• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.93-100
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• 2021

Since the IB (Immersed Boundary) method, which can perform coupling analysis with objects and fluids having an impermeable boundary of arbitrary shape on a fixed grid system, has been developed, the IB method in various CFD models is increasing. The representative IB methods are the directing-forcing method and the ghost cell method. The directing-forcing type method numerically satisfies the boundary condition from the fluid force calculated at the boundary surface of the structure, and the ghost-cell type method is a computational method that satisfies the boundary condition through interpolation by placing a virtual cell inside the obstacle. These IB methods have a disadvantage in that the computational algorithm is complex. In this study, the simplified immersed boundary (SIB) method enables the analysis of temporary structures on a fixed grid system and is easy to expand to three proposed dimensions. The SIB method proposed in this study is based on a one-field model for immiscible two-phase fluid that assumes that the density function of each phase moves with the center of local mass. In addition, the volume-weighted average method using the density function of the solid was applied to handle moving solid structures, and the CIP method was applied to the advection calculation to prevent numerical diffusion. To examine the analysis performance of the proposed SIB method, a numerical simulation was performed on an object falling to the free water surface. The numerical analysis result reproduced the object falling to the free water surface well.

• Journal of Conservation Science
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• v.28 no.1
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• pp.29-37
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• 2012

This study discusses a mercury amalgam gilding technique and examines how the color, surface and section of the gilt layer changes as the condition of heat treatment with mercury amalgam gilt object is changed. Some previous studies have mentioned reasons for various colors on gilt bronze artifacts depending on gilding manufacture and environment. However, reason for reddish color with gold on the artifacts' surface brought on high temperature corrosion has yet to be discussed and analyzed. A methodology was found in representing the mercury amalgam gilding technique and heat treatment test. According to the result of the heat treatment test, in the conditions of higher temperature and longer time, the oxidized layer on the gilt layer was distributed more widely and in the part when the oxide layer was eliminated, the gilt layer with a reddish color was observed. Moreover, in the surface observation of the specimen on which yellow and reddish colors were agitated, the changing aspects of its surface condition differed by colors. When investigated the section, it was observed that the void density and size became larger. After a test, the surface components changed; the temperature of heat treatment increased, component ratio of Hg and Au decreased gradually but component ratio of Cu increased. In regard to the gilt layer, as the time was longer and the temperature became higher for the heat treatment, the component ratio of Au and Cu by layers tended to change in inverse proportion. It is concluded that gilding techniques and the burial environment can make a difference in the surface color of the gilt layer on the gilt bronze artifacts, the high temperature corrosion that occurs by heat after they are manufactured is also one of the factors that affects their surface color.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.484-488
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• 2010

Infrared emissivity is one of the most important factors for the temperature measurement by infrared thermography. Although the infrared emissivity of an object can be measured from the ratio of blackbody and the object, at room temperature it is practically difficult to measure the value due to the background effects. Hence, quantitative reflectance of bare steel plate and the surface of coating was measured by FT-IR spectroscopy and emissivity was calculated from this. The emissivity of polished bare steel surface was from 0.06 to 0.10 and the value for the unpolished bare steel can not be achieved because optical characteristics changes of surface roughness induces erroneous results. Emissivity of transparent paint coated steel was from 0.50 to 0.84. Depends on the IR absorption regions, which is a characteristic value of the coating, emissivity changes. This study suggests surface condition of material, thickness, roughness et cetra are important factor for IR optical characteristics. Emissivity measurement by reflection method is useful technique to be applied for metal and it with coating applied on the surface. The range of experimental errors of temperature can be narrowed by the application of infrared thermography from the measured thermal emissivity.

• The Korean Journal of Air & Space Law and Policy
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• v.19 no.1
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• pp.9-35
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• 2004

A launching State shall be absolutely liable to pay compensation for damage caused by its space object on the surface of the earth or to aircraft in flight. The compensation which the launching State shall be liable to pay for damage under "the Convention on International Liability for Damage caused by Space Objects" shall be determined in accordance with international law and the principles of justice and equity, in order to provide such reparation in respect of the damage as will restore the person, natural or juridical, State or international organisation on whose behalf the claim is presented to the condition which would have existed if the damage had not occurred. In the event of damage being caused elsewhere than on the surface of the earth to a space object of one launching State or to persons or property on board such a space object by a space object of another launching State, and of damage thereby being caused to a third State or to its natural or juridical persons, the first two States shall be jointly and severally liable to the third State, to the extent indicated by the following: If the damage has been caused to the third State on the surface of the earth or to aircraft in flight, their liability to the third State shall be absolute; If the damage has been caused to a space object of the third State or to persons or property on board that space object elsewhere than on the surface of the earth, their liability to the third State shall be based on the fault of either of the first two States or on the fault of persons for whom either is responsible. The Insurance requirements are satisfied for a launch or return authorised by a launch permit if the holder of the permit or authorisation is insured against any liability that the holder might incur to pay compensation for any damage to third parties that the launch or return causes; and the Commonwealth is insured against any liability that Commonwealth might incur, under the Liability Convention or otherwise under international law, to pay compensation for such damage. The liability for Damage caused by Space Objects should be regulated in detail in Korea.

• Journal of Construction Engineering and Project Management
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• v.5 no.4
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• pp.16-22
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• 2015

This paper presents an automated computer vision-based system to update BIM data by leveraging multi-modal visual data collected from existing buildings under inspection. Currently, visual inspections are conducted for building envelopes or mechanical systems, and auditors analyze energy-related contextual information to examine if their performance is maintained as expected by the design. By translating 3D surface thermal profiles into energy performance metrics such as actual R-values at point-level and by mapping such properties to the associated BIM elements using XML Document Object Model (DOM), the proposed method shortens the energy performance modeling gap between the architectural information in the as-designed BIM and the as-is building condition, which improve the reliability of building energy analysis. Several case studies were conducted to experimentally evaluate their impact on BIM-based energy analysis to calculate energy load. The experimental results on existing buildings show that (1) the point-level thermography-based thermal resistance measurement can be automatically matched with the associated BIM elements; and (2) their corresponding thermal properties are automatically updated in gbXML schema. This paper provides practitioners with insight to uncover the fundamentals of how multi-modal visual data can be used to improve the accuracy of building energy modeling for retrofit analysis. Open research challenges and lessons learned from real-world case studies are discussed in detail.

• Advances in concrete construction
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• v.8 no.1
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• pp.55-64
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• 2019

Chloride corrosion has become the main factor of reducing the service life of reinforced concrete structures. The object of this paper is to propose a theoretical model that predicts the service life of chloride-corrosive concrete under fatigue load. In the process of modeling, the concrete is divided into two parts, microcrack and matrix. Taking the variation of mcirocrack area caused by fatigue load into account, an equation of chloride diffusion coefficient under fatigue load is established, and then the predictive model is developed based on Fick's second law. This model has an analytic solution and is reasonable in comparison to previous studies. Finally, some factors (chloride diffusion coefficient, surface chloride concentration and fatigue parameter) are analyzed to further investigate this model. The results indicate: the time to pit-to-crack transition and time to crack growth should not be neglected when predicting service life of concrete in strong corrosive condition; the type of fatigue loads also has a great impact on lifetime of concrete. In generally, this model is convenient to predict service life of chloride-corrosive concrete with different water to cement ratio, under different corrosive condition and under different types of fatigue load.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.177-184
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• 2003

In this study we performed optimal design for the vehicle mechanical component which satisfies both a sufficient stiffness and a lightweight using topology optimization technique. The FEA for the initial model before optimal design is performed by ABAQUS/Standard. And, we suggest optimization model using the topology optimal design program Altair Optisturuct 3.6. The FEA of optimal design is performed under the same condition as the initial model. We performed the FEA fur the topology optimal design model and verified the validity of the present method.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.94.1-94
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• 2001

Arc sensor gives important groove information during welding. Automatic seam tracking control system with arc sensor has significant characteristics such that bead formation is given as decentralization of penetration and formation of concave bead profile and that a turning point of transverse weaving with constant arc length control is decided whether or not torch height reaches to a specified setting level. Furthermore, the rotating action of the arc prevents hanging of weld bead and forms flat bead surface under high speed welding condition. The variation of groove and deposition area can be detected from the trace of weaving. The area and width of weaving trace has close correlation with the area of groove and deposition. In this paper, main object of this system is to realize an adaptive microprocessor based controller ...

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.707-712
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• 2008

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

• 보존과학연구
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• s.27
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• pp.215-226
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• 2006

In the field conservation treatment, it is important that the method chosen to lift an object out of the ground depends on its surrounding weather, strength, size, composition, and condition. This paper describes a physical support(Urethane bandage, De naturation - polyisoprene resin) created for lifting delicate relics in this field. The advantage of Urethane bandage method is of conveniently portable size, and it's convenient for use, while curing time is very fast.(approx. 5~10minute)Denaturation -polyisoprene resin is able to be soft by the hot water(approx. $60^{\circ}C$ ). so it's good to stick to the relic surface of an indeterminate form. The results of use of these reinforcement methods are of utility value.