• 한국표면공학회지
• /
• 제49권3호
• /
• pp.280-285
• /
• 2016

In this study, we investigated the influences of potassium fluoride(KF) addition on the surface characteristics of plasma electrolytic oxidation(PEO) coating produced on Al alloy. The PEO of marine grade Al alloy(5083 grade) was conducted in KOH 1g/L solution adding different concentrations of KF(0, 1 and 2 g/L) under a galvanostatic regime. With KF addition, unusual behavior was observed on the voltage-time characteristic curves, which can be characterized by the following process: (i) initial rapid increase in voltage (ii) a short plateau after 1st breakdown (iii) gradual increase in voltage (iv) intermittent fluctuation of voltage after 2nd breakdown. The SEM observation revealed irregular surface morphology with KF addition, as compared with one formed without KF addition, which had a reticulate structure. The XRD analysis detected the formation of aluminium hydroxide fluoride hydrate($H_{4.76}Al_2F_{3.24}O_{3.76}$) on surface grown by PEO process with KF. Particularly, at very early stage of the process (~ 120 s), thin film was formed having nanoporous structure, and F element was confirmed on surface by EDS analysis. The thickness and surface roughness of the coating increased with increasing KF concentration. As a result, KF addition was found to be less beneficial influences on PEO of marine grade Al alloy, and therefore needs further research to improve its capability.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.75.2-75.2
• /
• 2013

Atomic layer deposition (ALD), utilizing self-limiting surface reactions, could offer promising perspectives for future efficient energy conversion devices. The capabilities of ALD for surface/interface modification and construction of novel architectures with sub-nanometer precision and exceptional conformality over high aspect ratio make it more valuable than any other deposition methods in nanoscale science and technology. In the context, a variety of researches on fabrication of active materials for energy conversion applications by ALD are emerging. Among those materials, one-dimensional nanotubular titanium dioxide, providing not only high specific surface area but also efficient carrier transport pathway, is a class of the most intensively explored materials for energy conversion systems, such as photovoltaic cells and photo/electrochemical devices. The monodisperse, stoichiometric, anatase, TiO2 nanotubes with smooth surface morphology and controlled wall thickness were fabricated via low-temperature template-directed ALD followed by subsequent annealing. The ALD-grown, anatase, TiO2 nanotubes in alumina template show unusual crystal growth behavior which allows to form remarkably large grains along axial direction over certain wall thickness. We also fabricated dye-sensitized solar cells (DSCs) introducing our anatase TiO2 nanotubes as photoanodes, and studied the effect of blocking layer, TiO2 thin films formed by ALD, on overall device efficiency. The photon convertsion efficiency ~7% were measured for our TiO2 nanotubebased DSCs with blocking layers, which is ~1% higher than ones without blocking layer. We also performed open circuit voltage decay measurement to estimate recombination rate in our cells, which is 3 times longer than conventional nanoparticulate photoanodes. The high efficiency of our ALD-grown, anatase, TiO2 nanotube-based DSCs may be attributed to both enhanced charge transport property of our TiO2 nanotubes photoanode and the suppression of recombination at the interface between transparent conducting electrode and iodine electrolytes by blocking layer.

• 한국재료학회지
• /
• 제21권11호
• /
• pp.592-595
• /
• 2011

It is well known that modified 9Cr-1Mo steel has a low thermal expansion and high thermal conductivity with excellent high temperature properties compared to austenitic stainless steel. For these advantages, the steel is very popular for the boiler tube of thermal power plants. Normalizing is commonly utilized to obtain martensite in this steel, which shows an unusual toughness for martensite. However, some accidents related to this steel have been reported recently, opening the necessity for further study. As a particular behavior of the steel, an abrupt drop of the impact value has been identified upon tempering at 750$^{\circ}C$ for about 1 hour. It is well known that $Fe_3C$ forms during autotempering and turns to $Cr_2C$ at an early stage and then transforms to $Cr_{23}C_6$. In this study, the cause of the abrupt drop of the impact value was investigated with an impact test, microstructural observation, nanodiffraction and phase analyses using instruments such as optical and transmission electron microscopes (TEM) with an extraction carbon replica of the carbides. The analyses revealed that the $M_2C$ that formed when retained for about 1 hour at 750$^{\circ}C$ causes a drastic decrease in the mechanical properties. The sharp drop in mechanical properties, however, disappeared as the $M_2C$ transformed into $M_{23}C_6$ with longer retention.

• 대한두경부종양학회지
• /
• 제13권1호
• /
• pp.74-80
• /
• 1997

We have experienced 5 cases of unusual well differentiated thyroid carcinoma with insular component during the past 5 years. 4 cases were presented with cervical masses but I case (patient 2.) was initiallty with lung and brain metastasis. The tumors from 4 cases showed invasive growths but that of 1 cases(patient 1.) showed intrathyroidal. Total thyroidectomy and cervical lymphnode dissection(CCND or RND) was performed in 4 cases but only RND was performed in spite of mediastinal metastasis of the tumor in patient 5 under the patient's choice. During the follow-up period, we also performed radical nephrectomy and metastatectomy for the kidney and iliac bone metastasis respectively, in patint 2. Microcsopically, the tumors showed the insular growth patterns, focally(less than 50%) in 3 cases and predominantly(more than 75%) in 2 cases. And the insular componentas were combined with papillary carcinoma in 2 cases and follicular carcinoma in 3 cases. Cervical lymphnode metastases were confirmed in 4 cases. Patient 2 died of disease with metastases to lung, brain, bone and kidney, 52 months after initial therapy. Patient 1, 3 and 4 are alive and have no recurrence and distant metastasis. Patient 5 is also alive with the mediastinal metastasis. In our experience, the well differentiated thyroid carcinomas with insular component showed characteristic histologic features, aggressive behavior in initial presentation and unfavorable prognosis regardless of the percentage of the insular component.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2010년도 제39회 하계학술대회 초록집
• /
• pp.304-304
• /
• 2010

The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

• Bulletin of the Korean Chemical Society
• /
• 제22권9호
• /
• pp.979-983
• /
• 2001

Thermoanaerobacter ethanolicus is a strictly anaerobic and thermophilic bacterium whose optimum temperature ranges over $65-68^{\circ}C.$ T. ethanolicus was known to contain a bipolar very long chain fatty acyl component such as $\alpha$, $\omega-1316-dimethyloctacosanedioate$, as one of the major membrane components. However, exact physiological role of this unusual component in the membrane remains unknown. Such a very long chain fatty acyl component, $\alpha$, ${\omega}-1316-dimethyloctacosanedioate$, dimethyl ester (DME C30), was isolated, and purified from the membrane of T. ethanolicus. As a function of added concentrations of the $\alpha$, $\omega-1316-dimethyloctacosanedioate$, dimethyl ester (DME C30) or cholesterol into the standard liposomes, the acyl chain ordering effect was investigated by the steady-state anisotropy with 1,6-diphenyl-1,3,5-hexatriene (DPH) as a fluorescent probe. Acyl chain order parameter (S) of vesicles containing DME C30 is higher comparing with phosphatidylcholine (PC) only vesicles. This result was discussed thermodynamically with the aid of the simulated annealing molecular dynamics simulations. Through the investigation of all the possible conformational changes of DME C30 or cholesterol, we showed that DME C30 is very flexible and its conformation is variable depending on the temperature comparing with cholesterol, which is rigid and restricted at overall temperature. We propose that the conformational change of DME C30, not the configurational change, may be involved in the regulation of the membrane fluidity against the changes of external temperature.

• 한국융합학회논문지
• /
• 제13권1호
• /
• pp.387-398
• /
• 2022

본 논문은 독거노인의 복합적 행태를 이종 사물인터넷 센서들과 딥러닝 기법을 활용하여 인지하고 낙상, 잦은 기침, 수면의 질 감소, 발열 및 비정상적 생활 동선의 발생 등 위급하거나 건강이 저하되는 상황을 적시에 보호자 및 의료복지 담당자에게 알리고 적정한 후속 서비스를 추천 및 수행할 수 있는 시스템을 논한다. 독거노인들의 생활을 최대한 방해하지 않기 위하여 전면 비접촉식 상황 인식 기술을 선보인다. 본 논문은 센서 데이터의 수집 및 분석 체계의 설계와 구현 방법은 물론, 서울시 총 5개구 거주 독거노인들을 대상으로 실증한 경험을 통해 설치, 설정, 운영 및 유지 보수 측면에서의 다양한 문제점들을 서술하고 해당 시스템의 전국 확산에 대비한 향후 발전 방향을 제언한다.

• 문화기술의 융합
• /
• 제10권4호
• /
• pp.367-372
• /
• 2024

발달장애는 전체 장애인 수 중에 비교적 낮은 수치에 해당되지만 장애의 정도에서 전반적으로 중증 장애로 분류되고 있다. 이러한 발달장애는 초기에 발견이 된다면 적응력과 초기 대응에 의한 치료 효과가 향상될 수 있지만, 대부분의 부모들은 자신의 아이에게서 징후를 발견하지 못하거나 치료시기를 놓치는 경우가 대다수이다. 본 논문에서는 특이적 행동특성을 기반으로 하는 초기 발달장애 징후를 객관적으로 볼 수 없는 부모나 유아기관 관계자들을 위해 발달장애 초기 특이행동 중 손 퍼덕대기(Hand-Flapping)를 인식할 수 있는 발달장애 진단 알고리듬개발의 선행연구를 수행하였다. 인지영역과 손가락을 정확하게 인식하여, 손퍼덕임 수를 정확하게 카운트하는 것을확인할 수 있었다. 빅데이터를 활용한 알고리듬의 고도화 및 기능적 성능 확장을 통해 다양한 행동패턴의 진단이 가능한 알고리듬 연구가 지속적으로 수행 및 확대될 것으로 전망된다.

• 대한소아치과학회지
• /
• 제30권3호
• /
• pp.341-347
• /
• 2003

Smith-Magenis syndrome(이하 SMS)은 제 17번 상염색체의 부분적 결손으로 발생하는 다발성 선천적 기형 및 정신지체를 특징으로 하는 증후군으로 1 : 25,000의 빈도로 발생하는 것으로 알려져 있다. 이 증후군은 작은 키와 단두증(brachycephaly)을 동반한 편평한 중안면, 처진 입, 종종 두드러지게 붉은 뺨, 성인에서 돌출된 턱 등의 특징적인 얼굴 생김새, 만성이염, 청각 손상, 사시와 근시를 포함한 눈의 이상, 목 쉰 소리, 짧은 손가락과 발가락, 심장 질환, 비뇨기 질환, 척추 만곡, 비정상적 걸음걸이, 통각에 둔감함 등의 신체적 특징을 지닌다. 특히 유아기에는 토실토실한 아기 얼굴, 행복한 기분, 드문 울음소리, 낮은 근 긴장도, 섭식 장애 등의 특징이 있다. 수면 장애를 포함하여 언어 지체 및 발음 장애, 발달지체, 학습 장애, 정신지체, 활동항진과 자해, 폭발적 분노, 지속되는 짜증, 파괴적이고 공격적인 행동, 흥분성, 흥분시에 팔로 안거나 손을 끼우는 행동 등의 행동 발달적 특징을 나타낸다. 본 증례는 3세 3개월된 남아로 생후 10개월에 SMS를 진단받은 환자로 상악 좌측 제 1유구치의 통증을 주소로 본과에 내원하였으며, 임상 및 방사선학적으로 다발성 우식증을 보였으며, 소아과 주치의에게 의뢰한 결과 심내막염의 예방을 위한 항생제의 처치를 처방 받고, 환아의 행동 발달적 문제로 인해 물리적 속박의 방법 하에 외래에서 치료되었다. 이 증례를 통해 SMS라는 희귀한 증후군에 관하여 보고하고자 한다.

• 환경생물
• /
• 제37권3호
• /
• pp.343-350
• /
• 2019

도토리거위벌레는 큰턱을 이용하여 도토리에 구멍을 뚫고 가지를 자르는 독특한 행동을 한다. 이러한 행동을 이해하기 위해 다양한 현미경을 이용하여 구기의 해부학적 특징을 관찰하였다. 실체현미경을 이용한 연구에서는 도토리거위벌레 수컷의 평균 내전건과 외전건의 두께는 각각 32.87 ㎛, 53.83 ㎛이었고, 암컷의 평균 내전건과 외전건의 두께는 각각 40.81 ㎛, 75.55 ㎛이었다. 내전건과 외전건의 유의한 두께 차이로 인해 큰턱을 닫는 힘보다 벌리는 힘이 더 강하다는 것을 유추할 수 있다. 광학현미경을 이용한 관찰에서는 주둥이 안쪽에 위치한 내전건과 외전건의 너비 차이와 큰턱 쪽에서는 원형으로 위치하며 두부로 갈수록 납작해져 두부 외피 안쪽에 근육으로 연결된다는 것을 확인할 수 있었고, 내전건의 위치와 모양의 변화에 대한 관찰을 수행하였다. 전자현미경을 통한 연구에서는 외전건이 내전건보다 더 굵으며 이로 인해 큰턱을 안쪽으로 당기는 힘보다 바깥쪽으로 밀어내는 힘이 더 크다는 것을 확인하였다. 관찰 결과를 바탕으로, 도토리거위벌레, 밤바구미, 왕거위벌레의 큰턱의 형태와 이빨의 위치 그리고 큰턱의 움직임에 대해 비교 분석하였고, 도토리거위벌레가 보여주는 특징적인 행동은 해부학적/형태적 특징과 연관되어 있음을 확인할 수 있었다.