• 한국재료학회지
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• 제10권12호
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• pp.799-806
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• 2000

63Sn-37Pb에 Cu$_{6}$Sn$_{5}$를 분산시킨 760$\mu\textrm{m}$크기의 솔더범프를 Au(0.5$\mu\textrm{m}$)/Ni(5$\mu\textrm{m}$)/Cu(27$\pm$20$\mu\textrm{m}$) BGA 기판에 스크린)/Ni(5im)/Cu(27:201m) B3GA 기판에 스크린 프린팅법으로 제조하여, 리플로우 피크온도 유지시간, 15$0^{\circ}C$ 시효처리 시간에 따른 전단강도를 분석하였다. Cu$_{6}$Sn$_{5}$를 첨가한 솔더범프는 피크온도에서 30초간 유지시에는 63Sn-37Pb 솔더범프보다 높은 전단강도를 나타내었으나, 피크온도 유지시간을 60초 이상으로 증가시킴에 따라 전단강도가 63Sn-37Pb 솔더범프보다 저하하였다. 전단시험 후 솔더범프의 파단면은 초기에 전단 균열의 점진적인 전파에 의해 발생된 파괴부위와 점진적 균열전파에 의한 면적 감소로 솔더범프가 급격히 떨어져 나가면서 발생한 파괴부위로 구분할 수 있었다 피크온도 유지시간, 15$0^{\circ}C$ 시효처리 시간 및 Cu$_{6}$Sn$_{5}$ 첨가량에 무관하게 점진적 파괴모드에 의한 균열 전파길이가 증가할수록 솔더범프의 전단강도가 감소하였다.감소하였다.

• Journal of Welding and Joining
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• 제34권3호
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• pp.23-30
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• 2016

This paper discusses the optimization of friction stir spot welding (FSSW) process parameters for joining Aluminum alloy (AA6061-T6) with Magnesium alloy (AZ31B) sheets. Prior to optimization an empirical relationship was developed to predict the Tensile Shear Fracture Load (TSFL) incorporating the four most important FSSW parameters, i.e., tool rotational speed, plunge rate, dwell time and tool diameter ratio, using response surface methodology (RSM). The experiments were conducted based on four factor, five levels central composite rotatable design (CCD) matrix. The maximum TSFL obtained was 3.61kN, with the tool rotation of 1000 rpm, plunge rate of 16 mm/min, dwell time of 5 sec and tool diameter ratio of 2.5.

• 한국정밀공학회지
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• 제18권7호
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• pp.65-71
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• 2001

The development process of the polishing system for the aspherical lens mold for opto-electronics industry is described. The system uses the method that polishing tool is scanned on the surface under PC-NC control for the aspherical lens mold. The two axes interpolation of the minimum translation mechanism is applied to give uniform working condition by motion analysis. An aspherical surface is divided into multiple sections and each dwell time is calculated from the polishing rate model based on the Preston equation. As result of form error compensation experiment, initial form error is decreased about 25% while an average value of surface roughness is also reduced successfully from 180nm to 19nm.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.829-838
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• 2002

A constant volume combustion chamber is used to investigate the flame kernel development of gasoline air mixtures under various ignition systems, ignition energies and spark plugs. Three kinds of ignition systems are designed and assembled, and the ignition energy is controlled by the variation of the dwell time. Several kinds of spark plugs are also tested. The velocity of flame propagation is measured by a laser deflection method, and the combustion pressure is analyzed by the heat release rate and the mass fraction burnt. The results represent that as the ignition energy is increased by enlarging either dwell time or spark plug gap, the heat release rate and the mass fraction burnt are increased. The electrodes materials and shapes influence the flame kernel development by changing he transfer efficiency of electrical energy to chemical energy. The diameter of electrodes also influences the heat release rate and the burnt mass fraction.

• 경영과학
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• 제19권1호
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• pp.13-28
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• 2002

This Paper discusses how to estimate the container yard space of a port container terminal as well as how much the Inventory level of containers Is affected by related factors such as allowable dwell time for containers, handling volume per containership, and loading/unloading productivity of a port container terminal. Under the assumption of static relations among the factors, a model for estimating the container yard space is suggested. In terms of arrival patterns of containers, sub-models for export, import, and transshipment containers are constructed separately. A numerical example and the sensitivity analysis for some parameters are provided to help intuitive understanding the characteristics of the suggested model. The experimental results show that the allowable dwell time for containers is the most critical one of the factors to influence on the maximum Inventory level of containers.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.370-375
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• 2002

Recently, the interest on micro optical parts has increased rapidly with the development of technology related to microsystems. Among the optical parts, micro lens is one of the most broadly used micro parts. To mass-produce the micro lenses, it is very effective to use the mold insert and injection molding process. There are many methods to fabricate the mold insert for micro lenses: electroforming, etching, mechanical micromachining and so on. In this study, we fabricated the mold insert for micro lenses using a micro ball endmill to apply mechanical micromaching method and analyzed the effect of main process parameters such as spindle speed, feed rate, dwell time on the processed surface. Then, using fabricated the mold insert we fabricated the micro lenses through injection molding process.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.1-8
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• 2020

This paper studied a method of estimating target information using a radar in wireless communication. Position information on the target can be estimated angle, distance and velocity. The velocity information can be estimated since the Doppler frequency is changed in the moving target. The signal incident on the receiving array antenna is multiplied by the delay time and the reference signal to represent the output signal. This output signal is estimated by applying FFT (Fast Fourier Transform) after calculating signal correlation through correlation integrator. Since the output signal must be calculated within the correlator, it should be processed with the Dwell time. The correlation signal of the correlation integrator outside this Dwell time is indicated by the velocity measurement error. The FFT is applied to the signal that has passed through the correlated integrator in order to estimate the distance of the signal. The Doppler resolution must be improved because the FFT estimates target information using the Doppler information. The Doppler resolution decreases with increasing the integration time. The velocity information estimation should have no spread of the velocity. As a result of the simulation, there was no spread of the target velocity in this study.

• 한국정밀공학회지
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• 제26권9호
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• pp.143-147
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• 2009

Inkjet printing makes use of ink droplets to form required patterns on a substrate. In order for the inkjet technology to produce reliable patterning tools, the jetting performance needs be controlled precisely. For controlling ink jetting performance, input waveform should be properly designed. In the past, the research was focused on designing dwell time of the input waveform for controlling jetting speed. However, the jetting performance is also closely related to rising and falling time. In this study, the effect of the rising and falling time on droplet speed will be investigated by measuring the droplet speed. In this study, the power OP amp (PA98A) was used in order to drive piezo inkjet head by amplifying the waveform generated from arbitrary function generator. The experimental results show that change of rising and falling time in the waveform not only affect the droplet speed but also optimal dwell time.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 춘계학술대회
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• pp.605-608
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• 2009

이동 목표물 및 기상 현상 등의 원격탐지를 위한 레이다 시스템에서는 수신되는 전자파 반사 신호로부터 유용한 정보를 추출하기 위하여 각 거리별로 도플러 스펙트럼의 추정이 필요할 수 있다. 그러나 이제까지 일반적으로 적용되어졌던 FFT 주파수 추정방법은 안테나의 dwell time 이 짧은 경우 해상도 문제가 발생하거나 또는 상대적으로 강한 반사 신호의 부엽 확산으로 인하여 상대적으로 약한 목표물의 탐지가 어려울 수 있다. 따라서 본 논문에서는 이러한 문제점을 개선하기위하여 시간영역에서의 도플러 신호모델 파라메터 추정을 통한 효율적인 도플러 스펙트럼 추정방법에 관하여 비교하고 고찰하였다.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.40-46
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• 2001

An experimental investigation is proceeded to study on the relationship between spark ignition characteristics and the performances of an S. I. engine. The ignition parameters examined in this study are the ignition energy and discharging duration. The combustion pressure and exhaust gas are measured during the experiment. From the measured data of cylinder pressure, the heat release rate, the mass fraction burned, and the COV of IMEP are calculated. The dwell time and the injection time are varied. A single cylinder engine and a 30kW dynamometer are employed. Four different kinds of ignition systems are assembled, and one commercial ignition system is adopted. The experimental results show that the ignition energy is increased as the dwell time extended until the ignition energy is saturated. The higher ignition energy is effective in achieving the laster burning velocity and less producing HC emission. However, when the amount of ignition energy is similar, while the discharge duration becomes longer, the burning velocity is reduced but the engine operation becomes stable in terms of the COV of IMEP.