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Composting of the Pig Manure Used with the Ceramic Biocarrier (복합세라믹 담체를 이용한 돈분 퇴비화 연구)

  • Hwang, Joon-Young;Lee, Jong-Eun;Chang, Ki-Woon
    • Journal of the Korea Organic Resources Recycling Association
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    • v.11 no.2
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    • pp.110-116
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    • 2003
  • This study was executed to evaluate the utilization and efficiency of the ceramic biocarrier as the promoter of decomposing on the organic matters for the composting using with pig manure by analyzing of the physico-chemical properties during composting. The treatments of this experiment were consisted of the control(C),microorganism(M), M with natural zeolite(M+Z), M with synthesized zeolite(M+SZ), and M with ceramic biocarrier(M+CZ). The process term of composting was conducted for 30days in the rapidly fermented machine(as pilot system). The results of the physico-chemical properties of the composts were as follows. The changes of temperature during composting was not relative with the microorganism and zeolite materials used in the composts. At all of the treatments were similar to changing of temp. from the initial stage to the final stage. But the added microorganism treatments were higher than control. And the entire pH value of treatments were appeared the same that above temperature result, also the M+CZ and M+SZ treatment among the treatment were higher. At the results of T-C, T-N and C/N ratio, in case of T-C value, the M+CZ treatment was highly more decreased than others. However at the T-N value, there were not the differences from the each treatment. And the C/N ratio was changed according to the changes of T-C and T-N value. Especially, at the M+CZ aud M+SZ treatments were remarkably reduced by about 21.4-23.3 value. In the result of G.I for evaluating of the compost humidity, the M+CZ and M+SZ treatments were close up approximately 110 value compared with the control(G.I value 100). Therefore, the examined ceramic biocarrier amended with compost-promoting-bacteria could be applied to the production of many high quality fertilizers. It is also expected that the results of this researches could be applied to the recycle of the organic wastes based on the experimental results of ceramic biocarrier and compost-promoting-bacteria application.

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A Study on Development of Guideline on Writing Technical Document for Electrical Medical Devices: Dental X-ray Equipment (치과용엑스선장치의 기술문서 작성을 위한 가이드라인 개발 연구)

  • Lee, Seung-Youl;Kim, Jae-Ryang;Lee, Jun-Ho;Park, Chang-Won
    • Journal of radiological science and technology
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    • v.39 no.4
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    • pp.651-660
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    • 2016
  • Due to recent population aging, the number of check-up for senior citizens has increased steadily. According to this trend, the market size of dental X-ray equipment and the number of approval and review for these devices have simultaneously increased. The technical document of medical device is required for approval and review for medical device, and medical device companies needs to have work comprehension and expertise, as the document needs to include the overall contents such as performances, test criteria, etc.. Yet, since most of domestic manufacturers or importers of medical devices are small businesses, it is difficult for them to recruit professional manpower for approval of medical devices, and submission of inaccurate technical documents has increased. These problems lead to delay of the approval process and to difficulties in quick entering into the market. Especially, the Ministry of Food and Drug safety (MFDS) standards of a dental extra-oral X-ray equipment, a dental intra-oral X-ray equipment, an arm-type computed tomography, and a portable X-ray system have been recently enacted or not. this guideline of dental X-ray equipment adjusting revised standards was developed to help relative companies and reviewers. For this study, first, the methods to write technical document have been reviewed with revised international and domestic regulations and system. Second, the domestic and foreign market status of each item has been surveyed and analyzed. Third, the contents of technical documents already approved by MFDS have been analyzed to select the correct example, test items, criteria, and methods. Finally, the guideline has been developed based on international and domestic regulation, through close review of a consultative body composed of academic, industrial, research institute and government experts.

Study about porous of Korean traditional pottery (한국전통옹기의 통기성에 관한연구)

  • Kim, Seok-Ho
    • Journal of Science of Art and Design
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    • v.9
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    • pp.5-24
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    • 2006
  • Human hunted and picked to survive and a vessel was made naturally to store something being hunted and picket, which was a great invention. In modern times, society changed and development of science gave us convenience in making a vessel and various kinds of store instruments which was made of pure natural material, of new stuff, such as plastic and iron. but human became to be inclined to regress into nature because of problems of environment. We can say that the representative trend is well-being, after all this is a symptom to return to life being persued by predecessors before the science civilization was developed. Ancestors have lived with nature, adapted themselves to it. For examples they have built the house which became to be a part of nature and just like it, and studied a method of storing food to eat for four seasons, then displayed a storagehouse and storage containers everywhere of the house. Now Korean has the custody of kimchi in refrigerator at every house, but our forefathers controled a timing to eat food with studying a method of storage to put to use nature. With hot wind of well-being, Korean food is becoming to be globalized, according to this, concern about the wisdom of progenitors is growing more and more. It's an example that the world shows concern seriously about the pottery, which have stored kimchi for a long time fleshly, in globalization of kimchi. This study have three purposes, the first. checking documents about the development history of pottery which is a kind of ceramic, and then the second, through an scientific experiment, with studying characteristic of pottery being built by the wisdom of ancestors, informing the merit of pottery and necessity to the world, and futhermore, the third, working up the development of close environmental vessels putting to use the characteristic of pottery.

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토양 및 지하수 Investigation 과 Remediation에 대한 현장적용

  • Wallner, Heinz
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2000.11a
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    • pp.44-63
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    • 2000
  • Situated close to Heathrow Airport, and adjacent to the M4 and M25 Motorways, the site at Axis Park is considered a prime location for business in the UK. In consequnce two of the UK's major property development companies, MEPC and Redrew Homes sought the expertise of Intergeo to remediate the contaminated former industrial site prior to its development. Industrial use of the twenty-six hectare site, started in 1936, when Hawker Aircraft commence aircraft manufacture. In 1963 the Firestone Tyre and Rubber Company purchased part of the site. Ford commenced vehicle production at the site in the mid-1970's and production was continued by Iveco Ford from 1986 to the plant's decommissioning in 1997. Geologically the site is underlain by sand and gravel, deposited in prehistory by the River Thames, with London Clay at around 6m depth. The level of groundwater fluctuates seasonally at around 2.5m depth, moving slowly southwest towards local streams and watercourses. A phased investigation of the site was undertaken, which culminated in the extensive site investigation undertaken by Intergeo in 1998. In total 50 boreholes, 90 probeholes and 60 trial pits were used to investigate the site and around 4000 solid and 1300 liquid samples were tested in the laboratory for chemical substances. The investigations identified total petroleum hydrocarbons in the soil up to 25, 000mg/kg. Diesel oil, with some lubricating oil were the main components. Volatile organic compounds were identified in the groundwater in excess of 10mg/l. Specific substances included trichloromethane, trichloromethane and tetrachloroethene. Both the oil and volatile compounds were widely spread across the site, The specific substances identified could be traced back to industrial processes used at one or other dates in the sites history Slightly elevated levels of toxic metals and polycyclic aromatic hydrocarbons were also identified locally. Prior to remediation of the site and throughout its progress, extensive liaison with the regulatory authorities and the client's professional representatives was required. In addition to meetings, numerous technical documents detailing methods and health and safety issues were required in order to comply with UK environmental and safety legislation. After initially considering a range of options to undertake remediation, the following three main techniques were selected: ex-situ bioremediation of hydrocarbon contaminated soils, skimming of free floating hydrocarbon product from the water surface at wells and excavations and air stripping of volatile organic compounds from groundwater recovered from wells. The achievements were as follows: 1) 350, 000m3 of soil was excavated and 112, 000m3 of sand and gravel was processed to remove gravel and cobble sized particles; 2) 53, 000m3 of hydrocarbon contaminated soil was bioremediated in windrows ; 3) 7000m3 of groundwater was processed by skimming to remove free floating Product; 4) 196, 000m3 of groundwater was Processed by air stripping to remove volatile organic compounds. Only 1000m3 of soil left the site for disposal in licensed waste facilities Given the costs of disposal in the UK, the selected methods represented a considerable cost saving to the Clients. All other soil was engineered back into the ground to a precise geotechnical specification. The following objective levels were achieved across the site 1) By a Risk Based Corrective Action (RBCA) methodology it was demonstrated that soil with less that 1000mg/kg total petroleum hydrocarbons did not pose a hazard to health or water resources and therefore, could remain insitu; 2) Soils destined for the residential areas of the site were remediated to 250mg/kg total petroleum hydrocarbons; in the industrial areas 500mg/kg was proven acceptable. 3) Hydrocarbons in groundwater were remediated to below the Dutch Intervegtion Level of 0.6mg/1; 4) Volatile organic compounds/BTEX group substances were reduced to below the Dutch Intervention Levels; 5) Polycyclic aromatic hydrocarbons and metals were below Inter-departmental Committee for the Redevelopment of Contaminated Land guideline levels for intended enduse. In order to verify the qualify of the work 1500 chemical test results were submitted for the purpose of validation. Quality assurance checks were undertaken by independent consultants and at an independent laboratory selected by Intergeo. Long term monitoring of water quality was undertaken for a period of one year after remediation work had been completed. Both the regulatory authorities and Clients representatives endorsed the quality of remediation now completed at the site. Subsequent to completion of the remediation work Redrew Homes constructed a prestige housing development. The properties at "Belvedere Place" retailed at premium prices. On the MEPC site the Post Office, amongst others, has located a major sorting office for the London area. Exceptionally high standards of remediation, control and documentation were a requirement for the work undertaken here.aken here.

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Performance of Drip Irrigation System in Banana Cultuivation - Data Envelopment Analysis Approach

  • Kumar, K. Nirmal Ravi;Kumar, M. Suresh
    • Agribusiness and Information Management
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    • v.8 no.1
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    • pp.17-26
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    • 2016
  • India is largest producer of banana in the world producing 29.72 million tonnes from an area of 0.803 million ha with a productivity of 35.7 MT ha-1 and accounted for 15.48 and 27.01 per cent of the world's area and production respectively (www.nhb.gov.in). In India, Tamil Nadu leads other states both in terms of area and production followed by Maharashtra, Gujarat and Andhra Pradesh. In Rayalaseema region of Andhra Pradesh, Kurnool district had special reputation in the cultivation of banana in an area of 5765 hectares with an annual production of 2.01 lakh tonnes in the year 2012-13 and hence, it was purposively chosen for the study. On $23^{rd}$ November 2003, the Government of Andhra Pradesh has commenced a comprehensive project called 'Andhra Pradesh Micro Irrigation Project (APMIP)', first of its kind in the world so as to promote water use efficiency. APMIP is offering 100 per cent of subsidy in case of SC, ST and 90 per cent in case of other categories of farmers up to 5.0 acres of land. In case of acreage between 5-10 acres, 70 per cent subsidy and acreage above 10, 50 per cent of subsidy is given to the farmer beneficiaries. The sampling frame consists of Kurnool district, two mandals, four villages and 180 sample farmers comprising of 60 farmers each from Marginal (<1ha), Small (1-2ha) and Other (>2ha) categories. A well structured pre-tested schedule was employed to collect the requisite information pertaining to the performance of drip irrigation among the sample farmers and Data Envelopment Analysis (DEA) model was employed to analyze the performance of drip irrigation in banana farms. The performance of drip irrigation was assessed based on the parameters like: Land Development Works (LDW), Fertigation costs (FC), Volume of water supplied (VWS), Annual maintenance costs of drip irrigation (AMC), Economic Status of the farmer (ES), Crop Productivity (CP) etc. The first four parameters are considered as inputs and last two as outputs for DEA modelling purposes. The findings revealed that, the number of farms operating at CRS are more in number in other farms (46.66%) followed by marginal (45%) and small farms (28.33%). Similarly, regarding the number of farmers operating at VRS, the other farms are again more in number with 61.66 per cent followed by marginal (53.33%) and small farms (35%). With reference to scale efficiency, marginal farms dominate the scenario with 57 per cent followed by others (55%) and small farms (50%). At pooled level, 26.11 per cent of the farms are being operated at CRS with an average technical efficiency score of 0.6138 i.e., 47 out of 180 farms. Nearly 40 per cent of the farmers at pooled level are being operated at VRS with an average technical efficiency score of 0.7241. As regards to scale efficiency, nearly 52 per cent of the farmers (94 out of 180 farmers) at pooled level, either performed at the optimum scale or were close to the optimum scale (farms having scale efficiency values equal to or more than 0.90). Majority of the farms (39.44%) are operating at IRS and only 29 per cent of the farmers are operating at DRS. This signifies that, more resources should be provided to these farms operating at IRS and the same should be decreased towards the farms operating at DRS. Nearly 32 per cent of the farms are operating at CRS indicating efficient utilization of resources. Log linear regression model was used to analyze the major determinants of input use efficiency in banana farms. The input variables considered under DEA model were again considered as influential factors for the CRS obtained for the three categories of farmers. Volume of water supplied ($X_1$) and fertigation cost ($X_2$) are the major determinants of banana farms across all the farmer categories and even at pooled level. In view of their positive influence on the CRS, it is essential to strengthen modern irrigation infrastructure like drip irrigation and offer more fertilizer subsidies to the farmer to enhance the crop production on cost-effective basis in Kurnool district of Andhra Pradesh, India. This study further suggests that, the present era of Information Technology will help the irrigation management in the context of generating new techniques, extension, adoption and information. It will also guide the farmers in irrigation scheduling and quantifying the irrigation water requirements in accordance with the water availability in a particular season. So, it is high time for the Government of India to pay adequate attention towards the applications of 'Information and Communication Technology (ICT) and its applications in irrigation water management' for facilitating the deployment of Decision Supports Systems (DSSs) at various levels of planning and management of water resources in the country.

A Study on Angels' Costumes in Religious Paintings (종교화에 나타난 천사의 복식에 관한 연구)

  • Kim Hae Jon
    • Journal of the Korean Society of Clothing and Textiles
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    • v.3 no.1
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    • pp.1-11
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    • 1979
  • This is a study on angels' costumes in religious paintings, especially as this relates to the questions of concepts and theological symbolism. Angels, as spiritual creatures in Christian thought, play the role of praising God's glory, as messengers of God, the role of guarding Israel and the Church, and protecting or punishing human beings. Sometimes the angels appear in incarnate form. They display no sexual differences and are not able to procreate. The angels' funtional classification being thus; nevertheless, they are pictured in various costumes and appearances according to characteristics of the paintings. The angel Michael appears as a man of dignity when pictured as a guard; the angel Gabriel in the annunciation is often portrayed as a woman of mystical beauty. Under the Renaissance, the mighty cherubim and seraphim at Yahweh's throne are degraded as plump child-angels, or winged child-heads looking alike Eros or Cupid. They have become playful and all too obviously non-heavenly chrubs, accepted features of the Temple decorations. However, cherubim are often depicted as naked or wrapped around with a piece of cloth and accompanied with wind, which symbolizes the Glory of God. The angels, costumes without seam are hung over or wrapped around the body, and when sewn they are simple and ample enough that they fall in a great many folds. However, by the 14C. angels are mostly dressed in costumes common to all Europe, and after that angels gradually appear in folk costumes; for example Italian, Flemish, etc. Dalmatic, the typical costume of Byzantine often shows up as angels' dresses even after the period. Originally the dalmatic was the Roman tunic to which Eastern influences added. The Roman clavus on the tunic had gradually lost distinction until, by the Imperial epoch, it was worn by the lowest servants. It was proudly therefore, as 'The servants of God', that the early Christians are shown wearing the clavus on their wide, ungirdled, sleeved dalmatics. In addition to their costume, angels have some other distinct charateristics. First, angels have a halo around their head; this symbolizes their holiness. Second, angels wear a narrow diadem or a queen's crown that seems to denote their glorious status close to God's throne. Third, the cloth band across the breast resembles a priest's stole, which suggests the sacred role of a priest and symbolizes the grace santified. Fourth, lilies in the annunciations are symbols of Mary's virginity. chastity, innocence and heavenly bliss. Angels hold palms or olives in their hands. The former denote prosperity. beauty and the Christians' reward after death; the latter represent peace and amity. the imperial crown made of olives means victory. Fifth, angels in paintings always have a pair of wings, which can be traced to scripture where cherubim and seraphim are described as having pairs of wings. Angels' wings often have colors of the rainbow, and the rainbow is compared to God's glory. Sixth, generally artists paint angels' costumes as white, blue, green, gold and purple. Other colors such as red rarely appear. According, to scriptures it is believed that angels should be depicted 'as white as snow'. According to the biblical expressions of angels as lightning, sun or a pillar of fire, angels should be described as creatures of light. Nevertheless being a form of art, religious paintings may differ in their presentation according to an artist's inspiration and intention. Since religious paintings illustrated above were almost all done before the Reformation, symbols of colors used in the Catholic Church will also be mentioned. The white color symbolizes chastity, purity, brightness, delight and divinity. Green represents new birth, eternal life, spiritual revival and the expectance of the grace of God. Blue, the color of sapphires, denotes chastity and truth. Red, the color of rubies, represents divinity, love and religious passion. Violet is the color of dignity, indicating the sovereign, royal or imperial power and the great Sacrifice of Christ. As mentionad above, angels' costumes were expressed in accordance with contemporary patterns or as indicated in the Bible, and accesories and colors correspond with Christian symbols. Therefore these facts should be taken into consideration when it comes to the study of costume history.

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A Transmission Electron Microscopy Study on the Crystallization Behavior of In-Sb-Te Thin Films (In-Sb-Te 박막의 결정화 거동에 관한 투과전자현미경 연구)

  • Kim, Chung-Soo;Kim, Eun-Tae;Lee, Jeong-Yong;Kim, Yong-Tae
    • Applied Microscopy
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    • v.38 no.4
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    • pp.279-284
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    • 2008
  • The phase change materials have been extensively used as an optical rewritable data storage media utilizing their phase change properties. Recently, the phase change materials have been spotlighted for the application of non-volatile memory device, such as the phase change random access memory. In this work, we have investigated the crystallization behavior and microstructure analysis of In-Sb-Te (IST) thin films deposited by RF magnetron sputtering. Transmission electron microscopy measurement was carried out after the annealing at $300^{\circ}C$, $350^{\circ}C$, $400^{\circ}C$ and $450^{\circ}C$ for 5 min. It was observed that InSb phases change into $In_3SbTe_2$ phases and InTe phases as the temperature increases. It was found that the thickness of thin films was decreased and the grain size was increased by the bright field transmission electron microscopy (BF TEM) images and the selected area electron diffraction (SAED) patterns. In a high resolution transmission electron microscopy (HRTEM) study, it shows that $350^{\circ}C$-annealed InSb phases have {111} facet because the surface energy of a {111} close-packed plane is the lowest in FCC crystals. When the film was heated up to $400^{\circ}C$, $In_3SbTe_2$ grains have coherent micro-twins with {111} mirror plane, and they are healed annealing at $450^{\circ}C$. From the HRTEM, InTe phase separation was occurred in this stage. It can be found that $In_3SbTe_2$ forms in the crystallization process as composition of the film near stoichiometric composition, while InTe phase separation may take place as the composition deviates from $In_3SbTe_2$.

Media Work as Creative Labor?: Toward Critical Inquiry of Media Work with Critical Cultural Economy (창의적 일로서의 미디어 노동?: 미디어 노동의 문화경제 분석을 위한 시론)

  • Seo, Dong-Jin
    • Korean journal of communication and information
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    • v.57
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    • pp.33-48
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    • 2012
  • Over the last decades, the issue of work or labor has played a critical role in prevailing discourses to represent the changed economic reality. Aesthetic labor, cultural work, network labor, team-work and alike, have played a dazzling role to represent the emerging economic order, employing the word of labor. Certainly, it is not less than a part of a wide range of shifts in order to make capital work with more effect by making up a workable and governable subject. In this article, I try to examine shifts around the media work which has contributed to expand the new discourse of 'labor.' I will say that it is quite crucial for accounting for the reality of media work to shed light on moves to represent media work, and, among others, one to transform the subjectivity involved in it among others. Furthermore, it would be necessary to take a close look at the subjectivity of media work and its modification to deal with and eliminate the precariousness of media work. Saying about media work without paying any attention to heterogenous and various practices to compose a media work, one is forced to regard media work as the matter of economic and legal interests. In addition, it would bring about that the cultural political concerns of media work will be detached from critical sight of the media cultural studies. Referring to major studies around media work in critical media studies, cultural studies and political economy of communication, this article will briefly look into the arrangement of contentions around subjectivity of media work in South Korea. And it will try to suggest what cultural-political strategy we need to investigate, fighting against the hegemonic power to generate and regulate media work and its workers in precarious conditions. It does not intend to search the media work and its complicated realities in detail in South Korea. I wish that it would make a preliminary step to propose and elaborate the critical analysis of media work and its form of subjectivities.

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Microbiological Status and Guideline for Raw Chicken distributed in Korea (국내 유통 닭고기의 미생물 수준과 위생관리기준 적합성)

  • Kim, Hye-Jin;Kim, Dongwook;Song, Sung Ok;Goh, Yong-Gyun;Jang, Aera
    • Korean Journal of Poultry Science
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    • v.43 no.4
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    • pp.235-242
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    • 2016
  • This study was conducted to investigate the microbiological sanitation status of raw chicken meat distributed in Korea, and potential changes in chicken breast quality during storage. The microbiological sanitation status analysis of raw chicken involved studying the results of microbiological monitoring for a 5-year period (2010~2014) by the Korean Food and Drug Administration. Furthermore, the microbiological status of raw chicken meat in meat packing centers and shops in Seoul/Gyeonggi, Kangwon, and Chungcheong Provinces was investigated from July to August 2015. The total bacterial counts of chicken meat in the packaging centers and meat shop of these Provinces were below the level specified in the Korean Meat Microbiological Guideline ($1{\times}10^7$ colony forming units [CFU]/g) and showed a similar microbiological sanitation status with results of the microbiological monitoring for the analyzed 5-year period. To evaluate the relationship between quality change and microbiological level of the meat distributed in Korea, the pH and microbiological and sensory quality characteristics of the chicken breast samples during storage at $4{\pm}2^{\circ}C$were determined. On day 4, the total bacterial count of the chicken breast was 6.76 log CFU/g, which was close to the official $1{\times}10^7CFU/g$ standard, the pH was 5.96, and the overall acceptability was reduced significantly (p<0.05). In particular, the aroma score was <5, indicating that the consumer panel expressed a negative perception even though the chicken contained a lower microbial level than that specified in the Korean microbiological guideline. These results suggest that the current Korean microbiological guideline for raw chicken meat may require a stricter level of up to $1{\times}10^6CFU/g$ to satisfy both meat safety standards and organoleptic quality for consumers.

A Study on the Volatility of Global Stock Markets using Markov Regime Switching model (마코브국면전환모형을 이용한 글로벌 주식시장의 변동성에 대한 연구)

  • Lee, Kyung-Hee;Kim, Kyung-Soo
    • Management & Information Systems Review
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    • v.34 no.3
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    • pp.17-39
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    • 2015
  • This study examined the structural changes and volatility in the global stock markets using a Markov Regime Switching ARCH model developed by the Hamilton and Susmel (1994). Firstly, the US, Italy and Ireland showed that variance in the high volatility regime was more than five times that in the low volatility, while Korea, Russia, India, and Greece exhibited that variance in the high volatility regime was increased more than eight times that in the low. On average, a jump from regime 1 to regime 2 implied roughly three times increased in risk, while the risk during regime 3 was up to almost thirteen times than during regime 1 over the study period. And Korea, the US, India, Italy showed ARCH(1) and ARCH(2) effects, leverage and asymmetric effects. Secondly, 278 days were estimated in the persistence of low volatility regime, indicating that the mean transition probability between volatilities exhibited the highest long-term persistence in Korea. Thirdly, the coefficients appeared to be unstable structural changes and volatility for the stock markets in Chow tests during the Asian, Global and European financial crisis. In addition, 1-Step prediction error tests showed that stock markets were unstable during the Asian crisis of 1997-1998 except for Russia, and the Global crisis of 2007-2008 except for Korea and the European crisis of 2010-2011 except for Korea, the US, Russia and India. N-Step tests exhibited that most of stock markets were unstable during the Asian and Global crisis. There was little change in the Asian crisis in CUSUM tests, while stock markets were stable until the late 2000s except for some countries. Also there were stable and unstable stock markets mixed across countries in CUSUMSQ test during the crises. Fourthly, I confirmed a close relevance of the volatility between Korea and other countries in the stock markets through the likelihood ratio tests. Accordingly, I have identified the episode or events that generated the high volatility in the stock markets for the financial crisis, and for all seven stock markets the significant switch between the volatility regimes implied a considerable change in the market risk. It appeared that the high stock market volatility was related with business recession at the beginning in 1990s. By closely examining the history of political and economical events in the global countries, I found that the results of Lamoureux and Lastrapes (1990) were consistent with those of this paper, indicating there were the structural changes and volatility during the crises and specificly every high volatility regime in SWARCH-L(3,2) student t-model was accompanied by some important policy changes or financial crises in countries or other critical events in the international economy. The sophisticated nonlinear models are needed to further analysis.

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