Distribution of spontaneous combustion three zones and optimization of nitrogen injection location in the goaf of a fully mechanized top coal caving face

In order to effectively prevent and control spontaneous combustion of residual coal in the goaf and reduce the waste of nitrogen caused by setting the position of nitrogen injection, 1303 fully mechanized coal caving faces of the Jinniu Mine are studied. By deploying a bundle tube monitoring system in the inlet air side and return air side of the goaf, changes in gas concentration in the goaf are continuously monitored. In addition, the distribution area for spontaneous combustion three-zone in the goaf is divided into heat dissipation zone, oxidized spontaneous combustion zone, and suffocation zone. Simulations from the COMSOL Multiphysics 5.3 software provide insight based on the three zones division standard of spontaneous combustion in the goaf. The gradual deepening of the nitrogen injection position into the goaf affects the lower limit of the oxidized spontaneous combustion zone significantly, but the impact on the upper limit of the oxidized spontaneous combustion zone is not obvious and is negligible. With regard to the width of the oxidized spontaneous combustion zone, it initially decreases followed by a gradual increase. Numerical calculations suggest the optimal nitrogen injection position is 40 m from the roof cutting line, with an oxidized spontaneous combustion zone width of 28 m. Based on the simulation analysis results, nitrogen injection controlling measures have been adopted for spontaneous combustion of residual coal in the goaf of the 1303 fully mechanized coal caving faces, and coal self-ignition in the goaf has been successfully extinguished.

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Effect Analysis of Nitrogen Injection on the Variation of “Oxidation Zone” in Coal Mine Gob Based on Numerical Simulation

The Open Fuels & Energy Science Journal ◽

10.2174/1876973x01609010047 ◽

2016 ◽

Vol 9 (1) ◽

pp. 47-54

Author(s):

Jing Shen ◽

Mingran Chang

Keyword(s):

Numerical Simulation ◽

Coal Mine ◽

Heat Dissipation ◽

Spontaneous Combustion ◽

Oxidation Zone ◽

Effect Analysis ◽

Mine Fire ◽

Nitrogen Injection ◽

The Difference ◽

Residual Coal

One of the main reasons for coal mine fire is spontaneous combustion of residual coal in gob. As the difference of compaction degree of coal and rock, the underground gob can be considered as a porous medium and divided into “three zones” in accordance with the criteria. The “three zones” are “heat dissipation zone”, “oxidation zone” and “choking zone”, respectively. Temperature programming experiments are taken and numerical simulation with obtained experimental data is utilized to analyze the distribution of “three zones” in this paper. Different width and depth of “oxidation zone” are obtained when the inlet air velocity is changed. As the nitrogen injection has inhibition effect on spontaneous combustion of residual coal in gob, nitrogen is injected into the gob. The widths of “oxidation zone” are compared before and after nitrogen injection. And ultimately the optimum location and volume of nitrogen injection are found out.

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Research on determining reasonable negative pressure based on the control of the goaf

Journal of Mines, Metals and Fuels ◽

10.18311/jmmf/2021/27799 ◽

2021 ◽

Vol 69 (4) ◽

pp. 121

Author(s):

Wang Yue-hong ◽

Wu Yi ◽

Zhang Jiu-ling ◽

Li Zhi

Keyword(s):

Negative Pressure ◽

Combustion Zone ◽

Heat Dissipation ◽

Spontaneous Combustion ◽

Three Dimensional ◽

Gas Extraction ◽

Deep Part ◽

Contour Map ◽

Beam Tube ◽

Dimensional Distribution

In order to study the law of spontaneous combustion in goaf under the condition of gas extraction, the method of beam tube monitoring and numerical analysis is adopted to obtain three dimensional distribution of oxygen concentration and contour map under the condition of different negative pressure. Based on the way of regression analysis, reasonable negative pressure are determined. The results show that with the increase of negative pressure, the spontaneous combustion “three-zone” in goaf: the heat dissipation zone and the spontaneous combustion zone become wider and the suffocation zone narrows. At the same time, the trend of spontaneous combustion zone presents to the deep part of the goaf; the amount of gas extraction increases first and then decreases with the increase of negative pressure. Combined with the trend of spontaneous combustion zone and the amount of gas extraction in goaf, and the reasonable negative pressure value is 32kpa and verified.

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The Fouling of Axial Flow Compressors: Causes, Effects, Susceptibility, and Sensitivity

Volume 4: Cycle Innovations; Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine ◽

10.1115/gt2009-59239 ◽

2009 ◽

Cited By ~ 24

Author(s):

Cyrus B. Meher-Homji ◽

Mustapha Chaker ◽

Andrew F. Bromley

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Simulation Analysis ◽

Pressure Ratio ◽

Axial Flow ◽

Design Parameters ◽

Comprehensive Treatment ◽

Performance Deterioration ◽

And Control ◽

The Impact

Increased fuel costs have created a strong incentive for gas turbine operators to understand, minimize and control performance deterioration. The most prevalent deterioration problem faced by gas turbine operators is compressor fouling. Fouling causes a drop in airflow, pressure ratio and compressor efficiency, resulting in a “re-matching” of the gas turbine and compressor and a drop in power output and thermal efficiency. This paper addresses the causes and effects of fouling and provides a comprehensive treatment of the impact of salient gas turbine design parameters on the susceptibility and sensitivity to compressor fouling. Simulation analysis of ninety two (92) gas turbines of ranging from a few kW to large engines rated at greater than 300 MW has been conducted. It is hoped that this paper will provide practical information to gas turbine operators.

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Games and network structures on corruption, income inequality, and tax control

Contributions to Game Theory and Management ◽

10.21638/11701/spbu31.2020.09 ◽

2020 ◽

Vol 13 ◽

pp. 152-172

Author(s):

Elena Gubar ◽

◽

Edgar J. Sánchez Carrera ◽

Suriya Kumacheva ◽

Ekaterina Zhitkova ◽

...

Keyword(s):

Simulation Analysis ◽

Research Work ◽

Evolutionary Model ◽

Real Income ◽

Public Authorities ◽

Tax System ◽

The Poor ◽

Corrupt Behavior ◽

And Control ◽

The Impact

The income tax system is the main instrument of fiscal policy that aims to improve income distribution and economic growth, but the problem arises when there is corrupt behavior in that system. While the tax audit is a tax control tool that is costly, the tax system should guarantee, however, the instruments for tax collection. In this research work, we formulate a model in which all taxpayers decide to pay taxes or not according to their personal income, individual preferences with respect to the audit and tax control information perceived in their social environment. We develop a theoretical model to study the structure of citizen networks that must pay taxes. First, we assume that citizens are classified by two social groups, the rich and the poor. When all citizens are taxpayers, but public authorities are corrupt, we show that the poor group is the most affected by corruption. However, when taxpayers are corrupt or tax evaders, we implement mechanisms to audit and control this corrupt behavior. Hence, we show that this situation of corruption and control of tax payments can be represented by several well-known theoretical games. Then, we apply the evolutionary theory of the game in the network considering that each taxpayer receives information from his∖her neighbors about the probability of audit and that he∖she could react according to his∖her risk status and real income. Such behavior forms a group of informed agents that propagate the information beyond the proportions of the informed and uninformed contributors that are modified. Our evolutionary model in the structure of the network describes the changes in the population of taxpayers driven by the impact of information on the future fiscal audit. Our simulation analysis shows that the initial and final preferences of taxpayers depend on important parameters, that is, taxes and fines, audit information and costs.

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Influential Node Identification in Command and Control Networks Based on Integral k-Shell

Wireless Communications and Mobile Computing ◽

10.1155/2019/6528431 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15

Author(s):

Yunming Wang ◽

Bo Chen ◽

Weidong Li ◽

Duoping Zhang

Keyword(s):

Network Performance ◽

Simulation Analysis ◽

Command And Control ◽

Control Network ◽

Control Networks ◽

Influential Nodes ◽

Influential Node ◽

And Control ◽

Global And Local ◽

The Impact

Influential nodes act as a hub for information transmission in a command and control network. The identification of influential nodes in a network of this nature is a significant and challenging task; however, it is necessary if the invulnerability of the network is to be increased. The existing k-shell method is problematic in that it features a coarse sorting granularity and does not consider the local centrality of nodes. Thus, the degree of accuracy with which the influential nodes can be identified is relatively low. This motivates us to propose a method based on an integral k-shell to identify the influential nodes in a command and control network. This new method takes both the global and local information of nodes into account, introduces the historical k-shell and a 2-order neighboring degree, and refines the k-shell decomposition process in a network. Simulation analysis is carried out from two perspectives: to determine the impact on network performance when influential nodes are removed and to obtain the correlation between the integral k-shell value and its propagation value. The simulation results show that the integral k-shell method, which employs an algorithm of lower complexity, accurately identifies the influence of those nodes with the same k-shell values. Furthermore, the method significantly improves the accuracy with which the influential nodes can be identified.

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Simulation Analysis of Rabbit Chase Models on a Cellular Manufacturing System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.315.78 ◽

2013 ◽

Vol 315 ◽

pp. 78-82 ◽

Cited By ~ 2

Author(s):

Mohd Norzaimi Bin Che Ani ◽

Aimuni Binti Ismail ◽

Shaliza Azreen Mustafa ◽

Chin Jeng Feng

Keyword(s):

Lean Manufacturing ◽

Manufacturing System ◽

Cellular Manufacturing ◽

Simulation Analysis ◽

Cellular Manufacturing System ◽

Lot Size ◽

Cycle Times ◽

Production Flexibility ◽

And Control ◽

The Impact

Cellular manufacturing system facilitates lean manufacturing in terms of production flexibility and control simplification. The paper presents a case study on a newly constructed cellular manufacturing system adopted by an electronic assembly factory as the back end process. The original rabbit chase is infeasible in this case because products handled are multi-types and multi-paths. Further, the cycle times are largely imbalance. The application of two proposed rabbit chase models was investigated through computer simulations enhanced with ANOVA and surface response methodology. The allocation of operators and the impact of changing lot size to the performances of the cell are investigated. For the findings, there are clear indications of the effects of the number of operators and the lot size for the performances of the system, regardless which rabbit chase model used.

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Suppressed, but Not Forgotten

Swiss Journal of Psychology ◽

10.1024/1421-0185/a000033 ◽

2011 ◽

Vol 70 (1) ◽

pp. 5-11 ◽

Cited By ~ 8

Author(s):

Beat Meier ◽

Anja König ◽

Samuel Parak ◽

Katharina Henke

Keyword(s):

Memory Trace ◽

Thought Suppression ◽

Test Phase ◽

Indirect Test ◽

Final Test ◽

Test Experiment ◽

And Control ◽

Cue Words ◽

The Impact

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.

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Research Participation Experiences of Informants of Suicide and Control Cases

Crisis ◽

10.1027/0227-5910/a000025 ◽

2010 ◽

Vol 31 (5) ◽

pp. 238-246 ◽

Cited By ~ 9

Author(s):

Paul W. C. Wong ◽

Wincy S. C. Chan ◽

Philip S. L. Beh ◽

Fiona W. S. Yau ◽

Paul S. F. Yip ◽

...

Keyword(s):

Ethical Issues ◽

Research Participation ◽

Self Report ◽

Initial Contact ◽

Psychological Autopsy ◽

Autopsy Study ◽

The People ◽

And Control ◽

The Impact

Background: Ethical issues have been raised about using the psychological autopsy approach in the study of suicide. The impact on informants of control cases who participated in case-control psychological autopsy studies has not been investigated. Aims: (1) To investigate whether informants of suicide cases recruited by two approaches (coroners’ court and public mortuaries) respond differently to the initial contact by the research team. (2) To explore the reactions, reasons for participation, and comments of both the informants of suicide and control cases to psychological autopsy interviews. (3) To investigate the impact of the interviews on informants of suicide cases about a month after the interviews. Methods: A self-report questionnaire was used for the informants of both suicide and control cases. Telephone follow-up interviews were conducted with the informants of suicide cases. Results: The majority of the informants of suicide cases, regardless of the initial route of contact, as well as the control cases were positive about being approached to take part in the study. A minority of informants of suicide and control cases found the experience of talking about their family member to be more upsetting than expected. The telephone follow-up interviews showed that none of the informants of suicide cases reported being distressed by the psychological autopsy interviews. Limitations: The acceptance rate for our original psychological autopsy study was modest. Conclusions: The findings of this study are useful for future participants and researchers in measuring the potential benefits and risks of participating in similar sensitive research. Psychological autopsy interviews may be utilized as an active engagement approach to reach out to the people bereaved by suicide, especially in places where the postvention work is underdeveloped.

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