scholarly journals Modeling of electric mass transfer process in controlled electrochemical resistance

2021 ◽  
Vol 2131 (4) ◽  
pp. 042050
Author(s):  
D D Fugarov ◽  
E Y Gerasimenko ◽  
A N Gerasimenko
Keyword(s):  
Electric Fields ◽  
Concentration Field ◽  
Operator Method ◽  
Analytical Description ◽  
Mass Transfer Process ◽  
Electrode Processes ◽  
Different Temperatures ◽  
Electric Mass Transfer ◽  
Object Of Study ◽  
Physical And Chemical

Abstract The aim of the study is to mathematically simulate the concentration field of an electrolyte in a controlled electrochemical resistance. All processes occurring in the object are considered isothermal, the electric fields in all fragments of the electrochemical resistance are potential, plane-parallel. All physical and chemical parameters of the object’s materials are constant values. The kinetics of all electrode processes in the object of study is controlled by the diffusion stage in the electrolyte. As a research method, the operator method of Laplace and Fourier – expansion is used to obtain an analytical description of the concentration field of the electrolyte. In the course of the study, a mathematical model of the concentration field of the electrolyte with a uniform distribution of the current density was obtained. An analytical expression is obtained that allows to construct the surface of the change in the concentration of the electrolyte in the controlled electrochemical resistance. The concentration profiles of the electrolyte at different temperatures and the time dependences of the change in the concentration of the electrolyte are calculated.

Study of Whiskers to be Used in Composite Materials

2021 ◽  
Vol 316 ◽  
pp. 51-55
Author(s):  
Tamara I. Shishelova ◽  
Vadim V. Fedchishin ◽  
Mikhail A. Khramovskih
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Chemical Properties ◽  
High Strength ◽  
Rapid Expansion ◽  
Physical And Chemical Properties ◽  
Reinforcement Fiber ◽  
Object Of Study ◽  
Physical And Chemical ◽  
And Chemical Properties

Rapid expansion of technologies poses higher requirements to structural materials and items made of them. Conventional materials are being replaced by composite materials (composites). Different additives enhancing the properties of initial materials are used as reinforcement fibers of composites. Utilization of micro-and nanosize particles for production of present-day materials is paid much attention to. Whiskers are among such materials. These crystals have high strength, high chemical and temperature resistance. But for rational utilization of whickers of different chemical composition in composite materials one should know their physical and chemical properties. Objectives of the paper: to study physical and chemical properties of whiskers in different compounds, their composition and structure; to prove experimentally the feasibility of utilizing whiskers as a reinforcement fiber of composite materials. Object of study: specimens of whiskers of silicon nitride (Si3N4), aluminum oxide (Al2O3), aluminum nitride (AlN), and mullite (Al6Si2O13). Methods of investigation: thermal study of specimens, study of mechanical properties and chemical strength, and IR-spectroscopy. Results of study: specimens of whiskers have been studied and their mechanical properties have been tabulated for comparison. Extensive thermal investigation was followed by deduction of regularities and identification of chemical properties of whiskers. IR-spectra of whiskers have been studied and conclusions on molecular composition and on presence of impurities in some whiskers have been made.

STORAGE TEMPERATURE AS A FACTOR OF FAT MIGRATION IN GLAZED SUGARY CONFECTIONERY PRODUCTS

1970 ◽  
pp. 78-80
Author(s):  
N. B. Kondratyev ◽  
Е. V. Kazantsev ◽  
O. S. Rudenko ◽  
N. А. Petrova ◽  
I. А. Belova
Keyword(s):  
Fatty Acids ◽  
Migration Rate ◽  
Unsaturated Fatty Acids ◽  
Storage Temperature ◽  
Polymorphic Form ◽  
Specific Rate ◽  
Confectionery Products ◽  
Different Temperatures ◽  
Physical And Chemical Quality ◽  
Physical And Chemical

The fat migration processes by changing the fatty acid composition of individual parts of glazed sweets with praline-type bodies (based on peanuts) during storage at different temperatures was studied. The main mechanism of mass transfer is considered to be the fat migration through the volume of products through the capillaries. The maximum migration rate of the liquid fat phase is at a storage temperature of 23-25 ° C in samples without transisomers of unsaturated fatty acids. Its reduction is possible with the introduction of 20-30% lauric acid into the fat fraction of products. The crystalline structure of the confectionery fats included in the candy fillings has a significant effect on the migration rate of the liquid fat phase into the glaze. The smallest one corresponded to fats in the β-polymorphic form with an admixture of no more than 3% crystals in the β'-polymorphic form. The specific rate of fat migration has been calculated taking into account the size of a glazed sweets model samples. When in storage temperature increases from 18 to 27 ˚С, it increased 1.7 times. The results of studies of changes in the composition of fatty acids of model samples individual parts of glazed sweets during storage at temperatures of 18 and 27 °C are presented. The proposed approach makes it possible to predict the fat migration processes rate. The comprehensive assessment methodology, which includes the determination of physical and chemical quality indicators during storage, the regularities of fat migration and microbiological changes, will justify the requirements for the technology parameters and the recipe composition of glazed sugary confectionery products with a given expiration date.

Investigations on condensation phenomena in mercury vapour

1934 ◽  
Vol 30 (2) ◽  
pp. 216-224
Author(s):  
P. C. Ho
Keyword(s):  
Surface Tension ◽  
Chemical Properties ◽  
Mercury Vapour ◽  
Physical And Chemical Properties ◽  
Critical Supersaturation ◽  
Different Temperatures ◽  
Image Position ◽  
Physical And Chemical ◽  
Theoretical Considerations ◽  
And Chemical Properties

Owing to its physical and chemical properties being greatly different from those of any of the liquids which have hitherto been used in the Wilson cloud chamber, mercury has been used in the experiments described in this paper and the condensation phenomena of its vapour at different temperatures observed. Before constructing the apparatus it was considered necessary to get from theoretical considerations some idea about the magnitude of the critical supersaturation for mercury vapour in equilibrium with a drop carrying unit charge. Assuming that J. J. Thomson's formula.where s is the supersaturation of mercury vapour in equilibrium with a drop of mercury of radius a, charge e, density σ and surface tension T, the value of which is assumed here to be independent of the radius of the drop, K the specific inductive capacity of the dielectric surrounding the drop, and R the gas constant for one gramme of weight, all at temperature θ, can be applied to the present problem, this critical supersaturation sm is given by the formula

Smart Hydrogels for Pharmaceutical Applications

2017 ◽  
pp. 1133-1164
Author(s):  
Snežana S. Ilić-Stojanović ◽  
Ljubiša B. Nikolić ◽  
Vesna D. Nikolić ◽  
Slobodan D. Petrović
Keyword(s):  
Electric Fields ◽  
Polymer Network ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Stimuli Responsive ◽  
Crosslinking Degree ◽  
Color Transparency ◽  
Hydrogel Network ◽  
Physical And Chemical ◽  
Responsive Hydrogels

The latest development in the field of smart hydrogels application as drugs carriers is shown in this chapter. Hydrogels are three-dimensional polymer network consisting of at least one hydrophilic monomer. They are insoluble in water, but in the excess presence of water or physiological fluids, swell to the equilibrium state. The amount of absorbed water depends on the chemical composition and the crosslinking degree of 3D hydrogel network and reaches over 1000% of the xerogel weight. Stimuli-responsive hydrogels exhibit significant change of their properties (swelling, color, transparency, conductivity, shape) due to small changes in the external environment conditions (pH, ionic strength, temperature, light wavelength, magnetic or electric fields, ultrasound, or a combination thereof). This smart hydrogels, with different physical and chemical properties, chemical structure and technology of obtaining, show great potential for application in the pharmaceutical industry. The application of smart hydrogels is very promising and at the beginning of the development and exploitation.

scholarly journals The Influence of Different Pre-Treatments on the Quality and Nutritional Characteristics in Dried Undersized Yellow Kiwifruit

2020 ◽  
Vol 10 (23) ◽  
pp. 8432
Author(s):  
Cinzia Mannozzi ◽  
Urszula Tylewicz ◽  
Silvia Tappi ◽  
Marco Dalla Rosa ◽  
Pietro Rocculi ◽  
...  
Keyword(s):  
Electric Fields ◽  
Bioactive Compounds ◽  
Osmotic Dehydration ◽  
Drying Time ◽  
Production Chain ◽  
Processing Technologies ◽  
Dpph Method ◽  
Nutritional Characteristics ◽  
Different Temperatures ◽  
Good Retention

Undersized kiwifruits are considered waste; therefore, there is a need to develop sustainable processing technologies for their valorization, in order to have a positive economic impact on their entire production chain. Therefore, the aim of this study was to apply pulsed electric fields (PEF) combined with osmotic dehydration (OD) and air drying (AD) to develop a novel yellow kiwifruit dried snack with high nutritional functionality. In particular, the effect of the different pre-treatments, PEF (200 V/cm) and/or OD (trehalose at 40%), on the color, bioactive compounds content and antioxidant activity (AA) was evaluated on kiwifruit chips air-dried at three different temperatures (50, 60, 70 °C). The results showed that better color maintenance was observed at the drying temperature of 60 °C. Concerning the bioactive compounds, a good retention in total polyphenols (TP), vitamin C content and AA with the DPPH method was obtained on OD and PEF kiwifruit dried snacks, similar to that of control samples. Instead, the ABTS method showed the best AA in PEF and OD/PEF samples. In general, a shorter drying time in the OD- and PEF-treated samples could contribute to the higher sustainability of the process.

scholarly journals Bilayer lead oxide X-ray photoconductor for lag-free operation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Oleksandr Grynko ◽  
Tristen Thibault ◽  
Emma Pineau ◽  
Gytis Juska ◽  
Alla Reznik
Keyword(s):  
Real Time ◽  
Electric Fields ◽  
Lead Oxide ◽  
Thick Layer ◽  
Hole Mobility ◽  
Direct Conversion ◽  
Complete Suppression ◽  
Bilayer Structure ◽  
X Ray ◽  
Different Temperatures

AbstractPolycrystalline Lead Oxide (poly-PbO) was considered one of the most promising photoconductors for the direct conversion X-ray medical imaging detectors due to its previous success in optical imaging, i.e., as an optical target in so-called Plumbicon video pick-up tubes. However, a signal lag which accompanies X-ray excitation, makes poly-PbO inapplicable as an X-ray-to-charge transducer in real-time X-ray imaging. In contrast, the recently synthesized Amorphous Lead Oxide (a-PbO) photoconductor is essentially lag-free. Here, we report on our approach to a PbO detector where a thin layer of a-PbO is combined with a thick layer of poly-PbO for lag-free operation. In the presented a-PbO/poly-PbO bilayer structure, the poly-PbO layer serves as an X-ray-to-charge transducer while the a-PbO acts as a lag prevention layer. The hole mobility in the a-PbO/poly-PbO bilayer structure was measured by photo-Charge Extraction by Linearly Increasing Voltage technique at different temperatures and electric fields to investigate charge transport properties. It was found that the hole mobility is similar to that in a-Se—currently the only commercially viable photoconductor for the direct conversion X-ray detectors. Evaluation of the X-ray temporal performance demonstrated complete suppression of signal lag, allowing operation of the a-PbO/poly-PbO detector in real-time imaging.

Effect of Phosphate and Silica on the Rate of Crystallization of Sucrose

2005 ◽  
Vol 1 (5) ◽  
Author(s):  
Ms. Aamarpali Ratna Puri ◽  
S. Kaur
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Mother Liquor ◽  
Crystal Surface ◽  
Mass Transfer Process ◽  
Sugar Solution ◽  
Local Conditions ◽  
Concentration Difference ◽  
Different Temperatures ◽  
Sucrose Crystals

Sucrose Crystallization is a mass transfer process. Sucrose molecule's migration from solution to crystal is driven by concentration difference between the mother liquor and the crystal surface; the coefficient of super saturation is the most important parameter for the process. Supersaturation of sugar solution depends on the purity and brix of the mother liquor. It has large influence on product's quantity and quality (crystal yield, crystal size and size distribution) and on the cost of production i.e output/hour and energy consumption. However there is still no generally applicable theory, which permits an accurate prediction of the effects of all the factors that govern the industrial processes of crystallization from solution. The crystal growth depends on the viscosity, which further depends on the nature and amount of impurities. If the local conditions are favourable, localized layers of molecules of impurity can statistically remain on the surface for a period of time. On the other hand, if the interaction between the impurity and the layer is weak, then there will be competition between impurity and sucrose molecules thus affecting the sucrose crystal growth rate. In the present study, the growth rate of sugar crystals was studied, using two-litre automatic laboratory vacuum pan, under controlled conditions in the presence of impurities. The effect of phosphate and silica (adding one at time) on the growth rate of sugar crystals was studied at two different temperatures 328 and 338K and with two different seed sizes of sucrose (850 and 600µm). The growth rate was studied at two degrees of supersaturation (1.10 and 1.15). The growth rate of sucrose crystals (with or without added impurities) showed significant increase with the 10°C rise in temperature. The growth rate of sucrose crystals increased with the increase in the level of phosphate but decreased with the increase in the level of silica in sugar solution.

THE MONTE CARLO METHOD APPLIED TO CARRIER TRANSPORT IN Si/SiGe QUANTUM WELLS

2005 ◽  
Vol 19 (21) ◽  
pp. 3353-3377 ◽  
Author(s):  
V. A. VETTCHINKINA ◽  
A. BLOM ◽  
M. A. ODNOBLYUDOV
Keyword(s):  
Monte Carlo ◽  
Quantum Wells ◽  
Electric Fields ◽  
Carrier Transport ◽  
Impurity Scattering ◽  
Resonant Scattering ◽  
Interface Roughness ◽  
The Monte Carlo Method ◽  
Analytic Expressions ◽  
Different Temperatures

We present a complete Monte Carlo simulation of the transport properties of a Si/SiGe quantum well. The scattering mechanisms, viz. intervalley phonons, acoustic phonons, interface roughness and impurity scattering (including resonant scattering), are considered in detail, and we derive analytic expressions for the scattering rates, in each case properly taking the quantized electron wave functions into account. The numerically obtained distribution function is used to discuss the influence of each scattering mechanism for different electric fields applied parallel to the interfaces and also different temperatures.

scholarly journals EUCLIDEAN RESONANCE: APPLICATION TO PHYSICAL AND CHEMICAL EXPERIMENTS

2006 ◽  
Vol 20 (06) ◽  
pp. 627-658 ◽  
Author(s):  
B. IVLEV
Keyword(s):  
Electric Fields ◽  
Isotope Separation ◽  
Nuclear Fission ◽  
Particle Decay ◽  
Semiclassical Methods ◽  
Wide Range ◽  
Tunnel Barriers ◽  
Physical And Chemical ◽  
Nuclear Processes ◽  
Complex Trajectories

The phenomenon of Euclidean resonance (a strong enhancement of quantum tunneling through a nonstationary potential barrier) is applied to disintegration of atoms and molecules through tunnel barriers formed by applied constant and time-dependent electric fields. There are two different channels for such disintegration, electronic and ionic. The electronic mechanism is associated with the ionization of a molecule into an electron and a positive ion. The required frequencies are in a wide range between 100 MHZ and infrared. This mechanism may constitute a method of selective destruction of chemical bonds. The ionic mechanism consists of dissociation of a molecule into two ions. Since an ion is more massive than an electron, the necessary frequency is about 1 MHZ. This provides a theoretical possibility of a different method of isotope separation by radio frequency waves. The small sub-barrier tunneling probability of nuclear processes can be dramatically enhanced by collision with incident charged particles. Semiclassical methods of theory of complex trajectories have been applied to nuclear tunneling, and conditions for the effect have been obtained. The enhancement of α particle decay by incident proton with energy of about 0.25 MeV has been demonstrated. The general features of this process are common for other sub-barrier nuclear processes and can be applied to nuclear fission.

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