• Journal of Korea Port Economic Association
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• v.28 no.3
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• pp.111-125
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• 2012

This study investigates the behavioral characteristic difference of the container volumes of three ports-Gwangyang, Incheon, and Pyeongtaek-Dangjin. All series span the period January 2003 to December 2011. I first test whether the series are stationary or not. I can reject the null hypothesis of a unit root in each of the level variables and of a unit root for the residuals from the cointegration at the 5 percent significance level. I hitherto make use of error-correction model and find that Gwangyang port is the slowest in adjusting the short-run disequilibrium, whereas the adjustment speed of Incheon is much faster than that of Gwangyang. The impulse response functions indicate that container volumes increase only a little to the negative shocks in exchange rate, while they respond positively to the shocks in the business activity in a great magnitude and decay very slowly to its pre-shock level. meaning that the shocks last very long. The accumulative response to the exchange rate increase of 20 won per dollar and the 5 point industrial production increase is the smallest in Gwangyang, no more than a half of that of two ports. The intervention-ARIMA models also forecast that Gwangyang port will have much lower growth rate than Incheon and Pyeongtaek-Dangjin port in trading volumes.

• Research in Community and Public Health Nursing
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• v.11 no.2
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• pp.538-555
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• 2000

The purpose of this study, in which 573 students from 2 high schools in Kang Nung city participated was to identify the attitude and experience of sexual harassment. This information will provide useful data, and promote a more systematic sexual harassment education program. The subjects of this study were 278 male students and 295 female students. The data was collected from September 25 to October 6. 2000. The data was analyzed using the statistical Computer package. SPSS to manipulate the data along with frequency, percentage, and mean t-test. The results from this study were summarized as follows. 1. The results from this comparison between two groups were significant in their attitude on sexual harassment(t=-2.26. p=0.024). Female students had higher scores than male students. 2. As a cause of sexual harassment. 'A man's misjudgement regarding a women as sexual objects(n=130: 22.7%)'. 'Patriarchal system of unequal distribution of power and status between the sexes(n=105: 18.3%)'. 'The effect of sexual stimulatives. (pornography. pornovideo. TV program ect.)(n=89: 15.5%)'. 3. As a countermeasure for prevention, 'Punishment, law and regulation of the sexual harasser(n = 151; 26.4%)', 'A preventive education of sexual harassment in adolescence (n = 125: 21.8%)'. 'Reformation of gender inequality and sex discrimination in the socio-structure(n=76; 13.3%)'. 4. Out of 573 students who participated in this study, 209(36.5%) students reported experiencing an incident of sexual harassment. For 278 males who participated in this study, 88(31.7%) had experienced an incident of sexual harassment. For the 295 females who participated in this study, 121(41.0%) had experienced an incident of sexual harassment. The type of sexual harassment is reported physical sexual harassment(n = 248: 40.5%), verbal sexual harassment(n = 226; 36.7%), and visual sexual harassment(n=139: 22.6%). 5. Their age in which they had experienced harassment was usually 'after 16 years of age(n=122: 58.4%)'. The age of harassers were mostly teenagers(n=112; 53.6%). The relationship to the with sexual harasser was a stranger (n=85; 40.7%), or a friend(n=78: 37.3%). After the incident of sexual harassment occurred, some students informed friends (n=114: 54.5%), 63(30.1%) told no one. Male students' feelings after the experienced harassment ranged from: 'be interesting', 'be pleasant'. Female students' feelings after the experienced harassment ranged from; 'be surprised', 'get a shock', 'fear', 'shame'.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.8-15
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• 2016

The purpose of this study is to design a model with the structural stability so as not to lose the operational function due to structural plastic or fail of a sliding blast door by blast pressure to this aim, a numerical simulation was performed using full-size experiments and M&S (Modeling & Simulation) of the sliding blast door. The sliding blast door ($W3,000{\times}H2,500mm$) under the blast load is in the form of a sliding type 2-way metal grill, which was applied by a design blast pressure (reflected pressure $P_r$) of 17 bar. According to the experimental results of a real sliding blast door under blast load, the blast pressure reached the sliding blast door approximately 4.3 ms after the explosion and lasted about 4.0 ms thereafter. The maximum blast pressure($P_r$) was 347.7 psi (2,397.3 kPa), it is similar to the UFC 3-340-02 of Parameter(91 %). In addition, operation inspection that was conducted for the sliding blast door after real test showed a problem of losing the door opening function, which was because of the fail of the Reversal Bolt that was installed to prevent the shock due to rebound of the blast door from the blast pressure. According to the reproduction of the experiment through M&S by applying the blast pressure measurement value of the full-size experiments, the sliding blast door showed a similar result to the full-size experiment in that the reversal bolt part failed to lose the function. In addition, as the pressure is concentrated on the failed reversal bolt, the Principal Tensile Failure Stress was exceeded in only 1.25 ms after the explosion, and the reversal bolt completely failed after 5.4 ms. Based on the result of the failed reversal bolt through the full-size experiment and M&S, the shape and size of the bolts were changed to re-design the M&S and re-analyze the sliding blast door. According to the M&S re-analysis result when the reversal bolt was designed in a square of 25 mm ($625mm^2$), the maximum pressure that the reversal bolt receives showed 81% of the principal tensile failure stress of the material, in plastic stage before fail.

• Journal of Korea Port Economic Association
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• v.25 no.3
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• pp.269-282
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• 2009

This study investigates the difference of behavioral patterns between the import container volume of all ports and that of Gwangyang port in Korea. All series span the period January 1999 to December 2008. I first test whether the series are stationary or not. I can reject the null hypothesis of a unit root in each of the level variables and of a unit root for the residuals from the cointegration at the 5 percent significance level. I hitherto make use of variance decompositions and impulse response functions, both of which have now been widely used to examine how much movement in one variable can be explained by innovations in different variables and how rapidly these fluctuations in one variable can be transmitted to another. The variance decompositions for the import container volume show that the proportions of the forecast error variance of import container volumes explained by themselves are 30 and 26 per cent after 12 months, respectively. As a result, innovations in exchange rate and business activity explain 70 and 74 per cent of the variance in the import container volume. All in all, innovation accounting indicates that import container volumes are not exogenous with respect to exchange rate and business activity. The impulse responses indicate that container volumes decrease sharply to the shocks in exchange rate and decay very slowly to its pre-shock level, while container volumes respond positively to the shocks in the business activity and disappear very slowly, showing that the shocks last very long. Furthermore Gwangyang port is more sensitive to the change of the exchange rate and the industrial production than all ports.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.154-159
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• 2019

The glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system was fabricated by using yttrium oxide and iron oxide that it can reduce the melting temperature and affect the homogenization. Zirconium sulfate was used as a nucleation agent. Calcium phosphate was used to improve the flow the glass so as reduce the viscosity of the glass. The glass-ceramics met a thermal shock test of more than $750^{\circ}C$ and the temperature at which the coefficient of thermal expansion rapidly increased at over $800^{\circ}C$ was shifted by about the above $30^{\circ}C$. Therefore, it is concluded that the glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system with yttrium oxide and iron oxide was founded to have good melting conditions and excellent thermal expansion resistance at high temperature such as special field for kitchen utensils.

• Land and Housing Review
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• v.13 no.4
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• pp.45-53
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• 2022

This paper investigates empirically the lead-lag relation between the 'apartment price index' and 'Internet search volume'. This study uses Naver Trend Index as a proxy for Internet search volume. An increase in Internet search volume on the apartment price index indicates an increase in people's attention to an apartment. Different from previous studies exploring the relation between 'the released price index of the apartment' and 'Naver Trend Index', this study investigates the relation of the Naver Trend Index with 'the fundamental price component of an apartment' and 'the transitory price component of an apartment', respectively. The results of the Granger causality test reveal that there are bidirectional Granger causalities between the 'released price' and Naver Trend Index. In addition, the 'fundamental price component of an apartment' and Naver Trend Index have a feedback relation, while 'the transitory price component of an apartment' Granger causes the Naver Trend Index uni-directionally. The impulse response function analysis indicates that the shock of apartment prices increases Naver Trend Index in the first month. Overall, The close relationship between apartment prices and Naver Trend Index suggests that increases in the movement of apartment prices are positively associated with public attention on the apartment market.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• The Korea Journal of Herbology
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• v.39 no.3
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• pp.107-114
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• 2024

Objective : Cicadae Periostracum (CP), which is the discarded shell of the Cryptotympana atrata (Fabricius, 1775), is a recognized component of oriental medicine for treatment sore throat, itching, shock, sedation, edema. However, the safety and toxicity of CP have not yet been established. It has been reported that symptoms of addiction or side effects may occur in patients who take high doses of CP or who are hypersensitive to it. Therefore, we investigated the acute toxicity of an CP extracts in Sprague-Dawley (SD) rats. Methods : To study acute toxicity, five SD rats of each sex per group were treated with CP extracts at single doses of 0, 500, 1000, or 2000 mg/kg administrated by oral gavage, and body weight, clinical signs, and mortality were observed after dosing. At the end of 14-day observation period, all animals were sacrificed and complete hematological and macroscopic examinations were performed. Results : There were no dead animal and test article-related effects on body weight change or the gross finding. No toxicologically significant results were observed between control and treated groups in hematology. Although salivation related to stress at the highest dose was observed in clinical signs immediately after administration, it is considered to have no toxicological significance. Conclusion : As the results, we did not find any adverse effect at the dose levels of 500, 1000, or 2000 mg/kg in rats. The minimal lethal dose was considered to be over 2000 mg/kg body weight in rats.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.386-399
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• 2023

Microplastics and nanoplastics (NMPs) are considered one of hazardous contaminants in marine ecosystems due to their toxic effects, such as reproduction disorder and oxidative stress, on marine organisms. Although water temperature is rising due to global climate change, little information on the toxicological interaction between NMPs and temperature is available. Therefore, in this study, we confirmed the toxicity of NMPs (polystyrene [PS] beads; 0.05- and 6-㎛) on brackish water fleas (Diaphanosoma celebensis) depending on increased temperature (30℃ and 35℃) at individual and molecular levels. In the chronic toxicity test, the group exposed to high temperatures showed an earlier first reproduction time compared to the normal temperatures group, but it was delayed by co-exposure to NMPs at 35℃. Notably, the total reproduction decreased significantly only after 0.05-㎛ PS beads exposure at 30℃. Interaction analysis showed that first reproduction time, modulation of the antioxidant-related gene (GSTS1), heat shock gene (Hsp70), and ecdysteroid pathway-related genes (EcR_A, EcR_B, and CYP314A1) were closely related to temperature and PS beads size. These results indicate that microplastics have size-dependent toxicity, and their toxicity can be enhanced at high temperatures. In addition, higher temperatures and PS beads exposure may have negative effects on reproduction. This study suggests that various factors such as water temperature should be considered when evaluating the toxicity of microplastics in marine ecosystems, and provides an understanding of the complex toxic interaction between water temperature and microplastics for marine zooplankton.

• Journal of Oral Medicine and Pain
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• v.31 no.1
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• pp.79-89
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• 2006

The aim of this study is to know how the rat submandibular gland changes under various emotional stress condition, using molecular biological methods. Restraint and chronic unpredictable mild stress (CUMS) experiment is conducted on fifty one 7-week old Sprague-Dawley rats (restraint stress experiment: 21, CUMS: 30). The rats were sacrificed, the submandibular glands were excised immediately at certain time, and examined by the use of immunohistochemistry and western blotting. In CUMS experiment, sucrose preference test, water intake change, weight change were implemented at 1 week interval for the experimental period The results are as follows: 1. The number of clusterin-secreting cells of restraint stress group compared to control group showed significantly decreasing tendency in all experimental groups except for the 1st hour group (p<0.001 in the 9th, 24th, 72nd, 120th, and 168th hour group). 2. The number of clusterin-secreting cells of CUMS group compared to control group showed significantly increasing tendency in the 2nd week group (p<0.01), and significantly decreasing tendency in the 4th and 5th week group (p<0.001). 3. Sucrose preference test in CUMS experiment showed significant difference between the 5th week experimental group and control group (p<0.01). 4. Weight change in CUMS experiment showed significant difference between the 5th week experimental group and control group (p<0.01), but water intake change didn't show significant difference compared to control group. 5. In western blot analysis, clusterin expression was decreased on a gradual basis in due time compared to the control group in the restraint stress group. As for CUMS group (chronic unpredictable mild stress group), it was increased till the 2nd week and decreased till the 5th week after that, which is similar to immunohistochemical analysis result and the decreasing tendency of sucrose preference and weigh changes. Through the test, it was proved that expression of clusterin in saliva glands decreases after receiving either acute or chronic stress, indicating relation with depression caused by chronic stress. Unlike other data, however, apoptotic tendency was hardly found in tissues. Diverse possibilities could be suggested on that: first, the stress was not enough to expedite apoptosis; second, apoptosis-related protein was already being secreted though not detected with microscope; third, clusterin, a major secretion molecule of saliva, decreased with saliva's malfunction due to stress. In the respect, it will be necessary to examine proteins expressed in case of cell death or other heat-shock proteins at the same time, in order to see whether any cellular change or death is caused by decreasing clusterin under high stress, and whether the original state is restored as time goes by under mild stress, through longer-term tests using even higher acute stress.