scholarly journals INFLUENCE OF THE CAPACITANCE OF THE CAPACITOR OF THE DISCHARGE CIRCUIT OF SEMI-CONDUCTOR ELECTRIC DISCHARGE INSTALLATIONS ON THEIR OUTPUT CURRENTS OF LIMITED DURATION

2021 ◽  
Vol 2021 (58) ◽  
pp. 5-13
Author(s):  
A.А. Shcherba ◽  
◽  
N.І. Suprunovska ◽  
M.O. Lomko ◽  
◽  
...  
Keyword(s):  
Electric Discharge ◽  
Discharge Current ◽  
Storage Capacitor ◽  
Fixed Duration ◽  
Maximum Value ◽  
Wide Range ◽  
Spark Erosion ◽  
Semiconductor Switch ◽  
Discharge Duration ◽  
Technological Mode

Based on the analysis of transient processes of oscillatory and aperiodic discharges of the storage capacitor of the electric discharge installation to the load, it is proved that an increase in its capacity always causes an increase in the value of the discharge current corresponding to a fixed duration of the discharge, less than the duration of reaching the maximum value of the discharge current. For the capacities of the discharge capacitor varied over a wide range, the change in the value of the discharge current in the load during its forced interruption at a certain time was studied. Based on this study, we proposed a method for increasing the rate of rising of impulse currents in the load, which consists in choosing a discharge capacitor with a larger capacity compared with a capacity sufficient to implement the desired technological mode, and forced interrupting the current in the load at a certain point in time, which corresponds to a certain fixed duration discharge (less than the duration of reaching the maximum value of the discharge current when the capacitor capacity is sufficient to implement the required technological mode). The forced limitation of the discharge duration is carried out by a fully controlled semiconductor switch. This method can be used as the basis for the production of spark erosion nano-sized powders of metals and alloys. Ref. 15, fig. 3, table .

scholarly journals REGULATION OF OUTPUT DYNAMIC CHARACTERISTICS OF ELECTRIC DISCHARGE INSTALLATIONS WITH RESERVOIR CAPACITORS

2021 ◽  
Vol 2021 (3) ◽  
pp. 3-9
Author(s):  
A.A. Shcherba ◽  
◽  
N.I. Suprunovska ◽  
M.A. Shcherba ◽  
S.S. Roziskulov ◽  
...  
Keyword(s):  
Electric Discharge ◽  
Dynamic Characteristics ◽  
Discharge Current ◽  
Discharge Process ◽  
Storage Devices ◽  
Linear Resistance ◽  
Maximum Current ◽  
Semiconductor Switch ◽  
Discharge Duration ◽  
Current Value

The paper reveals the dependences of the output dynamic characteristics of semiconductor electric discharge installations (EDIs) with reservoir capacitors on the features of the change in the value of their capacitance. In particular, it is substantiated that for any fixed discharge duration less than the duration of reaching the maximum discharge current, an increase in the capacitance of such storage devices causes an increase in the value of the final discharge current both at aperiodic and oscillatory discharges in the linear resistance of the technological load. The change in the value of the discharge current in the load in the case of forced interruption of this current at a certain moment of time is investigated. Based on the obtained regularities, the authors of the work proposed to use the capacitance of the EDI's capacitor, which is larger than capacitance required to implement the maximum value of the discharge current in the load. Using a capacitor with a larger capacity and a fully controlled semiconductor switch in the discharge circuit of the EDI, it is possible to obtain the required maximum current value at a shorter duration of the discharge process. Thus, it is possible to regulate the main dynamic parameters of pulse currents in the load – the rate of their rise and/or their duration by changing the value of the capacitance of the discharge capacitor EDI. This approach is expedient for increasing the productivity of EDIs, focused on the production of dispersed spark powders of metals and alloys. References 15, figures 3.

Reactive Ion Etching Induced Surface Damage of Silicon Carbide

2005 ◽  
Vol 483-485 ◽  
pp. 765-768 ◽  
Author(s):  
Jun Hai Xia ◽  
E. Rusli ◽  
R. Gopalakrishnan ◽  
S.F. Choy ◽  
Chin Che Tin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Reactive Ion Etching ◽  
Surface Damage ◽  
Textured Surface ◽  
Rf Power ◽  
Power Devices ◽  
Ion Etching ◽  
Maximum Value ◽  
Wide Range ◽  
Coarse Surface

Reactive ion etching of SiC induced surface damage, e.g., micromasking effect induced coarse and textured surface, is one of the main concerns in the fabrication of SiC based power devices [1]. Based on CHF3 + O2 plasma, 4H-SiC was etched under a wide range of RF power. Extreme coarse and textured etched surfaces were observed under certain etching conditions. A super-linear relationship was found between the surface roughness and RF power when the latter was varied from 40 to 160 W. A further increase in the RF power to 200 W caused the surface roughness to drop abruptly from its maximum value of 182.4 nm to its minimum value of 1.3 nm. Auger electron spectroscopy (AES) results revealed that besides the Al micromasking effect, the carbon residue that formed a carbon-rich layer, could also play a significant role in affecting the surface roughness. Based on the AES results, an alternative explanation on the origin of the coarse surface is proposed.

scholarly journals Physicochemical Properties and Heavy Metal Concentration in Soil of Industrial Area, Zirani, Savar, Dhaka

2015 ◽  
Vol 8 (1) ◽  
pp. 65-68 ◽  
Author(s):  
MS Rahaman ◽  
F Nessa ◽  
MM Hoque ◽  
M Rehnuma ◽  
MS Islam
Keyword(s):  
Heavy Metals ◽  
Agricultural Production ◽  
Reference Value ◽  
Nutrient Status ◽  
Heavy Metal Concentration ◽  
Industrial Area ◽  
Total N ◽  
Maximum Value ◽  
Wide Range ◽  
Recommended Level

Zirani of Savar is an important industrial area of the country which provides wide range of potentiality for economic development. The purpose of the study was to observe the nutrient status and heavy metals concentration of the soil in Zirani, Savar, Dhaka. Nine soil samples were collected and analyzed through different methods for analyzing pH, OC, N, K, P, S and the heavy metals including Zn, Cd, Cu, and Pb, were investigated using Atomic Absorption Spectroscopy (AAS) technique. The analyzed result revealed the soil surrounding the dumping site was slightly acidic which is not harmful for agricultural production. The highest value of OC was recorded 2.14% at point 3 and the lowest value was 1.92% which was found in point 2 that is greater than the reference value. Except total N concentration, the amount of available P, K, and S were greater than their recommended level. In addition the result showed that the concentration of Cu and Pb were much higher than their recommended level and the maximum value of Cu was 0.09 ppm and 0.762 ppm was the maximum concentration of Pb. and the concentration of Zn and Cd were within tolerable limit. Zn at point 3 showed higher concentration which was 3.05 ppm. The maximum value of Cd was 0.09 ppm that was found at station 1 under point 3.J. Environ. Sci. & Natural Resources, 8(1): 65-68 2015

scholarly journals Field and Laboratory-based Approach for the Determination of Friction Angle of Geological Discontinuities of Malaysian Granites

2011 ◽  
Vol 28 (2) ◽  
pp. 151 ◽  
Author(s):  
R. A Ghani ◽  
T. L Goh ◽  
A. M Hariri ◽  
Y. N Baizura
Keyword(s):  
Friction Angle ◽  
Roughness Coefficient ◽  
Average Value ◽  
Peak Friction Angle ◽  
Maximum Value ◽  
Wide Range ◽  
Discontinuity Surfaces ◽  
Geological Discontinuities ◽  
Range Of Values

The basic friction angle, Φb for artificially sawn discontinuity planes for fresh granite, as determined by tilt testing, has an average value of 30º. For the natural rough discontinuity surfaces, a wide range of values have been determined for the peak friction angle, Φpeak ranging from 47º to a maximum value of 80º, depending on the joint roughness coefficient (JRC). The average values of the friction angles for the different degrees of roughness were as follows: JRC 2–4 = 58°; JRC 6–8 = 60°; JRC 8–10 = 47°; JRC 12–14 = 60°; JRC 14–16 = 71° ; JRC 18–20 = 80°.

scholarly journals Biological and Ethological Response of Black Sea Golden Grey Mullet (Chelon auratus Risso, 1810) Fries to Different Salinities and Temperatures

2020 ◽  
Vol 20 (11) ◽  
pp. 777-783
Author(s):  
Victor Nita ◽  
Magda Nenciu
Keyword(s):  
Black Sea ◽  
Tolerance Test ◽  
Temperature Tolerance ◽  
Shallow Waters ◽  
Grey Mullet ◽  
Maximum Value ◽  
Wide Range ◽  
Extreme Salinity ◽  
Controlled Rearing ◽  
Sea Area

The aim of this paper was to investigate the biological and ethological response of golden grey mullet Chelon auratus (Risso, 1810) fries collected from Romanian Black Sea shallow waters to different salinities and temperatures, in order to document the optimal conditions for controlled rearing. The species’ potential for aquaculture is enhanced by its eurihalyne and eurithermal adaptability, allowing it to grow in a variety of ecosystems, including the Romanian Black Sea area, with its highly variable salinity and temperature specificities. Three experimental set-ups were designed: a salinity tolerance test, with 5 salinity regimes (0.3‰, 5‰, 10‰, 15‰ and 20‰), a temperature tolerance experiment, involving both temperature decrease (down to 8°C) and increase (up to 34°C), and an extreme salinity test, reaching a maximum value of 95‰. The aggregated results obtained from the three experiments indicated that golden grey mullet fries can indeed tolerate a wide range of temperatures (8°C - 36°C) and salinities (5‰-70‰), with the optimal range between 10‰ and 30‰ salinity, at temperatures of 10°C - 25°C. The practical purpose of this investigation was supporting the diversification of local mariculture species, as mullets can be excellent candidates for the enhancement of aquaculture in the area.

Some results of research autonomous plasma formation (apf)

2016 ◽  
Author(s):  
Шамсиев ◽  
A. Shamsiev ◽  
Шамсиев ◽  
M. Shamsiev
Keyword(s):  
Discharge Current ◽  
Peak Power ◽  
Scientific Explanation ◽  
Plasma Formation ◽  
Power Installation ◽  
Unusual Behavior ◽  
Generalized Characteristics ◽  
Wide Range

This article analyzes the results of the study of autonomous plasma formations (APF), received at facilities BL-1 and BL-2. Particularly noted a significant reduction in power installation BL-2 (2,5-3,6 kvt) compared with a peak power of BL-1 (641,25kvt), while maintaining the density of the discharge current> = 104 A\mm2.Analyzed generalized characteristics APF plants (averaging 100 experiments) and their unusual properties, which were observed only once and are not amenable to scientific explanation. Presented photos (8 pictures), the most typical installation APF BL-2 and made an attempt to explain their unusual behavior. It is shown that the installation of the BL-2 provides a wide range of opportunities for further detailed study of the properties of the APF, and in particular in terms of their practical use. The disadvantage of setting the BL-1 and BL-2, as of today, is the formation at the same time, a minimum of 2 APF. What makes certain difficulties in the calculation of their features.

Influence of a Magnetic Obstacle on Forced Convection in a Three-Dimensional Duct With a Circular Cylinder

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Xidong Zhang ◽  
Hulin Huang ◽  
Yin Zhang ◽  
Hongyan Wang
Keyword(s):  
Pressure Drop ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Three Dimensional ◽  
Separated Flow ◽  
Optimum Conditions ◽  
Nusselt Numbers ◽  
Maximum Value ◽  
Wide Range ◽  
The Mean

The predictions of flow structure, vortex shedding, and drag force around a circular cylinder are promoted by both academic interest and a wide range of practical situations. To control the flow around a circular cylinder, a magnetic obstacle is set upstream of the circular cylinder in this study for active controlling the separated flow behind bluff obstacle. Moreover, the changing of position, size, and intensity of magnetic obstacle is easy. The governing parameters are the magnetic obstacle width (d/D = 0.0333, 0.1, and 0.333) selected on cylinder diameter, D, and position (L/D) ranging from 2 to 11.667 at fixed Reynolds number Rel (based on the half-height of the duct) of 300 and the relative magnetic effect given by the Hartmann number Ha of 52. Results are presented in terms of instantaneous contours of vorticity, streamlines, drag coefficient, Strouhal number, pressure drop penalty, and local and average Nusselt numbers for various magnetic obstacle widths and positions. The computed results show that there are two flow patterns, one with vortex shedding from the magnetic obstacle and one without vortex shedding. The optimum conditions for drag reduction are L/D = 2 and d/D = 0.0333–0.333, and under these conditions, the pressure drop penalty is acceptable. However, the maximum value of the mean Nusselt number of the downstream cylinder is about 93% of that for a single cylinder.

Finite Element Analysis on Frame-Type Hydraulic Press

2011 ◽  
Vol 199-200 ◽  
pp. 1623-1628 ◽  
Author(s):  
Da Sen Bi ◽  
Dan Dan Liu ◽  
Liang Chu ◽  
Jian Zhang
Keyword(s):  
Finite Element ◽  
Working Conditions ◽  
Manufacturing Industry ◽  
Effective Strain ◽  
Work Load ◽  
Hydraulic Press ◽  
Element Analysis ◽  
Maximum Value ◽  
Wide Range ◽  
Cylinder Port

Hydraulic press is important pressure processing equipment, which has a wide range of applications in production and manufacturing industry. The structure of hydraulic press frame has an extremely significant effect on safety and usability. Against the structure of frame-type hydraulic press in this paper, a solid model has been built with CAD program Pro/E and the hydraulic press frame under working conditions is simulated by finite element simulation program ANSYS. This paper analyses the variation of stress, strain and frame deformation under working conditions, and the dangerous sections of hydraulic press frame can be found under the maximum work load. The research results show: The maximum value of effective strain and effective stress can be found in the screw holes of cylinder port, the maximum value of stress and strain in the direction of hydrocylinder force can be found in the confluence of upright column and lower beam, the maximum value of effective displacement and the displacement in the direction of hydrocylinder force can be found in cylinder port and part of upper beam.

scholarly journals DISCREPANCY PARAMETERS OF APPROXIMATIONS OF DISCRETELY SPECIFIED DEPENDENCIES BY ANALYTICAL FUNCTIONS AND SEARCH CRITERIA FOR OPTIMAL VALUES OF THEIR COEFFICIENTS

2021 ◽  
Vol 2021 (59) ◽  
pp. 11-19
Author(s):  
S.M. Zakharchenko ◽  
◽  
N.A. Shydlovska ◽  
I.L. Mazurenko ◽  
◽  
...  
Keyword(s):  
Power Function ◽  
Mathematical Expectation ◽  
Discharge Current ◽  
Electrical Resistance ◽  
Approximation Error ◽  
Analytical Functions ◽  
Spark Erosion ◽  
Instantaneous Values ◽  
Optimal Values

Universal discrepancy parameters of approximations of discretely specified dependencies by analytical functions and search criteria for optimal values of their coefficients, as well as analysis of features of their application are described. Discrepancy parameters of approximations, which do not depend on the ranges of variation of the values of functions and the number of points of a discretely specified dependence, are proposed. They can be effective for objectively comparing the quality of approximations of any dependencies by any functions. Approximations of a discretely specified dependence of the mathematical expectation of the equivalent electrical resistance of a layer of aluminum granules during spark-erosion dispersion in water on the instantaneous values of the discharge current are carried out. As approximating functions, we chose a power function with an exponent factor –1 and a function based on exponential. Using the criteria of the least approximation error, the optimal values of the coefficients of both approximating functions are founded. It is shown in which cases it is advisable to use the combined search criteria for the optimal values of the coefficients of the approximating functions, and in which are enough simple one-component ones. Ref. 27, fig. 2, tables 2.

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