scholarly journals Impact of type of the roof rocks on location and range of endogenous fires particular hazard zone by in goaf with caving

2018 ◽  
Vol 29 ◽  
pp. 00005 ◽  
Author(s):  
Magdalena Tutak ◽  
Jarosław Brodny
Keyword(s):  
Occupational Safety ◽  
Heating Process ◽  
Coal Oxidation ◽  
Self Heating ◽  
Geological Conditions ◽  
Hazard Zone ◽  
Endogenous Fire ◽  
Roof Rocks ◽  
The Impact

Hazard of endogenous fires is one of the basic and common presented occupational safety hazards in coal mine in Poland and in the world. This hazard means possibility of coal self-ignition as the result of its self-heating process in mining heading or its surrounding. In underground coal-mining during ventilating of operating longwalls takes place migration of parts of airflow to goaf with caving. In a case when in these goaf a coal susceptible to self-ignition occurs, then the airflow through these goaf may influence on formation of favorable conditions for coal oxidation and subsequently to its self-heating and self-ignition. Endogenous fire formed in such conditions can pose a serious hazards for the crew and for continuity of operation of mining plant. From the practical point of view a very significant meaning has determination of the zone in the goaf with caving, in which necessary conditions for occurence of endogenous fire are fulfilled. In the real conditions determination of such a zone is practically impossible. The main aim of the analysis was to determine the impact of type of the roof rocks forming the goaf on the location and range of endogenous fires particular hazard zone by in these goaf. For determined mining-geological conditions, the critical value of velocity of airflow and oxygen concentration in goaf, conditioning initiation of coal oxidation process were determined.

Assessment of the impact of nanoparticles on the activity of biomimetic membrane

2021 ◽  
Vol XXXVII (1) ◽  
pp. 89-100
Author(s):  
Dorota Kondej
Keyword(s):  
Occupational Safety ◽  
Biological Membranes ◽  
Structure And Function ◽  
Lipid Monolayer ◽  
Biomimetic Membranes ◽  
Safety And Health ◽  
Biomimetic Membrane ◽  
And Function ◽  
The Impact

This paper presents basic information on a structure and function of biological membranes. Types of biomimetic membranes modelling properties of biological membranes were introduced. The method of testing surface properties of a lipid monolayer, which is the basic type of biomimetic membranes, was described. The presented method makes it possible to evaluate the effect of nanoparticles on the surface activity of biomimetic membranes based on the determination of the surface index MA. This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

scholarly journals Characterization of Self-Heating Process in GaN-Based HEMTs

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1305 ◽  
Author(s):  
Daniel Gryglewski ◽  
Wojciech Wojtasiak ◽  
Eliana Kamińska ◽  
Anna Piotrowska
Keyword(s):  
Communication Systems ◽  
Accurate Determination ◽  
Heating Process ◽  
Equivalent Circuits ◽  
High Electron ◽  
Thermal Impedance ◽  
Self Heating ◽  
Gan Hemt

Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This is especially true for systems operating with variable-envelope signals where accurate determination of self-heating effects resulting from strong- and fast-changing power dissipated inside transistor is crucial. In this work, we have developed an advanced measurement system based on DeltaVGS method with implemented software enabling accurate determination of device channel temperature and thermal resistance. The methodology accounts for MIL-STD-750-3 standard but takes into account appropriate specific bias and timing conditions. Three types of GaN-based HEMTs were taken into consideration, namely commercially available GaN-on-SiC (CGH27015F and TGF2023-2-01) and GaN-on-Si (NPT2022) devices, as well as model GaN-on-GaN HEMT (T8). Their characteristics of thermal impedance, thermal time constants and thermal equivalent circuits were presented. Knowledge of thermal equivalent circuits and electro–thermal models can lead to improved design of GaN HEMT high-power amplifiers with account of instantaneous temperature variations for systems using variable-envelope signals. It can also expand their range of application.

scholarly journals Analysis of Stability Factors of Roadway Roof and Determination of Unsupported Roof Distance

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Sen Yang ◽  
Xinzhu Hua ◽  
Xiao Liu ◽  
Chen Li
Keyword(s):  
Influencing Factors ◽  
Geological Conditions ◽  
Mine Roadway ◽  
Flac 3D ◽  
Roof Stability ◽  
Analysis Of Stability ◽  
The Stability ◽  
The Impact ◽  
The Relationship

To determine the impact of influencing factors on unsupported roof stability in coal mine roadway, a mechanical model of the unsupported roof was built. FLAC 3D numerical simulation was utilized to study the stability of the unsupported roof under the influence of the depth of the roadway, the thickness of the roof, and the unsupported-support distance. In view of the key influencing factors, the geological conditions of the site, and the relationship between the tensile stress and tensile strength of the unsupported roof, the maximum unsupported roof distance during roadway excavation was determined. Considering the surplus safety factor of the unsupported roof, the reasonable unsupported roof distance during the excavation of roadway 150802 was finally determined to be 2.08 m. The comprehensive roadway excavation speed increased by 62.7%, achieving a monthly progress over 500 m.

scholarly journals Influence of the Volumetric Expenditure of Air Supplied to the Longwall Through the “Y” Ventilation System on the Location of an Area at the Risk of an Endogenic Fire

2020 ◽  
Vol 3 (1) ◽  
pp. 206-215
Author(s):  
Magdalena Tutak
Keyword(s):  
Oxygen Content ◽  
Research Methodology ◽  
Ventilation System ◽  
The Self ◽  
Hard Coal ◽  
Heating Process ◽  
Air Velocity ◽  
Self Heating ◽  
Air Stream ◽  
Endogenous Fire

AbstractIn the case of longwall ventilation, in the underground hard coal mines, a phenomenon related to the migration of a certain amount of the air stream supplied to the longwall deep into goaf zones occurs. One of the wall ventilation systems, in which this phenomenon is quite intense, is the so called “Y” ventilation system. This migration is immensely unfavorable because it can lead to the self-heating process of coal left in a goaf and, consequently, to an endogenous fire. Such a fire is a great threat to both the safety and continuity of operation processes. For this reason, various activities are undertaken to prevent such a fire from occurring in goaf zones. One solution is a method presented in this article. It aims at determining an area in goaf zones, where an endogenous fire may occur. The study focused on the longwall ventilated with the Y system. This area was determined based on two criteria, namely air velocity and oxygen content. The study was carried out for various volumes of air supplied to the longwall. Therefore, the purpose of the study was to develop research methodology and determine the location of an area at the risk of an endogenous fire. The location of this area was determined for three different volume expenditures of air supplied to the longwall ventilated with the Y system.

scholarly journals Influence of the Permeability of the Longwall Goaf Zones on the Location of an Area With Explosive Methane Concentration Levels

2020 ◽  
Vol 3 (1) ◽  
pp. 238-247
Author(s):  
Magdalena Tutak ◽  
Dorota Palka
Keyword(s):  
Oxygen Concentration ◽  
Preventive Measures ◽  
Concentration Level ◽  
Practical Importance ◽  
Hard Coal ◽  
Endogenous Fire ◽  
The One ◽  
Roof Rocks ◽  
The Impact ◽  
Concentration Levels

AbstractOne of the basic ventilation hazards and, at the same time most dangerous, in hard coal mines is the methane hazard. During the exploitation process using the longwall system with the breaking down of roof rocks, methane is released into mining excavations from both mined coal and the one left in goaves. Significant amounts of methane also flow from the underworked and overworked seams, through cracks and fissures formed in the rock mass. When accumulated at an explosive concentration level in goves and at an appropriate oxygen concentration level and the occurrence of a trigger (e.g. a spark or endogenous fire), methane may either explode or ignite. These are immensely dangerous phenomena. Therefore, the possibility of their occurrence should be limited. The article presents the results of the research aimed at determining the impact of the permeability of goaf zones on the distribution of methane and oxygen concentration levels in these goaves. The study was carried out for the longwall ventilated with the Y system. The model analysis was conducted, the results of which allowed the authors to determine these distributions. On their basis, both the location and size of the areas in which hazardous methane concentrations could occur were designated. The results are of great practical importance as they indicate areas in goaves where preventive measures should be implemented.

Assessment of sensitivity of the efficiency of regional tax spending towards investment attractiveness of the types of economic activity carried out by the residents of advanced development territory

2020 ◽  
pp. 98-110
Author(s):  
Evgeniya Mikhailovna Popova ◽  
Guzel Mukhtarovna Guseinova ◽  
Sergei Borisovich Milov
Keyword(s):  
Economic Activity ◽  
Socioeconomic Development ◽  
Federal District ◽  
Tax Incentives ◽  
Capital Investments ◽  
The Subject ◽  
Investment Process ◽  
The Impact ◽  
Advanced Development

The deficit of subnational budgets and deceleration capital investments in multiple Russian regions increase the relevance of research aimed at improvement of tax incentivizing practice of the regional investment process. The studies focused on determination of the impact of socioeconomic and institutional factors upon the efficiency of investment tax expenses obtained wide circulation within the foreign scientific literature. The subject of this article is the assessment of sensitivity of the efficiency of regional tax expanses towards investment attractiveness of the types of economic activity carried out by the residents of territories of advanced socioeconomic development, created in the subjects of Far Easter Federal District. The scientific novelty and practical values of this research consists in substantiation of the reasonableness of assessment of investment attractiveness of the types of economic activity that are stimulated by tax incentives. Methodology for assessing investment attractiveness is proposed and tested. The conclusion is made that in case of low investment attractiveness of the type of economic activity, which was planned to support by tax incentives, it is required to conduct and additional analysis to avoid unjustified tax expanses.

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