• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.878-887
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• 2001

Experimental investigation has been carried out to examine the operating characteristics of a bubble pump for diffusion absorption refrigerator. The effects of heat input and delivery height on generation rate of refrigerant vapor and circulation rate of solution have been investigated. as a result heat input and delivery height increase, circulation rate of solution increases. And the smaller the tube diameter, the larger the circulation rate of solution. Pumping ratio increases to a critical point and then decrease with the increase of heat input, and it increases with the increase in delivery height. In this paper, Marcus's analytical theory was also examined. It was found that the Marcus\`s analytical theory of a bubble pump was not appropriate for a bubble pump using ammonia aqueous solution as a working fluid.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.287-292
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• 2004

An experimental investigation was carried out to study the performance of a bubble pump for the diffusion absorption refrigerating system. Ammonia was used as the refrigerant and the helium was charged in order to balance the pressure between the low and high pressure side. As experimental variables, the concentration of ammonia charged into system, heat input, and the pressure of helium were selected. Experimental results show that the generation rate of ammonia vapor and the circulation rate of diluted ammonia solution were increased as the heat input increases, but the ratio of the solution to vapor flow rate was decreased. The generation rate of refrigerant vapor and the circulation rate of diluted ammonia solution increased as the system pressure decreased. Finally under the condition of 25 bars, the concentration of rich ammonia solution was not affected by the generation rate of ammonia vapor and the circulation of diluted ammonia solution.

• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.65-70
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• 2005

A phase mixture model was employed to simulate the deformation behaviour of metallic materials covering a wide grain size range from micrometer to nanometer scale. In this model a polycrystalline material is treated as a mixture of two phases: grain interior phase whose plastic deformation is governed by dislocation and diffusion mechanisms and grain boundary 'phase' whose plastic flow is controlled by a boundary diffusion mechanism. The main target of this study was the effect of grain size on stress and its strain rate sensitivity as well as on the strain hardening. Conventional Hall-Petch behaviour in coarse grained materials at high strain rates governed by the dislocation glide mechanism was shown to be replaced with inverse Hall-Petch behaviour in ultrafine grained materials at low strain rates, when both phases deform predominantly by diffusion controlled mechanisms. The model predictions are illustrated by examples from literature.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.4
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• pp.481-492
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• 1992

Author measured the bonding strength between Dental Porcelain and Nonprecious Dental Alloy and analyzed diffusion Phenomena at the interfaceby by Auger electron spectroscopy and also Electron spectroscopy for Chemical Analysis. The each specimen was sputtered with Al, Cr, In and Sn. 1. Ni whic is the main element of the matris of dental nonprecious alloy diffuse more than the other element and the Ni diffusion rate of each specimen was well coordinated with the bonding strength of each. 2. The Sn thin film suppress the diffusion rate of Ni of matrix into the Dental Porcelain than the In or Cr thin films. 3. The Al thin film suppress the diffusion rate of Ni than the Sn thin film. 4. The main coponent of dental porcelain : Al, Si, Mo diffused into the matrix of alloy. It means that the each element of dental alloy and dental porelain diffused into the each other part.

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.347-353
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• 2022

Agarose hydrogel, a solid electrolyte, was investigated voltammetrically in terms of transport properties and natural convection effects using a ferrocenyl compound as a redox probe. To confirm the diffusion properties of solute on the agarose interface, the diffusion coefficients (D) of ferrocenemethanol in agarose hydrogel were determined by cyclic voltammetry (CV) according to the concentration of agarose hydrogel. While the value of D on the agarose interface is smaller than that in the bulk solution, the square root of the scan rate-dependent peak current reveals that the mass transport behavior of the solute on the agarose surface shows negligible convection or migration effects. In order to confirm the reduced natural convection on the gel interface, scan rate-dependent CV was performed in the solution phase and on the agarose surface, respectively. Slow scan voltammetry at the gel interface can determine a conventional and reproducible diffusion-controlled current down to a scan rate of 0.3 mV/s without any complicated equipment.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.192-198
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• 1996

We present a theoretical formulation of diffusion process on solid surface based on multidimensional transition state theory (TST). Surface diffusion of single adatom results from hopping processes on corrugated potential surface and is affected by surface vibrations of surface atoms. The rate of rare events such as hopping between lattice sites can be calculated by transition state theory. In order to include the interactions of the adatom with surface vibrations, it is assumed that the coordinates of adatom are coupled to the bath of harmonic oscillators whose frequencies are those of surface phonon modes. When nearest neighbor surface atoms are considered, we can construct Hamiltonians which contain terms for interactions of adatom with surface vibrations for the well minimum and the saddle point configurations, respectively. The escape rate constants, thus the surface diffusion parameters, are obtained by normal mode analysis of the force constant matrix based on the Hamiltonian. The analysis is applied to the diffusion coefficients of W, Ir, Pt and Ta atoms on the bcc(110) plane of W in the zero-coverage limit. The results of the calculations are encouraging considering the limitations of the model considered in the study.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.689-697
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• 1998

In this work, we studied the equilibrium, rate and rate determining step of uranium adsorption on RGP resins of MR type prepared by varying the degree of crosslinking and the amount of diluent. The equilibrium of uranium adsorption on RGP resins were well explained by Frendrich isotherm as well as Langmuir isotherm model. The amount of adsorption and adsorption rate increase with the adsorption temperature. The heat of the adsorption was 11 kcal/mol. The adsorption rates of uranium on RGP resins were decreased in the order of RGP-10(50)>RGP-1(50)>RGP-2(50)>RGP-5(50)>RGP-0(50) and RGP-2(75)>RGP-2(100)>RGP-2(50)>RGP-2(30)>RGP-2(0). The diffusion resistance of uranium into RGP resin increased as follows; molecular diffusion < pore diffusion < surface diffusion. On the other hand, the surface diffusion was more dominative than the pore diffusion in intraparticle region. Thus, this result indicates that the adsorption mechanism of uranium on RGP resins is intraparticle diffusion controlled.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.46-53
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• 2016

Effect of heating rate on microstructure of brazed joints with STS 304 Printed Circuit Heat Exchanger (PCHE),which was manufactured as large-scale($1170(L){\times}520(W)){\times}100(T)$, mm), have been studied to compare bonding phenomenon. The specimens using MBF 20 was bonded at $1080^{\circ}C$ for 1hr with $0.38^{\circ}C/min$ and $20^{\circ}C/min$ heating rate, respectively. In case of a heating rate of $20^{\circ}C/min$, overflow of filler metal was observed at the edge of a brazed joints showing the height of filler metal was decreased from $100{\mu}m$ to $68{\mu}m$. At the center of the joints, CrB and high Ni contents of ${\gamma}$-Ni was existed. For the joints brazed at a heating rate of $0.38^{\circ}C/min$, the height of filler was decreased from $100{\mu}m$ to $86{\mu}m$ showing the overflow of filler was not appeared. At the center of the joints, only ${\gamma}$-Ni was detected gradating the Ni contents from center. This phenomenon was driven from a diffusion amount of Boron in filler metal. With a fast heating rate $20^{\circ}C/min$, diffusion amount of B was so small that liquid state of filler metal and base metal were reacted. But, for a slow heating rate $0.38^{\circ}C/min$, solid state of filler metal due to low diffusion amount of B reacted with base metal as a solid diffusion bonding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.137-140
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• 2003

Cu+ ions drift diffusion in different dielectric materials is evaluated. The diffusion is investigated by measuring shift in the flatband voltage of capacitance/voltage measurements on Cu gate capacitors after bias temperature stressing. At a field of 1.lMV/cm and temperature $200^{\circ}C$, $250^{\circ}C$, $300^{\circ}C$ for 1H, 2H, 5H. The Cu+ ions drift rate of polyimide$(2.8{\leq}k{\leq}3.2)$ is considerably lower than thermal oxide. Also Cu+ drift rate of polyimide is similar to PECVD oxide. But, polyimide film is even more resistant to Cu drift diffusion and thermal effect than Thermal oxide, PECVD oxide: This results got a comparative reference. The important conclusion is that polyimide film is strongly dielectric material by thermal effect and Cu drift diffusion.

• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.74-81
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• 2010

In this study, soot formation characteristics on the instability of laminar diffusion flames were investigated experimentally using a concentric co-flow burner. When a small amount of air was supplied through an inner nozzle, a stable propane laminar diffusion flame became unstable and began to oscillate mainly due to the dilution effect. The increase of air flow rate transformed an oscillating non-sooting flame into a stable nonsooting flame. When the air flow rate was continuously increased an inner flame was formed and the flame was changed to an oscillating sooting flame, an oscillating non-sooting flame and finally a stable non-sooting hollow flame. When the air flow rate was decreased, a non-sooting hollow flame was eventually changed back to a stable non-sooting flame. The presence of an inner flame, however, altered the soot formation characteristics of a flame. More soot production was observed with the presence of an inner flame. The increased or decreased soot formation/oxidation rates, the radiation heat loss, and the heating effect of inner flames are most likely to be responsible for the observed instability of laminar diffusion flames.