• Structural Engineering and Mechanics
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• 제68권6호
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• pp.747-760
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• 2018

In the present study, a methodology for developing fragilities of arch concrete dams to assess their performance against seismic hazards is introduced. Firstly, the probability risk and fragility curves are presented, followed by implementation and representation of the way this method is used. Amirkabir arch concrete dam was subjected to non-linear dynamic analyses. A modified three dimensional rotating smeared crack model was used to take the nonlinear behavior of mass concrete into account. The proposed model considers major characteristics of mass concrete. These characteristics are pre-softening behavior, softening initiation criteria, fracture energy conservation, suitable damping mechanism and strain rate effect. In the present analysis, complete fluid-structure interaction is included to account for appropriate fluid compressibility and absorptive reservoir boundary conditions. In this study, the Amirkabir arch concrete dam is subjected to a set of 8 three-component earthquakes each scaled to 10 increasing intensity levels. Using proposed nonlinear smeared crack model, nonlinear analysis is performed where the structure is subjected to a large set of scaled and un-scaled ground motions and the maximum responses are extracted for each one and plotted. Based on the results, fragility curves were plotted according to various and possible damages indexes. Discrete damage probabilities were calculated using statistical methods for each considered performance level and incremental nonlinear analysis. Then, fragility curves were constructed based on the lognormal distribution assumption. Two damage indexes were introduced and compared to one another. The results indicate that the dam has a proper stability under earthquake conditions at MCE level. Moreover, displacement damages index is more conservative and impractical in the fragility analysis than tensional damage index.

• 폴리머
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• 제24권2호
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• pp.149-158
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• 2000

흡유성이 우수한 발포 폴리우레탄(EPU)을 제조하기 위하여 soft segment로는 친유성 polyol인 polypropyleneglycol (PPG)를 사용하고 hard segment로는 toluenediisocyanate (TDI)와 $H_2O$를 사용하였다. Soft segment 함량이 흡유성과 발포체의 기계적 특성에 미치는 영향을 조사하기 위하여 PPG 평균 분자량((equation omitted) 1000, 2000, 3000)에 따라 one-shot법으로 EPU를 제조한 결과 PPG 평균분자량이 3000에서 1000으로 감소할수록 흡유량과 인장강도는 각각 1460%에서 3010%, 0.26 $kg_{f}$ /$cm^2$에서 0.55 $kg_{f}$ /$cm^2$로 동시에 증가하였다. Hard segment 함량비인 (isocyanate index, r=[NCO]/[OH] r이 1.0에서 1.2로 증가할수록 allophanate와 biuret 결합 형성에 기인하여 EPU의 인장강도가 0.56$kg_{f}$ /$cm^2$에서 0.95 $kg_{f}$ /$cm^2$로 증가하였으나, surfactant (S-A)의 함량은 1.0 pbw에서 2.5 pbw로 증가할수록 closed cell 구조의 형성으로 인하여 흡유량이 3634%에서 3312%로 감소됨을 알 수 있었다.

• 한국음향학회지
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• 제35권2호
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• pp.92-101
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• 2016

교실 음환경은 학생들에게 매우 중요한 요소로 학습효과와 학업 성취에 매우 큰 영향을 미친다는 연구결과가 다수 발표되고 있다. 그러나 학교 교실의 신축이나 리모델링 시에 가이드라인 및 설계방안이 제시된 바 없어 적절한 음환경을 실현하는데 큰 어려움을 겪고 있다. 따라서 본 연구에서는 이론적 수식과 현장실험을 통하여 교실의 음환경 기준을 만족하기 위한 다양한 설계방안을 제시하고자 한다. 이를 위해 국내 중 고등학교의 교실에서 실내음향성능 기준을 만족하기 위해 필요한 최소 흡음면적을 계산하였다. 또한 교실의 천장 및 뒷벽의 다양한 마감상태에 따른 실내음향성능을 알아보고자 현장실험을 진행하여 실험 결과를 비교 분석하였다. 연구 결과, 국내 교실 천장에 현재 거의 모든 학교에서 시행하고 있는 것처럼 천정흡음재를 설치하지 않아도 잔향시간 기준인 0.8 s를 만족할 수 있는 것으로 나타났다. 특히, 천장 일부 면적에 반사재를 적용하되 면적의 비율이 흡음 2 : 반사 1이면서 가로로 구획하는 것이 음압레벨을 향상시키며 전체가 흡음인 경우와 비슷한 명료도[$C_{50}$, $D_{50}$, RASTI(Rapid Speech Transmission Index)]를 확보할 수 있다.

• 한국축산식품학회지
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• 제43권3호
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• pp.428-440
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• 2023

Global meat consumption is increasing worldwide, however, supply remains lacking. Several alternative protein sources, such as cultured meat, plant-based protein production, and edible insects, have been proposed to overcome this shortage. Interestingly, edible insects are characterized by superior digestive and absorptive qualities that make them the ideal replacement for traditional protein production. This study aims to further the processing ability of insect protein by investigating the effects of various pre-treatment methods, such as blanching (HB), roasting (HR), and superheated steam (HS), on the nutritional properties and physicochemical characteristics of proteins extracted from Hermetia illucens larvae. The drying rate, pH value, color analysis, amino and fatty acid profile, as well as bulk density, shear force, and rehydration ratios of the above pre-treatment methods, were explored. HS was found to have the highest drying rate and pH value analysis showed that HB and HS samples have significantly higher values compared to the other modalities. Raw edible insects had the highest value in the sum of essential amino acid (EAA) and EAA index when compared to EAAs. HB and HS showed significantly lower bulk density results, and HS showed the highest shear force and the highest value in rehydration ratio, regardless of immersion time. Therefore, taking the above results together, it was found that blanching and superheated steam blanching pre-treatment were the most effective methods to improve the processing properties of H. illucens after hot-air drying.