• 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.

• 인터넷정보학회논문지
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• 제23권4호
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• pp.11-19
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• 2022

본 논문은 컨볼루션 신경망(CNN)을 이용하여 폭발물 성분의 용량별로 분류할 때의 성능을 평가하는 연구이다. 기존의 폭발물 분류 방식 중에 IMS 증기 탐지기 방식은 폭발물의 농도가 사용자가 장비에서 설정한 임계치를 넘어야만 폭발물의 존재 여부를 판단한다. IMS 증기 탐지기는 폭발물이 존재하더라도 임계치를 넘지 않는 양이면 폭발물이 존재하지 않는다고 판단하는 문제가 있다. 따라서 폭발물 성분의 농도가 임계치를 넘지 않는 양일 때에도 폭발물 성분을 검출하는 방안이 필요하다. 이에 따라 본 논문에서는 폭발물 시계열 데이터를 Gramian Angular Field(GAF) 알고리즘으로 이미지화를 진행한 후 이미지와 영상처리뿐만 아니라 시계열 데이터 처리에도 뛰어난 성능을 보이는 딥러닝 모델인 컨볼루션 신경망(CNN)으로 직접 label을 설정해서 지도학습을 진행한 결과 폭발물 성분의 농도가 임계치를 넘지 않는 양일 때에도 폭발물 성분이 존재한다고 판단함과 동시에 폭발물 성분의 종류와 폭발물 성분의 농도의 양을 같이 판단할 수 있는지 성능평가를 진행했다.

• 비파괴검사학회지
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• 제29권6호
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• pp.570-578
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• 2009

Excitation and propagation of guided waves are very complex problems in pipes due to their dispersive nature. Pipes are commonly used in the oil, chemical or nuclear industry and hence must be inspected regularly to ensure continued safe operation. The normal mode expansion(NME) method is given for the amplitude with which any propagating waveguide mode is generated in the pipes by applied surface tractions. Numerical results are calculated based on the NME method using different sources, i.e., non-axisymmetric partial loading and quasi-axisymmetric loading sources. The sum of amplitude coefficients for 0~nineth order of the harmonic modes are calculated based on the NME method and the dispersion curves in pipes. The superimposed total field which is namely the angular profile, varies with propagating distance and circumferential angle. This angular profile of guided waves provides information for setting the transducer position to find defects in pipes.

• 한국정보과학회논문지:시스템및이론
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• 제30권11호
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• pp.663-674
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• 2003

범프 매핑은 복잡한 모델링 과정 없이 기하 매핑을 통하여 땅콩 껍질의 돌기와 같은 객체 표면의 세밀한 부분을 표현해내는 기법이다. 그러나 이 기법은 법선 벡터 쉐이딩과 같은 상당한 복잡도를 가진 연산을 픽셀 당 처리해줘야 하므로, 이의 하드웨어 구현은 상당한 비용을 필요로 한다. 본 논문에서는 극 좌표계를 이용한 새로운 범프 매핑 알고리즘 및 하드웨어 구조를 제안한다. 이는 참조 공간으로의 변환을 위한 새로운 벡터 회전 방식과 연산이 최소화된 조명 계산 방식을 갖는 구조로, 기존의 구조에 비해 범프 매핑을 효과적으로 수행한다. 결과적으로 제안하는 구조는 범프 매핑에 필요한 연산 및 하드웨어를 상당량 줄였다.

• 전자공학회논문지S
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• 제34S권5호
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• pp.1-14
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• 1997

We consider transmission beamforming techniques for frequency-division-duplex (FDD) wireless communication systems using adaptive arrays to improve the signal quality of the array transmission link. We develop a simple effective transmission beamforming technique based on an approximated frequency tranlsation (AFT) to derive the tranmsiion beamforming weights from the uplink channel vector. This technique exploits the invariance of the short-time averaged fast fading statistics to small frequency translations. A simple approximate relationship that relates the transmission channel vector to the reception channel vector is derived. We have developed its practical alternative in which the frequency translation of the channel vector is performed at the principal angle of arrival (AOA) of the u;link synthestic angular spectrum instead of the mean AOA. To analyze the performance of the proposed methods, we consider the power loss incurred by applying the estimated channel vector instead of the true downlink channel vector. The performance is analyzed as a function of the mean AOA, the angular spread, the number of elements, frequncy difference between the uplink and the downlink, and the angle distribution. Their performance is also compared with that of the direct weight reuse method and the AOA based methods.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.663-663
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• 2002

The National Oceanographic Research Institute of KOREA started to survey for the basic data necessary to territorial sea and EEZ identification and marine development with Multi-Beam Echo Sounder(L3 SeaBeam 2112) since 1996. The Multi-Beam surveys has provided a very new and precise way of describing the morphology and nature of the underwater seabed. Multi-Beam Echo Sounder systems employ sound waves propagating at angles which vary from vertical to nearly horizontal. The locations on the bottom where echoes are generated cover a swath whose port to starboard width may be equal to many times the water depth. Newer Multi-beam bathymetric sonars provide both a beam by beam depth and backscatter amplitude of the bottom. But The backscattered amplitude didn't use for identification of bottom properties because backscatter amplitude effects by the many environmental variables of underwater and seabed. We investigates the utilization of geo-referenced backscatter amplitude and analysis of relationship between The Backscattered Amplitude and Sidescan Sonar imagery from Sea Beam 2112. For the backscattered amplitude imagery mainly represents the properties of sediment, we computed the beam geometry, time-varied amplifier gain, and mainly incidence angle to the topography using bathymetric model at each ping. In this paper, those issues are illustrated, and the angular independent imagery based on swath topographic model is described.

• 한국군사과학기술학회지
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• 제19권4호
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• pp.435-442
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• 2016

For inertial navigation systems, initial information such as position, velocity and attitude is required for navigation. Self-alignment is the process to determine initial attitude on stationary condition using inertial measurements such as accelerations and angular rates. The accuracy of self-alignment is determined by inertial sensor error. As soon as an inertial navigation system is powered on, the temperature of accelerometer rises rapidly until temperature stabilization. It causes acceleration error which is called temperature stabilizing error of accelerometer. Therefore, temperature stabilizing error degrades the alignment accuracy and also increases alignment time. This paper suggests a method to calculate azimuthal attitude using curve fitting of horizontal control angular rate in fixed-gain self-alignment. It is verified by simulation and experiment that the accuracy is improved and the alignment time is reduced using the proposed method under existence of the temperature stabilizing error.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.271-274
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• 1998

Ultrasonic sensors are becoming indispensable components in every sector of automation equipments due to many advantages. But the main purposes of the noncontact sensing device are rather narrowly confined within object detection and distance measurement. To widen the realm of the applications to object recognition, ultrasonic sensors need to improve the recognition resolution to a certain amount. To resolve the problem of spatial resolution restriction, an increased number of the sensors in the forms of a linear array or 2-dimensional array of the sensor has been used. Also better resolution has been obtained by shifting the array in several steps using mechanical actuators. For an object recognition using ultrasonic sensors, measurements of distance, shift, oblique angle in certain ranges should be obtained. But a little attention has been paid to the measurement of angles. In this paper we propose a practical method for an object angular value detection in addition to distance measurement in ultrasonic sensor array system with little additional hardware burden. Using the established measurement look-up table for the variations of distance, shift, angle and transmitter voltages for each sensor characteristics, a set of different return echo signals for adjacent receivers are processed to provide enhanced angular value reading for an object.

• Journal of Information Display
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• 제12권4호
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• pp.167-171
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• 2011

The angular distribution of the luminance on each optical component of 40-inch light-emitting diode backlight was measured and studied, using the optical-simulation method. Several scattering functions were investigated as the reflection distribution function of the scattering dots printed on the bottom surface of the light guide plate (LGP). It was found that both the diffuse Lambertian and near-specular Gaussian scattering functions were necessary for the successful reproduction of the experimental angular distribution of the luminance. The optimization of the scattering parameters included in these scattering functions led to almost the same luminance distribution as that obtained from the experiment. This approach may be an effective way of indirectly estimating the reflection distribution function of the scattering dots of the LGP, which cannot be made accessible through any other experimental method.

• 센서학회지
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• 제25권2호
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• pp.79-85
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• 2016

This paper proposes a threshold-based fall recognition algorithm to discriminate between falls and activities of daily living (ADL) using a tri-axial accelerometer and a bi-axial gyroscope sensor mounted on the upper sternum. The experiment was executed ten times according to the proposed experimental protocol. The output signals of the tri-axial accelerometer and the bi-axial gyroscope were measured during eight falls and eleven ADL action sequences. The threshold values of the signal vector magnitude (SVM_Acc), angular velocity (${\omega}_{res}$), and angular variation (${\theta}_{res}$) parameter were calculated using MATLAB. From the preliminary study, three thresholds (TH1, TH2, and TH3) were set so that the falls could be distinguished from ADL. When the parameter SVM_Acc is greater than 2.5 g (TH1), ${\omega}_{res}$ is greater than 1.75 rad/s (TH2), and ${\theta}_{res}$ is greater than 0.385 rad (TH3), these action sequences are recognized as falls. If at least one or more of these conditions is not satisfied, the sequence is classified as ADL.