• Geophysics and Geophysical Exploration
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• v.10 no.2
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• pp.147-153
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• 2007

The conjugate gradient (CG) method is one of the most efficient algorithms for solving a linear system of equations. In addition to being used as a linear equation solver, it can be applied to a least-squares problem. When the CG method is applied to large-scale three-dimensional inversion of magnetotelluric data, two approaches have been pursued; one is the linear CG inversion in which each step of the Gauss-Newton iteration is incompletely solved using a truncated CG technique, and the other is referred to as the nonlinear CG inversion in which CG is directly applied to the minimization of objective functional for a nonlinear inverse problem. In each procedure we only need to compute the effect of the sensitivity matrix or its transpose multiplying an arbitrary vector, significantly reducing the computational requirements needed to do large-scale inversion.

• Journal of Environmental Impact Assessment
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• v.28 no.1
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• pp.23-34
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• 2019

Global warming becomes a serious issue that poses subsidiary issues like a sea level rise or a capricious climate over the world. Because of severe heat-wave of the summer in Korea in 2016, a big attention has been focused on urban heat island since then. Not just about heat-wave itself, many researches have been concentrated on how to adapt in this trendy warming climate and weather in a small scope. A big part of existing studies is mitigating "Urban Heat Island effect" and that is because of huge impervious surface in urban area where highly populated areas do diverse activities. It is a serious problem that this thermal context has a high possibility causing mortality by heat vulnerability. However, there have been many articles of a green infrastructures' cooling impact in summer. This research pays attention to measure cooling effect of a street planting considering urban canyon and type of green infrastructures in neighborhood scale. This quantitative approach was proceeded by ENVI-met simulation with a spatial scope of a commercial block in Seoul, Korea. We found the dense double-row planting is more sensitive to change in temperature than that of the single-row. Among the double-row planting scenarios, shrubs which have narrow space between the plant and the land surface were found to store heat inside during the daytime and prevent emitting heat so as to have a higher temperature at night. The quantifying an amount of vegetated spaces' cooling effect research is expected to contribute to a study of the cost and benefit for the planting scenarios' assessment in the future.

• Journal of Engineering Education Research
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• v.9 no.4
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• pp.5-9
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• 2006

In this research, a case study for cooperative learning practiced in a design class for environmental engineering was presented. Designing a treatment facility for urban diffuse pollution was a main problem given to the participants. Turn-key system for civil works were simulated throughout class works. Twenty five students were grouped into four virtual companies and assigned own position from chairperson to workers. Each group competed throughout establishing design concept regarding order, expense calculation, process distribution, actual calculation. Best design with lowest bidding won the first place. For evaluating class effectiveness, one student from each group were monitored thorough semester. Participants were improved for their understanding about company establishment, turn-key system management, awareness about personal management, and presentation skills. Tension of the class was effectively elevated as well.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.53-59
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• 2018

Water pollution is drastically increasing day by day, because of the enhancement in use of livestock, urban sewage detergents and fertilizers. Moreover increase in concentration of phosphorous and nitrogen contained in sewage, leads to green tide problem in the rivers and causes marine pollution. For this problem to solve, several technologies are being researched and developed. Among them, this experiment is a study on Bench-scale STP based on internationally certified sewage treatment equipment by MEPC. 227(64) of IMO. The purpose of this study is to compare the biological treatment efficiency of phosphorus of Bench-scale STP. The ratio of C : N : P was set to 10 : 5 : 3 and 10 : 3 : 1 as the operating conditions. And the operation cycle was set to anoxic(mixed) 70 min - aeration 50 min (70-50), anoxic(mixed) 90 min - aeration 60 min (90-60). As a result, the phosphorous treatment efficiency was 88% at average, and the treatment efficiency was steady at 90-60 better than 70-50. The efficiency of the bench-scale STP has been verified through this experiment and additional experiments are required to derive the optimal operating conditions.

• KSBB Journal
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• v.27 no.4
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• pp.215-221
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• 2012

Synthetic plastics are important in many branches of industry. Although synthetic plastics provide numerous benefits, they also cause a significant environmental pollution problem because of their non-readily-biodegradability. Biodegradation may provide solution to the problem, but not enough is known about the biodegradation mechanisms of synthetic plastics. This review has been written to provide an overview of the current state of synthetic plastics (polyethylene, polyurethane, nylon, polyvinyl alcohol) biodegradation. Several biodegradation mechanisms of a few selected synthetic plastics are also presented.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.4
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• pp.767-779
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• 2017

Automated mission planning for unmanned aerial vehicles (UAVs) is difficult because of the propagation of several sources of error into the solution, as for any large scale autonomous system. To ensure reliable system performance, we quantify all sources of error and their propagation through a mission planner for operation of UAVs in an obstacle rich environment we developed in prior work. In this sequel to that work, we show that the mission planner developed before can be made robust to errors arising from the mapping, sensing, actuation, and environmental disturbances through creating systematic buffers around obstacles using the calculations of uncertainty propagation. This robustness makes the mission planner truly autonomous and scalable to many UAVs without human intervention. We illustrate with simulation results for trajectory generation of multiple UAVs in a surveillance problem in an urban environment while optimizing for either maximal flight time or minimal fuel consumption. Our solution methods are suitable for any well-mapped region, and the final collision free paths are obtained through offline sub-optimal solution of an mTSP (multiple traveling salesman problem).

• The Journal of Korea Robotics Society
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• v.17 no.3
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• pp.334-338
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• 2022

In visual simultaneous localization and mapping (vSLAM), the correct recognition of a place benefits in relocalization and improved map accuracy. However, its performance is significantly affected by the environmental conditions such as variation in light, viewpoints, seasons, and presence of dynamic objects. This research addresses the problem of feature occlusion caused by interference of dynamic objects leading to the poor performance of visual place recognition algorithm. To overcome the aforementioned problem, this research analyzes the role of scene semantics in correct detection of a place in challenging environments and presents a semantics aided visual place recognition method. Semantics being invariant to viewpoint changes and dynamic environment can improve the overall performance of the place matching method. The proposed method is evaluated on the two benchmark datasets with dynamic environment and seasonal changes. Experimental results show the improved performance of the visual place recognition method for vSLAM.

• Journal of the Korean housing association
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• v.21 no.2
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• pp.101-109
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• 2010

Various environmental problems due to rapid industrialization and urbanization have worsened to such an extent that they threaten the environmental restitution of the globe and become a critical international issue. Korean government has presented the concept of green growth as a new state vision for the next 60 years and is making efforts to solve these environmental problems. Daegu Metropolitan City has faced various environmental problems including overpopulation of the city, traffic pollution, household waste accumulation and the green zone problem because of the increase of urbanization over the last few decades. As such urbanization continues, the quality of residential environments is rapidly deteriorating and the intensive use of the land leads to an increase of building area, raising the temperatures of cities. There have therefore been demands for healthy, pleasant and satisfying residential environments and for the improvement of existing residential environments, and this demand has been fully recognized by society. Nevertheless, current residential complex developments concentrate only on raising the efficiency of land use. In related laws of the past (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) an attempt was made to impose a standard to segmentalize the building-to-land ratio, floor area ratio and regulations of number of floors vertically. However, these laws have now been abolished and the regulations are being eased. The purpose of this study was to analyze the characteristics of the floating wind before and after the vertical segmentation of residential areas (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) by using KLAM_21, a model that enables analysis and prediction of the flow and generation of cold wind. The purpose is also to present a plan to improve the quality of residential areas when developing a building lot and redeveloping housing areas.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2009.11a
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• pp.109-112
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• 2009

Various environmental problems due to the rapid industralization and urbanization have been worsened as much as to threaten the environmental restitution of globe and become a critical international issue. Korean government presented the green growth as a new state vision for 60 years afterwards and is making efforts to solve the environmental problems. Daegu metropolitan city has faced various environmental problems including overpopulation of cities, traffic pollution, household wastes and green zone problem because of urbanization for the last decades. As such urbanism continues, the quality of residential environment is rapidly deteriorating and the intensive use of land leads to increase of building area raising the temperature of cities. Therefore there have been demands for the healthy, pleasant and satisfying residential environment and the improvement of residential environment and such recognition rises from society in full measure. Nevertheless the current residential complex concentrates only on raising the efficiency of land use. Related laws in the past(Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) tried to prepare a standard to segmentalize the building-to-land ratio, floor area ratio and regulations of number of floors vertically, but currently it is abolished and the regulations are becoming eased. The purpose of this study was to analyze the characteristics of the floating wind before and after the vertical segmentation of residential areas(Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) by using KLAM_21, a model that enables analysing and predicting the flow and generation of clod wind, and to present a plan to improve the quality of residential areas afterwards when developing building lot and re-developing housing areas.

• Korean Journal of Construction Engineering and Management
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• v.15 no.3
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• pp.103-112
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• 2014

Since recent construction projects become larger and complicated, the level of difficulty of management skill is rising, and the risk is increasing accordingly so the necessity of improving management skill of projects is increasing. In order to solve this problem, Construction Management system was preferentially introduced in construction projects but in case of domestic construction industry, separate contracts by business boundary are being made so the actual state is that the function of the Construction Management system is not properly operated over the overall projects. The partial operation of Construction Management system like this may impose many restrictions on converged and combined projects such as smart grid and intelligent buildings etc. in the future. For improvement of management skill of domestic construction projects, the competence of project management skill by work areas that can overcome heterogeneity of the current project management skill shall be secured, and any factor that impedes cooperation ability shall be found and that shall be solved. Therefore, the difference of work competency of project management system of construction and electrical construction is to be analyzed by utilizing IPA model in this study, and a plan to introduce the project management system of electrical construction for efficient operation of projects is to be looked into.