COMPUTER SIMULATION OF METHANE MIGRATION IN LONGWALL PANELS WITH DESCENSIONAL VENTLIATION

It is important to study the methane transport phenomenon in a longwall panel under descensional ventilation conditions. In this paper the gob area is divided into a number of nodes to represent the rectangular percolating elements. The connectionslbetween nodes (elements) become branches ,so that a network can be formed. Using the mechanics of porous media fluid flow the mathematical model of air and gas flows has been established. Based on the existing ground pressure theories，the porosity of the inhomogeneous porous media in the gob can be given. In computer simulation it is considered that air pressure and temperature are functions of position；air density，viscosity ，and natural ventilation pressure are functions of temperature，pressure and methane concentration rand the resistance varies with air density and viscosity. Finally，the calcu-lation results are given to show the differences between ascensional and descensional ventilation methods.     

Analysis of Heat Environment Indexes Using Integrated Remote Sensing and Site Measurement Techniques in a Community

Remote sensing and on？site measurement are used to determine the heat environment within a community, and are compared the differences for heat analysis. The two methods perform differently for various underlying surfaces. The individual methods can detect different aspects of the heat environment, which used in combination are useful for heat island research. The differences in estimated air and surface temperatures are smaller in open space and more obvious for vegetated surfaces. Ventilation does not affect the difference between air and surface temperature in open areas, and the vegetation surface and shading moderates surface temperature more effectively than the water surface; The forest is a type of underlying surface with heat comfortable, in which the feeling of air temperature is much difference to the structure of heat environment that should be survey and detected separately. The two methods can be used to study different aspects of the heat environment, thus forming a comprehensive approach for planners in urban and rural spaces.     

Quasi-Newton Method for Optimal Blank Allowance Balancing

A balancing technique for casting or forging parts to be machined is presented in this paper.It allows an optimal part setup to make sure that no shortage of material(undercut)will occur during machining.Particularly in the heavy part in- dustry,where the resulting casting size and shape may deviate from expectations,the balancing process discovers whether or not the design model is totally enclosed in the actual part to be machined.The alignment is an iterative process involving nonlinear con- strained optimization,which forces data points to lie outside the nominal model under a specific order of priority.Newton methods for non-linear numerical minimization are rarely applied to this problem because of the high cost of computing.In this paper, Newton methods are applied to the balancing of blank part.The aforesaid algorithm is demonstrated in term of a marine propeller blade,and result shows that The Newton methods are more efficient and accurate than those implemented in past research and have distinct advantages compared to the registration methods widely used today.     

ELASTOPLASTIC ANALYSIS OF THICK-WALL CYLINDER CONSIDERING THE MATERIAL＇S DILATANCY CHARACTER

Impermeable bentonite or its mixtures have been proposed as candidate materials to be used in the geotechnical disposal of radioactive nuclear waste. These materials are filled in the space between a canister containing radioactive nuclear waste and an underground chamber to absorb the radionuclide emitting from the canister and simultaneously retard its migration accompanying the permeation of underground water to prevent the surrounding environment from pollution. On the basis of the established elastoplastic strain-hardening mechanical model considering the material‘s dilatancy character, the authors carry out the stress-strain analysis of a thick-wall cylinder in a plane strain state subjected to a pressure difference between internal and external pressures. The analysis may be expected to be a theoretical basis for developing a coupled shear and permeability test apparatus for conducting a permeability test along a sheared plane in a specimen. The apparatus will be used to study the effects of shear strain on the variation of geotechnical materials′ permeability coefficient in order to evaluate the influence of shear strain caused by nonuniform deformation and/or earthquake on the long-term safety of the disposal system of radioactive nuclear waste. The theoretical analysis methods in this paper can be directly spread to the analysis of the deformation and stability of tunnels or roadways driven in soft soils or high moisture-bearing soft rocks.     

The operating point and selection of the fan in mine areas of high altitude

The atmosphere pressure, temperature and air density decrease with the increase of the altitude. But the air quantity in the mines and the air quantity supplied by the fan remain constant in spite of the change of the altitude.As the altitude increases, the decrease of air density causes the pressure losses of the mine and the air pressure of the fan to fall down proportionally; and for the same reason the output power of the motor is reduced, too. Thus the selection procedure of the fan is simplified. It isn't necessary to carry out complicated altitude correction in the ventilation design. Both the fan and the motor can be selected with normal methods. The only difference is that the practical operating point of the fan is lower than the one which is expected according to the design. The air pressure of the operating point of the fan is the designed air pressure of the operating point multiplied by the altitude correct coefficient. The air quantity of both operating points of the fan are equal.The paper expounds in theory the mine ventilation in areas of high altitude. The theory has been proved by a lot of data from tests. The paper serves as a theoretical reference for the design of mine ventilation in areas of high altitude and is of value to the work in practice.     

THE THEORY AND METHOD OF OPTIMUM PLANNING OF A MINING AREA

Being aimed at the vital decisive problems to be solved during.making long-term planning and overall planning of the development of coal mining areas of China, this paper presents comprehensive theories and methods for the choice of mining area optimum planning schemes by use of combining technic analysis with system simulation and system optimization.The main contents are as follows: the prediction of technic and economic indexes in the developing process of existing mining areas and new mining area, including computer simulation analysis of maximum possibility of output growth in a working mine, the effect of technic progress on productive development, and grey predictive model of the change of technic and economic indexes; the dynamic simulation model of the mining area system, including five subsystem models; mining area output, investment, economic benefit, number of workers and staff of a mining area, mining area population, and ecologic environmental dynamic change under different schemes;the 0--1 programming, the goal programming and the analytic hierarchy process for contrast analysis optimization of mining area planning schemes.     

Evolved clustering analysis of 300 MW boiler furnace pressure sequence based on entropy characterization

The furnace process is very important in boiler operation,and furnace pressure works as an important parameter in furnace process.Therefore,there is a need to analyze and monitor the pressure signal in furnace.However,little work has been conducted on the relationship with the pressure sequence and boiler’s load under different working conditions.Since pressure sequence contains complex information,it demands feature extraction methods from multi-aspect consideration.In this paper,fuzzy c-means analysis method based on weighted validity index(VFCM)has been proposed for the working condition classification based on feature extraction.To deal with the fluctuating and time-varying pressure sequence,feature extraction is taken as nonlinear analysis based on entropy theory.Three kinds of entropy values,extracted from pressure sequence in time-frequency domain,are studied as the clustering objects for work condition classification.Weighted validity index,taking the close and separation degree into consideration,is calculated on the base of Silhouette index and Krzanowski-Lai index to obtain the optimal clustering number.Each time FCM runs,the weighted validity index evaluates the clustering result and the optimal clustering number will be obtained when it reaches the maximum value.Four datasets from UCI Machine Learning Repository are presented to certify the effectiveness in VFCM.Pressure sequences got from a 300 MW boiler are then taken for case study.The result of the pressure sequence case study with an error rate of 0.5332%shows the valuable information on boiler’s load and pressure sequence in furnace.The relationship between boiler’s load and entropy values extracted from pressure sequence is proposed.Moreover,the method can be considered to be a reference method for data mining in other fluctuating and time-varying sequences.     

Error Analysis on the Positioning Accuracy of a Pneumatic Vibration Isolator

A method of error analysis on the positioning accuracy of a pneumatic vibration isolator was proposed. First, the necessity of positioning accuracy was studied, in addition to the key factors associated with positioning accuracy. These analyses indicated that the positioning accuracy of the pneumatic vibration isolator was mainly attributed to the position error of the push button and the gap between the spindle and valve stem. Second, the error model of the positioning accuracy of the pneumatic vibration isolator was established through geometric simplification and geometric calculation. There are different methods used to calculate the position error of the push button for the different valves. Finally, an example analysis evaluating the impact of a specific two-position three-way valve on the positioning accuracy was given by means of error distribution. Experimental results validated the accuracy of the error model and the example analysis. This error model can be used to guide the structural parameter optimization design according to the requirements for positioning accuracy.     

A new method of rapid quality detection of vacuum insulation panels

A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measuring gas pressure for VIPs,connecting an internal measurement gauge to external data acquisition units is problematic.The thin high barrier film covering the panel’s core usually prevents external electrical wires or mechanical devices being connected to the inside of the VIPs.To solve this problem,a micro capacitive pressure sensor with 0 to 250 Pa detection range is developed to detect the vacuum pressure.The sensor has high linearity and a sensitivity of 10 mV/Pa.Moreover,through the communication mode study,an ultrasound communications system for VIPs is designed.It shows from operation that this system is stable and reliable,and quick for communication speed.This new method enables the quality detection of VIPs to be completed within 1 second.The minimum detectable pressure of VIPs is below 1 Pa,and the measurement error can be controlled around 5%.     

A successful case of hydrocarbon dew point analysis during mixing of natural gases in transmission pipeline

The occurrence of liquid condensation in natural gas accounts for new challenges during the interoperability between transmission networks,where condensation would lead to higher pressure drops,lower line capacity and may cause safety problem.A successful case of hydrocarbon dew point （HCDP） analysis is demonstrated during the mixing of natural gases in the transmission pipeline.Methods used to predict the HCDP are combined with equations of state （EOS） and characterization of C6＋ heavy components.Predictions are compared with measured HCDP with different concentrations of mixed gases at a wide range of pressure and temperature scopes.Software named ＂PipeGasAnalysis＂ is developed and helps to systematic analyze the condensation problem,which will provide the guidance for the design and operation of the network.