scholarly journals ANALYTICAL NONLINEAR-PROBABILISTIC MODEL OF THE EQUIVALENT ELECTRICAL RESISTANCE OF A LAYER OF METAL GRANULES

2021 ◽  
Vol 2021 (5) ◽  
pp. 3-10
Author(s):  
S.M. Zakharchenko ◽  
◽  
N.A. Shydlovska ◽  
Keyword(s):  
Mathematical Expectation ◽  
Discharge Current ◽  
Probabilistic Model ◽  
Electrical Resistance ◽  
Nonlinear Models ◽  
Correction Coefficient ◽  
Analytical Functions ◽  
Instantaneous Values ◽  
Optimal Values ◽  
Working Liquid

As a result of processing the experimental data, an analytical continuous nonlinear-probabilistic model of the equivalent electrical resistance of a layer of metal granules in the working liquid was created. It is described by four equations: the modified Gaussian distribution and the dependences on the instantaneous values of the discharge current in the layer of metal granules of the mathematical expectation, dispersion and correction coefficient of the range of its equivalent electrical resistance. Based on the form of the dependences obtained during the experiments and the physics of the processes that occur in this case, two main groups of analytical functions are considered that approximate the obtained dependences. Criteria and methods for finding the optimal values of their coefficients are described. The adequacy of the approximation of each of the three obtained dependences by several analytical functions was investigated, the optimal values of the coefficients of which were found by the described method. Analytical functions was compared, which approximate the dependence of the mathematical expectation of the equivalent electrical resistance of a layer of metal granules on the instantaneous values of the discharge current in it with the known nonlinear models of the resistance of such a medium. References 33, figures 3, tables 3.

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.

scholarly journals DISCRETE NONLINEAR-PROBABILISTIC MODEL OF THE EQUIVALENT ELECTRICAL RESISTANCE OF A LAYER OF METAL GRANULES

2021 ◽  
Vol 2021 (2) ◽  
pp. 3-12
Author(s):  
N.A. Shidlovska ◽  
◽  
S.M. Zakharchenko ◽  
Keyword(s):  
Method Of Moments ◽  
Discharge Current ◽  
Probabilistic Model ◽  
Electrical Resistance ◽  
Probabilistic Models ◽  
Tap Water ◽  
Plasma Erosion ◽  
Spark Erosion ◽  
Trailing Edges ◽  
Normal Law

Two strategies for constructing nonlinear-probabilistic models of the equivalent electrical resistance of a layer of metal granules at their spark-erosion and plasma-erosion treatment and algorithms for their implementation are presented. A method for taking into account the parametric properties of such loads in their nonlinear and nonlinear-probabilistic models is described. Based on the data of direct experiments, the distributions of the electrical resistance of a layer of aluminum granules in tap water were obtained for eleven fixed values of the discharge current in it for both the leading and trailing edges of its pulses. The features of these distributions are described for different edges of the discharge current pulses. It has been proved that the obtained distributions can be adequately described by the normal law. The parameters of the normal law for each distribution obtained as a result of direct experiments are founded by the method of moments. A nonlinear-probabilistic model of the equivalent electrical resistance of a layer of aluminum granules in tap water is created, taking into account the main hysteresis of the dependence of resistance on current. It is shown that at large values of discharge currents, the nonlinear-probabilistic model of the equivalent electrical resistance of the layers of metal granules tends to degenerate into a nonlinear model. References 27, figures 4

scholarly journals STUDY OF STATIC AND DYNAMIC PARAMETERS OF HYDROCLEAVING DEVICE

2019 ◽  
Vol 2 (4) ◽  
pp. 89-97
Author(s):  
Aleksey Kordubaylo ◽  
Boris Simonov ◽  
Yuri Pronkin
Keyword(s):  
Oil And Gas ◽  
Static Pressure ◽  
Physical Simulation ◽  
Thrust Force ◽  
Dynamic Parameters ◽  
Study Results ◽  
Pressure Pulses ◽  
Maximal Pressure ◽  
Optimal Values ◽  
Working Liquid

In the work current importance of creation of hole electro driven pulse seismic sources for treatment of productive collectors of oil and gas deposit in order to hydrocarbons extraction intensification is justified. Study results of transfer center of strike pulses to extracting column are represented. The center is represented with hydrocleaving device. Objectives of the work are: establishing of dependences of plunger dies thrust force of hydrocleaving device on static pressure of working liquid in chamber, discovering of optimal values of hydrostatic pressure for provision of maximal pressure pulses in the chamber. Analytical dependence of thrust force on pressure in the chamber is obtained. Values of static strain of pipe fragment with diameter 122mm and wall thickness 9 mm under action of calculated thrust force are determined by methods of numerical simulations. Strains of fragment of the same pipe are experimentally studied under action of prototype thrust force. It is established that at pressure in the chamber up to 10MPa pipe strain at action axis is elastic up to 1mm. Repeatability of physical and numerical measurements is within 10%. With further increasing of the pressure up to 40 MPa the strain is elastic plastic up to 2.2mm. Using the method of physical simulation, it is established that pressure pulses in hydrocleaving device reach maximal values (up to 12 MPa) when values of preliminary static pressure are from 17 MPa up to 21MPa. However, increasing of strike energy above 180 J do not influence on value of pulse pressure significantly. Previously the devices of such type were not studied and were not applied in dynamic working modes. In the work recommendations for construction change of hydrocleaver for improvement of its dynamic parameters are formulated.

scholarly journals Production of Ultrafine Grained Hardmetals by Electrical Resistance Sintering

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 159 ◽  
Author(s):  
Jesús Cintas ◽  
Raquel Astacio ◽  
Francisco Cuevas ◽  
Juan Montes ◽  
Thomas Weissgaerber ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Electrical Resistance ◽  
Processing Parameters ◽  
Medium Frequency ◽  
Main Achievement ◽  
Processing Times ◽  
Ultrafine Grained ◽  
Protective Atmospheres ◽  
Optimal Values

In this work, powders of cemented ultrafine WC-6 wt.% Co were consolidated. The feasibility of the medium frequency electrical resistance sintering (MF-ERS) technique were studied to prevent WC grain growth during consolidation. Porosity and hardness were measured at different zones of the MF-ERS compacts. The compacts showed a slight inhomogeneity in their properties across their section, but it was controlled by choosing suitable values of the processing parameters. The optimal values for the material studied were current intensities between 7 and 8 kA and sintering times between 600 and 800 ms. The main achievement using this consolidation method was that sintered compacts essentially maintained the initial WC grain size. This was attained to processing times of less than 2 s, and without the need for using protective atmospheres.

scholarly journals GA-optimized model predicts dispersion coefficient in natural channels

2009 ◽  
Vol 40 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Gokmen Tayfur
Keyword(s):  
Objective Function ◽  
Dispersion Coefficient ◽  
Mean Absolute Error ◽  
Nonlinear Models ◽  
Error Function ◽  
Model Performance ◽  
Absolute Error ◽  
Model Parameters ◽  
Longitudinal Dispersion Coefficient ◽  
Optimal Values

Models whose parameters were optimized by genetic algorithm (GA) were developed to predict the longitudinal dispersion coefficient in natural channels. Following the existing equations in the literature, ten different linear and nonlinear models were first constructed. The models relate the dispersion coefficient to flow and channel characteristics. The GA model was then employed to find the optimal values of the constructed model parameters by minimizing the mean absolute error function (objective function). The GA model utilized an 80% cross-over rate and 4% mutation rate. It started each computation with a population of 100 chromosomes in the gene pool. For each model, while minimizing the objective function, the values of the model parameters were constrained between [−10, +10] at each iteration. The optimal values of the model parameters were obtained using a calibration set of 54 out of 80 sets of measured data. The minimum error was obtained for the case where the model was a linear equation relating dispersion coefficient to flow discharge. The model performance was then satisfactorily tested against the remaining 26 measured validation datasets. It performed better than the existing equations. It yielded minimum errors of MAE = 21.4 m2/s (mean absolute error) and RMSE = 28.5 m2/s (root mean-squares error) and a maximum accuracy rate of 81%.

scholarly journals A New Iterative Algorithm Based on Correction of Sensitivity Matrix for Electrical Resistance Tomography

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Yutong Chen ◽  
Yan Han ◽  
Wuqiang Yang ◽  
Kun Li
Keyword(s):  
Image Reconstruction ◽  
Electrical Resistance ◽  
Reconstruction Algorithm ◽  
Large Error ◽  
Correction Coefficient ◽  
Sensitivity Matrix ◽  
Electrical Resistance Tomography ◽  
Two Phase ◽  
The Difference ◽  
Theoretical Sensitivity

Electrical resistance tomography (ERT) is used to reconstruct the resistance/conductivity distribution. Usually, a uniform distribution is assumed as the initial condition to obtain a generic sensitivity matrix, which may be very different from a theoretical sensitivity matrix, resulting in a large error. The aim of this study is to analyse the difference between a generalized sensitivity matrix and a theoretical sensitivity matrix and to improve image reconstruction. The effect of the generic sensitivity matrix and theoretical sensitivity matrix on image reconstruction is analyzed. The error caused by the use of the generic sensitivity matrix is estimated. To reduce the error, an improved iterative image reconstruction algorithm is proposed, which is based on calculation of the error between the generic sensitivity matrix and the theoretical sensitivity matrix, and a correction coefficient with a penalty. During the iterative process, the resistivity distribution and sensitivity matrix are alternatively corrected. Simulation and experimental results show that the proposed algorithm can improve the quality of images, e.g., of two-phase distributions.

The First Experience with new Small-Sized Commercial Tem (TEM -100) and Biological Specimens

1990 ◽  
Vol 48 (1) ◽  
pp. 611-611
Author(s):  
Jovan Vukovié
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Liquid Nitrogen ◽  
Boiling Temperature ◽  
Resolution Power ◽  
Application Fields ◽  
Working Liquid

Conventional electron microscope TEM -100 (Made by “ELECTRON”, Sumy, USSR; Fig. 1) was presented at the XI Int. Congress on Electron Microscopy (Kyoto) by I.S. Lyalko et al. (1,2). The purpose of the microscope constructors were to design a small-sized general conventional TEM for various application fields. The microscope have mini lenses, which winding is placed in closed casing and soaked in working liquid (low boiling temperature) but upper part of the casing being water cooled.In this communication we gave our first experience and impression as a customer, beginning from the montage, the instruction and the testing of the microscope to our application in the field of biological specimens. Just after montage of the microscope on the second floor, the test of the point resolution power was performed by Ir specimen. It was achieved 0.5 nm (Fig. 2 and 3) on the roll film (ORWO 22 DIN) with 300 OOOx magnification and anticontamination device. The ultimate vacuum (about 10exp-6 mm Hg, ion discharge pump) also achieved using large trap cooled by liquid nitrogen.

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