最新刊期
卷 48 ， 期 2 ， 2016
- 摘要：Abstract:In order to deal with the possible sudden water pollution incidents of the South-to-North Water Diversion Project,a technical system of sudden water pollution emergency regulation and treatment was established,which integrates the five links of numerical simulation,evaluation and diagnosis,tracing prediction,emergency regulation,and pollution treatment.This system includes water quantity and quality simulation technology,water quality safety evaluation and diagnosis technology,sudden water pollution tracing prediction technology,water pollution emergency regulation technology,and water pollution emergency treatment technology.The results could be applied to demonstration project and system platform,ensure water quality safety of the main of middle routes of South to North Water Diversion Project,and realize the target of transporting a canal of clean water to the North.关键词：theMainofMiddleRoutesofSouth-to-NorthWaterDiversionProject;suddenwaterpollutionincidents;technicalsystemofemergencyregulationandtreatment
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发布时间：2023-11-14 - 摘要：Abstract:The climate change impact on flood protection is a global issue.With climate warming and the rapid development of urbanization,flood protection of China will face with the great challenge from the heavy rainfall and extreme events such as flood disaster.How the occurrence trends and variation of extreme floods under climate change,has become the forefront questions of research.Aiming at the serious flood disaster in China,the influence of climate change on flood disaster was described from the global to China,and the latest and cutting edge researches were reviewed.Some countermeasures and suggestions for reducing the loss of flood disaster under climate change were proposed as the reference for the future study of climate change impact on flood protection.For example,the basic research of climate impacts on extreme hydrological events including non stationarity resulting from climate and hydrological indices,the nonlinear problems and temporal variability of water cycle factors and uncertainty of hydrological and climate modelling should be strengthen.Adaptive measures research of flood protection including adaptive capability and manner under climate change should be also paid more attention.关键词：climate change;flood disaster;non-stationarity;research progress;adaptive strategy
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发布时间：2023-11-14 - 摘要：Abstract:To avoid any adverse influences on the downstream aquatic lives or agricultural production due to low-temperature water discharging from a large reservoir,it is necessary to predict accurately the stratified water temperature distributions in the deep water region before a high dam.The 3 D turbulence mathematical model was proposed to simulate water temperature with the boundary condition and the initial condition obtained from a 2 D turbulent water temperature model.A case study was conducted at the constructed Ertan reservoir within a range of 1 km from the dam.A comparison analysis was conducted between water temperature from the simulation model and the site observations.The simulation of water temperature fits with the observation quite well.Therefore,the proposed 3 D turbulent mathematical model can satisfactorily predict the stratified water temperature and the flow structures within the deep reservoir in front of the dam.关键词：reservoir;watertemperature;numericalsimulation;3-Dflow
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发布时间：2023-11-14 -
FlowVisualizationExperimentalStudyonTurbulent CoherentStructureinVegetatedOpen ChannelFlow
摘要：Abstract:The flow visualization technology and digital image processing theory were used to study the turbulent coherent structures in vegetated open channel flow.It was demonstrated that the plants in channel has changed the coherent structure which is totally different from that of open channel flows.According to the characteristics of the coherent structure,the flow was divided into three regions.In the vegetation inner region,the wake burst phenomenon and simil Karman vortex streets coexist and the vortex structure is affected by the dimeter and the arrangement patten of the vegetation.In the region near the top of the vegetaion,the coherent structure is complicated and changes frequently.The bursting phenomenon in boundary and large eddy pairing phenomenon in freely mixing layer appear at the same time in this region,and the bursting period has negetative correlation with velocity,the mean penetration depth of vortex has positive correlation with velocity and submergence.The out region is similar to the free shear turbulence flow which appears in the outer layer of traditional open channel,having the structures of vortex stretching and turbulence intermittent.The coherent structures of the three regions are different from but interact on each other.关键词：flowvisualization;vegetatedopenchannelflow;turbulence;coherentstructure;burstphenomenon;vortexstructure- 1739
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发布时间：2023-11-14 - 摘要：Abstract:The watershed of main stream between the Yalong river confluence to Pinshan station is the main sediment yield area in the Jinsha river.After impoundment,density current may form in Xiluodu and Xiangjiaba reservoirs,two large scale key reservoirs on the Jinsha river.Based on different regulation modes,the production condition of density current was simulated and predicted by adopting ASM(algebraic slip mixture) model,the density current front movement rule was discussed.The results indicated that a stably moving density current was difficult to form in the Xiluodu and Xiangjiaba reservoirs under their normal pool level of power generation while it likely occurred in the flood season.In these two reservoirs,turbidity current usually formed when the inflow sediment concentration was suddenly increased by over 1.0 kg/m3 in a certain flow range.In addition,movement speed of density current front showed linear dependence with sediment concentration and had no obvious relationship with channel bed slope.The conclusion could be used to the decision making of the density current operation.关键词：riversedimentengineering;turbiddensitycurrent;ASMtwo phaseflowmodel;Xiluodureservoir;Xiangjiabareservoir
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发布时间：2023-11-14 - 摘要：Abstract:The fixed pier of continuous bridges almost bear all the longitudinal seismic load under strong earthquakes,which can cause the damage of the fixed pier and the expansion joint prone to damage and even result into falling beam.In order to solve the shortcoming of the continuous bridges,one idea using anti seismic potential of sliding piers to bear the longitudinal seismic force together with fixed pier was put forward.The locking dowel was designed to be installed between the sliding piers and beams，which would restrict the relatively displacement between the sliding piers and beams under strong earthquakes and help the piers to collaboratively bear the longitudinal seismic force,then reduce the seismic response of continuous bridges.The structural form and working principle were introduced.Mechanical model and the corresponding numerical simulation method were proposed.Based on the numerical simulation method,a seven span continuous bridge was used to an example and the finite element model of the bridge was established,then the performance of seismic damping and parameters impacts on it were analyzed.Results indicated that the seismic performance of continuous bridge can be significantly improved by setting the locking dowel between its main beam and sliding piers.Besides,the damping effect of the device was getting more better with the connection stiffness increased,but the damping effect of the device was not more change with the recovery coefficient of pounding.关键词：continuousbridges;lockingdowel;connectionstiffness;recoverycoefficient;dampingeffect;seismicresponse
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发布时间：2023-11-14 - 摘要：Abstract:In order to reveal the inner flow characteristics of cavity gyrating flow,the velocity characteristics of Gongboxia horizontal gyrating discharge tunnel were studied based on the numerical simulation and experimental results. The results indicated that with the increase of the radial,the tangential velocity increased at first，and then decreased, and had a distribution characteristics of combined vortex,while the axial velocity increased rapidly at first,and then changed slowly.The cavity gyrating flow in gyrating discharge tunnel was mainly tangential flow and axial flow,and changed from the tangential flow into the axial flow along the gyrating discharge tunnel,which was proved by the rotation angle.The freedom degree and energy loss of cavity gyrating flow were reflected by the combined vortex index,which decreased with the decrease of the radial in the range from -0.8 to 0.5.The variations of the combined vortex index indicated that the cavity gyrating flow changed from quasi forced vortex to quasi free vortex along the gyrating discharge tunnel.The computational formulas for pressure and discharge were established based on the motion rule of combined vortex,and the combined vortex motion law of the cavity gyrating flow was verified by the numerical datum.The results can provide a reference for the internal micro flow study of the cavity gyrating flow.关键词：cavitygyratingflow;velocitycharacteristic;tangentialvelocity;combinedvortex;numericalsimulation
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发布时间：2023-11-14 - 摘要：Abstract:A new herringbone water sediment separation structure was designed to continuously separate coarse particle from debris flow.Calculation method of structural strength and stability should be determined before it used in debris flow mitigation.Theoretical analysis showed that the calculation methods of draining dyke is similar to that of traditional close type dam,and debris flow force,which include debris flow gravity,impact force of rock blocks,debris flow dynamical pressure,mainly loaded on the ribbed beam of the herringbone water sediment separation grid.By simplifying structural mechanical model,calculation formulas of the ribbed beam’s strength and stability were determined,which can be used to determine optimal sectional type and dimension of the grid.关键词：debrisflow;water sedimentseparation;preventionproject;structuralstrength
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发布时间：2023-11-14 - 摘要：Abstract:The single cleavage semi circle compression (SCSCC) plate specimens of sandstone,which are the sample of improved rectangular plate,were subjected to the split Hopkinson pressure bar.The model Ⅰ and mixed model Ⅰ Ⅱ rock dynamic fracture tests were conducted，the numerical simulation under the same condition with that of experiments was analyzed,and the failure modes for both tests and simulation were studied.Meanwhile, the crack arrest was also studied.The results showed that during the crack propagation,the model Ⅰ crack grew towards the right of the specimen which along the original direction,and the mixed model Ⅰ Ⅱ crack grew towards the axis of symmetry(maximum stress zone) of the specimen,meanwhile, the crack arrest phenomenon can be observed.Strain gauge method was an effective way to monitor the failure time.It was feasible to solve the dynamic destruction of rock materials in numerical simulation by using the modified maximum principal stress criterion and crack softening (CS) failure criterion,in additions,it described the complete stress strain failure process of material.The SCSCC specimens of mixed model Ⅰ Ⅱ had obvious advantages in the field of crack arrest.And because it was a large dimension specimen,it can reduce the effect that caused by the non uniformity of the rock.关键词：dynamiccrackpropagation;splithopkinsonpressurebartest;singlecleavagesemicirclecompression(SCSCC);numericalsimulation;fracturedamage
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发布时间：2023-11-14 - 摘要：Abstract:To investigate the influences of high temperature on mechanical behaviors of steel tube reinforced concrete column, the central compressive test on steel tube (ST) reinforced recycled aggregate concrete (RAC) column after exposed to 500C and 700C with/without carbon fiber reinforced polymer (CFRP) reinforcement were conducted. The failure modes, ultimate load carrying capacities and displacements, together with the strain response of the ST reinforced RAC columns were studied. The results showed that the high temperature have great influences on the failure modes and ultimate load carrying capacities. For the specimens with CFRP reinforcement, a great increase on load carrying capacity and displacement, however, the failure mode was changed from ductile to brittle failure. Moreover, the highest increase on load carrying capacity was found on the specimens with 50% RAC and CFRP reinforcement when compared to the ones with 0% and 100% RAC. The displacement and strain development curves were calculated by using an ABAQUS code, and the results were in good agreement with the experimental results. For the specimens with CFRP reinforcement, the deformations of steel tube, RAC and CFRP under compressive loading were investigated, and the strengthened mechanism was found.关键词：recycled concrete;Steel reinforced concrete;High temperature;Strengthening;Column
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the mechanisms of soil plugging effect inside sleeve of cast-in-place piles driven by vibratory hammers,finite element and infinite element coupling model were established by using the commercial code ABAQUS,to simulate the full penetration process of the sleeve driven by using high frequency vibratory hammers.The results indicated that the soil plug inside the sleeve forms soil arch during vibratory sleeve driving,which leads to the obvious increase of inner frictional resistance.The soil plug of this section withstands the major part of the inner frictional resistance.The soil strength and cohesive force decrease during vibratory sleeve driving, which is induced by cyclic shearing action in the shear interface.As a result,the soil plug inside sleeve is incompletely plugged mode and the penetration resistance is less than that of other installation methods.The inner frictional resistance decreases with the increase of vibration frequency and sleeve diameter.The inner frictional resistance of sand is larger than that of clay,and decreases with the increase of density.The distributions of soil plug resistance were also studied,and a simplified formula was obtained to calculate the soil plug resistance.关键词：sleeveforcast-in-placepile;highfrequencyvibration;soilpluggingeffect;innerfrictionalresistance
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发布时间：2023-11-14 - 摘要：Abstract:In the design and application process of shear wall with double steel plates and filled concrete,there is no universal approach,code and specification for this new type structure.In order to study the axial mechanical behavior of this new type structure,axial compressive tests on four wall specimens were conducted.The mechanical behavior and failure modes were analyzed under axial compressive loads,and the influence of the distance to thickness ratio and the number of pull bolt on the local bucking of steel plates,failure modes and bearing capacity were investigated.The results indicated that the distance to thickness ratio has significant effect on initial buckling of steel plate and failure modes of shear wall but little effect on the stiffness and bearing capacity of walls.关键词：shear wall with double steel plates and filled concrete;distance to thickness ratio;axial compressive behavior;local bucking
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发布时间：2023-11-14 - 摘要：Abstract:In order to develop a constitutive relation which is able to describe the phase transition and the plasticity behavior of NiTi alloy,based on the irreversible thermodynamics,two internal variables were assumed to characterize the phase transformation evolution and the plastic evolution respectively,then a master equation was derived.Rewritten in one dimension incremental form,the constitutive model was program implemented with Fortran code,in which the parameters were determined in combining with the uniaxial experiment and the nonlinear fitting.The model validation was carried out by comparing the predicted results with five uniaxial tesile tests under different strain rates,and the results showed that the proposed phenomenological constitutive model can not only describe very well the phenomenon of parent phase transformation and martensite plastic yield, but also the strain rate effect.关键词：irreversiblethermodynamics;phasetransformationevolution;plasticevolution;shapememoryalloy;phenomenologicalconstitutivemodel
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发布时间：2023-11-14 - 摘要：Abstract:A feature dimension reduction means based on affine clustering was worked out to solve the problem of the features of rich model’s high-dimension and dimension disaster led by much redundancy.This method analyzed the structure of rich model and defined sub model feature distance with nonlinear distance definition,using the affine clustering algorithm and the image spectrum theory to determine the clustering center of features.The sub model feature which has a high occurrence probability in the clustering center was considered as the optimal clustering center,and conducted steganalysis by Fisher ensemble classifier.The experiment showed that the testing error rate EOOB can be decreased by 1%～2% compared to original feature for the steganalysis of S-UNIWARD,WOW,HUGO stegography by the dimension reduction means when the dimensionality of SRM (spatial rich model) is down to 5 525.Therefore,the method in this paper will fulfill the improvement in feature dimension reduction and the effect of steganalysis.关键词：steganalysis;affinitypropagationclustering;richmodel;dimension reduction
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发布时间：2023-11-14 - 摘要：Abstract:To address the issue that the existed signcryptoin schemes fail to resist the quantum attack,a new signcryption scheme that has the light key overhead was constructed,by combining the Niederreiter public cryptosystem and CFS signature scheme.The proposal employs the decode algorithm of Goppa code to authenticate the message,and keeps the secret of the message by syndrome decoding algorithms. Analysis showed that the proposed scheme has the security of IND-CCA2 and EUF-CMA in the random oracle model.The proposed scheme has high performance.Compared with “sign then encrypt” method,the ciphertext of the new scheme is reduced by 44.4% in the case that both of them have the same size of the public key.Compared with the standard signcryption scheme,the computation of the signcryption and unsigncryption is also greatly reduced.The proposal could be adapted as one of the signcryption scheme that resisting the quantum attack.关键词：post-quantumcryptography;publickeycryptosystem;digitalsignature;signcryption
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发布时间：2023-11-14 - 摘要：Abstract:The method of finite project geometry was used to determine almost all weight hierarchies of the VI-5 subclass weight hierarchies of q-ary linear codes with dimension 5.For the one-to-one correspondence relationship between Hamming weight hierarchy and difference sequence,the determination of weight hierarchy can be converted into the determination of difference sequence.By constructing difference sequences under several different conditions,the necessary condition of the VI-5 class can be proved almost sufficient.So almost all weight hierarchies of the VI-5 class were determined.关键词：Hammingweight;linearcodes;differencesequence;finiteprojectivegeometry
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发布时间：2023-11-14 - 摘要：Abstract:In order to get the secure routing in Ad Hoc networks,based on the reliable backbone networks,a secure routing protocol was proposed.The trust evaluation mechanism was introduced to select the trust backbone nodes,the behavior of the node was evaluated and the malicious nodes was isolated from the network.Then the network was clustered by backbone nodes which act as the cluster head nodes.The reliable backbone network was established by cluster head nodes and cluster member nodes.At last,the secure routing protocol was established based on the reliable backbone network.Simulation results showed that the proposed secure routing protocol can improve the network performance significantly even under attacking when compared with other typical routing protocols.
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that the existing trust models could not solve malicious nodes in wireless sensor networks effectively and the problem that counter-intuitive results may appear when combining evidence, a detection scheme based on improved D-S evidence theory was proposed. The inherent deficiency of the D-S evidence theory was analyzed, a new variable was defined to describe the difference among trust evidence, and the original D-S evidence theory combination rule was modified to obtain more accurate results. Based on those improvements, a detection scheme to identify and isolate misbehaviors nodes in WSNs was proposed. Moreover, simulations were carried out to verify the effectiveness of the proposed scheme. Simulation results showed that this model could find and isolate malicious nodes quickly and accurately, suppress nodes collusion and improve network performance. Compared with other existing trust models, this model has more security, robustness and accuracy.关键词：detectionscheme;D-Sevidencetheory;performancesimulation;trustevaluation
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发布时间：2023-11-14 - 摘要：Abstract:Combing with the characteristics of embedded device firmwares,an improved fuzzy test method was proposed.After analyzing the attack surface of the firmwares from the standpoint of exploits utilization,several security rules were derived.By introducing the crisis weights of test cases in taint analytical results,a set of fuzzy test cases that are corresponding to crisis weights was designed.The method was used to dig vulnerabilities in popular equipments,and many zero-day exploits were found.Experimental results showed that this method is effective and practical.关键词：embeddeddevice;firmware;vulnerabilitydetecting;taint;riskweight
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of blindness and poor efficiency of traditional fuzzing,a feedback fuzzing method was proposed.This method can improve the test effect by optimizing the process of traditional fuzzing.Firstly,original sample files were collected via a web crawler to ensure the diversity of them.Then,the best seed file was selected from a large number of sample files,to avoid redundant testing while ensuring adequate testing space.Finally,test cases were generated by mutating the seed file,and the mutation parameters was continuously adjusted according to the testing result based on improved roulette wheel selection strategy,in order to find as many software failures as possible.A prototype system named OSSRWSFuzzer was implemented,which had found 56 failures of WPS Office for Linux in experiments,and its test effect is obviously better than that of the existing fuzzers.关键词：feedbackfuzzing;optimizingseedselection;roulettewheelselection
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发布时间：2023-11-14 - 摘要：Abstract:In order to protect data integrity in the steam data scenario,a dynamic authentication model based on dynamic chameleon authentication tree was constructed.The dynamic chameleon authentication tree does not require a predefined tree size at the setup phase and supports adaptive expand,therefore it is suitable for the steam data environment.In this model,insert,query and authentication operations for stream data were achieved.Comparison with the static chameleon authentication tree showed that the insert operation of the dynamic chameleon authentication tree is more stable,and the authentication path returned by the query operation is shorter.As a result,the present model has the advantages of less time and space consumptions,as well as better authentication efficiency.At last,some experiments were carried out,and the results indicated that the dynamic chameleon authentication tree is more efficient during insert,query and authentication operations compared to the static chameleon authentication tree.关键词：streamingdata;authenticationtechnology;thechameleon;hashfunction
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the accuracy and efficiency of video content management,a combined method of improved SURF and K-means was proposed to extract the DNA of video,which referenced the bioinformatics to identify and analysis videos.By extracting SURF features on video key frames,a feature set was formed.Then,the feature set was processed by K-means,and a model of bag of words was built.Finally,SURF features were quantized visual vocabulary by the model of bag of words and encoded as video DNA.The experimental results showed that the proposed algorithm of extraction of video DNA has high accuracy and good robustness,and can make improvement in terms of time cost.关键词：contentmanagement;featureextraction;videoDNA;SURF algorithm
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发布时间：2023-11-14 - 摘要：Abstract:Inordertohandlethechannelconditiondistortionsbetweentrainandtestspeechinspeakerverification,basedonthedeepneuralnetworks,achanneladaptationapproachwasproposed.First,severalphoneticdeepneuralnetworks(DNNs)weretrainedonthespeechdatasetswithdifferenttypesofchannelconditions.Theacousticfeaturesderivedfromspeakerutteranceswerethenadaptedtoobtaindeepbottleneckfeatures(DBFs)usingtheseDNNs.DBFswereconcatenatedandafeaturedimensionreductionwasperformedusingPCA.Finally,theseDBFsweremodeledbytheidentityvector(i-vector)modelingtechniquewhichisthemostpopularandefficientapproachforspeakerverification.Theachievedi-vectorsfortargetspeakerandtestutteranceswerethenusedtoachievethefinalverificationscores.ResultsontheNISTSRE2010coretestevaluationtaskdemonstratedthatcomparedtothei-vectorbaselinesystem,theproposedapproachiseffectivetoeliminatechanneldistortionsforspeakerverification,andachievessignificantperformanceimprovements.关键词：channeladaptation;deepneuralnetwork;deepbottleneckfeature;i-vector;speakerverification
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发布时间：2023-11-14 - 摘要：Abstract:In order to achieve the dual functions of online/offline signcryption and broadcast signcryption,combining the thinking of online/offline signcryption and broadcast signcryption,an identity-based online/offline broadcast signcryption scheme was proposed.In this scheme,the offline stage is not irrelevant to the information that will be signcrypted,and in the online stage,the broadcast ciphertext will be generated and then sent to multi-receivers.During the scheme design,hash function operation, bilinear paring operation and Exclusive-OR operation were used.Based on some related cryptography hard problems,the scheme’s confidentiality and unforgery were testified under the random oracle model.Finally,the computation efficiency of the proposed scheme was analyzed.关键词：online/offline;broadcastsigncryption;bilinearparing;randomoraclemodel
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the efficiency of existing multi-signature schemes based on bilinear pairings and relieve the inherent key escrow problems in the identity-based multi-signature scheme,an RSA-based certificateless multi-signature scheme was proposed,which was constructed on Zhang and Mao’s certificateless signature scheme.In this scheme,only L+9 exponential operations 5L+1 multiplications are needed, and the signature length is (L+2)|n|，where L is the number of signers and |n| is the binary length of the system parameter n.The proposal is free of key escrow and secure in the random oracles model.关键词：RSA;certificatelesssignature;multi-signature;randomoracle
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发布时间：2023-11-14 - 摘要：Abstract:In order to resolve the problems of bag of visual words model(BoVWM) based object retrieval methods,such as low time efficiency,low distinction of visual words and weakly visual semantic resolution because of missing spatial information and quantization error,a novel object retrieval method was proposed.Firstly,E2LSH is used to identify and eliminate the noise key points and similar key points,consequently,the efficiency and quality of visual words was improved.Then,the stop words of dictionary were eliminated by Chi-square model to improve the distinguish ability of visual dictionary.Finally,the spatially-constrained similarity measurement was introduced to accomplish object retrieval,and a robust re-ranking method with the K-nearest neighbors of the query for automatically refining the initial search results was introduced.Experimental results on Oxford5K and Flickr1 datasets indicated that the distinguish ability of visual semantic expression is effectively improved and the object retrieval performance is substantially boosted compared with the traditional methods.关键词：objectretrieval;bagofvisualwordsmodel;E2LSH;spatially-constrainedsimilaritymeasure;Chi-squaremodel
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发布时间：2023-11-14 - 摘要：Abstract:The consumption problem is the bottleneck of utilizing large-scale of wind power,and dispatch decisions are the cores to absorb wind power.Aiming at the characteristics of randomness and volatility of wind power,a reserve requirement model of integrated wind power was established based on the relationship among the probability distribution of wind power forecasting error and power fluctuation and reserve requirement variations.The uncertainty of wind power output was quantified.In order to solve the consumption problem of wind power,in dispatch decisions,wind power was considered as sources which can actively participate in the dispatch and the reserve-coordinated-optimization dispatch model of the wind power dynamic acceptance interval was constructed.The uncertainty of wind power and makes reasonable integrated wind power capacity interval schedule and unit commitment schedule were considered,which ensures the security of power system while meeting the economy of system operation.The modified IEEE6 bus and IEEE118 bus systems were used to verify the accuracy and effectiveness of the proposed model. The results provided a method to absorb wind power reasonably and in a maximum degree in power system with large-scale of wind power.关键词：windpower;operatingreserve;coordinatedoptimizationdispatch;mixedintegerquadraticprogram;windcurtailment
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发布时间：2023-11-14 - 摘要：Abstract:The elastohydrodynamic lubrication (EHL) of filtering reducer turning arm bearing was studied by considering the load,the contact geometry parameters and the real surface roughness.A mixed lubrication model was established to analyze the film thickness ratio,contact load ratio and subsurface von Mises stress of contact zone under rated operating condition and at other speed and temperature.Besides,the effects of groove curvature radius and surface roughness on bearing’s lubrication performance were studied either by this model.Results indicated that high speed would improve the lubrication performance by turning mixed lubrication to full-film lubrication.The rise of temperature led to a decrease of lubricant viscosity,deteriorating the lubrication condition and increasing the subsurface von Mises stress.The increase of inner groove curvature radius led to a continuous increase of the subsurface von Mises stress and a first decrease then an increase and again a monotonically decrease trend of film thickness ratio,while the increase of outer groove curvature radius resulted in a continuous increase of the subsurface von Mises stress and a first slight increase and then a steady decrease of the film thickness ratio.Decreasing surface roughness could improve the lubrication conditions,but if the surface was smooth enough,it was not only no use to decrease the surface roughness to reduce dry contact area,but also had a bad effect on subsurface von Mises stress and increased the processing costs greatly.关键词：mixedlubrication;subsurfacevonMisesstress;groovecurvatureradius;surfaceroughness
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发布时间：2023-11-14 - 摘要：Abstract:The properties of powder bed have an important influence on the forming process in the additive manufacturing technology.The forming process of powder bed for additive manufacturing was analyzed,and a simulation and analysis method was proposed based on discrete element method.The influences of particle size distribution and layer thickness on the properties of powder bed were studied.The results showed that the packing density and average coordination number increase with the increase of layer thickness,and trend to be stable at last.When the layer thickness is 80 or 400 μm,the packing densities and average coordination numbers of powder beds with monosize distribution and Gaussian distribution are almost equal with each other.At other layer thicknesses,the packing density of powder bed with Gaussian distribution initially is higher than that of monosize distribution initially,and the differential increases first and then decreases with the increasing layer thickness.Similarly,the average coordination number of powder bed with monosize distribution initially is higher than that of Gaussian distribution initially,and the differential increases first and then decreases with the increase of layer thickness.The research provides a guide to the determination of particle size distribution and layer thickness of powder bed for additive manufacture.关键词：additivemanufacturing;selectivelasersintering;discreteelementmethod;powderbedpacking;simulationandanalysis
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发布时间：2023-11-14 - 摘要：Abstract:To improve the practical application value of the traditional one-dimensional variable KE model, the method of constructing multi-dimensional variable kansei engineering (MVKE) model was proposed.Firstly,the space of multi-dimensional modeling features (MMFs) and emotion perception were set up.Next,the main features were determined and parameterized.Then,the mapping function relationship between the space of MMFs and kansei design was analyzed and the MVKE model based on the form,color,sound,material and related components of product was constructed by multiple regression analysis method.Finally,the method of the model construction and the performance evaluation of the model were described by a case of numerical control machine tools form design.The performance of the MVKE model was evaluated by validation experiment and comparative experiment.The validation experiment was used to evaluate the practicability of the model by comparing the values of the prediction and user survey.The comparative experiment was used to evaluate the accuracy between the one-dimensional variable KE model and the MVKE model by judging their goodness of fit.Experimental results revealed that the MVKE model has more excellent performance.It is more according with people's cognitive style,therefore it can aid emotional design effectively.关键词：kanseiengineering;multi-dimensionalvariable;modelconstruction;performanceevaluation
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发布时间：2023-11-14 - 摘要：Abstract:In order to resolve the problem of the low utilization rate of magnesium slag and high requirement of dimension stability for modern concrete,orthogonal test scheme was designed to study the drying shrinkage characteristics of magnesium slag composite admixture concrete by experiment.The shrinkage model of concrete was established through the analysis of the role of law and the mechanism of admixture by micro structure.Results showed that the drying shrinkage of magnesium slag composite admixture concrete increases with time in a trend of hyperbolic curve,which has significant correlation.The significant level of fitting parameters model has high,good correlation with each factor.The drying shrinkage of concrete decreases with magnesium slag dosage and admixture replacement rate,increases with powder composite rate.The order of importance is magnesium slag dosage,admixture replacement rate and powder composite rate.The effect of magnesium slag on drying shrinkage of concrete increases gradually with time,tends to be stable at 90 d.In this period,there is only shrinkage,no expansion and expandable harm in concrete.So it is feasible to add proper amount of magnesium slag to compensate the shrinkage of concrete.关键词：concrete;dryingshrinkage;magnesiumslag;shrinkagecompensation
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- 652
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发布时间：2023-11-14 - 摘要：Abstract:Carboxyl-terminated polypropylene glycol (CTPPG) and epoxy-terminated polypropylene glycol(ETPPG) were synthesized from polypropylene glycol(PPG),the differential scanning calorimetry,dynamic mechanical thermal analysis,impact strength and impact fracture surface of the three different end group polypropylene glycol modified epoxy resin were investigated.The results showed that with the increase of reactivity between the end group of polypropylene glycol and epoxy resin,the cured epoxy resin tends to form homogeneous structure,and the Tg depressed.Both of PPG and ETPPG can obviously increase the impact strength.Test results showed that polypropylene glycol toughening epoxy resin is by the way of plasticization,and epoxy-terminated polypropylene glycol toughening epoxy resin is by the way of increasing the flexibility of the crosslinked network.关键词：epoxy resin;reactive polypropylene glycol;toughening
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发布时间：2023-11-14 - 摘要：Abstract:Three kinds of fibers with different rate of moisture regain were selected to study the effect of hydrophilism of fibers on the durability of fiber reinforced concrete during freeze-thaw with the rapid freeze-thaw cycle experiment.Microstructure of fiber-cement matrix were observed using SEM before and after freeze-thaw.The results showed that compared with the hydrophobic fibers,since the latter can be tightly bonded with cement matrix together hydrophilic fibers can effectively inhibit the initial micro-defects of concrete and prevent the growth of micro-defects in the freeze-thaw cycles.Therefore,hydrophobic fiber concrete may even accelerate the growth of damage during freeze-thaw cycles,due to the interfacial performance between fibers and concrete is weak.With the increase of freeze-thaw cycles,the impact on frost resistance of concrete by the hydrophilic of fibers became more and more obvious.关键词：hydrophilia;hydrophobic;freeze-thaw cycles;rate of moisture regain;fiber concrete
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发布时间：2023-11-14
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