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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.
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.
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.
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.
정신분열병환자에 있어서 식후에 관찰되는 비정형 항정신병약물과 관련된 음식 갈망 회로 : 기능적 자기공명영상 연구
정범석(Bum Seok Jeong),이창화(Chang Hwa Lee),홍성균(Sung Kyoon Hong),최지욱(Jee Wook Choi),김지웅(Ji-Woong Kim),이선우(Sun Woo Lee) 대한생물치료정신의학회 2006 생물치료정신의학 Vol.12 No.2
목적 : 음식을 충분히 섭취한 정신분열병 환자에서 비정형 항정신병 약물 관련 음식 갈망 뇌 구조물 탐색. 방법 : 배고픔을 배제한 음식에 대한 갈망만의 뇌회로를 탐색하기 위해 음식을 충분히 섭취한 상태에서 음식물과 무생물 사진을 비정형 항정신병 약물을 복용 중인 정신분열병 집단 및 정상 대조 집단에게 수동적으로 보여주면서 기능적 뇌영상을 촬영하였다. 자극 파라다임은 24초짜리 세 블록으로 구성된 음식물 혹은 무생물 사진들로 구성된 블록 디자인을 사용하였다. 집단 별음식 갈망 관련 뇌 회로, 두 집단 간 음식 갈망 관련 뇌 활성도 차이, 뇌 활성도와 임상 변인과의 상관관계를 SPM2를 이용하여 분석하였다. 결과 : 식후에 촬영한 기능적 자기공명 영상 연구 결과 정신분열병 집단이 비정형 항정신병 약물을 복용함에도 불구하고 음식물 자극 및 음식 갈망 관련 회로의 활성도가 상대적으로 저조하였다. 시상 및 시상 하부의 활성도는 현재 약물의 복용 기간과 유의미한 역상관관계를 보였다. 결론 : 체중 혹은 음식 갈망을 증가시킨다고 알려진 비정형 항정신병 약물을 복용하더라도 음식을 충분히 섭취할 경우 음식 갈망 관련 뇌 활성도가 정상 대조 집단에 비해 증가하지 않으며, 항정신병 약물 관련 체중 증가 혹은 입맛 당김 현상이 지속적으로 약물을 복용에 따라 감소하게 되는 현상이 시상하부의 활성의 점차적 감소와 관련 있음을 시사한다. Objectives:To explore the neural correlates of antipsychotics related food craving in schizophrenic patients Methods:A T2<SUP>*</SUP>-weighted echoplanar imaging sequences obtained were used to collect 120 BOLD images during the passive seeing of food paradigm after meal. The food paradigm was consisted of three blocks of food pictures and three blocks of pictures of natural thing in both ten healthy volunteers and schizophrenic patients having second generation antipsychotics. The imaging data were investigated to find differences in the food cue and craving related network between healthy volunteers and schizophrenic patients after meal. The relationship between food cue or craving related neural activity and clinical variable was explored. Activation maps were acquired by means of the random effect model using SPM2. Results:Less extensive food cue and craving related regions were activated in schizophrenic patients having second generation antipsychotics after meal. Neural activities of both hypothalamus and thalamus were correlated with the prescribed duration of current antipsychotics. Conclusions:This study demonstrated that schizophrenic patients' brain is less respond to food cue after meal even though they are having second generation antipsychotics. The decrease of hypothalamic activity could explain the plateau phenomenon or decrease of both food craving and body weight according to persistent second generation antipsychotic medication.