515110836the National Natural Science Foundation of China,under grant No.41688103。
文摘The accurate estimation of fracture geometry parameters and the characterization of rock mass structure are two important topics in the geological disposal system of high-level radioactive waste(HLW).The Beishan area,as the current preselected area for China’s HLW disposal,has three subareas considered to be the key survey area at the stage of site selection.In this paper,a comprehensive survey method conducted on the outcrop is developed to estimate fracture geometry parameters.Results show that fracture occurrence obeys a Fisher distribution,fracture trace length obeys a normal distribution,and the distribution of spacing obeys a negative exponential distribution.An evaluation index,Rock Mass Structure Rating(RMSR),is proposed to characterize rock mass structure for the three subareas.The results show that the Xinchang area is more suitable to act as China’s HLW disposal repository site.At the same time,the index can also be applied to characterize surface rock mass structure and rock mass integrity at the site selection phase of HLW disposal.
基金Sponsored by the National Science Foundation for Young Scholars of China(Grant No.61605114).
文摘Geometry parameters of optical fiber are crucial in evaluating the quality of the optical fiber.Near⁃field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters.To distinguish the boundary between fiber core and cladding,it is necessary to illuminate the fiber.The end face of the core is a bright spot with unclear edge,so the true edge of the core and the cladding cannot be accurately judged.A method is proposed in this paper to measure the geometry parameters of optical fiber by Bessel function fitting.Theoretically,the solution to the electromagnetic vector of mode field satisfies Bessel function,and the boundary between the core and the cladding can be precisely extracted by Bessel function fitting.Edges of the fiber were fitted by elliptical curves,and the geometry parameters of the fibers could be calculated.Results show that the maximum deviations of the diameters and the average differences of the fibers were decreased under normal and abnormal conditions respectively.The proposed method is an efficient way to obtain edge data and can improve the accuracy and stability of geometry parameters of optical fibers.
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
基金The National Natural Science Foundation of China(No.52338011,52378291)Young Elite Scientists Sponsorship Program by CAST(No.2022-2024QNRC0101).
文摘To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is developed to identify the geometric parameters.The study utilizes a common precast element for highway bridges as the research subject.First,edge feature points of the bridge component section are extracted from images of the precast component cross-sections by combining the Canny operator with mathematical morphology.Subsequently,a deep learning model is developed to identify the geometric parameters of the precast components using the extracted edge coordinates from the images as input and the predefined control parameters of the bridge section as output.A dataset is generated by varying the control parameters and noise levels for model training.Finally,field measurements are conducted to validate the accuracy of the developed method.The results indicate that the developed method effectively identifies the geometric parameters of bridge precast components,with an error rate maintained within 5%.
基金Funded by the National Nature Science Foundation of China(No.19632004,No.10172074) the Research Foundation for the Doctor al Program of Higher Education of China (No.98056113) Guang dong Province Nature Science Foundation ( No. 980573, No.0401154)
文摘The bubble deformation processes were reported when gas was injected into polyme r melt flow field in another paper, the experiments showed that the deformation was severely affected by the volume of the bubble, and in turn, for the different bubbles, several different deformation processes were presented d uring their movement along the flow channel. In addition, we could find that the magnitude of the bubble volume was dependent upon the pressure difference of th e gas injection pressure and the melt pressure. In this paper, more experimental conditions were changed to investigate the parameters relevant to the detachmen t of bubbles from the injection nozzle. The experimental results show that the p ressure difference, the melt flow velocity as well as the melt pressure were all critical for the parameters, such as the bubble detachment time, the maximum bu bble diameters and the magnitude of the bubble volume. The morphology changes of bubble were very large when the flow field was abruptly changed, and the situat ions were more complicated.
基金supported by National Natural Science Foundation of China(No.52179132)Program for Science&Technology Innovation Talents in Universities of Henan province(No.20HASTIT013)Sichuan University,State Key Lab Hydraul&Mt River Engn(No.SKHL2007)。
文摘This paper develops a model that only requires two sets of small-size rock specimens with the ratio of the structural geometry parameter maximum to minimum ae,max:ae,min≥3:1 to determine the rock fracture and strength parameters without size effect and predict the actual structural performance of rock.Regardless of three-point-bending,four-point-bending,or a combination of the above two specimen types,fracture toughness KICand tensile strength ftof rock were determined using only two sets of specimens with ae,max:ae,min≥3:1.The values KICand ftwere consistent with those determined using multiple sets of specimens.The full structural failure curve constructed by two sets of small-size specimens with ae,max:ae,min≥3:1 can accurately predict large-size specimens fracture failure,and±10%upper and lower limits of the curve can encompass the test results of large-size specimens.The peak load prediction curve was constructed by two sets of specimens with ae,max:ae,min≥3:1,and±15%upper and lower limits of the peak load prediction curve can cover the small-size specimen tests data.The model and method proposed in this paper require only two sets of small-size specimens,and their selection is unaffected by the specimen type,geometry,and initial crack length.
基金supported by the National Natural Science Foundation of China (10872096)the Open Fund of State Key Laboratory of Explosion Science and Technology, Beijing University of Science and Technology (KFJJ09-13)
文摘Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.
基金Supported by Plan Project of Beijing College Students' Scientific Research and Entrepreneurial Action,Major State 973 Program of China(2013CB834400)National Natural Science Foundation of China(11175002,11335002,11375015,11461141002)+2 种基金National Fund for Fostering Talents of Basic Science(NFFTBS)(J1103206)Research Fund for Doctoral Program of Higher Education(20110001110087)China Postdoctoral Science Foundation(2015M580007)
文摘The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with πh11/2×γh11/2^-1.The energy spectra,electromagnetic transition probabilities B（M1） and B（E2）,angular momenta,and K-distributions are studied.It is demonstrated that the chirality still remains not only in the yrast and yrare bands,but also in the two higher excited bands whenγ deviates from 30°.The chiral geometry relies significantly on γ,and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands.
基金supported by the National Natural Science Foundation of China(No.52278126)the Young Scientists Fund of the National Natural Science Foundation of China(No.52308113)the National Natural Science Foundation of China(No.52408111).
文摘The natural convective heat transfer coefficient(hn,c)of the human body is a critical parameter for developing a comprehensive mathematical model of human thermal regulation.As age-dependent personalized thermal comfort models advance,the hn,c for children and adolescents need increased attention.This study analyzed the hn,c of 36 human models across six age groups using a numerical simulation method validated by experimental data from the thermal manikin.Our results indicate that hn,c on the human body surface decreases progressively with age.The average hn,c of children and adolescents was higher than those of adults(18-70 yr)by 11.66%(4-6 yr),9.23%(7-10 yr),6.67%(11-12 yr),3.89%(13-15 yr),and 1.67%(16-17 yr).The distribution of hn,c across the human body surface is non-uniform,with the highest values observed on the face,hands,feet,and inner arm regions near the torso.For the upper limbs(hands,forearms,upper arms),lower limbs(feet,thighs,calves),and trunk(chest,back,pelvis),hn,c generally decreased with increasing height level.Body segment length directly influences boundary layer development,exhibiting an inverse relationship with hn,c.Based on geometric dimension analysis,a prediction model for local hn,c was developed,incorporating temperature differences and characteristic dimensions.These findings offer a reference for selecting hn,c in developing personalized thermal comfort models.
