• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.2
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• pp.73-79
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• 2001

Experiment were carried out to investigate the heat transfer characteristics of an aluminum foam block as a porous heat sink on a heat source by a vertical air jet impingement that can be applied for electronics cooling. The performance of the aluminum foam heat sink was evaluated by the convective heat transfer coefficient on the heat source. At a fixed porosity, pore density ($\beta$) of the foam and Reynolds number Re were varied in the range of $\beta$a=10, 20, 40 PPI(Pore Per Inch) and $850\leqRe\leq25000$. A nozzle diameter and the nozzle-to-plate spacing were also varied. It was found that the convective heat transfer was enhanced by the aluminum foam heat sink with lower pore density due to relatively intensified flow through the foam block. The aluminum foam block with much reduced weight shows slightly better performance with larger Nusselt number, compared with the convectional heat sink.

• Journal of Urban Science
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• v.10 no.1
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• pp.11-20
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• 2021

In this study, the vibration characteristics were theoretically analyzed by modeling a free isotropic rotating disk with an outer periphery with a fixed inner periphery, paying attention to disks used as storage devices for information devices, especially magnetic disks, magneto-optical disks, and compact disks in which the head and disk are non-contact. Iluminate with Composite materials represented by fiber-reinforced plastics (FRP) have high specific strength (strength/density) and specific stiffness (narrowness/density). It is used in the elements, and its use is rapidly expanding. Under this circumstance, the disk currently manufactured using an isotropic material made of various plastic materials such as aluminum or polycarbonate as a base material is an extremely anisotropic material made of a composite material, and the circumferential stiffness of the disk is made of reinforcing fibers in the circumferential direction. It is modeled as an anisotropic rotating disk with increased, and its influence on the vibration characteristics is revealed.

• Communications of the Korean Mathematical Society
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• v.12 no.4
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• pp.985-998
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• 1997

For n random strips chosen so as to meet a fixed bounded convex set K of the plane we let $\nu$ be the number of intersection regions that meet K. We develop the integral formula for the mean value of $\nu$ and $\nu^2$ involving the area and the perimeter of K and the breadths of the strips. We get some geometric inequalities in way of studying integral geometry.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.395-398
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• 1989

A two dimensional pseudo-homogeneous model for the methanol reforming reaction was developed and its steady and dynamic states were studied by a computer simulation. The reactor tube diameter, the catalyst density in the fixed bed, the feed flow rate, the feed temperature and the external temperature were chosen to be adjusted to determine the length of the reactor. The dynamics of the reactor showed that the system was highly nonlinear and sensitive to the feed disturbances.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.72-78
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• 1996

The breakthrough curves of a sampling tube were studied to predict the service life of a respirator cartridge for organic vapors. The fixed bed adsorption model was applied to respirator cartridge and it's variables were calculated from tile experiment of sampling tube. By the experiment and simulation, it was possible to predict the service life of a respirator cartridge, however, not adequate at low $CCl_4$ concentration less than 700ppm and at high air humidify. The breakthrough curves of sampling tube were irregular compare to that of respirator cartridge due to .packing density.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.320.1-320.1
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• 2013

We have investigated the effect of surface passivation for crystalline silicon solar cell using ozone-based atomic layer deposited (ALD) $Al_2O_3$. We examined passivation properties such as uniformity, carrier lifetime, thickness, negative fixed charge density at AlOx/Si interface, and reflectance. The influences of process temperature and heat treatment were investigated using microwave photoconductance decay (PCD). Ozone-based ALD $Al_2O_3$ film shows the best carrier lifetime at lower deposition temperature than $H_2O$-based ALD.

• Journal of Korean Foot and Ankle Society
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• v.7 no.2
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• pp.151-156
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• 2003

Purpose: Proximal crescentic metatarsal osteotomy(PMO) is one of the most common procedures for correcting moderate to severe degree hallux valgus deformity. Although screw fixation is used for osteotomy site stability, loss of reduction can occur. The purpose of this study is to compare the sagittal plane stability of the conventional crescentic PMO fixed with a single screw with that of the crescentic PMO fixed with 1 screw and 2 supplemental K -wires. Material and Methods: Ten matched pairs of cadaveric foot specimens were used for the proximal crescentic metatarsal osteotomy. For one foot specimen of each pair, crescentic osteotomy was fixed with 4mm long threaded cannulated screw, while the matched pair was prepared by adding two axial 1.6mm K-wires to the conventionally fixed 4mm screw. The extensometer was used to measure the osteotomy gap as the metatarsal head was loaded continuously until failure using a servohydraulic MTS Mini Bionix test frame. The strength of fixation was normalized with the bone mineral density (BMD) of the paired specimen $(N{\times}cm^{2}/gm)$, Result: The average strength of the crescentic PMO with axial K-wire fixation ($458.8cm^{2}/gm$, S.D. 434.3) was significantly higher than the standard crescentic PMO ($367.5cm^{2}/gm$, S.D. 397,9) (p=0.05). Conclusion: Supplemental fixation with two axial K-wires can be added to the crescentic PMO to enhance the initial fixation stability to prevent the loss of reduction or dorsal malunion.

• Journal of Environmental Science International
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• v.31 no.6
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• pp.479-490
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• 2022

This study was to evaluate the utilization of terrestrial light detection and ranging for forest inventory in coniferous forests. Heights and diameter of the stand trees were measured manually using the traditional measurement method and the method using terrestrial LiDAR. The results of two methods were compared and analyzed to evaluate accuracy and feasibility. The terrestrial LiDAR used fixed and handy types to compare the accuracy between different operational methods. Comparative analyses used a paired t-test and Bland-Altman plot analysis. In the case of tree heights, the average of difference between the traditional method and terrestrial LiDAR for each plot was 0.81 m, -0.07 m, and 0.13 m for fixed type; 2.88 m, 1.19 m, and 0.93 m for the handy type. In the case of tree diameter at breast height, the average value of the difference between traditional methods and terrestrial LiDAR for each plot was 0.13 cm, -0.66 cm, and -0.03 cm for fixed type; 2.36 cm, 2.13 cm, and 1.92 cm for the handy type. The values from the method using the fixed type was highly consistent with that using the traditional measurement methods; the average difference was closer to zero. The crown density influences the precision of the height measurement using terrestrial LiDAR in coniferous forests. Therefore, future studies should focus on verifying the accuracy of terrestrial LiDAR in forests and on expanding the utilization of terrestrial LiDARs according to their operational methods.

• Journal of Forest and Environmental Science
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• v.28 no.4
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• pp.263-267
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• 2012

Characteristics of charcoals manufactured in each temperature as 400, 600 800, 1,000 and $1,200^{\circ}C$ were examined. Sapwood and heartwood of Quercus variabilis that one of major species in charcoal materials were used for this experiment. Charcoal density was decreased highly 38-60% compared with wood density and density of sapwood was slightly decreased but heartwood was not changed with increasing carbonization temperature increase. Weight loss of sapwood and heartwood charcoal increased as carbonization temperature increases, and there is no difference between sapwood and heartwood charcoal. Refining degree of sapwood and heartwood charcoal was zero in charring over $800^{\circ}C$. Moisture and ash of sapwood and heartwood charcoal in each carbonization temperature were not differed between sapwood and heartwood. Volatile of sapwood charcoal was slightly higher than that of heartwood, and decreased as carbonization temperature increases. As the carbonization temperature increased, fixed carbon of sapwood and heartwood charcoal increased. Calorific values of charcoal prepared at $600^{\circ}C$ were 7,200-7,300 cal/g and then decreased slightly as carbonization temperature increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.669-673
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• 2008

ITO thin film was deposited on PC substrate in Facing Targets Sputtering (FTS) system with various sputtering conditions. After it is applied to external bending force, we investigated how change the surface and electrical property of as-deposited ITO thin film. As the L(face-plate distance) of substrate decreases, it found that the maximum crack density is increasing at the center position and decreasing crack density as goes to the edge. So to apply same curvature (r) and bending force to PC substrate with ITO thin film, we fixed the L that is equal to curvature radius (2r). Before bending test, ITO thin films that deposited in the input current of 0.4 A and thickness of 200 nm already had biaxial tensile failure because of each different CTE (Coefficient of Thermal Expansion) and Others had been shown no bending or crack. After bending test, all samples had been shown cracks at about 200 times and as increasing the crack density, resistivity increased.