• Structural Engineering and Mechanics
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• 제89권4호
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• pp.335-347
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• 2024

This study pioneers the exploration of creep and shrinkage behavior in ambient-cured geopolymer concrete (GPC), a vital yet under-researched area in concrete technology. Focusing on the influence of sodium hydroxide (NaOH) solution concentration, the research utilizes low calcium fly ash (Class-F) and alkaline solutions to prepare two sets of GPC. The results show distinct patterns in compressive strength development and dry shrinkage reduction, with a 14 M NaOH solution demonstrating a 26.5% lower dry shrinkage than the 16 M solution. The creep behavior indicated a high initial strain within the first 7 days, significantly influenced by curing conditions and NaOH concentration. This study contributes to the existing knowledge by providing a deeper understanding of the time-dependent properties of GPC, which is crucial for optimizing its performance in structural applications.

• 한국지반신소재학회논문집
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• 제10권4호
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• pp.105-112
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• 2011

본 논문에서는 지속하중이 작용하는 보강토 구조물의 시간의존적 장기거동에 관한 수치 모델링 기법을 다루었다. 먼저 Power Law 기반의 크리프 모델을 이용하여 지오그리드와 뒤채움흙의 크리프 거동의 모델링에 대한 적용성을 검토 하였으며 나아가 보강토 교대 구조물의 장기 거동에 대한 해석에 적용하였다. 그 결과 Power Law 기반의 크리프 모델은 지오그리드와 뒤채움흙으로 구성되는 보강토 교대 구조물에 지속하중 작용시 발생하는 크리프 변형을 적절히 모사할 수 있는 것으로 검토되었으며 크리프 변형이 발생할 수 있는 뒤채움흙을 사용하는 경우 교대 벽체 및 상판기초에 허용치를 초과하는 변위가 발생할 수 있는 것으로 검토되었다. 본 연구에서 얻어진 결과의 실무적 적용 방안에 대한 내용을 기술하였다.

• Steel and Composite Structures
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• 제27권2호
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• pp.185-192
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• 2018

Fly ash can significantly improve concrete workability and performance, and recycling fly ash in concrete can contribute to a cleaner environment. Since fly ash influences pozzolanic reactions in concrete, mechanical behaviors of concrete containing fly ash differ from traditional concrete. Creep behaviors of fly ash concrete filled steel tube arch were experimentally investigated for 10% and 30% fly ash replacement. The axes of two arches are designed as circular arc with 2.1 m computed span, 0.24 m arch rise, and their cross-sections are all in circular section. Time dependent deflection and strain of loading and mid-span steel tube were measured, and long term deflection of the model arch with 10% fly ash replacement was significantly larger than with 30% replacement. Considering the steel tube strain, compressive zone height, cross section curvature, and internal force borne by the steel tube, the compressive zone height and structural internal forces increased gradually over time due to concrete creep. Increased fly ash content resulted in more significant neutral axis shift. Mechanisms for internal force effects on neutral axis height were analyzed and verified experimentally.

• Animal Bioscience
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• 제35권2_spc호
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• pp.356-363
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• 2022

This paper is a review of some experiments using black soldier fly (BSF) and its by-product to explore their nutritional value, production potential in Indonesia and its application in the ration of ruminants. Evaluation on the effect of milk replacer, creep feed containing BSF, BSF frass and the possibility to use lactic acid bacteria from BSF as probiotics are presented. Utilization of BSF larvae in milk replacer as skim and cream milk substitute showed that there were similarity on physiological, hematological status and performance of goat kids compared to those offered goat milk or commercial milk replacer. In addition, BSF larvae can be used to substitute soybean meal in the creep feed for post weaning goat kids without any differences in weight gain and blood profiles. However, utilization of BSF frass in the fattening goat ration resulted lower digestibility of dry matter and organic matter due to the chitin content in the frass. Black soldier fly larvae grown on chicken manure harbour lactic acid bacteria (LAB) which have potential as probiotics for ruminants. In general, BSF larvae has potential as ingredient for milk replacer, creep feed, fattening ration, and source of LAB for probiotics.

• 한국지반신소재학회논문집
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• 제9권4호
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• pp.75-84
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• 2010

본 연구에서는 띠형 섬유보강재의 인장특성, 크리프 변형, 내시공성 및 내구성을 평가하기 위한 일련의 장기성능 평가시험을 수행하였다. 또한 시험결과를 바탕으로 장기설계인장강도 산정을 위한 강도감소계수를 평가하였다. 먼저, 크리프 변형 특성을 평가하기 위해 단계 등온법과 시간-온도 중첩법을 이용하였으며, 크리프 감소계수는 1.6을 적용하는 것이 바람직한 것으로 평가되었다. 다음으로 입도 조정된 화강풍화토를 성토재로 사용하여 수행한 내시공성 시험 결과, 보강재의 강도특성에 영향을 미치는 원사의 손상이 거의 없는 것으로 확인되어, 장기설계인장강도에 큰 영향을 미치지 않을 것으로 분석되었다. 마지막으로 내구성 평가 결과, 내화학성, 내미생물 및 내후성을 고려한 강도감소계수는 1.1을 적용하는 것이 합리적인 것으로 평가되었다.

• 한국안전학회지
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• 제14권1호
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• pp.208-215
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• 1999

급냉응고 강화된 Al-9.45wt%Fe-4.45wt%Cr 합금의 크 거동을 40~115Mpa 응력범위와, 300~$441^{\circ}C$(0.53~0.66Tm) 온도 범위에서 조사하였다. 이 계열의 합금은 비행기 및 자동차의 구조용재료 혹은 엔진용 부품에 많이 사용되고 있으며, 재료의 사용이 주로 고온에서 이루어지므로 안전성을 확보하기 위해서는 크 실험이 특히 중요하다. 이 합금의 크 실험 결과 응력지수와 크 활성화에너지가 높았으며 실험 응력과 온도에 크게 좌우되었다. 크 응력이 조대화에 강하게 영향미치는 것으로 보이기 때문에 모든 크 시편의 분산입자의 조대화율은 등온 소둔시편 보다도 더 빠르게 나타났다. 분산상과 연결된 전위는 고응력, 저온의 크 시편에서 더욱 자주 관찰되었다. Power law creep에서의 크 변형 속도는 문턱응력과 전위분리기구를 포함하는 Sherby와 Rosler/Arzt식으로 예견되는 것과 일치함을 발견하였다. 이 합금에서 분산상은 void생성원으로 작용하였으며 소위 입계파괴인 입자내의 연성파괴의 원인이 되었다. 생성된 void는 성장하여 Al기지내의 분산상과 분리되고, 슬립에 의해 결정립계에 집적되어 결국 입계파괴가 일어났다. 그러므로 이들 분산상이 $Al_{13}Fe_4$, $Al_{13}Cr_2$ and $Al_2O_3$의 형성에 의해 파괴 기구의 중요한 역할을 함이 입증되었다.nd $Al_2O_3$의 형성에 의해 파괴 기구의 중요한 역할을 함이 입증되었다.

• 한국재료학회지
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• 제4권4호
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• pp.445-452
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• 1994

가압 경수로 핵연료의 중성자 조사 조건에서 Zircaloy피복관의 3축방향으로의 변동거동은 집합도 계수에 따른 크립 이방성고 조사성장 이방성을 통하여 분석될 수 있다. 이러한 크립과 조사성장의 이방성이 Zircaloy피복관의 각 축방향 변형율에 미치는 영향을 평가할 수 있는 방법론이 제시되었다. 연소 후 측정된 KOFA Zircaloy-4피복관의 변형율과 핵연료 성능 분석 코드의예측치를 토대로 하여 각 축방향 변형율을 계산한 결과 KOFA Aircaloy-4 피복관의 원주방향 변형은 크립에 의해 주로 일어난 반면, 피복관의 길이방향 변형은 조사성장에 의하여 일어났으나 낮은 조사량에서는 크립의 영향도 상당히 큰것으로 나타났다.

• Geomechanics and Engineering
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• 제31권1호
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• pp.31-52
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• 2022

Investigating and evaluating the long-term creep behavior of historical buildings built on seismic zones is of great importance in terms of transferring these structures to future generations. Furthermore, assessing the earthquake behavior of historical structures such as masonry stone bridges is very important for the future and seismic safety of these structures. For this reason, in this study, earthquake analyses of a masonry stone bridge are carried out considering strong ground motions and various water levels. Tokatli masonry stone arch bridge that was built in the 10th century in Turkey-Karabük is selected for three-dimensional (3D) finite difference analyses and this bridge is modeled using FLAC3D software based on the three-dimensional finite difference method. Firstly, each stone element of the bridge is modeled separately and special stiffness parameters are defined between each stone element. Thanks to these parameters, the interaction conditions between each stone element are provided. Then, the Burger-Creep and Drucker-Prager material models are defined to arch material, rockfill material for evaluating the creep and seismic failure behaviors of the bridge. Besides, the boundaries of the 3D model of the bridge are modeled by considering the free-field and quiet boundary conditions, which were not considered in the past for the seismic behavior of masonry bridges. The bridge is analyzed for 6 different water levels and these water levels are 0 m, 30 m, 60 m, 70 m, 80 m, and 90 m, respectively. A total of 10 different seismic analyzes are performed and according to the seismic analysis results, it is concluded that historical stone bridges exhibit different seismic behaviors under different water levels. Moreover, it is openly seen that the water level is of great importance in terms of earthquake safety of historical stone bridges built in earthquake zones. For this reason, it is strongly recommended to consider the water levels while strengthening and analyzing the historical stone bridges.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.476.2-476
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• 2001

• Asian-Australasian Journal of Animal Sciences
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• 제24권6호
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• pp.851-856
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• 2011

This study was conducted to evaluate the effects of flavor supplementation on pre- and post-weaning performance and behavior of piglets and sows. A total of 30 sows (Landrace${\times}$Yorkshire) and their litters were employed in this study. Sows were randomly assigned to 3 dietary treatments (10 replications per treatment). Dietary treatments included: i) CON, basal diet; ii) TRT1, CON+0.1% vanilla supplement; iii) TRT2, CON+0.1% cheese supplement. The behavior of sows (nursery, eating and standing) and piglets (eating, sleeping and fighting) in each treatment was monitored throughout experiment. Each piglet was weighted at 5, 10, 15 and 21 d after birth to evaluate the average daily gain. Sows and piglets were bled on the weaning d to evaluate the blood characteristics. Back fat and estrus interval were investigated. In this study, there were no differences (p>0.05) in diarrhea score and blood characteristics among treatments. Likewise, the behavior was not influenced (p>0.05) by the dietary flavor supplementation. However, administration of flavor increased (p<0.05) the pre-weaning feed intake, post-weaning average daily gain (ADG) and gain/feed (G/F) ratio. No significant difference was observed (p>0.05) on the blood characteristics, behavior, backfat loss and estrus interval among treatments. In conclusion, administration of flavor could increase creep feed intake pre-weaning and piglet ADG post-weaning, whereas inclusion of flavor had no influence on blood characteristics and performance in sow and piglets.