• Clinical and Experimental Reproductive Medicine
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• v.35 no.3
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• pp.203-212
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• 2008

Objective: During cryopreservation process, cold shock and cryo-injury affect the fertilizing capacity of the sperm by damaging cell membranes with loss of functional integrity. A longstanding concept for preventing the cryo-damage is to stabilize the plasma membrane by incorporating cholesterol. This study was to determine the effects of cholesterol in freezing media on the motility and functional integrity of human sperm after cryopreservation. Methods: Control group (non-cholesterol treated) and different concentrations of cholesterol-treated sperm (14 healthy males) were frozen and thawed. After freezing and thawing of sperm, the quality of sperm was evaluated by sperm analysis, acrosome reaction test and sperm chromatin structure assay. Results: When human sperm were incubated in sperm freezing medium (SFM) containing $0.5{\mu}g$ cholesterol and then freezing/thawing, the motility of sperm have significantly improved compared to those untreated cholesterol ($33.46{\pm}1.48%$ vs. $30.10{\pm}1.07%$, p<0.05). The rate of calcium ionophore-induced acrosome reactions in post-thawed sperm was significantly higher than that ($53.60{\pm}1.60%$ vs. $47.40{\pm}1.86%$, p<0.05) in SFM containing cholesterol. Sperm chromatin structure assay revealed that DNA damage to the sperm in the cholesterol-treated group was lower than that of non-treated group. Conclusion: These results suggest that increased cholesterol content of sperm plasma membrane by supplementation of cholesterol in SFM improves sperm motility, capacitation status, and DNA integrity. Therefore, addition of cholesterol into SFM could be a useful for protecting human sperm from cold shock and cryo-injury during cryopreservation.

• Journal of Korea Port Economic Association
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• v.27 no.1
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• pp.263-280
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• 2011

The global financial crisis, triggered by the subprime mortgage crisis in 2007, has put the world economy into the recession with financial market turmoil. I tested whether variables were cointegrated or whether there was an equilibrium relationship. Also, Generalized impulse-response function (GIRF) and accumulation impulse-response function (AIRF) may be used to understand and characterize the time series dynamics inherent in economical systems comprised of variables that may be highly interdependent. Moreover, the IRFs enables us to simulate the response in freight to a shock in the USD/JPY exchange rate, Dow Jones industrial average index, Dow Jones volatility, Chinese Import volatility. The result on the cointegration test show that the hypothesis of no cointergrating vector could be rejected at the 5 percent level. Also, the empirical analysis of cointegrating vector reveals that the increases of USD/JPY exchange rate have negative relations with freight. The result on the impulse-response analysis indicate that freight respond negatively to volatility, and then decay very quickly. Consequently, the results highlight the potential usefulness of the multivariate time series techniques accounting to behavior of Freight.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.51-56
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• 2015

It has been used various pad finish materials to enhance the reliability of solder joint and recently Electroless Ni Electroless Pd Immersion Gold (the following : ENEPIG) pad has been used more than others. This study is about reliability according to being used in commercial Electrolytic Ni pad and ENEPIG pad, and was observed behavior of various Cu contents. After reflow, the inter-metallic compound (IMC) between solder and pad is composed of $Cu_6Sn_5$ (Ni substituted) by using EDS, and in case of ENEPIG, between IMC and Ni layer was observed the dark layer ($Ni_3P$ layer). Additional, it could be controlled the thickness of dark layer according to Cu contents. Investigated the different fracture mode between electrolytic Ni and ENEPIG pad after drop shock test, in case of soft Ni, accelerated stress propagated along the interface between $1^{st}$ IMC and $2^{nd}$ IMC, and in case of ENEPIG pad, accelerated stress propagated along the weaken surface such as dark layer. The unstable interface exists through IMC, pad material and solder bulk by the lattice mismatch, so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface. Therefore, it is strongly requested to control solder morphology, IMC shape and thickness to improve the solder reliability.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.158-166
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• 2009

To obtain the fundamental data for the mass seedling production of grunt, Hapalogenys nitens, we investigated the influence of salinity and cold water temperature on hatching and survival of eggs and growth and survival of larvae and fry. In regards to salinity, we surveyed the hatching rate and floating rate of fertilized eggs, the floating rate and survival rate of hatching larvae, and the survival and growth of fry. In respect to cold temperature, we investigated the influence of degree of daily temperature decrease, acute temperature shock, and slow temperature decreases on the survival, feeding and swimming activities of fry. In the salinity experiment, the hatching and floating rates of fertilized eggs, and the floating and survival rates of hatching larvae, were shown to be higher in seawater than in brackish water. Growth and survival of larvae and fry were not different between seawater (25~32 psu) and brackish water (5~20 psu), but were significantly lower in freshwater. In the cold-temperature test, three tests showed that rearing of fry in cold water and acutely decreasing water temperature to less than $10^{\circ}C$ reduced the survival, feeding and swimming activities of the fry. Therefore, we concluded that low salinity (less than 32 psu) could reduce the hatching rate and survival of eggs, but the growth and survival of fry were not influenced by salinity, and cold water (less than $10^{\circ}C$) decreased metabolism of grunt. During winter, we found a low-temperature limit at $8^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.1
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• pp.17-36
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• 1984

Since 1973, the competition on the development of fuel saving type internal combustion engines has become severe by the two times oil shock, and new type engines are reported every several months. Whenever these new type engines are developed, new designs are required and they will be offered in the market after performing the endurance test for a long time. But the engine market is faced with a heavy burden of finance, as the developing of a new engine requires tremendous expenses. For this reason, the computer simulation method has been lately developed to cope with it. The computer simulation method can be available to perform the reasonable research works by the theoretical analysis before carrying out practical experiments. With these processes, the developing expenses are cut down and the period of development is curtailed. The object of this study is the development of simulation computer program for the small naturally aspirated four-stroke diesel engine which is intended to product by the original design of our country. The process of simulation is firstly investigated for the ideal engine cycle, and secondly for the real engine cycle. In the ideal engine cycle, each step of the cycle is simulated by the energy balance according to the first law of thermodynamics, and then the engine performance is calculated. In the real cycle imulation program, the injection rate, the preparation rate and the combustion rate of fuel and the heat transfer through the wall of combustion chamber are considered. In this case, the injection rate is supposed as constant through the crank angle interval of injection and the combustion rate is calculated by the Whitehouse-Way equation and the heat transfer is calculated by the Annand's equation. The simulated values are compared with measured values of the YANMAR NS90(C) engine and Mitsubishi 4D30 engine, and the following conclusions are drawn. 1. The heat loss by the exhaust gas is well agree with each other in the lower load, but the measured value is greater than the calculated value in the higher load. The maximum error rate is about 15% in the full load. 2. The calculated quantity of heat transfer to the cooling water is greater than the measured value. The maximum error rate is about 11.8%. 3. The mean effective pressure, the fuel consumption, the power and the torque are well agree with each other. The maximum error is occurred in the fuel consumption, and its error rate is about 7%. From the above remarks, it may be concluded that the prediction of the engine performance is possibly by using the developed program, although the program needs to reform by adding the simulation of intake and exhaust process and assumping more reliable mechanical efficiency, volumetric efficiency, preparation rate and combustion rate.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.39.3-40
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• 2015

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument optimized to the first small satellite of NEXTSat series. The capability of both imaging and low spectral resolution spectroscopy in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the main targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design of the NISS with two linear variable filters is optimized to have a wide field of view ($2deg.{\times}2deg.$) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. The mechanical structure is considered to endure the launching condition as well as the space environment. The dewar inside the telescope is designed to operate the infrared detector at 80K stage. From the thermal analysis, we confirmed that the telescope and the dewar can be cooled down to around 200K and 80K, respectively in order to reduce the large amount of thermal noise. The stray light analysis is shown that a light outside a field of view can be reduced below 1%. After the fabrications of the parts of engineering qualification model (EQM), the NSS EQM was successfully assembled and integrated into the satellite. To verify operations of the satellite in space, the space environment tests such as the vibration, shock and thermal-vacuum test were performed. Here, we report the results of the critical design review for the NISS.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.1
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• pp.47-53
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• 2017

In this study we surveyed the preferences of consumer packaging for mini pot flower plants to improve the flower market application in Korea. The surveys were consisted of the consumers residing in Seoul metropolitan (221), Gyeonsang (70), Jeonla (29), Chungceong (19), Gangwon (7), other provinces (3). A total of 349 eligible respondents (male 173, female 176) were surveyed with a self-administered questionnaire asking on the general characteristics for residents, packaging material, packaging design, type of flower pot, degree of transparency, convenience, consumer's demand for packaging development, a significant point when purchasing the flower pot product. The collected date was analyzed using a chi-square (${\chi}^2$) statistical test in SPSS program. Most residents prefer for mini pot flower plants packed with packaging characteristics of plastic material (56.4%), packaging design of separated type (76.2%), angled type (62.5%), and transparency (48.6%). The other question results showed that major consumer's demand for mini pot flower plants is maintaining the freshness quality and stability structure for them. Transparency of packaging can also affect directly the preferences for purchasing the mini pot flower plants. The packaging structure with a proper shape design may protect the fresh mini pot flower plants from shock or any other damage during distribution. The results of this study help to provide consumer's demand for packaging development and to give the greatest advantages in terms of production and marketability of mini pot flower plants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.528-534
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• 2020

The early development and use of plate heat exchangers (PHE) were in response to stringent statutory requirements from dairy products in the late 19th century, but PHEs were not exploited commercially until the 1920s. Since then, although the basic concept of PHEs has changed little, its design and construction have progressed significantly to accommodate higher temperatures and pressures, as well as large heat exchanging capacities. The development of current chevron-type corrugated heat plates has been ongoing since the oil shock in the 1970s to improve energy efficiency. The development trend of PHEs is consistent with the development of larger heat plates with better thermal efficiency, lower pressure drop, and good flow distribution. In this study, the thermal performance of small heat plates (PHE-S) and large heat plates (PHE-L) with the same plate depth and corrugation pitch were analyzed experimentally for each channel (H, M, and L type) to suggest development directions of heat plates. The test results showed that for the convectional heat transfer coefficient, the PHE-S was on average, 16.5% higher in the H type, 25% higher in the M type, and 40% higher in the L type than PHE-L. In the case of the pressure drop, the PHE-S was 19% higher in the H type, 46% higher in the M type, and 61% higher in the L type than PHE-L. These results were attributed to the differences in fluid distribution areas between the PHE-S and PHE-L, among other potential causes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.135-146
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• 2020

To define an interface in a conventional level-set method, an analytical function must be revealed for an interfacial geometry. However, it is not always possible to define a functional form of level sets when interfaces become complex in a Cartesian coordinate system. To overcome this difficulty, we have developed a new level-set formalism that discriminates the interior from the exterior of a CAD modeled interface by parameterizing the stereolithography (STL) file format. The work outlined here confirms the accuracy and scalability of the hydrodynamic reactive solver that utilizes the new level set concept through a series of tests. In particular, the complex interaction between shock and geometrical confinements towards deflagration-to-detonation transition is numerically investigated. Also, a process of flame spreading and damages caused by point source detonation in a real-sized plant facility have been simulated to confirm the validity of the new method built for reactive hydrodynamic simulation in any complex three-dimensional geometries.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.418-421
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• 2002

Fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a plane-focus x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the transmission type target (anode) is connected to the ground potential. The maximum voltage and current of the power supply were -100 kV (peak value) and 3.0 mA, respectively. In this experiment, the tube voltage was regulated from 20 to 25 kV, and the tube current was regulated by the filament temperature and ranged from 1.0 to 3.0 mA. The exposure time is controlled in order to obtain optimum film density, and the focal spot diameter was about 10 mm. The polycapillary plate is J5022-21 made by Hamamatsu Photonics Inc., and the outside and effective diameters are 87 and 77 mm, respectively. The thickness and the hole diameter of the polycapillary are 1.0 mm and 25 ${\mu}$m, respectively. The x-rays from the tube are formed into parallel beam by the polycapillary, and the radiogram is taken using an industrial x-ray film of Fuji IX 100 without using a screen. In the measurement of image resolution, we employed three brass spacers of 2, 30, and 60 mm in height. By the test chart, the resolution fell according to increases in the spacer height without using a polycapillary. In contrast, the resolution slightly fell with corresponding increases in the height by the polycapillary. In angiography, fine blood vessels of about 100 ${\mu}$m are clearly visible.