• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.864-868
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• 2005

This paper develops an analysis model of a piezoelectric transducer. The transducer considered in this paper is a bolt-clamped Langevin-type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analytical model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic and the metal block. The analysis model is verified by calculating the variations of the resonance frequency due to the contact area and comparing them with reported experimental results.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.86-90
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• 2018

Standards related to express the non-flatness of a wafer are reviewed and discussed, for example, bow, warp, and sori. Novel wafer warpage measurement method is proposed for 3D stacked IC application. The new way measures heat transfer from a heater to a wafer, which is a function of the contact area between these two surfaces and in turn, this contact area depends on the wafer warpage. Measurement options such as heating from room temperature and cooling from high temperature were experimentally examined. The heating method was found to be sensitive to environmental conditions. The cooling technique showed more robust and repeatable results and the further investigation for the optimal cooling condition is underway.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.41-49
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• 2016

To evaluate lubrication properties by surface roughness under boundary and mixed lubrication, a new approach is suggested by both asperity flow and contact with stochastic characteristics. Many researchers already have studied the effect of surface roughness on flow. But, it has become important to research of the phenomenon of asperities contact in surfaces because the growth of asperities contact area under heavy load conditions. In this paper, flow factors in the average flow model derived by Patir and Cheng were used, and a multi-asperity contact model was included to calculate lubrication properties of a surface with a randomly generated rough surface. A numerical analysis using the average Reynolds equation with both the average flow model and the asperity contact model was conducted, and the results were compared with those from previous research. The results showed that the influence of asperities on lubrication and the friction coefficient changed rapidly on application of contact model.

• Structural Engineering and Mechanics
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• v.44 no.1
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• pp.61-72
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• 2012

The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.21-26
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• 2005

Breakdown characteristics and survival probability of turn-to-turn models were investigated under ac and impulse voltage at 77K. For experiments, two test electrode models were fabricated: One is point contact model and the other is surface contact model. Both are made of copper wrapped by O.025mm thick polyimide film(Kapton). The experimental results were analyzed statistically using Weibull distribution in order to examine the wrapping number effects on voltage-time characteristics under ac voltage as well as under impulse voltage in LN$_{2}$. Also survival analysis were performed according to the Kaplan-Meier method. The breakdown voltages of surface contact model are lower than that of point contact model, because the contact area of surface contact model is wider than that of point contact model. Besides, the shape parameter of point contact model is a little bit larger than that of surface contact model. The time to breakdown t$_{50}$ is decreased as the applied voltage is increased, and the lifetime indices slightly are increased as the number of layers is increased. According to the increasing applied voltage and decreasing wrapping number, the survival probability is increased.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.147-151
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• 2002

The resistances of metal2 contact to metall and poly Si are checked by various RF etch conditions in terms of pre-cleaning. The changes of resistance are evaluated by statistical analysis method(SAS) for the AC bias power, coil power and RF target. The contact area on poly Si is shown by TEM image and the distributions of contact resistance according to ar etch target and RTP are investigated. The RTP groups have larger variations than normal RF etch targets. When the RF etch target becomes lower and coil power becomes higher, the resistances of metal2 contact to metals and poly Si have lower contact resistance. But the condition of AC bias power did not satisfied low meta12 contacts resistance for metall and poly Si simultaneously. The R-square of ststistical analysis was 0.98 for resistances of meta12 contact to poly Si and 0.87 for resistances of meta12 contact to metall.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.67-68
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• 2023

After mixing the pozzolan-based powder and water repellent with porosity into the cement mortar, microanalysis and measurement of the water repellent contact angle confirmed that the NZS specimen using natural zeolite had the highest contact angle. The specific surface area is increased due to the porosity of natural zeolite, so the adhesion of silane-siloxane is relatively better than that of FA, and it is judged to have a uniform distribution inside the mortar.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.136-139
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• 1995

This paper summarizes recent development in the silicon cell area : PERL (passivated emitter, rear locally diffused cells) ,BCSC ( buried contact solar cells ) rind Hybrid buried contact / PERL cells.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.841-842
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• 2011

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.158-165
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• 2020

Buoys are a necessary component for the safety of vessel traffic. However, if the buoy becomes inoperable from damage and loss, it can have significant impact on vessel traffic safety as well as unexpected budget spending. The purpose of this study was to evaluate the risk of accidental contact by applying the marine traffic assessment index that can reflect the traffic flow in the sea area. First, Busan Port No. 5 fairway, with a high number of buoys and many contact accidents, was set as the sea area for assessment. to investigate the status of accidental contact and evaluate risk of contact accidents based on the IALA Waterway Risk Assessment Programme (IWRAP MkII) and Potential Assessment of Risk Model (PARK Model). As a result, buoys are near the P recautionary Area wherein the traffic flow was complicated by the Masan port vessel and Busan new port vessel, and buoys are near the entrance of the Gadeok waterway, wherein vessels show a pattern of navigation across the fairway and buoys are near the breakwater in the inner fairway were considered as high risk for contact accidents. This study can be used as basic data for establishing an integrated model to evaluate the risk of buoy contact accidents.