最新刊期
卷 49 ， 期 5 ， 2017
- 摘要：Abstract:As the era of the post-hydropower in China comes,the dam reconstruction works are increasing.In general,the river diversion for dam reconstruction consist of some original dam structures and some newly built diversion structures.Hence,compared to the diversion system for a newly built dam,the constraints and risk sources are more complicated in the diversion system for dam reconstruction.In this study,we will explored the risk evaluation of river diversion and the risk characteristics evolution rules.Based on the comprehensive analysis of diversion system for dam reconstruction,the main risk factors and risk modes were summarized,and the expressions of risk patterns were built.Those patterns included the upstream water level risk pattern,the downstream water level risk pattern and the discharge risk pattern.Then the multi-dimension risk discriminant was built on the ground of above expressions.Aiming at the flood uncertainty in the system,using the Copula function to describe the joint distribution of the flood peak and volume as well as taking account of the flow discharge rules and the operating regulation of discharge structures,the multi-dimension risk analysis model was built by sampling the flood routing,calculating hydraulic elements and integrating them into risk discriminant with Monte-Carlo method.The qualitative analysis showed that the above risk patterns were not fully correlated because of the differences in function and design standards of diversion structures,and the risk ruled by multi-dimensional distribution.Since the risk feature was decided by specified configuration,a typical case was provided,which used the original dam as upstream cofferdam and blocks the discharge way as construction pit.The quantitative risk analysis showed that there was a dominant risk pattern shifting point,beside which the discharging risk pattern took over downstream water level risk pattern as dominant risk pattern.The driving factor was the discharge rate of diversion system,and the shifting point corresponds to the upper risk limit that downstream cofferdam could defend.The research can serve as references for diversion risk evaluation and diversion scheme optimization for a dam reconstruction.关键词：dam reconstruction;construction diversion;risk feature;multi-dimensional risk
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发布时间：2023-11-14 - 摘要：Abstract:The development and application of big data technology has a deep influence on the national governance model,corporate decision-making architecture,business strategy and personal lifestyle.The data aggretation not only increases the risk of user privacy leaks,but the huge information and potential value contained in big data also attract more potential attackers.Moreover,the big data application is a cross-disciplinary application,which introduces not only a lot of new technologies but more and higher risks.The definition and characteristics of big data is reviewed,and the big data architecture and big data security system are put forward in this paper.Based on this system,the security challenges facing the current big data and research progress of big data security technologies are analyzed from four perspectives:laws and regulations,standards,data life cycle protection and big data platform key technology.Laws and regulations in America,European Union,China and the research status of big data security standarlization of International Organization for Standardization,America,China and so on was introduced.Big data platform is needed to realize the collection,transmission,storage and analysis and so on in big data lifecycle.In this paper,the security problems and key technologies of big data are analyzed from two dimensions of big data lifecycle and big data platform.The lifecycle includes collection,storage,usage,distribution and deletion five phases.Data value is determined by the data quality of the collection phase.Data and model inconsistency detection and data cleaning are the main technical means to improve data quality.The processed big data is transmit to external entities in big data distribution phase,so the protection of privacy and sensitive information is essential.The retalted key technologies are data anonymity,privacy-protecting data retrieval and analysis.The big data management support the effective use of big data and ensure big data security,which mainly contains metadata management and data lineage.The problems of authentication,data isolation,data encryption storage,big data platform border protection and audit between big data components can be solved by the big data platform security with the key technologies such as authentication,access control,data encryption and audit.At present,a perfect big data security standard system is still lacking in the world.The norms and guidance for privacy protection,data sharing,cross-border data transmission from standards are urgent needed.With the rapid development of big data analysis technology,it’s difficult to predict the challenge of privacy protection and sensitive information protection from big data association analysis in the future.The existing data masking and privacy protection technology will face a great challenge.The data analysis without exposure to data privacy and sensitive information can be achieved by data homomorphic encryption,but the existing homomorphic encryption algorithm is far from mature.The current authentication,data encryption and access control in the big data platform use the traditional technology,which can’t adapt to the new environment with large scale of data,complex processing logic and huge amount of users.Some of the big data security key technologies are also worthy of indepth study in the performance and availability for early practical application.In addition,using big data pro-cessing technology to develop security applications such as network security situation perception,intrusion detection and network threat intelligence analysis,and using big data technology to resist attacks against big data have become a new research trend in the field of big data security.The development of big data security requires the united support and promotion of laws and regulations,standards and key technologies.关键词：big data;security;authentication;access control;privacy protection
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发布时间：2023-11-14 - 摘要：Abstract:Rigid bracing dome is a new type of cable structure and broken cables (rods) analysis is very important for the failure mechanism and collapse performance of vcts structure.The structural mechanical properties of the broken cable (or rod) are analyzed by the Newmark time integration method of the transient dynamics.The response rate and dynamic magnification factor are given,and the influence degree of the broken cable (or rod) on the structure is analyzed by these parameters.The members are divided into global sensitivity components,local sensitivity components and insensitive components through the cable (or rod) breaking caused by the destruction of strength and excessive displacement of the other cables.The importance coefficient of the member is defined,and component importance is analyzed.Research shows that because the inner and outer ring rod,outer oblique rod or outer support rod is break,the structure will undergo a progressive collapse and are global sensitivity component.Lateral upper cable,middle upper cable,internal upper cable,middle oblique rod,internal oblique rod and internal support rod are locally sensitive components.The component importance of outer ring rod is the first,and internal upper cable is the last.关键词：rigid bracing dome;broken cables (or rods) analysis;sensitivity;component importance
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发布时间：2023-11-14 - 摘要：Abstract:Scaling off is one of the most common diseases that are found on earthen sites.This disease greatly threats the long-term preservation of earthen structures.Recently,lots of studies were carried out to solve this problem by various methods,however,little positive results was achieved in the aspect of in-situ reinforcement project.Currently,the research topic of slope reinforcement as well as solid and water conservation by moss has been studied by a lot of researchers.In this paper,for the purpose of earthen sites reinforcement,the moss was used to change the condition of earthen structure surface and multiple test methods were carried out to assess the reinforcement effectiveness by this biological method.This paper took the earthen sites of Qinghai area as an example,in situ research,measuring the surface insertion resistance by using micro-penetrometer before and after the growth of moss,and comparatively analyzing the change of surface checking.In the laboratory,the earthen sites were divided into five layers from the outer to the inner.Then the X diffraction instrument was used to analyze the mineral composition in each soil layer;particles of each soil layer were analyzed by laser particle size analyzer;and the ion Chromatography was used to analyze the salt content of each soil layer.The field experiments showed that with the moss growing up,the surface insertion resistance of moss solid crust has a significantly increase than the scaling off crust.Moreover,the crack of scaling off was repaired in this process.Additionally,laboratory experiments showed that: firstly,no significant change existed on the mineral composition and contents in the soil layer of moss and scaling off.Secondly,the particle size of soil tented to be decreasing,however,the content of silt and clay increased.Thirdly,the salt content in the powder layer of moss decreased significantly,salt content of other soil layer was greatly improved.After the growth of moss,the strength and particle structure of the scaling off on the original wall surface were obviously improved,and the salt enrichment had been effectively changed.The whole engineering performance of soil mass was improved after the growth of moss.Therefore,it has a broad prospect for the study of reinforcement of moss to scaling off.关键词：moss;scaling off;strength;mineral composition;granularity analysis;salt content
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发布时间：2023-11-14 -
Effect of Surfactants on the Microporous Aeration Oxygenation Performance Based on Air Bubble Theory
摘要：Abstract:In the sewage treatment plants,lakes,reservoirs,estuaries and aquaculture ponds where the dissolved oxygen level needs to be elevated by artificial aeration,it is very important to maintain the dynamic equilibrium of dissolved oxygen through the aerator.There are always surfactants in the domestic sewage and urban wastewater.When these waste waters flow into the above aerated water body,they would affect the oxygenation performance and mass transfer effect of aeration system.In order to investigate the effect of surfactants on the oxygenation performance of microporous aeration system,a series of microporous aeration tests were carried out in a glass tank of 2.0 m long,0.8 m wide and 0.8 m high,in five different air flow rates and anionic surfactant concentration,according to the Standard Test Method for Oxygen from American Society of Civil Engineers (ASCE).The microporous aeration plate fixed in the center of the tank bottom was taken as aerator and the anionic surfactant,i.e.,sodium dodecyl benzene sulfonate (SDBS),was used introduced.Based on the theory of air bubble mass transfer,the oxygen mass transfer coefficient,Sauter mean diameter and form factor were calculated and analyzed.The results showed that,at 1.0 mg/L SDBS concentration,the oxygen volumetric mass transfer coefficient was increased and the oxygen mass transfer effect was improved in different air flow rates.But at 1.0～5.0 mg/L SDBS concentration,with the increase of the concentration,the oxygen volumetric mass transfer coefficient decreased.The Sauter mean diameter of the bubbles in water containing surfactant was decreased by 22.76 % compared to pure water.The variation of the form factor was small,and thus the air bubbles were kept in the almost spherical shape.While,in the tests without surfactants,the form factor of the bubbles had a larger variation and the shape of the air bubbles tended to be flat.关键词：microporous aeration system;anionic surfactant;oxygen mass transfer coefficient;Sauter mean diameter;form factor- 2524
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发布时间：2023-11-14 - 摘要：Abstract:It is necessary to assume the position and shape of the basal failure surface when analyzing the flexural toppling of countertendency layered slope.At present,the common assumed form of failure surface is a linear type failure plane,perpendicular to the discontinuities.However,the assumed failure surface is not consistent with the actual failure surface from actual field investigations.In order to solve the above problem,an algorithm to search the basal failure surface for improving the computational reliability of flexural toppling was proposed in this paper.Based on the principle of Pan Jiazheng,the basal failure surface was assumed to be a surface that required the minimum external force to trigger overall failure of a slope.In the searching process for the basal failure surface,the failure modes (shear failure and bending tensile failure) of the rock strata were determined by mechanical analyses.Then,the possible failure area of rock strata was determined based on the toppling failure conditions of the last piece of rock stratum,and the possible failure strata were divided into several groups.The minimum external force F satisfied for overall failure in each group was calculated through the limit equilibrium method and failure modes of rock strata.Eventually,by constantly changing the searching angle,a series of F were obtained.Among these forces,the minimum one was taken as the final external force satisfied for overall failure of the slope; the failure surface corresponding to final external force was regarded as the basal failure surface of the slope,and the corresponding strata group was considered as the most dangerous group.In this paper,taking a slate slope in South Anhui as an engineering example,the results showed that the obtained failure surface was consistent with the actual failure surface of the selected example.Therefore,the effectiveness of the new searching algorithm developed in this study was validated.关键词：countertendency layered slope;flexural toppling;basal failure surface;principle of Pan Jiazheng;limit equilibrium method
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发布时间：2023-11-14 - 摘要：Abstract:Different geometric scales have different effects on model flow and sediment motion characteristics,so does with model sand wave similarities.Firstly,for model sand that is satisfied with incipient motion similarity,the variation laws of settling velocity deviations with different geometric scales are numerically analyzed when prototype sand diameter,λ(γs-γ)/γ and η are the same.The results showed that for the case of λl<1,the settling velocity deviations of model sand increase rapidly with the decreasing geometry scales.While for the case λl≥1,the settling velocity deviations of model sand rise firstly and then fall with the increasing geometry scales,reaching its peak when the geometry scale is 2.Besides,to better understand model sand similarities at a large settling velocity deviation and deviation characteristics of model sand wave height and length from those of the prototype at different geometry scales,the normal flume experiments are designed with λl=0.84,1.59 and 2.06,respectively.The results represented that both sand wave height deviation and sand wave length deviation were less than 6 % in these three experiments.The sand wave with λl=0.84 was relatively smaller while the sand waves with λl=1.59 and λl=2.06 were relatively larger.Finally,the following conclusions were reached by integrating theoretical analysis with flume experiment methods:1） for geometric normal model,when λl<1 and model sand and prototype sand had the same weight ratio,the settling velocity of model sand was relatively smaller,resulting in slower sediment deposition rate.Furthermore,both sand wave height and sand wave length were smaller than those of the prototype.When λl≥1,the settling velocity of model sand was relatively larger,resulting in a greater sediment deposition rate.Moreover,both sand wave height length were larger than those of the prototype.2）When λl≥1 and both sand wave height deviation and sand wave length deviation were less than 6 %,the model sand wave height and length had satisfied similarities.关键词：geometric scales;sand wave height;sand wave length;similarity of sand wave;settling velocity
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发布时间：2023-11-14 - 摘要：Abstract:Due to the frequent occurrence of heavy rainfalls,landslides and debris flows in mountain regions,a large amount of sediments enter into rivers in different ways,silt up riverbed and change the river pattern,especially in wide-narrow reaches which cause water level to increase sharply and induce flood disasters.In order to study the mechanism of water level change under different river morphology and sediment supply changes in mountain rivers,the experiment was conducted.The correlation between the hydraulic parameters,the river morphology and the sediment supply was discussed.The experimental results showed that the hydraulic parameters were affected by river width and riverbed gradient under clear-water condition and the response of water flow to riverbed change was delayed.The sediment supply affected river morphology and further affected the flow parameters.The water depth changed more obviously compared to the clear-water condition.With the sediment supply being increased,more sediments silted in the riverbed,raised the riverbed towards the upstream.At the top of the siltation,a hydraulic jump was found to occur accompanied with a sharp increase of water level,leading the water up to the floodplain.Thus,the upstream sediment supply exacerbated the riverbed elevation,especially in the wide-narrow regions,where sediment was easily silted and water level increased steeply causing flood to occur.The flow-sediment disasters prevention should be the focus of these areas.关键词：river morphology;sediment supply;channel response;water level change;flow-sediment disasters
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发布时间：2023-11-14 - 摘要：Abstract:At present,the coefficient of earth pressure at rest (K0) of collapsible loess is unable to reflect the influence of pressure and water content.In order to obtain the calculation method of K0 under coupling conditions of pressure and moisture,experimental research of variation rules of K0 during the wetting process for original loess was carried out.Firstly,a concept of wetting level was introduced to describe the moisture condition of soil.Secondly,stepped wetting tests were performed on loess under net vertical pressure to investigate the correlation between K0 and the wetting level,matric suction,as well as vertical strain.Lastly,the conclusion of stepped wetting tests was verified through centrifugal model tests for the loess collapsibility.The experimental results showed that: 1) the concept of wetting level,reflecting the initial condition of moisture content and the process of wetting of loess,had a specific physical meaning;2) K0 of original loess increased linearly with increasing wetting level.Additionally,the rate of increase of K0 depended on the vertical pressure;the greater vertical pressure the slower the rate of increase;3) during the wetting process under different but constant vertical pressure,K0 increased linearly with decreasing suction.However,the greater the vertical pressure the slower the rate of increase.The influence of matric suction on K0 was similar to that of wetting level;4) data on ε(vertical strain) versus K0 during wetting processes under different vertical pressures were distributed in a narrow range,which could be described using a hyperbolic curve.There was a small difference between the ε-K0 curves of different pressure and water action sequences.On the basis of stepped wetting tests,an empirical formula for K0 was established with the vertical pressure,wetting level and vertical strain as independent variables.关键词：collapsible loess;coefficient of earth pressure at rest;wetting level;vertical pressure;matric suction;vertical strain
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发布时间：2023-11-14 - 摘要：Abstract:There were big amount of large-size sediments such as pebbles and boulders on the bed of mountain rivers in Southwest China,which adjusting the surrounding water structure and sediment transportation,and thus greatly affected the process of bed transformation.In this study,the influence of boulders on flow movement with shallow depth conditions was analyzed and discussed.The research included both the field investigation of typical riverbed and open channel experiments,in which the Acoustic Doppler Velocimeter (ADV) was used to measure the three-dimensional velocities in vicinity of the boulder to understand the flow mechanism better.The analysis showed that the effect of boulder on longitudinal velocity concentrated in the central plain at the downstream of the boulder,especially in the far-wake region,and the longitudinal impact of boulder was concentrated at the range of -1<Δx/D<2,the near-bottom velocity changed significantly near the boulder,and the boundary height of far-wake region raised from about (0.3～0.4)D in the less influenced upstream region to about (0.5～0.7)D at the more influenced downstream region;the values of turbulence kinetic energy and Reynolds stress in central plain were much higher than those measured at the left and right sides,both increased sharply by about (1～10),(1～16) times compared with the initial value and both of their peak occurred at the end of the far-wake region;the flow structure also was found to be greatly affected by the boulder particle submergence degree (H/D,the ratio between mean water depth and boulder effective diameter),the influence on the hydraulic parameters such as velocity,turbulence kinetic energy and Reynolds stress firstly increased with the increase of the boulder particle submergence degree (H/D),reached at a maximum value at the critical-submergence degree of H/D=1.2,and then decreased.With different particle submergence degree (H/D),different hydraulic parameters’ recovery length and the scale of far-wake region were comparable.In summary,the boulder has great impact on flow structure through changing surrounding longitudinal velocity,turbulent parameters and the distribution of far-wake region,the details of effective factors and the laws should be further analyzed.关键词：mountain rivers;boulder;relative submergence degree;flow structure
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发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the failure mechanisms of box girders with corrugated steel web (BGCSW),static and fatigue tests were performed on two BGCSWs respectively.Crack initiation and propagation evolution process were detected,and the failure mode,bearing capacity,loading-deflection curve and loading-stress curve were analyzed.Besides,beam deflection under 100 kN was calculated using the formula in mechanics of materials.The experimental results indicated that: Failure started with crack initiation and propagation throughout the concrete bottom plate,then followed by the slip between webs and bottom plate,and eventually fractured in shear at concrete dowel.Therefore,FRP or pre-stressed bar reinforcement in bottom plate should be adopted in practical engineering to retard the crack initiation and propagation. BGCSW exhibited good fatigue resistance because of the slow propagation of fatigue cracks.The fatigue life exceeded 6×106 cycles under the cyclic loading of half static capacity. BGSCW followed the quasi plane assumption,because the concrete plate was in the deformation of bending when the webs was sustain in shearing. The deflection calculating by the formula was slightly lower than that of experiment,which can be ascribed to that the effect of corrugated steel beam shearing deformation on the deflection was neglected.关键词：box girders with corrugated steel web;failure mode;crack initiation;crack propagation
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发布时间：2023-11-14 - 摘要：Abstract:In view of the characteristics of multi-domain optical networks under hierarchical PCE architecture,a novel key management scheme (referred to as KMS-KI) based on key hypergraph and identity-based cryptography was proposed in this paper.Differing from the classic decentralized key managements based on logic key tree,the key relationship of multi-domain optical networks was firstly modeled into key hypergraph with two layers,namely the vertices represented by points and the key relation at all levels described with hyperedge.In this way,the key layered relation of network can be better reflected in the model of key hypergraph.And then,the master keys,the public keys and private keys,the session keys,the layer group keys and the inter-domain keys were generated respectively and dynamically managed by using hierarchical identity-based cryptography and improved private key generation strategies.By the way,the security protection of private keys and the problem of single point’s failure of private key generation center were better solved.Meanwhile,by fusing the idea of member characteristic value,when the members join or leave the group,the remaining group members automatically used the key value of the pPCE or cPCE to calculate and update the group key.So,the risk that the new group key was uncovered by adversary was greatly reduced.The analytical results showed that,KMS-KI scheme has the forward and backward security,confidentiality of private keys and the ability of resisting collusive attack.Meanwhile,it not only supported hierarchical identity-based cryptography,but also had achieved better comprehensive performance than typical decentralized schemes in terms of numbers of the key storage,numbers of cPCE communication,encryption and decryption times.关键词：multi-domain optical networks;key management;key hypergraph;identity-based cryptography
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of gyro drift and noise disturbance in human motion capture system,an adaptive Gauss-Newton/complementary filter fusion algorithm based on the information fusion of multi sensors was proposed.The Gauss-Newton method was first adopted to process the data measured by accelerometer and magnet.Then components extracted from the acceleration and magnetic intensity were converted from reference coordinate system to carrier coordinate by quaternion,and the difference between converted value and current time value was introduced into the Gaussian Newton iterative algorithm for real time value estimation of the quaternion.The time of iteration was shortened and the convergence speed of algorithm was improved afterwards by optimizing the optimal value of the step length. Furthermore,an adaptive complementary filter was proposed to compensate the gyro drift and attitude information solved by Gauss-Newton method was used as observation vector. Then,the high-pass filter and the low-pass filter were used to process the gyroscope data,accelerometer and magnetometer data optimized by Gauss-Newton algorithm.To obtain the optimal estimation after fusion,the gravity vector and geomagnetic reference vector adaptive filter parameters were used to adjust the weights of different algorithms in real time.The results showed that the algorithm effectively reduced the interferences caused by gyro divergence,linear acceleration and magnetic field.Under the condition of magnetic interference,the value of error was 0.94 °.Under the condition of free movement,the value of error was 1 °.Compared with extended Kalman filter fusion algorithm,the algorithm execution time is reduced by 25 %.Therefore,the performance of motion capture system was effectively improved.关键词：sensor;information fusion;Gauss Newton algorithm;complementary filter;human motion capture
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发布时间：2023-11-14 - 摘要：Abstract:The local binary fitting(LBF) model fits energy function with local neighborhood information of the image. Since it is equivalent to the local average filtering inside and outside the active contour, LBF has some noise immunity for Gaussian noise. However, it cannot obtain satisfactory segmentation results for salt and pepper noise. In this paper, a novel model integrating a local fitting term into the fitting term of LBF was proposed to enhance the robustness for the salt and pepper noise. The new fitting term was equivalent to the local median filtering inside and outside the active contour, which is insensitive to the salt and pepper noise. As the edge stop function of the original model is based on image gradient information, which is difficult to distinguish the weak edge of the image and is sensitive to all kinds of noise, a new edge detection operator was proposed to redefine the edge stop function to further improve the noise immunity of the model. In order to keep the stability of the active contours, the original model must be periodically initialized to ensure the level set function be a signed distance function and the re-initialization performs a large amount of computation. In our model, a punish energy term was introduced to eliminate the re-initialization. Compared with CV model, LBF model and LIF mode, experiments on images corrupted by different noise demonstrated that the proposed model was effective and more superior for noise image segmentation.关键词：image noise;fitting term;edge detection operator;reinitialization
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发布时间：2023-11-14 - 摘要：Abstract:Convex hull is one of the essential issues in computational geometric of planar points set.In recent years,many scholars have put forward many excellent algorithms to calculate the convex hull of the plane point set in real time,which,however,still can not satisfy the practical real-time demand.To this end,a simple but efficient and fast convex hull algorithm is proposed in this paper.Due to the fact that the convex hull points must be located at the edge of the planar point set,the algorithm in this paper can quickly find out the few candidate points of the convex wrapping point,which is the core advantage of this algorithm.Then,by using a simple and effectively-improved Graham scan algorithm which is also put forward by this paper,or any other existing convex hull methods,the points set of the convex hull can be calculated quickly and accurately.Conventional Graham scan algorithm calculate convex hull with one basis point.Based on the convex hull of distribution of candidate points set,the improved algorithm of this paper divides basis points into four subsystems,namely 4 basis points are tested respectively in each part,then mergers all the test results of each parts,and finally gets the complete convex hull.In the experiment,a set of public animals bone points clouds were used.The convex hull calculation is perfectly correct,but the calculation time of this algorithm is 2.22 times less than that of other algorithms when the number of points is about 3×105.When the number of points is about 3×106,the computation time of this algorithm is 5.42 times less than that of other methods.The more points,the more obvious advantages of this algorithm.关键词：convex hull;a preconditioning algorithm;an improved Graham scan algorithm;planar points set
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发布时间：2023-11-14 - 摘要：Abstract:The theory of solution space model has practical significance to improve the performance of Gene Expression Programming (GEP) algorithms.There are few studies on the GEP solution space model,and the theoretical research on GEP phenotype is also scarce.To address this problem,a GEP solution space model based on phenotype was proposed.Firstly,by defining the height of GEP chromosome phenotype,a theorem and the proof of the upper bound of single gene chromosome and polygene chromosome manifestation were given.To ensure the boundedness and calculability of the GEP phenotype solution space model,the general formula of height upper bound of GEP chromosome phenotype with the minimum number of operators 1 or 2 was calculated,by using the ability of GEP algorithm to find out the function.Secondly,on basis of the definition for upper bound theorem of GEP phenotype height,the GEP solution space model based on phenotype was constructed,and the properties and theorems of GEP phenotype solution space model were summarized.By further defining the concept of the complete solution space of the GEP phenotype,the distribution of the optimal solution in the GEP phenotype solution space and the complete solution space were explored.It was found that the optimal solution of the subspace in the complete solution space largely increased in proportion to the order number of subspace.Based on the knowledge of phenotypic spatial model,the basic idea and control strategy of limiting the GEP population search space were put forward,and the effectiveness of various GEP improvement algorithms in the literature was explained by the theories of space model.关键词：gene expression programming;phenotype;symbolic regression;space model
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发布时间：2023-11-14 - 摘要：Abstract:To address the problems that the traditional fruit fly algorithms cannot steadily bad converge,and effectively balance the global and local searching ability,a novel fruit fly optimization algorithm based on population density was proposed.Firstly,by utilizing the advantages of existing methods,the fruit flies were divided into the searching fruit flies and the following fruit flies,which were then used for global searching and local searching,respectively.Secondly,in order to improve the stability of global searching process,the partition sampling strategy based on optimal interval avoidance was used to update the positions of searching fruit flies in each iteration process.The strategy selected the fruit flies with the best performances in each iteration to construct the optimal fruit fly group,and determined the optimal interval according to the ranges of the fruit flies in each dimension.Then,the new positions of the searching fruit flies were determined by sampling the interval except for the optimal interval.Finally,in order to balance the global and local searching ability,the conception of population density was introduced,and the dynamic population size adjustment of different types of fruit flies was achieved by thresholding the population density.The experimental results of typical test functions showed that the partition sampling strategy based on optimal interval avoidance achieved higher global optimization ability compared to traditional rand functions.Compared to traditional optimization algorithms,the proposed algorithm obtained high optimization accuracy and stability while guaranteeing the convergence speed,achieving obvious improvements on comprehensive performances.The simulation results of the anomaly detection showed that,the fruit fly algorithm based on the partition sampling and population density can avoid local optimum effectively,and is effective in obtaining the optimal values of important parameters of the anomaly detection classifier.关键词：fruit fly algorithm;convergence stability;global searching;local searching;anomaly detection
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发布时间：2023-11-14 - 摘要：Abstract:Array codes are widely used to improve the fault tolerance ability of redundant arrays inindependent disks(RAID) storage system.With the in-depth understanding of RAID storage system,the update efficiency of array codes has gradually become an important performance metric.In order to deal with the low update efficiency problem of current triple fault tolerant horizontal array codes,a new kind of low-density and triple fault tolerant horizontal array code called inverse code was proposed.Unlike the traditional array codes whose encoding process was determined by using special geometric methods,the encoding process of inverse codes were determined by constructing coding distribution matrix in generator matrix.Firstly,a matrix structure based on GF(2w) called inverse structure matrix was proposed,which is a super-regular matrix and contains only three rows of elements.Secondly,bit square matrices of size w×w were used to represent the elements of GF(2w).Finally,the coding distribution matrix with low density property was produced by a new optimized algorithm and used to determine the encoding process of inverse code.Theoretical analysis showed that the inverse code was maximum distance separable and obtained the optimal storage efficiency.Moreover,the parameters of inverse code were not constrained to be prime numbers and more continuous compared with other triple fault tolerant horizontal codes such as STAR code and RDP code.Experimental results showed that inverse code had the advantages in sparse degree,update efficiency,encoding and decoding efficiency over CRS code whose encoding process was determined by constructing generator matrix.Compared with STAR code and RDP code,the update efficiency of inverse code was improved by 20 % on average.Besides,different kinds of ‘XOR scheduling’ techniques were used to improve the decoding efficiency of inverse code.关键词：RAID;horizontal array code;triple fault tolerance;low-density;update efficiency
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发布时间：2023-11-14 - 摘要：Abstract:Currently,system-level fault of underwater junction box can be detected only through specific indicators.Furthermore,the selection of indicators and the fault threshold value setting depends on experience.To address these problems,a fault detection method of underwater junction box based on the body's immune defense mechanism was proposed.By reference to the danger theory of body immunity,the signal conversion mechanism of the DCA (dendritic cell algorithm) was adopted,and the definition of input signals and anomaly appraisal method of the DCA were improved for online fault detection of underwater junction box.Firstly,according to the observation that change is usually the symptom of system in danger,the method of extracting danger signal based on the change of system features was proposed to improve the self-adaptability of input signals classification of DCA.Secondly,to solve the problem that DCA can only detect anomaly data items and cannot detect system-level failures,an appraisal method of system-level anomaly based on cell concentration was proposed.Finally,our method was tested with the gradual failure data of underwater junction box,and compared performance with PCA (principal component analysis).The results showed our method can effectively detect the gradual failures with higher accuracy.Moreover,it can detect fault earlier than PCA.In conclusion,our method is effective in fault detection of underwater junction box.关键词：artificial immune systems;dendritic cells;danger theory;junction box;fault detection
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发布时间：2023-11-14 - 摘要：Abstract:The channel estimation accuracy could be improved significantly by sparse channel estimation methods with a priori sparsity,that is,a small number of significant paths and large time delays in wireless channels.In view of non-optimal selection of atoms when minimizing residual norm error in greedy algorithms and the performance degradation of generalized orthogonal matching pursuit (gOMP) caused by selection of excessive atoms,an algorithm named optimized generalized orthogonal matching pursuit (OgOMP) was proposed.In the procedure of selecting atoms in OgOMP,the criterion of selecting an atom which had the maximal absolute inner product with residual was substituted by a new criterion which selected an atom with minimum residual norm error.In order to delete wrongly chosen atoms,an atom refine procedure which selected the atoms with maximal channel fading factors was added to make a second choice for selected atoms at each iteration.The number of selected atoms was the same as the channel sparsity and then wrongly chosen atoms were deleted for guaranteeing the sparsity consistency between reconstructed signals and original signals.Finally,the performance of gOMP and OgOMP were compared in terms of the channel estimation mean square error,the bit error rate, the convergence of residual with different pilot numbers and selected atom numbers.It was shown that OgOMP could save 4 dB signal to noise ratio at same bit error rate and gain maximum 5 dB at 20 dB signal to noise ratio compared with gOMP;The convergences of residual of gOMP and OgOMP were superior to MP;More pilots could improve channel estimation mean square error in both two algorithms and OgOMP needed fewer pilot overhead with the same channel estimation performance;When different atom numbers were used at each iteration the performance of OgOMP was almost the same and it was more stable compared with gOMP.Experiments verified the effectiveness of OgOMP.关键词：channel estimation;Compressed sensing;generalized orthogonal matching pursuit;OFDM
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发布时间：2023-11-14 - 摘要：Abstract:In the existing DOA estimation methods based on coprime array,discarding the non-uniform virtual elements in the difference coarray leads to the decrease of the number of the resolvable sources.In order to solve the problem,a DOA estimation method based on matrix completion was proposed.Firstly,according to the correspondence between the difference coarray and the wave path difference,a Toeplitz array covariance matrix was constructed,of which some elements are zero.Additionally,the DOA estimation model was established based on matrix completion and it was proved that the proposed model satisfied null space property.Secondly,according to the low rank matrix completion theory,the DOA estimation was transformed into the minimization of the nuclear norm,and then the Toeplitz matrix was recovered to the full covariance matrix by the fixed-point iterative algorithm.Finally,the DOA estimation was transformed into the determination of polynomial roots by singular value decomposition on the Toeplitz matrix.Simulation results showed the effectiveness and superiority of the proposed method.The experimental results showed that it can effectively fill the holes of the difference coarray,increase the available DOFs and the number of the resolvable signals.Meanwhile,it can eliminate the influence of the basis mismatch on the estimation performance in traditional sparse reconstruction methods due to the discretization in angel domain.Compared with the existing methods,the proposed method improved the DOA estimation accuracy and resolution.关键词：array signal processing;underdetermined DOA estimation;coprime array;matrix completion;nuclear norm
- 2530
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- 5088
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the output problem of a class of non-matching uncertain nonlinear systems represented by gas metal arc welding (GMAW),a sliding mode control method based on variable power law was proposed.Firstly,the first derivative of the output of system with non-matching uncertainty was obtained by using the sliding mode differentiator.Since the terminal sliding mode is stable in a finite time interval,the method has high estimation precision and the advantage that the speed the estimation error convergence is fast.Then,the paper put forward a new kind of exponential reaching law,and proved that under the same gain,the approach speed was faster than the existing various kinds of reaching laws.Furthermore,the approach speed of the proposed reaching law can be adaptively controlled,which not only ensured the system trajectory in the global scope to reach the sliding surface in a limited time,but also avoided the chattering around the sliding surface.Finally,the simulation results of sliding mode control method with the variable power reaching law and ones with traditional reaching laws are compared in controlling the arc length of non-interfered GMAW.Then,the tracking effect of arc length were compared and the steady-state errors were analyzed.The results showed that the sliding mode method with the variable power reaching law and variable structure can effectively improve the fastness of the system convergence.In conclusion,the sliding mode control method had strong robustness to the non-matching uncertain nonlinear system.关键词：mismatched;uncertainties;pure feedback;sliding mode
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- 2726
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发布时间：2023-11-14 - 摘要：Abstract:Traditional dust collecting equipments cannot capture fine particles from coal-fired flue gas efficiently due to their small sizes.A heterogeneous condensation technology was proposed for a wet flue gas desulfurization (WFGD) system to improve its efficiency of removing fine particles.Numerical study was first carried out to present the growth of coal-fired fly ash and inorganic salt particles as nucleation for heterogeneous condensation under supersaturated water vapor environment.The results indicated that the diameter of fine particles increases from tenfold to hundreds of times in a very short time with the presence of heterogeneous condensation of water vapor on the surface of fine particles under a flue gas temperature of 323 K.In addition,higher vapor supersaturation and larger initial particle diameter are beneficial to the grown up of fine particles.Experiments were then conducted to verify the numerical results and evaluate the practical effect of the technology on growth and removal of coal-fired fine particles and inorganic salt particles in a wet flue gas desulfurization system containing supersaturated water vapor with the help of PDA and ELPI.The temperature of desulfurated flue gas was in the range of 40～50 ℃.The results indicated that fine particles grow larger by 3～5 times in a very short time in the presence of heterogeneous condensation,changing from submicron particles to micron-sized dusty droplets.Hydrophilic inorganic salt particles deliquesce much more easily,forming solution droplets,which could be nucleated and grew up under the condition of saturation degree close to 1.Due to its good ability of capturing these grown dusty droplets,wire-mesh demister was employed to promote the growth and removal of fine particles combined with heterogeneous condensation.The number concentration of fine particle decreases significantly from 9.5×106/cm3 to 5×106/cm3 and the mass concentration is reduced sharply from 80 mg/m3 to 20 mg/m3.The corresponding removal efficiencies of fine particles are 50 % and 75 %,respectively.关键词：coal-fired fly ash;inorganic salt;fine particle;nucleation;condensation growth;heterogeneous condensation
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发布时间：2023-11-14 - 摘要：Abstract:With the wide applications of hydraulic technology,higher requirements have come into being for torque pulsation of motors.Generally,the commonly used hydraulic motors consists one rotor corresponding to one stator,they cannot achieve the differential connection to meet the needs of complex conditions.The double-stator hydraulic motor can be formed by the inner and outer motors in one case,and this motor can realize the differential connection.According to the principle of differential cylinder,a differential connection method was put forward through the analysis of the structure of double-stator hydraulic motor.The double-stator hydraulic motor can achieve a variety of differential connections through the different combinations of inner and outer motors.Through the analysis of differential connection of double-stator hydraulic motor,the specific relation between inner and outer motor in differential connection was obtained.The inner motor realizes the working principle of the pump,and it is rotated by the outer motor,meanwhile it will provide high-pressure oil to outer motor,so the inner and outer motors affect each other.The theoretical flow rate and theoretical torque were received by analyzing the instantaneous displacement of inner and outer motor theoretically.Under the premise that the inner motor output flow pulsation,the fluctuant factor was adopt to analyze the general rule of the output torque ripple of the double-stator hydraulic motor,the torque curve of this motor in differential with different φ0 was obtained by Matlab.The experimental platform of double-stator hydraulic motor in differential was built,and the relevant data were collected to depict the diagram of uniformity coefficient of double-stator hydraulic motor.The results showed that the lag angle has a great impact on the output torque pulsation of the double-stator hydraulic motor in differential connection,the output torque of double-stator hydraulic motor in differential connection could be more stable by adjusting the lag angle reasonably.The research can provide reference for the design and application of double-stator hydraulic motor in differential connection.关键词：double-stator hydraulic motor;differential connection;torque pulsation;flow pulsation;lag angle
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- 2742
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发布时间：2023-11-14 - 摘要：Abstract:With the rapid development of science and technology,traditional mechanical drive can not meet the engineering practical needs.Electromechanical integrated piezoelectric movable tooth drive,which has a vital application prospect in fields such as aeronautics and astronautics,micro robot,precitioning etc.,is a new mixed drive which integrates piezoelectric driving,movable tooth drive and harmonic drive and has advantages of larger transmission ratio,lower speed and larger output torque.On the basis of working principle for the piezoelectric movable tooth drive,the forces equations of the drive's elements are established from the piezoelectric nonlinear characteristic and statics relationship of the movable tooth drive.Applying optimization design principle,the design variables,objective functions and design constraints of optimization system are defined,and optimization mathematics models of output torque of the drive system are established.Using numerical method,the changes of output torque of the drive with exciting voltage and rotational angle of tooth carrier are given.The optimized results of output torque are solved by Matlab software.Besides,the parameters changes and output torque with parameters before and after optimization are compared.Results show that a directly proportional relationship is determined between output torque and exciting voltage.The torque is changed periodically with tooth carrier with a period of π/435.The optimized maximum output torque is 0.91 Nm, increased by 111.63 %.In addition,the changing of wave generator offset is largest before and after optimization.So the load-bearing capacity of the piezoelectric movable tooth drive is enhanced.These results provide a basis for modifying the structure and improving performance of the drive.关键词：piezoelectric driving;movable tooth drive;output torque;optimization;parameters influence
- 2569
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- 2323
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发布时间：2023-11-14 - 摘要：Abstract:A prediction method based on computational fluid dynamic and dynamic mesh technology was proposed to solve the problem of the porous aerostatic spindle rotation error quantitatively accurate in theory.First of all,the geometric models with different waveform and amplitude were established according to the experimental data based on the frequency and amplitude of the spindle rotor roundness error.Then the N-S equation and Newton’s laws of motion were solved to figure out the influence law of the roundness error on rotary error by FLUENT.The influence of the force of the X/Y direction,velocity distribution,pressure distribution and displacement trajectory of rotor with different waveforms and different amplitudes were studied,and the analysis of the influence law of roundness error on rotation error was achieved.The calculation results showed that the roundness error is the main factor of the rotary errors which deteriorates significantly with the increase of amplitude error and the rotary error caused by even wave is significantly lower than the odd wave.Finally,a high precision rotary error measurement experiment platform was set up to measure the rotation error of the porous aerostatic spindle.The measured rotation error is 50 nm (including the rotation error caused by vertical degree,cylindrical degree,roundness and etc.) and the calculated rotation error is 23 nm,accounting for 46 % of the experimental date.It can be concluded that the roundness error is the main factor affecting the rotation accuracy of the spindle, and the validity and accuracy of the rotary error analysis method are also verified.关键词：porous;aerostatic bearing;roundness error;rotation accuracy
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发布时间：2023-11-14
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