• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.588-597
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• 2016

In this study, we attempted to improve the biogas production efficiency by varying the mixing ratio of the mixed sludge of organic wastes in the improved single-phase anaerobic digestion process. The types of organic waste used in this study were raw sewage sludge, food wastewater leachate and livestock excretions. The biomethane potential was determined through the BMP test. The results showed that the biomethane potential of the livestock excretions was the highest at $1.55m^3CN4/kgVS$, and that the highest value of the composite sample, containing primary sludge, food waste leachate and livestock excretions at proportions of 50%, 30% and 20% respectively) was $0.43m^3CN4/kgVS$. On the other hand, the optimal mixture ratio of composite sludge in the demonstration plant was 68.5 (raw sludge) : 18.0 (food waste leachate) : 13.5 (livestock excretions), which was a somewhat different result from that obtained in the BMP test. This difference was attributed to the changes in the composite sludge properties and digester operating conditions, such as the retention time. The amount of biogas produced in the single-phase anaerobic digestion process was $2,514m^3/d$ with a methane content of 62.8%. Considering the value of $2,319m^3/d$ of biogas produced as its design capacity, it was considered that this process demonstrated the maximum capacity. Also, through this study, it was shown that, in the case of the anaerobic digestion process, the two-phase digestion process is better in terms of its stable tank operation and high efficiency, whereas the existing single-phase digestion process allows for the improvement of the digestion efficiency and performance.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.380-391
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• 1993

The experimental study was made to propose the treatment method of wastewater in the high-density fish culture system. The BOD to COD ratios of effluents were almost same to 0.65 in the eel-farm, but were various in the farm rearing together with tilapia etc. A BOD rate curve of the eel-farm effluent could be described mathematically by the equation, $BODu=14.1(1-10^{-0.222t})+30.9(1-10^{-0.035(t-8)})$. Nitrification in Biological Fluidized Bed(BFB) system to treat the fish-farm wastewater could be reduce ammonium level up to $65{\sim}79\%$ when ammonium loading rates were between 0.014 and 0.075g $NH_4/g$ BVS-day. Nitrification efficiency was decreased by organic matters in the wastewater when ammonium loading was low(0.014 g $NH_4/g$ BVS-day). T-N removal ratios were decreased to increase loading in denitrification process, because of low C/N ratio. Based on much higher biological mass concentrations, BFB system takes many advantages of a practical viewpoint, such as stability of treatment efficiency and reduction of necessary site area for the facility, as compared with conventional treatment systems.

• Journal of Korean Society of Transportation
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• v.23 no.5 s.83
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• pp.47-55
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• 2005

Roads deeply affect the life of people and keep doing an important role to support economic growth of a country. According to the budget plan of the ministry of construction and transportation of Korea, 8.1 trillion won have been allotted for road investment in the year of 2002 which occupy 61% of the transportation infrastructure special account (13.3 trillion won) and 4.7% of the total national budget (1,740 trillion won). It is true that services generated from road investment such as mobility enhancement and increased accessibility have shown positive effects through shortened travel time and decreased vehicle operating cost. However, it is also notable that many negative effects are gradually being discussed and those are nowadays getting severer due to enhanced people interests about road construction, increased concerns on environment and active public involvement that were evoked by traffic accidents, air pollution & noise and destruction of environment. Road construction processes in Korea are normally governed by administrative sectors (suppliers) not by users. These processes ate very weak to accomodate user s needs and community concerns thus easy to fail finalizing a road project without hassles. A public hearing process is supposed to be held in the processes of detailed design step and the environmental impact analysis. However, it is not enough to grab user's needs and community concerns. Increased public involvement frequencies, optimized public involvement timing and enhanced depth of public involvement magnitude are suggested to improve the current poor public involvement schemes in road planning and design processes. The application of these recommended methods to the road planning and design processes may guarantee the change from the current supplier-oriented schemes to the new user-oriented one. Also, this study suggests to reset objectivity and clarity of road construction process, to make conciliation guidelines based on many practical cases that produced good results, to introduce public involvement techniques in a stepwise basis, and to foster the professionals via education and training programs.

• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.41-49
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• 2018

The purpose of this study is to fabricate a full scale road embankment using lightweight air foamed soil as a soil material on soft ground and to investigate its material characteristics and behavior in order to promote dredged soil utilization and minimize ground improvement. As a result of the laboratory test of the onsite mixed samples, the total unit weight of the specimens decreased almost linearly until curing 28 days. In particular, the total unit weight after 28 days of curing was reduced to about 81% of the slurry state before curing, which will be useful in the formulation of similar native soil materials in the future. The unconfined compressive strength began to decrease with the 14th day of curing as shown in the previous study. When the cement content is increased, the strength decreases sharply at a small strain change after the occurrence of the maximum compressive strength, and the maximum strength is exhibited in a range of a smaller axial strain than normal range. The settlement at the surface layer of the ground due to the lightweight embankment was about 1 / 2.75 of the soil embankment and was in agreement with the unit weight ratio (1 / 2.7) of the embankment materials. This indicates the cause and effect of the settlement due to the difference in self weight of the embankments. Also, the difference in settlement between soil and lightweight embankment increased with increasing depth. This shows that the difference in the point at which the settlement is terminated is clear. The ground horizontal displacement under the lightweight embankment was about 15~20% smaller than that of the soil embankment and the depth of occurrence was also 4.5~5.0m shallower in the lightweight embankment.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.183-193
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal fetid. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about $60^{\circ}$in the northern part and $83^{\circ}$in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9 MPa and that of weak sandstone was 10 MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north(east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30~$36^{\circ}$for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described abode. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures. the stability of 니ope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.430-440
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal field. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about 60$^{\circ}$ in the northern part and 83$^{\circ}$ in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9MPa and that of weak sandstone was 10MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north (east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30∼36$^{\circ}$ for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described above. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures, the stability of slope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.509-523
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• 2015

This study introduces newly implemented geological well logs database for Jeju public water wells, built for a research project focusing on integrated hydrogeology database of Jeju Island. A detailed analysis of the existing 1,200 Jeju Island geological logs for the public wells developed since 1970 revealed six major indications to be improved for their use in Jeju geological logs DB construction: (1) lack of uniformity in rock name classification, (2) poor definitions of pyroclastic deposits and sand and gravel layers, (3) lack of well borehole aquifer information, (4) lack of information on well screen installation in many water wells, (5) differences by person in geological logging descriptions. A new Jeju geological logs DB enabling standardized input and output formats has been implemented to overcome the above indications by reestablishing the names of Jeju volcanic and sedimentary rocks and utilizing a commercial, database-based input structured, geological log program. The newly designed database structure in geological log program enables users to store a large number of geology, well drilling, and test data at the standardized DB input structure. Also, well borehole groundwater and aquifer test data can be easily added without modifying the existing database structure. Thus, the newly implemented geological logs DB could be a standardized DB for a large number of Jeju existing public wells and new wells to be developed in the future at Jeju Island. Also, the new geological logs DB will be a basis for ongoing project 'Developing GIS-based integrated interpretation system for Jeju Island hydrogeology'.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.263-270
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• 2010

This is a research on development of water purification equipment called artificial floating island (=AFI) for the stagnant water area which can secure exuberant landscape and water-friendility. The equipment devised in this study is designed to make up the weakness of conventional AFIs and improves the removal efficiency of pollutants using the mixture of media and plants. The air compressor positioned at the inlet releases air with inflow continuously, the water pump at the outlet sprays as a form of fountain with causing a disturbance on stable water column, then, both of them contribute improvement of water quality over a large area. We applied Bio-stone as a media in this system and performed an experiment of pre-efficiency test, and we concluded that the higher pollutants concentration of inflow, the higher removal efficiency we obtained. At the result of lab-scale experiment, in the case of high-concentration inflow, in the removal efficiency of SS is 62.2%, BOD is 50.2%, COD is 55.1%, T-N is 31.6%, T-P is 38.4%. In addition, to evaluate the field application, we set up the facilities in Sin-gal lake located in Yongin-Si Gyeonggi-Do, and researched on the removal efficiency of outflow relative to the inflow. As a result, SS is 53.5%, BOD is 32.8%, COD is 36.9%, T-N is 22.6%, T-N is 33.2%.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.711-722
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• 2011

Beam-column gravity or Intermediate Moment frames subjected to unexpected large displacements are vulnerable when no seismic details are provided, which is typical. Conversely, economic efficiency of those frames is decreased if unnecessary special detailing is applied as the beam and column size becomes quite large and steel congestion is caused by joint transverse reinforcement in beam-column connections. Moderate seismic design is used in Korea for beam-column connections of buildings with structural walls, which are to be destroyed when the unexpected large earthquake occurs. Nonetheless, performance of such beamcolumn connections may be substantially improved by the addition of steel fibers. This study was conducted to investigate the effect of steel fibers in reinforced concrete exterior beam-column connections and possibility for the replacement of some joint transverse reinforcement. Ten half-scale beam-column connections with non-seismic details were tested under cyclic loads with two cycles at each drift up to 19 cycles. Main test parameters used were the volume ratio of steel fibers (0%, 1%, 1.5%) and joint transverse reinforcement amount. The test results show that maximum capacity, energy dissipation capacity, shear strength and bond condition are improved with the application of steel fibers to substitute transverse reinforcement of beam-column connections. Furthermore, several shear strength equations for exterior connections were examined, including the proposed equation for steel fiber-reinforced concrete exterior connections with non-seismic details.

• Journal of the Korean Institute of Educational Facilities
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• v.3 no.3
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• pp.59-70
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• 1996

장안초등학교는 한국전쟁 이후인 1955년에 개교된 초등학교이다. 처음에는 8학급의 가교사시설에 18학급으로 편성되어 초기부터 시설이 양적으로 부족하였다. 또한 이 지역의 학생수 증가로 거의 매년에 걸쳐 학급수의 증가와 교실증축이 함께 이루어 졌다. 현재 건물의 건립년도를 살펴보면 1965년 6월에 처음 신관 1층 부분이 건설되어 70년대와 80년대에 걸쳐 꾸준히 증축되어 왔으며, 대지 동측의 별관은 1993년 12월에 건설된 새건물로, 학교교사 건물이 30년된 건물과 최근의 건물이 함께 공존하고 있다. 철근콘크리트 건물이 구조적으로는 100년도 견딘다 하지만 실제로는 약 30년이면 콘크리트의 산성화가 가속화되면서 구조적으로 안전하지 못하다는 학설이 인정되어, 최근 30년이 경과된 학교 건축의 재건축이 사회적 문제로 대두되고 있다. 실제로는 25년이상 경과된 건물에서도 구조적인 하자가 발생하는 예 가 많아 교육부에서는 대체로 25년이상 경과된 건물에 대하여 재건축을 실시하고 있다. 장안초등학교는 20년에서 30년 경과된 건물이 많은 부분을 차지하는 관계로 재건축이 실시되는 예이다. 아직까지 사용이 가능하다고 판단되는 건물은 본관의 남측부분의 교사(1983년 증축)과 신관의 우측부분(1985년 9월 23일 증축)과 별관(1993년 12월 14일 신축)교사동을 들수 있다. 때문에 이 부분에 대하여 철거할 것인가 혹은 그대로 사용할 것인가에 대한 의견이 있어, 최종적으로 별관은 그대로 사용하는 것을 원칙으로 하고 본관 남측부분은 가장 마지막 건설시기에 철거하고 신관 우측부분은 규모가 작아 철거하기로 하였다. 학교건축은 다른 일반건물과는 달리 교육이라는 기능을 충분히 발휘할수 있는 공간구성이 필수적이라 할수 있다. 여기서 말하는 교육이란 예전의 주입식 교육이 아니라 21세기를 바라보는 정보화 세계화를 지향하는 교육으로 학생 개개인의 창의성과 자주성을 발휘시킬수 있는 교육이라는 점에 대하여 의견은 없을 것이다. 이러한 교육이란 다양한 교육방법을 전제로 하며 하나의 학년을 하나의 학습그룹으로 생각하는 것은 중요한 출발점이 될 것이다. 한 학년의 그룹을 교대상의 기본으로하여 이러한 그룹에 대하여 일제학습, 그룹학습, 팀티칭, 개별학습이 이루어 질수 있는 공간을 제공하는 점을 본 장안초등학교 기본계획에서 출발점으로 하였다. 물론 학교전체 학생을 콘트롤할 수 있는 교육방법도 존재한다. 선진 외국의 예를 살펴보면 아동의 능력별 교육을 위하여 무학년제(Non-Grade)를 도입하는 경우도 있지만 아직 우리나라에서는 학급단위가 중요시되고 있다. 이 학급단위는 교육단위이면서 생활지도 단위이기도 하다. 이러한 점을 인식하여 학교건축의 간장 기본 단위가 되는 보통교실 계획을 보통교실과 오픈스페이스를 연속시킨 유니트로 계획하여 일제학습, 그룹학습, 팀티칭, 개별학습 등이 이루어 질수 있도록 하였다. 실제로는 36학급을 계획할 경우, 한학년의 6개 학급이 하나의 공통된 공간내에 그룹핑 되는 것이 바람직하지만(제3안의 배치에서 제안하여 보았지만 북측교실, 오픈스페이스의 통로화등의 문제점이 있었다), 그 규모가 너무 커서 3개학급을 하나의 유니트로 하였다. 물론 한학년이 동일한 층에 배치시켜 서로의 관련성을 높게 하였다. 특별교실 계획은 보통교실과의 관련성과 장래 지역개방의 역할을 고려하여 계획하여야 할 것이다. 장안 초등학교의 경우는 별관을 그대로 사용 한다는 조건이 있기 때문에 기존의 편복도 형식의 교실에서는 보통교실 계획의 어려움이 있어 특별 교실동으로 고려하였다. 때문에 지역개방에 대해서는 문제점을 안고 있다. 체육관은 기준령에는 권장시설로 되어 있지만 학교시설에 필수적인 시설이라 생각한다. 체육은 국민건강에 직결되기 때문이다. 또한 체육관 건설은 실외체육 실내체육에 대응할 뿐 아니라 학교 행사등에 유용히 사용되기 때문에 더욱 필요시설이라 할수 있겠다. 또한 지역개방을 위하여 정문 혹은 후문 가까이에 배치시키는 것은 필수적이다. 별관, 체육관, 운동장, 후문측에 12학급용의 단독건물 등의 기본적인 제약조건을 고려하여 배치하자면 자연히 교실동들이 분산되는 결과를 낳게된다. 이러한 각각의 교사동을 A동을 중심으로 구름다리로 연결하여 동선의 불편함을 해소시켰다. 주차장은 후문 가까이에 약 10정도의 주차공간이 확보가능하다. 이외에는 운동장을 사용하는 방법과 체육관의 1층부분을 필로티로 하여 그곳에 20대 정도 주차시키는 방안이 있다. 주차는 많을수록 편리는 하겠지만 제한된 대지에 모두 만족 시켜주기는 불가능하다. 공공용의 주차와 소방에 필요한 동선이 요구된다. 특히 도심주차난을 생각할 때는 차라리 적극적으로 지하주차장을 계획하는 방안이 있을 것이다. 마지막으로 현재 67학급은 초대형 규모로 초등학교 규모로는 적합하지 못하다. 장래를 고려하여 48학급에서 최종적으로 36학급으로 계획하였으나 한동안은 67학급이 그대로 유지될 것으로 보인다. 신설 초등학교가 가까운 시기에 개교될 것을 기대한다.