• 열처리공학회지
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• 제21권3호
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• pp.137-143
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• 2008

Effect of quenching medium on the mechanical properties of ductil iron GCD 50 has been investigated using ADI treated specimens. The specimens have been austenitized at $900^{\circ}C$ for 2 hours, followed by controlled cooling to $800^{\circ}C$ under the cooling rate of $0.05^{\circ}C/sec$, then austempered at $380^{\circ}C$, $330^{\circ}C$, $280^{\circ}C$ and $230^{\circ}C$ for 1 hour. The specimens treated in the salt of 5% water were found to have higher tensile strength than that of the normal salt bath. Elongation and impact energy increased in proportion to the increase of retained austenite volume fraction. The increase of cooling rate of the salt by the addition of 5% water to the salt resulted in the increase of retained austenite volume fraction and the formation of fine bainitic ferrite.

• 한국전산유체공학회지
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• 제21권1호
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• pp.110-116
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• 2016

The present study numerically investigated the deformation of the interface of two-phase fluids flow in a blast furnace. To simulate three-dimensional(3D) incompressible viscous two-phase flow in the furnace filled with the air and molten iron, the volume of fluid(VOF) method based on the finite volume method has been utilized. In addition, the porous medium with the porosity has been considered as the bed of the particles such as cokes and char etc. For the comparison, the single phase flow and the two-phase flow without the porosity have been simulated. The two-phase flow without porosity condition revealed the smooth parabolic profile of the free surface near the outlet. However, the free surface under the porosity condition formed the viscous finger when the free surface was close to the outlet. This viscous finger accelerated the velocity of the free surface falling and the outflow velocity of the fluids near the outlet.

• 한국습지학회지
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• 제14권2호
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• pp.193-198
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• 2012

본 연구는 우리나라 멸종위기종인 조름나물의 삽목 증식 시, 지하경의 길이 및 마디 수에 따른 증식 효율을 살펴보기 위해, 조름나물 지하경의 길이와 마디 수를 다양하게 만들어 삽목한 후 생장량을 비교하였다. 지하경의 길이 생장과 부피 생장은 긴 길이의 삽목 조건(10-18cm)에서 가장 높았다. 그러나 상대 길이 생장은 짧은 길이(2-4cm)와 중간 길이(4-10cm)에서 더 높은 값을 보였으며, 상대 부피 생장은 중간 길이(4-10cm)에서 가장 높았다. 삽목에 이용한 지하경의 마디 수는 생장량의 증가에 기여하지 않았다. 본 연구 결과 조름나물의 지하경 삽목은 4-10cm의 길이에서 가장 효율적인 것으로 확인되었다.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.931-947
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• 2016

The effects of nanotechnology and smartness on the buckling reduction of pipes are the main contributions of present work. For this ends, the pipe is simulated with classical piezoelectric polymeric cylindrical shell reinforced by armchair double walled boron nitride nanotubes (DWBNNTs), The structure is subjected to combined electro-thermo-mechanical loads. The surrounding elastic foundation is modeled with a novel model namely as orthotropic nonhomogeneous Pasternak medium. Using representative volume element (RVE) based on micromechanical modeling, mechanical, electrical and thermal characteristics of the equivalent composite are determined. Employing nonlinear strains-displacements and stress-strain relations as well as the charge equation for coupling of electrical and mechanical fields, the governing equations are derived based on Hamilton's principal. Based on differential quadrature method (DQM), the buckling load of pipe is calculated. The influences of electrical and thermal loads, geometrical parameters of shell, elastic foundation, orientation angle and volume percent of DWBNNTs in polymer are investigated on the buckling of pipe. Results showed that the generated ${\Phi}$ improved sensor and actuator applications in several process industries, because it increases the stability of structure. Furthermore, using nanotechnology in reinforcing the pipe, the buckling load of structure increases.

• Geomechanics and Engineering
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• 제12권2호
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• pp.327-346
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• 2017

Laminated plates have many applications in different industrials. Buckling analysis of these structures with the nano-scale reinforcement has not investigated yet. However, buckling analysis of embedded laminated plates with nanocomposite layers is studied in this paper. Considering the single-walled carbon nanotubes (SWCNTs) as reinforcement of layers, SWCNTs agglomeration effects and nonlinear analysis using numerical method are the main contributions of this paper. Mori-Tanaka model is applied for obtaining the equivalent material properties of structure and considering agglomeration effects. The elastic medium is simulated by spring and shear constants. Based on first order shear deformation theory (FSDT), the governing equations are derived based on energy method and Hamilton's principle. Differential quadrature method (DQM) is used for calculating the buckling load of system. The effects of different parameters such as the volume percent of SWCNTs, SWCNTs agglomeration, number of layers, orientation angle of layers, elastic medium, boundary conditions and axial mode number of plate on the buckling of the structure are shown. Results indicate that increasing volume percent of SWCNTs increases the buckling load of the plate. Furthermore, considering agglomeration effects decreases the buckling load of system. In addition, it is found that the present results have good agreement with other works.

• Computers and Concrete
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• 제24권5호
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• pp.445-452
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• 2019

In this paper, dynamic stress, strain and deflection analysis of concrete pipes conveying nanoparticles-water under the seismic load are studied. The pipe is buried in the soil which is modeled by spring and damper elements. The Navier-Stokes equation is used for obtaining the force induced by the fluid and the mixture rule is utilized for considering the effect of nanoparticles. Based on refined two variables shear deformation theory of shells, the pipe is simulated and the equations of motion are derived based on energy method. The Galerkin and Newmark methods are utilized for calculating the dynamic stress, strain and deflection of the concrete pipe. The influences of internal fluid, nanoparticles volume percent, soil medium and damping of it as well as length to diameter ratio of the pipe are shown on the dynamic stress, strain and displacement of the pipe. The results show that with enhancing the nanoparticles volume percent, the dynamic stress, strain and deflection decrease.

• 한국초지조사료학회지
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• 제23권2호
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• pp.95-100
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• 2003

알팔파 종자를 $3\;mg/{\ell}$의 2,4-D를 첨가한 SH 배지에서 배양하여 캘러스를 유도하였으며, 캘러스를 SH 배지에 $5\;mg/{\ell}$의 NAA와 $2\;mg/{\ell}$의 kinetin을 첨가한 배지에서 28~30일간 배양하고, $11\;mg/{\ell}$의 2,4-D와 $1\;mg/{\ell}$의 kinetin을 첨가한 배지에서 3~5일간 배양 후, $1.6\;g/{\ell}$의 (${NH_4}_2{SO_4}$와 $5.75\;g/{\ell}$의 proline을 첨가한 배지에서 21~25일간 배양하여 완전히 재분화된 식물체와 많은 수의 shoot를 얻었다. 알팔파의 재분화 과정에서 뿌리가 유도되는 효율을 높이기 위해, SH salt의 양과 호르몬 양을 달리한 8종의 배지에서 각각 뿌리가 유도되는 정도를 조사해 본 결과, SH 기본배지를 사용한 것에 비해 IBA를 첨가했을 때 뿌리 유도율이 높았으며, 배지 1 리터당 1.5 mg의 IBA를 첨가했을 때 부리 유도율이 56.0%로서 가장 높았다. 또한 SH salt의 양을 1/2로 줄이고 IBA 첨가량을 다르게 하여 뿌리 유도율을 조사했을 때, SH 기본배지를 사용한 것에 비해 SH salt의 양을 1/2로 줄이고 뿌리 유도율이 높아졌으며, IBA를 첨가했을 때 푸리 유도율이 높았다. 이상의 결과에서 알팔파의 뿌리를 유도하기 위한 배지는, IBA 첨가량을 $1.5\;mg/{\ell}$로 하고 SH salt의 양을 1/2로 줄여서 사용하는 것이 좋을 것으로 판단된다.

• 한국환경보건학회지
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• 제29권1호
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• pp.34-42
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• 2003

The objective of this study is to investigate the waste recycling possibility, practicability, economic efficiency and acid gas sorbent use of the hard-shelled mussel. This study is to investigate the hydration/calcination reaction and fixed bed reactor. The physical-chemical characteristics of the hard-shelled mussel were analyzed by ICP SEM-EDX, BET and pore volume. Thus, the results could be summarized as follows; Hard-shelled mussel can be used as iron-manufacture and chemical sorbents considering more than 53.7% of the mussel is lime content. The SO$_2$removal efficiency of the hard-shelled mussel after calcined hydration increased thirty times as a result of the higher pore size, specific surface area and pore volume. Also, the CaO content, pore volume, pore size distribution and specific surface area greatly influenced the SO$_2$ and NOx removal reactivity. The optimum particle diameter average of hard-shelled mussel was $\pm$100 mesh, which was applied to the sorbent on the medium/small scale waste incinerator and flue gas desulfurization processes.

• 한국음향학회지
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• 제24권8호
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• pp.447-453
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• 2005

수중 초음파 (5, 10, 15 MHz)를 사용하여 적조 플랑크톤 Cochlodinium polykrikoides (식물 플랑크톤, 편모조류)의 후방산란 특성을 파악하기 위한 음향 실험을 실시하였다 적조 산란체의 적조주의보 (300 cells/a) 보다 적은 양의 개체 수 변화를 탐지하였고, 개체군 밀도와 후방 산란신호와의 상관관계를 시간영역에서와 주파수 영역에서 확인하였다. 또한, fluid-sphere model[1]을 이용한 이론적인 체적 산란강도를 계산하여 실측 체적 산란강도와 비교한 결과가 잘 일치하였다.

• 한국수정란이식학회지
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• 제30권3호
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• pp.171-174
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• 2015

Four pluriparous Korean black goat does were superovulated with FSH and mated with fertile bucks. Anesthetized animals were placed in lateral recumbency, then size 8 Foley catheter was inserted into the uterus through the cervix under the vaginal speculum and the balloon was inflated to fix the catheter in the uterine body. The opposite end of the catheter was connected to a 3-way and a flushing medium was infused into the uterus. Modified Dubecco's PBS with 1% FBS was used as the flushing medium. Four goats were allocated in two groups depending on the type of medium infusion into uterus. Injection group; the flushing medium was injected into uterus and the infused medium was collected by to-and-fro method using a syringe. Gravity-flow group; the flushing medium was allowed to enter the uterus by gravity flow by lifting the medium bottle and drained out of the uterus into a collecting tube. All four goats had catheter inserted through the cervix and uteri flushed successfully. The volume (recovery rate) of recovered medium varied considerably from 87 ml/200 ml (43.5%) to 148 ml/160 ml (92.5%). Nine embryos/ova in total were recovered from Gravity-flow group goats. Although the embryo recovery rate was low, the possibility of a transcervical embryo recovery in Korean black goat had been proven in this preliminary experiment.