• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1361-1368
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• 2011

Fatigue crack propagation behavior and the fatigue life in-high performance steel were investigated by means of fatigue crack propagation tests under constant loading conditions of 'R=0.1 and f=0.1 Hz', 'R=0.3 and f=0.3 Hz', and 'R=0.5 and f=0.5 Hz' for the load ratio and frequency, respectively. A modified Forman model was developed to describe the fatigue crack propagation behavior for the conditions. The modified Forman model is applicable to all fatigue crack propagation regions I, II, and III by implementing the threshold stress intensity factor range and the effective stress intensity factor range caused by crack closure. The results show that predicted fatigue lives of Forman and modified Forman models were 8,814 and 12,292 cycles, respectively when the crack propagated approximately 5.0 mm and the load ratio and frequency were both 0.1. Comparison of the test results indicates that the modified Forman model showed much more effective fatigue crack propagation behavior in high-performance steel.

• Development and Reproduction
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• v.6 no.1
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• pp.37-44
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• 2002

First sexual maturity, sex ratio, spawning frequency, deposition of the egg capsules and fecundity of the female Rapana venosa(Valenciennes) inhabited in the artificially closed slag deposit area, Gwangyang Bay were investigated by histologicai and visual observations for natural living resource management. The rate of individuals reaching the first sexual maturity was 51.6％ in females measuring 7.1~8.0 cm in shell height, and 100％ in those > 10.1 cm. The total number of egg capsules per individual and the mean number of eggs in an egg capsule were 192~382 and 500, respectively. However, the number of eggs per individual and sizes of egg capsules under lower salinity and deficient food conditions in the closed slag deposit area were smaller than those under the optimum salinity and sufficient food conditions in the open regions. Fecundities of the species were approximately from 96,000 to 191,000 eggs/individual with two to low broods(spawning frequencies) during the spawning season. The duration of development in egg capsules was 18~19 days at about 18~2$0^{\circ}C$. R. venosa is a species whose embryos hatch as veliger larvae, not juvenile snail. The sex ratio of female : male was not significantly different from 1 : 1($\chi$$^2$= 0.23, p>0.05).

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.579-584
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• 1998

Polymer dispersed liquid crystal(PDLC) composite films were made by polymerization induced phase separation method using UV-curing to investigate the effect of fabrication conditions, such as photoinitiator concentration, film thickness, polymerization temperature, and electric field during polymerization, etc., on the electro-optic properties. As the amount of photoinitiator increased, the driving voltage of PDLC device increased due to the increase of small-size liquid crystal phases. This was considered as the results from the increased interfacial area between liquid crystal (LC) and polymer matrix, since LC molecules at the interfacial regions were relatively difficult to response for the applied electric field. When the higher molecular weight oligomer (PTDA-1000) was used as matrix, the initial transmittance was observed to be relatively higher than that for the lower molecular weight oligomer (PTDA-250). Saturation transmittance for PTDA-1000 was observed at relatively lower voltage than that for PTDA-250, of which transmittance was not saturated even at 60 V. As polymerization temperature increased, the initial transmittance of resulting PDLC film increased due to the larger LC droplets formation and the more matched refractive index between LC and matrix than those cases for the lower polymerization temperature. Though driving voltage decreased for the thinner film, it was considered that optimum thickness of the film should be maintained to get some practical contrast, which is the ratio of off- and on-state transmittance. Furthermore, electro-optic properties such as initial transmittance, driving voltage, and response time were observed to be considerably affected by application of external field during polymerization.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.573-579
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• 1994

1-O-oleoyl glycerol, 2-O-oleoyl myo-inositol and methyl 2-O-oleoyl-${\alpha}$-D-glucopyranoside were used as surfactants in this study. The solution properties and solubilization process of those nonionic surfactants were examined by the phase equilibria. As a result of this study, we have found that phase behavior of two component systems of surfactants/$H_2O$/cyclohexane depends on temperature respectively. The three phase regions of three component systems appeared in the temperature range of $27^{\circ}C{\sim}32^{\circ}C$, $36^{\circ}C{\sim}45^{\circ}C$ and $38^{\circ}C{\sim}52^{\circ}C$ and solubilization of water and oil was high in those three phase ranged As the temperature was varied in the two component systems, liquid crystals of hexagonal were observed to in the case of 1-O-oleoyl glycerol, and liquid crystal of lamella types were observed in the case of 2-O-oleoyl myo-inositol and methyl 2-O-oleoyl-${\alpha}$-D-glucopyranoside.

• Journal of the Korean Society of Food Culture
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• v.20 no.5
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• pp.594-602
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• 2005

The purpose of this study was to investigate eating behaviors related to snack and self-purchasing snack (SPS) among elementary school children. Self-administered questionnairs were completed by 352, 5th and 6th grade elementary school students living in 3 different regions which included apartment region in Bundangn, Sungnam (apartment group, n=116), residences in Seodaemun-Gu and Mapo-Gu, Seoul (kang-buk group, n=103) and residence in industrial region in Sungnam (industry group, n=133). The results were as follows: A significantly higher proportion (64.7%) of the apartment group had breakfast every morning than those of kang-buk (48.6%) or industry (52.1%) group (p<0.01). As for the frequency rate of snack and self-purchasing snack (SPS), 53.9% of the subjects answered taking snack more than once per day, 22.8%, once for few days and 23.3%, almost not. However, 15.5% of the subject had SPS once or more per day, 30.7%, 1-2 times per week and 22.4%, almost not. Those of apartment group showed significantly lower SPS frequencies (p<0.01), since higher proportions answered having SPS 1-2times per week (40.9%) and almost not (31.3%) compared to other groups. The reasons for having SPS turned out to be 'hunger' 54.7%, 'being habitual', 15.9%, 'bing bored', 15.7% and 'with peers' 13.7%. When subjects selected SPS foods, they considered taste (31.5%), price (23.0%), mood at the time (14.1%), sanitorial aspect (10.2%) and quantity (10.1%) rather than nutritional aspect (7.2%). Subjects' pocket money was estimated as 3736 won per week and SPS expense per time as 706 won. But subjects who spent more than 2000 won for SPS expense were significantly higher (33.0%) in apartment group than those of other groups (p<0.01). The favorite snack items that subjects having at home were fruit, ice cream, milk and yoghurt, cookies, ramen and bread in order. And favorite SPS items turned out to be ice cream, cookies, duckbokki, frozen bars, gum, chocholate and candy in order. The frequency rate of SPS were evaluated to be significantly related by several variables: those living in apartment area (p<0.01), those taking breakfast regularly (p<0.01), those of normal weight status by Rohrer index (p<0.05) and those receiving less pocket money (p<0.01) showed lower SPS frequency rate.

• Journal of the Korean Geographical Society
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• v.42 no.1 s.118
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• pp.41-62
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• 2007

This paper aims to interpret the changes of the regional inequality between Seoul Metropolitan Area(SMA) and Non-SMA after 1981 on the regulationist approaches that examine institution changes and power dynamics that motivate regional disparities in South Korea. Despite the restrict laws and aims that alms to reduce the concentration into SMA before 1988, the acts were not executed effectively due to the structural selectivity of the bureaucratic authoritarian state of those years. Thus, the regional concentration phenomena of SMA was intensified in the 1980s. However, the democratization in 1987 invoked Non-SMA regions to claim their regional development and it also forced the state to mediate the conflicting interests between the regional agents protesting the SMA concentration and the Capital agents supporting the SMA deregulation. From the early 1990s. the state launched a series of national strategies and policies to diminish regional inequality. They included execution of the existing acts mitigating SMA concentration and construction of industrial complexes in the underdeveloped areas of Non-SMA. Thus, the equalizing polities led the reduction of the concentration of SMA from 1989 to 1997. However, the financial crisis of Korea in 1997 intensified the claims of the Capital agents to deregulate the SMA control. The circumstance also forced the state towards the Capital side that request the deregulation of SMA control. As the result, the regional disparity between SMA and Non-SMA has been enlarged again since 1998.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.699-712
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• 2000

Juam lake is a major water resource for the industrial and agricultural activities as well as the resident life of Kwangju and Chonnam regions. However, the water quality of the lake is getting worse due to a large quantity of pollutant inflowing to the lake. Thus, the strategy for achieving the water quality goal of the lake should be developed as soon as possible. When there are various alternatives that can be used as the strategy, several criteria based on the achievement degree of water quality goal, the applicability of technique and social environment, and the reasonableness of the cost required are made to evaluate and rank the alternatives. However, it is difficult to make a decision when there are multiple criteria and conflicting objectives and specifically the estimated values of criteria contain elements of uncertainty. The uncertainty stems from the lack of available information, the randomness of future situation, and the incomplete knowledge of expert. As the degree of uncertainty is higher, the decision becomes more difficult. In this study, a fuzzy decision-making method is presented to assist decision makers in evaluating various alternatives under uncertainty. The method allows decision makers to characterize the associated uncertainty by applying fuzzy theory and incorporate the uncertainty directly into the decision making process for selecting the "best" alternative so decisions can be made that are more appropriate and realistic than those made without taking uncertainty in account.

• Journal of Digital Convergence
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• v.18 no.3
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• pp.259-266
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• 2020

This paper attempted to find the convergence factors related to the organizational citizenship behavior of hospital administration staff(HAS). The survey was conducted on 274 administrative staff at 22 hospitals in J regions randomly selected using self-administered questionnaires. The survey period took about a month from July 1 to July 31, 2019. The hierarchical multiple regression analysis shows the following results. The organizational citizenship behavior of respondents turned out to be significantly higher in following groups: The higher the procedure justice, sub-areas of organization justice, the higher the intragroup trust, and the higher the organizational commitment. Their explanatory power was 41.9%. The results of the study indicate that the efforts, to increase organization justice, intragroup trust and organizational commitment, are required to improve organizational citizenship behavior among HAS. The above results are expected to be utilized in human resource management and industrial health education of medical institutions that enhance organizational citizenship behavior of HAS. Later research requires the establishment of a structural equation model that affects organizational citizenship behavior of HAS.

• Journal of Digital Convergence
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• v.18 no.8
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• pp.21-27
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• 2020

This paper studies the impact of domestic and foreign economic activity on mobility among regions. The shortage of human resources and demand continues in Eastern Europeans. Especially Ukrainians, have entered the Polish labor market to make up for the scarce areas. As a result, Poland's supply and demand in Ukraine is disproportionate. Minimum wage increases are putting continued pressure on employers. Therefore, the regression equation in the form of job-seeker's economic activity ratio, y= AX²+B,(x=settlers) can be used to grasp the relationship between curves. According to the domestic and foreign workers who migrated, economic activities was rather than increasing the local population, the settlers of nearby large cities is more proportional. Empirical analysis has shown that the human resource hub has increased migration to large cities and industrial. The hub 'A'nation has been created for mobility in 4th wave re-industry, and the same re-industrialization (N₂) in other cities has attracted nearby human resources, but not settle. After all, the hub relationship between N₁ and N₂ is a mobile relationship. Due to wage inequality or a positive wellbeing chasm, workers are not settled plant area but a nearby city, or commuting between borders is easy to go into the hub central city. However, this proved on emerging from the relatively temporary settlers in the AI era.

• Journal of Environmental Science International
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• v.23 no.10
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• pp.1703-1718
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• 2014

An eco-friendly integrated multi-trophic aquaculture (IMTA) farming technique was developed with the goal of resolving eutrophication by excess feed and feces as fish-farming by-products. A variety of seaweed species were tried to remove inorganic nutrients produced by fish farming. However, there have been few trials to use Sargassum fulvellum in an IMTA system, a species with a relatively wide distribution across regions with various habitat conditions, great nutrient removal efficiency and importance for human food source and industrial purposes. In this regard, our study tried to examine feasibility of using S. fulvellum in an IMTA system by analyzing growth characteristics of the species in an IMTA system comprising of rockfish (Sebastes shlegeli), sea cucumber (Stichopus japonocus) and the tried S. fulvellum (October 2011 - November 2012). We also monitored environment conditions around the system including current speed, water temperature and inorganic nutrient level as they may affect growth of S. fulvellum. S. fulvellum in the IMTA system, which were $15.72{\pm}5.67mm$ long at the start of the experiment in October 2011, grew to a maximum of $1093{\pm}271.13mm$ by May 2012. In September, seaweed growth was reduced to a minimum of $280{\pm}70.43mm$ in length. Then, S. fulvellum began to grow again reaching $325{\pm}196.19mm$ by November 2012. Wet weight of the seaweed was $4.01{\pm}1.89g$ at the start of the experiment and reached a maximum of $109.26{\pm}34.23g$ in May. The weight gradually declined to a low of $15.12{\pm}8.40g$ in September 2012. Weight began to increase once more, rising to $39.27{\pm}21.69g$ by November. During the experiment, the average velocity at the surface and the bottom was 6.5 cm/s and 3.4 cm/s, respectively. The water temperature ranged $5.0-23.5^{\circ}C$, which was considered suitable for growing S. fulvellum. Results of the study indicated no significant differences in inorganic nutrients between pre- and post-IMTA installation. It was thus concluded that S. fulvellum can be a suitable seaweed species to be used in an IMTA system.