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A New RF Window Designed for High-Power Operation in an S-band LINAC RF System
Youngdo Joo,Seung-Hwan Kim,Woonha Hwang,Jiwan Ryu,Sungjoo Roh 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6
A new RF window is designed for high-power operation at the Pohang Light Source-II (PLSII) S-band linear accelerator (LINAC) RF system. In order to reduce the strength of the electric field component perpendicular to the ceramic disk, which is commonly known as the main cause of most discharge breakdowns in ceramic disk, we replace the pill-box type cavity in the conventional RF window with an overmoded cavity. The overmoded cavity is coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the iris and the number of possible mode competitions. The finite-difference time-domain (FDTD) simulation, CST MWS, was used in the design process. The simulated maximum electric field component perpendicular to the ceramic for the new RF window is reduced by an order of magnitude compared with taht for the conventional RF window, which holds promise for stable high-power operation.
Development of new S-band RF window for stable high-power operation in linear accelerator RF system
Joo, Youngdo,Lee, Byung-Joon,Kim, Seung-Hwan,Kong, Hyung-Sup,Hwang, Woonha,Roh, Sungjoo,Ryu, Jiwan Elsevier 2017 Nuclear instruments & methods in physics research. Vol.866 No.-
<P><B>Abstract</B></P> <P>For stable high-power operation, a new RF window is developed in the S-band linear accelerator (Linac) RF systems of the Pohang Light Source-II (PLS-II) and the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL). The new RF window is designed to mitigate the strength of the electric field at the ceramic disk and also at the waveguide-cavity coupling structure of the conventional RF window. By replacing the pill-box type cavity in the conventional RF window with an overmoded cavity, the electric field component perpendicular to the ceramic disk that caused most of the multipacting breakdowns in the ceramic disk was reduced by an order of magnitude. The reduced electric field at the ceramic disk eliminated the Ti–N coating process on the ceramic surface in the fabrication procedure of the new RF window, preventing the incomplete coating from spoiling the RF transmission and lowering the fabrication cost. The overmoded cavity was coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the waveguide-cavity coupling structure and the possibility of mode competitions in the overmoded cavity. A prototype of the new RF window was fabricated and fully tested with the Klystron peak input power, pulse duration and pulse repetition rate of 75 MW, 4.5 μ s and 10 Hz, respectively, at the high-power test stand. The first mass-produced new RF window installed in the PLS-II Linac is running in normal operation mode. No fault is reported to date. Plans are being made to install the new RF window to all S-band accelerator RF modules of the PLS-II and PAL-XFEL Linacs. This new RF window may be applied to the output windows of S-band power sources like Klystron as wells as the waveguide windows of accelerator facilities which operate in S-band.</P>
Youngdo Joo(주영도),Changbum Kim(김창범),Ilmoon Hwang(황일문),Chongdo Park(박종도) 한국진공학회(ASCT) 2011 Applied Science and Convergence Technology Vol.20 No.1
포항광가속기의 섹터 진공용기에 부착된 빔위치측정기의 수직방향 위치 읽음 값이 갑자기 변하는 오류가 관찰되었다. 이 오류의 원인을 알기 위해서 섹터 진공용기의 양 끝단에 있는 빔위치측정기의 전극을 통한 고주파전달 산란계수를 측정하였다. 급한 변화를 보이는 섹터 진공용기에서는 측정한 산란계수의 첨단 값이 빔위치측정기의 작동 주파수 내에 존재함을 확인하였고, 전산시늉을 통해 빔위치측정기의 작동 주파수내 첨단 주파수가 가로 전장 모드의 공진모드와 일치함을 확인하였다. A sudden step change is observed in the vertical position readings from beam position monitors (BPMs) mounted at the several sector vacuum chambers of Pohang Light Source. To study the source of this sudden step change, we measured the RF transmission scattering matrix (S₂₁) through the pickup electrodes of BPMs mounted at the both ends of the sector vacuum chamber. The measured S₂₁ graph of the sector vacuum chambers suffering sudden step change has a peak in the BPM operation frequency bandwidth. Otherwise that of the other sector vacuum chambers doesn’t have a peak. It is shown by the numerical simulation that the peak found in the BPM operation frequency bandwidth corresponds to the longitudinal harmonic of transverse electric resonance mode.
Meta-analysis identifies a <i>MECOM</i> gene as a novel predisposing factor of osteoporotic fracture
Hwang, Joo-Yeon,Lee, Seung Hun,Go, Min Jin,Kim, Beom-Jun,Kou, Ikuyo,Ikegawa, Shiro,Guo, Yan,Deng, Hong-Wen,Raychaudhuri, Soumya,Kim, Young Jin,Oh, Ji Hee,Kim, Youngdoe,Moon, Sanghoon,Kim, Dong-Joon,Ko BMJ Publishing Group Ltd 2013 Journal of medical genetics Vol.50 No.4
<P><B>Background</B></P><P>Osteoporotic fracture (OF) as a clinical endpoint is a major complication of osteoporosis. To screen for OF susceptibility genes, we performed a genome-wide association study and carried out de novo replication analysis of an East Asian population.</P><P><B>Methods</B></P><P>Association was tested using a logistic regression analysis. A meta-analysis was performed on the combined results using effect size and standard errors estimated for each study.</P><P><B>Results</B></P><P>In a combined meta-analysis of a discovery cohort (288 cases and 1139 controls), three hospital based sets in replication stage I (462 cases and 1745 controls), and an independent ethnic group in replication stage II (369 cases and 560 for controls), we identified a new locus associated with OF (<I>rs784288</I> in the <I>MECOM</I> gene) that showed genome-wide significance (p=3.59×10<SUP>−8</SUP>; OR 1.39). RNA interference revealed that a <I>MECOM</I> knockdown suppresses osteoclastogenesis.</P><P><B>Conclusions</B></P><P>Our findings provide new insights into the genetic architecture underlying OF in East Asians.</P>
안영도(Youngdo Ahn),한상욱(Sangwook Han),이성주(Sung Joo Lee),신종원(Jong Won Shin) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.11
최근 self-supervised learning 모델의 출력을 입력 특징으로 활용해서 음성인식, 화자인식, 음성감정인식에 높은 성능을 향상을 보인 바 있다. 본 논문은 한국어 음성감정인식 데이터셋에 대해 self-supervised learning 모델로써 wav2vec 특징을 기존의 음향적 특징을 비교한다. 한국어 음성감정인식 데이터셋 Korean Emotion Speech Dataset에서 제공하는 성별, 화자, 문장, 감정 라벨을 활용하여 t-SNE에 두 가지 특징을 살펴본다. 두 가지 특징에 대해 support vector machine 및 multi-layer perceptron 모델로 감정인식 성능 weighted average(WA)와 unweighted accuracy(UA)를 비교하였을 때, 두 모델에 대해 wav2vec 특징이 더 높은 음성감정인식 성능을 보여주었다.
분자운동론에 의한 Met-enkephalin의 모의 가열냉각구조
원영도,주충열,최윤수 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-
생명현상을 조절하는 신경전달체나 호르몬의 대부분은 수백개 정도의 원자를 포함하는 중간 크기의 분자이다. 생체내에서 이들 분자의 작용구조를 결정하는데 따르는 여러가지 어려움을 극복하기 위하여 이론적 접근방법인 모의 가열냉각실험이 시도되었다. 모의 가열냉각실험에서는 Monte Carlo법 또는 분자운동론법을 채택할수 있다. 본 연구에서 Met - enkephalin을 대상으로 분자운동론 모의 실험을 수행하여 이를 모의 가열냉각에 채택하는 것에 대한 실효성을 조사하였다. 분자운동론 모의실험결과 생성되는 궤적이 방대한 상태공간을 거치게 되므로 분자 형태 분류방법을 향상시킬 필요가 있다. Neurotransmitters and hormones are mid - size molecules of hundreds of atoms and control life phenomena. In order to overcome difficulties in determing the active conformation of these molecules in vivo, we have tried a simulated annealing procedure. One can employ either molecular dynamics or Monte Carlo technique for simulated annealing. We carried out molecular dynamics based annealing simulation with a molecular model of Met - enkephalin and evaluate the feasibility of using molecular dynamics simulation techniques in the simulated annealing procedure. We find that it is necessary to devise a refined classification for molecular conformations to deal with trajectories on the vast phase space.