• Progress in Medical Physics
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• v.31 no.4
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• pp.135-144
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• 2020

Purpose: Gafchromic films for proton dosimetry are dependent on linear energy transfers (LETs), resulting in dose underestimation for high LETs. Despite efforts to resolve this problem for single-energy beams, there remains a need to do so for multi-energy beams. Here, a bimolecular reaction model was applied to correct the under-response of spread-out Bragg peaks (SOBPs). Methods: For depth-dose measurements, a Gafchromic EBT3 film was positioned in water perpendicular to the ground. The gantry was rotated at 15° to avoid disturbances in the beam path. A set of films was exposed to a uniformly scanned 112-MeV pristine proton beam with six different dose intensities, ranging from 0.373 to 4.865 Gy, at a 2-cm depth. Another set of films was irradiated with SOBPs with maximum energies of 110, 150, and 190 MeV having modulation widths of 5.39, 4.27, and 5.34 cm, respectively. The correction function was obtained using 150.8-MeV SOBP data. The LET of the SOBP was then analytically calculated. Finally, the model was validated for a uniform cubic dose distribution and compared with multilayered ionization chamber data. Results: The dose error in the plateau region was within 4% when normalized with the maximum dose. The discrepancy of the range was <1 mm for all measured energies. The highest errors occurred at 70 MeV owing to the steep gradient with the narrowest Bragg peak. Conclusions: With bimolecular model-based correction, an EBT3 film can be used to accurately verify the depth dose of scanned proton beams and could potentially be used to evaluate the depth-dose distribution for patient plans.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.3
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• pp.18-23
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• 2009

This paper focuses on development of new conveyer directly driven by the contact-less energy transmission system. The effect of the resonant circuit and the flux linkage characteristics caused from that are analyzed by using 3D finite element analysis. From the result it is shown that the resonant circuit needs to transfer energy from the primary core to the secondary core. Also the influence of the linear induction motor on the contact-less energy transmission system is presented. New conveyer and the experimental apparatus was manufactured by using the contact-less energy transmission system and the linear induction motor. Possibility of realization of the conveyer is proved by comparison the simulation result which is obtained by using 2D finite element analysis with experimental one and the characteristic of the voltage and resonant current.

• Progress in Medical Physics
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• v.6 no.1
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• pp.39-47
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• 1995

In order to accurate treat damage induced by ionizing radiation in biological system on the cellular or subcellular level with physical parameters characterising the radiation, specific primary ionization (SPI) is introduced as the parameter which does not suffer from limitation of linear energy transfer (LET). In this present study, we calculate specitic primayt ionization with total ionization cross section (TICS) of electrons, protons and alppa particles incident on water. The used energy ranges cover those that have been freqently used in radiobioligical experiments. For electrons above 1 keV, we have relativistic corrections and also compare the results with other data. For electrons energies below 100keV, our results are in excellent agreement with theoretical calculations published recently by (perris and zarris 1987). These results may be easily applied by the interested radiobiogists.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1165-1169
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• 2012

The fluorescence intensity of DNA-intercalated ethidium with [ethidium]/[DNA base] being 0.005 was quenched upon the binding of another intercalating ligand, meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP). Addition of $Ca^{2+}$ enhanced the quenching efficiency. The range of separations between donor and acceptor molecules, within which total quenching occurs, was calculated using a one-dimensional resonance energy transfer mechanism to be 9.5 base-pairs or $32.3{\AA}$ in the absence of $Ca^{2+}$ ions. The distance increased to 18.7 base-pairs or about $63.6{\AA}$ in the presence $100{\mu}M$ $Ca^{2+}$. Considering that (1) $Ca^{2+}$ had little effect on the binding modes of ethidium and TMPyP, which was investigated by reduced linear dichroism and (2) spectral overlap between the emission spectrum of ethidium and the absorption spectrum of TMPyP was maintained in the presence of $Ca^{2+}$, contributions from orientation factor and spectral overlap to $Ca^{2+}$-induced enhancement in DNA mediated energy transfer was limited. Although there is no direct evidence, electron transfer along the DNA stem may accompany the observed fluorescence quenching. In this respect, DNA bound $Ca^{2+}$ act as a partially conducting medium.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.266-271
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• 2001

Buoyancy-driven natural convection is analysed by employing a linear stability theory in hori-zontal porous media with net through flow. Darcy's law is used to model the flow characteristics in porous media. Bated on the results of linear stability analysis, a heat transfer correlation was obtained by employing weakly nonlinear analysis. As the net through flow increases, the system becomes more stable and the effect of the Darcy-Rayleigh number on the Nusselt number decreases.

• The Korean Journal of Food And Nutrition
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• v.29 no.6
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• pp.829-834
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• 2016

Free radicals originate due to the radiolysis of cytoplasmic water with low "Linear Energy Transfer" (LET) radiations. Naringenin (Ng) is a natural antioxidative compound found in citrus fruits. This study revealed that Naringenin (Ng) reduced the radiation damage of critical organs by scavenging oxidative free radicals. In the study, Ng was orally administrated to rats daily for 7 consecutive days, prior to whole body exposure to gamma-rays. The scavenging efficacy was evaluated biochemically by measuring the concentration of cytotoxic byproducts and the activity of enzymes relevant to oxidative free radicals, after extracting the organs from the exposed rat. We observed increased levels of malondialdehyde (MDA) concentration, and decrease in the activities of superoxide dismutase (SOD) and catalase (CAT) in the exposed control group. However, pretreatment with Ng significantly reduced the MDA concentration, and increased the activities of SOD and CAT, as compared to the control group, due to the free radical scavenging by Ng. The results indicate that Ng administration prior to irradiation could protect critical organs from radiation damage.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.381-385
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• 2006

The temperature dependence on the electron transfer rate constant $(k_{app})$ for hydroquinone redox center in $H_2Q(CH_2)_n$SH-SAMs (n = 1, 4, 6, 8, 10, and 12) on gold electrode was investigated to obtain reorganization energy $(\lambda)$ using Laviron’s formalism and Arrhenius plot of ln $[k_{app}/T^{1/2}]$ vs. T^{-1} based on the Marcus densityof-states model. All the symmetry factors measured for the SAMs were relatively close to unity and rarely varied to temperature change as expected. The electron tunneling constant $(\beta)$ determined from the dependence of the $k_{app}$ on the distance between the redox center and the electrode surface gives almost the same $\beta$ values which are quite insensitive to temperature change. Good linear relationship of Arrhenius plot for all $H_2Q(CH_2)_n$SH-SAMs on gold electrode was obtained in the temperature range from 273 to 328 K. The slopes n Arrhenius plot deduced that $\lambda$ of hydroquinone moiety is ca. 1.3-1.4 eV irrespectively of alkyl chain length of the electroactive SAM.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.706-712
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• 1986

The unsteay heat transfer from an isothermal circular cylinder in fluctuating cross flow is simulated numerically, for the case where the amplitude of the oscillating velocity is small compared with the mean velocity. By solving the linear perturbation equations derived from the unsteady full Navier-Stokes and the energy equations, the amplitude and the phase of heat transfer response are obtained in the range of Reynolds number R$_{3}$ < 40. The effects of the velocity, the cylinder radius and the frequency on the response are expressed graphically in terms of the normalized velocity and the cylinder radius.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.33 no.12
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• pp.91-98
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• 2017

In this study, the effect of window installation position in the residential building with the external insulation was numerically investigated in terms of insulation performance and heating/cooling energy consumption. For different window positions, 2-D heat transfer simulation was conducted to deduce the linear thermal transmittance, which was inputted to the dynamic energy simulation in order to analyze heating/cooling energy consumption. Simulation results showed that the linear thermal transmittance ranges from 0.05 W/mK to 0.7 W/mK, and is reduced as the window is installed near the external finish line. Indoor surface temperature and TDR analysis showed that the condensation risk is the lowest when the window is installed at the middle of the insulation and wall structure. It was also found that the window installation near the external finish can reduce the annual heating/cooling energy consumption by 12~16%, compared with the window installation near the interior finish. Although the window installation near the external finish can achieve the lowest heating/cooling energy consumption, it might lead to increased condensation risks unless additional insulation is applied. Thus, it can be concluded that the window should be installed near the insulation-wall structure junction, in consideration of the overall performance including energy consumption, condensation prevention and constructability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1550-1553
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• 2020

In this paper, we maximize the lifetime of a multi-hop path through a cooperative wireless energy sharing scheme between constituent nodes in a wireless multi-hop communication. Considering a bidirectional multi-hop communication environment, we present an optimization problem to maximize path lifetime by adjusting the amount of energy each node needs to share with its neighboring nodes. On the basis of solidarity property, i.e., the lifetime of the multi-hop path is maximized when the lifetimes of all nodes are the same, we convert the considered optimization problem into a linear programming problem and solve it easily. Simulation result shows that the proposed two-way wireless energy sharing method maximizes the path lifetime of multi-hop communications and approximately doubles the path lifetime compared with the one-way energy sharing method.