• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.89-97
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• 2006

Purpose : To evaluate MR image qualities we developed a new MRI phantom with the fixation structures necessary to position it into coil firmly. Materials and methods : We designed MRI phantom for eight evaluation items such as slice thickness accuracy, high contrast spatial resolution, low contrast object detectability, geometry accuracy, slice position accuracy, image intensity uniformity, percent signal ghosting and signal to noise ratio. For the positioning of phantom at coils, the fixation structures were set up on the surface of phantom. Six different MRI units were used for test the possibility for the clinical application and their image qualities were evaluated. Results : We acquired appropriate MR image qualities enough for the evaluation on all used MR units and confirmed that their evaluations were within reliable values compared to real ones for some items. The positioning of our phantom into head coils with fixation structures worked well for proper imaging. Conclusion : We found that our prototype of MRI phantom had the possibility of clinical application for MR image quality assessment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.166-173
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• 2014

A noncontact nondestructive testing (NDT) method is proposed to detect the damage of pipeline structures and to identify the location of the damage. To achieve this goal, a scanning laser source actuation technique is utilized to generate a guided wave and scans a specific area to find damage location more precisely. The ND: YAG pulsed laser is used to generate Lamb wave and a piezoelectric sensor is installed to measure the structural responses. The measured responses are analyzed using three dimensional Fourier transformation (3DFT). The damage-sensitive features are extracted by wavenumber filtering based on the 3D FT. Then, flaw imaging techniques of a pipeline structures is conducted using the damage-sensitive features. Finally, the pipes with notches are investigated to verify the effectiveness and the robustness of the proposed NDT approach.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.3
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• pp.231-238
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• 2007

This paper describes the availability of the forthcoming integrated GNSS(Global Navigation Positioning System) positioning that includes GPS(Global Positioning System), Galileo, and QZSS(Quasi-Zenith Satellites System). We built a signal propagation model that identifies direct, multipath, and diffraction signals, using the principles of specular reflection and ray tracing technique. The signal propagation model was combined with 3D GIS(three-dimensional geographic information system) in order to measure the satellite visibility and positioning error factors, such as the number of visible satellites, average elevation of visible satellites, optimized DOP(dilution of position) values, and the portion of multipath-producing satellites. Since Galileo and QZSS will not be fully operational until 2010, we used a simulation in comparing GPS and GNSS positioning for a $1km{\times}1km$ developed area in Shinjuku, Tokyo. To account for local terrain variation. we divided the target area into 40,000 $5m{\times}5m$ grid cells. The number of visible satellites and that of multipath-free satellites will be greatly increased in the integrated GNSS environment while the average elevation of visible satellites will be higher in the GPS positioning. Much decreased PDOP(position dilution of precision) values indicate the appropriate satellite/user geometry of the integrated GNSS; however, in dense urban areas, multipath mitigation will be more important than the satellite/user geometry. Thus, the efforts for applying current technologies of multipath mitigation to the future GNSS environment will be necessary.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.258-263
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• 1995

미래 정보와 시대에서 중추적인 역할을 할 광관련 멀티미디어 장비들은 최근 관련 산업계에서 주목을 받기 시작하고 있고 특히 기존 VTR(Video Tape Recorder) 시장을 대체할 차세대 DVDR(Digital Video Disk Recorder)는 기술전쟁이라고 할 정도로 선진 기업의 연구가 치열해지고 있다. DVDR 시스템에서는 필요한 정보들을 레이저빔을 이용한 광학신호로 바꾸어 광디스크에 기록, 재생하는 광픽업이 절대적으로 필요하게 된다. 그런데 광픽업의 위치추종기구인 Actuator는 정확한 위치추종(.+-.1.$\mu$m 오차이내)을 할 수 있는 성능이 요구되며 서보의 특성상 20KHz 이하에서 불필요한 모우드가 가진되지 않는 정밀부품이어야 하므로 Actuator 각 부품의 동적인 특성을 명확히 규명할 필요가 있다. 따라서 본 연구에서는 우선 Actuator 각 부품과 가동부 전체의 중량 및 진동해석을 통해 동특성을 조사하였다. 그리고 Actuator의 중요한 기본성능중 하나인 구동감도 확보여부를 검토할 필요가 있기 때문에 유한요소법 프로그램인 ANSYS를 이용하여 자기회로 부분에 대한 해석을 구하였다. 또한 가동부와 자기회로 등 하위부품을 조립하는 과정에서 발생하는 조립오차로 인해 불필요한 공진과 회전형상이 야기될 수 있으므로 동특성 및 문제점 파악을 위한 민감도 분석이 필요하다. 따라서 본 연구에서는 가동부의 관성 모멘트 값과 강체에 대한 일반식을 이용한 자체 프로그램을 작성하여 조립공차를 구하였다. 이와같은 과정을 통해 구해진 설계값을 바탕으로 실제 제작된 Actuator에 대해서는 비접촉식 측정방법을 통해 동특성값을 측정하였고 이를 해석값과 상호 비교하였다.동강성행렬법(dynamic stiffness matrix method)을 이용하여 해석하고자 한다. 수준임이 입증되었다. 본 연구의 결과를 토대로우리나라 젊고 건강한 남성에게 적합한 무게상수는 작업자군에 대하여 25.05kg, 학생군에 대하여 20.24kg 으로 나타나 이는 미국 NIOSH 안전기준과 대체로 일치함을 발견하였다.ive structures utilized in Client/server architecture for distribution and cooperative processing of application between server and client this study presents two different data management methods under the Client/server environment; one is "Remote Data Management Method" which uses file server or database server and. the other is "Distributed Data Management Method" using distributed database management system. The result of this study leads to the conclusion that in the client/server environment although distributed application is assumed, the data could become centralized (in the case of file server or database server) or decentralized (in the case of distributed

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.39-46
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• 2014

Network RTK positioning, one of GNSS positioning systems, is currently very popular due to its easy operation and low cost. However, the network RTK positioning unquestioningly accepts observation result acquired with an ambiguity fixed-solution regardless of different field conditions and situations, and then it is applied to the practice. This paper, therefore, has investigated the effects of field conditions obtained network RTK survey data for the area with obstacles on the variation of positioning accuracy. Being explained in detail, after conducting survey by GPS-only positioning and combined GPS/GLONASS observations giving changes to the distance from obstacles and elevation angles, and then accuracy results of each positioning method were compared each other. As a result, while GPS-only point positioning method showed more stable results than combined GPS/GLONASS method in the areas with no obstacles, combined method gave better result than GPS-only for the areas with presence of obstacles. Based on the results of this experiment, when the further study is conducted with a variety of different field conditions affecting the survey accuracy, it can be expected that the accuracy of network RTK survey method would become to more popular.

• Korean Journal of Plant Resources
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• v.35 no.1
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• pp.134-167
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• 2022

This study conducted monitoring of flora and vegetation in order to utilize basic data for forest wetland conservation targeting outstanding forest wetlands located in the eastern part of Jeonnam Province. The survey was carried out for a total of 54 times from May 2020 to October 2020, 1-2 times each for each season. The vascular plants of outstanding forest wetland in eastern Jeollanam-do were 93 families, 251 genera, 336 species, 5 subspecies, 47 varieties, 7 forma, and a total of 395 taxa. This was about 8.5% of 4,641 species of vascular plants in Korea Peninsula. A total of 8 taxa and 12 taxa were identified Korea endemic plants and rare plants respectively. A total of 68 taxa and 19 taxa of floristic target plants and invasive alien plants were classified each. the naturalized Index was 4.83% and the urbanized Index was 5.90%. As a result of the analysis by wetland type of the forest wetlands, obligate upland plants were the highest in the forest wetlands in the eastern Jeonnam province (61.4%), with unclassified wetland plants 19.1%, facultative wetland plants 8.2%, and obligate wetland plants 4.6%, facultative upland plants 4.5%, and facultative plants 2.3% were confirmed in the order.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.742-750
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• 2020

The flow noise generated by hull appendages is directly related to the performance of the sonar in terms of self-noise and induces a secondary noise source through interaction with the propeller and rudder. Thus, the noise in the near field should be analyzed accurately. However, the acoustic analogy method is an indirect method that is not used to simulate the propagation of an acoustic signal directly; therefore, diffraction, reflection, and scattering characteristics cannot be considered, and near-field analysis is limited. In this study, the propagation process of flow noise in water was directly simulated by using the lattice Boltzmann method. The lattice Boltzmann method could be used to analyze flow noise by simulating the collision and streaming processes of molecules, and it is suitable for noise analysis because of its compressibility, low dissipation rate, and low dispersion rate characteristics. The flow noise source was derived using Reynolds-averaged Navier-Stokes equations for the hull appendages, and the propagation process of the flow noise was directly simulated using the lattice Boltzmann method by applying the developed flow-acoustic boundary conditions. The derived results were compared with Ffowcs Williams-Hawkings results and hydrodynamic pressure results based on the receiver location to verify the usefulness of the lattice Boltzmann method within the near-field range in comparison with other techniques.

• Research in Plant Disease
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• v.15 no.3
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• pp.170-174
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• 2009

In this paper, we report a characterization of Prunus necrotic ringspot virus (PNRSV) isolate. The virus was identified from 'Yumyeong' peach showing mild mosaic on leaves in commercial orchard of 'Umsung', Chungbuk province in Korea. The virus isolate produced ringspot symptom on the inoculated cotyledons and systemic mosaic and malformation on the upper leaves of Cucumis sativus. Systemic mottles were appeared in Chenopodium quinoa. When the buds of the virus infected stem were grafted on the healthy young Prunus persica GF305 seedlings, line pattern with mosaic appeared within 3 months. Isometric virus-like particles were found in parenchyma cells and plasmodesmata of C. sativus leaves inoculated mechanically with the virus. The cDNA fragments of PNRSV coat protein (CP) region, approximately 675bp, were synthesized from genomic RNA extracted from virus-infected leaves by RT-PCR using specific primer pairs. Partial nucleotide sequences of the CP regions were determined and analyzed with the known PNRSV. The CP gene of PNRSVKorea isolates showed 93.9~94.7% similarity to the 4 known PNRSV isolates.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.71-79
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• 2011

The objective of the imaging pipeline is to transform the original scene into a display image that appear similar, Generally, gamma adjustment or histogram-based method is modified to improve the contrast and detail. However, this is insufficient as the intensity and the chromaticity of illumination vary with geometric position. Thus, MSR (Multi-Scale Retinex) has been proposed. the MSR is based on a channel-independent logarithm, and it is dependent on the scale of the Gaussian filter, which varies according to input image. Therefore, after correcting the color, image quality degradations, such as halo, graying-out, and dominated color, may occur. Accordingly, this paper presents a novel color correction method using a modified image formation model in which the image is divided into three components such as global illumination, local illumination, and reflectance. The global illumination is obtained through Gaussian filtering of the original image, and the local illumination is estimated by using JND-based adaptive filter. Thereafter, the reflectance is estimated by dividing the original image by the estimated global and the local illumination to remove the influence of the illumination effects. The output image is obtained based on sRGB color representation. The experiment results show that the proposed method yields better performance of color correction over the conventional methods.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.93-100
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• 2009

This paper presents a step up four channel DC-DC converter using charge pump voltage doubler structure. Our goal is to design and implement DC-DC converter for capacitive SP4T RF MEMS switch in front end module in wireless transceiver system. Charge pump structure is small and consume low power 3.3V input voltage is boosted by DC-DC Converter to $11.3{\pm}0.1V$, $12.4{\pm}0.1V$, $14.1{\pm}0.2V$ output voltage With 10MHz switching frequency. By using voltage level shifter structure, output of DC-DC converter is selected by 3.3V four channel selection signals and transferred to capacitive MEMS devices. External passive devices are not used for driving DC-DC converter. The total chip area is $2.8{\times}2.1mm^2$ including pads and the power consumption is 7.52mW, 7.82mW, 8.61mW.