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A 20~32 GHz GaN Power Amplifier MMIC Using Lange Couplers for Wideband Operation
Woojin Chang,Haecheon Kim,Byoung-Gyu Min,Ho-Kyun Ahn,Jae-Won Do,Kyu Jun Cho,Dong-Min Kang,Hong-Gu Ji,Sung-Il Kim,Sang-Heung Lee,Jong-Min Lee,Dong-Young Kim,Hyung-Sup Yoon,Sung-Jae Chang,Yoo-Jin Jang,J 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
In this paper, we demonstrated a K-/Ka-band monolithic microwave integrated circuit (MMIC) power amplifier (PA) designed and fabricated using a AlGaN/GaN 0.15 μm hetero-structure field effect transistor (HFET) on SiC technology. Lange couplers and 2-way combiners were used for combining GaN HFETs and stages of the PA circuit. Especially, six Lange couplers in the PA MMIC were applied for wideband amplification of the PA MMIC. Microstriplines and open-stubs were used for matching circuits, except for MIM capacitors acting as DC blocks in the PA MMIC. In each bias circuit of the PA, two MIM capacitors were used for less vulnerable characteristics of the PA to lengths and diameters of bonding wires. The PA has been achieved a 3 dB bandwidth of 12 GHz, a gain, S21, of 7.8~10.7 dB, an input reflection coefficient, S11, of - 22~-10 dB and an output reflection coefficient, S22, of -41~-12 dB for 20~32 GHz. And also a saturated output power of 31.2 dBm was achieved at 28 GHz.
DEVELOPMENT OF A WEB-BASED OPEN SOURCE CAE PLATFORM FOR SIMULATION OF IC ENGINES
Woojin Lee,Donghee Kim,Yeongdo Park,Kang Yul Huh 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.1
Computer Aided Engineering (CAE) software has become an essential element in design, simulation, manufacturing and even marketing in the automotive industry as well as in other major manufacturing companies. Multiphysics simulation of IC engines may be one of the most challenging areas both technically and scientifically, since it requires sound basis and experience for diverse physical phenomena. There are quite a few commercial softwares currently available for various elements of CAE, which require substantial investment cost for licensing, personnel and computing facilities. There is a current consensus for the need of low cost CAE based on open sources through which professionals may contribute to new modeling features and validation through a free access web-based platform. There are several high quality open sources available under General Public Licence (GNU-GPL) which allow free utilization and development. Some of them have features as competitive as their commercial counterparts, whereas their interface in general may not be as user-friendly as most commercial software. In this work, we introduce a web-based platform with selected open source programs and their performance will be shown for some example cases. All these programs are downloadable, while remote job access and postprocessing can be performed by cloud computing facilities.
Nostril Base Augmentation Effect of Alveolar Bone Graft
Lee, Woojin,Park, Hyung Joon,Choi, Hyun Gon,Shin, Dong Hyeok,Uhm, Ki Il Korean Society of Plastic and Reconstructive Surge 2013 Archives of Plastic Surgery Vol.40 No.5
Background The aims of alveolar bone grafting are closure of the fistula, stabilization of the maxillary arch, support for the roots of the teeth adjacent to the cleft on each side. We observed nostril base augmentation in patients with alveolar clefts after alveolar bone grafting. The purpose of this study was to evaluate the nostril base augmentation effect of secondary alveolar bone grafting in patients with unilateral alveolar cleft. Methods Records of 15 children with alveolar clefts who underwent secondary alveolar bone grafting with autogenous iliac cancellous bone between March of 2011 and May of 2012 were reviewed. Preoperative and postoperative worm's-eye view photographs and reconstructed three-dimensional computed tomography (CT) scans were used for photogrammetry. The depression of the nostril base and thickness of the philtrum on the cleft side were measured in comparison to the normal side. The depression of the cleft side pyriform aperture was measured in comparison to the normal side on reconstructed three-dimensional CT. Results Significant changes were seen in the nostril base (P=0.005), the philtrum length (P=0.013), and the angle (P=0.006). The CT measurements showed significant changes in the pyriform aperture (P<0.001) and the angle (P<0.001). Conclusions An alveolar bone graft not only fills the gap in the alveolar process but also augments the nostril base after surgery. In this study, only an alveolar bone graft was performed to prevent bias from other procedures. Nostril base augmentation can be achieved by performing alveolar bone grafts in children, in whom invasive methods are not advised.
Enhanced Charge Injection in Pentacene Field‐Effect Transistors with Graphene Electrodes
Lee, Sangchul,Jo, Gunho,Kang, Seok‐,Ju,Wang, Gunuk,Choe, Minhyeok,Park, Woojin,Kim, Dong‐,Yu,Kahng, Yung Ho,Lee, Takhee Wiley - VCH Verlag GmbH & Co. KGaA 2011 Advanced Materials Vol. No.
<P><B>Pentacene organic field‐effect transistors</B> with multilayer graphene electrodes exhibit a lower contact resistance and lower charge‐injection barrier height than those with conventional Au electrodes. This enhancement in performance is related to the favorable dipole layer formation at the graphene/pentacene interface. </P>
Lee, Yoo-Hyun,Kwak, Jieun,Choi, Hyo-Kyoung,Choi, Kyung-Chul,Kim, Sunoh,Lee, Jeongmin,Jun, Woojin,Park, Hyun-Jin,Yoon, Ho-Geun UNKNOWN 2012 INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE Vol.30 No.1
<P>Manipulating acetylation status of key gene targets is likely to be crucial for effective cancer therapy. In this study, we utilized green tea catechins, epicatechin (EC), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) to examine the regulation of androgen receptor acetylation in androgen-dependent prostate cancer cells by histone acetyl-transferase (HAT) activity. EC, EGC and EGCG induced prostate cancer cell death, suppressed agonist-dependent androgen receptor (AR) activation and AR-regulated gene transcription. These results demonstrated a similar tendency to HAT inhibitory activities; EGCG>EGC>EC. The strongest HAT inhibitor among them, EGCG (50 µM), downregulated AR acetylation and finally, AR protein translocation to nucleus from the cytoplasmic compartment was effectively inhibited in the presence of the agonist. These results suggest another mechanism to develop effective therapeutics based on green tea catechins.</P>