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하모닉 코더를 위한 직선과 이산코사인변환 (DCT)을 이용한 하모닉 크기값 (Magnitude) 양자화 기법
최지욱,정규혁,이인성,Choi, Ji-Wook,Jeong, Gyu-Hyeok,Lee, In-Sung 한국음향학회 2008 韓國音響學會誌 Vol.27 No.4
본 논문은 음성신호의 주파수를 반으로 나누어 양자화 계수 추출에 직선과 DCT (Discrete Cosine Transform)를 혼합하여 사용한 양자화 기법을 제안한다. 하모닉 부호화기에서의 하모닉은 가변이므로 저주파에서의 하모닉만을 오버샘플링하여 차원을 고정한다. 고정된 차원의 스펙트럼 포락선을 직선으로 표현한 후 직선이 불연속인 주파수에서의 샘플값만을 전송한다. 이 논문에서는 저주파에서의 하모닉은 복원을 위해 고정된 직선의 계수를 사용하였고 고주파에서의 하모닉은 가변 DCT를 적용하여 직선과 DCT가 격합된 형태의 양자화기법을 제안한다. 제안된 양자화 기법의 성능평가는 스펙트럴의 크기값에 대한 Spectral Distortion (SD)값을 사용하였다. 실험결과 HVXC보다 제안된 양자화 기법의 SD가 0.3dB 정도 개선되었다. This paper presents a method of quantization to extract quantization parameters using the straight-line and DCT (Discrete Cosine Transform) for two splited frequency bands. As the number of harmonic is variable frame to frame, harmonics in low frequency band is oversampled to fix the dimension and straight-lines present a spectral envelope, then the discontinuous points of straight-lines in low frequency is sent to quantizer. Thus, extraction of quantization parameters using the straight-line provides a fixed dimension. Harmonics in high frequency use variable DCT to obtain quantization parameters and this paper proposes a method of quantization combining the straight-line with DCT. The measurement (If proposed method of quantization uses spectral distortion (SD) for spectral magnitudes. As a result, The proposed method of quantization improved 0.3dB in term of SD better than HVXC.
MSVQ(Multi-Stage Vector Quantization)를 이용한 임베디드 구조의 양자화
최지욱(Choi Ji Wook),정규혁(Jeong Gyu Hyeok),이인성(Lee In Sung) 대한전자공학회 2006 대한전자공학회 학술대회 Vol.2006 No.11
본 논문은 MSVQ를 이용한 임베디드 구조의 양자화기를 제안한다. 하모닉 주파수에서의 magnitude와 비하모닉 주파수에서의 magnitude를 각각 multi-stage 구조로 양자화한다. 이와 같은 구조는 하모닉 주파수에서의 magnitude와 비하모닉주파수에서의 magnitude 가 섞여있는 magnitude를 양자화하는 구조보다 코드북이 나뉘어 있어서 전송률이 낮은 경우에는 하모닉 주파수에서의 magnitude만을 양자화하는 코드북을 전송하는 구조로 사용할 수 있다. 또한 전송률이 높을때 는 비하모닉 주파수에서의 magnitude도 양자화하기 위한 코드북을 전송하는 것으로써 임베디드 구조의 정현파 양자화기를 제안한다. 이는 하모닉과 비하모닉 주파수에서의 magnitude를 두개의 양자화기를 이용하여 각각 양자화한 결과가 하모닉과 비하모닉 주파수에서의 magnitude를 함께 하나의 양자화기로 양자화 한 결과의 성능차가 많이 나지 않는다는 가정하에서다. 제안된 양자화 기법의 성능평가는 스펙트럴 크기 값에 대한 주파수 왜곡(SD:Spectral Distortion)값을 사용하였다.
항혈소판제 복용 환자의 구강 내 소수술 전 처치에 대한 제안
최지욱(Ji-wook Choi),최세경(Se-Kyung Choi),김남균(Nam-kyun Kim),최의영(Eui young Choi),차인호(In-Ho Cha),김형준(Hyung Jun Kim) 대한구강악안면외과학회 2009 대한구강악안면외과학회지 Vol.35 No.6
Purpose: Many patients in anti-platelet therapy have been consulted for bleeding risks before minor oral surgery. However, there has not been an established pretreatment protocol for treating these patients. The purpose of this study is to make a protocol for the preoperative management for patients in anti-platelet therapy. Patients and Methods: The existed consultation pattern of patients was examined in the Department of Oral and Maxillofacial Surgery, Yonsei Dental Hospital. Based on the observation, a protocol including classification of medical status of patients and the type of oral surgery in need was introduced. This protocol had been performed for 6 months. Result: Following this protocol, the frequency of consultation for bleeding risk was decreased. The number of minor oral surgeries with concurrent anti-platelet therapy was increased. There was no severe bleeding event observed among minor oral surgeries that were performed while maintaining anti-platelet therapy. Conclusion: This protocol can be used as a guideline for clinical practice of patients in anti-platelet therapy requiring minor oral surgery.
혼합치열기의 함치성 낭종 치료 시 영구치의 맹출과 자가치아이식
최지욱(Ji-wook Choi),최종명(Jong-Myung Choi),차인호(In-ho Cha),김형준(Hyung Jun Kim) 대한구강악안면외과학회 2009 대한구강악안면외과학회지 Vol.35 No.6
Purpose: Dentigerous cyst is the most common intra-osseous lesion of the jaw. Dentigerous cysts can cause delays in eruption of the affected permanent tooth in mixed dentition. It has been suggested that the affected permanent tooth could be erupted spontaneously after the dentigerous cyst was enucleated. But in some cases, orthodontic treatment or autotransplantation technique is known to be required. This study reviews previously performed prognoses of affected permanent teeth, which will lead to a more efficient treatment plan. Patients and Methods: With 28 patients who have undergone cyst enucleation and 10 patients who have undergone autotransplantation, the prognosis of permanent teeth was observed. Results: After cyst enucleation, spontaneous eruption of a permanent tooth was observed in 56.3% patients, orthodontic treatment was performed in 25% patients. The success rate of autotransplantation was 60.0 %. Discussion: The first choice for treatment of dentigerous cyst in mixed dentition is to guide spontaneous eruption of permanent teeth. For cases without enough eruption space, the orthodontic treatment should be considered. Autotransplantation should be considered when the spontaneous eruption is not expected. It should be considered that the rate of successful autotransplantation is decreased on maxilla anterior area.
최지욱(Ji-Wook Choi),황도경(Do-Kyung Hwang),안종우(Jong-Woo An),이장명(Jang-Myung Lee) 대한전자공학회 2019 전자공학회논문지 Vol.56 No.5
무인항공기가 모니터링과 같은 임무를 수행하기 위해서는 이륙, 착륙 및 비행 시 안정된 자세를 유지 하여야 된다. 기존의 드론은 비행 중 일 때, 이륙 지점으로 자동으로 돌아와 착륙하는 Return To Home 기능을 사용하는데, 이러한 방법은 GPS를 사용하여 착륙을 진행하기 때문에 정확한 지점에 착륙하기 어렵다는 단점을 가지고 있다. 본 논문에서는 쿼드로터형 무인 비행체에 비전 센서를 부착하여 착륙 지점을 인식하여 자동 착륙하는 알고리즘을 제안한다. 착륙 지점을 인식할 때 영상 입력을 사용하여 CNN(Convolutional Neural Network) 기반의 알고리즘을 사용하여 착륙 지점에 외란이 발생하거나 객체 인식 오류가 발생하는 것을 줄였으며, 비전 데이터를 이용하여 착륙 지점의 좌표를 계산하고, 착륙 지점에 정확하게 자동으로 랜딩을 수행하는 제어 기법에 대하여 다루었다. 알고리즘의 유효성을 입증하기 위하여 기존의 방식인 Return To Home 기능을 사용한 랜딩과, 제안하는 알고리즘을 적용한 랜딩의 GPS 데이터를 실험을 통해 비교하여 검증하였다. Unmanned aircraft must be in a stable position during takeoff, landing and flight to perform tasks such as monitoring. Existing drones use the Return To Home function, which automatically returns to the take-off point and landing when in flight. This method has the disadvantage that it is difficult to land at the correct point because the landing takes place using GPS. In this paper, we propose an algorithm that recognizes the landing point by attaching the vision sensor to the quadrotor type unmanned aerial vehicle and automatically landing. Using the CNN (Convolutional Neural Network) based algorithm, it is possible to reduce the occurrence of disturbance or object recognition error at the landing point, using the vision data to calculate the coordinates of the landing point and to control the landing precisely at the point. In order to verify the validity of the algorithm, the landing using the Return to Home function and the GPS data of the landing using the proposed algorithm were compared and verified by experiments.
김재영,최지욱,김남균,태일호,김성택,김형준,차인호,남웅,Kim, Jae-Young,Choi, Ji-Wook,Kim, Nam-Kyun,Tae, Il-Ho,Kim, Seong-Taek,Kim, Hyung-Jun,Cha, In-Ho,Nam, Woong 대한악안면성형재건외과학회 2009 Maxillofacial Plastic Reconstructive Surgery Vol.31 No.2
Eagle's syndrome refers to a symptomatic elongation of the styloid process or calcification of the stylohyoid and stylomandibular ligaments that usually accompanies facial and pharyngeal pain, dysphagia, and foreign-body sensation in the throat. Making an accurate diagnosis is difficult as Eagle's syndrome can be accompanied with referred pain to various areas of head and neck. Treatment options for Eagle's syndrome include non-surgical and surgical methods. The surest and the most effective method for relieving the symptom is surgical removal or reduction of the elongated styloid process. The present study reports two cases of female whom were diagnosed as "Eagle's syndrome" and whose chief complain was foreign-body sensation and pain in the throat on movement. Surgical removal via transoral approach of the elongated styloid process is a safe surgical option with favorable results compared to extraoral approach.
천동훈(Dong-Hun Cheon),이재욱(Jae-Wook Lee),우성현(Seong-Hyeon Woo),최지욱(Ji-Wook Choi),강호선(Ho-Sun Kang),이장명(Jang-Myung Lee) 제어로봇시스템학회 2021 제어·로봇·시스템학회 논문지 Vol.27 No.3
In this paper, we propose an adaptive four-leg landing system for a quadcopter to enable stable landing on inclined surfaces or rough terrain while maintaining its attitude. A rotorcraft has a disadvantage in that it must have a flat ground for landing because the existing landing gear system is fixed and cannot be changed according to ground conditions. The proposed adaptive landing system makes it possible for a quadcopter to operate in various environments with minimal sensors. For this purpose, a four-leg landing system with two degrees of freedom having a two-link structure was manufactured. Through kinematic analysis of the landing leg, the coordinates of the joint and end-effector were identified, and an equation for horizontal control was established. When landing on the slope, the ground surface was detected using force sensors, attached at the end of each leg. Adaptive landing control was performed according to the roll and pitch values of the inertial measurement unit sensor mounted on the quadcopter. The proposed system was pre-validated in the simulation environment of Matlab Simulink. The superiority of the proposed system was verified experimentally in various environments. In an indoor environment, the effectiveness of the system was verified in a situation where it landed at a constant speed using a testbed. Finally, the system stability was verified through flying and landing of the quadcopter in an outdoor environment.
즐례 : 면역억제제 치료에 각 장기간 다른 반응을 보인 현미경 다발혈관염 1예
이재준 ( Jae Joon Lee ),신종호 ( Jong Ho Shin ),방기태 ( Ki Tae Bang ),최지욱 ( Ji Wook Choi ),문현진 ( Hyun Jin Moon ),전재웅 ( Jae Woong Jeon ),정진욱 ( Jin Uk Jeong ) 대한내과학회 2014 대한내과학회지 Vol.86 No.1
Microscopic polyangiitis (MPA) is an idiopathic autoimmune disease characterized by systemic vasculitis associated with antineutrophil cytoplasmic autoantibodies. Interstitial lung disease is a less recognized manifestation of MPA and has a poor prognosis. A 61-year-old man presented with persistent cough, sputum and dyspnea. Laboratory examination revealed microscopic hematuria and renal insufficiency. Perinuclear anti-neutrophil cytoplasmic autoantibodies were positive according to serological testing. Computed tomography scans showed bibasilar reticulation and honeycombing in a peripheral distribution. Therefore, renal biopsy was performed, and MPA was diagnosed. After treating with corticosteroids and immunosuppressive agents, the patient had a complete renal response but progressive interstitial lung disease. We report a case of MPA presenting with interstitial lung disease in which the patient experienced different responses in each organ. (Korean J Med 2014;86:84-88)