• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.8
• /
• pp.975-983
• /
• 2011

A microfin on a heated surface and its effects of the heat transfer has been investigated. The thickness of the fin is about 8 micrometer to allow the flexible up-down motion of the fin. Two-way complete FSI (Fluid-Structure Interaction) method has been applied for the analysis. Firstly, the deformation of a microfin due to the pulsating flow is evaluated using structure analysis. The flow and temperature patterns are predicted by CFD (Computational Fluid Dynamics) method. At each time step, using the pressure force and temperature distribution from CFD, the deformation of the wing is evaluated by FEM. Also in order to estimate the resonance probability, the natural frequency of the wing structure is calculated by modal analysis. The proposed numerical procedure was validated through experiment using a single fin. Through this work, we show that the increase of 40% in heat transfer capacity using the microfin has been compared with that of flat plate case.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.1
• /
• pp.7-13
• /
• 2003

A hot press method was use for the optimal manufacturing condition for a shape memory alloy(SMA) composite. The bonding between the matrix and the reinforcement within the SMA composite by the hot press method was strengthened by cold rolling. In this study, the objective was to develop an on-line monitoring system for the prevention of the crack initiation and propagation by shape memory effort of SMA composite. Shape memory effect was used to prevent the SMA composite from cracking. For the system to be developed, an optimal hE parameter should be determined based on the degree of damage and crack initiation. When the SHA composite was heated by the plate heater attached at the composite, the propagating cracks appeared to be controlled by the compressive force of SMA.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.57-57
• /
• 2010

For thin panel welded structure, the various welding distortions were found due to the low resistance against welding deformation. Especially, buckling distortion induced in the thin panel welded structure produce severe problems related to cost in production stage and safety in service life. So, many researches including mechanical and thermal tensioning method for preventing the occurrence of buckling distortion in the production stage have been performed. The purpose of this study is to identify the behavior of longitudinal residual stress at the SA butt weldment with thin plate of 6mm thickness under tension load by 3 dimensional FEA. For it, mesh design for 3D FEA was constructed with 20 nodes brick element for butt weldment and 8 nodes shell element for base metal. According to FEA results, the longitudinal compressive strain inducing tensile residual stress at the butt weldment decreased. It was because the compressive thermal strain in way of weldment was reduced by tension load. The control effect of residual stress increased with an increase in tension load. So, if the amount of tension load applied to the weldment exceeds 1.5 times of longitudinal shrinkage force, the amount of longitudinal residual stress decreased below the critical value inducing the buckling distortion at the SA butt weldment. Its validity was verified by experiment.

• Korean Journal of Applied Biomechanics
• /
• v.25 no.3
• /
• pp.283-291
• /
• 2015

Objective : The purpose of this study was to determine the differences in the head and tibial acceleration signal magnitudes, and their powers and shock attenuations between flat-footed and normal-footed running. Methods : Ten flat-footed and ten normal-footed subjects ran barefoot on a treadmill with a force plate at 3.22m/s averaged from their preferred running speed using heel-toe running pattern while the head and tibial acceleration in the vertical axis data was collected. The accelerometers were sampled at 2000 Hz and voltage was set at 100 mv, respectively. The peak magnitudes of the head and tibial acceleration signals in time domain were calculated. The power spectral density(PSD) of each signal in the frequency domain was also calculated. In addition to that, shock attenuation was calculated by a transfer function of the head PSD relative to the tibia PSD. A one-way analysis of variance was used to determine the difference in time and frequency domain acceleration variables between the flat-footed and normal-footed groups running. Results : Peaks of the head and tibial acceleration signals were significantly greater during flat-footed group running than normal-footed group running(p<.05). PSDs of the tibial acceleration signal in the lower and higher frequency range were significantly greater during flat-footed running(p<.05), but PSDs of the head acceleration signal were not statistically different between the two groups. Flat-footed group running resulted in significantly greater shock attenuation for the higher frequency ranges compared with normal-footed group running(p<.05). Conclusion : The difference in impact shock magnitude and frequency content between flat-footed and normal-footed group during running suggested that the body had different ability to control impact shock from acceleration. It might be conjectured that flat-footed running was more vulnerable to potential injury than normal-footed running from an impact shock point of view.

• Food Science of Animal Resources
• /
• v.40 no.2
• /
• pp.286-296
• /
• 2020

This study investigates the utilization of an electric-field-induced super cooling system in long-term dry aging of beef loin. Analyzed quality properties of dry-aged beef loin applied with electric field refrigeration (EFR) versus commercial refrigeration (CR). Quality properties was including aging loss, pH, water holding capacity (WHC), cooking loss, color, warner-bractzler shear force (WBSF), total plate count (TPC), and thiobarbituric acid reactive substances (TBARS). Aging loss of wk 1 EFR was significantly lower than CR (p<0.05). pH of EFR was slow change tendency compared CR. WHC of both aging methods were higher with increase in aging duration. Cooking loss of wk 1, 2, 4, and 10 EFR were significantly lower than CR (p<0.05). Lightness and redness of EFR was slow change tendency compared CR. However, yellowness of EFR was increased until wk 2, 3, and significantly decreased at wk 10 (p<0.05), but yellowness of CR was decreased until wk 3 and significantly increased with an increasing aging weeks (p<0.05). Both aging methods of WBSF was decreased with increase in aging weeks; however, wk 10 of CR was significantly lower than EFR (p<0.05). TPC after wk 3 EFR groups were significantly lower than CR groups (p<0.05), and TBARS of EFR groups were significantly lower than CR (p<0.05). The present results show that application of the EFR system for dry aging beef loin can extends its shelf life and induce changes of several aging properties in similar to commercial aging.

• Smart Structures and Systems
• /
• v.13 no.4
• /
• pp.587-614
• /
• 2014

In recent years the interest in online monitoring of lightweight structures with ultrasonic guided waves is steadily growing. Especially the aircraft industry is a driving force in the development of structural health monitoring (SHM) systems. In order to optimally design SHM systems powerful and efficient numerical simulation tools to predict the behaviour of ultrasonic elastic waves in thin-walled structures are required. It has been shown that in real industrial applications, such as airplane wings or fuselages, conventional linear and quadratic pure displacement finite elements commonly used to model ultrasonic elastic waves quickly reach their limits. The required mesh density, to obtain good quality solutions, results in enormous computational costs when solving the wave propagation problem in the time domain. To resolve this problem different possibilities are available. Analytical methods and higher order finite element method approaches (HO-FEM), like p-FEM, spectral elements, spectral analysis and isogeometric analysis, are among them. Although analytical approaches offer fast and accurate results, they are limited to rather simple geometries. On the other hand, the application of higher order finite element schemes is a computationally demanding task. The drawbacks of both methods can be circumvented if regions of complex geometry are modelled using a HO-FEM approach while the response of the remaining structure is computed utilizing an analytical approach. The objective of the paper is to present an efficient method to couple different HO-FEM schemes with an analytical description of an undisturbed region. Using this hybrid formulation the numerical effort can be drastically reduced. The functionality of the proposed scheme is demonstrated by studying the propagation of ultrasonic guided waves in plates, excited by a piezoelectric patch actuator. The actuator is modelled utilizing higher order coupled field finite elements, whereas the homogenous, isotropic plate is described analytically. The results of this "semi-analytical" approach highlight the opportunities to reduce the numerical effort if closed-form solutions are partially available.

• Asian-Australasian Journal of Animal Sciences
• /
• v.29 no.1
• /
• pp.89-99
• /
• 2016

The effects of retail cut type on chemical, quality and nutritional characteristics of horse meat were studied. Jeju female breed horses (n = 9) at 32-mo-old were slaughtered and the carcasses at 24 h post-mortem were fabricated into 10 retail cuts including: tender-loin, loin, strip-loin, shoulder-chuck-roll, shoulder-clod, top-round, outside-round, brisket, short-plate-brisket, and shank. The results revealed that all of parameters (chemical, meat quality and nutritional composition) examined significantly (p<0.05) differed between the cuts. The chemical composition range (minimum to maximum) of cuts was found as such: moisture 65.06% to 71.69%; protein 19.07% to 21.28%; collagen 1.40% to 2.45%; fat 2.56% to 12.14% and cholesterol 55.76 to 79.50 mg/100 g. Shoulder-chuck-roll had the highest pH and water-holding capacity, while top-round had the highest cooking loss. Shear force ranged between the cuts from $2.80kg/cm^2$ to $4.98kg/cm^2$. The Cu, Fe, and Zn contents ranged between the cuts from 1.52 mg/kg to 2.75 mg/kg, 21.25 mg/kg to 30.85 mg/kg, and 16.51 mg/kg to 40.42 mg/kg, respectively. Additionally, most of the cuts studied showed favorable polyunsaturated fatty acid/saturated fatty acid, n-3/n-6 and essential amino acid/non-essential amino acid ratios.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.12
• /
• pp.1738-1746
• /
• 2002

In the FSI (Fluid-Structure Interaction) problems, two different governing equations are to be solved together. One is fur the fluid and the other for the structure. Furthermore, a kinematic constraint should be imposed along the boundary between the fluid and the structure. We use the combined formulation, which incorporates both the fluid and structure equations of motion into a single coupled variational equation so that it is not necessary to calculate the fluid force on the surface of structure explicitly when solving the equations of motion of the structure. A two-dimensional channel flow divided by a Bernoulli-Euler beam is considered and the dynamic response of the beam under the influence of channel flow is studied. The Navier-Stokes equations are solved using a P2P1 Galerkin finite element method with ALE (Arbitrary Lagrangian-Eulerian) algorithm. The internal structural damping effect is not considered in this study and numerical results are compared with a previous work fer steady case. In addition to the Reynolds number, two non-dimensional parameters, which govern this fluid-structure system, are proposed. It is found that the larger the dynamic viscosity and density of the fluid are, the larger the damping of the beam is. Also, the added mass is found to be linearly proportional to the density of the fluid.

• Korean Journal of Materials Research
• /
• v.26 no.11
• /
• pp.611-622
• /
• 2016

Particle morphology change and different experimental condition analysis during composite fabrication process by traditional ball milling with discrete element method (DEM) simulation were investigated. A simulation of the three dimensional motion of balls in a traditional ball mill for research on the grinding mechanism was carried out by DEM simulation. We studied the motion of the balls, the ball behavior energy and velocity; the forces acting on the balls were calculated using traditional ball milling as simulated by DEM. The effect of the operational variables such as the rotational speed, ball material and size on the flow velocity, collision force and total impact energy were analyzed. The results showed that increased rotation speed with interaction impact energy between balls and balls, balls and pots and walls and balls. The rotation speed increases with an increase of the impact energy. Experiments were conducted to quantify the grinding performance under the same conditions. Furthermore, the results showed that ball motion affects the particle morphology, which changed from irregular type to plate type with increasing rotation speed. The evolution was also found to depend on the impact energy increase of the grinding media. These findings are useful to understand and optimize the particle motion and grinding behavior of traditional ball mills.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.6
• /
• pp.2767-2772
• /
• 2013

Balance is the foundation for all active daily livings. Evaluation of balance has been conducted to measure postural sway of center of pressure(COP). The purpose of this study is to introduce the Balancia and to examine the validity and inter-, intra-reliability for measure of balance with stroke patients. COP was measured by Wii balance board. The subjects Participated in this study were 39 stroke patients. Intra- and inter-reliability was examined using intraclass correlation coefficient(ICC) with 95% confidence interval. In the result of intra- and inter-reliability, all COP parameters of postural sway showed high to very high reliability with ICC=.793-.939 and ICC=.791-.955. Validity was determined by correlation with Accusway force plate. There were high validity with ICC=.851-.955 between tools. According to these results, the Balancia showed high validity and reliability. It is a useful clinical tool for evaluating balance in stroke patients.