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A concept unifying the Armendariz and NI conditions
Young Chun,전영철,강성경,Key Nyoung Lee,이양 대한수학회 2011 대한수학회보 Vol.48 No.1
We study the structure of the set of nilpotent elements in various kinds of ring and introduce the concept of NR ring as a generalization of Armendariz rings and NI rings. We determine the precise relationships between NR rings and related ring-theoretic conditions. The [문자]othe's conjecture is true for the class of NR rings. We examined whether several kinds of extensions preserve the NR condition. The classical right quotient ring of an NR ring is also studied under some conditions on the subset of nilpotent elements.
Reflection-type optical waveguide index profiling technique
Youngchun Youk,Dug Young Kim 한국광학회 2005 Current Optics and Photonics Vol.9 No.2
We report a new configuration of a reflection-type confocal scanning optical microscope system for measuring the refractive index profile of an optical waveguide. Several improvements on the earlier design are proposed; a light emitting diode (LED) at 650 nm wavelength instead of a laser diode (LD) or He-Ne laser is used as a light source for better index precision, and a simple longitudinal linear scanning and curve fitting techniques are adapted instead of a servo control for maintaining an optical confocal arrangement. We have obtained spatial resolution of 700 nm and an index precision of 2×10-4. To verify the system's capability, the refractive index profiles of a conventional multimode fiber and a home-made four-mode fiber were examined with our proposed measurement method.
조영천(Youngchun Jo),강해용(Haeyong Kang),이현경(Hyunkyung Lee),전진호(Jinho Jeon),이현섭(Hyeonseop Lee) 한국물리학회 2024 새물리 Vol.74 No.1
비정질 InGaZn oxide(a-IGZO)는 넓은 밴드 갭을 갖는 금속 산화물 반도체로 광학적으로 투명하지만 산소 빈자리에 의한 밴드 갭 내 sub-gap 상태로 인해 가시광 영역의 빛을 흡수할 수 있는 것으로 알려져 있다. 본 연구에서는 용액 공정 기반의 a-IGZO 채널 층으로 이루어진 포토트랜지스터에서 sub-gap 상태를 제어하고 변화된 광전자 특성을 분석하였다. 채널 층 위에 얇은 산화알루미늄(AlO<SUB>x</SUB>)을 증착한 소자에서는 가시광 영역의 빛에 대해 광 전류가 증가하는 것을 확인하였다. 또한 a-IGZO 박막을 UV ozone으로 표면 처리한 경우 450 nm 파장의 가시광선 영역에서 지속적인 광 전도 현상이 감소하는 것을 확인하였다. 이러한 특성은 a-IGZO 박막의 흡수 계수, 광학 밴드 갭 분석으로 a-IGZO 박막 내 산소 빈자리 농도 변화에 기인한 것임을 규명하였고, AlOx 증착과 UV ozone 처리를 통해 광 전류와 광 전도 현상을 제어하고 포토센서 및 뉴로모픽 분야 응용 가능성을 제시할 수 있었다. Optoelectronic properties of a phototransistor made from solution-processed amorphous InGaZn oxide (a-IGZO) were investigated. This wide bandgap metal oxide semiconductor is known for its optical transparency, yet it exhibits visible light absorption attributed to sub-gap states resulting from oxygen vacancies. The study found that depositing a thin layer of aluminum oxide (AlO<SUB>x</SUB>) on the transistor channel led to an increase of photocurrent in the visible spectrum. Additionally, surface treatment of the a-IGZO thin film with UV ozone reduced persistent photoconductivity at 450 nm. Analysis of the absorption coefficient and optical band gap indicated that the results were associated with changes in the oxygen vacancy states within the a-IGZO thin film. The ability to control photocurrent and persistent photoconductivity through the deposition of aluminum (Al) and UV ozone treatment opens up exciting possibilities for applications in photosensors and neuromorphic systems.
강영춘(Youngchun Kang),장진만(Jinman Jang),김준완(Junewan Kim),김영수(Youngsoo Kim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Idle vibration, hot issue of the NVH problem has been studied for a long time. Engine excitation is the source of the idle vibration and Engine mount system, drive line and suspension system are main force transfer paths to the body. To predict the idle vibration performance in the beginning or prototype of a car developing program is very important process and therefore building the CAE model for idle vibration analysis became one of the most important works of car maker. The CAE model must have the force transfer systems that are mentioned before such as engine mounting system, drive line and exhaust system for the real situation. In this paper, CAE model for idle vibration analysis is validated by comparing test results from the bench made for the experiment testing a specific character of transfer systems in particular. Also, this CAE model is very useful in order to improve idle vibration performance in the level of chassis system.
김영춘(Youngchun Kim),최해범(Heabum Choi),김정숙(Jeongsook Kim) 한국무역학회 2009 한국무역학회 세미나 및 토론회 Vol.2009 No.8
This research was performed in information system in Korean Tariff Administration, and it is true that most tariff administration is administered by information system. Therefore, a customer satisfaction improvement strategy is being presented as an alternative with extensive customer service research and its analysis. variables were used to measure customer's satisfaction level : practical satisfaction lelel, factor satisfaction level. These variables are directly cited from customer satisfaction research reference in the Korean Administration Ministry. Accuracy, security, customer service, efficiency, and agility were used in the factor satisfaction level. research. Research showed the actual satisfaction level has annually increased. It is necessary that quality management and service toward customer should be increased to elevate its overall satisfaction level. Research result in portfolio also demonstrates some critical factors in actual satisfaction improvement strategy : cost-effectiveness relationship, customer service toward customer and their easy access, and product and its reliance.
스월 유동과 나선형 그레인에 의한 하이브리드 로켓 연로의 연소율 향상
황영춘(Youngchun Hwang),이창진(Changjin Lee) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.4
하이브리드 로켓 연료의 연소율 향상을 위해서 스월 유동을 이용한 방법과 나선형 그레인 방법의 두 가지 방법을 사용하여 연소율 증가에 대한 실험 연구를 수행하였다. 스월 유동을 적용하기 위해서 두 가지의 인젝터를 사용하였으며 스월 수 3.61인 인젝터를(Type II) 사용할 때 더 높은 연소율 증가를 나타내었다. 그러나 두 가지 인젝터 모두에서 공통으로 연료 앞부분에서 연소가 집중적으로 발생하는 현상이 발생하였다. 나선형 그레인에 의한 연소율 증가를 실험하기 위하여 피치 6과 피치 100인 두 종류 연료를 사용하였다. 스월 유동이 없는 인젝터를 사용할 경우 피치 6 그레인에서는 강한 난류의 발생에 따른 연소율 향상이 더 크게 일어나는 것을 확인할 수 있었다. 그러나 스월 인젝터와 나선형 그레인을 동시에 적용하여 실험한 결과에 의하면,Type II 인젝터와 피치 100 그레인를 적용할 경우에 가장 높은 연소율 증가를 이루었다. 이것은 인섹터에서 발생한 스월 유동이 나선형 그레인을 통해 연료의 출구까지 유지되었기 때문인 것으로 판단된다. Experimental tests have been done with swirl injector and helical grain configuration to increase the regression rate of hybrid rocket solid fuel. Two types of injector were designed to evaluate the swirl effect of oxidizer stream on the increase in the regression rate. Results showed Type II injector with swirl number of 3.61 induced the better regression rate than Type I injector. Meanwhile, fuels with two different pitch number of 6 and 100 were used to analyzes the flow characteristics on the enhancement of regression rate. Test with fuels of pitch 6 showed better increase in the regression rate than in the pitch l0 when no swirler was imposed. This is due to the generation of strong turbulences in the oxidizer stream along the pitch 6 configuration. However, the regression rate could be increased further in the fuel with pitch 100 than with pitch 6 when swirl flow was imposed by Type II injector. This result implied that the fuel with pitch 100 could take a role of sustainer of the imposed swirl by swirler II instead of turbulence generator.
Refractive Index Profiling of a Core-Doped Photonic Crystal Fiber
Youk, Youngchun,Kim, Soan,Oh, Kyunghwan,Kim, Dug Young IEEE 2007 IEEE photonics technology letters Vol.19 No.11
<P>Direct refractive index profiling for a core-doped photonic crystal fiber with complex and nonsymmetric refractive index structure has been demonstrated for the first time. A new index profiling technique based on a reflectivity measurement technique using a confocal microscope has been employed. This improved, straightforward, and robust method enables us to measure the index structure of a complex structured fiber with high refractive index precision and spatial resolution</P>