• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.679-687
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• 2017

This study examines financial factors affecting cash holdings of firms in the domestic capital markets. Specifically, this study focuses on regional firms with headquarters in Chungcheong province, the Republic of Korea, which features little previous research concentrating on the firms in the particular region. Three primary hypotheses were empirically tested utilizing robust econometric models, including static panel data, Tobit regression, and logistic models.Results reveal only five explanatory variables, including DSO, LIQUID, LEVERAGE, PMARGIN, and SIZE, showed statistically significant effects on the level of cash holdings among the nine variables studied. In addition two IDVs, LEVERAGE and FOS, showed significant differentiated effects between firms with headquarters in North and South Chungcheong regions. With continued debate among interested parties on the optimal level of cash reserves, the study provides a new vision for the optimal cash reserves for firms with headquarters in Chungcheong Province, where unprecedented socio-economic factors are driven.

• Journal of Elementary Mathematics Education in Korea
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• v.20 no.1
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• pp.71-104
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• 2016

The aim of this study is to look into the didactical background for teaching percent in elementary school mathematics and offer suggestions to improve teaching percent in the future. In order to attain these purposes, this study examined key ideas with respect to the didactical background on teaching percent through a theoretical consideration regarding various studies on percent. Based on such examination, this study compared and analyzed textbooks used in the United States, the United Kingdom, and South Korea. In the light of such theoretical consideration and analytical results, this study provided suggestions for improving teaching percent in elementary schools in Korea as follows: giving much weight on percent, emphasizing the concept of percent as a ratio, underlining the various kinds of change problems, emphasizing informal strategies of students before teaching the percent formula, and utilizing various models actively.

• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.439-449
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• 2005

Distributed main memory database management systems (DMM-DBMSs) store the database in main memories of the participating sites. They provide high performance through fast access to the local databases and high speed communication among the sites. Recently, a lot of research results on DMM- DBMSs has been reported. However, to the best of our knowledge, there is no known research result on the performance of the catalog management schemes for DMM-DBMSs. In this work, we evaluated the performance of the partitioned catalog management schemes through experimental analysis. First, we classified the partitioned catalog management schemes into three categories : Partitioned Catalogs Without Caching (PCWC), Partitioned Catalogs With Incremental Caching (PCWIC), and Partitioned Catalogs With Full Caching (PCWFC). Experiments were conducted by varying the number of sites, the number of terminals per site, buffer size, write query ratio, and local query ratio. Experiments show that PCWFC outperforms the other two schemes in all cases. It also means that the performance of PCWIC gradually increases as time goes by. It should be noted that PCWFC does not guarantee high performance for disk-based distributed DBMSs in cases when the workload of individual site is high, catalog write ratio is high, or remote data objects are accessed very frequently. Main reason that PCWFC outperforms for DMM-DBMSs is that query compilation and remote catalog access can be done in a very high speed, even when the catalogs of the remote data objects are frequently updated.

• Journal of The Geomorphological Association of Korea
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• v.15 no.2
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• pp.55-65
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• 2008

In order to examine the runoff characteristics of scoria cones in Jeju Island, hydrological observations were conducted in the experimental basin (5.1 ha) of Eoseungsaeng-oreum which has been predominantly covered with Carpinus laxiflora and Quercus serrata. Although runoff has continuously occurred during the observed period, the baseflow gradually increased from April and decreased from October. The peak flow approximately corresponded to every rainfall events except for the rainfall events which has slight total precipitation and no previous precipitation. The experimental basin shows flash runoff response and short lag time; the mean lag time is 35.8 minutes. Although the runoff ratio of quick flow is proportional to total precipitation, the increasing rate is low and the maximum runoff ratio is 24.7%. In addition, the runoff ratio is less than 1% in 68.3% of the rainfall events, suggesting that the portion of quick flow to total precipitation is low. The rainfall events with relatively long event time demonstrated a secondary peak generated by translatory flow. The runoff characteristics seem to be related to local impermeable beds in the experimental basin.

• Journal of the Korea Society of Computer and Information
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• v.26 no.8
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• pp.139-147
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• 2021

In this study, we proposed the possibility of reliability analysis of risk index by using Monte Carlo simulation as basic data of safety accident occurrence data and expert opinion by construction industry type. Through this, it is expected that risk index for safety accidents according to detailed types of works will be presented stochastically and it will be possible to predict the risk factors and the expected range of damage based on the reliability analysis in the construction safety management plan. It will also reduce many of the planning risks that are common to decision makers in the field of construction management. In identifying risks, road bridge construction was classified into earthworks, drainage works, and bridge construction, and possible safety accidents were classified based on expert data. The risk index was calculated for each detailed construction of road and bridge construction, drainage construction, and bridge construction.

• Journal of Embryo Transfer
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• v.19 no.3
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• pp.283-289
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• 2004

This study was conducted to determine the effects of incubation time after cooling on mouse meiotic spindle and chromosome alignment and the optimal incubation time for their restoration. Oocytes at the metaphase II were obtained from superovulated mice. Control oocytes were held at 37$^{\circ}C$ during the experiment. Oocytes were rapidly cooled to $0^{\circ}C$, held for 30 minutes, warmed and incubated at 37$^{\circ}C$ for 5, 15, 30, 60 and 120 minutes, respectively. The morphological features of spindle and chromosomes in oocytes were evaluated by immunofluorescent staining. Meiotic spindle of control oocytes exhibited a normal-looking bipolar configuration(barrel-shaped) and highly fluorescent microtubles. The chromosomes were clustered in a discrete bundles at metaphase plate. Disassembly of meiotic spindle and chromosome dispersion were occurred immediately after chilling of oocyte. Fluorescence intensity index(FIS), normal chromosomes aligned and normal spindle configuration were compared according to incubation time at 37$^{\circ}C$. Restoration of a barrel-shaped spindle and normal chromosome alignment was occurring after 5 minutes incubation at 37$^{\circ}C$, improved as a incubation time increased, and decreased gradually after 120 minutes incubation(P<0.05). The optimal incubation time for restoration of meiotic spindle and chromosomes in cooled oocytes was 60 minutes.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.49-56
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• 2010

Developments of radioprotective agents are important issues for minimizing the troubles and the effective treatments in radiotherapy. But few agents are useful in clinical and practical fields. It was shown that trace elements in alcohol beverages might have radioprotective effect. In this study, the types of cell death of lymphocytes according to the commercial alcohol beverage was investigated. Normal healthy volunteers ingested distilled water, beer or soju containing $81.5mg{\cdot}dl^{-1}$ ethyl ahcohol, respectively. After 2 hours, their blood were sampled with their consents. Fraction of lymphocytes was isolated by density gradient method with Histopaque-1077 (Sigma) and irradiated with dose from 0.5 to 5 Gy. After 60 hour incubation, the cells were harvested and analysed by flow cytometry. Cell viability was decreased by dose dependent manner. Cell viability of beer group was reduced about 15% compared with control group. Apoptosis in soju group was reduced about 20% compared with control group. Apoptosis of beer and control groups are similar. Necrosis of soju group significantly increased about 35% compared with control group. Early apoptosis of beer group was increased compared with control group. Early apoptosis of soju group was decreased about 25% compared with control group. Late apoptosis of beer and control group was increased by dose dependent manner. Late apoptosis of soju group was increased about 20-30% compared with control group. Late apoptosis of soju was increased and the radioprotective effect of soju was minimal because late apoptosis induced the cell necrosis. In case of soju trace elements, total cell apoptosis was decreased about 20% and early cell apoptosis was remarkably low. In this case, mitotic cells death may be dominant mechanism. Therefore, trace elements in soju may not be effective radioprotective agents.

• Korean Journal of Poultry Science
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• v.32 no.2
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• pp.125-133
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• 2005

Morphometric changes in testicular Sertoli and Leydig cells from hatching to adulthood were studied using Korean native chickens of 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 21, 24, 28, 32, 44, 52 and 64 weeks (n=13 chickens per group) of age. The objective of this study was to understand the developmental phase of the Sertoli and Leydig cells with age. Testis of chickens was fixed by whole body perfusion using a fixative containing $2.5\%$ glutaraldehyde in cacodylate buffer, processed and embedded in Epon-araldite. Using 1 Um sections stained with methylene blue-azure II, qualitative and quantitative (stereological) morphological studies were performed. The average volume of a testis of 1 week old Korean native chickens was determined as $0.148\;cm^3$ and the parameter increased linearly from 1 week to 21 weeks days $(28.86\;cm^3)$, and did not change from 21 weeks to 64 weeks. The volume density of the seminiferous tubules increased with age from $32.6\%$ at week 1 to $92.89\%$ at week 64. The volume density of the interstitium represents $67.4\%$ of the testicular parenchyma at week 1. This proportion progressively diminished during development to reach a value of $7.11\%$ at week 64. The volume density of the Leydig cells decreased almost linearly from 1 week $(4.9\%)$ to 14 weeks $(1.7\%)$ and remained unchanged thereafter. In contrast, the Sertoli cells occupied a volume density of $3.4\%$ at week 1, increased progressively up to 18 weeks of age $(10.79\%)$ and remained unchanged thereafter. The absolute volume of the Leydig and Sertoli cells per testis increased significantly from week 1 to week 21 but did not change significantly from week 24 to week 64. The number of Leydig cells per testis increased almost linearly from 1 week to 21 weeks, remained high and unchanged with advancing age. The number of Sertoli cells per testis increased gradually with age from 1 week to 14 weeks and remained unchanged thereafter.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.285-294
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• 2021

This study analyzes the factors that determine the attitude toward the electronic wristband(smartband) to check the position of self-quarantine subjects due to COVID-19. Furthermore, I analyze the interaction of class and age among the factors that determine attitudes toward the electronic wristband. In this study, the attitude toward self-quarantine electronic wristband is analyzed as a binary logit model, focusing on class and age. As a result of the analysis, the middle class significantly agreed with the self-quarantine electronic wristband compared to the lower class, and the older the person, the more in favor. On the other hand, the interaction between the class and the age shows that the age weakens the positive effect on the attitude of the self-quarantine electronic wristband in the middle and upper middle classes. The implication of this study is that it is necessary to push for mandatory electronic wristband in areas with high proportion of high-aged people with positive attitude toward self-quarantine electronic wristband and in the same age group, the approval rate is low, so it is necessary to promote mandatory electronic wristband in areas where the vulnerable class is dense.

• Korean Journal of Environment and Ecology
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• v.30 no.6
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• pp.1022-1031
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• 2016

Relationships of standing biomass with biodiversity and structural diversity were examined in the Quercus mongolica-dominated forest in Mt. Jeombong, Gangwon-do. We examined the standing biomass of the Q. mongolia community ($311.1ton{\cdot}ha^{-1}$) from 2004 to 2013, and the observed major species were Q. mongoilca, Carpinus cordata, Tilia amurensis whose standing biomasses were $206.3ton{\cdot}ha^{-1}$ (66.3%), $36.9ton{\cdot}ha^{-1}$ (11.9%), and $30.6ton{\cdot}ha^{-1}$ (9.8%), respectively. Although the number of Q. mongolica individuals was very small compared with total density, the reason that Q. mongolica showed the most biomass than other species is due to greater average diameter at breast height (DBH) and the higher number of $DBH{\geq}50cm$ individuals. We calculated the range of Shannon index (H') and Shannon evenness (J') in the Q. mongolica community, and they were gradually increased in time, showing 2.015~2.166, 0.673~0.736, respectively. Their H' and J' showed positive linear relationships with their standing biomass. This indicates that the spatial distribution of the standing biomass in Q. mongoilca community becomes more homogeneous with time and this homogenization appears in various species in the community. In addition, we estimated biomass-species index (BS) and abundance-biomass-speciesdiversity (ABS) and they also showed gradual increase in time, ranging from 3.746 to 3.811 and from 4.781 to 5.028, respectively. Their indices showed positive linear relationships with the standing biomass. This can be explained from the observations of variations in standing biomass with tree diameters as the differences in the average standing biomass in the community have reduced gradually in time. Moreover, it is expected that increase in the structure diversity of the Q. mongoilca community enhances the efficiency in carbon sequestration and productivity, so the community can be developed to a more sustainable ecosystem with more abundant resources. Thus, applications of uneven-aged plantations with considerations of local ecological properties can be a very efficient reforestation method to ensure stable support of biodiversity and productivity.