• Geomechanics and Engineering
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• 제22권5호
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• pp.415-431
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• 2020

In this study, dynamics responses of advanced composite plates resting variable elastic foundations via a quasi-3D theory are developed using an analytical approach. This higher shear deformation theory (HSDT) is included the shear deformation theory and effect stretching that has five unknowns, which is even inferior to normal deformation theories found literature and other theories. The quasi-three-dimensional (quasi-3D) theory accounts for a parabolic distribution of the transverse shear deformation and satisfies the zero traction boundary conditions on the surfaces of the advanced composite plate without needing shear correction factors. The plates assumed to be rest on two-parameter elastic foundations, the Winkler parameter is supposed to be constant but the Pasternak parameter varies along the long side of the plate with three distributions (linear, parabolic and sinusoidal). The material properties of the advanced composite plates gradually vary through the thickness according to two distribution models (power law and Mori-Tanaka). Governing differential equations and associated boundary conditions for dynamics responses of the advanced composite plates are derived using the Hamilton principle and are solved by using an analytical solution of Navier's technique. The present results and validations of our modal with literature are presented that permitted to demonstrate the accuracy of the present quasi-3D theory to predict the effect of variables elastic foundation on dynamics responses of advanced composite plates.

• 터널과지하공간
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• 제29권5호
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• pp.356-366
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• 2019

다양한 TBM 성능 예측 모델이 개발되었기만 대부분 관입율 예측에 한정되어 있다. 일부 모델들이 수식과 그래프를 이용하여 TBM 가동율을 추정하는 방법을 제시하기도 하지만, TBM 가동율에 대한 연구는 매우 드문 편이다. TBM 가동율은 TBM 장비의 종류, 운영, 유지보수, 지질 조건, 시공자의 경험 등에 영향을 받는다. 본 연구에서는 100여개 이상의 사례 분석을 통해서 TBM 가동율과 RMR, 암종 등의 지반 조건, TBM의 종류, 터널의 연장 및 직경 등과의 관계를 조사하였다. 단순 및 다중 회귀분석을 수행하여 TBM 가동율 예측모델을 개발하였다. 암종 등의 지반조건, TBM의 종류, 터널의 연장 및 직경 등을 설명 변수로 갖는 회귀모델은 낮은 상관계수를 나타내었다. RMR을 설명변수로 갖는 회귀모델이 더 높은 상관계수를 나타내었다.

• Steel and Composite Structures
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• 제18권2호
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• pp.443-465
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• 2015

In this paper, an efficient and simple trigonometric shear deformation theory is presented for thermal buckling analysis of functionally graded plates. It is assumed that the plate is in contact with elastic foundation during deformation. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. Unlike the conventional trigonometric shear deformation theory, the proposed sinusoidal shear deformation theory contains only four unknowns. It is assumed that the mechanical and thermal non-homogeneous properties of functionally graded plate vary smoothly by distribution of power law across the plate thickness. Using the non-linear strain-displacement relations, the equilibrium and stability equations of plates made of functionally graded materials are derived. The boundary conditions for the plate are assumed to be simply supported on all edges. The elastic foundation is modelled by two-parameters Pasternak model, which is obtained by adding a shear layer to the Winkler model. The effects of thermal loading types and variations of power of functionally graded material, aspect ratio, and thickness ratio on the critical buckling temperature of functionally graded plates are investigated and discussed.

• 지구물리
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• 제5권1호
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• pp.63-71
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• 2002

적분 방정식법은 매우 강력한 3차원 전자탐사 모델링 기법이다. 그러나 이 방법은 이상체내에의 전기장의 계산을 위하여 대형 선형 방정식의 해를 구해야 하므로 계산시간이 많이 소요된다는 단점이 있다. 특히 3차원 역산의 경우에는 이러한 적분방정식의 단점은 치명적이 될 수 밖에 없다. 이러한 단점을 극복하기 위하여 다양한 근사법이 개발되었지만, 이들 방법은 모두 Green 텐서의 적분을 수행해야 하며, 이 적분은 상당한 계산시간이 소요된다. 한편 전자탐사에서 Green 텐서는 거리가 증가함에 따라 급격히 감소하는 양상을 보이므로, 모델링을 위하여 이상체를 여러 개의 미소요소로 분할할 경우, 먼 거리에 있는 미소요소는 측정 미소요소에서의 전기장에 크게 영향을 미치지 못한다. 본 논문에서는 이점에 착안하여 먼 거리에 있는 미소요소에 의한 Green 텐서를 무시함으로써 획기적으로 계산시간을 단축할 수 있었다. 결과의 정확성 검토를 위하여 간단한 형태의 이상체에 대하여 본 방법을 사용하여 전기장을 계산한 결과 적분 방정식법, 확작 Born 근사 및 급수법의 결과와 거의 일치하는 정확한 결과를 얻을 수 있었으며, 계산시간을 단축할 수 있었다.

• 천문학회지
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• 제52권4호
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• pp.133-144
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• 2019

We develop forecast models of daily probabilities of major flares (M- and X-class) based on empirical relationships between photospheric magnetic parameters and daily flaring rates from May 2010 to April 2018. In this study, we consider ten magnetic parameters characterizing size, distribution, and non-potentiality of vector magnetic fields from Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) and Geostationary Operational Environmental Satellites (GOES) X-ray flare data. The magnetic parameters are classified into three types: the total unsigned parameters, the total signed parameters, and the mean parameters. We divide the data into two sets chronologically: 70% for training and 30% for testing. The empirical relationships between the parameters and flaring rates are used to predict flare occurrence probabilities for a given magnetic parameter value. Major results of this study are as follows. First, major flare occurrence rates are well correlated with ten parameters having correlation coefficients above 0.85. Second, logarithmic values of flaring rates are well approximated by linear equations. Third, using total unsigned and signed parameters achieved better performance for predicting flares than the mean parameters in terms of verification measures of probabilistic and converted binary forecasts. We conclude that the total quantity of non-potentiality of magnetic fields is crucial for flare forecasting among the magnetic parameters considered in this study. When this model is applied for operational use, it can be used using the data of 21:00 TAI with a slight underestimation of 2-6.3%.

• Advances in Computational Design
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• 제4권3호
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• pp.273-294
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• 2019

In this paper is presented the minimum cost (optimal design) for reinforced concrete circular isolated footings based on an analytic model. This model considers a load and two moments in directions of the X and Y axes, and the pressure has a variation linear, these are the effects that act on the footing. The minimum cost (optimal design) and the Maple program are shown in Flowcharts. Two numerical experiments are shown to obtain the minimum cost design of the two materials that are used for a circular footing supporting an axial load and moments in two directions in accordance to the code of the ACI (American Concrete Institute), and it is compared against the current design (uniform pressure). Also, the same examples are developed through the normal procedure to verify the minimum cost (optimal design) presented in this document, i.e., the equations of moment, bending shear and punching shear are used to check the thickness, and after, the steel areas of the footing are obtained, and it is compared against the current design (uniform pressure). Results section show that the optimal design is more accurate and more economical than to any other model. Therefore, it is concluded that the optimized design model presented in this paper should be used to obtain the minimum cost design for the circular isolated footings.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.257-268
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• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• 해양환경안전학회지
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• 제25권2호
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• pp.244-250
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• 2019

엽상형 해조류의 간접적인 건중량 추정을 위해 구멍갈파래(Ulva australis), 잎파래(Ulva linza), 개도박(Pachymeniopsis lanceolata), 방사무늬김(Pyropia yezoensis)의 형태적 특성과 생체량의 관계를 분석하였다. 시료는 2017년 2월부터 2018년 12월 까지 남해안 6곳에서 채집되었으며, 총 319개체가 분석에 사용되었다. 엽상형 해조류 네 종의 길이와 생체량에 대한 상대성장 지수는 0.28로 일반적인 1/4 (0.25) 지수법칙에 해당하였다. 네 종의 엽체의 표면적과 습중량은 각각 건중량과 유의한 선형관계를 보였으며, 건중량의 94 ~ 99%를 설명할 수 있었다. 이 결과는 엽상형 해조류의 표면적 또는 습중량을 통해 개체의 건중량을 매우 정확하게 추정할 수 있다는 것을 의미한다. 이 방법론은 실험실 연구에서 건중량을 직접 측정할 수 없을 때 쉽고 빠르게 활용할 수 있으며, 추가적으로 소요되는 시간과 비용을 절약할 수 있을 것이다.

• Asian-Australasian Journal of Animal Sciences
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• 제32권9호
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• pp.1389-1396
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• 2019

Objective: The current study analysed the relationships between methane ($CH_4$) output from animal and dietary factors. Methods: The dataset was obtained from 159 Dorper${\times}$thin-tailed Han lambs from our seven studies, and $CH_4$ production and energy metabolism data were measured in vivo by an opencircuit respiratory method. All lambs were confined indoors and fed pelleted diet during the whole experimental period in all studies. Data from two-thirds of lambs were used to develop linear and multiple regressions to describe the relationship between $CH_4$ emission and dietary variables, and data from the remaining one third of lambs were used to validate the established models. Results: $CH_4$ emission (g/d) was positively related to dry matter intake (DMI) and gross energy intake (GEI) (p<0.001). $CH_4$ energy/GEI was negatively related to metabolizable energy/gross energy and metabolizable energy/digestible energy (p<0.001). Using DMI to predict $CH_4$ emission (g/d) resulted in a coefficient of determination ($R^2$) of 0.80. Using GEI, digestible energy intake, and metabolizable energy intake predict $CH_4$ energy/GEI resulted in a $R^2$ of 0.92. Conclusion: the prediction equations established in the current study are useful to develop appropriate feeding and management strategies to mitigate $CH_4$ emissions from sheep.

• 한국농림기상학회지
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• 제23권2호
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• pp.134-140
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• 2021

농업용 유리온실 또는 플라스틱하우스의 투과율을 산정하거나 영농형 태양광 하부 작물의 수광량을 평가할 때, 그리고 작물 군락 광합성량을 모의하거나 분석할 때에 직달과 산란 일사량을 구분하여 접근할 필요가 있다. 본고에서는 산란과 직달 일사량 자료의 농업적 활용 촉진을 위해 나주에서 2019년 5월부터 2020년 11월까지 측정한 자료를 공개하였다. 또한, 기존 연구에서 9개의 산란계수 추정식을 본 자료로 검증하였다. 추정식들 대부분은 결정계수(R²)가 0.79~0.80, RMSE가 0.13~0.15의 범위를 가졌다. 직달·산란 일사량의 농업적 활용을 높이기 위해 본 데이터뿐만 아니라 다양한 자료가 관측되고 공개되어야 할 것이고, 그에 따른 추정식도 정교화될 필요가 있다.