• 센서학회지
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• 제11권2호
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• pp.102-110
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• 2002

본 논문에서는 부착현상에서 자유로운 다결정실리콘의 표면을 만들기 위하여 새롭게 표면개질 물질로 사용한 dichlorodimethysilane (DDMS, $(CH_3)_2SiCl_2$)에 대하여 화학적, 기계적 특성에 대해 조사하였다. 주된 전략은 기존의 octadecyltrichlorosilane (ODTS)이나 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) 같은 monoalkyltrichlorosilane (MTS, $RSiCl_3$) 계열의 물질을 dialkyldichlorosilane (DDS, $R_SiCl_2$)와 같은 두 개의 짧은 고리를 가진 물질로 대체하는 것이다. DDMS는 짧은 두 개의 고리를 가지고 있어서 다결정실리콘 표면에 빨리 코팅된다. 3 mm까지의 긴 외팔보에 코팅을 한 경우, 희생층 제거시 부착현상 뿐만 아니라 사용중 부착현상도 방지할 수 있었다. DDMS 코팅된 다결정실리콘의 표면은 ODTS 나 FDTS 코팅된 표면보다 더 만족스러운 소수성과 지속적인 안정성과 열적 안정성을 가지고 있었다. 또한 DDMS 코팅은 더 쉽게 사용할 수 있고 장기간 용기에 저장할 수 있으며 온도의 의존성이 낮으며, 가격도 상대적으로 낮은 특징을 가지고 있다. 이 새로운 표면개질 물질을 사용하면 기존에 비해 구조물을 아이소옥탄으로 세척 후 곧바로 건조하는 간단한 공정을 가지고 있어서 공정시간을 줄일 수 있다.

• 지구물리와물리탐사
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• 제15권2호
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• pp.57-65
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• 2012

탄성파 수치 모형 계산에 있어서 다양한 방법들이 개발되어 적용되었다. 최근에는 특히 탄성파 수치 모형 계산에 있어 혁신적인 방법인 SEM (Spectral Element Method)가 개발되어 사용되어 왔다. 이 방법은 지형을 자유롭게 표현하는데 있어 유연한 유한요소법의 장점에 정확성을 높인 방법이다. 일반적으로 Weak Formulation 형태의 파동방정식에 육면체 요소와 Gauss-Lobatto-Legendre 적분법을 적용한 방법이 널리 사용된다. 일반적인 SEM에서는 PML (Perfectly Matched Layer)경계조건을 적용하기 어려워 속도-응력 변분식으로 파동방정식을 변경하였다. CFS-PML (Complex frequency Shifted PML)경계조건을 ADE (Auxiliary Differential Equation)방정식으로 변경하여 속도-응력 파동방정식에 적용함으로써 분리할 필요가 없는 PML을 적용한 SEM 수치 모형 계산 알고리듬을 구현하였다. 1차원 수치모형과 3차원 수치모형 실험을 통하여 SEM에 적용한 비분리 CFS-PML이 유한경계에서 인공적으로 반사되는 반사파를 효과적으로 제거하는 것을 확인하였다.

• 화약ㆍ발파
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• 제23권2호
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• pp.57-66
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• 2005

A major concern with blasting at surface mines is generation of ground vibration, air blast, flyrock, dust & fume and their impact on nearby structures and environment. A study was conducted at a coal mine in India which produces 10 million tonne of coal and 27 million cubic meter of overburden per annum. Draglines and shovels with dumpers carry out the removal of overburden. Detonation of 100 tonnes of explosives in a blasting round is a common practice of the mine. These large sized blasts often led to complaints from the nearby inhabitants regarding ground vibrations and their affects on their houses. Eighteen dragline blasts were conducted and their impacts on nearby structures were investigated. Extended seismic arrays were used to identify the vibration characteristics within a few tens meters of the blasts and also as modified by the media at distances over 5 km. 10 to 12 seismographs were deployed in an array to gather the time histories of vibrations. A signature blast was conducted to know the fundamental frequency of the particular transmitting media between the blast face and the structures. The faster decay of high frequency components was observed. It was also observed that at distances of 5km, the persistence of vibrations in the structures was substantially increased by more 10 seconds. The proximity of the frequency of the ground vibration to the structure's fundamental frequencies produced the resonance in the structures. On the basis of the fundamental frequency of the structures, the delay interval was optimized, which resulted into lower amplitude and reduced persistence of vibration in the structures.

• 대한화학회지
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• 제55권1호
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• pp.50-56
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• 2011

(2, 4-difluoro-phenyl)-(2-phenyl-1H-quinolin-4-ylidene)-amine의 전기화학적 환원에 대하여 실온에서 순환전압전류 기술을 사용한 유리탄소전극(GCE)에서 N,N-dimethylformamide 하에서 0.1 M tetrabutylammoniumbromide로 조사하였다. 이민의 환원은 각각 한 전자를 포함하면서 2단계의 성공적인 단계로 일어난다. 이 매개물에서 처음 피크는 유리탄소전극 표면에서 약 -0.793 V(vs Ag/$Ag^+$)로 관측되었다. 그리고 그것은 더욱 안정하고 2번째 피크와 비교하여 명확하게 설명된다. 연구된 용매 매개물에서 이민의 확산계수($D_0$)는 수정된 Randles-Sevcik 식을 이용해 계산되었다. 반응 종들의 전자 이동 계수($\alpha$) 또한 계산되었다.

• 전기화학회지
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• 제18권2호
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• pp.45-50
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• 2015

본 연구에서는 리튬 이온 전도성 세라믹 고체전해질($Li_{1+x+y}Al_xTi_{2-x}Si_yP_{3-y}O_{12}$, LATP)의 알칼라인 용액 내에서의 화학적 안정성을 증가시키기 위하여, 고체전해질 표면을 질화 공정 처리를 통해 개질하였다. LATP 고체전해질의 화학적 안정성 및 전기화학 특성과 관련된 고체전해질 표면 형상 및 구조 특성 등을 X-선 회절법, X-선 광전자 분광법, 주사 전자 현미경 및 임피던스 측정을 통하여 분석하였다. 질화 처리된 LATP 시료를 30일간 알칼라인 용액에 담지하여, 표면 처리하지 않은 시료와 비교시 향상된 화학적 안정성을 나타냈으며, 이를 하이브리드 리튬-공기 전지에 적용하여 비교시 개선된 충방전 분극 및 효율 특성을 보였다. 이러한 결과를 바탕으로 질화 처리 공정을 통한 표면 개질은 알칼라인 용액내에서의 세라믹 고체전해질의 화학적 안정성을 증가시키는데 효과적으로 도움이 될 것으로 판단된다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1995년도 춘계학술대회
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• pp.89-89
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• 1995

Surface epithelial cells isolated from hamster tracheas and grown on a thick collagen gel become a highly enriched population of mucus-secreting cells. Epithelial cells from tracheas of hamsters were collected using enzymatic procedures and cultured under various conditions. The medium used consisted of a 1:1 mixture of medium 199 and Dulbecco's modified Eagle's (DME) medium which was conditioned before use. Insulin, transferrin, hydrocortisone, epidermal growth factor, and extract from bovine hypothalamus were used as supplement. Due to relatively low basal rates of min secretion from in vitro cultures, cultures are generally radiolabeled using $^3$H-glucosamine as a metabolic precursor. The radiolabeled mucinsreleased are quantitated by precipitation with TCA/PTA. Using this cell culture system, we investigated mucin release of goblet cells by altering the media bathing the apical surface of hamster tracheal surface epithelial(HTSE) cells. Acidic media added sulfuric acid caused sigcificant increases in mucin relesse (155${\pm}$20% at pH 4 and 146${\pm}$16% at, pH 5). Ammonium hydroxide also increased mucin release at pH 9.0(156${\pm}$17%) and pH 10(295${\pm}$9%) respectively. This additional mucin release seems to be associated with cell membrane damage as indicated by release of cellular LDH. SP stimulates secretion of mucin in cultured HTSE cells(154${\pm}$16% at 1${\times}$10$\^$-6/M and 165${\pm}$25% at 1${\times}$10$\^$-5/M. PAF at 5${\times}$10$\^$-6/M and 5${\times}$10$\^$-5/M enhanced by HTSE cells in vitro 168${\pm}$34% and 259${\pm}$30% of mucin secretion, respectively. The increase in mucin release by PAF and SP was not secondary to cell damage or necrosis. SP and PAF may be in mediating mucous secretion induced by inflammation irritantion and infection.

• 한국지진공학회논문집
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• 제11권4호
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• pp.25-31
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• 2007

For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.

• Macromolecular Research
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• 제14권6호
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• pp.646-653
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• 2006

Highly hydrophilic, uniform, superparamagnetic and nontoxic maltotrionic acid (MA)-coated magnetite nano-particles (MAM) were prepared and characterized by TEM, DLS, XRD and VSM. MA was used to improve the biocompatibility, monodispersity and non-specific intracellular uptake of nanoparticles. Folic acid (FA) was subsequently conjugated to the MAM to preferentially target KB cells (cancer cells) that have folate receptors expressed on their surfaces and to facilitate nanoparticles in their transit across the cell membrane. Finally, fluorescence isothiocyanate (FITC) was added to the nanoparticles to visualize the nanoparticle internalization into KB cells. After the cells were cultured in a media containing the MAM and MAM-folate conjugate (FAMAM), the results of fluorescence and confocal microscopy showed that both types of nanoparticles were internalized into the cells. Nevertheless, the amount of FAMAM uptake was higher than that of MAM. This result indicated that nanoparticles modified with MA and FA could be used to facilitate the nanoparticle uptake to specific KB cells (cancer cells) for molecular imaging.

• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.1996-2002
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• 2007

The redox behavior of a [Ni6(μ3-Se)2(μ4-Se)3(Fe(η 5-C5H4P-Ph2)2)3] (= [Ni-Se-dppf], dppf = 1,1-bis(diphenylphosphino) ferrocene) cluster was studied using platinum (Pt) and glassy carbon electrodes (GCE) in nonaqueous media. The cluster showed electrochemical activity at the potential range between +1.6 and ?1.6 V. In the negative region (0 to ?1.6 V), the cluster exhibited two-step reductions. The first step was one-electron reversible, while the second step was a five-electron quasi-reversible process. On the other hand, in the positive region (0 to +1.6 V), the first step involved one-electron quasi-reversible process. The applicability of the cluster was found towards the electrocatalytic reduction of CO2 and was evaluated by experiments using rotating ring disc electrode (RRDE). RRDE experiments demonstrated that two electrons were involved in the electrocatalytic reduction of CO2 to CO at the Se-Ni-dppf-modified electrode.

• 상하수도학회지
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• 제33권2호
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• pp.131-140
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• 2019

This study used a packed column reactor and a horizontal flow mesh reactor to examine the removal of copper ions from aqueous solutions using pine bark, a natural adsorbent prepared from Korean red pine (Pinus densiflora). Both equilibrium and nonequilibrium adsorption experiments were conducted on copper ion concentrations of 10mg/L, and the removals of copper ions at equilibrium were close to 95%. Adsorption of copper ions could be well described by both the Langmuir and Freundlich adsorption isotherms. The bark was treated with nitric acid to enhance efficiency of copper removal, and sorption capacity was improved by about 48% at equilibrium; mechanisms such as ion exchange and chelation may have been involved in the sorption process. A pseudo second-order kinetic model described the kinetic behavior of the copper ion adsorption onto the bark. Regeneration with nitric acid resulted in extended use of spent bark in the packed column. The horizontal flow mesh reactor allowed approximately 80% removal efficiency, demonstrating its operational flexibility and the potential for its practical use as a bark filter reactor.