• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.361-369
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• 2017

Setting time of cement-based materials can represent a developing strength in early-age mixture, and it can be used a significant parameter of high-performance concrete having various mix-proportions. Generally, initial and final setting time of concrete is measured by penetration resistance method that used a wet-sieving mortar mixture, therefore, it hardly represents the setting time of sound concrete including coarse aggregate. Recently, several nondestructive methods, such as ultrasonic velocity and impendence measurement, are proposed to evaluate the setting time of fresh concrete. This study attempts to measure an electrical resistivity using four-electrode method for evaluation of setting time in early-age cement-based materials. For this purpose, total 10 mixtures are prepared as different mix-proportions including chemical admixture. Based on the experimental results, two electrical parameters, such as initial electrical resistivity and rising time, are proposed to reflect a microstructure development by hydration of cement-based materials. As a result, proposed parameter is also discussed with the measured setting time by penetration resistance method.

• Explosives and Blasting
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• v.24 no.1
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• pp.21-28
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• 2006

Rock mass classification systems such as RMR and Q system have been widely served as a simple empirical approach for the design of various rock mass structures in the stage of site survey as well as under the construction. For the RQD determination, the boring is partially carried out and what is more, the survey boring is not normally carried out under construction. Therefore RQD is frequently determined by empirical method or indirect method. Since it is difficult to determine the discontinuity characteristics such as RQD, spacing, persistence, filling and so on, it is essential to develop suitable and simple systems without drilled core and a cert 없 n number of representative parameters. One of the primary objectives of the classification systems for a practicing engineer has been to make it simple to use as a preliminary design tool for the structures in rock mass. In the present study, the modifications for both the RMR and GSI system are suggested by authors to introduce new classification system as well as to improve the scope of some of the existing classification systems for a practicing engineer.

• Korean Journal of Poultry Science
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• v.44 no.4
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• pp.253-258
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• 2017

This study was aimed at evaluating the additivity of crude protein digestibility in mixed diets of corn and soybean meal (SBM), and comparing direct and indirect methods for evaluating crude protein (CP) digestibility. Totally, five hundred and twenty-five 18-day-old broiler chickens were grouped into 7 blocks based on body weight, and randomly allocated to 6 treatment groups in a randomized complete block design. The basal diet, diet 3, was corn-SBM-based, containing 65% corn and 28% SBM. Diets 1 and 5 contained corn and SBM, respectively, as the sole CP source. To use the difference method, 2 diets, diets 2 and 4, were prepared by mixing corn and SBM at the expense of the basal diet, respectively. Diet 2 contained 79% corn and 14% SBM, and diet 4 contained 32.5% corn and 34% SBM. To evaluate the additivity of digestibility values, the difference between measured values for the mixed diets (diets 2, 3, and 4) and predicted values calculated using the measured values for diets 1 and 5 was examined. The apparent (AID) and standardized (SID) ileal digestibility of CP in SBM differed between the direct and indirect methods; however, corresponding digestibility did not differ for corn. Additionally, the predicted and measured digestibility of both AID and SID differed in diets 2 and 3, implying that the digestibility values obtained from diets 1 and 5 were not additive for mixed diets. In conclusion, this study showed that digestibility evaluated by direct and indirect methods depends on the ingredients having different CP concentrations, and this finding may be considered to improve the accuracy of feed formulation for broiler chickens.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.48-51
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• 2011

사장교에서 케이블은 하중을 지지하는 주요 부재로, 케이블 장력은 사장교의 건전성과 안전도 평가에 있어서 매우 중요한 변수이다. 케이블 장력을 추정하기 위한 대표적인 방법으로는 로드셀을 이용한 직접법과 진동 계측 자료를 이용한 간접법 등이 있으며, 최근에는 자기장-응력 관계를 이용한 EM(Elasto-Magnetic) 센서 측정법이 개발되어 케이블 장력 추정에 적용되었다. 본 논문에서는 세 가지 장력 추정 기법을 실제 시공중인 사장교에 적용하여, 그 성능을 상호 비교하였다. 본 연구는 한국의 KAIST와 미국 Northeastern 대학교의 공동연구로 수행되었다. 대상 교량은 부산 화명동과 김해 초정리를 연결하기 위해 현재 건설중인 화명대교이다. 화명대교의 교량 형식은 2주탑 콘크리트 사장교 (주탑 경간장 270m, 총 사장교 구간장 500m)이며, 사장재로는 MS (Multi-Strand) 형 케이블이 사용되었다. 실험 당시 화명대교는 중앙경간의 폐합 후 선형관리를 위한 장력조정작업을 수행하였으며, 케이블 재긴장시의 정확한 장력관리를 위하여 로드셀을 이용한 Lift-off test방법으로 케이블의 장력을 측정하였다. 이와 동시에 두 개의 케이블을 대상으로 진동 가속도 센서와 EM 센서를 설치하고 장력 계측을 수행하였으며, 재긴장 단계별 장력 변화치를 지속적으로 계측하였다. 계측된 결과를 바탕으로 케이블 장력 추정 기법의 정확성 및 실교량에서의 활용성을 비교하였다.

• Tuberculosis and Respiratory Diseases
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• v.59 no.4
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• pp.356-360
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• 2005

Background : This study examined the clinical utility of using indirect chest radiography during a physical examination of new conscripts for determine the presence of pulmonary tuberculosis. Methods : Over an eight-month period, this study examined 25386 people who underwent a physical examination after conscription. The abnormal findings on mass miniature radiography were followed-up using direct chest radiography. The positive predictive value of mass miniature radiography and direct chest radiography was compared. The incidence, degree of infiltration and clinical outcome of active pulmonary tuberculosis were also evaluated during a follow-up examination. Results : The positive rate of mass miniature radiography was 1.19% (n=302). Various lesions were identified: Parenchymal lesions (n=109), mediastinal lesions (n=6), cardiovascular lesions (n=45), pleural lesions (n=49), bony lesions (n=90) and miscellaneous lesions (n=7). The incidence of active pulmonary tuberculosis by mass miniature radiography was 0.26% (n=67). The first diagnosis was made in 50 people; active pulmonary tuberculosis (n=42), pneumonia (n=1), a mediastinal mass (n=1), a rib fracture (n=2) and a pneumothorax (n=4). Most cases of active pulmonary tuberculosis were mildly infiltrated and either improved or were cured by the follow-up examination. Conclusion : Although mass miniature radiography in a physical examination after conscription has limitations, but it is a useful means for detecting the presence of early disease, particularly in active pulmonary tuberculosis.

• Journal of Energy Engineering
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• v.10 no.1
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• pp.40-48
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• 2001

디젤엔진에 적합한 환경 친화적 연료로 평가받고 있는 디메틸에테르(DME)를 기존의 메탄올 탈수화에 의한 간접법 대신 합성 가스로부터 직접 합성법으로 제조하였다. 합성가스에서 메탄올을 합성하는 경우에 비해 화학 평형 상의 이점 때문에 DME를 합성하는 것이 경제적이며 이는 실험 결과와 일치하였다. 기상 반응기에서 메탄올 탈수촉매의 부가에 의한 메탄올 환산 생산량은 메탄올 합성촉매에 의한 생산량에 비해 두 배 이상의 증가를 보인다. 메탄올 탈수촉매를 Cu로 개질한 효과는 없었으며, 메탄올 탈수촉매로서 순수 감마알루미나가 가장 우수한 반응성을 보였다. 반응 조건이 25$0^{\circ}C$, 30atm일 때 고려된 GHSV 범위에서 촉매 적정 혼합비는 7:3, 합성 가스의 조성비는 $H_2$/CO=1일 때 가장 좋은 선택도와 수율을 나타내었다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.226-227
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• 2010

슈퍼커패시터의 성능을 시험하기 위해 필요한 기존의 실험방법들에는 충방전을 통한 커패시턴스의 측정, AC 임피던스 법에 의한 등가직렬저항(ESR)의 측정 및 자연방전의 측정 등이 포함되는데, 이러한 방법들은 번거롭고 많은 시간을 소요하므로 대량 생산되는 슈퍼커패시터의 모든 셀의 특성을 파악하는데 사용하기는 곤란하다. 따라서 본 논문에서는 전기화학적 임피던스 분광법에 의해 슈퍼커패시터의 등가 임피던스 모델의 파라미터를 추출하고 이를 이용하여 슈퍼커패시터의 제반 특성들을 간접적으로 파악함으로써, 번거로운 여러 가지 실험 없이 전기화학적 임피던스 분광법만으로 슈퍼커패시터의 성능을 판별할 수 있는 새로운 방식을 제안한다.

• Membrane Journal
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• v.27 no.3
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• pp.248-254
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• 2017

In order to secure the reliability of pathogenic microorganisms such as Cryptosporidium and Giaridia, which are chlorophilic protozoans, membrane filtration systems have been widely used in water purification process. hese integrity tests are classified into direct and indirect methods. Based on the bubble point theory, the pressure-based test in the direct method is presented in the USEPA Guidance Manual with sensitivity to detect a minimum size of pathogenic microorganisms of $3{\mu}m$ or more. Indirect methods are widely used in that they are capable of continuous operation in on-line state, but there is a very low sensitivity of damage detection compared to the direct method, and there is a limit that can not specify the damage area, so it is necessary to improve this sensitivity. In this study, we compared the LRVDIT and UCL values according to the type of membrane defect, number of fiber breaks, and initial set pressure value through the Integrity Test by Pressure Decay Test (PDT).

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.172-172
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• 2018

물이용의 기후변화 취약성은 기후변화 뿐 아니라 이의 직, 간접적 영향으로 인한 물수요량 변화 등의 다양한 요소에 의한 영향을 받기 때문에 그 정도를 파악하기가 어렵다. 또한 기존의 대부분의 물이용 취약성 평가 연구는 단순 기후요소의 변화만 고려한 경우가 대부분이고 사회경제적 요소의 변화를 반영하지 않았다는 한계가 있다. 따라서 본 연구에서는 강 유역에서 미래 기후 변화와 사회경제적 변화에 따른 물이용 취약성 평가방법을 개발하고, 한강에 적용함으로서 다양한 사회경제시나리오에 따른 강유역의 물이용 취약성이 어떠한 영향을 받는지에 대한 이해에 주안점을 맞췄다. 개발한 평가방법은 지표기반 접근법으로, 다기준 의사결정기법인 Technique for Order of Preference by Similarity to Ideal Solution(TOPSIS)를 사용하였다. 이 방법은 IPCC의 취약성분석 방법에 사용되고 있으며, 취약성에 대한 정의에 따라 결과 값이 적응능력, 노출, 민감도로 구성되어있다. 사용된 지표 자료는 통계청 등 다양한 국가 통계자료를 기반으로 한 자료뿐 아니라, 일부분은 수문모형인 SWAT(Soil and Water Assessment Tool)모델로부터 모의된 결과를 포함한다. 기후시나리오로 Representative Concentration Pathways(RCPs), 사회경제시나리오로는 Shared Socioeconomic Pathways(SSPs)를 사용하였다. 본 연구의 물이용 취약성 평가결과는 사회경제적 요소의 변화를 기존의 평가방법에 추가 반영하여 미래 전망을 제시하는 향후 수자원 정책 방향에 기초자료로 활용될 수 있을 것이다.

• Journal of Korea Multimedia Society
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• v.9 no.8
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• pp.1086-1094
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• 2006

The CT is all relation knowledge and technology which are applied to make the culture contents. Recently demand regarding the CT is increasing rapidly with a great growth and high technology of culture contents industry. In this paper we suggest a CT technology valuation model for promoting R & D results and technical diffusion of the CT. Also, It is shown how to derive a value of the CT using simulation. For it, we study a classification and distinctive characteristics of the CT. And this paper reviews the methods of technology valuation that have been developed by valuation specialists.