• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.289-299
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• 2014

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-a'-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution ($SiO_2$-to-$Na_2O$ ratio or $M_s$ of 1-2) to provide a total alkalinity of 0.05 ($Na_2O$-to-binder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on $M_s$, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2004년도 학술대회지
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• pp.71-76
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• 2004

This paper investigate that the effect of the concrete containing mineral admixtures(pozzolanic materials such as fly-ash, ground granulated blast-furnace slag, silica fume and meta kaolin) on the resistance properties to chloride ion invasion. The purposed testing procedure was applied to the concrete added mineral admixtures for $3\sim4$ replacement ratios under W/B ratios ranged from 0.40 to 0.55. Specimens were immersed in $3.6\%$ NaCl solution for 330 days, and penetration depth, water soluble chloride contents and acid soluble chloride contents were measured in 28, 91, 182 and 330 days. Then, diffusion coefficient were calculated using total chloride contents. As a results. the kinds of mineral admixture and replacement ratios had a great effect on the resistance property of the concrete to chloride ion invasion compared with the plain concrete. And the optimal replacement ratios of mineral admixture had a limitation for each admixtures. The amount of acid soluble chloride ions and water soluble chloride ions were varied with the kinds of mineral admixtures and the penetration depth from the concrete skin. Chloride diffusion coefficient of each concretes decreased with the time elapsed. and the diffusion coefficients of the concrete immersed salt water for 330 days had a establishment with the compressive strength measured before immersing.

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.56-62
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• 2012

본 연구는 초고강도콘크리트의 배합에 사용되는 3성분계 혼합시멘트의 최적조합을 도출하기 위한 실험연구이다. 3성분계 혼합시멘트는 포틀랜드시멘트, 고로슬래브 미분말 0%, 30%, 40%, 50% 및 플라이애시 0%, 10%, 20%, 30%로 구성하였다. 물결합재비 0.18의 초고강도콘크리트를 대상으로 각 실험체의 압축강도와 공극구조를 조사한 결과, 플라이애시 10%, 고로슬래그 미분말 30%를 혼합한 3성분계 혼합시멘트를 사용한 콘크리트의 압축강도는, 50nm 이상의 공극량 감소에 의해, Plain 콘크리트에 비해 현저히 증가하였다.

• 유기물자원화
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• 제16권3호
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• pp.65-74
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• 2008

본 연구에서는 서로다른 4지역의 도시 생활 쓰레기의 성상 및 물리 화학적 조성을 조사 하였다. 생활 쓰레기 연료화시설 설치 및 자료확보 차원 매립장 관리차원에서 매우 필요한 연구이다. 평균 밀도는 $79{\sim}199.8kg/m^3$ 범위내의 결과를 얻었다. 생활 쓰레기는 8.87%의 음식물류, 38.8%의 종이류, 34.12%의 플라스틱류 및 비닐류, 7.16%의 섬유류, 0.96%의 목재류 1.3%의 고무 및 가죽류 등으로 구성되어 있다. 생활쓰레기의 대부분은 음식물, 종이류, 플라스틱류 등으로 이루어져 있으며 94% 정도가 가연 성분이다. 삼성분 분석에서는 17.38%의 수분 및 69.03%의 가연분 그리고 6.24%의 회분으로 이루어져 있다. 원소분석결과는 탄소 산소 수소 순으로 이루어져 있다. 생활쓰레기의 저위 발열량은 2973.8kcal/kg 이며 고위 발열량은 5209.94 kcal/kg 결과를 얻었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권6호
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• pp.1522-1545
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• 2012

Call admission control (CAC) plays an important role in mobile cellular network to guarantee the quality of service (QoS). In this paper, a dynamic hybrid CAC scheme with integrated cutoff priority and handoff queue for mobile cellular network is proposed and some performance metrics are derived. The unique characteristic of the proposed CAC scheme is that it can support any number of service types and that the cutoff thresholds for handoff calls are dynamically adjusted according to the number of service types and service priority index. Moreover, timeouts of handoff calls in queues are also considered in our scheme. By modeling the proposed CAC scheme with a one-dimensional Markov chain (1DMC), some performance metrics are derived, which include new call blocking probability ($P_{nb}$), forced termination probability (PF), average queue length, average waiting time in queue, offered traffic utilization, wireless channel utilization and system performance which is defined as the ratio of channel utilization to Grade of Service (GoS) cost function. In order to validate the correctness of the derived analytical performance metrics, simulation is performed. It is shown that simulation results match closely with the derived analytic results in terms of $P_{nb}$ and PF. And then, to show the advantage of 1DMC modeling for the performance analysis of our proposed CAC scheme, the computing complexity of multi-dimensional Markov chain (MDMC) modeling in performance analysis is analyzed in detail. It is indicated that state-space cardinality, which reflects the computing complexity of MDMC, increases exponentially with the number of service types and total channels in a cell. However, the state-space cardinality of our 1DMC model for performance analysis is unrelated to the number of service types and is determined by total number of channels and queue capacity of the highest priority service in a cell. At last, the performance comparison between our CAC scheme and Mahmoud ASH's scheme is carried out. The results show that our CAC scheme performs well to some extend.

• 한국건축시공학회지
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• 제20권4호
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• pp.321-330
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• 2020

지오폴리머의 반응성은 원재료의 구성성분 및 Si/Al비, Na/Al비, 물-결합재비, 비정질 요소 등을 고려하여 명확한 메커니즘을 규명하는 것은 매우 중요하다. 따라서 원재료 및 알칼리 활성화제의 구성성분을 고려한 %Na₂O, M_s는 반응성을 결정하는 중요한 요소가 된다. 하지만 다수의 연구에서는 알칼리 활성화제의 농도와 양생 조건 등의 기본적인 요소만을 고려하는 한계점을 나타내고 있다. 따라서 본 연구에서는 %Na₂O, Ms 및 고로슬래그 미분말의 혼입량에 따른 지오폴리머 페이스트의 강도특성, 반응열, 길이변화, 미세구조 분석을 실시하였다.

• Geomechanics and Engineering
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• 제20권2호
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• pp.155-164
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• 2020

In recent years, the stability, safety and comfort of trains has received increased attention. The mechanical characteristics and differential settlement of the foundation are the main problems studied in high-speed railway research. The mechanical characteristics and differential settlement of the foundation are greatly affected by the ground treatment. Additionally, the effects of train load and earthquakes have a great impact. The dynamic action of the train will increase the vibration acceleration of the foundation and increase the cumulative deformation, and the earthquake action will affect the stability of the substructure. Earthquakes have an important practical significance for the dynamic analysis of the railway operation stage; therefore, considering the impact of earthquakes on the railway substructure stability has engineering significance. In this paper, finite element model of the CFG (Cement Fly-ash Gravel) pile + cement-soil compacted pile about composite foundation is established, and manual numerical incentive method is selected as the simulation principle. The mechanical characteristics and differential settlement of CFG pile + cement-soil compacted pile about composite foundation under train load are studied. The results show: under the train load, the neutral point of the side friction about CFG pile is located at nearly 7/8 of the pile length; the vertical dynamic stress-time history curves of the cement-soil compacted pile, CFG pile and soil between piles are all regular serrated shape, the vertical dynamic stress of CFG pile changes greatly, but the vertical dynamic stress of cement-soil compacted pile and soil between piles does not change much; the vertical displacement of CFG pile, cement-soil compacted pile and soil between piles change very little.

• 대한영양사협회학술지
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• 제9권2호
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• pp.159-171
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• 2003

The food composition tables are frequently used to health and nutrition practices. But it is difficult to find out food exchange lists with food exchange groups in the food composition table. Over 2500 items and many kinds of nutrients are in the food composition table. But now food exchange lists are used a few foods. The internet demands the users needs for obtaining more food exchange lists and nutrient information from food composition. This basic study is to solve the users need and the supply more efficient and effective manipulation system for e-food exchange database construction and search system:ENECC/e-food exchnage(E-Nutrition Education and Couseling Center/e-food exchange). This paper introduces the food exchange database construction and search system(ENECC/e-food exchange) using the formula which calculates the food exchange quantity of 6 food exchange groups and added one extra groups(alcohol) based on the internet. The ENECC/e-food exchange database is basically based on the 6th food composition table(2001) of the National Rural Living Science Institution in Rural Development Administration, Korea. The e-food exchange database are consisted of 2,261 foods in 6 basic food groups and one extra groups by using ENECC calculating formula. Also, the e-food exchange database has the proximate composition, mineral and vitamin content such as energy, moisture, protein, fat, carbohydrate, ash, calcium, phosphorus, iron, sodium, potassium, retinol equivalent, retinol, â-carotene, thiamin, riboflavin, niacin, ascorbic acid, refuse per 100g of each food.

• 한국구조물진단유지관리공학회 논문집
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• 제16권3호
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• pp.67-74
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• 2012

바이오매스에서 얻어지는 바이오차는 토질 개량제와 탄소 격리제로 제한적인 분야에서 성공적으로 사용되고 있다. 현재 산업전반에서 CO2 에 의한 환경에 부정적인 영향을 완화시키고 지속가능성을 증진시키기 위한 연구가 활발히 진행되고 있다. 이에 본 연구에서는 고탄소 바이오차를 탄소 격리제 또는 시멘트의 혼화재로써 활용 가능성을 평가하고자 하였다. 견목재에서 얻어진 바이오차를 혼화재로 사용하여 시멘트 배합조건을 달리하면서 모타르의 압축강도, 마이크로구조, 압축강도, 유동성, 중량감소와 같은 화학적, 물리적 재료성질을 평가하였다. 또한 플리이애쉬를 사용한 모르타르의 역학적 특성과 비교 평가하였다.

• 한국식품영양과학회지
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• 제8권1호
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• pp.9-14
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• 1979

The consumption of catchup is increasing due to the raising of income level and food industry and westernization of dietary life followed by economic growth. In this paper I picked up three kinds of food produced by two foreign food companies and three kinds of food by two domestic companies. The average results by experimentation on the nutritive ingredients and the standard quality was as follows; A. Nutritve ingredients; 1) Water content a) Domestic 68.3% b) Foreign 69.1% 2) Protein content a) Domestic 2.2 g b) Foreign 2.1 g 3) Fat content a) Domestic 0.1 g b) Foreign 0.1 g 4) Carbohydrate content a) Domestic 25.1 g b) Foreign 24.6 g 5) Mineral content (Ash) a) Domestic 4.4 g b) Foreign 3.9 g 6) Calcium content a) Domestic 33.5 mg b) Foreign 24.2 mg 7) Phosphorus content a) Domestic 16.1 mg b) Foreign 24.2 mg 8) Vitamin C content a) Domestic 14.6mg b) Foreign 16.0 mg B. Standard quality 1) Remains after evaporation a) Domestic 41.7% b) Foreign 38.4% 2) Free mineral acid content a) Domestic none b) Foreign none 3) Tar chromatophore a) Domestic $trace(Acid)^+$ b) Foreign none 4) Heavy metalic $elements^*$ 5) Sodium chloride content a) Domestic 3.3% b) Foreign 3.3% 6) pH level a) Domestic 3.83 b) Foreign 3.76 + The tar chromatophore elements could not be accurately measured by chromatography. * The heavy metalic elements were both under safety levels in the domestic and foreign products.