• Korean Journal of Food Science and Technology
• /
• v.14 no.4
• /
• pp.342-349
• /
• 1982

Filefish muscle in the form of thin plate $(5{\times}10{\times}0.4\;cm)$ was dried in a forced air dryer at $47.5^{\circ}C$ to study the relation between dehydration mechanism and water activity. The dryer was designed in such a way that the temperature, relative humidity and velocity of air could be controlled. The whole dehydration process of the filefish muscle was divided into two different drying rate periods, constant and falling rate period. During the constant drying rate period, the drying rate was proportional to the square root of air velocity under the conditions of constant temperature and relative humidity of air. The falling rate period was further divided into two different falling drying rate periods, first and second falling rate period. The first falling rate period was an unsaturated surface drying period caused by partial unsaturation of the drying surface with capillary condensed free water diffused from the internal part of the filefish muscle. At this stage he drying rate was mainly dependent on the relative humidity at constant air temperature, and case-hardening phenomenon started at the end of this stage. The moisture content and the water activity at which the second falling rate period started were not constant, because the drying rate of the first falling rate period was strongly dependent on the air humidity. The second falling rate period was again divided into two drying rate periods, former and latter period. The drying rates of both of these periods were independent on the external air humidity. During the former period of the second falling rate period, the dehydration was proceeded by diffusion and vaporization of capillary condensed free water in filefish muscle. The diffusion coefficient of water was $2.89{\times}10^{-10}m^2/sec\;at\;47.5^{\circ}C$. At this stage, the case-herdening continued until the water activity reduced to 0.7. The latter period of the second falling rate period started at the water activity of 0.45. The dedydration was proceeded by diffusion and vaporization of bound water, which adsorbed in multimolecular layers, through the hardened drying surface. The number of molecular layers was 4, and the diffusion coefficient of water during this stage was $4.38{\times}10^{-11}m^2/sec\;at\;47.5^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.37-43
• /
• 2017

This review investigates the basic principle of physical interactions and failure mechanisms introduced in the materials and inner parts of semiconducting components under electromagnetic pulses (EMPs). The transfer process of EMPs at the semiconducting component level can be explained based on three layer structures (air, dielectric, and conductor layers). The theoretically absorbed energy can be predicted by the complex reflection coefficient. The main failure mechanisms of semiconductor components are also described based on the Joule heating energy generated by the coupling between materials and the applied EMPs. Breakdown of the P-N junction, burnout of the circuit pattern in the semiconductor chip, and damage to connecting wires between the lead frame and semiconducting chips can result from dielectric heating and eddy current loss due to electric and magnetic fields. To summarize, the EMPs transferred to the semiconductor components interact with the chip material in a semiconductor, and dipolar polarization and ionic conduction happen at the same time. Destruction of the P-N junction can result from excessive reverse voltage. Further EMP research at the semiconducting component level is needed to improve the reliability and susceptibility of electric and electronic systems.

• Composites Research
• /
• v.32 no.5
• /
• pp.199-205
• /
• 2019

The composite material has the advantage that the fibers can be arranged in a desired direction and can be manufactured in one piece. However, micro voids can be formed due to micro air, moisture or improper curing temperature or pressure, which may cause the deterioration in mechanical strength. In this paper, the composite panels with different thicknesses were made by varying the curing pressure in an autoclave vacuum bag process and their microporosities were evaluated. Microporosity was measured by image analysis method, acid digestion method, and combustion method and their correlation with ultrasonic attenuation coefficient was analyzed. From the test results, it was found that the acid digestion method had the highest accuracy and the lower the curing pressure, the higher the microporosity and the ultrasonic attenuation coefficient. In addition, the microporosity and the ultrasonic attenuation coefficient were increased as the thickness of the composite panel was increased at the same curing pressure.

• Korean Chemical Engineering Research
• /
• v.49 no.5
• /
• pp.605-610
• /
• 2011

Phase holdup characteristics of relatively large and small bubbles were investigated in a three-phase(gasliquid-solid) fluidized bed of which diameter was 0.105 m(ID) and 2.5 m in height, respectively. Effects of gas(0.01~0.07 m/s) and liquid velocities(0.01~0.07 m/s) and particle size($0.5{\sim}3.0{\times}10^{-3}m$) on the holdups of relatively large and small bubbles were determined. The holdups of two kinds of bubbles in three phase fluidized beds were estimated by means of static pressure drop method with the knowledge of pressure drops corresponding to each kind of bubble, respectively, which were obtained by dynamic gas disengagement method. Dried and filtered air which was regulated by gas regulator, tap water and glass bead of which density was $2500kg/m^3$ were served as a gas, a liquid and a fluidized solid phase, respectively. The two kinds of bubbles in three-phase fluidized beds, relatively large and small bubbles, were effectively detected and distinguished by measuring the pressure drop variation after stopping the gas and liquid flow into the column as a step function: The increase slope of pressure drop with a variation of elapsed time was quite different from each other. It was found that the holdup of relatively large bubbles increased with increasing gas velocity but decreased with liquid velocity. However, the holdup showed a local minimum with a variation of size of fluidized solid particles. The holdup of relatively small bubbles increased with an increase in the gas velocity or solid particle size, while it decreased slightly with an increase in the liquid velocity. The holdups of two kinds of bubbles were well correlated in terms of operating variables within this experimental conditions, respectively.

• Tuberculosis and Respiratory Diseases
• /
• v.64 no.1
• /
• pp.48-51
• /
• 2008

Chronic expanding hematoma of the thorax is a specific subtype of the chronic empyema. It presents as a slowly expanding intrathoracic mass which result in dyspnea or recurrent hemoptysis. The symptoms develop months or years after tuberculous pleurisy, trauma or surgery. Usually, it shows three common findings: a giant mass lesion in the thorax, some surrounding calcifications, the absence of signs or symptoms of infection. We report a case of chronic expanding hematoma of the thorax, initially presenting as massive hemoptysis through bronchopleural fistula which resulted in radiologic findings of new air-fluid level within the previous pleural lesion filled with unknown materials.

• Korean Journal of Plant Resources
• /
• v.29 no.5
• /
• pp.579-587
• /
• 2016

The final goal of this research is to develop a miniaturized botanical biofilter using a wick-typed automatic humidifier for stabilizing soil moisture content (SMC) and purifying indoor air pollutants by the biofilter. This new biofilter equipped with wick-typed automatic humidifier was manufactured as more compacted design removing an absorption tower-typed humidifier compared with the previous big-sized biofilter made in 2015. This study was performed to compare changes of SMCs among floors depending on the number of wicks installed on the humidifier within the novel biofilter, and to compare changes of SMCs and plant growth parameters before and after planting Spathiphyllum wallisii ‘Mauna Loa’ on the biofilter. SMCs among floors depending on the number of wicks were similar, and all regression lines of SMCs showed almost horizontal lines because of long-term stability on SMCs. Comparing plant growth parameters of S. wallisii ‘Mauna Loa’ before planting and at 30 days after planting on the biofilter, all growth parameters were not statistically significant. Thus, SMCs of the biofilter were more stabilized using this humidifying apparatus regardless of the number of wicks than the previous biofilter using absorption tower-typed humidifying apparatus.

• Korean Journal of Materials Research
• /
• v.9 no.8
• /
• pp.792-797
• /
• 1999

The 8mol.%Y$_2$$O_3$-$ZrO_2$mainly employed as an electrolyte of solid oxide fuel cells(SOFCs) shows excellent electrical properties but has a weakness in the mechanical properties. Since the electrolyte of SOFCs requires both good electrical and mechanical properties, this study was conducted to meet both requirements. The electrolyte thin films were produced on the LSM(cathode material) substrate of a cell and Si wafer. Four electrolyte film types of single layer and the multiple layer, consisting of 3-YSZ(3mol.%$Y_2$$O_3$) with excellent mechanical properties and 8-YSZ with the excellent electric conduction, were produced by electron beam coating technology. Ther crystal structure and the mechanical properties were also analysed. As the results of the study, the 3-YSZ thin film turned out to be in the tetragonal, partially monoclinic phase, while the 8-YSZ thin film showed the cubic phase. The residual stress in the multiple layer was lower than that of the single layer. The microhardness of the multiple layer was similar to that of the existing 8-YSZ single layer both before and after annealing treatment.

• Analytical Science and Technology
• /
• v.11 no.3
• /
• pp.189-193
• /
• 1998

Binary alloys, $MoRu_3$ and $MoRh_3$, have been prepared using arc melting furnace. Mo and the noble metals Ru and Rh are the constituents of metallic insoluble residues, which were found in the early days of the post-irradiation studies on uranium oxide fuels. Detailed structural informations about these alloys have not been reported on JCPDS files of ICDD (International Centre for Diffraction Data). The results of X-ray diffraction study showed that the alloy was crystallized in hexagonal close-packing, well known as ${\varepsilon}$-phase. The X-ray diffraction patterns of these alloys matched well to that of $WRh_3$ with $P6_3/mmc$ of space group. The lattice parameters, a and c, were calculated using the least squares extrapolation. It was found from X-ray photoelectron spectroscopic measurements that Mo on the surface of the alloy was oxidized to Mo(6+), which could be removed by sputtering with Ar ions for approximately 15 minutes. The changes in binding energy of Mo, Ru, and Rh on the surface of the alloy were not observed. Magnetic susceptibility measurements resulted in the typical Pauli-paramagnetic behavior in the temperature range of 2 to 300 K.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7667-7671
• /
• 2015

Recently, Zinc coating is often used with environment friendly features and high performance. Generally The coating temperature is one of main factors for determining coating thickness and coating ability, so the optimal coating temperature is strongly required. In this paper, the thermo-flow simulation considering the air flow inside the coating rooms for analyzing the temperature distributions of Zinc spray coating room was performed. Two spray coating rooms, preheating room and drying room were all modeled by SolidWorks program and the temperature distributions were analyzed by Flow simulation program. The analysis results were verified with the measured data by thermal image camera. The characteristics of temperature distributions of the first spray room and the second spray room were understood and the results showed that the temperatures of two spray coating room were low compared with the target temperature $25^{\circ}C$. To the exclusion of heater addition, the simulation with all the same conditions exclusive the exhaust fan was performed, which showed that the temperatures of the first and the second spray rooms increased by $6.2^{\circ}C$ and $5.8^{\circ}C$. This analysis can be applicable for designing a new spray coating room for improving performance.

• Journal of the Korean Society of Mechanical Technology
• /
• v.20 no.6
• /
• pp.763-769
• /
• 2018

In this research, in order to improve the heat retention of greenhouse, comparative analysis of the heat flux of the marketed multi-later insulating curtain was carried out. Experiments is conducted by fabricating a test apparatus for investigating the heat flux characteristics. The multi-later insulating curtain used for the experiment was compared using the P, N, S, U and T company, which are commercially available, and the heat flux due to temperature difference between the experimental apparatus and the outside was compared and analyzed. When the internal temperature of the experimental result is the maximum temperature $60^{\circ}C$, the heat flux of multi-later insulating curtain is T Co.($73.1W/m^2$) > S Co.($119.5W/m^2$) > U Co.($155W/m^2$) > N Co.($163.1W/m^2$) > P Co.($177.7W/m^2$). The heat flux means the quantity of heat passing through the unit time per unit area, and the higher the numerical value, the higher the quantity of heat passing through the multi-layer insulating curtain. This can be determined that high heat fluxes produce low heat resistance. Further, it has been found that the weight of the insulating curtain is largely unrelated to the heat insulating property, and the heat insulating curtain having a thickness containing a high internal air layer is excellent in the heat insulating property. In the future when manufacturing a heat insulating curtain, It is judged that it is desirable to manufacture a combination of heat insulating materials that contain a high internal air layer content and that can maintain the air layer even for long-term use while minimizing the volume.