• 한국전자파학회지:전자파기술
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• 제6권4호
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• pp.20-27
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• 1995

본 논문에서는 직선 배열 응원에 의한 초음파 트랜스듀서의 목적 지향성에 대한 Beam forming을 Gauss 소거법을 이용하여 수치 계산하였다. 하나의 System으로 여러 가지의 조건에 대한 지향성 합성의 실현을 목적으로 하였으며, 목적 지향성으로는 계산에 의해 합성된 선음원에 의한 지향성과 임의로 설정한 Beam 폭의 변화와 방사 방향의 회전에 대한 준이상 Beam을 선택하여 지향성 합성을 시융레이션 하였다. 수치 계산에는 PC(CPU: 80486DX2, RAM 16Mbyte)를 이용하였으며, 수치 계산 결과, 반복법(LMS볍, DFP볍)에 비해 훨씬 빠른 지향성 합성이 가능하고, 또 System 안정도 면에서도 매우 양호함을 확인했다.

• 한국안전학회지
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• 제20권2호
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• pp.151-157
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• 2005

One of the most significant parts in the international major meetings is to stand attendants over various danger and keep the safe of the nation. The International major meetings such as the summit, the athletic meeting are often held around the world while the activity of the terrorists unseen increases at the high speed. The goal of this thesis is to present some effective ways for successful opening of the international event. Some of the proposals that I come up with the research can be summarized as follows: the smooth cooperation between countries, the control for NGO's demonstration, the training and the best use of security personnel, finally the understanding of peoples and forming sympathy from them.

• 소성∙가공
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• 제10권3호
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• pp.206-213
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• 2001

Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heat. Since the flow stress of deformation is sensitive to temperature, implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study, a series of compression tests were conducted for SAF 2507 super duplex stainless steel at various temperatures and strain rates. The accumulation of plastic work was calculated through numerical integration and converted into the elevation of temperature. Subsequent logarithmic interpolation deduced isothermal flow surfaces, which were primary input data of finite element analysis. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database. The effect of accounting deformation heat was more noticeable in high-speed forming process.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.850-853
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• 2005

This paper presents issues of display hardware architecture, relating to memory, display driver IC architecture, and chip-to-chip interface. To achieve a low power and low cost mobile phone, not only the display architecture must be carefully selected, but also the driver-ICs optimized to accommodate the different modes of operation found in typical handheld devices. The technique of forming a photo sensor in each pixel using TFT and display module architecture are developed to add multi functions in display such as fingerprint recognition, image scanning, and integrated touch screen. Detailed architectures of IC partitioning, high-speed serial interface, D/A converter, and multi functions such as fingerprint recognition and image scanning using photo sensors are important to a power optimized system.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.258-261
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• 2002

Electrical forming dependent current-voltage (I-V) and numerically derived differential conductance(dI／dV) characteristics have been presented in the multi-layer nano-crystalline silicon／oxygen (no-Si／O) superlattice. Distinct staircase-like features, indicating the presence of resonant tunnel barriers, are clearly observed in the dc I-V characteristics. Also, all samples showed a continuous change in current and zero conductivity around OV corresponding to the Coulomb blockade in the calculated dI／dV-V curve. Also, Ra-man scattering measurement showed the presence of a nano-crystalline Si structure. This result becomes a step in the right direction for the fabrication of silicon-based optoelectronic and quantum devices as well as for the replacement of silicon-on-insulator (SOI) in high speed and low power silicon MOSFET devices of the future.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.16-20
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• 2002

This paper describes the resistive FET mixer with low IF for the 4-Ch DBF(Digital Beam Forming) receiver with LNA(Low Noise Amplifier). 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 ㎓, 2.08 ㎓ and 10㎒, respectively. The RF input power, LO input power and Vgs are used -10㏈m, 6㏈m and -0.4 V, respectively. In the 4-Ch resistive FET mixer with LNA, the measured IF and harmonic components of 10㎒, 20㎒, 2.09㎓ and 4.17㎓ are about -12.5 ㏈m, -57㏈m, -40㏈m and -54㏈m, respectively. The IF output power observed at each channel of 10㎒ is about -12.5㏈m and it is higher 27.5 ㏈m than the maximum harmonic component of 2.09㎓. Each IF output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• 소성∙가공
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• 제13권1호
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• pp.59-64
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• 2004

Nano-scratch tests were performed on PMMA thin films spin-coated on a Si substrate using an atomic force microscopy (AFM) with loads ranging form 10nN to 100nN. At low loads, a ridge pattern was formed on the PMMA thin film surface. No wear particles were observed during the pattern-forming mild wear. At high loads, severe wear by plowing occurred, accompanied by wear particles. The film with the highest hardness showed the highest wear resistance. Friction force generated during the scratching was measured, which was closely related with surface deformation of the film. A simple empirical equation to deduce scratch hardness of the film from a linear fixed-distance scratch test was proposed, and scratching-speed dependency of the scratch hardness was displayed.

• 펄프종이기술
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• 제31권1호
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• pp.52-60
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• 1999

Drainage rate in wet-end, which has significant influences on the production capacity, product quality and process economics in papermaking, becomes an important factor in the modern high speed papermaking processes owing to increased level of fines contained in today's pulp materials and increased papermaking system closure. A study was carred out to investigate the influence of beating and fines content on natural and vacuum dewatering using a vacuum drainage tester. Increase in beating and accumulation of fines in the stock decreased natural dewatering, Vacuum dewatering effect, however, increased substantially as beating and fines content were increased. But this increase in vacuum dewatering decreased again when a stock is severely beaten or fines content is greater than 35%. Above this level of fines content, mobile fines migrates to the interstices of the forming web to cause sealing or plugging which restrict fluid movement through the web.

• 전자공학회논문지S
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• 제34S권9호
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• pp.31-40
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• 1997

This paper presents a hybrid WDM/TDM channel acess protocol for high speed WDM networks based on passive double star topology. In the proposed scheme, all nodes in a network are splitted into groups forming passive double star topology and each node has a tunable transmitter and a fixed receiver. WDM channels are allocated to the groups, which are used as home channels to transmit or receive packets. TDM frames of the WDM channel are composed of the same number of slots as that of groups, and all nodes in a group transmit packets simultaneously at each slot. The proposed scheme reduces the system complexity and the number of the required WDM channels. It was proved that the proposed protocol is less sensitive to the propagation delay and maintaining its superior transmission performance by employing the efficient transmission schedule based on passive double star topology.

• 한국기계가공학회지
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• 제7권4호
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• pp.56-61
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• 2008

Cropping metal materials is widely used for feeding processes of various forming method, such as forging, extrusion, drawing, and upsetting. However, cropping has many weak points, which are material loss in part of cutting, chip creation, and much use of lubrication oil, etc. In this study, instead of cropping, a novel process is proposed to cut metal materials, especially stainless steel bar which is known very difficult to crop. Results of FE-analysis will be shown to verify the proposed method comparing with those of the conventional cropping process. Also, fitting products were successfully forged using the fabricated billet by the proposed process.