• Earthquakes and Structures
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• 제11권5호
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• pp.823-840
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• 2016

The plastic hinge lengths of beams and columns are a critical demand parameter in the nonlinear analysis of structures using the finite element method. The numerical model of a plastic hinge plays an important role in evaluating the response and damage of a structure to earthquakes or other loads causing the formation of plastic hinges. Previous research demonstrates that the plastic hinge length of reinforced concrete (RC) columns is closely related to section size, reinforcement ratio, reinforcement strength, concrete strength, axial compression ratio, and so on. However, because of the limitations of testing facilities, there is a lack of experimental data on columns with large section sizes and high axial compression ratios. In this work, we conducted a series of quasi-static tests for columns with large section sizes (up to 700 mm) and high axial compression ratios (up to 0.6) to explore the propagation of plastic hinge length during the whole loading process. The experimental results show that besides these parameters mentioned in previous work, the plastic hinge of RC columns is also affected by loading amplitude and size effect. Therefore, an approach toward considering the effect of these two parameters is discussed in this work.

• 한국수산과학회지
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• 제28권5호
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• pp.589-598
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• 1995

본 연구는 수온과 크기의 영향을 포함하는 양식굴 C. gigas의 단위시간당 여과수량 산출식을 제시하였다. 여수율의 측정은 폐쇄순환계에서 지표물질의 농도 저감속도를 측정하는 간접법으로 수행되었으며, 지표물질은 배양한 규조류 Chaetoceros calcitrans를 사용하였고, 이 규조의 $chlorophyll-\alpha$양에 직선적으로 비례하는 675nm의 흡광도 값으로 부터 농도감소계수 Z를 구하고, Z를 감소율로 변환하여 수량 V에서 여수율 FR을 산출하였다. $Z=-In(\frac{C_t}{C_0})/t$, $FR=V{\codt}(1-e^{-z})$ 양식굴의 여수율은 다음과 같이 수온 및 개체건조 육중량을 변수로 하는 지수함수식으로 나타낼 수 있다. 여수율은 수온과 더불어 지수함수적으로 증가하며, 상한측 임계온도는 $28-29^{\circ}C$ 사이에 있는 것으로 여겨진다. $\frac{FR}{DW}$, 1/hr/g, dry meat wt = $Exp(0.208{\cdot}T-4.324){\cdot}(DW)^{-0.7771}$, FR, 1/hr/animal = $Exp(0.208{\cdot}T-4.324){\cdot}(DW)^{0.223}$

• 한국구조물진단유지관리공학회 논문집
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• 제16권3호
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• pp.23-30
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• 2012

콘크리트 표면에 존재하는 균열은 염소이온의 침투에 대한 빠른 침투 통로가 되어 내구성능을 저하시킬 수 있다. 균열을 제어하기 위하여 설계적 측면에서 높은 철근비로 균열폭을 감소시킬 수는 있으나, 이러한 균열이 실질적으로 내구성을 저하시키는데에 따른 검토 및 내구성 향상을 유도할 수 있는 방법이 필요하다. 표면도막공법은 균열폭이 작은 경우에 균열을 실링하여 염소이온 침투를 차단하는데 가장 간단한 방법중의 하나이며, 경제성 대비 성능도 만족할 만 하다. 그래서 표면도막공법이 콘크리트와 균열을 함침하여 유해물질의 침투로 인한 철근의 부식을 제어하기 위한 유효성을 검토하는 연구가 필요하다. 본 연구는 표면도막공법으로 압축응력 인가로 인한 미세균열을 통한 염소이온 침투의 제어 가능성을 검토하고자 하였다. 실험결과는 염소이온은 압축응력 인가율 50~70%, 탄산화는 70~80%의 범위에서 임계응력이 존재하는 것으로 나타났는데, 이 임계치 이상을 초과하게 되면 상대적으로 심각한 열화가 진전되는 것을 확인할 수 있었다. 또한, 표면도막공법은 균열치료효과를 얻는데 유효한 것으로 판단되었다.

• 경영과학
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• 제32권3호
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• pp.13-28
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• 2015

Using the most recent dataset of Korea and U.S. household finance, this study analyzed demand and adequacy of private pensions for pre-retirees. For this purpose, 2013 Korean Retirement and Income Study (KReIS) of national pension research institute in Korea and 2013 SCF (Survey of Consumer Finances) of FRB in U.S. were used. For comprehensive comparisons of the two countries, this study classified the private pension into sub-categories such as personal pension, corporate pension, and retirement benefits, and used three different criteria including ownership, accumulated present value of each pension, and income replacement ratio of each pension. After controlling for other factors, educational level of householder and household income were critical determinants of size and adequacy of private pension in both countries. Different from Korean households, householders' gender, marital status, and health status had an important effect on the private pension size and adequacy in the U.S. In addition, home ownership significantly increased only private pension adequacy in Korea, and also increased ownership rate, size, and adequacy of private pension in the U.S. Results of this study provide useful implications for future pension system and policy in Korea.

• 동력기계공학회지
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• 제17권4호
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• pp.94-102
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• 2013

Manufactured $SiC_f/SiC$ composites by NITE method was investigated fracture characteristics according to the size of the surface crack. Coated surface crack with a $SiO_2$ colloid in several ways was evaluating the possibility of healing. The strength of CCS and UCS is 313 and 230MPa, respectively and it is about 1/3 of the SPS. Bending strength of $SiC_f/SiC$ composites has no effect with the pre-crack size to the critical crack size. $SiC_f/SiC$ composites can not generate large amount of $SiO_2$ oxides to the bottom of crack, and is only generated randomly on surfaces, and can not contribute to the recovery of bending strength.

• 대한조선학회논문집
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• 제57권5호
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• pp.271-277
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• 2020

Recoverability and vulnerability of navy ships under underwater explosion are critical verification factors in the acquisition phase of navy ships. This paper aims to establish numerical analysis techniques for the underwater explosion of navy ships. Doubly Asymptotic Approach (DAA) Equation of Motion (EOM) of primary shock wave and secondary bubble pulse proposed by Geers-Hunter was introduced. Assuming a non-compressive fluid, reference solution of the DAA EOM of Geers-Hunter using Runge-Kutta method was derived for the secondary bubble pulse phase with an assumed charge conditions. Convergence analyses to determine fluid element size were performed, suggesting that the minimum fluid element size for underwater explosion analysis was 0.1 m. The spherical and cylindrical fluid domains were found to be appropriate for the underwater explosion analyses from the fluid domain shape study. Because the element size of 0.1 m was too small to be applied to the actual navy ships, a very slender beam with the square solid section was selected for the study of fluid domain existence effect. The two underwater explosion models with/without fluid domain provided very similar results in terms of the displacement and stress processes.

• 한국가시화정보학회지
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• 제15권2호
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• pp.16-20
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• 2017

A coffee-ring effect is from capillary flow by different evaporation rate across the droplet. The capillary flow tends particles to accumulate at the edges of the droplet and makes the ring-shaped stain pattern. These coffee-ring formation and suppression of coffee-ring have been a critical role in printing and coating technologies. In this study, we present the experimental study on coffee-ring effect of silver nanowire inside the evaporating sessile droplet. Size and concentration effect of nanowires at coffee-ring effect has been investigated. From the coffee-ring, we observed the regimes of connected rings and disconnected ones and measure the resistivity of single ring pattern with different nanowire length.

• 에너지공학
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• 제11권1호
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• pp.74-80
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• 2002

본 연구는 불꽃 점화 기관의 실린더내의 연료 액적의 기화과정에 대한 수치 해석이다. 본 연구의 특징은 무차원 임계 액적 수명시간을 정의하여 가솔린엔진의 흡입 및 압축행정동안 연료 액적의 가열 및 기화과정을 모델화한 것이다. 수치해석 결과는 압축행정동안 기체 온도 및 압력의 동시적 증가는 액적의 기화율에 서로 보상적인 영향을 미치려는 경향을 보이고 있다. 즉 실린더 내 환경의 변화는 연료 액적의 기화과정에 민감하지 않다는 것을 보이고 있다. 이 프로그램은 압축행정 말기에 완전히 기화할 수 있는 액적의 크기를 예측할 수 있다.

• Journal of Welding and Joining
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• 제19권3호
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2003년도 춘계 학술발표회 논문집
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• pp.351-357
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• 2003

In absorption system, the performance of the absorber is critical the overall system performance, size, and first-cost. The objective of this paper is to provide a comprehensive review of the significant effects that researchers have made to numerically analysis model the coupled heat and mass transfer process that occur during falling-film absorption and experimental researches. This study includes experimental work in the enhancement of absorption performance, the effect of the geometry of a vertical absorber, and the effect of configuration of absorption system. This paper is used to highlight key areas which need attention such as film ans vapor hydrodynamics, especially the non-periodicity, instability, and recirculatory motion of waves in the vertical absorber case.