994 resultados para Simulate


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Population data which collected and saved according to administrative region is a kind of statistical data. As a traditional method of spatial data expression, average distribution in every administrative region brings population data on a low spatial and temporal precision. Now, an accurate population data with high spatial resolution is becoming more and more important in regional planning, environment protection, policy making and rural-urban development. Spatial distribution of population data is becoming more important in GIS study area. In this article, the author reviewed the progress of research on spatial distribution of population. Under the support of GIS, correlative geographical theories and Grid data model, Remote Sensing data, terrain data, traffic data, river data, resident data, and social economic statistic were applied to calculate the spatial distribution of population in Fujian province, which includes following parts: (1) Simulating of boundary at township level. Based on access cost index, land use data, traffic data, river data, DEM, and correlative social economic statistic data, the access cost surface in study area was constructed. Supported by the lowest cost path query and weighted Voronoi diagram, DVT model (Demarcation of Villages and Towns) was established to simulate the boundary at township level in Fujian province. (2) Modeling of population spatial distribution. Based on the knowledge in geography, seven impact factors, such as land use, altitude, slope, residential area, railway, road, and river were chosen as the parameters in this study. Under the support of GIS, the relations of population distribution to these impact factors were analyzed quantificationally, and the coefficients of population density on pixel scale were calculated. Last, the model of population spatial distribution at township level was established through multiplicative fusion of population density coefficients and simulated boundary of towns. (3) Error test and analysis of population spatial distribution base on modeling. The author not only analyzed the numerical character of modeling error, but also its spatial distribution. The reasons of error were discussed.

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Earlier studies on the distribution of geological environmental indicators in China revealed drastic changes from a zonal climate pattern (planetary-wave-dominant pattern) in the Paleogene to a monsoon-dominant one in the Neogene, which suggested an inception of the initial East-Asian summer monsoon. However, there are different views about the time and causes of the changes.Here, we attempt to compile a series of paleoenvironmental maps based on newly collected climate indicators from the literatures and chronologically constrained evidence of geological maps in order to re-examine the temporal and spatial evolution of climate belts in China during the Cenozoic with special emphasis on the changes of the arid belt. These indicators include mammalian fauna, coal, carbonate concretions, jarosite, salt, gypsum deposits and pollen assemblages etc, with chronological controls that we believe reliable. Pollen assemblages and mammalian fauna have been classified into three categories (arid, semi-arid/sub-humid, humid) to reflect the intensity of aridity/humidity. Salt, jarosite and gypsum deposits are classified as the arid indicators. Carbonate concretions and coal are classified into the semi-arid/sub-humid and humid one respectively. Paleoenvironmental maps at 8 time slices have been reconstructed. They are the Paleocene, Eocene, Oligocene, Miocene, Early Miocene, Middle Miocene, Late Miocene and Pliocene.And furthermore, we attempt to use IAP^AGCM to simulate the evolution of climate belts in emphasizing on the changes of the rain band, and compare the results with the paleoenvironmental maps in order to examine the causes of the drastic paleoenvironmental changes near the Oligocene/Miocene boundary. 36 sensitive numerical experiments are carried out using the IAP__AGCM to analyze the impacts of the uplift of the Himalayan-Tibetan complex, shrinkage of the Paratethys Sea, expansion of the South China Sea and the development of the polar ice sheets on rain band in China.The main conclusions are as follows:The obtained results essentially confirm the earlier conclusions about a zonal climate pattern in the Paleogene and a different pattern in the Neogene, and illustrate that a monsoon-dominant environmental pattern with inland aridity formed by the Early Miocene, which is temporally consist with the onset of eolian deposits in China.Cenozoic cooling and the formation of polar ice sheets are unlikely the main causes to the changes of environmental patterns mentioned above in China. But northern hemispheric cooling and the ice-sheets can intensify the Siberian High Pressure, and strengthen the winter monsoon circulations and enhance the aridity in the west part of China. These results support the earlier studies.Shrinkage of the Paratethys Sea and uplift of the Himalayan-Tibetan complex played important roles in strengthening the East Asian monsoon and induceing the above changes of environmental pattern, which is consistent with the earlier studies. Furthermore, "the monsoon-dominant pattern" appears when the Himalayan-Tibetan complex reaches to about 1000-2000 meters high and the Paratethys Sea retreats to the Turan Plate.4) Expansion of the South China Sea is another significant factor that drives the evolution of environmental patterns. We believe that the above three factors co-act and drive the change of the environmental patterns from a planetary-wave-dominant one to a monsoon-dominant one. However, the impacts of each factor vary by regions. The uplift mainly increases the humidity in Southwestern China and the aridity in northwestern country. The shrinkage mainly increases the humidity in Northern China and also enhances the aridity in the northwestern country. The expansion greatly increases the humidity in the south part of China.

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With the improving of mantle convection theory, the developing of computing method and increasing of the measurement data, we can numerically simulate more clearly about the effects on some geophysical observed phenomenons such as the global heat flow and global lithospheric stress field in the Earth's surface caused by mantle convection, which is the primary mechanism for the transport of heat from the Earth's deep interior to its surface and the underlying force mechanism of dynamics in the Earth.Chapter 1 reviews the historical background and present research state of mantle convection theory.In Chapter 2, the basic conception of thermal convection and the basic theory about mantle flow.The effects on generation and distribution of global lithospheric stres s field induced by mantle flow are the subject of Chapter 3. Mantle convection causes normal stress and tangential stresses at the bottom of the lithosphere, and then the sublithospheric stress field induces the lithospheric deformation as sixrface force and results in the stress field within the lithosphere. The simulation shows that the agreement between predictions and observations is good in most regions. Most of subduction zones and continental collisions are under compressive. While ocean ridges, such as the east Pacific ridge, the Atlantic ridge and the east African rift valley, are under tensile. And most of the hotspots preferentially occur in regions where calculated stress is tensile. The calculated directions of the most compressive principal horizontal stress are largely in accord with that of the observation except for some regions such as the NW-Pacifie subduction zone and Qinghai-Tibet Plateau, in which the directions of the most compressive principal horizontal stress are different. It shows that the mantel flow plays an important role in causing or affecting the large-scale stress field within the lithosphere.The global heat flow simulation based on a kinematic model of mantle convection is given in Chapter 4. Mantle convection velocities are calculated based on the internal loading theory at first, the velocity field is used as the input to solve the thermal problem. Results show that calculated depth derivatives of the near surface temperature are closely correlated to the observed surface heat flow pattern. Higher heat flow values around midocean ridge systems can be reproduced very well. The predicted average temperature as a function of function of depth reveals that there are two thermal boundary layers, one is close to the surface and another is close to the core-mantle boundary, the rest of the mantle is nearly isothermal. Although, in most of the mantle, advection dominates the heat transfer, the conductive heat transfer is still locally important in the boundary layers and plays an important role for the surface heat flow pattern. The existence of surface plates is responsible for the long wavelength surface heat flow pattern.In Chapter 5, the effects on present-day crustal movement in the China Mainland resulted from the mantle convection are introduced. Using a dynamic method, we present a quantitative model for the present-day crustal movement in China. We consider not only the effect of the India-Eurasia collision, the gravitational potential energy difference of the Tibet Plateau, but also the contribution of the shear traction on the bottom of the lithosphere induced by the global mantle convection. The comparison between our results and the velocity field obtained from the GPS observation shows that our model satisfactorily reproduces the general picture of crustal deformation in China. Numerical modeling results reveal that the stress field on the base of the lithosphere induced by the mantle flow is probably a considerable factor that causes the movement and deformation of the lithosphere in continental China with its eflfcet focuing on the Eastern China A numerical research on the small-scale convection with variable viscosity in the upper mantle is introduced in Chapter 6. Based on a two-dimensional model, small-scale convection in the mantle-lithosphere system with variable viscosity is researched by using of finite element method. Variation of viscosity in exponential form with temperature is considered in this paper The results show that if viscosity is strongly temperature-dependent, the upper part of the system does not take a share in the convection and a stagnant lid, which is identified as lithosphere, is formed on the top of system because of low temperature and high viscosity. The calculated surface heat flow, topography and gravity anomaly are associated well with the convection pattern, namely, the regions with high heat flow and uplift correspond to the upwelling flow, and vice versa.In Chapter 7, we give a brief of future research subject: The inversion of lateral density heterogeneity in the mantle by minimizing the viscous dissipation.

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Online shopping has been a growing phenomenon all over the world as well as China in the recent years. Studies on online shopping with clickstream data have become a new research stream. But it is a pity that the online conversion rate is low. Accordingly, we can study on online consumers focusing on their shopping motivation, and put their shopping motivation and clickstream behavior into an integrative frame, study on the both construction and their relationship, and then we can get insight in chinese online consumers. This study has two processes. First, this study will use the questionnaire to explore all kinds of consumers’ online shopping motivation, and then emend the questionnaire and form the ultimate one for the second process. Second, we will simulate a shopping site to get clickstream data, participants need to complete the ultimate questionnaire at the same time. We will analyse the integrated data from two measures, cluster analysis separately, and explore the correspondence between the two cluster methods. Results show that, first, Chinese online shoppers contain five steady motivation factors: usefulness, fashion involvement, ease of use on searching, ease of use on alternative evaluation, ease of use after trade. Fashion involvement is comparatively independent, while the other have correlations between each two. Second, Chinese consumers can be clustered into five steady clusters according to online shopping motivation: functional shoppers, following shoppers, surfing shoppers, conflicting shoppers, e-laggard. The five clusters have significant differences on job, monthly income and online shopping experience of late six months, while have no significant differences on gender, age and education. Third, Chinese consumers can be clustered into five steady clusters according to clickstream data: functional browsers, hedonic browsers, impulsive shoppers, comparative shoppers and knowledge building browsers. The five clusters have significant differences only on age, while have no significant differences on other demographic variables. Fourth, the cluster methods according to motivation and according to clickstream data are two comparatively independent cluster frame, but they have limit correspondence.

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The Bifurcation Interpreter is a computer program that autonomously explores the steady-state orbits of one-parameter families of periodically- driven oscillators. To report its findings, the Interpreter generates schematic diagrams and English text descriptions similar to those appearing in the science and engineering research literature. Given a system of equations as input, the Interpreter uses symbolic algebra to automatically generate numerical procedures that simulate the system. The Interpreter incorporates knowledge about dynamical systems theory, which it uses to guide the simulations, to interpret the results, and to minimize the effects of numerical error.

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Both multilayer perceptrons (MLP) and Generalized Radial Basis Functions (GRBF) have good approximation properties, theoretically and experimentally. Are they related? The main point of this paper is to show that for normalized inputs, multilayer perceptron networks are radial function networks (albeit with a non-standard radial function). This provides an interpretation of the weights w as centers t of the radial function network, and therefore as equivalent to templates. This insight may be useful for practical applications, including better initialization procedures for MLP. In the remainder of the paper, we discuss the relation between the radial functions that correspond to the sigmoid for normalized inputs and well-behaved radial basis functions, such as the Gaussian. In particular, we observe that the radial function associated with the sigmoid is an activation function that is good approximation to Gaussian basis functions for a range of values of the bias parameter. The implication is that a MLP network can always simulate a Gaussian GRBF network (with the same number of units but less parameters); the converse is true only for certain values of the bias parameter. Numerical experiments indicate that this constraint is not always satisfied in practice by MLP networks trained with backpropagation. Multiscale GRBF networks, on the other hand, can approximate MLP networks with a similar number of parameters.

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Studying chaotic behavior in nonlinear systems requires numerous computations in order to simulate the behavior of such systems. The Standard Map Machine was designed and implemented as a special computer for performing these intensive computations with high-speed and high-precision. Its impressive performance is due to its simple architecture specialized to the numerical computations required of nonlinear systems. This report discusses the design and implementation of the Standard Map Machine and its use in the study of nonlinear mappings; in particular, the study of the standard map.

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Two kinds of process models have been used in programs that reason about change: Discrete and continuous models. We describe the design and implementation of a qualitative simulator, PEPTIDE, which uses both kinds of process models to predict the behavior of molecular energetic systems. The program uses a discrete process model to simulate both situations involving abrupt changes in quantities and the actions of small numbers of molecules. It uses a continuous process model to predict gradual changes in quantities. A novel technique, called aggregation, allows the simulator to switch between theses models through the recognition and summary of cycles. The flexibility of PEPTIDE's aggregator allows the program to detect cycles within cycles and predict the behavior of complex situations.

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The characteristics of a compact plate-fin reformer (PFR) which integrates endothermic and exothermic reactions into one unit have been investigated by experiment as well as by numerical simulation. One reforming chamber was integrated with two vaporization chambers and two combustion chambers to constitute a single unit of PFR. In the PFR, which is based on a plate-fin beat exchanger, catalytic combustion of the reforming gas is used to simulate the fuel cell anode off gas (AOG) which supplies the necessary heat for the methanol steam reforming. Temperature distributions in all chambers and composition distribution in reforming chamber have been studied, and the effect of the ratio of H2O/CH3OH on the performance of the PFR has also been investigated. A model of the PFR was derived using a three-dimensional numerical model for a cross-current flow arrangement. Theoretical predictions of the temperature distributions in the PFR were in good agreement with experimental values. In addition, the numerical model was able to accurately predict the methanol conversion and the reformate composition in reforming chamber. © 2005 Elsevier B.V. All rights reserved.

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A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectrum of the anion SO. Geometry optimizations and harmonic vibrational frequency calculations have been performed on the XA(1) state of SO2 and (XB1)-B-2 state of SO2. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of SO2. The theoretical spectra obtained by employing CCSD(T)/6-31 I+G(2d,p) values are in excellent agreement with the experiment. In addition, the equilibrium geometric parameters, r(c)(OS) = 0.1508 +/- 0.0005 nm and theta(e)(O-S-0) = 113.5 +/- 0.5 degrees, of the (XB1)-B-2 state of SO2, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. (c) 2005 Elsevier B.V. All rights reserved.

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This document contains the 'hard' code for the Java program "AgileSim_updated.java", complete with comments. This program accompanies the article "Process Control in Agile Supply Chain Network" and was the program used to simulate the data for the illustrative example in the article.

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Essery, RLH & P, Etchevers, (2004). Parameter sensitivity in simulations of snowmelt. Journal of Geophysical Research, 109, doi:10. 1029/2004JD005036.

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Essery, RLH & JW, Pomeroy, (2004). Vegetation and topographic control of wind-blown snow distributions in distributed and aggregated simulations. Journal of Hydrometeorology, 5, 735-744.

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Hutzler, S., Weaire, D., Cox, S.J., Van der Net, A. and Janiaud, E. (2007) Pre-empting Plateau: the nature of topological transitions in foam. Europhys. Lett. 77: 28002 Sponsorship: EPSRC / ESA / ESTEC / Science Foundation Ireland/ Gulbenkian Foundation

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Kingston-Smith, A. H., Bollard, A. L., Humphreys, M. O,, Theodorou, M. K. (2002). An assessment of the ability of the stay-green phenotype in Lolium species to provide an improved protein supply for ruminants. Annals of Botany, 89(6), 731-740. Sponsorship: BBSRC/MAFF/Milk Development Council/Meat and Livestock Commission/Industry. RAE2008