• Journal of the Korean Institute of Landscape Architecture
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• v.47 no.6
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• pp.12-23
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• 2019

The purpose of this study was to develop and study an experiential natural education program that could emphasize the importance of the natural environment by providing natural experience opportunities using the natural resources of the urban forest parks using Youngheung Park in Suwon, Gyeonggi Province as a target site. The research target was limited to Suwon Yeongheung Park, which had the potential to become a place for education, where urban forest conservation and sustainable use already coexist. The natural education resources derived by surveying and analyzing the basic environment and the ecology of plants and animals in Suwon Yeongheung Park were organized to establish program goals, directions, and themes. Suwon Yeongheung Park is a water-rich forest that forms an ecological system of wetlands, including rice paddies, muknon wetlands, and dungbun, near a valley area. The U-shaped walkway was smoothly formed along the ridge and includes Doran-gil, which is among the Palochrome Road, designated by the city of Suwon. The soil is acidic, with a pH 4.40, due to urban pollution and acid rain, and is not good for plant growth. Most of the artificial forests, natural forests, and arable land were found using land use and extant life surveys. Old trees were distributed in artificial forests, the oak clusters in natural forests, and the fields and darrinones were distributed in the arable areas. As the forest vegetation declined, the cedar forest was underway, and the cedar trees and red bean pear trees were cultivated due to their adaptability to the urban environment. There are 13 large of 180 sacks, one being 109 centimeters in diameter, the largest silvery tree, and 105 oak trees, provide food and shelter for animals. Six species of waterfowl that used the 22 kinds of forest wetlands, while four species of amphibians and two species of reptiles reside in the wetlands. Natural Monument No. 327, Mauryuk, Class II Endangered Wildlife, was also observed in the wetlands. Eight other species of surface dragonflies and three species of butterflies were observed. By systemizing the resources, members, and characteristics of the forest ecosystems in Suwon Yeongheung Park based on five criteria, the program for a hands-on natural education was presented with the aim of understanding the urban forest ecosystem in Suwon Yeongheung Park, having an affinity with the city, and recognizing its relationship with the community and society. However, further research is needed as there are limitations of research on programs characterized by different ages and classes.

• KDI Journal of Economic Policy
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• v.32 no.1
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• pp.131-169
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• 2010

I develop a matching model in which risk-averse workers face borrowing constraints and make a labor force participation decision as well as a job search decision. A sharp distinction between unemployment and out of the labor force is made: those who look for work for a certain period but find no job are classified as the unemployed and those who do not look for work are classified as those out of the labor force. In the model, the job search decision consists of two steps. First, each individual who is not working obtains information about employment opportunities. Second, each individual who decides to search has to take costly actions to find a job. Since individuals differ with respect to asset holdings, they have different reservation job-finding probabilities at which an individual is indifferent between searching and not searching. Individuals, who have large asset holdings and thereby are less likely to participate in the labor market, have high reservation job-finding probability, and they are less likely to search if they have less quality of information. In other words, if individuals with large asset holdings search for job, they must have very high quality of information and face very high actual job-finding probability. On the other hand, individuals with small asset holdings have low reservation job-finding probability and they are likely to search for less quality of information. They face very low actual job-finding probability and seem to remain unemployed for a long time. Therefore, differences in the quality of information explain heterogeneous job search decisions among individuals as well as higher job finding probability for those who reenter the labor market than for those who remain in the labor force. The effect of the extended maximum duration of unemployment insurance benefits on the aggregate labor market and the labor market flows is investigated. The benchmark benefit duration is set to three months. As maximum benefit duration is extended up to six months, the employment-population ratio decreases while the unemployment rate increases because individuals who are eligible for benefits have strong incentives to remain unemployed and decide to search even if they obtain less quality of information, which leads to low job-finding probability and then high unemployment rate. Then, the vacancy-unemployment ratio decreases and, in turn, the job-finding probability for both the unemployed and those out of the labor force decrease. Finally, the outflow from nonparticipation decreases with benefit duration because the equilibrium job-finding probability decreases. As the job-finding probability decreases, those who are out of the labor force are less likely to search for the same quality of information. I also consider the matching model with two states of employment and unemployment. Compared to the results of the two-state model, the simulated effects of changes in benefit duration on the aggregate labor market and the labor market flows are quite large and significant.

• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.200-206
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• 2016

The 7-week feeding experiment was conducted to investigate the effects of one experimental diet (ED) and five different commercial diets (CDs) on growth and body composition of juvenile olive flounder, Paralichthys olivaceus. An ED was formulated to contain 50.0% crude protein (CP) from fishmeal, casein, zein and wheat flour and 15.0% crude lipid (CL) from squid liver oil. Five CDs for seawater fish were two domestic E commercial diet (DECD) and C commercial diet (DCCD), three imported H commercial diet (IHCD), M commercial diet (IMCD) and O commercial diet (IOCD) containing 53.1~58.0% CP and 4.8~12.7% CL, respectively. Each diet was fed to triplicate groups of juvenile olive flounder initially weighing $29.1{\pm}0.8g/fish\;(mean{\pm}SD)$ in a flow-through seawater system with a water temperature of $23.4{\sim}28.0^{\circ}C$. Weight gain (WG) was significantly greatest in fish fed the IMCD; intermediate responses were observed for fish fed the DECD, DCCD, and IOCD, while the IHCD and the ED produced the lowest WG values. Feed efficiencies (FE) were similar to WG excluding fish fed the DCCD; FE was also greatest in fish fed the DCCD. Survival with no significant difference approached 100% for fish fed the all six diets in this experiment. Whole-body crude protein and ash contents were not affected excluding moisture and crude lipid by the different type of diets. Therefore, type of diets appeared to be important factor in influencing WG, FE and whole-body moisture and crude lipid of juvenile olive flounder; the best diet for juvenile olive flounder was determined to be the imported commercial M diets containing intermediate protein (55.9%) and lipid (12.7%) in natural seawater based on highest WG, and FE, respectively. This study indicates that the one commercially formulated diet containing intermediate protein and lipid used in this experiment could be a practical diet for juvenile olive flounder; these differences in growth performance between ED and CDs may be due to different dietary protein and lipid levels.

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

• Journal of The Korean Association For Science Education
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• v.19 no.2
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• pp.185-193
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• 1999

The long term trend of studensts' science achievement is a very important factor to check the effectiveness of science educational policy. However, up to date no such effort to understand the trend of Korean students' science achievement has been put into action. Recently, the Science Education Center in Korea National University of Education has been attempted to collect nation wide data for students' science achievement. The first part of the effort was to develop item pools. This study was the second part to collect nation wide data and to check any change during the two year time interval. In this study, the item pools developed by Kwon et. al.(1998) were used with some modification. The data were collected two times; February 1997 and March 1999. The subjects collected nationally were 8,766 students in 1997 and were 4,398 in 1999. The subjects were collected randomly but stratified by region and sex. As the results, the trends of achievement change during the two years were different from elementary to high school. The achievement scores were decreased in elementary schools and increased in high school. In case of middle schools, the change was not significant. However, even in elementary schools the knowledge on theory was increased significantly while knowledge on facts and principles were decreased. In contrast, the knowledge on fact showed the most increase in high schools. In this study, the data were analysed in light of region, sex, behavioral objective levels(ability) and context of test items. The science achievement monitoring system developed by the Science Education Center in Korea National University of Education can be an effective tool for monitoring students' achievement on the national level.

• Journal of The Korean Association For Science Education
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• v.18 no.1
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• pp.61-70
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• 1998

This study investigated the effects of grouping (group composition) in cooperative learning strategy upon students' achievement, the attitude toward science instruction, the perception of learning environment, and the self-esteem. Three different groups were used in this study. For the two treatment groups with cooperative learning strategies, High-Medium-Low ability grouping (HML) and High-Low I Medium-Medium ability grouping (HL/MM) were used. For the control group, traditional instruction was used. Before the instructions, the short-version Group Assessment of Logical Thinking, the test of attitudes toward science instruction, the perception questionnaire of learning environment, and the questionnaire of self-esteem were administered, and their scores were used as covariates. Mid-term examination score was used as a blocking variable. After the instructions, a researcher-made achievement test consisting of three subtests (knowledge, understanding, and application), the test of attitude toward science instruction, the perception questionnaire of learning environment, and the questionnaire of self-esteem were administered. The ANCOVA results revealed that there were significant interactions between the instruction and the level of prior achievement although there were no significant differences in all subtest scores of the achievement test. The high-level students in the HL/MM cooperative group performed better than those in the control group and the HML cooperative group. The low-level students in the HL/MM cooperative group also performed better in the subtest of knowledge than those in the other groups. However, the medium-level students in the HML cooperative group scored better than those in the control group and the HL/MM cooperative group. Significant main effect was also found in the perception of learning environment but not in the attitude toward science instruction and self-esteem. The cooperative groups, regardless of grouping, exhibited more positive perception than the control group.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.327-336
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• 2011

Reported causes of mandibular nerve injury in relation to neuropathic pain in dentistry include extraction, dental implant surgery, oral and maxillofacial surgery, periodontal treatment, and root-canal therapy. This study analyzed the characteristics of pharmacologic management of neuropathy after root-canal therapy. 32 patients who complain of abnormal sensation or pain after root-canal therapy and were referred to Department of Oral Medicine and the Temporomandibular Joint and Orofacial Pain Clinic at the Dental Hospital of Yonsei University, Seoul, Korea from 2004 to 2011 enrolled in this analysis and improvement of symptom was evaluated after pharmacologic management. Thirty-two patients who had hypoesthesia or dysesthesia at the initial visit were analyzed(9 men, 23 women; mean age: 44 years). The causes of neuropathy were local anesthesia(46.9%), chemical trauma from the sealant in root-canal(25%), endodontic surgery(15.6%), and unknown causes(12.5%). Medications such as steroids, anticonvulsants, antidepressants, and analgesics were took for improvement of symptoms and titrated for a variety of period from 1 week to 11 months. It was found that neuropathy of the inferior alveolar nerve and the lingual nerve was in 25 and 7 patients. The improvement of neurosensory disturbance and no improvement after pharmacotherapy was in 21(66%) and 11(34%) patients respectively. The hypoesthesia and dysesthesia was improved 67% and 65% respectively. These results suggest that symptomatic improvement by pharmacologic management can be possible in patients with neuropathy after root-canal therapy. But improvement of symptoms was influenced by the causes and degree of nerve injury, the periods of pharmacotherapy, and the choice of treatment methods. So, further investigation is needed by quantitative measurement of more variables in more individuals.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.225-235
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• 2009

A common procedure of restoration of endodonticlly treated tooth with fiber-reinforced post is followed by core build-up after post cementation. However, this technique is complex and time-consuming. The aim of this study was to compare fracture strength of premolar, restored with various methods of core fabrications on fiber-reinforced posts and casting metal restoration. Forty five freshly extracted human mandibular premolars were obtained and devided into 5 groups acconding to the type of post and methods of core build-up. In Group A, D.T. $Light-post^{(R)}$ were cemented with $DUO-LINK^{TM}$ and then $LIGHT-CORE^{TM}$ was used for core restoration. In Group B, D.T. $Light-post^{(R)}$ and $DUO-LINK^{TM}$ were used for cementing in the postspace, and $DUO-LINK^{TM}$ was used again for core restoration. In Group C, $Light-post^{(R)}$ bonding and the core build-up were performed simultaneously by using $DUO-LINK^{TM}$. In Group D, $LuxaPost^{(R)}$ was bonded by using $LuxaCore^{(R)}-Dual$. Again, $LuxaCore^{(R)}-Dual$ was used for core restoration. In Group E, $LuxaPost^{(R)}$ bonding and the core build-up were performed simultaneously by using $LuxaCore^{(R)}-Dual$. Axial reduction was formed parallelly as possible and 45 degree bevel was made at buccal occlusal surface. Crowns were fabricated and cemented. Each tooth was embedded in self-curing acrylic resin to the level of 2mm below the CEJ. Specimens were fixed on universal testing machin such that the axis of the tooth was at 45 degree inclination to the horizontal plane, and compressive force was applied at a crosshead speed of 1mm/min until failure occurred. The mean fracture strength was the highest in group A followed by descending order in group B, D, E and C. However, there were no statistically significant differences between groups with regard to the fracture strength. The type of the post or build-up methods of the core does not seem to influence the fracture strength.

• Sleep Medicine and Psychophysiology
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• v.14 no.2
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• pp.86-91
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• 2007

Background: Actigraphy is a reliable and valid method for assessing sleep in normal, healthy populations, but it may be less reliable and valid for detecting disturbed sleep in patients. In this study, we attempted to assess the utility of actigraphy in the estimation of sleep quality in patients with obstructive sleep apnea syndrome (OSAS), a major sleep disorder. Method: We analyzed the data of patients who underwent polysomnography (PSG) and actigraphy simultaneously for one night at the Center for Sleep and Chronobiology, Seoul National University Hospital from November 2004 to March 2006. Eighty-nine subjects with OSAS alone and 21 subjects with OSAS and periodic limb movement disorder (PLMD) were included for final data analyses between groups. Polysomnographic and actigraphic data were also compared. Results: In subjects with mild OSAS (RDI<15), modretae ($15{\leq}RDI$<30), and OSAS with PLMD, PSG and actigraphy did not show significant difference in total sleep time and sleep efficiency. However in severe ($30{\leq}RDI$) OSAS subjects, PSG and actigraphy showed significant difference in total sleep time and sleep efficiency. In all patients, no correlations were found between sleep parameters from PSG and from those using actigraphy. Conclusions: We suggest that in severe OSAS patients, PSG is the diagnostic tool. In mild and moderate cases, actigraphy might be used as a screening tool.

• Journal of Oral Medicine and Pain
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• v.33 no.3
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• pp.257-267
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• 2008

The mentophysical disease causes diseases in digestive, respiratory, circulating systems, including chronic pain, through combined reactions from different individual characteristics, mental stress and temperamental factors. The most common symptom related to orofacial area is pain and the contributive factors include biological, behavioral, environmental, social, emotional, recognitive factors. These factors affect the course of the symptom according to individual's character and human nature. In pain, sleep acts as a contributive factor, and pain could bring about sleep disturbance and vice versa. Deterioration of sleep quality would act as a factor that aggravates mental stress. Therefore, relatively accurate and simple mental examinations and sleep quality test should be carried out for the patients with symptoms related to orofacial area. This study evaluated the mental state in relation to the sleep quality which could affect orofacial pain. The number of poor sleeper was 18 in male subjects, and 1 in female subjects and PSQI global index was higher in male($6.11{\pm}2.38$) than female($4.67{\pm}2.18$). SCL-90-R index showed no sex difference. Poor sleeper showed significantly high value in SOM, O-C, I-S, ANX, PHOB, PSY, GSI, PST. When SCL-90-R T scores were compared according to sleep quality, higher the subjective sleep quality score, O-C and I-S showed significant increase. As sleep disturbances score increased, PAR, PSY, PST showed statistically significant increase. In comparison of SCL-90-R T score according to daytime dysfunction, statistically significant increase in DEP, ANX, HOS, PHOB, PAR, GSI was observed. Therefore, the quality of sleep and psychological status have a high correlation. This is likely to influence chronic pain in the orofacial field. As a result, clinicians treating orofacial pain should evaluate the sleep quality and psychological status of the patient. Further studies of larger sample sizes including various age, occupation, and pain groups are necessary in order to apply the results to clinical practice.