• Korean Journal of Mathematics
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• v.13 no.2
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• pp.161-176
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• 2005

We consider a model of population dynamics whose mortality function is unbounded. We note that the regularity of the solution depends on the growth rate of the mortality near the maximum age. We propose Gauss-Legendre methods along the characteristics to approximate the solution when the solution is smooth enough. It is proven that the scheme is convergent at fourth-order rate in the maximum norm. We also propose discontinuous Galerkin finite element methods to approximate the solution which is not smooth enough. The stability of the method is discussed. Several numerical examples are presented.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.12-16
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• 2016

Friction stir welding(FSW) was studied using commercial tool, FLOW-3D. The purpose of this study is to suggest a method to apply frictional heat in Computational fluid dynamics(CFD) analysis. Cylindrical tool shape was used, and the interface cells between tool surface and workpiece were tracked by its geometrical relations in order to consider the frictional heat in FSW. After tracking the interface cells, average area concept was used to calculate the frictional heat, which is related to interface area. Also three-dimensional heat source and visco-plastic flow were modeled. The frictional heat generation rate calculated numerically from the suggested algorithm was validated with the analytical solution. The numerical solution was well matched with the analytical solution, and the maximum percentage of error was around 3%.

• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.1-9
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• 2002

This paper presents simple models for flow and the PIG dynamics when it passes through a $90^{\circ}$ curved section of pipeline. The simulation has been done with two different operational boundary conditions. The solution fur non-linear hyperbolic partial equations for flow is given by using MOC. The Runge-Kuta method is used to solve the initial condition equation fur flow and the PIG dynamics equation. The simulation results show that the proposed model and solution can be used fur estimating the PIG dynamics when the pig runs in the pipeline including curved section. In this paper, dynamic modeling and its analysis for the PIG flow through $90^{\circ}$ curved pipe with compressible and unsteady flow are studied. The PIG dynamics model is derived by using Lagrange equation under assumption that it passes through 3 different sections in the curved pipeline such that it moves into, inside and out of the curved section. The downstream and up stream flow dynamics including the curved sections are solved using MOC. The effectiveness of the derived mathematical models is estimated by simulation results fur a low pressure natural gas pipeline including downward and upward curved sections. The simulation results show that the proposed model and solution can be used for estimating the PIG dynamics when we pig the pipeline including curved section.

• Journal of Photoscience
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• v.9 no.2
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• pp.134-137
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• 2002

PYP consists of a water-soluble apoprotein and 4-hydroxycinnamyl chromophore bound to Cys69 via thiolester linkage, Upon absorption of a photon, the photocycle is initiated, leading to formation of several photo-intermediates. Among them, M intermediate is important to understand the signal transduction mechanism of PYP, because it is a putative signaling state. As well known, the dynamics of a protein is closely correlated with the occurrence of its function. Here we report the results of IO ns molecular dynamics (MD) simulation for the M intermediate in aqueous solution and discuss the characteristic feature of this state from a viewpoint of structural fluctuation.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.11
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• pp.1048-1052
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• 2013

Recently, many countries have attempted to protect their satellites from damage caused by space debris. To design these collision avoidance maneuvers, optimal algorithms based on numerical simulations are widely used due to their practicality. However, these algorithms often require a great expenditure of time in order to find solutions. Therefore, in this paper, a simple analytical strategy is suggested to find the initial prediction required to find these numerical solutions for collision avoidance maneuvers by using relative dynamics for the rendezvous and docking problems. For this analytical strategy, the simple dynamics on the CW (Clohessy-Wiltshire) frame is adopted as an attempt to introduce an analytical solution.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.746-750
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• 2011

Fluorescence correlation spectroscopy (FCS) is an emerging fluorescence technique used to study the dynamics of proteins on a millisecond to microsecond time scale at the single-molecule level. Solution pH-modulated protein conformational changes can be manifested by binding rate, fluorescence lifetime, and binding specificity of a probe molecule. The fluorescence lifetime of Nile red (NR) bound to apomyoglobin (apoMb) was measured to be $6{\pm}0.3$ ns, much longer than that in water solution ($2.9{\pm}0.2$ ns). As the unfolding population of apoMb increased by lowering pH of solution, the fraction for the longer lifetime of NR decreased with an increasing fraction for the shorter lifetime of NR in water. Unlike 1-anilino-8-naphthalene sulfonic acid, which has many lifetimes due to nonspecific binding to the unfolded apoMb, NR bound to apoMb possesses only a single lifetime. These results suggest that NR binds specifically to native apoMb and thus can be utilized to probe the folding/unfolding dynamics of apoMb using FCS.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.347-351
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• 2008

Acetyl-CoA carboxylase (ACC) is an excellent candidate for antibiotics drug target, which mediates malonyl-CoA synthesis from acetyl-CoA through acetylation process. It is also involved in the committed step of fatty acid synthesis which is essential for living organisms. We have determined the three dimensional structure of C terminal domain of HP0371, biotin-carboxyl carrier protein of H. pyroli, in solution state using heteronuclear multi-dimensional NMR spectroscopy. The structure of HP0371 shows a flatten b-sheet fold which is similar with that of E. coli. However, the sequence and structure of protruding thumb are different with that of E. coli and the thumb shows different basis of structural rigidity based on backbone dynamics data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.58-64
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• 2004

A new method to obtain approximate solutions by placing the only poles of the slow subsystem for the two-time-scale aircraft dynamic systems. The two kinds of approximate solutions are obtained by a matrix block diagonalization. One is called the uncorrected solution, and the other is called the corrected solution. The former has an error of $O({\varepsilon})$, and the latter has an error of $O({\varepsilon}^2)$. Of course, both solutions are robust enough even though they are reduced solutions. The excellence of the proposed method is illustrated by an numerical example of an aircraft longitudinal dynamics.

• Advances in aircraft and spacecraft science
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• v.5 no.3
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• pp.335-348
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• 2018

The structural dynamics (SD) behavior of Elastic Flapping Wings (EFWs) is investigated analytically as a novel approach in EFWs analysis. In this regard an analytical SD solution of EFW undergoing a prescribed rigid body motion is initially derived, where the governing equations are expressed in modal space. The inertial forces are also analytically computed utilizing the actuator induced acceleration effects on the wing structure, while due to importance of analytical solution the linearity assumption is also considered. The formulated initial-value problem is solved analytically to study the EFW structural responses, where the effect of structure-actuator frequency ratio, structure-flapping frequency ratio as well as the structure damping ratio on the EFW pick amplitude is analyzed. A case study is also simulated in which the wing is modeled as an elastic beam with shell elements undergoing a prescribed sinusoidal motion. The corresponding EFW transient and steady response in on-off servo behavior is investigated. This study provides a conceptual understanding for the overall EFW SD behavior in the presence of inertial forces plus the servo dynamics effects. In addition to the substantial analytical results, the study paves a new mathematical way to better understanding the complex role of SD in dynamic EFWs behavior. Specifically, similar mathematical formulations can be carried out to investigate the effect of aerodynamics and/or gravity.

• Current Optics and Photonics
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• v.8 no.1
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• pp.86-96
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• 2024

This research investigation employs a terahertz (THz) time-domain spectroscopy system to study the terahertz spectral characteristics of five different citrates in both solution and solid state. The citrates under examination are lithium citrate, monosodium citrate, disodium citrate, trisodium citrate, and potassium citrate. The results show that the THz absorption coefficients of the first four citrate solutions exhibit a decreasing trend with increasing concentration. However, the potassium citrate solution shows an opposite phenomenon. At the same time, the absorption coefficients of lithium citrate, trisodium citrate, and potassium citrate solutions are compared at the same concentration. The results indicate that the absorption coefficient of citrate solution increases in proportion to the increase of metal cation radius, which is explained from the perspective of the influence of metal cations on hydrogen bonds. In addition, we also study the absorption peaks of solid citrates, and characterize the formation mechanism of the absorption peaks by molecular dynamics simulations. This methodology can be further extended to the study of multitudinous salts, presenting theoretical foundations for the detection in food and medicine industries.