• 대한금속재료학회지
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• 제48권4호
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• pp.357-362
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• 2010

Ferromagnetic Mn-Al nanoparticles were prepared using a plasma arc discharge method. The influence of the process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother materials, although the difference diminished with the reaction time. As the $H_2$ content in the reaction gas increased, both the vaporization rate and the particle size increased. With 30 at.% Mn, the average particle diameter was 35.2 nm under a pure Ar gas condition, whereas it was 95.4 nm at a Ar:$H_2$ ratio of 60:40. With the addition of a small amount of carbon, ${\varepsilon}$-phase nanoparticles were successfully synthesized. After a heat treatment in a vacuum for 30 min at $500^{\circ}C$, the nonmagnetic ${\varepsilon}$-phase was transformed into the ferromagnetic ${\tau}$-phase, and a very high coercivity of nearly 5.6 kOe was achieved.

• 한국CDE학회논문집
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• 제4권3호
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• pp.247-258
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• 1999

With the contemporary CAD/CAM system, where the tool path is generated and verified purely based on the geometric operation, geometric accuracy of the machined surface cannot be guaranteed dut to the cutting mechanics, meaning that the cutting mechanics should be incorporated in some fashion. In this paper, we incorporate the instantaneous cutting force and the tool deflection phenomena in predicting the machined surface for the finish-cut and milling operation. For the given NC dat including cutting conditions, the developed algorithm computes cutting force and deflection amount along the tool trajectory, and outputs the 3D graphic model of the machined surface together with error analysis. The validity and accuracy of the presented method has been tested by the actual cutting experiments. Experimental results and accuracy enhancement method together with implementing architecture of the VMCS (Virtual Machining CAM System) are discussed in the paper.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.379-386
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• 2001

Fluid viscous dampers have been used as energy dissipators or STU's (Shock Transmission Unit) in earthquake resistant designs for bridges. Viscous dampers have many advantages compared to other friction type or visco-elastic type of dampers. They do neither increase internal pier forces due to their out of phase response, nor produce reaction forces at the low velocities associated with thermal movements. Therefore, they anable the super structure to restore itself perfectly after a severe movement dut to seismic excitations. This paper investigates the response of bridges designed with viscous dampers in regard to damping coefficients, properties of dampers, and arrangements of dampers. For this purpose, time-history dynamic analyses have been performed using a very simple model relevant to a typical bridge example. Based on the results, it presents some design duidelines on how to determine a proper damping ratio and on how to arrange dampers. In usual cases, damping coefficients corresponding to about 0.2-0.3 of damping ratios seem to be very effective in bridge designs.

• 대한전기학회논문지
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• 제36권10호
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• pp.703-712
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• 1987

A position detection method for 2 phase bifilar permanent magnet step motors is proposed. The back emfgenerated on 2 phase windings by rotor permanent magnet is calculated using motor terminal voltage and current by analog circuit, and the rotor position output is obtained from tese back emf signals through some logical manipulation circuit. This position detector functionally acts like a 2 channel optical incremental encoder, and it is also shown by experimental results that it works well over wide range of speed or under resonant condition where the rotor rings around the detent position. Its resolution is twice of the number of steps per revolution. Bu software implemented on micro-processor, the reliability of position output is enhanced, detecting and correcting error dut to external and/ or internal noise.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.360-360
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• 2010

반도체 산업은 지속적인 design rule 감소로 인해 직접도 및 Pin Count가 점점 증가함에 따라 보증해야할 회로의 수와 기능이 더불어 증가하고 있으며, 그 중 Test Cost 감소 방법 확보가 시급하게 되었다. 이에 따라 Test Cost 감소와 직결된 Test Time 감소 방법이 다양하게 제시되고 연구되고 있다. 본 논문은 Test Time의 한 부분인 반도체 검사 장비 (Automatic Test Equipment)의 효율적인 제어 방법을 제공함으로써, 관련 분야의 이해를 돕고자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.19-22
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• 1997

The objective of this research is to use an analytical and experimental approach to develop optimal tool geometry for high speed machining. The tool geometry parameters and cutting process have complex relationships. Until now, numerous cutting tests were needed to acquire optimal design of endmill for the purpose of high speed machining, dut to the insufficient knowledge about process in high speed machining. In order to improve the cutting ability of endmill, a model for optimal cutter shape was developed to minimize resultant cutting force by combing cutting force and wear test and surface roughness test from optimized and conventional cutter with the same cutting condition. Using various tools with different geometry, relationships between the tool geometry parameter, rake angle, clearance angle, lengh of cutter have been stuied.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.818-823
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• 2003

본 논문에서는 입력 매칭(input matching) BIST(Built-In Self-Test) 회로를 이용한 RF font end의 새로운 결함 검사방법을 제안한다. BIST 회로를 가진 RF front end는 1.8GHz LNA(Low Noise Amplifier: 저 잡음 증폭기)와 이중 대칭 구조의 Gilbert 셀 믹서로 구성되어 있으며, TSMC 0.25$\mu\textrm{m}$ CMOS 기술을 이용하여 설계되었다. catastrophic 결함 및 parametric 변동을 가진 RF front end와 결함을 갖지 않은 RF front end를 판별하기 위해 RF front end의 입력 전압 특성을 조사하였다. 본 방법에서는 DUT(Device Under Test: 검사대상이 되는 소자)와 BIST 회로가 동일한 칩 상에 설계되어 있기 때문에 측정할 때 단지 디지털 전자계와 고주파 전압 발생기만이 필요하며, 측정이 간단하고 비용이 저렴하다는 장점이 있다. BIST 회로가 차지하는 면적은 RF front end가 차지하는 전체면적의 약 10%에 불과하다. 본 논문에서 제안하는 검사기술을 이용하여 시뮬레이션해 본 결과 catastrophic 결함에 대해서는 100%, parametric 변동에 대해서는 약 79%의 결함을 검출할 수 있었다.

• 반도체디스플레이기술학회지
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• 제5권4호
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• pp.17-22
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• 2006

In the manufacturing processes of semiconductor, test process is important for quality of products. In the manufacturing process of dynamic memory, memory test is more important. So, automatic test equipment(ATE) is used necessarily. But, according to increase of speed of dynamic memory operation, the rapid test equipment is needed. Impedance matching between ATE and dynamic memory is expected to be an important problem for making a rapid test equipment over 1Gbps. According to increase of speed, inner impedance of ATE also works on important parameter for test. This paper is about the method that is for impedance matching of inner impedance and coaxial cable occurring in manufacturing of ATE. We proved effects of inner impedance by electric theory and verified the method of impedance matching using computer simulation.

• 산업기술연구
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• 제27권A호
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• pp.169-175
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• 2007

In High-Speed DSP systems, crosstalk between transmission lines of multi-channel can degrade the performance of equipment operations. This paper presents a microwave board to measure multi-channel coaxial cable assembly. The designed board has good performances from DC to 3 GHz, which have improved characteristic impedance, reduced crosstalk by using via fence, and low transmission loss. Using the designed board, we can measure characteristics of DUT(Device Under Test) such as return loss, insertion loss, crosstalk phase delay, and characteristic impedance. The measured results are used to improve performances of a produced coaxial cable assembly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1133-1135
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• 2004

Superconducting transmission power cable is one of interesting parts in power application using high temperature superconducting wire. One of important parameters in high-temperature superconducting (HTSC) cable design is transport current distribution because it is related with current transmission capacity and ac loss. In this paper, the transport current and magnetic field distributions at conducting layers were investigated through the analysis of the equivalent circuit for HTSC power cable with shield layer. The transport current distribution due to the pitch length and winding direction was improved in case of HTSC power cable with shield layer.