最新刊期
卷 46 ， 期 2 ， 2014
- 摘要：Abstract:Based on RNG κ-ε two-equation model, the volume of fraction method for free surface calculation and dynamic mesh model,the steel arch-gate closing process was simulated successfully at middle-gate chamber with abrupt lateral expansion and bottom offset aerator outlet in spillway tunnel.The variation regular of hydraulic characteristics including flow pattern,cavity length and wall pressure were mainly researched in the Ogee curve section of spillway tunnel assisted by experiment method.The results showed that the worse flow regimes including bottom cavity reflux and lateral wall water wing would gradually weaken and disappear finally.The cavity length increases linearly.If the gate opening is large than 1/2,there are higher pressure peak value and pressure gradient in impacted scope.However,if the gate opening is less than 1/2,the pressure peak would gradually decrease and disappear with the arch-gate closing.Besides,the computational results agreed well with experimental results to verify the validity of numerical method.关键词：RNG;κ;-;ε;two-equation model;dynamic mesh model;dynamic layer updating method;abrupt lateral enlargement and vertical drop;cavity;pressure
- 2256
- |
- 4
- |
- 5
发布时间：2023-11-14 - 摘要：Abstract:A new type of flexible steel rock-shed was proposed to protect the Shaping bridge,which is situated at the exit of the Shaping tunnel on the Du-Wen highway and across the Minjiang River,from the rockfall.The rock-shed consists of steel arch ring,steel pipe,double-layer flexible protective nets,the metallic dampers on the supporting structure of arch ring and rubber cushion.An optimum structure was obtained through calculation and simulation of the dynamic finite element to make sure that the force supported by arch ring is less than the punching strength which supported by the T-beam flange plate under a given impact energy.On the basis of it,a new type of flexible protective shed-tunnel was designed.The application results showed that the technology has played an active role to ensure the Du-Wen highway is open to traffic successfully.关键词：Shaping bridge;rockfall hazards;energy dissipation;flexible steel rock-shed
- 2223
- |
- 0
- |
- 4
发布时间：2023-11-14 - 摘要：Abstract:The wide gradual reach is a common form of natural rivers because of the impacts of flow and sediment conditions, and man-made projects.Based on the flood process and erosion and deposition of hydrological observational cross section in a gradual width river, the hydrodynamic characteristics was simulated and analyzed by means of a two-dimensional flow model. The comparison between observation and simulation showed that the intensities of increase and decrease of flood depend on the value and duration of flood process, and the velocity distribution at any cross section often change with the variation of asymmetry river wide, which affects the bed deformation in the whole reach considering the effect of sediment critical incipient velocity.关键词：gradual channel;embankment project;flood process;channel evolution
- 2292
- |
- 0
- |
- 5
发布时间：2023-11-14 - 摘要：Abstract:Connotation of water-saving irrigation was elaborated, and the factors of water-efficient irrigation developing were analyzed.Three items of sub-indices of engineering,agriculture and management water-saving were adopted. Firstly, main ingredients with thirty-three indices of the sub-indices were extracted to reduce the number of evaluation indices and establish index system of regional water-saving irrigation developing level evaluation model.Secondly,combination weights were formed from both of objective weight determined by entropy weight method and subjective weight determined by analytic hierarchy process method.Finally,the set pair analysis was selected for analysis.The evaluations showed that two regions are of general,seven regions are of relatively poor,twelve regions are of poor,and the rations of them in all regions are 9%,33% and 58%,respectively.The results indicated that water-efficient irrigation developing level of every region is still lower,and the overall of Sichuan province is evaluated with level of poor.Therefore,the model has a strong practicality to evaluate the water-saving irrigation development in different regions.关键词：water-saving irrigation developing level;evaluation model set pair analysis;combination weights;Sichuan province
- 2190
- |
- 6
- |
- 3
发布时间：2023-11-14 - 摘要：Abstract:The liquid cross-flow has important influence on bubble formation and aeration is important to flow field characteristics in plug-flow aeration tank.A 3D acoustic Doppler velocimeter (ADV) was used to measure the flow field in an aeration tank of large scale and flow field characteristics were analyzed for the further study of flow field characteristics in aeration tank.The results showed that flow velocity distribution had characteristics of medial small and lateral large after the flow passed bend and cross flow existed.After the flow entered straight, the velocity distribution constantly adjusted and difference between medial and lateral water flow velocity decreased and the deeper shallow water was,the faster flow rate adjusted.Compared with clear water when the aeration plate was open,velocity near the surface decreased and that deep below the surface increased at the aeration plate upstream section,but velocity downstream was opposite. Turbulence intensity after aeration was much larger than that before aeration at the aeration plate downstream section.关键词：aeration tank;Orbal oxidation ditch;acoustic Doppler velocimeter;flow field;turbulence intensity
- 2297
- |
- 0
- |
- 4
发布时间：2023-11-14 - 摘要：Abstract:A new multi-objective optimization scheme based on surrogate modeling was proposed.Taking the Dapoling catchment as a case study, the response relationship between the parameter of Xin’anjiang model and different objectives was constructed based on multivariate adaptive regression splines,to estimate the Pareto sets or non-dominant solutions.Four objective functions of overall water balance error,root mean square error,relative error of peak flows,and low flows were used to optimize model parameters,and four evaluation criteria of Nash-Sutcliffe efficiency coefficient (NSE),relative error of peak flow and runoff volume (REPF and RERV),and time error of peak flow (TEPF) were selected to quantify the goodness-of-fit of observations against simulation model calculated values.In addition,four uncertainty criteria were applied to assess the hydrological uncertainty ranges with the Pareto solutions for ten flood events.Results demonstrated that the surrogate-modeling based method increases the feasibility of applying parameter optimization to computationally intensive simulation models via reducing the number of simulation runs.Simultaneously,uncertainty analysis results also revealed that the proposed method based on surrogate modeling is high efficiency and easy to operate.Thereby,the method is feasible for practical operations for complex simulation models in model calibration and uncertainty analysis.关键词：Xin’anjiang model;parameter calibration;multi-objective optimization;surrogate modeling;uncertainty analysis
- 2895
- |
- 2
- |
- 9
发布时间：2023-11-14 - 摘要：Abstract:To discuss the difference of mechanical behavior of marble buried deeply in high stress caused by different stress paths and reveal the influence of unloading on rocks’mechanical properties,a series of triaxial tests under loading and unloading conditions were carried out on the marble samples from the tunnel of Jinping Secondary Hydropower Project.The results showed that when marble is broken,the vertical and horizontal strain under unloading condition are smaller than that under triaxial compression tests,and the brittle features of rocks are more conspicuous under unloading condition.The secant modulus and Poisson ratio have good linear relationship with confining pressure in different stress paths.The secant modulus under unloading condition is smaller than that under triaxial compression test,but Poisson ratio is on the contrary.The failure face of marble is more rough under unloading condition,and the cohesion cdecreases 36.4% while the internal friction angle φincreases 35.4% relatively with the loading tests.The shear strength in unloading condition is lower than that in loading condition when normal stress is below 45 MPa,and damage occurs more.These results showed that the influence of unloading should be considered fully during the excavation of deep underground engineering.关键词：deeply buried marble;unloading triaxial test;strength property;deformation property
- 2429
- |
- 4
- |
- 5
发布时间：2023-11-14 - 摘要：Abstract:The strength and deformation characteristics of coarse-grained soils and reinforced coarse-grained soils were studied based on large-scale triaxial shearing tests.Experimental results showed that the stress-strain relationships of coarse-grained soils and reinforced coarse-grained soils are similar under different confining pressures,both showing strain hardening.Reinforcement effect is not obvious when the axial strain is small,and the reinforcement effect gradually starts to work with the increment of axial strain.Reinforced coarse grained soil has a larger cohesion c,while the inner friction angel φnearly keeps changeless.And it’s axial strain decreases, volumetric strain increases.Applicability analysis of Duncan-Chang model showed that Duncan-Chang model can reflect the tangent elastic moduli of reinforced coarse-grained soils,but can’t reflect its deformation well.A function was put forward to fit axial strain and lateral strain, and a volumetric strain function was established for coarse-grained soils and reinforced coarse-grained soils,and then the volumetric strain of the soil-sample was predicted.关键词：reinforced coarse-grained soil;large scale triaxial test;volumetric strain
- 2570
- |
- 2
- |
- 8
发布时间：2023-11-14 - 摘要：Abstract:A novel total variational model with strict convexity was proposed to solve the problem that the‘step-casing effect’ and image blurring are always with the existing variational models for multiplicative noise removal.Firstly,the fidelity term of the modified model was derived by applying the maximum likelihood estimate method and the Bayesian formulation.Then,the new total variational model was developed by combining the fidelity term,a fitting term and a hybrid measurement.An alternating minimization algorithm was used to find out the minimizer of such an objective function and proved the convergence for the variational problem.Finally,the numerical experiments showed that the texture details in the denoised images are kept and the ‘step-casing effect’ is suppressed.关键词：image denosing;multiplicative noise;variational approach;convex function
- 3217
- |
- 6
- |
- 2
发布时间：2023-11-14 - 摘要：Abstract:Based on image force field transformation, a novel algorithm was proposed to track the hand during hand over face occlusion in sign language video.First, the frames with a hand occluding the face and those with only a face were transformed to force field images.Then the force field images were partitioned into sub-images and the histograms of each sub-image were calculated.For each sub-image, the histogram of frame with only a face was subtracted from the frame with a hand occluding the face to get the difference histogram.Finally, for each sub-image the difference histogram was compared to threshold to get the position of the hand.Experimental results showed that the proposed algorithm is capable of real-time tracking of hand.关键词：hand detection;sign language video;force field transformation;histogram
- 2221
- |
- 2
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:In order to overcome the limitation of Bag of Features (BoF),which ignores the space time relationship of local features in human action recognition,a space time coding (STC) method for local feature was proposed by involving the space time locations of local features into feature coding phase to directly model their space time relationship.First,the local features were projected into a sub space-time-volume (sub-STV) to obtain their space time coordinates.Second,their appearance information and space time locations were encoded simultaneously.After that,the statistics results generated by feature pooling upon these codes were utilized for action classification.To achieve better performance,the multi-scale STC and locality-constrained STC were also proposed.In action classification,a locality-constrained block sparse representation classifier (LBSRC) was adopted to improve the action recognition accuracy.The experimental results on KTH,Weizmann,and UCF sports benchmark datasets showed that the proposed methods can effectively represent the space time relationship of local features and improve the action recognition accuracy.关键词：pattern recognition;action recognition;bag of features;sparse representation
- 3180
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:In order to revoke private key leaks or malicious users in a signcryption system,a new revocable identity-based signcryption scheme was proposed.In this scheme,the master key was randomly divided into two parts,which were used to construct the initial key and generate updated key,respectively.Furthermore,they were used to generate (designcryption) signcryption key randomly,thus the proposed scheme can revoke users and resist key compromise attack.In the standard model,it was shown that the new scheme has IND-CCA2 security under the hardness of DBDH problem and EUF-CMA security under the hardness of CDH problem.关键词：revocation;signcryption;key compromise;standard model
- 2623
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The traditional techniques generally do not resolve the problem of low efficiency caused by the count of failed tests due to different faults.Besides,programmers are difficult to finally fix the fault according to the suspiciousness of a program element which lacks program context.A program spectrum concept lattice-based software fault localization (PSCL-SFL) technique was proposed.Firstly,program spectra were abstracted according to test history,and then program spectrum concept lattice was constructed,so the generalization or specialization of program elements and tests could be hierarchically showed.Secondly,a novel suspiciousness computation was defined by PSCL-SFL technique.Finally,based on wasted effort metric,the experiment on a real program Tetris showed the effective of PSCL-SFL technique.关键词：program spectrum;fault localization;concept lattice;suspiciousness
- 2853
- |
- 4
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Existing approaches for service behavioral adaptation often only focus on eliminating behavioral incompatibility between services and ignore user requirements,thus it is required to verify whether the adaptor-based service composition satisfies user requirements.This makes the process of adaptor-based service composition complex and inefficient. To solve this problem,a requirement driven approach for service behavioral adaptation was presented by considering user requirements in the process of adaptor generation.The syntax and semantics of the requirement model were also proposed.It was proved that the adaptor generated by utilizing the proposed approach not only eliminates behavioral incompatibility between services, but also makes the adaptor-based service composition satisfy temporal properties given by user requirements without performing verifications.A case analysis indicated the feasibility and validity of the proposed approach.关键词：Web service;FSM model;behavioral model;adaptor;user requirement
- 2722
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:Existing high-order co-clustering algorithm just can be suitable for analyzing star-structure high-order heterogeneous data.In order to analyze net-structure high-order heterogeneous data,a high-order co-clustering algorithm based on graph partitioning was proposed.The problem of high-order co-clustering was converted to optimal problem of graph partitioning of minimum normal cut.In order to reduce computational complexity,the optimal problem was converted to semi-definite problem.Experimental studies showed that the qualities of clustering results of GPHCC are superior five pair-wise coclustering algorithms and five high-order co-clustering algorithms.关键词：net-structure;high-order heterogeneous data;co-clustering;spectral clustering
- 2411
- |
- 2
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:To solve the problem that virtual backbone networks (VBN) based on UDG model can’t improve the tactical capability and efficiency of data link,a distributed algorithm called DBCDS for constructing VBN based on DGB model was put forward.DBCDS algorithm consisted of three steps.In neighbor discovery step,each node got the information within its 2-hop neighborhood by transmitting and receiving HELLO messages.In step two,a distributed idea was employed to construct a minimum dominating set (MDS).Finally,some optimal nodes were selected to interconnect MIS,and thus formed a CDS.The theoretical analysis showed that the message complexity of DBCDS was O(n),the time complexity was O(Δ) at most, and the approximation factor was 8.Simulation result confirmed the validity of DBCDS algorithm.The comparison with classical TWLZD algorithm showed that DBCDS had lower message and time overhead,which means DBCDS may have some application prospect for the data link network of wide battlefield.关键词：alien platform data link;distributed;DGB model;virtual backbone network
- 1998
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Most of the traditional radio models are invalid due to the special propagation environment on lunar.A novel path loss prediction method for lunar surface was proposed. Firstly,a theoretical segment model according to communication distance was established and three propagation scenarios were analyzed. Then the multiple isolated obstacles on propagating path were considered, which would not only lead to an additional transmission loss but also affect the segment parameters. The present method was applied on a real lunar surface scenario provided by National Aeronautics and Space Administration (NASA). The simulation results showed that the prediction results are very close to measurements by Apollo project. This segment prediction model could be very useful on system parameters design and performance analysis of lunar communication system.关键词：propagation loss;prediction model;lunar surface;Bremmer series
- 2843
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:A multi-channel cognitive radio model was proposed to guarantee the communication quality of primary user (PU) and improve the spectrum utilization of secondary user (SU). This model was implemented through cooperative detection between SUs and cooperative communication between SU and PU. When PU’s presence was detected by SU’s cooperative detection, PU’s data was relayed through SU’s cooperative communication in half a frame, and then SU’s data was transmitted by itself in the left frame. While PU’s communication quality was guaranteed, SU’s throughput was maximized through jointly allocating SU and power. Simulation results showed that compared with the traditional non-cooperative model, both the throughputs of PU and SU are improved in the proposed cooperative model.关键词：cognitive radio;cooperative communication;throughput;statistics;signal interference
- 2362
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:In order to detect hypernasal automatically for cleft palate patients, based on Shannon energy and Mel frequency cepstrum coefficient acoustic features and by combining with Gaussian mixture model classifier, an automatic hypernasal detection algorithm was proposed. The experiment results showed that the presented method achieved a good performance on the detection of four levels of hypernasal, such as normal, low-level, moderate-level and high-level. The average classification accuracies for four levels of hypernasal were over 79%. Moreover, the correct recognition accuracy using energy plus Mel frequency cepstrum coefficient feature set reached up to 85%. The classification of hypernasal levels has important clinical applications.关键词：cleft palate speech;hypernasality;Shannon energy;Mel frequency cepstrum coefficient;Gaussian mixture model classifier
- 2539
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:A joint optimization algorithm which combines M-QAM with HARQ protocol is proposed for the multi-branch two-top cooperation diversity system to minimize the symbol error rate (SER) and maximize the throughput. Using moment generating function (MGF), the probability density function of SNR among relay nodes and the destination node were calculated, and the formulas of the SER for M-QAM were derived in non-cooperative and cooperative HARQ protocols over Nakagami-m fading channels. Then, by utilizing the state transition probability of relay, the throughput in closed-form in cooperative HARQ protocols was derived. The simulation results showed that the decrease of modulation order Mcould lead to the decrease of the SER, and cooperative HARQ protocols by MGF could obtain lower SER and better throughput compared with non-cooperative HARQ protocols. In view of M-QAM with HARQ protocol, the increment of relay could lead to the increment of system throughput and the decrement of the SER, and then the performance of System is improved.关键词：Nakagami-;m;fading channel;moment generating function;hybrid automatic repeat request;multiple quadrature amplitude modulation
- 2222
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Aiming at rotor speed identification of bearingless induction motor, a novel speed-sensorless vector control scheme of bearingless induction motor based on reactive power model reference adaptive system (MRAS) of torque winding was proposed. Using the instantaneous reactive power calculated from back-electromotive force multiplied by the stator current as the adjustable model, and establishing the relationships between the speed and the reactive power of torque windings, the presented method eliminated the integration process and the effect of stator resistance in traditional MRAS method, and then realized the on-line rotor speed identification.Simulation results showed that the rotor speed of bearingless induction motor can be precisely inspected in low and high speed operation with load disturbances and the stable sensorless suspension operation can be achieved with good dynamic and static performance by using the proposed method.关键词：bearingless induction motor;reactive power;MRAS;speed-sensorless
- 2055
- |
- 8
- |
- 2
发布时间：2023-11-14 - 摘要：Abstract:According to the characteristics of randomness and intermittent of wind power,a multipoint DC voltage adaptive droop control strategy was proposed for the interconnection of wind farms by VSC-MTDC. Under this control strategy, all converters which have power regulation ability would share the task of stable dc voltage. The converter which has already operated closely to the rating would share little unbalanced wind power, meanwhile the converter which has much available headroom would share more unbalanced wind power, thus avoiding the possible overloading which may occur with fixed value of power-voltage droop. Finally, simulation was processed with PSCAD/EMTDC. The simulation results showed that the proposed control which needn’t communication, is suitable for interconnection by VSC-MTDC of wind farms whose flow changes frequently.关键词：wind farms;VSC-MTDC;adaptive droop;multipoint DC voltage control
- 2675
- |
- 0
- |
- 9
发布时间：2023-11-14 - 摘要：Abstract:Oil contaminants of the hydraulic system in the gas drilling process were analyzed and a dynamic equilibrium equation of pollutants and pollutant control equations were established.According to pollution control equation,hydraulic system filter device optimization measures were proposed to further improve the design and preferred filter programs,and the main design parameters of the new back oil filter were determined.By builting a downstream particle concentration equation of the back oil filter pollutants,and calculating downstream particle concentration of pollutants to the back oil filter and non-return oil filter of the hydraulic system,it was shownd that when installing a new oil return filter,the filter of speed obviously improved,and after a certain time,the downstream particle concentration of pollutants decreased significantly.关键词：hydraulic system;pollutants;control equations;hydraulic oil;gas drilling;filtering device
- 1895
- |
- 8
- |
- 2
发布时间：2023-11-14 - 摘要：Abstract:In order to overcome the shortcomings of the existing swing check valves that generate noise and are easy to be damaged by impact when they are subjected to high reverse pressure and high flow speed,a new shuttle-type check valve was designed.The basic structure and the work principle of this new check valve were introduced.Moreover,the characteristics of the turbulent flow in the check valve and the governing equations based on Reynolds average method were analyzed.The operation process of the shuttle-type check valve was then simulated using the standard k-ε model.Further more,through several ways including opening discharge hole on the bearing,reducing sudden change of the diameter of the valve body,and setting curved outer surface on the core,a structural optimization algorithm that aims to minimize the pressure drop was proposed.Numerical simulation results showed that the pressure drop in the optimized structure can be reduced by 21%.关键词：shuttle-type check valve;computational fluid dynamics;digital simulation;optimization design
- 2633
- |
- 2
- |
- 2
发布时间：2023-11-14 - 摘要：Abstract:Based on the analysis of working principle of half toroidal CVT,and guided by Hertz contact theory,the contact stress calculation formula of half toroidal CVT was established. Taking a company’s prototype for example,the change laws and influencing factors of the contact stress were discussed.Studies showed that in the case of constant axial force, the contact pressure and stress are larger and relate to the location of the contact point,the contact position is closer to the axis of the cone,the contact ellipse’s major axis is longer,and the contact ellipse’s minor axis is smaller.The contact stress decreases with the increases of torus radius,cavity radius,and half cone angle.The contact stress have high sensitivity with cavity radius,and low sensitivity with torus radius and half cone angle.If the contact type of the cone disk and the roller is line contact,contact stress can be reduced significantly.The research results can provide theoretical reference for design of half toroidal CVT.关键词：half toroidal traction CVT;contact stress;contact eclipse;Hertz contact theory
- 2658
- |
- 2
- |
- 3
发布时间：2023-11-14 - 摘要：Abstract:The friction and wear performances of pure carbon and metal-impregnated carbon against a contact wire at a high speed with electric current were investigated using a block-on-ring friction tester.Using the correlation coefficient theory,the correlation between the vibration acceleration and arc discharge energy was analyzed quantificationally.It was found that there was an obvious correlation between the vibration acceleration and arc discharge energy.Test results showed that the friction coefficients decreased with the increase of vibration acceleration at a high speed with electric current. However,the wear rates of two materials increased with the increase of vibration acceleration.The wear resistance of the metal-impregnated carbon was better than that of the pure carbon.Arc erosion wear of the two materials was aggravated gradually with increasing vibration.The arc erosion mechanism of the metal-impregnated carbon was attributed to layered spalling.Erosion pit and thermal stress cracking were the main arc erosion mechanism of the pure carbon strip.The conductivity of the pure carbon strip was super to that of metal-impregnated carbon under the condition of high sliding speeds with electric current.关键词：friction and wear;vibrations;pure carbon strip;metal-impregnated carbon strip
- 1844
- |
- 2
- |
- 7
发布时间：2023-11-14 - 摘要：Abstract:Dimanganese trioxide (Mn2O3) was prepared by thermal decomposition of manganese sulfate (MnSO4).Decomposition gas released during the Mn2O3 preparation was used to leach pyrolusite ore.The thermal decomposition of MnSO4showed that 850 ℃ was the best temperature for Mn2O3preparation.Characterization results with XRD and FTIR showed that the decomposition product at 850 ℃ was single phase cubic Mn2O3 with manganese content of 68.93%.SO2and SO3 were both observed in the decomposition gas with mole ratio of about 7, indicating the majority of SO2in the decomposition gas.The extraction experiment showed that the extraction of pyrolusite using decomposition gas was entirely feasible.At 60 ℃ and with 0.1 mol/L initial H2SO4,the SOx absorption efficiency and Mn extraction rate reached separately 99.73% and 94.37%.The presented technology cauld only avoid the wastewater problem which always involves in liquid-phase methods,but also realize the simultaneous resource recovery of decomposition gas and low-grade pyrolusite.关键词：Mn;2;O;3;MnSO;4;thermal decomposition gas;pyrolusite;resource recovery
- 1867
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:A pre-production-scale investigation was accomplished to the combined “anaerobic digestion-anoxia-aerobic-constructed wetland”system.The mechanism of anaerobic filters was investigated through the tracer study and mass balance calculation,the CODCr removal efficiencies of anaerobic filter was analyzed, and the effect of hydraulic retention time (HRT) on the efficiency and operational characteristics of the large height-diameter ratio anaerobic filter reactor were evaluated.The results revealed that the anaerobic reactor started successfully after 65 days at medium-low temperature.During the stable running period,when the hydraulic retention time (HRT) was 72 h,the removal rate of COD(Cr) was remained about 37.8%.The combined process which consisted of aerobic digestion-anoxic regulation-waterfall aeration contact oxidation-vegetated constructed wetland to deal with decentralized domestic sewage could achieve good removal effect,the average concentration of the effluent were 39.3 mg/L,the average removal rate in turn were 86.2%,which reached the class A emission standard in the“urban sewage treatment plant pollutant discharge standard”(GB18918—2002).关键词：anaerobic treatment;large height-diameter ratio;anaerobic filter;domestic wastewater
- 1755
- |
- 0
- |
- 1
发布时间：2023-11-14 - 摘要：Abstract:By using the phase composition analysis,differential scanning calorimetry (DSC)/thermogravimetric (TG) and SEM,the phase composition,pyrolysis characteristics and microstructure changes of recycled gypsum and its mechanisms were studied to reveal the differences among recycled gypsum,natural gypsum and plaster of paris.The results showed that the phase composition,pyrolysis characteristics and microstructure of recycled gypsum had changed.CaSO4·1/2H2O in the R-P reduced approximately 3.5%,and the first and second dehydration temperature dropped 8 ℃ and 6 ℃,respectively.The recycled gypsum crystal became irregularity,had uneven distribution of grain,and the crystal cracks and porosity also increased.The analysis showed that the reduction of CaSO4·1/2H2O in R-P is due to the decrease of the content of CaSO4·1/2H2O and uneven particle size distribution in the RG.And the main reason of the great difference of pyrolysis characteristics between natural and recycled gypsum is that the crystallization water dehydration enthalpy decreases and the particle size reduces.关键词：recycled gypsum;pyrolysis characteristics;phase composition;microstructure;mechanism
- 1845
- |
- 0
- |
- 10
发布时间：2023-11-14 - 摘要：Abstract:A group of S45C medium carbon steel specimen was nitrided by plasma nitriding using a mixture of 40% N2-60% H2.The processes were carried out at 500 ℃ for three different time durations of 8,20 and 48 hours.The effect of case depth on fatigue performance of S45C was investigated.The thickness of compound layer for these three time durations were 6 μm,8 μm,12 μm,respectively. Plasma nitriding treatment enhanced the surface hardness and the surface compressive residual stress.The compound layer was composed of the γ-Fe4N phase.Rotating bending fatigue test showed that plasma nitriding treatment increased the fatigue strength of S45C by 190% with respect to the untreated specimen because of the increase of the case depth and the expansion of compressive residual stress in the case depth.The stress intensity factor calculated from the facet area was independent of the number of cycles to failure and was found as at 3.6 MPa·m1/2.These fish-eye cracks were originated from inclusions in the case depth，and were calcium oxide,aluminum oxide and manganese sulfide.关键词：plasma nitriding;fatigue;X-ray diffraction;stress intensity factor
- 2296
- |
- 6
- |
- 3
发布时间：2023-11-14 - 摘要：Abstract:Rotating bending (50 Hz)fatigue tests were performed at room temperature,200 ℃ and 350 ℃,respectively,to evaluate the influence of temperature on the fatigue resistance and fatigue crack growth rates of TC17 alloy.Variation of sample deflection was used to analyze the evolution of crack growth rate at different temperatures.By using scanning electron microscopy,the crack initiation and propagation behavior were examined.The results showed that the portion of fatigue life attributed to crack initiation was more than 90% in the high-cycle regime in this investigation.Not only the crack initiation but also crack propagation was promoted at elevated temperature.关键词：titanium alloy;high temperature fatigue;S;-;N;curve;crack growth
- 2659
- |
- 18
- |
- 5
发布时间：2023-11-14
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0