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영상처리에 의한 자기카메라의 결함검출능 향상에 관한 연구
이진이(Jinyi Lee),황지성(Jiseong Hwang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The quantitative magnetic field around crack and its processed results could be obtained by using magnetic camera, and the crack could be inspected and evaluated quantitatively. In addition, the magnetic camera has to uphold with large lift-off to protect sensors from weak environment such as high temperature and mechanical vibration. However, the sensor sensitivity would be decreased when the lift-off was increased. Correspondingly, the improved techniques such as introducing a magnetic lens, increasing a S/N ratio, improving the ground method, developing an exclusive AD converter, and using a low-pass-filter, for increasing sensitivity of magnetic camera and probability of crack detection, have been studied. However, the unspecified noise from the signal lines could not be excluded exactly, and could be confused noise with small crack. This paper proposes a magnetic field image processing algorithm which could minimize or ignore the unspecified noise.
수직자화와 자기광학센서를 이용한 비파괴 탐상의 이론적 고찰
이진이(Jinyi Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
This paper describes a new magnetization method which have the following characteristics: high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as a multiple crack. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B<SUB>Z</SUB>, is almost uniform over the no-crack area (denoted as B<SUB>Z,BASE</SUB>), while the magnetic flux density is smaller in the surroundings of the crack (denoted as B<SUB>Z,CRACK</SUB>). If BZ,BASE is a bit larger than the saturated magnetic flux density of the MO sensor(B<SUB>S</SUB>), then small magnetic domains occur over the crack area and a large domain over the non-crack area because B<SUB>Z,CRACK</SUB> is smaller than B<SUB>S</SUB>.
이진이(Jinyi Lee),이재선(Jae Sun Lee),레후이민(Hui-Minh Ley),신기수(Ki Su Shin) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4
탄환에 회전관성을 부여하여 안정된 탄도를 가지게 하기 위하여 강선이 도입되고 있다. 강선은 배관의 안쪽에 나선형 구조를 가지므로 응력집중이 발생하기 쉽다. 또한, 반복적인 인장하중에 기인하여 피로 균열의 진전이 용이하다. 반면에 구조적인 측면에서 결함 검출이 용이하지 않다. 본 연구에서는 산과 골 사이에 센서를 밀착시킬 수 있는 구조의 결함 탐상 장치를 개발하였다. 강선의 마모는 물론 길이 4㎜, 깊이 0.5㎜, 폭 0.1㎜의 결함을 검출할 수 있었다. Rifles are introduced in a barrel for having a stable trajectory due to the rotary inertia. However, the spiral concavo-convex shape has a stress concentration. Also, the crack is difficult to inspect due to its complex structure. A non-destructive testing method is proposed in this paper. Each tip of sensors is closely contacted with the edge of concavo-convex rifle. Not only the damaged convex part, but also a crack with the length of 4㎜, depth of 0.5㎜, width of 0.1㎜ under the edge was detected.
이진이(Jinyi Lee),황지성(Ji-Seong Hwang),서정원(Jung-Won Seo) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A novel nondestructive testing (NDT) system, which is able to detect a crack with high speed and high spatial resolution, is urgently required for inspecting small cracks on express train wheels. This paper proposes a high speed scan type magnetic camera, which uses the multiple amplifying circuits and the crack indicating pulse output system. The linearly integrated Hall sensors are arrayed in parallel, and the Hall voltages from each sensor in the scanning direction are obtained and amplified. High-speed NDT can be achieved by using the exclusive analog-digital converter and micro-processor because the ? V<SUB>H</SUB>/V x value, which provides the most important crack information, can be obtained by buffering and calculating. The effectiveness of the novel method was verified by examine using cracks on the wheel specimen model.
이동 통신망에서 위너필터 예측에 의한 대역폭예약 할당기법
이진이(Jinyi Lee) 한국정보기술학회 2007 한국정보기술학회논문지 Vol.5 No.4
In wireless mobile networks, the amount of bandwidths required by connections can be predicted and reserved to service coming mobile hosts. This paper presents a bandwidth reservation allocation method based on Wiener prediction theory in predicting and reserving its demands for future handoff connections. The proposed method has the potential to improve on CDP(connection dropping probability) for handoff connections by predicting and reserving their bandwidth demands, and it can also improve on resource utilization by predicting resource requirements with accuracy. Wiener-based on prediction method can predict the amount of resource required by handoff connections at a future time with past resource demands. So, this scheme is much simpler to implement than mobility prediction resource reservation scheme which needs estimation of connection arrival process, per-connection bandwidth demand, estimation of connection and channel holding time distribution, and so on. Also Wiener-based on prediction scheme remains equal prediction performance with mobility-based on prediction scheme[1]. We compare via simulation the performance of the proposed methods with the existing GCAS(guard channel allocation scheme)in terms of CDR, CBR, and bandwith utilization. The results reveal that our proposed bandwidth allocation method generates better performance than the existing GCAS method.
이진이(Jinyi Lee),황지성(Ji-Seong Hwang),권석진(Seok-Jin Kwon),서정원(Jung-Won Seo) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
A novel nondestructive testing (NDT) system, which is able to detect a crack with high speed and high spatial resolution, is urgently required for inspecting small cracks on express train wheels. This paper proposes a high speed scan type magnetic camera, which uses the multiple amplifying circuits and the crack indicating pulse output system. The linearly integrated Hall sensors are arrayed in parallel, and the Hall voltages from each sensor in the scanning direction are obtained and amplified. High-speed NDT can be achieved by using the exclusive analog-digital converter and micro-processor because the ∂VH/∂x value, which provides the most important crack information, can be obtained by buffering and calculating. The effectiveness of the novel method was verified by examine using cracks on the wheel specimen model.