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- 저자 : Cho Woojin (검색결과 195 건)
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Woojin Cho,Jason T. Le,Adam L. Shimer,Brian C. Werner,John A. Glaser,Francis H. Shen 대한정형외과학회 2022 Clinics in Orthopedic Surgery Vol.14 No.1
Background: The use of translaminar screws may serve as a viable salvage method for complicated cases. To our understanding, the study of the feasibility of translaminar screw insertion in the actual entire subaxial cervical spine has not been carried out yet. The purpose of this study was to report the feasibility of translaminar screw insertion in the entire subaxial cervical spine. Methods: Eighteen cadaveric spines were harvested from C3 to C7 and 1-mm computed tomography (CT) scans and three-dimensional reconstructions were created to exclude any bony anomaly. Thirty anatomically intact segments were collected (C3, 2; C4, 3; C5, 3; C6, 8; and C7, 14), and randomly arranged. Twenty-one segments were physically separated at each vertebral level (group S), while 9 segments were not separated from the vertebral column and left in situ (group N–S). CT measurement of lamina thickness was done for both group S and group N–S, and manual measurement of various length and angle was done for group S only. Using the trajectory proposed by the previous studies, translaminar screws were placed at each level. Screw diameter was the same or 0.5 mm larger than the proposed diameter based on CT measurement. Post-insertion CT was performed. Cortical breakage was checked either visually or by CT. Results: When 1° and 2° screws of the same size were used, medial cortex breakage was found 13% and 33% of the time, respectively. C7 was relatively safer than the other levels. With larger-sized screws, medial cortex breakage was found in 47% and 46% of 1° and 2° screws, respectively. There were no facet injuries due to the screws in group N–S. Conclusions: Translaminar screw insertion in the subaxial cervical spine is feasible only when the lamina is thick enough to avoid any breakage that could lead to further complications. The authors do not recommend inserting translaminar screws in the subaxial cervical spine except in some salvage cases in the presence of a thick lamina.
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Cho Woojin,Wang Wenhai,Lim Hyun Jin,Bucklen Brandon S. 대한척추외과학회 2023 Asian Spine Journal Vol.17 No.1
Study Design: Cadaveric biomechanics study.Purpose: This study investigated the effects of unilateral sacroiliac joint (SIJ) fixation for fusion with/without L5–S1 fixation on contralateral SIJ range of motion (ROM).Overview of Literature: SIJ fusion raises concerns that unilateral SIJ stabilization for fusion may increase contralateral SIJ mobility, leading to accelerated SIJ degeneration. Also, prior lumbosacral fixation may lead to accelerated SIJ degeneration, due to adjacent level effects. SIJ fixation biomechanics have been evaluated, showing a reduced-ROM, but SIJ fixation effects on contralateral nonfixated SIJ remain unknown.Methods: Seven human lumbopelvic spines were used, each affixed to six-degrees-of-freedom testing apparatus; 8.5-Nm pure unconstrained bending moments applied in flexion-extension, lateral bending, and axial rotation. The ROM of left and right SIJ was measured using a motion analysis system. Each specimen tested as (1) intact, (2) injury (left), (3) L5–S1 fixation, (4) unilateral stabilization (left), (5) unilateral stabilization+L5–S1 fixation, (6) bilateral stabilization, and (7) bilateral stabilization+L5–S1 fixation. Both left-sided iliosacral and posterior ligaments were cut for injury condition to model SIJ instability before surgery.Results: There were no statistical differences between fixated and contralateral nonfixated SIJ ROM following unilateral stabilization with/without L5–S1 fixation for all loading directions (<i>p</i>>0.930). Injured condition and L5–S1 fixation provided the largest motion increases across both joints; no significant differences were recorded between SIJs in any loading direction (<i>p</i>>0.850). Unilateral and bilateral stabilization with/without L5–S1 fixation reduced ROM compared with the injured condition for both SIJs, with bilateral stabilization providing maximum stability.Conclusions: In the cadaveric model, unilateral SIJ stabilization with/without lumbosacral fixation did not lead to significant contralateral SIJ hypermobility; long-term changes and <i>in vivo</i> response may differ.
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Woojin Cho,Mark J. Sokolowski,Amir A. Mehbod,Francis Denis,Timothy A. Garvey,John Perl,Ensor E. Transfeldt 대한정형외과학회 2013 Clinics in Orthopedic Surgery Vol.5 No.1
Background: Anterior interbody fusion has previously been demonstrated to increase neuroforaminal height in a cadaveric model using cages. No prior study has prospectively assessed the relative change in magnetic resonance imaging (MRI) demonstrated neuroforaminal dimensions at the index and supradjacent levels, after anterior interbody fusion with a corticocancellous allograft in a series of patients without posterior decompression. The objective of this study was to determine how much foraminal dimension can be increased with indirect foraminal decompression alone via anterior interbody fusion, and to determine the effect of anterior lumbar interbody fusion on the dimensions of the supradjacent neuroforamina. Methods: A prospective study comparing pre- and postoperative neuroforaminal dimensions on MRI scan among 26 consecutive patients undergoing anterior lumbar interbody fusion without posterior decompression was performed. We studies 26 consecutive patients (50 index levels) that had undergone anterior interbody fusion followed by posterior pedicle screw fixation without distraction or foraminotomy. We used preoperative and postoperative MRI imaging to assess the foraminal dimensions at each operated level on which the lumbar spine had been operated. The relative indirect foraminal decompression achieved was calculated. The foraminal dimension of the 26 supradjacent untreated levels was measured pre- and postoperatively to serve as a control and to determine any effects after anterior interbody fusion. Results: In this study, 8 patients underwent 1 level fusion (L5-S1), 12 patients had 2 levels (L4-S1) and 6 patients had 3 levels (L3-S1). The average increase in foraminal dimension was 43.3% (p < 0.05)−19.2% for L3-4, 57.1% for L4-5, and 40.1% for L5-S1. Mean pre- and postoperative supradjacent neuroforaminal dimension measurements were 125.84 mm2 and 124.89 mm2, respectively. No significant difference was noted (p > 0.05). Conclusions: Anterior interbody fusion with a coriticocancellous allograft can significantly increase neuroforaminal dimension even in the absence of formal posterior distraction or foraminotomy; anterior interbody fusion with a coriticocancellous allograft has little effect on supradjacent neuroforaminal dimensions.
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조우진(Woojin Cho),강동수(Dongsu Kang) 한국정보과학회 2021 정보과학회 컴퓨팅의 실제 논문지 Vol.27 No.10
해양시정은 항공기 이착륙, 항해, 해양레저 활동에 직접적인 영향을 미친다. 본 연구는 시정을 예측하기 위해 머신러닝 방법인 LSTM(Long Short-Term Memory)를 이용한다. 기상 데이터는 2012년부터 2017년까지 서해 덕적도의 군사 분야와 민간 분야 기상 데이터를 수집하여 전처리한다. 전체 6년의 기간 중 5년은 LSTM 모델에 학습시키고, 남은 1년은 검증 데이터로 사용한다. 그리고, 기존 예측에서 사용하였던 인자인 시정, 풍속, 기압, 습도, 기온 인자에 해수면온도와 해기차를 추가하여 성능 차이를 비교한다. 실험 결과는 실제값과 예측값의 차이가 수치적으로 적은 값을 보인다. Sea visibility directly affects aircraft takeoff and landing, navigation, and marine leisure activities. In this paper, we used the Long Short-Term Memory (LSTM) of machine learning method to predict sea visibility. We collected and then preprocessed the weather data of the Deokjeok Island in the West Sea from 2012 to 2017 in the military and civilian sectors. The LSTM model was trained for five years of the entire six-year period, and the remaining one year was used as verification data. We compared performance differences by adding sea surface temperature and air-sea temperature difference to factors used in existing predictions such as visibility, wind speed, atmospheric pressure, humidity, and temperature. The experimental results showed that the difference between the actual and predicted values was numerically small.
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소형 가스엔진 열병합발전의 운전거동 예측을 위한 컴퓨터 시뮬레이션
조우진(Woojin Cho),이관수(Kwan-Soo Lee),김인규(In-Kyu Kim) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.12
The present study developed a computer simulation program to determine the optimum strategy and capacity of a micro combined heat and power(CHP) system. This simulation program considered a part-load electrical/thermal efficiency and transient response characteristics of CHP unit. The result obtained from the simulation was compared with the actual operation of 30 ㎾ gas engine driven micro CHP system. It was found that the simulation could reproduce the daily operation behavior, such as operating hours and mean load factor, closely to the actual behavior of the system and could predict the amount of electrical/thermal output and fuel consumption with the error of less than 12%.
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사전학습 언어모델 기반의 한국어 질문-답변 데이터 증강 방법
조우진(Woojin Cho),이혁준(Hyukjoon Lee) 한국정보과학회 2021 정보과학회 컴퓨팅의 실제 논문지 Vol.27 No.12
자연어처리는 최근 인공지능이 각광을 받으며 비약적인 발전을 이루고 있다. 자연어처리의 여러 문제 중 질문-답변은 인공지능이 문단 내에서 질문에 맞는 답을 찾아주는 문제다. 인공지능 문제에서 우수한 성능을 달성하기 위해서는 인공지능 모델과 학습 데이터셋의 확보가 매우 중요하다. 특히 질문-답변 데이터셋은 질문-답변의 문법, 관계 등 인간의 직접적 개입이 많이 요구되어 데이터 구축이 쉽지 않다. 이런 문제점을 해결하기 위해 본 논문에서는 답변 생성, 질문 생성, 필터링의 3 단계로 구성된 질문-답변 데이터 증강 방법을 제안한다. 증강된 데이터를 이용하여 학습시킨 모델의 질의응답 성능이 KorQuAD 데이터만으로 학습시킨 모델에 비해 F1-score 기준 최대 1.13 증가한 결과를 얻을 수 있음을 실험을 통해 보인다. Natural language processing (NLP) has recently made rapid progress with artificial intelligence (AI) in the spotlight. Among the many problems of NLP, question-answer (QA) is a problem in which an AI algorithm finds the right answer to the question within a paragraph. Securing artificial intelligence models and training data are utmost important to achieve good performance of AI. In particular, QA data requires a lot of direct human intervention due to grammars and relationships between questions and answers, making it difficult to obtain a data set. To solve this problem, this paper proposes a QA data augmentation method consisting of four steps: answer generation, question generation, round-trip filter technique, and verification. Experiment results shows that the QA performance of the model trained using the augmented data could achieve up to 1.13-fold increase in terms of F1-score compared to the model learned by using KorQuAD data only.
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