• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.50-56
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• 2012

This study investigates flow fields and energy dissipation due to regular wave interaction with a perforated vertical breakwater, through velocity data measurement in a two-dimensional wave tank. As the waves propagate through the perforated breakwater, the incoming wave energy is reflected back to the ocean, dissipated due to very turbulent flows near the perforations and inside the chamber, and transmitted through the perforations of the breakwater. This transmitted energy is further reduced due to the presence of the perforated back wall. Hence most of the energy is either reflected or dissipated in the vicinity of the structure, and only a small amount of the incoming wave energy is transmitted through the structure. In this study, particle image velocimetry (PIV) technique was employed to measure two-dimensional instantaneous velocity fields in the vicinity of the structure. Measured velocity data was treated statistically, and used to calculate mean flow fields, turbulence intensity and turbulent kinetic energy. For investigation of the flow pattern, time-averaged mean velocity fields were examined, and discussed using the cross-sections through slot and wall for comparison. Flow fields were obtained and compared for various cases with different regular wave conditions. In addition, turbulent kinetic energy was estimated as an approach to understand energy dissipation near the perforated breakwater. The turbulent kinetic energy was distributed against wave height and wave period to see the dependence on wave conditions.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.11-17
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• 2008

Critical erosion kinetic energy models for radial/median cracks and lateral cracks in a workpiece are established in this study. We used experimental results to demonstrate that the fracture erosion resistance and erosion machining number could be used to evaluate the brittle fracture resistance and machinability of a workpiece. Erosion kinetic energy models were developed to predict brittle fracture and ductile shear, and a critical erosion kinetic energy model was developed to predict the transition from brittle fracture to ductile shear. These models were verified experimentally.

• Korean Journal of Applied Biomechanics
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• v.21 no.3
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• pp.317-325
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• 2011

The purpose of this study was to investigate the contributions of body joints to the kinetic energy of the clubhead in the golf swing. Three dimensional swing analysis was conducted on the seven KPGA golfers. The subjects were asked to swing with 45 inches of driver. The work done by body joints were computed by utilizing the inverse dynamics method. The order of work done by the body joints was lumbar > left hip > right shoulder > left wrist > right wrist > right hip at the first phase. At the second phase, the order of work done by the body joints was trunk > left elbow > right wrist > right shoulder > left wrist > right wrist. At the third phase, the order of work done by body joints was lumbar > right shoulder > left shoulder > left elbow > right wrist > right elbow. The sum of the work done by the body joints was lumbar > shoulder > wrist on the average. The kinetic energy of the club head was 430.11${\pm}$24.35 J and the subject's swing efficiency was shown as 31.82${\pm}$4.86% on the average. The contributions of body joints to the kinetic energy of the clubhead was the order of lumbar > upper right shoulder > left elbow > right wrist during the down swing.

• Environmental Engineering Research
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• v.11 no.5
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• pp.250-256
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• 2006

The combustion kinetics of poly(ethylene terephthalate) (PET) was studied by the dynamic model which accounts for the thermal decomposition of polymer at any time. The kinetic analysis was performed by a conventional nonisothermal thermogravimetric (TG) technique at several heating rates between 10 and 40 K/min in air atmosphere. The thermal decomposition of PET in air atmosphere was found to be a complex process composed of at least two stages for which kinetic values can be calculated. The combustion kinetic analysis of PET gave apparent activation energy for the first stage of $257.3{\sim}269.9\;kJ/mol$, with a value of $140.5{\sim}213.8\;kJ/mol$ for the second stage. To verify the effectiveness of the kinetic analysis method used in this work, the kinetic analysis results were compared with those of various analytical methods. The kinetic parameters were also compared with values of the pyrolysis of PET in nitrogen atmosphere.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.383-388
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• 2008

We are now developing a CFD program, AIRVIEW, with several numerical models and the SIMPLER solving method for constructing flow field and thermal comfort. This study is carried out for evaluating an accuracy of AIRVIEW. Comparisons of accuracy are carried out using Phoenics Version 3.4. In this study, we compare the turbulent kinetic energy distribution and local turbulent Re number obtained with Phoenics with those results simulated by AIRVIEW for three kinds of duct. It is observed from comparison of results that the turbulent kinetic energy values are significant due to the large velocity gradients in the region of flow. Numerical results for turbulent kinetic energy distribution and local turbulent Re number are that a good degree of agreement is found.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1096-1103
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• 2014

This paper proposes a novel strategy for attenuating the output power fluctuation of the wind farm (WF) in a range of tens of seconds delivered to the grid, where the kinetic energy caused by the large inertia of the wind turbine systems is utilized. A control scheme of the two-level structure is applied to control the wind farm, which consists of a supervisory control of the wind farm and individual wind turbine controls. The supervisory control generates the output power reference of the wind farm, which is filtered out from the available power extracted from the wind by a low-pass filter (LPF). A lead-lag compensator is used for compensating for the phase delay of the output power reference compared with the available power. By this control strategy, when the reference power is lower than the maximum available power, some of individual wind turbines are operated in the storing mode of the kinetic energy by increasing the turbine speeds. Then, these individual wind turbines release the kinetic power by reducing the turbine speed, when the power command is higher than the available power. In addition, the pitch angle control systems of the wind turbines are also employed to limit the turbine speed not higher than the limitation value during the storing mode of kinetic energy. For coordinating the de-rated operation of the WT and the storing or releasing modes of the kinetic energy, the output power fluctuations are reduced by about 20%. The PSCAD/EMTDC simulations have been carried out for a 10-MW wind farm equipped with the permanent-magnet synchronous generator (PMSG) to verify the validity of the proposed method.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.127-136
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• 2000

Molecular dynamics simulations have been carried out to investigate the scattering and penetration properties of hydrogen ions with the normal incident angle to Ni (100) surface. The initial kinetic energies of hydrogen ions range from 100 to 1,600 eV. The simulation results are used to assess the applicabilities of theoretical predictions based on the binary collision approximation, and, in the high kinetic regime, theoretical results for scattering energies were shown to he a good agreement with molecular simulations. The angle dependencies on both scattering and penetration distributions were found in the longitudinal direction, but not in the azimuthal direction except for the high kinetic energy of 1,600 eV.

• International Journal of High-Rise Buildings
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• v.1 no.2
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• pp.73-80
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• 2012

In order to use sea breezes to counter the heat island phenomena, i.e. to promote urban ventilation, it is necessary to clarify the effect of building morphology and height on large-scale wind fields. In this study, the sea breeze in the vicinity of the Kanto Plain in Japan is simulated using a mesoscale meteorological model incorporating an urban canopy model, and the inland penetration of sea breezes is accurately reproduced. Additionally, a mean kinetic energy balance within a domain (Control Volume; CV) moving along the sea breeze is analysed. From the results, it is clarified that the sea breeze is interrupted by the resistance and turbulence caused by buildings at the centre of Tokyo. The interruption effect is increased in accordance with the height of these buildings. On the other hand, adverse pressure gradients interrupt in the internal region.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.175-183
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• 2003

The purpose of this study was to analyze the kinetic energy of putter head and ball movements during the process of impact. Highly skilled 5 golfers(less than 1 handicap) participated in this study and the target distance was 3 m. Movements of ball and putter head were recorded with 2 VHS video cameras(60 Hz, 1/500 s shutter speed). Small control object($18.5{\times}18.5{\times}78.5\;cm$) was used in this sdtuldy. Analyzing the process of impact, putter was digitized before 0.0835 s and after 0.0835 s of impact. Ball was digitized 0.1336 s after impact. The results showed that the maximum speed was appeared at Impact and prolonged for a while. Contact point of the club head was within 0.7 cm to the z axis. After contacting the club head, the ball was moved above the ground level(slide) and returned to the ground with sliding and rolling. After contacting the ground, the speed of ball was relied on the surface of the ground. During impact, 70% of kinetic energy of club head has been transferred to the ball.

• Journal of Biosystems Engineering
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• v.37 no.6
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• pp.385-397
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• 2012

Purpose: Drying characteristics of sawdust was studied under batch mode using lab scale microwave dryer. The objective of this study was to investigate the effect of material load and microwave output power on drying characteristics of sawdust. Methods: Material load and microwave output power were varied from 23 to 186 g and 530 to 370 W respectively. Different kinetic models were tested to fit the drying rates of sawdust. Similarly, the activation energy was calculated by employing the Arrhenius equation. Results: The drying efficiency increased considerably, whereas the specific energy consumption significantly decreased with increase in material load and microwave output power. The cumulative energy efficiency increased by 9%, and the specific energy consumption decreased by 8% when the material load was increased from 23 to 186 g. The effective diffusivity increased with decrease in material load and increase in microwave output power. The previously published model gave the best fit for data points with $R^2$ and RMSE values of 0.999 and 0.01, respectively. Conclusions: The data obtained from this study could be used as a basis for modeling of large scale industrial microwave dryers for the pellet production.