• Journal of Welding and Joining
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• 제13권4호
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• pp.65-74
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• 1995

The weld seam tracking sensor is indispensable to improve the flexibility of automatic arc welding systems. Among the position sensing methods available, a laser displacement sensor is one of the most prevailing methods. In this study, a laser displacement sensor was examined on detecting the weld seam of lap joints in sheet metal arc welding. The output signal of the laser displacement sensor may ontain severe fluctuation from the effect of arc light, spatters, fume, etc. So a variety of signal processing methods was applied to smooth the output signal of the sensor. And then the weld joint was determined by using the central difference method. It was revealed that the quadratic mean method plays an important role in detecting the weld seam during welding especially.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2003년도 하계학술대회 논문집
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• pp.188-192
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• 2003

Pole placement method is widely used in controller design. For the stability of the closed loop system, user-specified desired locations including extra pole locations in the s-plane is chosen and by some procedure, feedback gain is obtained. In this paper, only desired pole location is used, and the calculation process is done for attaining linear quadratic stability. Similarly transformation is used for this. By computer simulations using MATLAB, the effectiveness is shown.

• ETRI Journal
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• 제36권4호
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• pp.686-689
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• 2014

This paper studies energy-efficiency (EE) power allocation for cognitive radio MIMO-OFDM systems. Our aim is to minimize energy efficiency, measured by "Joule per bit" metric, while maintaining the minimal rate requirement of a secondary user under a total power constraint and mutual interference power constraints. However, since the formulated EE problem in this paper is non-convex, it is difficult to solve directly in general. To make it solvable, firstly we transform the original problem into an equivalent convex optimization problem via fractional programming. Then, the equivalent convex optimization problem is solved by a sequential quadratic programming algorithm. Finally, a new iterative energy-efficiency power allocation algorithm is presented. Numerical results show that the proposed method can obtain better EE performance than the maximizing capacity algorithm.

• 전자공학회논문지B
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• 제30B권6호
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• pp.67-75
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• 1993

ECG pattern was classified using a back-propagation neural network. An improved feature extractor of ECG is proposed for better classification capability. It is consisted of preprocessing ECG signal by an FIR filter faster than conventional one by a factor of 5. QRS complex recognition by moving-window integration, and peak extraction by quadratic approximation. Since the FIR filter had a periodic frequency spectrum, only one-fifth of usual processing time was required. Also, segmentation of ECG signal followed by quadratic approximation of each segment enabled accurate detection of both P and T waves. When improtant features were extracted and fed into back-propagation neural network for pattern classification, the required number of nodes in hidden and input layers was reduced compared to using raw data as an input, also reducing the necessary time for study. Accurate pattern classification was possible by an appropriate feature selection.

• 한국정보전자통신기술학회논문지
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• 제15권5호
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• pp.343-348
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• 2022

STAP 시스템은 레이더 신호의 클러터와 재밍을 억제하지만 최적의 성능을 위해서는 많은 수의 샘플이 필요하다. 많은 수의 샘플은 처리 계산을 증가시키기 때문에 신호 랭크를 감소키기 위한 변환 방법이 필요하다. LCMV 빔형성 방식은 도달 방향에 대한 왜곡 없는 제약을 쉽게 설정할 수 있고 빔형성 스케일링이 우수하여 전체 랭크를 낮출 수 있다. 본 연구에서는 제안된 QPC(Quadratic Pattern Constraints) 및 LCMV 빔형성 방법을 사용하여 목표물의 정보를 추정한다. 제안 방법은 2차 패턴 구속 조건으로 구속 조건의 수에 따라 원하는 방향으로 빔 패턴 제어를 수행할 수 있다. 시뮬레이션을 통해 제안한 알고리즘으로 원하는 목표물 각도를 추정한다. 추정방향[10° 0° 10°], [-50° -10° 10° 50°], [-50° -10° 0° 10° 50°]에서는 각 목표뮬의 정보를 정확하게 추정하였다. 그러나 목표물[-50° -5° 10° 20°]는 정확하게 추정하지 못했다. 각도 분해능이 10°이상일 때 제안된 알고리즘에 의해서 원하는 목표물이 추정되었지만, 각도 분해능이 10°미만인 경우 원하는 목표물을 정확하게 추정할 수 없었다.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2006년도 하계 학술대회 논문집
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• pp.25-28
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• 2006

In this paper, we say the shading correction system supporting multi-resolution for camera. The shading effect is caused by non-uniform illumination, non-uniform camera sensitivity, or even dirt and dust on glass (lens) surfaces. In general this shading effect is undesirable [1]. Eliminating it is frequently necessary for subsequent processing and especially when quantitative microscopy is the fine goal. The proposed system is available on thirty nine kinds of image resolutions scanned by interlaced and progressive type. Moreover, the system is using various continuous quadratic equations instead of using the piece-wise linear curve which is composed of multiple line segments. Finally, the system could correct the correct effect without discontinuity in any image resolution. The proposed system is also experimentally demonstrated with Xilinx Virtex FPGA XCV2000E- 6BG5560 and the TV set.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2003년도 하계학술대회 논문집
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• pp.268-271
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• 2003

There are several methods for the design of 2D filter. Notable among them is McClellan transform method. This transform allows us to obtain a high order 2D FIR filter through mapping the 1D frequency points of a 1D prototype FIR filter onto 2D frequency contours. We design 2D filter using this transform. Then we notice for mapping deviation of the 2D filter. In this paper, Quadratic programming (QP) method allows us to obtain coefficients of McClellan transform. Then we compare deviation of QP method with least-squares(LS) method. Elliptic filter is used for comparison. The optimal cutoff frequencies of a 1D filter are obtained directly from the QP method. Also several problem of LS method are solved.

• Structural Engineering and Mechanics
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• 제49권3호
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• pp.411-425
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• 2014

This paper presents the processing of nonlinear features associated with a damage event by quadratic time-frequency distributions for damage identification in a frame structure. A time-frequency distribution is a function which distributes the total energy of a signal at a particular time and frequency point. As the occurrence of damage often gives rise to non-stationary, nonlinear structural behavior, simultaneous representation of the dynamic response in the time-frequency plane offers valuable insight for damage detection. The applicability of the bilinear time-frequency distributions of the Cohen class is examined for the damage assessment of a frame structure from the simulated acceleration data. It is shown that the changes in instantaneous energy of the dynamic response could be a good damage indicator. Presence and location of damage can be identified using Choi-Williams distribution when damping is ignored. However, in the presence of damping the Page distribution is more effective and offers better readability for structural damage detection.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.397-402
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• 2003

The FM demodulation method for a bulk homodyne laser interferometer is presented. The Doppler frequency that represents the surface velocity of a vibrating object is obtained by using the bulk homodyne laser interferometer, and converted to the voltage signal by using the proposed analogue FM demodulation circuit. The DC offsets of the interferent signals that are obtained from the bulk homodyne interferometer are eliminated by using a simple subtraction. The new method for compensation of the asymmetry of each channels is presented. The light power variation of the interferometer is normalized by using the Auto Gain Controller(AGC). The proposed FM demodulation algorithm is proved by the theoretical method, and validated by the experimental results. In experiments, the proposed FM demodulation algorithm is compared with the conventional demodulation methods.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.793-796
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• 2017

영상신호는 신호를 처리하는 과정에서 다양한 잡음에 의해 훼손되어지며, 이러한 신호를 복원하기 위한 많은 연구가 이루어지고 있다. 영상에 첨가되는 잡음에는 salt and pepper 잡음, AWGN(additive white Gaussian noise) 및 두 잡음이 혼합된 복합잡음이 대표적이다. 따라서 본 논문에서는 복합잡음 환경에서 훼손된 영상을 복원하기 위해, 잡음 판단을 통해 국부 마스크의 중심화소가 salt and pepper 잡음인 경우, 2차원 스플라인 보간법 및 메디안 필터로 처리하고, AWGN인 경우, 화소변화에 따른 가중치 필터로 처리하는 알고리즘을 제안하였다.