• Steel and Composite Structures
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• 제6권3호
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• pp.221-236
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• 2006

The objective of this work is to describe the main steps involved in the derivation of a GBT (Generalised Beam Theory) formulation to analyse the vibration behaviour of loaded cold-formed steel members and also to illustrate the application and capabilities of this formulation. In particular, the paper presents and discusses the results of a detailed investigation about the local and global free vibration behaviour of lipped channel simply supported columns. After reporting some relevant earlier GBT-based results dealing with the buckling and vibration behaviours of columns and load-free members, the paper addresses mostly issues concerning the variation of the column fundamental frequency and vibration mode nature/shape with its length and axial compression level. For validation purposes, some GBT-based results are also compared with values obtained by means of 4-node shell finite element analyses performed in the code ABAQUS.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.134-154
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• 2000

New engine design changes and ever increasing requirements make the design of gear oils challenging. Proper understanding of fundamental lubrication theory and formulation knowledge is necessary to develop new gear oils. This paper provides an overview on fundamentals of lubrication theory and functions of each additive. Also, key technical issues facing gear oils are discussed.

• Wind and Structures
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• 제23권6호
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• pp.543-558
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• 2016

The response of functionally graded ceramic-metal plates is investigated using theoretical formulation, Navier's solutions, and a new displacement based on the high-order shear deformation theory are presented for static analysis of functionally graded plates. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. Numerical results of the new refined plate theory are presented to show the effect of the material distribution on the deflections, stresses and fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the static and free vibration behavior of functionally graded plates.

• 대한수학회지
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• 제46권5호
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• pp.1041-1069
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• 2009

We study the periodic homogenization of the non-stationary Stokes equations. The fundamental homogenization theorem and corrector theorem are proved under a very general assumption on the viscosity coefficients and data. The proofs are based on a weak formulation suitable for an application of classical Tartar's method of oscillating test functions. Such a weak formulation is derived by adapting an argument in Teman's book [Navier-Stokes Equations: Theory and Numerical Analysis, North-Holland, Amsterdam, 1984].

• Natural Product Sciences
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• 제6권1호
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• pp.25-30
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• 2000

To analyse scientifically the fundamental formulation theory and drug interaction of Chungpegagan-tang, the extraction level of puerarin and daidzin, the transforming activity of puerarin and daidzin to daidzein by human intestinal bacteria and in vitro cytotoxicity against tumor cell lines of Chungpesagan-tang were investigated. When Puerariae Radix was extracted with Chungpesagan-tang composing herbal medicines, the puerarin extraction level from these polyprescriptions was decreased by the extraction with Raphani Semen or Cimicifugae Rhizoma, but the other herbal medicines increased it. The activity transforming puerarin and daidzin to daidzein by human intestinal bacteria was increased by Raphani Semen, Cimicifugae Rhizoma and Angelicae Tenuissimae Radix, but decreased by Scutellariae Radix and Rhei Rhizoma. Puerariae Radix did not showed in vitro cytotoxicity against tumor cell lines. However, by its anaerobic incubation with human intestinal bacteria, it showed a potent cytotoxicity. When the main components, puerarin and daidzin, of Puerariae Radix were incubated with human intestinal bacteria, the main metabolites were daidzein and calycosin. These metabolites had the most potent cytotoxicity, compared to those of puerarin and daidzin. Raphani Semen, Rhei Rhizoma and Chungpesagan-tang had also the potent cytotoxicity against tumor cell lines by the anaerobic incubation with human intestinal bacteria.

• Advances in nano research
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• 제15권2호
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• pp.141-153
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• 2023

The main objective of this paper is to develop the finite element study on the nonlinear free vibration of functionally graded nanocomposite spherical shells reinforced with graphene platelets under the first-order shear deformation shell theory and von Kármán nonlinear kinematic relations. The governing equations are presented by introducing the full asymmetric nonlinear strain-displacement relations followed by the constitutive relations and energy functional. The extended Halpin-Tsai model is utilized to specify the overall Young's modulus of the nanocomposite. Then, the finite element formulation is derived and the quadrilateral 8-node shell element is implemented for finite element discretization. The nonlinear sets of dynamic equations are solved by the use of the harmonic balance technique and iterative method to find the nonlinear frequency response. Several numerical examples are represented to highlight the impact of involved factors on the large-amplitude vibration responses of nanocomposite spherical shells. One of the main findings is that for some geometrical and material parameters, the fundamental vibrational mode shape is asymmetric and the axisymmetric formulation cannot be appropriately employed to model the nonlinear dynamic behavior of nanocomposite spherical shells.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.1-14
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• 2016

The Carrera Unified Formulation (CUF) is here extended to perform free-vibrational analyses of rotating structures. CUF is a hierarchical formulation, which enables one to obtain refined structural theories by writing the unknown displacement variables using generic functions of the cross-section coordinates (x, z). In this work, Taylor-like expansions are used. The increase of the theory order leads to three-dimensional solutions while, the classical beam models can be obtained as particular cases of the linear theory. The Finite Element technique is used to solve the weak form of the three-dimensional differential equations of motion in terms of "fundamental nuclei", whose forms do not depend on the adopted approximation. Including both gyroscopic and stiffening contributions, structures rotating about either transversal or longitudinal axis can be considered. In particular, the dynamic characteristics of thin-walled cylinders and composite blades are investigated to predict the frequency variations with the rotational speed. The results reveal that the present one-dimensional approach combines a significant accuracy with a very low computational cost compared with 2D and 3D solutions. The advantages are especially evident when deformable and composite structures are analyzed.

• 대한한의학회지
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• 제19권1호
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• pp.220-233
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• 1998

This study was made to objectify the principle of oriental medical prescriptions so that we could obtain the principle and the formulation of them For that purpose, we analysed the formula and rule of 205 prescriptions recorded in Gum-goe-yo-rak, which have a few of components, and are widely used in clinical from ancient times to these days. At first we classified those prescriptions by their effect. Then we re-classified the herbs of the effect groups into four natures (cold, hot, warm and cool) and five kinds of flavors (sour, bitter, sweet, acrid and salty). And we classified the herbs into three grades - superior, medium, and inferior - which were used in Shen Nong's Herbal Classic. By these means, we statistically evaluated the prescriptions recorded in Gum-goe-yo-rak based on the Four Regular Components(Monarch, Minister, Assistant, and Laborer). As a result we could obtain some facts about the prescriptions recorded in Gum-goe-yo-rak, those are what kind of herbal material was used frequently and distribution of the natures flavors and grades according to thier effects. And we are sure that these results can be great help for establishment of fundamental formulation of theory of traditional herbal medicinal polyprescription.

• Smart Structures and Systems
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• 제19권4호
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• pp.441-448
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• 2017

This paper uses the four-variable refined plate theory for the free vibration analysis of functionally graded material (FGM) rectangular plates. The plate properties are assumed to be varied through the thickness following a simple power law distribution in terms of volume fraction of material constituents. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Equations of motion are derived from the Hamilton's principle. The closed-form solutions of functionally graded plates are obtained using Navier solution. Numerical results of the refined plate theory are presented to show the effect of the material distribution, the aspect and side-to-thickness ratio on the fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the free vibration behavior of functionally graded plates.

• Journal of Computational Design and Engineering
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• 제2권3호
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• pp.157-164
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• 2015

This paper discusses an optimization-based approach for the design of a product platform for industrial three-axis linear-type robots, which are widely used for handling objects in manufacturing lines. Since the operational specifications of these robots, such as operation speed, working distance and orientation, weight and shape of loads, etc., will vary for different applications, robotic system vendors must provide various types of robots efficiently and effectively to meet a range of market needs. A promising step toward this goal is the concept of a product platform, in which several key elements are commonly used across a series of products, which can then be customized for individual requirements. However the design of a product platform is more complicated than that of each product, due to the need to optimize the design across many products. This paper proposes an optimization-based fundamental framework toward the design of a product platform for industrial three-axis linear-type robots; this framework allows the solution of a complicated design problem and builds an optimal design method of fundamental features of robot frames that are commonly used for a wide range of robots. In this formulation, some key performance metrics of the robot are estimated by a reducedorder model which is configured with beam theory. A multi-objective optimization problem is formulated to represent the trade-offs among key design parameters using a weighted-sum form for a single product. This formulation is integrated into a mini-max type optimization problem across a series of robots as an optimal design formulation for the product platform. Some case studies of optimal platform design for industrial three-axis linear-type robots are presented to demonstrate the applications of a genetic algorithm to such mathematical models.