• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.187-193
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• 1994

일반 콘크리트 (설계강도 $\sigma_{28}=210 kg/\textrm{cm}^2$)에 산업폐기물인 Fly Ash를 혼합하고 기포재 (Air Entrainment Agent) 첨가에 따른 Fly Ash-Concrete의 물성 변화를 시험하였다. Fly Ash-Concrete의 slump를 6, 8, 10cm로 고정시킨후, 각각의 slump 반죽상태에다 기포재, Neopor-400을 25,000cc/$\textrm{m}^3$, 50,000cc/$\textrm{m}^3$, 75,000cc/$\textrm{m}^3$으로 증가시켰다. 이때 기포재 증가에 따른 공기량 변화와 압축강도 $(\sigma_7 과 \sigma_{28})$ 를 측정하였다. 또한 기포재를 첨가한후, 60분과 90분까지 방치하고, 60분후와 90분후의 공기량과 압축강도 $(\sigma_7 과 \sigma_{28})$ 변화를 측정하였다. 시험결과에 의하면, 기포재가 첨가되는 시간에서부터 60분, 90분 동안 방치하면 공기량은 감소된다. 동시에 압축강도는 점진적으로 증가된다. KSF 5405가 요구하는 slump값이 90분 이내에 $12\pm0.5$의 범위에 들어 가기 위해서는 기포재는 50,000cc/$\textrm{m}^3$-75,000cc/$\textrm{m}^3$만큼 첨가되어야 한다. 이때의 7일 압축강도가 170-200kg/$\textrm{cm}^2$이고 28일 압축강도는 215-290kg/$\textrm{cm}^2$이다. 이 값은 설계강도 $\sigma$28=210kg/$\textrm{cm}^2$ 보다 최고 약 40%까지 증가율을 보여 주었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.341-345
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• 2011

본 연구는 충청북도 충주시 동량면과 금가면에 위치하고 있는 대전천을 대상으로 하상토 입경, 수위-유량의 변화에 따른 유사량 특성을 분석하였다. 하상재료 조사는 매 0.5 km 마다 17개 지점의 시료를 채취하였으며, 현장에서 채취한 하상토는 흙의 입도분포(KSF2302)시험법에 따라서 입경분석을 하였다. 측정 지점은 흐름이 안정적이며, 와류, 사수, 역류가 없고 접근이 용이하며 하상변동이 적은 지점을 고려하여 선정하였고, 유사의 이동이 활발한 시기인 7월에서 9월까지 평 저수기 20회, 홍수기 24회, 총 44회에 걸쳐 유량 및 부유사량을 현장 관측하였다. 평 저수시의 유속측정을 위해 초음파유속계를 사용하였으며, 홍수시에는 표면 부자를 사용하였다. 유량계산시에 면적은 중간단면법을 사용하여 유량을 계산하였다. 유량측정과 동시에 부유사 시료를 채취하였으며 부유사 관측에는 수심적분 채취접을 적용, 부유사농도는 여과법을 시행하였다. 본 하천의 현장실험 측정성과와 수리특성을 기초자료로 하여 각 회차에 걸친 총유사량의 산정을 SCST(Solution for Computing Sediment Transport)를 사용하였으며, 총유사량을 산정하는 Einstein공식, van Rijn공식, Toffaleti공식, Shen&Hung공식, Yang(1979)공식, Ackers & White공식, Engelud&Hansen공식, Ranga Raju공식 등 10개 공식을 적용하여 비교 분석을 수행하였다. 이중에서 관측된 부유사량을 고려하여 검토한 결과 Yang(1979)공식을 이용하여 추정한 총유사량이 가장 적합한 것으로 판단되었다. 그 결과 수위-유량관계곡선 및 유량-총유사량 관계곡선을 개발하였으며, 효과적인 치수 및 이수계획의 수립 등 수자원 기본자료로서 이용될 것이다.

• Asian Journal of Innovation and Policy
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• v.2 no.1
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• pp.63-96
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• 2013

There is the need for performance evaluation and the identification of key success factors for utilizing technology roadmaps (TRM), but relevant research does not yet exists in this field. In Korea, the Small and Medium Business Administration has implemented the "Support Program for the Individual Company Technology Roadmaps" to promote the establishment of technology development strategies by SMEs. This study developed the framework and indices for performance analysis, designed and implemented survey for TRM performance analysis, and analyzed TRM performance of the companies that have participated in the above program from 2008 to 2011. This study compared the supported 97 companies and 102 companies not supported and analyzed quantitative and qualitative performance and satisfaction levels among the supported companies to compare low-performance companies and high-performance companies. This study aims to examine the KSF of TRM in terms of input and process. Also we suggested significant insights into the performance of TRM in terms of output.

• Journal of KSNVE
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• v.9 no.6
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• pp.1180-1186
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• 1999

The aim of this study is to investigate the sound insulation performance of windows according to the sound source in the field test. For this purpose, an experiment was performed by KSF 2235(method for field measurements of sound insulation of windows and doors). Based on this code, the sound insulation performance fo the windows was measured for different incident angles of the sound and the effect of incident angle was obtained and discussed. Finally, it was found that the sound insulation performance of the windows was affected by the incident angle of sound source, and the sound insulation rating scale was different for the same window. The main factor changing insulation rating scale is considered to be the sound transmission through the carck of the folding part between the two pieces of wndows. Therefore, when evaluating the sound insulation performance of the windows for the field test, first of all the place of the sound source should be identified and generalized.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.57-60
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• 2011

EPS패널의 열방출율과 가스유해성에 대한 연구는 꾸준히 진행되어왔다. 그러나 그 동안의 시험 결과는 KSF ISO 5660-1(콘칼로리미터) 시험규정에 의한 소형시편을 이용한 것으로 난연제의 과다투입 또는 심재의 변형이 쉬워 결과를 신뢰하기 힘들고 실제 생산되는 크기의 샌드위치패널의 난연성능을 판단하기 힘들다. 따라서, 보다 정확한 실물화재시험의 필요성이 요구되고 있다. 난연 EPS샌드위치패널과 일반EPS샌드위치패널의 실물화재 실험결과 난연EPS샌드위치패널은 기타재료의 샌드위치패널과 열방출율, 연기발생율, 부분별 온도분포, 플래시오버등과 같은 난연성능이 EPS샌드위치패널과 우레탄폼패널보다 우수하며, 글라스울과 비슷한 성능을 나태내는 것을 확인 할 수 있다. 그래서 시공성, 경제성 등의 EPS샌드위치패널의 장점을 그대로 유지하며 난연제의 코팅법을 통해 우수한 난연성능을 확보하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.34-41
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• 2020

Ready-mixed concrete is unconsolidated concrete typically transported to construction sites by using mixer trucks. A proper rotation of concrete is necessary to prevent its solidification in mixer trucks during transport: in accordance with the manufacturing method and quality inspection prescribed in KSF4009, this movement is maintained after the manufacturing of concrete in professional production plants and the addition of water, solid materials, and admixtures. Unfortunately, mixer truck parts wear out over long periods of time. In order to improve the wear resistance of the main part of mixer trucks, we used a steel plate with good wear resistance or partially added a reinforcement plate. In this study, we first tested the properties of concrete (as required for the DEM), and then carried out mixing and discharge simulations to define the actual operating conditions of mixer trucks. For each condition, we calculated the amount and location of wear. The reliability of our results was finally verified by comparing them with the measurement values. Overall, this study provided basic data for an optimal design of mixer trucks: one that would reduce the vehicles' weight and production costs.

• Journal of Ocean Engineering and Technology
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• v.36 no.3
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• pp.161-167
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• 2022

Three-dimensional finite element analysis (3D-FEA) models have been used to evaluate the shock-resistance responses of various equipments, including armaments mounted on a warship caused by underwater explosion (UNDEX). This paper aims to check the possibility of using one-dimensional (1D) FEA models for the shock-resistance responses. A frigate was chosen for the evaluation of the shock-resistance responses by the UNDEX. The frigate was divided into the thirteen discrete segments along the length of the ship. The 1D Timoshenko beam elements were used to model the frigate. The explosive charge mass and the stand-off distance were determined based on the ship length and the keel shock factor (KSF), respectively. The UNDEX pressure fields were generated using the Geers-Hunter doubly asymptotic model. The pseudo-velocity shock response spectrum (PVSS) for the 1D-FEA model (1D-PVSS) was calculated using the acceleration history at a concerned equipment position where the digital recursive filtering algorithm was used. The 1D-PVSS was compared with the 3D-PVSS that was taken from a reference, and a relatively good agreement was found. In addition, the 1D-PVSS was compared with the design criteria specified by the German Federal Armed forces, which is called the BV043. The 1D-PVSS was proven to be relatively reasonable, reducing the computing cost dramatically.

• Korean Journal of Construction Engineering and Management
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• v.15 no.5
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• pp.127-137
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• 2014

Project Financing (PF) development project is the type which influences national economy and building industry largely because it is exerted by using borrowed money from many kinds of investors and huge amount of financial raising. Many domestic PF projects are focused mainly on the profit maximization lacking in a sufficient feasibility study. Nowadays many projects are suspending due to the global finance debacle and stagnation of real estate industry. Therefore, in this paper, risk factors of PF project are deducted and Key Success Factors (KSFs) are derived through Factor-Analysis and qualified using Fuzzy-AHP method. And through the evaluation of the derived success factors in real projects, a strong correlationship has been identified between the score of each PF success factor and the level of success and/or expected rate of return (ROR). So, the result of this paper can help decision makers of the PF projects make a better decision and give a meaningful guidance in achieving successful PF projects.

• Korean Journal of Agricultural Science
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• v.43 no.4
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• pp.656-664
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• 2016

Gear reducers are widely used for various agricultural machinery applications such as greenhouses, tractors, and agricultural vehicles. However, thermal deformation and surface pitting at gear tooth flank frequently occur in gear reducers due to high torque. Thus, surface heat treatment of gears is required to improve wear and fatigue resistance. The objective of this study was to simulate the load capacity of the agricultural gear reducer. The simulation was performed for the following three surface heat treatment methods: untreated gears, nitriding heat treatment, and induction hardening method, those mostly used for agricultural gear reducers. The load capacity of the gear reducer was simulated using the safety factor, limit bending stress, and limit contact stress of the gear. The simulation of the load capacity was conducted using KISSsoft commercial software for gear analysis. The main results of simulation test were as follows: first, the nitriding heat treatment resulted in the highest safety factor for bending stress, which was increased about 77% from those of the untreated gears. Second, the induction hardening was the highest safety factor for contact stress, which was increased about 150% from those of the untreated gears. The safety factor for contact stress of the induction hardening was increased about 64% from those of the nitriding heat treatment. The study result suggested that the surface heat treatments could enhance load capacity and that the method of surface heat treatment should be determined based on simulation results for appropriate use scenarios.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.1-7
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• 2020

GGBFS(Ground Granulated Blast Furnace Slag) is one of the most actively used mineral admixtures with excellent long-aged strength and chloride diffusion resistance. Unlike Standard covering GGBFS in Japan and the U.K., the domestic standard for GGBFS does not contain low fineness of GGBFS under 4000 grade. In this paper, several basic tests are carried out for the concrete with 3,000 grade GGBFS concrete and ternary blended concrete for reducing hydration heat by mixing 4,000 grade GGBFS and fly ash, such as fresh concrete properties, compressive strength, and shrinkage properties. The air content and slump between the ternary blended concrete and the concrete with low-fineness GGBFS showed the similar level, and the results of difference in setting time from them were less than 20 minutes, showing no significant difference. In the evaluation of compressive strength and shrinkage characteristics, the ternary blended concrete showed lower long-aged strength and higher shrinkage than the low-fineness GGBFS concrete.