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1.
In the HFC network, the funnelling effect of noise is the main restrict matter of raising the rate in the up stream channel. The requirements for the wide band services in a up stream channel are fist studied, and used as the criteria to compare the transfer ways each other used in up stream channel. Then, the ways in DOCSIS are analyzed, which were used to resist the noise, and the effect is showed by an example. The raised ability of resisting noise in the CDMA is obtained by reducing the transfer rate. Although it has a little better performance in resisting noise, but the rate is low and can not meet the requirements of wide band services. A kind of network structure is given, in which the users are connected in serial way, the noise funnelling is eliminated and have a high rate in the up stream channel. It is suitable for the wide band services, but the technology realizing the network structure needs perfecting.  相似文献   

2.
The problems are discussed in positive pressure mechanical air supply system design, when the actual status is far different from what figures in the code based. Expressions must be used to determine the supply air rate. The rate between length and width of rectangle air channel should be less than 6. To avoid some uncertain factor, correction factor for absolute coarseness should choose the bigger figure. The smoke control and extraction design of smoke controlling stair hall must be divide into two parts: The overground and the underground. When setting positive pressure mechanical air supply system in smoke controlling stair hall, the outer window in the hall must be fixed. To insure the inner surface of smoke controlling stair hall keep compact and lubricity, communion should be done with governor of builders.  相似文献   

3.
Survivability is defined as the capability of a system to fulfill its mission, in a timely manner, in the presence of attacks, or accidents. A key characteristic of survivable systems is their capability to deliver essential services in the face of attack, failure, or accident. Thus, it is important to deliver essential services in the survivability network system. Mobile Agent has a character of motion besides reactive, autonomy and oriented-objective as a new technology. By discussing the characters of survivability network system and mobile agent, this paper presents a model for essential services mobility based on mobile agent-MESMMA. This paper mainly focuses on the design of both MESMMA system and mobile agent inner architecture.  相似文献   

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When a fire happens at the subway platform, the downward ventilation at the staircase which connects the hall and platform can prevent smoke spreading into the hall and provides guiding air for evacuation people. To investigate the influence of the ventilation rate on the smoke movement, the air velocity at the staircase was measured under three ventilation modes. Numerical model was established to simulate the real fire scenario. It is shown that the downward air velocity under fire is greater than that without fire, and the traditional design procedure without considering complex factors interaction in real fire scenario should be improved; when fire is near the staircase, smoke easily spills from the smoke screen to the concourse. And smoke concentration of concourse is even higher than that of platform because the hall is under air supply mode; when the fire locates at the public area of the platform, turning on the tunnel fans can increase the downside flow at the staircase. However exceeding high flow can produce disturbance and destroy the smoke stratification, so more area will be filled with smoke. Therefore, reasonable smoke management scheme is as important as smoke exhausting system capability.  相似文献   

7.
LI Yong  ZHU Dan  PENG Jie 《保鲜与加工》2004,(3):157-159167
To improve the quality of services ,especially the quality of information services is the most important factor which hels securities companies to win the furious competition. Many securities companies can' t use their mass history data very well. The company exists many database environment, so it's very difficult to integrate the different data resources. OLAP technology provides a good resolution for this matter. Through using Data Warehouse , OLAP technology ,theory of DSS and securities analysis, this paper provides a system resolution of securities analysis OLAP system, and through this system to aid management decision and provides better information services for customers.  相似文献   

8.
In this paper, the space origin and space types of the cliff-side Buddhist hall are discussed. With quite a few examples, the space character and space arrangement of the cliff-side Buddhist hall in Ba-shu area are inquired with multi aspects such as the line of sight, scale, lighting and inner and outer flow of the space.  相似文献   

9.
Ecosystem services imply the natural environmental conditions and their effectiveness formed and sustained by ecosystems and ecological processes. From the view of city planning, in this paper, the evolution of the conception of ecological service-value and the relationship between the ecological service-value and city planning are reviewed. At the same time, it raised a conception about ecological space service value and negative ecological effect and an innovation proposal on city planning is presented.  相似文献   

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The interaction of phonons and the thermoequilibrium of a crystal are analyzed with Boltzmann equation and Landau equation.The thermoequilibrium of a crystal is the result of interaction of phonons.There is no interaction of phonons in the harmonic approximation. A cbystal can not reach the state of thermoequilibrium in the harmonic approximation.  相似文献   

12.
According to the urgent need for motorcycle parts enterprise to improve the ability of information exchange and business collaboration between the production process and other links such as the marketing, design, production planning, outsourcing, purchasing and delivering, an integration framework of the intergraded workshop production management system for motorcycle parts enterprise is presented. It can be integrated with the designing and production planning management systems upwards, the workshop equipments and workers downwards, and the subcontract production and supply chain management systems outwards. Then, some key technologies are studied, such as the realization scheme of system integration based on Service Oriented Architecture (SOA), the data integration and sharing mechanism of heterogeneous information system based on eXtensible Markup Language (XML), and the real-time interaction technology of workshop information based on the multi-functional interactive information terminals, etc. Finally, the system is developed and successfully applied in a motorcycle parts enterprise, and good results are obtained.  相似文献   

13.
The whole reliability index of a slope is derived through using the strength reduction method in the finite element analysis, which can make use of the former finite element program and can be used to both linear and nonlinear finite element analysis. The affection of the evaluation of derivative and the selection of reliability analysis methods is discussed, which shows that it is very important to select the type of limit state function of the slope stability. A new iterafive formula, which can consider the correlation of fundamental parameters, is proposed for FORM, and the convergence is very well.  相似文献   

14.
PFI is one of the novel approaches for the private finance in public works. The initiative aims on encouraging the private sector to undertake infrastructure projects and the provision of services on a project basis, rather than by the traditional means of procurement. PFI has been widely applied in a large number of fields in public works of government. PFI has become one of the government's main instruments for delivering higher quality and more effective public services. Two of the principal tenets of PFI is: the first is to secure value for money for the public sectors and the second to transfer the ongoing risk in the continued delivery of a service away from the public sector to the private sector.  相似文献   

15.
A method of constructing GPS-based positioning services system by means of JAVA technology is introduced in this paper. The position data, which are sent from GPS satellites, are received by GPS receiving terminal and are analyzed by mobile computing client developed on J2ME in accordance with the differential GPS algorithm. The client submits special position querying information to position server in way of wireless GPRS network. After computing and data querying, the server developed by J2EE returns results to the mobile device. Then, the mobile computing client displays the position map or carries out further processing. All of these form a highly precise location-based services system.  相似文献   

16.
In this paper,a new method of water flushing recovery of waste glsss is presented. The equipment of separation of glass from waste materials and it' s mechanisms are described.The relationship between the efficiency of separation of glass from waste materials and the physical and mechanical properties of these waste materials is analyzed. The experimental results of recovery of waste glass are given. It is found that the efficiency of recovery of glass is more than 90%.  相似文献   

17.
For the benefit of environment protection and sustainable economic development especially in western china, to build more hydroelectric power stations is a basic policy of our government. Xiluodu project is the biggest underground hydroelectric power station. which includes 18 power generation units with a capacity more than 12 600 MW. By establish a set of heat and humidity balance equations applying on the Xiluodu project underground workshop with its boundary conditions, this paper has present an one_dimensional heat conduction model to simulate its dynamical heat transfer process. On the purpose of compare deferent design schemes of HVAC system, a package of software for numerical simulation is developed. In this paper,we have also recommend some criteria for the evaluation of HVAC system design schemes. The computation result has show that if utilizing the reservoir water and AC chiller to process the air,combing other anti_humidification technical measures,it will assure the anticipated air quality of underground facilities.  相似文献   

18.
Taking the effect of industrial workshop’s aspect ratio on indoor temperature distribution as research object,using finite volume numerical method to dispersed solving for mass conservation equation and energy conservation equation.This paper research distribution of streamline and isotherm and variation of Nu in industrial workshop of different aspect ratio with Ra among 10 3~10 6.The results of analysis indicate that when increasing Ra,heat transmission form turns heat conduction into convection heat transfer,the isotherms change from vertical to horizontal gradually.The indoor streamlines form two vortexes around the model boundary,the vortexes are broken up with Ra.It’s separated into two vortexes when B=0.5 or B=1.And it’s separated into three vortexes when B=3 or B=2 with slight turbulent state. Nu increases with the increase of Ra and the related curve presents power exponent.when B=3 Nu is the largest and indicate that the total quantity of heat transfer at most by high temperature wall face cold wall.  相似文献   

19.
Calculating generalized inverse of a matrix is a basic algorithm for inverstigating linear equations and optimization problems. In this paper we investigate the algorithm of generalized inversion of a matrix by using Orthogonalized Back-Propagation Algorithm (OBPA). There is no problem for convergence in OBPA. It is shown how OBPA avoids some of the difficulties posed by the Back-Propagation(BP)algorithm.  相似文献   

20.
There exists muchinterference in machining internal spiral groove with big lift angle and small size, whichis a difficult problem. The design and calculation of tool section is analyzed in this paper while differentcutters are utilized to machine the groove when the tool axis is parallel or skew to that of the work piece. The approximating method of using circular-arc cutter is put forward, which is proved by the calculation and analysis to be a feasible method within range of the permissible error. The digital simulation of machining internal spiral groove which is finished by different methods, such as simulation of tool path, error analysis, verification of the cutter design and so on, has been done through typical software such as the Program files function of I-DEAS and the Manufacturing Module of UG.  相似文献   

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