• Korean Journal of Biological Psychiatry
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• v.4 no.1
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• pp.67-73
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• 1997

The changes of electroencephalogram(EEG) in patients with dementia are most commonly studied by analyzing power or magnitude in certain traditionally defined frequency bands. However because of the absence of an identified metric which quantifies the complex amount of information, there are many limitations in using such a linear method. According to chaos theory, irregular signals of EEG can also result from low dimensional deterministic chaos. Chaotic nonlinear dynamics in the EEG can be studied by calculating the correlation dimension. The authors have analyzed EEG epochs from three patients with dementia of Alzheimer type and three matched control subjects. The multichannel correlation dimension is calculated from EEG epochs consisting of 15 channels with 16,384 data points per channel. The results showed that patients with dementia of Alzheimer type had significantly lower correlation dimension than non-demented controls on 12 channels. Topographic analysis showed that the correlation dimensions were significantly lower in patients with Alzheimer's disease on frontal, temporal, central, and occipital head regions. These results show that brains of patients with dementia of Alzheimer type have a decreased complexity of electrophysiological behavior. We conclude that the nonlinear analysis such as calculating correlation dimension can be a promising tool for detecting relative changes in the complexity of brain dynamics.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.219-235
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• 2014

With the development of the technology of underwater moving bodies, the need for developing the knowledge of surface effect interaction of free surface and underwater moving bodies is increased. Hence, the two-phase flow is a subject which is interesting for many researchers all around the world. In this paper, the non-linear free surface deformations which occur during the water-exit of a circular cylinder due to its buoyancy are solved using finite volume discretization based code, and using Volume of Fluid (VOF) scheme for solving two phase flow. Dynamic mesh model is used to simulate dynamic motion of the cylinder. In addition, the effect of cylinder mass in presence of an external force is studied. Moreover, the oblique exit and entry of a circular cylinder with two exit angles is simulated. At last, water-exit of a circular cylinder in six degrees of freedom is simulated in 3D using parallel processing. The simulation errors of present work (using VOF method) for maximum velocity and height of a circular cylinder are less than the corresponding errors of level set method reported by previous researchers. Oblique exit shows interesting results; formation of waves caused by exit of the cylinder, wave motion in horizontal direction and the air trapped between the waves are observable. In 3D simulation the visualization of water motion on the top surface of the cylinder and the free surface breaking on the front and back faces of the 3D cylinder at the exit phase are observed which cannot be seen in 2D simulation. Comparing the results, 3D simulation shows better agreement with experimental data, specially in the maximum height position of the cylinder.

• KSBB Journal
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• v.11 no.4
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• pp.405-410
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• 1996

This paper discussed the dispersion effect according to the geometrical variation of an internal-loop spparatus by the method of pulse injection of a tracer. The Bodenstein number, which is the dimensionless group characterizing the effect of dispersion, was decreased with increasing the superficial gas velocity in the 50L and the 500L apparatus. But, in the 5L apparatus, the Bodenstein number was increased with increasing the superficial gas velocity in the range of 0 to 2cm/sec but above that range the rate of increase was dropped down to give a constant value because of the phenomenon of gas disengagement. The principle of similarity based on dimensional analysis was applied to design a pilot scale internal-loop apparatus. The effect of dispersion was examined in three different internal-loop apparatus to give the following correlation with major geometric and fluid dynamic properties as variables. B0=4.4014ReG0.117 ReL-0.0065(Hr/Dr)0.76(Dd/Dr)-0.76

• Smart Structures and Systems
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• v.20 no.2
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• pp.127-137
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• 2017

Identification of damping characteristics is of significant importance for dynamic response analysis and condition assessment of structural systems. Damping is associated with the behavior of the energy dissipation mechanism. Identification of damping ratios based on the sensitivity of dynamic responses and the model updating technique is investigated with numerical and experimental investigations. The effectiveness and performance of using the sensitivity-based model updating method and vibration monitoring data for damping ratios identification are investigated. Numerical studies on a three-dimensional truss bridge model are conducted to verify the effectiveness of the proposed approach. Measurement noise effect and the initial finite element modelling errors are considered. The results demonstrate that the damping ratio identification with the proposed approach is not sensitive to the noise effect but could be affected significantly by the modelling errors. Experimental studies on a steel planar frame structure are conducted. The robustness and performance of the proposed damping identification approach are investigated with real measured vibration data. The results demonstrate that the proposed approach has a decent and reliable performance to identify the damping ratios.

• Korean Institute of Interior Design Journal
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• v.22 no.5
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• pp.311-319
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• 2013

Buildings of the de-constructive tendency beyond definite forms are being constructed in countries with economic power, technical skills and open culture because they require social conditions to accommodate those buildings as well as a lot of construction expenses. Frank Gehry and Zaha Hadid can be chosen as the representative architects of de-constructivism series who are currently working hard. Though both of them are architects belonging to the de-constructivism category, their works show different construction due to the differences in architectural philosophy and working ways. Gehry consider Architect as a fine art and enjoy (sculpture) three-dimensional structure work through Rough Model. With increasing demand for landmark atypical buildings, Hadid has been frequently awarded in the recent series of International Competitions and deals with a lot of cultural works. Affected by absolutism, Hadid showed various diagonal lines in her early construction and works based on the theme of dynamics such as lightness, gliding and light contact with the ground etc. Hadid's Architecture which worked under the theme of dynamic contains a variety of diagonal lines that might cause the viewers to have difficulty on spatial awareness, thus It is known that Hadid's Architecture has lower efficiency on the Circulation and difficulty on spatial cognition compared to the typical museum. According to the research findings of the previous paper that space understanding of viewers on Frank Gehry Museum consisting of complicated planes is generally better than that of them on a typical museum, the purpose of this study is to find out the Circulation efficiency and spatial cognition of Hadid Museum by explaining the space structure of dynamic Hadid Museum and the difference compared to typical museum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.996-1001
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• 2006

Automatic washing machines have been improved and popularized steadily since the first electric washing machine was produced in the early 1900's. Appliance industry has tried to obtain the performance of washing machine with large capacity, high energy efficiency, low vibration and low noise levels. As the installation peace of a washer becomes closer to the living space, vibration and noise problems become more important challenges. In general, a washing machine has four legs to support its body. Four legs of the washing machine should be attached on a floor. If not so, it may cause severe vibration or walking in the spin-drying process. Unfortunately, the floor of an ordinary house is bumpy in general, and the consumers will not accept bolting washing machines to a foundation; moreover, sometimes they move the location of their washing machines to utility rooms or bath rooms or kitchens and don't care for leveling the legs exactly. In this study, we devise an auto-leg system that prevents the occurrence of abnormal vibration and walking of washing machines. It is simply composed of a spring and a friction damper. Some experiments are implemented to show the dynamic characteristics of the three-dimensional auto-legged washing machine model that is located on the even or uneven ground. A spring parameter is optimized to adjust the length of the auto-leg system automatically up to 10 mm irregularity, and the friction damper is designed to decrease a resonance induced by the spring of the auto-leg system. Some numerical results show that placing the proposed auto-leg system in a washing machine makes good performance with low vibration, as well as low noise, regardless of the unevenness of the floor.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.29-38
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• 2018

Three-dimensional continuum modeling of dynamic soil-pile-structure interaction embedded in a liquefiable sand was carried out. Finn model which can model liquefaction behavior using effective stress method was adopted to simulate development of pore water pressure according to shear deformation of soil directly in real time. Finn model was incorporated into Non-linear elastic, Mohr-Coulomb plastic model. Calibration of proposed modeling method was performed by comparing the results with those of the centrifuge tests performed by Wilson (1998). Excess pore pressure ratio, pile bending moment, pile head displacement-time history according to depth calculated by numerical analysis agreed reasonably well with the test results. Validation of the proposed modeling method was later performed using another test case, and good agreement between the computed and measured values was observed.

• Structural Engineering and Mechanics
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• v.91 no.6
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• pp.551-565
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• 2024

This study presents a methodical investigation into improving structural designs through the analytical examination of the dynamic behavior of functionally graded plates (FGPs) resting on viscoelastic foundations. By employing a four variable first-order shear deformation theory, the study computes non-dimensional frequencies for a variety of porous FGPs with diverse graded patterns and porosity distributions. Different gradient patterns of the plates are considered, and three distinct functions-sigmoid (S-FGM), exponential (E-FGM), and power-law (P-FGM)-are utilized to assess material performance in specific directions. The equations of motion are derived and solved using both Navier's method and Hamilton's principle. Analytical solutions for vibration frequency are provided to validate the proposed methodology against existing literature. Furthermore, a comprehensive parametric analysis is conducted, taking into account various factors such as ceramic material, porosity distribution, gradient index, length-to-thickness ratio, gradient pattern, and damping coefficient. The findings suggest that enhancing the damping coefficient of the viscoelastic foundation can significantly improve the free-vibrational response of functionally graded material plates.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.319-334
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• 2024

The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.287-294
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• 2007

A static aeroelastic analysis for supersonic aircraft wing equipped with external store under the wing lower surface is performed using computational fluid dynamics (CFD) and computational structural technology(CST) coupling methodology. Two mapping algorithms, which are the pressure mapping algorithm and the displacement mapping algorithm, are used for CFD/CST coupling. A three-dimensional unstructured Euler code and finite element analysis program are used to calculate the flow properties and the structural displacements, respectively. The coupling procedure is repeated in an iterative manner until a specified convergence criterion is satisfied. Static aeroelastic analysis for a typical supersonic flight wing is performed and final converged wing configuration is obtained after several iterations.