最新刊期
卷 47 ， 期 1 ， 2015
- 摘要：Abstract:Along with the increasingly sharp and complex network space competition and confrontation, security issues have extended to the traditional area at an unprecedented depth and breath. With the emerging of new types of network forms and services such as the mobile Internet, the Internet of next generation, the Internet of things, the cloud computing, the named data networks and the big data, security requirements have transformed from a single user to multiple users on at least one of both communication ends. In this paper, the main characteristics of modern cryptography in multiparty scenarios are summarized. One is the change of end-to-end multiparty pattern, which changes from the one-to-one situation to the one-to-many, many-to-one and many-to-many situations, where the multiple users are dynamically defined by the access structure. The another is the change of multiple location pattern, where both the computing and processing are executed from the locality to the remote sides, including outsourced computation, outsourced signal processing and outsourced aggregation. The research line of attribute-based encryption (ABE) is mainly introduced, focusing on study of traceable and revocable attribute-based encryption in the multi-authority setting. Finally, some valuable applications of the research results are presented, including the chip development and applications of the proposed cryptographic primitives, which focus on the access control of the encrypted data and the biometric-based identity authentication.关键词：applied cryptography;multi-party mode;location off-side mode;multi-party cryptography;outsourced cryptography
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that K-means algorithms is highly sensitive to initial clusters centers in text clustering, an initial cluster center selection algorithm based on the correlative degree of features was proposed. Features with high correlative degree were chosen after reducing dimensions and a new dataset was created. Subsequently, a candidate initial cluster center set was constructed by merging the similar documents in the new dataset using “OR operation”. Finally, the best centers from the candidate dataset were obtained through computing document density and following the minimax principle. The results of five experimental datasets showed that most F-scores are more than 90%, and entropies are below 0.5. Comparison with the K-means algorithms of Mahout showed that the improved algorithm can choose higher quality centers and produce better clustering results.关键词：K;-means;feature correlative degree;initial cluster center;text clustering
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发布时间：2024-08-19 - 摘要：Abstract:In response to the demand for the consistency migration policy of virtual domain among hybrid clouds, a mechanism of virtual domain migration called IDVE was proposed. Via the protocol of consistency migration of virtual domain between the data centers and using encrypted virtual tunnel to migrate virtual network, the proposed mechanism makes the topology of virtual domains and network configurations unchanged. This scheme meets the needs of consistency migration among data centers, and lets the topology of networks and configurations set up in advance when virtual machines begin to migrate, which greatly reduces downtime of migration. The results of experiments showed that when migrating, virtual tunnel decreases up to 25%, and downtime is only 0.81 seconds, meeting the actual needs.关键词：inter-datacenter;consistent migration;virtual domain
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发布时间：2024-08-19 - 摘要：Abstract:In order to eliminate the security threat to HTML5 applications posed by debugging JavaScript code during attack process, a method of protecting JavaScript code through anti-debugging was proposed. The JavaScript debugging principle on Firefox and Chrome was analyzed, and the runtime features introduced by these mainstream browsers’ debuggers were explored. Then combined with these features and some penalties to the debugging behavior, some anti-debugging approaches were devised and applied to achieve anti-debugging protection on Web applications. The experiments showed that these anti-debugging approaches can effectively protect Web applications from being debugged dynamically without much overhead.关键词：HTML5;JavaScript code protection;anti-debugging
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发布时间：2024-08-19 - 摘要：Abstract:With massive feature set and high-dimensional sample set,steganalysis has a increasingly demanding for classifiers.Based on ensemble classifier,a kind of selective ensemble classifier for universal steganalysis was proposed.At first,some base learners were generated based on the random forest and then some of them were wept out using GASEN(genetic algorithm based selective ensemble) algorithm.At last,remaining base classifiers were given different weights according to the optimal weight vector from genetic optimization to get used to the weighted vote integration. Experiments showed that the elective ensemble classifier performed better than existing single classifier. Compared with the existing ensemble classifier, especially in the case of larger base classifiers or higher number of features, the computational complexity was slightly increased, but the error rate reduced effectively.关键词：steganalysis;ensemble classifier;selective ensemble;Genetic algorithm;weighted vote
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发布时间：2024-08-19 - 摘要：Abstract:To detect new high-distributed low-rate QoS violation driven by LDoS attack and guarantee high network QoS,a novel recognition scheme was proposed with the consideration of multiple network features in both macro and micro aspects.At micro-level feature, the weighted sum of FLAG control bits was used to describe an internal micro-change in TCP package header.Meanwhile,the power spectral density(PSD) feature of I-I-P triple was calculated in order to reflect the inherent periodicity of LDoS Attack;at macro-level feature,R feature was introduced to mark the change in ratio of sent_flow and received_flow. Multi-dimensional observation state sequences can be constituted with these features that further form multi-stream fused hidden Markov model (MF-HMM).MF-HMM was applied to automatically recognize QoS violation.In addition,Kaufman algorithm was used to dynamically adjust and upgrade threshold value.Experiments showed that the approach effectively reduces the false-positive rate and false-negative rate in recognition.Moreover,it has an especially high recognition rate for new high-distributed low-rate QoS violation driven by LDoS even in complexity background network traffic.关键词：multi-stream fused HMM;network QoS;power spectrum density PSD;Kaufman algorithm
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发布时间：2024-08-19 - 摘要：Abstract:NSS and NTRUSign are two typical digital signature schemes based on NTRU-lattice.For the purpose of solving security problems and speeding up the algorithm,a new scheme based on NTRU was proposed.Its security foundation,lattice reduction attack,and transcript analysis attack were shown.Performances of three schemes of the proposed one,NTRUSign,and its improvement scheme,NSS_Hu, were compared. The result showed that the proposed scheme could accelerate 1/7 without decreasing its security on the degree of complexity theory in total.关键词：lattice;NTRU;lattice reduction;digital signature scheme
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发布时间：2024-08-19 - 摘要：Abstract:Recent studies on virtual machine introspection mostly build guest VM state by the use of guest OS kernel data structures and kernel functions, which can be maliciously subverted. They are unable to resist direct kernel structure attacks. In view of the above situation, the capability of VMI was analyzed thoroughly, and then the possibilities of using hardware architectural knowledge and virtualization extension knowledge to construct VMI technology were explored and the possible attacks that can be detected and foiled by this mechanism were discussed. Collection and monitoring of system calls using the proposed method were described and the efficient of the monitored system was analyzed.关键词：Virtual machine;introspection;virtualization extensions
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发布时间：2024-08-19 - 摘要：Abstract:The galleries of high core wall rockfill dams on thick overburden layer is subjected to complicated loads，and its safety is the key to the project.In order to study the safety of galleries of this kind of dam,taking the Changheba dam as a background,and using the finite element analysis,the leakage from the destruction to the watertight seal was simulated.Based on the sub-model method,nonlinear elastic model was used for the gallery concrete.Cracking process and failure process of the gallery were conducted.Meanwhile the actual dam construction process and reservoir impounding process were considered.Through the analytical results the crack propagation,cracking direction and breakage feature were learned.Furthermore some reasonable suggestions were given,which can be used as reference to changheba project and similar project.关键词：gallery;crack;high rockfill dam with earth core;Changheba Hydropower Station;concrete
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发布时间：2024-08-19 - 摘要：Abstract:The landform and kinematics characteristics of Mahu ancient landslides in Leibo County,Sichuan Province were analyzed in detail to obtain it’s causes aimed at the new finding of it’s scale.Analysis on the riverbed of ancient Huanglang River,the plane range and depth of the ancient landslide was done on the basis of borehole and ultrasonic measurement of the terrain of the dammed lake bottom.Based on the site investigation of shape,structure and geological environment,the landform was analyzed,the periodizations of the landslides were described,and the movement of each landslide event was concluded.The energy conservation equation was used to calculate the velocity,which helps to confirm the causes of the ancient landslides.The results showed the landslide has a super large-scale,with surface area of 18.2 km2 which includes the underwater part and volume of about 20×108 m3.The ancient landslides can be divided into three zones according its composition and four events according its order.The landslide slided along the high and steep formation interface with huge scale,huge velocity and longer distance,it may be caused by earthquake;analysis of the landform and kinematics of ancient landslides is a good method to help confirming their causes.关键词：landform analysis;energy conservation equation;kinematics;causes;Mahu;earthquake landslide;dammed lake
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发布时间：2024-08-19 - 摘要：Abstract:In order to overcome the limitation of test study and reveal the inner field of gyrating discharge tunnel,the cavity gyrating flow of Gongboxia horizontal gyrating discharge tunnel was simulated using Realizable k-ε turbulence model based on prototype and experiment tests.The simulation results indicated that the contours of radial pressure were some concentric circles with the cavity as the center approximately and presented axial symmetrical distribution.The velocity in gyrating area and cavity area had an obvious character of zoning.Kinetic energy of gyrating area changed from the tangential momentum into the axial kinetic energy along the gyrating discharge tunnel,and the same results can be obtained from the variation of rotation angle.The cavity varied greatly with the axial and radial position in the gyrating discharge tunnel.The radial profiles of turbulent kinetic energy and turbulent dissipation rate indicated that the cavity gyrating flow remarkably enhances the efficiency of energy dissipation due to the strong turbulent water in the interface between water and air and the wall friction caused by centrifugal force.The results showed that the simulation can describe the inner field of the cavity gyrating flow objectively through comparison of hydraulic characteristics obtained by simulating and testing, and provides a reference for the application of the cavity gyrating flow in gyrating discharge tunnel.关键词：cavity gyrating flow;numerical simulation;hydraulic characteristics
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发布时间：2024-08-19 - 摘要：Abstract:In order to test the flow exchange behavior in the channel-floodplain system,a particle tracking code based on Lagrangian particle tracking method (LPTM) was used to further analysis flow interaction between the main channel and floodplains in Truckee River at McCarran,Nevada.The particle trajectory,the residence time distribution (RTD) and the spatial interaction frequencies were examined under two different frequency flood events.Results showed that the lateral flow traveling distance is enhanced by higher discharge.The RTD showed that the higher discharge leads to a shorter mean residence time,and the ratio of particles amount that involved in exchanges between main channel and floodplain is larger in a stronger overbank flow event.The spatial interaction frequencies revealed that the discharge has significant impacts on the longitudinal traveling distance per a single interaction of the released particles.It indicated that the overall exchange is stronger at a higher flow and the local exchange is relatively weaker than in a lower flood event.The LPTM approach can provide a reference for the river modification and restoration.关键词：Truckee River;flood;particle tracking;floodplain;connectivity
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发布时间：2024-08-19 - 摘要：Abstract:The flow in 180° turning pools was studied by a numerical simulation method, and the results showed that the mainstream flowed close to sidewalls, and big size recirculation areas appeared on both sides of the mainstream. This poor flow pattern was adjusted by setting rectifier plates, and the hydraulic characteristics of flow structure were studied. The results showed that the mainstream zone was in the middle of the 180° turning pool, and the velocity attenuation was significant after adding rectifier plates. Recirculation zone sizes and velocity values in the upstream of turning part were similar to those of general pools. For reflux zones of the turning part and the downstream, their sizes were reduced, and velocities were weakened.
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发布时间：2024-08-19 - 摘要：Abstract:The flow-sediment regime entering the lower Yellow River (LYR) has changed significantly since 1986.In order to study this phenomenon,the reach-scale bankfull channel dimensions (bankfull width, depth, area, et al.)of the braided reach were calculated annually during the period from 1986 to 2012,based on the surveyed post-flood profiles at 28 sedimentation sections,using an integrated method which integrates a geometric mean based on the log-transformation with a weighted average based on the spacing between two consecutive sections.The results indicated that the magnitude of each reach-scale bankfull channel dimension responded well to the accumulative effect of incoming flow and sediment conditions during both the flood seasons and non-flood seasons.Empirical relationships for the braided reach were developed between the reach-scale bankfull channel geometry and the previous four-year average integrated incoming discharge-sediment condition.These relationships demonstrated different impacts of discharge and incoming sediment coefficient on the channel geometry with relatively high correlation coefficients between them.关键词：continuous aggradation;continuous degradation;flow and sediment regime;bankfull channel geometry;lower Yellow River(LYR)
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发布时间：2024-08-19 - 摘要：Abstract:The world cultural heritage—Fujian earth building has often affected by the typhoon and extreme weather,and the durability of its structure has decreased continuously.Using statistical methods of soil and water loss and field test,rammed earth erosion loss rule and loss measurement formula were studied,revealing the loss mechanism of rammed earth by wind and rain erosion,rainfall infiltration wall material weakening performance,and wind driven rain hiting the walls,resulting in material particle splash erosion and denudation.And it was proved that the raindrop impact load is the direct motive erosion loss.Combined with the local meteorological data,the rammed earth annual erosion was calculated,which can be used to predict the residual life of the wall,and to provide a adaptive scientific basis for protection of Fujian earth building.关键词：earth building;rammed earth;wind rain erosion;erosion mechanism
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发布时间：2024-08-19 - 摘要：Abstract:Low cycle fatigue behaviors of Q345B steel and smooth welded joint were experimentally investigated. The tests were carried out on a servo-hydraulic machine under fully reversed strain-control at constant strain rate of 0.005 s-1. The cyclic stress response characteristics,strain-life and strain-energy relationships of both base metal and welded joint were obtained and analyzed in the strain regime of 0.3%~0.7%. The results showed that Q345B showed significant cyclic hardening or softening respectively when the strain amplitudes were larger or lower than 0.4%,while welded joint showed obvious cyclic hardening. The low cycle conversion life,fatigue strength and fatigue life of welded joint significantly decreased. The test data were used to derive suitable Coffin-Manson parameters and the strain-life,energy-life relationships were further determined. The increase of cyclic hardening caused by mechanical inhomogeneity was the main reason to the weakening low cycle fatigue properties of welded joint.关键词：smooth welded joint;low cycle fatigue;cyclic hardening;fatigue life
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发布时间：2024-08-19 - 摘要：Abstract:Based on the buckling theory of thin-walled members and the total potentials of cold-formed Z and C purlins whose lateral restraints are ignored,the formulae of rotation and lateral displacement of the purlins were obtained under wind suction on the principle of variation.Considering the nonlinear strain energy generated during flexural-torsional buckling by the stress before buckling,the expression of critical moment of Z and C purlins was obtained on the basis of stationary value of total potential energy.The rotation,lateral displacement and buckling moment were compared with numerical results using shell elements of ANSYS and found to be in excellent agreement with ANSYS.关键词：purlin;linear analysis;torsional restraint;critical moment;cold-formed steel
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发布时间：2024-08-19 - 摘要：Abstract:In order to study earthquake resistance behavior of top and seat angle joint of special-shaped concrete-filled rectangular composite tubular column with steel beam,the low cyclic loading experiment and ANSYS nonlinear finite element analysis on the joints were conducted.The results indicated that the destruction of joints derives from buckling of steel beam flange and yielding of top and seat angle steel,then plastic hinges are formed and a large rotation deformation is generated.The shapes of hysteresis curves of all specimens are full and present inverted “S”,the displacement ductility factors are greater than 2.55,and the energy dissipation capacities of all specimens are good.There is a great influence of top and seat angle thickness and high-strength bolt diameter on the bearing capacity of joints.If the thickness of top and seat angle and the diameter of high-strength bolt are increased,the displacement ductility factors of joints are decreased slightly,but ultimate bearing capacities are obviously enhanced.The stress distributions and the finite element failure characteristics of joints are basically consistent with the test phenomena,and yield bearing capacity and ultimate bearing capacity of the finite element calculations agree well with the experimental results;there is little effect of axial compression ratio on the earthquake resistance behavior of joint.Compared with high-strength bolt,there is a more significant influence of top and seat angle on the stiffness and bearing capacity of joint.关键词：special-shaped concrete-filled rectangular composite tubular column;earthquake resistance behavior;nonlinear finite element analysis;ultimate bearing capacity
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发布时间：2024-08-19 - 摘要：Abstract:To study the Internet public opinion evolution, an analysis method taking the parameters’ increment of the network and the Agent as the study object， which was based on social network analysis (SNA), was proposed. By the quantitative analyses of SNA properties, the general evolution rules of the incident in the Internet public opinion were revealed. The information for decision of guiding the public opinion was provided according to the rule. The method was verified with the records of an incident in Tianya BBS forum and the result showed that the study is practically useful.关键词：Internet public opinion;SNA;public opinion evolution;evolution characteristics
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发布时间：2024-08-19 - 摘要：Abstract:To study the Internet public opinion evolution, an analysis method taking the parameters’ increment of the network and the Agent as the study object， which was based on social network analysis (SNA), was proposed. By the quantitative analyses of SNA properties, the general evolution rules of the incident in the Internet public opinion were revealed. The information for decision of guiding the public opinion was provided according to the rule. The method was verified with the records of an incident in Tianya BBS forum and the result showed that the study is practically useful.关键词：Internet public opinion;SNA;public opinion evolution;evolution characteristics
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发布时间：2024-08-19 - 摘要：Abstract:In order to solve the problem of multiple attribute group decision with multi-granularity uncertain linguistic assessment information,where the information of attribute weights is incomplete, a group decision making method based on projection and dominance degree was proposed. Firstly, the uncertain linguistic evaluation matrices with multi-granularity were transformed to two-tuple decision matrices according to the continuous interval two-tuple ordered weighted harmonic (ITC-OWH) operator. By using projection method, a goal programming model was set up to determine the attribute weights vector of individual decision maker.Then, under every decision makers, integrative attribute dominance degree between pairwise comparisons of arbitrary alternatives was computed, and a group integrative dominance degree matrix was obtained based on integrative dominance degree matrices and expert weight vector.The rank results were determined by integrative dominance degree of alternatives.An example of submarine design scheme selection problem showed the effectiveness and feasibility of the proposed method.关键词：multiple attribute group decision making;multigranularity;uncertain linguistic variable;projection;dominance degree
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发布时间：2024-08-19 - 摘要：Abstract:In order to obtain the robust local feature descriptor, a local feature descriptor based on nonsubsampled contourlet transform (NSCT) domain was proposed, which does not need to estimate the main direction in the construction process. Firstly, the affine invariant region was detected using Hessian-Affine detector and then was normalized. Secondly, the normalized region was decomposed by NSCT to get multiple support regions of different scales and resolutions. Thirdly, the support regions were divided based on intensity orders. Finally, each sub-region was described as a vector and the local feature descriptor was obtained by aggregating the vector of each sub-region. The experimental results showed the good effectiveness of the proposed descriptor for the image with blurring, viewpoint changes, affine changes, linear illumination changes and JPEG compression changes.关键词：feature descriptor;local feature;nonsubsampled contourlet transform;intensity order
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发布时间：2024-08-19 - 摘要：Abstract:In order to improve the transmission performance of traditional least square(LS) and discrete Fourier transform(DFT) algorithm for broadband mobile satellite channel,an improved power judgement-based LS algorithm named PLS and a PLS with zero padding interpolation algorithm named PLS_ZP were proposed. Based on DFT estimation algorithm,PLS algorithm utilized the fading characteristics of broadband mobile satellite channel,got the power threshold by limiting the number of the effective taps and removed the noise outside the taps.PLS_ZP algorithm improved the original interpolation algorithm in frequency domain by means of the principle that zero padding of the time domain is equivalent to interpolation of the frequency domain, then utilized all the estimated pilot frequency information. Theoretical and experiment results showed that channel estimation mean square error(MSE) and bit error rate(BER) of the proposed algorithm are better than traditional algorithms,and the algorithm complexity is lower for hardware implementation.关键词：channel estimation;mobile satellite channel;power judgement;zero padding;interpolation
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发布时间：2024-08-19 - 摘要：Abstract:In TDD-MIMO systems, the antenna correlation has a great impact on the system performance. In order to overcome this problem, a hybrid precoding scheme was proposed. In this scheme, the channel was estimated at the BS by a low complexity channel estimation method. Then, the correlation factor of the channel was calculated to select the proper precoding method. If the correlation factor was bigger than the threshold, the covariance-based precoding was employed. Otherwise, the LR-based precoding was employed. Simulation results showed that the proposed low-complexity precoding scheme can make full use of the characteristic of the two precoding methods in different correlation ranges, and improve the BER performance and capacity. The effectiveness of the proposed scheme was also verified by the simulation.关键词：TDD-MIMO systems;correlation;reciprocity;hybrid precoding transmission
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发布时间：2024-08-19 - 摘要：Abstract:A method of power quality real-time status diagnosis based on cloud model was proposed.The normal cloud model for each power quality index was established based on long-term power quality data of each monitoring point.The anomaly threshold determined by the normal cloud outline was used to diagnose the power quality status in the process of monitoring.This method can accurately identify the abnormal power quality status,and find out the potential issue of abnormal operation on the basis of long-term operation characteristics of the power grid. Practical engineering example proved the validity and practicality of the proposed method.关键词：cloud model;power quality;national standard;real-time status diagnosis;IEC 61850
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发布时间：2024-08-19 - 摘要：Abstract:Aimed at the secondary pollution control of ammonia-containing wastewater and exhaust gas from the chilled ammonia based CO2 capture process,a method was proposed to use waste water partly replacing process water for two stage ammonia washing and to remove the absorbed ammonia by two stage rectification.Referring to the low temperature and low concentration conditions involved in the process,the VLE data of NH3-CO2-H2O system was calculated.On the basis of the VLE curves,mass transfer analysis was made to the simultaneous absorption of NH3 and CO2.The results show that the ammonia pollution control standards of 10 mg/m3 for exhaust gas and 15 mg/L for wastewater both can be satisfied without increasing energy consumption for distillation.关键词：aqueous ammonia based CO;2;capture;ammonia-containing exhaust gas;ammonia-containing wastewater;absorption and rectification;vapor liquid equilibrium
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发布时间：2024-08-19 - 摘要：Abstract:Aimed at the secondary pollution control of ammonia-containing wastewater and exhaust gas from the chilled ammonia based CO2 capture process,a method was proposed to use waste water partly replacing process water for two stage ammonia washing and to remove the absorbed ammonia by two stage rectification.Referring to the low temperature and low concentration conditions involved in the process,the VLE data of NH3-CO2-H2O system was calculated.On the basis of the VLE curves,mass transfer analysis was made to the simultaneous absorption of NH3 and CO2.The results show that the ammonia pollution control standards of 10 mg/m3 for exhaust gas and 15 mg/L for wastewater both can be satisfied without increasing energy consumption for distillation.关键词：aqueous ammonia based CO;2;capture;ammonia-containing exhaust gas;ammonia-containing wastewater;absorption and rectification;vapor liquid equilibrium
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发布时间：2024-08-19 - 摘要：Abstract:A new type of dry gas seal with bi-direction trapezoid grooves used as the containment seal for a pump was introduced and main geometrical parameters of the seal were defined.Based on gas lubrication theory,a numerical simulation model of the flow field between the seal faces of the seal was established.In order to obtain the pressure distribution,gas velocity field,opening force of the gas film,and seal leakage,the Fluent software was used to simulate the gas flow between the faces.The influences of the geometrical parameters,such as groove depth,groove width ratio,groove inlet angle,and groove length ratio on the face opening force and leakage were discussed.The results showed that both the opening force and the leakage increased with the increased of groove depth,width ratio,and length ratio and decreased with the increase of groove inlet angle. The results could provide the basis for design and further investigation of the dry gas seal with bi-direction trapezoid grooves.关键词：trapezoid groove;dry gas seal;flow field;numerical simulation;containment seal
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发布时间：2024-08-19 - 摘要：Abstract:Two reaction systems of carbonthermal reduction of fluorapatite were investigated in the tube furnace with protecting nitrogen,one of which contained 5%Al2O3,and the other didn’t contain any Al2O3.The results showed that the conversion fraction and the conversion rate of fluorapatite with 5%Al2O3 are both higher.The analysis of XRD for the compositions of solid state products is consistent with the analysis of thermodynamics.The products of Al2SiO5,AlPO4 and CaAl2Si2O8 in 5%Al2O3 reaction system cause the amount of liquid phase the increase of and then enhance the carbonthermal reduction.The solid state carbothermal reduction reaction of fluorapatite in the present of SiO2 and Al2O3 belongs to gas-liquid-solid reaction and the reaction process meets the kinetic equation which was derived from the theory of layer growth based on reaction-diffusion.And more, the enhanced effect of adding Al2O3 is more prominent at relative lower temperature or at the initial reaction stage especially.
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发布时间：2024-08-19 - 摘要：Abstract:Response surface methodology(RSM) was applied for optimizing the enhanced coagulation process by preozonation for Taihu lake water.Based on single-factor experiments,three independent variables(ozone dosage,coagulant dosage and residence time) were selected as affecting factors and three dependent variables(chemical oxygen demand(CODMn) removal efficiency,turbidity removal efficiency and operating cost) as responses.An experimental design of three factors and three levels was arranged through Box-Benhnken design (BBD).According to the proposed quadratic models,maximal CODMnand turbidity removal efficiencies and minimal operating costs are obtained at following optimum condition:The ozone dosage,coagulant dosage and residence time are found to be 0.9 mg/L,35 mg/L and 17 min for aluminum sulfate(AS) and 0.9 mg/L,24 mg/L,and 17 min for polymerization aluminum chloride(PAC),respectively.关键词：preozonation;coagulation;Box-Benhnken design;response surface methodology
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发布时间：2024-08-19 - 摘要：Abstract:To improve the bearing capacity of orthogonal variable transmission ratio face gear,the influence of basic parameters of gear pair on strength characteristics was discussed.According to spatial gear meshing theories,differential geometry and design of machinery, the meshing coordinate and the equation of tooth surface were established.The methods for calculating the pressure angle and the principal curvature of variable transmission ratio face gear were acquired.The force analysis in the meshing process was performed.A method to calculate the strength of orthogonal variable transmission ratio face gear pair was established,and then the variation regulation of contact and bending stresses that changed with the basic parameters of the gear pair was derived.The comparison with the result of the transmission test and the theoretical data verified the calculation method.关键词：mechanical strength;stress analysis;variable transmission ratio;face gear;curvature
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发布时间：2024-08-19 - 摘要：Abstract:By using theoretical modeling,simulation and experiment,the static clamping force characteristics was studied in terms of the operation parameter,structural parameter,lubrication conditions,and strength of the wedge type power chuck.The investigation performed showed that friction,especially the friction taking place on the contact surface between the wedge actuator and base jaw,is a great influence on the magnitude of static clamping force.Before the twice clamping a workpiece using a chuck,it is suggested to operate the chuck with thrice virtual travel to reduce the deterioration of lubrication condition.The chuck structure which has a higher clamping efficiency will have a fewer static clamping force loss caused by the enlargement of friction.With comprehensive consideration of magnitude and stability of static clamping force,the wedge angle of chuck should be selected from 10° to 20°.The maximum static clamping force is limited by the strength of chuck,especially by the strength of wedge type teeth of base jaw.关键词：wedge type power chuck;static clamping force;friction;stability of clamping force
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发布时间：2024-08-19 - 摘要：Abstract:A real time estimation model of contour error and the approach of error compensation were developed to improve the machine precision of complex space contour curve.Only information on the tool position and the reference input positions defining the desired curve were employed to model contour error instead of searching the whole curve for saving time.The output values of the next instant,which was estimated by Z transformation based on the servo control system of machine tool,were applied to estimate the contour error using the above-mentioned method.After that,the compensation terms of each axis were generated using Taylor series expansion in the form of one-or two-order expression and an estimation of the contour error at next time.These were then added to the reference position inputs for the next instant in order to reduce the contour error during the machining process.The error compensation model of space line,cylindrical spiral and B-Spline were simulated,and “S” shape B-Spline curve was experimented.The results showed that the proposed solution can reduce contour error effectively.关键词：space curve;contour error;local estimation model;Taylor series;error compensation
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发布时间：2024-08-19 - 摘要：Abstract:In order to solve the low detection accuracy of pitting corrosion in field signature method(FSM),a mathematical model of subdivided resistor network was proposed to assess pitting corrosion by the analysis of the relationship between pitting corrosion,main and assistant voltages based on the influence on current distribution of pitting corrosion.Since different pitting corrosion with different positions,different depths or different diameters have certain different influences on main and secondary voltages,main and secondary voltages can be introduced to assess pitting corrosion.The essence of this method was to introduce a number of known parameters to calculate pitting corrosion which contains multiple parameters.Theoretical analysis and experiment results showed that this method can greatly improve the detection accuracy of pitting corrosion in FSM, and FSM is developed.
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发布时间：2024-08-19
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