共查询到19条相似文献，搜索用时 197 毫秒
1.
The integration of water quality analysis simulation program （WASP） with a geographical information system （GIS） is presented.This integration was undertaken to enhance the data analysis and management ability of the widely used water quality model.Different types of data involved in WASP modeling were converted and integrated into GIS using a database method.The spatial data modeling and analysis capability of GIS were used in the operation of the model.The WASP water quality model was coupled with the environmental fluid dynamics code （EFDC） hydrodynamic model.A case study of the Lower Charles River Basin （Massachusetts,USA） water quality model system was conducted to demonstrate the integration process.The results showed that high efficiency of the data process and powerful function of data analysis could be achieved in the integrated model,which would significantly improve the application of WASP model in water quality management. 相似文献
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Negative skin friction （NSF） is one of the important problems when designing a pile foundation. How- ever, the influence of loading sequence on the dragload and downdrag for pile foundation is seldom studied. In this paper, a three-dimensional numerical model was established using FLAC3D. Compared with the results of model test, the established model could be used to study the NSF of pile foundation. The influencing factors were discussed in- cluding the length-diameter ratio of pile and the loading sequence of pile head load and surcharge. A case history was analyzed using FLAC3D. The calculated results are in good agreement with the measured results. It is concluded that the dragload and downdrag are remarkably influenced by the loading sequence of pile head load and surcharge. The dragload and downdrag reach the maximum values under the condition of surcharge after pile head load. 相似文献
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In the investigation of accidental explosion scene, the damage on the glass is one of the typi-cal traces which can be used to decide the characteristic of the explosion source. To analyze the re-sponse of glass under the blast load, a numerical model was developed. In the model, the brittleness glass model was adopted. A‘node release’method, which had some special merits compared with the erosion method was used to simulate the rupture of the glass In the calculation, several problems which play major role in the response of the glass were discussed. The velocity and the displacement of the glass fragment were two major factors. The numerical results are very helpful for the design and hazard assessment. 相似文献
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In this study, a simple roller burnishing tool was made to operate burnishing processes on A356/5%SIC metal matrix composite fabricated by electromagnetic stir casting under different parameters. The effects of burnishing speed, burnishing force and number of burnishing passes on the surface roughness and tribological properties were measured. Scanning electron microscopy （SEM） graphs of the machined surface with PCD （insert-10） tool and roller burnished surface with tungsten carbide （WC） roller were taken into consider- ation to observe the surface finish of metal matrix composites. The mechanical properties （tensile strength, hardness, duc- tility） of A356/5%SIC metal matrix composites were studied for both unburnished samples and burnished samples. The results revealed that the roller burnished samples of A356/ 5%SIC led to the improvement in tensile strength, hardness and ductility. In order to find out the effects of roller bur- nishing process parameters on the surface roughness of A356/ 5%SIC metal matrix composite, response surface methodol- ogy （RSM） （Box-Behnken design） was used and a prediction model was developed relevant to average surface roughness using experimental data. In the range of process parameters, the result shows that roller burnishing speed increases, and surface roughness decreases, but on the other hand roller burnishing force and number of passes increase, and surface roughness increases. Optimum values of burnishing speed （1.5 m/s）, burnishing force （50 N） and number of passes （2） during roller burnishing of A356/5%SIC metal matrix com- posite to minimize the surface roughness （predicted 1.232 μm） have been found out. There was only 5.03% error in the experimental and modeled results of surface roughness. 相似文献
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Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force （Fz） and surface roughness （Ra）. In the present work, the performance of PVD/TiA1N coated carbide inserts was investigated using response surface methodology （RSM） for turning Ti-6A1-4V. The effects of process parameters such as speed （v）, feed （/＇）, depth of cut （d） and back rake angle （Ty） on Fz and Ra were investi- gated. The experimental plan used for four factors and three levels was designed based on face centered, central composite design （CCD）. The experimental results indi- cated that Fz increased with the increase in d, f and decreased with the increase in v and yy, whereas Ra decreased with the increase in v and 7y, and increased with d and v. The goodness of fit of the regression equations and model fits （R2） for Fz and Ra were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model. 相似文献
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Based on pseudo strain energy density （PSED） and grey relation coefficient （GRC）, an index is proposed to locate the damage of beam-type structures in time-domain. The genetic algorithm （GA） is utilized to identify the structural damage severity of confirmed damaged locations. Furthermore, a systematic damage identification program based on GA is developed on MATLAB platform. ANSYS is employed to conduct the finite element analysis of com- plicated civil engineering structures, which is embedded with interface technique. The two-step damage identification is verified by a finite element model of Xinxingtang Highway Bridge and a laboratory beam model based on polyvi- nylidens fluoride （PVDF）. The bridge model was constructed with 57 girder segments, and simulated with 58 meas- urement points. The damaged segments were located accurately by GRC index regardless of damage extents and noise levels. With stiffness reduction factors of detected segments as variables, the GA program evolved for 150 generations in 6 h and identified the damage extent with the maximum errors of 1% and 3% corresponding to the noise to signal ratios of 0 and 5%, respectively. In contrast, the common GA-based method without using GRC index evolved for 600 generations in 24 h, but failed to obtain satisfactory results. In the laboratory test, PVDF patches were used as dynamic strain sensors, and the damage locations were identified due to the fact that GRC indexes of points near damaged ele- ments were smaller than 0.6 while those of others were larger than 0.6. The GA-based damage quantification was also consistent with the value of crack depth in the beam model. 相似文献
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A novel photocatalytic reactor was developed to remove （1,1-bis（4-chlorophenyl）-2,2,2-trichloroethane） （DDT） from water. In the reactor, a cenosphere was used to support TiO2 film made by means of sol-gel. Because the cenospheres were coated with TiO2, their specific gravity was slightly increased from the original 0.6-0.8 to 0.8-0.9, so that they were able to be suspended in water. With the mixed operation of a bubbler, the water in the reactor was in a well-fluidized state. The bottom of the reactor is a sand filter bed, which can be used to prevent the photocatalyst from being lost. A mathematical model of the reactor has been developed in the two primary influential factors： ultraviolet （UV） light intensity and photocatalyst concentration. With such a model, the reactor can be designed more reasonably. 相似文献
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To predict the economic loss of crops caused by acid rain, we used partial least squares （PLS） regression to build a model of single dependent variable - the economic loss calculated with the decrease in yield related to the pH value and levels of Ca^2＋, NH4^＋, Na^＋, K^＋, Mg^2＋, SO4^2-, NO3^-, and Cl^- in acid rain. We selected vegetables which were sensitive to acid rain as the sample crops, and collected 12 groups of data, of which 8 groups were used for modeling and 4 groups for testing. Using the cross validation method to evaluate the performace of this prediction model indicates that the optimum number of principal components was 3, determined by the minimum of prediction residual error sum of squares, and the prediction error of the regression equation ranges from -2.25% to 4.32%. The model predicted that the economic loss of vegetables from acid rain is negatively corrrelated to pH and the concentrations of NH4^＋, SO4^2-, NO3^-, and Cl^- in the rain, and positively correlated to the concentrations of Ca^2＋, Na^＋, K^＋ and Mg^2＋. The precision of the model may be improved if the non-linearity of original data is addressed. 相似文献
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1 Introduction The 5-hydroxytryptamine type 3 (5-HT3) receptorantagonists[1-2]are currently used in the treatment ofchemotherapy and radiotherapy induced emesis . Thecompounds are based onthe parent structure showninFig.1 ,the aromatic systems include mono- and bicy-clic rings ,with or without heteroatoms ,and with vari-ous substitution patterns .This range of structural vari-ation makes it difficult to treat the analysis of thesecompounds .Fig .1 Parent structure of 5-HT3antagonists With t… 相似文献
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THANG Truong Cong KIM Young Suk RO Yong Man KANG Jungwon KIM Jae-Gon 《浙江大学学报(A卷英文版)》2006,7(5):764-772
INTRODUCTION Scalable video coding (SVC) (Schwarz et al., 2004) is the most promising video format for appli- cations of collaborative communication. First, SVC format, which is extended from the latest advanced video coding (AVC), is appropriate for creating a wide variety of bitrates with high compression effi- ciency. Second, an original SVC bitstream can be easily truncated in different ways to meet various characteristics and variations of devices and connec- tions. The scalabil… 相似文献
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A new model was developed to describe the diffusion limitation on free radical polyme-rization. In this model the termination
rate coefficient (k
t) and propagation rate coefficient (k
p) were expressed as a function of bulk viscosity (η). This model was used to simulate the batch thermal polymerization of
styrene (St) and the continuous thermal bulk copolymerization of St (monomer 1) and maleic anhydride (MAH, monomer 2) in a
CSTR with on-line monitor of the rheological behavior. The simulated results on polymerization conversion, copolymer composition,
molecular weight and its distributions were compared with the experimental data, and the results calculated by two previous
gel-effect models i.e. Martin-Hamielec and Tulig-Tirrell models. It was found that the present model produces better prediction
than that of the Tulig-Tirrell model and has the same accuracy as that of the Martin-Hamielec model, but is much simpler.
Project (29734130) supported by Natural Science Foundation of China. 相似文献
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基于MATCONT的电力系统电压稳定分岔及控制仿真试验 总被引：1，自引：0，他引：1
介绍了电力系统ODE模型中引起电压失稳的常见分岔类型及分岔控制的基本概念;运用基于Matlab的数值分岔分析软件MATCONT对一个经典单机—动态负荷系统进行了分岔分析,验证了PQ动态负荷模型系统存在着鞍结分岔(SNB)现象,而RL动态负荷模型系统并无分岔现象产生.为延迟PQ动态负荷模型系统的鞍结分岔点,在原系统中引入了线性状态反馈控制和SVC控制两种分岔控制方法.MATCONT仿真结果显示,这两种控制方法均能够有效延迟鞍结分岔,从而提高系统的电压稳定性,并可通过选择合理的反馈控制器增益及SVC增益获得理想的分岔控制效果. 相似文献
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Response surface methodology was used to optimize the medium for antifungal active substance production from Streptomyces lydicus E12 in flask cultivation. Initially, the component factors, which influence antifungal substance production, were studied by varying one factor at a time. Starch, soybean cake powder, K2HPO4·3H2O and MgSO4·7H2O were found to have a significant effect on the production of antifungal substances by the traditional design. Then, a Box–Behnken design was applied for further optimization. A quadratic model was found to fit antifungal active substance production. The analysis revealed that the optimum values of the tested variable were starch 84.96 g/L, soybean cake powder 4.13 g/L, glucose 5 g/L, MgSO4·7H2O 1.23 g/L, K2HPO4·3H2O 2.14 g/L and NaCl 0.5 g/L. The test result of 67.44% antifungal inhibition agreed with the prediction and increased by 14.28% in comparison with the basal medium. 相似文献
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The scalable extension of H.264/AVC, known as scalable video coding or SVC, is currently the main focus of the Joint Video Team‘s work. In its present working draft, the higher level syntax of SVC follows the design principles of H.264/AVC.Self-contained network abstraction layer units (NAL units) form natural entities for packetization. The SVC specification is by no means finalized yet, but nevertheless the work towards an optimized RTP payload format has already started. RFC 3984, the RTP payload specification for H.264/AVC has been taken as a starting point, but it became quickly clear that the scalable features of SVC require adaptation in at least the areas of capability/operation point signaling and documentation of the extended NAL unit header. This paper first gives an overview of the history of scalable video coding, and then reviews the video coding layer (VCL)and NAL of the latest SVC draft specification. Finally, it discusses different aspects of the draft SVC RTP payload format, including the design criteria, use cases, signaling and payload structure. 相似文献
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In order to separate ZSM-5 zeolite powders from solution easily, a series of magnetic ZSM-5 zeolites were prepared by hydrothermal synthesis with the addition of magnetic Fe3O4 panicles during the crystalline process. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, infrared （IR） spectrum, energy dispersive X-ray （EDX）, specific surface area, magnetic susceptibility and adsorption capability. It was found that the magnetic ZSM-5 zeolites had good magnetism and the magnetic susceptibility increased with the increasing amount of Fe3O4 panicles. Compared with the pure ZSM-5 zeolite, the adsorption capability of magnetic ZSM-5 zeolites was acceptable. When the magnetic zeolites were used to adsorb Pb^2＋ from solution, the magnetic zeolite powder could be conveniently separated with magnetic separation technology. 相似文献
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Sammy Perone Stephen J. Molitor Aaron T. Buss John P. Spencer Larissa K. Samuelson 《Child development》2015,86(3):812-827
Executive functions enable flexible thinking, something young children are notoriously bad at. For instance, in the dimensional change card sort (DCCS) task, 3‐year‐olds can sort cards by one dimension (shape), but continue to sort by this dimension when asked to switch (to color). This study tests a prediction of a dynamic neural field model that prior experience with the postswitch dimension can enhance 3‐year‐olds' performance in the DCCS. In Experiment 1A, a matching game was used to preexpose 3‐year‐olds (n = 36) to color. This facilitated switching from sorting by shape to color. In 3 , 3‐year‐olds (n = 18) were preexposed to shape. This did not facilitate switching from sorting by color to shape. The model was used to explain this asymmetry. 相似文献
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According to most theories, in a simple contingency learning situation, excitatory learning occurs when the probability of the unconditioned stimulus in the presence of the conditioned stimulus (p1) is higher than the probability of the unconditioned stimulus in the absence of the conditioned stimulus (p2). In Rescorla and Wagner??s (1972) model, this prediction varies, depending on the parameters used. In the following experiments, we evaluated whether the difference between p1 and p2 that is required to produce excitatory conditioning is the same, independent of the specific value of p1, or whether this difference varies proportionally to p1??s value. To do so, an appetitive procedure of Pavlovian conditioning with rats was used. In four experiments, we compared different levels of contingency (low, medium and high) and found that the difference between p1 and p2 that is required to produce excitatory conditioning increases when the value of p1 is higher. The possibility of analyzing contingency learning as a discrimination between p1 and p2 is also discussed. 相似文献