• The Magazine of the IEIE
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• v.29 no.6
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• pp.76-80
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• 2002

'Liquid Crystal의 상전이(相轉移)와 광학적 이방성(異方性)이 1888년과 1889년 F. Reinitzer와 O. Lehmann에 의해 Monatsch Chem.과 Z.Physikal.Chem.에 각각 보고된 후 부터 제2차 세계대전이 끝난 뒤인 1950년대 까지는 Liquid Crystal을 단지실험실에서의 기초학문 차원의 연구 대상으로만 다루어 왔다. 1963년 Williams가 Liquid Crystal Device로는 최초로 특허 출원을 하였으며, 1968년 RCA사의 Heilmeier등은 Nematic 액정(液晶)에 저주파(低周波) 전압(電壓)을 인가하면 투명한 액정이 혼탁(混濁)상태로 변화하는 '동적산란(動的散亂)'(Dynamic Scattering) 현상을 이용하여 최초의 DSM(Dynamic Scattering Mode) LCD(Liquid Crystal Display)를 발명하였다. 비록 150V 이상의 높은 구동전압과 과소비전력의 특성 때문에 실용화에는 실패하였지만 Guest-Host효과와 Memory효과 등을 발견하였다. 1970년대에 이르러 실온에서 안정되게 사용 가능한 액정물질들이 합성되고(H. Kelker에 의해 MBBA, G. Gray에 의한 Cyano-Biphenyl 액정의 합성), CMOS 트랜지스터의 발명, 투명도전막(ITO), 수은전지등의 주변기술들의 발전으로 인하여 LCD의 상품화가 본격적으로 이루어지게 되었다. 1971년에는 M. Shadt, W. Helfrich, J.L. Fergason등이 TN(Twisted Nematic) LCD를 발명하여 전자 계산기와 손목시계에 응용되었고, 1970년대 말에는 Sharp에서 Dot Matrix형의 휴대형 컴퓨터를 발매하였다. 이러한 단순 구동형의 TN LCD는 그래픽 정보를 표시하는 데에는 품질의 한계가 있어 1979년 영국의 Le Comber에 의해 a-Si TFT(amorphous Silicon Thin Film Transistor) LCD의 연구가 시작되었고, 1983년 T.J. Scheffer, J. Nehring, G. Waters에 의해 STN(Super Twisted Nematic) LCD가 창안되었고, 1980년 N. Clark, S. Lagerwall 및 1983년 K.Yossino에 의해 Ferroelectric LCD가 등장하여 LCD의 정보 표시량 증대에 크게 기여하였다. Color화의 진전은 1972년 A.G. Ficher의 셀 외부에 RGB(Red, Green, Blue) filter를 부착하는 방안과, 1981년 T. Uchida 등에 의한 셀 내부에 RGB filter를 부착하는 방법에 의해 상품화가 되었다. 1985년에는 J.L. Fergason에 의해 Polymer Dispersed LCD가 발명되었고, 1980년대 중반에 이르러 동화상(動畵像) 표시가 가능한 a-Si TFT LCD의 시제품(試製品) 개발이 이루어지고 1990년부터는 본격적인 양산 시대에 접어들게 되었다. 1990년대 초에는 STN LCD의 Color화 및 대형화(大型化) 고(高)품위화에 힘입어 Note-Book PC에 LCD가 본격적으로 적용이 되었고, 1990년대 후반에는TFT LCD의 표시품질 대비 가격경쟁력 확보로 인하여 Note-Book PC 시장을 독점하기에 이르렀다. 이후로는 TFT LCD의 대형화가 중요한 쟁점으로 부각되고 있고, 1995년 삼성전자는 당시 세계최대 크기의 22' TFT LCD를 개발하였다. 또한 LCD의 고정세(高情細)화를 위해 Poly Si TFT LCD의 개발이 이루어졌고, 디지타이져 일체형 LCD의 상품화가 그 응용의 폭을 넓혔으며, LCD의 대형화를 위해 1994년 Canon에 의해 14.8', 21' 등의 FLCD가 개발되었다. 대형화 방안으로 Tiled LCD 기술이 개발되고 있으며, 1995년에 Sharp에 의해 21' 두장의 Panel을 이어 붙인 28' TFT LCD가 전시되었고 1996년에는 21' 4장의 Panel을 이어 붙인 40'급 까지의 개발이 시도 되었으며 현재는 LCD의 특성향상과 생산설비의 성능개선과 안정적인 공정관리기술을 바탕으로 삼성전자에서 단패널 40' TFT LCD가 최근에 개발되었다. Projection용 디스플레이로는 Poly-Si TFT LCD를 이용하여 $25'{\sim}100'$사이의 배면투사형과 전면투사형 까지 개발되어 대형 TV시장을 주도하고 있다. 21세기 디지털방송 시대를 맞아 플라즈마디스플레이패널(PDP) TV, 액정표시장치 (LCD)TV, 강유전성액정(FLCD) TV 등 2005년에 약 1500만대 규모의 거대 시장을 형성할 것으로 예상되는 이른바 '벽걸이TV'로 불리는 차세대 초박형 TV 시장을 선점하기 위하여 세계 가전업계들이 양산에 총력을 기울이고 있다. 벽걸이TV 시장이 본격적으로 형성되더라도 PDP TV와 LCD TV가 직접적으로 시장에서 경쟁을 벌이는 일은 별로 없을 것으로 보인다. 향후 디지털TV 시장이 본격적으로 열리면 40인치 이하의 중대형 시장은 LCD TV가 주도하고 40인치 이상 대화면 시장은 PDP TV가 주도할 것으로 보는 시각이 지배적이기 때문이다. 그러나 이러한 직시형 중대형(重大型)디스플레이는 그 가격이 너무 높아서 현재의 브라운관 TV를 대체(代替)하기에는 시일이 많이 소요될 것으로 추정되고 있다. 그 대안(代案)으로는 비교적 저가격(低價格)이면서도 고품질의 디지털 화상구현이 가능한 고해상도 프로젝션 TV가 유력시되고 있다. 이러한 고해상도 프로젝션 TV용으로 DMD(Digital Micro-mirror Display), Poly-Si TFT LCD와 LCOS(Liquid Crystals on Silicon) 등의 상품화가 진행되고 있다. 인터넷과 정보통신 기술의 발달로 휴대형 디스플레이의 시장이 예상 외로 급성장하고 있으며, 요구되는 디스플레이의 품질도 단순한 문자표시에서 그치지 않고 고해상도의 그래픽 동화상 표시와 칼라 표시 및 3차원 화상표시까지 점차로 그 영역이 넓어지고 있다. <표 1>에서 보여주는 바와 같이 LCD의 시장규모는 적용분야 별로 지속적인 성장이 예상되며, 새로운 응용분야의 시장도 성장성을 어느 정도 예측할 수 있다. 따라서 LCD기술의 연구개발 방향은 크게 두가지로 분류할 수 있으며 첫째로는, 현재 양산되고 있는 LCD 상품의 경쟁력강화를 위하여 원가(原價) 절감(節減)과 표시품질을 향상시키는 것이며 둘째로는, 새로운 타입의 LCD를 개발하여 기존 상품을 대체하거나 새로운 시장을 창출하는 분야로 나눌 수 있다. 이와 같은 관점에서 현재 진행되고 있는 LCD기술개발은 다음과 같이 분류할 수 있다. 1) 원가 절감 2) 특성 향상 3) New Type LCD 개발.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.579-589
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• 2009

Hwang River in South Korea, has experienced channel adjustments due to dam construction. Hapcheon main dam and re-regulation dam. The reach below the re-regulation dam (45 km long) changed in flow regime, channel width, bed material distribution, vegetation expansion, and island formation after dam construction. The re-regulation dam dramatically reduced annual peak flow from 654.7 $m^3$/s to 126.3 $m^3$/s and trapped the annual 591 thousand $m^3$ of sediment load formerly delivered from the upper watershed since the completion of the dam in 1989. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that non-vegetated active channel width narrowed an average of 152 m (47% of 1982) and non-vegetated active channel area decreased an average of 6.6 km2 (44% of 1982) between 1982 and 2004, with most narrowing and decreasing occurring after dam construction. The effects of daily pulses of water from peak hydropower generation and sudden sluice gate operations are investigated downstream of Hapcheon Dam in South Korea. The study reach is 45 km long from the Hapcheon re-regulation Dam to the confluence with the Nakdong River. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that the non-vegetated active channel width narrowed an average of 152 m (47% reduction since 1982). The non-vegetated active channel area also decreased an average of 6.6 $km^2$ (44% reduction since 1982) between 1982 and 2004, with most changes occurring after dam construction. The average median bed material size increased from 1.07 mm in 1983 to 5.72 mm in 2003, and the bed slope of the reach decreased from 0.000943 in 1983 to 0.000847 in 2003. The riverbed vertical degradation is approximately 2.6 m for a distance of 20 km below the re-regulation dam. It is expected from the result of the unsteady sediment transport numerical model (GSTAR-1D) steady simulations that the thalweg elevation will reach a stable condition around 2020. The model also confirms the theoretical prediction that sediment transport rates from daily pulses and flood peaks are 21 % and 15 % higher than their respective averages.

• Journal of Korean Society of Forest Science
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• v.82 no.3
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• pp.235-245
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• 1993

This study was carried out to understand the stand structure based on the compositional characteristics of natural deciduous forest dominated by Quercus species, which will provide with fundamental ecological and silvicultural information for effective forest management. Of two tracts selected from the Seoul National University Research Forests, one is located in Kwangju-Gun Kyunggi-Do, and the other in Kwangyang-Gun Chollanam-Do. Point-quarter sampling method w-as employed to survey woody vegetation confined to larger than 6cm in DBH. The numbers of sample points were 152 and 187, in Kwangju-Gun and Kwangyang-Gun, respectively. Comparative analysis for two forest tracts was made as follows ; 1) species composition by calculation of importance values ; 2) number of stems per hectare for major tree species ; 3) species diversity for the forests in two locations ; 4) inter-species association based on $X^2$ test. The relative dominate of Quercus speices showed 88% at Kwangju-Gun, Kyunggi-Do and 50% at Kwangy-ang-Gun. Chollanam-Do. Such high dominance occurred due to high importance values of Quercus variahilis and Q. mortgolica in both locations. Quercus serrata showed low value at Kwangju-Gun. Kyunggi-Do whereas Q. acutissirna, Q. dentata and Q. aliena did none at Kwangyang-Gun. Chollanam-Do. The species diversity and evenness in oak communities exhibited 0.82 and 0.61, respectively at Kwangju-Gun. Kyunggi-Do, while those did 1.09 and 0.73 at Kwangyang-Gun, Chollanam-Do. Therefore, it was considered that Ku-angju-Gun region was disturbed severely by human activities but Kwangyang-Gun region eras less disturbed. Frequent appearance of Carpinus and Acer species indicates increase in diversities and better development of succession at Kwangyang-Gun region.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.2
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• pp.150-157
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• 2006

The aim of the present study was to investigate the effect of combined extract of safflower seed with herbs on the improvement of blood glucose, lipid peroxides, lipids in the plasma and liver of strpetozotocin-induced diabetic rats. Rats in the experimental group were orally administered with combined extract of safflower seed (100 mg, 200 mg/kg B.W.) with herbs (Ophiopogon japonicus Ker-Gaqler, Glycyrrhiza uralensis Fisch, Mori Folium, Poria cocos, Rehmannia glutinosa, Eriobtrya japonica, Aralia continentalis Kitagawa, Zizyphus jujuba var, Cornus officinalis, Paeonia suffruticosa, Trichosanthes kirilowii Maxim and Schizandra chinensis Baill) for 4 weeks. Body weight gain and food efficiency ratio were significantly lower in diabetic groups than those of control group. These were no protective effect of the supplementation of combined extract of safflower seed with herbs. Concentration of blood glucose was significantly higher in the diabetic groups than those in the control group. Blood glucose concentration was remarkably lower supplementation of combined extract of safflower seed (200 mg/kg B.W.) with herbs. There was no significant difference of plasma lipid peroxides among experimental groups, while liver lipid peroxides of diabetic group was significantly higher in control group. But supplementation of combined extract of safflower seed with herbs was induced markedly lower in liver lipid peroxides in diabetic rats. Diabetic groups had markedly higher levels in triglycerides, LDL-cholesterol and atherogenic index, while had lower HDL-cholesterol level. Triglyceride levels of plasma and liver were significantly lower with combined extract of safflower seed with herbs. But total cholesterol, phospholipid and free fatty acid were no differing significantly among experimental groups.

• Childhood Kidney Diseases
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• v.11 no.2
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• pp.247-254
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• 2007

Purpose : Continuous renal replacement therapy(CRRT) has been the first choice for the treatment of acute renal failure in critically ill children not only in western countries but also in Korea. However, there are very few studies that have analyzed the outcome and prognosis of this modality in Korean children. We performed this study to evaluate the factors associated with the outcome and prognosis of patients treated with CRRT. Methods : We retrospectively reviewed the medical records of 32 children who had received CRRT at Severance hospital from 2003 to 2006. The mean age was 7.5 years(range 4 days-16 years) and the mean body weight was 25.8 kg (range 3.2-63 kg). Results : Eleven(34.4%) of the 32 patients survived. Bone marrow transplantation and malignancy were the most common causes of death and underlying disease leading to the need for CRRT Mean patient weight, age, duration of CRRT, number of organ failures, urine output, estimated glomerular filtration rate(eGFR), C-reactive protein, and blood urea level did not differ significantly between survivors and nonsurvivors. (1) Pediatric risk of mortality(PRISM) III score at CRRT initiation($9.8{\pm}5.3$ vs. $26.7{\pm}7.6$, P<0.0001), (2) maximum pressor number ($2.1{\pm}1.2$ vs. $3.0{\pm}1.0$, P=0.038), and (3) the degree of fluid overload($5.2{\pm}6.0$ vs. $15.0{\pm}8.9$, P=0.002) were significantly lower in survivers than in nonsurvivors. Multivariate analysis revealed that fluid overload was the only independent factor reducing survival rate. Conclusion : CRRT was successfully applied to the treatment of acute renal failure in a wide range of critically ill children. To improve survival, we suggest the early initiation of CRRT to prevent the systemic worsening and progression of fluid overload in critically ill children with acute renal failure. (J Korean Soc Pediatr Nephrol 2007;11:247-254)

• The Korean Journal of Nuclear Medicine
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• v.26 no.2
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• pp.299-306
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• 1992

Gastic emptying scan in diabetic patients is widely used to assess the degree of motility disturbance and the symtoms such as nausea, vomiting, bloating, abdominal pain and early gastric fullness which we can't find anatomic lesion by fiberoscopic or barium study In order to determine the relationship among diabetic gastropathy, neropathy, retinopathy and disease duration, gastric emptying scan using $^{99m}Tc-tin$ colloid labeled scramble egg in hamburger was performed in 10 healty male controls and 50 diabetic patients which were subdivided to no neuropathy, peripheral neuropathy and autonomic neuropathy groups according to the degree of diabetic neuropathy and no retinopathy, background retinopathy and proliferative retinopathy groups according to the degree of diabetic retinopathy. After medication of cisapride for 2 weeks, we observed the presence of improvement of gastric motility in diabetics. The results were as following: 1) In controls, gastric emptying time (GET1/2) was $75{\pm}13.6$ min and 2 hour gastric retension rate (GRR2) was $32{\pm}11.1%$. 2) In diabetics, GET/2 was prolonged more than 2 hours and GRR2 was $58{\pm}23.1%$. According to degree of neuropathy, GET1/2 was prolonged more than 2 hours in all three groups and GRR2 was $54{\pm}24.1%$ in no neuropathy group, $57{\pm}24.3%$ in peripheral neuropathy group and $69{\pm}24.6%$ in autonomic neuropathy group. According to degree of retinopathy, GET1/2 was $110{\pm}23.4$ min in no retinopathy group and prolonged more than 2 hours in other two groups and GRR2 was $45{\pm}21.6%$ in no retinopathy group, $71{\pm}19.7%$ in background retinopathy group and $73{\pm}21.5%$ in proliferative retinopathy group. 3) After cisapride medication for 2 weeks, GET1/2 and GRR2 were improved as $90{\pm}14.6$ min and $40{\pm}13.8%$ (initial GET1/2 and GRR2 were above 2 hours and $61{\pm}15.4%$). We can conclude from above findings that gastropathy in diabetic neuropathy suggesting main underlying factor in motility disorder The degree of retinopathy and disease duration were correlated with severity of gastropathy in diabetics. From the results of gastric emptying scan, we can conclude that cisapride was useful drug for improving diabetic gastropathy and gastric emptying scan was valuable for assessing severity of diabetic gastropathy as non-invasive method.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.147-156
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• 2006

This study was conducted to investigate natural distribution of aquatic plane and to find out natural aquatic plants which highly absorb nutrient N and P. We surveyed vegetation within ${\pm}2m$ from streamside in 12 tributaries of the West Nakdong river watershed during May to October in 2003. Hydrophytes surveyed in tributaries of the West Nakdong river watershed were 27 families, 61 genera, 76 species, 3 varieties. Major dominance species of aquatic plants were Z. latifolia, P. communis, P. thunbergii, P. arundinacea, P. japonica, and P. distichum var. indutum. Aquatic plants having high production ability of biomass were Z. latifolia, P. communis, P. arundinacea, P. japonica, and E. crus-galli var. echinata. In the vertical distribution of hydrophytes within streams, dominant species were P. thunbergii and P. japonica in the upper stream, but dominant species in the downstream were P. communis and Z. latifolia. Species diversity or aquatic, plants was reduced, but their biomass and nutrient (T-N and T-P) content per the natural area unit $(m^2)$ were increased in the downsteaam. Nutrient N and P content of aquatic plants per the natural area unit were high at Joman river, Pyeonggangcheon, Bulam drainage canal, and Hogyecheon. Fifty-seven species of aquatic plants having high biomass were grounped into 4 categories $(I{\sim}IV)$ according to their nutrient content per dry weight unit. I group $(T-N,\;\geqq20gkg^{-1}\;&\;P_2O_5,\;\geqq7gkg^{-1})$ was comprised of 3 submerged plants (H. verticillata, P. crispus, and C. demersum), e emergent plants (O. javanica, P. distichum var. indutum, and R. sceleratus), 1 suspended plant (T. japonica), and 1 riparian plant (A. lobatum). Otherwise, in classification of natural hydrophytes according to their nutrient content per natural area unit, Z. latifolia, P. communis, P. longiseta, P. arundinacea, and P. distichum var. indutum possessing great biomass productivity as emergent plants were included in I group $(T-N,\;\geqq1gm^{-2}\;&\;P_2O_5,\;\geqq0.7gm^{-2})$.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.96-115
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• 2017

Understanding effects of thermal pollution and acidification has long been a concern of aquatic ecologists, but it remains largely unknown in Korea. This study was performed to elucidate the effects of thermal wastewater effluent (TWE) and acid rain on water quality and attached algae in a small mountain stream, the Buso Stream, a tributary located in the Hantan River basin. A total of five study sites were selected in the upstream area including the inflowing point of hot-spring wastewater (HSW), one upstream site (BSU), and three sites below thermal effluent merged into the stream (1 m, 10 m and 300 m for BSD1, BSD2, and BSD3, respectively). Field surveys and laboratory analyses were carried out every month from December 2015 to September 2016. Water temperature ranged $1.7{\sim}28.8^{\circ}C$ with a mean of $15.0^{\circ}C$ among all sites. Due to the effect of thermal effluent, water temperature at HSW site was sustained at high level during the study period from $17.5^{\circ}C$ (January) to $28.8^{\circ}C$ (September) with a mean of $24.2{\pm}3.7^{\circ}C$, which was significantly higher than other sites. Thermal wastewater effluent also brought in high concentration of nutrients(N, P). The effect of TWE was particularly apparent during dry season and low temperature period (December~March). Temperature effect of TWE did not last toward downstream, while nutrient effect seemed to maintain in longer distance. pH ranged 5.1~8.4 with a mean of 6.9 among all sites during the study period. The pH decrease was attributed to seasonal acid rain and snow fall, and their effects was identified by acidophilic diatoms dominated mainly by Eunotia pectinalis and Tabellaria flocculosa during March and August. These findings indicated that water quality and periphyton assemblages in the upstream region of Buso Stream were affected by thermal pollution, eutrophication, and acidification, and their confounding effects were seasonally variable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.34-42
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• 2016

In order to prepare for the type approval test for the United States Coast Guard (USCG) Phase-II of Ballast Water Treatment System (BWTS), a phytoplankton mass culture was conducted in a mesocosm enclosure. We evaluated the response of the phytoplankton community after nutrient addition (+N, +P, and +NP) and investigated the development of the species with increasing culture time. After nutrient dosing, the phytoplankton population significantly (p < 0.05) increased from day 1 to day 3, depending on the nutrient treatments In particular, the specific growth rate of the phytoplankton community in the case of +NP treatment and + N treatment were estimated to be $2.47d^{-1}$ and $1.98d^{-1}$, respectively. The phytoplankton population density in the case of + NP treatment was approximately 50 times higher than that of the control group, suggesting that these treatments could be useful for mass culturing phytoplankton (> 75% of natural community) for the approval regulation of USCG Phase-II. In the phytoplankton community of the mesocosm, Pseudo-nitzchia spp. dominated in the logarithmic growth phase. The cell density decreased significantly (p < 0.05) with increasing time, coinciding with the nutrient limitation. At that time, the dominance of Pseudo-nitzchia spp. shifted to that of Cylindrotheca closterium. Therefore, the optimum nutrient concentration ($N:30{\mu}M$, $P:3{\mu}M$) and reasonable harvesting time (after 3 days in summer) found in this study for the mass culturing of phytoplankton may be helpful to meet the USCG Phase-II biological criteria to be used in BWTS.

• Journal of Food Hygiene and Safety
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• v.18 no.3
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• pp.139-145
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• 2003

The purpose of this study was to investigate the awareness and practice of Korean consumer on food safety. A telephone survey was conducted from 1,040 adults randomly selected from each province and large city of Korea. Therefore, 12.4% of the subjects experienced foodborne illness at least once a year and 0.3% was hospitalized due to the illness. General restaurant (37.2%) and home (21.2%) were the main causative place of foodborne illness, and the most frequently associated foods were meat and meat products (41.7%) and fish and fish products (18.7%). Regarding the causative agent of foodborne illness, the respsondents were aware of Cholera (75.5%), Vibrio gastroenteritis (73%), Shigellosis (65.5%), Bacillary dysentery (65.5%) and Salmonellosis (47.5%) very well; however very few were aware of Listeriosis (9.9%) and brucellosis (8.3%) and ever believed they were not food-related illness. When the survey data were analyzed based on 3 models (Model 1: Knowledge about the pathogens associated food and water, Model 2: The awareness of food safety, Model 3: Attitudes and behavior about foodborne disease prevention and measure) by Multiple regression analysis. The results showed that the awareness of the causative agent of foodborne illness was significantly related with the previous experience of foodborne illness (OR: 1.714) followed by education level (OR: 0.536) and married status (OR: 0.527). The awareness of food safety was significatly related with education level (OR: 0.702). Education (OR: 0.816) and gender (OR:0.650) were the main factors affecting the awareness of the practice to prevent foodborne illness. However, the previous experience of foodborne illness and food safety education, and the awareness of food safety did not show any correlation, suggesting that the experience and awareness of foodborne illness do not affect the real practice of food safety.