• 콘크리트학회논문집
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• 제29권3호
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• pp.315-322
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• 2017

본 연구는 결합재에 따른 자기충전 콘크리트의 현장 최적배합비의 선정 및 이에 따른 현장 시공성과 경제성을 평가하기 위한 것이다. 결합재로 슬래그 함량이 46.5%인 슬래그계와 $C_2S$함량이 51.4%인 벨라이트계, 그리고 석회석 미분말이 사용되었다. 물-시멘트비를 대상으로 유동성, 충전성, 재령별 압축강도를 측정하여 현장 최적배합조건을 선정하였으며, 이에 따른 평가항목으로 응결시간, 블리딩, 침하깊이, 단열온도 상승시험을 실시하였다. 현장 시공성 및 경제성 평가를 위하여 현장시공에 따른 콘크리트 물량과 재료비를 분석하였다. 실험결과, 유동성 및 압축강도에 만족하는 물-시멘트비는 슬래그계 41.0%, 벨라이트계 51.0%이며, 응결시간 및 블리딩량 종료시간은 슬래그계가 빨랐지만, 블리딩량은 슬래그계가 큰 것으로 나타났다. 단열온도 상승량 및 상승속도는 벨라이트계가 낮은 것으로 나타났다. 또한 배처 플랜트의 최적 배합시간은 75초가 적합하였으며 생산량은 $100{\sim}110m^3/hr$이었다. 재료비 및 콘크리트 물량에서 벨라이트계가 슬래그계보다 각각 14.0% 및 3.3% 절감되는 것으로 나타났기 때문에, 재령별 압축강도 발현을 제외하면 벨라이트계 자기충전 콘크리트가 시공성 및 경제성 등에서 우수하였다.

• 한국건설순환자원학회논문집
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• 제6권2호
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• pp.89-96
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• 2011

본 연구는 플라이 애시의 치환범위 상향에 따른 콘크리트의 제반 특성을 분석하여 추후 성능 향상을 위한 기초자료로 제공하기 위해 플라이 애시의 치환범위 0-40 % 및 양생 온도 $5-35^{\circ}C$에 따른 기초적 특성을 분석하였다. 그 결과 유동성은 FA의 증가에 따라 비례적으로 증가하였으나, 공기량은 감소하였다. 응결시간은 치환율 증가 및 저온일수록 지연되는 특성을 나타냈으며, 간이단열온도이력은 FA 치환율이 40 %까지 증가함에 따라 최고온도는 $8^{\circ}C$정도 낮아졌고, 최고온도 도달시간은 13시간 정도 지연되는 것을 알 수 있었다. FA 치환 상향에 따른 압축강도는 양생온도가 높을수록 플레인 대비 강도증진성이 향상됨을 알 수 있었다. 중성화의 경우는 FA 치환율이 증가할수록 깊이가 점차 커지는 것을 알 수 있어 중성화 대책에 대한 지속적인 연구가 필요할 것으로 판단되었다.

• 한국화재소방학회논문지
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• 제33권6호
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• pp.9-19
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• 2019

건축물의 화재안전성평가를 위한 화재시뮬레이션에서 화원면적 및 격자크기의 변화는 예측결과에 큰 영향을 미칠 수 있다. 따라서 동일한 최대 열발생률을 갖는 화원의 면적 변화가 구획화재의 예측결과에 미치는 영향이 검토되었으며, 동일한 화원면적의 조건에서 격자크기에 대한 예측결과의 의존도가 동시에 검토되었다. 주요 결과로서, 특성화재직경을 기준으로 6개 이상의 격자가 삽입되면 화원면적이 변화되더라도 격자크기는 화재의 열 및 화학적 특성에 큰 영향을 미치지 않았다. 또한 화원면적의 변화는 구획 내부에서 허용피난시간(ASET)과 관련된 주요 물리량의 예측결과에 상당한 차이를 야기하였다. 그러나 개구부를 기준으로 일정 거리 이상의 구획외부에서는 화원면적의 변화가 전반적 화재특성에 미치는 영향이 크지 않음이 확인되었다.

• 콘크리트학회논문집
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• 제12권2호
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• pp.99-107
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• 2000

This research investigates experimentally an effect on the properties of the high flowing concrete to be poured in the under-ground slurry wall of Inchon LNG receiving terminal(#213,214-TK) according to variations of concrete materials. Variables for sensitivity test were selected items as followings. 1) Concrete temperature (3cases), 2) Unit water (5cases), 3) Fineness modulus of fine aggregate (5cases), 4) Particle size of lime stone powder (3cases), 5) Replacement ratio of blast-furnace slag (4cases) and 6) Addition ratio of high range water reducing agent (5cases). And fresh conditions of the super flowing concrete should be satisfied with required range including slump flow(65$\pm$5cm), 50cm reaching time of flow(4~10sec), V-lot flowing time(10~ 20sec), U-box height(min. 300mm) and air content(4$\pm$1%). As results for sensitivity test, considered flow-ability, self-compaction and segregation resistance of the high flowing concrete, material variations and conditions of fresh concrete should be satisfied with the range as follwings. 1) Concrete temperature are 10~2$0^{\circ}C$(below 3$0^{\circ}C$), 2) Surface moisture of fine aggregate is within $\pm$ 0.6%, 3) Fineness modulus of fine aggregate is 2.6$\pm$0.2, 4)Replacement ratio of blast-furnace slag is 45~50% and 5) Addition ratio of high range water reducing agent is within 1%. Based on the specification for quality control, we successfully finished concrete pouring on the under-ground slurry wall having 75,000㎥(#213,214-TK) and accumulated real date in site.

• 한국환경보건학회지
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• 제34권1호
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• pp.70-75
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• 2008

The Chinese cabbage kimchi, baechoo-kimchi, is the most popular type of kimchi in Korea. This study was performed to investigate the changes of index microorganisms (aerobic bacteria, psychrotrophilic bacteria, coliforms, and Escherichia coli), lactic acid bacteria, pH, and acidity of kimchi during the long-term fermentation and ripening. A homemade-style traditional Korean baechoo-kimchi, was prepared from Chinese cabbage, red pepper, green onion, garlic, ginger, and salt-fermented anchovy sauce, and then incubated at $10^{\circ}C$ for 28 days. In the baechoo-kimchi, the number of aerobic bacteria increased with time. The number of psychrotrophilic bacteria maintained their numbers $(10^4CFU/g)$ in the kimchi during the fermentation. Coliforms and E. coli were not detected in the kimchi. The pH of kimchi decreased and the acidity of kimchi increased over time. Lactic acid bacteria, which are representative of fermentative microorganisms in the kimchi process showed rapid growth in the earlier stage of fermentation and increased steadily after 7 days. The counts of lactic acid bacteria were at a level of $10^4CFU/g$ early in the fermentation stage, reaching a level of $10^8CFU/g$ after 14 days, and at this point pH was 4.18 and acidity reached 0.63, indicating that the optimal state of kimchi fermentation. This study suggests that the lactic acid bacteria which were proliferated in kimchi during the ripening and fermentation could contribute to improving the taste and flavor of kimchi and inhibit the growth of pathogenic microorganisms that might exist in kimchi.

• 대한치과의사협회지
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• 제49권4호
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• pp.211-218
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• 2011

Purpose: An impacted tooth is defined as a tooth that shows delayed eruption and is expected to erupt incompletely by clinical and radiograph examination despite it reaching its expected time of eruption. The aims of this study were to investigate the clinical and radiological characteristics and treatment duration and method of impacted teeth in Korean patients. Materials and Methods: For this study we used clinical records, study models, panoramic radiographs and intraoral photographs of patients who attended Gachon University Gil Hospital Orthodontic Department between 2005 and 2008. There were 164 patients with a total number of 202 impacted teeth. Results: Male patients shows a little more prevalence than female patients (1.13:1). The under 12 age group had the highest prevalence of tooth impaction, and the over 19 age group showed the least prevalence of tooth impaction. The ratio of tooth impaction between the left to right ratio was 1.73:1 and maxilla and mandible was 1.84:1. The impacted teeth were most commonly positioned buccally (76 cases, 41.5%). Full nap closure technique (108 cases, 81.2%)was most frequently used for attachment of surgical traction hooks. Maxillary canine impaction was most commonly encountered both in male and female patients. The mean treatment period was 12.2 months and the success rate of treatment was 90.3%. The canine tooth shows the longest treatment time and highest failure rate. The ankylosis was the major cause of failure. Conclusion: Impacted teeth most commonly show in left side maxilla in the under 12 age group. And it is most commonly positioned buccally. The mean treatment period was 12.2 months, and the success rate of treatment was 90.3%.

• 대한물리의학회지
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• 제11권1호
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• pp.11-21
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• 2016

PURPOSE: This study was examined the effects of aerobic exercise using a step box and lower extremity strengthening exercise with an elastic band on the balance ability and lower extremity muscular strength in elderly subjects. METHODS: Forty-one healthy adults were randomly divided into experimental group 1 (Exp 1, n=14), experimental group 2 (Exp 2, n=14), and a control group (n=13). The Exp 1 conducted lower limb strengthening exercise using an elastic band and the Exp 2 performed aerobic exercise with a step box 50 minutes per day, twice per week, for eight weeks. RESULTS: There was significant increase in the Exp 1 and Exp 2 in comparison of the change of lower limb muscle strength according to measurement time (p<.05). But there was no significant difference according to intervention methods. In one-leg standing test change among the three groups after the intervention, the Exp 1 and Exp 2 saw significant improvement compared to the control group (p<.05) but there was no significant difference according to intervention methods. The change of the functional reaching test results, the Exp 1 and Exp 2 saw significant improvement according to the time of measurement. In the change of the Timed Up and Go test, there was significant improvement in the Exp 1 and Exp 2 compared to the control group (p<.01), but there was no significant difference according to intervention methods. CONCLUSION: Exercise to lower extremity strengthening program accompanied with aerobic exercise is considered more effective in dynamical balance and ability to walk.

• 한국식품과학회지
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• 제36권1호
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• pp.116-122
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• 2004

L. acidophilus를 면 제조 시에 첨가할 목적으로 MRS broth 배지를 이용하여 $37^{\circ}C$에서 3일 동안 배양시킨 후 면의 주원료인 밀가루, 물, 소금의 혼합액에 L. acidophilus를 선택 접종시켜 72시간 배양 발효시킨 결과 발효물에 젖산이 6.821mg/g, 초산이 0.191 mg/g 생성되어 발효물에서 젖산의 함량이 높았다. 배양기간 중 발효물의 pH는 저하되며 총산도가 증가되었다. 식염첨가 발효물의 점도는 발효시간의 경과에 따라 증가되었으나, 식염을 첨가하지 않은 발효물의 점도는 감소하였다. 한편 식염을 첨가하지 않은 발효물은 변질이 되어 식염이 보존성에 미치는 효과를 알 수 있었고 형태적 관찰에서 발효물에서 L. acidophilus의 전형적인 간균 형태를 보이고 있음을 확인할 수 있었다.

• Journal of Biosystems Engineering
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• 제41권2호
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• pp.85-92
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• 2016

Background: The same plant, Camellia sinensis, is used to produce all types of tea, and the differences among the various types arise from the different processing steps that are used. Based on the degree of fermentation, tea can be classified as black, green, white, or oolong tea. Of these, black tea is the most or fully fermented tea. The oxidized polyphenolic compounds such as theaflavins (TF) and thearubigins (TR) formed during fermentation are responsible for the color, taste, flavor, and aroma of black tea. Results: Research indicates that an optimum ratio of TF and TR (1:10) is required to ensure a quality cup of tea. The concentrations of TF and TR as well as desirable quality characteristics increase as fermentation time increases, reaching optimum levels and then degrading if the fermentation time is prolonged. It is also necessary to control the environment for oxidation. There are no established environment conditions that must be maintained during the fermentation of the ruptured tea leaves. However, in most cases, the process is performed at a temperature of $24-29^{\circ}C$ for 2-4 h or 55-110 min for orthodox tea or crush, tear, and curl (CTC) black tea, respectively, under a high relative humidity of 95-98% with an adequate amount of oxygen. Conclusion: The polyphenolic compounds in black tea such as TF and TR as well as un-oxidized catechins are responsible for the health benefits of tea consumption. Tea is rich in natural antioxidant activities and is reported to have great potential for the management of various types of cancers, oral health problems, heart disease and stroke, and diabetes and to have other health benefits such as the ability to detoxify, improve urine and blood flow, stimulate, and improve the immune system.

• Journal of Biosystems Engineering
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• 제39권4호
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• pp.330-335
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• 2014

Purpose: This study was conducted for enhancing the performance of a conventional quick freezer by introducing the supercooling state, using a low-temperature coolant. Methods: In the present investigation, the supercooling process was executed prior to quick freezing for reducing the time by which the temperature passes the zone of maximum ice crystal formation. Every food has different nucleation points and hence, we used silicone oil as the coolant for supercooling for easy modification of temperature. Additionally, for quick freezing, we used liquid nitrogen spray. Results: Using the heat exchanger-type precooler with silicone oil, the temperature of the chamber was easily changed for enabling supercooling. Particularly, the results of the freezing test with garlic indicated that this system improved the hardness of garlic after it was thawed, compared to the conventional freezing method. Conclusions: Before quick freezing, if the food item is subjected to the supercooling state, the time from nucleation to the temperature reaching the frozen state ($-5^{\circ}C$, which is the maximum ice crystal formation zone) will be shorter than that incurred using quick freezing alone. The combination of the heat exchanger-type supercooler and liquid nitrogen sprayer is expected to serve as a promising technology for improving the physicochemical qualities of frozen foods.