• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.84-89
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• 2001

Ultrasonic pulse echo method comes to be difficult to apply to the multi-layered structure with very thin layer, because the echoes from the top and the bottom of the layer are overlapped. Conventionally method, deconvolution technique has been used for the decomposition of overlapped UT signals, however it has disabilities when the waveform of the transmitted signal is distorted according to the propagation. In this paper, the wavelet transform based deconvolution (WTBD) technique is proposed as a new signal processing method that can decompose the overlapped echo signals in A-Scan signal with superior performances compared to the conventional deconvolution technique. Performances of the proposed method are shown by through computer simulations using model signal with noise and are demonstrated by through experiments for the fabricated acryl rod with a thin steel plate bonded to it.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1375-1378
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• 1997

In this paper, we presents the algorithm which is to recognize the traffic sign on the road the traffic signal in a video image for autonomous navigation. First, the rocognition of traffic sign on the road can be detected using boundary point estimation form some scan-lines within the lane deducted. For this algorithm, index matrix method is used to detemine what sign is. Then, the traffic signal recognition is performed by usign the window minified by several scan-lines which position may be expected. For this algoritm, line profile concept is adopted.

• 한국멀티미디어학회논문지
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• 제20권10호
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• pp.1662-1670
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• 2017

A-Scan NDT equipment is widely used in the industrial field because it is inexpensive and easy to carry but it is necessary to have a skilled inspection specialist who is trained to analyze the waveform of ultrasonic signal. Since the welding quality is judged subjectively by the specialist, there is a problem in the reliability of the quality. In the C-Scan NDT which overcomes the shortcomings of the A-Scan, welding part can be represented in the form of two dimensional image by combining one dimensional ultrasonic waveform so that the quality of welding can be grasped without the help of specialist. In order to develop C-Scan NDT, it is necessary to develop an array type two dimensional transducer and an algorithm to composing image by combining ultrasonic signals generated from a two dimensional transducer. In addition, the noise component must be minimized in the ultrasonic signal in order to display the quality of welding in the form of images. Therefore we propose a method to remove noise component from the ultrasonic wave and construct a two dimensional ultrasonic image.

• 융합정보논문지
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• 제11권11호
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• pp.17-22
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• 2021

전자전에서 레이더 신호 해석은 수신한 레이더 신호에서 추출한 신호제원(방향, 주파수, 펄스반복주기, 펄스 폭, 스캔주기)으로 레이더 종류를 식별하는 기술이다. 그러나 신형 레이더, 위협환경이 고도화되면서 레이더 종류를 식별하는 과정에서 레이더 식별 모호성(Ambiguity)가 발생한다. 본 논문에서는 기존 방법의 문제점을 분석하고 새로운 방법을 제안한다. 이 기술은 레이더 스캔 주기의 펄스 도착시간 차이와 스캔주기 판별 최소 수집 개수로 스캔주기 유효성을 판별한다. 실험에 의하여 입력된 신호세기의 RMS((Root Mean Square)와 무관하게 스캔 주기 결과를 도출하는 것을 입증했다.

• Investigative Magnetic Resonance Imaging
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• 제19권4호
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• pp.212-217
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• 2015

Purpose: For a single time-point hyperpolarized $^{13}C$ magnetic resonance spectroscopy imaging (MRSI) of animal models, scan-time window after injecting substrates is critical in terms of signal-to-noise ratio (SNR) of downstream metabolites. Pre-scans of time-resolved magnetic resonance spectroscopy (MRS) can be performed to determine the scan-time window. In this study, based on two-site exchange model, protocol-specific simulation approaches were developed for $^{13}C$ MRSI and the optimal scan-time window was determined to maximize the SNR of downstream metabolites. Materials and Methods: The arterial input function and conversion rate constant from injected substrates (pyruvate) to downstream metabolite (lactate) were precalibrated, based on pre-scans of time-resolved MRS. MRSI was simulated using two-site exchange model with considerations of scan parameters of MRSI. Optimal scan-time window for mapping lactate was chosen from simulated lactate intensity maps. The performance was validated by multiple in vivo experiments of BALB/C nude mice with MDA-MB-231 breast tumor cells. As a comparison, MRSI were performed with other scan-time windows simply chosen from the lactate signal intensities of pre-scan time-resolved MRS. Results: The optimal scan timing for our animal models was determined by simulation, and was found to be 15 s after injection of the pyruvate. Compared to the simple approach, we observed that the lactate peak signal to noise ratio (PSNR) was increased by 230%. Conclusion: Optimal scan timing to measure downstream metabolites using hyperpolarized $^{13}C$ MRSI can be determined by the proposed protocol-specific simulation approaches.

• 한국자기학회지
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• 제26권3호
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• pp.92-98
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• 2016

신호증강효과기법을 이용한 자기공명혈관술에서 뇌동맥을 half scan factor에 따른 절반스캔과 완전스캔의 영상을 평가하는데 목적으로 한다. 뇌혈관성 질환이 없는 환자(n = 30)를 대상으로 절반스캔과 완전스캔 하였고, 뇌동맥의 관심영역을 세 영역(C1, C2, C3)에서 7~8 mm의 범위로 설정하였다. MIP로 재구성한 영상으로 신호강도를 SNR(signal to noise ration), PSNR(peak signal noise to ratio), RMSE(root mean square error), MAE(mean absolute error)을 산출하고 paired t-test를 이용하여 통계분석 하였다. 스캔시간은 절반스캔(4분 53초), 완전스캔(6분 04초)이었다. 뇌혈관의 모든 ROI의 평균 측정 범위(7.21 mm)이었고, 첫번째 C1의 SNR은 완전스캔(58.66 dB), 절반스캔(62.10 dB)이었고, 양의 상관관계($r^2=0.503$)이고, 두 번째 C2의 SNR은 완전스캔(70.30 dB), 절반스캔(74.67 dB)이고 양의 상관관계($r^2=0.575$)이었다. 세 번째 C3의 완전스캔 SNR(70.33 dB), 절반스캔 SNR (74.64 dB)로 양의 상관관계를 ($r^2=0.523$)로 분석되었다. 절반스캔과 완전스캔의 비교에서 SNR($4.75{\pm}0.26dB$), PSNR($21.87{\pm}0.28dB$), RMSE($48.88{\pm}1.61$)이었고 MAE($25.56{\pm}2.2$)로 산출되었다. SNR은 두 검사 스캔에서 통계학적으로 유의하지 않았고 (p-value > .05) 영상의 질에서는 많은 차이가 없어 완전스캔을 사용하였을 때보다 적은 시간이 소요되는 절반스캔을 적용하여 검사하여도 된다.

• 한국정밀공학회지
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• 제16권7호
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• pp.32-39
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• 1999

Digital signal processor (DSP) is used to obtain the peak value and the time difference of ultrasonic signals, to make digital filter, and to derive mathematical transformation from analog circuit. In this study, C-scan system and control program have been developed to high speed data acquisition. This system consists of signal processing parts (DSP, oscilloscope, pulser/receiver, digitizer), scanner, and control program. The developed system has been applied to a practical ultrasonic testing in overlay weld, and demonstrated high speed with precision

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.353-356
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• 2011

전파를 수집하고 분석하는 신호수신시스템은 실 운용환경에서 검증되기 전에 정밀한 모의전파신호원을 이용한 정량적인 성능예측 및 실 환경과 유사한 모의전파환경에서 검증되어야한다. 신호수신 시스템은 전파의 주파수(Frequency), 펄스 변조(Pulse Modulation), 스캔 변조(Scan Modulation), 펄스 내 위상변조(Phase Modulation On Pulse), 펄스 내 주파수 변조(Frequency Modulation On Pulse) 등 다양한 신호특성에 대한 측정, 분석능력을 갖는다. 이러한 신호원들은 기본으로 실험실 환경에서 모의발생 되어야 하고 전파가 다수 존재하는 복잡한 전파환경 또한 모의되어야 한다. 본 논문에서는 효과적인 전파신호원의 모의발생, 운용시나리오에 따른 정밀고주파시험신호 모의방법에 관한 연구 결과를 서술한다.

• 전자공학회논문지
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• 제54권3호
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• pp.78-86
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• 2017

본 논문에서는 은폐 물체 탐지를 위해 인체에 무해한 음향신호 중 파라메트릭 배열을 이용한 음향 탐지 시스템을 제안한다. 제안된 탐지 시스템은 파라메트릭 배열 현상으로부터 생성되는 고 지향성 Chirp 신호를 송신신호로 사용하고, Dechirp 처리 과정을 통해 수신신호의 신호 대 잡음비를 개선하여 거리 분해능을 향상시키는 기법을 사용한다. 제안된 파라메트릭 배열 시스템의 송신센서는 $8{\times}2$ 배열로 구축하였으며, 센서 배열의 빔 폭은 수평방향 약 $7^{\circ}$와 수직방향 약 $26^{\circ}$를 형성한다. 제안된 시스템을 검증하기 위해 물체 탐지 및 가시화를 위한 2축 구동 제어 선형 스테이지를 구축하였으며, 이를 이용하여 은폐된 물체에 대한 A-scan, B-scan 및 C-scan 실험을 진행하였다. 실험 결과, 천에 은폐된 동판과 파이프를 탐지하고 형상을 확인하였으며, 가시화된 형상에서 동판은 $0.015m^2$, 파이프는 $0.046m^2$의 오차를 보여주었다.

• Imaging Science in Dentistry
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• 제31권3호
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• pp.175-179
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• 2001

Cystic lymphangioma is an uncommon benign developmental tumor of the lymphatic system, seen rarely in adults. A 23-year-old man visited DKUDH complaining of the painless swelling in the right submandibular area. It was reported that swelling had increased since 5 months ago. Clinically, fltriangle uctuant and mobile mass was palpated at the right submandibular area. CT scan showed a large, well-defined, homogenous low density mass, measuring 5.0 × 2.5 × 4.0 cm. T1W MRI scan demonstrated a large, multiseptated homogenous low signal mass with septum and rim enhancement. Proton-density and T2W MRI scan showed mass of high signal intensity. MRI scan was able to delineate better the enhanced multi septation and extent of the lesion. Histopathologically, a lobulated cystic mass lined by a layer of flattened endothelium was observed.