• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.885-892
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• 2012

Energy transfer dynamics of excited vibrational energy of OH stretching bonds in liquid water is theoretically studied. With time-dependent vibrational Hamiltonian obtained from a mixed quantum/classical calculation, we construct a master equation describing the energy transfer dynamics. Survival probability predicted by the master equation is compared with numerically exact one and we found that incoherent picture of energy transfer is reasonably valid for long-time population dynamics. Within the incoherent picture, we assess the validity of independent pair approximation (IPA) often introduced in the theoretical models utilized in the analysis of experimental data. Our results support that the IPA is almost perfectly valid as applied for the vibrational energy transfer in liquid water. However, proper incorporation of radial and orientational correlations between two OH bonds is found to be critical for a theory to be quantitatively valid. Consequently, it is suggested that the Forster model should be generalized by including the effects of the pair correlations in order to be applied for vibrational energy transfer in liquid water.

• Structural Engineering and Mechanics
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• v.21 no.6
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• pp.621-634
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• 2005

A direct transfer substructure method is presented in this paper for analyzing the dynamic characteristics and the seismic random responses of a series reactor. This method combines the concept of FRF (frequency response function) and the transfer matrix algorithm with the substructure approach. The inner degrees of freedom of each substructure are eliminated in the process of reconstruction and the computation cost is reduced greatly. With the convenient solution procedure, the dynamic characteristics analysis of the structure is valid and efficient. Associated with the pseudo excitation algorithm, the direct transfer substructure method is applied to investigating the seismic random responses of the series reactor. The numerical results demonstrate that the presented method is efficient and practicable in engineering. Finally, a precise time integration method is employed in performing a time-history analysis on the series reactor under El Centro and Taft earthquake waves.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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• pp.1-11
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• 1998

For the analysis of phonon heat transfer within short time and spatial scales, conventional macroscopic heat conduction equations with jump boundary conditions are tried and the results are compared to those of equation of phonon radiative transport(EPRT), which is one of microscopic transport equation. In transient state the macroscopic temperatures show far different behavior from EPRT. In steady state the hyperbolic temperatures with temperature jump at the wall from time relaxation model agrees well with EPRT temperatures. Since EPRT is also an approximate form of microscopic transport equation and there are no experimental results to verify the proposed model in this study, we can not conclude whether the approaching method from this study is valid or not. To the authors' knowledge, there are no experimental results available which can be used to test the validity of these models. Such an experiment, while difficult to conduct, would be invaluable.

• Journal of Welding and Joining
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• v.13 no.4
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• pp.85-102
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• 1995

Weld quality of GMA welding processes is closely related to arc stability. Although many researches on arc stability have been performed, real-time estimation of arc stability has not been attempted. For instance, Mita proposed a off-line statistical method in which short circuiting and arcing time, and voltage and current wave forms were sampled to assess arc stability. But this method is not suitable to assess arc stability for GMA welder which employ inverter power source due to its controlled current and voltage wave forms. In this paper, the relationship between are stability and wire feed rate fluctuation is analyzed to propose new criterion for inverter power source. When arc voltage and arc current and arcing time are analyzed, we can assess arc stability only for short circuit transfer mode. When wire feed rate is analyzed, we can estimate arc stability udner the condition of spray transfer mode as well. Hence, the wire feed rate is chosen for monitoring process variable to cover possible metal transfer modes in GMAW. Through this research, it has been identified that arc stability in GMA welding processes is closely related to wire fed rate. When inverter power source is used, conventional statistical method of estimating arc stability, such as Mita index, is no longer valid due to its controlled voltage and current wave forms. Arc stability has been also examined in phase plane diagram.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1295-1302
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• 2018

In the present investigation, we have studied the magnetohydrodynamic (MHD) heat transfer of peristaltic flow in a tube. The analysis is made without imposing any assumption to obtain the streamline and isothermal line directly. Galerkin's finite element method has been used on the governing Navier-Stoke's equation in the form of ${\psi}-{\omega}$. The graphs of the computed longitudinal velocity, temperature and pressure are plotted against different value of the emerging parameter by using the stream function and vorticity. The results are valid beyond the long wavelength and the low Reynolds number limits. We conclude that higher values of the parameters are not independent of the time mean flow rate.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.68-77
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• 2005

A transient liquid crystal technique has become one of the most effective ways in measuring the local heat transfer coefficients on the entire surface. The key Point of this technique is to convert the inlet flow temperature into an exponential temperature profile using a mesh heater. In order to verify the validity of this technique. the heat transfer characteristics on the wall surface by a pair of longitudinal vortices is investigated experimently and numerically. A standard ${\kappa}-{\varepsilon}$ is used for the numerical analysis of turbulent flow field. It is found from experiment and numerical analysis that two peak values exist over the whole domain. as the longitudinal vortices move to the farther downstream. these peak values decrease and the dimensionless averaged Nusselt number with the lapse of time is maintained nearly at constant values. The experiment results obtained from the present experiment in terms of the transient liquid crystal technique are in good agreement with the numerical results. Therefore, the transient liquid crystal technique developed for the measurement of heat transfer coefficient is proved to be a valid method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1656-1665
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• 1997

The intake noise, a major source of vehicle noises, has rapidly become a noticeable, and has been studied to reduce the level. Traditionally, the intake system has been developed through a experiment, namely, the trial and error process. This approach requires very high cost and long time consuming to develop the systm. Recently, FEM and BEM are becoming useful in analysis of the intake system, and the results of analysis are very valid. But because this techniques also require high cost and long analysis time, this technique is generally not practical tool at the early stage of the development. In this study, the software was developed to predict and analyze the acoustic characteristics of the intake system. It was based on the Transfer Matrix Method and operated to analyze a simplified intake system in a personal computer. It can be used early in the design stage of development of the intake system. This study presented a improvement to reduce the level of the intake noise, which modified the specification of the intake system. And the improvement were verified by NIT/SYSNOISE, FE analysis commercial software, and testing a prototype.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1648-1655
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• 1997

The intake noise, a major source of vehicle noises, has rapidly become a noticeable, and has been studied to reduce the level. Traditionally, the intake system has been developed through a experiment, namely, the trial and error process. This approach requires very high cost and long time consuming to develop the system. Recently, FEM and BEM are becoming useful in analysis of the intake system, and te results of analysis are very valid. But because these techniques also require high cost and long analysis time, these are generally not practical tool at the early stage of the development of an intake system. In this study, the software was developed to predict and analyze the acoustic characteristics of an intake system. It was based on the Transfer Matrix Method and operated to analyze a simplified intake system in a personal computer. It can be used early in the design stage of development of the intake system. This study presented an improvement to reduce the level of an intake noise. It was to select the optimum position of a resonator and verified by NIT/SYSNOISE, FE analysis commercial software, and testing a prototype.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.225-240
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• 2022

Gyeonggi-do comprises several types of areas, including urban, semi-urban, and rural areas. The availability of public transportation services varies depending on the area types, but the fare structure is based on a simple transfer rule, i.e., a transfer is free when completed within 30 minutes. As a result, users in non-urban areas with a poor frequency of public transportation services do not receive transfer discounts because most of the bus routes in these areas have a gap of more than 30 minutes between services. In terms of equality of opportunity, the transfer rule is being applied unfavorably and, as a result, equality of opportunity of the non-urban commuter is severely affected. Therefore, this study analyzed the user benefits mainly stemming from transfer fares using the smart card data of commuters using public transportation in Gyeonggi-do. An index called the beneficiary rate of the free transfer was developed and a scenario analysis was conducted based on the various levels of the rate. The results of this analysis proved that the users of public transportation services in non-urban areas in Gyeonggi-do can only receive transfer benefits by the extended time for free transfer and not by the implementation of a uniform policy irrespective of the type of area. The study also suggested an equitable fare transfer system and policy alternatives.

• Journal of the Korea Society of Computer and Information
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• v.24 no.5
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• pp.41-47
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• 2019

A BIS(Bus Information System) collects, processes and analyzes information such as real-time location and operation status during bus operation. And It is a system that provides valid information to citizens, drivers, traffic centers and bus companies. Transport information system sent by an each bus is collected through GPS(Global Positioning System), DSRC(Dedicated Short Range Communications), Beacon and passed to transport information center. BIS data by collected is handled and analyzed. Next, it is transmitted to citizen, drivers and bus companies in real time. The result of 5 times simulation satisfied the test criteria(error range ${\pm}10m$) with an average error range of 3.306m, and the reliability is increased. In this paper, we propose a improved location transfer component that can provide users to quicker and more accurate location information than existing BIS using GPS of smart phone. It can be seen that reliability is improved by securing improved bus position data.