• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.1-8
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• 2024

For measuring the performance of passive sonars, we usually consider the maximum Detection Range (DR) under the environment and system parameters in operation. In shallow water, where sound waves inevitably interacts with sea surface or bottom, detection generally maintains up to the maximum range. In deep water, however, sound waves may not interact with sea surface or/and bottom, and thus there may exist shadow zones where sound waves can hardly reach. In this situation, DR alone may not completely define the performance of each sonar. For complete description of sonar performance, we employ the concept 'Robustness Of Detection (ROD)'. In the coastal region of the East Sea, the spatial variations of water masses have close relations with DR and ROD, where the two parameters show reverse spatial variations in general. The spatial and temporal analysis of the temperature by employing the Empirical Orthogonal Function (EOF) shows that the 1-st mode represents typical pattern of seasonal variation and the 2-nd mode represents strength variations of mixed layers and currents. The two modes are estimated to explain about 92 % of the variations. Assuming two types of targets located at the depths of 5 m (shallow) and 100 m (deep), the passive sonar performance (DR) gives high negative correlations (about -0.9) with the first two modes. Most of temporal variations of temperature occur from the surface up to 200 m in the water column so that when we assume a target at 100 m, we can expect detection performance of little seasonal variations with passive sonars below 100 m.

• Journal of Korea Water Resources Association
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• v.57 no.2
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• pp.111-125
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• 2024

The study has examined alterations in groundwater quality by investigating the influence of rainfall on electrical conductivity (EC) and nitrate concentration in the groundwater of the Geum River Basin in South Korea. Mann Kendall and Sen's Slope estimator were employed to analyze the trends and estimate the trend's magnitude. The administrative map of the study area was utilized to assess the trends of these parameters within each administrative region. Seventeen years (from 2005 to 2021) of data on EC, groundwater levels (GWL), precipitation, and six years (from 2015 to 2020) of nitrate concentration data were utilized for this analysis. The results indicate that, in most administrative regions, there has been an increase in nitrate concentration, and EC, whereas precipitation has seen a slight decrease in a downstream and an increasing trend in upstream. The correlation coefficients calculated between these parameters reveal that there is no direct impact of precipitation on nitrate and EC, but a negative correlation was observed between GWL and EC. The most significant increasing trend in nitrate concentration was observed in two districts (Iksan and Gunsan ), which correspond to regions with significant agricultural activity; about 50% of these districts area are used for agricultural activities.

• Korean Journal of Environmental Biology
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• v.42 no.1
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• pp.15-27
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• 2024

The goal of this study was to provide basic data necessary for managing fish in the Seomgang River by confirming diversity of fish species in the Seomgang River and determining the degree of change in fish species through a comparison with earlier related work. Growth rate, obesity level, and temporal and spatial reproductive capacities were analyzed to determine growth characteristics of dominant species. Fish fauna and structure of the fish community were surveyed at three different time points from October of 2020 to August of 2021 at eight sites. In addition, growth characteristics of Zacco platypus from June of 2021 to July of 2022 at four sites were determined. A total of 3,999 individuals, 43 species, and ten families of fish were identified. Among these species, 19 (44.19%) were Korean endemic species and four (9.30%) were endangered species. The dominant species was Z. platypus. Pungtungia herzi was identified as a subdominant species. An analysis of length-weight relationships and condition factor (k) of Z. platypus confirmed a good state of growth. As a result of a frequency analysis of the total length, the life cycle of the Z. platypus population living in the Seomgang River was found to be stable. According to gonadosomatic index (GSI) analysis, the spawning season of Z. platypus was estimated to occur after May, consistent with the literature.

• Journal of the Health Care and Life Science
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• v.10 no.2
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• pp.253-258
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• 2022

It is a widely known fact that MAC addresses can be collected using Wi-Fi from mobile phones that people carry. However, since collecting and using MAC addresses without individual consent entails many legal problems, it was difficult to actively utilize them. In order to prevent invasion of privacy information due to unintentional exposure of these MAC addresses in recent years, the method of protecting privacy information by exposing a randomly generated virtual MAC address rather than the MAC address of the actual device is applied to all mobile devices. is becoming By exposing a randomly generated virtual MAC address on a device, it becomes impossible to identify and track an individual using the MAC address. However, the fact that various facts can be estimated through MAC Address collection is still valid. By expanding the application of Random MAC Address, the possibility of invasion of privacy information has been completely removed from the MAC address that has been raised in the past, so that it can be used more actively than in the past. In this paper, we propose a method for automatically collecting and analyzing statistical information of hospital visitors using MAC addresses. The collection of hospital visitors using MAC Address is a low cost and relatively accurate method, and the analysis of hospital visitors through steady collection can provide very objective and scientific evidence for hospital operation.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.459-465
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• 2012

This study was conducted to obtain investigated characteristic factors which has an influence on nitrous oxide ($N_2O$) emissions related to the environment change of nitrogen application level, rainfall and temperature. It was done by the carrot cultivation at black volcanic ashes soil in the experimental field of Jeju Special Self-governing Province Agricultural Research and Extension Services from 2010 to 2011. During the carrot cultivation period, the more amount of nitrogen fertilizer applied, the more amount of $N_2O$ emissions were released. Generally $N_2O$ emissions were so deeply released to climate as that in the first and middle of cultivation with heavy rainfall released amount is high, otherwise it was released very low at the end of cultivation and drought season. $N_2O$ emissions type was considered to relate with the rainfall pattern and soil water content. We obtained the result correlated with $N_2O$ emissions, in 2010, as the soil water and soil temperature were significant to $0.5718^{**}$ ($r$) and $0.4908^{**}$ ($r$) respectively, but soil EC was not significant to 0.2704 ($r$). In 2011, soil water was significant to $0.3394^*$ ($r$), but soil temperature and soil EC were not significant to 0.2138 ($r$) and 0.2462 ($r$) respectively. Also, $NO_3$-N and soil nitrogen ($NO_3-N+NH_4-N$) were not significant to 0.0575 ($r$) and 0.0787 ($r$) respectively. During the carrot cultivation period, the average emissions factor released by the nitrogen fertilizer application for 2 years was presumed to be 0.0025 $N_2O$-N kg / N kg. This factor was 4 times than the IPCC (0.0100 $N_2O$-N kg / N kg) factor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.583-595
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• 2014

Currently, Korean transportation policies are aiming for increase of safety and environment-friendly and efficient operation, by avoiding construction and expansion of roads, and upgrading road alignments and facilities. This is revealed by that there have been 22 road expansion projects (30%) and 50 road improvement projects (70%) under the 3rd Five-Year Plan for National Highways ('11~'15), while there were 53 road expansion projects (71%) and 22 road improvement projects (29%) under the 2nd Five-Year Plan for National Highways. For more effective road improvement projects, there is a need of choosing projects after an objective and scientific safety assessment of each road, and assessing safety improvement depending on projects. This study is intended to develop a model for this road safety analysis and assessment. The major objective of this study is creating a road safety analysis and assessment model appropriate for Korean society, based on the HSM (Highway Safety Manual) of the U.S. In order to build up data for model development, the sections thought to have identical geometrical structure factors in 5 lines, Cheonbuk province, were divided as homogeneous sections, and representative values of geometric structures, facilities, traffic volume, climate conditions and land usage were collected from the 1,452 sections divided. In order to build up data for model development, the sections thought to have identical geometrical structure factors in 5 lines, Cheonbuk province, were divided as homogeneous sections, and representative values of geometric structures, facilities, traffic volume, climate conditions and land usage were collected from the 1,452 sections divided. The collected data was processed correlation analysis of each road element was implemented to see which factor had a big effect on traffic accidents. On the basis of these results, then, an accident model was established as a negative binomial regression model.Using the developed model, an Crash Modification Factor (CMF) which determines accident frequency changes depending on safety performance function (SPF) predicting the number of accident occurrence through traffic volume and road section expansion, road geometric structure and traffic properties, was extracted.

• Korean Journal of Weed Science
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• v.2 no.1
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• pp.20-30
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• 1982

A field experiment was conducted in 1981 at the Crop Experiment Station, Suweon, Korea, in machine transplanted paddy rice field, to study the effectiveness of single herbicide, mixture, and systematic application of herbicides on diversity of weed control spectrum. The rice variety planted was Taebaegbyeo, Indica ${\times}$ Japonica cross bred. Experimental field was dominated by Echinochtoa crusgalli, Eleocharis kuroguwai, and Scirpus hotarui, and importance values based on dry weight of these weeds were 89%, 5%, and 3%, respectively. The mixture or systematic treatments of herbicide were generally more effective than single herbicide applications on weed control. Coefficients of similarity based on floristic composition after herbicide application between Perfluidone (5G) and Chloromethoxynil (7G), and between Pertluidone (5G) and Bifenox (7G), and between Perfluidone (5G) and three types of Butachlor (6G) were low, and these sets seemed to be a good mixture herbicide in paddy fields. While, Perfluidone (5G) had low coefficient of similarity with other single herbicides tested. The information on coefficient of similarity could be used as parameter for selecting herbicides to increase the efficiency of herbicidal performance. Simpson's indices from Butachlor (3.5G)/SL-49 (7G), Butachlor (3.5G)/Pyrazolate (6G), and Perfluidone (5G) treatments were high, and these herbicide treatments tended to the weed community type simplified, while the indices from Perfluidone (5G) + Chloromethoxynil (7G), Butachlor (6G) fb Perftuidone (5G), and Butachlor (4G)/Naproanilide (6G) treatments were low, and these herbicide treatments caused to the community type diversified in terms of floristic composition.

• The Korean Journal of Mycology
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• v.29 no.1
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• pp.15-21
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• 2001

This study was conducted to investigate the immunomodulatory activities of proteoglycan extracted from cultured mycelia of Ganoderma lucidum IY009. The proteoglycan contained two polymer peaks, one was the higher MW peak of 2,000 kD and the other was low peaks of 12kD. To understand the part of strong pharmaceutical activity between two peak, the proteoglycan was separated by ultrafiltration and column chromatography and then examined the various pharmaceutical effects. High molecular weight fraction possesing high content of ${\beta}-linked$ glucan was exhibited high antitumor activity, against sarcoma 180 bearing ICR mouse. And also, anticomplementary activity was highly observed in high molecule fraction than low it fraction. When the raw 264.7 and murine peritoneal macrophage treated with low fraction, high fraction and other stimuli. The activities inducing tumor necrosis factor of the high factions were $2.2{\sim}2.5$ times stronger than that of low fraction.

• The Korean Journal of Financial Management
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• v.23 no.2
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• pp.109-141
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• 2006

The central factor in the pecking order theory of financial structure is the asymmetric distribution of information between managers and less-informed outside investors. Myers and Majluf (1984) show that this asymmetry leads managers to prefer internal funds to external funds. Funds are raised through equity issues only after the capacity to issue debt has been exhausted. In contrast, according to static tradeoff theory, an optimum financial structure exists by the tradeoff between tax saving by debt and bankruptcy costs. This study examines the recent changes of Korean firms' financial structure and financing behavior and the determinants of financial structure. The sample of firms comes from the period of $1996{\sim}2004$, and the number of firms is 32,003. The major findings are as follows. First, in contrast with previous studies using US firms as sample, Korean firms have been using debt financing as their major financing instrument. Especially, the firms in the fund deficit situation relies much more on $long{\sim}term$ and $short{\sim}term$ debts rather than on equity issues. Second, as is the case with previous studies using US firms sample indicates, the financing deficit variable can not explain perfectly the net debt issue. However, compared with net equity issue variable, net debt issue variable is more closely related to the financing deficit variable. Third, when financing deficit variable is added to the current list of explanatory variables of financial structure determinants model, it has a significant and positive explanatory power. In addition, the coefficients of determinants are much improved. Thus, it is concluded that although pecking order theory is not perfect, it appears to be more useful compared to static tradeoff theory, at least in explaining the recent financing behavior of Korean manufacturing firms.

• The Korean Journal of Pesticide Science
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• v.6 no.1
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• pp.16-24
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• 2002

Research trends in the measurement of foliar uptake of pesticides and the recently proposed action mechanism of the surfactant-induced uptake of pesticides were reviewed with the related reports and studies. Major techniques used in those fields are bioassay, radiotracer techniques with leaves or cuticular membrane. Recently, a new method using Congo Red as a tracer was proposed. The limiting factor in the pesticides uptake into leaves is the waxy layer which consists of the epicuticular and cuticular wax. Physico-chemical parameters such as molar volume, water solubility and partition coefficient of pesticides have limited influences on the pesticide uptake into leaves. Polydisperse ethoxylated fatty alcohol surfactants are well known as the good activator for many pesticides. It is now generally agreed that uptake activation is not related to the intrinsic surface active properties of surfactants such as surface activity, solvent property, humectancy and critical micelle concentration. Recent studies using ESR-spectroscopy revealed that the surfactants have an unspecific plasticising effect on the molecular structure of the wax and cuticular matrix, leading to increased mobilities of pesticides. Penetration of surfactants into waxy layer altered the pesticide mobility in wax and the partition coefficient of pesticide, and then the pesticides penetration into leaves was enhanced temporally. The enhancing effect of surfactant could be significantly different depending on the carbon number of aliphatic moiety and the number of ethoxy group in polyoxyethylene chain of surfactants. It is suggested that the rate of penetration of surfactants should have a significant relationship with the rate of penetration of pesticides.