scholarly journals STUDIES OF THE SHAPED CHARGES EFFECT WITH A HEMISPHERICAL ECCENTRIC SHAPE RECESS FOR THE ROCKS DESTRUCTION

2021 ◽  
Vol 13 (2) ◽  
pp. 281-291
Author(s):  
Dam THANG ◽  
◽  
Vladimir BELIN ◽  
Tran DOANH ◽  
◽  
...  
Keyword(s):  
Short Circuit ◽  
Utilization Rate ◽  
Destructive Effect ◽  
Rock Destruction ◽  
Large Loss ◽  
Different Types ◽  
Destruction Zone ◽  
Explosive Charges ◽  
Optimal Effect ◽  
Destruction Of Rocks

The method of outdoor installation of explosive charges is usually used in the destruction of rocks in conditions in which the method of drilling and blasting using borehole or borehole charges is difficult to apply due to objective conditions. The productivity of rock destruction by the outdoor installation of a concentrated charge is very low. This is due to the fact that such an explosion is characterized by a large loss of energy in the environment. The destruction of rocks by an explosion using shaped charges (CW) to destroy the rock is one solution to increase the useful energy of the destruction of the rock compared to charges placed outside. To achieve the optimal effect of destruction of the rock by cumulative charges, it is necessary to, so that for each type of rock, a specific type of shaped charges can be determined with the appropriate performance and efficiency of the use of explosives. The stronger the rock, the more efficient the short-circuit should be, and vice versa. Thus, for effective rock crushing, it is necessary to develop and produce a number of different types of shaped charges. The use of shaped explosive charges allows you to increase the utilization rate of the useful energy of the explosion and increase the destruction zone of the rock. At a fixed mass of the explosive, the destructive effect of the explosive charge placed on the surface of the rock, it depends on the shape of the charge and the geometric parameters of the charge. Shaped charges with an eccentric hemispherical shape have a coefficient of use of the useful energy of the explosion for the destruction of rock, more than 2.4 times compared to conventional concentrated charges of the same mass.

scholarly journals The Influence of Room and Pillar Method Geometry on the Deposit Utilization Rate and Rock Bolt Load

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4770 ◽  
Author(s):  
Krzysztof Skrzypkowski
Keyword(s):  
Three Dimensional ◽  
Rock Bolt ◽  
Utilization Rate ◽  
Variable Geometry ◽  
Rock Destruction ◽  
Destruction Zone ◽  
Increased Strength ◽  
Rock Bolt Support ◽  
Bolt Spacing ◽  
Bolt Support

In this article, a model of ore deposit in form of a lense carried out in the MineScape program, is presented. The lense had a thickness of 30 m, length along the strike 200 m, and the depth buried was for 80 m to 110 m below the surface. In the first layer, counting from the lowest level, a room and pillar method with variable geometry was designed. The width and length dimensions for rooms and pillars were: 4 m, 5 m and 6 m, respectively. For the selected part of the deposit, three variants of the system with variable geometry of rooms and pillars were designed, for which the deposit utilization coefficient was determined. The next stage of the research was to determine the influence of the geometry of the pillars and rooms on the range of the rock destruction zone around room excavations. For this purpose, numerical calculations using the three-dimensional Examine 3D program, based on the boundary element method, were made. The results of numerical tests were used to calculate the load of the rock bolt support, which is currently used in the zinc and lead underground mine “Olkusz-Pomorzany” in Poland. Currently in the mine, the bolt spacing is 1 m × 1 m, and the technology for fixing the bolt rod is based on resin cartridges that completely fill the bolt hole. In order to spread the spacing of the rock bolt support and to apply segmental fixing of the bolt rod, in the laboratory tests, rock bolt supports with increased strength were tested. Based on the results obtained, it was found that the rock bolt can be installed segmentally, using a cement grout, and its spacing can be increased to 2 m.

scholarly journals Comparison of Thermal Stress during Short-Circuit in Different Types of 1.2 kV SiC Transistors Based on Experiments and Simulations

2017 ◽  
Vol 897 ◽  
pp. 595-598
Author(s):  
Diane Perle Sadik ◽  
Jang Kwon Lim ◽  
Juan Colmenares ◽  
Mietek Bakowski ◽  
Hans Peter Nee
Keyword(s):  
Thermal Stress ◽  
Short Circuit ◽  
Thermal Simulation ◽  
Temperature Evolution ◽  
Power Devices ◽  
Different Types ◽  
Transient Thermal

The temperature evolution during a short-circuit in the die of three different Silicon Carbide1200-V power devices is presented. A transient thermal simulation was performed based on the reconstructedstructure of commercially available devices. The location of the hottest point in the device iscompared. Finally, the analysis supports the necessity to turn off short-circuit events rapidly in orderto protect the device after a fault.

scholarly journals Behavior of an Inductive Loop Sensor in the Measurement of Partial Discharge Pulses with Variations in Its Separation from the Primary Conductor

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2324 ◽  
Author(s):  
Jorge Ardila-Rey ◽  
Aldo Barrueto ◽  
Alvaro Zerene ◽  
Bruno Castro ◽  
José Ulson ◽  
...  
Keyword(s):  
Short Circuit ◽  
Partial Discharges ◽  
Active Components ◽  
Insulation System ◽  
Small Current ◽  
Inductive Loop ◽  
Fixed Distance ◽  
Different Types ◽  
Current Design ◽  
Insulating Properties

Ideally, an insulation system must be capable of electrically insulating the active components of a machine or device subjected to high voltages. However, due to the presence of polluting agents or imperfections inside or on the surface of the insulation, small current pulses called partial discharges (PDs) are common, which partially short-circuit the insulation and cause it to lose its insulating properties, and thus its insulation capacity, over time. In some cases, measurements of this phenomenon are limited by the type of sensor used; if it is not adequate, it can distort the obtained results, which can lead to a misdiagnosis of the state of the device. The inductive loop sensor has experimentally been demonstrated to be capable of properly measuring different types of PDs. However, because of its current design, there are several practical limitations on its use in real devices or environments. An example is the presence of a primary conductor located at a fixed distance from the sensor, through which PD pulses must flow for the sensor to capture them. In this article, the sensor’s behavior is studied at different separation distances from the line through which the PD pulses flow. In addition, the measuring capacity of the sensor is tested by removing the presence of the primary conductor and placing the sensor directly over the line through which the PD pulses of a real device flow.

Calculation and Analysis of Three-Phase Transformer Short-Circuit Current

2014 ◽  
Vol 986-987 ◽  
pp. 1914-1917
Author(s):  
Pei Ming Pan ◽  
Huan Lian ◽  
Fei Xiang Hui ◽  
Wei Pu Tan
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Stable Operation ◽  
Application Range ◽  
Three Phase ◽  
Different Types ◽  
Calculation Results ◽  
Current Calculation ◽  
Important Significance ◽  
Selection Of

Analysis the important significance of transformer short-circuit current calculation for the stable operation of power system. Lead to three different types of transformer short-circuit current calculation methods, this literature uses a simplified example to compare the characters among three methods. Meanwhile, calculation by using the theory to get a quantitative range of simplified method. The calculation results and theory support each other, finally, summarizing the application range of the three methods, and offering a reference for reasonable selection of short-circuit current methods.

scholarly journals Influence of Different Types of Recombination Active Defects on the Integral Electrical Properties of Multicrystalline Silicon Solar Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Dominik Lausch ◽  
Christian Hagendorf
Keyword(s):  
Solar Cells ◽  
Electrical Properties ◽  
Short Circuit ◽  
Type A ◽  
Crystal Defects ◽  
Process Conditions ◽  
Type B ◽  
Si Solar Cells ◽  
Different Types ◽  
The Impact

In this contribution the influence of different types of recombination-active defects on the integral electrical properties of multicrystalline Si solar cells is investigated. Based on a previous classification scheme related to the luminescence behavior of crystal defects, Type-A and Type-B defects are locally distinguished. It is shown that Type-A defects, correlated to iron contaminations, are dominating the efficiency by more than 20% relative through their impact on the short circuit current ISC and open circuit voltage VOC in standard Si material (only limited by recombination active crystal defects). Contrarily, Type-B defects show low influence on the efficiency of 3% relative. The impact of the detrimental Type-A defects on the electrical parameters is studied as a function of the block height. A clear correlation between the area fraction of Type-A defects and both the global Isc and the prebreakdown behavior (reverse current) in voltage regime-2 (−11 V) is observed. An outlier having an increased full-area recombination activity is traced back to dense inter- and intragrain nucleation of Fe precipitates. Based on these results it is concluded that Type-A defects are the most detrimental defects in Si solar cells (having efficiencies > 15%) and have to be prevented by optimized Si material quality and solar cell process conditions.

scholarly journals Effects of lightning impulse front time on substation grounding system performance

2020 ◽  
Vol 20 (2) ◽  
pp. 569
Author(s):  
Muhammad Adnan ◽  
Zulkurnain Adul Malek ◽  
Nur Syazwani Mohd Din ◽  
Muhammad Irfan Jambak ◽  
Zainuddin Nawawi ◽  
...  
Keyword(s):  
Short Circuit ◽  
Lightning Discharge ◽  
Soil Resistivity ◽  
Grounding System ◽  
Step Voltage ◽  
Different Types ◽  
Lightning Impulse ◽  
Touch Voltage ◽  
Ground Potential

<table width="593" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="387"><p>The role of the grounding system in the safety of the power system and protection of personnel is obvious during an unexpected short circuit or lightning discharge at the substation. The aim of this work is to analyze the effects of several parameters: lightning impulse front time, soil resistivity and types of grid materials on the grounding system of the Substation. The ground potential rise (GPR), touch voltage and step voltage of a 50 m x 60 m grounding grid buried at a depth of 0.5 m were computed using CDEGS when injected by impulse with different front times. Results show that the shorter the front time of lightning impulse waveform, the higher the value of GPR, touch voltage and step voltage. Meanwhile, when the value of soil resistivity is increased, the value of GPR, touch voltage and step voltage is also increased. Lastly, different types of grid conductor materials give different values of GPR, touch voltage and step voltage. However, it can be said that the differences are too small to be of any significance.</p><p> </p></td></tr></tbody></table>

scholarly journals Determination of the Extent of the Rock Destruction Zones around a Gasification Channel on the Basis of Strength Tests of Sandstone and Claystone Samples Heated at High Temperatures up to 1200 °C and Exposed to Water

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6464
Author(s):  
Krzysztof Skrzypkowski ◽  
Krzysztof Zagórski ◽  
Anna Zagórska
Keyword(s):  
Numerical Simulations ◽  
High Temperatures ◽  
Laboratory Tests ◽  
Coal Gasification ◽  
Structural Parameters ◽  
Underground Coal Gasification ◽  
Rock Destruction ◽  
Gasification Process ◽  
Destruction Zone ◽  
Gasification Channel

This article presents the results of laboratory tests regarding the influence of high temperatures on changes in the strength and structural parameters of rocks that are present in the immediate vicinity of a gasification channel. Sandstone and claystone samples were heated at 300 °C, 600 °C, 900 °C and 1200 °C. Additionally, the heated samples were placed in water for 24 h. The results of the laboratory tests were used in the numerical simulation using RS2 software. The main goal of modeling was to determine the extent of the rock destruction zone around the gasification channel for dry and wet rock masses. In the numerical simulations, three widths of the gasification channel and three ranges of high-temperature impact were modeled. On the basis of the obtained results, it was found that the extent of rock destruction, both in the roof and in the floor, is greater by several percent for a wet rock mass. For the first time, this research presents the effect of water on heated rock samples in terms of the underground coal gasification process. The results of laboratory tests and numerical simulations clearly indicate a reduction in strength, deformation and structural parameters for the temperature of 1200 °C.

scholarly journals THE RELATIONSHIP BETWEEN COMPRESSIVE STRENGTH AND DENSITY OF POLYSTYRENE LIGHTWEIGHT CONCRETE WITH MIX PROPORTIONS

2021 ◽  
pp. 1-7
Author(s):  
Faisal K. Abdulhussein ◽  
Qais Frayyeh ◽  
Marwan Al-Shaikhli ◽  
Zahraa F. Jawad ◽  
Mohammed Salman5
Keyword(s):  
Fire Resistance ◽  
Absorption Rate ◽  
Building Materials ◽  
Elevated Temperatures ◽  
Lightweight Concrete ◽  
Short Circuit ◽  
Different Types ◽  
Aerated Concrete ◽  
Resistance Performance ◽  
The Relationship

Autoclaved aerated concrete (Called Thermostone in Iraq) is one of the popular building materials that are used in various purposes in construction industries. It is factory-made material that can be moulded into blocks which can be used in framework buildings. However, these buildings are under the risk of fire since it has different cusses such as arson and electrical short circuit. It is important to find ways to improve counter such phenomenon. Therefore the objective of this paper is investigating the fire resistance performance of Thermostone with and without plastering. Five different samples were used for the test, four of them were covered with different types of plastering. Three tests were employed for this study: Compressive, absorption, and density test. For all tests, the samples were exposed to elevated temperatures from 250 °C to 900 °C. It was shown that plastered samples have demonstrated a higher fire resistance and lower absorption rate than non-plastered ones.

scholarly journals Multi-objective source scaling experiment

2021 ◽  
Author(s):  
D. Costley ◽  
Luis De Jesús Díaz, ◽  
Sarah McComas ◽  
Christopher Simpson ◽  
James Johnson ◽  
...  
Keyword(s):  
Shock Wave ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Engineer Research ◽  
Different Types ◽  
Source Scaling ◽  
Explosive Charges ◽  
A Site ◽  
Development Center ◽  
The U.S

The U.S. Army Engineer Research and Development Center (ERDC) performed an experiment at a site near Vicksburg, MS, during May 2014. Explosive charges were detonated, and the shock and acoustic waves were detected with pressure and infrasound sensors stationed at various distances from the source, i.e., from 3 m to 14.5 km. One objective of the experiment was to investigate the evolution of the shock wave produced by the explosion to the acoustic wavefront detected several kilometers from the detonation site. Another objective was to compare the effectiveness of different wind filter strategies. Toward this end, several sensors were deployed near each other, approximately 8 km from the site of the explosion. These sensors used different types of wind filters, including the different lengths of porous hoses, a bag of rocks, a foam pillow, and no filter. In addition, seismic and acoustic waves produced by the explosions were recorded with seismometers located at various distances from the source. The suitability of these sensors for measuring low-frequency acoustic waves was investigated.

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