Zigbee-Based Positioning System For Coal Miners

AbstractChina's present communication systems in coal mine can not effectively provide the information such as dynamic distribution of coal miners in work and production environment. Hence, rescue efforts are hard to be carried out in case of coal mine accident. To deal with this problem, the paper at first introduces the characteristics, structure and network construction method of ZigBee protocol. Then, by using the ZigBee technology based on IEEE802.15.4 criteria, the wireless communication network and the structure of ZigBee communication module for coal mine are studied and designed. At last, multilateration positioning algorithm is employed to realize the positioning of coal miners. Coal miner positioning system enters into computer management system via network, laying important actual significance to the production safety and emergent resuce of coal mine

Study on coal mine macro, meso and micro safety management system

SummaryIn recent years, the coal mine safety production situation in our country improved year by year, but severe accidents still occurred; the accidents caused great economic loss to the national economy. According to statistical analysis, almost all of the coal mine accidents will expose the hidden danger in before, most of the accidents caused due to safety management not reaching the designated position and the hidden danger management does not take any decision in time. Based on the coal mine safety management holes in our country, the coal mine macro, meso and micro safety management system was established in this paper, which includes meaning and conception of the theories of the macro, meso and micro safety management, and also includes the matching hardware equipment, in order to achieve the hidden danger's closed-loop control and dynamic early warning in the process of coal mine production

The Calculation Method of Safety Degree and Its Application in Coal Mine Enterprises

In order to evaluate the situation of safety production of coal mine enterprises effectively, quantitative analysis is necessary and very important. Safety degree of coal mine enterprises based on the concept of safety degree is defined and the method of calculating quantitatively the safety degree is put forward. The validity of this method is verified by empirical research in view of micro‐ and macroanalyses. In view of micro analysis the safety degree is derived with the calculation method based on information of one coal mine. The safety degree of this coal mine went through rapid increase period, stable period, and slow increase period. Macroresearch results show that the situation of safety production of coal mine enterprises in China has significantly been improving and the level of safety degree also has been increasing year by year since 1979, the year when the policy of reform and opening began. The reasons are the advancement of technology, strengthening of safety management and education, increasing of safety investment, and perfection of policies, laws, and regulations. These achievements can provide quantitative method for assessing the status of coal mines

The Relation of Gas Seepage and Coal Body Damage Under the True Three Dimension Stress

AbstractThe law of gas flow is the basis of coal and gas outburst prevention and gas drainage rate increase. Thus the relation of gas seepage and coal body damage under the true three dimension stress is studied. The research results show that when volume stress is not change with the change of pore pressure the permeability of coal body change with the parabolic law. The relation of damage and permeability of coal body is established. It can be known that during load of coal body the greater the damage occur, the more the permeability of coal body after unload decrease than primary permeability of coal body

Designing a Programming Contract Library for Java

Programmers are now developing large and complex software systems, so it’s important to have software that is consistent, efficient, and robust. Programming contracts allow developers to specify preconditions, postconditions, and invariants in order to more easily identify programming errors. The design by contract principle [1] was first used in the Eiffel programming language [2], and has since been extended to libraries in many other languages. The purpose of my project is to design a programming contract library for Java. The library supports a set of preconditions, postconditions, and invariants that are specified in Java annotations. It incorporates contract checking for objects of classes following the bean notation [3]. The library also supports checking for user-defined functions as contract conditions. This feature allows the user to check for complex contract conditions. In addition to these, the library supports contracts using lambdas in Java 8 [4], which to our knowledge has not been done in previous works on Java contracts. While the results show us that enabling contracts lowers the performance of the system, especially when lambda contracts are used, we also demonstrate how careful design can significantly reduce the overhead

Numerical Simulation on the Gas Explosion Propagation Related to Roadway

AbstractBased on the combustion, explosions and air dynamics and related theory etc, this paper describes the mathematical model of gas explosion in detail, combined with the gas explosion transmission mechanism, make a research on two wave-three area structure of gas explosion and the energy change rule of the array face of precursor wave and the array face of flame wave, with the fluid dynamics analysis Fluent software, this paper makes a numerical simulation and analysis on the overpressure transmission rule when gas explosion takes place in different types roadways. The results of the study show that: Fluent software can be used to accurately simulate gas explosion condition, when explosion wave spreads in the roadway turns, the bigger of the overpressure value in corner, the stronger of the destructive power; when tunnel has bifurcation, the overpressure will release in bifurcation, but explosions wave with flame wave will produce more powerful destruction effect. The research results can be used as a certain reference for how to prevent and control the gas explosion, and how to reduce the power of the gas explosion etc

Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.Comment: 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.0443

Experimental Study on Quantitative Application of Electromagnetic Radiation Excited by Coal-rock Fracture

A coal-rock uniaxial compression experimental investigation was conducted in laboratory. Electromagnetic radiation (EMR) and acoustic emission (AE) signals were gained during coal-rock fracture under different antenna types and arrangements. The results show that EMR excited by coal-rock fracture are broadband frequency, the EMR and AE signals are from the same source, but their generation mechanism is different. Under the same frequency band of antenna, the EMR amplitude from antenna parallel with crack plane is bigger than from antenna vertical to crack plane. Thus, EMR signals from developing crack propagates along the crack surfaces, which are principle contributions to total EMR signals and the EMR signals from antenna reflect the crack state parallel with receiving direction plane of antenna in coal-rock under uniaxial compression. A quantitative relationship between EMR frequency along the major crack plane and crack was derived by previous studies, which can be used into applications for coal-rock dynamic disaster prediction in the future

Numerical simulation of airflow distribution in mine tunnels

Based on 3D modelling of typical tunnels in mines, the airflow distribution in a three-center arch-section tunnel is investigated and the influence of air velocity and cross section on airflow distribution in tunnels is studied. The average velocity points were analyzed quantitatively. The results show that the airflow pattern is similar for the three-center arch section under different ventilation velocities and cross sectional areas. The shape of the tunnel cross section and wall are the critical factors influencing the airflow pattern. The average velocity points are mainly close to the tunnel wall. Characteristic equations are developed to describe the average velocity distribution, and provide a theoretical basis for accurately measuring the average velocity in mine tunnels. Keywords: Mine tunnel, Turbulence, Airflow distribution, Three-center arch, Average velocit