• Smart Structures and Systems
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• v.26 no.5
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• pp.657-666
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• 2020

A rotational pulse-echo ultrasonic propagation imager that can inspect cylindrical specimens for material nondestructive evaluations is proposed herein. In this system, a laser-generated ultrasonic bulk wave is used for inspection, which enables a clear visualization of subsurface defects with a precise reproduction of the damage shape and size. The ultrasonic waves are generated by a Q-switched laser that impinges on the outer surface of the specimen walls. The generated waves travel through the walls and their echo is detected by a Laser Doppler Vibrometer (LDV) at the same point. To obtain the optimal Signal-to-Noise Ratio (SNR) of the measured signal, the LDV requires the sensed surface to be at a right angle to the laser beam and at a predefined constant standoff distance from the laser head. For flat specimens, these constraints can be easily satisfied by performing a raster scan using a dual-axis linear stage. However, this arrangement cannot be used for cylindrical specimens owing to their curved nature. To inspect the cylindrical specimens, a circular scan technology is newly proposed for pulse-echo laser ultrasound. A rotational stage is coupled with a single-axis linear stage to inspect the desired area of the specimen. This system arrangement ensures that the standoff distance and beam incidence angle are maintained while the cylindrical specimen is being inspected. This enables the inspection of a curved specimen while maintaining the optimal SNR. The measurement result is displayed in parallel with the on-going inspection. The inspection data used in scanning are mapped from rotational coordinates to linear coordinates for visualization and post-processing of results. A graphical user interface software is implemented in C++ using a QT framework and controls all the individual blocks of the system and implements the necessary image processing, scan calculations, data acquisition, signal processing and result visualization.

• Journal of The Korean Association For Science Education
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• v.35 no.2
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• pp.231-245
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• 2015

Flipped learning can be used as an innovative teaching method in science education. This study analyzes video clip produced by pre-service elementary school teachers for flipped learning and explore strategies to organize effective visualization. The pre-service elementary school teachers focused on providing information on macroscopic natural phenomenon using concrete case selection strategy for earth science class. They used marker and spatial transformation elements effectively, but their efforts to link the elements to the experience of students were not sufficient. In addition, it was very rare to put the contents into simplified drawing or provide extreme cases to enhance the imagery of students. In addition, it is necessary to provide specific case of multi-modal and link the material to the experience of students closely through familiar cases or analogical model to establish an effective visual teaching material. It may also be needed to present simplified drawing for enhancing imagery and provide extreme cases to make students have an opportunity to infer a new situation.

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.40-45
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• 2016

Elimination of the smear layer and bacteria in the root canal is the most important in the endodontic treatment, and various irrigation devices have been developed. Nevertheless, it is hard to eliminate the smear layer and bacteria completely. In this paper, a micro bubble irrigation system has been developed for the root canal cleaning of tooth. Micro bubbles are generated when pressurized fluids passing through a porous material inside a hand-piece nozzle, and the bubbly flows excited by ultrasonic vibration are observed using a high-speed camera and a microscope. The results show that the diameter and number of bubbles increases with the applied pressure, and there found an optimum excitation frequency in order to minimize the bubble size. From in-vitro tests, it is also verified that the developed bubble irrigation system has the ability of antibacterial and infection removal. Thus, this biocompatible system would be well suited for root canal cleaning.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.93-98
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• 2012

In order to capture the fast crack propagation in an unmanipulated concrete fracture test, we employed mechanoluminascent(ML) material, which emits visible light when stressed, as a crack visualization tool. Three-point bending fracture test setup, a paint type ML material and a high speed camera were used to capture the images of fast moving cracks. The maximum size of coarse aggregates of concrete was used as an experimental parameter. The crack images, loading, and crack mouth opening displacement were successfully recorded as a function of time elapsed. From the test results, several interesting cracking behavior in the unmanipulated fracture test was observed in such that (1) the crack moves fast while the load is slowly decreased after the maximum loading, and (2) the crack in concrete with larger coarse aggregates moves faster than the others.

• Korean Journal of Computational Design and Engineering
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• v.21 no.3
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• pp.224-233
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• 2016

We propose a new method to visualize 3D models for FDM (Fused Deposition. Modeling) printing that appearance of the printed results can be predicted more realistically as that the efficiency of the modeling-printing process can be improved. The layered nature of horizontal slicing and the vibratory nozzle movements of customer-level FDM 3D printers leaving the characteristic patterns of noisy stripes on the surfaces of printed objects make difficulties in prediction of printed result in company with the thermal contraction of filament material. First, our method analyses the G-codes generated by common slicers to obtain proper outlines and take advantages of a modified version of Perlin noise based texturing method for rendering efficiency and enough number of control parameters on the visual details. The results show improved rendering details of pre-visualization of FDM printing.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.79-95
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• 2019

The material analysis of an offshore structure is generally conducted in the contract design phase for the price quotation of a new offshore project. This analysis is conducted manually by an engineer, which is time-consuming and can lead to inaccurate results, because the data size from previous projects is too large, and there are so many materials to consider. In this study, the piping materials in an offshore structure are analyzed for contract design using a big data framework. The big data technologies used include HDFS (Hadoop Distributed File System) for data saving, Hive and HBase for the database to handle the saved data, Spark and Kylin for data processing, and Zeppelin for user interface and visualization. The analyzed results show that the proposed big data framework can reduce the efforts put toward contract design in the estimation of the piping material cost.

• Journal of the Korean Society for Library and Information Science
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• v.58 no.2
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• pp.225-249
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• 2024

The purpose of this study is to develop an evaluation tool for map-based data visualization platforms and to conduct heuristic usability evaluations on existing platforms representing inter-regional information. We compared and analyzed the usability evaluation criteria of map-based platforms from the previous studies along with Nielsen's (1994) 10 usability evaluation principles. We proposed nine evaluation criteria, including (1) visibility, (2) representation of the real world, (3) consistency and standards, (4) user control and friendliness, (5) flexibility, (6) design, (7) compatibility, (8) error prevention and handling, and (9) help provision and documentation. Additionally, to confirm the effectiveness of the proposed criteria, four experts was invited to evaluate five domestic and international map-based data visualization platforms. As a result, the experts were able to rank the usability of the five platforms using the proposed map-based data visualization usability evaluation criteria, which included quantified scores and subjective opinions. The results of this study are expected to serve as foundational material for the future development and evaluation of map-based visualization platforms.

• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.22-28
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• 2010

In the present study, we performed the velocity field measurement in a microchannel using a focal length variable micro liquid lens. The liquid lens is used as a beam expander in a micro-PIV system to acquire the scatter image of the seeded particle. A thin film-type micro liquid lens was made of PDMS material and it was attached on top of the 700-micron-wide working fluid supply channel trench. As a result, the focal length and contact angle of the liquid lens changed with variations in applied pressure.

• Journal of the Korean Society of Visualization
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• v.5 no.1
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• pp.12-15
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• 2007

Macromolecule diffusion in cells and tissues is important for cell signaling, metabolism and locomotion. Biophysical methods, including non-invasive or minimally invasive in-vivo photobleaching techniques and single quantum-dot tracking, have been used to measure the rates of macromolecule diffusion in living cells and tissues, including central nervous system and tumors. Mathematical modeling and statistical analysis of experimental data revealed various modes of diffusion, which are strongly coupled with spatiotemporal changes in nanoscale structures and material properties.

• East Asian mathematical journal
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• v.36 no.4
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• pp.455-474
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• 2020

In this study, we investigate the latus rectum, one of the geometric measures of the conics, as one of the ways in which learners harmonize the geometric and algebraic approaches to conics from a pedagogical point of view. We also introduce the conical curve of Biot as presented in 'The Discourse on the Latus Rectum in conics(2013)' by Takeshi Sugimoto and reinterpret it for visualization and use as teaching material. Therefore, we expect that the importance of mathematical concepts will be recognized in conics and students can experience geometry learning that is explored in the school field and have a positive effect in developing the power to apply even in the context of applied problems.