最新刊期
卷 49 ， 期 1 ， 2017
- 摘要：Abstract:President Xi Jinping has recently declared that marching toward the deep earth is a strategically scientific and technological challenge we must overcome.In China,the exploitation of deep earth resources has become an important direction for the future development of science and technology.Unfortunately,there is little knowledge available about the nature of the deep earth so far.Many research organizations,such as ICDP and GFZ,have been carrying out research regarding the nature and basic laws of the deep earth.Therefore,it is extremely critical to plan in advance,control the high ground of research,and promote the fundamental and frontier researches.In this paper,the inevitable trend of the exploitation of deep earth resources and utilization of deep underground space was extensively analyzed from the point of view of deep earth energy and human survival.Three research issues regarding moving into the deep earth were proposed,namely,the detection of deep geological structures,the study of the basic laws of deep underground behavior,and the utilization of deep underground space and resource exploitation.By focusing on the state long-term strategies for the deep underground resource exploitation,energy reserve and nuclear waste disposal,three disruptive idea and technologies related to the research of deep earth were proposed,namely,the fluidized mining of deep underground mineral resources,the utilization of deep underground space and the construction of underground cities,and the design of deep underground laboratories and ecological living capsules.Finally,by focusing on the cutting-edge studies of deep underground rock mechanics,the fluid mechanics of deep underground porous media,deep underground seismology and geophysics,and deep underground microbial energy traceability,a few key points of deep earth research were addressed,which are in-situ fidelity coring technology;non-conventional rock mechanics theories;transparentization and visualization methods for deep underground geological formations and mining processes;deep underground seismology and geophysics;deep underground microbiology;deep underground mining and energy storage;deep groundwater storage;migration and quality conservation;underground space ecology and energy circulation system;etc.Based on the breakthrough of the disruptive ideas and technologies of some significant research areas,a world-leading scientific base for deep earth research with a Chinese characteristic can be formed.关键词：deep earth science;exploitation of deep underground resources;fluidized mining of deep underground mineral resources;utilization of deep underground space;deep underground laboratories;deep underground space and ecological living capsules
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发布时间：2023-11-14 - 摘要：Abstract:Big data contains the high social,economic,and scientific value.It has been being spotlighted all around the academia and industry.The key technology can be divide into three levels:the data platform,the analysis platform,and the presentation platform.Among these,analysis platform is the bridge that transforms big data into real value.Generally,there are four specific attributes of big data,known as the volume,variety,velocity,and value.They extend the value space of big data.Meanwhile,they become great challenges of big data analysis.There are three major issues:Multi-sourced and heterogeneous big data,storage of tremendous unstructured data,and sparse value in fast changing big data.The three central scientific problems in big data analysis are representation,storage,and prediction of big data.Traditional methods cannot handle big data well.New methods for big data are imperative.Human brains are naturally excellent big data processor.Neural networks are computational replications of big data analysis principles in human brains.Neural networks are the most successful methods for big data analysis.Simulating neural structure in the brain to build neural network structure models and simulating memory mechanism in the brain to develop learning algorithms are two basic methodology in neural networks research.The history of neural networks research has ups and downs.Today,with the support from developing computational power,big data analysis using neural networks has achieved great success,especially in big data applications,for example,audio big data analysis,visual big data analysis,medical big data analysis.Neural networks are leading the artificial-intelligence researches.AlphaGo beating human champion in Go game attracted even more public interest."Big data+Neural Networks" is becoming one of the driving forces of innovation,social promotion,and living development.It can be clearly demonstrated how perfectly matched and mutually reinforcing are big data and neural networks by reviewing the basic concepts and key technology in big data as well as inducing the research framework of neural networks.On the one hand,neural networks are capable for extracting abstract features from raw data.They can combine multiple information sources,process heterogeneous data,and capture dynamic change in data.They are the bridge to implementation of big data value transformation.On the other hand,large volume of big data provide tremendous training samples which enable the training of neural networks with large number of parameters.However,there are still some problems in the "big data+neural networks" pattern.In the aspect of neural networks research,the structure is needing further investigation and development;the scale of network is lacking theoretical guideline;and the learning algorithm is having some inherent problem.In the aspect of big data there are also three core scientific problems:how to ensure the consistency in high-dimensional sparse space;how to implement the "knowledge-only" storage;and how to depict temporal correlation and implement big data prediction.Much more investigations in this area are still in urgent need,including those from theoretical and practical aspects.In particular,cross domain researches are important.Research in the area can be act in coordination with that in understanding big data processing in human brains.More combination with cognitive science and neuroscience are needed to resolve the fundamental scientific problems in neural networks research and big data,in which way the research of big data analysis using neural networks could be improved.关键词：big data;neural networks;artificial intelligence
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发布时间：2023-11-14 - 摘要：Abstract:The ecological environment effects and regulations of the hydropower project have been the hot spots of the international water conservancy scientific research for a long time.The construction and operation of reservoir in Southwestern China,which belongs to the typically ecological vulnerable area,will inevitably change the hydrological processes of rivers,sequentially influencing the biogeochemical behaviors of biogenic elements and the corresponding material field,energy field,chemical field and biological field.Consequently, the ecological function of river ecosystem will be seriously affected by the hydropower development.Based on the present situation of fragile ecology in Southwestern China,two key scientific issues were proposed in this project:1) the evolution and cumulative effects of the material and energy flow process in river under the condition of hydropower development in Southwestern China;2) the disturbance effects of high dams and large reservoirs on the important organism and habitats in river as well as the responses mechanisms of the ecological system.Additionally,three key technical problems that need to conquer urgently were raised:1) multi-objective ecological and hydrological processes regulation and engineering technologies of the hydropower cascade development;2) key technologies of the important fish protection and habitat restoration in the case of hydropower cascade development;3) protection and recovery technologies to maintain the ecological system stability of the large river basin.Lastly,three key technical problems were divided into four frontier research aspects and outlook:1) conducting the researches of ecological influencing mechanisms and restoration following the progressive levels of courses with "abiotic level (water,sand,salt,temperature)-biotic level (microorganisms,algae,zoobenthos,rare and endemic fish)-system level (aquatic habitat,bank slop transition zone,water-land coupling system,basin)";2) illustrating the effects of basin cascade reservoirs (group) on the biogeochemical process of biogenic elements as well as its cumulative effects and building the coupling model with multi-dimension and multi-levels;3) revealing the disturbance law of the keystone species and their habitats in river posed by cascade high dams and large reservoirs,analyzing the response processes of ecological system to the hydropower development,developing the technologies of fish habitat restoration and spanning the high dam;4) the research of river health problem has been transformed from concept to application,and their application in river ecological restoration and regulation are the directions of future development.关键词：cascade development;high dam and large reservoir;ecological protection;environmental implication
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发布时间：2023-11-14 - 摘要：Abstract:For a super-large hydraulic complex,comprehensive regulation is complicated due to flood control,power generation and ship navigation,and it is difficult to ensure the security in this situation.In order to solve the safety operation problems and satisfy the demands of long-term safety operation for large hydraulic complex,this project summarizes three common scientific technology problems in this field on the basis of research progresses and engineering practice in the world:1) hydraulic disaster-causing mechanism of high speed flow,high pressure transient flow and high head seepage,operation response and performance attenuation of dam and reservoir banks under the complicated operating conditions;2) safety control index and comprehensive safety evaluation theory of hydraulic complex operation;3) new monitor and detection technology and equipment of multiple factors considering coupling effects on safety operation.Faced the specific safety problems of hydraulic complex, five frontier technologies need to be broken through urgently:1) real-time operation technology of flood control and discharge safety;2) safety and intelligence operation technology of hydro-power system;3) combined optimal control technology of power generation,flood discharge and ship navigation;4) risk control and safety technology in the initial stage of hydraulic complex operation;5) long-term operation technology for safety of high dam structure and stability of reservoir bank under the complicated operating conditions.At last,the future research of control and safety operation for super-large hydraulic complex should be around the innovation of theoretical approach,detection equipment,security technology of hydraulic complex,real-time operation technology and system integration technology.关键词：hydraulic complex;flood discharge;power generation;ship navigation;regulation and control;safety operation
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发布时间：2023-11-14 - 摘要：Abstract:The basin area of the Yangtze River is 1.8×106 km2 with more than 40% ratio of population and GDP in China.This area is the strategic region of water resources,the main base of hydropower development,the connection of waterway and rare aquatic natural resources in east-midwest of China,which both natural conditions and human activities,significant changes had taken place in the temporal and spatial distributions of sediment production and transports in the Yangtze River,which considerably affected river development and utilization as well as protection.The requirements of sediment control were proposed to meet the rapid economic and social developments and ecological civilization construction.Meanwhile,the basic conditions of sediment control were achieved during the development of river engineering and the utilization of sediment resources.However,sediment is both disastrous and resource so that further investigation is required to solve the contradiction and unity between sediment control and river function.The main goals of the national key research project "the Yangtze River sediment control and river channel evolution and control technology" were revealing the relationship between the distribution of sediment transport in Yangtze River,and river development as well as protection research,and proposing the basic theory and key technology for the needs of sediment control and river evolution in the economic,social and ecological environment along the Yangtze River.This project focused on sediment sources and the variation patterns of spatial sediment distribution in the Yangtze River,response mechanism to the changes of water and sediment transport,the patterns of water and sediment transport of the Yangtze River and Dongting Lake,Poyang Lake River with the control of water hydropower engineer projects,bed restore process and multiple effects of flood,shipping and riverbank,and synergy theory and method of sediment control in the Yangtze River with the developments of multi-scale,multi-target and multi-process control technologies for river sediment control.According to this project,firstly,the variation trend of spatial and temporal patterns of water and sediment,and the response mechanism of river evolution were revealed.Secondly,sediment transport and sedimentation process of the Yangtze River,Dongting Lake and Poyang Lake with combination of reservoirs were quantitatively predicted.Bed restore process,relative balance state and driving mechanism were revealed.Flood control,shipping and riverbank were clarified considering multiple effects of river restore system.Thirdly,the theoretical framework of sediment regulation and control in Yangtze River,as well as the index system,method and model of sediment regulation were established.Finally,the river control technology combined with multi-scale,multi-objective and multi-process sediment modification was proposed,which was applied in engineering projects.The research of this project promoted the development of river dynamics,the utilization and protection of water resources in the Yangtze River,which provided the basis for the development of social economy and the ecological protection of river basin,with great social economic and environmental benefits.关键词：the Yangtze River;water and sediment variations;sediment control;bed evolution;channel governance
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发布时间：2023-11-14 - 摘要：Abstract:Due to the capability of reproducing complex nonlinear characteristics of cyclic behavior,the Bouc-Wen smooth hysteresis model was widely used in the seismic analysis of soil.In order to study the complex dynamic characteristics of gravel material,i.e.,the dynamic shear modulus,damping ratio,and accumulative deformation of soil,under cyclic loading,Bouc-Wen constitutive model was applied to soil drawing stress-strain hysteresis loops and the model parameters were analyzed in this paper.The method of parameter sensitivity analysis and simulation of experimental data was applied to Bouc-Wen model.Discussions were made on the parameters of the Bouc-Wen model and their influences on the dynamic stress-strain hysteresis loops and the dynamic shear modulus ratio and damping ratio.According to the mean curve of the attenuation dynamic shear modulus ratio and the increasing damping ratio of gravel materials based on statistical experimental data of gravel materials in China and overseas,the parameters of the Bouc-Wen model were determined by genetic algorithm program written in MATLAB.Accumulative deformation characteristics of core gravelly soil of Nuozhadu rockfill Dam under cyclic loading was studied by conducting GDS dynamic triaxial experiments.The stress strain hysteresis loops measured from cyclic triaxial tests were simulated by Bouc-Wen model.From the parameter analysis and simulation of experimental data,the applicable ranges of the Bouc-Wen model parameters used in geotechnical engineering were given.The mean square error of dynamic shear modulus ratio and damping ratio fitting curves were less than 0.4%.The accumulative axial strain of cyclic triaxial experiment measurement and calculated value during eight vibration periods for gravel soil were 1.2% and 1.18%,respectively.The conclusions could be made that Bouc-Wen model was able to describe the dynamic modulus and damping and accumulative deformation characteristic of gravel material accurately based on parameters scopes reported in this paper,which is helpful for dynamic characteristics analysis of gravel materials.关键词：gravel material;Bouc-Wen model;dynamic shear modulus;damping;accumulative strain
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发布时间：2023-11-14 - 摘要：Abstract:In the past half century,China has constructed more dams than any other country in the world.The impact of the blast load on the safety of a concrete dam needs to be assessed.The effects of different locations for underwater contact explosion on two different types of concrete gravity dams with and without folding slope on upstream face were compared and studied.Firstly,the numerical model was given to simulate the explosion response of concrete slabs in air and the damage and failure state of the concrete slabs.Through the comparative analysis of physical experiments and numerical experiments of damage to concrete slab results,the accuracy and reliability of the numerical model used in this study were verified.Then,taking concrete gravity dam as the research subject, by considering the dynamic coupling relationship of explosive-reservoir water-air-structure of the concrete gravity dam,analysis was made on the dynamic response and damage property of the two different types of gravity dams with and without folding slope on upstream face subject to underwater contact explosion.And the results showed the folding slope on upstream face of gravity dam decreases the dynamic responses of acceleration,velocity and displacement.Furthermore,the damage of gravity dam without folding slope was more serious subject to underwater contact explosion on upstream face.The results also showed that the folding slope on upstream face of gravity dam could effectively absorb the stress wave generated by the explosion and effectively reduce the damage of concrete gravity dam.关键词：numerical analysis;concrete gravity dam;underwater contact explosion;dynamic response;damage
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发布时间：2023-11-14 - 摘要：Abstract:The dynamic control of flood limited water level (DC-FLWL) belongs to the research field of risk operation.The risk source mainly comes from the uncertainty of inflows,including the risk from the forecasting error in real-time operation and the potential risk in the design phases from insufficient consideration about the uncertainty of design flood.A new model considering capacity compensation and the uncertainty of design flood for cascade reservoirs was developed to calculate the bound of DC-FLWL.Firstly,the probable maximum FLWL was defined by analyzing the principle of capacity compensation and an explicit expression of flood control risk was given.The joint distribution of the upstream and interval floods was established by a Copula function.When the downstream reservoir encountered a certain design flood,the possible range of upstream flood could be obtained,thus the uncertain design floods could be obtained.By simulating the operation of the cascade reservoirs under a risk constraint,the DC-FLWL could be calculated.The proposed method was applied to Pankou-Huanglongtan cascade reservoirs in Du River basin,and the results were compared with homogeneous frequency and typical year methods.It showed that:1) By employing empirical information from the historical flood data, the proposed method can provide reference information to the simulation of the design floods of cascade reservoirs;2) The bound of DC-FLWL obtained by the proposed method was much safer than the homogeneous frequency and typical year methods;3) The bound of DC-FLWL for HLT could be widened from[240.00,247.00] m to[240.00,248.21] m,which would increase 13 and 11 million kW·h extra hydropower generation during a wet year in 2000 and a dry year in 1994,respectively.The proposed method could give a sufficient consideration about the capacity compensation regulation and design flood uncertainty of cascade reservoirs, and the bound of DC-FLWL could be calculated while no flood control risk was increased.关键词：FLWL;dynamic control bound;capacity compensation regulation;uncertainty;risk
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发布时间：2023-11-14 - 摘要：Abstract:Water temperature(WT) variation at downstream of the dam after impoundment of the Three Gorges Reservoir (TGR) influenced the critical life cycle stages of the Four Major Chinese Carps to a certain extent.The degrees of WT variation in the Middle Yangtze River after impoundment of the TGP were quantitatively assessed,then effects of WT variation on the Four Major Chinese Carps were analyzed.25 WT parameters with ecological interpretations by Indicators of WT Alteration method were generated based on daily data of the Yichang hydrologic station from 1983 to 2013.The variation degree of 25 parameters after impoundment of the TGR was calculated by the range of variability approach,the linear regression method by F-test was used to evaluate trend of WT parameters with high alteration.Then relationship between spawning time of the Four Major Chinese Carps to variation of WT parameters was analyzed,to study the response of four carps spawning to WT change.The results showed:the total alteration of WT had reached to 44.2%,7 parameters representing high alteration in WT were found out,which were mean monthly WT respectively in January,April,October,November and December,arising date in the lowest WT,and arising date that WT arriving in 18℃,the corresponding WT alteration degree had reached to 87.9%,75.8%,74%,100%,100%,74%,89.9%,these all gave explanations of obvious change in WT alteration downstream of the dam after impoundment of the TGR.Compared to the same period before impoundment of the TGR,the average released WT were 2.3℃ and 1.7℃ lower in April and May during drawdown period,thereby the significant change of arising date that WT arriving in 18℃ was occurred,from 19 June in pre-impoundment period to 4 May in post-impoundment period,averagely postponed by 15 days.The spawning season of the Four Major Chinese Carps was closely related to the arising date that WT arriving in 18℃.Due to the lower released WT by the TGR,the first spawning time of the Four Major Chinese Carps had postponed from April to mid-May,and the whole spawning season had been shortened.The results might provide scientific reference for the experimental ecological operation of the TGR on natural reproduction of the Four Major Chinese Carps.关键词：Three Gorges Reservoir;indicators of water temperature alteration;the Four Major Chinese Carps;ecological operation
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发布时间：2023-11-14 - 摘要：Abstract:Disasters caused by the extreme precipitation events have serious impacts on natural and social system.In this study,the statistical characteristics of the probability distributions of the precipitation extremes in different areas of the Minjiang River basin were explored and their applicability was discussed.Based on the annual maximum (AM) and peak over threshold (POT) of extreme precipitation series from 15 sites in the Minjiang River basin during 1962-2012,the generalized extreme value distribution and generalized Pareto distribution were used to investigate statistic characteristics.The parameters of GEV and GPD distribution functions were estimated by the L-moments method,and the precipitation extremes with different return period were calculated by the robust distribution which was determined with K-S test.The results showed that there were 5 sites that belong to extreme-Ⅱ distribution and the rest sites to Weibull distribution when the AM series were fitted by GEV distribution.All the sites belonged to extreme-Ⅱ distribution when the POT series were fitted by GEV distribution.Furthermore,the optimal distributions of 13 sites were GPD distribution for POT series and all of the robust distributions were GEV distribution for AM series.The maximal precipitation was concentrated in the middle and lower reaches of Minjiang river,while the upstream precipitation was relatively small.Finally,the difference of precipitation extremes with different return period did not exceed 6 mm in regions with little rainfall.In rainy regions,the difference was more than 20 mm when the return period was 50 or 100 years.It was believed that these two kinds of distributions are applicable to Minjiang River basin but GEV distribution is more suitable for AM series and GPD distribution is more suitable for POT series.The precipitation extremes of different return periods were different when calculated by the robust distribution of different series.The difference along with the return period was increased but associated with the precipitation of the sites.关键词：Minjiang basin;precipitation extremes;return period;probability distribution;L-moments
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发布时间：2023-11-14 - 摘要：Abstract:In order to obtain the dynamic characteristics of the end face engagement worm gear,the relationship of carrying capacity and deformation between different structure types of worm was analyzed,and the scientific analysis and demonstration were made.The Dynamic analysis model of worm was set up by using the finite element method,and transient dynamic analysis of meshing moment was analyzed.At first,by transient dynamics analysis which based on the dynamic model,the contact stress,equivalent effective stress and Total deformation of the end face engagement worm gear were obtained,respectively.Secondly,the dynamic characteristics of the end face engagement worm gear were analyzed theoretically and compared.The transient dynamic performance and deformation were analyzed and compared,respectively between the end face engagement worm gear and anti-backlash double-roller enveloping hourglass worm gearing,and between the end face engagement worm gear and double roller end face meshing worm pair.The results showed that the worm gear are at least simultaneously engaged with eight pairs of teeth,and the yellow part can clearly see the maximum stress at the tooth top.Under the same condition,the contact stress of the end face of the engaging worm gear is reduced more than 33%,compared with the backlash double roller enveloping hourglass worm.The maximum equivalent stress of the end face engagement worm gear is only 22% of backlash double roller worm,equivalent stress of the end face of the worm have a clear relationship with selecting the location of spiral position.Compared with the double roller end face meshing worm pair,the end face meshing worm pair has strong anti-deformation ability. Transient analysis result of double roller end worm showed that when t=0.056 5 s the deformation of the worm is significant over time.This method provides a theoretical basis and engineering applications for the new worm reducer,and other applications in the field.关键词：end face engagement;transient dynamic analysis;capacity
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发布时间：2023-11-14 - 摘要：Abstract:Based on the load increment method and the pressure perturbation method,the dynamic performance of liquid hydraulic spindle system was researched.Using the finite difference method,the nonlinear oil film force was calculated by solving the Reynolds equation of unsteady oil film pressure distribution which was included in the micro-scale velocity slip effect.Four dynamic stiffness and damping coefficients reflecting the dynamic characteristics of the oil film were calculated by using the load increment method and the pressure perturbation method,and were used to the analysis of hydraulic spindle system.The research results showed that:Velocity slip caused a certain impact on dynamics of hydraulic spindle stiffness and damping performance.The maximum decreasing ratios of dynamic stiffness coefficient Kxx,Kxy,Kyx and Kyy which were caused by velocity slip were 4.85%,4.85%,7.20%,7.16% respectively.Velocity slip reduced the oil film damping coefficient Cyx,Cxy and Cyy, the change rule of damping coefficient Cxx by slippage effect was more complex.With the increasing eccentric quality of the rotor, running track of the spindle axis was in the expanding,and the stability of the system decreased continuously.The experiment of the measuring path of the shaft verified the correctness and validity of the orbit of shaft centre model.关键词：liquid hydraulic bearing;velocity slip;orbit of shaft center;characteristic coefficient;eccentric mass
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发布时间：2023-11-14 - 摘要：Abstract:The traditional stiffness analysis method can only get the analytical stiffness expression of the regular structure.But for the irregular components,it should be simplified as many parts of certain regular component.The accuracy of stiffness matrix is reduced due to over-simplification.In order to optimize the mechanical system parameters based on stiffness,it is necessary to solve the problem of normalized stiffness matrix of irregular components.Taking the U-shape axis in 3-URS (U-hooke joint,R-revolute joint,S-spherical joint) parallel mechanism as an example,the method for solving stiffness matrix of the complex component was proposed based on multiple linear regression theory.Each element of the stiffness matrix was considered as a regression coefficient.Multiple sets of force and displacement pairs were obtained by adopting ANSYS software and then used to solve the regression coefficients based on multiple linear regression analysis.The regression coefficients were arranged in a form of 6×6 stiffness matrix and it was mainly used for superposition.In order to reduce the computational difficulty and improve the computational efficiency,t-test was applied on every regression coefficients and those non-significant variables would be eliminated to simplify the equation form with a certain precision.Then F-test and goodness of fit test were both performed on the simplified results to verify the regression effect.Finally,the method was applied to solve the stiffness matrix of U-shaped axis complex element.Twenty four sets of sample data were obtained by the experiment method.The 6×6 stiffness matrix of regression coefficients were computed based on multiple linear regression theory.The partial matrix elements became zero after the t-test.Finally,the stiffness matrix of the mechanism was obtained after F-test and goodness of fit test.The accuracy of the method was verified by comparing the deformation values computed by ANSYS analysis and calculated by the stiffness matrix under the same external forces.The results showed that the maximum error is only 0.11%.关键词：irregular component;stiffness matrix;multiple linear regression;synthetic test
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发布时间：2023-11-14 - 摘要：Abstract:The wind turbine blade is gradually developing towards large scale.In order to improve the excitation ability of wind turbine blade fatigue test and shorten the test cycle,the coupling vibration of two exciters has become a promising development direction in fatigue test methods.First of all,the coupling characteristic test of two exciters was carried out,the blade test plan of excitation source speed,phase and amplitude was designed.The wind turbine blade was tested under the effect of this excitation source,in which the two exciters initial speed were set to 35 r/min.The results showed that two excitation speed difference was in the range of ±5 r/min,phase existed coupling phenomenon and the blade amplitude was disorderly.In order to improve the synchronization effect of two exciters,based on the analysis of the existing control strategy,using parallel cross coupled structure,the sliding mode variable structure control algorithm was developed by using the Lyapunov function and the asymptotic stability of the algorithm was proved.Finally,a set of 10 MW large test platform of wind turbine blade fatigue was built,the fatigue excitation control system based on distributed network bus was developed,and the sliding mode variable structure control algorithm was applied to aeroblade 2.0~54.38 wind turbine blade fatigue test,in which test was driven by two exciters.Test results showed that in both the excitation source speed were 35 r/min,the rotational two exciters phase keep step,phase can also basic synchronized,and the blade amplitude was the largest and very stably.Under the different initial speed drive,respectively set as 40 and 30 r/min,the speed of the two exciters can quickly follow and keep respectively.Due to the inconsistency of the two rotational speeds,the amplitude of the blade was fluctuating.The test results showed that although the electromechanical coupling between two exciters was sequestration,the development of the sliding mode variable structure control algorithm could make two exciters keep step with rotational speed,phase,and had a good robust property,effectively guarantee the smooth progress of fatigue test.关键词：wind turbine blade;excitation system;coupling;decoupling algorithm;fatigue test
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发布时间：2023-11-14 - 摘要：Abstract:The lower outlet SO2 concentration of flue gas and emission standards were achieved mainly through the desulfurization reaction occurred on the surface of the carriers of catalyst in desulfurization reactor.The effects of important structural and operational parameters of the desulfurization reactor on desulfurization percent need to be clearly investigated to predict the desulfurization percent accurately.Based on the finite element software ANSYS,the unsteady flow and catalytic oxidation reaction in the reactor were simulated,the effects of SO2 concentration,empty tower gas velocity and the catalyst packing bed height on the desulfurization percent were investigated by means of a method of reducing effective reaction volume.The regularities of desulfurization percent and outlet concentration of SO2 vs.time were also studied.By comparing the simulated data with the experimental results,the mathematical model of reaction rate for the catalytic desulfurization was corrected.The results showed that the desulfurization percent became lower during heating of the carriers of catalyst,both the desulfurization percent and SO2 outlet concentration of the reactor would decreased with the increasing inlet concentration of SO2,the effect of the space velocity on the desulfurization percent was great,the operation of the desulfurization system became abnormal at too high or too low space velocity and the desulfurization percent increased with the increasing catalyst packing bed height.Therefore,the reaction rate constant could be corrected based on the changing operation temperature during heating stage of hot flue gas with the good agreement with the industrial data.It is feasible in simulating the unsteady flow and chemical reaction that the unsteady model could be simplified by gradually reducing the total reaction volume of computational domain instead of reducing reaction surface area.The high desulfurization percent could be obtained when the space velocity is in the range from 0.2 to 0.3 m/s.Besides,it is suitable that the catalyst packing bed height ranges from 1 600 to 1 800 mm.The results could provide important basis for engineering design of catalytic desulfurization reactor.关键词：flue gas;catalysis;desulfurization;numerical simulation
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发布时间：2023-11-14 - 摘要：Abstract:The milling is a critical process of cermets-preparation.Roll milling is a low-cost and widely applied method in the industrial production.To analyze quantitatively the effects of milling time on the Ti(C0.7,N0.3)-based cermets,the grain size,micro-strain,lattice parameter of Ti(C0.7,N0.3), the microstructure and physical/mechanical properties such as shrinkage,density,hardness,transverse rupture strength of sintered Ti(C0.7,N0.3)-based cermets were investigated at fixed ball-to-powder weight ratio,milling speed,milling medium using wet-milling.The results showed that when the milling time increased, the grain size of Ti(C0.7,N0.3) descended but the micro-strain of Ti(C0.7,N0.3) rose,and the lattice parameters of Ti(C0.7,N0.3) increased,which was correlated with the increase of micro-strain and oxidation of some mixed materials.In the microstructure of sintered bodies,the average grain size of the hard phases declined with the milling time.Some porosities of around 0.1 μm were formed in the cermets when the milling time reached 72 and 96 h,which was relevant with the degassing reaction due to increase of oxygen contents and degradation of the wettability between Ti(C,N) and Ni.The numbers of bright cores in the microstructure drop owing to Mo-content declining but Ti-content increasing. The rims got thinner with the milling time extended, which was related with the solubility of the particles having different sizes and their homogeneity.Additionally,the hardness of the Ti(C0.7,N0.3)-based cermets was raised. The transverse rupture strength of the cermets was elevated initially but then reduced, and the detrimental effect of porosities on the strength outweighed the favorable effect of grain refinement.关键词：Ti(C;0.7;,N;0.3;)-based cermets;milling time;lattice parameters;micro-strain;core-rim structure Ti(C,N)
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发布时间：2023-11-14 - 摘要：Abstract:Magnetic Fe3O4 and Co were loaded on the face of reduced graphene oxide (RGO) to form newly multiphase composite magnetic materials (CF-RGO),taking the advantage of the ability of transition metals to activate peroxymonosulfate (PMS),and decreasing the secondary pollution of residual metal.The efficiency of PMS,RGO,CF-RGO,RGO/PMS,Co/PMS,and CF-RGO/PMS systems on removing acid orange 7 (AO7) were compared,and the effects of different initial pHs,CF-RGO dosages and AO7 concentraions on removal of AO7 were investigated by CF-RGO-activated PMS.Results suggested that AO7 could hardly be removed by PMS RGO,CF-RGO and RGO/PMS systems,while the systems of CF-RGO/PMS and Co/PMSPMS could remove efficiently,and the removal capacity of CFRGO/PMS system was apparently higher than Co/PMS system.For the system of CF-RGO/PMS,the removal efficiency of AO7 increased first and then decreased with the increase of pH,and the removal rate reached a maximum at pH=5.0.The effect of CF-RGO dosage on AO7 removal showed a positive correlation basically.The increase of AO7 initial concentration would reduce the removal capacity of system,with the decrease of the removal rate of AO7.The dosing of tertiary butanol (TBA) and ethyl alcohol (ETOH) confirmed that the major radical formed was sulfate radical (·SO4-) at pH=5.0,which suggested a major role of ·SO4- in degrading AO7. In addition,the catalytic activity and stability were good after using three times repeatedly.The investigation of residual Co and Fe showed that this kind of catalyst had little secondary pollution on water.The study indicated that CF-RGO could activate PMS quickly and remove AO7 efficiently as a catalyst,with good reutilization and little secondary pollution. On the conditions of pH of 5.0,initial concentrations of AO7 and PMS of 0.03 mmol/L and 0.2 mmol/L,and the dosage of CF-RGO of 0.003 g,CF-RGO PMS system could remove AO7 efficiently,with the maximum rate reaching 95.8%.关键词：magnetic graphene;transition metal;sulfate radical;acid orange 7;removal rate
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- 5975
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- 1
发布时间：2023-11-14 - 摘要：Abstract:The dialdehyde cellulose (DHBC) was abtained by oxidation of bacterial cellulose (BC) using sodium periodate at 40℃ and pH 1.0 in the dark.And then three kinds of dialdehyde bacterial cellulose-gelatin composites (DB-G) (DB-G5,DB-G10,DB-G15,respectively) were prepared by reaction of DHBC and gelatin solution at 50℃and pH 6.0±0.1.By FTIR spectra analysis,the absorption peak of CO (1 740 cm-1) of DB-G disappeared,on the contrary,and the typical bands for amide Ⅰ v(CO)appeare at 1 600~1 680 cm-1 and for amide Ⅱ v(N-H) at 1 500~1 550 cm-1,in which the absorption peaks become hypsochromic shift and widening with the increase of bonding gelatin.According to the degradation test results in the simulated body fluid(SBF),DHBC and DB-G showed good biodegradable and the cycle of degradation are basically 60~90 d.The pore diameter of DB-G5,DB-G10 and DB-G15 gradually decrease based on the analysis and test of DB-G by specific surface area,pore diameter distribution and SEM.From the test results of pyrolytic temperature (TG/DTG),compared with the BC,the pyrolysis temperature of DHBC fall rapidly,and the maximum weight loss temperature(Tmax) drop 80.1℃.The thermal stability of DB-G was improved considerably after crosslinking with gelatin,in which Tmax were greater than 340℃,but Tmax of DB-G10 and DB-G15 were less than 2℃.Similarly,from tensile strength test,DB-G15 is not further improved than DB-G10 with the increase of gelatin.Comprehensive analysis,the appropriate mass ratio of DHBC and gelatin is 1:10 that DB-G10 can be as a kind of potential biomass-based tissue engineering scaffold material.关键词：bacterial cellulose;gelatin;scaffold material
- 2024
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- 2158
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The anomaly detection of network traffic in practice requires both high detection rate and low false alarm rate.To address this problem,a detection approach based on multidimensional time series analysis was proposed.Firstly,the network traffic was observed in a long time,and multiple network features were chosen for building the network behavior model.Subsequently,multiple features were predicted by the method of time series analysis.Then the degree of deviation between the predict value and the real value was calculated and updated.Finally,the state of whether the network flow is normal was determined by using support vector machine to classify the degree of deviation in time series.This method has been applied to real-time monitoring and protection on a campus key server.The results showed that it can detect anomalies effectively in network traffic.关键词：anomaly detection;time series;network traffic;multiple features;network security
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- 4117
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- 6
发布时间：2023-11-14 - 摘要：Abstract:In TrustZone architecture,a malicious CA occupying session resources for a long time usually introduces DOS attacks.To solve this problem,a TrustZone session scheduling protocol(TSSP) was proposed.Combined with the features of session execution in TrustZone architecture,the construction method of session waiting queue and execution queue was introduced.Meanwhile,the calculation methods of session priority in waiting list and session surplus value in executing list were proposed.Based on this, the session scheduling strategy was detailed described.The experimental results showed that this protocol could ensure that session with high priority be executed first and could resist DOS attack induced by malicious CA occupying session resources for a long period of time.Finally,the security and performance evaluations of the system added with session scheduling mechanism were done.The results showed that on the premise of ensuring system security the performance overhead added is between 0.01 and 0.27 s.关键词：denial-of-service attack;session scheduling;security
- 2965
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- 2092
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- 0
发布时间：2023-11-14 - 摘要：Abstract:With the development of computer and network technologies,the core codes of softwares are facing the risk of being reversed.To protect the core codes from being reserved,virtual machine-based (VM-based) software protection methods using virtualization technology were widely used because of its hard-understanding virtual instructions and high protection strength.However,traditional protection methods cannot resist semantic-based attacks,and lead to a serious threat to the software safety.Existing VM-based software protection methods cannot effectively cope with semantic-based attacks,which leverage the data flow and control flow information to obtain the core codes.To solve the problem,an effective protection system called DAS-VMP was proposed,with which semantics analysis based attacks can be defeated.In this paper,the key technologies of semantic-based attack were analyzed,and a method using complex obfuscation of the data flow and execution flow to defeat the sematic-based attacks was presented.In order to prevent attacker from analyzing the core algorithm,DAS-VMP obfuscated the data flow of handlers in virtual machine,and then more complex and diverse data flow structures were obtained.Moreover,to resist the attacker's symbolic execution,the predicate information in the virtual machine was hidden by DAS-VMP.On the purpose of making the execution flow complex,a double process mechanism to control the execution flow during the execution process was introduced,which made the software execution process more difficult to be tracked.Theoretical analysis and experimental results showed that DAS-VMP performs significantly well in resisting semantic-based attacks.Furthermore,it had less impact on performance overhead comparing to two existing commercial VM-based software protection methods.关键词：VM-based software protection;data flow obfuscation;semantics attack
- 3070
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- 2327
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The open-source feature of Android brings the convenience for both developers and attackers.As a result,there exist lots of attacks,such as user privacy information leak,remote controll attack,system broken attack etc.In order to improve the legality and efficiency of privacy leakage detection,an automatic detection system named LeakDetector based on static taint tracking was proposed.In the system,the forest of leakage classification was used to detect the privacy leaks of an application.First of all,LeakDetector constructed some databases of privacy leakages using similar applications.Then Random Forest was used to turn the databases into a forest of leakage classification.The accuracy of result was improved by multiple-part voting mechanisms.The voting and reusable feature of the forest of leakage classification could improve the validity of privacy leakage detection results and reduce the workload of detectors.In addition,LeakDetector provided a function to locate the leak points,which could enrich the concise test results,and get the sinks and sources of the privacy leakage data flows in the application.Sixty-five weather apps were collected from five third-markets to generate leak databases and a forest of leakage classification was made.When a new testing weather app was input into the forest of leakage classification,twelve warnings classified into five leakage types were obtained.These five leakage types included leaking phone information through the Internet,leaking phone information to local log,leaking local log to content,leaking local log through the Internet and leaking local file through the Internet.Finally,the locations of the sinks and sources were identified through the function of reverse location.The experimental results showed LeakDetector could detect the privacy leakage from applications with an accuracy rate of 91.6%.Moreover,the reverse-location function could localize the leakage sources and leakage points.关键词：privacy leakage;Android;reverse engineering;machine learning
- 2712
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- 2019
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The existing supervised detection algorithms have low precision when they detect shilling attacks.To address this problem,a shilling attack detection algorithm based on the features of popularity and novelty degree was proposed.Firstly,according to the difference between genuine and attack profiles in choosing items to rate,several features were extracted,which can effectively distinguish normal and attack users in perspective of popularity and novelty.Secondly,an ensemble detection framework based on these features was proposed.The Boosting technology was used to generate different base classifiers and the detection results were obtained by combining the predicted results of the base classifiers with weight.The experimental results showed that the shilling attack detection algorithm based on the features of popularity and novelty degree can improve the precision and recall of attack detection.关键词：shilling attacks;item popularity;item novelty;Boosting technology;ensemble detection
- 3065
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- 2151
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- 1
发布时间：2023-11-14 - 摘要：Abstract:To address the problem of data flow leak caused by taint analysis,a method for binary code anti-Taint analysis was proposed.The core code was located by implanting tags during development or typing the address after development.To protect the sensitive data and improve the ability of resisting taint analysis,the anti-taint analysis was designed by bleaching the taint.Besides,for the variety of protective methods,three kinds of anti-taint analysis methods were proposed respectively for data substitution,data match and stack operation.The results showed that the proposed methods can effectively improve the ability of resisting taint analysis and would not result a large performance loss.关键词：dynamic analysis;data flow protection;taint analysis;reverse analysis
- 2904
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- 3665
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- 0
发布时间：2023-11-14 - 摘要：Abstract:DPA is widely used in the present as a new type of password attack technology,especially the most widely used glitch attack,which can break a large number of existing password program. In this paper,to resist DPA attacks especially glitch attacks,a new password structure of a low-consumption S-box based on AES was constructed by converting inputs into the composite field for seeking inverse,and converting them back to finite field for outputs.Then based on the idea of secret sharing,a new one was obtained by grouping S-box through the steps of affine transformation,inversion transformation and inverse-affine transformation.Compared to the classical scheme proposed by Nikova Svetla,the occupied space and consumption were reduced by using the method of correction terms.The analysis and experiments showed that the proposed scheme has better consumption characteristics,and the same level of resistance for first order DPA attack and glitch attack compared with the scheme of Nikova Svetla.关键词：secret sharing;AES;first order DPA attack;glitch attack;S-box
- 2819
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- 2178
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- 5
发布时间：2023-11-14 - 摘要：Abstract:Due to the lack of security design,vulnerabilities of traditional Industrial Control Networks (ICS) protocols can be easily exploited remotely from TCP/IP network.In this paper,a novel security enhanced Modbus/TCP protocol called trusted Modbus/TCP was proposed for ICS network based on remote attestation and trusted hardwares.For bidirectional authentication,the proposed protocol modified the original Modbus/TCP communication stack of both field devices and control devices in ICS.Based on a white list,the identities of communication devices and the information of security status were attested.Updates of these information were maintained by an on-line attestation sever,and lately pushed to the field devices in order to reduce its burden.The protocol data were protected in two ways.Firstly,all data couldn't be tampered without knowing by legal devices who had the authenticating key protected by trusted hardwares;secondly,sensitive Modbus/TCP operation data was encrypted under the protection of trusted hardwares.To the authors' best knowledge,there is as yet no paper in the open literature that introduced trusted components into Modbus/TCP network to secure the communication between ICS devices.The trusted Modbus/TCP protocol was described with the HLPSL language.The four security properties, including integrity,authenticity,confidentiality and the freshness of protocol data,were verified with the SPAN tools without finding intruding path.The most time-consuming cryptographic operations for authentication were used only when establishing the communication session or after previous authentication failed.Moreover,the time cost could be reduced rapidly after adopting the latest dedicated trusted hardware for the ICS,compared to the experiments using current Trusted Platform Module (TPM).The overheads of increased protocol packet size compared to the original protocol were μs-level.In conclusion,the trusted Modbus/TCP proposed is practical for the ICS,since it could not only protect protocol data transferred on Modbus/TCP network from illegal entities,but also protect the data from legal entities whose system was tampered.关键词：communication security;secure protocol;industrial control system;Modbus/TCP;remote attestation
- 2842
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- 2476
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- 2
发布时间：2023-11-14 - 摘要：Abstract:In order to deal with the shortages of traditional alerts aggregation and correlation methods on rationality and accuracy,an aggregation method based on multistage division and a correlation method based on Markov chains model were presented.Firstly,the network alerts were described by intrusion detection message exchange format.If the time internals of alerts were shorter than the predefined threshold,the alerts would be divided into the same time window,and the time windows were extended automatically based on the temporal relationship of alerts.Then,the alerts were divided respectively according to the attributes of attack types,time windows,subnet masks,IP addresses and ports.To aggregate the similar alerts generated by the attacks which used the same router,host or port,the aggregation processes on the stages of subnet,host and service were respectively carried out based on attributes matching.On this basis,alerts correlation graph was generated by using one-step Markov chains model.In the graph,the directed edges represented the conditional transition probabilities between attack types,and the transition probabilities were calculated by the number of adjacent alerts.Finally,in the experiment,DARPA2000 traffic data was handled by the intrusion detection system Snort which was been configured as the most strict mode.After generating intrusion alerts set of LLDoS1.0 attack scenario,the above aggregation and correlation methods were conducted on the alerts of five types.The most ideal internal threshold of the self-extending time windows was further determined by parameter optimization.In this way,the alerts were reduced by the multistage aggregation effectively,and the results of aggregation were in accordance with the distribution of alerts source IP and source ports.Moreover,the accuracy rate of alerts correlation was calculated by comparing the correlation results with the official description of LLDoS1.0.Experiments demonstrated that the accuracy rate of the proposed method was 97.94%,which was 2.29% higher than that of traditional method.关键词：network security;intrusion detection;alerts aggregation;time windows;multistage division
- 2875
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- 3758
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- 2
发布时间：2023-11-14 - 摘要：Abstract:For the serious quantization error in vector quantitation coding,the sparse coding is only a shallow learning model which caused the codeword lack selectivity for image features.In this paper,an image classification method based on deep learning coding model was proposed.Firstly,the deep learning network unsupervised RBM was used to encode SIFT features and generate visual dictionary instead of the traditional K-means clustering.Then,the unsupervised RBM learning was steered by using a regularization scheme,which decomposes into a combined prior for the sparsity of each feature's representation as well as the selectivity for each codeword.Finally,the initial dictionary was fine-tuned to be discriminative through the supervised learning from top-down labels.To train SVM classifier and complete image classification,the representation features based on image deep learning were obtained.The experimental results demonstrated that the proposed method can overcome the disadvantage of vector quantization coding and sparse coding.Moreover,the classification performance can be boosted effectively.关键词：image classification;bag of visual words model;deep learning coding model;sparse coding;restricted Boltzmann machine
- 2844
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- 2948
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发布时间：2023-11-14
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