• Journal of Intelligence and Information Systems
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• v.16 no.3
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• pp.77-97
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• 2010

Market timing is an investment strategy which is used for obtaining excessive return from financial market. In general, detection of market timing means determining when to buy and sell to get excess return from trading. In many market timing systems, trading rules have been used as an engine to generate signals for trade. On the other hand, some researchers proposed the rough set analysis as a proper tool for market timing because it does not generate a signal for trade when the pattern of the market is uncertain by using the control function. The data for the rough set analysis should be discretized of numeric value because the rough set only accepts categorical data for analysis. Discretization searches for proper "cuts" for numeric data that determine intervals. All values that lie within each interval are transformed into same value. In general, there are four methods for data discretization in rough set analysis including equal frequency scaling, expert's knowledge-based discretization, minimum entropy scaling, and na$\ddot{i}$ve and Boolean reasoning-based discretization. Equal frequency scaling fixes a number of intervals and examines the histogram of each variable, then determines cuts so that approximately the same number of samples fall into each of the intervals. Expert's knowledge-based discretization determines cuts according to knowledge of domain experts through literature review or interview with experts. Minimum entropy scaling implements the algorithm based on recursively partitioning the value set of each variable so that a local measure of entropy is optimized. Na$\ddot{i}$ve and Booleanreasoning-based discretization searches categorical values by using Na$\ddot{i}$ve scaling the data, then finds the optimized dicretization thresholds through Boolean reasoning. Although the rough set analysis is promising for market timing, there is little research on the impact of the various data discretization methods on performance from trading using the rough set analysis. In this study, we compare stock market timing models using rough set analysis with various data discretization methods. The research data used in this study are the KOSPI 200 from May 1996 to October 1998. KOSPI 200 is the underlying index of the KOSPI 200 futures which is the first derivative instrument in the Korean stock market. The KOSPI 200 is a market value weighted index which consists of 200 stocks selected by criteria on liquidity and their status in corresponding industry including manufacturing, construction, communication, electricity and gas, distribution and services, and financing. The total number of samples is 660 trading days. In addition, this study uses popular technical indicators as independent variables. The experimental results show that the most profitable method for the training sample is the na$\ddot{i}$ve and Boolean reasoning but the expert's knowledge-based discretization is the most profitable method for the validation sample. In addition, the expert's knowledge-based discretization produced robust performance for both of training and validation sample. We also compared rough set analysis and decision tree. This study experimented C4.5 for the comparison purpose. The results show that rough set analysis with expert's knowledge-based discretization produced more profitable rules than C4.5.

• Journal of Korean Society of Forest Science
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• v.42 no.1
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• pp.1-38
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• 1979

The woody species of Genus Ilex which are endemic to Korea are distributed on limited area due to solely temperature factor. There is some differences according to species, however in general, the evergreen Ilex are found along southern coastal area of Korean Peninsula and near islands where the cold index does not exceed $-5^{\circ}C$. But Ilex macropoda and the variety, only deciduous ones, are grown in temperate zone of the peninsula and some islands. The list of Ilex species of Korea are as follows. Ilex cornuta Lindley et Pax., I. crenata Thunb. var. microphylla Max., I. crenata Thunb., I. rotunda Thunb., I. macropoda Miq., I. macropoda Miq. var. pseudo-macropoda Loensner, I. integra Thunb. The author surveyed the populations of Ilex species as many as possible and data of some characters such as leaf shape, spine, fruit shape, stomata density, sex ratio in natural communities, etc. are collected. Almost all the Ilex species in Korea show sporadic distribution. This means quite small sized populations isolate distantly each other eliminating the change of gene exchange in between. Particularly Ilex conuta and I. crenata show the morphological differentiation among populations as well as significant individual variation within a population. These were true with such characteristics, leaf shape, leaf dimension, leaf margin, fruit shape, spine, and stomata density. The founded are that the fruit length and the stomata density counted on the beneath surface of leaves of Ilex cornuta increased with the decrease of latitude. These are naturally closely related with the cold index values. The table shown below indicates the correlation between mean stomata density per $0.3642mm^2$ and cold index values. These relation however were not observed on Ilex crenata. The most dominated natured in relation to individual variation were outline of leaf, the number of marginal spine, the shape of leaf cross section and the degree of luster of the upper leaf surface. As shown in photos 5~7, these variations are agreed at a glance. There are reports that the development of marginal spines in some Ilex species is associated with the juvenility and topophysis. In present study, these two factors were neglected because of the intended sampling procedure. Of Ilex rotunda, population difference with the characteristics of leaf length is recognized but not for leaf width, petiole length, and fruit size. However, individual variations within a population were significantly large. In case of Ilex integra, only individual differences within population were calculated statistically for such characteristics as leaf length, leaf width, and petiole length. As to natural population, the sex ratio was 1:2 (female to male) for Ilex cornuta, and 1:1 for Ilex crenata. The tendency of more male than female in I. cornuta was agreed to other observations. Preparing the tip cutting of length 10cm, and treating with IBA, then attaching earth ball to the cut end, very successful rooting percentages were obtained. Asexual propagation has the advantages of maintaining the heterozygosity of existing varieties and overcoming the difficulties of delayed seed germination frequently encountered with Ilex species. Considering a great deal of variation in morphological traits, a good possibility of selection breeding for decorative and ornamental purposes exists. At present, these evergreen Ilex are ignored by local people as nuisance weedy shrubs. So the proper protection measures should promptly be taken.

• Journal of dental hygiene science
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• v.8 no.2
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• pp.81-87
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• 2008

The purpose of this study was to examine the oral health state, oral health awareness and oral health behavior of middle school students in a bid to raise concerns about oral health problems in a local community and help ensure the efficiency of oral health programs. The subjects in this study were 662 seventh graders in 14 different middle schools located in the city of Hwaseong. The findings of the study were as follows: Frist, In terms of indices related to dental caries, DMFT index numbered 2.0. Secondly, as to subjective oral health state, 22 percent of the boys and 10.9 percent of the girls found their own oral cavity to be healthy, and the gap between them and the others was statistically significant different(p=.000). Thirdly, in regard to tooth-related habits, the girls brushed their teeth more often than the boys(p=.000). Fourthly, for snack-intake habits, the largest number of the boys ate between meals once(42.1%), and the second largest group of them did it two or three times(31.3%). Fifthly, regarding how they felt about dental treatment, the greatest number of the boys and girls replied there's nothing special when they were asked about their mood in case of seeing a dentist next day. The second largest group answered they would get a little nervous. As to mood while waiting for treatment, the greatest number of the boys and girls answered they would get a little nervous. In regard to mood while lying on a dental chair, the largest group replied they would be nervous. Concerning mood while lying on a dental chair for scaling, most of them answered they would get nervous.

• The Korean Journal of Ecology
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• v.24 no.5
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• pp.281-288
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• 2001

The relationships between the growths of Abies koreana W. and climatic factors were analyzed by the use of tree-ring analysis at the subalpine belt of Mt. Halla National Park. The four cores were extracted from each 21 trees at north-facing slope (1,900m a.s.1.). The site chronology was established on the periods from 1912 to 1999. The growth of A. koreana was very poor, in particular in the years of 1982, 1988 and 1996. Simple correlation was employed to analyze the relationship between the growth of A. koreana and climatic factors. The result of simple correlation indicates that the growth of A. koreana represent positive correlations both with the mean temperatures of April and previous November, and the precipitation of previous December and January. The presence of large number of frost-damaged scars in the individual trees of A. koreana implies that local freezing temperature conditions at Mt. Halla have occurred in 1964, 1965 and 1966. The correlations between the fir chronology SOI(Southern Oscillation Index) of previous January, February and November were significantly positive. The growth ratio of A. koreana demonstrates that this species is sensitive to seasonal variations. As the winter temperature rises, the growth ratio of A. koreana decreases, on the other hand, the increase of autumn temperature accelerates the growth ratio of A. koreana. The growth decline of A. koreana was observed from 51 cores out of the 54 cores, and the overall growth declines have initiated at 1978, 1982 and 1988. Distinct growth decline of A. koreana in the range of 70% is noticed at 34 cores out of the 51 cores. The decline of, A. koreana growth appears to be related to the winter temperature which has increased since mid-1970s.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.73-86
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• 2004

In order to estimate the post-ingestion bioavailability of heavy metals and to assess the risk of adverse health effects on human exposure to toxic heavy metals, environmental geochemical surveys were undertaken around the Dogok Au-Ag-Cu and the Hwacheon Au-Ag-Pb-Zn mine sites. Human risk assessment of toxic heavy metals was performed with the results of the SBET(simple bioavailability extraction test) analysis for soil and chemical analytical data for crop plant and water. Arsenic and other heavy metals were highly elevated in tailings from the Dogok(218 As mg/kg, 90.2 Cd mg/kg, 3,053 Cu mg/kg, 9,473 Pb mg/kg, 14,500 Zn mg/kg) and the Hwacheon(72 As mg/kg, 12.4 Cd mg/kg. 578 Pb mg/kg, 1,304 Zn mg/kg) mines. These significant concentrations can impact on soils and waters around the tailing dumps. The quantities of As, Cd and Zn extracted from paddy soils in the Hwacheon mine using the SBET analysis were 55.4%, 20.8% and 26.4% bioavailability, respectively, and for farmland soils in the Dogok mine, 40.8%, 37.6% and 33.0% bioavailability, respectively. From the results of human risk assessment, HI(Hazard Index) value exceeded 1.0 for As in the Hwacheon mine and for Cd in the Dogok mine. Thus, toxic risks for As and Cd exist via exposure(ingestion) of contaminated soil, water and rice grain in these mine sites. The cancer risk for As by the consumption of rice and groundwater in the Hwacheon mine area was 8E-4 and 1E-4, respectively. This risk level exceeds the acceptable risk(1 in 100,000) for regulatory purpose. Therefore, regular ingestion of locally grown rice and ground-water by the local population can pose a potential health threat due to long-term arsenic exposure.

• Korean Journal of Health Education and Promotion
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• v.24 no.5
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• pp.119-135
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• 2007

Objectives: The efficacy, feasibility, and safety of bench-step aerobics (BSA) program in overweight or obese Korean adult women have been implied. However, there has been almost no evidence for its psychological benefits. As such, the purpose of this study was to investigate the psychological benefits of BSA program in overweight or obese (body mass index ${\geq}\;23\;kg/m^2$) Korean adult women. Method: Anger, exercise self-efficacy, exercise-related affect, and body image of overweight or obese women who participated in a 12-week BSA program (n=15) were compared with those of their counterparts in the control group (n=13). Subjects were selected among public health center visitors and those recruited by putting an advertisement in local newspapers and the public health center homepage. Data from the exercise and control groups were collected before and after the 12-week BSA program (from August to November in 2006) at the public health centers. The exercise program consisted of 45 to 60 min moderate-intensity (40/50 to 50/60% of their hear rate reserve) BSA performed for 3 days a week. Results: After the BSA program, body image of the subjects in the exercise group was significantly improved and there was a significant difference between the exercise and control groups. Anger, exercise self-efficacy, and exercise-related affect were improved after the BSA program but the changes did not reach the level of statistical significance and there were no significant differences between the exercise and control groups. Conclusions: In conclusion, BSA appears to significantly enhance body image in overweight or obese Korean adult women but its effects on anger, exercise self-efficacy, and exercise-related affect do not appear to be statistically significant. Further studies involving different subjects, particularly whose levels of anger are high or whose levels of exercise-related affect are low to exclude the influence of the ceiling or floor effect, are warranted in a randomized controlled design.

• Sleep Medicine and Psychophysiology
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• v.24 no.1
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• pp.55-61
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• 2017

Objectives: Suicide is one of the leading causes of death among young adults. We investigated whether anxiety level and sleep quality were related to suicide ideation among university students. Methods: Questionnaires were distributed to 1094 students at a local college. The scale for suicide Ideation, the Hospital Anxiety-Depression scale, the Pittsburgh Sleep Quality Index, and Morningness-eveningness questionnaires were used. Multiple linear regression analysis was conducted to examine the relationship between these variables and suicide ideation. Results: Among the 292 students who answered the suicide ideation questionnaire, 31 students had a high suicide ideation score and 261 patients had a low suicide ideation score. Demographic variables that showed significant differences between the two groups were gender, exercise, chronotype, sleep quality, depression and anxiety. The results of multiple linear regression analysis showed that suicidal ideation increased as the level of sleep quality decreased. There was no significant relationship between depression and suicidal ideation. Another multiple linear regression analysis was performed to evaluate the relationship between sleep quality sleep related factors. This suggested the quality of sleep decreased as weekend oversleep increased. Conclusion: The results of this study showed that when anxiety was higher and the quality of sleep was lower, the more suicide ideation increased. Therefore, improving sleep quality and reducing anxiety are important strategies for reducing suicidal ideation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.71-80
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• 2001

To understand paleoceanographic environmental changes in the Esat Sea during the transitional period between Holocene and last glacial maximum, geochemical high resolution study was conducted by using a piston core(95PC-1) samples collected from the southernmost part of the Ulleung Basin. Geochemical results reveal that major distinctive paleoceanographic variations in transitional period are prominent. Major elemental concentrations show distinctive variations between glacial and Holocene suggesting changes in sediment supply. $TiO_2/Al_2O_3$ ratio of the sediment indicates different sediment composition between Holocene and glacial period. The content of total organic carbon ranging from 0.5% to 4% during transitional period. These vslues showed 2-4 times and two times higher than those of last glacial and Holocene, respectively. The C/N ratios deduced from organic matters exceed10 during transitional period suggesting terrigenous organic matter are supplied from continent, especially during last glacial maximum. Carbonate contents are relatively stable during Holocene and last glacial maximum with gradual decrease during glacial period with high fluctuation during transitional period. The variations of chemical index of weathering (CIW) also show a distinctive variation between glacial and Holocene, which is coincident with those of carbonate and organic carbon. The grain size distribution indicates that the difference content of silt fraction during Holocene and glacial period is closely related with climatic effect during glacial period. Therefore geochemical differences in sediment composition between Holocene and last glacial maximum is thought to be related to paleoceanographic, sea-level change and local paleoclimatic changes.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.5 no.1
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• pp.1-8
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• 2012

Purpose: The purpose of this study is to report the preliminarily result of the radiologic disappearance of the calcific material, regardless of the size, type or location, on one-time ultrasonographic (US) assisted needling for calcific tendinitis of the shoulder. Materials and Methods: From March to August 2011, 46 patients (47 shoulders) with symptomatic calcific tendinitis were treated by one-time US assisted needling. Initially, a diagnostic US was performed with patient to determine the locations, numbers and sizes of calcific deposits. After 1% lidocaine local anesthesia, the calcific material was punctured with an 18-gauge needle under US monitoring. If no calcific material was aspirated after 2 or 3 additional attempts, the deposits was performed multiple puncture to achieve decompression. And then all patients were performed subacromial corticosteroid injection. All patients were followed up 4 weeks after procedure. To assess the radiologic disappearance after one-time US assisted needling, simple radiographs of the treated shoulder were performed and size, dense, and morphology of the calcific deposits were compared with those in baseline radiographs. For clinical evaluations, visual analogue scale for pain and function (PVAS and FVAS), and American Shoulder and Elbow Surgeons (ASES) score were assessed. Results: There were 11 male and 35 female patients with the mean age of 53.8 years (28-71). The morphology of the calcific deposits were 31 type A and 16 type B by French Arthroscopic Society classification and mean size was $2.9{\pm}6.7$ mm before the procedure. At 4 weeks after the index procedure, the radiographic unchanged group was included in 10 cases and changed group was 37 cases. No intergroup difference for the clinical results after the procedure was evident, but group FAS classification before the procedure was significantly different (p=0.011). Conclusion: At 4 weeks after one-time US assisted needling for calcific tendinitis of the shoulder, the radiographic size- or dense-changed cases were showed in 79%, regardless of the size, type or location of the calcific material. But the radiographic nearly or complete disappearance were showed in only 21%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.83-90
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• 2004

This study was conducted to examine the effects of $\beta$3-adrenergic receptor polymorphism on the blood glucose level and obesity in 530 volunteers, who attended a weight loss program in a local obesity clinic. The age differences in total subjects and the distribution of male and female were 26.55$\pm$0.31 yr, 9.1% (n=48), 90.9% (n=492). The genotype distribution of $\beta$3-AR gene polymorphism were WW type 75%, WR type 22% and RR type 3%. Among many parameters, fasting blood glucose was significantly higher in WR＋RR type (p=0.001) compared with WW type. When the subjects were divided into two groups by 6.105 mmol/L of the fasting blood glucose level, the frequency of hyperglycemia was 23.3% in WW type subjects, while there was a increase to 35.6% in WR＋RR type subjects (p=0.011, $\chi$$^2$-analysis). When hyperglycemia group was compared with normoglycemia group, obesity index (p=0.044), %body fat (p=0.046) and TG (p=0.000) were significantly higher, and HDL (p=0.006) was significantly lower in the hyperglycemia. When all of the above factors were included in stepwise logistic regression analysis to find risk factors of hyperglycemia, the results were that the odds ratio for hyperglycemia were 2.015 (p=0.011) for WR+RR type of $\beta$3-AR gene, 2.165 (p=0.000) for TG and 0.419 (p=0.059) for HDL cholesterol. There was a significantly positive correlation between the blood glucose vs BMI, WHR, body fat in the WW type (r=0.099, 0.119, 0.082) However, in the WR and RR type there were no significance between the blood glucose vs BMI, WHR, body fat. These data suggest that the WR＋RR genotype of $\beta$3-AR has a very strong association with increased blood glucose level and might be a significant risk factor for hyperglycemia among Korean subjects.