最新刊期
卷 49 ， 期 4 ， 2017
- 摘要：Abstract:Fiber gypsum composite material has good physical and mechanical properties,but the study of using it as infilled wall materials is less.To study the seismic behavior of fiber gypsum infilled wall RC frame and the effects of constructional details of infilling wall have on the RC seismic behavior,four one-bay and one-story specimens,including one bare frame without infilling walls,one shale brick infilling wall with rigid connection to RC frame,two fiber gypsum infilling walls,where one fiber gypsum wall was with flexible connections and another with rigid connection,were designed with half-scale and tested under low-cycle reversed loads.The damage behavior,hysteresis curves,skeleton curves,stiffness degradation,bearing capacity,deformation capacity and energy-dissipation capacity of the specimens were analyzed.The results showed that the infilling wall could improve the bearing capacity and energy-dissipation capacity of the frame structure.Compared with traditional RC frame with shale brick infilling wall,the RC frames with fiber gypsum infilled wall has a better bearing capacity and deformation capacity.The fiber gypsum infilling wall RC frame with flexible connections has a better seismic behavior to the fiber gypsum infilling wall RC frame with rigid connections.Therefore,compared with the traditional masonry infilled wall,fiber gypsum infilled wall has a better practical value and application prospect in the actual engineering.关键词：fiber gypsum infilled wall;seismic behavior;quasi-static test;synergy
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发布时间：2023-11-14 - 摘要：Abstract:The stability of high and steep rocky slopes is crucial in hydropower projects.It is difficult to identify the key factors that affect the slope stability so that the specific support design and construction are implemented.By using the high and steep slope near the Changheba Hydropower Station water intake location as an example,combined with the geologic investigation,the key factors such as the combination damage of fissures J3,J7 and other structural planes of controlling the slope stability were analyzed,and the corresponding excavation support plan was proposed based on the geographical position partition.The rock mass was reviewed by different parts and different elevations during the construction,The main slope failure modes were slumping (sliding),dumping and tension,the loosing and broken rock mass cutting by different cracks.The slope was partitioned on the basis of the rock mass rating,which guided the supporting design of correction.The most key factor to control the slope stability was discussed,which was the J3 cracks.The differences and effectiveness were compared between the previous design and the corrective design.The analysis of the monitoring data suggested that the informationized construction had an obvious effect on controlling the slope stability,and no engineering problems were found from then on and the slope was stable at present.关键词：informationized construction;review of rock mass;rocky slope;the Changheba Hydropower Station;monitoring analysis
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发布时间：2023-11-14 - 摘要：Abstract:Geo-mechanical model test is an important method to study the stability safety of high dams.How to establish the criterion of dam failure through the test result,to judge the failure process of the dam failure,and to obtain the compressive stability safety factor in geo-mechanical model test are the key technical problems.In this study,the more mature cusp-catastrophe model and its standard potential function formula were introduced to deduce the corresponding discriminant instability of mutations,and the criterion of instability based on cusp-catastrophe theory was established.Meanwhile,the finite element calculation and analysis were carried out by means of related calculation examples.According to the relationship between the displacement and the overload coefficient in the results of finite element calculation,the instability criterion of cusp-catastrophe model was established and the overload safety factor was proposed.By comparing the calculated results with the instability criterion based on the run-through of plastic zone and un-convergence of finite element calculation,the reliability and applicability of the instability criterion of cusp-catastrophe model was proven.It was then applied to the geo-mechanical model test of danba hydropower station.Based on the test results,the displacement field of gate and gravity dam section under the action of normal pool level load and overloading after strength-decreasing were obtained.The deformation distribution characters of gate and gravity dam section for typical measurement points were reached,and the overall developing process of displacement and crack and its failure mechanism were revealed.The safety evaluation of model experiment indicates that the strength margin coefficient was 1.18 and the overloading coefficient was 1.8~2.0;and the global stability safety factor for gate and gravity dam was 2.12~2.36.According to catastrophe theory,the instability criterion was established and the failure process and the compressive stability safety factor were proposed.Comparing with the results of instability criterion analysis based on the conventional geo-mechanical model test,the analysis result indicated the rationality of the instability criterion of cusp catastrophe model based on the results of geo-mechanical model test.关键词：cusp catastrophe theory;finite element method;geo-mechanical model test;instability criterion
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发布时间：2023-11-14 - 摘要：Abstract:Due to the effects of foundation embedded depth and characteristic of axisymmetric deformation of sand have not been considered simultaneously on the failure mechanism,the Berezantzev's theory for predicting the bearing capacity of a deep circular foundation in sand have not been able to support data from the in-situ tests completely,especially for lower foundation embedded depth(2 ≤ H/b ≤ 5).By analyzing the relationships among the movement of soil particles,soil compaction and shear failure of the soil,the failure process of sand ground was systematically researched in theory.The damaged ground could be divided into three zones:a highly compressed zone Ⅰ,a radial shear zone Ⅱ,and a slightly compressed zone Ⅲ.A resistance shearing force exists in an upward direction on the soil annulus above the zone Ⅲ,similar to the conclusion drawn by Berezantzev.The extents of zones Ⅰ,Ⅱ,Ⅲ were determined by considering the combined effects of buried depth,the relative density of sand and the roughness of base on the failure mode of sand ground.A new model of ground failure was developed to calculate the ultimate bearing capacity of sand under the deep circular foundation for the relative buried depth (H/b) between 2 and 5.According to the static equilibrium of the free body in the damaged ground,the ultimate bearing capacity of the deep circular foundation in sand was deduced.Some practical calculations showed that the ultimate bearing capacity factor,Nγq,determined using the present method was less than that using the earlier semi-empiric formulas proposed by Berezantzev,Terzaghi and Durgunoglu in different internal friction angle decreased with the increase of the relative depth.The ultimate bearing capacity of deep circular foundation calculated in this paper was closer to those given in the specifications than those calculated by earlier semi-empiric formulas.关键词：deep circular foundation;bearing capacity;sand;axisymmetric deformation;soil compaction;foundation embedded depth
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发布时间：2023-11-14 - 摘要：Abstract:The single working condition and objective optimizationis often based on experience and thus global optimal solution cannot be reached for the structure layout of main frame of tainter gate (cantilever length of main girder,unit stiffness ratio of main frame,and radius of tainter gate) and hydraulic hoist.Global layout optimization of tainter gate and hoist system under multi-conditions and objectives is carried out based on the current design code for steel gate in water resources and hydropower projects of China and the design of hydraulic steel structures and the design of spillway tainter gates of America.The optimization objectives are:1) The positive bending moment in the middle of the girder is equal to the absolute value of negative moment of the support,and the maximum value reaches the minimum in the conditions of normal water level of the full closeure,check flood water level of instant open and full open;2) The radius of the tainter gate reached is the minimum,and the maximum value of absolute value of negative moment of the strut tends to minimum in the conditions;3) The capacity of hydraulic hoist tends to minimum in the conditions.The constraints are determined to be:1) Range of cantilever length of main girder;2) Range of unit stiffness ratio of main frame;3) Operation conditions of hydraulic hoist in the opening and closing processes of tainter gate;4) Range of the ratio between the radius and height;5) Allowable range of opening force of hydraulic hoist;6) Layout requirements of hydraulic hoist.Global layout optimization of tainter gate and hoist system under multi-conditions and objectives is built based on the above conditions.The optimal structures of the main frame and hoist are obtained by solving the engineering example:the non-dimensional cantilever length was 0.160,and the non-dimensional unit stiffness ratio of girder and strut was 8.69,the non-dimensional ratio between the radius and height was 1.3,and the non-dimensional lifting point position between the side wall of pier was 0.13,and the angle between the pull rod and the strut was 34.6° when the gate was full closed.The results showed that the method of global layout optimization of tainter gate and hoist system under multi-conditions and objectives was simple and practical.Moreover,the internal force of the tainter gate and the capacity of the hoist were greatly reduced and achieves the unity of security and economy of the global optimization layout of tainter gate and hoist. It also makes up for the deficiencies that cannot consider different working conditions,and the random arrangement of the cantilever length of main girder,unit stiffness ratio of main frame,radius and hydraulic hoist by experience,and also provides the simple method of the global optimal arrangement for the revision of the codes of China and America.关键词：radial steel gate;hoist arrangement;global structural layout optimization;multi conditions optimization;multi objectives optimization
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发布时间：2023-11-14 - 摘要：Abstract:A comparatively new method of aeration assisted leaching was proposed to solve the bad copper leaching effect of Yangla copper mine (YCM) due to the poor permeability of the heap during abiotic heap leaching,the desideratum of which was improving the permeability of the heap leaching system.Firstly,in view of the problems happening in YCM and the shortage of the present seepage theory in analyzing the complicated seepage laws,a theory of porous and fractured media of the ore-rock granular was proposed to study the impact mechanism of the forced aeration on the permeability of the heap leaching system.Secondly,ore particle size distribution and its type of YCM were analyzed and classified.Lastly,the column leaching experiments with different aeration intensities (AI) were conducted indoors.Pores development of the specimens were analyzed using CT,then SEM and fractal geometry theory were employed to study the fractal dimensions,dynamic permeability coefficient (DPC) and fracture ratio (DFR) of the granular surface when AI was different.The results show that the particles type of YCM belongs to a-type and that particles within the ore heap of YCM are loose and fine with a higher density indicating an improper particle size distribution.From CT analysis,although the porosity is decreased,the acid leaching reaction degree of the ore is intensified to enlarge the ore particles quantities and pore number when air is pumped into the heap leaching system.Therefore,the copper leaching performance is likely to be increased since the blocked seepage channels are effectively broken through.From SEM and the fractal geometry theory analysis,DPC and DFR within the leaching system are increased by the forced aeration.Therefore,the leaching reaction degree and percolation performance of the solutes within the leaching solution may be greatly enhanced to improve the copper leaching effect performance.关键词：abiotic heap leaching;aeration assisted leaching;leaching effect;CT;SEM;fractal geometry theory
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发布时间：2023-11-14 - 摘要：Abstract:Fire induced collapse failure mode is different from other instantaneous collapse,such as that induced by earthquake,impacting or exploding.The whole collapse is a combination of complex processes including quasi-static equilibrium and dynamic process.In order to research the nonlinear dynamic response of progressive collapse analysis on the composite frame with concrete filled steel tubular (CFST) columns and RC slabs due to local fire.A static-dynamic analytic conversion procedure has been developed based on the restart and predefined-field function in the finite element code ABAQUS.This paper presents a FE model of 9-story composite spatial frame to investigate the mechanism of progressive collapse when 6th corner floor catches fire.The composite frame members of columns and steel beams used nonlinear fiber beam elements,and RC slabs used layered shell elements.The user-defined uniaxial constitutive material models of core concrete and steel were incorporated in subprogram UMAT.The results showed that the analytic procedure switch between static and dynamic analysis was effective to investigate the progressive collapse of composite frame subjected to fire,and it could shorten the calculation time and show the dynamic characteristics of progressive collapse.Local progressive collapse was observed in the composite frame when the corner column was destroyed.Collapse critical fire resistance time was 253 min (4.2 h),greater than the individual component.The displacement of top column included five stages when it was subjected to fire,including inflation deformation in early heating stage,localized failure of heated columns,transient equilibrium phase,unloading phase and the localized collapse phase.The first four stages were long quasi-static analysis and the fifth stage was a nonlinear dynamic problem.The redistribution of internal forces during unloading followed the "shortest path principle" in general.关键词：concrete filled steel tube;progressive collapse;fire response;fiber beam element model;a static-dynamic analytic conversion procedure;nonlinear analysis
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发布时间：2023-11-14 -
Research on the Prediction Model of Deformation of High Core Rockfill Dam During Construction Period
摘要：Abstract:In the situation that deformation monitoring section of high rockfill dam is limited,and the traditional single point deformation prediction model is difficult to reflect the overall trend of dam deformation effectively,the separation space-time deformation prediction model constructed by single-point sequence fitting and spatial expansion during construction can overcome some drawbacks of single point series models.The vertical and horizontal single point deformation model of physical causes was derived and established based on the existing theory of coarse grained soil deformation calculation,and then the space-time deformation prediction model of high rockfill dam was constructed by using kriging technique for spatial expansion based on single point model.The primary deformation datas analysis results of Pubugou high rockfill dam showed that the vertical,horizontal deformation model and spatial interpolation model of physical causes can simulate and reflect the measuring point distortion tendency well with a high precision.The model can realize three dimensional prediction according to the monitoring sequence of the whole deformation of high core rockfill dam,describes the dam three dimensional distortion tendency well,and has a certain application and promoted value to related projects.关键词：high core rockfill dam;physical causes;spatial expansion;kriging interpolation;space-time deformation- 2301
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发布时间：2023-11-14 - 摘要：Abstract:The contact face of rock-anchored beam in underground powerhouse is the weak part of the overall structure; it is thus an important content for finite element analysis of rock-anchored beam to establish reasonable contact face simulation method.For the contact problem of rock-anchored beam and surrounding rock of underground powerhouse,the mathematical and mechanical models were established to simulate the nonlinear characteristics of the contact surface of rock-anchored beam and surrounding rock.Based on the Desai thin-layer element,a mathematical form of contact element,which is simple and convenient for finite element calculation,was derived.By combining nonlinear elastic theory with elastic plasticity theory,a three-dimensional nonlinear mechanical model,which could simulate the nonlinear phenomena on elastic stage and damage softening phenomena on plastic stage of contact element,was proposed.In view of the deformation characteristics of contact elements such as closing,opening and shearing slip,a segmented safety factor,with considering the bonding,cracking and slip phenomena of contact face,was proposed.The finite element iteration method of the model was discussed in detail,and the finite element program was implemented accordingly.The proposed model was applied to the calculation of rock-anchored beam in an underground powerhouse.Compared with equivalent continuum model,the calculation results of the proposed model show that the stresses in rock-anchored beam are smaller,and the loads are mainly borne by long bolts.The overall deformation of the rock-anchored beam is increased by 2~3 mm,which means that the contact face decreases the overall stability of rock-anchored beam.The safety factor at the contact face is also slightly smaller and localized tensile damage occurs,which is consistent with the cracking of the contact face of rock-anchored beam in actual engineering.Therefore,the proposed model can reasonably reflect the nonlinear contact characteristics of the contact face,and it provides an effective finite element analysis method for the stability analysis of rock-anchored beam in Underground Powerhouse.关键词：rock-anchored beam;contact face;nonlinear model;damage softening;finite element simulation
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发布时间：2023-11-14 - 摘要：Abstract:A new resin material is developed,which is completely transparent and has more brittle rock-like fracture properties than before.Its tension-compression ratio is up to 1/6.6 at -15~-10℃ and open fractures can be made inside.Water injection device,loading equipment and technological methods are correspondingly designed.Experiments on hydraulic fracturing are carried out.Cases of two different internal water pressures under uniaxial compression and one constant internal water pressure under biaxial compression are investigated.Failure and secondary crack propagation processes of the specimen are described and analyzed in detail,and the produce condition and mechanism are studied.Furthermore,comparative study on specimen failure and secondary crack propagation between cases of water pressure and no water are also conducted.Besides,numerical simulation is carried out using FLAC3D.Based on isotropic fluid model of FLAC3D,a new elastic-brittle constitutive model is introduced and mechanical parameters and permeability coefficients of damaged elements are redefined.The superfine and reasonable form of unit division is also required.The numerical simulation results are in good agreement with the testing results in this paper,which suggests the effectiveness of the new numerical simulation method.
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发布时间：2023-11-14 - 摘要：Abstract:According to alternative load path method,three double-span assemblies with double web angles connection based on different span ratios (1.0:0.6,1.0:1.0,1.0:1.4) of steel frame were chosen as the research objects.The failure mode,mechanical behavior,the resistance mechanism of specimens and the failure mechanism of joint were studied by monotonic static loading tests and numerical analysis under the condition of progressive collapse.The results showed that the failure of all specimens are the fracture of double angles connecting the failure column and beam due to severe tension,in which the axial force in the beams,the beam end rotation angle and the dimension of angles are main factors influencing the fracture of the angle leg.The deformation patterns and failure modes,as well as the peak loads,of three specimens are very close.Whereas the horizontal displacement of the failure column corresponding to the peak load reduces with the increase of span ratio successively.Differently,the short beam bears most horizontal load and is failure before long beam for the internal force redistribution of assemblies,which lead to the rotation at beam end of the short beam being greater than the long one under large deformation.And the plastic rotations at beam end of the specimens with unequal spans are larger than the specimen with equal spans.The process of anti-collapse mechanism appears the flexure-catenary mixed phase and catenary phase,in which the reliably tension force between beam and column could make the catenary mechanism of the structure into full play.Moreover,assisted by the validated numerical models considering the material and geometrical nonlinearities,contact nonlinearity and the fracture of the steel,the effect of the restraints provided by peripheral components on anti-collapse performance of assembly with such connection is analyzed in-depth.Then,if the side columns has enough rigidity,the restraints provided by peripheral components has little effect on enhancing the bearing capacity of assembly.关键词：steel frame;double web angles connection;different span ratios;static test;anti-collapse mechanism
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发布时间：2023-11-14 - 摘要：Abstract:Parallel lines and polygons consisting of parallel structure appear more in images.In the past,the parallelism of two straight lines was judged according to their line slope,and the detection of polygons consisting of parallel structure required prior information or specific polygons.The research on the detection of general parallel structures was little.After full study of characteristics of parallel structures,the definition of parallel operator based on distance information was proposed in this paper,which was used to realize the detection of parallel structures in images.Firstly,the definition of parallel operator was given by using the relation between the point-to-line distance and the point-to-point distance.Secondly,parallel point groups were obtained according to the defined parallel operator once the valid pixels were got in images.Thirdly,parallel point groups were merged based on the direction information,and parallel lines were then detected using Hough transform.Finally,the existence of the segments between intersections of lines was verified,and polygons were thus attained according to the endpoint location of existing segments.Experimental results showed the parallel operator defined in this paper could be used to detect the parallel point groups in the real image well,which could even more resist the large noise when the accuracy of parallelism was not high;the parallel structure detection algorithm based on parallel operator showed good detection of the parallel straight lines and polygons consisting of parallel structure in the image.The main work of this paper was:1)Proposed the definition of parallel operator according to the distance information between two points.2)Used the parallel operator to detect the parallel lines and polygons consisting of parallel structure in the image,which provided a new idea for related research.3)Gave an effective method to extract valid pixels which made the algorithm more robust to noise and reduced the computational load.The proposed algorithm could detect parallel structures accurately in the image and was universal in practical applications.关键词：parallel operator;parallel structure;parallel lines;polygons consisting of parallel lines
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发布时间：2023-11-14 - 摘要：Abstract:According to insufficient research on the effect of evaporation duct on the propagation of electromagnetic wave in the bay area of West Indian Ocean,PJ evaporation duct model and parabolic equation method were used to investigate the feasibility of forecasting methods based on meteorological and hydrological data in the area.Firstly,the main idea and basic flow of the two models were summed up.The applicability of the two models in the bay area of West Indian Ocean was studied by using hydrometeorological data and range results of a navigation radar measured in the experiments during a certain month.The conclusion showed that the predicted range values were approximately equal to the measured ones.The probability of the difference (≤ 25%) was 91.3%.In addition,the prediction effect of the model was not the same in different time periods.Specifically,the average value of the percentage of distance deviation corresponding to the time period(06:00:00-12:00:00UTC) was the biggest,and the variance of the percentage of distance deviation corresponding to the time period(12:00:00-18:00:00UTC) was the biggest.Moreover,the deviation of the distance had a significant dependence on all kinds of meteorological and hydrological factors,among which ASTD(air sea temperature difference) had the strongest correlation.Finally,the spatial and temporal variability of minimum trapping frequency in these areas were also obtained using PJ model and reanalysis data (CFSRv2 which was tested using buoy data).The results showed that microwave can be trapped easily in some regions of bay area and OTH phenomenon happened all the time.However,there were also some regions near Yemen,Oman and Socotra Island,where microwave cannot be trapped easily.In order to get OTH phenomenon in these regions,the higher frequency microwave was necessary.关键词：West Indian Ocean;evaporation duct model;parabolic equation method;reanalysis data
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of performance degradation and divergence of the Gaussian nonlinear filter in the large initial deviation conditions,a new nonlinear filtering method called the iterated update extended Kalman filter (IU-EKF) was proposed.The new approach was carried out by introducing the current time measurement information gradually to the measurement update process with part of gain in pseudo-time. Meanwhile,since the multi-step measurement update process introduced the process noise at each step,the cross-covariance between the measurement noise and the posteriori state estimation error after each step was substituted into the covariance matrix,whose trace was then differentiated with respect to the standard Kalman gain and the result was set to zero.The optimal Kalman gain expression under correlated noise condition was derived then.At last,the number of iterations was adjusted adaptively according to the posteriori measurement residuals.In the premise of ensuring a certain filtering accuracy,the computational complexity of the algorithm was reduced.Taking the two-dimensional target tracking problem as an example,the algorithm was compared with EKF,IEKF,UKF and CKF respectively under the large initial deviation conditions.The influence of different iterations on the filtering accuracy was also compared and analyzed.The simulation results showed that the algorithm was more efficient than EKF,and the algorithm was superior to the classical Gaussian hypothesis filters under the conditions of large initial deviation.Furthermore,when the number of iterations was increased by 1,2,5,10,20,the filtering accuracy of the algorithm was improved,but the growth ratewas gradually slowed down.关键词：nonlinear system;iterated measurement update;extended Kalman filter;target tracking
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that the existing semantically searchable encryption schemes could not realize ranking verification,a novel method was proposed in this paper which could not only support the semantic search,but also verify the ranking of the search results.Firstly,the relevant score and the weighted zone score were introduced to construct a more accurate inverted index structure.Using the non-linear order preserving encryption mechanism,the search results were sorted efficiently by the cloud server,which reduced the computation and communication overheads.Then,the query keywords were semantically extended based on the WordNet.Based on the semantically extended tree,the most relevant semantically extended words were selected.Combining the semantic similarity and relevance score,a two-factor ranking algorithm was designed to accurately sort the search results.Moreover,a set of keywords were inserted to the bloom filter.The message authentication codes of the bloom filter,security index and encrypted files were calculated to build the verifiable information.In the search phase,the bloom filter was used to verify the existence of the query keywords in the index.And the integrity and correctness of the index and files could be verified by the message authentication codes.The index tree was constructed to improve the search efficiency.Finally,the proposed scheme was compared with the related schemes in terms of functions,storage overheads and search overheads.And simulation experiments were carried out on the cost of building index and verifiable information,semantic extensions,encrypting queries,querying and verifying.The comparative analysis showed that the advantage of the proposed scheme in terms of semantic search,ranking and verifying.The experimental results demonstrated that the proposed scheme not only realizes the semantic search and the search results ranking,but also supports the ranking result verification.关键词：cloud computing security;searchable encryption;semantic similarity;weighted zone score;ranking verification
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发布时间：2023-11-14 - 摘要：Abstract:Three forgery attacks on Liu Li et al.'s RSA-based certificateless multi-signature scheme were first presented.It could be found that their scheme was vulnerable to key replacement attacks.The scheme also could not resist conspiracy attack of dishonest signers or a dishonest signer with a malicious key generation center (KGC).Analysis revealed that the main reason of insecurity of the original scheme was that the forgery of a valid individual signature was equivalent to the forgery of a valid multi-signature generated by an adversary.Sincethe existing security models of certificateless multi-signature were not so rigorous,an improved security model was developed in this paper.It guaranteed that the multi-signature was valid if and only if every individual signature was valid.By means of signing the part of the user's public key in the stage of partial private key generation,and binding the individual signature and user's public key to hash function in the stage of multi-signature generation,an improved scheme resistant to conspiracy attack was proposed.The improved scheme did not rely on secure channels and had better efficiency.The costs were reduced by L exponentiations and L-3 multiplications in the stage of multi-signature generation and three exponentiations in the stage of multi-signature verification,where L was the number of signers.The size of the signature was decreased by|N|bits,where|N|was the binary length of the system parameter N.The individual signature was provably secure under assumptions of intractability of RSA and discrete logarithm.The unforgeability of multi-signature was achieved through the collision resistance property of hash function.关键词：RSA;certificateless multi-signature;conspiracy attack;security model;hash function
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发布时间：2023-11-14 - 摘要：Abstract:When new members were involved in the development and maintenance of software projects,they usually need to spendmuch time to understand the architecture and function of the system.To help them understanding a software systemand quickly grasp the system,somekey classes were in general given priority to be recommended as soon as possible.A large number of studies have shown that the software system has aclear form of complex network topology.Therefore,we could build software network models,and then identified important classes in software systems by means of network node importance measurement,so as to help new members to master the core structure and function of the system quickly.Previously,there were many methods for measuring the importance of node in a network.But most methods considered only the degree of neighbor node or the weight of edge.As a metric successfully applied to evaluate the productivity of a scholar,little was known about whether h-index was suitable to identify key classes in weighted software network.In this paper,based on the degree of node and the weight of edge,three variations of h-index (i.e.,H-NWD,A-NWD,G-NWD) were proposed to measure the importance of the classes on three open-source software projects (i.e.,Jung,Ant,and Maven) built by corresponding model of weighted software network.The feasibility of proposed measures was validated by comparing them with the five existing centrality measures of complex network(i.e.,degree centrality,betweenness centrality,closeness centrality,eigenvector centrality and pageRank centrality).The results showed that the proposed index of H-NWD and G-NWD was effective in identifying the key classes,and the intersection reached more than 80% with the existing metrics.In the case of determining class modifications,the rank value of important class nodes identified by H-NWD was much higher and the other class nodes identified by H-NWD were modified more frequently.Compared to existing indicators,it was more accurate in identifying key classes.关键词：key class;h-index;software network;node importance;centrality measure
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at the problem of phase difference estimation for non-half period sampled signals,a phase correction correlation-based of phase difference estimation for non-half period sampled signals was proposed.Firstly,a phase match-based frequency estimation method was utilized to estimate the frequency of sampled signals.Secondly,cross-correlation signals were gained by cross-correlation of sampled signals and the new cross-correlation signals were constructed by shifting sampled signals and cross-correlation,which had the same error term with the original cross-correlation signals.Thirdly,phase correction cross-correlation signals were gained by means of two cross-correlation signals.Finally,estimated phase difference was obtained by utilizing phase correction cross-correlation signals and estimated frequency.Theoretical analysis indicated that the proposed method had eliminated the influence of non-half period sampled signals on phase difference estimation,and achieved unbiased phase difference estimation without estimating signal amplitudes.To validate the effectiveness and superiority of the proposed method,simulation on conditions of different phase differences,signal-to-noise ratios(SNRs),signal lengths was performed.Then,the application experiment was conducted by using Coriolis mass flowmeters.Simulation and experimental results demonstrated that the proposed method improved the estimation precision of phase difference.Its estimation performance was better than those of the cross-correlation method,the data extension-based correlation method and the quadrature delay estimator and its estimation errors were closer to CRLB by comparison.The measurement results of Coriolis mass flowmeters validated the effectiveness of the proposed method in practice.关键词：phase difference estimation;phase correction;non-half period sampled signals;frequency estimation
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发布时间：2023-11-14 - 摘要：Abstract:The gray value features of images were used to describe targets in robust visual tracking via L1 minimization (L1 tracking algorithm).However,the ignorance of structural information between the templates and inaccurate modeling of target appearance changes leaded to a low tracking accuracy.What's more,since the low resolution image block with 12×15 was adopted to balance the tracking speed and tracking effect,it was difficult to obtain sufficient information to represent the target.To solve the problem of the L1 tracking algorithm,a visual tracking method based on online low-rank sparse representation was proposed.Firstly,in order to take advantage of the ability to represent target appearance changes of principal component analysis (PCA) basis vectors,the PCA basis vector template was used to describe target appearance changes.To take occlusion into account,the occlusion and other abnormal noise were modeled with the trivial template.Consequently,the candidate target was represented as a linear combination of PCA basis templates and trivial templates.Secondly,for the optimization problem of object representation model,a low-rank and L1,1 regularization constraint were added on the PCA basis template coefficients and a L1,1 regularization constraint on the trivial template coefficients.Then the inexact augmented lagrange multiplier(IALM) method was adopted to solve the representation coefficients.Thirdly,visual tracking was achieved by taking the reconstruction error of the unoccluded part and sparse error term as an observation model in particle filter framework.Finally,to avoid model drifting,an occlusion detection updating mechanism was proposed to update templates.In the experiments of 8 video image sequences with 32×32 image block resolution,compared with four state-of-the-art trackers,the proposed algorithm had achieved the highest average overlap rate of 0.78 and the lowest average center error of 4.05.Accordingly,the experimental results demonstrated that the proposed algorithm had better tracking accuracy and robustness.关键词：visual tracking;low-rank representation;sparse representation;PCA basis vector
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发布时间：2023-11-14 - 摘要：Abstract:In order to meet the high requirements of realistic and complex scene rendering in the field of visual flight simulation,this paper proposed an anti-aliasing rendering structure for large scenes based on deferred shading,to achieve realistic rendering for a global landscape and all kinds of effects.The incompatible problems that built-in hardware anti-aliasing CSAA did not work with deferred shading were mainly solved by our rendering architecture,which depended on generating a multi-render target G-Buffer with CSAA anti-aliasing in the deferred phase and performing the final lighting calculation by recovering the geometry edge through the transparency mask information recorded in a particular channel during the shading phase.At the same time,different rendering components were set different levels of anti-aliasing to balance between efficiency and effectiveness.To improve anti-aliasing effects,the LOD model-building technology was used and the important post-process boundary information were marked.Owing to the final sampling multiples of different load components form actual training and the data and effect performance of the experiment,the visual system developed by rendering architecture had reached high real-time performance.It usually met over 60 fps,which greatly reduced latency and blocking.Meanwhile,the anti-aliasing effect was better than SRAA algorithm.Therefore,the visual system could achieve the best combination of performance and quality.It can achieve the purpose of flight simulation training identificated by training experts.关键词：anti-aliasing;CSAA;deferred shading;LOD;rendering structure
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发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the inhibition effect of prior rejuvenation on the initiation of electrical tree and the propagation of the tree in the cross-linked polyethylene cable under combined AC voltage and switching overvoltage,the prior rejuvenation cable samples were prepared by injecting siloxane liquid into the core of new cables with a pressure,and the new cable samples and the prior rejuvenation cable samples were subjected to accelerated aging experiment using the water-needle electrical method and subjected to the switching overvoltage.By optical microscope,the propagation of the branches in the cable samples were observed,and its average length of branches and electrical tree initiation rate were calculated,at different aging stages,and the microstructure and chemical elements in the prior rejuvenation cable insulation were analyzed by SEM and EDS,and the results show that the repaired cable contains the repair fluid product,which can inhibit the initiation of electric tree and the growth of trees.The simulation model of the trees in the cable was established by using the finite element simulation software,and the electric field distributions of the trees in the prior rejuvenation cable and the new cable were analyzed under the AC voltage and the switching overvoltage,and the results show that the rejuvenation liquid can reduce the electric field strength of the water needle tip,the electrical tree tip and water tree terminals.The results show that:the prior rejuvenation can uniform electric field of the water needle tip and reduce the electrical tree initiation rate under the switching overvoltage,but also can weaken the electric field of the electrical tree tip and water tree terminals,and inhibit the branch growth in XLPE cables.关键词：cross linked polyethylene;switching overvoltage;water tree;electric tree;rejuvenation liquid
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发布时间：2023-11-14 - 摘要：Abstract:Due to the independent control of active and reactive power,voltage source converter (VSC) base on HVDC system can not only distribute power in DC system,but also improve the stability of AC system connected by VSC-HVDC.In order to fully excavate the reactive power potential of VSC,and to improve the voltage stability of AC system,a voltage stability control strategy based on VSC-HVDC interconnected system was proposed.In VSC-HVDC system,rectifier station was controlled by DC voltage margin and droop,and the inverter station was controlled by constant DC voltage.The limit value of active current was calculated based on reactive current.Then,the dynamic limiter controllers of the active current were respectively designed for rectifier and inverter stations to expand the limit value of reactive current.Without interstation communications,apart of active capacity of VSC-HVDC system was converted to reactive capacity,which increased the reactive output of the VSC stations and reduced the reactive adjustment burden of AC system in the case of disturbance or fault.Finally,simulations with PSCAD/EMTDC verified that the control strategy proposed in the paper took full use of the power adjustment ability and enhanced the voltage stability of AC system connected by VSC-HVDC.The strategy provides a new solution for voltage stability of AC system connected by VSC-HVDC.关键词：voltage source converter(VSC);DC voltage margin control;droop control;reactive current;dynamic limiter controller;voltage stability
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发布时间：2023-11-14 - 摘要：Abstract:With the rise of safety,economic and environmental protection requirements of power systems,replacingthe insulation materials to enhance the performance of oil-immersed distribution transformer is high needed.Based on the classical theory of heat transfer,"Loading guide for oil-immersed power transformers" and "Design and application of liquid-immersed transformers using high-temperature insulation material",the well-distributed high temperature insulation system of oil-immersed distribution transformer using new insulation materials was studied.According to the performance differences between new insulation materials and conventional insulation materials,the heat dissipating capacity of the well-distributed high temperature transformer and the conventional transformer was compared using the theory of heat convection.According to the guidelines,the overload temperature limit of oil-immersed transformers in different insulation systems were determined and the hot spot temperature calculation model suitable for the well-distributed high temperature transformer wasobtained.In order to obtain the differences of heat resistance,the permissible overload times of different transformers under long term emergency load was compared.On the basis of performance comparison,a structure optimization method for the well-distributed high temperature transformer was proposed and the manufacturing cost changes were calculated.It was found thatwhile the heat dissipation capability of the well-distributed high temperature transformer is 80.2% of that of the conventional transformer,the heat resistance of the former is up to 119% of the latter.The conclusion showed that a well-distributed high temperature transformer could be obtained by reducing the winding radius,the iron core volume,the tank volume,the amount of the insulating material,simultaneously widening the oil path,the oil inlet and outlet diametersand increasing the number of the radiators.The hot spot temperature limit can be raisedfrom 140℃ to 170℃ with the total costincreaseof 34% by replacing the conventional insulation materials with new insulation materials and optimizing the structure.关键词：oil-immersed distribution transformers;well-distributed high temperature insulation system;heat dissipating capacity;heat resistance;structure optimization
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发布时间：2023-11-14 - 摘要：Abstract:With the application of nickel alloy electron beam welding in industry,especially in critical long service equipment such as aircraft engine and gas turbines etc.,it is necessary to systematically analyze and study the high cycle fatigue properties and fracture mechanism of nickel alloy electron beam welding joint.Fatigue tests were carried out using the rotary bending high cycle fatigue testing machine.The stress-life (S-N) curves and fatigue fracture of the base metal and welded joints were obtained from experiments.Then,the fatigue fracture surfaces were examined by scanning electron microscope (SEM).The fatigue crack initiation and extension zones of the base metal and welded joints under different stress amplitude were analyzed and determined,in which the crack initiation location was affected by the stress amplitude.Finally,the effect of the location and size of microcracks on the fatigue properties of the welded joint was discussed by the finite element method (FEM).The experimental and simulation results showed that:the stress-life (S-N) curves distribution trend of the base metal and welded joints is consistent,and fatigue strength of the welded joint is lower than the base metal,which there is small difference nearby the 107 cycle.With the high stress amplitude (low cycle fatigue life stage),fatigue crack initiates from multiple point at the surface for base metal and welded joints.The fracture position of welded joints is located in the weld fusion zone and heat affected zone.The fatigue crack initiation transforms from surface to subsurface in the low stress amplitude (high cycle fatigue stage).The fatigue fracture of the welded joints is located in the heat affected zone and base metal near the heat affected zone.The existence of microcracks is beneficial to the propagation of crack by FEM.Under the tensile stress,the transverse microcracks are better than the longitudinal crack to propagate along the stress direction.With the increase of the microcrack size,the microcracks are easier to cross each other and form longer cracks,to reduce the fatigue performance.The results also showed that the electron beam welding only affects the fatigue strength of the material,the fatigue failure property and the fatigue crack initiation position is the transcrystalline cleavage fracture and directly affected by the stress amplitude,respectively,which is consistent with the base metal.关键词：GH80A;electron beam welding joint;rotary bending fatigue;heat affected zone;finite element method
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at the shortcoming of Hilbert-Huang transform method,where the end effect and false intrinsic mode function issue exist during its application,based on the analysis of the reasons of these problems,an improved Hilbert-Huang transform method was proposed by using boundary extreme mean extension and false mode selecting approach.Firstly,according to the characteristics of the signal endpoint and its adjacent extreme points,the value of the envelope at the two ends of the signal was estimated,and the estimated value were added to the extreme value sequence,therefore the data extension was reasonable and the end effect could be solved.Then,the false mode selecting algorithm based on the orthogonality of each intrinsic mode function was used to select sensitive mode functions.The validity of this improved method was verified by a simulation signal analysis.Finally,the method was applied into engine abnormal sound fault diagnosis.The results showed that the improved method has a good result in dealing with the shortcoming of traditional Hilbert-Huang transform and the fault feature of engine abnormal sound signal can be obtained effectively.关键词：Hilbert-Huang transform;empirical mode decomposition;end effect;false mode component;boundary extreme mean extension
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发布时间：2023-11-14 - 摘要：Abstract:External leakage is a common fault of control valve,which can cause loss of energy resources,the pollution to our living environment,and even serious accidents.It is relatively inefficient to use chemical sensors arranged outside the valve to detect the leakage,because the leakage accidents cannot be prevented in time.In order to help the control valve automatically perceive the external leakage,a novel method based on flow rate self-sensing of the control valve was presented.The proposed method used specific data such as the fluid pressure and the degree of corresponding opening of the valve to establish a self-sensing model of the flow rate,which could be easily implemented in industrial fields.During steady state operation,there was a nominal mass flow rate through the control valve.The mass flow rate of the inlet of the control valve was equal to that of the valve outlet.When an external leakage developed,the level of the mass flow rate of the outlet dropped,and some other operating parameters of the control loop would change.Feedback regarding the operating parameters such as the controlled fluid pressure and the degree of corresponding opening of the control valve was provided to the valve controller,and the controller altered the drive signal to the actuator of the control valve to change the flow rate to offset the external leakage.Consequently,mass flow rate to the control valve increased.By estimating the mass flow rate of the controlled fluid over time,a diagnostics unit could be programmed to detect the increases of the mass flow rate of the controlled fluid.The diagnostics unit could further be programmed with a nominal maximum flow rate above which the diagnostics routine would generate an external leakage signal.Additionally,the valve with the self-sensing model could be considered as a flowmeter,which helped the plants eliminate the flow rate measurement devices in the pipeline system.The results showed that the control valve with the self-sensing model could automatically identify the external leakage in time,which validated the proposed method.关键词：control valve;external leakage;self-sensing;operating data;flow mass rate
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发布时间：2023-11-14 - 摘要：Abstract:Position changes of the machine tool's moving parts result in changes of the machine tool's mass matrix,stiffness matrix and damp matrix,which leads to the complexity and uncertainty for predicating the dynamic characteristics of the whole machine tool.Thus,a method to research machine tool's dynamic characteristics in the generalized machining space was proposed based on the response surface theory.In this method,the natural frequency was taken as the critical index to describe the whole machine tool dynamic characteristics,with which the mathematic relationship between dynamic characteristics and spatial poses were analyzed.Then,the orthogonal experiment design and the response surface method (RSM) were combined to establish the response surface model for predicating the varying dynamic characteristics,and their variation regularities in machining space were discussed.Furthermore,an algorithm was put forward to calculate the effect factors,which represented how the changes of each axial displacement impact on the dynamic characteristics of the whole machine tool.With the obtained variation regularities and effect factors,the optimal machining region and machining route were determined.The proposed method was applied in a three-axis vertical machining center to verify its feasibility.The various pose combinations of the moving parts were arranged as the samples by the orthogonal experiment design,and the natural frequencies related to the first five orders were acquired by conducting the modal analyses with the ANSYS software.Utilizing the acquired dynamic data,a second-order polynomial response surface model was established to describe the connections between the pose features and the natural frequencies.And the accuracy of the established model was validated after calculating the valuating indexes.Accordingly,this model was adopted to achieve the variation regularities and effect factors of the natural frequencies due to the displacement changes of x,y,z directions,which explained that the spatial poses affected the dynamic characteristics of the whole machine tool significantly,providing a theoretical support for the process planning and dynamic optimization of the machine tool.关键词：machine tool dynamic characteristics;machining space;response surface method;natural frequency
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发布时间：2023-11-14
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