• Smart Structures and Systems
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• 제13권6호
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• pp.1041-1063
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• 2014

This work introduces a two-module robotic pipe inspection system with ultrasonic NDE device to evaluate the integrity of pipe structures. The proposed robotic platform has high mobility. The two module mobile robot platform overcomes pipe obstacle structures such as elbow, or T-branch joints by cooperative maneuvers. Also, it can climb up the straight pipeline at a fast speed due to the wheel driven mechanism. For inspection of pipe structure, SH-waves generated by EMAT are applied with additional signal processing methods. A wavelet transform is implemented to extract a meaningful and specific signal from the superposed SH-wave signals. Intensity ratio which is normalized the defect signals intensity by the maximum intensity of directly transmitted signals in the wavelet transforms spectrum is applied to evaluate defects quantitatively. It is experimentally verified that the robotic ultrasonic inspection system with EMAT is capable of non-destructive inspection and evaluation of defects in pipe structure successfully by applying signal processing method based on wavelet transform.

• Journal of Biosystems Engineering
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• 제39권3호
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• pp.174-183
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• 2014

Purpose: A robust, efficient auto-grading computer vision system for meat carcasses is in high demand by researchers all over the world. In this paper, we discuss our study, in which we developed a system to speed up line processing and provide reliable results for pork grading, comparing the results of our algorithms with visual human subjectivity measurements. Methods: We differentiated fat and lean using an entropic correlation algorithm. We also developed a self-designed robust segmentation algorithm that successfully segmented several porkcut samples; this algorithm can help to eliminate the current issues associated with autothresholding. Results: In this study, we carefully considered the key step of autoextracting lean tissue. We introduced a self-proposed scheme and implemented it in over 200 pork-cut samples. The accuracy and computation time were acceptable, showing excellent potential for use in online commercial systems. Conclusions: This paper summarizes the main results reported in recent application studies, which include modifying and smoothing the lean area of pork-cut sections of commercial fresh pork by human experts for an auto-grading process. The developed algorithms were implemented in a prototype mobile processing unit, which can be implemented at the pork processing site.

• 한국통신학회논문지
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• 제29권8B호
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• pp.755-761
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• 2004

본 논문은 무선랜 기술을 활용한 초고속 무선인터넷 서비스에서 사용자 인증방식에 사용되는 프로토콜의 설계와 구현에 관한 것이다. IEEE 802.l1b를 기반으로 한 공중 무선랜 서비스는 최근 고속 무선 인터넷 접속 솔루션으로써 각광받고 있다. 공중 무선랜 환경에서는 특히 중앙 집중화된 인증방법과 향상된 보안대책이 필요하며 사용자 단말의 이동 시 로밍에 대한 보장이 요구된다. 본 논문에서는 IEEE 802.1x에 기반의 사용자 인증보안 기능을 설계하고 방법과 실제 임베디드 리눅스를 기반으로 한 무선랜 Access Point(AP)에서 구현하여 동작을 시험하였으며. 로밍 시 필요한 IAPP 절차에 대하여 검토하였다. 또한 업체를 통한 상용화를 진행하며, KT 네스팟 인증시스템과 정상적인 연동기능 및 관리기능이 동작함을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.19-20
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• 2006

As the Mobile and Display technology are being developed quickly, new wireless devices are released in great numbers. They reduce existing devices' life time and demand a reduction of developing period of portable devices. With these demands, existing film cutting mold used many films of portable devices, especially LCD Display, needs to be more precise, and cheaper. In this research, we have analyzed machining characteristics of cutter shapes, materials, and cutting conditions for application to other films. Cutter edge was machined by slot cutting method and CAD program to select the cutter shape and cutter angle. Also, we have determined the optimal cutting conditions using high speed machining experiments to improve the productivity.

• 한국생산제조학회지
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• 제21권3호
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• pp.479-486
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• 2012

This paper presents a high-speed automatic micro-alignment system that is a part of an inspection machine for small-sized molded lenses of mobile phones, palm-top computers, and so on. This work was motivated by the shortcomings of existing highest-grade commercial machine. A simple tip/tilt/Z parallel mechanism is designed based on kinematic couplings, which is a 3-degree-of-freedom (3-DOF) moderate-cost alignment stage. It is used to automatically adjust the posture of each lens on the tray, which is impossible by the conventional instrument. Amplified piezoelectric actuators are used to ensure the accuracy and dynamic response. Forward kinematic analysis and simulation show that the parasitic motion is small enough compared to the actuator stroke. From the workspace analysis of the moving platform, it is clear that the output motion range satisfies the design requirements.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.4103-4117
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• 2014

Image processing and computer vision algorithms are gaining larger concern in a variety of application areas such as robotics and man-machine interaction. Vision allows the development of flexible, intelligent, and less intrusive approaches than most of the other sensor systems. In this work, we determine the location and orientation of a mobile robot which is crucial for performing its tasks. In order to be able to operate in real time there is a need to speed up different vision routines. Therefore, we present and evaluate a method for introducing parallelism into the multiple non-overlapping camera pose estimation algorithm proposed in [1]. In this algorithm the problem has been solved in real time using multiple non-overlapping cameras and the Extended Kalman Filter (EKF). Four cameras arranged in two back-to-back pairs are put on the platform of a moving robot. An important benefit of using multiple cameras for robot pose estimation is the capability of resolving vision uncertainties such as the bas-relief ambiguity. The proposed method is based on algorithmic skeletons for low, medium and high levels of parallelization. The analysis shows that the use of a multiprocessor system enhances the system performance by about 87%. In addition, the proposed design is scalable, which is necaccery in this application where the number of features changes repeatedly.

• 한국통신학회논문지
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• 제23권4호
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• pp.940-949
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• 1998

본 논문에서는 고속 무선채널올 통해 실시간 동영상 정보를 전송할 때 이동 수신측에서 적응적 버퍼제어방법을 사용함으로서 셀 경계에서 핸드오버 등으로 인해 발생되는 지연 스파이크(delay spike)에 대해 효과적으로 대처할 수 있는 방안을 제안한다. 제안한 방법을 확인하기 위해 무선채널의 랜덤오류와 버스트 오류 및 핸드오버 등에 의한 패킷 전송지연 특성을 모델링하고, 본 논문에서 제안한 방식과 기존에 제안된 방식을 패킷 전송지연 모델에 적용하여 지연 및 지연 스파이크에 의한 수선버퍼의 적응도를 비교, 평가하였다. 또한 H.263방식으로 압축한 동영상 데이터를 제안한 알고리즘에 적용해 봄으로서 버퍼지연과 버퍼넘침 발생 등이 기존-의 방식에 비해 감소함을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제2권2호
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• pp.117-123
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• 2002

This paper describes the design for the resistive FET mixer with low If for the 4-Ch DBF(Digital Beam Forming) receiver This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(If) considered in this research are 2.09 GHz, 2.08 CHz and 10 MHz, respectively. This mixer is composed of band pass filter, a low pass filter and a DC bias circuit. Super low noise HJ FET of NE3210S01 is considered in design. The RE input power, LO input power and Vcs are used -10 dBm, 6 dBm and -0.4 V, respectively. In the 4-Ch resistive FET mixer, the measured If and harmonic components of 10 MHe, 20 MHz and 2.087 CHz are about -19.2 dBm, -66 dBm and -48 dBm, respectively The If output power observed at each channel of 10 MHz is about -19.2 dBm and it is higher 28.8 dBm than the maximum harmonic component of 2.087 CHz. Each If output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• 한국통신학회논문지
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• 제27권7A호
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• pp.629-634
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• 2002

차세대 무선 통신 시스템은 현재의 시스템보다 고속 인터넷 접속 및 무선 이동 컴퓨팅과 같은 무선 멀티미디어 서비스를 제공할 것으로 예상된다. 사용자의 서비스 품질(QoS)에 대한 요구와 각각의 응용 프로그램에 따라, 이러한 요구를 충족시킬 만한 많은 무선 통신 시스템이 제안되고 있다. 시공간 전송 다이버시티 기법 중 하나인 시공간 블록 부호 시스템은 플랫 페이딩을 기반으로 하는 간단한 최대 우도 복호 알고리즘을 사용하기 때문에 무선 채널의 불완전성에 기인하는 심볼간 간섭에 대한 고려가 필요하다. 본 논문에서는 이러한 문제를 해결하기 위해 적응형 등화기를 이용한 시공간 전송 다이버시티 시스템을 제안한다. 제안된 시스템은 다중 접속 간섭을 유발하는 간섭을 효과적으로 제거할 수 있다. 모의 실험을 통하여 제안된 시스템이 비트 오율 성능을 개선시키는 것을 확인하였다.

• 한국통신학회논문지
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• 제37권5B호
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• pp.365-369
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• 2012

동기식 고속 광전송망에서 망간 delay보상을 통한 동기제어는 매우 중요하다. 본 연구에서는 광선로의 길이에 따른 time delay를 보상하기 위하여 Rayleigh 산란광을 이용한 OTDR방식의 delay 측정장치를 제작하여 평균화 횟수와 광펄스의 peak power에 따른 파형변화를 관찰하고 기존에 활용되고 있는 방식과의 정확도에 대한 비교측정을 통해 실제 시스템에 적용타당성에 대한 검증실험을 실시한 결과 최대 0.06usec 이내의 측정오차와 0.021usec의 측정표준편차로서 이동통신 광중계기와 기지국 장비간 delay 제어에 적용이 가능함을 확인하였다.