• Computers and Concrete
• /
• 제7권4호
• /
• pp.331-346
• /
• 2010

We present a quadrilateral finite element with an embedded crack that can be used to model tensile fracture in two-dimensional concrete solids and the crack growth. The element has kinematics that can represent linear jumps in both normal and tangential displacements along the crack line. The cohesive law in the crack is based on rigid-plasticity with softening. The required material data for the concrete failure analysis are the constants of isotropic elasticity and the mode I softening curve. The results of two well known tests are presented in order to illustrate very satisfying performance of the presented approach to simulate failure of concrete solids.

• 한국표면공학회지
• /
• 제21권2호
• /
• pp.76-82
• /
• 1988

The bright nickel electroplatings were carried out the Watt bath containg a solobel saccharin as class I brightner and para substituted benzaldehydes as class II one. Extended Huckel MO calculation was done and polarization was measured to examine between $\pi$-electron density and the brightness. The correlation is also investigated between $\pi$-electron density of oxygen atom of aldehyde group and slope of polarization curve. As a result of the analysis of rate equation of nucleation, the surface energy of the deposited particle was obtained from the slope of the plot of $\ell$nI against 1/η2, and also the reat equation of nucleation found to influnced on the leveling on the basis of adsorption theory. We have proposed the general electroplating mechanism that is applied other to all other electroplating but nickel one. The above elucidated mechanism can be extended can be extended to the all electroplating other than bright nickel electroplating.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권8호
• /
• pp.938-945
• /
• 2005

The microstructure evolution in hot forging process is composed of dynamic recrystallization during deformation as well as grain growth during dwell time. Therefore, the control of forging parameters such as strain, strain rate. temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. Modeling equations are developed to represent the flow curve. grain size. recrystallized volume fraction and grain growth phenomena by various tests. The developed modeling equations were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The large exhaust valve spindle (head diameter of 512mm) was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to each 1080 and 1150$^{\circ}C$. Numerical calculation was performed by DEFORM-2D. a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. In order to obtain the fine and homogeneous microstructure and good mechanical properties in forging. the FEM would become a useful tool in the simulation of the microstructure development. In forging, appropriate temperature, strain and strain rate and rapid cooling are required to obtain the fine grain microstructure The optimal forging temperature and effective strain range of Nimonic 80A for large exhaust valve spindle are about 1080$\∼$l120$^{\circ}C$ and 150$\∼$200$\%$.

• Journal of Veterinary Science
• /
• 제21권3호
• /
• pp.35.1-35.11
• /
• 2020

Background: Despite common use of tylosin in turkeys, the pharmacokinetic (PK) data for this drug in turkeys is limited. Within a few months of growth, PK of drugs in turkeys undergoes changes that may decrease their efficacy due to variable internal exposure. Objectives: The objective of this study was to investigate the influence of age on the PK of a single intravenous (i.v.) and oral administration of tylosin to turkeys at a dose of 10 and 50 mg/kg, respectively. Methods: Plasma drug concentrations were measured using high-performance liquid chromatography with UV detection. The PK parameters were assessed by means of non-compartmental approach and were subjected to allometric analysis. Results: During a 2.5-month-long period of growth from 1.4 to 14.7 kg, the median value for area under the concentration-time curve after i.v. administration increased from 2.61 to 7.15 mg × h/L and the body clearance decreased from a median of 3.81 to 1.42 L/h/kg. Over the same time, the median elimination half-life increased from 1.03 to 2.96 h. For the oral administration a similar trend was noted but the differences were less pronounced. Bioavailability was variable (5.76%-21.59%) and age-independent. For both routes, the plasma concentration of the major tylosin metabolite, tylosin D, was minimal. Protein binding was age-independent and did not exceed 50%. Allometric analysis indicated a relatively poor predictivity of clearance, volume of distribution and elimination half-life for tylosin in turkeys. Conclusions: Age has a significant impact on tylosin PK in turkeys and dosage adjustment may be needed, particularly in young individuals.

• 한국산림과학회지
• /
• 제111권4호
• /
• pp.594-602
• /
• 2022

본 연구는 편백의 초기생장에 대한 slurry composting and biofiltration(SCB)액비의 효과를 분석하기 위해 대조구(control), 화학비료처리구(chemical fertilizer : CF), 퇴비처리구(compost : CP), 저농도액비처리구(low liquid fertilizer : LLF) 및 고농도액비처리구(high liquid fertilizer : HLF)로 조성하여 처리구별 5본씩 3반복 실험을 하였다. 생장량분석 결과, 고동노액비를 200% 처리한 HLF-200처리구에서 가장 높은 생장량을 보였다. 시비효과를 분석하기 위해 HLF-200처리구와 대조구를 대상으로 근원직경 및 수고 생장모델을 개발하였다. 그 결과, 대조구와 HLF-200처리구 근원직경생장모델의 경우 각각 Schumacher 동형방정식 및 Schumacher 다형방정식이 가장 적합한 것으로 나타났으며, 수고생장모델의 경우 Gompertz 다형방정식이 가장 적합한 것으로 나타났다. 결정된 모델에 따른 생장곡선을 통해 근원직경과 수고의 생장량 및 생장률 모두 대조구보다 HLF-200처리구가 높아 시비효과가 있는 것으로 나타났으며, SCB액비를 통한 시비처리가 편백의 초기생장 증진에 적합한 것으로 판단되었다.

• 콘크리트학회지
• /
• 제4권1호
• /
• pp.81-87
• /
• 1992

본 논문에서는 강섬유 혼입량과 강섬유 형상비에 대한 강섬유보강콘크리트의 휨 피로거동을 분석하기 위하여 일련의 강섬유보강콘크리트 시험체에 대하여 피로실험을 수행하였다. 피로실험은 3점 휨 실험법으로 실시하였으며, 실험시 각 시험체의 하중반복회수에 대한 중앙처짐과 피로파괴시의 반복회수를 조사하였다. 이들 실험 결과를 토대로 반복회수에 대한 강섬유보강콘크리트의 중앙처짐, 비탄성변형에너지 및 탄성변형형에너지등을 비교 분석하였으며, 강섬유보강콘크리트의 S-N선도를 작도하였다. 연구결과, 강섬유 혼입량이 클수록 영구변형에 손실되는 에너지가 크게 감소하고, 균열 확대에 소모되는 에너지가 증가하였으며, 동일한 강섬유 혼입량을 갖는 강섬유콘크리트의 경우 강섬유 형상비가 클수록 탄성변형에너지는 작았다. 아울러 본 피로실험 결과를 회귀분석하여 구한 S-N선도에 의하면 강섬유 혼입량이 1.0%인 강섬유보강 콘크리트의 반복회수 200만회에 대한 피로초기균열 발생시의 정적강도의 약 70%로 나타났다.

• 수산해양기술연구
• /
• 제36권3호
• /
• pp.234-243
• /
• 2000

This paper is to study population ecological characteristics, including growth parameters, survival rate, instantaneous coefficients of natural and fishing mortalities, and age at first capture of the soft-shelled clam, Mya japonioa in the intertidal zone of South Sea in Korea. For describing growth of the clam a von Bertalanffy growth model was adopted, The von Bertalanffy growth curve had an additive error structure and the growth parameters estimated from a non-linear regression were SH/sub ∞/=79.83mm, K=0.26, and t/sub 0/= -0.01. Survival rate (S) of the soft-shelled clam was 0.26 (SD=0.02). The instantaneous coefficients of natural mortality (M) was estimated to be 0.78/year and fishing mortality (F) 0.57/year for the soft-shelled clam. The age at first capture (t/sub c/) was estimated as 2.69 year. The mean densities of the soft-shelled clam by bottom type were 3.40 inds./m²(SE=0.18) in the sand, 63.4 inds./m²(SE= 0.53) in the muddy sand, and 0 inds./m2 (SE=0) in the gravelly sand. The mean densities of the soft-shelled clam by 3 different areas were 4.88 inds./m²(SE=0.09), 2.61 inds./m²(SE=0.13), 7.20 inds./m²(SE=0.18), respectively and the biomass of the clam were estimated as 131mt, 121mt, 665mt, respectively. An yield-per-recruit analysis showed that the current yield-per-recruit of about 8.30g with F=0.57/year and the age at first capture (t/sub c/) 2.69 year, was lower than the maximum possible yield-per-recruit of 9.60g. Fixing to at the current level and increased fishing intensity (F) could produce an increase in the predicted yield-per-recruit from 8.30g to about 9.40. However, estimated yield-per-recruit increased to 1.30g by decreasing to from the current age (2.69 year) to age two with F fixed at the current level. Yield-per-recruit was estimated under harvest strategies based on F/sub max/ and F/sub 0.1/.

• 한국전기전자재료학회논문지
• /
• 제31권6호
• /
• pp.386-391
• /
• 2018

An epitaxial GaN layer was grown on a cone-shape-patterned sapphire substrate (PSS) (Sample A) and an AlN-buffered PSS (Sample B) with two growth steps under the same process conditions by employing the hydride vapor phase epitaxy (HVPE) method. We have investigated the characteristics of the GaN layer grown on two kinds of substrates at each growth step. The cross-sectional SEM image of the GaN layer grown on the two types of substrates showed growth states of GaN layers formed during the 1st and 2nd growth steps with different growth durations. Dislocation density was obtained by calculation using the FWHM value of the rocking curve for (002) and (102). Sample A showed 2.62+08E and 6.66+08E and sample B exhibited 5.74+07E and 1.65+08E for two different planes. The red shift was observed is photoluminescence (PL) analysis and Raman spectroscopy results. GaN layers grown on AlN-buffered PSS exhibited better optical and crystallographic properties than GaN layers grown on PSS.

• Korean Chemical Engineering Research
• /
• 제48권1호
• /
• pp.58-67
• /
• 2010

본 연구에서는 국내 상용 순환유동층 보일러에서 연료로 사용하고 있는 저급 국내무연탄과 혼소용 연료로 이용할 예정인 목재펠릿의 각각의 연소 특성을 조사하기 위해 열중량 분석기(TGA)를 이용하여 비등온 실험(5, 10, 20, $30^{\circ}C/min$) 및 등온 조건으로 촤 연소 실험을 수행하였다. 목재펠릿의 경우는 승온 속도에 따라 차이가 있으나, 국내무연탄에 비해 낮은 온도인 $200{\sim}620^{\circ}C$ 사이에서 연소되었으며, 최대 반응속도를 나타내는 온도 또한 국내무연탄의 그것에 비해 매우 낮음을 알 수 있었다. 비등온 실험 결과를 Friedman 방법으로 해석한 결과, 무게감량이 가장 큰 2차 구간에서의 목재펠릿 및 국내무연탄의 활성화에너지는 44.12, 21.45 kcal/mol이었으며, 반응차수 및 빈도인자는 각각 5.153, 0.7453 및 $4.01{\times}10^{16}$, $1.39{\times}10^6(s^{-1})$임을 확인할 수 있었다. 또한 등온 조건으로 촤 연소 실험 결과, 화학반응 율속단계에서의 목재펠릿 및 국내무연탄의 활성화에너지는 각각 27.5, 51.2 kcal/mol이었으며, 빈도인자는 각각 $2.55{\times}10^{12}$, $1.49{\times}10^{10}(s^{-1})$임을 확인할 수 있었다. 국내무연탄에 비해 목재펠릿이 낮은 온도에서 연소 반응이 시작이 되고 반응차수 및 빈도인자가 높아 반응속도를 빠를 것으로 판단되어 혼소 시 연소 제어가 잘 이루어질 경우, 연소로 내의 연소 분위기가 향상될 것으로 예상된다.

• 한국심리학회지 : 문화 및 사회문제
• /
• 제28권3호
• /
• pp.331-352
• /
• 2022

본 연구는 청소년의 게임이용시간과 자기통제의 시간에 따른 변화와 적응적 게임활용이 지니는 종단적 매개효과를 검증하기 위하여 잠재성장모형을 활용하였다. 적응적 게임활용의 종단매개효과 검증을 위하여 한국콘텐츠진흥원에서 주최한 2019 게임이용자패널연구 학술대회 참여를 통해 제공받은 청소년 863명의 게임이용자패널조사 4개년 응답자료를 활용하였다. 본 연구모형을 분석하기 위하여 SPSS 21.0과 Mplus 6.12를 활용하여, 각 변인의 시점별 정규성을 확인 후 상관분석, 종단적 매개분석을 순차적으로 실시하였다. 연구결과를 요약하면 다음과 같다. 첫째, 잠재성장모형을 분석한 결과, 게임이용시간과 적응적 게임활용, 자기통제는 모두 시간에 따라 선형적으로 성장하였다. 둘째, 측정된 변인들의 초기치와 변화율 간 관계를 분석한 결과 게임이용시간이 자기통제에 미치는 직접적인 영향은 유의하지 않았으나 적응적 게임활용을 통해 자기통제에 정적으로 유의한 영향을 미치는 것으로 나타났다. 지속적인 적응적 게임활용은 자기통제수준을 높이는 것으로 확인되었다. 셋째, Sobel 검증 결과, 적응적 게임활용의 초기치와 변화율 모두 완전 매개효과를 갖는 것으로 나타나 종단매개효과가 유의함을 확인하였다. 본 연구는 청소년의 자기통제 수준이 게임이용시간과 적응적 게임활용의 변화양상에 따라 변화를 보이는 종단적 과정을 통해 적응적 게임활용의 중요성을 확인하였다.