• The Journal of Korean Academy of Prosthodontics
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• v.15 no.1
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• pp.34-42
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• 1977

The author attempted to observed the histological changes of the temporomandibular joints of rabbits by including malocclusion. Thirth-two healthy male rabbits were devided into two groups; control and experimental group. Eight rabbits were kept as control group, while metal crowns were seated on unilateral lower molar teeth of twenty-four rabbits as experimental group. And the interocclusal distance of the incisal edge was kept 1.5mm from the begining to the end of the experimental periods. Rabbits of each group, one of control group and three of the experimental gorup, were killed at the intervals of one day, three days, one week, two weeks, four weeks, six weeks, eight weeks, and twelve weeks after experiment. The temporomandibular joint including condyle head, articular disc and glenoid fossa were excised and decalcified. The decalcified sections were made histologic sections. The results obtained were as follows. 1. The regressive changes of the condylar head were the main reaction in this experiment that consist of decreasing or increasing thickness of the fibrocartilage zone with hyaline degeneration, decreasing of the cellularity of the proliferative zone, and the irregularity of the arrangement of chondrocytes and size of the lacunae of cartilage cells with chondroclasia and osteoclasia in hypertrophic zone. 2. The regressive changes of the condylar surface of the crown seated side were persisted to the end of the experiment. 3. On the non-crown seated side, severe aggressive changes occurred in initial stage, but hyperplastic changes of the condylar surface noted in the middle of the experimental periods. 4. Although aggressive changes occurred in initial stage of experiment on the non-crown seated side, hyperplastic changes of the condylar surface were noted in the middle of the experimental periods, and remodeling appeared at the termination of the experimental periods. 5. The articular disc exhibited pannus formation on both crown seated and non crown seated side from the beginning of the experiment. The pannus persisted throughout the experiment on the crown seated side, but on the non-crown seated side it disappeared from six week group.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.331-337
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• 2010

This study compared the macro and micro electrochemical characteristics at the local area of welding metal on dissimilar welding parts for type 304 stainless steel (SS) and type 316L SS. The materials are used for double wall gas pipe of duel fuel engine for a ship. The various potentiodynamic experiments were performed several times in 10% ${H_2C_2O_2}{\cdot}{H_2O}$ solution using macro and micro methods, respectively. The micro electrochemical experiments conducted to resolve at local area on cross-section of dissimilar welding materials by micro-droplet cell device. The micro-droplet cell techniques can be used almost electrochemical experiments to resolve corrosion characteristics of the limited electrode area of the metallic surface between wetted spot of working electrode and tip of sharpened capillary tube. The results of macro electrochemical experiments show that resistance of active dissolution reaction at welding zone was high due to low current density by formation of passivation protection film at passive region. According to the micro electrochemical experiment, the corrosion current density of welding zone and bond zone were relatively high.

• KSBB Journal
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• v.9 no.3
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• pp.239-245
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• 1994

The effects of reaction temperature and the level of hydration(water activity) were studied for gas phase reactions of alcohol oxidase and alcohol dehydrogenase immobilized on DEAE-cellulose and controlled pore glass(CPG). Optimum reaction temperature zone of gas phase reaction was similar to that of aqueous phase reaction. The activity of alcohol oxidase increased dramatically and the stability decreased when the water activity was increased from 0.3 to 0.8. The apparent activation energies of the gas phase reaction decreased approaching the values obtained in the aqueous phase reaction as the water activity increased. In the both cases of alcohol oxidase and alcohol dehydrogenase, the rate constants of the gas phase reaction were lower than those of aqueous phase reaction by two orders of magnitude and these results could be correlated to the vapor-liquid equilibrium data of the substrate, ethanol.

• Journal of the Mineralogical Society of Korea
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• v.25 no.1
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• pp.23-36
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• 2012

Morphological and mineralogical characteristics of laumontite and adularia in the breccia zone in a fault, Yangbuk-myeon, Gyeongju, Korea suggest that they formed by reaction with hydrothermal alteration related to fault activity. Laumontite commonly occurring in the breccia zone is related to the presence of hydrothermal fluids bearing alkaline elements in the zone. Laumonite is characterized by elongated columnar form with aspect ratio varying 5~10. Laumontite and adularia whose characteristic euhedral forms are indicative of the latest product formed as rapid precipitation from fluids or replacements of Ca-plagioclase. Hydrothermal fluids reacted with intensively fractured granite, typical with high permeability, leached alkaline elements such as Ca, K, allowing laumontite and adularia to be precipitated under neutral to weak alkaline conditions. It is noteworthy that the formation process and genesis of low temperature minerals such as laumontite and adularia are very similar to those formed by wallrock alteration or hydrothermal alteration that occurred in epithermal deposits. Taking into account its characteristic morphology and chemistry, authigenic K-feldspar that commonly forms at low temperature in many fault zones must be adularia.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.210-220
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• 1996

The purpose of this study is to develop the processing techniques of Fiber Reinforced Metal by Liquid Phase Diffusion Bonding method with SiC fiber as a reinforcing material and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements in reaction and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements is reaction zone among CP Ti/Ti-15wt%Cu-20wt%Ni(TCN20)/SiC long fiber were investigated by Optical Microscope, SEM/EDX, EPMA, X-ray and AES. The results obtained in this study are as follows. 1) When Ti matrix composite materials are fabricated under the bonding condition of 1273Kx1200sec, the SiC long fiber was the most suitable reinforcing material for Ti matrix composite materials. 2) With SiC long fiber under same condition, a TiC layer(1.0-1.6$\mu\textrm{m}$) was observed on the surface of SiC long fiber. 3) Liquid Phase Diffusion Bonding has shown the feasibility of production of Ti matrix composite materials.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.5
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• pp.654-664
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• 2017

The temperature profiles upon high speed impact of reactive structural materials were analyzed. A two color pyrometer, which included high-speed camera, spectral splitter, and band pass filters, was utilized to measure transient temperature profiles during and after reactive metal samples impacted into steel plate with velocities of 1600~1700 m/s. The spatial temperature distribution was analyzed from the ratio of spectral radiances at two different wavelength in infrared zone, i.e. 700 and 900 nm. The measured temperatures were calibrated with black body source. Two different types of metal samples, namely aluminum and nickel, were employed to understand reaction behavior upon the impact of samples in ambient condition. According to our experiments, the Ni sample appeared to barely react with ambient air producing an instant small fireball, while Al sample reacts violently with air generating a relatively prolong fireball.

• Geotechnical Engineering
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• v.6 no.4
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• pp.43-52
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• 1990

To investigate the effects of soil properties of the soft zone around a pile subjected 1,o the horizontal harmonic vibration, the parametric study is perfomed. The determination of the soil reaction or stiffness of the Winkler springs representing the soil around a pile is performed by dividing the soil profile into a number of homogeneous obtained from this study are as follows : 1) The real and imaginary parts of the stiffness show clear variations for the different shear modulus ratios, poisson's ratios, and distance retios to outer boundary as the dimensionless frequency increases. The differences are more pronounced for the imaginary part of the stiffness. 2) The stiffness of soil shows clear decrease. The real parts of the stiffness show larger as the frequency increases. On the other hand, the imaginary parts of the stiffness show smaller.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.71-78
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• 1998

The flame stabilization and the combustion characteristics of diffusion flame formed in the wake of a cylindrical bluff body with fuel injection are studied. With the turbulence generator, the flame stability limits and ion currents were measured and analyzed. The results from this experimental study are summarized as follows. The region with highest average value of ion currents in the middle of flame is moved to the upstream side by the turbulent components of main stream. The flame mass with partially active reaction is moved fast for uniform flow and turbulence generator G3, but the flame mass with relatively slow reaction is moved slowly for turbulence generator G1. If the turbulence generator with strong turbulent component is installed, the turbulent time scale is increased with movement from main stream side to recirculation zone as well as the flame stability limits is deteriorated. Though the special dominant frequency is not appeared in the eddy which exists in flame, high frequency characteristics are appeared in uniform flow and turbulence generator G3, and low frequency characteristics are appeared in uniform flow, turbulence generator G3 and G1.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.159-165
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• 1999

Experimental studies have been performed to observe the basic phenomena of waste bed combustion in MSW incinerator. A reduced scale apparatus was utilized to simulate the combustion behavior in real plant with 1-dimensional transient behavior at the experimental setup, which uses wet cubic wood with ash content as simulated waste. LHV (lower heating value) of solid fuel, fuel particle size and flow rate of combustion air were taken as important parameters of the bed combustion. For the quantitative analysis, FPR (flame propagation rate), TBT (total burn-out time) and PBT (particle burn-out time) was defined. LHV represent the capability of heat release of the fuel, so that a higher LHV results in faster reaction rate of the fuel bed, which is shown by higher FPR. Fuel particle size is related with surface area per unit mass as well as heat and mass transfer coefficient. As the particle size increases the FPR decreases owing to decreasing specific surface area. Air injection supplies oxygen to the reaction zone. However oversupply of combustion air increases convection cooling of the bed and possibly extinguishes the flame.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.411-418
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• 2020

A reformer is a device for producing hydrogen used in fuel cells. Among them, methanol steam reformer uses methanol as fuel, which is present as a liquid at room temperature. It has the advantage of low operating temperature, high energy density, and high hydrogen production. The purpose of this study is to improve the internal flow of the pressure vessel when a bundle of methanol steam reformer in the pressure vessel goes out to a single outlet. An analysis of equilibrium reaction to methanol steam reforming reaction was conducted using Aspen HYSYS^® (Aspen Technology Inc., Bedford, USA), and based on the results, computational analysis was conducted using ANSYS Fluent^® (ANSYS, Inc., Canonsburg, USA). For comparison of the results, the height of the pressure vessel, outlet diameter, and fillet was set as variables, and the optimum geometry was selected by comparing the effects of gravity and the amount of negative pressure.