• Journal of Periodontal and Implant Science
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• v.39 no.4
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• pp.385-390
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• 2009

Purpose: In this study we evaluated the morphologic aspects of defects created by a piezoelectric ultrasonic scaler with scaler tip on casting gold alloy using scanning electron microscope (SEM) images and defect surface profiles. Methods: 54 blocks of type III casting gold alloy (Firmilay, Jellenko Inc, CA, USA) were scaled by a piezoelectric ultrasonic scaler (P-MAX, Satelec, France) with scaler tip (No. 1 tip) on a sledge device. 2-dimensional profiles of defects on all samples were investigated by a surface profilometer (a-Step 500, KLA-Tencor, CA, USA). The selected working parameters were lateral force (0.5 N, 1.0 N, 2.0 N), mode (P mode, S mode), and power setting (2, 4, 8). SEM images were obtained. Defect surface profiles were made on Microsoft Excel program using data obtained by a surface profilometer. Results: Among P mode samples, there were similarities on defect surface profiles and SEM images regardless of lateral force. The defects created in P mode were narrow and shallow although the depth and the width increased as power setting changed low (2) to high (8). In P mode samples, the defect depth was the greatest when lateral force of 0.5 N was applied. However all the depths were smaller than 1 m. SEM images of Lateral force of 0.5 N, S mode, power setting 2 and 4 were similar to that of P mode, but the other SEM images of S mode showed discernible changes. Defect depth of S mode samples was the greatest when lateral force of 1.0 N was applied. Conclusions: Within the limitations of this study, it can be concoluded that removing capability of piezoelectric scaler with scaler tip becomes maximized as power level becomes higher but the capability is restricted when excessive lateral force is applied on scaler tip.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.6
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• pp.33-41
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• 2015

Scaled model of a dual-mode ramjet engine with large backward-facing step, as a component of the rocket-based combined cycle engine, was designed. Design parameters were derived for this engine with the consideration of application for the rocket-based combined cycle engine. Design methodology was established for these design parameters. The design was partially verified through numerical study. Flow characteristics of the dual-mode ramjet engine with large backward-facing step was investigated experimentally. The design methodology for relevant design parameters established in this study was verified as feasible.

• Structural Engineering and Mechanics
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• v.50 no.2
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• pp.137-149
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• 2014

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.533-540
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• 2010

This study was to suggest the proper level of touch sensibility for twenties while flicking touch phones. A rapid prototype of $480{\times}800$ pixel size was developed for the experiment. Participants were 20 undergraduates, not visually and physically handicapped in using touch phones. 15 different modes, with each mode changing in velocity when flicking the prototype were randomly presented to each subject. The subjects were asked to score what they felt in each mode on a 1-to-6 Likert scale. The data was analyzed by the one-way ANOVA procedure. Each mode showed significant differences in 8 representative emotions except for exclusivity feeling and fresh feeling. Each velocity mode was scaled by the multidimensional scaling technique. Then, vector coordinates in each emotion were obtained by simple regression analysis. 15 velocity modes and each emotion were joint-plotted by the MDS, PROXSCAL. The findings in this study could be basic data for studying affective touch sensibilities in multiple ways.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1709-1717
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• 2015

In remote islands PV (Photo Voltaic) panel with BESS (Battery Energy Storage System) supplies electric power to the customers in parallel operation with EG (Engine Generator) to save fuel consumption and to mitigate environmental load. BESS operates in voltage control mode when it supplies power to the load alone, while it operates in current control mode when it supplies power to the load in parallel with EG. This paper proposes a smooth mode change scheme from current control to voltage control of BESS by adding proper initial value to the integral part of voltage control, and a smooth mode change scheme from voltage control to current control by tracking the EG output voltage to the BESS output voltage using PLL (Phase-Locked Loop). The feasibility of proposed schemes was verified through computer simulations with PSCAD/EMTDC, and the feasibility of actual hardware system was verified by experiments with scaled prototype. It was confirmed that the proposed schemes offer a seamless operation in the stand-alone power system in remote islands.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.646-649
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• 2002

In this paper, a low-voltage CMOS squarer and a four-quadrant analog multiplier are presented. It is based on a source-coupled pair and a scaled-floating voltage generator which are modified to work as a voltage squaring and a sum/difference circuits. The proposed squarer/multiplier have been simulated with HSPICE, where -3㏈ bandwidth of 10MHz is achieved. The power consumption is about 0.6㎽, from a ${\pm}$1.5V supply, and the total harmonic distortion is less than 0.7%, with a 1.2V peak-to-peak 1MHz input signal.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.541-544
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• 1999

The main objective of this study is to develope the PSC-I girder for long span bridge. This study investigates the structural behavior of Postcracking stage and efficiency of proposed PSC-I girder using 1/2 scaled prototype beam specimen. Three specimens are tested under three point static loading system. Ideally, the Load-displacement relationship is trilinear. The crack patterns and failure mode of each specimen are reported in this paper and they are compared to each other with ductility and strength.

• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.70-75
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• 2012

An optimization methodology for designing a dielectric-filled plasmonic slot waveguide is presented. The genetic algorithm combined with a rigorous analysis based on the finite element method is used to optimize a nano-scaled plasmonic slot waveguide to have high mode confinement and a long propagation length, for which the objective function is defined as a figure of merit combining both propagation parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.519-524
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• 1999

A bulb-tee sectioned girder is proposed for long span bridge exceeding 40 meters. The proposed bulb-tee girder is developed by non-linear analysis process. This study investigates the structural behavior and efficiency of proposed bulb-tee sectioned girder using 1/2 scaled prototype beam specimen. Three specimens are tested under three point static loading system. The crack patterns, failure mode and ultimate load capacity of each specimen are reported in this paper and they are compared to each other.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.668-674
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• 2001

An experimental study was performed for two types of co-axial cylindrical shell structures in order to establish the relationship between in-air dynamic characteristics and in-water ones and to observe hydrodynamic mass effects on their mode shapes when submerged. The outer cylinders are prepared with two kinds to get more insights on the fluid-structure interaction phenomena: one is flexible, which means that the outer cylinder has almost same stiffness as the inner one, and the other is a rigid one whose stiffness is more than ten times of the inner one's(it might be regarded as the scaled-down model of the reactor internals). The finite element. analyses were also implemented to support the experimental results. The results show that the natural frequencies of a co-axial cylindrical shell structure in water are remarkably lower than those in air due to the fluid mass effects. In case of the flexible-to-flexible cylinders, there exist in-phase and out-of-phase mode shapes and they are affected by the annular gap between the. co-axial cylinders. For the in-phase mode the in-water natural frequency decreases exponentially as the gap increases, while it slightly increases in case of the out-of-phase mode due to the squeezing effect of the gap fluid. In the flexible-to-rigid case, the normalized natural frequency(in-water frequency/in-air one) of the inner cylinder(core barrel model) ranges between in-phase and out-of-phase mode frequencies of the flexible-to-flexible co-axial cylindrical structure having identical dimensions. Also the normalized natural frequency of the inner cylinder of the flexible-to-rigid one moves from near of the in-phase mode frequency into the out-of-phase mode value of the flexible-to-flexible case as circumferential mode number(n) increases.