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1.
In this paper,a novel WLAN system,Cognitive WLAN over Fiber (CWLANoF),is introduced in the first place.Moreover,when CWLANoF has more channels than STAs,a new channel allocation scheme is proposed using the Hungarian algorithm,which is demonstrated to be the optimal one.Furthermore,when CWLANoF has fewer channels than STAs,it is possible for more than one STA to share the same channel simultaneously based on the new features of CWLANoF.And the power control scheme is proposed for this kind of sharing,considering efficiency and fairness.Finally,extensive simulation results illustrate the significant performance improvement of the proposed channel allocation scheme and power control scheme.  相似文献   

2.
The comparative study between unsteady flow models in alluvial streams shows a chaotic residue as for the choices of a forecasting model. The difficulty resides in the choice of the expressions of friction resistance and sediment transport. Three types of mathematical models were selected. Models of type one and two are fairly general, but require a considerable number of boundary conditions, which related to each size range of sediments. It can be a handicap during rivers studies which are not very well followed in terms of experimental measurements. Also, the use of complex models is not always founded. But then, the model of type three requires a limited number of boundary conditions and solves only a system of three equations at each time step. It allows a considerable saving in calculating times.  相似文献   

3.
The paper investigates the internal structures of hereditary inductive types in logical type theory. By defining a bisimulation equality on the inhabitants of each hereditary inductive type, one is able to show that the inhabitants of a hereditary inductive type satisfy the basic properties of sets. A hereditary inductive type can therefore be conceived as a universe of sets.  相似文献   

4.
Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year’s running. It is beneficial for the system to operate for long period.  相似文献   

5.
The constitutive model of rock can be built by mechanics elements because there are many kinds of damages in rock under varied loads. It is resumed that rock contains many microstructures and a structure of Bingham. The microstructure consists of two embranchments that are the unit of a spring and a gliding slice in series and the unit of a spring and a cementation bar in series, the two units connect each other in parallel. These microstructures are arranged disorderly or in the order of a certain state. A certain distribution of microstructures represents one type of rock. Two kinds of rock's constitutive relationship were deduced by using the model. One is the model in which many parallel microstructures and a structure of Bingham connect in series. And it is used to homogeneous rock. The other is the model in which many microstructures and a structure of Bingham connect in series. And it is used to the rock with much crack or microcrack in a certain direction. The two kinds of constitutive relationship were verified by the studied cases. The constitutive model of rock built by using mechanics elements is verified to be reasonable. Moreover, different types of rocks may be described with mechanics elements with different distributions.  相似文献   

6.
Based on the multipole expansion theory of the potential, a satisfactory interpretation is put forward of the exact nature of the approximations of asymptotic boundary condition (called the ABC) techniques for the numerical solutions of open-boundary static electromagnetic-field problems, and a definite physical meaning is bestowed on ABC, which provide a powerful theoretical background for laying down the operating rules and the key to the derivation of asymptotic boundary conditions. This paper is also intended to reveal the shortcomings of the conventional higher-order ABC, and at the same time to give the concept of a new type of higher-order ABC, and to present a somewhat different formulation of the new nth-order ABC. In order to test its feasibility, several simple problems of electrostatic potentials are analyzed. The results are found to be much better than those of conventional higher-order ABCs.  相似文献   

7.
An artificial magnetic conductor (AMC) chessboard reflector is designed which shows low backscattered radar cross sections (RCS) in a broad frequency band in this paper. Designed by the phase cancellation principle, a conventional chessboard low RCS metasurface can be formed by polarization-dependent mushroom-shaped AMCs. Two new features are added to this design based on the conventional chessboard metasurface. Firstly, the long edge of the metallic patch on the AMC element is concave to obtain a broader bandwidth. Then, the width of the patch in each AMC block is tapered in one direction to further extend the operating bandwidth for RCS reduction. The backscattered RCS of the tapered AMC reflector is numerically investigated and compared with a non-tapered one. It is found that by introducing the above features, an RCS reduction greater than 10.dB can be obtained by the reflectors with relative bandwidth of 46% in the X-band.  相似文献   

8.
This paper proposes a new criterion called the ratio of safety margin(RSM)for use in the areas of the global factor of safety,reliability and limit states analyses with reference to their respective allowable criteria.An equation for calculating RSM based on the reliability index is formulated.Efforts for proving the applicability of this criterion include a theoretical demonstration in a simple one-variable case;an investigation on a test problem involving two random variables,followed by a slope stability study on a 156 m high embankment dam and an illustrative example presented in a EuroCode 7 guidebook.Calculation of the ratios of safety margin in the three areas provides a quantitative way to accommodate the analytical results within the same theoretical framework and makes the outcomes mutually comparable and supportive,which is much more enlightening than that would be the case by considering only one of them.Calculating RSMs for reliability and limit states methods has also helped solve the key issue concerning the uniqueness of the partial factors calibrated from a particular‘target case’.  相似文献   

9.
The gas torque in a twin-rotor piston engine (TRPE) was modeled using adiabatic approximation with instantaneous combustion. The first prototype of TRPE was manufactured. This prototype is intended for high power density engines and can produce 36 power strokes per shaft revolution. Compared with the conventional engines, the vector sum of combustion gas forces acting on each rotor piston in TRPE is a pure torque, and the combustion gas rotates the rotors while compresses the gas in the compression chamber at the same time. Mathematical modeling of gas force transmission was built. Expression for gas torque on each rotor was derived. Different variation patterns of the volume change of working chamber were introduced. The analytical and numerical results is presented to demonstrate the main characteristics of gas torque. The results show that the value of gas torque in TRPE falls to be less than zero before the combustion phase is finished; the time for one stroke is 30° in terms of the rotating angle of the output shaft; gas torque in one complete revolution of the output shaft has a period which is equal to 60° and it is necessary to put off the moment when gas torque becomes zero in order to export the maximum energy.  相似文献   

10.
A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation (PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is pres-ented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The re-suits of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.  相似文献   

11.
针对现代战争中地下维修器材库选址的特殊性,构建了基于区域确定的模糊优化选址方法,利用微分法选择最优库址区域,根据诸多影响因素建立选址评价指标体系,利用AHP法确定权重,运用多级模糊综合评判进行优化选择,确定最优选址方案.较好地解决了普遍进行选址前期工作量大的难题.  相似文献   

12.
针对河流-三角洲储层沉积微相自动识别问题,根据取芯井分析资料和专家解释结果,确定研究区块的沉积微相类型和地质规律,建立了标准模式库和专家经验库,选择和提取判别特征指标的基础上,构建了可同时处理定性专家知识和定量数据的加权模糊推理神经网络进行微相判别的方法.考虑过渡性沉积相在识别中存在的多解性,在小层对比基础上,参照邻井同层微相识别结果,依据区块地质规律采用模糊逻辑推理方法确认和修正微相识别类型,保证平面沉积相和小层单井相的一致性.通过对实际资料处理,其方法的符合率达到84.1%.  相似文献   

13.
电子政务决策支持系统中数据仓库的研究与设计   总被引:6,自引:0,他引:6  
通过对数据仓库技术及决策支持系统的研究,提出了基于数据仓库的电子政务决策支持系统。如何构建异构的电子政务数据仓库,使之能为电子政务中政府决策提供支持是一个较为复杂的问题。通过对电子政务决策支持系统中数据仓库的研究,重点介绍了数据仓库的设计过程和关键技术,设计了相应的数据仓库,并且提供了具体的实施方案。  相似文献   

14.
从数据挖掘和数据仓库的基本概念入手 ,简要介绍了数据挖掘和数据仓库的特点和其研究的现实意义。然后介绍了模糊理论 ,由于模糊理论贴近于人们的自然思维习惯 ,所以 ,可把它应用到数据挖掘中 ,这样更加有利于解决现实问题 ,更好地在数据仓库中实现信息的挖掘。并且 ,以一个商品查询系统为例 ,对基于模糊理论的数据仓库中数据挖掘的算法给出了其实现方法。结果证明这是可行的 ,并具有一定的现实意义。  相似文献   

15.
以工业工程的精益思想为基础,以J物流公司W仓库为例,对物流企业货物搬运系统进行研究。通过实地走访、观察、操作发现货物到达仓库进行转运时现场布局、解封登记流程以及货物搬运流程存在问题,以布局优化、双手作业分析、流程程序分析等理论方法为基础,提出合理可行的优化方案,降低人力成本和时间成本,从而提高货物搬运系统的效率。  相似文献   

16.
总图运输设计方案的模糊评价   总被引:5,自引:0,他引:5  
利用模糊数学的方法对总图运输设计方案进行了评价。确定了方案评价中定量指标的隶属函数,提出了定性指标隶属函数的确定方法——模糊多相综合统计法,建立了总图运输设计方案模糊评价的数学模型。  相似文献   

17.
提出了一种改进的粒子群优化算法,并将其应用于集成电路布线,建立了相应的优化模型。对于给定的版图布线平面,该算法结合无网格算法的思路,首先由障碍图形和各个线网的端点生成一个包含最短路径的无网格访问点阵,然后根据粒子群算法的思路建立初始粒子位置矩阵,并利用其全局寻优功能找到当前布线路径上的最短路径.  相似文献   

18.
采用弗诺德模型,建立比例为1/2的大空间缩尺模型试验系统,开展高架仓库ESFR自动喷水灭火系统的火灾模型试验。自动喷水灭火系统方案为:在最高处高达16 m的高架仓库内,喷头采用快速响应早期抑制喷头(ES-FR喷头),喷头设置距地面为12 m的位置,按间距3.0 m×2.9 m布置,喷头上安装直径为700 mm、中间最大高度为150 mm的圆锥形集热板。该方案基本上可以将该仓库内的火灾控制在三排货架的范围内,而不再向周围货架蔓延。  相似文献   

19.
为将模糊的集成电路版图进行复原,探讨了Lucy-Richardson滤波、维纳滤波、拉格朗日乘法算子最小二乘方滤波方法.研究发现:噪声模糊图像进行复原时,Lucy-Richardson方法基本恢复不出集成电路版图,维纳滤波的去噪声明显但是图像清晰度不够,拉格朗日乘法算子最小二乘方滤波复原版图清晰;恢复清晰集成电路的版图可以用于集成电路的结构分析和集成电路失效机理诊断.  相似文献   

20.
针对我国工程索赔经验少、索赔专家稀缺的实际情况,提出了一种基于Web的工程索赔决策支持系统,首先综合了数据仓库,联机分析处理,数据挖掘技术于一体的综合决策支持系统,给出了数据仓库、模型库和知识库的具体设计,最后对系统的实现作了简要的介绍,该系统的应用旨在建立一个功能强大的在线工程索赔支持平台,共享索赔专家丰富的知识和经验,帮助承包商完成复杂的索赔工作。  相似文献   

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