Data-driven approaches such as neural networks are increasingly used for deep excavations due to the growing amount of available monitoring data in practical projects.However,most neural network models only use the da...Data-driven approaches such as neural networks are increasingly used for deep excavations due to the growing amount of available monitoring data in practical projects.However,most neural network models only use the data from a single monitoring point and neglect the spatial relationships between multiple monitoring points.Besides,most models lack flexibility in providing predictions for multiple days after monitoring activity.This study proposes a sequence-to-sequence(seq2seq)two-dimensional(2D)convolutional long short-term memory neural network(S2SCL2D)for predicting the spatiotemporal wall deflections induced by deep excavations.The model utilizes the data from all monitoring points on the entire wall and extracts spatiotemporal features from data by combining the 2D convolutional layers and long short-term memory(LSTM)layers.The S2SCL2D model achieves a long-term prediction of wall deflections through a recursive seq2seq structure.The excavation depth,which has a significant impact on wall deflections,is also considered using a feature fusion method.An excavation project in Hangzhou,China,is used to illustrate the proposed model.The results demonstrate that the S2SCL2D model has superior prediction accuracy and robustness than that of the LSTM and S2SCL1D(one-dimensional)models.The prediction model demonstrates a strong generalizability when applied to an adjacent excavation.Based on the long-term prediction results,practitioners can plan and allocate resources in advance to address the potential engineering issues.展开更多
The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered ...The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered from SELENE mission, revealed the lunar far side gravity field for the first time in history owes to 4-way Doppler data. Lunar deflections of the vertical and their meridional and prime vertical components are calculated from SGM90d, and then their global distributions are also given in the paper. The gradients of lunar deflections of the vertical are defined and computed as well. The correlations between the lunar deflections of the vertical and the lunar terrain have been fully discussed. Many different characteristics of lunar deflections of vertical have been found between the near side and the far side of the Moon, which may be caused from the lithospheric compensation and the uplifting of mantle.展开更多
This work studies large deflections of slen- der, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed con- tinuous load and a concentrated load at the free end ...This work studies large deflections of slen- der, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed con- tinuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be non- linearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by com- paring them with results from previous studies and with a laboratory experiment.展开更多
Islands and the mainland are separated by seas,and the distances between them might be so long that the height on the mainland cannot be exactly translated to the islands,resulting in different height systems on the m...Islands and the mainland are separated by seas,and the distances between them might be so long that the height on the mainland cannot be exactly translated to the islands,resulting in different height systems on the mainland and the islands.In this study,we used astrogeodetic deflections of the vertical and ellipsoidal heights of points on the mainland and island near their coastlines to implement height connection across sea areas.First,the modeled gravity and modeled astrogeodetic vertical deflections of segmentation points along connecting routes over the sea between the mainland and the island were determined by Earth Gravity Model(EGM),and the ellipsoidal heights of segmentation points were determined by the satellite altimetry data sets.Second,we used a linear interpolation model to increase the precision of the vertical deflections of segmentation points.Third,we computed the geopotential difference of points between the mainland and the island using a method derived from geopotential theory and the astronomical leveling principle.Finally,we estimated the normal height of the point on the island using the geopotential-difference iterative computation approach.Using observed data of normal heights,ellipsoidal heights,and astrogeodetic vertical deflections referring to height sites in Qingdao,Shandong Province,we conducted a numerical experiment involving the normal height connection across sea regions.We determined the data of the ellipsoidal heights and gravity of segmentation points along the connecting route across the water in the numerical experiment using DTU10.The distance of the height connection across the sea was approximately 10.5 km.According to China's official leveling specifications,the experimental results met the criterion of third-class leveling precision.展开更多
This paper deals with the research of accuracy of differential equations of deflections. The basic idea is as follows. Firstly, considering the boundary effect the meridian midsurface displacement u=0, thus we derive ...This paper deals with the research of accuracy of differential equations of deflections. The basic idea is as follows. Firstly, considering the boundary effect the meridian midsurface displacement u=0, thus we derive the deflection differential equations; secondly we accurately prove that by use of the deflection differential equations or the original differential equations the same inner forces solutions are obtained; finally, we accurately prove that considering the boundary effect the meridian surface displacement u = 0 is an exact solution. In this paper we give the singular perturbation solution of the deflection differential equations. Finally we check the equilibrium condition and prove the inner forces solved by perturbation method and the outer load are fully equilibrated. It shows that perturbation solution is accurate. On the other hand, it shows again that the deflection differential equation is an exact equation.The features of the new differential equations are as follows:1. The accuracies of the new differential equations and the original differential e-quations are the same.2. The new differential equations can satisfy the boundary conditions simply.3. It is advantageous to use perturbation method with the new differential equations.4 We may obtain the deflection expression(w)and slope expression (dw/da) by using the new differential equations.The new differential equations greatly simplify the calculation of spherical shell. The notation adopted in this paper is the same as that in Ref. [1]展开更多
This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one ...This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one thousand finite element cases were numerically analyzed,followed by extensive parametric studies.Surrogate models were developed via ensemble learning methods(ELMs),including the e Xtreme Gradient Boosting(XGBoost),and Random Forest Regression(RFR)to predict the maximum lateral wall deformation(δhmax).Then the results of ELMs were compared with conventional soft computing methods such as Decision Tree Regression(DTR),Multilayer Perceptron Regression(MLPR),and Multivariate Adaptive Regression Splines(MARS).This study presents a cutting-edge application of ensemble learning in geotechnical engineering and a reasonable methodology that allows engineers to determine the wall deflection in a fast,alternative way.展开更多
There exist three types of convolution formulae for the efficient evaluation of gravity field convolution integrals,i.e.,the planar 2D convolution,the spherical 2D convolution and the spherical 1D convolution.The larg...There exist three types of convolution formulae for the efficient evaluation of gravity field convolution integrals,i.e.,the planar 2D convolution,the spherical 2D convolution and the spherical 1D convolution.The largest drawback of both the planar and the spherical 2D FFT methods is that,due to the approximations in the kernel function,only inexact results can be achieved.Apparently,the reason is the meridian convergence at higher latitudes.As the meridians converge,the Δ φ ,Δ λ blocks do not form a rectangular grid,as is assumed in 2D FFT methods.It should be pointed out that the meridian convergence not only leads to an approximation error in the kernel function,but also causes an approximation error during the implementation of 2D FFT in computer.In order to meet the increasing need for precise determination of the vertical deflections,this paper derives a more precise planar 2D FFT formula for the computation of the vertical deflections.After having made a detailed comparison between the planar and the spherical 2D FFT formulae,we find out the main source of errors causing the loss in accuracy by applying the conventional spherical 2D FFT method.And then,a modified spherical 2D FFT formula for the computation of the vertical deflections is developed in this paper.A series of numerical tests have been carried out to illustrate the improvement made upon the old spherical 2D FFT.The second part of this paper is to discuss the influences of the spherical harmonic reference field,the limited capsize,and the singular integral on the computation of the vertical deflections.The results of the vertical deflections over China by applying the spherical 1D FFT formula with different integration radii have been compared to the astro_observed vertical deflections in the South China Sea to obtain a set of optimum deflection computation parameters.展开更多
Distance between the main land and island is so long that it is very difficult to precisely connect the height datum across the sea with the traditional method like the trigonometric leveling, or it is very expensive ...Distance between the main land and island is so long that it is very difficult to precisely connect the height datum across the sea with the traditional method like the trigonometric leveling, or it is very expensive and takes long time to implement the height transfer with the geopotential technique. We combine the data of GPS surveying, astro-geodesy and EGM2008 to precisely connect the orthometric height across the sea with the improved astronomical leveling method in the paper. The Qiongzhou Strait is selected as the test area for the height connection over the sea. We precisely determine the geodetic latitudes, longitudes, heights and deflections of the vertical for four points on both sides across the strait. Modeled deflections of the vertical along the height connecting routes over the sea are determined with EGM2008 model based on the geodetic positions and heights of the sea segmentation points from DNSC08MSS model. Differences of the measured and modeled deflections of the vertical are calculated at four points on both sides and linearly change along the route. So the deflections of the vertical along the route over the sea can be improved by the linear interpolation model. The results are also in accord with those of trigonometirc levelings. The practical case shows that we can precisely connect the orthometric height across the Qiongzhou Strait to satisfy the requirement of order 3 leveling network of China. The method is very efficient to precisely connect the height datum across the sea along the route up to 80 km.展开更多
High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not...High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not been systematically studied.In this paper,the impact of influential factors,including phantom characteristic represented by the ratio of DMSO and thawing time(TT),needle properties represented by needle external diameter(NED)and operating factors such as needle insertion velocity(IV),insertion positions(IP)and repeated insertion times(RITs)are analyzed by orthogonal experiment design.The range calculation shows the most sensitive parameters to phantom deformations are RITs,IV and DMSO while the most sensitive parameters to needle deflection are DMSO,TT and NED.By variance analysis,the significant factors on maximum tissue deformation(MTD)are IV,followed by RITs,DMSO and IP.And NED and TT have nearly no significant impact on MTD.The significant sequence on maximum needle deflection(MND)is as follows:DMSO,TT and NED.Results show that,among all impacting factors,phantom deformation is susceptible to both material properties and operative factors while the needle deflection is more susceptible to material properties of the phantom,which can help researchers in related fields to conduct experiments in a more precise manner and better understand the needle-phantom interaction mechanism.展开更多
The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FR...The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FRP bars are tested to understand their flexural behaviour.In this study is investigated the way of failure of beams reinforced internally with carbon FRP(CFRP)bars and their mechanical properties.Two sets of concrete beams reinforced with different diameters of CFRP bars are designed and tested under four-point loading methods.In general,beams reinforced with FRP bars show more deflections and greater values of crack width than beams reinforced with conventional steel,which is due to their low modulus of elasticity and general stiffness.In this paper is presented the calculation and comparison of deflection using different methods,such as ACI 440,CAN/CSA,Eurocode and experimental loading tests.The evaluation is done comparing the results of every method.This study is effective when we use beams with one layer of reinforcement.展开更多
The paper presents an improved technique of calculating total deflections of flexural reinforced concrete elements that takes discrete crack formation into account. The technique is based on determining the curvature ...The paper presents an improved technique of calculating total deflections of flexural reinforced concrete elements that takes discrete crack formation into account. The technique is based on determining the curvature of the cross section of reinforced concrete elements with cracks and fissures in the area between cracks. The curvature of the element is calculated using a non-linear function of the deformation of concrete under compression. Approximating dependency of concrete resistance on compression developed by one of the authors is presented. An algorithm of finding the curvature and formulas for calculating curvature and deflection are provided. The function of the curvature distribution along the length of a flexible element is proposed by the authors. The paper also presents the results of the author＇s experimental research. The characteristics of samples tested are described. The experimental research results of deflections of fiexural reinforced concrete elements made of conventional and high-strength concretes are presented. Comparison of the values calculated using the technique with those obtained from the experimental research as well as those calculated according to existing regulations in Russia, USA and Europe is drawn.展开更多
In this paper,a comparative analysis of two beams’deflections,one supported-embedded beam and a bi-supported beam,is presented.For such comparison,first the respective second-order linear Ordinary Differential Equati...In this paper,a comparative analysis of two beams’deflections,one supported-embedded beam and a bi-supported beam,is presented.For such comparison,first the respective second-order linear Ordinary Differential Equations(ODEs)were obtained.Along with the boundary conditions,there are two Boundary Value Problems(BVPs),making it possible to perform their numerical and analytical solutions.For numerical solutions,a Matlab algorithm was implemented based on the Finite Difference Method(FDM).The analytical solutions were also obtained for comparison with the numerical ones and with the validation method.In the end we analyzed the shapes of the elastic lines of the two beams caused by the loads coming from the weight of each one.展开更多
This paper investigates off-equatorial plane deflections and gravitational lensing of both null signals and massive particles in Kerr spacetime in the weak deflection limit,considering the finite distance effect of th...This paper investigates off-equatorial plane deflections and gravitational lensing of both null signals and massive particles in Kerr spacetime in the weak deflection limit,considering the finite distance effect of the source and detector.This is the effect caused by both the source and detector being located at finite distances from the lens although many researchers often use the deflection angle for infinite distances from sources and detectors.The deflection in both the and directions is computed as a power series of M/r_(0) and r_(0)/rsd,where M,rs.d are the spacetime mass and source and detector radi,respectively,and r_(0) is the minimal radial coordinate of the trajectory.The coefficients of these series are simple trigonometric functions of Ge,the extreme value of the coordinate of the trajectory.A set of exact gravitational lensing equations is used to solve for ro and Ge for given deviation angles so and Sp of the source,and two lensed images are always obtained.The apparent angles and their magnifications of these images and the time delays between them are solved.Additionally,their dependences on various parameters,particularly spacetime spin a,are analyzed in depth.We find that generally two critical spacetime spin values exist that separate the case of test particles reaching the detector from different sides of the z axis from the cases in which the images appear from the same side in the celestial plane.Three potential applications of these results are discussed.展开更多
In this work, we develop a general perturbative procedure to determine the off-equatorial plane deflections in the weak deflection limit in general stationary and axisymmetric spacetimes, enabling the existence of the...In this work, we develop a general perturbative procedure to determine the off-equatorial plane deflections in the weak deflection limit in general stationary and axisymmetric spacetimes, enabling the existence of the generalized Carter constant. Deflections of both null and timelike rays, with the finite distance effect of the source and detector considered, are obtained as dual series of M/r_(0) and r_(0)/r_(s,d.) These deflections enable a set of exact gravitational lensing equations from which the apparent angular positions of the images are solved. The method and general results are then applied to the Kerr-Newmann, Kerr-Sen, and rotating Simpson-Visser spacetimes to study the effect of the spin and characteristic(effective) charge of the spacetimes and the source altitude on the deflection angles and image apparent angles. We find that, generally, both the spacetime spin and charge affect only the deflections from the second non-trivial order, whereas the source altitude influences the deflection from the leading order.Because of this, measuring the effects of the spacetime spin and charge from the apparent locations of the images in gravitational lensing in realistic scenarios is difficult. We also present the off-equatorial deflections in the rotating Bardeen, Hayward, Ghosh, and Tinchev black hole spacetimes.展开更多
Machine learning methods have advantages in predicting excavation-induced lateral wall displacements.Due to lack of sufficient field data,training data for prediction models were often derived from the results of nume...Machine learning methods have advantages in predicting excavation-induced lateral wall displacements.Due to lack of sufficient field data,training data for prediction models were often derived from the results of numerical simulations,leading to poor prediction accuracy.Based on a specific quantity of data,a multivariate adaptive regression splines method(MARS)was introduced to predict lateral wall deflections caused by deep excavations in thick water-rich sands.Sensitivity of lateral wall deflections to affecting factors was analyzed.It is disclosed that dewatering mode has the most significant influence on lateral wall deflections,while the soil cohesion has the least influence.Using crossvalidation analysis,weights were introduced to modify the MARS method to optimize the prediction model.Comparison of the predicted and measured deflections shows that the prediction based on the modified multivariate adaptive regression splines method(MMARS)is more accurate than that based on the traditional MARS method.The prediction model established in this paper can help engineers make predictions for wall displacement,and the proposed methodology can also serve as a reference for researchers to develop prediction models.展开更多
The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To addres...The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.展开更多
Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These r...Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These residual charges lead to jet deflection.This study introduces a novel noncontact electric field-driven(NEFD)jet micro 3D printing technique to address these challenges.By decoupling the high-voltage power supply from both the printing material and substrate,NEFD jet micro 3D printing eliminates the pathway for charge injection into the printing material,reducing residual charges by a factor of five or more compared to EHD jet printing.Our research revealed an inherent attractive force between the material jet and previously deposited material,regardless of the material used.Furthermore,we demonstrate that employing a pre-defined allowance printing strategy during fabrication reduces the standard deviation of actual fiber spacing values from 11.4μm to 1.5μm,thereby improving the fiber spacing consistency.This enhanced control enabled the successful fabrication of line patterns with 20±1μm fiber diameters and 61.1±1.9μm fiber spacing,demonstrating the feasibility of NEFD jet micro 3D printing.This technique offers a novel solution for mitigating the challenges associated with electric fields and charge accumulation in EHD jet printing,paving the way for enhanced resolution and material compatibility in micro-/nanoscale additive manufacturing.展开更多
The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comp...The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comparing the experimental data,with computational efficiency enhanced through improved mesh refinement.Penetration simulations involving deformable projectiles at various incident angles analyzed the effects of aggregate volume fraction and particle size on ballistic trajectory and terminal deflection.Sensitivity analysis reveals a strong power-law relationship between aggregate content and the projectile's deflection angle.The increase in aggregate content will enhance the confinement effect,shorten the intrusion distance of the projectile,and lead to a decrease in the deflection angle of the projectile.The effect of aggregate particle size on the projectile deflection angle follows a Gaussian distribution.The maximum deflection angle occurs when the aggregate particle size is between 2.7 and 3.1 times the projectile diameter.An increase in particle size reduces the number of aggregate-mortar interfaces at the same aggregate volume fraction,leading to an enlargement of the damage zone in concrete,a decrease in the number of cracks,and an increase in crack length.These findings enhance the understanding of concrete penetration mechanisms and offers valuable insights for engineering structure protection.展开更多
Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to t...Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.展开更多
Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ...Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42307218)the Foundation of Key Laboratory of Soft Soils and Geoenvironmental Engineering(Zhejiang University),Ministry of Education(Grant No.2022P08)the Natural Science Foundation of Zhejiang Province(Grant No.LTZ21E080001).
文摘Data-driven approaches such as neural networks are increasingly used for deep excavations due to the growing amount of available monitoring data in practical projects.However,most neural network models only use the data from a single monitoring point and neglect the spatial relationships between multiple monitoring points.Besides,most models lack flexibility in providing predictions for multiple days after monitoring activity.This study proposes a sequence-to-sequence(seq2seq)two-dimensional(2D)convolutional long short-term memory neural network(S2SCL2D)for predicting the spatiotemporal wall deflections induced by deep excavations.The model utilizes the data from all monitoring points on the entire wall and extracts spatiotemporal features from data by combining the 2D convolutional layers and long short-term memory(LSTM)layers.The S2SCL2D model achieves a long-term prediction of wall deflections through a recursive seq2seq structure.The excavation depth,which has a significant impact on wall deflections,is also considered using a feature fusion method.An excavation project in Hangzhou,China,is used to illustrate the proposed model.The results demonstrate that the S2SCL2D model has superior prediction accuracy and robustness than that of the LSTM and S2SCL1D(one-dimensional)models.The prediction model demonstrates a strong generalizability when applied to an adjacent excavation.Based on the long-term prediction results,practitioners can plan and allocate resources in advance to address the potential engineering issues.
文摘The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered from SELENE mission, revealed the lunar far side gravity field for the first time in history owes to 4-way Doppler data. Lunar deflections of the vertical and their meridional and prime vertical components are calculated from SGM90d, and then their global distributions are also given in the paper. The gradients of lunar deflections of the vertical are defined and computed as well. The correlations between the lunar deflections of the vertical and the lunar terrain have been fully discussed. Many different characteristics of lunar deflections of vertical have been found between the near side and the far side of the Moon, which may be caused from the lithospheric compensation and the uplifting of mantle.
文摘This work studies large deflections of slen- der, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed con- tinuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be non- linearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by com- paring them with results from previous studies and with a laboratory experiment.
基金financially supported by the foundation of the Key Laboratory of Marine Environmental Survey Technology and Application,Ministry of Natural Resources,China (No. MESTA-2020-B006)the National Natural Science Foundation of China (No.41774001)
文摘Islands and the mainland are separated by seas,and the distances between them might be so long that the height on the mainland cannot be exactly translated to the islands,resulting in different height systems on the mainland and the islands.In this study,we used astrogeodetic deflections of the vertical and ellipsoidal heights of points on the mainland and island near their coastlines to implement height connection across sea areas.First,the modeled gravity and modeled astrogeodetic vertical deflections of segmentation points along connecting routes over the sea between the mainland and the island were determined by Earth Gravity Model(EGM),and the ellipsoidal heights of segmentation points were determined by the satellite altimetry data sets.Second,we used a linear interpolation model to increase the precision of the vertical deflections of segmentation points.Third,we computed the geopotential difference of points between the mainland and the island using a method derived from geopotential theory and the astronomical leveling principle.Finally,we estimated the normal height of the point on the island using the geopotential-difference iterative computation approach.Using observed data of normal heights,ellipsoidal heights,and astrogeodetic vertical deflections referring to height sites in Qingdao,Shandong Province,we conducted a numerical experiment involving the normal height connection across sea regions.We determined the data of the ellipsoidal heights and gravity of segmentation points along the connecting route across the water in the numerical experiment using DTU10.The distance of the height connection across the sea was approximately 10.5 km.According to China's official leveling specifications,the experimental results met the criterion of third-class leveling precision.
文摘This paper deals with the research of accuracy of differential equations of deflections. The basic idea is as follows. Firstly, considering the boundary effect the meridian midsurface displacement u=0, thus we derive the deflection differential equations; secondly we accurately prove that by use of the deflection differential equations or the original differential equations the same inner forces solutions are obtained; finally, we accurately prove that considering the boundary effect the meridian surface displacement u = 0 is an exact solution. In this paper we give the singular perturbation solution of the deflection differential equations. Finally we check the equilibrium condition and prove the inner forces solved by perturbation method and the outer load are fully equilibrated. It shows that perturbation solution is accurate. On the other hand, it shows again that the deflection differential equation is an exact equation.The features of the new differential equations are as follows:1. The accuracies of the new differential equations and the original differential e-quations are the same.2. The new differential equations can satisfy the boundary conditions simply.3. It is advantageous to use perturbation method with the new differential equations.4 We may obtain the deflection expression(w)and slope expression (dw/da) by using the new differential equations.The new differential equations greatly simplify the calculation of spherical shell. The notation adopted in this paper is the same as that in Ref. [1]
基金supported by the High-end Foreign Expert Introduction program(No.G20190022002)Chongqing Construction Science and Technology Plan Project(2019-0045)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJZD-K201900102)The financial support is gratefully acknowledged。
文摘This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one thousand finite element cases were numerically analyzed,followed by extensive parametric studies.Surrogate models were developed via ensemble learning methods(ELMs),including the e Xtreme Gradient Boosting(XGBoost),and Random Forest Regression(RFR)to predict the maximum lateral wall deformation(δhmax).Then the results of ELMs were compared with conventional soft computing methods such as Decision Tree Regression(DTR),Multilayer Perceptron Regression(MLPR),and Multivariate Adaptive Regression Splines(MARS).This study presents a cutting-edge application of ensemble learning in geotechnical engineering and a reasonable methodology that allows engineers to determine the wall deflection in a fast,alternative way.
文摘There exist three types of convolution formulae for the efficient evaluation of gravity field convolution integrals,i.e.,the planar 2D convolution,the spherical 2D convolution and the spherical 1D convolution.The largest drawback of both the planar and the spherical 2D FFT methods is that,due to the approximations in the kernel function,only inexact results can be achieved.Apparently,the reason is the meridian convergence at higher latitudes.As the meridians converge,the Δ φ ,Δ λ blocks do not form a rectangular grid,as is assumed in 2D FFT methods.It should be pointed out that the meridian convergence not only leads to an approximation error in the kernel function,but also causes an approximation error during the implementation of 2D FFT in computer.In order to meet the increasing need for precise determination of the vertical deflections,this paper derives a more precise planar 2D FFT formula for the computation of the vertical deflections.After having made a detailed comparison between the planar and the spherical 2D FFT formulae,we find out the main source of errors causing the loss in accuracy by applying the conventional spherical 2D FFT method.And then,a modified spherical 2D FFT formula for the computation of the vertical deflections is developed in this paper.A series of numerical tests have been carried out to illustrate the improvement made upon the old spherical 2D FFT.The second part of this paper is to discuss the influences of the spherical harmonic reference field,the limited capsize,and the singular integral on the computation of the vertical deflections.The results of the vertical deflections over China by applying the spherical 1D FFT formula with different integration radii have been compared to the astro_observed vertical deflections in the South China Sea to obtain a set of optimum deflection computation parameters.
基金supported by the National Natural Science Foundation of China (Grant No. 40974004)the National High-Technology Research and Development Program of China (863 Program,Grant No. 2009AA121405)+1 种基金the Key Laboratory of Surveying and Mapping Technology on Island and Reef of NASMG,China (Grant No. 2011A01)the Key Laboratory of Advanced Engineering Surveying of NASMG,China (Grant No. TJES1101)
文摘Distance between the main land and island is so long that it is very difficult to precisely connect the height datum across the sea with the traditional method like the trigonometric leveling, or it is very expensive and takes long time to implement the height transfer with the geopotential technique. We combine the data of GPS surveying, astro-geodesy and EGM2008 to precisely connect the orthometric height across the sea with the improved astronomical leveling method in the paper. The Qiongzhou Strait is selected as the test area for the height connection over the sea. We precisely determine the geodetic latitudes, longitudes, heights and deflections of the vertical for four points on both sides across the strait. Modeled deflections of the vertical along the height connecting routes over the sea are determined with EGM2008 model based on the geodetic positions and heights of the sea segmentation points from DNSC08MSS model. Differences of the measured and modeled deflections of the vertical are calculated at four points on both sides and linearly change along the route. So the deflections of the vertical along the route over the sea can be improved by the linear interpolation model. The results are also in accord with those of trigonometirc levelings. The practical case shows that we can precisely connect the orthometric height across the Qiongzhou Strait to satisfy the requirement of order 3 leveling network of China. The method is very efficient to precisely connect the height datum across the sea along the route up to 80 km.
基金Supported by Zhejiang Provincial Natural Science Foundation of China(Grant No.LSD19H180004)National Major Scientific Research Instrument Development Project of China(Grant No.81827804)and Science Fund for Creative Group of NSFC(Grant No.51821903).
文摘High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not been systematically studied.In this paper,the impact of influential factors,including phantom characteristic represented by the ratio of DMSO and thawing time(TT),needle properties represented by needle external diameter(NED)and operating factors such as needle insertion velocity(IV),insertion positions(IP)and repeated insertion times(RITs)are analyzed by orthogonal experiment design.The range calculation shows the most sensitive parameters to phantom deformations are RITs,IV and DMSO while the most sensitive parameters to needle deflection are DMSO,TT and NED.By variance analysis,the significant factors on maximum tissue deformation(MTD)are IV,followed by RITs,DMSO and IP.And NED and TT have nearly no significant impact on MTD.The significant sequence on maximum needle deflection(MND)is as follows:DMSO,TT and NED.Results show that,among all impacting factors,phantom deformation is susceptible to both material properties and operative factors while the needle deflection is more susceptible to material properties of the phantom,which can help researchers in related fields to conduct experiments in a more precise manner and better understand the needle-phantom interaction mechanism.
文摘The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FRP bars are tested to understand their flexural behaviour.In this study is investigated the way of failure of beams reinforced internally with carbon FRP(CFRP)bars and their mechanical properties.Two sets of concrete beams reinforced with different diameters of CFRP bars are designed and tested under four-point loading methods.In general,beams reinforced with FRP bars show more deflections and greater values of crack width than beams reinforced with conventional steel,which is due to their low modulus of elasticity and general stiffness.In this paper is presented the calculation and comparison of deflection using different methods,such as ACI 440,CAN/CSA,Eurocode and experimental loading tests.The evaluation is done comparing the results of every method.This study is effective when we use beams with one layer of reinforcement.
文摘The paper presents an improved technique of calculating total deflections of flexural reinforced concrete elements that takes discrete crack formation into account. The technique is based on determining the curvature of the cross section of reinforced concrete elements with cracks and fissures in the area between cracks. The curvature of the element is calculated using a non-linear function of the deformation of concrete under compression. Approximating dependency of concrete resistance on compression developed by one of the authors is presented. An algorithm of finding the curvature and formulas for calculating curvature and deflection are provided. The function of the curvature distribution along the length of a flexible element is proposed by the authors. The paper also presents the results of the author＇s experimental research. The characteristics of samples tested are described. The experimental research results of deflections of fiexural reinforced concrete elements made of conventional and high-strength concretes are presented. Comparison of the values calculated using the technique with those obtained from the experimental research as well as those calculated according to existing regulations in Russia, USA and Europe is drawn.
文摘In this paper,a comparative analysis of two beams’deflections,one supported-embedded beam and a bi-supported beam,is presented.For such comparison,first the respective second-order linear Ordinary Differential Equations(ODEs)were obtained.Along with the boundary conditions,there are two Boundary Value Problems(BVPs),making it possible to perform their numerical and analytical solutions.For numerical solutions,a Matlab algorithm was implemented based on the Finite Difference Method(FDM).The analytical solutions were also obtained for comparison with the numerical ones and with the validation method.In the end we analyzed the shapes of the elastic lines of the two beams caused by the loads coming from the weight of each one.
基金Partially Supported by the Wuhan University Students Innovation and Entrepreneurship Program。
文摘This paper investigates off-equatorial plane deflections and gravitational lensing of both null signals and massive particles in Kerr spacetime in the weak deflection limit,considering the finite distance effect of the source and detector.This is the effect caused by both the source and detector being located at finite distances from the lens although many researchers often use the deflection angle for infinite distances from sources and detectors.The deflection in both the and directions is computed as a power series of M/r_(0) and r_(0)/rsd,where M,rs.d are the spacetime mass and source and detector radi,respectively,and r_(0) is the minimal radial coordinate of the trajectory.The coefficients of these series are simple trigonometric functions of Ge,the extreme value of the coordinate of the trajectory.A set of exact gravitational lensing equations is used to solve for ro and Ge for given deviation angles so and Sp of the source,and two lensed images are always obtained.The apparent angles and their magnifications of these images and the time delays between them are solved.Additionally,their dependences on various parameters,particularly spacetime spin a,are analyzed in depth.We find that generally two critical spacetime spin values exist that separate the case of test particles reaching the detector from different sides of the z axis from the cases in which the images appear from the same side in the celestial plane.Three potential applications of these results are discussed.
基金Supported by the National Natural Science Foundation of China。
文摘In this work, we develop a general perturbative procedure to determine the off-equatorial plane deflections in the weak deflection limit in general stationary and axisymmetric spacetimes, enabling the existence of the generalized Carter constant. Deflections of both null and timelike rays, with the finite distance effect of the source and detector considered, are obtained as dual series of M/r_(0) and r_(0)/r_(s,d.) These deflections enable a set of exact gravitational lensing equations from which the apparent angular positions of the images are solved. The method and general results are then applied to the Kerr-Newmann, Kerr-Sen, and rotating Simpson-Visser spacetimes to study the effect of the spin and characteristic(effective) charge of the spacetimes and the source altitude on the deflection angles and image apparent angles. We find that, generally, both the spacetime spin and charge affect only the deflections from the second non-trivial order, whereas the source altitude influences the deflection from the leading order.Because of this, measuring the effects of the spacetime spin and charge from the apparent locations of the images in gravitational lensing in realistic scenarios is difficult. We also present the off-equatorial deflections in the rotating Bardeen, Hayward, Ghosh, and Tinchev black hole spacetimes.
基金Financial support from the National Natural Science Foundation of China(Grant No.42177179)is gratefully acknowledged.
文摘Machine learning methods have advantages in predicting excavation-induced lateral wall displacements.Due to lack of sufficient field data,training data for prediction models were often derived from the results of numerical simulations,leading to poor prediction accuracy.Based on a specific quantity of data,a multivariate adaptive regression splines method(MARS)was introduced to predict lateral wall deflections caused by deep excavations in thick water-rich sands.Sensitivity of lateral wall deflections to affecting factors was analyzed.It is disclosed that dewatering mode has the most significant influence on lateral wall deflections,while the soil cohesion has the least influence.Using crossvalidation analysis,weights were introduced to modify the MARS method to optimize the prediction model.Comparison of the predicted and measured deflections shows that the prediction based on the modified multivariate adaptive regression splines method(MMARS)is more accurate than that based on the traditional MARS method.The prediction model established in this paper can help engineers make predictions for wall displacement,and the proposed methodology can also serve as a reference for researchers to develop prediction models.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3009400)the National Natural Science Foundation of China(Grant Nos.42307218 and U2239251).
文摘The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.
基金supported by National Natural Science Foundation of China(Grant Nos.52275345,52175331,51875300)Support Plan for Outstanding Youth Innovation Team in Universities of Shandong Province,China(Grant No.2021KJ044)Natural Science Foundation of Shandong Province,China(Grant No.ZR2020ZD04).
文摘Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These residual charges lead to jet deflection.This study introduces a novel noncontact electric field-driven(NEFD)jet micro 3D printing technique to address these challenges.By decoupling the high-voltage power supply from both the printing material and substrate,NEFD jet micro 3D printing eliminates the pathway for charge injection into the printing material,reducing residual charges by a factor of five or more compared to EHD jet printing.Our research revealed an inherent attractive force between the material jet and previously deposited material,regardless of the material used.Furthermore,we demonstrate that employing a pre-defined allowance printing strategy during fabrication reduces the standard deviation of actual fiber spacing values from 11.4μm to 1.5μm,thereby improving the fiber spacing consistency.This enhanced control enabled the successful fabrication of line patterns with 20±1μm fiber diameters and 61.1±1.9μm fiber spacing,demonstrating the feasibility of NEFD jet micro 3D printing.This technique offers a novel solution for mitigating the challenges associated with electric fields and charge accumulation in EHD jet printing,paving the way for enhanced resolution and material compatibility in micro-/nanoscale additive manufacturing.
基金funded by the National Natural Science Foundation of China(Grant Nos.12472390 and 12102292)the special fund for Science and Technology Innovation Teams of Shanxi Province(Grant No.202204051002006)。
文摘The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comparing the experimental data,with computational efficiency enhanced through improved mesh refinement.Penetration simulations involving deformable projectiles at various incident angles analyzed the effects of aggregate volume fraction and particle size on ballistic trajectory and terminal deflection.Sensitivity analysis reveals a strong power-law relationship between aggregate content and the projectile's deflection angle.The increase in aggregate content will enhance the confinement effect,shorten the intrusion distance of the projectile,and lead to a decrease in the deflection angle of the projectile.The effect of aggregate particle size on the projectile deflection angle follows a Gaussian distribution.The maximum deflection angle occurs when the aggregate particle size is between 2.7 and 3.1 times the projectile diameter.An increase in particle size reduces the number of aggregate-mortar interfaces at the same aggregate volume fraction,leading to an enlargement of the damage zone in concrete,a decrease in the number of cracks,and an increase in crack length.These findings enhance the understanding of concrete penetration mechanisms and offers valuable insights for engineering structure protection.
文摘Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.
基金supported by the National Natural Science Foundation of China(No.12002102)。
文摘Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.
