最新刊期
卷 38 ， 期 2 ， 2006
- 摘要：Abstract:Channel confluences are common in natural rivers and many hydraulic engineering projects.The flow structure at confluences become very complex because of the interaction between tributary and Main River. The experiments were performed in a combined flume with 30° angle between main and tributary flume located at Sichuan University. The velocity was measured using a three component Acoustic Doppler Velocimeter (ADV) over a grid defined throughout the junction region. Based on the analysis of the velocity at confluence, the distinctive characteristics of a channel confluence flow may be divided into several zones including a zone of separation immediately downstream of the junction branch channel, a maximum and minimum velocity region at upstream and downstream in the confluent channel, and a shear plane developed between the two combining flows at downstream of confluent channel. In addition, there are different direction secondary circulations at the high and low velocity zone.关键词：confluent river;flow structure;Acoustic Doppler Velocimetry
- 1728
- |
- 6
- |
- 19
发布时间：2023-11-28 - 摘要：Abstract:Support Vector Machine (SVM) as a machine learning method is based on solid theory foundation of Statistical Learning Theory, and focuses on small samples. It has good generalization and has received good applications. The theory and characteristics of SVM are expatiated, and then the application of SVM to a long term prediction annual electricity consumption from 1978 to 1998 of Sichuan province is proposed. Immune evolutionary algorithm (IEA) that is an efficient random global optimization technique is used to optimize the kernel parameter of SVM. The design idea and characteristics of IEA-SVM are introduced. The results show that the accuracy is higher than those based on partial least square (PLS). It proves that the IEA-SVM method is very effective by the theoretical analysis and practical application.关键词：support vector machine;immune evolutionary;parameter optimization;prediction of annual electricity consumption
- 1466
- |
- 6
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:Khadori power station in Georgia with a transbasin diversion system take water from two rivers. The two branch tunnels have different length, which confluence into main tunnel. This paper analyses characteristics of the diversion system, such as different water level of upstream, different length of branch tunnel and complex flow at branch tunnel junction. Numerical simulation is set up by the method of characteristics. It solves the highest and the lowest water level of fluctuating in surge chamber at the most disadvantagous conditions. The results of numerical simulation are similar to which of model tests.The numerical simulation model set up in this paper is conducive to develop power station with the transbasin diversion system.关键词：transbasin;transient;diversion system;Khadori power station
- 1530
- |
- 2
- |
- 3
发布时间：2023-11-28 - 摘要：Abstract:Aimed at densely fractured rock masses, the paper sets up the saturated unsaturated seepage flow mathematic model for atomized rain infiltration using equivalent continuum theory. Atomized rain strengths are selected according to the model experiment. Combined with natural rainfall, numerical analysis on atomized rain infiltration in fractured rock slope is conduced. The results show that pore water pressure increases quickly and transient saturated zone which is disadvantagous to the slope stability is easily formed in great storm zone, relative to thin frog zone and natural rainfall zone. So slope surface protection and inside bailing within great storm zone should be emphasised.关键词：seepage flow;atomized rain;fractured rock masses;transient saturated zone
- 1754
- |
- 4
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:The strain stress curve and the J -integral were carried out using MTS machine for 00Cr17Ni14Mo2. Energy release rates G and the J -integral were evaluated based on the virtual crack closure technique and the method for Rice's J -integral. We also get G and J -integral by using the software of Ansys with the same force. Then comparing the solution of caculation with the value of experimental, which shows that they are in good agreement.关键词：00Cr17Ni14Mo2;J -integral;energy release rate;virtual crack close technique;finite element method
- 1807
- |
- 8
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:Peak strength, mechanical behavior, and pattern of shear band (SB) of anisotropic jointed rock specimen were modeled by FLAC. The failure criterion of intact rock was a composite Mohr-Coulomb criterion with tension cut-off and the post-peak constitutive relation was linear strain-softening. Joint was treated as quadrate elements of ideal plastic material beyond peak strength. Intact rock without joint has a higher peak strength. Shear strain of jointed rock is concentrated into joint or new generated SBs. Peak strength of jointed rock depends on the joint inclination (JI). The new SBs are origanated from the two ends of joint and propagate along their inherent directions. For moderate JI, lower strength and the behavior of jointed rock specimen are mainly governed by joint. For lower or higher JI, the peak strength of jointed rock specimen is higher and the strain softening behavior is apparent. For lower JI, slip along SB has a greater contribution to the axial strain of jointed rock, leading to steeper post peak stress strain curve. For higher JI, the slope of post-peak stress-strain curve is not dependent on JI since JI does not influence the thickness and the inclination of SB.关键词：single jointed rock specimen;joint inclination;stress-strain curve;peak strength;shear band;strain-softening
- 1630
- |
- 14
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:In order to study the relation of the period-doubling bifurcation and the Hopf bifurcation,the period-doubling bifurcation problems of a vibro-impact system is investigated when the periodical solutions lose its stability. First, the process of establishing the Poincaré map of the 1-1 motion of this system is provided. Second, the probability of the period-doubling bifurcation is analysed according to the Eigenvalue cross the unit circle. Finally, numerical simulation results demonstrate it. The typical period-doubling bifurcation is found. After the Hopf bifurcation in a non-resonance case, the non typical period doubling bifurcations occur while one single parameter varies crossing the resonance neighborhood. The number of orbits of the period doubling bifurcation cascade depends on the order of strong (weak) resonance.关键词：vibro-impact system;period-doubling bifurcation;strong (weak) resonance;Hopf bifurcation
- 2190
- |
- 4
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:Because of too small values(from 10-5 to 10-6)of flexibility matrix, it is prone to influencing from noise. Flexibility matrix elements show whole structural information, its maximal changes may not coincide with damage location. Hence damage detection by flexibility matrix still exists a good many limitation. Virtual flexibility matrix is built from modal test. The relation equation between virtual flexibility matrix and local stiffness change is completed by virtual forces. Damage location and severity are simultaneously obtained by generalized strain changes. It showed that the method is feasible through dynamic model test of simply supported beam.关键词：Virtual flexibility matrix;Impulse vibration test;Crack damage;Identification
- 2315
- |
- 6
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:In this paper, the non-linear dynamic stability of viscoelastic transmission belt with time dependent velocities is investigated. Based on the constitutive description of Kelvin viscoelastic material and the motion equation of the axially moving belt, the nonlinear dynamic model that dominates the transverse vibration of the viscoelastic transmission belt is established.Then the non linear dynamic stability is studied by using multiple scale method. It is found that: 1) for fluctuation frequency away from zero or two times the natural frequency, the amplitudes of vibration are bounded and the phases are the logarithm functions in time. The non-linear effects become important for velocities close to critical velocity. 2) for fluctuation frequencies close to zero, the amplitudes of vibration are bounded. 3) for fluctuation frequencies close to two times the natural frequency, two non-trivial solutions bifurcate from the trivial steady-state solution. There are two supercritical pitchfork bifurcation points. Passing through the first bifurcation point, the trivial solution looses stability and a non-trivial solution is obtained.If frequency is increased and pass through the second bifurcation point, the trivial solution is again stale and non trivial solutions disappear.关键词：transmission belt;viscoelasticity;non-linear dynamic stability;bifurcation
- 1529
- |
- 16
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:Based on the two-film mass transfer theory, a model for SO2 absorption in flue gas with landfill leachate coupled with ammonia desorption was put forward, which includes diffusion and reaction processes, and assumes that thermodynamic equilibrium among the reacting species exists in the bulk liquid. The rigorous numerical approach only requires the definition of individual reactions in the system, and the solution is independent of specific assumptions made, or operational variables. The model was validated using experimental conditions in packed column. The equations in the model could be solved using Maple 8.0 with boundary conditions obtained by rational estimation of the parameters involved. Then the model was used to calculate concentration profiles in the liquid film, partial pressure, mass transfer rate, pH profiles, enhancement factor and individual film resistances along the column. The calculated results were compared to experimental data and a good agreement was achieved.The study provided a basic study for theoretical analysis and engineering design of the process of SO2 absorption into flue gas with landfill leachate coupled with ammonia desorption and other wet FGD process.关键词：flue gas desulfurization;landfill leachate;numerical simulation;sulfur dioxide
- 1416
- |
- 6
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:The experiments of anaerobic fermentation hydrogen bio-production (HBP) from simulated starch wastewater were conducted in continuous and batch reactor. Effects of organic loading rate (OLR) and pH on hydrogen production capacity and liquid products were investigated. The biogas yield and hydrogen yield increased with the increasing of OLR in CSTR. After the ethanol-type fermentation was obtained, at pH 3.9, the CSTR obtained maximum biogas yield and hydrogen yield（87.5?ml H2/g starch） simultaneously when the organic loading rate was at 22.0?kg COD/(m3·d). In batch reactor, hydrogen yields increased with the increasing of initial pH value from 3.5 to 4.3, then decreased and kept stabilization at pH 4.3 and 5. The maximum hydrogen yield was 80.0?ml?H2/g starch at initial pH?4.3. The results indicated that it's possible to produce hydrogen from starch wastewater.关键词：hydrogen production;OLR;simulated starch wastewater
- 1675
- |
- 12
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:By hydrothermal method, using hexadecyltrimethylammonium bromide as template agent, industrial Na2O·(3.3～3.5) SiO2 as cheap silica source, adding V5+ in the synthesis process, the mesoporous molecular sieves containing vanadium were synthesized. The oxidation of styrene was studied as a model reaction and proper parameters were selected: n(Si)∶n(CTAB)∶n(V)=1∶0.2∶ 0.08, pH=9.5, crystallizing time 48 h. Mesoporous molecular sieve V-MCM-41 with surface area (BET) = 1003 m2/g and average pore size of 3.944 nm was synthesized. After thermal-treating at 800 ℃ for 12 h, the surface area (BET) and pore diameter remain 81.6% and 58.6%. The good thermal stability of the mesoporous molecular sieves V-MCM-41were proved by BET data and XRD spectra.关键词：heteroatom V-MCM-41;hydrothermal synthesis;catalytic oxidation;styrene
- 1814
- |
- 22
- |
- 5
发布时间：2023-11-28 - 摘要：Abstract:Experiments were carried out to investigate forced convective heat transfer of distilled water flowing through quartz microtubes with inner diameter of 242, 315 and 520 μm. The microtube was heated directly by electrifying a brass wire with diameter 80 μm,which was coiled evenly up around the microtube to keep a constant heat flux.The wall average temperature was obtained according to relationship between wire resistance and temperature and achieved the synchronization of heating and measuring temperature.As the Reynolds number varied in the range from 100 up to 7000,the Nusselt numbers were measured.The experimental results were compared with the classical convective heat transfer correlations in laminar,transitional and turbulent regimes for conventional tubes.The comparison results indicated that the Nusselt number may be less than the classical laminar correlations when Reynolds number is lower.The Nusselt number quickly increases with the increase of Reynolds number. As Reynolds number is larger than 1700～1900 and 4000～5500, the corresponding Nusselt number will reach the value of the transitional correlations or that of the turbulent correlations.关键词：quartz micrtoube;micro heat transfer;constant heat flux heating;nusselt numbe
- 1677
- |
- 18
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:An approach for robot soccer path planning is proposed, which is based on conventional artificial potential field. In the robot court field, robots get repulsion position vector produced by obstacle robots and boundaries of robot court, and attraction position vector and angle by ball. All the vectors are used to result in the next path point so as to form a path which can avoid obstacles and get to the goal in the dynamic circumstance. The simulated experiments indicate that this approach achieves real time path planning for robot soccer.关键词：path planning;artificial potential field;position vector;robot soccer
- 1957
- |
- 32
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The basic principle and method of time series analysis and its application in thermal error modeling on NC machine tools were presented. How to utilize the thermal error serials surveyed to identify, model, predict and compensate was discussed in detail. The compensation system was composed of the computer and the controller of machine tool. The controller of machine tool, making use of the compensating values computed by the computer through time series analysis model established, ordered knife rest a additional movement to realize the real time compensation of machine tool thermal errors. The experimental results showed that the sizes variations of the workpieces could be reduced from 25 μm to 10 μm and then the machining precision of machine tool is highly improved. Therefore, the feasibility and validity of time series analysis in the application of thermal error modeling on NC machine tools have been proved.关键词：machine tool;thermal error;time series analysis;modeling
- 2149
- |
- 20
- |
- 15
发布时间：2023-11-28 - 摘要：Abstract:The idea of Knowledge Discovery is used to solve the dificulty decision process knowledge acquisition. The concept of Process Decision Data Table (PDDT) is defined to store process data. An improved process decision tree learnning arithmetic is proposed,which is based on CLS. ID3 is used to measure the fundamentality of condition attribute to decision rules in PDDT. The principle of process decision tree predigestion and the method of translateing it to decision rules are given.关键词：CAPP;decision tree;CLS;ID3
- 1642
- |
- 2
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:Nanoparticles of mesoporous TiO2 were synthesized TiOSO4 and NaOH in aqueous solution by precipitatioan method with PEG as template.The optimum conditions were obtained by orthogonal test.The prepared powders were investigate by XRD 、AFM、high resolution TEM、Surface area & Porosity Analyzer. The results showed that TiO2 was anatase with high thermal stability,the surface area was 121 m2·g-1, the mean grain size of crystal was 13 nm,the mean pore size was 10 nm，the mean grain size of nanoparticles was less than 100 nm.关键词：nanoparticle;mesoporous;TiO2;anatase;precipitatioan
- 1831
- |
- 2
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The microstructure and mechanical properties of as cast Mg Sn binary alloys were studied by optical microscopy, scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX) Analysis, X-ray diffraction (XRD) quantitative and qualitative analysis, tensile strength and micro-hardness testing. The results showed that Mg-Sn binary alloy is composed of α-Mg matrix and Mg2Sn. The mechanical tests indicated that the micro-hardness of the alloy increases when Sn content raises, the main reason of which was the dispersion strengthening of Mg2Sn and the grain refinement strengthening of Sn. The tensile strength and elongation of the alloys grow with the increase of Sn content when the content of Sn≤5%(wt). The grain refinement of Sn acts as the leading role in this content range of Sn. The tensile strength and especially elongation decline for Mg-10%Sn alloy, which owes mainly to the disappearance of grain refinement strengthening and the increase of brittle Mg2Sn phase.关键词：Mg-Sn binary alloy;as-cast microstructure;mechanical properties
- 2207
- |
- 106
- |
- 20
发布时间：2023-11-28 - 摘要：Abstract:Metal plate and strip of different variety and different width require different primordial crown of roller. In practical process, the crown is designed by trial and accumulative experience, leading to low efficiency, high cost and big error. The paper sets up a mathematic model for forecasting the primordial crown of the roller in rolling metal plate and strip with different variety and width. The model is optimized and then practiced. The results show that the model adapting sinusoidal curve to forecast the roller crown can obviously reduce the double-rib wave and thus improve the flatness of the plate.关键词：metal plate;roller crown;plate shape
- 1465
- |
- 2
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:A kind of macromolecular coupling agent was synthesized,and the effect of the coupling agent amount to the reinforement of rubber was tested.The testing figure showed a special reinforcement by means of controlling the amount of the coupling agents, especially to the tensile strength,200% (MPa) modules,hardness cross-link density and elongation at break of rubber composites.The coupling agents contain more sulfur is better. Rubber composites comprise the coupling agents have more anti aging than comprise "Si69".关键词：coupling agent;silica;clay;calcium carbonate;rubber
- 1866
- |
- 2
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The combustibility and thermal stability of fire-retardant viscose rayon were evaluated by 45°Slope Burning Method, Limit Oxygen Index(LOI), Differential Scanning Calorimetry(DSC), Thermogravimetry Analysis(TGA). The results indicated that modified fiber could reach the limit oxygen index fire retardant standard(LOI≥28),and fire retardant standard of Japan industry standard JIS 1091-77(Times of ignition≥3 times). The data showed that the fire retardant rayon was a durable fire retardant viscose rayon. The analysis of the fiber's thermal degradation mechanism suggests that the flame retardants play a multi role of catalytic dehydration and carbonization, heat absorption, condensation phase and gas phase flame retardation.关键词：fire-retardant viscose rayon;hexa(alkoxy)cyclotriphosphazene;combustibility;thermal
- 2612
- |
- 152
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The security policies play important roles in information security and trusted computing environments. An extensible and de centralized security policy management framework was proposed to manage security policies consistently in multi domain environments. Ｔhis framework employs a common, precise and neutral specification language of security policies to describe security policies， analyzes the security models and its policies to extract policy semantics, and builds a security policies model framework to perform a universal API to manage and control the access, authorization, cryptograph, confidentiality, integrity and availability among the policies of different domain, entities and facilities. A basic framework of security policies was implemented in Java language.关键词：security policy;security policies management framework;information security;autonomous domain;multi-domain
- 1893
- |
- 4
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:Remote backup systems provide system continuous availability even when disasters hit the primary system and is a significant technique used to support disaster backup and recovery. Existing remote backup systems offer lower transaction throughput. In this study, an optimized O2-safe approach was put forward.This method reconstructs dependency between transactions by inserting lock requests on data based on CSB timestamp rather than FCFS mode at the backup, and so sufficiently exploits parallelism between transactions in the backup system. Its correctness and efficiency were validated both theoretically and experimentally. Experimental results showed that optimized O2-safe has high transaction throughput without risking loss of transactions in case of primary failures.关键词：disaster recovery;data backup;remote backup;distributed transaction processing
- 1828
- |
- 2
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:A Single Sign On(SSO) model based on B/S architecture was proposed for integrating the enterprise's applications, and the solution to keep the passwords synchronized was discussed also. The SSO model integrates the enterprise's legacy applications based on C/S into B/S structure, adopting AD, ActiveX and Kerberos authentication. So the users are able to invoke the C/S applications in the IE as well as the Web applications, and it strengthens the security of user access by Kerberos authentication.关键词：AD;ADSI;Kerberos;password synchronized;SSO
- 2001
- |
- 20
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:To construct BDH (Bilinear Diffie-Hellman) parameter generator in key evolving schemes, the security of BDH problem was researched.The origin of BDH problem was reviewed. Then based on the admissible bilinear map,the decisional BDH problem, computational BDH problem and some variants were analyzed, respectively. As a result, some useful corollaries about BDH security were obtained. Finally, BDH parameter generators using Weil pairing and Tate pairing on supersingular elliptic curves were constructed. The generators could be widely applied to identity based cryptography.关键词：Bilinear Diffie-Hellman problem;Weil pairing;Tate pairing;elliptic curves
- 2218
- |
- 4
- |
- 10
发布时间：2023-11-28 - 摘要：Abstract:Based on genetic algorithm, an improved method for scheduling arrival aircrafts at an airport with multiple runways was studied. Scheduling arrival aircrafts is a typical non linear combinatorial optimization problem, and the application of genetic algorithm to this problem was explored.A sequence of aircrafts was a chromosome. We designed the crossover operator and mutation operator. In decoding phase, first we assigned the runway, then we used the improved moving method to remove the conflict between aircrafts, insert idle time, decide the sequence and time of aircrafts landing. The simulation result demonstrated that the presented algorithm can assist controllers to make decisions.关键词：genetic algorithms;scheduling arrival aircrafts;idle time
- 1635
- |
- 4
- |
- 14
发布时间：2023-11-28 - 摘要：Abstract:To improve stability of the signal source and perform sweeping detection, as well as extract abundance and reliable signal, the direct digital synthesis technology was employed to design the generator of source which formes a sweeping frequencies sine wave output from 1 MHz to 20 MHz. The planar spiral coil was connected as an amplitude modulation circuit. The same coil was made use of differential architecture for signal detection and extraction. The MC1595 was utilized to compose a phase detector, in which difference of phases varies with change of frequencies. A low pass filter was designed to filter the carry waves of the sweeping source. Thereby the system obtained abundance data and its stability was improved. Further, the spatial resolution of the system was enhanced. All of the above is in favor of using software in magnetic focused conductivity tomography system to reconstruct the image of conductivity within human body.关键词：magnetic focused conductivity tomography (MFCT);signal resource;focused coil;multiplier;signal extraction
- 1740
- |
- 8
- |
- 1
发布时间：2023-11-28
- 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