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Approximate natural vibration analysis of rectangular plates with openings using assumed mode method
조대승,Nikola Vladimir,최태묵 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.3
Natural vibration analysis of plates with openings of different shape represents an important issue in naval architecture and ocean engineering applications. In this paper, a procedure for vibration analysis of plates with openings and arbitrary edge constraints is presented. It is based on the assumed mode method, where natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. The presented solution represents an extension of a procedure for natural vibration analysis of rectangular plates without openings, which has been recently presented in the literature. The effect of an opening is taken into account in an intuitive way, i.e. by subtracting its energy from the total plate energy without opening. Illustrative numerical examples include dynamic analysis of rectangular plates with rectangular,elliptic, circular as well as oval openings with various plate thicknesses and different combinations of boundary conditions. The results are compared with those obtained by the finite element method (FEM) as well as those available in the relevant literature, and very good agreement is achieved.
조대승,김병화,김경수 대한조선학회 2010 International Journal of Naval Architecture and Oc Vol.2 No.2
The structural intensity analysis, which calculates the magnitude and direction of vibrational energy flow from vibratory velocity and internal force at any point of a structure, can give information on dominant transmission paths, positions of sources and sinks of vibration energy. This paper presents a numerical simulation system for structural intensity analysis and visualization to apply for ship structures based on the finite element method. The system consists of a general purpose finite element analysis program MSC/Nastran, its pre- and post-processors and an in-house program module to calculate structural intensity using the model data and its forced vibration analysis results. Using the system, the structural intensity analysis for a 4,100 TEU container carrier is carried out to visualize structural intensity fields on the global ship structure and to investigate dominant energy flow paths from harmonic excitation sources to superstructure at resonant hull girder and superstructure modes.
조대승,Nikola Vladimir,최태묵 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
A simple and efficient vibration analysis procedure for stiffened panels with openings and arbitraryboundary conditions based on the assumed mode method is presented. Natural frequencies and modes are determinedby solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange'sequations of motion, where Mindlin theory is applied for plate and Timoshenko beam theory for stiffeners. The effect ofstiffeners on vibration response is taken into account by adding their strain and kinetic energies to the correspondingplate energies whereas the strain and kinetic energies of openings are subtracted from the plate energies. Differentstiffened panels with various opening shapes and dispositions for several combinations of boundary conditions areanalyzed and the results show good agreement with those obtained by the finite element analysis. Hence, the proposedprocedure is especially appropriate for use in the preliminary design stage of stiffened panels with openings.
조대승,이상직,이기철,장응찬,권태동,이수천 한국운동영양학회 2001 Physical Activity and Nutrition (Phys Act Nutr) Vol.5 No.2
Though skeletal muscle protein makes up more than 60% of whole body protein and protein metabolism in skeletal muscle, which accounts for more than 25% of the whole body protein turnover, it has received relatively little attention in comparison to carbohydrate and fat metabolism in the exercise science field. Among amino acids, the branched-chain amino acids(BCAA) taken up by the muscle, rather than the liver, to contribute to oxidative metabolism during endurance exercise. Moreover, since the oxidation of BCAA in muscles may exceed the catabolic capacity to increase BCAA availability, plasma BCAA levels may decline during endurance exercise. And also, an increase in FFA availability during endurance exercise alter the plasma ratio of free tryptophan to BCAA. It has been hypothesized that and increase in the plasma ratio of free tryptophan to BCAA concentration during endurance exercise is cause of central fatigue due to increased uptake of tryptophan in the brain and increased synthesis of serotonin. Based on these hypothesis, it has been suggested that supplementation of BCAA before endurance exercise may inhibite an increase in the plasma ratio of free tryptophan to BCAA concentration and improve endurance exercise performance. And also, another way to manipulate the plasma concentration of free tryptophan is carbohydrate feedings. However considerable controversy surround the relationship of the supplementation of BCAA and(or) carbohydrate to endurance exercise performance. Future study, therefore, is obviously required to verify the effects of hormones and secondary metabolites on central fatigue and endurance performance after BCAA supplementation. For objective study, more research must be conducted to investigate the effects of amount and time of BCAA supplementation, moreover exercise intensity and duration.