• Journal of Bio-Environment Control
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• v.17 no.3
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• pp.197-203
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• 2008

This study was performed to check the structural safety of modified 1-2W Greenhouses to be utilized fur growing Paprika. This type of greenhouse was derived from being remodeled by enhancing the column height of conventional 1-2W type greenhouses. According to the results of structural analysis performed by SAP-2000, there was not significant change in critical snow depth in spite of increasing the column height of 1.2 m by welding. But the critical wind velocities were shown to be $26.0\sim4l.0m/s$, which were $3\sim18%$ lower wind velocities compared with those critical velocities estimated for typical type of 1-2W greenhouse. Under the wind loads, those maximum section forces such as shear force, axial force, and bending moment, together with the deformed frame shape of strained greenhouse, were almost similar in both typical type and modified type. Maximum bending moment of column was found at eave's height of column on windward side. Under the snow loads, those maximum section forces such as shear farce, axial force, and bending moment, together with the deformed frame shape of strained greenhouse, were almost similar in both typical type and modified type. Maximum section forces except axial force was found at eave's height of column. Maximum axial force was found at inner column. Soil bearing capacity together with the total foundation resistance against wind upheaval was found to be consistently safe enough to resist to both wind load and snow load.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.341-345
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• 2020

An in situ regeneration of activated carbon bed using an ozonated water was studied in order for avoiding the carbon loss, contaminant emission and time consuming for discharge-regeneration-repacking in a conventional thermal regeneration process. Using phenol and polyethylene glycol (PEG) as adsorbates, the adsorption breakthrough and in situ regeneration with the ozonated water were repeated. These organics were supposed to degrade by the oxidation reaction of ozone, regenerating the bed for reuse. As the number of regeneration increased, the adsorption capacity for phenol was reduced, but the change was stabilized showing no further reduction after reaching a certain degree of decrement. The reduction of adsorption capacity was due to the increase of pore size resulting in the decrease of specific surface area during ozonation. The adsorption capacity of phenol decreased after the ozonated regeneration because the in-pore adsorption was prevalent for small molecules like phenol. However, PEG did not show such decrease and the adsorption capacity was constantly maintained after several cycles of the ozonated regeneration probably because the external surface adsorption was the major mechanism for large molecules like PEG. Since the reduction in the pore size and specific surface area for small molecules were proportional to the duration of contact time with the ozonated water, careful considerations of the solute size to be removed and controlling the contact time were necessary to enhance the performance of the ozonated in situ regeneration of activated carbon bed.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.123-130
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• 2010

In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;=\;1.3$). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.13-20
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• 2011

There are many mountains in Korean Peninsula, and those used for the construction of roads and railways sectors are forming slopes. Slope collapse occurs with falling rocks and landslide because of the relaxation of the thawing rocks. The heavy rain in summer can also significantly contribute to the process, and abnormal climate change is much more influential than before. Therefore, rockfall-related accidents in rainy season are easily accessible in media every year. There has been a lot of research on application of strengthening compensation of the sections in order to minimize casualties and property damage. Rockfall Protection Net, however, has not been focused on much in the field yet. This study highlights the need of Rockfall Protection Net, since it can segregate the falling rocks inside the net relatively safely. Although there has been a little doubt about the effectiveness of rockfall protection facilities, it is obvious that relevant studies dealing with the solidity of the net are necessary for the rockfall protection net to be capable of supporting rockfall energies. As a result, Expanded metal strength is much more durable compared to the PVC coating net, and it is regarded as an excellent alternative material for the Rockfall Protection Net. In this study, the applicability of Expanded Metal as the alternative of Rockfall Protection Net is verified experimentally.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.525-534
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• 2010

A road curbstone is a structure installed at the boundary of the sidewalk and the street with the objectives of road drainage, drawing attention and such. The current general construction method of curbstones places foundation concrete for the curbstones first, waits until the concrete reaches the strength to support the curbstones, places the curbstones on top, and then places the gutter and rear filling concrete. Such method has the issues of poor compaction and weakened bond strength of concrete due to split placing of concrete, and causes the curbstones to easily separate due to vehicle impact or earth pressure, in turn creating maintenance costs and spoiling the aesthetics. To improve such conventional construction methods, an all-in-one method was developed using formwork rail and jig where both the curbstones and gutter can be worked at the same time, and to evaluate the structural performance, static tests of lateral loading test, pullout test, and bending test were executed, and dynamic tests such as pendulum test and actual vehicle impact test were executed. In all tests, the all-in-one construction method using formwork rail and jig was shown to be superior to the conventional construction method by the increase of construction quality and bond strength of concrete.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.203-213
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• 2024

This study delves into the mechanical properties of fiber-reinforced cement composites(FRCC) concerning the dispersion method of multi-walled carbon nanotubes(MWCNTs). MWCNTs find utility in industrial applications, particularly in magnetic sensing and crack detection, owing to their diverse properties including heat resistance and chemical stability. However, current research endeavors are increasingly directed towards leveraging the electrical properties of MWCNTs for self-sensing and smart sensor development. Notably, achieving uniform dispersion of MWCNTs poses a challenge due to variations in researchers' skills and equipment, with excessive dispersion potentially leading to deterioration in mechanical performance. To address these challenges, this study employs ultrasonic dispersion for a defined duration along with PCE surfactant, known for its efficacy in dispersion. Test specimens of FRCC are prepared and subjected to strength, drawing, and direct tensile tests to evaluate their mechanical properties. Additionally, the influence of MWCNT dispersion efficiency on the enhancement of FRCC mechanical performance is scrutinized across different dispersion methods.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.73-85
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• 2009

An investigation was conducted to get the basic data for establishing structural safety and environmental management of tomato greenhouses in Chungnam region. The contents of the investigation consisted of actual state of greenhouse structures and environmental control facilities. Most of greenhouses were arch type single-span plastic houses and they had too low height for growing tomatoes. Frameworks of multi-span greenhouses were suitable, but those of single-span were mostly insufficient. Every greenhouse had thermal curtain movable or covering fixed inside the greenhouse for energy saving, and heating facilities were mostly warm air heater. Irrigation facilities were mostly drip tube and controlled by manual operation or timer. Almost all of the greenhouses didn't install high level of environmental control facilities such as ventilator, air circulation fan, $CO_2$ fertilizer, insect screen, supplemental light, and cooling device.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1860-1864
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• 2006

본 연구는 강우시 발생되는 강우유출수와 합류식하수관거월류수에 의해 하천으로 유입되는 오염부하를 저감시키기 위한 공법으로, 고수부지 및 제방사면부와 둔치부를 형상화하여 pilot를 제작하였고, 연속적으로 시운전을 한 SRTS(Stormwater Runoff Treatment System)에 관한 것이다. SRT system 내부의 사면수처리부와 평면수처리부에는 다공성 콘크리트를 충진하였다. system 상부에는 식생을 조성하여 뿌리가 수면에 닿아 영양물질을 흡수하는 목적으로 사면수처리부와 평면수처리부에 각각 정육각형과 직사각형인 식생포트를 탈.부착이 가능하도록 고안하였다. 내부에서는 토양과 수처리조 사이에 연결관을 부착하였고, 모세관현상에 의해 토양이 수분을 흡수하도록 구성하였다. pilot plant는 유입부, 사면 수처리부, 평면 수처리부, 유출부로 나누었다. 유입부는 유입펌프와 V-notch로 구성하였고, 유입펌프는 2대를 설치하여 1시간 간격으로 연속적 유입으로 유량조절이 가능하도록 상호교대 운전을 하였다. 평면 수처리부$(W(1.0m){\times}(L(2.4m){\times}H(0.6m))$는 장방형의 접촉산화조로서 하부에 슬러지 침전 및 저류를 위한 hopper를 설치하여 슬러지의 원활한 수집 및 인발이 가능하도록 하였다. 유출부는 사각weir를 설치하였다. 강우유출수의 pH는 $7.27{\sim}7.92$이고, DO농도는 $7.12{\sim}7.88mg/l$로 관측되었다. 2차처리수의 pH는 평균7.4이고 DO농도는 최저 4.5 mg/l에서 최고 8.9 mg/l로 평균 6.8 mg/l로 관측되었다. 또한 강우유출수의 유입수의 T-N, T-P 농도는 각각 $17.5{\sim}22.5mg/l,\;8.9{\sim}11.4mg/l$의 범위이고, 2차 처리수의 유입수의 T-N, T-P 농도와 유사하였다.적인 방법론을 제시할 수 있을 것으로 사료된다.첨두홍수량을 저류하기 위해서 상대적으로 넓은 저류면적이 필요한 것으로 나타난다. 대등한 수위감소값의 홍수저감효과를 발휘하기 위해서 본 연구에서는 On-Line 저류지 면적은 Off-Line 저류지에 비 두배 이상이 필요한 것으로 보여졌다.들에 관한 정보는 종종 현장관측에서 조차 무시되는 경우가 많다. 이에 본 연구에서는 수질모형의 매개변수 중 특히 수리특성에 관련된 매개변수들이 수질에 미치는 영향을 파악하는 것을 목적으로 하고 있다. 이를 위해 적용된 수질모형은 QualKo를 사용하였으며, 대상 하천은 낙동강 본류 경남구간 시점 부근인 회천 합류 전부터 낙동강 본류 경남구간 종점 부근인 밀양강 합류 전까지의 경남 오염총량관리 기본계획 시 구축된 모형 매개변수를 바탕으로 분석을 수행하였다. 일차오차분석을 이용하여 수리매개변수와 수질매개변수의 수질항목별 상대적 기여도를 파악해 본 결과, 수리매개변수는 DO, BOD, 유기질소, 유기인 모든 항목에 일정 정도의 상대적 기여도를 가지고 있는 것을 알 수 있었다. 이로부터 수질 모형의 적용 시 수리 매개변수 또한 수질 매개변수의 추정 시와 같이 보다 세심한 주의를 기울여 추정할 필요가 있을 것으로 판단된다.변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주식시장에 적합한 거래전략은 반전거래전략이고, 이 전략의 유용성은 투자자가 설정한 투자기간보다 더욱 긴 분석기간의 주식가격정보에 의하여 최대한 발휘될 수 있음을 확인하