• Journal of Technologic Dentistry
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• v.36 no.2
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• pp.83-89
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• 2014

Purpose: This study is to evaluate the effect of modeling liquid on the shear-bond strength between zirconia core and veneering ceramic. Methods: Disk-shaped (diameter: 12.0mm; height: 3.0mm) zirconia were randomly divided into six groups according to the surface conditioning method and whether modeling liquid is used or not to be applied (N=60, n=10 per group): group 1-control group with distilled water(ZD); group 2-control group with modeling liquid(ZM); group 3-airborne particle abrasion with $110-{\mu}m$ $Al_2O_3$(AD) with distilled water; group 4-airborne particle abrasion with $110-{\mu}m$ $Al_2O_3$ with modeling liquid(AM); group 5-liner with distilled water(LD); group $6{\pounds}{\neq}liner$ with modeling liquid(LM). Contact angles were determined by the sessile drop method at room temperature using a contact angle measurement apparatus. The specimens were prepared using dentin veneering ceramics, veneered, 3mm high and 2.8mm in diameter, over the cores. The shear bond strength test was performed in a Shear bond test machine. Load was applied at a cross-head speed of 0.50mm/min until failure. The fractured zirconia surfaces were evaluated by using stereomicroscope (${\times}30$). Collected data were analyzed using SPSS(Statistical Package for Social Sciences) Win 12.0 statistics program. Results: ZD showed the highest contact angle($50.6{\pm}5.4^{\circ}$) and LD showed the lowest value($6.7{\pm}1.3^{\circ}$). Control groups and zirconia liner groups were significantly higher contact angle than liner groups(p<0.05). LD was the highest shear bond strength($43.9{\pm}3.8MPa$) and ZD was the lowest shear bond strength($24.8{\pm}4.9MPa$). Shear bond strengths of control groups and contact angle of liner groups were not significantly different((p>0.05). Liner groups presented adhesive failures. The others groups showed cohesive and adhesive failures. Conclusion: Modeling liquid groups showed lower contact angles and lower shear bond strength compared to those of distilled water groups.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2509-2518
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• 2013

Augmented reality (AR) technology visualizes a real type object that cannot simulate in virtual reality technology by overlapping a virtual object and real object in a computer system. This study suggests a methodology and prototype system for applying AR system to rebar distribution work in a civil engineering project. Rebar work in civil engineering project is a representative activity that is progressed by empirical approach of skilled labor rather than formalized manual. AR technology improves the constructability of rebar work because AR tool can identify missing rebars and different rebars comparing with the drawings. AR system developed in this study can enhance the understanding of rebar work using 3D modeling with real image of construction site and save construction cost by reducing reconstruction work.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.131-138
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• 2012

This paper aims to present accurately analytical modeling method for underpinning using uncertainty reduction, obtained from comparison between numerical analysis and Site measuring data during construction and service stages. Combination of various conditions should be considered for using numerical analysis to predict the behavior of the structure accurately, even though complexly considered the conditions, real construction should be secured the stability by applying the actual instrument measurement data because predicted results are including the considerable uncertainty. In order to secure the stability during construction, the real time instrument measurements together with numerical analysis results performed before construction state are complementary used actively. From the results of this study, the significant settlements are occurred not only in underpass structure of adjacent excavation area but also in the permanent steel pipe structures were analyzed. From the site measurement results of underpass settlement, the settlements are occurred in every stages of excavation, furthermore observed tendency is asymmetrical excavation patterns are settled more than symmetrical excavation patterns. The essential consideration points for numerical analysis are construction sequence, the direction of the existing facilities, the methods of elements modeling, the applied factors for nature of material and different results would be occurred depending upon inputting the above factors.

• Journal of the Korea Institute of Building Construction
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• v.15 no.3
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• pp.317-327
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• 2015

Many construction projects have extensively adopted building information modeling (BIM), and various institutions and standards have been developed domestically in Korea. However, the current process that is used to calculate building space area has a significant shortcoming in that there are two different laws to apply the method of measurement considering space boundaries for building element guidelines. For example, space area can be calculated by a polygon, which is modeling using a BIM-based computer aided design program, such that the space polygon is always exported as an inner-edge type. In this paper, we developed an automated algorithm to convert coordinates of space representation using industry foundation classes based BIM data. The proposed algorithm will enable engineers responsible for space management to use a BIM-based model directly in the space programming process without having to do additional work. The proposed process can help ensure that space area is more accurately and reliably.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.26.3-26.3
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• 2008

This research develops a GPS-based formation-flying testbed (FFTB) for formation navigation and control. The FFTB is a simulator in which spacecraft simulation and modeling software and loop test capabilities are integrated for test and evaluation of spacecraft navigation and formation control technologies. The FFTB is composed of a GPS measurement simulation computer, flight computer, environmental computer for providing true environment data and 3D visualization computer. The testbed can be simulated with one to two spacecraft, thus enabling a variety of navigation and control algorithms to be evaluated. In a formation flying simulation, GPS measurement are generated by a GPS measurement simulator to produce pseudorange, carrier phase measurements, which are collected and exchanged by the flight processors and subsequently processed in a navigation filter to generate relative and/or absolute state estimates. These state estimates are the fed into control algorithm, which are used to generate maneuvers required to maintain the formation. In this manner, the flight processor also serves as a test platform for candidate formation control algorithm. Such maneuvers are fed back through the controller and applied to the modeled truth trajectories to close simulation loop. Currently, The FFTB has a closed-loop capability of simulating a satellite navigation solution using software based GPS measurement, we move forward to improve using SPIRENT GPS RF signal simulator and space-based GPS receiver

• Journal of KIBIM
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• v.10 no.4
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• pp.50-59
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• 2020

Recently, the government has actively promoted the introduction of BIM at the national level to improve the efficiency and productivity of the construction industry, and private interest in the application of BIM has also increased. However, despite the large amount of references and information, not much research has been done in quantitative ways to accurately measure the performance of BIM projects. The purpose of this study is to review performance measurement cases using ROI, investment effect analysis, and queue model analysis using domestic and overseas BIM guideline research and to present standard templates that can quantitatively measure BIM performance records according to domestic conditions based on this. Performance measurement trends and cases according to the application of BIM were analyzed, and nine quantification elements were derived from this, and based on this, a performance measurement data collection template at the BIM life cycle stage was prepared. Detailed items and contents were prepared for the nine quantification elements, and the final template consisted of a total of 43 questions, divided into the entire stage (15), the beginning (8), the middle (8), and the latter (12) areas. It is expected that by using the standard template of railway BIM performance records developed in this study, the BIM design stage will be diagnosed and the deficiencies will be supplemented, which will be the basic data for measuring actual quantitative performance in all life cycle performance of future BIM projects.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.68-73
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• 2009

One of the traditional optical methods to monitor a tool is a CCD sensor-based vision system which captures an aspect of the tool in real time. In the case using the CCD sensor, specific lens-modules are necessary to monitor the tool with higher resolution than its pixel size, and a microprocessor is required to attain desired data from captured images. Thus theses additional devices make the entire measurement system complex. Another method is to use a pair of an optical source and a detector per measuring axis. Since the method is based on the intensity modulation, the structure of the measurement system is simper than the CCD sensor-based vision system. However, in the case measuring the three dimensional position of the tool, it is difficult to apply to micro machine-tools because there may not be space to integrate three pairs of an optical source and a detector. In this paper, in order to develop a tool-origin measurement system which is employed in micro machine-tools, the improved method to measure a tool origin in x, y and z axes is introduced. The method is based on the intensity modulation and employs one pair of an optical source radiating divergent beams and a quadrant photodiode to detect a three dimensional position of the tool. This paper presents the measurement models of the proposed tool-origin sensor. The models were verified experimentally The verification results show that the proposed method is possible and the induced models are available for design.

• Journal of Ocean Engineering and Technology
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• v.36 no.5
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• pp.340-352
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• 2022

This article presents a modeling method for the uncorrelated measurement error of the ultra-short baseline (USBL) acoustic positioning system for aiding navigation of underwater vehicles. The Mahalanobis distance (MD) and principal component analysis are applied to decorrelate the errors of USBL measurements, which are correlated in the x- and y-directions and vary according to the relative direction and distance between a reference station and the underwater vehicles. The proposed method can decouple the radial-direction error and angular direction error from each USBL measurement, where the former and latter are independent and dependent, respectively, of the distance between the reference station and the vehicle. With the decorrelation of the USBL errors along the trajectory of the vehicles in every time step, the proposed method can reduce the threshold of the outlier decision level. To demonstrate the effectiveness of the proposed method, simulation studies were performed with motion data obtained from a field experiment involving an autonomous underwater vehicle and USBL signals generated numerically by matching the specifications of a specific USBL with the data of a global positioning system. The simulations indicated that the navigation system is more robust in rejecting outliers of the USBL measurements than conventional ones. In addition, it was shown that the erroneous estimation of the navigation system after a long USBL blackout can converge to the true states using the MD of the USBL measurements. The navigation systems using the uncorrelated error model of the USBL, therefore, can effectively eliminate USBL outliers without loss of uncontaminated signals.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.389-398
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• 2012

In this study, structural strain responses of the jacket-type Uldolmok tidal current power plant structure under severe tidal environments were measured and analyzed using long-term measurement system during construction and also operation. It was observed that there were significant changes in strain responses at the steps of jacket lifting, block loading, pile ejection and insertion. Strains due to dead loads and tidal loads were analyzed before and after removal of a jacket leg, and it was also found that the strains due to dead load were much significantly changed after jacket leg removal. From the measurement data during operation, it was found that strain responses were fluctuated with M2 and M4 tidal periods and also relatively short period of about 10 min due to the peculiar tidal characteristics in the Uldolmok strait. Finally, the neural network-based non-parametric estimation models were investigated to build up the signal-based structural damage monitoring system.

• Korean Journal of Optics and Photonics
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• v.26 no.1
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• pp.30-37
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• 2015

The design and implementation of a radiative temperature measurement system for a flash light are carried out. Since a massive amount of energy is emitted within a very short time, it is impossible to measure the temperature of a flash with a conventional method. It is also irrelevant to measure one with an optical noncontact method. In this paper, a radiative temperature measurement system using the ratio of spectral radiances over mid- and long-wavelength infrared (IR) is designed and implemented. The implemented system utilizes optical bandpass filters to divide the wavelengths within the mid- and long-wavelength IR ranges, and pyroelectric IR detectors to measure the incident optical power of each wavelength-divided channel. It is shown that the measured radiative temperature of a flash is in the range of 1393 to 1455 K. This temperature-measurement system can be utilized to obtain information about the spectral radiance of a flash as a light source, which is of crucial importance to approaching the modeling and simulation of the various effects of a flash.