• The Korean Journal of Financial Management
• /
• v.24 no.2
• /
• pp.41-79
• /
• 2007

This study examines the expiration-day effects of stock index futures and options in the Korean stock market. The so-called 'expiration-day effects', which are the abnormal stock price movements on derivatives expiration days, arise mainly from cash settlement. Index arbitragers have to bear the risk of their positions unless they liquidate their index stocks on the expiration day. If many arbitragers execute large buy or sell orders on the expiration day, abnormal trading volumes are likely to be observed. If a lot of arbitragers unwind positions in the same direction, temporary trading imbalances induce abnormal stock market volatility. By contrast, if some information arrives at market, the abnormal trading activity must be considered a normal process of price discovery. Stoll and Whaley(1987) investigated the aggregate price and volume effects of the S&P 500 index on the expiration day. In a related study, Stoll and Whaley(1990) found a similarity between the price behavior of stocks that are subject to program trading and of the stocks that are not. Thus far, there have been few studies about the expiration-day effects in the Korean stock market. While previous Korean studies use the KOSPI 200 index data, we analyze the price and trading volume behavior of individual stocks as well as the index. Analyzing individual stocks is important for two reasons. First, stock index is a market average. Consequently, it cannot reflect the behavior of many individual stocks. For example, if the expiration-day effects are mainly related to a specific group, it cannot be said that the expiration of derivatives itself destabilizes the stock market. Analyzing individual stocks enables us to investigate the scope of the expiration-day effects. Second, we can find the relationship between the firm characteristics and the expiration-day effects. For example, if the expiration-day effects exist in large stocks not belonging to the KOSPI 200 index, program trading may not be related to the expiration-day effects. The examination of individual stocks has led us to the cause of the expiration-day effects. Using the intraday data during the period May 3, 1996 through December 30, 2003, we first examine the price and volume effects of the KOSPI 200 and NON-KOSPI 200 index following the Stoll and Whaley(1987) methodology. We calculate the NON-KOSPI 200 index by using the returns and market capitalization of the KOSPI and KOSPI 200 index. In individual stocks, we divide KOSPI 200 stocks by size into three groups and match NON-KOSPI 200 stocks with KOSPI 200 stocks having the closest firm characteristics. We compare KOSPI 200 stocks with NON-KOSPI 200 stocks. To test whether the expiration-day effects are related to order imbalances or new information, we check price reversals on the next day. Finally, we perform a cross-sectional regression analysis to elaborate on the impact of the firm characteristics on price reversals. The main results seem to support the expiration-day effects, especially on stock index futures expiration days. The price behavior of stocks that are subject to program trading is shown to have price effects, abnormal return volatility, and large volumes during the last half hour of trading on the expiration day. Return reversals are also found in the KOSPI 200 index and stocks. However, there is no evidence of abnormal trading volume, or price reversals in the NON-KOSPI 200 index and stocks. The expiration-day effects are proportional to the size of stocks and the nearness to the settlement time. Since program trading is often said to be concentrated in high capitalization stocks, these results imply that the expiration-day effects seem to be associated with program trading and the settlement price determination procedure. In summary, the expiration-day effects in the Korean stock market do not exist in all stocks, but in large capitalization stocks belonging to the KOSPI 200 index. Additionally, the expiration-day effects in the Korean stock market are generally due, not to information, but to trading imbalances.

• Asia pacific journal of information systems
• /
• v.19 no.1
• /
• pp.1-31
• /
• 2009

This paper empirically examines factors that potentially influence the success of a Web-based semantic search engine. A research model has been proposed that shows the impact of quality-related factors upon the effectiveness of a semantic search engine, based on DeLone and McLean's(2003) information systems success model. An empirical study has been conducted to test hypotheses formulated around the research model, and statistical methods were applied to analyze gathered data and draw conclusions. Implications for academics and practitioners are offered based on the findings of the study. The proposed model includes three quality dimensions of a Web-based semantic search engine-namely, information quality, system quality and service quality. These three dimensions each have measures designed to collectively assess the respective dimension. The model is intended to examine the relationship between measures of these quality dimensions and measures of two dependent constructs, including individuals' net benefit and user satisfaction. Individuals' net benefit was measured by the extent to which the user's information needs were adequately met, whereas user satisfaction was measured by a combination of the perceived satisfaction with search results and the perceived satisfaction with the overall system. A total of 23 hypotheses have been formulated around the model, and a questionnaire survey has been conducted using a functional semantic search website created by KT and Hakia, so as to collect data to validate the model. Copies of a questionnaire form were handed out in person to 160 research associates and employees working in the area of designing and developing semantic search engines. Those who received the form, 148 respondents returned valid responses. The survey form asked respondents to use the given website to answer questions concerning the system. The results of the empirical study have indicated that, of the three quality dimensions, information quality was found to have the strongest association with the effectiveness of a Web-based semantic search engine. This finding is consistent with the observation in the literature that the aspects of the information quality should serve as a basis for evaluating the search outcomes from a semantic search engine. Measures under the information quality dimension that have a positive effect on informational gratification and user satisfaction were found to be recall and currency. Under the system quality dimension, response time and interactivity, were positively related to informational gratification. On the other hand, only one measure under the service quality dimension, reliability was found to have a positive relationship with user satisfaction. The results were based on the seven hypotheses that have been accepted. One may wonder why 15 out of the 23 hypotheses have been rejected and question the theoretical soundness of the model. However, the correlations between independent variables and dependent variables came out to be fairly high. This suggests that the structural equation model yielded results inconsistent with those of coefficient analysis, because the structural equation model intends to examine the relationship among independent variables as well as the relationship between independent variables and dependent variables. The findings offer some useful implications for owners of a semantic search engine, as far as the design and maintenance of the website is concerned. First, the system should be designed to respond to the user's query as fast as possible. Also it should be designed to support the search process by recommending, revising, and choosing a search query, so as to maximize users' interactions with the system. Second, the system should present search results with maximum recall and currency to effectively meet the users' expectations. Third, it should be capable of providing online services in a reliable and trustworthy manner. Finally, effective increase in user satisfaction requires the improvement of quality factors associated with a semantic search engine, which would in turn help increase the informational gratification for users. The proposed model can serve as a useful framework for measuring the success of a Web-based semantic search engine. Applying the search engine success framework to the measurement of search engine effectiveness has the potential to provide an outline of what areas of a semantic search engine needs improvement, in order to better meet information needs of users. Further research will be needed to make this idea a reality.

• Journal of Preventive Medicine and Public Health
• /
• v.29 no.2 s.53
• /
• pp.239-254
• /
• 1996

Health services on industrial noisy environment have been provided only for noise-induced hearing loss management until now. But gradually, modem diseases and death have come to be related to stress and mental health deeply, therefore noise-induced mental disorder, like a stress became very important. In this point, the purpose of this study was to analyze the relationship between noise exposure level in worksite and workers' stress symptoms. This study included a survey of 786 manual workers selected from 89 worksites in 21 factories in Puchon. The results were as follows: 1. For demographic characteristics, most of the workers were males(80.8%), the $20\sim29years$ old were 34.5% and those who graduated from high school were 65.3%. The workers whose monthly income ranged from 100,000 to 800,000 won were 37.5% and who have a religion were 47.9%. 2. For occupational characteristics, workers who had worked $1\sim5$ years in the factories were 33.0%. Those who were much for them workload were 43.9% and who worked more than 8 hours a day were 73.9%. Those who were disatisfied with their job and pay were 31.9% and 50.6%. The workers who responsed ventilation condition of their worksites were bad were 51.9% and the dissatisfed with working environment of their worksites were 45.9%. 3. Workers who were suffering from tinnitus were 53.3% and those who perceived hearing loss were 50.1%. Persons who reported they always wore earplugs at work were 35.4%. Those who felt earplugs bigger than their ears were 30.6% and those who experienced eardiseases caused by earplugs were 25.6%. 4. For the noise exposure level in worksite, workers who were exposed to $80\sim90dB$ were 30.3%, $90\sim100dB$ were 26.4% and $50\sim70dB$ were 19.2%. 5. Workers' stress symptoms were significantly related to marital status and their monthly income(p<0.05). Workers who were single and had lower monthly income showed higher PSI (Psychiatric Symptom Index) scores than those who were married and had higher monthly income. Higher PSI scores were also significantly related to $1\sim2$ days hight-work per week, much for them workload, dissatisfaction with their job, and bad relationship with their bosses and coworkers. 6. Higher PSI scores were significantly related to severe tinnitus and perceived hearing losso(p<0.001). Workers who felt the earplugs they use did not fit their ears showed significantly higher PSI scores(p<0.01). Workers who reported that they did not feel they need earplugs showed. significantly higher PSI scores (p<0.05). Increased experience of eardisease caused by earplugs that did not fit were also significantly related to higher PSI scores(p<0.01). 7. The higher noise exposure level in worksite from 80dB was, the more severe stress symptoms including PSI subparts were reported; Anxiety, Anger, Depression, and Cognitive disorder(p<0.001). 5. According to the results of stepwise multiple regression analysis, factors affecting workers' PSI scores were perceived hearing loss$(R^2=0.160)$, noise exposure level in worksite$(R^2=0.110)$, realtionship with coworkers, amount of workload, monthly income and relationship with bosses orderly and the total $R^2$ of this 6 factors was 0.371. 9. The most significant factors that have impact on manual workers' stress symptoms were perceived hearing loss and noise exposure level in worksite, especially noise exposure level in the worksite was the most affective factor on the depression symptom.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.23 no.3
• /
• pp.191-200
• /
• 2017

Proper packaging design can meet both the environmental and economic aspects of packaging materials by reducing the use of packaging materials, waste generation, material costs, and logistics costs. Finite element analysis(FEM) is used as a useful tool in various fields such as structural analysis, heat transfer, fluid motion, and electromagnetic field, but its application in the field of packaging is still insufficient. Therefore, the application of FEM to the field of packaging can save the cost and time in the future research because it is possible to design the package by computer simulation, and it is possible to reduce the packaging waste and logistics cost through proper packaging design. Therefore, this study investigated the FEM papers published in Korea for the purpose of helping research design using FEM program in the field of packaging in the future. In this paper, we analyzed the 29 papers that were directly related to the analysis of FEM papers published in domestic journals from 1991 to 2017. As a result, we analyzed the research topic, FEM program, and analysis method using each paper, and presented the direction that can be applied in future packaging field. When the FEM is applied to the packaging field, it is possible to change the structure and reduce the thickness through the stress and vibration analysis applied to the packaging material, thereby reducing the cost by improving the mechanical strength and reducing the amount of the packaging material. Therefore, in the field of packaging research in the future, if the FEM is performed together, economical and reasonable packaging design will be possible.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.17 no.1
• /
• pp.36-42
• /
• 2013

Purpose: Recently with CT developed, various studies for reduction of exposure dose is underway. Study of bismuth shields in these studies is actively underway, and has already been applied in the clinical. However, the application of the PET/CT examination was not activated. Therefore, through this study, depending on the application of bismuth shields in the PET/CT examination, we want to identify the quality of the image and the impact on the SUV. Materials and Methods: In this study, to apply to the shielding of the breast, by using the bismuth shields that contains 0.06 mmPb ingredients, was applied to the PET/CT GEMINI TF 64 (Philips Healthcare, Cleveland, USA). Phantom experiments using the NEMA IEC Body Phantom, images were acquired according to the presence or absence of bismuth shields apply. Also, When applying, images were obtained by varying the spacing 0, 1, 2 cm each image set to the interest range in the depth of the phantom by using EBW-NM ver.1.0. Results: When image of the PET Emission acquires, the SUV was in increased depending on the use of bismuth shields, difference in the depth to the surface from deep in the phantom increasingly SUV increased (P<0.005). Also, when using shields, as the more gab decreased, SUV is more increased (P<0.005). Conclusion: Through this study, PET/CT examination by using of bismuth shields which is used as purpose of reduction dose be considered. When using shields, the difference of SUV resulting from the application of bismuth shields exist and that difference is more decreased as gab of shields and surface is wider. Therefore, setting spacing of shield should be considered, if considering the reduction of the variation of SUV and image quality, disease of deep or other organs should be a priority rather than superficial disease. Through this study, when applying identified to clinical examination, the reduction of unnecessary exposure is considered.

• The Korean Journal of Food And Nutrition
• /
• v.16 no.3
• /
• pp.197-202
• /
• 2003

The purpose of this study was to investigate basic factors of obesity, nutrient intakes, behaviors of dietary life, daily energy expenditure and emphasize on the necessity of school education. Because the growing prevalence of obesity have required a need for health education in school. The results were as follows. 1. The average height of boys and girls was l59${\pm}$13cm(boys), l54${\pm}$11cm(girls). The average weight of them was 68${\pm}$16kg(boys), 70${\pm}$13kg(girls). BMI(body mass index) of them was 26.9${\pm}$3.4(boys), 29.5${\pm}$2.9(girls). 2. For energy and protein, the average intakes of subjects were higher than recommended dietary allowances for Koreans(7th Ed). The average intakes of vitamin A and ascorbic acid were much lower than the recommended dietary allowances. 3. Most of subjects prefer fast food, rich snacks and overeating, irregular meal amount and these dietary behaviors were severe problems. 4. Total energy expenditure was 1,933kcal in boys and 1,789kcal in girls. To reduce weight and treat obesity, the required energy intake to subjects was 1,546kcal(boys) and 1,431kcal(girls). If we prepared the effective program for obesity, school education should be integrated within the larger community. Parents of students and students may be educated to make good health changes in the home. Nutrition education has a direct impact on their life style of their food intake and nutritional status. The use of multi-component obesity treatments will be effective in a school setting. It is more effective to encourage health habits in school, house and it should be integrated within the larger community.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.9
• /
• pp.4517-4525
• /
• 2016

Background: Sperm DNA damage is underlying aetiology of poor implantation and pregnancy rates but also affects health of offspring and may also result in denovo mutations in germ line and post fertilization. This may result in complex diseases, polygenic disorders and childhood cancers. Childhood cancer like retinoblastoma (RB) is more prevalent in developing countries and the incidence of RB has increased more than three fold in India in the last decade. Recent studies have documented increased incidence of cancers in children born to fathers who consume alcohol in excess and tobacco or who were conceived by assisted conception. The aetiology of childhood cancer and increased disease burden in these children is lin ked to oxidative stress (OS) and oxidative DNA damage( ODD) in sperm of their fathers. Though several antioxidants are in use to combat oxidative stress, the effect of majority of these formulations on DNA is not known. Yoga and meditation cause significant decline in OS and ODD and aid in regulating OS levels such that reactive oxygen speues meditated signal transduction, gene expression and several other physiological functions are not disrupted. Thus, this study aimed to analyze sperm ODD as a possible etiological factor in childhood cancer and role of simple life style interventions like yoga and meditation in significantly decreasing seminal oxidative stress and oxidative DNA damage and thereby decreasing incidence of childhood cancers. Materials and Methods: A total of 131 fathers of children with RB (non-familial sporadic heritable) and 50 controls (fathers of healthy children) were recruited at a tertiary center in India. Sperm parameters as per WHO 2010 guidelines and reactive oxygen species (ROS), DNA fragmentation index (DFI), 8-hydroxy-2'-deoxy guanosine (8-OHdG) and telomere length were estimated at day 0, and after 3 and 6 months of intervention. We also examined the compliance with yoga and meditation practice and smoking status at each follow-up. Results: The seminal mean ROS levels (p<0.05), sperm DFI (p<0.001), 8-OHdG (p<0.01) levels were significantly higher in fathers of children with RB, as compared to controls and the relative mean telomere length in the sperm was shorter. Levels of ROS were significantly reduced in tobacco users (p<0.05) as well as in alcoholics (p<0.05) after intervention. DFI reduced significantly (p<0.05) after 6 months of yoga and meditation practice in all groups. The levels of oxidative DNA damage marker 8-OHdG were reduced significantly after 3 months (p<0.05) and 6 months (p<0.05) of practice. Conclusions: Our results suggest that OS and ODD DNA may contribute to the development of childhood cancer. This may be due to accumulation of oxidized mutagenic base 8OHdG, and elevated MDA levels which results in MDA dimers which are also mutagenic, aberrant methylation pattern, altered gene expression which affect cell proliferation and survival through activation of transcription factors. Increased mt DNA mutations and aberrant repair of mt and nuclear DNA due to highly truncatred DNA repair mechanisms all contribute to sperm genome hypermutability and persistant oxidative DNA damage. Oxidative stress is also associated with genome wide hypomethylation, telomere shortening and mitochondrial dysfunction leading to genome hypermutability and instability. To the best of our knowledge, this is the first study to report decline in OS and ODD and improvement in sperm DNA integrity following adoption of meditation and yoga based life style modification.This may reduce disease burden in next generation and reduce incidence of childhood cancers.

• Journal of dental hygiene science
• /
• v.11 no.5
• /
• pp.389-395
• /
• 2011

The purpose of this study was to examine dental hygiene students' achievement motivation and factors affecting dental hygiene students' achievement motivation by the general characteristics of subjects in this study. The subjects in this study were 450 who were selected by convenience sampling from three different three-year-course colleges. After a survey was conducted, the answer sheets from 421 respondents were analyzed. The collected data were analyzed, which made use of t-test, ANOVA and Kruscal-Wallis test. The findings of the study were as follows. 1. The dental hygiene students investigated got 3.34 in achievement motivation. They got the highest score of 3.78 in the item 'I perform what I have to do with a sense of responsibility.' and they got the lowest score of 2.67 in the item 'I like to do something risky.' 2. Concerning links between their general characteristics and achievement motivation, the students whose academic year was higher(p<0.001) and who had more clinical practice experiences (p<0.01) were better motivated than their counterparts. As to connections between achievement motivation and expected post-graduation length of service, those who replied that they planned to find another job after getting married were better motivated(p<0.05). Regarding relationship between achievement motivation and a will to work abroad, the students who had a stronger will to work abroad were better motivated. 3. As a result of checking the influence of their general characteristics on achievement motivation, stronger motivation was found among the students whose academic year was higher(p<0.01), who intended to work until marriage(p<0.01) and who didn't plan to keep working after marriage(p<0.05) when the other variables were controlled. Therefore dental hygiene students should be taught to look at things positively when they enter college, and they should also be educated to become progressive to keep working for their lifetime instead of just getting a temporary job after graduation.

• Journal of dental hygiene science
• /
• v.13 no.1
• /
• pp.36-44
• /
• 2013

The purpose of this study was to provide basic data for healthy and effective dental management by providing the knowledge and information on periodontal health promotion as well as high dental health interests, by doing a comparative analysis of the effect of dental health knowledge and oral hygiene management skills of people in their 20s on periodontal health status assessment, to find periodontal disease early and prevent it targeting 130 adults in their 20s who visited dental hygienic lab for comprehensive dental hygiene care and treatment from September 25 to October 30. The data collected used SPSS 18.0. To present the technical characteristics of the data, frequency was used and chi-squared test through cross-analysis was conducted to investigate dental health knowledge and the relevance between the variables of oral hygiene management skills of general characteristics. To examine periodontal health status assessment, t-test and One-way ANOVA and Turkey post-hoc tests were carried out at the 5% significance level. Regression analysis was performed to investigate the impact of dental health knowledge and oral hygiene management skills on dental health status assessment. As a result of this study, as dental health knowledge on tooth brushing of people in their 20s increased, plaque index reduced, as dental health knowledge on periodontal disease increased, plaque index reduced. Dental health status assessment according to a total number of times tooth brushing, tooth brushing methods, whether to use dental hygiene devices, smoking status, drinking frequency per week, whether to have oral health education was statistically significant. To improve the level of dental health knowledge and oral hygiene management skills, oral health education should be strengthened as well as the publicity through the media to have the information on oral health and learn it.

• Korean Journal of Environmental Agriculture
• /
• v.29 no.3
• /
• pp.227-231
• /
• 2010

Slurry composting biofiltration(SCB) is considered as a treatment to produce a better fertilizer resource than raw pig slurry as it reduces odor and improves nutrients imbalance. For the agricultural use of SCB slurry as a nutrient source with minimum environmental impact, it is important to investigate the effect of different rate of SCB slurry application on nutrient (particularly for nitrogen) uptake and growth of crops. This study was conducted to investigate the influence of fertigation using pig slurry(PS) on growth and yield of red pepper and to evaluate the appropriate PS concentration in fertigation for soils with different nitrate concentration. To evaluate the effects of fertigation applied PS as a substitute of chemical fertilizer(CF), a single application of three different concentrations of PS: $N_{0.5}$ (43 mg/L), $N_{1.0}$ (86 mg/L) and $N_{1.5}$ (131 mg/L) were compared with CF $N_{1.0}$ (89 mg/L) as a control nitrogen fertilizer. Statistical analysis showed that the growths of red pepper were not affected by treatments. In addition, the yields were no significant difference among treatments, though the highest yield was obtained in PS $N_{1.0}$ by 20,580 kg/ha. In soil chemical properties, nitrate nitrogen on soil of between PS N1.0 and CF $N_{1.0}$ treatment showed similar patterns although they were higher than the preplant nitrogen content. Also, there was no significant difference in yield of red pepper between PS and CF treatment applied as fertigation on soils where nitrate nitrogen contents of each soil contains 10, 100 and 200 mg/kg respectively. Consequently, the application of PS, such as SCB, as a substitute of CF is available for growth and yield of red pepper, there could be accordingly estimated the optimal fertigation concentration of PS for red pepper cultivation.