• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.49.1-49.1
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• 2019

Giant radio relics in the outskirts of galaxy clusters have been observed and they are interpreted as synchrotron emission from relativistic electrons accelerated via diffusive shock acceleration (DSA) in weak shocks of Ms < 3.0. In the DSA theory, the particle momentum should be greater than a few times the momentum of thermal protons to cross the shock transition and participate in the Fermi acceleration process. In the equilibrium, the momentum of thermal electrons is much smaller than the momentum of thermal protons, so electrons need to be pre-accelerated before they can go through DSA. To investigate such electron injection process, we study the electron pre-acceleration in weak quasi-perpendicular shocks (Ms = 2.0 - 3.0) in an ICM plasma (kT = 8.6 keV, beta = 100) through 2D particle-in-cell simulations. It is known that in quasi-perpendicular shocks, a substantial fraction of electrons could be reflected upstream, gain energy via shock drift acceleration (SDA), and generate oblique waves via the electron firehose instability (EFI), leading the energization of electrons through wave-particle interactions. We find that such kinetic processes are effective only in supercritical shocks above a critical Mach number, $Ms{\ast}{\sim}2.3$. In addition, even in shocks with Ms > 2.3, energized electrons may not reach high energies to be injected to DSA, because the oblique EFI alone fails to generate long-wavelength waves. Our results should have implications for the origin and nature of radio relics.

• Journal of Ocean Engineering and Technology
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• v.35 no.3
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• pp.229-237
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• 2021

A numerical hydrodynamic performance analysis of the pitch-type multibody wave energy converter (WEC) is carried out based on both linear potential flow theory and computational fluid dynamics (CFD) in the unidirectional wave condition. In the present study, Salter's duck (rotor) is chosen for the analysis. The basic concept of the WEC rotor, which nods when the pressure-induced motions are in phase, is that it converts the kinetic and potential energies of the wave into rotational mechanical energy with the proper power-take-off system. This energy is converted to useful electric energy. The analysis is carried out using three WEC rotors. A multibody analysis using linear potential flow theory is performed using WAMIT (three-dimensional diffraction/radiation potential analysis program), and a CFD analysis is performed by placing three WEC rotors in a numerical wave tank. In particular, the spacing between the three rotors is set to 0.8, 1, and 1.2 times the rotor width, and the hydrodynamic interaction between adjacent rotors is checked. Finally, it is confirmed that the dynamic performance of the rotors slightly changes, but the difference due to the spacing is not noticeable. In addition, the CFD analysis shows a lateral flow phenomenon that cannot be confirmed by linear potential theory, and it is confirmed that the CFD analysis is necessary for the motion analysis of the rotor.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.265-269
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• 1995

Complexation of ortho-xylyl-17-crown-5 (X17C5) with alkali metal ions in acetonitrile was studied by 7Li and 23Na NMR spectroscopy. The complex formation constants of X17C5 with LiI, LiSCN, NaI, and NaSCN were determined by investigating the changes in the chemical shifts as a function of the concentration ratio of X17C5 to metal ion. It was found that X17C5 forms 1:1 complex with Li+ and Na+ ions and the log Kf's for the complexation with LiI, LiSCN, NaI, and NaSCN were determined to be 2.88, 2.43, 2.53, and 2.30, respectively. In particular, the kinetics of complexation of X17C5 with Na+ was investigated by the method of 23Na NMR lineshape analysis. Activation energies were determined from Arrhenius plot of the resultant rate constant data to be 25.4 kJ/mol for NaI and 15.1 kJ/mol for NaSCN. Other kinetic parameters were also calculated by employing the Eyring equation. The decomplexation rates measured were 1.82 × 104 M-1s-1 for NaI and 1.50 × 104 M-1s-1 for NaSCN. It is concluded that the decomplexation mechanism is predominantly a bimolecular cation exchange for both cases.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.47.2-47.2
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• 2019

Observations indicate that turbulence in molecular clouds of the interstellar medium (ISM) is highly supersonic (M >> 1) and strongly magnetized (β ≈ 0.1), while in the intracluster medium (ICM) it is subsonic (M <~1) and weakly magnetized (β ≈ 100). Here, M is the turbulent Mach number and β is the ratio of the gas to magnetic pressures. Although magnetohydrodynamic (MHD) turbulence in such environments has been previously studied through numerical simulations, some of its properties as well as its consequences are not yet fully described. In this talk, we report a study of MHD turbulence in molecular clouds and the ICM using a newly developed code based the high-order accurate, WENO (Weighted Essentially Non-Oscillatory) scheme. The simulation results using the WENO code are generally in agreement with those presented in the previous studies with, for instance, a TVD code (Porter et al. 2015 &, Park & Ryu 2019), but reveal more detailed structures on small scales. We here present and compare the properties of simulated turbulences with WENO and TVD codes, such as the spatial distribution of density, the density probability distribution functions, and the power spectra of kinetic and magnetic energies. We also describe the populations of MHD shocks and the energy dissipation at the shocks. Finally, we discuss the implications of this study on star formation processes in the ISM and shock dissipation in the ICM.

• Computers and Concrete
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• v.32 no.4
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• pp.393-398
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• 2023

This paper provides the free vibrations of chiral carbon nanotubes. The governing equations of Flügge theory is considered for vibration frequencies of chiral single walled carbon nanotubes. The solution of frequency equation is obtained from a novel model for better representation of stubby and short vibration characteristics of chiral tubes with clamped-clamped and clamped-simply supported end conditions. For the harmonic response of this tube, the model displacement function is adopted. The variational approach Rayleigh-Ritz method with kinetic and strain energies are used. The Lagragian function is differentiated with respect to unknown functions. The frequency equation is written in compact form to solve with MATLAB software. The frequencies of chiral SWCNTs for first ten aspect ratios as small level are investigated. The results shown as for decreasing the aspect rations, the frequencies are increases. The presented results of this model are verified with experimental and numerical results, which found as an excellent agreement.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.11a
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• pp.98-104
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• 2000

The conventional model did not take momentum conservation into consideration when the electron absorbs and emits the photons. II-ray provides momentum conservations on any directions of the entering photons, and also the electrons have radial momentum conservations and fully elastic bouncing between two atoms, in the new atom model. Conventional atom model must be criticized on the following four points. (1) Natural motions between positive and negative entities are not circular motions but linear going and returning ones, for examples sexual motion, tidal motion, day and night etc. Because the radius of hydrogen atom's electron orbit is the order of 10$^{-11}$ m and the radia of the nucleons in the nucleus are the order of 10$^{-14}$ m and then the converging $\pi$-gamma rays to the nucleus have so great circular momentum, the electron can not have a circular motion. We can say without doubt that any elementary mass particle can have only linear motion, because of the $\pi$-rays'hindrances, nearthenucleus. (2) Potential energy generation was neglected when electron changes its orbit from outer one to inner one. The h v is the kinetic energy of the photo-electron. The total energy difference between orbits comprises kinetic and potential energies. (3) The structure of the space must be taken into consideration because the properties of the electron do not change during the transition from outer orbit to inner one even though it produces photon. (4) Total energy conservation law applies to the energy flow between mind and matter because we daily experiences a interconnection between mind and body. Conventional Concept of Electric Field must be extended in the case of the direct and alternating current. Conventional concept is based on coulomb's force while the electric potential in the direct and alternating current is from Gibb's free energy. And also conventional concept has not any consciousness with human being but the latters has a conscious sensibility. The cell emf is from the kinetic energy of the open $\pi$-rays flow through the conducting wire. The electric potential in alternating current is from that the trans-orbital moving of the induced change of magnetic field in the wire produces flows of open $\pi$-rays, which push the rotating electrons on the orbital and then make the current flow. Human consciousness can induce a resonance with the sensibility of the open $\pi$-rays in the electric measuring equipment. Specially treated acupunctures with Nasucon is for sending an acupunctural effect from one place to another via space by someone's will power.

• The Korean Journal of Physiology
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• v.20 no.2
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• pp.257-270
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• 1986

It has been reported that the luteal function may be regulated by the intracellular calcium in luteal cells (Higuchi et al, 1976; Dorflinger et at, 1984; Gore and Behrman, 1984) which is adjusted partially by $Ca^{++}-ATPase$ activities in luteal cell membranes (Verma and Pennistion, 1981). However, the physicochemical and kinetic properties of $Ca^{++}-ATPase$ in luteal membranes were not fully characterized. This study was, therefore, undertaken to partially characterize the physicochemical and kinetic properties of $Ca^{++}-ATPase$ system in luteal membranes and microsomal fractions, known as an one of the major $Ca^{++}$ storge sites (Moore and Pastan, 1978), from the highly luteinized ovary Highly luteinized ovaries were obtained from PMSG-hCG injected immautre female rats. Light membrane and heavy membrane fractions and microsomal fractions were prepared by the differential and discontinuous sucrose density gradient centrifugation method desribed by Bramley and Ryan (1980). Light membrane and heavy membrane fractions and microsomal fractions from highly luteinized ovaries are composed of the two different kinds of $Ca^{++}-ATPase$ system. One is the high affinity $Ca^{++}-ATPase$ which is activated in low $Ca^{++}$ concentration (Km, 10-30 nM), the other is low affinity $Ca^{++}-ATPase$ activated in higher $Ca^{++}$ concentration $(K_{1/2},\;40\;{\mu}M)$. At certain $Ca^{++}$ concentrations, activities of high and low affinity $Ca^{++}-ATPase$ are the highest in light membrane fractions and are the lowest in microsomal fractions. It appeares that high affinity $Ca^{++}-ATPase$ system have 2 binding sites for ATP (Hill's coefficient; around 2 in all membrane fractions measured) and the positive cooperativity of ATP bindings obviously existed in each membrane fractions. The optimum pH for high affinity $Ca^{++}-ATPase$ activation is around S in all membrane fractions measured. The lipid phase transition temperature measured by Arrhenius plots of high affinity $Ca^{++}-ATPase$ activity is around $25^{\circ}C$. The activation energies of high affinity $Ca^{++}-ATPase$ below the transition temperature are similar in each membrane fractions, but at the above transition temperature, it is the hightest in heavy membrane fractions and the lowest in microsomal fractions. According to the above results, it is suggested that intracellular $Ca^{++}$ level, which may regulate the luteal function, may be adjusted primarily by the high affinity $Ca^{++}-ATPase$ system activated in intracellular $Ca^{++}$ concentration range $(below\;0.1\;{\mu}M)$.

• Elastomers and Composites
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• v.42 no.1
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• pp.47-54
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• 2007

Reaction kinetics of polyurethane elastomers (PU) were studied using dynamic DSC and TGA for three PU samples of general purpose (Sample A), high temperature cross-likable CASE purpose with MOCA (Sample B), and RT cross-likable CASE purpose grade (Sample C). From DSC results, sample with MOCA(Sample B) showed lower shift of peak temperature, while showing broader thermograms than those of general purpose grade (Sample A). On the other hand, RT cross-linkable PU grade (Sample C) showed an interesting double mode reaction patterns, i.e., a lower temperature reaction at about $70\;^{\circ}C$, and a higher temperature reaction in the range of $140{\sim}170\;^{\circ}C$, indicating that it requires 2-step reaction process in order to complete the reaction. Once the cross-linking reaction completed, however, TGA results showed that all the samples would be considered to have similar chemical structures, showing similar decomposition processes. Sample C, especially, had showed decomposition properties of both Sample A and Sample B. Formation activation energies calculated from Kissinger method showed 10.39, 65.85, 36.52(Low $T_p$) and 18.21(High $T_p$) kcal/mol, while decomposition activation energies were 31.94, 30.84, 24.16 kcal/mol, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.10
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• pp.543-550
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• 2016

Amine-type PP-g-VBC-EDA adsorbent, which possesses anionic exchangeable function, was prepared through photoinduced graft polymerization of vinylbenzyl chloride (VBC) onto polypropylene non-woven fabric and subsequent amination reaction using ethylenediamine (EDA). Adsorption characteristics of anionic nutrients on the PP-g-VBC-EDA adsorbent have been studied by batch adsorption experiments. The equilibrium data well fitted the Langmuir isotherm model, and the maximum monolayer sorption capacity was found to be 59.9 mg/g for $NO_3-N$ and 111.4 mg/g for $PO_4-P$. The adsorption energies were higher than 8 kJ/mol indicating anion-exchange process as the primary adsorption mechanism. The pseudo-second order kinetic model described well the kinetic data and resulted in the activation energy of 9.8-36.7 kJ/mol suggesting that the overall rates of $NO_3-N$ and $PO_4-P$ adsorption are controlled by the chemical process. Thermodynamic parameters such as ${\Delta}G^o$, ${\Delta}H^o$ and ${\Delta}S^o$ indicated that the adsorption nature of PP-g-VBC-EDA for anionic nutrients is spontaneous and exothermic. The PP-g-VBC-EDA could be regenerated by washing with 0.1 N HCl.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.26-33
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• 2009

The phase-shift method and correlation constants, i.e., the unique electrochemical impedance spectroscopy (EIS) techniques for studying the linear relationship between the behavior ($-{\varphi}$ vs. E) of the phase shift ($90^{\circ}{\geq}-{\varphi}{\geq}0^{\circ}$) for the optimum intermediate frequency and that ($\theta$ vs. E) of the fractional surface coverage ($0{\leq}{\theta}{\leq}1$), have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at noble metal (alloy)/aqueous solution interfaces. At a Zr/0.2 M ${H_2}{SO_4}$ aqueous solution interface, the Frumkin and Temkin adsorption isotherms ($\theta$ vs. E), equilibrium constants (K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ for the Frumkin and K = $1.401{\times}10^{-16}\exp(8.1{\theta})mol^{-1}$ for the Temkin adsorption isotherm), interaction parameters (g = 3.5 for the Frumkin and g = 8.1 for the Temkin adsorption isotherm), rates of change of the standard free energy (r = $8.7\;kJ\;mol^{-1}$ for g = 3.5 and r = $20\;kJ\;mol^{-1}$ for g = 8.1) of H with $\theta$, and standard free energies ($96.13{\leq}{\Delta}G^0_{\theta}{\leq}104.8\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ and $0{\leq}{\theta}{\leq}1$ and ($94.44<{\Delta}G^0_{\theta}<106.5\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-16}\exp(-8.1{\theta})mol^{-1}$ and $0.2<{\theta}<0.8$) of H are determined using the phase-shift method and correlation constants. At 0.2 < $\theta$ < 0.8, the Temkin adsorption isotherm correlating with the Frumkin adsorption isotherm, and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are probably the most accurate, useful, and effective ways to determine the adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at highly corrosion-resistant metal/aqueous solution interfaces.