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G.729 코덱의 패킷 손실 영향 모델을 이용한 비 침입적 음질 예측 기법
이민기,강홍구,Lee, Min-Ki,Kang, Hong-Goo 한국음향학회 2013 韓國音響學會誌 Vol.32 No.2
본 논문은 패킷 손실의 영향을 이용한 비 침입적 음질 평가 방법을 제안한다. 패킷 손실은 패킷 기반의 통신 시스템에서 음질을 저하시키는 주된 요소이며 그 영향은 코덱에 내장된 패킷 손실 은닉 알고리듬에 의해 결정된다. 패킷 손실 영향을 반영한 음질평가 시스템을 위해 VoIP 에서 협대역 코덱으로 사용되는 코덱 중 하나인 G.729를 선택하였으며, 음성 특징에 따른 패킷 손실 영향을 구분하기 위해서 G.729 코덱의 음성 파라미터를 이용한 한 음성 특성 분류기를 설계하였다. 이후, 각각의 패킷 특성에 따른 음질 저하의 정도를 수치화하기 위해 원 PESQ-LQ점수와 상관계수를 최대화하는 음질 저하 가중치를 반복적으로 구하였으며, 최종 음질 저하는 가중합으로 구하였다. 그 결과 제안한 모델과 PESQ-LQ의 상관계수는 칩입 모델 에서는 0.8950를, 비 침입 모델 에서는 0.8911의 결과를 나타내었다. This paper proposes a non-intrusive speech quality estimation method considering the effects of packet loss to perceptual quality. Packet loss is a major reason of quality degradation in a packet based speech communications network, whose effects are different according to the input speech characteristics or the performance of the embedded packet loss concealment (PLC) algorithm. For the quality estimation system that involves packet loss effects, we first observe the packet loss of G.729 codec which is one of narrowband codec in VoIP system. In order to quantify the lost packet affects, we design a classification algorithm only using speech parameters of G.729 decoder. Then, the degradation values of each class are iteratively selected that maximizes the correlation with the degradation PESQ-LQ scores, and total quality degradation is modeled by the weighted sum. From analyzing the correlation measures, we obtained correlation values of 0.8950 for the intrusive model and 0.8911 for the non-intrusive method.
이민기,박근우,Lee, Min-Ki,Park, Kun-Woo 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.1
The determination of the direct kinematics of the parallel mechanism is a difficult problem but has to be solved for any practical use. This paper presents the efficient formulation of the direct kinematics for double parallel robot arm. The robot arm consists of two parallel mechanism, which generate positional and orientational motions, respectively. These motions are decoupled by a passive central axis which is composed of four revolute joints and one prismatic joint. For a set of given lengths of linear actuators, the direct kinematics will find the joint displacements of th central axis from geometric constraints in each parallel mechanism. Then the joint displacements will be converted into the position and the orientation of the end effector of the robot arm. The proposed formulation is decoupled and compacted so that it will be implemented as a real-time direct kinematics. With the proposed formulation, we analyze the motion of the double parallel robot and show its characteristics. Specially, we investigate the workspace in terms of positional space as well as orientational space.
이민기,김태성,박근우,Lee, Min-Ki,Kim, Tae-Sung,Park, Kun-Woo 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11
This research develops a low-cost and high accuracy kinematic calibration method based on the following principles: 1) the platform locations are accurately measured by a constrained movement to inspect a calibration target; 2) the constrained movement is chosen to guarantee the parameter observability; 3) the mechanical fixture to constrain the movement and the sensor to check the constrained movement are implemented by low-cost and high-accuracy devices; 4) the calibration is easily done at an industrial environment. The kinematic parameters calibrated with respect to a single plane aren't influenced due to the misalignment of the plane. A parameter observability is successfully obtained even through one planar constraint, which guarantees that all kinematic parameters are estimated by minimizing the cost function.
소셜 네트워킹을 위한 감성-기반 인터페이스의 설계 및 구현
이민기 ( Min-ki Lee ),이기영 ( Ki-young Lee ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.2
최근 세계적으로 소셜 네트워킹에 대한 관심과 스마트폰의 기술이 발전함에 따라 사용자를 위한 다양한 인터페이스가 요구되고 있다. 항상 사용자의 손이 닿는 곳, 바로 옆에 위치한 모바일 단말기에서 다양한 센서를 집약하여 감정을 인식하고 인식된 정보와 위치 정보를 결합하여 세계적으로 관심이 높은 소셜 네트워킹의 인터페이스를 설계하고 구현하였다.
〈학술논문 or 기술논문〉 Swing Arm 기구를 이용한 대형 구면 렌즈의 프로파일 측정에 관한 연구
이민기(Lee Min Ki),이응석(Lee Eung Suk),이종근(Lee Jong Gun) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Most precise large optics are manufactured by grinding, lapping and polishing process. Especially, profile of large optics decided for lapping process. Polishing process used to purposes to raise intensity of surface illumination. Like this evaluate the large optics parts which was produced in this way, and to measure is very difficult. A lot of effort and time will be consumed at polishing process if they will modify optical parts. As size is large size, it shall process similar a profile of a lens to a maximum design price at steps made up step by step lapping process before polishing processing. Generally, a profile of a lens divides it in contact formula way and non contact formula ways. But, the contact formula way the face of a lens can generate a scratch. Face measurement of the lens which used interferometer represented in non contact formula ways is difficult for measuring it if face reflectivity is low. To measure the face of a large spherical lens before polishing process at these papers as use swing a method and a laser for measurement knowing have a purpose.