• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.744-749
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• 2007

Kinematic and kinetic analysis has been performed for Soft Golf swings utilizing realistic three dimensional computer simulations based on three dimensional motion tracking data. Soft Golf is a newly developed recreational sport in South Korea aimed to become a safe and easy-to-learn sport for all ages. The advantage of Soft Golf stems from lighter weight of the club and much larger area of the sweet spot. This paper tries to look into kinematic and kinetic aspects of soft golf swings compared to regular golf swing and find the advantages of lighter Soft Golf clubs. For this purpose, swing motions of older aged participants were captured and kinematic analysis was performed for various kinematic parameters such as club head velocity, joint angular velocity, and joint range of motions as a pilot study. Kinetic analysis was performed by applying kinematic data to computer simulation models constructed from anthropometric database and the measurements from the participants. The simulations were solved using multi-body dynamics solver. Firstly, the kinematic parameters such as joint angles were obtained by solving inverse dynamics problem based on motion tracking data. Secondly, the kinetic parameters such as joint torques were obtained by solving control dynamics problem of making joint torque to follow pre-defined joint angle data. The results showed that mechanical loadings to major joints were reduced with lighter Soft Golf club.

• Journal of the Korean Vacuum Society
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• v.12 no.1
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• pp.25-34
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• 2003

Deposition behavior of hard amorphous carbon film was investigated by molecular dynamic simulation using Tersoff potential which was suggested for the interaction potential between carbon atoms. When high energy carbon atoms were collided on diamond (100) surface, dense amorphous carbon film could be obtained. Physical properties of the simulated carbon film were compared with those of the film deposited by filtered cathodic arc process. As in the experimental result, the most diamond-like film was obtained at an optimum kinetic energy of the incident carbon atoms. The optimum kinetic energy was 50 eV, which is comparable to the experimental observation. The simulated film was amorphous with short range order of diamond lattice. At the optimum kinetic energy condition, we found that significant amount of carbon atom were placed at a metastable site of distance 2.1 $\AA$. By melting and quenching simulation of diamond lattice, it was shown that this metastatic peak is Proportional to the quenching rate. These results show that the hard and dense diamond-like film could be obtained when the localized thermal spike due to the collision of high energy carbon atom can be effectively dissipated to the lattice.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.779-789
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• 2012

In the kinetic theory of dense fluids the many-particle collision bracket integral is given in terms of a classical collision operator defined in the phase space. To find an algorithm to compute the collision bracket integrals, we revisit the eigenvalue problem of the Liouville operator and re-examine the method previously reported [Chem. Phys. 1977, 20, 93]. Then we apply the notion and concept of the eigenfunctions of the Liouville operator and knowledge acquired in the study of the eigenfunctions to cast collision bracket integrals into more convenient and suitable forms for numerical simulations. One of the alternative forms is given in the form of time correlation function. This form, on a further manipulation, assumes a form reminiscent of the Chapman- Enskog collision bracket integrals, but for dense gases and liquids as well as solids. In the dilute gas limit it would give rise precisely to the Chapman-Enskog collision bracket integrals for two-particle collision. The alternative forms obtained are more readily amenable to numerical simulation methods than the collision bracket integrals expressed in terms of a classical collision operator, which requires solution of classical Lippmann-Schwinger integral equations. This way, the aforementioned kinetic theory of dense fluids is made fully accessible by numerical computation/simulation methods, and the transport coefficients thereof are made computationally as accessible as those in the linear response theory.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2017-2024
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• 2020

In this study, a fractional order proportional integral derivative (FOPID) controller is designed to create the reference power trajectory and to conquer the uncertainties and external disturbances. A fractional nonlinear model was utilized to describe the nuclear reactor dynamic behaviour considering thermal-hydraulic effects. The controller parameters were tuned using optimization method in Matlab/Simulink. The FOPID controller was simulated using Matlab/Simulink and the controller performance was evaluated for Hard variation of the reference power and compared with that of integer order a proportional integral derivative (IOPID) controller by two models of fractional neutron point kinetic (FNPK) and classical neutron point kinetic (CNPK). Also, the FOPID controller robustness was appraised against the external disturbance and uncertainties. Simulation results showed that the FOPID controller has the faster response of the control attempt signal and the smaller tracking error with respect to the IOPID in tracking the reference power trajectory. In addition, the results demonstrated the ability of FOPID controller in disturbance rejection and exhibited the good robustness of controller against uncertainty.

• Journal of the Korean Society of Combustion
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• v.7 no.1
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• pp.23-30
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• 2002

Instability of oblique detonation waves (ODW) at off-attaching condition was investigated through a series of numerical simulations. Two-dimensional wedge of finite length was considered in $H_2/O_2/N_2$ mixtures at superdetonative condition. Numerical simulation was carried out with a compressible fluid dynamics code and a detailed hydrogen-oxygen combustion mechanism. Present result reveals that there is a chemical kinetic limit of the ODW detachment, in addition to the theoretical limit predicted by Rankine-Hugoniot theory with equilibrium chemistry. Result also presents that ODW still attaches at a wedge as an oblique shock-induced flame showing periodically unstable motion, if the Rankine-Hugoniot limit of detachment is satisfied but the chemical kinetic limit is not. Mechanism of the periodic instability is considered as interactions of shock and reaction waves coupled with chemical kinetic effects. From the investigation of characteristic chemical time, condition of the periodic instability is identified as follows; at the detaching condition of the Rankine-Hugoniot theory, (1) flow residence time is smaller than the chemical characteristic time, behind the detached shock wave with heat addition, (2) flow residence time should be greater than the chemical characteristic time, behind an oblique shock wave without heat addition.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.161-164
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• 2015

A short kinetic mechanism for premixed benzene/air flames was developed with a reduction method of Simulation Error Minimization Connectivity Method(SEM-CM). It consisted of 38 species and 336 elementary reactions. Flame speeds were calculated and compared with those from full mechanisms and experiments of other researcher. Those comparisons are in good agreement between the full mechanism and the short mechanism at high pressure condition. In numerical work the running time with the short mechanism was over 10 times faster than one with the full mechanism.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.114-125
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• 2008

Current state and perspective of DNS of turbulence and turbulent combustion are discussed with feature trend of the fastest supercomputer in the world. Based on the perspective of DNS of turbulent combustion, possibility of perfect simulations of IC engine is shown. In 2020, the perfect simulation will be realized with 30 billion grid points by 1EXAFlops supercomputer, which requires 4 months CPU time. The CPU time will be reduced to about 4 days if several developments were achieved in the current fundamental researches. To shorten CPU time required for DNS of turbulent combustion, two numerical methods are introduced to full-explicit full-compressible DNS code. One is compact finite difference filter to reduce spatial resolution requirements and numerical oscillations in small scales, and another is well-known point-implicit scheme to avoid quite small time integration of the order of nanosecond for fully explicit DNS. Availability and accuracy of these numerical methods have been confirmed carefully for auto-ignition, planar laminar flame and turbulent premixed flames. To realize DNS of IC engine with realistic kinetic mechanism, several DNS of elemental combustion process in IC engines has been conducted.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.359-366
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• 2008

Current state and perspective of DNS of turbulence and turbulent combustion are discussed with feature trend of the fastest supercomputer in the world. Based on the perspective of DNS of turbulent combustion, possibility of perfect simulations of IC engine is shown. In 2020, the perfect simulation will be realized with 30 billion grid points by 1EXAFlops supercomputer, which requires 4 months CPU time. The CPU time will be reduced to about 4 days if several developments were achieved in the current fundamental researches. To shorten CPU time required for DNS of turbulent combustion, two numerical methods are introduced to full-explicit full-compressible DNS code. One is compact finite difference filter to reduce spatial resolution requirements and numerical oscillations in small scales, and another is well-known point-implicit scheme to avoid quite small time integration of the order of nanosecond for fully explicit DNS. Availability and accuracy of these numerical methods have been confirmed carefully for auto-ignition, planar laminar flame and turbulent premixed flames. To realize DNS of IC engine with realistic kinetic mechanism, several DNS of elemental combustion process in IC engines has been conducted.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.359-366
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• 2008

Current state and perspective of DNS of turbulence and turbulent combustion are discussed with feature trend of the fastest supercomputer in the world. Based on the perspective of DNS of turbulent combustion, possibility of perfect simulations of IC engine is shown. In 2020, the perfect simulation will be realized with 30 billion grid points by 1EXAFlops supercomputer, which requires 4 months CPU time. The CPU time will be reduced to about 4 days if several developments were achieved in the current fundamental researches. To shorten CPU time required for DNS of turbulent combustion, two numerical methods are introduced to full-explicit full-compressible DNS code. One is compact finite difference filter to reduce spatial resolution requirements and numerical oscillations in small scales, and another is well-known point-implicit scheme to avoid quite small time integration of the order of nanosecond for fully explicit DNS. Availability and accuracy of these numerical methods have been confirmed carefully for auto-ignition, planar laminar flame and turbulent premixed flames. To realize DNS of IC engine with realistic kinetic mechanism, several DNS of elemental combustion process in IC engines has been conducted.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.133-139
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• 2005

In this study, a three-dimensional transient simulation with a knock model was performed to predict knock occurrence and autoignition site in a heavy-duty LPG engine. A FAE (Flame Area Evolutoin) premixed combustion model was applied to simulate flame propagation. The coefficient of the reduced kinetic model was adjusted to LPG fuel and used to simulate autoignition in the unburned gas region. Engine experiments using a single-cylinder research engine were performed to calibrate the reduced kinetic model and to verify the results of the modeling. A pressure transducer and a head-gasket type ion-probe circuit board were installed in order to detect knock occurrences, flame arrival angles, and autoignition sites. Knock occurrence and position were compared for different piston bowl shapes. The simulation concurred with engine experimental data regarding the cylinder pressure, flame arrival angle, knock occurrence, and autoignition site. Furthermore, it provided much information about in-cylinder phenomena and solutions that might help reducing the knocking tendency. The knock simulation model presented in this paper can be used for a development tool of engine design.