• Journal of Intelligence and Information Systems
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• v.26 no.1
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• pp.119-133
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• 2020

Fama asserted that in an efficient market, we can't make a trading rule that consistently outperforms the average stock market returns. This study aims to suggest a machine learning algorithm to improve the trading performance of an intraday short volatility strategy applying asymmetric volatility spillover effect, and analyze its trading performance improvement. Generally stock market volatility has a negative relation with stock market return and the Korean stock market volatility is influenced by the US stock market volatility. This volatility spillover effect is asymmetric. The asymmetric volatility spillover effect refers to the phenomenon that the US stock market volatility up and down differently influence the next day's volatility of the Korean stock market. We collected the S&P 500 index, VIX, KOSPI 200 index, and V-KOSPI 200 from 2008 to 2018. We found the negative relation between the S&P 500 and VIX, and the KOSPI 200 and V-KOSPI 200. We also documented the strong volatility spillover effect from the VIX to the V-KOSPI 200. Interestingly, the asymmetric volatility spillover was also found. Whereas the VIX up is fully reflected in the opening volatility of the V-KOSPI 200, the VIX down influences partially in the opening volatility and its influence lasts to the Korean market close. If the stock market is efficient, there is no reason why there exists the asymmetric volatility spillover effect. It is a counter example of the efficient market hypothesis. To utilize this type of anomalous volatility spillover pattern, we analyzed the intraday volatility selling strategy. This strategy sells short the Korean volatility market in the morning after the US stock market volatility closes down and takes no position in the volatility market after the VIX closes up. It produced profit every year between 2008 and 2018 and the percent profitable is 68%. The trading performance showed the higher average annual return of 129% relative to the benchmark average annual return of 33%. The maximum draw down, MDD, is -41%, which is lower than that of benchmark -101%. The Sharpe ratio 0.32 of SVS strategy is much greater than the Sharpe ratio 0.08 of the Benchmark strategy. The Sharpe ratio simultaneously considers return and risk and is calculated as return divided by risk. Therefore, high Sharpe ratio means high performance when comparing different strategies with different risk and return structure. Real world trading gives rise to the trading costs including brokerage cost and slippage cost. When the trading cost is considered, the performance difference between 76% and -10% average annual returns becomes clear. To improve the performance of the suggested volatility trading strategy, we used the well-known SVM algorithm. Input variables include the VIX close to close return at day t-1, the VIX open to close return at day t-1, the VK open return at day t, and output is the up and down classification of the VK open to close return at day t. The training period is from 2008 to 2014 and the testing period is from 2015 to 2018. The kernel functions are linear function, radial basis function, and polynomial function. We suggested the modified-short volatility strategy that sells the VK in the morning when the SVM output is Down and takes no position when the SVM output is Up. The trading performance was remarkably improved. The 5-year testing period trading results of the m-SVS strategy showed very high profit and low risk relative to the benchmark SVS strategy. The annual return of the m-SVS strategy is 123% and it is higher than that of SVS strategy. The risk factor, MDD, was also significantly improved from -41% to -29%.

• Journal of agricultural medicine and community health
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• v.39 no.3
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• pp.137-145
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• 2014

Objectives: Colonoscopy is a popular tool for screening for colon cancer throughout the world. The incidence of polypectomy and follow-up colonoscopy are persistently increasing but the studies about follow-up test after polypectomy are still lack of its domestic sources. This study is designed to look into the recurrence rate of colon polyps and risk factors after polypectomy. Methods: This is a retrospective study by reviewing medical charts of 147 patients who underwent polypectomy and follow-up colonoscopy from Jan. 2000 to Mar. 2008. The Kudo classification was used to describe the polyps found in the colonoscopy. The follow-up period was defined as the term between polypectomy and the first colonoscopy follow up. Results: Seventy six point two percent of the enrolled patient were male and the mean age was $56.5{\pm}8.1$. Mean follow-up period was $24.9{\pm}13.7$ (6 - 65) months. The cumulative recurrence rate of 1 year was 11.6%. The rate of 2 years was 36.7% and that of 3 years was 55.8%. The number of polyps was the factor which statistically showed significant relation of its recurrence rate. The histological morphology characteristic of polyps could be one independent factor which may be associated to the recurrence of polyps. Conclusions: The importance of colonoscopy follow up after polypectomy was clearly emphasized through the cumulative recurrence rate of 55.8%. Therefore, there is a need for more domestic studies with a large number of patients about the recurrence of polyps after polypectomy.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.251-265
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• 1999

Various types of horizontal reference planes are used for diagnosis, treatment planning and evaluation of treatment results. But these reference Planes lack accuracy and repro-ducibility, and are mainly for Caucasian. Unlike the adult patients who have completed growth, the horizontal reference planes for growing children may change continuously during growth. Therefore this must be considered in selecting the horizontal reference plane. The purpose of this study was to Investigate the angle formed by the Sella-Nasion(SN) plane and Frankfort-Horizontal(FH) plane and evaluate the angle formed by FH plane and other horizontal reference planes in relation to different skeletal maturity and malocclusion types. 540 subjects with no orthodontic treatment history were chosen, and hand -wrist X-rays and lateral cephalometric X-rays were taken. According to SMA(Skeletal Maturity Assessment) of hand-wrist X-rays, the subjects were classified into 3 skeletal maturity groups : SMI 1-4 for group A, SMI 5-7 for group B and SMI 8-11 for group C. A second classification was made according to cephalometric analysis of lateral cephalograms. The subjects were classified into 3 malocclusion groups : Skeletal Class I, II and III malocclusion group. 10 measurements were evaluated. The results were as follows. 1. The angle formed by the SN plane and FH plane showed no difference among skeletal maturity groups, malocclusion groups, and between .sexes. 2. The angles formed by the SN plane and FH plane were $8.27^{\circ}{\pm}2.31^{\circ}$ for males and $8.59^{\circ}{\pm}2.24^{\circ}$ for females. The average value for females and males was $8.42^{\circ}{\pm}2.28^{\circ}$. 3. The angle formed by the FH plane and palatal plane was almost constant showing no difference among skeletal maturity groups, malocclusion groups, and between sexes($1.09^{\circ}{\pm}3.21^{\circ}$).

• Radiation Oncology Journal
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• v.29 no.2
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• pp.63-70
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• 2011

Purpose: To evaluate the extent of pain response and objective response to palliative radiotherapy (RT) for bone metastases from hepatocellular carcinoma according to RT dose. Materials and Methods: From January 2007 to June 2010, palliative RT was conducted for 103 patients (223 sites) with bone metastases from hepatocellular carcinoma. Treatment sites were divided into the high RT dose and low RT dose groups by biologically effective dose (BED) of 39 $Gy_{10}$. Pain responses were evaluated using the numeric rating scale. Pain scores before and after RT were compared and categorized into 'Decreased', 'No change' and 'Increased'. Radiological objective responses were categorized into complete response, partial response, stable disease and progression using modified RECIST (Response Evaluation Criteria In Solid Tumors) criteria; the factors predicting patients' survival were analyzed. Results: The median follow-up period was 6 months (range, 0 to 46 months), and the radiologic responses existed in 67 RT sites (66.3%) and 44 sites (89.8%) in the high and low RT dose group, respectively. A dose-response relationship was found in relation to RT dose (p=0.02). Pain responses were 75% and 65% in the high and low RT dose groups, respectively. However, no statistical difference in pain response was found between the two groups (p=0.24). There were no differences in the toxicity profiles between the high and low RT dose groups. Median survival from the time of bone metastases diagnosis was 11 months (range, 0 to 46 months). The Child-Pugh classification at the time of palliative RT was the only significant predictive factor for patient survival after RT. Median survival time was 14 months under Child-Pugh A and 2 months under Child-Pugh B and C. Conclusion: The rate of radiologic objective response was higher in the high RT dose group. Palliative AT with a high dose would provide an improvement in patient quality of life through enhanced tumor response, especially in patients with proper liver function.

• Journal of Korean Orthopaedic Sports Medicine
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• v.9 no.1
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• pp.48-57
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• 2010

Purpose: To compare the incidence and risk factors for osteoarthritis after anterior cruciate ligament (ACL) reconstruction between two groups using bone-patellar tendon-bone (BPTB) and hamstring tendon (HT) autograft. Materials and Methods: 53 cases of ACL reconstruction using patellar tendon and 40 cases using hamstring tendon were followed up at least 8 years. Radiographic evaluation was done according to the Kellgren and Lawrence's classification. Clinical functional testing (Lysholm Knee Scores, the Tegner activity scores) and laxity testing (Lachman, pivot shift tests), and the instrumented laxity testing with $Telos^{(R)}$ were all examined in relation to the development of osteoarthritis. Results: Radiographic osteoarthritic changes were detected in 24 patients (45.3%) in BPTB group and 14 patients (35.0%) in HT group. Accompanying meniscal injury (BPTB p<0.001; HT p=0.091), intervals from the injury to reconstruction of > 12 months (BPTB p=0.037; HT p=0.021), and patient's age at reconstruction of > 25 years (BPTB p=0.003; HT p=0.048) were found to be significant independent predictors of osteoarthritis. However, no statistically significant correlations were found between the development of osteoarthritis and the clinical outcome or the radiographic stability in both groups. Conclusion: Although ACL reconstruction using BPTB or HT autograft had good clinical results at an average follow-up of 10 years, considerable incidence of radiographic osteoarthritic changes were noted. Various factors such as accompanying meniscal injury, protracted time from injury to reconstruction, more than 25 years old at the time of reconstruction were related to radiographic osteoarthritic changes.

• Clinical and Experimental Pediatrics
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• v.52 no.6
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• pp.674-679
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• 2009

Purpose : The authors aimed to analyze the long-term effects of treatments, especially external beam radiotherapy (EBRT), in bilateral retinoblastoma patients. Methods : This retrospective study analyzed the medical records of 22 bilateral retinoblastoma patients who were registered between October, 1987 and October, 1998 and followed-up for more than 10 years. They were treated by enucleation, EBRT, and systemic chemotherapy. Age at diagnosis, sex, delay prior to treatment, Reese-Ellsworth (RE) classification, and the local treatment modalities were analyzed in relation to recurrence-free survival (RFS) and complications. Results : Median age at diagnosis was 7.0 months (range 1.7-31.6 months). Leukocoria was the most common presenting feature. Two patients had a familial history. The RE classifications of the 44 eyes were group II in 4, III in 14, IV in 4, and V in 22. At the end of a median follow-up period of 141 months (range 55-218 months), 20 patients were alive. The 10-year ocular survival rate of the 44 eyes was $56.8{\pm}7.5%$. The 10-year RFS and ocular survival rate of the 29 eyes treated by combined EBRT and chemotherapy were 75.9% and 86.2%, respectively. Treatment delay (>3 months) was found to be related to higher risk of recurrence. Complications after EBRT were cataract, retinal detachment, phthisis bulbi, and facial asymmetry. No patient developed a second malignancy during the follow-up period. Conclusion : Early detection and prompt treatment can increase ocular survival rates. In addition, careful attention should be paid to possible long-term sequelae in these patients.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.11-18
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• 2010

Purpose: In every time radiation therapy set up errors occur because internal anatomical organs move due to breathing and change of patient's position. These errors may affect the change of dose distribution between target area and normal structure. This study investigates the usefulness of body-fix in clinical treatment. Materials and Methods: Among 55~60 aged male patients who has hepatocellular carcinoma in area of liver's couinaud classification, we chose 10 patients and divided two groups by using body-fix or not. When applying body-fix, we maintained a vacuum of 80 mbar pressure by using vacuum pump (Medical intelligence, Germany). Patients had free breathing with supine position. After working to fuse and consist MV-CT (megavoltage computed tomography) with KV-CT (kilovoltage computed tomography) obtained by 5 times treatments, we compared and analyzed set up errors occurred to (Right to Left, RL) of X axis, (Anterioposterio, AP) of Z axis, (Cranicoudal, CC) of Y axis. Results: Average Set up errors through image fusion showed that group A moved $0.3{\pm}1.1\;mm$ (Cranicoudal, CC), $-1.1{\pm}0.7\;mm$ (Right to Left, RL), $-0.2{\pm}0.7\;mm$ (Anterioposterio, AP) and group B moved $0.62{\pm}1.94\;mm$ (Cranicoudal, CC), $-3.62{\pm}1.5\;mm$ (Right to Left, RL), $-0.22{\pm}1.2\;mm$ (Anterioposterio, AP). Deviations of X, Y and Z axis directions by applying body-fix indicated that maximum X axis was 5.5 mm, Y axis was 19.8 mm and Z axis was 3.2 mm. In relation to analysis of error directions, consistency doesn't exist for every patient but by using body-fix showed that the result of stable aspect in spite of changes of everyday's patient position and breathing. Conclusion: Using body-fix for liver cancer patient is considered effectively for tomotherapy. Because deviations between group A and B exist but they were stable and regular.

• Journal of the Korean association of regional geographers
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• v.6 no.1
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• pp.69-89
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• 2000

The regional geography had been at the height of prosperity in the first half of the twentieth century since Alexander von Humboldt and Carl Ritter. The geography remained stationary in the late 19th century had greatly developed around the regional geography in European countries since the early 20th century. Particularly, A. Hettner and O. $Schl{\ddot{u}}ter$ in Germany, Vidal de la Blache in France and A. J. Herbertson in Britain developed their own methods of regional studies and produced many results of empirical studies ; accordingly the regional geography had been at the height of prosperity in the 1920s and 1930s. This paper aims to study the regional concepts and the methods of regional studies of Germany geographers in the 1920s and 1930s. This study is useful to understand the current methods of classifications of regions and descripitive systems of regions. The noteworthy results of studies are summarized as follows : First, The regional geography of Germany had been developed by Hettner who regarded the geography as the chorological science of the earth's surface, $Schl{\ddot{u}}ter$ who did the geography as the study of cultural landscape and Penck's students, the morphologists of landscape (Landschaftsmorphologie). Hettner defined the geography as the chorological science, maintained that the earth's surface was classify according to its localized difference -continents, lands, districts and localities(Erdteile, $L{\ddot{a}}nder$, Landschaften und Ortlichkeiten) and emphasized on the total character of areas. He tried to classify downward from continents to localities based on the sizes of regions. He also gave the logic of causal relation to schematic approach(Das $L{\ddot{a}}nderkundliche$ Schema) and further developed it. $Schl{\ddot{u}}ter$ argued that The process of change on the landscape through time must be studied. And Passarge and Penck's pupils, morphologists of landscape, tried to classify the landscape synthetically. Thereafter, De Geer and $Gran{\ddot{o}}$ employed the creative methods of regional classification which used signs and simbols. Second, The regional geography of Germany differed from that of France on the next points ; 1. The former was analytic, but the latter was synthetic. 2. The former placed great emphasis on physical elements, terrain and climate etc., but the latter did great emphasis on both physical and human elements. 3. The former gave priority to the studies of large scale regions, but the latter did priority to the studies of small scale regions. In 1920s and 1930s the regional study of Germany geographers exerted direct influence on the development of geography of Japan. Especially, Tanaka Keiji, Japanese typical regional geographer, tried to classify Japan synthetically on the bases of terrain, climate, vegetation and human elements under the influence of European geographers. He exerted great influence on both Japanese and Korean geographers at that time.

• Journal of Food Hygiene and Safety
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• v.19 no.2
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• pp.60-65
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• 2004

120 samples of ready-to-eat salad product were purchased at department stores, marts and family restaurants in metro area. Coliform bacteria and food borne pathogenic bacteria were isolated from these samples. In 73 samples among the 120 salad product samples, coliform bacteria and food borne pathogenic bacteria were detected by 60.8％ of isolated rate. Salad were classified into organic and non-organic salad. According to a salad type, salad were classified into vegetable salad and mixed vegetable salad with fried chicken and extra food. According to a packing type, packed salad product and salad-bar product were classified. After the classification, the results of each cases were compared. There is no statistical relation between cultivation or packing methods and contaminated bacteria. But the incidence number of microbial strains was significantly different between vegetable salad and mixed vegetable salad(p＜0.005). In vegetable salad, more various strains were detected. E. coli was isolated in 10 cases among the 90 cases in non-organic vegetable and in 7 cases among the 30 cases in organic salad. Food borne pathogenic bacteria were isolated in non-organic vegetable salad product. Staphylococcus aureus was isolated in 4 cases of vegetable salad product and Salmonella spp. isolated in 1 case. After 5 times examination of each 4 market products, the total number of aerobic bacteria was average 4.8$\pm$0.19 log cfu/g. One sample from this product, saline and a detergent for vegetable were used for 3 minutes to notice the effect. As a result, when saline was used 5 times and detergent for vegetable was used 1 time, bacterial contamination was decreased up to 95.5％.

• Journal of Preventive Medicine and Public Health
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• v.1 no.1
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• pp.25-36
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• 1968

Introduction In order to improve medical education through the introduction of a concept of comprehensive health care of a community, an area surrounding the University Campus was chosen for the Community Health Service Project. It has been on operation for last 4 years with its major emphasis on family planning services, and maternal and child health care. The major objectives of this survey at the area are to obtain: 1) The demographic data, 2) The health need and trend of medical care, 3) The attitude and practice in maternity care to be used for further improvement of the planning and the services of the project. Population and Survey Method Out of three Dongs of the Community Health Service Area, only two Dongs namely Changchun and Yonhee were selected for the survey. Total number of households and population in the area studied was 3,683 and 21,857 respectively. An interview was performed with questionnaire schedule which was recorded by interviewers. This includes the degree of utilization of health services provided by the Community Health Service Program such as family planning, prenatal care during their last pregnancy, delivery history and complications of the delivery as well as the incidence of illnesses in general. Prior to the interview, all interviewers were trained for interviewing technique for two days. The survey was carried out during the period from October December 1967. Results 1) Demographic Data : 41.3% of the population studied were children under age 15 and only 3.5% were over 60 years of age. Crude birth rate and crude death rate of this area studied during the period of November 1966-October 1967 were 20.5 and 7.7 respectively. Infant mortality rate during the same period was 35.9. 50.4% of the 2,832 households fell into the category of middle class, 39.8% to the lower class and 9.5% to the upper class in economic condition. 19.8% of 2,832 householders had no formal education, 22.7% primary school, and 57.5% middle or higher school education. 2) Health Status and Utilization of the Community Health Service: Those who suffered from many illnesses during the month of October, 1967 were 690(4.6% of 14,891 persons). Classification of these patients into the type of disease shown respiratory diseases 27.4%, gastrointestinal diseases 18.1%, tuberculosis 10.9%, skin and genitourethral diseases 4.5% and gynecologic patients 4.5%. Only 55.9% of the patients received medical care at hospital or doctor's clinic. But among TB and gynecologic patients, 70.7% and 72.4% were treated at medical facilities. 10.6% of 2,832 householders interviewed has ever utilized the Community Health Service Program provided by the Yonsei Medical School, Classifying these clients into the type of service, 35.9% utilized the wellbaby clinic, 31.0% the family planning clinic, 14.7% the home delivery care, and the rest utilized other services such as the premarital guidance cinlic and the sanitary inspection service. 3) Maternity Care: 23.6% of 2,151 deliveries were done at medical facilities such as hospital, private clinic, while 76.4% were done at home. Acceptance rate of prenatal care was 32.6% as whole, but 49.6 of 774 women who had the prenatal care service had their deliveries at medical facility. 45.1% of total deliveries were attended by medical and or paramedical personnel. 75.8% of the deliveries of those received prenatal care were attended by medical and or paramedical personnel while only 27.8% of the deliveries of those who did not have prenatal care attended by medical and or paramedical personnel. 49.8% of deliveries of the upper class, 29.8% of the middle class and 9.9% of the lower class were attended by medical and or paramedical personnel. 6.2, 3.3% and 24.8% of mothers reported about their xeperience of edema, coma and fever during the period of trimester of pregnancy and puerperium. 4) Family Planning: The rate of practice of family planning was 27.9%. 31.7% of them were by IUD, 2.9% by oral pill, 15.2% by sterilization and the rest by traditional methods. Those women who had 3 to 4 children had highest(30.2%). Practice rate among the various methods of family planning, oral pill was the most popular method to whom had 2 or less children. In relation between the practicing rate of family planning and living standard, the upper, middle and lower class practiced 37.5, 29.4 and 19.9% respectively.