• Journal of Cadastre & Land InformatiX
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• v.50 no.1
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• pp.163-180
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• 2020

In this study, to build a spatial information infrastructure, which is a component of a smart city, a 3D digital twin model in the downtown area was built based on the latest spatial information acquisition technology, the drone. Several analysis models were implemented by utilizing. While the data processing time and quality of the three types of drone photogrammetry software are different, the accuracy of the construction model is ± 0.04 in the N direction and ± 0.03m in the E direction. In the m and Z directions, ± 0.02m was found to be less than 0.1m, which is defined as the allowable range of surveying performance and inspection performance for the boundary point in the area where the registration of the boundary point registration is executed. 1: 500 to 1 of the aerial survey work regulation: The standard deviation, which is the error limit of the photographic reference point of the 600 scale, appeared within 0.14 cm, and it was found that the error limit of the large scale specified in the cadastral and aerial survey was satisfied. In addition, in order to increase the usability of smart city realization using a drone-based 3D urban digital twin model, the model built in this study was used to implement Prospect right analysis, landscape analysis, Right of light analysis, patrol route analysis, and fire suppression simulation training. Compared to the existing aerial photographic survey method, it was judged that the accuracy of the naked eye reading point is more accurate (about 10cm) than the existing aerial photographic survey, and it is possible to reduce the construction cost compared to the existing aerial photographic survey at a construction area of about 30㎢ or less.

• Journal of Cadastre & Land InformatiX
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• v.50 no.1
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• pp.201-214
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• 2020

This study aimed to early detect damaged trees by pine wilt disease using the vegetation indices of UAV images. The location data of 193 pine wilt disease trees were constructed through field surveys and vegetation index analyses of NDVI, GNDVI, NDRE and SAVI were performed using multi-spectral UAV images at the same time. K-Means algorithm was adopted to classify damaged trees and confusion matrix was used to compare and analyze the classification accuracy. The results of the study are summarized as follows. First, the overall accuracy of the classification was analyzed in order of NDVI (88.04%, Kappa coefficient 0.76) > GNDVI (86.01%, Kappa coefficient 0.72) > NDRE (77.35%, Kappa coefficient 0.55) > SAVI (76.84%, Kappa coefficient 0.54) and showed the highest accuracy of NDVI. Second, K-Means unsupervised classification method using NDVI or GNDVI is possible to some extent to find out the damaged trees. In particular, this technique is to help early detection of damaged trees due to its intensive operation, low user intervention and relatively simple analysis process. In the future, it is expected that the utilization of time series images or the application of deep learning techniques will increase the accuracy of classification.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.149-158
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• 2017

Permeating injection is commonly known as an ideal type of injection in grouting reservoir embankment, yet often-combined permeating and fracturing injection grouting operation can disturb the original soil. A grouting method has been regarded as effective and developed to ameliorate the possible disturbance problem. It involves compaction grouting with low expansive pressure near the injection hole and repetitive injection and compaction with grout material that allows ideal permeating injection. This thesis develops Hybrid Grout (ie. HG grout) that allows various application in any ground condition combined together, has high fineness and low viscosity, and expands permeation injection to silty sand. It researches on the injection effect of permeable compaction grout which is done with PC packer and is a combination of HG grout and expansion agent to obtain permeation compaction effect on the area near grout injection spot by developing Permeable Compaction Type Packer(ie. PC packer). As the developed PC packer, HG grout, and and expansion agent (HI-E) are applied to reservoir embankment reinforcement grouting, possibile permeation compaction effect that satisfies reservoir embankment grouting standard is confirmed according to the research.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.90-96
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• 2009

The high rising building construction makes increasing the requirement of high strength concrete. Especially, the workability analysis is related with dispersion of admixture such as SF for improving strength and FA, BS for reducing construction cost and improving durability of Ultra High Strength Concrete which has over 100 MPa of compressive strength is very important. Precisely, decreases dispersion because of lumping situation of each admixture and it causes the workability of admixture is decreased. Therefore, the workability of cement paste is tested for analyze effects of pre-mixed cement for solving those problems with it to this research. The summary of the results are like below. First of all, OBS is increasing workability more than OFS. This result causes that the glassy surface of BS in the OBS is increasing workability and the absorption of admixture of FA in the OFS is decreasing workability. In the case of mixing methods, pre-mixing method is increasing workability more than normal one. This result shows that the normal mixing method is bad dispersion of binders. The other side, the pre-mixing method is good. Furthermore, depending on the mixing time, according to the increasing mixing time such as 30, 60, and 120 seconds, the dispersion of binders and workability turns better.

• Journal of the Korea Institute of Building Construction
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• v.18 no.3
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• pp.259-266
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• 2018

In recent years, the early strength of concrete is important in order to shorten the time of form removal at the construction site. The purpose of this study is to analyze the moment of form removal as investigating the amount of cement contents and the physical properties and strength of the concrete according to types of admixture in the curing temperature of $10^{\circ}C$ for concrete of 21 to 27 MPa. As a result, it was found that compressive strength of concrete could not be secured 5 MPa by 36 hours even if the amount of cement contents were increased to $360kg/m^3$ with plain admixture. Also, it was confirmed that the strength improvement rate was excellent when using the accelerating agent with polycarboxylic acid type, and the moment of compressive strength of 5 MPa was estimated at 30 hours.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.17-24
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• 2018

The pullout test, a nondestructive testing(NDT), for pre-installed inserts is perhaps the most widely used technique to estimate the in-situ compressive strength of concrete. It measures the force needed to pullout a standardized metal insert embedded into concrete members. The pullout test was certified by the American Society for Testing and Materials(ASTM) and Canadian Standards Association(CSA) as a reliable method for determining the strength of concrete in concrete structures under construction. To easily estimate the strength of ultra-high-strength concrete, a simplified pullout tester, primarily composed of a standard 12mm bolt with a groove on the shaft as a break-off bolt, an insert nut, and a hydraulic oil pump without a load cell, was proposed. Four wall and two slab specimens were tested for two levels of concrete strength, 80MPa and 100MPa, using a simplified pullout tester with a load cell to verify the advantages of the pullout test and simplified pullout test. The compressive strength of concrete, pullout load, and the rupture of the break-off bolt were measured 11 times, day 1 to 7, 14, 21, 28, and 90. The correlation of the pullout load and the compressive strength of each specimen show a higher degree of reliability. Therefore, a simplified pullout test can be used to evaluate the in-place strength of ultra-high-strength concrete in structures. The prediction equation for the groove diameter of the break-off bolt(y) with the concrete strength(x) was proposed as y=0.0184x+5.4. The results described in this research confirm the simplified pullout's utility and potential for low cost, simplicity, and convenience.

• Korean Journal of Construction Engineering and Management
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• v.15 no.2
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• pp.12-22
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• 2014

Recently, many people have been damaged seriously by construction noise. Accordingly, there have been increased the complaints and disputes. These complaints should be controlled strictly. Otherwise there could be delays or stops of project and losses of time and money. For this reasons, the Korean government is trying to convert from depending on the soundproof wall to noise control system focusing on noise sources. However, it is difficult to control the noise which is generated from construction site because construction equipment has very high noise level and construction noise generates temporarily and irregularly. Also, people do not know how much low frequency affect human body adversely because they cannot perceive low frequency noise easily. Hence, recently developed countries have conducted the research on the low frequency noise which damages on human physically and mentally. However, passive noise control is insufficient to reduce the low frequency noise, but only efficient to lower the high frequency noise. Thus, an approach which can complement limitations of passive noise control is needed. Therefore, the purpose of this research is to suggest the noise management model using active noise control on construction site. Also, ANC simulation has been conducted to examine its applicability on construction equipment. As a result, it is expected that there will be a reduction of construction noise and demages, as well as both mental and physical damages.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.13-19
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• 2016

Soft ground stabilization is needed to construct large civil facilities on the soft clay ground. Pre-loading method, which is accelerating consolidation method, is generally used to stabilize the soft ground. However, pre-loading method is required long construction period and quantities of fill material. Therefore, electro-osmosis method is used to replace pre-loading method for stabilizing the soft ground. Electro-osmosis method is disadvantageous in constructive and economic aspects because it is needed a metallic electrode. So, in order to solve the those disadvantages, plastic electrode was developed to replace metallic electrode. Plastic electrode, which is made by using nano-technology on existing Plastic Drain Board (PDB), was used to supply the electric power. In this study, therefore, the model test was conducted to confirm the effect of improvement and electrical characteristics of soft ground by spacing of plastic electrode. The result shows that the effect of improvement of soft ground was decreased up to 45% by increasing electrode spacing and electrical characteristics on the soft ground were influenced by consolidation settlement with electrode spacing.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.169-174
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• 2015

In this research, pristine graphene was synthesized using methane ($CH_4$) gas, and N-doped graphene was synthesized using pyridine ($C_5H_5N$) liquid source by chemical vapor deposition (CVD) method. Basic optical properties of both pristine and N-doped graphene were investigated by Raman spectroscopy and XPS (X-ray photoemission spectroscopy), and electrical transport characteristics were estimated by current-voltage response of graphene channel as a function of gate voltages. Results for CVD grown pristine graphene from methane gas show that G-peak, 2D-peak and C1s-peak in Raman spectra and XPS. Charge neutral point (CNP; Dirac-point) appeared at about +4 V gate bias in electrical characterization. In the case of pyridine based CVD grown N-doped graphene, D-peak, G-peak, weak 2D-peak were observed in Raman spectra and C1s-peak and slight N1s-peak in XPS. CNP appeared at -96 V gate bias in electrical characterization. These result show successful control of the property of graphene artificially synthesized by CVD method.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.97-101
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• 2016

ZnO has nanostructured material because of unique properties suitable for various applications. Amongst all chemical and physics methods of synthesis of ZnO nanostructure, the hydrothermal method is attractive for its simplicity and environment friendly condition. Nanostructure ZnO thin films have been successfully synthesized on fluorine doped tin oxide (FTO) substrate using hydrothermal method. A possible growth mechanism of the various nanostructures ZnO is discussed in schematics. The prepared materials were characterized by standard analytical techniques, i.e., X-ray diffraction (XRD) and Field-emission scanning electron microscopy (SEM). The XRD study showed that the obtained ZnO nanostructure thin films are in crystalline nature with hexagonal wurtzite phase. The SEM image shows substrate surface covered with nanostructure ZnO nanrod. The UV-vis absorption spectrum of the synthesized nanostructure ZnO shows a strong excitonic absorption band at 365 nm which indicate formation nanostructure ZnO thin film. Photoluminescence spectra illustrated two emission peaks, with the first one at 424 nm due to the band edge emission of ZnO and the second broad peak centered around 500 nm possibly due to oxygen vacancies in nanostructure ZnO. The Raman measurements peaks observed at $325cm^{-1}$, $418cm^{-1}$, $518cm^{-1}$ and $584cm^{-1}$ indicated that nanostrusture ZnO thin film is high crystalline quality. We trust that nanostructure ZnO material can be effectively will be used as a highly active and stable phtocatalysis application.