• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3051-3057
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• 2021

The concrete is considered as an important radiation shielding material employed widely in nuclear reactors, particle accelerators, laboratory hot cells and other different radiation sources. The present research is dedicated to the shielding properties study of the ordinary concrete reinforced with different weight fractions of lead oxide micro/nano particles. Lead oxide particles were fabricated by chemical synthesis method and their properties including the average size, morphological structure, functional groups and thermal properties were characterized by XRD, FESEM-EDS, FTIR and TGA analysis. The gamma ray mass attenuation coefficient of concrete composites has been calculated and measured by means of the Monte Carlo simulation and experimental methods. The simulation process was based on the use of MCNP Monte Carlo code where the mass attenuation coefficient (μ/ρ) has been calculated as a function of different particle sizes and filler weight fractions. The simulation results showed that the employment of the lead oxide filler particles enhances the mass attenuation coefficient of the ordinary concrete, drastically. On the other hand, there are approximately no differences between micro and nano sized particles. The mass attenuation coefficient was increased by increasing the weight fraction of nanoparticles. However, a semi-saturation effect was observed at concentrations more than 10 wt%. The experimental process was based on the fabrication of concrete slabs filled by different weight fractions of nano lead oxide particles. The mass attenuation coefficients of these slabs were determined at different gamma ray energies using ²²Na, ¹³⁷Cs and ⁶⁰Co sources and NaI (Tl) scintillation detector. The experimental results showed that the HVL parameter of the ordinary concrete reinforced with 5 wt% of nano PbO particles was reduced by 64% at 511 keV and 48% at 1332 keV. Reasonable agreement was obtained between simulation and experimental results and showed that the employment of nano PbO particles is more efficient at low gamma energies up to 1Mev. The proposed concrete is less toxic and could be prepared in block form instead of toxic lead blocks.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.1215-1218
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• 2021

한국을 방문하는 외국인들은 매년 증가하고 있고 방한 목적 중 식도락관광이 3위에 오를 만큼 세계에서 한국 음식은 위상이 높아지고 있다. 하지만, 한국에서의 알레르기 성분 표시는 법적 의무가 아니기 때문에 대부분의 한식당에서는 이를 표시하지 않고 있고 알레르기가 있는 외국인 관광객들은 한국 음식 섭취에 있어서 상당한 위험과 불편함을 부담하고 있다. 이에 본 논문에서는 머신러닝을 활용하여 사진 촬영만으로 쉽고 정확하게 알레르기 성분을 제공하고자 사물 이미지 데이터 전처리를 위한 HSV(Hue, Saturation, Value) 데이터 전처리 기법을 제안한다. 제안하는 기법은 이미지의 HSV의 평균 및 분산, 표준편차를 통해 불필요한 데이터를 제거한다. 성능평가에서는 비빔밥, 불고기, 제육볶음 등 사진 약 500장의 데이터 셋을 구성하여 HSV의 평균 및 분산을 통해 이미지를 제거하는 방식으로 구축한 데이터 셋을 TensorFlow를 통해 정확도와 학습시간을 측정한다. 측정결과, 제안하는 기법으로 구축한 데이터 셋은 최소 15%에서 최대 25% 높은 정확도와 최소 37.96%에서 최대 42.85% 높은 정도 낮은 학습시간을 보여주었다. 향후 HSV를 활용한 데이터 전처리 기법은 더 많은 데이터를 통해 더욱 구체적인 성능 분석이 필요하다. 또한, 실질적인 개발 및 구현을 통해 제안하는 데이터 전처리 기법의 더욱 현실적인 검증이 필요하다.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.2
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• pp.16-24
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• 2002

Classification of the land cover characteristics is a major application of remote sensing. The goal of this study is to propose an optimal classification process for electro-optical camera(EOC) of Korea Multi-Purpose Satellite(KOMPSAT). The study was carried out on Landsat TM, high spectral resolution image and KOMPSAT EOC, high spatial resolution image of Miho river basin, Korea. The study was conducted in two stages: one was image fusion of TM and EOC to gain high spectral and spatial resolution image, the other was land cover classification on fused image. Four fusion techniques were applied and compared for its topographic interpretation such as IHS, HPF, CN and wavelet transform. The fused images were classified by radial basis function neural network(RBF-NN) and artificial neural network(ANN) classification model. The proposed RBF-NN was validated for the study area and the optimal model structure and parameter were respectively identified for different input band combinations. The results of the study propose an optimal classification process of KOMPSAT EOC to improve the thematic mapping and extraction of environmental information.

• The Korean Journal of Ceramics
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• v.1 no.2
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• pp.91-95
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• 1995

Polycrystalline bismuth- and aluminum- substituted dysporsium and yttrium iron garnet (Bi2R3-xAlyFe5-yO12, R=Dy or Y, $0\leqx\leq3, \; 0\leqy\leq3$) films have been prepared by pyrolysis. The crystallization temperatures, the solubility limit of bismuth ions into the garnet phase, and magnetic and magneto-optic properties of the films have been investigated as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained unchanged at x>1.5, whereas, showed no changes as aluminum concentration (y) increased up to y=1.0 and then gradually increased at y>1.0. The solubility limit of bismuth ions was x=1.8 when y=0 but increased to x=2.3 when y=1.0. It was demonstrated that the magnetic and magneto-optic properties of the dysprosium iron garnet films could be tailored by bismuth and aluminum substitution suitable for magneto-optic recording as follows. The saturation magnetization and coercivity data obtained for the films indicated that the film composition at which the magnetic compensation temperature became room temperature was y=1.2 when x=1.0. Near this composition the coercivity and the squareness of the magnetic hysteresis loop of the films were several kOe and unit, respectively. The Curie temperatures of the films increased with the increase of x but decreaed with the increase of y, and was 150-$250^{\circ}C$ when x=1.0 and y=0.6-1.4. The Faraday rotation at 633 nm of the films increased as x increased but decreased as y increased, and was 1 deg/$\mu\textrm{m}$ when x=1.0 and y=1.0. Based on the data obtained, the appropriate film composition for magneto-optic recording was estimated as near x=1.0 and y=1.0 or $BiDy_2AlFe_4O_{12}$.

• Toxicological Research
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• v.6 no.2
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• pp.205-213
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• 1990

The regulation of neurotoxicants has usually been based upon setting reference doses by dividing a no observed adverse effect level (NOAEL) by uncertainty factors that theoretically account for interspecies and intraspecies extraploation of experimental results in animals to humans. Recently, we have proposed a four-step alternative procedure which provides quantitative estimates of risk as a function of dose. The first step is to establish a mathematical relationship between a biological effect or biomarker and the dose of chemical administered. The second step is to determine the distribution (variability) of individual measurements of biological effects or their biomarkers about the dose response curve. The third step is to define an adverse or abnormal level of a biological effect or biomarker in an untreated population. The fourth and final step is to combine the information from the first three steps to estimate the risk (proportion of individuals exceeding on adverse or abnormal level of a biological effect or biomarker) as a function of dose. The primary purpose of this report is to enhance the certainty of the first step of this procedure by improving our understanding of the relationship between a biomarker and dose of administered chemical. Several factors which need to be considered include: 1) the pharmacokinetics of the parent chemical, 2) the target tissue concentrations of the parent chemical or its bioactivated proximate toxicant, 3) the uptake kinetics of the parent chemical or metabolite into the target cell(s) and/or membrane interactions, and 4) the interaction of the chemical or metabolite with presumed receptor site(s). Because these theoretical factors each contain a saturable step due to definitive amounts of required enzyme, reuptake or receptor site(s), a nonlinear, saturable dose-response curve would be predicted. In order to exemplify this process, effects of the neurotoxicant, methlenedioxymethamphetamine (MDMA), were reviewed and analyzed. Our results and those of others indicate that: 1) peak concentrations of MDMA and metabolites are ochieved in rat brain by 30 min and are negligible by 24 hr, 2) a metabolite of MDMA is probably responsible for its neurotoxic effects, and 3) pretreatment with monoamine uptake blockers prevents MDMA neurotoxicity. When data generated from rats administerde MDMA were plotted as bilolgical effect (decreases in hippocampal serotonin concentrations) versus dose, a saturation curve best described the observed relationship. These results support the hypothesis that at least one saturable step is involved in MDMA neurotoxicity. We conclude that the mathematical relationship between biological effect and dose of MDMA, the first step of our quantitative neurotoxicity risk assessment procedure, should reflect this biological model information generated from the whole of the dose-response curve.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.158-165
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• 2017

The physical shape of an ultrasound transducer has not been considered in previous studies of the photoacoustic saturation effect, where a photoacoustic signal's magnitude linearly increases as an absorption coefficient increases and it is finally saturated. In this paper, the effect of a spherically focused ultrasound transducer on photoacoustic nonlinearity is investigated. The focused ultrasound transducer's spatial filtering effect on photoacoustic signals is analytically derived considering the combined concept of a virtual point detector and Green function approach. The ultrasound transducer's temporal response (i.e., transfer function) effect on photoacoustic signals is considered by integrating photoacoustic signal values within the absorption area covered by a spatial resolution of the ultrasound transducer. Results from the analytically derived expression show that the magnitude of photoacoustic signals measured by a spherical focused ultrasound transducer shows a maximum at a specific absorption coefficient, and decreases after that maximum point as an absorption coefficient is increased. The origin of this photoacoustic nonlinearity is physically understood by comparing the ultrasound transducer's transfer functions and photoacoustic resonance spectra. In addition, this physical interpretation implies that the photoacoustic nonlinearity is strongly dependent on the irradiance distribution inside an absorption medium.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.35-43
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• 2010

Partially saturated permeability should be defined by the function of suction (or degree of saturation) and porosity. However, commercial software and most researchers' model often describe as the function of suction. The stability of a soil slope can be affected by both hydraulic and shear strength properties of partially saturated soils. For both studies, we generally use an uncoupled seepage analysis program Seep/W(Geo-Slope, 2007) and a series stress-deformation analysis program Sigma/W, or slope stability analysis program Slope/W. Seep/W is performed for simulations of partially saturated flow problems in non-deformable soil media. However, under real situations, the water flow processes in a deformable soil are influenced by soil skeleton movement and the pore water pressure changed due to seepage will lead to changes in stresses and to deformation of a soil. Many researchers are currently developing their models for solving coupled hydro-mechanical problems to simulate slope stability during a rainstorm. For a proper implementation in the field, the developed model should be still needed in order to achieve appropriate accuracy of the solution for coupled hydro-mechanical problems in soil slope stability. Thus, the paper presents the comparison of slope stability between uncoupled and coupled analyses of seepage and stress deformation problems.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.326-331
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• 2018

Crop growth models are useful tools for understanding and integrating knowledge about crop growth. Models for predicting plant height, net photosynthesis rate, and plant growth of quinoa (Chenopodium quinoa Willd.) as a leafy vegetable in a closed-type plant factory system were developed using empirical model equations such as linear, quadratic, non-rectangular hyperbola, and expolinear equations. Plant growth and yield were measured at 5-day intervals after transplanting. Photosynthesis and growth curve models were calculated. Linear and curve relationships were obtained between plant heights and days after transplanting (DAT), however, accuracy of the equation to estimate plant height was linear equation. A non-rectangular hyperbola model was chosen as the response function of net photosynthesis. The light compensation point, light saturation point, and respiration rate were 29, 813 and $3.4{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, respectively. The shoot fresh weight showed a linear relationship with the shoot dry weight. The regression coefficient of the shoot dry weight was 0.75 ($R^2=0.921^{***}$). A non-linear regression was carried out to describe the increase in shoot dry weight of quinoa as a function of time using an expolinear equation. The crop growth rate and relative growth rate were $22.9g{\cdot}m^{-2}{\cdot}d^{-1}$ and $0.28g{\cdot}g^{-1}{\cdot}d^{-1}$, respectively. These models can accurately estimate plant height, net photosynthesis rate, shoot fresh weight, and shoot dry weight of quinoa.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.413-418
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• 2011

The thermodynamic properties of steam table are obtained by measurement or approximate calculation under appropriate assumptions. Therefore they are supposed to have basic measurement errors. And thermodynamic properties should be modeled through function approximation for using in numerical analysis. In order to make noised thermodynamic properties corresponding to measurement errors, random numbers are generated, adjusted to appropriate magnitudes and added to original thermodynamic properties. Both neural networks and quadratic spline interpolation method are introduced for function approximation of these modified thermodynamic properties in the saturated water based on pressure and temperature. In analysis spline interpolation method gives much less relative errors than neural networks at both ends of data. Excluding the both ends of data, the relative errors of neural networks is generally within ${\pm}0.2%$ and those of spline interpolation method within ${\pm}0.5$~1.5%. This means that the neural networks give smaller relative errors compared with quadratic spline interpolation method within range of use. From this fact it was confirmed that the neural networks trace the original values better than the quadratic interpolation method and neural networks are more appropriate method in modelling the saturated steam table.

• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.193-196
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• 2019

The design and control of thermal flow is important for the operation of high-power laser diodes (LDs). It is necessary to analyze and improve the thermal bottleneck near the active layer of an LD. As the error in prediction of the thermal resistance of an LD is large, typically due to the hyperbolic increase and saturation to linear increase of the thermal resistance as a function of thickness, it is helpful to use a simple, modified divergence model for the improvement and optimization of thermal resistance. The characteristics of LDs are described quite well, in that the values for simulated thermal resistance curves and the thermal cross section followed are almost the same as the values from the model function. Also, the thermal-cross-section curve obtained by differentiating the thermal resistance is good for identifying thermal bottlenecks intuitively, and is also fitted quite well by the model proposed for both a typical LD structure and an improved LD with thin capping and high thermal conductivity.