• Korean journal of applied entomology
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• v.59 no.2
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• pp.93-107
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• 2020

Adults of seven noctuid potential pests (Spodoptera frugiperda, S. litura, S. exigua, Ctenoplusia agnata, Mythimna loreyi, Athetis dissimilis, and A. lepigone) of soybean and maize in Suwon, Korea were identified by their morphological characteristics in the wing pattern and male genitalia and partial mitochondrial DNA sequences of cytochrome c oxidase subunit 1 gene. The generation number of adults that emerge annually in six species (except A. lepigone) was estimated from the data on density fluctuations of adults caught in sex pheromone traps in 2019 and the forecasted data using temperature-associated development and reproduction models for those species. S. frugiperda adults were caught from July 27th to October 31st in 2019, and hence were initially estimated to emerge three times per year. But, it was finally expected that S. frugiperda adults could possibly emerge a total of four times per year in Suwon, considering larval emergence observed during mid- and late June in other areas. Adult emergence of S. litura, S. exigua, C. agnata, and M. loreyi in 2019 was observed from May 29th to November 6th, from May 14th to November 6th, from May 26th to October 25th, and from May 31st to November 23rd, respectively. Annual adult emergence of these four species was estimated as at least four times. Adults of A. dissimilis were caught from May 26th to September 11th in 2019, and adult emergence was estimated at only twice per annum. It was postulated that the first adult populations of five species except the two Athetis species were probably migrated from other areas.

• The Korean Journal of Financial Management
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• v.25 no.4
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• pp.25-51
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• 2008

In this paper, we analyse empirically the fixed asset investment smoothing of working capital of firms listed on Korea Securities Market. The main results of this study can be summarized as follows. Firms will seek to lower long-term cost by smoothing fixed asset investment and maintaining stationary investment with working capital. Working capital is not only an important use of fund, but also a source of liquidity that should be used to smooth fixed asset investment relative to cash flow shocks if firms face financial constraints. Working capital investment is more sensitive than fixed asset investment to cash flow fluctuations. If firms face financial constraints, working capital investment will compete with fixed asset investment for the limited pool of available cash flows. So, fixed asset investment will have negative relationship with working capital investment. However, criticism that the positive correlation between cash flows and fixed asset investment could arise simply because cash flows is proxy variable for investment demand. Finally, controlling for the fixed asset investment smoothing effects of working capital results in a much larger estimate of the long run impact of financial constraints. Financial constraints is measured by dividend payout ratio and market access level. Fazzari et al. (1988), Fazzari and Petersen (1993), and Faulkender et al. (2008) emphasize that low dividend firms or market unaccessible firms are more likely to face financial constraints, and rarely make use of new equity issuing. The results from empirical analysis show that financial constraints can be better explained using 'adjustment cost' concept. Specifically, the results show that financial constraints exist and that in order to measure financial constraint effects more succinctly, fixed asset investment smoothing effects with working capital should be considered.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.1-8
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• 2020

Centrifugal pump is a facility that transfers energy to fluid through centrifugal force, which is usually generated by rotating the impeller at high speed, and is a major process facility used in many LNG production bases such as vaporization seawater pump, industrial water and fire extinguishing pump using seawater. to be. Currently, pumps in LNG plant sites are subject to operating conditions that vary depending on the amount of supply desired by the customer for a long period of time. Pumps in particular occupy a large part of the consumption strategy at the plant site, and if the optimum operation condition is not available, it can incur enormous energy loss in long term plant operation. In order to solve this problem, it is necessary to identify the performance deterioration factor through the flow analysis and the result analysis according to the fluctuations of the pump's operating conditions and to determine the optimal operation efficiency. In order to evaluate operation efficiency through experimental techniques, considerable time and cost are incurred, such as on-site operating conditions and manufacturing of experimental equipment. If the performance of the pump is not suitable for the site, and the performance of the pump needs to be reduced, a method of changing the rotation speed or using a special liquid containing high viscosity or solids is used. Especially, in order to prevent disruptions in the operation of LNG production bases, a technology is required to satisfy the required performance conditions by processing the existing impeller of the pump within a short time. Therefore, in this study, the rotation difference of the pump was applied to the ANSYS CFX program by applying the modified 3D modeling shape. In addition, the results obtained from the flow analysis and the curve fitting toolbox of the MATLAB program were analyzed numerically to verify the outer diameter correction theory.

• The Journal of Fisheries Business Administration
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• v.40 no.2
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• pp.49-70
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• 2009

This study proviedes GARCH model(Bollerslev, 1986) to analyze the structural characteristics of price volatility in domestic aquacultural fish market of Korea. As a case study, flatfish and rock-fish are analyzed as major species with relatively high portion in an aspect of production volume among fish captured in Korea. For analyzing, this study uses daily market data (dating from Jan 1 2000 to June 30, 2008) published by the Noryangjin Fisheries Wholesale Market which is located in Seoul of Korea. This study performs normality test on trading volume and price volatility of flatfish and rock-fish as an advanced empirical approach. The normality test adopted is Jarque-Bera test statistic. As a result, first, a null hypothesis that "an empirical distribution follows normal distribution" was rejected in both fishes. The distribution of daily market data of them were not only biased toward positive(+) direction in terms of kurtosis and skewness, but also characterized by leptokurtic distribution with long right tail. Secondly, serial correlations were found in data on market trading volume and price volatility of two species during very long period. Thirdly, the results of unit root test and ARCH-LM test showed that all data of time series were very stationary and demonstrated effects of ARCH. These statistical characteristics can be explained as a reasonable ground for supporting the fitness of GARCH model in order to estimate conditional variances that reveal price volatility in empirical analysis. From empirical data analysis above, this study drew the following conclusions. First of all, from an empirical analysis on potential effects of seasonality and the day of week on price volatility of aquacultural fish, Monday effects were found in both species and Thursday and Friday effects were also found in flatfish. This indicates that Monday is effective in expanding price volatility of aquacultural fish market and also Monday has higher effects upon the price volatility of fish than other days of week have since it has more new information for weekend. Secondly, the empirical analysis led to a common conclusion that there was very high price volatility of flatfish and rock-fish. This points out that the persistency parameter($\lambda$), an index of possibility for current volatility to sustain similarly in the future, was higher than 0.8-equivalently nearly to 1-in both flatfish and rock-fish, which presents volatility clustering. Also, this study estimated and compared and model that hypothesized normal distributions in order to determine fitness of respective models. As a result, the fitness of GARCH(1, 1)-t model was better than model where the distribution of error term was hypothesized through-distribution due to characteristics of fat-tailed distribution, was also better than model, as described in the results of basic statistic analysis. In conclusion, this study has an important mean in that it was introduced firstly in Korea to investigate in price volatility of Korean aquacultural fishery products, although there was partially a limited of official statistic data. Therefore, it is expected that the results of this study will be useful as a reference material for making and assessing governmental policies. Also, it is looked forward that the results will be helpful to build a fishery business plan as and aspect of producer, and also to take timely measures to potential price fluctuations of fishery products in market. Hence, it is advisable that further studies related to such price volatility in fishery market will extend and evolve into a wider variety of articles and issues in near future.

• Journal of Bio-Environment Control
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• v.18 no.2
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• pp.166-170
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• 2009

The temperature fluctuations was investigated in cold distribution chain of radish sprout, typical of commercial practice. Although the temperature of distribution chain was maintained below 5$^{\circ}C$ in precooling and packaging steps, and 10$^{\circ}C$ in transporting, temperature of loading step increased up to 18$^{\circ}C$ at market. Based on this investigation, the simulated cold distribution conditions were consisted of precooling and packaging step; 5$^{\circ}C$ for 12 hours and transporting and loading steps; 5$^{\circ}C$, 10$^{\circ}C$, 20$^{\circ}C$ and $^{\circ}C$ for 6 hours, and storage and market steps; 5$^{\circ}C$ and 10$^{\circ}C$ for 17 days. The radish sprouts were cultivated at 25$^{\circ}C$ and dark condition for S days and placed in light condition for greening. They were packaged by 25 ${\mu}m$ ceramic film after precooling for 6 hours in 5$^{\circ}C$. The fresh weight loss and visual quality of radish sprout decreased with the increase of the temperature in transporting and loading steps. The carbon dioxide content of packages increased, but the oxygen content decreased rapidly in 1day after storage, as the temperature of transporting and loading steps increased. The ethylene content in packages increased fastest in higher temperature of transporting and loading steps treatment, and showed highest in 5$^{\circ}C$-30$^{\circ}C$-10$^{\circ}C$ treatment (temperature of precooling and packaging steps for 12 hours - temperature of transporting and loading steps for 6 hours - temperature of storage step for 14 days) followed by 5$^{\circ}C$-20$^{\circ}C$-10$^{\circ}C$ treatment. The high temperature of transporting and loading steps resulted in deterioration qualities and atmosphere conditions in packages of sprout. These results suggested that the temperature fluctuation in distribution should influence the shelf-life of radish sprouts, even thought the periods of fluctuation was just 6 hours.

• Journal of Radiation Protection and Research
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• v.10 no.2
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• pp.96-108
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• 1985

A study for the assessment of natural environmental radiation exposure at a flat and open field of about $10,000m^2$ in area in CNU Daeduk campus has been carried out by means of gamma-ray scintillation spectrometry and thermoluminescence dosimetry for one year period of time from October 1984. The detectors used were 3'${\phi}{\times}$3' NaI(T1) and two different types of LiF TLD, namely, chip sealed in plastic sheet which tightly pressed on two open holes of a metal plate and Teflon disk. Three 24-hour cycles of in-situ spectrometry, and two 3-month and one 1-month cycles of field TL dosimetry were performed. All the spectra measured were converted into exposure rate by means of G(E) opertaion, and therefrom exposure rate due to terrestrial component of environmental radiation was figured out. Exposure rate determined by the spectrometry was, on average, $(10.54{\pm}2.96){\mu}R/hr$, and the rates of $(12.0{\pm}3.4){\mu}R/hr$ and $(11.0{\pm}3.6){\mu}R/hr$ were obtained from chip and disk TLD, respectively. Fluctuations in diurnal variation of the exposure rate measured by the spectrometry were noticeable sometime even in a single cycle of 24 hours. It is concluded that appropriately combined use of TLD with iu-sitn gamma-ray spectrometry system can give more accurate and precise measure of environmental radiation exposure, and further study for more adequate and sensitive TLD for environmental dosimetry, including improvement and elevation of accuracy in data assessment through inter-laboratory or international intercomparison is necessary.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.196-209
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• 2009

Occurrences of sandstorms in the deserts and loess of Mongolia and northern China and associated dustfall episodes in the Korean Peninsula were monitored during the period January through December, 2005. False colour images were made by directly receiving the NOAA Advanced Very High Resolution Radiometer (AVHRR) data, and the distribution and transport of sandstorms were analyzed. The ground concentrations for PM10, PM2.5 and visibility of the dustfall episodes (PM10 concentration over $190{\mu}g\;m^{-3}$) were analyzed at Cheongwon, located midway in South Korea, and in the leeward direction of the place of origin of the sandstorms. Variations in the concentrations of $O_3,\;NO_2$, CO and $SO_2$ were also compared with dust concentrations in the dustfall episodes. Fewer occurrences of strong sandstorms in the place of origin were observed in 2005, due largely to the accumulation of snow and mild fluctuations of high and low pressure systems in the place of origin, thereby accounting for a low frequency of dustfall episodes in Korea, compared with those during the period 1997-2005. A total of 7 dustfall episodes were monitored in Korea in 2005 that lasted 11 days. In summer, sandstorms occurred less frequently in the source region in 2005 due to high humidity and milder winds, thereby causing no dustfall episodes in Korea. In case the sandstorms occurring at the place of source head directly to Korea without passing through large cities and industrial areas of China, the PM2.5 concentrations were measured at 20% or lower than the PM10 concentrations. However, when the sandstorms headed to Korea via the industrial areas of eastern China, where they pick up anthropogenic air pollutants, the PM2.5 concentrations were at least 25% higher of the PM10 concentrations. On the other hand, over 5 cases were observed and analyzed in 2005 where the PM10 concentrations of sand dust originating from the deserts were measured at $190{\mu}g\;m^{-3}$ or lower, falling short of the level of a dustfall episode.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.881-897
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• 2019

We reconstructed and digitized the National Institute of Fisheries Science (NIFS) Serial Oceanographic observations (NSO) and Coastal Oceanographic observations (NCO) data attained prior to 1961 through historical oceanographic observation data rescue projects. Increasing trends of long-term sea surface temperature (SST) were shown from the NSO data of 21 available stations for the past 80 to 92 years. In general agreement with previous research results used in the data of the past 50 years, we calculated the rate of temperature rise. As a result of analyzing the spatial distribution of SST change rate in the Korean of shore region using selected oceanographic data, the West Sea and South Sea showed a higher tendency of temperature rise in the offshore area than in the coastal area. However, unlike the results of previous studies, the East Sea (Gangwon Line and Ulsan Line) showed a lower water temperature rise than the coastal stations. Annual fluctuations of NCO's SST data from 1989 to 1998 for three stations representing the East Sea, South Sea, and West Sea, (Jumunjin, Geomundo and Budo, respectively) revealed that the East Sea showed the highest SST increase for the 10 years. The increases were 1.63 ℃ at Jumunjin, 1.16 ℃ at Geomundo, and 0.79 ℃ at Budo. As a result of the investigation, it can be concluded that SST is repeatedly rising and falling with a period of 3 ~ 6 years. Especially, since the 1980s, most of the stations show positive anomalies of SST. Lastly, to understand ocean_atmosphere interactions, we analyzed the correlations between SST of the NCO stations and air temperature around them and the results were 0.76 for the South Sea (Geomundo), 0.34 for the West Sea (Budo), and 0.32 for the East Sea (Jumunjin) with the highest correlation in the South Sea.

• Journal of the Korean Institute of Navigation
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• v.4 no.2
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• pp.45-79
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• 1980

The aim of this paper is to analyze the mechanics of price formation in the tramp shipping. For the purpose of this study, the main characteristics of tramp freight rates and the market is examined, and a brief examination of the nature ofthe costs of operation is given which are essential for the understanding of the functioning of shipping firms as well as for the understanding of developments in the tramp freight market. The demand and supply relationships in the market is also analysed in detail. Tramp shipping is an industry that has a market which functions under conditions that are not dissimilar to the theoretical model of perfect competition. However, it does notmean that tramp shipping market is a perfectly competitive market. It is apparent that this realworld competitive system has its imperfections, which means that the market for tramp shipping is near to being a perfectly competitive market on an internaitonal scale and it is freight are therefore subjext to the laws of supply and demand. In theory, the minimum freight rate in the short term is that at which the lowest cost vessels will lay-up in preference to operating, and is equal to the variable costs minus lay-up costs; and this would imply that in all times except those of full employment for ships there is a tendency for newer low-cost, and, probably, faster vessels to be driving the older high-cost vessels in the breaker's yards. In this case, shipowners may be reluctant to lay-up their ships becasue of obligations to crews, or because they would lose credibility with shippers or financiers, or simply because of lost prestige. Mainly, however, the decision is made on strictly economic grounds. When, for example, the total operating costs minus the likely freight earnings are greater than the cost of taking the ship out of service, maintaining it, and recommissioning it, then a ship may be considered for laying-up; shipowners will, in other words, run the ships at freight earnings below operating costs by as much as the cost of laying them up. As described above, the freight rates fixed on the tramp shipping market are subject to the laws of supply and demand. In other words, the basic properties of supply and demand are of significance so far as price or rate fluctuations in the tramp freight market are concerned. In connection with the same of the demand for tramp shipping services, the following points should be brone in mind: (a) That the magnitude of demand for sea transport of dry cargoes in general and for tramp shipping services in particular is increasing in the long run. (b) That owning to external factors, the demand for tramp shipping services is capable of varying sharphy at a given going of time. (c) The demad for the industry's services tends to be price inelastic in the short run. On the other hand the demand for the services offered by the individual shipping firm tends as a rule to be infinitely price elastic. In the meantime, the properties of the supply of the tramp shipping facilities are that it cannot expand or contract in the short run. Also, that in the long run there is a time-lag between entrepreneurs' decision to expand their fleets and the actual time of delivery of the new vessels. Thus, supply is inelastic and not capable of responding to demand and price changes at a given period of time. In conclusion, it can be safely stated that short-run changes in freight rates are a direct result of variations in the magnitude of demand for tramp shipping facilities, whilest the average level of freight rates is brought down to relatively low levels over prolonged periods of time.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.4
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• pp.214-226
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• 2013

To understand the changing patterns in phytoplankton communities, we conducted 12 surveys along the Nakdong River, its estuary, and adjacent coastal areas between January 2011 and October 2012 (during the period of barrage construction and sediment dredging). Monthly precipitation ranged from 0 to 502 mm during the survey period, and salinity ranged between 0.1 psu and 0.3 psu in the Nakdong River, regardless of the depth, indicating no seawater influence, while salinity showed large seasonal fluctuations in the estuarine and coastal station, ranging from 0.1 psu to 34.8 psu. A total of 402 phytoplankton species were identified, 178 species from the river and 331 species from the estuary and coastal areas. Phytoplankton standing crop increased in 2012 compared to that in 2011, and was found to be highest in the river, followed by the estuary and coastal areas. Among the top 20 species in frequency of occurrence and dominance, Stephanodiscus spp., Aulacoseira granulata, and Aulacoseira granulata var. angustissima and Pseudo-nitzschia spp. were important species along the river-estuary-coastal areas. Diatoms were the major taxonomic group inhabiting the Nakdong river-estuary-coastal areas. A comparison of seasonal dominant phytoplankton species revealed a slight decrease over the years, from 13 species in 2011 to 10 species in 2012. However, no significant difference was found in the diversity of phytoplankton species between the two survey years, although lightly greater diversity was observed in the coastal areas than in the river and estuary. Cluster analysis with community composition data revealed that the community structure varied significantly in 2011 depending on the time of survey, while in 2012, it hardly showed any variation and was simpler. An increase in the phytoplankton standing crop, fewer dominant species, and simpler community structure in 2012 compared to those in 2011 are probably due to the rapid environmental changes along the Nakdong River. To investigate these ecological relationships, it is necessary to conduct further studies focusing on integrated analyses of biocenosis, including phytoplankton with respect to the changes in nutrient distribution, variation of freshwater discharge, and effect area of freshwater in the Nakdong estuary and adjacent coastal areas.