Analytical Prediction of the Cross-Over Point in the Temperature Coefficient of the Forward Characteristics of 4H−SiC p+−i−n Diodes

2015 ◽  
Vol 821-823 ◽  
pp. 628-631
Author(s):  
Luigi di Benedetto ◽  
Gian Domenico Licciardo ◽  
Salvatore Bellone ◽  
Roberta Nipoti
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Temperature Coefficient ◽  
Analytical Model ◽  
Simple Formula ◽  
Carrier Lifetime ◽  
Analytical Prediction ◽  
First Order ◽  
Different Temperatures ◽  
Crossing Point

ForwardJD–VDcurves of 4H−SiC p−i−n diodes are analyzed by means of an analytical model in order to justify the presence of a crossing−point. The interlacing behaviour occurring in theJD–VDcurves of 4H−SiC diodes at different temperatures is predicted by a simple formula, which can be used for a first-order design of such devices. Numerical simulation of diodes designed with different epilayer thickness and carrier lifetime values have been used in order to analyze the crossing−point behaviour. Comparisons with experimental data confirm the analytic and simulated results.

scholarly journals Approximate Analytical Models of Shock-Wave Structure at Steady Mach Reflection

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 305
Author(s):  
Mikhail V. Chernyshov ◽  
Karina E. Savelova ◽  
Anna S. Kapralova
Keyword(s):  
Experimental Data ◽  
Shock Wave ◽  
Comparative Analysis ◽  
Analytical Model ◽  
Mach Reflection ◽  
Supersonic Jet ◽  
Wave Structure ◽  
Analytical Models ◽  
Analytical Prediction ◽  
Shock Wave Structure

In this study, we obtain the comparative analysis of methods of quick approximate analytical prediction of Mach shock height in planar steady supersonic flows (for example, in supersonic jet flow and in narrowing channel between two wedges), that are developed since the 1980s and being actively modernized now. A new analytical model based on flow averaging downstream curved Mach shock is proposed, which seems more accurate than preceding models, comparing with numerical and experimental data.

scholarly journals Colour change and kinetics of winter jujube slices during pulsed air-jet impingement drying

2018 ◽  
Vol 36 (No. 4) ◽  
pp. 302-308
Author(s):  
Cao Yuxue ◽  
Wang Gao ◽  
Huang Yong ◽  
Zhu Rongguang ◽  
Wang Qiang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Colour Change ◽  
Jet Impingement ◽  
Colour Difference ◽  
Drying Time ◽  
First Order ◽  
Air Jet ◽  
Different Temperatures ◽  
Best Fitting

The colour and the characteristics of colour change curves of winter jujube slices at different temperatures (55, 60, 65, 70, and 75°C) by the single factor experiment during pulsed air-jet impingement drying were stidied. The experimental data of colour difference (ΔE*) were fitted and verified by classic colour change model of thin fruit and vegetable. The results showed that L*(whiteness/darkness) and –a* (redness/greenness) of winter jujube slices decreased with the increase of drying time at different drying temperatures, while the change in the early stage was rapid, the latter stage was slow. The b* (yellowness/blueness) increased with the increase of drying time at different drying temperatures. Under different drying temperatures, the colour difference (ΔE*) of winter jujube slices increased with the increase of drying time during the drying process, the change in the early stage was rapid, the latter stage was slow. When the drying temperatures were 55, 60, 65 and 75°C, the first order fractional model of the colour difference (ΔE*) obtained the best fitting results with experimental data. Meanwhile, when the drying temperature was 70°C, the first of the first order mode of the total colour difference (ΔE*) was the best.

scholarly journals MATHEMATICAL MODELS OF FERNETOELECTRIC POLARIZATION CHARACTERISTICS DESCRIBED WITHIN THE FRAMEWORK OF THE LANDAU - GINZBURG - DEVONSHIER THEORY

2021 ◽  
pp. 12-20
Author(s):  
LUBOV IGOREVNA MOROZ ◽  
◽  
ANNA GENNADIEVNA MASLOVSKAYA ◽  
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Numerical Simulation ◽  
Mathematical Models ◽  
Computational Results ◽  
First Order ◽  
First Order Phase Transition ◽  
Polarization Characteristics ◽  
Difference Methods ◽  
First Order Phase

The paper presents the overview and implementation of mathematical models of ferroelectric polarization characteristics within the framework of the Landau - Ginzburg theory. Mathematical models of polarization switching in ferroelectrics are formalized by means of several types of differential problems. Based on difference methods the computational schemes are constructed for various modifications of the Landau - Khalatnikov model. Numerical simulation of the polarization hysteresis in ferroelectrics with the first-order phase transition is performed. The computational results obtained in Matlab are compared with the experimental data.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Development and Validation of Derivative Spectroscopic Method for Simultaneous Estimation of Cefadroxil and Probenecid

2014 ◽  
Vol 7 (1) ◽  
pp. 2350-2355
Author(s):  
Pratik S Mehta ◽  
Pratik R. Patel ◽  
Rajesh R Parmar ◽  
M M K Modasiya ◽  
Dushyant A Shah
Keyword(s):  
Spectroscopic Method ◽  
Spectral Interference ◽  
Synthetic Mixture ◽  
Simultaneous Estimation ◽  
Zero Crossing ◽  
First Order ◽  
Derivative Spectroscopy ◽  
Development And Validation ◽  
Crossing Point

A novel, simple, accurate, sensitive, precise and economical derivative spectroscopic method was developed and validated for the determination of cefadroxil and probenecid in synthetic mixture. First order derivative spectroscopy method was adopted to eliminate spectral interference. The method obeys Beer’s Law in concentration ranges of 4-36 μg/ml for cefadroxil and of 5-25 μg/ml of probenecid. The zero crossing point for cefadroxil and probenecid was 260 nm and 237.8 nm respectively in 0.1N HCl. The method was validated in terms of accuracy, precision, linearity, limits of detection, limits of quantitation. This method has been successively applied to synthetic mixture and no interference from the synthetic mixture’s excipients was found.   

scholarly journals Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 1968 ◽  
Author(s):  
Sylvie Bilent ◽  
Thi Hong Nhung Dinh ◽  
Emile Martincic ◽  
Pierre-Yves Joubert
Keyword(s):  
Experimental Data ◽  
Linear Model ◽  
Dielectric Material ◽  
Pressure Sensors ◽  
Volume Ratio ◽  
Measurement Range ◽  
Polymer Foams ◽  
First Order ◽  
Non Linear ◽  
Flexible Pressure Sensors

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

scholarly journals Kinetics and Mechanism of the Change of the 4-Nitrobenzylthio-System into 4,4′-Diformylazoxybenzene in Alkaline Dioxane-Water Media

1985 ◽  
Vol 40 (11) ◽  
pp. 1128-1132
Author(s):  
Y. Riad ◽  
Adel N. Asaad ◽  
G.-A. S. Gohar ◽  
A. A. Abdallah
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Main Product ◽  
Reaction Medium ◽  
Aqueous Dioxane ◽  
Proton Abstraction ◽  
First Order ◽  
Water Media ◽  
Different Temperatures

Sodium hydroxide reacts with α -(4-nitrobenzylthio)-acetic acid in aqueous-dioxane media to give 4,4'-diformylazoxybenzene as the main product besides 4,4'-dicarboxyazoxybenzene and a nitrone acid. This reaction was kinetically studied in presence of excess of alkali in different dioxane-water media at different temperatures. It started by a fast reversible a-proton abstraction step followed by two consecutive irreversible first-order steps forming two intermediates (α -hydroxy, 4-nitrosobenzylthio)-acetic acid and 4-nitrosobenzaldehyde. The latter underwent a Cannizzaro's reaction, the products of which changed in the reaction medium into 4,4'-diformylazoxybenzene and 4,4'-dicarboxyazoxybenzene. The rate constants and the thermodynamic parameters of the two consecutive steps were calculated and discussed. A mechanism was put forward for the formation of the nitrone acid.Other six 4-nitrobenzyl, aryl sulphides were qualitatively studied and they gave mainly 4,4'-diformylazoxybenzene beside 4,4'-dicarboxyazoxybenzene or its corresponding azo acid.

Convective Losses From Cavity Solar Receivers—Comparisons Between Analytical Predictions and Experimental Results

1983 ◽  
Vol 105 (1) ◽  
pp. 29-33 ◽  
Author(s):  
A. M. Clausing
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Analytical Model ◽  
Excellent Agreement ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Refined Model ◽  
Wall Area

Cavity solar receivers are generally believed to have higher thermal efficiencies than external receivers due to reduced losses. A simple analytical model was presented by the author which indicated that the ability to heat the air inside the cavity often controls the convective loss from cavity receivers. Thus, if the receiver contains a large amount of inactive hot wall area, it can experience a large convective loss. Excellent experimental data from a variety of cavity configurations and orientations have recently become available. These data provided a means of testing and refining the analytical model. In this manuscript, a brief description of the refined model is presented. Emphasis is placed on using available experimental evidence to substantiate the hypothesized mechanisms and assumptions. Detailed comparisons are given between analytical predictions and experimental results. Excellent agreement is obtained, and the important mechanisms are more clearly delineated.

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