• 한국철도학회논문집
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• 제18권1호
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• pp.53-62
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• 2015

동평판재하시험기(LWDT)는 궤도노반 등의 다짐강성 측정을 위하여 개발된 시험기이며 낙하추를 자유낙하시킬 때 가속도계를 이용하여 다짐표면의 처짐량을 측정, 반무한 탄성체로 가정된 노반의 동탄성계수를 결정한다. 본 연구에서는 LWDT시험기의 구성과 구동 메커니즘 및 동탄성계수 추출공식의 유효성을 상세히 분석하였다. 특히, 2층구조 노반 위에서 LWDT 시험시 상부층의 강성평가 유효깊이를 유한요소해석으로부터 결정하였다. 또한, LWDT 시험시 노반의 강성 차이를 고려하여 사용할 수 있는 동탄성계수 추출공식 수정계수를 제시하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.529-535
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• 2017

본 연구에서는 복합재 압력용기의 성능지수를 최대화하기 위한 적층 설계변수의 영향도 평가 및 최적설계를 수행하였다. 복합재 압력용기의 성능지수에는 용기의 내부체적을 포함한 내압성능 및 경량화 개념이 함축되어 있다. 따라서 성능지수를 최대화하기 위하여 압력용기의 내부체적이 고정되어 있다는 가정 하에 헬리컬 및 후프 층의 두께와 후프 층의 길이, 총 세 가지 변수를 고려하였다. 선정된 변수들의 최적화를 위하여 대체모델의 구축에 필요한 반응표면법이 도입되었고, 변수의 영향도를 평가하기 위한 분산분석이 수행되었다. 최적설계 문제는 내압성능 제약조건 하에 성능지수를 최대화하는 문제로 정식화하였다. 도출된 최적화 모델에 대한 추가적인 수치해석을 통해 본 연구의 효용성을 입증하였다.

• 한국지반환경공학회 논문집
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• 제6권2호
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• pp.31-38
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• 2005

유동성 재료는 자기수평능력을 갖고 있으며, 액체와 같은 물질로 최대단위중량의 95~100 %의 자기 다짐율을 발휘할수 있다. 유동성 재료는 노동력이 적게 들고, 시공속도를 높일수 있으며, 접근이 어려운 장소에도 적용이 가능하면서도 재굴착이 용이한 장점이 있다. 따라서 각종 트렌치, 굴착작업, 지중구조물, 오수 및 유틸리티 관과 지중의 공동충전 등에 이용된다. 본 연구의 목적은 고함수비의 점성토와 폐스티로폼 입자, 안정재 등으로 구성된 유동성 재료의 공학적 특성을 평가하는 것이다. 이를 위하여 일축압축실험, 유동성 시험 및 모형충전성 실험을 실시하였으며 폐기물을 활용한 혼합토는 안정재의 양을 $1.0(kN/m^3){\sim}1.2(kN/m^3)$이상을 사용하면 유동성재료로서 사용가능한 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제48권1호
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• pp.41-49
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• 2020

Jabon (Anthocephalus cadamba) is a fast-growing wood species that is widely utilized for light construction and other purposes in Indonesia. The objectives of the current study were to determine the effects of monoethylene glycol (MEG) and SiO₂ nanoparticles (nano SiO₂) impregnation treatment on the dimensional stability and density of jabon wood and to identify the characteristics of impregnated jabon wood. Wood samples were immersed in water (as untreated), MEG, 0.5% MEGSiO₂, then impregnated by applying 0.5 bar of vacuum for 60 min, and then applying 2.5 bar of pressure for 120 min. The results showed that impregnation with MEG and Nano SiO₂ had a significant effect on the dimensional stability of jabon wood. Polymers can fill cell walls in wood indicated by increasing weight percentgain, antiswelling efficiency, bulking effect, and density, then decreasing in water uptake value. Jabon wood morphology by using SEM showed that MEGSiO₂ polymers can cover part of the pitsin the wood vessel wall of jabon. This finding was reinforced by EDX results showing that the silicon content was increased due to the addition of SiO₂ nano. The XRD diffraction pattern indicated that MEGSiO₂ treatment increased the degree of crystallinity in wood samples. Overall, treatment with 0.5% MEGSiO₂ led to the most improvement in the dimensional stability of 5-year-old jabon wood in this study.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.609-616
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• 2019

본 논문에서는 재난 재해시 이재민의 주거안전성을 확보하기 위해 단기 임시주거시설에 대한 설계 계획과 목업 제작을 통한 시공성, 주거환경성을 검증하였다. 특히, 재난 재해발생시 이주민이 응급구호시설로 인근 학교의 강당 또는 체육관을 활용하고 있지만 거주성이 확보에 문제가 있다. 이를 극복하기 위한 방안으로 30일 이내 거주하는 단기 임시주택을 제안하는 것이 연구목적이다. 이를 위해 경량이면서 단열이 확보가능한 복합패널을 선정하여 목업을 제작하였다. 복합 패널을 활용한 목업은 약 1시간안에 완성하여, 시공 용이성을 확인하였다. 또한 목업을 통해 실험실에서 결로와 누수실험을 진행하였다. 외부온도 약 $0^{\circ}C$, 실내온도 약 $32^{\circ}C$로 온도에서 결로현상은 발생하지 않았고, 열화상카메라를 통해 확인해보면 단열성능이 확보되는 것으로 판단되었다. 또한 시간당 60 mm의 강우를 모사하여 누수 실험을 진행한 결과 누수가 확인되지 않아 방수성능이 확보되는 것으로 판단된다. 본 연구는 기존 임시주거시설에서 모듈화된 평면, 시제품제작을 통한 시공용이성 확보, 향후 적재의 용이성을 확인하였다. 단열 및 방수성능이 확보되는 것을 확인하였다. 이를 통해 단기 임시주거시설에 대한 대안을 제시하였다.

• Safety and Health at Work
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• 제11권4호
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• pp.537-542
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• 2020

Background: Personal protective equipment (PPE) has been designed in such a way to reduce accident rates. Unfortunately, existing PPE is rather ineffective as it is not able to provide warning signals when hazard is around. The integration of intelligent systems is envisaged to increase the efficiency of existing PPE. Methods: This project designed a safety vest incorporated with metal detectors which can provide immediate warning to the field workers when there is metal hazard around. This product has greater freedom of design via smart manufacturing as it involves the assembly of few commercially available parts into a single entity. Briefly, the metal detector is a do it yourself (DIY) kit, and the safety vest is purchasable from any local market. The DIY kit was connected to a copper coil and being sewed into the safety vest. Results: The metal detector induces beeping sound when there is metal hazard around. A total of 121 engineering students were introduced to the prototype before being requested to answer a survey associated with the design. Respondents have rated >3.00/5.00 for the design simplicity, ease of usage, and light weight. Meanwhile, respondents suggested that the design should be further improved by increasing the metal detection range. Conclusion: It is envisaged that the introduction of this smart safety vest will allow the workers to carry out their duties securely by reducing the accident rates. Particularly, such design is expected to reduce workplace accident especially during night time at construction sites where the visibility is low.

• Computers and Concrete
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• 제29권 6호
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• pp.393-405
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• 2022

Lightweight concrete is a superior material due to its light weight and high strength. There however remain significant lacunae in engineering knowledge with regards to shear failure of lightweight fiber reinforced concrete beams. The main aim of the present study is to investigate the optimum usage of steel fibers in lightweight fiber reinforced concrete (LWFRC). Multi-scale finite element model calibrated with experimental results is developed to study the effect of steel fibers on the mechanical properties of LWFRC beams. To decrease the amount of steel fibers, it is preferred to reinforce only the middle section of the LWFRC beams, where the flexural stresses are higher. For numerical simulation, a multi-scale finite element model was developed. The cement matrix was modeled as homogeneous and uniform material and both steel fibers and lightweight coarse aggregates were randomly distributed within the matrix. Considering more realistic assumptions, the bonding between fibers and cement matrix was considered with the Cohesive Zone Model (CZM) and its parameters were determined using the model update method. Furthermore, conformity of Load-Crack Mouth Opening Displacement (CMOD) curves obtained from numerical modeling and experimental test results of notched beams under center-point loading tests were investigated. Validating the finite element model results with experimental tests, the effects of fibers' volume fraction, and the length of the reinforced middle section, on flexural and residual strengths of LWFRC, were studied. Results indicate that using steel fibers in a specified length of the concrete beam with high flexural stresses, and considerable savings can be achieved in using steel fibers. Reducing the length of the reinforced middle section from 50 to 30 cm in specimens containing 10 kg/m3 of steel fibers, resulting in a considerable decrease of the used steel fibers by four times, whereas only a 7% reduction in bearing capacity was observed. Therefore, determining an appropriate length of the reinforced middle section is an essential parameter in reducing fibers, usage leading to more affordable construction costs.

• Steel and Composite Structures
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• 제50권6호
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• pp.675-688
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• 2024

Cold-formed steel (CFS) is prone to buckling failure under loading. Lightweight concrete (LC) made of lightweight aggregate has light weight and excellent thermal insulation performance. However, concrete is brittle in nature which is why different materials have been used to improve this inherent behavior of concrete. The distortional buckling (DB) performance of cold-formed steel-lightweight concrete (CFS-LC) composite columns was investigated in this paper. Firstly, the compressive strength test of foam concrete (FC) and ceramsite concrete (CC) was carried out. The performance of the CFS-LC members was investigated. The test results indicated that the concrete-filled can effectively control the DB of the members. Secondly, finite element (FE) models of each test specimen were developed and validated with the experimental tests followed by extensive parametric studies using numerical analysis based on the validated FE models. The results show that the thickness of the steel and the strength of the concrete-filled were the main factors on the DB and bearing capacity of the members. Finally, the bearing capacity of the test specimens was calculated by using current codes. The results showed that the design results of the AIJ-1997 specification were closer to the experimental and FE values, while other results of specifications were conservative.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.318-318
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• 2022

Basil(Ocimum basilicum L.) is an annual herb that grows wild in hot and humid regions such as tropical Asia and Africa. This study was carried out for resource discovery, propagation, and DB construction of aromatic plants. In order to evaluate the genetic characteristics, 28 kinds of basil seeds were supplied from the Center for Genetic Resources. For basil characteristics, planting date, plant height, growth shape, leaf length, leaf shape, petiole color, petiole, stem color, flower color, after harvest, Ml length including roots, flower length, stem thickness and biological weight were measured. For anthocyanin analysis, only basil with purple color was selected, anthocyanins were extracted with 60% ethanol containing 1% citric acid, a standard quantitative curve was prepared with cyanidin-3-glucoside, and absorbance was measured at 525 nm. Basil planting started around June 16, and the flowering period lasted for a total of 18 days from July 19 to August 5. On August 6, when flowering was completed, morphological characteristics including flower color were measured at the site by an object. The measured basil plant length was 26.6-59.6 cm, leaf length 2.0-7.9 cm, leaf width 0.7-5.2 cm, and petiole 1.3-3.9 cm. The growth pattern of basil was generally straight, medium in shape. The color of the leaves was observed evenly by mixed green, purple, purple and green, and the recesses in the shape of the leaf were also conspicuously observed. A total of three basil flower colors were observed: white, light pink(149P 10P/84), and purple(37V 2.5RP 4/12). During the second growth survey after harvest, the total length including the basil roots is 26.7-52.0 cm, the flower length is 8.2-29.3cm, the stem thickness is 7.1-15.9mm, the number of stem nodes is 3-12 nodes, and the total weight of the basil was measured to be about 218-1540 g. There are a total of 16 types of basil expressed in purple, and the anthocyanin content was measured to be 73.74 ~ 380.72 mg/100g.

• 콘크리트학회논문집
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• 제26권1호
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• pp.3-12
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• 2014

복합트러스교는 프리스트레스 박스거더교의 복부를 강재 트러스로 대체한 교량으로 자중이 경감되는 구조적 장점과 복부 개방구조로 인한 경관성이 매우 우수하여 최근 들어 많이 사용되고 있다. 이러한 복합트러스교의 핵심기술은 강재 트러스와 콘크리트 슬래브를 연결하는 격점구조이며 지금까지 여러가지 격점구조들이 개발되어 실험적 검증을 통해서 실교량에 적용해 오고 있다. 이러한 격점구조는 격점부 국부적인 거동뿐만 아니라 복합트러스 거더의 휨 및 피로 등 전체적인 거동을 좌우하기 때문에 이에 대한 연구가 계속 진행되고 있다. 한편, 복합트러스 교량의 복부 개방구조는 프리스트레스 박스교량에 비해 비틀림 성능을 저하시키는 단점을 가지고 있어 편심하중을 받는 교량이나 곡선교 등에는 아직까지 적용된 사례가 없다. 따라서 복합트러스교가 보다 널리 사용되기 위해서는 비틀림 거동에 대한 정확한 분석이 필요한 상황이다. 기존 연구에서는 복합트러스교의 격점구조형식에 따른 비틀림 거동 특성을 알아보기 위해서 3가지 형태의 박스형 복합트러스 실험체를 제작하여 그 거동을 분석하였다. 이에 이 연구에서는 기존연구를 바탕으로 유한요소 해석프로그램을 이용하여 실험체를 모델링하고 시뮬레이션을 통해 그 거동을 분석하여 해석적으로 검증해 보았다.