• Journal of Biosystems Engineering
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• 제40권3호
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• pp.201-211
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• 2015

Purpose: Designing equipment for processing, sorting, and other post-harvest operations of agricultural products requires information about their physical properties. This study was conducted to investigate some of the mechanical and physical properties of Moringa oleifera L. pods and seeds. Methods: Properties such as the length, width, thickness, bulk density, porosity, mass, static coefficient of friction, and angle of repose were determined as a function of moisture content. Statistical data and force-deformation curves obtained at each loading orientation and moisture level were analyzed for bioyield point, bioyield strength, yield force, rupture point, and rupture strength using a testrometric machine. Result: The basic dimensions (length, width, and thickness) of moringa pods and seeds were found to increase linearly from 311.15 to 371.45 mm, 22.79 to 31.22 mm, and 22.24 to 29.88 mm, respectively, in the moisture range of 12 to 49.5% d.b. The coefficient of friction for both pods and seeds increased linearly with an increase in moisture content on all the surfaces used. The highest value was recorded on mild steel, with 0.581 for pods and 0.3533 for seeds, and the lowest on glass for pods, with a value of 0.501, and of 0.2933 for seeds on galvanized steel. The bioyield and rupture forces, bioyield and rupture energies, and deformation of the pods decreased with an increase in moisture content to a minimum value, then increased with further decrease within the moisture content range, while the yield force increased to a maximum value and then decreased as the moisture content increased. Conclusion: These results will help to determine the most suitable conditions for processing, transporting, and storing moringa pods, and to provide relevant data useful in designing handling and processing equipment for the crop.

• Advanced Composite Materials
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• 제17권3호
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• pp.247-258
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• 2008

This paper is concerned with the long-term performance of geo-textile (GT) composites in terms of creep deformation and frictional properties. Composites of PVA GT and HDPE GM were made to investigate the advanced properties of long-term performance related to waste landfill applications. The same experiments were also performed for typical polypropylene and polyester GT and compared to PVA GT/HDPE GM composites. We also develop high performance GT composites with GM by using PVA GT, which is capable of improving the frictional properties and thus enhances long-term performance of GT composites. Experimental study reveals that the friction coefficient of GT composites is relatively large compared with those of polyester and polypropylene non-woven GT as long as the friction media has similar size to the particles of domestic standard earth. In addition, the geo-composites bonded with geo-grid by a chemical process were investigated experimentally in terms of strain evaluation and creep response values. Geo-grid plays an important role as a reinforcing material. Three kinds of geo-grid were prepared as strong yarn polyester and they were woven type, non-woven type, and wrap knitted type. The sample geo-grids were then coated with PVC. The rib tensile strength tests were conducted to evaluate geo-grid products in terms of tensile strength with regard to single rib. The test was performed according to GRI-GGI. It was concluded again from the experiments that the tensile and creep strains of the geo-grid showed such stable values that the geo-grid prepared in this study could protect geo-textile partially in practical structures.

• 한국건축시공학회지
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• 제15권3호
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• pp.291-297
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• 2015

본 연구에서는 초고층 구조물 시공에 사용되는 80MPa의 고성능 콘크리트를 대상으로 높이가 200m부터 350m인 지점까지 압송계측 결과를 근거로 하여 압송성능과 고성능 콘크리트의 유동특성과의 상관관계를 분석하였다. 굳지 않은 콘크리트의 물성과 초기강도 및 기준 재령에서의 압축강도 및 탄성계수는 모두 품질기준을 만족함이 확인되었다. 또한, 높이별 최대 압송압력은 약 10~15%씩 증가하였으며, 시간당 토출량은 최소 $25m^3$를 만족하는 것으로 나타났다. 또한, 압송압력과 마찰계수는 슬럼프 플로우의 크기에 반비례하는 것으로 나타났으며, 압송압력과 마찰계수는 T-500이 높을수록 증가하는 경향을 보였다.

• Advances in nano research
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• 제13권1호
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• pp.97-111
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• 2022

In the present article, silica nanoparticles (SNPs) were exploited to improve the tribological and mechanical properties of vinyl ester/glass fiber composites. To the best of our knowledge, there hasn't been any prior study on the wear properties of glass fiber reinforced vinyl ester SiO₂ nanocomposites. The wear resistance is a critical concern in many industries which needs to be managed effectively to reduce high costs. To examine the influence of SNPs on the mechanical properties, seven different weight percentages of vinyl ester/nano-silica composites were initially fabricated. Afterward, based on the tensile testing results of the silica nanocomposites, four wt% of SNPs were selected to fabricate a ternary composite composed of vinyl ester/glass fiber/nano-silica using vacuum-assisted resin transfer molding. At the next stage, the tensile, three-point flexural, Charpy impact, and pin-on-disk wear tests were performed on the ternary composites. The fractured surfaces were analyzed by scanning electron microscopy (SEM) images after conducting previous tests. The most important and interesting result of this study was the development of a nanocomposite that exhibited a 52.2% decrease in the mean coefficient of friction (COF) by augmenting the SNPs, which is beneficial for the fabrication/repair of composite/steel energy pipelines as well as hydraulic and pneumatic pipe systems conveying abrasive materials. Moreover, the weight loss due to wearing the ternary composite containing one wt% of SNPs was significantly reduced by 70%. Such enhanced property of the fabricated nanocomposite may also be an important design factor for marine structures, bridges, and transportation of wind turbine blades.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.407-414
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• 2004

Interfacial properties between rock mass and shotcrete play a significant role in the transmission of loads from the ground to shotcrete. These properties have a major effect on the behaviours of rock mass and shotcrete. They, however, have merely been assumed in most of numerical analyses, and little care has been taken in identifying them. This paper aimed to identify interfacial properties including cohesion, tension, friction angle, shear stiffness, and normal stiffness, through direct shear tests as well as interface normal compression tests for shotcrete/rock cores obtained from a tunnel sidewall. Mechanical properties such as compression strength and elastic modulus were also measured to compare them with the time-dependent variation of interfacial properties. Based on experiments, interfacial properties between rock and shotcrete showed a significant time-dependent variation similar to those of its mechanical properties. In addition, the time-dependent behaviours of interfacial properties can be well regressed through exponential and logarithmic functions of time.

• Geomechanics and Engineering
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• 제37권3호
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• pp.253-262
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• 2024

Dynamic properties are pivotal in soil analysis, yet their experimental determination is hampered by complex methodologies and the need for costly equipment. This study aims to predict dynamic soil properties using static properties that are relatively easier to obtain, employing machine learning techniques. The static properties considered include soil cohesion, friction angle, water content, specific gravity, and compressional strength. In contrast, the dynamic properties of interest are the velocities of compressional and shear waves. Data for this study are sourced from 26 boreholes, as detailed in a geotechnical investigation report database, comprising a total of 130 data points. An importance analysis, grounded in the random forest algorithm, is conducted to evaluate the significance of each dynamic property. This analysis informs the prediction of dynamic properties, prioritizing those static properties identified as most influential. The efficacy of these predictions is quantified using the coefficient of determination, which indicated exceptionally high reliability, with values reaching 0.99 in both training and testing phases when all input properties are considered. The conventional method is used for predicting dynamic properties through Standard Penetration Test (SPT) and compared the outcomes with this technique. The error ratio has decreased by approximately 0.95, thereby validating its reliability. This research marks a significant advancement in the indirect estimation of the relationship between static and dynamic soil properties through the application of machine learning techniques.

• 감성과학
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• 제9권2호
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• pp.133-140
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• 2006

본 연구에서는 의복 착용 시 직물이 스치면서 발생하는 왕복마찰음에 대한 물리적 소리특성과 주관적 감각을 고찰하기 위해, 왕복운동을 이용한 직물마찰음발생장치를 개발하고 이 장치를 이용하여 5가지 직물의 왕복마찰음을 녹음한 후, 총음압(LPT), 음압차(${\Delta}L$), 주파수차(${\Delta}f$)를 계산하였다. 왕복마찰음에 대한 주관적 감각은 7개의 소리감각(부드러움, 시끄러움, 날카로움, 맑음, 거침, 높음, 유쾌함)에 대하여 의미미분척도로 평가되었다. 나일론 태피터와 폴리에스테르 레노 직물의 왕복마찰음은 높은 LPT를 나타내어 시끄럽고 날카롭고 거칠며 불쾌한 소리로 인지되었다. 반면 LPT와 ${\Delta}f$의 값이 작은 폴리에스테르 울트라스웨이드와 실크 크레이프드신 직물의 왕복 마찰음은 부드럽고 조용한 소리로 평가되었다. 마찰방향(왕복 방향, 한 방향)에 따른 직물의 마찰음 비교시, 왕복 방향 마찰음은 한 방향 마찰음보다 더 날카롭고 시끄럽고 거칠게 인지되었으며 마찰방향에 상관없이 LPT가 소리감각을 예측하는 중요한 요인으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.521-528
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• 2005

The evaluation process of rock mass properties intrinsically contains some uncertainty due to the inhomogeneity of rock mass and the measurement error. Although various empirical methods for the determination of rock mass properties were suggested, there is no way of integrating various information on rock mass properties except averaging. For these reasons, this research introduces evidence theory which can model epistemic uncertainty and yield reasonable rock mass properties through combining various information such as empirical equations, in-situ test results, and so on. Through the application of evidence theory to the real site investigation and in situ experiment results, an interval of deformation modulus, cohesion and friction angle of rock mass were obtained. The ratios between lower and upper bound of those properties ranges from 1.6 to 3.6. Numerical analyses of circular hole using the properties for TYPE-2 rock mass were carried out. The magnitude or size of plastic region and radial displacement in case of lower bound properties is about 4 times larger than that of upper bound properties.

• 한국산학기술학회논문지
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• 제17권10호
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• pp.280-288
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• 2016

본 연구의 목적은 마찰교반용접을 마그네슘 합금에 응용하기에 앞서 형상이 다른 두 종류의 용접 툴을 마찰교반용접 시험에 적용 및 비교하여 마그네슘 합금 마찰교반용접에 더 적합한 용접 툴을 제안하였다. 용접 툴의 효과를 알아보기 위해서 용접조건 변수 중 이송속도는 200mm/min으로 고정하였고 회전속도를 400, 600, 800rpm으로 변화시키면서 용접부의 거동과 용접 툴 변화에 따른 효과를 평가 및 관찰하였다. 기계적 물성 평가를 위해 인장시험과 경도시험을 수행하였으며, 용접부 내 거동 및 결함의 유무를 확인하기 위하여 용접부에 수직인 방향의 횡단면을 광학현미경을 통해 관찰하였다. 용접 툴에 관계없이 회전속도가 400rpm일 때 결함이 관찰되었으며, 회전속도가 증가할수록 결함이 감소하는 경향을 보였다. 최종적으로 회전속도 800rpm에서 결함이 없는 용접부를 얻었다. 용접 툴 변화에 따른 기계적 물성 평가 결과 C type 용접 툴을 적용한 경우 보다 우수한 결과가 나타났다. 기계적 물성이 가장 우수한 용접조건은 회전속도 800rpm, 이송속도 200mm/min 이었고, 이때 용접부의 인장강도, 항복강도 그리고 연신율은 모재 대비 90.0%, 69.1%, 83.2% 수준으로 각각 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.343-346
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• 2004

In recent years, various forms of indentation testing have been increasingly used to determine the material properties of specimens. This technique, particularly the nano-indentation method , has been extended to the testing of coating systems in order to calculate the individual properties of the thin coatings and the substrates. However, the interpretation of the test data to achieve this is complex and continues to be a widely studied subject. Based on the finite element method of coated surfaces indented by a Berkovich diamond tip, this paper describes methods for combining FEM and experimental indentation testing to determine coating modulus and hardness independent of substrate effects. Using this proposed methodology, testing and FEM to measure coefficients of friction of sheet steel for outer panel were studied.