• 농업과학연구
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• 제47권4호
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• pp.1057-1069
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• 2020

For most upland crops in Korea, underground water is used to ensure an adequate water supply. Thus, surface water storage tanks are needed to supply surface water from reservoirs or streams. This study discusses the design, manufacture and monitoring of a water storage tank capable of reliably supplying water to crops and preventing the inflow of floating debris. The study was conducted in an apple orchard in Yesan-gun, Chungcheongnam-do in Korea. Based on the water requirements of the crops and size of the orchard, a required flow volume of about 0.6 ㎥·h-1 was determined, along with a surface water storage tank capacity of 1.2 ㎥. Following a comparison with other materials, stainless steel (STS) was used to construct the water tank. The tank was designed to provide 14 hours of irrigation, enabling a small-capacity, cost-efficient tank design to be used. A surface water irrigation test was performed using the surface water storage tank. The average surface water irrigation flow rate was 0.00045 ㎥·m-2·h-1. The water quality test showed that the pH, suspended solids (SS), total nitrogen (TN), and total phosphorus (TP) values satisfied the reference values for agricultural water. The test results showed that the surface water storage tank evaluated in this study allows for crop irrigation when there is a lack of groundwater during droughts.

• 한국폐기물자원순환학회지
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• 제35권7호
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• pp.653-659
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• 2018

In the industrial wastewater that occupies a large proportion of river pollution, the wastewater generated in textile, leather, and plating industries is hardly decomposable. Though dyeing wastewater has generally been treated using chemical and biological methods, its characteristics cause treatment efficiencies such as chemical oxygen demand (COD) and suspended solids (SS) to be reduced only in the activated sludge method. Currently, advanced oxidation technology for the treatment of dyeing wastewater is being developed worldwide. Electro-coagulation is highly adapted to industrial wastewater treatment because it has a high removal efficiency and a short processing time regardless of the biodegradable nature of the contaminant. In this study, the effects of the current density and the electrolyte condition on the COD removal efficiency in dyeing wastewater treatment by using electro-coagulation were tested with an aluminum anode and a stainless steel cathode. The results are as follows: (1) When the current density was adjusted to $20A/m^2$, $40A/m^2$, and $60A/m^2$ under the condition without electrolyte, the COD removal efficiency at 60 min was 62.3%, 72.3%, and 81.0%, respectively. (2) The removal efficiency with NaCl addition was 7.9% higher on average than that with non-addition at all current densities. (3) The removal efficiency with $Na_2SO_4$ addition was 4.7% higher on average than that with non-addition at all current densities.

• Steel and Composite Structures
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• 제38권3호
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• pp.337-353
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• 2021

Micro-electro-mechanical systems (MEMS) are widely employed in sensors, biomedical devices, optic sectors, and micro-accelerometers. New reinforcement materials such as carbon nanotubes as well as graphene platelets provide stiffer structures with controllable mechanical specifications by changing the graphene platelet features. This paper deals with buckling analyses of functionally graded graphene platelets micro plates with two piezoelectric layers subjected to external applied voltage. Governing equations are based on Kirchhoff plate theory assumptions beside the modified couple stress theory to incorporate the micro scale influences. A uniform temperature change and external electric field are regarded along the micro plate thickness. Moreover, an external in-plane mechanical load is uniformly distributed along the micro plate edges. The Hamilton's principle is employed to extract the governing equations. The material properties of each composite layer reinforced with graphene platelets of the considered micro plate are evaluated by the Halpin-Tsai micromechanical model. The governing equations are solved by the Navier's approach for the case of simply-supported boundary condition. The effects of the external applied voltage, the material length scale parameter, the thickness of the piezoelectric layers, the side, the length and the weight fraction of the graphene platelets as well as the graphene platelets distribution pattern on the critical buckling temperature change and on the critical buckling in-plane load are investigated. The outcomes illustrate the reduction of the thermal buckling strength independent of the graphene platelets distribution pattern while meanwhile the mechanical buckling strength is promoted. Furthermore, a negative voltage, -50 Volt, strengthens the micro plate stability against the thermal buckling occurrence about 9% while a positive voltage, 50 Volt, decreases the critical buckling load about 9% independent of the graphene platelet distribution pattern.

• 한국융합학회논문지
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• 제13권4호
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• pp.287-292
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• 2022

본 논문에서는 소재의 강도에 따라 U 채널형상 제품의 판재성형공정에서 발생하는 스프링백 현상의 산포경향의 분석을 수행하였다. 성형공정의 유한요소해석 및 신뢰성 기반 최적화 기법을 적용하여 인장강도, 항복강도, 소재 두께 등 재질 산포와 마찰계수와 패딩력 등의 공정 산포를 고려하여 산포해석을 실시하였다. 산포해석 결과 산포에 유의한 영향을 미치는 인자는 항복강도와 인장강도 순으로 나타났으며, 소재의 인장강도가 클수록 스프링백 양은 증가하는 반면 스프링백의 산포량이 감소하는 것을 확인하였다. 주요 변형이 발생하는 펀치 어깨부와 다이 어깨부의 변형률과 응력 산포 분석을 통하여 스프링백 산포량 감소의 원인을 분석하였다. 본 논문에 제안된 산포분석기법을 활용할 경우 불가피하게 발생하는 성형공정의 산포를 예측하고 대응이 가능할 것으로 기대된다.

• 한국주조공학회지
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• 제41권6호
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• pp.543-549
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• 2021

알루미늄 주철은 내산화성, 내황화성 및 부식성이 우수하다. Ti, Ni 합금에 비해 비전략적 원소인 Fe를 사용하는 비용이 상대적으로 저렴하여 구조재 및 스테인리스강의 대체재로 기대되고 있다. 이는 스테인리스 스틸을 사용하는 경우에 비해 약 30%의 중량 감소 효과를 가져온다. 알루미늄 합금의 경우 최근 몇 년간 주철의 합금원소로 널리 사용되고 있는 원소이다. 실온에서 연성이 부족하고 600℃를 초과하면 강도가 급격히 감소하여 실용화가 지연되었다. 실온 연성이 약한 원인은 수소에 의한 환경 취화로 알려져 있으며, 이러한 특성의 약점을 개선하기 위해 다양한 합금원소의 첨가가 시도되고 있다. 회주철의 경도와 내마모성을 높이기 위해 주로 바나듐, 크롬, 망간 등의 합금원소를 사용하고 있지만, 이러한 원소를 포함하는 완제품의 가격과 합금화의 문제는 많은 한계가 있다.

• 자원리싸이클링
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• 제30권2호
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• pp.3-13
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• 2021

니켈은 우수한 인성, 전성과 함께 내식성 향상 효과 때문에 널리 사용된다. 따라서 니켈은 우리 일상 생활에서 없어서는 안 될 금속으로, 스테인리스강, 고강도합금, 전자기기 등 기초부터 첨단 응용 분야까지 널리 사용되고 있다. 최근 니켈은 2차 전지 및 커패시터의 주요 소재로 널리 사용되고 있다. 니켈의 사용량은 계속 증가하여 1970년대 전 세계적으로 연간 80만 톤에서 2010년대에는 약 200만 톤으로 증가했다. 그러나, 니켈은 지각 중 원소 존재도에서 23번째로 대표적인 희소금속이다. 본 연구에서는 니켈 제련기술의 현황과 생산량 및 사용 동향에 대해 조사하였다. 니켈은 광석의 종류에 따라 매우 다양한 제련법으로 추출된다. 이러한 다양한 니켈 제련기술은 니켈 2차 자원으로부터 니켈을 추출하는 새로운 재활용 프로세스의 개발에 필수적일 것이다.

• Steel and Composite Structures
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• 제44권1호
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• pp.81-89
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• 2022

The purposes of the present work it to study the effect of shear deformation on the static post-buckling response of simply supported functionally graded (FGM) axisymmetric beams based on classical, first-order, and higher-order shear deformation theories. The behavior of postbuckling is introduced based on geometric nonlinearity. The material properties of functionally graded materials (FGM) are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The equations of motion and the boundary conditions derived using Hamilton's principle. This article compares and addresses the efficiency, the applicability, and the limits of classical models, higher order models (CLT, FSDT, and HSDT) for the static post-buckling response of an asymmetrically simply supported FGM beam. The amplitude of the static post-buckling obtained a solving the nonlinear governing equations. The results showing the variation of the maximum post-buckling amplitude with the applied axial load presented, for different theory and different parameters of material and geometry. In conclusion: The shear effect found to have a significant contribution to the post-buckling behaviors of axisymmetric beams. As well as the classical beam theory CBT, underestimate the shear effect compared to higher order shear deformation theories HSDT.

• 국제초고층학회논문집
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• 제10권4호
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• pp.311-321
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• 2021

Perception of the public to structural fires is very important because there are only a number of tall timber buildings constructed in the world. People are hesitating to accept tall timber buildings, so it is essential to ensure the first generation of tall timber buildings to a very high standard, especially fire safety. Right now, there are no specific design standards or regulations for fire design of tall timber buildings in Europe. Even though heavy timber members have better fire resistance than steel components, many conditions still need to be verified before considering the use of timber materials, e.g. fire spread, post-fire collapse, etc. This research numerically explores the structural behaviours of a tall Glulam building when one of its internal Glulam (Glued laminated timber) columns fails after sustaining a full 120-min standard fire and is removed from the established finite element building model created in SAP2000. The numerical results demonstrate that the failure and removal of the selected internal Glulam column may lead to the local failure of the adjacent CLT (Cross laminated timber) floor slabs, but will not lead to large disproportionate damage and collapse of the whole building. Here, the building is assumed to be located in Glasgow, Scotland, UK.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.523-530
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• 2022

해수의 흐름이 존재하는 방조제 제체 보강공사 시 가장 큰 문제는 재료의 유출로, 콘크리트의 중력식 타설은 원활히 공극을 채우기 어렵고 굳지 않은 콘크리트의 시멘트는 해수에 분산될 확률이 높기 때문에 경화 후 품질의 신뢰성이 저하될 뿐만 아니라, 인근 환경에 악역향을 끼칠 수 있다. 이에 주입이 가능한 겔형태의 주입재가 필요하다, 본 연구에서는 급결성을 띠는 전기로환원슬래그 및 고로슬래그를 활용하여 초기 강도와 해수 침지에 따른 내구성 향상 효과를 평가하였다, 실험 결과 실리카계 약액과의 반응을 통해 흐름성을 갖는 겔형태의 주입재 제조가 가능하였으며 겔의 흐름성은 배합에 따라 105~143 mm 수준으로 현장모사 시험을 통해 외부 유출 없이 공극을 채울 수 있어 현장 적용성을 확인하였다.

• Earthquakes and Structures
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• 제23권6호
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• pp.493-502
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• 2022

In recent decades, infrastructural development has exploded, particularly in the coastal region of Saudi Arabia. The rising demand of most consumed aggregate in construction can be effectively compensated by the alternative material like scoria which lavishly exists in the western region. Scoria is characterized as lightweight aggregate beneficially used to develop lightweight concrete (LWC) - a potential alternative of normal weight concrete (NWC) ensuring reduction in the structural element's size, increase in building height, comparatively lighter foundation, etc. Hence, the goal of this study is to incorporate scoria-based structural lightweight concrete and evaluate its impact on superstructure and foundation design beside contributing to the economy of construction. Fresh, mechanical, and rheological properties of the novel LWC have been investigated. The structural analyses employ the NWC as well as LWC based structures under seismic and wind loadings. The commercial finite element package - ETABS was employed to find out the change in structural responses and foundations. The cost estimation and SWOT analysis for superstructure and foundation have also been carried out. It was revealed that the developed LWC enabled a more flexible structural design. Notable reduction in the steel and concrete prices of LWC might be possible in the low-rise building. It is postulated that the cost-effective and eco-friendly LWC will promote the usage of scoria as an effective alternative in Saudi Arabia and GCC countries for structurally viable LWC construction.