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시동/정지 반복에 따른 고분자전해질 연료전지의 성능 저하에 관한 연구
조유연,조은애,김정현 한국수소및신에너지학회 2009 한국수소 및 신에너지학회논문집 Vol.20 No.4
To investigate degradation mechanism of PEMFC operated with repetitive startup/shutdown cycling, i-V characteristics, impedance, cyclic voltamograms were measured. OCV decreased from 0.967 to 0.951 V while the cell voltage at 800mA/cm2 from 0.657 to 0.563V, implying that the electrodes rather than membrane electrolyte was damaged during the cycling operation. Electrochemical analyses supported that the performance degradation could be mainly attributed to degradation of the electrodes such as a decrease in electrochemical active surface area rather than degradation of membrane.
조유연,이대규,곽준영 한국세라믹학회 2022 세라미스트 Vol.25 No.4
In the fourth industrial revolution, the efficient processing of huge amounts of data is important due to the development of artificial intelligence (AI), internet of things (IoT), and machine learning (ML). The conventional computing system, which is known as von Neumann architecture, has been facing bottleneck problems because of the physical separation of memory and central processing unit (CPU). Many researchers have interested to study on neuromorphic computing, inspired by the human brain, to solve the bottleneck problems. The development of artificial neuromorphic devices, such as neuron and synaptic devices, is important to successfully demonstrate a neuromorphic computing hardware. Various Si CMOS transistor- based circuits have been investigated to implement the behaviors of the biological neuron and synapse; however, they are not suitable for mimicking the large-scale biological neural networks because of Si CMOS transistor’s scalability and power consumption issues. In this report, we review the recent research progress in artificial neurons and synaptic devices based on emerging materials and discuss the future research direction of artificial neural networks.
조유연 ( Yoo Yeon Jo ),정수권 ( Su Kwon Jung ),이오람 ( Oh Ram Lee ),김의용 ( Eui Young Kim ) 서울시립대학교 산업기술연구소 2006 산업기술연구소논문집 Vol.14 No.-
Heat transfer process is important for many applicable fields such as heat exchanger, construction material, and aircraft body. Heat conduction is much affected by contact resistance between two different material interfaces. In this study, various experimental conditions were tested to decrease contact resistance and to increase thermal conductivity with several coating materials. Aluminium pieces of 2 mm, 4 mm were used as test samples. Copper powder (a few micrometer diameter), copper powder/silicon oil (80/20 weight ratio), and conductive paste were used as coating materials. When the conductive paste and (copper powder+silicon oil) blend were used, thermal conductivity was higher than when no coating materials were used. However, when only the copper powder was used, thermal conductivity value was not stable enough.
실험계획법을 이용한 유연 디스플레이용 무색 투명 폴리이미드 필름의 광학 성능 최적화
오충석,조다운,유연수,남희은,장진해 한국반도체디스플레이기술학회 2022 반도체디스플레이기술학회지 Vol.21 No.1
As various flexible display products are released, the demand for high-performance colorless and transparent polyimide (CPI) film is continuously increasing. The primary purpose of this study is to establish a systematic procedure for optimizing the optical performance of CPI films by applying the response surface method. After selecting three key factors (monomer type, stirring time for varnish synthesis, and maximum temperature of vacuum furnace for film production) affecting optical performance based on experiences and references, CPI films were manufactured according to the experimental sequence designed by the central composite design, and then the yellowness index (YI) and optical transmittance (Tr) of the films were measured. When producing a CPI film by pouring varnish into a petri dish, the change in optical properties according to thickness should be considered, and there was a meaningful linear relationship between YI and Tr. The species of monomer and the maximum temperature were the critical factors that had an influence on YI and Tr, respectively. It is expected that the procedure proposed in this study can serve as a starting point for CPI film optimization studies considering the other factors that were not considered and responses such as thermal properties.
수인성 니켈 급성 노출이 붕어, Carassius carassius의 반수치사농도, 혈액학적 성상 및 혈장 성분에 미치는 독성 영향
주창훈,조아현,홍수민,정지호,유연아,조석원,송재희,김준환 (사)한국해양생명과학회 2022 한국해양생명과학회지 Vol.7 No.2
본 실험은 붕어(Crucian carp, Carassius carassius)(무게 39.7±3.1 g, 전장 14.8±0.5 cm)의 수인성 니켈 0, 10, 20, 40, 80 및 160 mg Ni2+/l 농도로 96시간 급성 노출을 실시하였다. 수인성 니켈에 노출된 붕어의 반수치사농도(LC50)는 117.69 mg Ni2+/l으로 나타났다. 혈액학적 성상에서RBC count는 수인성 니켈 96시간 급성 노출 중 48시간에서 유의적으로 증가한 반면, 96시간에서 유의적 감소가 나타났다. MCV와 MCH는 96시간에서 80 mg Ni2+/l 농도에서 유의적으로 증가했다. Calcium, magnesium, glucose, cholesterol, total protein, AST, ALT 및 ALP 와 같은 혈장성분은 수인성 니켈 노출에 의해 유의적 변화가 나타났다. 이 연구의 결과는 수인성 니켈 노출에 따른 붕어의 생존율, 혈액학적 성상 및 혈장 성분의 변화를 확인하고 이는 수인성 니켈의독성에 의한 것으로 판단했다.
중심정맥도관삽입술 시 위치이상의 빈도를 감소시키는 방법: 실시간 초음파 유도하 재위치
안홍준,김건동,조별님희,정원준,유연호,유승,이진웅,김승환,유인술,조용철 대한중환자의학회 2013 Acute and Critical Care Vol.28 No.4
Background: The purpose of this retrospective and prospective study is to evaluate the efficiency of ultrasound (US) guidance as a method of decreasing the malposition rate of central venous catheterization (CVC) in the emergency department (ED). Methods: We retrospectively enrolled 379 patients who underwent landmark-guided CVC (Group A) and prospectively enrolled 411 patients who underwent US-guided CVC (Group B) in the ED of a tertiary hospital. Malposition of the CVC tip is identified when the tip is not located in the superior vena cava (SVC). In Group B, we performed US-guided intravascular guide-wire repositioning and then confirmed the location of the CVC tip with chest radiography when the guide-wire was visible in any three other vessels rather than in the approached vessel. In the case of a guide-wire inserted into the right subclavian vein (SCV), the left SCV and both internal jugular veins (IJV) were referred to as the three other vessels. The two subject groups were compared in terms of the malposition rate using Fisher’s exact test (significance = p < 0.05)Results: There were 38 malposition cases out of a total of 790 CVCs. The malposition rates of Groups A and B were 5.5% (21) and 4.1% (17), respectively, and no statistically significant difference in malposition rate between the two groups was found. In Group B,the malposition rate was decreased from 4.1% (17) to 1.2% (5) after the guide-wire was repositioned with US guidance, which led to a statistically significant difference in malposition rate (p < 0.01). Conclusions: The authors concluded that repositioning the guide-wire with US guidance increased correct placement of central venous catheters toward the SVC.