고체 기준물질을 이용한 indium-doped CaZrO₃수소센서의 수소 감지 특성

박동섭,홍현석,박진수,박종욱 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

평면 후막형 이산화탄소 센서의 감지 특성

홍현석,박동섭,박진수,박종욱 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

Indium oxide계 후막 센서의 이산화질소 감지 특성

최성호,박종욱 한국센서학회 2002 센서학회지 Vol.11 No.4

Indium oxide-base 후막형 가스센서의 이산화질소(NO_2) 감지특성을 조사하였다. 기본 감지물질로는 In_2O_3, ITO(indium tin oxide)를 사용하였고, 여기에 WO_3와 Pd, Pt 귀금속 촉매를 첨가하여 이산화질소에 대한 반응특성을 실험하였다. 감도, 회복특성을 고려할 때, 350℃의 히터구동온도에서 가장 우수한 반응특성을 보였다. 1wt% 이상 WO_3 첨가시에 반응 감도(sensitivity)가 증가하였고, 귀금속 촉매인 Pd, Pt에 의해서도 감도특성이 향상되었다. 또한, 반복 on-off실험을 해서 신호의 안정성을 확인하였고 장기안정성 test에서도 우수한 특성을 나타내었다. The thick film of indium oxide-based semiconductor for the NO_2 detection have been prepared and their characteristics were investigated. It was shown that the optimum operating temperature of the sensors are 350℃ for In_2O_3-based sensor. NO_2 sensitivity increased as the WO_3 concentration increased to more than lwt%. The addition of Pd and Pt also enhanced the sensitivity to NO_2. Indium oxide-based sensors showed excellent reproducibility and stability for the detection of NO_2.

Effect of a Series Connection of a Bi-Electrolyte Hydrogen Sensor in a Leak Detector

( Hyeuk Jin Han ),( Chong Ook Park ),( Young Kyu Hong ),( Jong Suk Kim ),( Jeong Woo Yang ),( Yoon Seo Kim ) 한국센서학회 2015 센서학회지 Vol.24 No.1

Conventional leak detectors are widely based on helium gas sensors. However, the usage of hydrogen sensors in leak detectors has increased because of the high prices of helium leak detectors and the dearth in the supply of helium gas. In this study, a hydrogen leak detector was developed using solid-state hydrogen sensors. The hydrogen sensors are based on Park.Rapp probes with heterojunctions made by oxygen-ion conducting Yttria-stabilized zirconia and proton-conducting In-doped CaZrO3. The hydrogen sensors were used for determining the potential difference between air and air balanced 5 ppm of H2. Even though the Park.Rapp probe shows an excellent selectivity for hydrogen, the sensitivity of the sensor was low because of the low concentration of hydrogen, and the oxygen on the surface of the sensor. In order to increase the sensitivity of the sensor, the sensors were connected in series by Pt wires to increase the potential difference. The sensors were tested at temperatures ranging from 500.600oC.

Comparison of treatment effects between the modified C-palatal plate and cervical pull headgear for total arch distalization in adults

Chong Ook Park,Noor Laith Sa’aed,Mohamed Bayome,Jae Hyun Park,Yoon-Ah Kook,Young-Seok Park,Seong Ho Han 대한치과교정학회 2017 대한치과교정학회지 Vol.47 No.6

Objective: The purpose of this study was to evaluate the dental and skeletal effects of the modified C-palatal plate (MCPP) for total arch distalization in adult patients with Class II malocclusion and compare the findings with those of cervical pull headgear. Methods: The study sample consisted of the lateral cephalograms of 44 adult patients with Class II Division 1 malocclusion, including 22 who received treatment with MCPP (age, 24.7 ± 7.7 years) and 22 who received treatment with cervical pull headgear (age, 23.0 ± 7.7 years). Pre- (T1) and post-treatment (T2) cephalograms were analyzed for 24 linear and angular measurements. Multivariate analysis of variance was performed to evaluate the changes after treatment in each group and differences in treatment effects between the two groups. Results: The mean amount of distalization at the crown and root levels of the maxillary first molar and the amount of distal tipping was 4.2 ㎜, 3.5 ㎜, and 3.9˚ in the MCPP group, and 2.3 ㎜, 0.6 ㎜, and 8.6˚ in the headgear group, respectively. In addition, intrusion by 2.5 ㎜ was observed in the MCPP group. In both groups, the distal movement of the upper lip and the increase in the nasolabial angle were statistically significant (p < 0.001). However, none of the skeletal and soft tissue variables exhibited significant differences between the two groups. Conclusions: The results of this study suggest that MCPP is an effective treatment modality for total arch distalization in adults.

A Perovskite-Type Lanthanum Cobaltite Thin Film Synthesized via an Electrochemical Route and Its Application in SOFC Interconnects

Park, Beom-Kyeong,Song, Rak-Hyun,Lee, Seung-Bok,Lim, Tak-Hyoung,Park, Seok-Joo,Park, Chong-Ook,Lee, Jong-Won The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.14

<P>Metal oxides with a perovskite structure have attracted great interest in a wide range of technical applications, including solid oxide fuel cells (SOFCs), owing to their unique electronic, chemical, and structural features. Recently, significant efforts have been put into developing simple and cost-effective methodologies to controllably produce perovskite oxide layers for SOFC applications. In this study, we demonstrate the fabrication of a perovskite-type lanthanum cobaltite (LaCoO<SUB>3</SUB>) film via a facile electrochemical route and its feasibility as a conductive coating for metallic interconnects in SOFCs. A uniform, dense, and adhesive LaCoO<SUB>3</SUB> film with a thickness of about 1 μm (mixed with a small amount of Co<SUB>3</SUB>O<SUB>4</SUB>) is formed on a cobalt-coated stainless steel substrate through an electrodeposition process involving nitrate reduction and hydroxide precipitation, followed by thermal conversion in air. The fabricated perovskite film serves as an efficient conductive coating that can mitigate degradation in the electrical properties of metallic interconnects under typical SOFC operating conditions.</P>

Applicability of superposition for responses of resistive sensors in a diluted mixed gas environment

Park, Kwang-Min,Kim, Tae-Wan,Park, Jeong-Ho,Park, Chong-Ook Elsevier Sequoia 2017 Sensors and actuators. B Chemical Vol.239 No.-

<P><B>Abstract</B></P> <P>The potential for using superposition to predict the response of resistive-type gas sensors when they are exposed to more than a single gas was tested using two SnO<SUB>2</SUB>-based sensors. It is proposed that the selectivity of resistive-type gas sensors could be improved, or individual gas concentrations extracted, based on the observed response values of the sensors and a mathematical formulation. In this study, the behavior of several resistive gas sensors was tested in a mixed-gas environment of toluene and acetone, using a GASENTEST, which is an automatic gas sensor testing machine developed for this study. The measured responses were compared with calculated responses based on our mathematical formula. Additionally, the actual concentrations of the input gases were compared to the gas concentrations calculated from the observed response of the sensors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The potential of using superposition to predict the sensitivity of resistive type gas sensors. </LI> <LI> The measured sensitivity was compared with the calculated sensitivity based on our mathematical formula. </LI> <LI> The actual concentrations of the input gases were compared to the gas concentrations calculated from the observed response of the sensors. </LI> </UL> </P>

Design of a dual-layer ceramic interconnect based on perovskite oxides for segmented-in-series solid oxide fuel cells

Park, Beom-Kyeong,Kim, Dae-Wi,Song, Rak-Hyun,Lee, Seung-Bok,Lim, Tak-Hyoung,Park, Seok-Joo,Park, Chong-Ook,Lee, Jong-Won Elsevier 2015 Journal of Power Sources Vol.300 No.-

<P><B>Abstract</B></P> <P>A segmented-in series (SIS) SOFC consists of segmented unit cells connected in electrical series and shows improved stack efficiency over conventional SOFCs. In this design, a thin interconnect film provides both electrical contact and sealing between the anode of one cell and the cathode of the next; thus, it should have high conductivity and chemical/structural stability in both reducing and oxidizing atmospheres as well as impermeability to gases. Here, we report a dual-layer interconnect film for SIS–SOFCs comprising perovskite-type oxides, Sr<SUB>0.7</SUB>La<SUB>0.2</SUB>TiO<SUB>3</SUB> (exposed to a reducing atmosphere) and La<SUB>0.8</SUB>Sr<SUB>0.2</SUB>FeO<SUB>3</SUB> (exposed to an oxidizing atmosphere). The interconnect film is not only very dense but also highly conductive and stable under SOFC operating conditions; in particular, it shows an area-specific resistance of 19.6 mΩ cm<SUP>2</SUP> at 800 °C, which is much lower than the generally accepted limit for SOFCs. A flat-tubular SIS–SOFC fabricated using these interconnect films exhibits a power density as high as 340 mW cm<SUP>−2</SUP>, which proves the feasibility of the dual-layer interconnect design.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dual-layer interconnect design for segmented-in-series solid oxide fuel cells. </LI> <LI> The interconnect comprises two perovskite oxides, Sr<SUB>0.7</SUB>La<SUB>0.2</SUB>TiO<SUB>3</SUB> and La<SUB>0.8</SUB>Sr<SUB>0.2</SUB>FeO<SUB>3</SUB>. </LI> <LI> The interconnect exhibits low resistance and high stability in a dual atmosphere. </LI> <LI> The fuel cell with the interconnect films shows a power density of 340 mW cm<SUP>−2</SUP>. </LI> </UL> </P>

Facile Synthesis of Ca-Doped LaCoO₃ Perovskite via Chemically Assisted Electrodeposition as a Protective Film on Solid Oxide Fuel Cell Interconnects

Park, Beom-Kyeong,Song, Rak-Hyun,Lee, Seung-Bok,Lim, Tak-Hyoung,Park, Seok-Joo,Park, Chong-Ook,Lee, Jong-Won The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.9

<P>Interconnects in solid oxide fuel cells (SOFCs) serve two essential roles, namely, cell-to-cell electrical connection and the separation of fuel and oxidant gases. It is of practical significance to develop a protective coating that is capable of improving the surface stability of metallic interconnects while maintaining their electrical properties. Perovskite-type oxides are recognized as promising materials for protective coatings; however, it is difficult to fabricate high-density films by conventional powder-sintering processes. In this paper, we report a facile electrodeposition-based approach to preparing perovskite oxide films on SOFC interconnects. A high density, adhesive Ca-doped LaCoO3 perovskite film of similar to 1.3 mu m thickness is directly formed on an SOFC interconnect through the 'chemically assisted electrodeposition' of hydroxide combined with the thermal conversion of hydroxide to oxide. In the proposed synthesis method, the electrodeposition parameters, such as solution composition and deposition time, have a strong influence on the composition, microstructure, and adhesion of the perovskite oxide film. The fabricated film exhibits outstanding performance as a protective coating for SOFC interconnects, as evidenced by a low area-specific resistance of 14.4 m Omega cm(2) at 800 degrees C and high stability during both continuous operation and repeated thermal cycling. (C) 2016 The Electrochemical Society. All rights reserved.</P>

14q32.33 Deletion Identified by array-CGH in a 5-year old-girl with Seizure

Chong Kun Cheon,Sang-Jin Park,Ook Hwan Choi 대한의학유전학회 2011 대한의학유전학회지 Vol.8 No.1

14q32.33을 포함한 14번 염색체 장완 결실은 드문 질환이다. 14번 염색체의 말단 결실은 여러 임상증상을 공통적으로 보일 수 있으나 결실 절단부 (breakpoint)에 따라 표현형이 다양하게 발생할 수 있다. 저자들은 경련을 동반한 5세 여아에서 array comparative genomic hybridization (array-CGH)와 fluorescence in situ hybridization (FISH) 방법을 이용하여 이전 보고에 비해 가장 작은 14q32.33부위의 0.33Mb 크기의 말단 결실과 심하지 않은 표현형을 보이는 1례를 경험 하였기에 문헌고찰과 함께 보고하는 바이다. Deletions of 14q including band 14q32.33 are uncommon. Patients with terminal deletions of chromosome 14 usually share a number of clinical features. By molecular techniques (array comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH), we identified a young girl with 0.3 Mb terminal 14q32.33 deletion. Review of the nine cases with pure terminal 14q32.3 deletions described to date documented that our observation is the smallest terminal 14q deletion ever reported. The phenotype of our patient is much less severe than the phenotypes of the patients reported previously. We report our experience in examining the clinical, behavioral, and cognitive findings in a 5-year-old girl studied with chromosomal microarray hybridization and reviewed previously reported patients with 14q32 deletions.