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Effects of Crude Protein Levels in Total Mixed Rations on Dry Matter Intake, Digestibility and Nitrogen Balance in Early Pregnant Korean Black Goats (섬유질배합사료 내 조단백질 수준이 임신초기 흑염소의 건물섭취량, 소화율 및 질소출납에 미치는 영향)

  • HwangBo, Soon;Choi, Sun-Ho;Lee, Sung-Hoon;Kim, Sang-Woo;Kim, Young-Keun;Sang, Byung-Don;Jo, Ik-Hwan
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.27 no.2
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    • pp.93-100
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    • 2007
  • This study was conducted to determine the effects of different levels (10, 12 and 15%) of crude protein (CP) in total mixed ration (TMR) on dry matter intake, digestibility and nitrogen balance of Korean black goats in the stage of early pregnancy and to obtain information on their optimal dietary levels of CP. In the present study, 12 Does of Korean black goats in the early pregnancy were allotted to four unreplicated groups by dietary level of CP and then they were housed in individual metabolism cages with completely randomized design throughout 30 days with 20 days adaptation and 10 days collection periods. Does in Control were fed a conventional diet and does in TMR10, TMR12 and TMR15 were fed a diet adjusted to about 10, 12 and 15% CP, respectively. Dry matter(DM) contents ranged from 89 to 91% in treatments. There were no differences fur fiber contents among three CP levels of TMR, showing that ADF and NDF had 18.57 to 19.85, and 53.41 to 54.80, respectively. Crude protein contents for three TMR treaements had 10.61, 12.15 and 14.97%, respectively. However, non-fibrous carbohydrate (NFC) contents decreased with increasing CP levels in treatments. Meanwhile, Intakes of DM, nutrients and digestible nutrients were significantly (p<0.05) higher in TMR15 and control than in TMR10 and TMR12. Moreover, DM intake per metabolic body weight and theit ratio per body weight was significantly (p<0.05) higher for control and TMR15 than other treatments. DM digestibility was not significantly different among treatments, but ether extract digestibility of treatments was significantly (p<0.05) higher than that of control, but there was no significant difference among treatments. Nitrogen retention significantly (p<0.05) increased with increasing CP levels in TMR, and TMR15 was highest among treatments. Our results showed that the increasing CP levels in TMR increased DM intake and nitrogen retention and suggested that the optimal dietary CP levels under TMR feeding system in early pregnant Korean black goats could be estimated for at least 15%.

The Study of Dinning-out Behavior and Preference on Korean Foods by Age Groups (외식소비자의 연령별 외식행동과 한식에 대한 선호도 조사연구 - 서울, 경기, 천안 지역을 중심으로 -)

  • Yoon, Hei-Ryeo
    • Journal of the Korean Society of Food Culture
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    • v.20 no.5
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    • pp.608-614
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    • 2005
  • The object of this research is to analyze and classify the dining-out behavior and preference on Korean food by age groups and to make counter proposals for better marketing and planning strategies. Major dining out motives were lack of time, the easiness of preparation, and schedule. For lunch, the schedule was the major dining-out motive. For dinner, the respondents in their 30s and below answered social gathering was their major dining-out motive (40.7% and 31.3% respectively). On the other hand, for the respondents in their 40s and 50s, the family gathering was the major dining motive (50.4% and 55.3% respectively) (${\chi}^{2}=68.081,\;p<0.001$). For dining out frequency, 1-2 dining out per a week had the highest percentage, among which the respondents in their 30s was 42.9% (the highest) and the respondents in their 50s was 18% (the lowest). For the dining-out cost, the respondents in their 30s and below spent more on dinner rather than breakfast or lunch. For the menu preference of Korean foods, Doenjangjigae had the highest percentage. In case of Kimchi, the respondents in their 40s showed higher preference than the respondents in their 30s. Interestingly, the preference for Kimchi was higher in the respondents younger than 30 rather than in the respondents in their 30s. and the respondents older than 40 (p<0.05). Preference for Jangachi was considerably low in the respondents younger than 40, which implies that younger people don't incline to traditional Korean Mitbanchan. The dining-out motive was different in each age group. Now, the dining out motive is not restricted to home meal replacement. Social gatherings are increasing and the consumers of dining-out industry are being diversified. These suggest the increased need for classifying and analyzing the consumers by age groups to get more information on consumer behavior and tastes.

The Abuse and Invention of Tradition from Maintenance Process of Historic Site No.135 Buyeo Gungnamji Pond (사적 제135호 부여 궁남지의 정비과정으로 살펴본 전통의 남용과 발명)

  • Jung, Woo-Jin
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.35 no.2
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    • pp.26-44
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    • 2017
  • Regarded as Korea's traditional pond, Gungnamj Pond was surmised to be "Gungnamji" due to its geological positioning in the south of Hwajisan (花枝山) and relics of the Gwanbuk-ri (官北里) suspected of being components to the historical records of Muwang (武王)'s pond of The Chronicles of the Three States [三國史記] and Sabi Palace, respectively, yet was subjected to a restoration following a designation to national historic site. This study is focused on the distortion of authenticity identified in the course of the "Gungnamji Pond" restoration and the invention of tradition, whose summarized conclusions are as follows. 1. Once called Maraebangjuk (마래방죽), or Macheonji (馬川池) Pond, Gungnamji Pond was existent in the form of a low-level swamp of vast area encompassing 30,000 pyeong during the Japanese colonial period. Hong, Sa-jun, who played a leading role in the restoration of "Gungnamji Pond," said that even during the 1940s, the remains of the island and stone facilities suspected of being the relics of Gungnamji Pond of the Baekje period were found, and that the traces of forming a royal palace and garden were discovered on top of them. Hong, Sa-jun also expressed an opinion of establishing a parallel between "Gungnamji Pond" and "Maraebangjuk" in connection with a 'tale of Seodong [薯童說話]' in the aftermath of the detached palace of Hwajisan, which ultimately operated as a theoretical ground for the restoration of Gungnamj Pond. Assessing through Hong, Sa-jun's sketch, the form and scale of Maraebangjuk were visible, of which the form was in close proximity to that photographed during the Japanese colonial period. 2. The minimized restoration of Gungnamji Pond faced deterrence for the land redevelopment project implemented in the 1960s, and the remainder of the land size is an attestment. The fundamental problem manifest in the restoration of Gungnamji Pond numerously attempted from 1964 through 1967 was the failure of basing the restorative work in the archaeological facts yet in the perspective of the latest generations, ultimately yielding a replication of Hyangwonji Pond of Gyeongbok Palace. More specifically, the methodologies employed in setting an island and a pavilion within a pond, or bridging an island with a land evidenced as to how Gungnamji Pond was modeled after Hyangwonji Pond of Gyeongbok Palace. Furthermore, Chihyanggyo (醉香橋) Bridge referenced in the designing of the bridge was hardly conceived as a form indigenous to the Joseon Dynasty, whose motivation and idea of the misguided restoration design at the time all the more devaluated Gungnamji Pond. Such an utterly pure replication of the design widely known as an ingredient for the traditional landscape was purposive towards the aesthetic symbolism and preference retained by Gyeongbok Palace, which was intended to entitle Gungnamji Pond to a physical status of the value in par with that of Gyeongbok Palace. 3. For its detachment to the authenticity as a historical site since its origin, Gungnamji Pond represented distortions of the landscape beauty and tradition even through the restorative process. The restorative process for such a historical monument, devoid of constructive use and certain of distortion, maintains extreme intimacy with the nationalistic cultural policy promoted by the Park, Jeong-hee regime through the 1960s and 1970s. In the context of the "manipulated discussions of tradition," the Park's cultural policy transformed the citizens' recollection into an idealized form of the past, further magnifying it at best. Consequently, many of the historical sites emerged as fancy and grand as they possibly could beyond their status quo across the nation, and "Gungnamji Pond" was a victim to this monopolistic government-led cultural policy incrementally sweeping away with new buildings and structures instituted regardless of their original space, and hence, their value.

Soil Moisture Influence on Growth of Cover Vegetations and Water Economy (토양수분(土壤水分)이 피복용식물(被覆用植物)의 생장(生長) 및 수분경제(水分經濟)에 미치는 영향(影響))

  • Lee, Soo Wook
    • Journal of Korean Society of Forest Science
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    • v.33 no.1
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    • pp.1-32
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    • 1977
  • This study has been made to find out more effective way of vegetation establishment on severely denuded forest land from the viewpoint of soil moisture regimes. Various environmental factors were measured to estimate soil moisture conditions of different sites. Soil moisture influence on growth of over vegetations, water requirement and drought resistance were analyzed. The efficiency of water use was also reckoned at different fertility levels and different soil moisture conditions. This research is composed of field experiment and green house experiment. Field experiment includes height growth, survival and coverage analysis of cover vegetations (Robinia pseudoacacia L., Lespedeza bicolor Turcz, Arundinella hirta Tanaka var. ciliare Koidzumi.) with 4 fertility level treatments on 3 slopes (Steep: $37^{\circ}$, Moderate: $25^{\circ}$, Gentle; $17^{\circ}$) during dry season (1 April-30 June) and wet season (1 July-10 September). At the same time temperature, relative humidity and precipitation were measured to understand the environmental changes. Soil moisture conditions were measured with soil moisture meter with 24 soil cells. Green house experiment comprised height, fresh weight and dry weight measurements of cover vegetations with 4 fertility levels and 3 moisture conditions for 70 days. The results extracted from experiments are as follews. 1. Cover vegtations have 3 patterns of water requirement at the early stage of growth. a) Robinia type has high water requirement and weaker drought resistance. b) Lespedeza type has low water requirement and stronger drought resistance. c) Arundinella type has moderate water requirement and weaker drought resistance. 2. The vegetations have different optimum fertility levels in different soil moisture supply condition. a) Robinia needs a low fertility level in dry condition and a high level in wet condition. b) Lespedeza needs only low fertility level in all conditions. c) Arundinella needs a low fertility level in dry condition and a high level in wet condition. 3. The efficiency of water use (Water/1g dry weight) by fertility levels is different from one another. Robinia and Arundinella have a good efficiency at low fertility level in dry condition and at high fertility level in wet condition. Lespedeza has a good efficiency at low fertility level in all conditions. 4. $P_2O_5$ requirement of Robinia and Lespedeza is high, but that of Arundinella is low. Soil moisture condition has a great influence on $P_2O_5$ absorption in dendued forest land. Once Vegetations are established on suitable sites with optimum fertitity level according to different moisture condition, even the small amount of soil water in denuded land can he used with high efficiency and the effect of fertility treatment can be maximized.

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The Requirement and Effect of the Document of Carriage in Respect of the International Carriage of Cargo by Air (국제항공화물운송에 관한 운송증서의 요건 및 효력)

  • Lee, Kang-Bin
    • The Korean Journal of Air & Space Law and Policy
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    • v.23 no.2
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    • pp.67-92
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    • 2008
  • The purpose of this paper is to research the requirements and effect of the document of carriage in respect of the carriage of cargo by air under the Montreal Convention of 1999, IATA Conditions of Carriage for Cargo, and the judicial precedents of Korea and foreign countries. Under the Article 4 of Montreal Convention, in respect of the carriage of cargo, an air waybill shall be delivered. If any other means which preserves a record of the carriage are used, the carrier shall, if so requested by the consignor, deliver to the consignor a cargo receipt. Under the Article 7 of Montreal convention, the air waybill shall be made out by the consignor. If, at the request of the consignor, the carrier makes it out, the carrier shall be deemed to have done so on behalf of the consignor. The air waybill shall be made out in three original parts. The first part shall be marked "for the carrier", and shall be signed by the consignor. The second part shall be marked "for the consignee", and shall be signed by the consignor and by the carrier. The third part shall be signed by the carrier who shall hand it to the consignor after the goods have been accepted. Under the Article 5 of Montreal Convention, the air waybill or the cargo receipt shall include (a) an indication of the places of departure and destination, (b) an indication of at least one agreed stopping place, (c) an indication of the weight of the consignment. Under the Article 10 of Montreal Convention, the consignor shall indemnify the carrier against all damages suffered by the carrier or any other person to whom the carrier is liable, by reason of the irregularity, incorrectness or incompleteness of the particulars and statement furnished by the consignor or on its behalf. Under the Article 9 of Montreal Convention, non-compliance with the Article 4 to 8 of Montreal Convention shall not affect the existence of the validity of the contract, which shall be subject to the rules of Montreal Convention including those relating to limitation of liability. The air waybill is not a document of title or negotiable instrument. Under the Article 11 of Montreal Convention, the air waybill or cargo receipt is prima facie evidence of the conclusion of the contract, of the acceptance of the cargo and of the conditions of carriage. Under the Article 12 of Montreal Convention, if the carrier carries out the instructions of the consignor for the disposition of the cargo without requiring the production of the part of the air waybill or the cargo receipt, the carrier will be liable, for any damage which may be accused thereby to any person who is lawfully in possession of that part of the air waybill or the cargo receipt. According to the precedent of Korea Supreme Court sentenced on 22 July 2004, the freight forwarder as carrier was not liable for the illegal delivery of cargo to the notify party (actual importer) on the air waybill by the operator of the bonded warehouse because the freighter did not designate the boned warehouse and did not hold the position of employer to the operator of the bonded warehouse. In conclusion, as the Korea Customs Authorities will drive the e-Freight project for the carriage of cargo by air, the carrier and freight forwarder should pay attention to the requirements and legal effect of the electronic documentation of the carriage of cargo by air.

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Relationships between inbreeding coefficient and economic traits in inbred line of Duroc pigs (두록 계통조성 집단의 근교수준이 경제형질에 미치는 영향)

  • song, Na-Rae;Kim, Yong-Min;Kim, Doo-Wan;Sa, Soo-Jin;Kim, Ki-Hyun;Kim, Young-Hwa;Cho, Kyu-Ho;Do, Chang-hee;Hong, Joon-Ki
    • Korean Journal of Agricultural Science
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    • v.42 no.2
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    • pp.141-149
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    • 2015
  • The data of Duroc swine species that were born from 2000 to 2014 excluding missing ones collected by Korea National Institute of Animal Science were used in the present study. After removing missing data we used 9756 of productions data and 1728 of reproductive reference of breeding research to study the level of inbreeding and to investigate the impact on the reproductive traits, production traits. The correlation of reproductive traits and inbreeding coefficient are -0.07, -0.08 for total number pigs born, number of pigs born alive respectively and birth weight per litter is -0.10, number of pigs born alive per litter to 21days is -0.06 and body weight per litter to 21days is -0.09. The correlation coefficients of the inbreeding coefficients of reproductive traits are shown within 10% with negative correlation (P < 0.05). Days of 90kg and Backfat in the correlation coefficient and inbreeding coefficient production traits were not observed significant correlations, Average daily gain was investigated by the positive correlation of 0.05. According to the above results, the inbreeding level gave a negative effect on the improvement of the breed traits, investigating a relatively high compared to a negative effect on other traits. But overall correlation degree is less than 10% was observed. This inbreeding coefficient has not been clearly observed due to degeneration of the average inbreeding coefficients of these generations was maintained within 10% of the population. The scale of the experimental group was about 150 degree pig husbandry is very small compared to the advanced countries. However, the level of inbreeding in the population group with the appropriate mating combinations is maintained below 10% of population is thought to be small and can minimize the effects of inbreeding degeneration. further testing utilizing this selection is constantly considered to be necessary.

The Effect of Lime Application after Cultivating Winter Forage Crops on the Change of Major Characters and Yield of Peanut (동계사료작물 재배후 석회물질 시용이 땅콩의 주요 형질 및 수량에 미치는 영향)

  • Kim, Dae-Hyang;Chim, Jae-Seong
    • The Journal of Natural Sciences
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    • v.7
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    • pp.103-114
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    • 1995
  • These experiments were conducted for decrease of injury by continuous cropping in the peanut fields of Chonbuk Wangkungarea. The continuous cropping field for four years was used in this experiment. Italian ryegrass and rye were cultivated andlime materials were distributed for improvement of soil fertility. The results were as follows; 1. Forage crops were cultivatedand lime materials were distributed on the continuous cropping field of peanut. The organic matter content of the expermentalplot cultivating Italian ryegrass was only 1.25%. The organic matter content of soil cultivated Italian ryegrass after distributedmagnesium lime was 1.37% and that of soil cultivated Italian ryegrass after distributed gypsum was 1.30%. It was highcontent comparing to that of soil distributed lime materials only. The organic matter content of soil cultivated rye after distributed gypsum was 1.77%. 2. The phosphate content of soil cutivated Italian ryegrass was 332ppm. The phosphate content ofsoil cultivated Italian ryegrass after distributed magnesium lime was 34Oppm and that of soil cultivated Italian ryegrass afterdistributed gypsum was 31 2ppm. The phosphate content of soil cultivated rye only was 386ppm. The phosphate content ofsoil cultivated rye after distributed gypsum was 41 8ppm. This phosphate content was lower than that of soil distributed limematerials only. 3. The phytotoxin content of soil cultivated Italian ryegrass after distributed magnesium lime was decreased to17.7% and that of soil cultivated Italian ryegrass after distributed gypsum was decreased to 25.3%. The phytotoxin content ofsoil cultivated rye after distributed magnesium lime was decreased to 12.0% and that of soil cultivated rye after distributedgypsum was decreased to 12.8% comparing to the phytotoxin content of soil distributed lime materials only. Italian ryegrasswas effective to decrease phytotoxin among the forage crops and gypsum was effective among the lime materials. 4. Abacterial wilt and a late spot of peanut which were known as, main reason of continuous cropping failure were surveyed.lnccidence of a bacterial wilt was 3.4% in the plot cultivated Italian ryegrass only and that was 2.9% in the plot cultivated ryeonly. lnccidence of a bacterial wilt was 2.5% in the plot cultivated Italian ryegrass after distributed magnesium lime and thatwas 2.3% in the plot cultivated rye after distributed gypsum. Inccidence plot cultivated forage crops was lower than that of plotdistributed lime materials. 5. Inccidence of a late spot was high in the plot cultivated forage crops ony, but it was low in the plotcultivated forage crops after distributed lime materials comparing to that of the control plot. 6. The growth and yield of peanutwere bad in the plot cultivated forage crops only comparing to the control plot distributed lime materials only. These resultswere same in the plot cultivated rye after distributed lime materials, but the growth and yield were grown up in the plotcultured Italian ryegrass after distributed lime materials.

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Policy Direction for The Farmland Sizing Suitable to Regional Trait (지역특성을 반영한 영농규모화사업의 발전방향-충남지역을 중심으로-)

  • Shim, Jae-Sung
    • The Journal of Natural Sciences
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    • v.14 no.1
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    • pp.83-121
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    • 2004
  • This study was carried out to examine how solid the production foundation of rice in Chung-Nam Province is, and, if not, to probe alternative measures through the size of farms specializing in rice, of which direction would be a pivot of rice industry-oriented policy. The results obtained can be summarized as follows : 1. The amount of rice production in Chung-Nam Province is highest in Korea and the size of paddy field area is the second largest : This implying that the probability that rice production in Chung-Nam Province would be severely influenced by a global trend of market conditions. The number of farms specializing in rice becoming the core group of rice farming account for 7.7 percent of the total number of farm household in Korea. Average field area financial support which had been input to farm household by Government had a noticeable effect on the improvement of the policy of farm-size program. 2. Farm-size program in Chung-Nam Province established from 1980 to 2002 in creased the cultivation size of paddy field to 19,484 hectares, and this program enhanced the buying and selling of farmland and the number of farmland bargain reached 6,431 household and 16,517 hectares, respectively, in 1995-2002. Meanwhile, long-term letting and hiring of farmland appeared so active that the bargain acreage reached 6,970 hectares, and farm involved was 7,059 households, however, the farm-exchange-and-unity program did not satisfy our expectation, because the retirement farm operators reluctantly participated to sell their farms. Another reason that had delayed the bargain of farms rested on the general category of social complication attendant upon the exchange and unity operation for scattered farm. Such difficulties would work negative effects out to carry on the target of farm-size work in general. 3. The following measures were presented to propel the farm-size promotion program : a. Occupation shift project, followed by the social security program for retirement and elderly farm operators, should be promptly established and also a number of types of incentives for promoting the letting and hiring work and farm-exchange-and-unity program would also be set up. b. To establish the effective key system of rice production, all the farm operators should increase the unit area yield of rice and lower the production cost. To do so, a great deal of production teams of rice equipped with managerial techniques and capabilities need to be organized. And, also, there should be appropriate arrays of facilities including information system. This plan is desirable to be in line with a diversity of the structural implement of regional integration based on farm system building. c. To extend the size of farm and to improve farm management, we have to devise the enlargement of individual size of farm for maximized management and the utilization of farm-size grouping method. In conclusion, it can be said that the farm-size project in Chung-Nam Province which has continued since the 1980s was satisfactorily achieved. However, we still have a lot of problems to be solved to break down the barrier for attainment of the desirable farm-size operation work.. Farm-size project has fairly close relation with farm specialization in rice and, thus, the positive support for farm household including the integrated program for both retirement farmers and off-farm operators should be considered to pursue the progressive development of the farm-size program, which is key means to successful achievement of rice farming enforcement in Chung-Nam Province.

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A Study on Developing a VKOSPI Forecasting Model via GARCH Class Models for Intelligent Volatility Trading Systems (지능형 변동성트레이딩시스템개발을 위한 GARCH 모형을 통한 VKOSPI 예측모형 개발에 관한 연구)

  • Kim, Sun-Woong
    • Journal of Intelligence and Information Systems
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    • v.16 no.2
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    • pp.19-32
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    • 2010
  • Volatility plays a central role in both academic and practical applications, especially in pricing financial derivative products and trading volatility strategies. This study presents a novel mechanism based on generalized autoregressive conditional heteroskedasticity (GARCH) models that is able to enhance the performance of intelligent volatility trading systems by predicting Korean stock market volatility more accurately. In particular, we embedded the concept of the volatility asymmetry documented widely in the literature into our model. The newly developed Korean stock market volatility index of KOSPI 200, VKOSPI, is used as a volatility proxy. It is the price of a linear portfolio of the KOSPI 200 index options and measures the effect of the expectations of dealers and option traders on stock market volatility for 30 calendar days. The KOSPI 200 index options market started in 1997 and has become the most actively traded market in the world. Its trading volume is more than 10 million contracts a day and records the highest of all the stock index option markets. Therefore, analyzing the VKOSPI has great importance in understanding volatility inherent in option prices and can afford some trading ideas for futures and option dealers. Use of the VKOSPI as volatility proxy avoids statistical estimation problems associated with other measures of volatility since the VKOSPI is model-free expected volatility of market participants calculated directly from the transacted option prices. This study estimates the symmetric and asymmetric GARCH models for the KOSPI 200 index from January 2003 to December 2006 by the maximum likelihood procedure. Asymmetric GARCH models include GJR-GARCH model of Glosten, Jagannathan and Runke, exponential GARCH model of Nelson and power autoregressive conditional heteroskedasticity (ARCH) of Ding, Granger and Engle. Symmetric GARCH model indicates basic GARCH (1, 1). Tomorrow's forecasted value and change direction of stock market volatility are obtained by recursive GARCH specifications from January 2007 to December 2009 and are compared with the VKOSPI. Empirical results indicate that negative unanticipated returns increase volatility more than positive return shocks of equal magnitude decrease volatility, indicating the existence of volatility asymmetry in the Korean stock market. The point value and change direction of tomorrow VKOSPI are estimated and forecasted by GARCH models. Volatility trading system is developed using the forecasted change direction of the VKOSPI, that is, if tomorrow VKOSPI is expected to rise, a long straddle or strangle position is established. A short straddle or strangle position is taken if VKOSPI is expected to fall tomorrow. Total profit is calculated as the cumulative sum of the VKOSPI percentage change. If forecasted direction is correct, the absolute value of the VKOSPI percentage changes is added to trading profit. It is subtracted from the trading profit if forecasted direction is not correct. For the in-sample period, the power ARCH model best fits in a statistical metric, Mean Squared Prediction Error (MSPE), and the exponential GARCH model shows the highest Mean Correct Prediction (MCP). The power ARCH model best fits also for the out-of-sample period and provides the highest probability for the VKOSPI change direction tomorrow. Generally, the power ARCH model shows the best fit for the VKOSPI. All the GARCH models provide trading profits for volatility trading system and the exponential GARCH model shows the best performance, annual profit of 197.56%, during the in-sample period. The GARCH models present trading profits during the out-of-sample period except for the exponential GARCH model. During the out-of-sample period, the power ARCH model shows the largest annual trading profit of 38%. The volatility clustering and asymmetry found in this research are the reflection of volatility non-linearity. This further suggests that combining the asymmetric GARCH models and artificial neural networks can significantly enhance the performance of the suggested volatility trading system, since artificial neural networks have been shown to effectively model nonlinear relationships.

Ensemble Learning with Support Vector Machines for Bond Rating (회사채 신용등급 예측을 위한 SVM 앙상블학습)

  • Kim, Myoung-Jong
    • Journal of Intelligence and Information Systems
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    • v.18 no.2
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    • pp.29-45
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    • 2012
  • Bond rating is regarded as an important event for measuring financial risk of companies and for determining the investment returns of investors. As a result, it has been a popular research topic for researchers to predict companies' credit ratings by applying statistical and machine learning techniques. The statistical techniques, including multiple regression, multiple discriminant analysis (MDA), logistic models (LOGIT), and probit analysis, have been traditionally used in bond rating. However, one major drawback is that it should be based on strict assumptions. Such strict assumptions include linearity, normality, independence among predictor variables and pre-existing functional forms relating the criterion variablesand the predictor variables. Those strict assumptions of traditional statistics have limited their application to the real world. Machine learning techniques also used in bond rating prediction models include decision trees (DT), neural networks (NN), and Support Vector Machine (SVM). Especially, SVM is recognized as a new and promising classification and regression analysis method. SVM learns a separating hyperplane that can maximize the margin between two categories. SVM is simple enough to be analyzed mathematical, and leads to high performance in practical applications. SVM implements the structuralrisk minimization principle and searches to minimize an upper bound of the generalization error. In addition, the solution of SVM may be a global optimum and thus, overfitting is unlikely to occur with SVM. In addition, SVM does not require too many data sample for training since it builds prediction models by only using some representative sample near the boundaries called support vectors. A number of experimental researches have indicated that SVM has been successfully applied in a variety of pattern recognition fields. However, there are three major drawbacks that can be potential causes for degrading SVM's performance. First, SVM is originally proposed for solving binary-class classification problems. Methods for combining SVMs for multi-class classification such as One-Against-One, One-Against-All have been proposed, but they do not improve the performance in multi-class classification problem as much as SVM for binary-class classification. Second, approximation algorithms (e.g. decomposition methods, sequential minimal optimization algorithm) could be used for effective multi-class computation to reduce computation time, but it could deteriorate classification performance. Third, the difficulty in multi-class prediction problems is in data imbalance problem that can occur when the number of instances in one class greatly outnumbers the number of instances in the other class. Such data sets often cause a default classifier to be built due to skewed boundary and thus the reduction in the classification accuracy of such a classifier. SVM ensemble learning is one of machine learning methods to cope with the above drawbacks. Ensemble learning is a method for improving the performance of classification and prediction algorithms. AdaBoost is one of the widely used ensemble learning techniques. It constructs a composite classifier by sequentially training classifiers while increasing weight on the misclassified observations through iterations. The observations that are incorrectly predicted by previous classifiers are chosen more often than examples that are correctly predicted. Thus Boosting attempts to produce new classifiers that are better able to predict examples for which the current ensemble's performance is poor. In this way, it can reinforce the training of the misclassified observations of the minority class. This paper proposes a multiclass Geometric Mean-based Boosting (MGM-Boost) to resolve multiclass prediction problem. Since MGM-Boost introduces the notion of geometric mean into AdaBoost, it can perform learning process considering the geometric mean-based accuracy and errors of multiclass. This study applies MGM-Boost to the real-world bond rating case for Korean companies to examine the feasibility of MGM-Boost. 10-fold cross validations for threetimes with different random seeds are performed in order to ensure that the comparison among three different classifiers does not happen by chance. For each of 10-fold cross validation, the entire data set is first partitioned into tenequal-sized sets, and then each set is in turn used as the test set while the classifier trains on the other nine sets. That is, cross-validated folds have been tested independently of each algorithm. Through these steps, we have obtained the results for classifiers on each of the 30 experiments. In the comparison of arithmetic mean-based prediction accuracy between individual classifiers, MGM-Boost (52.95%) shows higher prediction accuracy than both AdaBoost (51.69%) and SVM (49.47%). MGM-Boost (28.12%) also shows the higher prediction accuracy than AdaBoost (24.65%) and SVM (15.42%)in terms of geometric mean-based prediction accuracy. T-test is used to examine whether the performance of each classifiers for 30 folds is significantly different. The results indicate that performance of MGM-Boost is significantly different from AdaBoost and SVM classifiers at 1% level. These results mean that MGM-Boost can provide robust and stable solutions to multi-classproblems such as bond rating.