• 한국분말재료학회지
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• 제28권2호
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• pp.127-133
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• 2021

One-dimensional (1D) piezoelectric nanostructures are attractive candidates for energy generation because of their excellent piezoelectric properties attributed to their high aspect ratios and large surface areas. Vertically grown BaTiO₃ nanotube (NT) arrays on conducting substrates are intensively studied because they can be easily synthesized with excellent uniformity and anisotropic orientation. In this study, we demonstrate the synthesis of 1D BaTiO₃ NT arrays on a conductive Ti substrate by electrochemical anodization and sequential hydrothermal reactions. Subsequently, we explore the effect of hydrothermal reaction conditions on the piezoelectric energy conversion efficiency of the BaTiO₃ NT arrays. Vertically aligned TiO₂ NT arrays, which act as the initial template, are converted into BaTiO₃ NT arrays using hydrothermal reaction with various concentrations of the Ba source and reaction times. To validate the electrical output performance of the BaTiO₃ NT arrays, we measure the electricity generated from each NT array packaged with a conductive metal foil and epoxy under mechanical pushings. The generated output voltage signals from the BaTiO₃ NT arrays increase with increasing concentration of the Ba source and reaction time. These results provide a new strategy for fabricating advanced 1D piezoelectric nanostructures by demonstrating the correlation between hydrothermal reaction conditions and piezoelectric output performance.

• BMB Reports
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• 제28권2호
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• pp.162-169
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• 1995

Rat brain succinic semialdehyde dehydrogenase (EC 1.2.1.24 SSADH) activity was detected in mitochondrial, cytosolic and microsomal fractions. Brain mitochondrial soluble SSADH was purified by ammonium sulfate precipitation, DEAE Sephacel, and 5'-AMP Sepharose 4B affinity chromatography. The purified enzyme was shown to consist of four identical subunits, and the molecular weight of a subunit was 55 kD. The $K_m$ for short chain aliphatic aldehydes and aromatic aldehydes were at the $10^{-3}M$ level but that for succinic semialdehyde was 2.2 ${\mu}M$. Either $NAD^+$ or $NADP^+$ can be used as a cofactor but the affinity for $NAD^+$ was 10 times higher than that for $NADP^+$. The brain cytosolic SSADH was also purified by ammonium sulfate precipitation, DEAE Sephacel, Blue Sepharose CL-6B and 5'-AMP Sepharose 4B affinity chromatography and its Km for short chain aliphatic aldehydes was at the $10^{-3}$ level but that for succinic semialdehyde was 3.3 ${\mu}M$. $NAD^+$ can be used as a cofactor for this enzyme. We suppose that both enzyme might participate in the oxidation of succinic semialdehyde, which is produced during GABA metabolism. The activity of both cytosolic and mitochondrial SSADH was markedly inhibited when the concentration of succinic semialdehyde was high. The reciprocal plot pattern of product inhibition and initial velocity indicated a sequential ordered mechanism for mitochondrial matrix SSADH. Chemical modification data suggested that amino acid residues such as cysteine, serine and lysine might participate in the SSADH reaction.

• 한국지반환경공학회 논문집
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• 제15권11호
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• pp.13-19
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• 2014

투수성 반응벽체 공법은 지하수 오염을 정화하는 대표적인 방법 중의 하나이다. 영양염류와 중금속 등 여러 가지 오염물질이 동시에 존재하는 경우 두 가지 이상의 반응성 매질을 적용한 반응벽체공법으로 복합오염물질의 제거가 가능하다. 본 연구에서는 반응성 매질로 제올라이트와 제강슬래그를 함께 사용하는 경우 복합오염물질의 제거능을 평가하였다. 영양염류인 암모늄과 인산염, 중금속인 카드뮴이 혼합된 복합오염물질에 대하여 연속회분식실험을 통하여 제올라이트 및 제강슬래그와의 반응순서에 따른 오염물질 제거능을 분석하였다. 연속회분식실험 결과에 의하면 제올라이트-제강슬래그 순서로 반응하는 경우 영양염류와 중금속의 복합오염물질에 대한 제거능이 더 좋은 것으로 나타났다.

• 대한수의학회지
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• 제39권5호
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• pp.1006-1012
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• 1999

This study was conducted to evaluate the ELISA kit for measuring the level of cortisol in the urine. The CV of within-run variation and day to day variation were 0.4~2.8 and 1.8~5.7, respectively. The minimum limitation of measurement was 1ng/ml. The cross reaction was high ($CR_{50}(%)=11.4{\sim}43.2$) in prednisolone, 11-deoxycortisol, 21-deoxycortisol and predinosone. There was low and no cross reaction in other steroid. To develop the ELISA kit we measured the cortisol level in diluted urine with PBS (procedure I), extracted urine with methylene chloride (procedure II) and extracted methylene chloride-extracted urine from thin-layer chromatography (procedure III). The CV value of procedure I, II, III was 9.4~28.3%, 7.2~8.9% and 2.5~5.7%, respectively. There was significant difference between procedure I with II, and pro-cedure I with III(p < 0.01), but no difference between procedure II with III significantly(p < 0.01). The mean UCCR of urine collected through am 8 to 10 was $9.5{\pm}7.6$(0.14~28.0) in 12-month-old dog(n = 47). In this study we can measure the cortisol level in extracted urine with methylene chloride and sequential thin-layer chromatography accurately using ELISA kit.

• 공업화학
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• 제10권6호
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• pp.889-894
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• 1999

유화중합법으로 마이크론 크기의 고분자 라텍스 입자 제조시, 라텍스 입자의 응집, 2세대 입자의 생성 등의 문제 때문에 원하는 형태, 크기, 구조를 지니는 입자를 제조하기가 매우 어려운 것으로 알려져 있지만 구조적, 기능적 고분자 미립자를 합성할 수 있는 장점이 있다. 따라서, 본 연구에서는 마이크론 크기의 라텍스 입자를 제조하는데 있어서, 미립자 성분으로 n-butyl acrylate(BA)를 선정하고, 개시제의 농도, 유화제의 양, 반응 온도, 가교제의 양 및 교반기의 속도 등의 반응 변수 조건에 따른 seed 유화 중합을 실시하여 각 반응 변수들이 입자의 크기 및 분산도에 미치는 영향에 대하여 조사하였다. 실험 결과를 바탕으로 반응 변수의 최적 조건들을 규명하여 연속적 seed 유화중합법으로 $0.14{\sim}3.67{\mu}m$의 평균 입자경을 갖는 poly(n-butyl acrylate)(PBA) 라텍스 입자를 제조할 수 있었다.

• 대한교통학회지
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• 제30권2호
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• pp.127-136
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• 2012

다중추돌사고의 형태는 연쇄 추돌이라고 불리우는 뒤로부터의 순차적인 추돌과 앞으로부터의 순차적인 추돌, 그리고 순서가 섞여 있는 추돌형태로 구분된다. 다중추돌사고에 대하여 몇가지 효과적인 재구성 해석 방안을 제시한다. 브레이크 다이브 등으로 인한 차량 파손과 승객 부상을 활용하는 전통적인 경험적 수법과 강체역학 범주내에서의 이론적인 해석 결과를 구하여 당장에의 실용적인 적용이 가능하도록 하였다. 국내에 보급이 확산되고 있는 영상사고기록장치를 활용하고 시뮬레이션 프로그램 등을 병행 활용하여 다중추돌사고를 효과적으로 해석하는 방안을 제시하였다. 저장 동영상에 대한 단순 직관적인 조사를 넘어설 수 있도록 동영상 분석 결과에 근거한 시뮬레이션 해석을 수행하여 다중추돌사고에 대한 구체적이고 다양한 정보의 획득을 가능하게 하여 원인 규명 및 책임 소재 등을 명확하게 구분할 수 있도록 하였다.

• 공업화학
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• 제30권2호
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• pp.198-204
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• 2019

고분자 복합재료는 높은 기계적 물성을 요구하는 산업용 소재로 널리 사용되고 있다. 이러한 고분자 복합재료에 사용되는 유리섬유나 무기충전제는 불균일한 분산 및 고분자와 충전제 간의 계면 접착력 저하에 의해 강도 저하와 같은 문제점이 상존한다. 본 연구에서는 열분해 반응을 통해 제조되는 비극성 폴리에틸렌 왁스에 대해 열분해 반응과 함께 연속적으로 극성 아크릴산 단량체를 그래프트 반응시켜 극성개질의 효율을 향상시킨 아크릴산 변성 폴리에틸렌 왁스를 합성하여, 이를 폴리아미드 매트릭스와 무기충전제인 유리섬유의 고분자 복합재료에 적용하여 폴리아미드 기반 고분자 복합재료의 물성에 미치는 영향을 조사하였다.

• 한국수소및신에너지학회논문집
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• 제2권1호
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• pp.29-37
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• 1990

The effect of pressure cycling of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ on the hydrogenation properties was investigated using the P-C-Isotherm curves and hydrogen absorption rate curves in the isotherm condition. The reversible hydrogen absorption capacity was decreased about 45 % after 3300 cycles. In the case of activated sample, the rate controlling steps of hydriding reaction changed from the surface reaction to the hydrogen diffusion process through hydride phase sequentially as reaction proceeded. After 3300 cycles, the sequential change of rate controlling step was same as activated one. However, the hydrogen absorption rate significantly decreased. It is suggested that the degradation of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ can be interpreted with the formation of $ZrFe_3$ phase at the particle surface.

• Clinical and Experimental Pediatrics
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• 제55권11호
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• pp.424-429
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• 2012

Purpose: Methods for quick and reliable detection of Streptococcus pneumoniae are needed for the diagnosis of pneumococcal disease and vaccine studies. This study aimed to show that sequential multiplex polymerase chain reaction (PCR) is more efficient than conventional culture in achieving S. pneumoniae -positive results. Methods: Nasopharyngeal (NP) secretions were obtained from 842 pediatric patients admitted with lower respiratory infections at Severance Children's Hospital in Korea between March 2009 and June 2010. For identification and serotype determination of pneumococci from the NP secretions, the secretions were evaluated via multiplex PCR technique with 35 serotype-specific primers arranged in 8 multiplex PCR sets and conventional bacteriological culture technique. Results: Among the results for 793 samples that underwent both bacterial culture and PCR analysis for pneumococcal detection, 153 (19.3%) results obtained by PCR and 81 (10.2%) results obtained by conventional culture technique were positive for S. pneumoniae. The predominant serotypes observed, in order of decreasing frequency, were 19A (23%), 6A/B (16%), 19F (11%), 15B/C (5%), 15A (5%), and 11A (4%); further, 26% of the isolates were non-typeable. Conclusion: As opposed to conventional bacteriological tests, PCR analysis can accurately and rapidly identify pneumococcal serotypes.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2283-2288
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• 2010

Nanostructured copper compounds were grown by electrochemical anodization of copper foil in aqueous NaOH under varying conditions including electrolyte concentration, reaction temperature, current density, and reaction time. Their morphology and atomic composition were investigated by using SEM, TEM, XRD, EDS and XPS. At the conditions ([NaOH] = 1 M, $20^{\circ}C$, $2\;mA\;cm^{-2}$), wire-like orthorhombic $Cu(OH)_2$ nanobundles with an average width of 100 - 300 nm and length of $10\;{\mu}m$ were synthesized with the preferential [100] growth direction. Furthermore, when the concentration decreased to 0.5 M NaOH, the 1D nanobundle structure became narrower and longer without any change in compositions or crystalline structure. Side reaction pathways appeared to compete with the 1D nanostructure formation channels: the formation of CuO nanoleaves at $50^{\circ}C$ via the sequential dehydration of $Cu(OH)_2$, CuO/$Cu_2O$ aggregates in 4 M NaOH, and $Cu_2O$ nanoparticles and CuO nanosheets at lower current density.