효율적인 비디오 텍스트 추출 및 인식

곽상신(Sangshin Kwak),최영우(Yeongwoo Choi),정규식(Kyusik Chung) 한국통신학회 1999 한국통신학회 학술대회논문집 Vol.1999 No.11

영화 비디오 자막 추출 및 추출된 자막 이미지 향상 방법

김소명(Somyung Kim),곽상신(Sangshin Kwak),최영우(Yeongwoo Choi),정규식(Kyusik Chung) 한국정보과학회 2002 정보과학회논문지 : 소프트웨어 및 응용 Vol.29 No.3·4

디지털 비디오 영상을 효과적으로 색인하고 검색하기 위해서 비디오의 내용을 함축적으로 표현하고 있는 비디오 자막을 추출하여 인식하는 연구가 필요하다. 본 논문에서는 압축되지 않은 비디오 영화 영상에 인위적으로 삽입한 한글 및 영어 자막을 대상으로 자막 영역을 추출하고, 추출된 자막 이미지를 향상시키는 방법을 제안한다. 제안한 방법의 특징은 동일한 내용의 자막을 갖는 프레임들의 위치를 자동으로 찾아서 동일 자막 프레임들을 다중 결합하여 배경에 포함되어 있는 잡영의 일부 또는 전부를 우선 제거한다. 또한, 이 결과 이미지에 해상도 증대, 히스토그램 평활화, 획 기반 이진화, 스무딩의 이미지 향상 방법을 단계적으로 적용하여 인식 가능한 수준의 이미지로 향상시킨다. 제안한 방법을 비디오 영상에 적용하여 동일한 내용의 자막 그룹 단위로 자막 이미지를 추출하는 것이 가능해졌으며, 잡영이 제거되고 복잡한 자소의 획이 보존된 자막 이미지를 추출할 수 있었다. 동일한 내용의 자막 프레임의 시작 및 끝 위치를 파악하는 것은 비디오 영상의 색인과 검색에 유용하게 활용될 수 있다. 한글 및 영어 비디오 영화 자막에 제안한 방법을 적용하여 향상된 문자 인식 결과를 얻었다. For an efficient indexing and retrieval of digital video data, research on video caption extraction and recognition is required. This paper proposes methods for extracting artificial captions from video data and enhancing their image quality for an accurate Hangul and English character recognition. In the proposed methods, we first find locations of beginning and ending frames of the same caption contents and combine those multiple frames in each group by logical operation to remove background noises. During this process an evaluation is performed for detecting the integrated results with different caption images. After the multiple video frames are integrated, four different image enhancement techniques are applied to the image: resolution enhancement, contrast enhancement, stroke-based binarization, and morphological smoothing operations. By applying these operations to the video frames we can even improve the image quality of phonemes with complex strokes. Finding the beginning and ending locations of the frames with the same caption contents can be effectively used for the digital video indexing and browsing. We have tested the proposed methods with the video caption images containing both Hangul and English characters from cinema, and obtained the improved results of the character recognition.

전압원 인버터의 모델 예측 제어에서 스위칭 손실을 줄이기 위한 최적의 제로 벡터 선택 방법

박준철(Jun-Cheol Park),곽상신(Sangshin Kwak) 전력전자학회 2014 전력전자학술대회 논문집 Vol.2014 No.11

Internal State Estimation Method of Film Capacitors used in Three-Phase DC to AC Converters and Comparisons with Electrolytic Capacitors

Hoang-Long Dang,Sangshin Kwak(곽상신) 대한전기학회 2023 전기학회논문지 Vol.72 No.6

Metalized polymer-film capacitors have acquired a distinctive position among a variety of capacitor types due to their self-healing ability. Therefore, these devices are appropriate for critical power applications that demand reliability and durability. Nevertheless, as converters are increasingly being used for transmissions in networks, it is essential to improve stability to ensure the safety of system operations. Therefore, it is necessary to have a monitoring process that enables predictive maintenance to evaluate the health status and ensure the stability of electrical systems. However, the research in this field concentrates on electrolytic capacitors; and the characteristics of electrolytic and film capacitors differ. Hence, the need for further investigation into film capacitors is evident. This research proposes a condition monitoring approach that employs frequency signal analysis to assess the health status of capacitors in a three-phase AC-DC converter. The capacitor current is subjected to discrete wavelet transform and normalized by various indices, which serve as the input for learning algorithms. In addition, for comparison, capacitor voltage, output current, and output voltage are investigated using the discrete wavelet transform and fast Fourier transform. In this study, various indexes including root-mean-squared value, variance, average, and median, are utilized as inputs for artificial intelligent models to investigate factors affecting film capacitors. Eight learning algorithms are implemented to monitor the health status of film capacitors. The results show that utilizing the discrete wavelet transform combined with indexes for capacitor current yields a high accuracy of approximately 99.85%. These findings offer valuable insights into monitoring film capacitors using advanced techniques, and are anticipated to be informative for practical applications of film capacitor monitoring.

데이터 기반 방식과 모델 기반 방식을 이용한 DC/AC 컨버터의 입력 커패시터 ESR 추정 비교 연구

박혜진(Hyejin Park),곽상신(Sangshin Kwak) 대한전기학회 2021 전기학회논문지 Vol.70 No.12

In this paper, the performance of the input capacitor state estimation algorithm of the DC/AC single-phase converter implemented using the model-based method and the data-based method is compared. The state of the capacitor is estimated through two existing algorithms implemented as a model-based method and the data based algorithm implemented as a data-based method. By applying the capacitor voltage and capacitor current data collected through the experiment to three methods, the equivalent series resistor (ESR) component was derived. The two model-based methods used in this paper are the method of estimating the ESR component using a bandpass filter and the method of using the average power loss. The data-based method estimates ESR using a component twice the fundamental frequency and a component twice the switching frequency in the frequency domain as input to the neural network. Comparing the results, it was confirmed that in the case of the model-based method, the deviation of the error according to the ESR was very large. On the other hand, in the case of the data-based method, it was confirmed that the estimation was made more accurately using data of a large amount of information. Therefore, it was confirmed that the data-based method showed excellent estimation results in all fields.

전력 반도체 기반의 고장 전류 제한기

김병준(Byungjun Kim),김남훈(Namhun Kim),곽상신(Sangshin Kwak) 전력전자학회 2017 전력전자학술대회 논문집 Vol.2017 No.7

모델예측제어기법들로 제어되는 3상 AC/DC 컨버터 동작 특성 및 직류 커패시터 상태 관계 분석 연구

김동연(Dongyeon Kim),김재창(Jae-Chang Kim),곽상신(Sangshin Kwak) 대한전기학회 2021 전기학회논문지 Vol.70 No.4

In this paper, six model predictive control techniques developed so far to be used to operate a three-phase active rectifier are classified. In addition, their input and output electrical performance are compared and analyzed. The six model predictive control techniques are largely classified into voltage-based (VOC) and direct power control (DPC) methods. In addition, VOC and DPC are classified into a basic control method and a modified control method divided into a vector selection method and an offset voltage injection method, respectively. The electrical characteristics of the input and the output side of the three-phase active rectifier operated by these six types of model prediction control algorithms are compared. In particular, the change of characteristics according to the variation of capacitance and equivalent series resistor (ESR) of the output DC link capacitor is investigated and analyzed. As a result, it is confirmed that the performance change of the three-phase active rectifier is greater due to the increase in the ESR than the decrease in the capacitance of the output DC link capacitor. In addition, it is confirmed that in both the basic and modified algorithms, the DPC-based model predictive control algorithm shows better performance in both the input current total harmonic distortion (THD) and the output voltage fluctuation in terms of increase of ESR and reduction of capacitance of capacitor than the VOC-based model predictive control technique. In the capacitor loss, the DPC-based control techniques show higher efficiency than the VOC-based control algorithm.

Cascaded H-Bridge 멀티레벨 인버터를 위한 개선된 모델 예측 제어 방법

노찬(Chan Roh),김재창(Jae-Chang Kim),곽상신(Sangshin Kwak) 대한전기학회 2018 전기학회논문지 Vol.67 No.7

In this paper, an improved model predictive control (MPC) method is proposed, which reduces the amount of calculations caused by the increased number of candidate voltage vectors with the increased voltage level in multi-level inverters. When the conventional MPC method is used for multi-level inverters, all candidate voltage vectors are considered to predict the next-step current value. However, in the case that the sampling time is short, increased voltage level makes it difficult to consider the all candidate voltage vectors. In this paper, the improved MPC method which can get a fast transient response is proposed with a small amount of the computation by adding new candidate voltage vectors that are set to find the optimal vector. As a result, the proposed method shows faster transient response than the method that considers the adjacent vectors and reduces the computational burden compared to the method that considers the whole voltage vector. the performance of the proposed method is verified through simulations and experiments.

전기 자동차 파워트레인의 모델링 및 동특성 분석

박광민(Gwangmin Park),이성훈(Seonghun Lee),진성호(Sungho Jin),곽상신(Sangshin Kwak) 大韓電子工學會 2011 電子工學會論文誌-SC (System and control) Vol.48 No.6

일반적인 내연기관 자동차와는 달리 전기자동차는 파워트레인을 구성하는 배터리 인버터 모터 등의 전기 동력 시스템들이 차량의 주행성능과 동역학 특성에 직접적인 영향을 준다. 따라서 전기 차량의 최종 운동 및 동특성을 예측하기 위해서 기계 및 전기전자 복합 시스템을 세부적으로 모델링하고 이를 통한 전체 파워트레인의 해석이 필요하다. 본 논문에서는 전기자동차의 최종 출력 성능을 예측하고 분석하기 위한 전기자동차의 파워트레인 시스템의 동적 모델을 유도하였다. 전기적인 신호로부터 최종 기계 동력 시스템으로 전달되는 입출력 변수의 상관관계를 수학적으로 모델링하여 개발하였다. 또한 전기자동차의 동특성을 시뮬레이션 할 수 있는 기준모델을 Matlab/Simulink 플랫폼 기반으로 개발하였으며 이를 이용하여 유도된 수학적 분석 모델을 검증하였다. 이를 통하여 속도 가속도 추진력 등의 주요 차량 주행성능을 비교 분석하였다. Unlike a typical internal combustion engine vehicle the powertrain system of the pure electric vehicle consisting of battery inverter and motor has direct effects on the vehicle performance and dynamics. Then the specific modeling of such complex electro-mechanical components enables the insight into the longitudinal dynamic outputs of the vehicle and analysis of entire powertrain systems. This paper presents the dynamic model of electric vehicle powertrain systems based on theoretical approaches to predict and analyze the final output performance of electric vehicles. Additionally the correlations between electric input signals and the final output of the mechanical system are mathematically derived. The proposed model for powertrain dynamics of electric vehicle systems are validated with a reference electric vehicle model using generic simulation platform based on Matlab/Simulink software. Consequently the dynamic analysis results are compared with electric vehicle simulation model in some parameters such as vehicle speed/acceleration and propulsion forces.

디젤 커먼레일 시스템용 스월 노즐의 분사율 특성에 대한 연구

김덕중(Deokjung Kim),이기수(Geesoo Lee),김현철(Hyunchul Kim),강우(Woo Kang),곽상신(Sangshin Kwak) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

Diesel engine vehicles use common rail systems to improve the fuel efficiency and reduce harmful emissions. The conventional common rail systems use solenoid-type injectors, but piezo injectors are being increasingly used because the magnetic force of the solenoid coil has limitation in terms of response time. In Korea, the independently developed atomization technology is not yet applied to general industries, and quite an amount of royalty is paid to overseas companies for importing CRDi injection nozzles. In this paper, for the examination of the performances of the CRDi injection nozzle that was manufactured as a trial product, an injection rate equipment was fabricated based on the Bosch method to study the effects of diverse injection conditions on the injection rate. The applicability of the trial product nozzle was verified via the comparative injection rate assessment, and the resulting injector response time was 0.21 ㎳, which was equivalent to that of the existing piezo injector.