• Composites Research
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• v.30 no.1
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• pp.35-40
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• 2017

In this study, natural fiber composites including flax fiber reinforcement was manufactured. It was tried to find optimum design of drill and machining factor for minimizing the damage during hole machining in natural fiber composites. Taguchi optimization was used for minimizing the number of experiments and evaluation of the effect of machining factor during hole machining in natural fiber composites. The experimental results indicate that the newly designed drill distributes cutting resistance well and minimizes surface roughness and produces fine surfaces. Developed new drill has been dispersed in the cutting resistance during processing, it was possible to obtain the smooth hole surface. Also, it was found that optimal rotational speed and feed rate of drill for hole machining.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.179-183
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• 2001

Magnetoresistance and Planar Hall effect of Glass/Ni$\sub$83/Fe$\sub$17/(2 nm)/[Cu(2 nm)Ni$\sub$83/Fe$\sub$17/(20 nm)]$\sub$50/ multilayer were measured. Repeated saw tooth like planar Hall effect signal was observed in the range of magnetization reversal process, while no sign of such saw tooth was observed in Magnetoresistance diagram. For the reason of saw tooth like signal, it is supposed that subsequent abrupt domain wall motion of each magnetic layer in the process of magnetization reversal process was observed in planar Hall effect in transverse direction to the current direction. This fine structure of planar Hall effect was observed for applied fields in any direction. Magnetoresistance curve did not show this fine structure of magnetization reversal, of course, since only net magnetization of each layer has to do with the resistivity. Extended research on the reason of this sawtooth like signal should be conducted.

• The KIPS Transactions:PartB
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• v.14B no.5
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• pp.351-360
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• 2007

Video Completion refers to a computer vision technique which restores damaged images by filling missing pixels with suitable color in a video sequence. We propose a new video completion technique to fill in image holes which are caused by removing an unnecessary object in a video sequence, where two objects cross each other in the presence of camera motion. We remove the closer object from a camera which results in image holes. Then these holes are filled by color information of some others frames. First of all, spatio-temporal volumes of occluding and occluded objects are created according to the centroid of the objects. Secondly, a temporal search technique by voxel matching separates and removes the occluding object. Finally. these holes are filled by using spatial search technique. Seams on the boundary of completed pixels we removed by a simple blending technique. Experimental results using real video sequences show that the proposed technique produces new completed videos.

• Journal of KIISE:Databases
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• v.35 no.1
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• pp.67-83
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• 2008

In order to realize ubiquitous computing, it is essential to efficiently use the resources and the computing power of mobile devices. Among others, memory efficiency, energy efficiency, and processing efficiency are required in executing the softwares embedded in mobile devices. In this paper, query processing over XML data in a mobile device where resources are limited is addressed. In a device with limited amount of memory, the techniques of XML. stream query processing need to be employed to process queries over a large volume of XML data Recently, a technique Galled XFrag was proposed whereby XML data is fragmented with the hole-filler model and streamed in fragments for processing. With XFrag, query processing is possible in the mobile device with limited memory without reconstructing the XML data out of its fragment stream. With the hole-filler model, however, memory efficiency is not high because the additional information on holes and fillers needs to be stored. In this paper, we propose a new technique called XFLab whereby XML data is fragmented with the XML labeling scheme which is for representing the structural relationship in XML data, and streamed in fragments for processing. Through implementation and experiments, XML showed that our XFLab outperformed XFrag both in memory usage and processing time.

• Journal of Digital Convergence
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• v.19 no.11
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• pp.341-349
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• 2021

We studies to verify results similar to those of previous experiments, and their potential as a lighting device through optical characteristics experiments and resonance and optical characteristics simulations of array devices. The photonic quantum ring (PQR) device having a mesa diameter of 40 ㎛ and an internal hole diameter of 3 ㎛ was fabricated. Through the near-field observation of the fabricated device, it was found that the PQR device operates even at ㎂, and also that the mesa and hole devices are driven independently of each other. As a result of measuring the wavelength spectrum of the device according to the location, the coupling phenomenon due to mesa and holes was confirmed.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.2
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• pp.1-9
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• 2003

We develop an experimental system to inspect a metal mask and, in this paper, introduce its inspection algorithm. This system is composed of an ASC(Area Scan Camera) and a belt type xy-table. The whole area of the metal mask is divided into several inspection blocks. The area of each block is equal to FOV(Field of View). For each block, the camera image is compared to the reference image. The reference image is made by gerber file. The rotation angle of the metal mask is calculated through the linear equation that is substituted two end points of horizontal boundary of a specific hole in a camera image. To calculate the position error caused by the belt type xy-table, HT(Hough-Transform) using distances among the holes in two images is used. The center of the reference image is moved as much as the calculated Position error to be coincided with the camera image. The information of holes in each image, such as centroid, size, width and height, are calculated through labeling. Whether a holes is mado correctly by laser machine or not, is judged by comparing the centroid and the size of hole in each image. Finally, we build the experimental system and apply this algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.9-16
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• 2016

A position control system composed of the PMLSM(Permanent Magnet Linear Synchronous Motor), unlike conventional linear permanent magnet synchronous motor is fixed to the permanent magnet moving coil rails (permanent magnet = stator, coil = mover), the coil is fixed, moving the permanent magnet, we propose a position control system (permanent magnet = mover, coil = stator) structure. Position is measured not using conventional encoder or resolver but by adopting vector control method using 2 hall sensors generating rectangular signal. This method estimate the velocity and position of mover by using the quadruple of two hall sensor signal instead of encoder signal. Vector control of PMLSM using 2 hall sensor generating rectangular wave is proved to control the system stable and efficiently through simulation. Also hardware experiment reveals that the position control performance is measured within the range of $30{\sim}50{\mu}m$ in the accuracy of $10{\sim}20{\mu}m$, which is improved twice to the conventional method. The proposed method exhibits its economical efficiency and practical usefulness. The vector control technique using two hall sensors can be installed in narrow place, accordingly it can be implemented on the system where the conventional encoder or resolver cannot operate.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.19-25
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• 2008

In this study, we fabricated Organic Thin Film Transistors(OTFTs) with $C_{60}$ hole injection layer between organic semiconductor(pentacene) and metal electrode, and we compared the electrical characteristics of OTFTs with/without $C_{60}$. When the $C_{60}$ hole injection layer was introduced, the mobility and the threshold voltage were improved from 0.298 $cm^2/V{\cdot}s$ and -13.3V to 0.452 $cm^2/V{\cdot}s$ and -10.8V, and the contact resistance was also reduced. When the $C_{60}$ is inserted, the hole injection was enhanced because the $C_{60}$ prevent the unwanted chemical reaction between pentacene and Au. Furthermore, we fabricated the OTFTs using Al as their electrodes. When the OTFTs were made by only aluminum electrode, the channel were not mostly made because of the high hole injection barrier between pentacene and aluminum, but when the $C_{60}$ layer with an optimal thickness was applied between aluminum and pentacene, the device performances were obviously enhanced because of the vacuum energy level shift of Al and the consequent decrease of the hole injection barrier which was induced by the interface dipole formation between $C_{60}$ and Al. The mobility and $I_{ON}/I_{OFF}$ current ratio of OTFT with $C_{60}/Al$ electrode were 0.165 $cm^2/V{\cdot}s$ and $1.4{\times}10^4$ which were comparable with the normal Au electrode OTFT.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.393-393
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• 2009

유기물 기반 태양전지의 낮은 전하수송 효율 문제(전하이동거리 약 ~20nm)를 개선하기 위해서는 생성된 전자-홀 쌍이 빠르게 전극 층으로 이동하도록 태양전지 의 층 구조 및 특성을 제어하는 것이 중요하다. 그 방안으로 무기물 반도체인 산화아연을 나노구조물 형태로 제어하여 전자 이동층(Electron Conductive Layer) 으로 도입, 생성된 전자의 이동 가능한 면적을 넓히고 전자수송효율을 높여 유무기 복합체 태양전지의 Fill Factor를 향상시켰다. 또한 제조된 산화아연 나노구조물의 산소플라즈마 처리와 같은 표면 처리를 통하여 유기물 층과의 흡착성을 높이고 나노구조물 표면에 oxygen을 침투시켜 전자 이동도를 향상시켰다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.740-743
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• 2010

본 논문에서는 홀 효과를 이용하여 차축(Tone Wheel) 회전에 따른 자속밀도의 변화를 감지하여 속도를 검출하는 자동차용 차륜 속도센서를 개발 제작하였다. 개발된 센서는 능동형 차속센서로서 마그네트 내장형 2-wire 홀 IC와 케이블 연결부를 ABS를 이용 하우징한 모형 구조로 제작 실험하였다. 기존의 능동형 차속센서 중 1개사의 자동차용 차속센서 부품의 특성을 분석하여 본 논문에서 제작한 센서와 각 특성을 비교하였다. 본 논문에서 개발된 차속센서는 12km/h 이하에서의 최소 감지스피드 성능, $80^{\circ}C$이하의 작동온도, 49% ~ 51%의 듀티 사이클$[T_{on}/(T_{on}+T_{off})]$ 동작 특성을 보였다. 본 논문에서 제작한 능동형 차속센서는 수동형과 비교하여 부품수가 적고 소형화 및 경량화, 에어 갭(Air Gap) 변화에도 민감하지 않으며 듀티 사이클과 저속에서의 검출능력이 우수한 특성을 지닌다.