• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3112-3121
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• 2021

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

• 한국세라믹학회지
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• 제32권1호
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• pp.95-105
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• 1995

Ceria(CeO2) stabilized zirconia(CeSZ) sol was synthesized with zirconium n-butoxide Zr(OC4H9)4 and cerium nitrate hexahydrate Ce(NO3)3.6H2O as precursors and ethylacetoacetate(EAcAc) as a chelating agent under atmosphere. CeSZ films were deposited on AISI 304 stainless steel using the prepared polymeric sol by dipcoating and the coating characteristics were investigated by XRD, ellipsometry, scratch test and SEM. The CeSZ film began to crystallize from amorphous to tetragonal phase at 40$0^{\circ}C$ and it was not converted into monoclinic phase up to 100$0^{\circ}C$ by the addition of 16mol% CeO2 as a stabilizer which could suppress phase transformation of zirconia. The CeSZ films were prepared by varying the EAcAc contents and the cncentration of CeSZ sol and measured the thickness and refractive index. From these results, it was found that the EAcAc contents and concentration of CeSZ coating sol evidently affect the densification of CeSZ film. The CeSZ film coated with 0.4M CeSZ sol and heat-treated at $600^{\circ}C$ for 10min had thickness of 50nm and 17% porosity. The CeSZ film on 304 stainless steel effectively acted as a protective layer against oxidation up to 80$0^{\circ}C$ and had superior corrosion resistance in 25% H2SO4 solution for 4.5 hrs.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.159-159
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• 2017

Ti-6Al-4V alloy have been used for dental implant because of its excellent biocompatibility, corrosion resistance, and mechanical properties. However, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton. For solving this problem, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements are known to play an important role in the bone formation and also affect bone mineral characteristics. Especially, Zn is essential for the growth of the human and Zn coating has a major impact on the improvement of corrosion resistance. Plasma electrolytic oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing TiO2(Zn-TiO2)coatings on Ti surface, and the a mount of Zn introduced in to the coatings can be optimized by altering the electrolyte composition. In this study, effect of Zn content on the corrosion behavior of Ti-6Al-4V alloy after plasma electrolytic oxidation were studied by SEM, EDS, XRD, AC impedance, and potentiodynamic polarization test. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67 mV/s and potential range from -1500 mV to +2000 mV. Also, AC impedance was performed at frequencies ranging from 10 MHz to 100 kHz for corrosion resistance.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.120-120
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• 2016

Ti-6Al-4V alloy have been used for dental implant because of its excellent biocompatibility, corrosion resistance, and mechanical properties. However, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton. For solving this problem, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements, such as strontium (Sr), magnesium (Mg), zinc (Zn), sodium (Na), silicon (Si), silver (Ag), and yttrium (Y) are known to play an important role in the bone formation and also affect bone mineral characteristics, such as crystallinity, degradation behavior, and mechanical properties. Especially, Zn is essential for the growth of the human and Zn coating has a major impact on the improvement of corrosion resistance. Plasma electrolytic oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing $TiO_2(Zn-TiO_2)$coatings on Ti surface, and the a mount of Zn introduced in to the coatings can be optimized by altering the electrolyte composition. In this study, corrosion behavior of Ti-6Al-4V alloy after plasma electrolytic oxidation in solutions containing Ca, P and Zn were studied by scanning electron microscopy (SEM), AC impedance, and potentiodynamic polarization test. A series of $Zn-TiO_2$ coatings are produced on Ti dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to +2000mV. Also, AC impedance was performed at frequencies ranging from 10MHz to 100kHz for corrosion resistance.

• Composites Research
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• 제13권6호
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• pp.1-8
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• 2000

무가압함침법에 의한 $Al_2O_{3p}$/AC8A 복합재료의 제조와, 제조법과 관련하여 부가적인 Mg의 첨가와 강화상의 부피분율이 $Al_2O_{3p}$/AC8A복합재료의 기계적 성질과 마모저항에 미치는 영향을 조사하였다. 강화상 입자와 기지재료의 일부를 분말로 조합한 혼합분말 속으로 기지금속을 자발적으로 침투시켜 부피분율이 20~40%인 $Al_2O_{3p}$/AC8A 복합재료를 제조할 수 있었다. 그러나 강화상의 부피분율이 40%인 복합재료의 경우 기공율의 상승으로 복합재료의 강도는 저하하였다. Mg의 첨가량이 5~7wt% 일 때 가장 높은 강도를 나타냈으며, 경도는 Mg 첨가량의 증가에 따라 점진적으로 상승하였다. $Al_2O_{3p}$/AC8A복합재료는 저속에서 기지재료에 비해 내마모성이 저하하였으나, 고속에서는 AC8A합금에 비해 약 5.5배의 우수한 내마모성을 나타냈다. 마모기구의 관찰에 의해 부피분율 20% $Al_2O_{3p}$/AC8A복합재료의 경우 연삭마모가 주된 마모기구임을 알 수 있었으며, 부피분율 40% $Al_2O_{3p}$/AC8A복합재료는 높은 기공율로 인한 마모 가중으로 저속에서도 경미한 응착마모가 관찰됐고 마찰 속도가 증가함에 따라 격심한 마모로 진행되었다.

• Transactions on Electrical and Electronic Materials
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• 제14권6호
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• pp.317-320
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• 2013

Partial discharge resistance for the epoxy systems with two diluents was investigated in the rod-plane electrodes arrangement, and the effect of electric frequency on the partial discharge resistance was also studied. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and 1,4-butanediol diglycidyl ether (BDGE) or polyglycol (PG) as a reactive diluent was introduced to the DGEBA system, in order to decrease the viscosity of the DGEBA epoxy system. BDGE was acted as a chain extender, and PG acted as a flexibilizer, after the curing reaction. To measure the partial discharge resistance, 5 kV alternating current (ac) with three different frequencies (60, 500 and 1,000 Hz) was applied to the specimen in a rod-plane electrode arrangement, at $30^{\circ}C$. PG had a good effect, while BDGE had a bad effect on the partial discharge resistance of the DGEBA system, regardless of the electric frequency.

• 전력전자학회논문지
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• 제15권3호
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• pp.218-225
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• 2010

본 논문은 인버터 AC 스폿용접시스템의 용접시간을 최소화하기 위한 방법에 관한 것이다. 기존의 SCR 회로방식을 이용한 스폿용접시스템의 경우 제어속도가 느리고 전류제어가 정밀하지 않다. 따라서 최근에는 인버터를 이용한 용접시스템이 점차 증가하고 있다. 2차전지의 전극과 같은 박판을 용접해야 하는 경우에는 용접시간이 수 [ms] 정도로 짧아야 한다. 수 [ms] 정도로 용접시간을 최소화하면서 수 천 [A]에 달하는 대전류를 흘리기 위해서 일반적으로 수십개의 스위칭 소자들을 병렬로 연결하여 사용하기도 한다. 본 논문에서는 단지 4개의 IGBT로 구성된 인버터와 60[Hz] 변압기만으로 수 [ms] 대의 용접이 가능한 비용절감형 용접시스템을 제안하고 특성을 분석하였다. 그리고 실험을 통하여 타당성과 효용성을 입증하였다.

• 식물병연구
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• 제15권3호
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• pp.202-208
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• 2009

유전자 변형 혹명나방 저항성벼의 주요 병해에 대한 저항성 변화를 온실과 포장에서 모본으로 사용된 낙동벼와 비교하였다. 포장에서 벼잎집무늬마름병과 벼깨씨무늬병의 발병 정도는 큰 차이가 없었다. 온실에서 인위적으로 병원균을 접종하여 벼도열병과 흰잎마름병에 대해 저항성 변화여부를 조사한 결과에서도 두 품종간에 큰 차이를 보이지 않았고, 인위접종한 벼잎집무늬마름병에 대한 감수성도 두 품종간에 비슷하여 포장에서의 결과와 같은 경향을 보였다. 형질전환 벼의 제초제 저항성 유전자(Bar 유전자)와 혹병나방 저항성유전자(Cry1Ac1 유전자)가 병원균으로 전이되는가의 여부를 조사하기 위하여 포장에서 발병한 도열병과 키다리병원균을 분리한 후 DNA를 추출하여 PCR을 실시한 결과 두 유전자 모두 병원균으로 전이되지 않은 것으로 확인되었다. 또한, 병원균과 저항성벼의 지속적인 접촉에 의한 유전자 전이 가능성을 확인하기 위하여 잎집무늬마름병균과 흰잎마름병균을 계대 접종한 후 DNA를 분리하여 조사한 결과에서도 저항성 유전자의 전이는 일어나지 않은 것으로 확인되어, 본 실험에서는 자연상태와 인위적인 조건 모두에서 유전자 전이를 찾아 볼 수 없었다.

• Progress in Superconductivity
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• 제13권2호
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• pp.111-116
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• 2011

Since superconducting wires have no resistance, electromagnets based on the superconducting wires produce no resistive heating with DC current as long as the current does not exceed the critical current of the wire. However, unlike resistive wires, superconducting wires exhibit AC heat loss. Embedding fine superconducting filaments inside copper matrix can reduce this AC loss to an acceptable level and opens the way to AC-capable superconducting coils. Here, we introduce an easy and accurate method to measure AC heat loss from sample superconducting coils by measuring changes in the rate of gas helium outflow from the liquid helium dewar in which the sample coil is placed. This method provides accurate information on total heat loss of a superconducting coil without any size limit, as long as the coil can fit inside the liquid helium dewar. With this method, we have evaluated AC heat loss of two superconducting solenoids, a 180-turn solid NbTi wire with 0.127 mm diameter (NbTi coil) and a 100-turn filamented wire with 1.4 mm diameter where 7 NbTi filaments were embedded in a copper matrix with copper to NbTi ratio of 6.7:1 (NbTi-Cu coil). Both coils were wound on 15 mm-diameter G-10 epoxy tubes. The AC heat losses of the NbTi and NbTi-Cu coils were evaluated as $53{\pm}4.7\;{\mu}W/A^2Hzcm^3$ and $0.67{\pm}0.16\;{\mu}W/A^2Hzcm^3$, respectively.

• Asian-Australasian Journal of Animal Sciences
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• 제23권10호
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• pp.1268-1275
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• 2010

Post-weaning diarrhoea (PWD) and oedema disease (ED) caused by E. coli F18 always result in economic losses to pig producers, and no effective methods of controlling PWD and ED are presently available. FUT1 has been identified as a candidate gene controlling the expression of E. coli F18 receptor. This study examined the correlation between F18ab and F18ac adhesion phenotypes and the polymorphism at position M307 of the FUT1 gene in three pig breeds (231 Large White, 107 Landrace and 109 Songliao Black). The results showed: i) Both the susceptible genotypes (GG and GA) and the adhesion phenotypes (adhesive or weekly adhesive) were dominant in all three breeds with frequencies over 95%. ii) Three adhesion patterns of the two F18 variants F18ab and F18ac, i.e., ($ab^+$, $ac^+$), ($ab^+$, $ac^-$) and ($ab^-$, $ac^-$), were found in all three breeds, and there was no significant difference in the distribution of adhesion phenotypes of the two variants (separately or jointly) among the three breeds (p>0.05). iii) The FUT1 M307 genotypes were completely associated with the F18ab adhesion phenotypes and very strongly associated with the F18ac adhesion phenotypes. All individuals of genotype AA were non-adhesive to both F18ab and F18ac. All individuals of genotype GG or GA were adhesive to F18ab, whereas 11% of them were non-adhesive to F18ac. These results suggest that the polymorphism at FUT1 M307 can be used for marker-assisted selection of PWD and ED resistant pigs.