• Journal of Wetlands Research
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• v.15 no.4
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• pp.535-541
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• 2013

The urbanization affects significantly on a natural water circulation system by increasing the imperviousness rate. It is also negatively affecting on urban temperature, environmental pollution, water quality, and aqua-ecosystems. The Korea MOE (Ministry of Environment) adapted a new environmental policy in order to reduce the impact of urbanization, which is the Green Stormwater Infrastructure (GSI) program. The GSI can be achieved by protecting conservable green spaces, enlarging more green spaces, and constructing more permeable pavements. The GSI is including many different techniques such as bioretention, rain garden, infiltration trench and so on. Also It is the infrastructures using natural mechanisms of soils, microorganisms, plants and animals on a water circulation system and pollutant reduction. In this research, a multi functional GSI technology with infiltration-filtration mechanisms has been developed and performed lab-scale tests to evaluate the performances about infiltration rate restoration and pollutant reduction. The most of pollutants including metals, organics and particulates were reduced about 50~90% due to water infiltration and storage functions. The clogging was found when the TSS loading rate was reached on $8.3{\sim}9.0kg/m^2$, which value is higher than the values in literatures. It means the new technology can show high performances with low maintenances.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.34-39
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• 2006

The land use pattern, water quality and vegetation were investigated in the six tributaries, including Hanggeumcheon and Satancheon of the Namhan hydrosphere, Iksancheon, Jeonjucheon and Gosancheon of the Mankyung hydrosphere as well as Jongeupcheon of the Dongjin hydrosphere. Forest and farmland area were extensive in Hanggeumcheon, Satancheon and Gosancheon. Farmland and livestock area were wide in Iksancheon. Jeonjucheon were occupied with broad urban. Industrial and urban area were extensive in Jongeupcheon. The loading amounts of biochemical oxygen demand (BOD), total nitrogen (T-N), total phosphorus (T-P) of Iksancheon and chemical oxygen demand (COD) of Jeonjucheon were determined to be very high, respectively. The quality of water in Hanggeumcheon, Satancheon and Gosancheon were determined to be good quality. The species diversity was lower in the down stream than in the upper stream except for the Gosancheon. Life form of plane were mostly perennial plane in the upper stream and annual plants in the down stream of rivers. It was estimated that there is high level of disturbance in the down stream of rivers. The quality of water was significantly correlated with farmland and forest area. In conclusion, human impact, such as farmland and housing lot exerted an influence on the disturbance of down stream and the water quality of rivers.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.401-407
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• 2010

This study was carried out to produce the characteristics of pollutant loads caused by a cherry tree plot as a nonpoint sources(NPS) unit in agricultural areas. The relationship between rainfall and runoff didn't show a good coefficient with 0.5. Despite precipitation amount was less than 20 mm, runoff occurred with $0.5\;m^3$ because of high rainfall intensity of 8.8 mm/hr. In contrast, runoff was not occurred when precipitation amount was 47.4 mm in one case. In that case the primal effect on runoff was not precipitation amount. Correlation between load of pollutants such as BOD, COD, TN and TP and runoff' volumes showed significantly positive values which were more than r = 0.92 for all pollutants except SS(r = 0.71). SS could be a proper factor for estimating pollutant loads of BOD, COD, TN and TP because of a high correlation more than r = 0.73 between SS load and pollutant loads of BOD, COD, TN and TP. Both Organics and nutrient pollutants could be reduced if we control SS in runoff. The highest concentration of TN was detected in the event which was affected by fertilization activities directly. Therefore fertilization must be considered as a function of impact parameters on TN load in agricultural areas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.103-109
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• 2017

We explored the influence of educational service quality on university image, student satisfaction, and word of mouth, as well as the causal association between university image, student satisfaction, and word of mouth. Second-order structural model testing was conducted with 274 questionnaires being used to analyze the hypotheses. The findings demonstrated, first, that educational service quality positively affected university image, student satisfaction, and word of mouth. The important sub-dimensions of educational service quality were teaching method, followed by lecture content, professor attitude, and communication through the second-order structural analysis. Second, university image positively affected student satisfaction and word of mouth. Third, student satisfaction positively affected word of mouth. Finally, for factor loading, the results of educational service quality indicated that teaching method(0.972) and lecture content(0.934) were the key factors in estimating the quality, revealing their significant and positive impact on university image, student satisfaction, and word of mouth. Thus, service providers should strengthen the teaching method and lecture content of educational service quality to enhance the university image, student satisfaction, and word of mouth of university performance from the perspective of university students.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.640-655
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• 2018

Recently, the construction of the urban area has been rapidly increasing, and the excavation work of the ground has been frequently performed at the upper part of the existing underground structures. Especially, when the structure is constructed after the excavation of the ground, the loading and unloading process in the ground under the excavation basement can affect the existing underground structures. Therefore, in order to maintain the stability of the existing underground structure due to the excavation of the ground, it is necessary to accurately grasp the influence of the excavation and the structure load in the adjoining part. In this study, the effect of the excavation of the ground and the new structure load on the existing tunnel was experimentally implemented and the influence of the adjacent construction on the existing tunnel was investigated. For this purpose a large testing model with 1/5 scale of the actual size was manufactured. The influence of ground excavation, width of the load due to new structure, and distance between centers of tunnel and of excavation on the existing tunnel was investigated. In this study, it was confirmed that the influence on the existing tunnel gets larger, as the excavation depth get deeper. At the same distance, it was confirmed that the tunnel displacement increased up to three times according to the increase of the building load width. That is, the load width influences the existing tunnel larger than the excavation depth. As the impact of the distance between centers of tunnel and of excavation, it was confirmed that tunnel crown displacement decreased by 48%. The result showed that a tunnel is located in the range of 1D (D: tunnel diameter) from the center of excavation, the effect of excavation is the largest.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.9
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• pp.517-525
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• 2015

This study analyzes water quality change trends in three major rivers in Daejeon and effect of discharge from Daejeon Wastewater Treatment Plant between 1992 and 2014. As of 2014, COD concentration in the Gab-cheon-A station is in level VI for Korea river water quality standard while BOD and TP are in level III. As expansions of the treatment plant, water quality in the Gab-cheon River has been improving accordingly. However, during the study period, TN concentrations of the headwater and the most downstream locations of the Gab-cheon River have increased about twice and three times, respectively. It was estimated that the treatment plant is responsible for 35%. 46%, 76% and 63% of BOD, COD, TN and TP loadings of the Gab-cheon River, respectively. It was also estimated that small tributaries and nonpoint sources are responsible for 54% and 47% of BOD and COD loadings of the Gab-cheon River. Therefore, it is recommended to further reduce nutrient loadings from the treatment plant and also reduce surface runoff organic loading from nonpoint sources including small tributaries and storm sewers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1373-1380
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• 2010

The plate loading test(PLT) and the field density test are mainly used on the construction of embankments to control the compaction of a limited layer thickness. These two test methods are very time consuming and inefficient, but they are still commonly used as the methods of quality control for soil compaction. In the last 3 decades, many devices such as geogauge, light falling weight deflectometer(LFWD) and dynamic cone penetrometer(DCP) etc., have been introduced into the engineering market with the objective of acquiring in situ stiffness properties of the compacted soil layers. Recently, a new type of sensor, called compactometer, which in mounted on the drum of a roller and measures impact forces continuously with GPS, called as Continuous Compaction Control(CCC), has come into use in many countries such as America, Germany, Japan and so on. The main objective of this paper is to assess the potential use of these new devices as quality control and assurance devices for compacted soil layers. Based on this study, compactometer and the LFWD results werestrongly correlated with the result obtained from the PLT and the field density test.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.595-602
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• 2006

An experimental study was conducted to investigate seismic behaviour of post-tensioned(PT) exterior slab-column connections used for the purpose to resist gravity loads only. For these, 2/3-scale, two PT post-tensioned exterior connections with two different tendon arrangement patterns and one conventional reinforced concrete(RC) exterior connection was tested under quasi-static, uni-directional reversed cyclic loading. During the lateral testing, gravity forces transferred to the column were kept constant to closely simulate a moment to shear ratio of a real building. One of the objectives of this study was to assess the necessity and/or the quantity of bottom bonded reinforcement needed to resist moment reversal which would occur under significant inelastic deformations of the adjacent lateral force resisting systems. The ACI 318 and 352 provisions for structural integrity were applied to provide the bottom reinforcement passing through the column for the specimens. Prior test results were also collected to conduct comparative studies for some design parameters such as the tendon arrangement pattern, the effect of post-tensioning forces and the use of bottom bonded reinforcement. Consequently, the impact of tendon arrangement on the seismic performance of the PT connection, that is lateral drift capacity and ductility, dissipated energy and failure mechanism, was considerable. Moreover, test results showed that the amount of bottom reinforcement specified by ACI 352. 1R-89 was sufficient for resisting positive moments arising from moment reversal under reversed cyclic loads. Shear strength of the tested specimens was more accurately predicted by the shear strength equation(ACI 318) considering the average compressive stress over the concrete($f_{pc}$) due to post-tensioning forces than that without considering $f_{pc}$.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.797-804
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• 2009

The structural designs of RC flat plates that have insufficient flexural stiffness due to lack of support from boundary beams may be governed by serviceability as well as a strength criteira. Specially, since over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction, a construction sequence and its impact on the slab deflections may be decisive factors in designs of flat plate systems. In this study, the procedure of calculating slab deflections considering construction sequences and concrete cracking effects is proposed. The construction steps and the construction loads are defined by the simplified method, and then the slab moments, elastic deflections, and the effective moment of inertia are calculated in each construction step. The elastic deflections in column and middle strips are magnified to inelastic deflections by the effective moment of inertia, and the center deflection of slab are calculated by the crossing beam method. The proposed method is verified by comparisons with the existing test result and the nonlinear analysis result. Also, by applications of the proposed method, the effects of the slab construction cycle and the number of shored floors on the deflections of flat plates under construction are analyzed.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.33-42
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall builidng, the probable structural impact of the 500-year design basis earthquake (DBE) or the 2400-year maximum credible earthquake (MCE) on the selected structural system should be considered at least in finalizing the design. In this study, seismic performance evaluation was conducted for concentrically braced steel highrise buildings that were only designed for wind by following the assumed domestic design practice. It was found that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seimsic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. The strength demand-to-strength capacity study based on the response spectrum analysis revealed that, due to the system overstrength factors mentioned above, wind-designed concentrically braced steel highrise buildings having a slenderness ratio of larger than six can withstand elastically even the maximum credible earthquake at the performance level of immediate occupancy.