• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.227-235
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• 2019

This study monitored Daecheong 1-bo, Daecheong-stream, which carried out the project in 2014, from 2015 to 2016. The technology applied to the stream was evaluated using Periphytic Algae to check contamination indicators and ecological health of the area with an integral river-bed protection using non-toxic materials. The water quality of the monitoring section was confirmed to be above the river environment standard (II), and it was confirmed that the Saproxenic taxa of the river bed protection were higher than the upper and downstream sections. The TDI, which is an index of attachment algae, was shown in the average 51.03 and 52.15 for the pilot project sections in 2015 and 2016, confirming that the index is of the "normal" grade. This is the other sections in the upstream and downstream sections showed higher than "bad", which is thought to have a positive effect on the habitat of the river ecosystem components, especially the microbial population in river bed protection.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.243-249
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• 2019

The purpose of this study is to analyze the reflectance of bed materials according to changes in the water level using a drone-based hyperspectral sensor. For this purpose, we took hyperspectral images of bed materials such as soil, gravel, cobble, reed, and vegetation to compare and analyze the spectral data of each material. To adjust the water level, we constructed an experimental channel to control the discharge and installed the bed materials within the channel. In this study, we configured 3 cases according to the water level (0.0 m, 0.3 m, 0.6 m). After the imaging process, we used the mean value of 10 points for each bed material as analytical data. According to the analysis, each material showed a similar reflectance by wavelength and the intrinsic reflectance characteristics of each material were shown in the visible and near-infrared region. Also, the deeper the water level, the lower the peak reflectance in the visible and near-infrared region, and the rate of decrease differed depending on the bed material. We expect the intrinsic properties of these bed materials to be used as basic research data to evaluate river environments in the future.

• Journal of the Korean Geotechnical Society
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• v.36 no.8
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• pp.61-72
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• 2020

It is generally considered that differences of axial stiffness between exiting pile and reinforcing pile affect the load distribution ratio during vertical extension remodeling. But there are few cases to verify the effect of stiffness by field load test on load distribution ratio in Korea. In this paper, a series of load tests for micropiles were carried out to evaluate the effect of axial stiffness on the load distribution ratio. First, different types of micropiles were constructed so that conventional micropiles simulated existing piles and waveform micropiles simulated reinforcing piles. Secondly, load tests were performed to evaluate the stiffness of each piles. After then, the raft was installed to make a piled raft system and load tests were applied on foundation to verify the effect of axial stiffness on the load distribution ratio. The experimental results show that the stiffness of waveform micropiles were 2.5 times larger than that of conventional micropiles, and the load distribution ratio between existing and reinforcing piles was increased according to axial stiffness of piles.

• Journal of the Economic Geographical Society of Korea
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• v.7 no.1
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• pp.1-27
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• 2004

In this paper we attempt to explore the institutional and clutural milieu of high-tech venture business cluster in Daegu City and provide policy implications for creating sustainable high-tech venture businesses cluster. Although since 1998 the Korean government has made explicitly a great deal of efforts to help attract and create high-tech new start-ups in non-capital cities such as the support of business incubating centers and the establishment of real service centres, it reveals that such policies are not so successful in creating a sustainable venture ecology. One of the most critical resions is that such policies are centred simply on building physical infrastructure such as incubating space and service centre with less concern with promoting venture business cluster reflecting cultural and institutional specificities in a given region. In this respect we argue that the focus of industrial policies to support promoting high-tech venture business clusters in non-capital cities urgently need to move towards to make it for firms to encourage entrepreneurship driving innovation and to create social capital incucing trust and networks amongst firms, universities, public &privite supporting agencies, together with the building up of physical infrastructure the existing policies have done.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.225-238
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• 2018

In this paper, to investigate the influence of installation damage, a variety of full-scale field installation tests with 15 geosynthetics reinforcements and fill materials of various grain size distribution have been performed. The full-scale field installation test was conducted with reference to the FHWA (2009) guidelines. The tensile strength tests were performed by sampling up to 20 specimens randomly from the excavated geosynthetics reinforcements after compaction of fill material, and the degree of decrease in tensile strength of reinforcements due to compaction was analyzed based on the experiment results. It was found that the degree of tensile strength reduction of geosynthetics reinforcements due to the compaction of fill material is greatly influenced by the type of reinforcement and the maximum diameter of fill material. In addition, it was found that the strength reduction ratio of PET geogrid (PVC coating) with relatively small stiffness was greatest, and that the larger the maximum grain size of the fill material, the greater the strength reduction ratio. And also, a more reasonable evaluation method for the installation damage reduction factor of geosynthetics reinforcements is proposed based on the results of full-scale field installation tests in present study and the existing test results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.669-676
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• 2018

Schedule management in construction work is an important step for determining the construction period. On the other hand, there is a difference between the planned schedule and execution schedule because the estimation and calculation of Non-Working days, in which possible at the design stage is not performed properly. This paper proposes a method for estimating the working days by analyzing characteristics of the major work type and estimating the Non-Working days reflecting the Chuseok and New Year Holidays, which is the closest method to the actual work in the schedule planning. By applying the correction factor of the existing method and the improved method for the same construction in the same site, improved method was reduced by 22 days (9.1%) based on the actual working days. The importance of schedule management was confirmed as an example by comparing the data before and after the application of the standard (plan). These results show that the schedule delays, which are caused by the inconsistency between actual working days calculation that had been practiced conventionally and the working days on the schedule table, can be prevented. In addition, it will help to establish a schedule plan that is closer to reality.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.2
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• pp.117-124
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• 2019

Parallel sparse solvers are essential for solving large-scale finite element models. This paper introduces the combination of iterative and direct solver that can be applied efficiently to problems that require continuous solution for a subtly changing sequence of systems of equations. The iterative-direct sparse solver combination technique, proposed and implemented in the parallel sparse solver package, PARDISO, means that iterative sparse solver is applied for the newly updated linear system, but it uses the direct sparse solver's factorization of previous system matrix as a preconditioner. If the solution does not converge until the preset iterations, the solution will be sought by the direct sparse solver, and the last factorization results will be used as a preconditioner for subsequent updated system of equations. In this study, an improved method that sets the maximum number of iterations dynamically at the first Krylov iteration step is proposed and verified thereby enhancing calculation efficiency by the frequency domain analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.677-685
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• 2018

In construction, schedule management is the basic but important step, for the effective schedule management, the preparation of the reasonable schedule table should be prioritized. In the design stage, the optimal construction period can be selected through comparison of various conditions and construction methods considering weather conditions and site characteristics. But, At the planning phase, it is difficult to select the effective method and calculate the proper construction period by the basic data(D/B) analysis. In this paper, the construction method considering characteristics of each type and conditions of existing city was selected. For the reasonable duration calculation, we analyzed the unit schedule for RC method for open type and Shield TBM method for tunnel type. The normal project duration of construction assuming of 1,200m of extension and every 200m of ventilation was prepared by integrating each unit schedule. It was analyzed that it took 893 days for the open type and 616 days for the tunnel type. The results of this study will help to make type selection and normal project duration more easily in the planning phase. If it is linked to the design stage, it will be easy to estimate the process and construction cost.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.2
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• pp.77-92
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• 2021

For the construction of a large underground space with a complex plant installed, it is necessary to analyze the stability considering the ground conditions and various load conditions. In this paper, finite element analysis was performed to analyze the support load that can be used in the design of a large underground space for high-density arrangement of complex plant. An analysis of underground continuous wall (D-wall) was performed considering the load and horizontal earth pressure in the large underground space. In addition, foundation ground analysis was carried out according to the load condition of the complex plant. In order to shorten the construction period, increase the space layout utilization, and secure the stability of the plant structure when installing the complex plant underground, the pipe rack module structure analysis was conducted. This study proposes a design and construction method for the optimal arrangement of underground complex plants using the analysis results.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.10
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• pp.3-12
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• 2018

This research aims at analyzing the changes in residential environment after a residential environment improvement project focusing on the analysis into the physical environment of a residential environment improvement project, and examining in what direction the changes by residents' own efforts occurred after public support, such as infrastructure. The present residence development method has become different from the previous pulling down method and is focused on regeneration. By examining in what direction the target residence is being changed because of the development by residents' own efforts after the government's public investment at this time, this study also aims at investigating the direction to develop a guideline for residential improvement for later improvement of deteriorated residence. As for the contents of the analysis, changes in public support, such as infrastructure, and other areas after the residential environment improvement project were compared and analyzed from the land use, street system, and condition of buildings before the residential environment improvement project through field survey, geographic information system(GIS), registered land and building data and so on. The biggest change since the support from the government was that at the beginning of the project, the application of special provision of building laws and different financial supports led to lots of newly built buildings. Since then, their number has decreased rapidly, and in most cases, there have been some changes in part, such as changes in the use of land or repair of disposal tanks. Most newly built buildings were multi-household houses, and it has caused road capacity and parking lot capacity, etc., to be exceeded, which has worsened the pleasantness of the living environment. In addition, other problems have also appeared, for example, the lack of residence supporting facilities yet with a higher level of residential density. Regarding the changes in the residential environment after the residential environment improvement project, maintenance of houses were conducted in some degree as diverse alleviation policies to improve poor residence, yet the absence of the guideline for the direction of developing the whole district has made the residence environment more dense and deteriorated. To solve these problems, in advance to a residential improvement project, specific management methods based on short-, mid- and long-term plans for the direction of development by residents' own efforts and a sustainable guideline seem to be necessary.