• 한국세라믹학회지
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• 제51권6호
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• pp.527-532
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• 2014

$0.97Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3-0.03LaFeO_3$ lead-free piezoelectric ceramics were fabricated by a solid state reaction method. $LaFeO_3$ additives were added to $Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ for volatile compensation of bismuth and sodium ions in the sintering process. To create A-site vacancies, the mole ratio and charge valence of A-site ions ($Bi^{3+}$, $Na^+$ and $K^+$) were controlled. The improved piezoelectric properties were observed by addition of $LaFeO_3$ and control of A-site vacancies. In particular, a $d_{33}^*(S_{max}/E_{max})$ value of 614pm/V and an electric field induced strain of 0.33% was observed in $0.97Bi_{0.505}(Na_{0.78}K_{0.22})_{0.485}TiO_3-0.03LaFeO_3$ ceramic.

• 한국분말재료학회지
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• 제16권2호
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• pp.91-97
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• 2009

Nanopowders of $Co_3O_4$ and FeAl were fabricated by high energy ball milling. Dense 4.25 $Co_{0.53}Fe_{0.47}-Al_2O_3$ composite was simultaneously synthesized and consolidated by high frequency induction heated combustion method within 2 min from mechanically activated powders. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure of 80 MPa.

• 대한금속재료학회지
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• 제47권11호
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• pp.754-758
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ composite was consolidated from mechanically synthesized powders by high frequency induction heating method within 2 min. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure. Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $7.6MPa{\cdot}m^{1/2}$ and $844kg/mm^{2}$ respectively.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3860-3865
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• 2023

A metallic microcell UO₂ pellet has a microstructure where a metal wall is connected to overcome the low thermal conductivity of the UO₂ fuel pellet. It has been verified that metallic microcell fuel pellets provide an impressive reduction of the fuel centerline temperature through a Halden irradiation test. However, it is difficult to predict the effective thermal conductivity of these pellets and researchers have had to rely on measurement and use of the finite element method. In this study, we designed a unit microcell model using a thermal resistance circuit to calculate the effective thermal conductivity on the basis of the microstructure characteristics by using the aspect ratio and compared the results with those of reported metallic UO₂ microcell pellets. In particular, using the thermal conductivity calculated by our model, the fuel centerline temperature of Cr microcell pellets on the 5th day of the Halden irradiation test was predicted within 6% error from the measured value.

• 한국농림기상학회지
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• 제21권4호
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• pp.229-237
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• 2019

본 연구는 1980년부터 2015년까지 논 농업기후지대에 대한 연 기준 증발산량(annual reference evapotranspiration, ET₀)을 추정하고 분석하였다. 기상청에서 수집한 61개 지점의 기상자료에 Penman-Monteith 방법을 적용하여 일별 기준 증발산량을 계산하였다. 1980년부터 2015년 동안의 연 기준 증발산량은 평균 1334.1±33.89 mm 이였으며, 해안 지대에서 가장 높게 나타났다. 기준 증발산량은 전체 지대에 대해서 약 2.81 mm/yr의 추세로 증가하였다. 하지만 변화율은 농업기후지대별로 다르게 나타났다. 특히 중부지대와 동부 해안 지대에서 연 기준 증발산량은 가장 크게 증가하였다. 상관계수 분석에 의하면, 연 기준 증발산량의 연 변화는 네가지 기후 요소(평균, 최저기온, 일조시간, 상대습도)와 가장 크게 연관이 있었다. 이 연구는 36년 동안 전체 한국 농업지대에서 연 기준증발산량의 변화를 겪고 있다는 것을 보여주고 있다. 온난화와 관련된 장기간의 연기준 온도의 변화와 공간적 패턴을 이해하는 것은 각 농업기후지대별 수자원 및 작물 관리를 효율적으로 할 수 있도록 도와줄 것으로 생각된다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제48권4호
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• pp.219-224
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• 2022

Objectives: There have been few studies to date on the residual effect of bisphosphonate. This study investigated the radiographic changes of mandibular cortical thickness upon bisphosphonate drug holiday. Materials and Methods: This retrospective study includes 36 patients diagnosed with MRONJ (medication-related osteonecrosis of the jaw) at Ajou University Dental Hospital in 2010-2021. All patients stopped taking bisphosphonate under consultation with the prescribing physicians. Panoramic radiographs were taken at the start of discontinuation (T₀), 12 months after (T₁), and 18 months after (T₂) discontinuation of bisphosphonate, respectively. Mental index and panoramic mandibular index were calculated using Ledgerton's method. Paired t-tests were used to analyze differences over time. Results: The difference in indices (mental index and panoramic mandibular index) between T₀ and T₁ was not statistically significant (paired t-test, P>0.05). However, the difference in these indices between T₁ and T₂ was statistically significant (paired t-test, P<0.05). Conclusion: The cortical thickness of the mandible decreased in the late stage (after 18 months) as observed by panoramic radiograph.

• 한국환경농학회지
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• 제35권3호
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• pp.166-174
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• 2016

농경지 토양에서 대상항생제 6종(amoxicillin, ampicillin, chlortetracycline, enrofloxacin, oxytetracycline, tetracycline을 아세트산 함유 아세토니트릴, Na₂Cit.5H₂O, Na₃Cit.2H₂O과 Na₂-EDTA로 추출 후 C₁₈으로 정제하여 LC-MS/MS로 분석하는 모니터링을 수행하였다. 그 중 2종의 항생제, chlortetracycline과 enrofloxacin이 국내 농경지 토양에서 검출되었다. 제안한 분석법은 토양 중 잔류 항생제 모니터링을 위한 빠르고 간편한 시험법이었고 다양한 활용이 가능할 것으로 보인다.

• Journal of Electrochemical Science and Technology
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• 제7권4호
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• pp.245-250
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• 2016

The layered $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composite with well crystalized and high specific capacity is prepared by molten-salt method and using the substitution of Na for Li-ion battery. The effects of annealing temperature, time, Na contents, and electrochemical performance are investigated. In XRD analysis, the substitution of Na-ion resulted in the P2-$Na_{2/3}MO_2$ structure ($Na_{0.70}MO_{2.05}$), which co-exists in the $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composites. The discharge capacities of cathode materials exhibited $284mAhg^{-1}$ with higher initial coulombic efficiency.

• 한국가금학회지
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• 제49권1호
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• pp.1-8
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• 2022

본 연구는 도축 중 실신방법과 가스종류가 계육 가슴살과 소장의 품질 특성에 미치는 영향을 조사하기 위해 실시하였다. 육계(Ross 308)를 각 10수씩 할랄법, CO₂ 및 N₂ 가스실신법으로 기절 후 도축하였다. 도축 후 계육 가슴살과 내장을 채취하여 실험에 사용하였다. 계육 가슴살에서 pH, 일반성분, 육색, 보수력, 가열감량 및 전단력을, 소장에서 pH, 육색, 두께 및 전단력을 분석하였다. 계육 가슴살에서 할랄 처리구에 비하여 CO₂ 가스실신 처리구는 pH가 높고 육색 가열감량이 낮았으며(P<0.05), N₂ 가스실신 처리구는 할랄 처리구와 유사한 pH, 색도, 전단력을 나타냈다(P>0.05). 또한, 소장에서는 할랄 처리구에 비하여 가스실신 처리구들이 pH, 명도가 낮으며 적색도, 황색도, 두께 및 전단력이 높았고 (P<0.05), CO₂ 가스실신 처리구 보다 N₂ 가스실신 처리구에서 낮은 pH, 적색도 및 황색도, 높은 명도, 두께, 전단력을 나타냈다. 결론적으로 가스실신법에서 CO₂ 가스로 야기된 식육의 변색과 조직감 저하를 N₂ 가스 사용으로 억제할 수 있을 것으로 판단되며, 향후 가스 종류와 농도가 식육의 변색에 미치는 기작에 관한 연구가 필요할 것으로 사료된다.

• 한국분말재료학회지
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• 제16권3호
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• pp.180-184
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• 2009

In this paper, the electrochemical non-enzyme immunosensor has been developed for the determination of salmonella antigen, using inverse voltammetry. For the estimation of salmonella antigen concentration, the $Fe_3O_4$ nanoparticles synthesized by microemulsion method were conjugated with salmonella antigen. Then, the immunocomplex between antibody immobilized on the transducer surface and antigen containing a magnetic nanoparticles was formed. From the linear relationship between the reduction peak current of Fe(III) and salmonella antigen concentration, it is suggested that the electrochemical non-enzyme biosensor is applicable to detect salmonella antigen in the concentration range of $10^1-10^5$ CFU/ml.