• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.1-8
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• 2013

This paper presents the results of experimental and numerical research on the slamming phenomenon. Two experimental techniques were proposed in this study. The traditional free drop tests were carried out. However, the free drop tests done in this study using an LM guide showed excellent repeatability, unlike those of other researchers. The coefficients of variation for the drop test done in this experiment were less than 0.1. The other experimental technique proposed in this study was a novel concept that used a pneumatic cylinder. The pneumatic cylinder could accelerate the specimen over a very short distance from the free surface. As a result, high rates of repeatability were achieved. In the numerical study, the development of in-house code and utilization of commercial code were carried out. The in-house code developed was based on the boundary element method. It is a potential code. This was mostly applied to the computation of the wedge entry problem. The commercial code utilized was FLUENT. Most of the previous slamming research was done under the assumption of a constant body velocity all through the impact process, which is not realistic at all. However, the interaction of a fluid and body were taken into account by employing a user-defined function in this study. The experimental and numerical results were compared. The in-house code based on BEM showed better agreement than that of the FLUENT computation when it cames to the wedge computation. However, the FLUENT proved that it could deal with a very complex geometry while BEM could not. The proposed experimental and numerical procedures were shown to be very promising tools for dealing with slamming problems.

• Ocean Systems Engineering
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• v.6 no.4
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• pp.377-400
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• 2016

Dropped objects are among the top ten causes of fatalities and serious injuries in the oil and gas industry (DORIS, 2016). Objects may accidentally fall down from platforms or vessels during lifting or any other offshore operation. Proper planning of lifting operations requires the knowledge of the risk-free zone on the sea bed to protect underwater structures and equipment. To this end a three-dimensional (3D) theory of dynamic motion of dropped cylindrical object is expanded to also consider ocean currents. The expanded theory is integrated into the authors' Dropped Objects Simulator (DROBS). DROBS is utilized to simulate the trajectories of dropped cylinders falling through uniform currents originating from different directions (incoming angle at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, and $270^{\circ}$). It is found that trajectories and landing points of dropped cylinders are greatly influenced by the direction of current. The initial conditions after the cylinders have fallen into the water are treated as random variables. It is assumed that the corresponding parameters orientation angle, translational velocity, and rotational velocity follow normal distributions. The paper presents results of DROBS simulations for the case of a dropped cylinder with initial drop angle at $60^{\circ}$ through air-water columns without current. Then the Monte Carlo simulations are used for predicting the landing point distributions of dropped cylinders with varying drop angles under current. The resulting landing point distribution plots may be used to identify risk free zones for offshore lifting operations.

• Asia-Pacific Journal of Business
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• v.14 no.1
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• pp.341-350
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• 2023

Purpose - How are gains from trade distributed between countries when economic integration is achieved through free trade? The purpose of this paper is to answer this question. Design/methodology/approach - This study attempts to address the issue of distribution of trade gains between participating countries following economic integration in terms of positive economics. The analysis is therefore based on a theoretical methodology. Findings - First, commodity prices fall and consumer surplus increases in both large and small countries. Second, when economic integration into free trade is achieved, gains from trade always exist in small countries. However, the size of trade gains depends on the degree of difference from the market size of the partner country, the large country. However, the size of the gains from trade depends on the extent of difference between the market size of the large country. If the market size of a large country is much larger and there is a large difference, trade gains will be very large, whereas if the market size is similar, profits of domestic firm will decrease. Therefore, in that case, the size of the gains from trade becomes relatively small because only the gains from exchange exists. On the other hand, in a large country with a large market size, there is a possibility of trade gains only when the market size is similar to that of a small country, which is a trading partner. However, if there is a large difference in market size, the decrease in profits of domestic firm is relatively larger than the increase in consumer surplus due to trade, and rather, a trade loss occurs. Research implications or Originality - Our analysis contributes to filling the gaps in the literature regarding the distribution of gains from trade, and from a policy point of view, it is meaningful in examining the impact of market size, an important variable considered in regional economic integration of countries.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.380-386
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• 2000

Alkaline phosphatase ($AP_{ase}$) activity was studied for the pure cultures and natural communities of phytoplankton. The Michaelis-Menten constant ($K_m$) showed large variation with species. Some green algae showed large $K_m$ ($650\;{\mu}M$ for Selenastrum capriconutum). Chlorella sp. and Nitzschia palea showed smaller Km (respectively1.7, 2.0 HM) than those of other species examined. The extracellular free enzyme in the filtrate of Anabaena flos-aquae showed smaller Km ($52\;{\mu}M$) than that of cellbound form ($276\;{\mu}M$). The $K_m$ ($12.0\;{\mu}M$) of summer phytoplankton in Lake Soyang. when Anabaena sp. was dominant species, was larger than that (1.5 HM) of spring phytoplankton when Asterionella sp. was the dominant. Although maximum activity($V_{max}$) in Lake Soyang was affected by the concentration of DIP within the lake, but the $V_{max}$ always varied not with the DIP concentration of the lake. Induction of $AP_{ase}$ may be more affected by the phosphate content within the cell of phytoplankton than by the concentration of DIP within the lake, The extracellular free $AP_{ase}$ activity accounted for $36{\sim}97%$ of total activity from fall to spring turnover in Lake Soyang. The $K_m$ ($1.1{\mu}3.5\;M$) of extracelluar free enzyme were simillar to those ($0.7{\mu}3.5\;M$) of the total activity. This indicates that the extracelluar free enzyme was derived from phytoplankton.

• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.8-15
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• 2003

In this study, chlorine dose at water storage tank was predicted to meet the recommended guideline for free chlorine residual in drinking water distribution system, using EPANET which is a computer program that performs extended Period simulation of hydraulic and water quality behavior within pressurized pipe networks. The results may be summarized as follows. The decay of chlorine residual by season varied considerably in the following order; in summer ($25^{\circ}C$) > spring and fall (15$^{\circ}C$) > winter (5$^{\circ}C$). For re-chlorination at water storage tank by season, season-varying chlorine dose was required at its maximum of 1.00 mg/l in summer and minimum of 0.40 mg/l in winter as free chlorine residual. The decay of chlorine residual through out the networks increased with water age spent by a parcel of water in the network except for some points with low water demand. In conclusion, the season-varying chlorine dose as well as the monitoring of water quality parameters at the some points which showed high decay of chlorine residual may be necessary to deliver the safe drinking water.

• Journal of the Korean Regional Science Association
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• v.11 no.1
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• pp.61-78
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• 1995

This study begins with a question of what spatial impact international trade policy would have following the Uruguay Round, particularly focusing on agricultural trade liberalization in Korea. Based upon the neoclassical urban economic model, it first identifies the channel in which agricultural market opening can ultimately affect both rural and urban are as; $\circled1$ Free trade will depress domestic price of agricultural products, $\circled2$ which will in turn depreciate agricultural land price. $\circled3$ The decrease in marginal supply cost for urban land will then facilitate urban sprawl, provided that the government relaxes restrictions on urban-rural land conversion. Theoretical analysis is further refined by empirical considerations that distinguish agricultural land value solely for production purpose from that for future urban, uses, and that distinguish the urbanization effect caused by the fall in the supply cost of urban land from that caused by the existing high level of demand. Utilizing the estimate of bid-price for paddy field derived from the revenue-cost relationship of rice production, simulation results show that the urban-rural boundary under trade liberalization can expand outward up to 70-85km radius in the Seoul metropolitan area, suggesting the emergency of a metropolis or even a megalopolis which extends from Seoul to the central part of the country. Since the geographic extent of urbanization effect can vary depending upon the urban spatial structure, however, it is recommended that the redevelopment option in the built - up area should always be tied up with the issue of whether to deregulate rural-to-urban land conversion.

• Journal of The Korean Society of Emergency Medicine
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• v.29 no.5
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• pp.423-429
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• 2018

Objective: Falling is a common cause of head injury in preschool aged children. We investigated the characteristics of mild head injuries caused by falling and the association between body weight and occurrence of traumatic brain injuries (TBI). Methods: This retrospective observational study was conducted on head-injured preschool-aged children that visited the emergency department from January 2012 to December 2015. Characteristics such as age, sex, weight, free fall height, floor type, and presence of TBI, as defined as cerebral hemorrhage or skull fracture, were investigated. We calculated body weight percentiles by calibrating age and weight and categorized them into four quartile ranges. We grouped all included cases into two groups according to the presence of TBI. The characteristics of the two groups were compared by using chi-square test, and the association with TBI was investigated by using binomial logistic regression. Results: A total of 701 children were included, and TBI was observed in 95 children. Children with TBI were younger. The proportion of children with TBI was higher in the third and fourth quartiles of the body weight group as well as according to soft floor and fall from high height (${\geq}1m$). The odds of soft floor being associated with TBI was higher than the odds for hard floor (odds ratio, 2.734; 95% confidence interval [CI], 1.597-4.680). The odds of high height (${\geq}1m$) being associated with TBI was higher than that for low height (odds ratio, 2.306; 95% CI, 1.155-4.601), and the odds ratio for the weight percentile group was 1.228 (95% CI, 1.005-1.499). Conclusion: Prevalence of TBI after falling in preschool-aged children might be associated with high fall-height and body weight quartiles.

• Journal of Environmental Science International
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• v.17 no.10
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• pp.1121-1127
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• 2008

The free-living amoeba and Acanthamoeba sp. are widely distributed in fresh water, soil, air and dust in the world. We studied distribution of amoeba from low Nakdong River(Mulgum and Maeri) and removal efficiency in water treatment process of Busan metropolitan city. During this investigation, water quality showed pH $7.4{\sim}9.6({\pm}1.1)$, water temperature $2.0{\sim}29.0({\pm}17)^{\circ}C$, turbidity $4.8{\sim}27.4({\pm}11.0)$ NTU, chlorophyll-a $10.3{\sim}109.0({\pm}44.3)\;mg/m^{3}$, BOD $1.7\sim4.9({\pm}2.6)$ mg/L, COD $3.1\sim-6.9({\pm}5.0)$ mg/L and total coliform $17\sim920({\pm}200.5)$ MPN/100 mL. The free-living amoeba were detected highly than Acanthamoeba sp., 11 out of 22 in raw water samples were positive (50%) for Acanthamoeba sp. from February 2005 to December 2005. The seasonal characteristics of tree-living amoeba and Acanthamoeba sp. in raw water were mainly distributed through the spring to the early fall. When tree-living amoeba and Acanthamoeba sp. were passed through the water treatment of pilot-plant, approximately 80% was sure to be removed through pre-ozonation, sedimentation, send filtration. 100% was removed after post-ozonation process. All of the isolated amoebas from Nakdong River were Acanthamoeba sp. AC311 18S ribosomal RNA gene with 98% nucleotide sequence homology.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.79-86
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• 2011

The contents of free amino acid in cabbage cultivars originated from China and Korea were measured to determine the quality for taste and nutrition. The experimental variables were season (spring-sowing and fall-sowing), leaf position (inside and outside), and the cabbage color (green and red). Eighteen free amino acids were detected at the range of 0-38 mg/g dry weight. The most abundant amino acid was serine(0-128 mg/g). Alanine, aspartate, glutamate, asparagine, histidine, and proline were relatively rich at 2-12 mg/g dry weight. Glycine were significantly increased in spring-sowing cabbages by 2-fold but proline was reversely decreased by 7-fold. The inside parts of cabbages contained significantly more alanine, glutamate, glycine, isoleucine, serine, and valine than the outside ones. The higher contents of isolecuine, leucine, proline, and valine were observed in the red cabbages than the green ones. The significant cross effects of season-color and position-color were also observed, indicating the red and the green cabbages were differently affected by season and tissue position.

• Atmosphere
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• v.14 no.4
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• pp.3-18
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• 2004

Neglecting the vertical transport from the surface, most of the previous studies on the long-range transport of pollutants have only considered the horizontal transport caused by the free atmosphere wind. I used a three dimensional numerical model, MM5 (The fifth generation Penn State Univ./NCAR Mesoscale Model) for the simulation of vertical transport of pollutants and investigated the mechanism of the vertical transport of atmospheric pollutants between planetary boundary layer(PBL) and free atmosphere by fronts. From the three dimensional simulation of MM5, the amount of pollutants transport from PBL to free atmosphere is 48% within 18 hour after the development of front, 55% within 24 hour, and 53% within 30 hour. The ratios of the vertically transported pollutant for different seasons are 62%, 60%, 54%, and 43% for spring, summer, fall, and winter, respectively. The most active areas for the vertical transport are the center of low pressure and the warm sector located east side of cold front, in which the strong upward motion slanted northward occurs. The horizontal advection of pollutants at the upper level is stronger than at the lower level simply because of the stronger wind speed. The simulation results shows the well known plum shape distribution of pollutants. The high concentration area is located in the center and north of the low pressure system, while the second highest concentration area is in the warm sector. It is shown that the most important mechanism for the vertical transport is vertical advection, while the vertical diffusion process plays an important role in the redistribution of pollutants in the PBL.