• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.287-293
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• 2008

The collimator which makes a collimated beam, is an essential instrument for assembly and evaluation of telescopes. Recently, the Cassegrain type collimator has been widely used for its compact size as the focal length of high resolution cameras becomes longer. However, this kind of collimator has a disadvantage in that the secondary mirror is a heat source which can degrade the evaluation accuracy for an IR camera system. In this paper, we present the fabrication and measurement process for an off-axis parabolic mirror with the physical diameter pf 1 m, effective diameter 930 mm, and the focal length 6 m. After four months of works we obtained the final surface wave-front error of 30.4 nm rms ($\lambda$/138, ${\lambda}=4.2\;{\mu}m$), which is capable of evaluation of an IR camera as well as a visible camera.

• Asia Marketing Journal
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• v.15 no.1
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• pp.57-81
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• 2013

The purpose of this paper is to seek ways to improve the competitiveness of Korea's fashion industry by utilizing the source of competitiveness of Japan's fashion industry, which represents the world's leading countries in terms of fashion, so that Korea can better enter the global fashion market. The study shall first compare the competitiveness of the Japanese and Korean fashion industries by utilizing the generalized double diamond model; second, provide an understanding of what the Japanese fashion industry can offer to Korean fashion industry and companies - that is, understand what the Japanese fashion industry's competitive edge is; and third, study the kind of global competitiveness that Korea's fashion industry must achieve. To adopt a generalized double diamond model to compare the competitiveness of the Korean and Japanese fashion industries, we selected 31 sub-variables to act as determinants of the model. That is, we extracted 31sub-variables by doing research of literature to analyze national competitiveness of the fashion industries. To measure these 31 sub-variables, secondary data was gathered. We collected data related to each sub-variable from various sources of Korea and Japan. And to calculate the competitiveness index, we took three steps with reference to previous studies. We found that status of the fashion industry of the two countries as it stands. That is, Japan is an advanced country of which fashion industry is domestic market-oriented while Korea is a small open economy that mainly focuses on the foreign market. Out of 31 proxy variables, Korea's fashion industry shows higher measurements relating to production and export than Japan, but Japan's fashion industry reports higher measurements than Korea in the fields of R&D, design and brand power, the rate of value added, the efficiency of companies and globalization. In order for Korea's fashion industry to achieve competitiveness in the global market, it should pursue the following development direction. First, it is very difficult for Korea to follow the footsteps of the U.S. and Japanese fashion industries that are able to take advantage of economies of scale, because Korea is smaller than those countries. Therefore, in the case of small economies such as Singapore, strengthening of international activities will practically improve domestic determinants that Korea should improve its domestic diamond by enhancing the current competitiveness of its international diamond. In other words, Korea needs to further endeavor to develop and expand global resources and markets as well as improve its competitiveness in terms of R&D, design and brand power, the rate of value-added, and the efficiency of companies. As the Korean fashion industry shows relatively advanced level of information technology and the fashion education system, it has considerable potential to grow. Korea is expected to have a huge growth potential since it has relatively higher level of information technology, fashion education system and activities than those of Japan in both the domestic diamond and international diamond. In particular, a better environment is laid out before Korea to gain competitiveness in the fashion industry due to the recently growing influence of the Korean Wave that Korea is expected to grow as a leader in the Asian market as well as in the global market.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.421-430
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• 2004

Clinically, it is almost impossible for a physician to distinguish subtle changes of frequency spectrum by using a stethoscope alone especially in the early stage of thrombus formation. Considering that reliability of mechanical valve is paramount because the failure might end up with patient death, early detection of valve thrombus using noninvasive technique is important. Thus the study was designed to provide a tool for early noninvasive detection of valve thrombus by observing shift of frequency spectrum of acoustic signals with computer aid diagnosis system. A thrombus model was constructed on commercialized mechanical valves using polyurethane or silicon. Polyurethane coating was made on the valve surface, and silicon coating on the sewing ring of the valve. To simulate pannus formation, which is fibrous tissue overgrowth obstructing the valve orifice, the degree of silicone coating on the sewing ring varied from 20％, 40％, 60％ of orifice obstruction. In experiment system, acoustic signals from the valve were measured using microphone and amplifier. The microphone was attached to a coupler to remove environmental noise. Acoustic signals were sampled by an AID converter, frequency spectrum was obtained by the algorithm of spectral analysis. To quantitatively distinguish the frequency peak of the normal valve from that of the thrombosed valves, analysis using a neural network was employed. A return map was applied to evaluate continuous monitoring of valve motion cycle. The in-vivo data also obtained from animals with mechanical valves in circulatory devices as well as patients with mechanical valve replacement for 1 year or longer before. Each spectrum wave showed a primary and secondary peak. The secondary peak showed changes according to the thrombus model. In the mock as well as the animal study, both spectral analysis and 3-layer neural network could differentiate the normal valves from thrombosed valves. In the human study, one of 10 patients showed shift of frequency spectrum, however the presence of valve thrombus was yet to be determined. Conclusively, acoustic signal measurement can be of suggestive as a noninvasive diagnostic tool in early detection of mechanical valve thrombosis.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.15-25
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• 2008

Ocean-bottom seismometer (OBS) positions are one of the key parameters in an OBS-airgun seismic survey for crustal structure study. To improve the quality of these parameters, we have developed a new method of determining OBS positions, using airgun shot data and bathymetric data in addition to available distance measurements by acoustic transponders. The traveltimes of direct water waves emitted by airgun shots and recorded by OBSs are used as important information for determining OBS locations, in cases where there are few acoustic transponder data (<3 sites). The new method consists of two steps. A global search is performed as the first step, to find nodes of the bathymetric grid that are the closest to explaining the observed direct water-wave traveltimes from airgun shots, and acoustic ranging using a transponder system. The use of precise 2D bathymetric data is most important if the bottom topography near the OBS is extremely rough. The locations of the nodes obtained by the first step are used as initial values for the second step, to avoid falling into local convergence minima. In the second step, a non-linear inverse method is executed. If the OBS internal clock shows large drift, a secondary correction for the OBS internal clock is obtained, as well as the OBS location, as final results by this method. We discuss the error and the influence of each measurement used in the determination of OBS location.

• Journal of Veterinary Clinics
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• v.27 no.6
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• pp.647-651
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• 2010

The advantages of the $CO_2$ laser are offset by the delay in laser wound healing secondary to thermal damage. To minimize the undesirable thermal damage of the $CO_2$ laser, investigators have developed technical advances in the delivery system of the laser energy. This study compared tissue healing of the continuous and the pulsed modes $CO_2$ laser wounds in an animal surgery model. Five healthy Landrace and Yorkshire mixed breeds of both genders were used (45-51 kg, 4-6 months old, three males and two females). A full thickness wound of skin ($2{\times}2{\times}2cm^2$) was made over on the each pig's both sides of dorsal midline at 0, 7, 14, and 18 days. The wounds created at 18, 14, 7 and 0 days were named post-wounding day (PWD) 3, 7, 14 and 21, respectively. In each pig, one wound (left side) was treated pulsed $CO_2$ laser and the other wound (right side) was treated continuous wave $CO_2$ laser. Each wound was closed with two interrupted suture of 3-0 sutures. At 21 days after initial wounding, each wound was taken for histological evaluations. The degrees of reepithelialization were performed more prominently in the pulsed mode group than in the continuous mode group. The degrees of granulation were greater significantly in pulsed mode group than those in the continuous mode on PWD 3 (p < 0.05). The degrees of fibroblasts in the pulsed mode group were greater significantly in comparison to those in the continuous mode group on PWD 7, (p < 0.05). In conclusion, reepithelialization, granulation and fibroblasts in the pulsed mode group were greater markedly in comparison to those in the continuous mode group. It was considered that pulsed mode $CO_2$ laser was more suitable for the skin incision than the continuous mode $CO_2$ laser.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.