• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.2
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• pp.112-118
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• 2010

The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.22 no.3
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• pp.287-296
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• 2015

Purpose: The purpose of this study was to examine the effects of forced air warming on intraoperative and postoperative body temperature, postoperative shivering and pain in patients undergoing laparoscopic cholecystectomy. Methods: A quasi-experimental design with nonequivalent control group was utilized. Fifty eight patients scheduled for laparoscopic cholecystectomy were recruited and assigned to the experimental group (n=29) or control group (n=29). For the experimental group, forced air warming was applied from right after induction and up to one hour after surgery. Body temperature, shivering score and pain score were measured in both groups at 15 minute intervals. Data were collected from September, 2013 to April, 2014. Data were analyzed using t-test, Bonferroni test and repeated measures ANOVA. Results: The experimental group showed higher body temperature than the control group during surgery. After surgery the experimental group showed higher body temperature, lower shivering and less pain compared to the control group. Conclusion: Results show that forced air warming is effective in enhancing body temperature and reducing shivering and pain. Therefore, forced air warming is recommended as an operative nursing intervention.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.915-922
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• 2010

This paper presents an efficient method for determining the forced response of a spinning flexible disk-spindle system supported by fluid dynamic bearings(FDBs) in a computer hard disk drive(HDD). The spinning flexible disk-spindle system is represented by the asymmetric finite element equations of motion originating from the asymmetric dynamic coefficients of the FDBs and the gyroscopic moment of a spinning disk-spindle system. The proposed method utilizes only the right eigenvectors of the eigenvalue problem to transform the large asymmetric finite element equations of motion into a small number of coupled equations, guaranteeing the accuracy of their numerical integration. The results are then back-substituted into the equations of motion to determine the forced response. The effectiveness of the proposed method was verified by comparing it with the responses from the classical methods of mode superposition with the general eigenvalue problems, and mode superposition with modal approximation. The proposed method was shown to be effective in determining the forced response represented by the asymmetric finite element equations of motion of a spinning flexible disk-spindle system supported by FDBs.

• Wind and Structures
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• v.16 no.6
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• pp.561-577
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• 2013

Rational Functions are used to express the self-excited aerodynamic forces acting on a flexible structure for use in time-domain flutter analysis. The Rational Function Approximation (RFA) approach involves obtaining of these Rational Functions from the frequency-dependent flutter derivatives by using an approximation. In the past, an algorithm was developed to directly extract these Rational Functions from wind tunnel section model tests in free vibration. In this paper, an algorithm is presented for direct extraction of these Rational Functions from section model tests in forced vibration. The motivation for using forced-vibration method came from the potential use of these Rational Functions to predict aerodynamic loads and response of flexible structures at high wind speeds and in turbulent wind environment. Numerical tests were performed to verify the robustness and performance of the algorithm under different noise levels that are expected in wind tunnel data. Wind tunnel tests in one degree-of-freedom (vertical/torsional) forced vibration were performed on a streamlined bridge deck section model whose Rational Functions were compared with those obtained by free vibration for the same model.

• Physical Therapy Rehabilitation Science
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• v.10 no.4
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• pp.398-405
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• 2021

Objective: The interest of clinicians is increasing due to the newly established medical insurance for pulmonary rehabilitation. Improvement of respiratory muscle strength and pulmonary function is an important factor in pulmonary rehabilitation, and this study aims to investigate the correlation between changes in respiratory muscle contraction thickness that can affect respiratory muscle strength and pulmonary function. Design: Cross-sectional observational study. Methods: Thirty-one subjects (male=13, female=18) participated in this study. The respiratory muscle strength was measured by dividing it into inspiratory/forced expiratory muscles, and the pulmonary function was measured by forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC. To evaluate the respiratory muscle length increase, in resting and concentric contraction thickness of diaphragm, external/internal oblique, transverse abdominis, and rectus abdominis were measured by using ultrasonography. Results: Inspiratory muscle strength showed a significant correlation with the length increase of the inspiratory muscle (r=0.368~0.521, p<0.05), and forced expiratory muscle strength showed a significant correlation with length increase of forced expiratory muscle (r=0.356~0.455, p<0.05). However, pulmonary function was not correlated with the length increase of the respiratory muscle. Conclusions: In this study, a correlation between respiratory muscle strength and respiratory muscle length increase was confirmed, but no correlation with the pulmonary function was found. It is considered that the respiratory muscle strength can be improved by increasing the respiratory muscle thickness through appropriate respiratory muscle training.

• Advances in nano research
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• v.12 no.6
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• pp.567-581
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• 2022

The free and forced vibration in addition to electric energy harvesting of a piezoelectric disk resting on two-parameter foundation modeled by modified couple stress as well as Kirchhoff plate theory is probed. The governing equations and boundary conditions are obtained using Hamilton's principle. Then, the free and forced vibration are solved using numerical solutions, generalized differential quadrature method (GDQM) and Newmark-beta method. The forced vibration is resulted from a base excitation load. Also, the possible voltage which can be harvested from this system is obtained using generalized integral quadrature method. The validity of the formulation and solution procedure is confirmed using a compassion study. The impact of parameters such as length effect, inner to outer radius ratio, and foundations parameters on the free and forced vibration as well as energy harvesting is investigated in detail. This paper can be a basis for future studies in the area of piezoelectric harvesters in small scales.

• Computers and Concrete
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• v.32 no.6
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• pp.553-565
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• 2023

This work is the first to apply nonlocal theory and a variety of deformation plate theories to study the issue of forced vibration and buckling in organic nanoplates, where the effect of the drag parameter inside the structure has been taken into consideration. Whereas previous research on nanostructures has treated the nonlocal parameter as a fixed value, this study accounts for its effect, and finds that its value fluctuates with the thickness of each layer. This is also a new point that no works have mentioned for organic plates. On the foundation of the notion of potential movement, the equilibrium equation is derived, the buckling issue is handled using Navier's solution, and the forced oscillation problem is solved using the finite element approach. Additionally, a set of numerical examples exhibiting the forced vibration and buckling response of organic nanoplates are shown. These findings indicate that the nonlocal parameter and the drag parameter of the structure have a substantial effect on the mechanical responses of organic nanoplates.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.959-965
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• 2024

The High Temperature Test Unit (HTTU) was an experimental set-up to conduct separate and integral effects tests of the Pebble Bed Modular Reactor (PBMR) core. The annular core consisted of a randomly packed bed of uniform spheres. Natural convection tests using both nitrogen and helium, and forced convection tests using nitrogen, were conducted. The maximum material temperature achieved during forced convection testing was 1200 ℃. This paper presents the numerical analysis of the flow and temperature distribution for a forced convection test using 3D CFD as well as a 1D systems-CFD computer code. Several modelling approaches are possible, ranging from a fully explicit to a semi-implicit method that relies on correlations of their associated phenomena. For the comparison between codes, the analysis was performed using a porous media approach, where the conduction and radiative heat transfer were lumped together as an effective thermal conductivity and the convective heat transfer was correlated between the solid and gas phases. The results from both codes were validated against the experimental measurements. Favourable results were obtained, in particular by the systems-CFD code with minimal computational and time requirements.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.942-951
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• 1993

The objective of this paper was to simulate the effect of intermittent forced aeration on cooling rate of stored paddy. Two-dimensional mathematical models were used to predict temperature in a paddy storage bin subjected to intermittent forced aeration.

• Structural Engineering and Mechanics
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• v.42 no.1
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• pp.95-119
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• 2012

In this paper, forced vibration differential equations of motion of Euler-Bernoulli beams with different boundary conditions and dynamic loads are solved using differential transform method (DTM), analytical solutions. Then, the modal deflections of these beams are obtained. The calculated modal deflections using DTM are represented in tables and depicted in graphs and compared with the results of the analytical solutions where a very good agreement is observed.