• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.543-547
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• 2005

The Belousov-Zhabotinskii system measured by a Pt electrode is investigated under external electrode current constraint. A dynamical analysis of the electrode reaction phase has been made by means of a linearized stability criterion valid for three-variable system. It turns out that limit cycle oscillatory regime and dynamical behaviors of the electrode reaction phase have been degenerated under periodical electrode current.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.379-387
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• 1999

In general, solving or analyzing nonilinear dynamical equations is very difficult and requires special techniques. To avoid these difficulties, systems are generally linearized in an attempt to predict their begavior. These linearized equations, however, may not predict true system behavior. Therefore, the nonlinear dynamical analysis using bifurcation theory may become a fundamental framework in understanding nonlinear situation in power systems. In this paper, we propose a systematic procedure based on a bifurcation theory to analyze nonlinear behaviors in power systems. We show usefulness of our procedure by applying 3-bus model system. In addition, we consider nonlinear model of SMES and verify the effect of SMES in power system's nonlinear behaviors.

• Journal of Astronomy and Space Sciences
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• v.31 no.3
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• pp.187-197
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• 2014

We have investigated the dynamical stability of the proposed companions orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al. 2010). The two candidate companions are of stellar to substellar nature, and were inferred from timing measurements of the system's primary and secondary eclipses. We applied well-tested numerical techniques to accurately integrate the orbits of the two companions and to test for chaotic dynamical behavior. We carried out the stability analysis within a systematic parameter survey varying both the geometries and orientation of the orbits of the companions, as well as their masses. In all our numerical integrations we found that the proposed SW Lyn multi-body system is highly unstable on time-scales on the order of 1000 years. Our results cast doubt on the interpretation that the timing variations are caused by two companions. This work demonstrates that a straightforward dynamical analysis can help to test whether a best-fit companion-based model is a physically viable explanation for measured eclipse timing variations. We conclude that dynamical considerations reveal that the proposed SW Lyncis multi-body system most likely does not exist or the companions have significantly different orbital properties from those conjectured in Kim et al. (2010).

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.149.2-149.2
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• 2011

We performed the cross-correlation analysis on energy-dependent light curves of the Z-type source GX 5-1. We observed X-ray delays of a few hundred seconds between hard (16-30 keV) and soft (2-5 keV) X-ray light curves. During these phenomena, the centroid frequency of horizontal branch oscillation (HBO) was found to shift to lower or higher frequency indicating towards the dynamical movement of a Compton cloud or an inner disk front. Both eastern and western approaches were used to unfold the X-ray continuum and systematic changes were observed in soft and hard X-ray spectral components. Simultaneous energy spectral and power density spectral study shows that the production of HBOs is closely related to the Comptonizing region rather than the accretion disk. We discuss the results in the context of re-condensation of coronal material in the inner accretion disk region.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.913-918
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• 2008

When developing railway vehicle system, investigation of the dynamical stability is essential as a virtual prototyping process. Not only the verification using the commercial analysis tools, systematic analysis using customized tools is also necessary, because these can give other points of view in stability, which is sometimes unable to evaluate in the former one. As a solver platform for customization, it is important to derive basic theory about flexible bodies and build flexible structure, which enables easy module insertion of user-created functions. In the paper, a flexible dynamic analysis system is developed, using absolute cartesian coordinate, modal coordinate and absolute nodal coordinate. Each coordinate system is verified by respective examples for every system. This solver system will play an important role for building the basic platform for analysis system, keeping pace with the concurrent development of the modules, such as wheel-contact force, constraints and user-defined force modules. Using the information from the analysis, the evaluation of the dynamic behavior of the train and its stability analysis will be available.

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.181-188
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• 1992

This paper provides an overview of system analysis of immunology. The theoretical research in this area is aimed at an understanding of the precise manner by which the immune system controls Infec pious diseases, cancer, and AIDS. This can provide a systematic plan for immunological experimentation by means of an integrated program of immune system analysis, mathematical modeling and computer simulation. Biochemical reactions and cellular fission are naturally modeled as nonlinear dynamical processes to synthesize the human immune system! as well as the complete organism it is intended to protect. A foundation for the control of tumors is presented, based upon the formulation of a realistic, knowledge based mathematical model of the interaction between tumor cells and the immune system. Ordinary bilinear differential equations which are coupled by such nonlinear term as saturation are derived from the basic physical phenomena of cellular and molecular conservation. The parametric control variables relevant to the latest experimental data are also considered. The model consists of 12 states, each composed of first-order, nonlinear differential equations based on cellular kinetics and each of which can be modeled bilinearly. Finally, tumor control as an application of immunotherapy is analyzed from the basis established.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.839-844
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• 2014

The gas-phase radical-radical reaction $O(^3P)$ + $C_2H_5$ (ethyl) ${\rightarrow}$ $H(^2S)$ + $CH_3CHO$(acetaldehyde) was investigated by applying a combination of vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed beam configuration and ab initio calculations. The two radical reactants $O(^3P)$ and $C_2H_5$ were respectively produced by photolysis of $NO_2$ and supersonic flash pyrolysis of the synthesized precursor azoethane. Doppler profile analysis of the nascent H-atom products in the Lyman-${\alpha}$ region revealed that the average translational energy of the products and the average fraction of the total available energy released as translational energy were $5.01{\pm}0.72kcalmol^{-1}$ and 6.1%, respectively. The empirical data combined with CBS-QB3 level ab initio theory and statistical calculations demonstrated that the title exchange reaction is a major channel and proceeds via an addition-elimination mechanism through the formation of a short-lived, dynamical addition complex on the doublet potential energy surface. On the basis of systematic comparison with several exchange reactions of hydrocarbon radicals, the observed small kinetic energy release can be explained in terms of the loose transition state with a product-like geometry and a small reverse activation barrier along the reaction coordinate.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.95-106
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• 2013

It is now generally known that dynamical climate modeling outputs include systematic biases in reproducing the properties of atmospheric variables such as, preciptation and temerature. There is thus, general consensus among the researchers about the need of bias-correction process prior to using climate model results especially for hydrologic applications. Among the number of bias-correction methods, distribution (e.g., cumulative distribution fuction, CDF) mapping based approach has been evaluated as one of the skillful techniques. This study investigates the uncertainty of using various CDF mapping-based methods for bias-correciton in assessing regional climate change Impacts. Two different dynamicailly-downscaled Global Circulation Model results (CCSM and GFDL under ARES4 A2 scenario) using Regional Spectial Model for retrospective peiod (1969-2000) and future period (2039-2069) were collected over the west central Florida. Total 12 possible methods (i.e., 3 for developing distribution by each of 4 for estimating biases in future projections) were examined and the variations among the results using different methods were evaluated in various ways. The results for daily temperature showed that while mean and standard deviation of Tmax and Tmin has relatively small variation among the bias-correction methods, monthly maximum values showed as significant variation (~2'C) as the mean differences between the retrospective simulations and future projections. The accuracy of raw preciptiation predictions was much worse than temerature and bias-corrected results appreared to be more significantly influenced by the methodologies. Furthermore the uncertainty of bias-correction was found to be relevant to the performance of climate model (i.e., CCSM results which showed relatively worse accuracy showed larger variation among the bias-correction methods). Concludingly bias-correction methodology is an important sourse of uncertainty among other processes that may be required for cliamte change impact assessment. This study underscores the need to carefully select a bias-correction method and that the approach for any given analysis should depend on the research question being asked.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.69-78
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• 2005

ARCO and TAO data which supply three dimensional global ocean information are assimilated to the background field from a general circulation model, MOM3. Using a variational Analysis using Filter (VAF), which is a spatial variational filter designed to reduce computational time and space efficiently and economically, observed ARGO and TAO data are assimilated to the OGCM-generated background sea temperature for the generation of initial condition of the model. For the assessment of the assimilation impact, a comparative experiment has been done by integrating the model from different intial conditions: one from ARGO-, TAO-data assimilated initial condition and the other from background state without assimilation. The assimilated analysis field not only depicts major oceanic features more realistically but also reduces several systematic model bias that appear in every current OGCMs experiments. From the 10-month of model integrations with and without assimilated initial conditions, it is found that the major assimilated characteristics in sea temperature appeared in the initial field remain persistently throughout the integration. Such implies that the assimilated characteristics of the reduced sea temperature bias is to last in the integration without rapid restoration to the non-assimilated OGCM integration state by dispersing mass field in the form of internal gravity waves. From our analysis, it is concluded that the data assimilation method adapted in this study to MOM3 is reasonable and applicable with dynamical consistency. The success in generating initial condition with ARGO and TAO data assimilation has significant implication upon the prediction of the long-term climate and weather using ocean-atmosphere coupled model.