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Changwan Son,Byungchae Kim,Jaehyuk Shin,Dagli, N. IEEE 2011 Journal of lightwave technology Vol.29 No.19
<P>Metal slab waveguide reflectors integrated with very compact high index contrast waveguides are described, designed and simulated. Reflection and transmission characteristics of such reflectors are studied using 2-D and 3-D finite different time domain (FDTD) simulations. It is shown that the reflection and transmission coefficients can be controlled by adjusting the gap and length of metals of the reflector. Reflection coefficients much higher than cleaved facets and even higher than metal coated facets are possible. Reflection coefficients of almost 97% are achievable using only 1 μm long reflectors. The sensitivity of obtained reflection as a function of alignment errors indicates that more than 90% reflectivity is possible with 0.1 μm alignment tolerance. It is also shown that very compact Fabry-Perot resonators with FSR of 67.1 nm are possible using such reflectors. These resonators are directly coupled to input and output waveguides and have 5 μ m active length and less than 7 μm overall length including mirrors.</P>
Interspecies Signaling through QscR, a Quorum Receptor of Pseudomonas aeruginosa
Changwan Ha,이준희,Seong Joon Park,Su-Jin Im,Su-Jin Park 한국분자세포생물학회 2012 Molecules and cells Vol.33 No.1
The QS machinery of Pseudomonas aeruginosa, an opportunistic human pathogen, consists of three acyl-homo-serine lactone (acyl-HSL) signaling systems, LasR-I, RhlR-I, and QscR. QscR, known as an orphan receptor and a repressor of other QS systems, operates its own regulon using N-3-oxododecanoyl HSL (3OC12), which is synthesized by LasI, as its signal. In this study, we addressed the role of QscR in interspecies communication. We found that QscR auto-activates its own transcription in the presence of 3OC12. In a single population of P. aeruginosa, where 3OC12 is the sole signal available for QscR, the QscR regulon is activated by 3OC12 produced by the LasI-R system. However, the broad signal specificity of QscR allowed it to respond to a non-P. aeruginosa signal, such as N-decanoyl HSL (C10) and N-3-hydroxydecanoyl HSL (3OHC10), which preferentially activated QscR to LasR. The signal extracts from Pseudomonas fluorescens and Burkholeria vietnamiensis also preferentially activated QscR. These non-P. aeruginosa signals activated QscR more strongly than 3OC12, the authentic P. aeruginosa signal. Since a variety of acyl-HSLs are produced in the multi-species habitat of nature, our study provides a clue for the particular situation that allows QscR to secede from the conventional QS cascade in mixed microbial community.
Changwan Han,Jaehyeok Doh 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.5
The objective of this study is to quantitatively analyze the static and fatigue characteristics of the repeated welding, operating temperatures, and surface defects (notches) in tubes with Al3003-O aluminum, which is applied to the heat exchangers. In particular, fatigue characteristics on actual aluminum tubes are evaluated. It was confirmed the grain size increases and the hardness decreases due to changes in the internal structure as the number of repeated welding increases. The fatigue limit of the aluminum tube at the operating temperature was 49.02 MPa which was lower than the room temperature. Also, the fatigue limit of the notched aluminum tube is measured to be 29.37 MPa which is reduced compared to that of the specimens without a notch; the fatigue notch factor is 1.67. Based on the Peterson equation, the material constants were derived by combining the results (fatigue notch factor, etc.) obtained through analysis and experiments. Derived material constants allow the prediction of fatigue limits for various defect (notch) sizes that may occur during the manufacturing and assembly of the heat exchanger.
( Changwan You ),( Kichul Kim ) 한국체육학회 2016 국제스포츠과학 학술대회 Vol.2016 No.1
Purpose: Since there is more emphasis on the teaching-learning assessment development in the second stage with the modification and supplement of the first stage, the development with information more suitable in the field is required. Therefore, more teachers are included in the development in order for higher suitability on the elementary, middle and high schools P.E. curriculums. The balance of theoretical and practical aspects is pursued through literature study, expert council and public hearing in the research process. Method: The ‘teaching-learning and its significance’ and ‘assessment and its significance’ in 2009 revised P.E. curriculum were ‘guidance by contents’ and ‘assessment by contents’ which become more specified in the second stage. The ‘guidance by contents’ was under the teaching and learning direction and planning which might be helpful in sequential understanding but they were not enough in delivering direct assistance on how to achieve the standard of accomplishments that were specified separately. Therefore, they are newly placed under the achievement standard for higher utilization of the standard of accomplishment. Result: One of the focusing of the second stage development is the reconstruction of the ``teaching and learning assessment direction`` to fit new P.E. curriculum. The framework of the 2009 revised P.E. curriculum are maintained while items unsuitable for implementation or that needs modification in the 2015 revised P.E. curriculum are reconstructed. Specialized curriculum in high school P.E. is added in the second stage which are ‘introduction to sports’, ‘P.E. and career exploration’ and ‘P.E. teaching’ in more clarified characteristics. The 2015 revised P.E. curriculum developed in such process were submitted in September, 2015 which went through the final review and announced. After the 2015 revised P.E. curriculum was announced, the second stage was established to modify and supplemented which was to concretize the ``teaching and learning method and assessing example by area`` for better application of the curriculum. Based on the study results, more suggestions were made for the development process of P.E. training, system improvement and their application in schools. Conclusion: After the announcement, the ``teaching-learning method and assessing example by area`` were defined in order to raise their application with appropriate examples to achieve the standard of accomplishment in elementary and middle schools with just one standard of accomplishment. Two areas per subject in high school elective courses and their appropriated standard of accomplishment were selected as its teaching and learning assessment example. The teaching and learning method and assessment examples developed in each area went through reviews and modifications by current teacher in elementary, middle and high schools to have higher completeness. This had been included in the appendix of the second development report.