• 한국정밀공학회지
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• 제17권3호
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• pp.184-191
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• 2000

Properties of pad are investigated to find the relationship between the chemical mechanical polishing(CMP) results, such as material removal rate and within wafer non-uniformity(WIWNU), and its properties. Polishing pressure is considered as important factors to affect the results, so behavior of ordinary polymer is studied to define the polishing result affecting properties of pad. Experimental setup is devised to identify the behavior of pad and several different pads are used in chemical mechanical polishing experiments to verify the correlations between pad properties and polishing results. The results indicate that the viscoelastic properties of pad had relationships with the polishing results, and shows correlation between suggested properties of pad and polishing result.

• Transactions on Electrical and Electronic Materials
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• 제10권5호
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• pp.156-160
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• 2009

In an ultrasonic motor, a piezoelectric ceramic material forms the active element which vibrates the stator, thus initiating the rotational motion. In the operation of ultrasonic motors, many factors exist that can affect the resonance characteristics of the piezoelectric ceramic component. For examples, these factors are the bonding conditions with the piezoelectric element, the magnitude of the input voltage, the normal force in the frictional drive and the emission of heat due to vibration and friction etc. Therefore, it is important to research properly the inclination for variation of piezoelectric ceramics in the circumstance where complex elements are involved. In this paper, we focus on the analysis of the resonance characteristics of an ultrasonic motor as a function of the magnitude of the input voltage and the normal force.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.393-396
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• 2006

This study present the experimental research investigating the influence of material factors such as a type or amount of superplasticizer, velocity agent, mineral admixture and steel fiber on the construction performance of fiber reinforced cementitious composites. As for the test results, it was found that the workability of fiber reinforced cementitious composites can be improved when the material factors were matched properly in amount and composition. Furthermore, it was shown that the smaller value of the aspect ratio of fiber improved the workability of fiber reinforced cementitious composites. And the fiber reinforced cementitious composites with better workability showed the enhanced compressive strength and flexural strength.

• Journal of Information Display
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• 제13권1호
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• pp.1-6
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• 2012

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and die-attach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, $R_{th}$ (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder, which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.86-90
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• 2000

In this study, A equipment for measuring the initial permeability of soft-ferrite powder was developed by using a differential transformer coil, and was investigated demagnetizing factors. To measure the initial permeability of magnetic ceramic powder is cumbersome since there are not any measuring equipment and method. Magnetic powder is currently used for a magnetic fluid and microwave absorber materials, and the initial permeability of the magnetic powder is very important to be evaluated a powder for some applications.

• Journal of electromagnetic engineering and science
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• 제13권3호
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• pp.158-164
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• 2013

This paper expands a previously proposed optimized higher order (2, 4) finite-difference time-domain scheme (H(2, 4) scheme) for use with lossy material. A low dispersion error is obtained by introducing a weighting factor and two scaling factors. The weighting factor creates isotropic dispersion, and the two scaling factors dramatically reduce the numerical dispersion error at an operating frequency. In addition, the results confirm that the proposed scheme performs better than the H(2, 4) scheme for wideband analysis. Lastly, the validity of the proposed scheme is verified by calculating a scattering problem of a lossy circular dielectric cylinder.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.866-869
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• 2000

To improve quality of the ground surface, we have to consider a number of parameters. But it is difficult to make experiment with many parameters. Most of all experiments try to search optimal grinding condition with conservative factors such as feed rate, depth of cut, wheel rotating speed, etc. But This paper attempts to view the significance of some different factors effecting on the surface roughness by introducing helical scan grinding method and material removal rate. The design of experiment is used to find the optimal grinding condition which minimizes the surface roughness value bout optical glass material. To analyze experimental results, ANOVA(ANalysis of VAriation) is used. Discussion on the result about helical scan grinding is also given.

• 한국정밀공학회지
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• 제12권11호
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• pp.36-44
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• 1995

When sliding a hard cylinder along the surface of glass, periodic surface cracks appear on the flat surface due to tensile stresses induced by the slider. These cracks propagate into the substrate and will affect the fracture properties of a body. Crack spacings and the directions of crack propagation into glass were calculated numerically by applying the finite element method and linear elastic fracture mechanics. The calculated crack spacings were in the range of the experimental results. Stress intensity factors and crack extension angles depended on the radius of slider and the load, and from these two factors the possible directions of crack propagation were calculated. The calculated propagation directions were in good agreement with real crack propagation.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.240-244
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• 1998

The analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composites using coal tar pitch as a matrix precursor at each cyle. Three factors were defined in analyzing the densification process: impregnation efficiency, retention efficiency, and overall densification efficiency. The relationships developed were applied to the experimental results for three densification cycles of C/C composites with pitches as an impregnant to evaluate the factors which may depend on the impregnant and on the route of carbonization. The impregnation efficiency increased with the repeated process cycles whereas the retention efficiency decreased irrespective of the impregnant and carbonization route. Carbonization route P+A+G, in which pressure carbonizationl (P) and graphitization (G) were done before after atmospheric pressure carboniztion (A) respectively, using impregnant of high carbon yields was the most effective method in densifying C/C composites.

• 한국주거학회논문집
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• 제7권2호
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• pp.69-77
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• 1996

Mobility in housing is a normative way to satisfy family needs for· better· living conditions. In the context of relative decisions. mobility can be understood as forced relocation or unforced relocation In making relocation. the household chooses a particular 'environmental quality profile. Therefore. the understanding of mobility and relocation in housing is needed for· the developing and planning of housing evnironment. The major findings are s follows ;1. The motives of mobility are composed of 4 factors('material porseperity’, 'convenience· safety'. environmental improvement' and 'forced relocation'). Especially, 'material prosperity' was defined the most fundamental factor· for. 2. The components of housing environment quality were composed of 3 factors related to the scale of home environment. They were 'neighborhood character factor', 'dwelling character· factor·'. And 'location character· factor'. The factor 'neighborhood character' was defined the basic factor· to choose for the housing environmental quality profile.3. It was examined that the motives of mobility and the components of home environmental quality were significantly different by the household characteristics (income. family life cycle. and tenure type).