This is a survey of the results in[14]regarding the isoperimetric problem in the Riemannian manifold.We consider a mean curvature type flow in the Riemannian manifold endowed with a non-trivial conformal vector field,...This is a survey of the results in[14]regarding the isoperimetric problem in the Riemannian manifold.We consider a mean curvature type flow in the Riemannian manifold endowed with a non-trivial conformal vector field,which was firstly introduced by Guan and Li[8]in space forms.This flow preserves the volume of the bounded domain enclosed by a star-shaped hypersurface and decreases the area of hypersurface under certain conditions.We will prove the long time existence and convergence of the flow.As a result,the isoperimetric inequality for such a domain is established.展开更多
Temporal interference(TI)is a form of stimulation that epitomizes an innovative and non-invasive approach for profound neuromodulation of the brain,a technique that has been validated in mice.Yet,the thin cranial bone...Temporal interference(TI)is a form of stimulation that epitomizes an innovative and non-invasive approach for profound neuromodulation of the brain,a technique that has been validated in mice.Yet,the thin cranial bone structure of mice has a marginal influence on the effect of the TI technique and may not effectively showcase its effectiveness in larger animals.Based on this,we carried out TI stimulation experiments on rats.Following the TI intervention,analysis of electrophysiological data and immunofluorescence staining indicated the generation of a stimulation focus within the nucleus accumbens(depth,8.5 mm)in rats.Our findings affirm the viability of the TI methodology in the presence of thick cranial bones,furnishing efficacious parameters for profound stimulation with TI administered under such conditions.This experiment not only sheds light on the intervention effects of TI deep in the brain but also furnishes robust evidence in support of its prospective clinical utility.展开更多
The 2025 M_(w)7.7 Myanmar earthquake highlighted the challenge of near-fault seismic intensity field reconstruction due to sparse seismic networks.To address this limitation,a framework was proposed integrating seismi...The 2025 M_(w)7.7 Myanmar earthquake highlighted the challenge of near-fault seismic intensity field reconstruction due to sparse seismic networks.To address this limitation,a framework was proposed integrating seismic wave simulation with a data-constrained finite-fault rupture model.The constraint is implemented by identifying the optimal ground motion models(GMMs)through a scoring system that selects the best-fit GMMs to mid-and far-field China Earthquake Networks Center(CENC)seismic network data;and applying the optimal GMMs to refine the rupture model parameters for near-fault intensity field simulation.The simulated near-fault seismic intensity field reproduces seismic intensities collected from Myanmar’s sparse seismic network and concentrated in≥Ⅷintensity zones within 50 km of the projected fault plane;and identifies abnormal intensity regions exhibiting≥Ⅹintensity along the Meiktila-Naypyidaw corridor and near Shwebo that are attributed to soft soil amplification effects and near-fault directivity.This framework can also be applied to post-earthquake assessments in other similar regions.展开更多
The thalamic reticular nucleus(TRN)plays a crucial role in regulating sensory encoding,even at the earliest stages of visual processing,as evidenced by numerous studies.Orientation selectivity,a vital neural response,...The thalamic reticular nucleus(TRN)plays a crucial role in regulating sensory encoding,even at the earliest stages of visual processing,as evidenced by numerous studies.Orientation selectivity,a vital neural response,is essential for detecting objects through edge perception.Here,we demonstrate that somatostatin(SOM)-expressing and parvalbumin(PV)-expressing neurons in the TRN project to the dorsal lateral geniculate nucleus and modulate orientation selectivity and the capacity for visual information processing in the primary visual cortex(V1).These findings show that SOM-positive and PV-positive neurons in the TRN are powerful modulators of visual information encoding in V1,revealing a novel role for this thalamic nucleus in influencing visual processing.展开更多
目的:分析人子宫珠蛋白与猫主要过敏原Fel d 1之间关系。方法 :运用ClustalW 1.83和MEGA5.1 Beta3软件比较人分泌球蛋白家族序列及猫过敏原Fel d 1两个亚基P30438和P30440之间的进化树形图;采用在线软件平台NetMHCII 2.2比较分析P30438...目的:分析人子宫珠蛋白与猫主要过敏原Fel d 1之间关系。方法 :运用ClustalW 1.83和MEGA5.1 Beta3软件比较人分泌球蛋白家族序列及猫过敏原Fel d 1两个亚基P30438和P30440之间的进化树形图;采用在线软件平台NetMHCII 2.2比较分析P30438与子宫珠蛋白典型序列P11684之间抗原性差异;利用Swiss-Model程序模拟并比较P11684、P30438和P30440的三级结构。结果 :分泌球蛋白家族充斥着大量冗余数据,经逐步聚类收缩至13个代表性序列进一步分析发现,整个分泌球蛋白家族划分成两个大家族三个亚家族,而子宫珠蛋白典型序列与猫主要过敏原Fel d 1的一个亚基P30438之亲缘关系最近,两者均具有与HLA高亲和力结合位点,而且三级结构相似。结论:子宫珠蛋白具有潜在的过敏原性。展开更多
Taking ancient village of Gelao Nationality in Wuchuan for example,theories of settlement geography were used to analyze settlement landscapes of ethnic groups with cultural peculiarity in certain regions from the per...Taking ancient village of Gelao Nationality in Wuchuan for example,theories of settlement geography were used to analyze settlement landscapes of ethnic groups with cultural peculiarity in certain regions from the perspectives of geographical and humanistic environment,distribution form,internal structure and settlement characteristics. Regional and national cultural characteristics were demonstrated to promote the inheritance,promotion and protection of such old and traditional civilization in terms of landscape,and provide valuable references for relevant researches.展开更多
During the braking process,a large amount of heat energy is generated at the friction surfaces between the brake disc and pads and rapidly dissipates into the disc volume.In this paper,a three-dimensional thermo-mecha...During the braking process,a large amount of heat energy is generated at the friction surfaces between the brake disc and pads and rapidly dissipates into the disc volume.In this paper,a three-dimensional thermo-mechanical coupling model of high-speed wheel-mounted brake discs containing bolted joints and contact relationships is established.The direct coupling method is used to analyze the temperature and stress of the brake discs during an emergency braking event with an initial speed of 300 km/h.A full-scale bench test is also conducted to monitor the temperatures of the friction ring and bolted joints.The simulation result shows that the surface temperature of the friction ring reaches its peak value of 414°C after 102 s of braking,which agrees well with the bench test result.The maximum alternating thermal stress occurs in the bolt hole where the maximum circumferential compressive stress is−658 MPa and the maximum circumferential tensile stress is 134 MPa.During the braking process,the out-of-plane deformation of the middle part of the friction ring is larger than that of the edge,which increases the axial tensile load of the connecting bolt.This work provides support for the design of brake discs and connecting bolts.展开更多
Visualization of complex geological structures can technically support the accurate prediction and prevention of coal mine disasters.This study proposed a new digital reconstruction method to visualize geological stru...Visualization of complex geological structures can technically support the accurate prediction and prevention of coal mine disasters.This study proposed a new digital reconstruction method to visualize geological structures based on establishing a virtual model in the digital twin system.This methodology for the digital reconstruction of complex fault structures comprises the following four aspects:(1)collection and fdelity of multi-physical feld data of the fault structures,(2)the transmission of multi-physical feld data,(3)the normalization of multi-physical feld data,and(4)digital model reconstruction of fault structures.The key scientifc issues of this methodology to be resolved include in situ fdelity of multi-feld data and normalized programming of multi-source data.In addition,according to the geological background and conditions in Da’anshan coal mine in western Beijing,China,a preliminary attempt is made to reconstruct a digital model of fault and fold structures using the methodology proposed in this study.展开更多
The cooperation between an autonomous vehicle and a nearby vehicle is critical to ensure driving safety in the laneexchanging scenario.The nearby vehicle trajectory needs to be predicted,from which the autonomous vehi...The cooperation between an autonomous vehicle and a nearby vehicle is critical to ensure driving safety in the laneexchanging scenario.The nearby vehicle trajectory needs to be predicted,from which the autonomous vehicle is controlled to prevent possible collisions.This paper proposes a lane-exchanging driving strategy for the autonomous vehicle to cooperate with the nearby vehicle by integrating vehicle trajectory prediction and motion control.A trajectory prediction method is developed to anticipate the nearby vehicle trajectory.The Gaussian mixture model(GMM),together with the vehicle kinematic model,are synthesized to predict the nearby vehicle trajectory.A potential-feldbased model predictive control(MPC)approach is utilized by the autonomous vehicle to conduct the lane-exchanging maneuver.The potential feld of the nearby vehicle is considered in the controller design for collision avoidance.On-road driving data verifcation shows that the nearby vehicle trajectory can be predicted by the proposed method.CarSim®simulations validate that the autonomous vehicle can perform the lane-exchanging maneuver and avoid the nearby vehicle using the proposed driving strategy.The autonomous vehicle can thus safely perform the laneexchanging maneuver and avoid the nearby vehicle.展开更多
Abstract The carbon-carbon bond between two nearest-neighboring atoms is mod- eled as a beam and the single-walled carbon nanotubes are treated as the space frame structures in order to analyze the mechanical properti...Abstract The carbon-carbon bond between two nearest-neighboring atoms is mod- eled as a beam and the single-walled carbon nanotubes are treated as the space frame structures in order to analyze the mechanical properties of carbon nanotubes. Based on the theory of Tersof- Brenner force feld, the energy relationships between the carbon-carbon bond and the beam model are obtained, and the stifness parameters of the beam are determined. By applying the present model, the Young’s moduli of the single-walled carbon nanotubes with diferent tube diameters are determined. And the present results are compared with available data.展开更多
In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboar...In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboard the Coriolis satellite. The two datasets cover a four-year period from October2011 to September 2015 in the global oceans. For the sea surface wind speed, the statistical comparison indicates good agreement between the HY-2 A scatterometer and WindSat with a bias of nearly 0 m/s and a root mean square error(RMSE) of 1.13 m/s. For the sea surface wind direction, a bias of 1.41° and an RMSE of 20.39° were achieved after excluding the data collocated with opposing directions. Furthermore,discrepancies in sea surface wind speed measured by the two sensors in the global oceans were investigated.It is found that the larger dif ferences mainly appear in the westerlies in the both hemispheres. Both the bias and RMSE show latitude dependence, i.e., they have signi?cant latitudinal ?uctuations.展开更多
As concentration distribution changes have important effects on material structures and properties,controlling the concentration distribution is essential to alloy performance.The aim of the present work is to control...As concentration distribution changes have important effects on material structures and properties,controlling the concentration distribution is essential to alloy performance.The aim of the present work is to control and adjust the concentration distribution by the static magnetic field.It is found that the magnetic field disperses grain boundary segregation and causes the uniform distribution of concentration.Further,by the three-dimensional computed tomography(3 D-CT) reconstruction,the flow distribution is seen and the effect mechanism of the magnetic field is revealed.The present work may clarify the ambiguous understanding on the effect of the static magnetic field on solidification process.展开更多
A mathematical model was developed to get an insight into 3D electromagnetic–thermal phenomena in an induction heated steel slab with a large width/thickness ratio by solving a fully coupled Maxwell equations and ene...A mathematical model was developed to get an insight into 3D electromagnetic–thermal phenomena in an induction heated steel slab with a large width/thickness ratio by solving a fully coupled Maxwell equations and energy conservation equation.The spatial heat radiation between the slab surface and the refractory wall in an induction furnace was considered.The electromagnetic induction and temperature distribution features inside the slab with time evolution were described.The effects of electromagnetic induction parameters,thermal conductivity of the material and process parameters on the induction heating process were theoretically examined.Numerical results show that the spatial distribution of induction heat generation inside the slab is non-uniform.The high work frequency and the low heat conductivity of slab increase the non-uniformity of slab induction heating process.The radiative heat loss and heat transfer between the slab and the metal parts used for holding the slab have an important effect on the slab surface temperature.It is necessary to separately control the current input in the multi-layer coil windings along the height direction of furnace and adopt the multi-step heating strategies with time evolution to improve the homogenization of the slab temperature.展开更多
In order to solve the problems which are widespread in potato seeding planter, such as lower operating efficiency, unideal performance index, higher replay rate and leakage rate and uneven spacing sowing in seeding op...In order to solve the problems which are widespread in potato seeding planter, such as lower operating efficiency, unideal performance index, higher replay rate and leakage rate and uneven spacing sowing in seeding operating, a trailed potato fertilization seeder was designed. The key components of the special structure had been got through the description of the structure and working principle of the whole machine. A crossing seed-taken technology along with the vibration component was adopted to achieve precision seeding. The results showed in the feld test of the machine： all the performance indexes of the machine met the agronomic requirement of potato planting; the multiple and missing index were low; it completed the ditching, fertilizing, seeding as well as ridging in one planting process; its operation effciency was high and the stability was good. This design of the trailed potato fertilization seeder provided a reference for the development of large traction-type potato seeding machine.展开更多
Hydraulic fracturing is widely used in geothermal resource exploitation, and many natural fractures exist in hot dry rock reservoirs due to in-situ stress and faults. However, the infuence of natural fractures on hydr...Hydraulic fracturing is widely used in geothermal resource exploitation, and many natural fractures exist in hot dry rock reservoirs due to in-situ stress and faults. However, the infuence of natural fractures on hydraulic fracture propagation is not considered in the current study. In this paper, based on the phase feld model, a thermo-hydro-mechanical coupled hydraulic fracture propagation model was established to reveal the infuence of injection time, fracturing method, injection fow rate, and natural fracture distribution on the fracture propagation mechanism. The results show that fracture complexity increases with an increase in injection time. The stress disturbance causes the fracture initiation pressure of the second cluster signifcantly higher than that of the frst and third clusters. The zipper-type fracturing method can reduce the degree of stress disturbance and increase fracture complexity by 7.2% compared to simultaneous hydraulic fracturing. Both low and high injection fow rate lead to a decrease in fracture propagation time, which is not conducive to an increase in fracture complexity. An increase in the natural fracture angle leads to hydraulic fracture crossing natural fracture, but has a lesser efect on fracture complexity. In this paper, we analyzed the infuence of diferent factors on initiation pressure and fracture complexity, providing valuable guidance for the exploitation of geothermal resources.展开更多
Porous rock chemical grouting simulation test was conducted using established large scale physical model.Chemical grout diffusing rule in porous media with different permeability was studied by monitoring the spontane...Porous rock chemical grouting simulation test was conducted using established large scale physical model.Chemical grout diffusing rule in porous media with different permeability was studied by monitoring the spontaneous potential and exciting current response during grouting.The results show that chemical grout spread evenly in all directions and diffusion areas are approximately concentric circles in the cross section of homogeneous transverse isotropic pore medium,the grout spread flling range can be quantitatively decrypted by the diffusion radius.The average diffusion speed and radius increase approximately as the square root with the permeability coeffcient in different permeability media under the same conditions.Calculation results using Maag cylindrical diffusion equation show that the calculated value of diffusion radius is in good agreement with the test value under different grouting pressures and permeability conditions.展开更多
We study electromechanical felds in the anti-plane deformation of an infnite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electro- elastic dielectrics with electri...We study electromechanical felds in the anti-plane deformation of an infnite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electro- elastic dielectrics with electric feld gradient in the constitutive relations is used. Special attention is paid to the felds near the surface of the hole.展开更多
Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and ...Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.展开更多
Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF...Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly developed.In the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent method.Four normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are formed.The fnal edge detection result is achieved by fusing the results of two thresholded ESMs.The experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.展开更多
The current research on the evaporation of ferrofuids mainly focuses on the characterization of ultra-low vapor pressure ferrofuids in vacuum and the theoretical analysis of the evaporation process.Few studies have fo...The current research on the evaporation of ferrofuids mainly focuses on the characterization of ultra-low vapor pressure ferrofuids in vacuum and the theoretical analysis of the evaporation process.Few studies have focused on the experimental validation of the proposed evaporation rate equations and on the comparison of the diferences in ferrofuid evaporation.In this study,based on the Bolotov’s model,an evaporation rate equation is deduced from the experimental model.The experimental study included a comparison of the evaporation,magnetic particle volume fraction,temperature,height of the fuid surface from the outlet,and magnetic feld of a kerosene-based ferrofuid and its base carrier liquid.The prepared sample was evaporated in a test tube,and the evaporation rate was calculated by measuring the weight loss of the sample.The experimental results show that the evaporation rate of the base carrier liquid is higher than that of the ferrofuid.The smaller the volume fraction of the magnetic particles,the greater the evaporation rate.The magnetic particles play a key role in preventing evaporation of the base liquid.The higher the temperature,the smaller the deviation of the evaporation rate from the predicted value.The evaporation rates obtained by the two control groups at the height of the fuid surface from the outlet were lower than the predict value.The magnetic feld had a certain promotional efect on the evaporation of the ferrofuid.The experimental results were consistent with the results obtained using Bolotov’s model.This research validates Bolotov’s model and shows that the model is somewhat biased but still responds well to diferent variables.展开更多
文摘This is a survey of the results in[14]regarding the isoperimetric problem in the Riemannian manifold.We consider a mean curvature type flow in the Riemannian manifold endowed with a non-trivial conformal vector field,which was firstly introduced by Guan and Li[8]in space forms.This flow preserves the volume of the bounded domain enclosed by a star-shaped hypersurface and decreases the area of hypersurface under certain conditions.We will prove the long time existence and convergence of the flow.As a result,the isoperimetric inequality for such a domain is established.
基金supported by the National Key Research and Development Program Project(2021YFC2400203)the Shaanxi Province Key Research and Development Program Project(2023-YBSF-120)+1 种基金the Shandong Provincial Natural Science Foundation(ZR2024QF287)the National Natural Science Foundation of China(31972907).
文摘Temporal interference(TI)is a form of stimulation that epitomizes an innovative and non-invasive approach for profound neuromodulation of the brain,a technique that has been validated in mice.Yet,the thin cranial bone structure of mice has a marginal influence on the effect of the TI technique and may not effectively showcase its effectiveness in larger animals.Based on this,we carried out TI stimulation experiments on rats.Following the TI intervention,analysis of electrophysiological data and immunofluorescence staining indicated the generation of a stimulation focus within the nucleus accumbens(depth,8.5 mm)in rats.Our findings affirm the viability of the TI methodology in the presence of thick cranial bones,furnishing efficacious parameters for profound stimulation with TI administered under such conditions.This experiment not only sheds light on the intervention effects of TI deep in the brain but also furnishes robust evidence in support of its prospective clinical utility.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2023C01National Natural Science Foundation of China under Grant No.52478570Distinguished Young Scholars Program of the Natural Science Foundation of Heilongjiang Province,China under Grant No.JQ2024E002。
文摘The 2025 M_(w)7.7 Myanmar earthquake highlighted the challenge of near-fault seismic intensity field reconstruction due to sparse seismic networks.To address this limitation,a framework was proposed integrating seismic wave simulation with a data-constrained finite-fault rupture model.The constraint is implemented by identifying the optimal ground motion models(GMMs)through a scoring system that selects the best-fit GMMs to mid-and far-field China Earthquake Networks Center(CENC)seismic network data;and applying the optimal GMMs to refine the rupture model parameters for near-fault intensity field simulation.The simulated near-fault seismic intensity field reproduces seismic intensities collected from Myanmar’s sparse seismic network and concentrated in≥Ⅷintensity zones within 50 km of the projected fault plane;and identifies abnormal intensity regions exhibiting≥Ⅹintensity along the Meiktila-Naypyidaw corridor and near Shwebo that are attributed to soft soil amplification effects and near-fault directivity.This framework can also be applied to post-earthquake assessments in other similar regions.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(32200789)the National Natural Science Foundation of China(32070990).
文摘The thalamic reticular nucleus(TRN)plays a crucial role in regulating sensory encoding,even at the earliest stages of visual processing,as evidenced by numerous studies.Orientation selectivity,a vital neural response,is essential for detecting objects through edge perception.Here,we demonstrate that somatostatin(SOM)-expressing and parvalbumin(PV)-expressing neurons in the TRN project to the dorsal lateral geniculate nucleus and modulate orientation selectivity and the capacity for visual information processing in the primary visual cortex(V1).These findings show that SOM-positive and PV-positive neurons in the TRN are powerful modulators of visual information encoding in V1,revealing a novel role for this thalamic nucleus in influencing visual processing.
文摘目的:分析人子宫珠蛋白与猫主要过敏原Fel d 1之间关系。方法 :运用ClustalW 1.83和MEGA5.1 Beta3软件比较人分泌球蛋白家族序列及猫过敏原Fel d 1两个亚基P30438和P30440之间的进化树形图;采用在线软件平台NetMHCII 2.2比较分析P30438与子宫珠蛋白典型序列P11684之间抗原性差异;利用Swiss-Model程序模拟并比较P11684、P30438和P30440的三级结构。结果 :分泌球蛋白家族充斥着大量冗余数据,经逐步聚类收缩至13个代表性序列进一步分析发现,整个分泌球蛋白家族划分成两个大家族三个亚家族,而子宫珠蛋白典型序列与猫主要过敏原Fel d 1的一个亚基P30438之亲缘关系最近,两者均具有与HLA高亲和力结合位点,而且三级结构相似。结论:子宫珠蛋白具有潜在的过敏原性。
文摘Taking ancient village of Gelao Nationality in Wuchuan for example,theories of settlement geography were used to analyze settlement landscapes of ethnic groups with cultural peculiarity in certain regions from the perspectives of geographical and humanistic environment,distribution form,internal structure and settlement characteristics. Regional and national cultural characteristics were demonstrated to promote the inheritance,promotion and protection of such old and traditional civilization in terms of landscape,and provide valuable references for relevant researches.
基金Supported by Natural Science Foundation of China(Grant No.52075032)Technology Research and Development Program Project of CHINA RAILWAY(Grant No.P2020J024).
文摘During the braking process,a large amount of heat energy is generated at the friction surfaces between the brake disc and pads and rapidly dissipates into the disc volume.In this paper,a three-dimensional thermo-mechanical coupling model of high-speed wheel-mounted brake discs containing bolted joints and contact relationships is established.The direct coupling method is used to analyze the temperature and stress of the brake discs during an emergency braking event with an initial speed of 300 km/h.A full-scale bench test is also conducted to monitor the temperatures of the friction ring and bolted joints.The simulation result shows that the surface temperature of the friction ring reaches its peak value of 414°C after 102 s of braking,which agrees well with the bench test result.The maximum alternating thermal stress occurs in the bolt hole where the maximum circumferential compressive stress is−658 MPa and the maximum circumferential tensile stress is 134 MPa.During the braking process,the out-of-plane deformation of the middle part of the friction ring is larger than that of the edge,which increases the axial tensile load of the connecting bolt.This work provides support for the design of brake discs and connecting bolts.
基金This study was financially supported by the Beijing Natural Science Foundation(8202041)National Natural Science Foundation of China(41872205)+1 种基金Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing(2018QN13)the Fundamental Research Funds for the Central Universities(2022YJSLJ08,2021YJSLJ10).
文摘Visualization of complex geological structures can technically support the accurate prediction and prevention of coal mine disasters.This study proposed a new digital reconstruction method to visualize geological structures based on establishing a virtual model in the digital twin system.This methodology for the digital reconstruction of complex fault structures comprises the following four aspects:(1)collection and fdelity of multi-physical feld data of the fault structures,(2)the transmission of multi-physical feld data,(3)the normalization of multi-physical feld data,and(4)digital model reconstruction of fault structures.The key scientifc issues of this methodology to be resolved include in situ fdelity of multi-feld data and normalized programming of multi-source data.In addition,according to the geological background and conditions in Da’anshan coal mine in western Beijing,China,a preliminary attempt is made to reconstruct a digital model of fault and fold structures using the methodology proposed in this study.
基金Supported by Project of National Natural Science Foundation of China(Grand No.52102469)Science and Technology Major Project of Guangxi(Grant Nos.AB21196029 and AA18242033)State Key Laboratory of Automotive Safety and Energy(Grant No.KF2014).
文摘The cooperation between an autonomous vehicle and a nearby vehicle is critical to ensure driving safety in the laneexchanging scenario.The nearby vehicle trajectory needs to be predicted,from which the autonomous vehicle is controlled to prevent possible collisions.This paper proposes a lane-exchanging driving strategy for the autonomous vehicle to cooperate with the nearby vehicle by integrating vehicle trajectory prediction and motion control.A trajectory prediction method is developed to anticipate the nearby vehicle trajectory.The Gaussian mixture model(GMM),together with the vehicle kinematic model,are synthesized to predict the nearby vehicle trajectory.A potential-feldbased model predictive control(MPC)approach is utilized by the autonomous vehicle to conduct the lane-exchanging maneuver.The potential feld of the nearby vehicle is considered in the controller design for collision avoidance.On-road driving data verifcation shows that the nearby vehicle trajectory can be predicted by the proposed method.CarSim®simulations validate that the autonomous vehicle can perform the lane-exchanging maneuver and avoid the nearby vehicle using the proposed driving strategy.The autonomous vehicle can thus safely perform the laneexchanging maneuver and avoid the nearby vehicle.
文摘Abstract The carbon-carbon bond between two nearest-neighboring atoms is mod- eled as a beam and the single-walled carbon nanotubes are treated as the space frame structures in order to analyze the mechanical properties of carbon nanotubes. Based on the theory of Tersof- Brenner force feld, the energy relationships between the carbon-carbon bond and the beam model are obtained, and the stifness parameters of the beam are determined. By applying the present model, the Young’s moduli of the single-walled carbon nanotubes with diferent tube diameters are determined. And the present results are compared with available data.
基金Supported by the Hainan Provincial Department of Science and Technology(No.ZDKJ2016015)the National Natural Science Foundation of China(No.41406198)the Special Project of Chinese HighResolution Earth Observation System(No.41-Y20A14-9001-15/16)
文摘In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboard the Coriolis satellite. The two datasets cover a four-year period from October2011 to September 2015 in the global oceans. For the sea surface wind speed, the statistical comparison indicates good agreement between the HY-2 A scatterometer and WindSat with a bias of nearly 0 m/s and a root mean square error(RMSE) of 1.13 m/s. For the sea surface wind direction, a bias of 1.41° and an RMSE of 20.39° were achieved after excluding the data collocated with opposing directions. Furthermore,discrepancies in sea surface wind speed measured by the two sensors in the global oceans were investigated.It is found that the larger dif ferences mainly appear in the westerlies in the both hemispheres. Both the bias and RMSE show latitude dependence, i.e., they have signi?cant latitudinal ?uctuations.
基金financially supported partly by National Natural Science Foundation of China (Nos. 51571056 and 51690164)“Shuguang Program” from Shanghai Municipal Education CommissionShanghai Science and Technology Committee Grant (19XD1401600, 19010500300)。
文摘As concentration distribution changes have important effects on material structures and properties,controlling the concentration distribution is essential to alloy performance.The aim of the present work is to control and adjust the concentration distribution by the static magnetic field.It is found that the magnetic field disperses grain boundary segregation and causes the uniform distribution of concentration.Further,by the three-dimensional computed tomography(3 D-CT) reconstruction,the flow distribution is seen and the effect mechanism of the magnetic field is revealed.The present work may clarify the ambiguous understanding on the effect of the static magnetic field on solidification process.
文摘A mathematical model was developed to get an insight into 3D electromagnetic–thermal phenomena in an induction heated steel slab with a large width/thickness ratio by solving a fully coupled Maxwell equations and energy conservation equation.The spatial heat radiation between the slab surface and the refractory wall in an induction furnace was considered.The electromagnetic induction and temperature distribution features inside the slab with time evolution were described.The effects of electromagnetic induction parameters,thermal conductivity of the material and process parameters on the induction heating process were theoretically examined.Numerical results show that the spatial distribution of induction heat generation inside the slab is non-uniform.The high work frequency and the low heat conductivity of slab increase the non-uniformity of slab induction heating process.The radiative heat loss and heat transfer between the slab and the metal parts used for holding the slab have an important effect on the slab surface temperature.It is necessary to separately control the current input in the multi-layer coil windings along the height direction of furnace and adopt the multi-step heating strategies with time evolution to improve the homogenization of the slab temperature.
基金Supported by Funding(2016YFD0701600)from Research and Development of Potato Harvesting Technology and EquipmentSpecial Funds for Construction of Modern Agricultural Technology System(CARS-10-P22)Study on Key Technical Equipment for Scale of Potato Planting(GA15B401)
文摘In order to solve the problems which are widespread in potato seeding planter, such as lower operating efficiency, unideal performance index, higher replay rate and leakage rate and uneven spacing sowing in seeding operating, a trailed potato fertilization seeder was designed. The key components of the special structure had been got through the description of the structure and working principle of the whole machine. A crossing seed-taken technology along with the vibration component was adopted to achieve precision seeding. The results showed in the feld test of the machine： all the performance indexes of the machine met the agronomic requirement of potato planting; the multiple and missing index were low; it completed the ditching, fertilizing, seeding as well as ridging in one planting process; its operation effciency was high and the stability was good. This design of the trailed potato fertilization seeder provided a reference for the development of large traction-type potato seeding machine.
基金supported by the National Natural Science Foundation of China(52174024).
文摘Hydraulic fracturing is widely used in geothermal resource exploitation, and many natural fractures exist in hot dry rock reservoirs due to in-situ stress and faults. However, the infuence of natural fractures on hydraulic fracture propagation is not considered in the current study. In this paper, based on the phase feld model, a thermo-hydro-mechanical coupled hydraulic fracture propagation model was established to reveal the infuence of injection time, fracturing method, injection fow rate, and natural fracture distribution on the fracture propagation mechanism. The results show that fracture complexity increases with an increase in injection time. The stress disturbance causes the fracture initiation pressure of the second cluster signifcantly higher than that of the frst and third clusters. The zipper-type fracturing method can reduce the degree of stress disturbance and increase fracture complexity by 7.2% compared to simultaneous hydraulic fracturing. Both low and high injection fow rate lead to a decrease in fracture propagation time, which is not conducive to an increase in fracture complexity. An increase in the natural fracture angle leads to hydraulic fracture crossing natural fracture, but has a lesser efect on fracture complexity. In this paper, we analyzed the infuence of diferent factors on initiation pressure and fracture complexity, providing valuable guidance for the exploitation of geothermal resources.
基金Financial support for this workprovided by the National Natural Science Foundation of China(Nos.61102117 and 41102201)
文摘Porous rock chemical grouting simulation test was conducted using established large scale physical model.Chemical grout diffusing rule in porous media with different permeability was studied by monitoring the spontaneous potential and exciting current response during grouting.The results show that chemical grout spread evenly in all directions and diffusion areas are approximately concentric circles in the cross section of homogeneous transverse isotropic pore medium,the grout spread flling range can be quantitatively decrypted by the diffusion radius.The average diffusion speed and radius increase approximately as the square root with the permeability coeffcient in different permeability media under the same conditions.Calculation results using Maag cylindrical diffusion equation show that the calculated value of diffusion radius is in good agreement with the test value under different grouting pressures and permeability conditions.
基金Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State EducationMinistry.
文摘We study electromechanical felds in the anti-plane deformation of an infnite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electro- elastic dielectrics with electric feld gradient in the constitutive relations is used. Special attention is paid to the felds near the surface of the hole.
基金National Key R&D Program of China under Grant Nos.2023YFA1606400 and 2022YFA1602303National Natural Science Foundation of China under Grants Nos.12335007,12035001,11921006,12347106,12147101,and 12205340+1 种基金Gansu Natural Science Foundation under Grant No.22JR5RA123U.S.Department of Energy(DOE),Office of Science,under SciDAC-5(NUCLEI collaboration)。
文摘Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.
基金supported National Natural Science Foundation of China (No.61102167)
文摘Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly developed.In the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent method.Four normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are formed.The fnal edge detection result is achieved by fusing the results of two thresholded ESMs.The experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.
基金Supported by National Natural Science Foundation of China(Grant Nos.51735006,51927810,U1837206)Beijing Municipal Natural Science Foundation of China(Grant No.3182013).
文摘The current research on the evaporation of ferrofuids mainly focuses on the characterization of ultra-low vapor pressure ferrofuids in vacuum and the theoretical analysis of the evaporation process.Few studies have focused on the experimental validation of the proposed evaporation rate equations and on the comparison of the diferences in ferrofuid evaporation.In this study,based on the Bolotov’s model,an evaporation rate equation is deduced from the experimental model.The experimental study included a comparison of the evaporation,magnetic particle volume fraction,temperature,height of the fuid surface from the outlet,and magnetic feld of a kerosene-based ferrofuid and its base carrier liquid.The prepared sample was evaporated in a test tube,and the evaporation rate was calculated by measuring the weight loss of the sample.The experimental results show that the evaporation rate of the base carrier liquid is higher than that of the ferrofuid.The smaller the volume fraction of the magnetic particles,the greater the evaporation rate.The magnetic particles play a key role in preventing evaporation of the base liquid.The higher the temperature,the smaller the deviation of the evaporation rate from the predicted value.The evaporation rates obtained by the two control groups at the height of the fuid surface from the outlet were lower than the predict value.The magnetic feld had a certain promotional efect on the evaporation of the ferrofuid.The experimental results were consistent with the results obtained using Bolotov’s model.This research validates Bolotov’s model and shows that the model is somewhat biased but still responds well to diferent variables.
