scholarly journals Experimental and Numerical Investigation of Temperature Development of Ohmic Heating Cured Nonmass Concrete under Subzero Temperature

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Beimeng Qi ◽  
Zheng Zhou ◽  
Weichen Tian ◽  
Mingzhe Ouyang ◽  
Xiaocheng Wang ◽  
...  
Keyword(s):  
High Efficiency ◽  
Carbon Nanofiber ◽  
Concrete Slab ◽  
Ohmic Heating ◽  
Sem Analysis ◽  
Subzero Temperature ◽  
Heating Process ◽  
Field Coupling ◽  
The Matrix ◽  
Solid Foundation

In this paper, carbon fiber/carbon nanofiber strengthening nonmass concrete slab was designed, and ohmic heating (OH) curing was used to promote the strength formation of the slab under −20°C. COMSOL multiphysical field coupling program has been used to simulate the heating process of nonmass concrete slabs under different conditions. COMSOL analysis results showed that the optimal loading power density of OH cured sample under −20°C was 1000 W/m2∼1200 W/m2. Moreover, numerical analysis results were experimentally validated by the multipoint temperature measurement method. Furthermore, the mechanical properties showed that the compressive strength of the sample cured by 2 days OH curing at −20°C reached up to 48.2 MPa. SEM analysis exhibited that OH curing could improve the interfacial transition zone (ITZ) between the fiber and the matrix, leading to a denser microstructure. This study proved that COMSOL program could provide good theoretical guidance for OH cured nonmass cement concrete under subzero temperature. This work establishes an accurate guideline for electric power supplementation, laying a solid foundation of winter construction with high efficiency and low energy consumption.

Microwave Heating: Selective Energy Deposition to Compounds Intercalated Into the Interlayer Spaces of Fluorinated Graphite

2011 ◽  
Vol 6 (2) ◽  
pp. 57-64
Author(s):  
Andrey V. Arzhannikov ◽  
Aleksandr N. Mikheev ◽  
Viktor G. Makotchenko ◽  
M. К. А. Thumm
Keyword(s):  
Microwave Heating ◽  
Energy Deposition ◽  
Ohmic Heating ◽  
Dielectric Permeability ◽  
Microwave Energy ◽  
Heating Process ◽  
Microwave Exposure ◽  
Intercalated Compounds ◽  
The Matrix ◽  
Process Energy

We carry out investigations on peculiarities of microwave heating of various chemical compounds. Studies are conducted with a microwave system Discover-S-Class, clocked at 2450 MHz with a controlled power microwave exposure from 0 to 300 Watts. Results of experiments on the heating of intercalated compounds with chlorine trifluoride and acetone, acetonitrile, benzene and carbon tetrachloride are described in this paper. It has been established that microwave energy deposition is determined by the complex dielectric permeability of the compounds (the presence of a dipole moment and its mobility) intercalated into the interlayer spaces of the matrix. It is shown that due to microwave energy deposition the decay of the matrix with the formation of nanostructured carbon occurs. The onset temperature for carbon formation is essentially lower in comparison with traditional convection heating. In the final stage of the microwave heating process energy deposition is also due to ohmic heating of the carbon

Estimates of blow-up time for a non-local problem modelling an Ohmic heating process

2002 ◽  
Vol 13 (3) ◽  
pp. 337-351 ◽  
Author(s):  
N. I. KAVALLARIS ◽  
C. V. NIKOLOPOULOS ◽  
D. E. TZANETIS
Keyword(s):  
Blow Up ◽  
Ohmic Heating ◽  
Numerical Estimate ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Stationary Solutions ◽  
Upper And Lower Bounds ◽  
Heating Process ◽  
Non Local ◽  
Initial Boundary Value

We consider an initial boundary value problem for the non-local equation, ut = uxx+λf(u)/(∫1-1f (u)dx)2, with Robin boundary conditions. It is known that there exists a critical value of the parameter λ, say λ*, such that for λ > λ* there is no stationary solution and the solution u(x, t) blows up globally in finite time t*, while for λ < λ* there exist stationary solutions. We find, for decreasing f and for λ > λ*, upper and lower bounds for t*, by using comparison methods. For f(u) = e−u, we give an asymptotic estimate: t* ∼ tu(λ−λ*)−1/2 for 0 < (λ−λ*) [Lt ] 1, where tu is a constant. A numerical estimate is obtained using a Crank-Nicolson scheme.

scholarly journals LMI-Based Stability Criterion of Impulsive T-S Fuzzy Dynamic Equations via Fixed Point Theory

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Ruofeng Rao ◽  
Zhilin Pu
Keyword(s):  
Fixed Point ◽  
Stability Criterion ◽  
High Efficiency ◽  
Fixed Point Theory ◽  
Point Theory ◽  
Linear Matrix ◽  
The Matrix ◽  
Matrix Exponential Function ◽  
Takagi Sugeno ◽  
First Time

By formulating a contraction mapping and the matrix exponential function, the authors apply linear matrix inequality (LMI) technique to investigate and obtain the LMI-based stability criterion of a class of time-delay Takagi-Sugeno (T-S) fuzzy differential equations. To the best of our knowledge, it is the first time to obtain the LMI-based stability criterion derived by a fixed point theory. It is worth mentioning that LMI methods have high efficiency and other advantages in largescale engineering calculations. And the feasibility of LMI-based stability criterion can efficiently be computed and confirmed by computer Matlab LMI toolbox. At the end of this paper, a numerical example is presented to illustrate the effectiveness of the proposed methods.

FOAMING AND MOISTURE CROSSLINKING OF VINYL TRIETHOXY SILANE GRAFTED ETHYLENE–PROPYLENE–DIENE TERPOLYMER

2022 ◽  
Author(s):  
Zhengwei Lin ◽  
Qinghong Zhang ◽  
Gongliang Wang ◽  
Jie Mao ◽  
Martin Hoch ◽  
...  
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Side Reaction ◽  
High Energy ◽  
Expansion Ratio ◽  
Ethylene Propylene ◽  
Foaming Process ◽  
The Matrix ◽  
High Energy Absorption ◽  
Ethylene Propylene Diene Terpolymer

ABSTRACT Moisture crosslinking of polyolefins has attracted increasing attention because of its high efficiency, low cost, and easy processing. However, the crucial shortcoming of moisture crosslinking is that the side reaction of peroxide scorch (precrosslinking) simultaneously occurs in silane grafting. It has been recognized that making peroxide precrosslinking useful is an effective way to broaden the application of moisture crosslinking. A novel foaming process combined with moisture crosslinking is proposed. The matrix of ethylene–propylene–diene terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide as initiator. Foaming was then carried out with azodicarbonamide (AC) as the blowing agent by making use of precrosslinking. Subsequently, the EPDM-g-VTES foams were immersed in a water bath to achieve moisture crosslinking with dibutyl tin dilaurate as the catalyst. The results showed that VTES was grafted onto EPDM and the EPDM-g-VTES foams were successfully crosslinked by moisture. The EPDM-g-VTES compounds with AC obtained great cells by compression molding with the help of precrosslinking. The mechanical property of the EPDM-g-VTES foam was improved by moisture crosslinking. The moisture-cured foam with 4 wt% AC had an expansion ratio of about three times, which could bear large deformation and showed a high energy-absorption effect.

scholarly journals The increased use value of bamboo leaves as silica source for t-type zeolite synthesis

2018 ◽  
Vol 197 ◽  
pp. 05003 ◽  
Author(s):  
Soni Setiadji ◽  
Citra Deliana Dewi Sundari ◽  
Endang Lala ◽  
Denia Febby Nurbaeti ◽  
Ira Novianti ◽  
...  
Keyword(s):  
Sem Analysis ◽  
High Price ◽  
Heating Process ◽  
Zeolite Synthesis ◽  
X Ray Diffraction ◽  
Cost Performance ◽  
Silica Source ◽  
Bamboo Leaves ◽  
Type Zeolite ◽  
The Cost

T-type zeolite can be used as catalyst, adsorbent, and membranes for gas separation. The synthesis of T-type zeolite needs to be optimized in both of the method and source of precursor, because of its relatively high price. In this research, the synthesis is done using silica extracted from bamboo leaves instead of commercial silica. This increases the value of the bamboo leaves and the cost-performance of zeolite synthesis. The silica was extracted from bamboo leaves ash using alkaline solvent. The extracted silica has 81.76% of purity and an amorphous phase. The T-type zeolite was synthesized using the molar composition of 0.15 Na2O : 0.025 Al : 0.15 K2O : 1 SiO2 : 15 H2O : 0.06 TMAOH, under hydrothermal method and heating process for 4 days, 60°C for 2 days and 120°C for the next 2 days. The characterization method using X-Ray Diffraction and Infra-Red Spectroscopy were performed to confirm the formation of T-type zeolite. The results of Scanning Electron Microscope (SEM) analysis show that the formed T-type zeolite has erionite cylindrical crystal shape.

scholarly journals Snow Melting Performance of Graphene Composite Conductive Concrete in Severe Cold Environment

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6715
Author(s):  
Xinjie Wang ◽  
Yongkang Wu ◽  
Pinghua Zhu ◽  
Tao Ning
Keyword(s):  
High Efficiency ◽  
Concrete Slab ◽  
Input Voltage ◽  
Electrode Spacing ◽  
Snow Melting ◽  
Electric Voltage ◽  
Cold Regions ◽  
Graphene Composite ◽  
Time Required ◽  
Snow Thickness

The use of conductive concrete is an effective way to address snow and ice accretion on roads in cold regions because of its energy saving and high efficiency without interruption of traffic. Composite conductive concrete was prepared using graphene, carbon fiber, and steel fiber, and the optimum dosage of graphene was explored with resistivity as the criterion. Subsequently, under the conditions of an initial temperature of −15 °C and a wind speed of 20 km/h, the extremely severe snow event environment in cold regions was simulated. The effects of electrode spacing and electric voltage on snow melting performance of conductive concrete slab were explored. Results showed that graphene can significantly improve the conductivity of conductive concrete; the optimal content of graphene was 0.4% of cement mass in terms of resistivity. The snow-melting power of conductive concrete slab decreased with increase in electrode spacing and increased with increase in on-voltage. For an optimal input voltage of 156 V and an optimal electrode spacing of 10 cm, the time required to melt a 24 h snow thickness (21 cm), accumulated during a simulated severe snow event, was only 2 h, which provides an empirical basis for the application of graphene composite conductive concrete to pavement snow melting in cold regions.

Numerical study of toroidal magnetic field on the self-gravitating protoplanetary disks

2020 ◽  
Vol 29 (09) ◽  
pp. 2050067
Author(s):  
Hanifeh Ghanbarnejad ◽  
Maryam Ghasemnezhad
Keyword(s):  
Magnetic Field ◽  
Accretion Disks ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Ohmic Heating ◽  
The Self ◽  
Toroidal Magnetic Field ◽  
Heating Process ◽  
Heating And Cooling ◽  
The Magnetic Field

In this paper, we study the self-gravitating accretion disks by considering the toroidal component of magnetic field, [Formula: see text] and wind/outflow in the flow and also investigate the effect of two parameters, [Formula: see text] and [Formula: see text] corresponding to magnetic field on the latitudinal structure of such accretion disks. The cooling of the disk is parameterized simply as, [Formula: see text] (where [Formula: see text] is the internal energy and [Formula: see text] is the cooling timescale and [Formula: see text] is a free constant) and the heating rate is decomposed into two components, magnetic field and viscosity dissipations. We have shown that when the toroidal magnetic field becomes stronger, the heating process (viscous and resistivity) and the radiative cooling rate increase. Ohmic heating is much bigger than viscous heating and cooling, so we must consider the role of the magnetic field in the energy equation. Our numerical solutions show that the thickness of the disk decreases with strong toroidal component of magnetic field. The magnetic field leads to production of the outflow in the low latitude. So, by increasing the toroidal component of the magnetic field, the regions which belong to inflow decrease and the disk is cooled.

Quality and proteome changes of beef M.longissimus dorsi cooked using a water bath and ohmic heating process

2016 ◽  
Vol 34 ◽  
pp. 259-266 ◽  
Author(s):  
Xiaojing Tian ◽  
Wei Wu ◽  
Qianqian Yu ◽  
Man Hou ◽  
Fei Jia ◽  
...  
Keyword(s):  
Ohmic Heating ◽  
Water Bath ◽  
Heating Process ◽  
Proteome Changes

Correlation of Electrical Conductivity and Thermal Properties of Native Starch during Ohmic Heating

2011 ◽  
Vol 7 (5) ◽  
Author(s):  
Lam-Lam Wong ◽  
Yong-Wei Xu ◽  
Zhan-Hui Lu ◽  
Li-Te Li
Keyword(s):  
Electrical Conductivity ◽  
Room Temperature ◽  
Ohmic Heating ◽  
Heating Process ◽  
Rapid Evaluation ◽  
Scanning Calorimetry ◽  
Heating Method ◽  
Starch Gelatinization ◽  
On Line ◽  
Water Ratio

Electrical conductivity of starch suspension during ohmic heating was applied to analyze the starch gelatinization process. Native starches from wheat, corn, rice, potato, sweet potato, and pea were prepared on a starch to water ratio of 1:3 (w/w) with adding 0.05 M potassium chloride. A laboratory scale ohmic heating setup was designed to heat the starch suspension from room temperature to 90°C at a controlled heating rate of 10°C/min operating at 50 Hz and 110 V. The results show that starch gelatinization temperatures could be precisely calculated from electrical conductivity of starch suspension during ohmic heating process. The starch gelatinization temperatures based on ohmic heating were comparable to those measured by differential scanning calorimetry (DSC). Highly significant correlation of onset temperature (R=0.9972) and peak temperature (R=0.9950) were observed. The ohmic heating method could provide an alternative way to DSC with a promising potential for on-line and rapid evaluation of starch gelatinization temperatures.

Influence of Hydrocolloid Concentration, Salinity and Citric Acid Addition on Heat Transfer in the Ohmic Heating Process

2011 ◽  
Vol 7 (5) ◽  
Author(s):  
Mostafa Keshavarz Moraveji ◽  
Emad Ghaderi ◽  
Reza Davarnejad
Keyword(s):  
Heat Transfer ◽  
Electrical Conductivity ◽  
Citric Acid ◽  
Ohmic Heating ◽  
Solid Particles ◽  
Heating Process ◽  
Process Conditions ◽  
Heating Rates ◽  
Acid Addition ◽  
Ph Level

In this article, the effects of Ohmic heating process conditions on electrical conductivity and heat transfer were investigated. In order to study the Ohmic heating process, various hydrocolloid solutions containing starch in water with concentrations of 4–8% in the static cells were used. Temperature increments increased electrical conductivity of the solution, linearly. The concentration of dispersed solid particles in the solution caused a progressive trend in time-temperature curve for hydrocolloid solutions (with concentrations of 4, 5.5 and 8%) without electrolytes. The electrical conductivity was raised by increasing temperatures. In order to consider the salinity impact on electrical conductivity and the heating rate, sodium chloride (with concentrations of 1–0.25%) was added to the solution. It was observed that the salt addition to the system had a major effect on electrical conductivity and time-temperature curves. The pH level was modified with Citric acid addition, and the influence of pH level on the time-temperature curves and heating rates were investigated. The Citric acid addition had no on significant effect on the time-temperature curves.

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