• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.443-448
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• 2016

A novel Permanent Magnet based Magneto Rheological (PM-MR) damper is proposed in this paper. The principle of proposed MR damper is achieved by designing a linearly varying magnetization area with-respect to the movable permanent magnetic based piston setup. Nowadays, commercially available MR damper uses electromagnetic coils for generating the variable magnetic fields corresponding to the variable damping force. The amount of magnetic field produced by the electromagnetic coils are depends on the biasing current of voltage source. The key enabling concept of the proposed MR damper is to replace the electromagnetic coils and the voltage sources by utilizing the variable area based permanent magnetic piston setup. The proposed unique design structure of PM-MR damper has an increasing shear mode damping force with the piston movement in both jounce and rebound motion. In this research, analytical model of the proposed structure is derived and the structural design of proposed concept is verified using numerical CAD tool. As a result, the damping force is increase when piston movement in both jounce and rebound motion.

• Computers and Concrete
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• v.25 no.1
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• pp.67-73
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• 2020

Traditionally used analytical approach to predict the fatigue failure of reinforced concrete (RC) structure is generally conservative and has certain limitations. The nonlinear finite element method (FEM) offers less expensive solution for fatigue analysis with sufficient accuracy. However, the conventional implicit dynamic analysis is very expensive for high level computation. Whereas, an explicit dynamic analysis approach offers a computationally operative modelling to predict true responses of a structural element under periodic loading and might be perfectly matched to accomplish long life fatigue computations. Hence, this study simulates the fatigue behaviour of RC beams with finite element (FE) assemblage presenting a simplified explicit dynamic numerical solution to show computer aided fatigue behaviour of RC beam. A commercial FEM package, ABAQUS has been chosen for this complex modelling. The concrete has been modelled as a 8-node solid element providing competent compression hardening and tension stiffening. The steel reinforcements are simulated as two-node truss elements comprising elasto-plastic stress-strain behaviour. All the possible nonlinearities are duly incorporated. Time domain analysis has been adopted through an automatic Newmark-β time incremental technique. The program consists of twelve RC beams to visualize the real behaviour during fatigue process and to obtain the reliability of the study. Both the numerical and experimental results indicate a redistribution of stresses along the time and damage accumulation of beam which severely affect the serviceability and ultimate capacity of RC beam. The output of the FEM analysis demonstrates good match with the experimental consequences which affirm the efficacy of the computer aided model. The controlled fatigue damage evolution at service fatigue load limits makes the FE model an efficient tool in predicting high cycle fatigue behaviour of RC structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.9
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• pp.745-751
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• 2014

For the multi-nozzle propulsion, the rupture pressure of nozzle closure has an effect on the initial strain rate of ignition. Moreover, the deviation of rupture pressure for each nozzle closure leads to side forces which can disturb the attitude control of rocket. When designed, it should be considered whether nozzle closures are ruptured equally and exactly in the intented pressure. In this paper, the rupture behavior is analyzed by analytical and experimental methods for plate and "+" notched nozzle closures. The rupture pressure and deviation for operating temperature, whether notched or not and notched directions are analyzed. This paper provides a comparison between rupture pressure prediction of finite elements method which tool is Abaqus/Explicit and results of the rupture test. Jonson-Cook shear failure model which corresponds to the damage initiation criterion were used in this simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.1976-1982
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• 2012

Compressor is one of the most widely employed component in fluid machinery system. It takes tremendous efforts to improve compressor efficiency which affects the coefficient of performance of air-conditioning and refrigeration systems directly. Among various types of compressor, scroll-type compressor is commonly prevalent one with its high compression capability despite relatively small size and weight. Numerous experimental studies have been done to develop for the scroll-type compressor; however, computational models to evaluate the compressor performance or efficiency are not much available in the course of compressor designing process. In this study, a computational model was developed on the basis of geometrical theory using 1-D commercial software AMESim. A simulation study was carried out using the model, and the simulation result was validated with analytical data. This research is expected to provide a viable tool for developing and optimizing a scroll-type compressor.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.242-251
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• 2020

In this study, the extraction efficiency and reflection coefficient by a two-dimensional OWC (Oscillating Water Column) WEC (wave energy converter) installed in front of a seawall was investigated for regular/irregular waves. The matched eigenfunction expansion method (MEEM) based on the linear potential theory was applied as an analytical tool. The diffraction problem by the incident wave in the open-chamber and the radiation problem by the oscillating pressure in the closed-chamber were solved to obtain the volume fluxes at the internal free-surface. Applying the volume fluxes into the continuity equation for the airflow in a chamber, we got the oscillating air pressure. The maximum extracted power and corresponding reflection coefficient were determined at the optimal turbine coefficient that maximizes the extracted power. OWC device designed for a high extracted efficiency simultaneously contributes to reduce reflected waves.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.94-101
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• 2012

Design reflects the time and cultural trends and thus can have different symbolic significance and functions depending on the perspective. While this is evident, corporations still insist that designers achieve viewers' complete understanding and satisfaction in their designs. Also, they refuse to accept the designers' interpretation on the grounds that they are subjective and incomplete interpretations even when in fact they are of superior intellectual standard. This problem is also found among the designers dealing with the clients. Thus, as long as all they are willing to accept is the fallibility of each other, the clash between designers and users is inevitable. To solve these problems, we need to have more objective and logical framework for achieving collective understanding on the interpretation of designs and symbols from the very stage of their development. The graphic design is a tangible product that represents the cultural phenomenon and needs to be interpreted as visual symbols. This makes the graphic design a semiological subject. Thus, a semiological approach will enable more analytical interpretations of polysemy of visual symbols. In this light, this study seeks to apply a semiological approach to suggest criteria for interpreting graphic designs as symbols. The criteria will serve as a useful tool for rational evaluation as well as strategic design development.

• Steel and Composite Structures
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• v.19 no.3
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• pp.569-583
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• 2015

Recent years, explosive welding structures have been widely used in many engineering fields. The bonding state detection of explosive welding structures is significant to prevent unscheduled failures and even catastrophic accidents. However, this task still faces challenges due to the complexity of the bonding interface. In this paper, a new method called dual-tree complex wavelet transform based permutation entropy (DTCWT-PE) is proposed to detect bonding state of such structures. Benefiting from the complex analytical wavelet function, the dual-tree complex wavelet transform (DTCWT) has better shift invariance and reduced spectral aliasing compared with the traditional wavelet transform. All those characters are good for characterizing the vibration response signals. Furthermore, as a statistical measure, permutation entropy (PE) quantifies the complexity of non-stationary signals through phase space reconstruction, and thus it can be used as a viable tool to detect the change of bonding state. In order to more accurate identification and detection of bonding state, PE values derived from DTCWT coefficients are proposed to extract the state information from the vibration response signal of explosive welding structure, and then the extracted PE values serve as input vectors of support vector machine (SVM) to identify the bonding state of the structure. The experiments on bonding state detection of explosive welding pipes are presented to illustrate the feasibility and effectiveness of the proposed method.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.27-36
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• 2011

In the proposed paper numerical calculations are carried out using two versions of a three-dimensional, timedomain panel method developed by the group of Prof. P. Sclavounos at MIT, i.e. the linear code SWAN2, enabling optionally the use of the instantaneous non-linear Froude-Krylov and hydrostatic forces and the fully non-linear SWAN4. The analytical results are compared with experimental results for three hull forms with increasing geometrical complexity, the Series 60, a reefer vessel with stern bulb and a modern fast ROPAX hull form with hollow bottom in the stern region. The details of the geometrical modeling of the hull forms are discussed. In addition, since SWAN4 does not support transom sterns, only the two versions of SWAN2 were evaluated over experimental results for the parent hull form of the NTUA double-chine, wide-transom, high-speed monohull series. The effect of speed on the numerical predictions was investigated. It is concluded that both versions of SWAN2 the linear and the one with the non-linear Froude-Krylov and hydrostatic forces provide a more robust tool for prediction of the dynamic response of the vessels than the non-linear SWAN4 code. In general, their results are close to what was expected on the basis of experience. Furthermore, the use of the option of non-linear Froude-Krylov and hydrostatic forces is beneficial for the accuracy of the predictions. The content of the paper is based on the Diploma thesis of the second author, supervised by the first one and further refined by the third one.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.1-9
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• 2012

Emerging three-dimensional television (3DTV) as a new IT product shows a possibility that television is not for just watching broadcasting, but an attractive tool for applying it to our real life. Three dimensional television is generally more effective and attractive than two-dimensional television (2DTV). But it still needs continuous technological improvement to solve its inherent limitations until many customers decide to purchase 3DTVs without hesitation. Innovative products like 3DTV encounter a quality problem leading purchase decision by customers. Quality is regarded as one of the most important factors affecting customers to adopt and use the product. Furthermore, measuring quality effectively is considerable for the 3DTV research. In this paper, we suggest the Analytic Hierarchy Process(AHP) method for evaluating 3DTVs in a view of quality. We describe quality criteria affecting the 3DTV selection through a literature survey and develope an analytical method for measuring quality. We classify the quality of 3DTV into four types and suggest a concept of the quality ratio as a measurement criteria instead of the quality gap. Though a numerical example, we show how priorities of 3DTV with versatile manufacturers is computed.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.41-48
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• 2013

Emerging three-dimensional television (3DTV) as a new IT product shows a possibility that television is not for just watching broadcasting, but an attractive tool for applying it to our real life. Three dimensional television is generally more effective and attractive than two-dimensional television (2DTV). But it still needs continuous technological improvement to solve its inherent limitations until many customers decide to purchase 3DTVs without hesitation. Innovative products like 3DTV encounter a quality problem leading purchase decision by customers. Quality is regarded as one of the most important factors affecting customers to adopt and use the product. Furthermore, measuring quality effectively is considerable for the 3DTV research. In this paper, we suggest the Analytic Hierarchy Process(AHP) method for evaluating 3DTVs in a view of quality. We describe quality criteria affecting the 3DTV selection through a literature survey and develope an analytical method for measuring quality. We classify the quality of 3DTV into four types and suggest a concept of the quality ratio as a measurement criteria instead of the quality gap. Though a numerical example, we show how priorities of 3DTV with versatile manufacturers is computed.