• 한국전자파학회논문지
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• 제15권9호
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• pp.848-855
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• 2004

본 논문에서는 긴 코드 DS/CDMA DMB 하향링크 시스템에서의 신호공간에 기초한 새로운 채널추정기법을 제안한다. 신호공간과 잡음공간과의 직교성을 이용하는 종래의 부분공간 방식과는 달리 신호공간만을 이용하여 채널응답을 추정할 수 있다. 신호공간만을 이용하므로 제안된 기법은 종래의 부분공간 방식에서의 연산복잡도 문제를 해결할 수 있고 따라서 실제 구현 가능한 적절한 사이즈의 공분산 행렬로 부분공간 분석을 통한 채널추정기법에 사용될 수 있다. 논문을 통하여 제안된 기법과 관련된 수식을 도출하고 시뮬레이션 및 수치결과를 통해 제안된 기법의 유효성을 보인다.

• 한국음향학회지
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• 제31권5호
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• pp.340-351
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• 2012

본 논문에서는 입체음향효과의 향상을 위한 스테레오-10.2채널의 블라인드 업믹스 알고리즘을 제안하였다. 최근에, 소비자들은 더 나은 입체음향효과나 3D 사운드를 즐기길 원하고 다양한 멀티채널 포맷의 등장으로 업믹스 알고리즘들이 연구 되어 왔다. 그러나 기존의 업믹스 알고리즘들은 공간정보를 왜곡하는 문제점을 가지고 있었다. 이러한 문제점을 해결하기위해 전 후방 채널에 대한 이득 조절 및 10.2 채널의 각 채널별 믹싱 알고리즘을 제안한다. 기존의 상용화된 멀티채널 업믹스 알고리즘들과의 주관적 평가 실험결과 제안한 알고리즘은 입력신호의 공간정보를 유지하면서 입체음향효과를 향상시킨 것으로 확인되었다.

• 정보보호학회논문지
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• 제13권5호
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• pp.49-56
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• 2003

본 논문에서는 웨이블릿(wavelet) 변환을 이용한 효율적인 블라인드(blind) 워터마킹 알고리즘을 제안한다. 제안한 알고리즘에서는 원영상을 1-단계 웨이블릿 변환영역으로 변환하여 고주파 부분에 워터마크를 삽입한다. 워터마크의 삽입은 삽입하고자하는 워터마크 값에 따라 웨이블릿 변환 영역 중 HL, LH, HH 밴드에 각각의 서로 대응되는 위치에 있는 웨이블릿 계수값을 교환함으로써 이루어진다. 그리고 워터마크의 추출은 원영상이 없이도 웨이블릿 계수 값간의 관계에 의해 워터마크가 삽입된 영상만으로 가능하다. 실험결과 워터마크가 삽입된 영상은 시각적으로 손상을 감지하기 어려울 만큼 우수한 화질을 가졌으며. 다양한 공격에도 강인성을 보였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.231-234
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• 2001

In this paper, we present a robust watermarking technique based on a DCT-domain watermarking approach and an order statistic(OS) filter. The proposed technique inserts one watermark into each of four coefficients within a 2 ${\times}$ 2 block which is scanned on DCT coefficients in the zig-zag ordering from the medium frequency range. The detection algorithm uses an adaptive trimmed mean operator as a local estimator of the embedded watermark to obtain the desired robustness in the presence of additive Gaussian noise and JPEG compression attacks. The performance is analyzed through statistical analysis and numerical experiments. It is shown that the robustness properties against additive noise and JPEG compression attacks are more enhanced than the previous techniques.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권1호
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• pp.117-123
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• 2014

The fabrication and characterization of a Si/ZnO thin film heterojunction ultraviolet photodiode has been presented in this paper. ZnO thin film of ~100 nm thick was deposited on <100> Silicon (Si) wafer by atomic layer deposition (ALD) technique. The Photoluminescence spectroscopy confirms that as-deposited ZnO thin film has excellent visible-blind UV response with almost no defects in the visible region. The room temperature current-voltage characteristics of the n-ZnO thin film/p-Si photodiodes are measured under an UV illumination of $650{\mu}W$ at 365 nm in the applied voltage range of ${\pm}2V$. The current-voltage characteristics demonstrate an excellent UV photoresponse of the device in its reverse bias operation with a contrast ratio of ~ 1115 and responsivity of ~0.075 A/W at 2 V reverse bias voltage.

• 대한통합의학회지
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• 제11권3호
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• pp.147-157
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• 2023

Purpose : Stroke patients exhibit considerable variations in gait patterns. Stroke patients generally show abnormal muscle tone and gait. This study was performed to evaluate the effects of treadmill gait training combined with muscle tone control technique (TM) on gait ability in patient with chronic stroke. Methods : A single-blind, randomized controlled trial was conducted with 36 patient with chronic stroke. They were randomly allocated 2 groups; treadmill gait training combined with muscle tone control technique group (TM group; n=18) and conservative treatment group (CG group; n=18). The TM group received 15 minutes muscle tone control technique and 15 minute treadmill gait training. In the conservative treatment group received 30 minutes conservative physical therapy. Each group performed 30 minutes a day 3 times a week for 8 weeks. The primary outcome gait ability were measured by gait measurement system (Optogait, Microgate, Italy) and 10 m walking test (10MWT). An independent t-test was used to statistically analyze the pre-test and pos-ttest gait ability results. Results : Both groups demonstrated significant improvement of outcome in gait ability during intervention period. TM group showed significant differences in gait ability as compared to the CG groups (p<.05). TM group showed significant differences in 10MWT as compared to the CG groups (p<.05). Our results showed that TM was more effective on gait ability in patients with chronic stroke. Conclusion : Our findings of this study confirmed that the treadmill gait training combined with muscle tone control technique provided significant improvements on gait ability in patient with chronic stroke. Therefore treadmill gait training combined with muscle tone control technique may positive influenced gait ability. This study will be able to be used as an intervention data for recovering gait ability in patients with chronic stroke.

• Archives of Plastic Surgery
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• 제33권5호
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• pp.552-556
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• 2006

Purpose: As the use of computed tomographic scanning spread, the diagnosis of blow-out fractures of the medial orbital wall increased. Conventionally, the surgery of blow-out fractures in medial orbital wall was performed by various approaches with external incision or endoscopic approach. Although the field of orbital surgery has progressed significantly during the last decade, accurate realignment and replacement of component is difficult due to lack of visualization of the fracture site, blind dissection of the orbital wall, and difficulty in insertion of implant. In order to overcome these shortcomings, we explored the use of endoscopic transnasal approach together with subciliary approach. Methods: The entrapped periorbital tissues in the ethmoid sinus were completely reduced endoscopically, and the bone defect of medial orbital wall was reconstructed with $Medpor^{(R)}$ insertion via subciliary approach. This technique was applied to 13 patients who had medial orbital wall fracture. Results: The patients were followed-up for 3 to 24 months with an average of 9 months. The postoperative courses were satisfactory in all cases. Conclusion: The conjunction of endoscopic transnasal and subciliary approach technique seems to produce good results in medial orbital wall fracture.

• 한국콘텐츠학회논문지
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• 제7권8호
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• pp.1-12
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• 2007

본 논문은 스테레오 사운드에서 합쳐지기 이전의 개별적인 사운드를 분리해내는 기법을 제안한다. 기존의 Degenerate Unmixing Estimation Technique (DUET) 알고리즘의 W-Disjoint Orthogonal 가정에 기반을 두고 있으며, Windowed-Fourier 변환을 사용하여 시간-주파수 영역에서 주요 프로세스를 수행한다. 제안된 방식은 패닝 인덱스의 거리차이에 따라 가중치를 준 마스크를 사용하는 기법과 양쪽 채널의 성분을 비교하여 바이너리 기반의 마스크를 사용하는 방식이다. 전자는 부드러운 분리 특성을 보여주며, 후자는 높은 분리 특성을 보여주었다. 마지막에 실험을 통해 기존의 방식과 제안된 방식을 비교함으로써, 제안된 방식이 기존 방식 보다 좋은 성능을 가지고 있음을 알아볼 것이다.

• 대한조선학회논문집
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• 제49권6호
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• pp.498-503
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• 2012

Independent component analysis (ICA) technique based on statistical independency of the signals is known as suitable to identify the source signals by measuring and separating mixed signals through transfer paths and has successfully applied in the field of medical care, communications and so forth. In this study, the ICA technique is introduced for the identification of excitation sources from measured vibration signals of structures, which can be done by evaluating negentropy of centered and whitened vibration signals and correlation of separated signals. To validate the method, numerical analyses are carried out for a plate and a cylinder structure. The results show that the method can be applied efficiently to source identification of complex structures. Nevertheless, additional studies would be required to complement problems of occasional inaccuracy.

• Structural Monitoring and Maintenance
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• 제2권4호
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• pp.399-418
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• 2015

Automated damage detection through Structural Health Monitoring (SHM) techniques has become an active area of research in the bridge engineering community but widespread implementation on in-service infrastructure still presents some challenges. In the meantime, visual inspection remains as the most common method for condition assessment even though collected information is highly subjective and certain types of damage can be overlooked by the inspector. In this article, a Frequency Response Functions-based model updating algorithm is evaluated using experimentally collected data from the University of Central Florida (UCF)-Benchmark Structure. A protocol for measurement selection and a regularization technique are presented in this work in order to provide the most well-conditioned model updating scenario for the target structure. The proposed technique is composed of two main stages. First, the initial finite element model (FEM) is calibrated through model updating so that it captures the dynamic signature of the UCF Benchmark Structure in its healthy condition. Second, based upon collected data from the damaged condition, the updating process is repeated on the baseline (healthy) FEM. The difference between the updated parameters from subsequent stages revealed both location and extent of damage in a "blind" scenario, without any previous information about type and location of damage.