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All-Optical Ultrasound Transducer Using CNT-PDMS and Etalon Thin-Film Structure
Geonwook Yoo,Hyunmin Yoon,Jeongmin Heo,Thakur, Ujwal Kumar,Hui Joon Park,Hyoung Won Baac,Junseok Heo IEEE 2015 IEEE photonics journal Vol.7 No.6
<P>Compared with conventional piezoelectric transductions, an all-optical high-frequency ultrasound (HFUS) transducer is a promising modality for high-resolution ultrasound imaging. We demonstrate an all-optical HFUS transducer by integrating a carbon nanotube-polydimethylsiloxane composite film with an etalon thin-film structure incorporating SiO<SUB>2</SUB>/TiO<SUB>2</SUB> distributed Bragg reflectors and an SU-8 resonator. The optical and acoustic characteristics are investigated for two different configurations (forward and backward operation modes). The maximum amplitude of the pulse echo in backward mode is approximately twofold higher than that of the forward mode. This difference is contributed by the increased reflectance and the absorptive loss of the incident pulsed laser in the forward mode. The pulse echo from the transducer exhibits a broad frequency bandwidth of 27 MHz. Furthermore, the scalability of the 2-D all-optical transducer array is also evaluated by characterizing the optical properties of the etalon across an area of 0.1 × 0.2 mm<SUP>2</SUP>. Our experimental results show that the proposed transducer is a promising candidate for high-resolution ultrasound imaging systems.</P>
Yoo, Geonwook,Lee, Sungho,Yoo, Byoungwook,Han, Chuljong,Kim, Sunkook,Oh, Min Suk IEEE 2015 IEEE electron device letters Vol.36 No.11
<P>We demonstrate a two-dimensional (2D) multilayered molybdenum disulfide (MoS<SUB>2</SUB>) transistor with molybdenum (Mo) side and edge contacts, which is deposited using a dc-sputtering method. It exhibits field-effect mobility of 23.9 cm <TEX>$^{\mathrm {2}}$</TEX>/Vs and ON/OFF ratio of <TEX>$10^{\mathrm { {6}}}$</TEX> in a linear region. A current–voltage study under different temperatures (300–393 K) reveals that the Mo–MoS<SUB>2</SUB> transistor shows a band transport characteristics, and a Schottky barrier height of 0.14 eV is estimated using a thermionic emission theory. Finally, the side and edge contacts of Mo–MoS<SUB>2</SUB> are confirmed through the transmission electron microscope analysis. Our results not only show that Mo can be an alternative contact metal to other low work-function metals but also that the edge contact may play an important role in resolving the performance degradation over thickness increase of the MoS<SUB>2</SUB> channel layer.</P>
전건욱(Geonwook Jeon),강성진(Sung-Jin Kang) 한국정책분석평가학회 2005 政策分析評價學會報 Vol.15 No.3
The Korean army is tends to mainly operate for preparation of military evaluation and accident prevention so far, when focused on unit management. Also it is being operated both training and unit management with restricted manpower, and it endeavors to improve the efficiency of unit management. The main objective of this study is to suggest a new methodology for relative efficiencies of the military units which is similar in size. The methodology used the IDEA(Imprecise Data Envelopment Analysis) model which is able to measure relative efficiencies for similar units and complement the drawbacks of the DEA(Data Envelopment Analysis). When the input and output variables are selected, efficient and inefficient military units were identified by using IDEA model. The IDEA model is able to analyze specific units where the inefficiency exists. This study also suggests both an additive IDEA model to become an efficient unit and profiling model to identify priority ranking between efficient units. The suggested models from this study are able to apply in all areas which requires efficiency scores between groups.