• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.121-127
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• 2018

A system for diagnosing surface defects of long and large pipe inner overlay welds, 1m in diameter and 6m in length, was developed using a Liquid Penetrant Test (PT). First, CATIA was used to model all major units and PT machines in 3-dimensions. They were used for structural strength analysis and strain analysis, and to check the motion interference phenomenon of each unit to produce two-dimensional production drawings. Structural strength analysis and deformation analysis using the ANSYS results in a maximum equivalent stress of 44.901 MPa, which is less than the yield tensile strength of SS400 (200 MPa), a material of the PT Machine. An examination of the performance of the developed equipment revealed a maximum travel speed of 7.2 m/min., maximum rotational speed of 9 rpm, repeatable position accuracy of 1.2 mm, and inspection speed of $1.65m^2/min$. The results of the automatic PT-inspection system developed to check for surface defects, such as cracks, porosity, and undercut, were in accordance with the method of ASME SEC. V&VIII. In addition, the results of corrosion testing of the overlay weld layer in accordance with the ferric chloride fitting test by the method of ASME G48-11 indicated that the weight loss was $0.3g/m^2$, and met the specifications. Furthermore, the chemical composition of the overlay welds was analyzed according to the method described in ASTM A375-14, and all components met the specifications.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.588-597
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• 2016

According to an annual industrial accident report from Ministry of Employment of Labor, among the various types of accidents, the number of accidents from construction industry increases every year with the percentage of 27.56% as of 2014. In fact, this number has risen almost 3% over the last four years. Currently, among the industrial accidents, heavy machinery causes most of the tragedy such as collision or narrowness. As reported by the government, most of the time, both heavy machinery drivers and workers were unaware of each other's positions. Nowadays, however when society requires highly complex structures in minimal time, it is inevitable to allow heavy construction equipments running simultaneously in a construction field. In this paper, we have developed Approach Detection System for excavator in order to reduce the increasing number. The imaged based Approach Detection System contains camera, approach detection sensor and Around View Monitor (AVM). This system is also applicable in a small scale construction fields along with other machineries besides excavators since this system does not require additional communication infra such as server.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.865-871
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• 2011

Presently, the location and direction information are certainly needed for the autonomous vehicle of the ship. Among them, the direction information is a essential elements to automatic steering system. And the gyro-compass, the magnetic-compass and the GPS compass are the sensor indicating the direction. The gyro-compasses are mainly used in the large-sized ship of the GMDSS(Global Maritime Distress & Safety System). The precision and the reliability of the gyro-compasses are excellent but big volume and high price are disadvantage. The magnetic-compass has relatively fine precision and inexpensive price. However, the disadvantage is in the influence by the magnetism object including the steel structure of a ship, and etc. In the case of the GPS compass, the true north is indicated according to the change of the location information but in case of the minimum number of satellites or stopping of a ship or exercise in the error range, the exact direction cannot be obtained. In this paper, the performance of the GPS compass was improved by using the least-square curve fitting method for the mutual trade off of the angle sensor. The algorithm which improves the precision of an azimuth by applying the weighted value according to the size of covariance error was proposed with GPS-compass and magnetic compass. The characteristic and the performance of the proposed algorithm were analyzed and verified through experimentation. The applicability of the proposed algorithm was shown through the experimental result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.427-436
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• 2016

Due to disasters such as earthquakes and landslides in urban areas, persons have been buried inside collapsed buildings and structures. Rescuers have mainly utilized detection equipment by applying sound, video and electric waves, but these are expensive and due to the directional approaches onto the collapsed site, secondary collapse risk can arise. In addition, due to poor utilization of such equipment, new human detection technology with quick and high reliability has not been utilized. To address these issues, this study develops a wireless signal-based human detection module that can be loaded into an Unmanned Aerial Vehicle (UAV). The human detection module searches for the 3D location for buried persons by collecting Wi-Fi signal and barometer sensors data transmitted from the mobile phones. This module can gain diverse information from mobile phones for buried persons in real time. We present a development framework of the module that provides 3D location data with more reliable information by delivering the collected data into a local computer in the ground. This study verified the application feasibility of the developed module in a real collapsed area. Therefore, it is expected that these results can be used as a core technology for the quick detection of buried persons' location and for relieving them after disasters that induce building collapses.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.23-30
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• 2015

Developed in this study were Octagonal-hollow-section(OHS) struts, whose compressive strengths against flexural and local buckling is higher than H-shape or rectangular-hollow-section(RHS) struts with the same unit weight. OHS members are also advantageous in handling and storing compared to circular hollow sections(CHS). OHS members were fabricated from HR Plates by cold forming and fillet welding. 5 numbers of 20m long OHS struts were assembled, each of which consist of two 9.6m long OHS member and two end connection elements made of cast iron. The compressive strength of the OHS strut was evaluated by comparing the test results, design codes and FEM analysis each other. Test results show that all of the struts have almost same or larger compressive strength than Korean Road Bridge Design Code(KRBDC) (2012). The initial imperfections can be estimated by using measured strains and are turned out to be less than L/450 for all the struts tested. The results of FEM analysis show that the variation of initial imperfection has less effects on the compressive strength for struts with vertical surcharge than for those with self-weight only, while the strength decreases as the initial imperfection increases. As the result of this study, the allowable initial imperfection for 20m long OHS struts is recommended to be less than L/350 on job sites.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.409-422
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• 2017

In order to understand the environmental factors affecting the waterbird community in winter, we divided the watershed into 6 sections and investigated the size of the stream, the water quality, benthic invertebrates, and fish including birds. The influences on the community of water birds in Wonju stream were river structure, temperature and water quality. Among the structure of the river, the factors affecting the waterbird community in winter were the width of the stream and the width of the flowing water. The wider the width, the more species and the number of the winter waterbirds were. As the width of river water was wide, the smaller the width and width of the waterway, the fewer the population. The temperature changes of the wintering season affected the community of water birds because it led to freezing of rivers. The sections that were not frozen showed a significant increase and decrease in the temperature drop and rise. The values of pH, water temperature, COD, BOD, TN, TP and total E. coli increased with the increase of the downstream waterbirds population in the water quality survey. The water quality of S6 was affected by the downstream sewage treatment plant The number of wintering waterbirds was also highest. The effluent from the sewage treatment plant seems to have a considerable influence on the water quality. The increase of several items such as TN promotes the nutrition of the river, which leads to the accumulation of organic matter and the proliferation of aquatic organisms. This may be the cause of the increase in winter waterbirds as a food source. The benthic macroinvertebrate communities and fish communities did not show any correlation with the wintering water-birds communities.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.135-144
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• 2007

Recently, fiber-reinforced plastic(FRP) wraps are blown as an effective material for the enhancement and rehabilitation of aged concrete structures. The purpose of this investigation is to experimentally investigate behavior of concrete cylinder wrapped with FRP materials. Experimental parameters include compressive strength of concrete cylinder, FRP material, and confinement ratio. This paper presents the results of experimental studies on the performance of concrete cylinder specimens externally wrapped with aramid, carbon and glass fiber reinforced Polymer sheets. Test specimens were loaded in uniaxial compression. Axial load, axial and lateral strains were investigated to evaluate the stress-strain behavior, ultimate strength ultimate strain etc. Test results showed that the concrete strength and confinement ratio, defined as the ratio of transverse confinement stress and transverse strain were the most influential factors affecting the stress-strain behavior of confined concrete. More FRP layers showed the better confinement by increasing the compressive strength of test cylinders. In case of test cylinders with higher compressive strength, FRP wraps increased the compressive strength but decreased the compressive sham of concrete test cylinders, that resulted in prominent brittle failure mode. The failure of confined concrete was induced by the rupture of FRP material at the stain, being much smaller than the ultimate strain of FRP material.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.306-314
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• 2006

Instrumented indentation technique is a new way to evaluate nondestructive such mechanical properties as flow properties, residual stress and fracture toughness by analyzing indentation load-depth curves. This study evaluated quantitatively the flow properties of steels and residual stress of weldments. First, flow properties can be evaluated by defining a representative stress and strain from analysis of deformation behavior beneath the rigid spherical indenter and the parameters obtained from instrumented indentation tests. For estimating residual stress, the deviatoric-stress part of the residual stress affects the indentation load-depth curve, so that by analyzing the difference between the residual-stress-induced indentation curve and residual-stress-free curve, the quantitative residual stress of the target region can be evaluated. The algorithm for flow property evaluation was verified by comparison with uniaxial tensile test and the residual stress evaluation model was compared to mechanical cutting and ED-XRD results.

• Spatial Information Research
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• v.22 no.1
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• pp.65-73
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• 2014

Recently indoor navigation with indoor map such as Indoor Google Maps is served. For the services, constructing indoor data are required. CityGML and IFC are widely used as standards for representing indoor data. The data models contains spatial information for the indoor visualization and analysis, but indoor navigation requires semantic and topological information like graph as well as geometry. For this reason, IndoorGML, which is a GML3 application schema and data model for representation, storage and exchange of indoor geoinformation, is under standardization of OGC. IndoorGML can directly describe geometric property and refer elements in external documents. Because a lot of data in CityGML or IFC have been constructed, a huge amount of construction time and cost for IndoorGML data will be reduced if CityGML can help generate data in IndoorGML. Thus, this paper suggest practical use of CityGML including deriving from and link to CityGML. We analyze relationships between IndoorGML and CityGML. In this paper, issues and solutions for linkage of IndoorGML and CityGML are addressed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.290-300
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• 2009

The existing numerical methods on the vertical membrane breakwater have employed a linear analysis where the variable membrane tension occurring during membrane motions is assumed to be very negligible compared to the initial tension. In the present study, a quasi-nonlinear analysis is attempted such that the temporary tension of the membrane is substituted by the average tension for a wave period that is sought by an iterative calculation. The results showed that with the increase of the wave period the reflection coefficients appeared larger and the transmission coefficients smaller compared to the results of the linear analysis. The application of the quasi-nonlinear analysis also showed that the performance of the structure is closely dependent on the horizontal deformation of the membrane. In order to suppress the horizontal deformation, it may be required to take the larger initial tension of the membrane or to put additional mooring lines in the middle of the vertical faces of the membrane. But for theses methods to be effective, a largely sized surface float should be installed to secure enough buoyancy to support such downward forces.