• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.253-260
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• 2019

Radiation dose enhancement is a method of increasing the cross section of interaction, thus increasing the deposited dose. This can contribute to linear energy transfer, LET and relative biological effectiveness, RBE. Previous studies on dose enhancement have been mainly focused on X, ${\gamma}-rays$, but in this study, the dose enhancement was analyzed for proton using Monte Carlo simulation using MCNP6. Based on the mathematical modeling method, energy spectrum and relative intensity of spread out Bragg-peak were calculated, and evaluated dose enhancement factor and dose distribution of dose enhancement material, such as aurum and gadolinium. Dose enhancement factor of 1.085-1.120 folds in aurum, 1.047-1.091 folds in gadolinium was shown. In addition, it showed a decrease of 95% modulation range and practical range. This may lead to an uncertain dose in the tumor tissue as well as dose enhancement. Therefore, it is necessary to make appropriate corrections for spread out Bragg-peak and practical range from mass stopping power. It is expected that Monte Carlo simulation for dose enhancement will be used as basic data for in-vivo and in-vitro experiments.

• Journal of Magnetics
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• v.21 no.1
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• pp.115-124
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• 2016

The present study analyzes T1 TSE and T1 slice sel. IR (dark_fluid) signal strength according to the degree of gadolinium contrast agent dilution and analyzes the turbo factors with regard to changes in the maximum and overall signal strength to study correlations between changes and signal-to-noise ratios (SNRs) and compare peak-to-peak SNR (PSNR) enhancement in order to improve the quality of T1-weighted images. Enhancement TR (600 msec) evaluated to determine the T1 TSE turbo factor and obtain the maximum signal strength, T1WI were used sequentially to experiment with turbo factors_1-4. T1 slice sel. IR (dark-fluid) was used to sequentially test turbo factors_2-5 but not turbo factor_1 at a TR (1500 msec) and compare data at an increase in T1 of 900 msec. The T1 TSE was reduced according to the contrast agent concentration. Phantom signal strength increased, whereas turbo factors_1-4 exhibited maximum signal strength at a concentration of 3 mmol, followed by a gradual decrease. In the turbo factors_2-5, the signal strength increased sharply to maximum signal strength at 0.7 mmol, followed by a reduction. T1 TSE had a greater maximum signal strength than did T1 slice sel. IR (dark_fluid). A comparison of SNR found that T1 TSE imaging was superior (33.3 dB) in turbo factor_1 and T1 slice sel. IR (dark_fluid) was highest (33.9 dB) at turbo factor_5. A PSNR comparison analysis was not sufficient to distinguish between the images obtained with both techniques at 30 dB or higher under all experimental conditions.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2197-2204
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• 2015

In recent years, medical image diagnosis has growing significant momentous in the medicinal field. Brain and lung image of patient are distorted with salt and pepper noise is caused by moving the head and chest during scanning process of patients. Reconstruction of these images is a most significant field of diagnostic evaluation and is produced clearly through techniques such as linear or non-linear filtering. However, restored images are produced with smaller amount of noise reduction in the presence of huge magnitude of salt and pepper noises. To eliminate the high density of salt and pepper noises from the reproduction of images, a new efficient fuzzy based median filtering algorithm with a moderate elapsed time is proposed in this paper. Reproduction image results show enhanced performance for the proposed algorithm over other available noise reduction filtering techniques in terms of peak signal -to -noise ratio (PSNR), mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), image enhancement factor (IMF) and structural similarity (SSIM) value when tested on different medical images like magnetic resonance imaging (MRI) and computer tomography (CT) scan brain image and CT scan lung image. The introduced algorithm is switching filter that recognize the noise pixels and then corrects them by using median filter with fuzzy two-sided π- membership function for extracting the local information.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.363-371
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• 2020

The parameters of the modified BM and JONSWAP spectra are estimated using spectral data set off Namhangjin, located in the east coast of Korea, collected during high wave events. The parameters of the modified BM spectrum were estimated to be 1.04 and 0.27, which were similar to the conventional values of 1.098 and 0.30, but showed significant differences in statistical terms. On the other hand, the peak enhancement factor of JONSWAP spectrum was estimated to be 1.4, which was substantially small compared to the conventional value of 3.3. The RMSE differences from the fitted results of the two spectra were small, approximately 0.2. In the frequency range greater than the peak frequency, however, the spectral energy density showed relatively mild decrease with increase of the frequency, compared to the standard forms of the modified BM and JONSWAP spectra.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.738-741
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• 2004

This study is concerning on modeling to predict the flexural behaviors of FRP-confined concrete structural members. For compressive behaviors of confined concrete by FRP jackets, the hypoelasticity-based constitutive law of concrete has been presented under the basis of three-dimensional stress states. The strength enhancement of concrete wrapped by FRP jackets has been determined by the failure surface of concrete in tri-axial states, and its corresponding peak strain is computed by the strain enhancement factor. The behavior of FRP jackets has been modeled using the mechanics of orthotropic laminated composite materials in two-dimensional stress states. To be based on the three-dimensional constitutive laws, an algorithm for the prediction of flexural bending behaviors of FRP-confined concrete structural member has been presented.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.60-73
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• 1997

By introducing a compressive-strained quanternary InGaAsP quantum-wells instead of a conventional ternary InGaAs quantum-wells in 1.55.mu.m DFB-LD, the lasing performances canb e improved and the problems caused by the thickness non-uniformity and the compositional abruptness among the hetero-interpaces canb e relaxed. In this paper, we investigated an iptimum InGaAsP/InGaAsP multiple-quantum-well(MQW) structure as an active layer in a direct-modulated 1.55.mu. DFB-LD from the view point of threshold current, chirping charcteristics, and resonance frequency. The optimum compressive-strained MQW structure was revealed as InGaAsP/InGaAsP structure with strain amount of about 1.2%, number of wells $N_{w}$ of 7, well width $L_{w}$ of 58.agns.. The threshold current density J of 500A/c $m^{2}$, the linewidth enhancement factor a of 1.8, and differential resonance frequency of d $f_{r}$/d(I-I)$^{1}$2/=2GHz/(mA)$^{1}$2/(atI=2 $I_{th}$) were expected in 1.55.mu.m .gamma./4-shifted DFB-LD with the cavity length of 400.mu.m long and kL value of 1.25. These values are considerably improved ones compared to those of 1.55um DFB-LD with InGaAs/InGaAsP MQW which have enhancement factor and the resonance frequence frequency by the detuning of lasing wavelength and gain-peak wavelength. It was found that the linewidth enhancement factor of 20% and differential resonance frequency of 35% without the degradation of the threshold current density could be enhanced in the range of -15nm~-20nm detuning which can be realized by controlling the thickness and Incomposition of InGaAsP well. well.and Incomposition of InGaAsP well. well.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1338-1348
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• 2004

A simplified method that models the deflagration process occurring in closed or vented vessels is described. When combustion occurs within the spherical or cylindrical vessels, the flame moves spherically or segmentally to the vessel periphery. The volume and area of each element along the propagating flame front are calculated by using simple geometrical rules. For instabilities and turbulence resulting in enhanced burning rates, a simple analysis results in reasonable agreement with the experimental pressure transients when two burning rates (a laminar burning rate prior to the onset of instability and an enhanced burning rate) were used. Pressure reduction caused by a vent opening at predetermined pressure was modeled. Parameters examined in the modeling include ignition location, mixture concentration, vented area, and vent opening pressure. It was found that venting was effective in reducing the peak pressure experienced in vessels. The model can be expected to estimate reasonable peak pressures and flame front distances by modeling the enhanced burning rates, that is, turbulent enhancement factor.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.435-446
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• 2016

In this study, hydrodynamic and mooring analysis for LNG FSRU moored by an internal turret with 9 mooring lines are numerically performed using commercial softwares, Hydrostar and Ariane. Met-ocean combinations for screening method are taken from wave governed condition(BV Rule Note NR 493) with relative heading between wave and wind between −45° and +45° and relative heading between wind and current between −30° and +30°. Extreme mooring analysis and sensitivity analysis are performed for intact and damaged (=one line missing) conditions and the parameters for sensitivity analysis are wave peak period, peak enhancement factor and line pretension. In the viewpoint of the design tension in mooring line, chain diameter is designed to satisfy safety factor for each conditions. As the chain diameter is increased from 152mm to 171mm, the designtension is reduced while the minimum breaking load is increased.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.1
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• pp.97-109
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• 2004

The disposal of stormwater is one of the major problems in urban water management. One method of reducing peak runoff rates and other detrimental impacts of stormwater is detention storage. Detention ponds as a water quality control alternatives have been investigated by a number of researchers. Recognizing multiple roles such as flood peak attenuation, pollution removal and aesthetic enhancement, the design and management of detentions ponds deserve more research. The purpose of this research is to establish design criteria wet detention ponds to improve water quality. Water quality in detention pond discharge might be improve with physical, chemical and biological alterations. Physical alteration was focused in this study. There are several methods for estimating the suspended solid control capability of wet detention ponds. Existing models of suspended solids removal are based on sedimentation and gravity settling theory. The pollutant trap efficiency of pond is a function of several interrelating factors. Detention time is the most important factor, because it determine gravity settling quantities of pollutants. Desirable modification of physical factors for improvement of water quality in wet detention ponds are volume ratio, area ratio, length to width ratio, depth, out let location, bottom soil type. In order to apply design procedure in actual site, Namak new town development area was selected.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.177-185
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• 2000

In this study, the characteristics of various electricity and high resistivity ash collection were measured at superimposed nanosecond pulse energization. The pulse was generated through the hydrogen thyratron. Superimposed pulse was nanosecond duration pulse that had fast pulse rising time 100[ns], short pulse width 500∼850[ns] and pulse fall time 400∼750[ns]. The results of this study are summarized as followings; Frist, compared with the DC ESP(electrostatic precipitator), superimposed pulse ESP could induce higher peak voltage, and had the about 30[%] reduction of ESP collection area and 50∼80[%] reduction of power consumption. showing the same efficiency. Second, enhancement factor H had 1.9∼3.6 with the increase of migration velocity.