• Computers and Concrete
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• 제30권2호
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• pp.127-141
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• 2022

In this paper, a numerical procedure is proposed for achieving the minimum cost design of reinforced concrete polygonal column cross-sections under compression and biaxial bending. A methodology is developed to integrate the metaheuristic algorithm Quantum Particle Swarm Optimization (QPSO) with an algorithm for the evaluation of the strength of reinforced concrete cross-sections under combined axial load and biaxial bending, according to the design criteria of Brazilian Standard ABNT NBR 6118:2014. The objective function formulation takes into account the costs of concrete, reinforcement, and formwork. The cross-section dimensions, the number and diameter of rebar and the concrete strength are taken as discrete design variables. This methodology is applied to polygonal cross-sections, such as rectangular sections, rectangular hollow sections, and L-shaped cross-sections. To evaluate the efficiency of the methodology, the optimal solutions obtained were compared to results reported by other authors using conventional methods or alternative optimization techniques. An additional study investigates the effect on final costs for an alternative parametrization of rebar positioning on the cross-section. The proposed optimization method proved to be efficient in the search for optimal solutions, presenting consistent results that confirm the importance of using optimization techniques in the design of reinforced concrete structures.

• 한국지리정보학회지
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• 제11권1호
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• pp.58-67
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• 2008

지형은 연료의 구성과 기상 및 산불로부터 발생하는 에너지의 흐름에 영향을 미쳐 산불행동에 관여하는 인자이다. 따라서 지형에 따른 산불피해도를 정략적으로 해석할 수 있다면, 산불위험도 작성 및 진화대원 안전 확보에 있어 기초 자료로 응용될 수 있다. 이를 위해 본 연구에서는 삼척(2000년 발생), 청양(2002년 발생), 양양(2005년 발생) 산불을 대상으로 산불피해도를 분석하고 지형을 구분한 다음 통계분석을 실시하여 두 인자간의 상관관계를 알아보았다. 산불피해도는 산불 전후 Landsat TM 영상에서 추출한 정규탄화지수(Normalized Burn Ratio)의 차이를 이용하였다. 지형은 지형위치지수(Topographic Position Index)를 이용해 Weiss(2001)가 제시한 10개로 구분하였다. 분석결과 산지수로, 능선, 산복사면 등의 지형에서 산불피해도가 높게 나타났으며, 곡저구릉, 평탄곡지, 평지 등의 지형은 산불피해도가 낮게 나타났다. 이를 임상별로 세분해 보면 산불피해도는 침엽수림에서 활엽수림에 비해 지형에 더 민감하게 반응한 것으로 나타났다.

• 디지털융복합연구
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• 제14권10호
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• pp.83-93
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• 2016

본 논문은 우리나라 정보통신 분야의 특허출원인 간 네트워크 특성이 기술혁신에 미치는 영향을 알아보기 위해 연구하였다. 이를 위해 특허 데이터를 토대로 정부 공공기관, 대학교, 대기업, 중소기업 등 각 혁신 주체의 네트워크 특성 요인과 특허피인용 횟수 간 관계를 소셜네트워크분석법(Social Network Analysis)과 부정적 이항분포 모델(Negative Binomial Regression)을 사용하여 분석하였다. 분석 결과, 우리나라 정보통신분야 혁신 네트워크는 밀도 0.009의 좁은세상 네트워크 유형을 보이고 있다. 또한, 연결중심성, 근접중심성은 특허피인용수로 대표되는 혁신 성과에 긍정적인 영향을 미치는 것으로 나타났는데에 반해, 구조적공백 지수 중 효율성은 유의미한 영향을 미치지 못했고, 제약성은 유의미한 부정적인 영향을 미치는 것으로 나타났다. 이것은 본 네트워크의 혁신 주체 간 연결이 매우 가까워 정보 지식의 확산이 빠르다는 것이고, 이에 반해 정보 지식의 원천이 한정되어 있어 다양하고 창의적인 혁신에는 한계가 있다는 것을 의미한다. 이에 이 결과를 토대로 각 혁신 주체의 효율성 및 다양성을 개선하기 위한 정책을 수립해야 한다.

• 한국가스학회지
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• 제16권5호
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• pp.47-51
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• 2012

본 연구에서는 3가지의 서로 다른 단면형상을 갖는 밀봉 링의 변형거동 안정성을 FEM으로 해석하였다. NBR 소재로 제조한 밀봉 링의 변형거동 안정성을 고찰하기 위해 초기 압축률로 25%를 적용하였다. 작동유체의 압력을 최대 $25kgf/cm^2$까지 올렸을 때 발생한 최대변형률, 최대응력, 최대접촉법선응력을 해석하였다. FEM 결과에 의하면, 밀봉 링의 중심부에 빈 공간을 확보한 중공오링과 중공사각링의 최대 변형률은 기존 오링에 비해 높아졌지만, 최대응력과 최대접촉법선응력은 떨어지는 것으로 나타났다. 결국, 밀봉 링이 장수명의 내구 안정성을 확보하기 위해서는 중심부에 빈 공간을 확보하는 것이 권장된다. 그렇지만, 접촉식 밀봉 링의 밀봉 안전성을 확보하기 위해서는 밀봉 링을 하나의 몸체로 설계하는 것이 바람직하다.

• 한국인쇄학회지
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• 제24권2호
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• pp.61-68
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• 2006

Rubber rollers in off-set printing process are one of the most important factor, transferring the ink and water to the plate. Each different roughness of roller surface and different rubber compounds could effect to ink transparency and printability. Three different rubber compounds (NBR, EPDM, PU) and each different roughness of roller surface would show us different result of ink transparency and density of actual printing result. There might be a differences from actual printing result not only the amount of transferred ink, but there is also some other point we should check it out. According to the result of this studies, we found that different rubber compounds and their surface roughness directly effect to the rate of ink transfer. It also shows that the amount of transferred ink is not even and stable amount what we expect to get optimum printability. To reach a targeted printability with rollers, firstly it is necessary to choose correct rubber compounds with certain purpose and the roughness of roller surface has to be as smooth as less than $5{\mu}m{\sim}7{\mu}m$.

• 한국의류학회지
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• 제32권9호
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• pp.1397-1406
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• 2008

This research was to develop Taekwondo trunk protector(Hogu) and head protector's sizing systems corresponding the regulations by World Taekwondo Association. These sizing systems were established using 2003-2004 Size Korea anthropometric data. The result can be summarized as follows: According to the analysis of correlation, most measurements had high relationship with weight for Hogu and head girth for head protector. Six sizes(47, 54, 59, 64, 70, 76) for Hogu and 4 sizes(52, 54, 56, 60) for head protector were suggested in this study. Hogu sizes indicate body weights and head protector sizes express head girth measurements. By the comparison between current Hogu sizes and new sizes, the smaller sizes of new Hogu were bigger than current sizes in bust girth, back fastening length, shoulder length. On the other hand, the bigger sizes of new Hogu were larger than current sizes in bust girth, back fastening length, shoulder length. In addition, new Hogu's lengths were shorter than current Hogu in all sizes. The lengths of Neck to collar bone in new Hogu sizes were longer than current Hogu. In case of the head protector, there were no measurements besides outer circumference of helmet in recognized specifications of WTF. Therefore some referable measurements such as head girth, head length, bitragion arc, sagital arc were suggested in new size specification. When helmet sizes were suggested, the thickness of the NBR foam also were considered.

• 한국방재학회 논문집
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• 제8권2호
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• pp.23-30
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• 2008

UHPCC는 고성능, 고강도와 우수한 역학적 특성을 지니고 있다. UHPCC는 동일한 하중 하에서 타 재료에 비해 단면을 축소할 수 있는 장점이 있으나, 보통콘크리트에 비해 외국에서 수입하는 실리카흄이 많이 사용되는 배합이 되어 제작비용을 증가시키는 원인이 된다. 최밀 충전구성에 의한 UHPCC의 우수한 역학적 특성은 분체에 해당되는 아주 가는 입경의 골재를 치환함으로서 변화시킬 수 있다. 본 연구는 실리카흄과 실리카플로우를 석회석 미분말로 치환된 UHPCC의 특성을 파악하고자 한다. 본 실험 시편은 치환종류에 따라 크게 세 가지로 분류한다. 압축강도와 플로우를 비교 검토하였으며, SEM, XRD와 NMR 방법등을 사용하여 미세조직과 수화반응 현상을 분석하였다. 결론적으로 석회석 미분말로의 치환은 UHPCC 구조부재의 시공 단가를 감소시키며, 굳지 않은 UHPCC의 특성을 향상시키는 유용한 치환이 된다고 볼 수 있다.

• Elastomers and Composites
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• 제15권3호
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• pp.147-154
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• 1980

The cellular rubber products for industrial purpose have been applied in many fields such as auto-motive parts, ship-building, machinery, sports goods, diving suit or interior housings etc. The purpose of this dissertation is to study the physical properties of celluar rubber products particulary for those elastomers such as EPDM, CR and NBR with heat resistance property, weather proofness, and oil resistance characteristics respectively, aiming at improving their quality, and renovating the manufacturing know-how which is beyond our technical power at the present time in Korea. In order to meet this requirement an ideal recipe is being shown for the three elastomers, and also a practical recipe which is easily available in terms of compounding ingredients in domestic market has set up as shown in Table 1. for the investigation of vulcanization characteristics by means of Rheometer. The optimum Mooney viscosity of compounded rubber was found to be approximately $ML_{1+4}(100^{\circ}C)$ $30\sim45$. Excess mustication makes a dispersion of ingredients worse, consequently it causes deformation of shapes and heterogenous cell distribution. In other words the articles are rejected because of its insufficient workmanship. The results of physical properties of the products are indicated in Table 3. It has shown that the quality meet requirement when tested in accordance with ASTM D572, 573 and D 395. The test results o CR/IR blends in terms of hardness, volume change by blowing, tensile strength and elongation have been shown.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1428-1435
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• 2019

The total ionizing dose (TID) and non ionizing energy loss (NIEL) effects of 100 MeV phosphorous ($P^{7+}$) and 80 MeV nitrogen ($N^{6+}$) ions on 200 GHz silicon-germanium heterojunction bipolar transistors (SiGe HBTs) were examined in the total dose range from 1 to 100 Mrad(Si). The in-situ I-V characteristics like Gummel characteristics, excess base current (${\Delta}I_B$), net oxide trapped charge ($N_{OX}$), current gain ($h_{FE}$), avalanche multiplication (M-1), neutral base recombination (NBR) and output characteristics ($I_C-V_{CE}$) were analysed before and after irradiation. The significant degradation in device parameters was observed after $100MeV\;P^{7+}$ and $80MeV\;N^{6+}$ ion irradiation. The $100MeV\;P^{7+}$ ions create more damage in the SiGe HBT structure and in turn degrade the electrical characteristics of SiGe HBTs more when compared to $80MeV\;N^{6+}$. The SiGe HBTs irradiated up to 100 Mrad of total dose were annealed from $50^{\circ}C$ to $400^{\circ}C$ in different steps for 30 min duration in order to study the recovery of electrical characteristics. The recovery factors (RFs) are employed to analyse the contribution of room temperature and isochronal annealing in total recovery.

• 한국환경복원기술학회지
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• 제25권5호
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• pp.43-57
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• 2022

This study aims to classify forest fire-affected areas, identify forest types by the intensity of forest fire damage using multi-time Landsat-satellite images before and after forest fires and to analyze the effects of artificial restoration sites and natural restoration sites. The difference in the values of the Normalized Burned Ratio(NBR) before and after forest fire damage not only maximized the identification of forest fire affected and unaffected areas, but also quantified the intensity of forest fire damage. The index was also used to confirm that the higher the intensity of forest fire damage in all forest fire-affected areas, the higher the proportion of coniferous forests, relatively. Monitoring was conducted after forest fires through Normalized Difference Vegetation Index(NDVI), an index suitable for the analysis of effects by restoration type and the NDVI values for artificial restoration sites were found to no longer be higher after recovering the average NDVI prior to the forest fire. On the other hand, the natural restoration site witnessed that the average NDVI value gradually became higher than before the forest fires. The study result confirms the natural resilience of forests and these results can serve as a basis for decision-making for future restoration plans for the forest fire affected areas. Further analysis with various conditions is required to improve accuracy and utilization for the policies, in particular, spatial analysis through forest maps as well as review through site checks before and immediately after forest fires. More precise analysis on the effects of restoration will be available based on a long term monitoring.