最新刊期
卷 41 ， 期 6 ， 2009
- 摘要：Abstract:To reveal the effects of the hydraulic parameters and rock properties on the characters of the high-pressure cavitating water jets and to research the mechanism of the rock-breaking ability of the water jets affected by these characters, experiments of figureing out the rock breaking effect of the water jet on the rocks with different porosity rate,were carried out under the different confining pressures and pump pressures. The results showed that the rock breaking efficiency (erosion quality and erosion depth) increased along a conic with the pump pressure increased while decreased along another conic with the confining pressure increased. The length of the bubble cloud, which decided the valid stand-off distance and affected the rock breaking efficiency, decreased along a cubic with the confining pressure increased and increased with the pump pressure increased. Under the experimental condition, when the pump pressure was 7 MPa, the cavitating phenomenon appeared and the sandstone which uniaxial compressive strength was 96 MPa could be broken. It was concluded that the rock breaking ability of the water jets was affected by the porosity rate of the rock, and higher the porosity of rock is, the more easily the rock could be broken.关键词：high-pressure cavitating water jets;rock breakage;confining pressure;pump pressure
- 3116
- |
- 194
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:A new approach of natural disaster risk degree assessment, Set Pair Analysis Method (SPAM) has been suggested. The method takes the fuzzy of grade standards into full account and avoids the values of discrepancy uncertainty coefficient. It is simple for concept, calculation and application, and the results of evaluation are feasible. The natural disaster risk degree assessment of all provinces in China has been researched. The results have shown that the presented method is satisfied.关键词：natural disaster;risk degree assessment;set pair analysis;connection degree
- 3164
- |
- 206
- |
- 20
发布时间：2023-11-28 - 摘要：Abstract:On 12 May 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan province, China. Wenchuan earthquake inevitably impaired the stability of mountains in the course of massive reverse-thrust strike-slip motion in the fault zone. Geohazards were triggered with the types of rock fall, rock avalanches, landslides, debris flows,and earthquake-lakes. In this paper, the types and characteristics of dammed lakes induced by Wenchuan earthquake are analized. The dammed lakes would seriously influence the river sediment transportation, fluvial processes and ecoenvironment. Consequently , the guidline and effective approaches for river restoration of dammed lake are susggested, so as to mitigate hazard loss and make the rivers influenced by the dammed lake serve us better.关键词：earthquake;dammed lake;river;stream restoration
- 3156
- |
- 600
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:Based on the study of mineralogical content，shapes and surface roughness，performance testing of the concrete formed by the aggregate，the applicabilities of the aggregate used in a certain hydropower project was explained on the aspect of its thermal and physicochemical properties．It was considered that these properties did reduce the formation of concrete crack effectively and consequently，the concrete quality of the dam be guaranteed inherently．关键词：mass concrete;crack;aggregate;mineralogical analyse
- 2674
- |
- 280
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract: In order to eliminate the accumulative probability errors resulting from using indirect variables in the Hoek-Brown criterion, the equivalent Mohr-Coulomb parameter probabilities were estimated directly from its basic variables. On the basis of a brief introduction of the Hoek-Brown criterion, the Rosenblueth point estimate and Monte-Carlo methods were selected to calculate the equivalent Mohr-Coulomb parameter probabilities of rock mass for a slope and the reliability index and failure probability of slope stability by two different methods as well. Although only a little difference existed in the computational results calculated by the two methods, but only a small amount of calculations are needed in the Rosenblueth point estimate method. Because the Rosenblueth point estimate method is simple, it can be used to estimate parameter probability, stability reliability and failure probability related to rock mass in engineering.关键词：Hoek-Brown criterion;equivalent shear strength;slope stability;reliability analysis;point estimate method
- 2388
- |
- 246
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:The research report about 3-D numerical simulation of overflow on overtopped cofferdams is very deficient because of the wide flow range and the complex boundary. The turbulent model was applied for the complementation between physical model test and numerical simulation. The overflows on the upper and lower cofferdams, the foundation pit, and the riverway were numerically simulated. The spillway capacity of the overtopped cofferdams was calculated under the typical flood conditions. The characteristics of aerated flow on the energy dissipation flatforms, the 3-D flow fields, and the pressure distributions were described. The results showed that the calculated relationships between the upstream water level and the overflow discharge of upper cofferdam agreed well with the model test results under the major flood conditions,and deviated from the model test results under the minor flood conditions. It is useful that the the structured mesh lines are generated generally according to the flow direction to simulate practical overflow well.关键词：overtopped cofferdam;3-D numerical simulation;structured mesh
- 2867
- |
- 186
- |
- 5
发布时间：2023-11-28 - 摘要：Abstract:In convergent-divergent tunnel the erosion effects of cavitation on an aluminium hydrofoil of raf61 was studied. The images of the cavitation erosion on the hydrofoil were gained using SEM. The digital image processing technique was applied to direct measure the cavitation erosions by evaluating the damage on the hydrofoil’s surfaces. It detected the edge of the pits and statistical the values of pit-number, size and area etc. It’s more reliable to characterize cavitation intensity and lead to a better understanding of cavitation erosion phenomenon.关键词：hydrofoil;cavitation;digital image processing;detection;pit
- 2797
- |
- 206
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:In order to evaluate the effect of parameters’ measurements to the uncertainty of groundwater flow, a conditional model for groundwater flow based on the Karhunen-Loeve decomposition and perturbation expansion is proposed, in which the spatial variability of log conductivity, recharge and boundary conditions are considered together. The derivation of the numerical modeling for groundwater flow subject to conditioning points of multiple random fields are also studied. The numerical experiments show that for some special covariance functions and lower-order Karhunen-Loeve expansion, the proposed model has high efficiency and satisfactory accuracy comparing to Monte Carlo simulation. The conditional simulation reduces the overall head variance. For the cases with larger correlation length and more conditional points, the reduction to the overall uncertainty is more significant. The variance reduction also depends on the locations of conditioning points. The conditioning points should be located in the region that may bring the largest reduction to the uncertainty. In reality, the measurement scheme should be determined by the real flow and type of parameters.关键词：conditional simulation;Karhunen-Loeve expansion;covariance function;variance;nonstationary
- 3663
- |
- 580
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:Under artificial freezing conditions, including different freezing directions, as well as the constant and sine varying freezing temperature models, the frost heave was studied. The effects of temperature field, frost-heave amount, water content and dry density on the frost heave were analyzed. The test results indicated that the frost heave amount of the top-bottom sine freezing sample was the least and that of the bottom-top constant freezing sample was the most, under the same experimental conditions. The distribution laws of water ratio and dry density of the top-bottom constant/sine-temperature and bottom-top constant temperature artificial freezing samples were the same, which demonstrated that the water migration rules were similar with the same freezing power from cooling side under the same experimental conditions.关键词：artificial freezing;freezing temperature model;temperature field;frost-heave amount
- 2831
- |
- 204
- |
- 5
发布时间：2023-11-28 - 摘要：Abstract:Road filling is often used to increase the width or height of road. In order to solve the problem that the designed grade of road filling slope is unstability and the method of decrease the grade of slope filling can’t be used to enhance the filling slope stability,because of the orographic condition limit,the concept of pre-reinforced by anti-sliding piles in road filling slope was proposed. The method of numerical simulation used to simulate designed slopes and four different pile sizes used in pre reinforced road filling slope. According to the analysis of the stability and distribution of equivalent plastic strain, the best pre reinforced pile size to reinforce road filling slope was obtained. The FEM method was adopted to analyze the value and distribution of soil pressure and pile displacement of selected pile.关键词：pre-reinforcement;road filling slope;interaction mechanism;anti-sliding pile
- 3198
- |
- 268
- |
- 3
发布时间：2023-11-28 - 摘要：Abstract:The stress distributions of two teeth with normal shape and bent root were compared.Two three-dimensional finite element models of the teeth with normal shape and bent root were established according to CT.The loads corresponding to bodily,tipping,and intruded movements were applied to the two models.The von Mises stresses on the roots and periodontal ligaments of the two models were compared.The results showed that the stress distributions of the two models were similar.The stresses in the two models were gradually increased from the root apexes to the alveolar crests under bodily and tipping movements.The maximum stresses in the two models were located at the distal root apexes under intruded movements.The stresses of the model with bent root were much higher than those of the model with normal shape.The maximum von Mises stress on the periodontal ligament with bent root was so high that could cause root resorption. It was concluded that because bent root could increase the stresses in the root and periodontal ligament, the special orthodontic therapy should be developed to treat the teeth with abnormal root morphologies.关键词：orthodontic therapy;lateral incisor;root resorption;three-dimensional finite element model;stress distribution of root
- 3249
- |
- 240
- |
- 3
发布时间：2023-11-28 - 摘要：Abstract:A method of zone refining was applied to purify the industrial yellow phosphorus to obtain ultra-pure phosphorus. The influence of variable zone lengths, zone passes, moving speed and the impurity of raw materials on the purification process was studied. The results indicated that after 5 zone passes, the 12 impurities’ (Fe, Ca, Co, Mg, Cr, Cd, Mn, Ni, Cu, Pb, Zn, Al) content reached to the level of 6 N (99.9999%) except arsenic under the conditions of moving speed 10 mm/h, zone length 0.1L and the arsenic content of raw material 14301 ng/g. After 30 zone passes, the amount of impurities were about 100 ng/g, which could satisfy the demands of semiconductor and pharmaceutical industries.关键词：zone refining;yellow phosphorus;impurity;purification
- 2690
- |
- 210
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:In order to evaluate and control the hazards of coal dust explosion in coal mines and power plants, the explosion characteristics of bituminous coal dusts were tested in a Siwek 20 litre spherical vessel. The effects of particle size of coal dust, coal dust concentration and ignition energy on maximum explosion pressures，maximum rates of pressure rise, explosion indices and minimum explosible concentrations were discussed. The finer sizes have lower minimum explosible concentrations and higher explosion intensity. When particle sizes of coal dust are less than 75 μm，minimum explosible concentrations and explosion intensity approach a limiting value. In the concentration range measured ( less than 700 g/m3), maximum explosion pressures, maximum rates of pressure rise and explosion indices increase along with the increase of coal dust concentrations. Explosion intensity rapidly enhances along with ignition energy augmenting. Explosion reaction is weak while ignition energy is less than 1 kJ. The results will provide important reference for understanding the explosion hazard of coal dust, controlling coal dust explosion and making inherent safety design.
- 3276
- |
- 348
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:WO3/ZrO2 solid superacid catalysts were prepared by using Zr(OH)4 as supporter with ultrasonic impregnation and general impregantion,respectively. The catalysts were characterized by means of BET, XRD, NH3-TPD and SEM. The results revealed that the catalyst prepared with ultrasonic impregnation, compard with general impregantion, possessed large surface areas and supported more dispersion tungste active component. Calcined at high temperature, ZrO2 in the catalyst yet existed mainly in the tetragonal phase and the catalyst presented higher acidic strength and acid amounts. Furthermore, the catalyst was dispersed in small particle and gave strong catalytic activity in the catalytic oxidative desulfurization of diesel.关键词：solid superacid;ultrasonic impregnation;supported catalyst;tungsten oxide;catalytic activity
- 3180
- |
- 336
- |
- 5
发布时间：2023-11-28 - 摘要：Abstract:Batch experiments were carried out to study the performances of three kinds of nitrification sludge of seeding sludge (S1) and nitrification sludge (S2 and S3) taken from a bioreactor run with inorganic or organic ammonia containing wastewater for a long time. The performances of seeding sludge (S1) were set as control, and the nitrification sludge (S2) showed a higher ammonia oxidation rate, a larger half saturation constant, a stronger tolerance to nitrite, a higher nitrite oxidation rate and an average nitrite accumulation of (63.58±4.19)%. The produced nitrite could be further oxidized into nitrate. The nitrification sludge (S3) had a lower ammonia oxidation rate, a smaller half saturation constant, a weaker tolerance to nitrite, a lower nitrite oxidation rate and an average nitrite accumulation of (92.17±2.67)%. The produced nitrite concentration came to stable because it could not been oxidized into nitrate. The ratio of maximum specific ammonia oxidation rate to half saturation constant (Rma/KSa) showed that the activity of nitrite bacteria in both nitrification sludge S2 and S3 was increased.
- 2634
- |
- 203
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:The landfill leachate was treated by the combination of anaerobic fluiized bed and outside circle three-phase aerobic fluidized bed systems. The influent CODCr concentration, influent NH3-N concentration, anaerobic CODCr removal rate, anaerobic NH3-N removal rate and other factors were studied on the CODCr and NH3-N removal rate of the Landfill Leachate. The experimental results showed that the landfill leachate of low NH3-N concentration has good treatment efficiency by the joint system, when the total HRT, influent CODCr concentration, influent NH3-N concentration of the treatment systems were 10.5 h, 2817.2～4383.88 mg/L, 303.12～445.43 mg/L,respectively, the removal rates of CODCr and NH3-N were 86.79%～98.85% and 81.14%～94.01%. The Volumetric loading for CODCr and NH3-N achieved an average of 7.38 kg/(m3·d) and 0.37 kg/(m3·d). When the CODCr value of Landfill Leachate below 3400 mg/L, there were high CODCr removal rate of 86.79%～98.85%, when NH3-N concentration below 400 mg/L, the NH3-N in the system had a higher removal rate of 81.14%～94.01%. It was proved that to improve the removal rate of anaerobic CODCr and NH3-N and reduce the NH3-N concentration of anaerobic effluent, will help improve the overall CODCr and total NH3-N removal rate of the combined systems.关键词：landfill leachate;anaerobic fluidized bed;outside the circle three-phase aerobic fluidized bed
- 3128
- |
- 184
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:The hydrodynamic property and gas liquid mass transfer efficiency of membrane separation reactor with inner loop carriers was studied in the tap water test. The result showed that the critical gas velocity needed by circulation fluidization state was 6.2~7.7 m/h when the carrier holdup and liquid flow were 2%~8% and 0~16 L/h,respectively . After the carrier was added, the gas holdup and oxygen transfer coefficient can be improved with the increase of gas velocity and be reduced with increase of carrier holdup. Gas holdup was 0.65%~3.5% and oxygen transfer coefficient was 8.32~28.0 h-1when carrier holdup, liquid flow and gas velocity were 0~6%,5.3 L/h and 7.5~30.1 m/h,respectively . The circulating time and mixing time can be reduced with increase of gas velocity and carrier holdup. The circulating time was 2.9~34 s and mixing time was 10.2~41.9 s when carrier holdup, liquid flow and gas velocity were 0~6%, 5.3 L/h and 3.8~22.6 m/h, respectively.关键词：membrane;bioreactor;gas-liquid mass transfer
- 2326
- |
- 210
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:Based on comparative tests of removal effect between Ecological Floating-Beds (EFBs) planted with Canna indica and Acorus calamus and the unplanted bed, the mechanism of EFBs was investigated through the tracer study and mass balance calculation. Results of the study showed that, the average removal efficiencies of TN,TP and CODCr of EFBs planted with Canna indica and Acorus calamus were 29.5%,28.7%,23.7% and 31.8%,27.9%,24.4%, the average removal loadings were 1.141,0.111,0.684 g·m-2·d-1 and 1.244,0.108,0.689 g·m-2·d-1, respectively, apparently higher than those of the unplanted bed.The removal effect exhibited positive relationships with the plants growth with the correlation coefficient higher than 0.786(p＜0.05) in both units.The sedimentation of nitrogen and phosphorus was the dominating pathway for pollutants removal in EFBs, while plants uptake contributed to only about 10% of total pollutants removed. The study indicated that plants help to keep the flow pattern of EFBs more close to plug flow pattern, good DO concentration gradient distribution and decontamination by filtration of roots, testifying that plants played a critical role in pollutants removal in EFBs.关键词：Ecological Floating-Beds (EFBs);removal effect;DO concentration gradient;flow pattern;purification mechanism
- 3320
- |
- 222
- |
- 7
发布时间：2023-11-28 - 摘要：Abstract:Isothermal oxidation behavior of pure nickel and its lanthanum ion-implanted sample were studied at 900 ℃ in air. The surface morphology and microstructure of NiO films formed on both samples were examined by scanning electronic microscopy(SEM) and transmission electronic microscopy(TEM). Laser Raman spectrometer and X-ray diffraction spectrometer(XRD) were used to study the stress status in NiO films formed on La-free and La-implanted nickel. Secondary ion massive spectrum(SIMS) was used to examine Ni, O and La element depth distribution in oxide films. Results showed that La implantation remarkably reduced the growing speed and grain size of NiO film. Meanwhile it changed the oxide film growing mechanism from predominant Ni2+ cation outward diffusion to O2- anion inward diffusion. XRD and Raman testing results showed the stress declination effect due to La-implantation, while the discrepancy between the two testing results was fully analyzed regarding to the heterogeneous stress distribution in oxide film and the rare earth effect during the film growing process.关键词：ion-implantation;SIMS;Raman;lanthanum;nickel oxide
- 2686
- |
- 188
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The transformation of preparation temperature field of large area CdTe films was simulated, and the effect of temperature field’s uniformity on CdS/CdTe solar cells was investigated by the characteration of I-V、C-V and Deep Level Transient Spectroscopy(DLTS). The result showed that the uniformity of temperature field has effect on Isc and FF, but lacks impact on Voc. Least dark saturated current density、more higher carrier concentration and better photovoltaic performance were observed in the sample prepared at 580 ℃; The response of deep-level impurities in CdTe films is consistent with temperature and frequency, but the sample(580 ℃) has less deep-level impurities’ recombination because of lower hole trap concentration. 8.2% efficiency of the CdS/CdTe solar cells was reached by improved the uniformity of temperature field.关键词：CdTe thin films;CdS/CdTe solar cells;Deep Level Transient Spectroscopy(DLTS)
- 3305
- |
- 228
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:Calcium polyphosphates(CPP)were modified by doping alkali metals ions(K+ and Na+ ) with different proportions to study its degradability and mineralization ability. Doped CPP samples were immersed in simulated body fluids(SBF) during 1,2,3, 7,14,21,28 and 35 days to study the degradability and mineralization ability. The weight loss of degraded samples, Ca2+and PO43-concentrations change, and pH value in SBF were measured to characterize the degradability. Doped CPP samples were characterized by XRD, FTIR and SEM. The results showed that doping proportion with molar ratio higher than 5% largely accelerated degradation rate. Higher doping proportion of K+ and Na+ resulted in positive effect on the degradability and mineralization ability of CPP.关键词：calcium polyphosphates(CPP);alkali metals;doping;degradation;mineral precipitation
- 3351
- |
- 196
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The combination of superplastic differential temperature drawing (SDTD) and sizing was investigated with thermal-mechanical coupled numerical simulation and experiment. Initial blank of the bracket with large drawing ratio was calculated. In the simulation, the power-law constitutive model of AA5083 was established as function of temperature and implanted in software MARC through new complied subroutine. In SDTD practice, the temperature of female die was kept at 525 ℃, i.e. the optimal superplastic temperature of AA5083, and the punch was cooled by the flowing water throughout the forming process. Also, the sizing process was carried out at 525 ℃. Under the guide of the numerical simulation, two sets of tools were fabricated and the bracket was successfully manufactured via the combination of SDTD and sizing. Results revealed that the formed bracket has a sound uniform thickness distribution. Good agreement was obtained between the formed thickness profiles and the predicted ones.关键词：superplasticity;numerical simulation;differential temperature drawing;sizing;subroutine;5083 aluminum alloy
- 2568
- |
- 228
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:In order to enlarge the absorbed intensity of nano-TiO2 in visible light, Ag/TiO2 nanoparticles were prepared mainly from industrial H2TiO3 and AgNO3 by a simple method. It was characterized by X-ray powder diffraction(XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis. XRD patterns showed that TiO2 existed as anatase and silver existed as elemental form in nano composite particles. XPS results showed that the binding energies of silver were 367.476 eV (3d3/2) and 373.453 eV (3d5/2), which were lower than those of simple silver (368.4 eV and 374.4 eV), since the preparation temperature of Ag/TiO2 was higher than simple silver and led to Ag cluster growth. SEM and TEM results showed that the particle size of nano-composite particles was about 30 nm. Moreover, UV-vis refractive spectrums showed that its photocatalytic wavelength was apparently red shift, and the absorbed intensity of nano TiO2 in visible light was enlarged.关键词：titanium dioxide;silver;nanoparticles;characterization
- 3878
- |
- 358
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:In order to change the current passive network security defense situation depending on traditional network security tools, such as firewall, network vulnerability scanning and intrusion detection etc, the artificial immune technology is applied to network security situation awareness.This technology adopts intrusion detection model based on immune to realize the detection of known and unknown intrusion behaviors, and establishes real-time and quantitative network risk evaluation model based on the corresponding relationship between the antibody concentration variation of biological immune system and the intrusion rate of pathogen. During the trend forecast of network security situation, ARMA model based on time series is adopted to make real time and quantitative analysis and forecast on network security situation and its future trend, in this way, it can reduce the risk of network attack effectively and improve the emergency logistic support ability of network information system. The experiment result shows that this system can adjust network security strategy timely and efficiently, provide overall security guarantee for the system and is a good solution to active network security defense.关键词：artificial immunity;network security;network security situation
- 4467
- |
- 328
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:One of the prevalent methods in short-term air traffic flow management is Ground-Delay Programming. Serious flight delays will be caused by increasing air traffic demands. To solve this problem,a Random Ground-Holding Model Based on Grouped Scheduling was proposed.Considering the rationality of the successive tasks flights scheduling, the Grouped Scheduling method was introduced. The interdependent influence of arrivals and departures was considered in the model.With the different object of successive tasks influence，delay time and the delay cost, the model provided three factor to define the priority.The model introduced the random variables, with the dynamic characteristics of weather. The true data of flight plan was used to test the model many times. The results validated the flexibility and practicability of this model.关键词：air traffic management;ground-delay programming;grouped scheduling;delay cost
- 2988
- |
- 200
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:In order to overcome the problem of high-dimensionality of gene expression data, a linear-based method for dimensionality reduction was proposed. Using Locality Preserving Projections (LPP) incorporated with the class information, the gene expression data were mapped into a feature subspace. Different from Principal Component Analysis (PCA) which searches the direction of maximal variance, CPP seeks a feature subspace that reflects the class information of the samples and by using CPP the dimensions of the data can be reduced while preserving the class information. Experiment results on real gene expression data compared with the classical linear technology PCA showed that CPP can identify the class feature better and obtain much better efficiency of visualization after dimensionality reduction via CPP than PCA.关键词：gene expression data;Class Preserving Projection;visualization;clustering analysis
- 2626
- |
- 262
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:To solve the problem that Non-functional property specification & verification in web service (WS) flow has become indispensable,an ontology-based approach was presented for specifying and verifying time constraints consistency in WS flow. Time OWL-S was built to express basic time information of WS flow roundly. Meanwhile, Petri Nets Ontology was enriched with time semantic information, which can describe WS semantics based on OWL. The mapping definition between Time OWL-S and extended Petri Nets Ontology was also given. Through extending OWL-S API，annotated OWL-S model was transformed into PNML, a standard format to describe Petri Nets Ontology. A verification system was taken to illustrate the correctness and feasibility of the verification process.
- 3201
- |
- 314
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:The Tableaux based on “unfolding gradually” may produce a lot of repetitive intermediate concept descriptions in deciding the satisfiabilities of acyclic concepts in a variety of description logics, which wastes large space. To tackle this problem, a novel Complete Disjunctive Normal Form (CDNF) algorithm was presented to check the satisfiabilities of acyclic ALCN-concepts. CDNF algorithm built disjunctive normal forms connected by roles in different levels directly on input concept description, and reorganized the input concept description into some hierarchical complete disjunctive normal forms whose satisfiabilities are already known, thus “worked out” satisfiabilities in a real sense. CDNF algorithm employed “one-step” unfolding pattern and acts directly on input concept description, thus eliminated description overlaps to the largest extent. As a result, CDNF algorithm had better performance than tableaux by saving spatial cost linearly or even exponentially.关键词：reasoning on satisfiability;disjunctive normal form;ALCN
- 3477
- |
- 188
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:In order to improve the simulation of Air Traffic Control(ATC) Simulator System, a new simple and useful model of aircraft flight simulation was created,which including the simulation of parameters of aircraft performance, flight rules and aviation procedures were rebuilt. The effect of weather on flight was considered in the model. These simulation were taken in light of aircraft flight effect such as ground movement, ascend/descend, acceleration/deceleration etc.A modeling based on real radar track information was given and the model was proved of high degree in simulation when it was applied in air traffic control radar simulator. Besides, this model can be applied in air control procedure analysis, flight plan preview, air flux analysis and airport construction evaluation.关键词：flight simulation;Air Traffic Control(ATC);real track modeling;weather modeling
- 3700
- |
- 286
- |
- 3
发布时间：2023-11-28 - 摘要：Abstract:In order to reduce the hybrid decision systems including the missing value attributes, which are lost or represent “do not care” conditions, a generalized incomplete rough set model based on neighborhood relations, the discrimination methods of the missing value and a hybrid reduction algorithm were proposed. The model approximates an arbitrary subset in the universe with neighborhood granules, and the generalized neighborhood relations are the generalization of the asymmetry similarity relations and the tolerance relations. The discrimination methods of the lost or “do not care” conditions were proposed based on the assumption of the consistency classification, and the influence of the noise samples and the neighborhood values to the classification accuracy was presented as well. The validity and feasibility of the algorithm were demonstrated by the results of experiments on five UCI machine learning databases.关键词：generalized incomplete;hybrid decision system;neighborhood;rough set;reduction
- 2723
- |
- 212
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:To solve the problem which the interval number of accessing label will increase by exponent when the number of label increases for the traditional ALOHA algorithm, a new algorithm about frame time interval upswing algorithm was put forward. This new algorithm absorbed the strongpoint of the dynamic time interval algorithm and the problem which the system efficiency begin debases when the number of system label became quite big was solved. The system capability was enhanced accordingly, through limiting the value of length of frame and M. The advantage and disadvantage of the performance of three algorithm (EDFSA, BFSA and DFSA) were compared through the simulation experiment. It was concluded that time cost of EDFSA algorithm increased 85% and 92% comparing respectively with the BFSA algorithm and the DFSA algorithm when identifying 1000 tags,and higher efficiency of EDFSA algorithms will be obtained when identifying more tags.关键词：RFID;EPC Gen2;anti-collision algorithm;dynamic frame time slot algorithm
- 4496
- |
- 528
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:According to the characteristics of magneto-rheological (MR) variable damping and stiffness and the requirements of landing gear, an absorber consisted of a MR damper and MR elastomer part in parallel is proposed, which can be applied to the landing absorbing system of airplane, Its control model is formulated. Due to the discontinuous dynamics of landing, a hybrid controller based on acceleration feedback control and LQG control is derived.The simulation is carried out to validate the effect of the proposed absorber and the derived control strategy. The results show that the landing gear based on the variable damping and stiffness absorber can reduce the peak value of impact during landing without increasing the stroke of absorber, and improve the ride comfort during sliding compared to the passive gear.关键词：magneto-rheological variable stiffness;magneto-rheological variable damping;absorber;acceleration feedback;LQG
- 3629
- |
- 256
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:Designing software algorithms for critical steps, which can not be implemented by software according to standards directly, is an important and difficult task because those steps need the intervention and experience of engineers.Software algorithms for two critical steps in SY/T 6477-2000/API 579,the metal loss dimension determination and the subsections generation,were proposed. The metal loss dimension determination can not be implemented directly because of its dependence on graph. To solve this problem, Critical Thickness Profiles (CTP) graph was constructed using linear interpolation, and then the software algorithm for dimension determination of metal loss was designed based on the CTP graph. The subsections generation can not be implemented directly because of its dependence on the experience of engineers. To handle this problem, the cyclical iteration which used the change rate of Remaining Strength Factor (RSF) as the termination condition, was designed. Utilizing the cyclical iteration, the software algorithm for subsections generation was designed.The validity of the algorithm was proved. The program flow charts of both software algorithms were given in order to provide direct instructions for software implementation.关键词：pipeline assessment software;software algorithm;dimension determination of metal loss;subsections generation
- 2599
- |
- 176
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:In order to have a better damping effect, the design parameters of the built-in damping boring bar should be optimized in the design stage. It is generally believed that the establishment of its simplified kinetic model for frequency domain analysis was a simple method. However, the traditional method that was described in S.A Tobias’s book applied only to the constant frequency. In order to overcome this problem, the global optimization search numerical method was used to solve several parameters,which made the damping boring bar has the minimal value of the relative vibration amplitude when the exciting frequency of vibration was in a wide range of changes. In order to obtain the conclusive optimal parameters, the parameters were amended by the frequency response curve with the smallest area method. The optimized damping boring bar and the same size solid boring bar’s BODE chart were drawn. The charts showed that the amplitude of the optimized damping boring bar of which are significantly smaller than the solid damping boting bar’s.关键词：damping boring bar;dynamic model;parameters optimization
- 2924
- |
- 580
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:Based on quasi-statics model of rolling bearing and the calcuation of its dynamic stiffness, considering the impact of speed, initial preload, thermal preload and oil thickness on bearing stiffness, bearing operating stiffness was obtained. Using bearing operating stiffness as spindle supporting stiffness, the parameterized FEM model of motorized spindles was established to analyze dynamic characteristics of spindles. Analysis results showed that those parameters are the key influence factors on dynamic characteristics for grinding motorized spindle, such as initial preload, suspending length of grinding wheel, spacing between front and rear bearings, front bearing set spacing and inner diameter of rotor.关键词：ultra-high-speed;motorized spindles;bearing operating stiffness;dynamic characteristics
- 3005
- |
- 240
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:In multi-sensor environment when availability of measurement is uncertain, it is difficult to construct uniform global observation vector and observation matrix appropriately. To resolve the problem, a measurement fusion algorithm for uncertain measurement was presented. By defining availability function for each dimension of observation vectors to construct generalized observation vectors and covariance matrixes, the uncertainty of measurement was expressed, and formal valid measurement was obtained. The existing measurement fusion algorithm of parallel filtering was then generalized to uncertain scenario, and optimal fusion result can be obtained. To be convenient for numerical calculation, a suboptimal algorithm was put forward also. Simulation results showed that the method presented can deal with the multi-sensor measurement fusion of uncertain availability correctly and calculational cost is almost as the same as one of existing algorithm for certain measurement.关键词：measurement fusion;parallel filtering;uncertain measurement;availability function;generalized measurement vector
- 3370
- |
- 502
- |
- 1
发布时间：2023-11-28 - 摘要：Abstract:The autostereoscopic display is an important display technology method of sub-pixel arrangement for the multi-view autostereoscopic display based on step parallax barriers was proposed. The view number matrixes were built and the sub-pixel arrangement results were obtained for different inclined angles of parallax barriers and different view numbers of images.The rules of sub pixel arrangements were analyzed. A demo of a multi-view autostereoscopic display based on step parallax barriers using the sub-pixel arrangements presented very good stereo images.关键词：autostereoscopic display;step parallax barrier;sub-pixel;view number matrix;pixel cell
- 3255
- |
- 244
- |
- 4
发布时间：2023-11-28 - 摘要：Abstract:In order to solve the problem that the Multi-objective Evolutionary Algorithm (MOEA) used in reactive power optimization currently has the shortcomings of time consuming computation, poor orientability and applicability,a ε-omination based MOEA was applied in reactive power optimization.According to different significance among objective components, an adaptive ε-omination was created and relevant post-evaluation fuzzy logic controller was established to select solution. IEEE14, IEEE30 and IEEE118 systems were utilized to test the approach against some other state-of-the-art MOEAs and the results showed that the method could maintain good search results, save a lot computation time and fit to real-time control.
- 3158
- |
- 214
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:Transmission over wireless fast time varying channels can lead to Inter-cell interference (ICeI) and Inter-carrier Interference (ICaI) in multiple-input multiple output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. To decrease the impact of the interference, it is considered that each cell can select different order Fractional Fourier transform (FrFT) suitable for the different interference environments to modulate and demodulate the symbols,and a model for MIMO-OFDM based on FrFT is proposed.The Interference Restricted Combination (IRC) equalizer is designed to suppress the interference. Because of the use of Hybrid Automatic Repeat Request (HARQ) technique in practical communication, it is unnecessary to minimize the bit error rate of first transmission. Therefore, more reasonable rule for optimizing FrFT order is proposed, which maximizes the channel capacity under the constraint condition that received symbol SINR reach threshold value,and the optimal IRC equalizer based on optimal FrFT are derived. The system simulation results proved that the rule is available and the ICeI and ICaI can be suppressed effectively. Furthermore, the system throughput also increases obviously by updating the optimal order.关键词：MIMO;OFDM;Fractional Fourier Transform;interference suppression
- 3047
- |
- 310
- |
- 2
发布时间：2023-11-28 - 摘要：Abstract:In order to compare the complexity and performance of Sum-of-sinusoids (SoS) models for uncorrected Rayleigh fading channels, the second-order statistical formula for deterministic SoS model was derived, which showed that the variance of cross-correlation was not zero. Then, the requirements of signal′s angle of arrival(AoA) for statistical models were proved, which was used to compare with different selections. Simulation results showed that deterministic model has lower complexity but poor performance of independence between multiple channels, however statistical model has ideal statistical properties with proper AoA.关键词：channel models;Rayleigh fading;Sum-of-sinusoids(SoS) simulator;Angle of arrival (AoA)
- 3017
- |
- 694
- |
- 0
发布时间：2023-11-28 - 摘要：Abstract:Conventionally,filters were applied to eliminate the interferential acoustic signal in acoustic signal processing.However, the interferential signal with the same frequency as the acoustic logging signal can not be filtered. Considering that the logging signal and the interferential signal are generated by independent sources, and received by different receivers,an independent component analysis algorithm named AMUSE was applied to separate the logging signal and the interferential signal from the receiver signals. Also, considering that the energy of the logging signal is much bigger than that of the interferential signal, the energy of the receiver signals were used to estimate the amplitude of the acoustic logging signal. Thus the acoustic logging signal could be estimated both in waveform and amplitude, and the accuracy of the acoustic logging data would be improved.
- 2385
- |
- 228
- |
- 0
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