• Nuclear Engineering and Technology
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• v.41 no.4
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• pp.531-544
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• 2009

This paper is intended to provide key issues and current research outcomes on accelerator-based Boron Neutron Capture Therapy (BNCT). Accelerator-based neutron sources are efficient to provide epithermal neutron beams for BNCT; hence, much research, worldwide, has focused on the development of components crucial for its realization: neutron-producing targets and cooling equipment, beam-shaping assemblies, and treatment planning systems. Proton beams of 2.5 MeV incident on lithium target results in high yield of neutrons at relatively low energies. Cooling equipment based on submerged jet impingement and micro-channels provide for viable heat removal options. Insofar as beam-shaping assemblies are concerned, moderators containing fluorine or magnesium have the best performance in terms of neutron accumulation in the epithermal energy range during the slowing-down from the high energies. NCT_Plan and SERA systems, which are popular dose distribution analysis tools for BNCT, contain all the required features (i.e., image reconstruction, dose calculations, etc.). However, detailed studies of these systems remain to be done for accurate dose evaluation. Advanced research centered on accelerator-based BNCT is active in Korea as evidenced by the latest research at Hanyang University. There, a new target system and a beam-shaping assembly have been constructed. The performance of these components has been evaluated through comparisons of experimental measurements with simulations. In addition, a new patient-specific treatment planning system, BTPS, has been developed to calculate the deposited dose and radiation flux in human tissue. It is based on MCNPX, and it facilitates BNCT efficient planning based via a user-friendly Graphical User Interface (GUI).

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.413-416
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• 2008

A synthesis route to ordered mesoporous carbons with controllable nitrogen content has been developed for high-performance EDLC electrodes. Nitrogen-doped ordered mesoporous carbons (denoted as NMC) were prepared by carbonizing a mixture of two different carbon sources within the mesoporous silica designated by KIT-6. Furfuryl alcohol was used as a primary carbon precursor, and melamine as a nitrogen dopant. This synthesis procedure gave cubic Ia3d mesoporous carbons containing nitrogen as much as 13%. The carbon exhibited a narrow pore size distribution centered at 3-4 nm with large pore volume (0.6-1 cm3 g-1) and high specific BET surface area (700-1000 m2 g-1). Electrochemical behaviors of the NMC samples with various N-contents were investigated by a two-electrode measurement system at aqueous solutions. At low current density, the NMC exhibited markedly increasing capacitance due to the increase in the nitrogen content. This result could be attributed to the enhanced surface affinity between carbon electrode and electrolyte ions due to the hydrophilic nitrogen functional groups. At high current density conditions, the NMC samples exhibited decreasing specific capacitance against the increase in the nitrogen content. The loss of the capacitance with the N-content may be explained by high electric resistance which causes a significant IR drop at high current densities. The present results indicate that the optimal nitrogen content is required for achieving high power and high energy density simultaneously.

• Korean Journal of Materials Research
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• v.14 no.4
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• pp.270-275
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• 2004

Due to the luminescence by$ Er ^{ 3+}$ activator, Er-doped $LaPO_4$ powders can be applied for optical amplification materials. In this study, $LaPO_4$:Er nanoparticles were synthesized in solution system using a high-boiling coordinating solvent and their properties were investigated through various spectroscopic techniques. The nanoparticles were to take a single phase of monazite structure by a X-ray diffraction analysis and to have the 5-6 nm of particles size with narrow size distribution by a TEM. And it was confirmed by the EA and FT-IR analyses that the surfaces of nanoparticles are coordinated with the solvent molecules, which will possibly keep from agglomerating between LaPO$_4$:Er nanoparticles. In the emission spectrum of $LaPO_4$:Er nanoparticle at NIR region, on the other hand, it was measured that the emission intensity is very weak, which is due to the transition from $^4$$I_{(13/2)}$ to $^4$$I_{(15/2)}$ of $Er^{3+ }$ion. It was interpreted that the weak luminescence of $LaPO_4$:Er is originated from the hydroxyl groups adsorbed on the surfaces of the nanoparticles, because OH group acts as an efficient quencher for the $^4$$I_{(13/2)}$ \longrightarrow $^4$$I_{(15/2)}$ emission of $Er^{3+}$ activator. But the co-doping of Yb$^{3+}$ as a sensitizer in this nanoparticle results in the increase of the emission intensity at 1539 nm due to the effective energy transfer from $Yb^{3+}$ to $Er^{3+}$ . In addition, the synthesized nanoparticles exhibited good dispersibility with some polymers and effective luminescence at NIR region.n.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.1 no.1
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• pp.58-67
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• 2020

Terrestrial ecosystems influence climate change via their climate regulation function, which is manifested within the carbon, water, and energy circulation between the atmosphere and surface. However, it has been challenging to quantify the climate regulation of terrestrial ecosystems and identify its regional distribution, which provides useful information for establishing regional climate-mitigation plans as well as facilitates better understanding of the interactions between the climate and land processes. In this study, a land surface model (LSM) that represents the land-atmosphere interactions and plant phenological variations was introduced to assess the contributions of terrestrial ecosystems to atmospheric warming or cooling effects over East Asia over the last half century. Three main climate-regulating components were simulated: net radiation flux, carbon exchange, and moisture flux at the surface. Then, the contribution of each component to the atmospheric warming or cooling (negative or positive feedback to the atmosphere, respectively) was investigated. The results showed that the terrestrial ecosystem over the Siberian region has shown a relatively large increase in positive feedback due to the enhancement of biogeochemical processes, indicating an offset effect to delay global warming. Meanwhile, the Gobi Desert shows different regional variations: increase in positive feedback in its southern part but increase in negative one in its eastern part, which implies the eastward movements of desert areas. As such, even though the LSM has limitations, this model approach to quantify the climate regulation is useful to extract the relevant characteristics in its spatio-temporal variations.

• Nuclear Engineering and Technology
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• v.6 no.2
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• pp.97-111
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• 1974

The adsorption mechanism of Cs-137 in low level radioactive solution by vermiculite treated with Na ion is studied in order to investigate its effective utilization for the radioactive effluent treatment. The beneficial role of Na-vermiculite is that Na ion can induce the wider c-axis spacing in which Cs ion can be sorbed in vermiculite. Cation exchange capacity and distribution coefficient of cesium seems to be influenced by the variation of c-axis spacing of vermiculite. Comparative identification and detection with the characteristic analyses of X-ray diffraction and electron diffraction patterns, diffrential thermal analysis and electron microscopy of Na-, K- and Cs-vermiculite are studied for the phemomena of Cs adsorption by vermiculite. This importance of the utilization in terms of adsorption and fixation of cesium involving vermiculite is discussed. It is found that the Na-vermiculite is valuable outside charging material for high level radioactive liquid waste storage tank of underground to protect the pollution of the underground water.

• Molecules and Cells
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• v.19 no.3
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• pp.356-364
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• 2005

Intramolecular excimer formation of 1,3-di(1-pyrenyl) propane(Py-3-Py) and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to evaluate the effect of ethanol on the rate and range of lateral and rotational mobilities of bulk bilayer structures of synaptosomal plasma membrane vesicles (SPMVs) from the bovine cerebral cortex. Ethanol increased the excimer to monomer fluorescence intensity ratio (I'/I) of Py-3-Py in the SPMVs. Selective quenching of both DPH and Py-3-Py by trinitrophenyl groups was used to examine the range of transbilayer asymmetric rotational mobility and the rate and range of transbilayer asymmetric lateral mobility of SPMVs. Ethanol increased the rotational and lateral mobility of the outer monolayer more than of the inner one. Thus ethanol has a selective fluidizing effect within the transbilayer domains of the SPMVs. Radiationless energy transfer from the tryptophans of membrane proteins to Py-3-Py was used to examine both the effect of ethanol on annular lipid fluidity and protein distribution in the SPMVs. Ethanol increased annular lipid fluidity and also caused membrane proteins to cluster. These effects on neuronal membranes may be responsible for some, though not all, of the general anesthetic actions of ethanol.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1043-1058
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• 1990

The Strain rate effect in electro-magnetic forming, which is one of the high velocity forming methods, is studied by the finite element method in this paper. The forming process is simplified by neglecting the coupling between magnetic field and work-piece deformation, and the impulsive magnetic pressure is regarded as inner pressure load. A rate-dependent elasto-plastic material model, of which tangential modulus depends of effective strain rate, is proposed. The model is shown to well describe the transient increase of yield stresses, the decreases of the final displacement and yield stress, the decrease of the difference in the distribution of deformation along the axial direction, and the change of deformation mechanism due to strain rate effect. As a result, displacement, final deformed shape, radial velocity, deformation energy, and the changes of effective stress, effective strain and effective strain rate through plastic working are given. Based on the results, the effectiveness of this model and the strain rate effect of the deformation process of the work-piece are discussed.

• The Journal of Korean Medicine
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• v.26 no.1 s.61
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• pp.85-92
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• 2005

Objective: A number of candidate genes have been in implicated in the pathogenesis of obesity in humans. Tumor necrosis factor-alpha $(TNF-{\alpha})$ is expressed primarily in adipocytes, and elevated levels of this cytokine have been linked to obesity and insulin resistance. Recently, the A allele of a polymorphism at position 308 in the promoter region of $TNF-{\alpha}$ (G-308A) has been shown to increase transcription of the gene in adipocytes. Therefore, we designed this study to test whether obese and non-obese subjects differ in $TNF-{\alpha}$ genotype distribution, and how the genotypes affect anthropometric parameters, including degrees of body mass index (BMI). Methods : The study included 153 obese but otherwise healthy women ($BMI{\geq}kg/m^2$, range 25-54.7, age range 15-40 years) and 82 non-obese healthy women ($BMI, age range 15-40 years). Total fat mass and percent body fat were determined by dual-energy X-ray absorptiometry. Genomic DNA was extracted and used for Ncol restriction fragment length polymorphism (RFLP) based genotyping of $TNF-{\alpha}$. Results: No differences were observed for allelic and genotype frequencies between the obese ($BMI{\geq}25$) and non-obese women. Also, no association of TNF-(l polymorphism was observed with body mass index (BMI) for genotype in obese women. In addition, age, pertent body fat, BMI, and cholesterol levels did not differ by $TNF-{\alpha}$ genotype. However, waist-to­hip ratio (WHR) was significantly lower in subjects with $TNF-{\alpha}$ GA or AA genotype (0.94 0.07 vs. 0.920.03, P<0.005). Conclusion: These results suggest that $TNF-{\alpha}$ promoter polymorphism at position-308 is not a significant factor for BMI, but affects the WHR in obese healthy women from Koreans.

• Applied Biological Chemistry
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• v.26 no.1
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• pp.47-52
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• 1983

The size distribution and changes of volume and grain hardness of ‘Sedohadaka', waked barley of various polishing yields during hydration process at various temperatures were investigated, and were analyzed kinetically, Both major and minor diameter of barley grain decreased linearly during polishing, and the decreasing rate of major diameter was greater than that of minor diameter. The volume change of barley grain could be expressed as a power of hydration time, and a break point was found in case of non-polished barley. The changing rate of grain hardness followed the equation of a first-order reaction, and the reaction rate constant increased with decreasing polishing yields and at higher temperature in the range of $20{\sim}60^{\circ}C$. The activation energy of hardness change reaction of polished barley during hydration were ranged $5.1{\sim}7.8Kcal/mole$, and 13.3Kcal/mole of non-polished barley.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.99-105
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• 2015

Bottom ash and fly ash are by-product from thermoelectric power plants. Fly ash is recycled to various field. However, though an output of bottom ash have increased each year, most of them is reclaimed in ash landfill. It is necessary to find a solution that bottom ash is recycled economically and know characteristics of bottom ash to recycle. It is goal to investigate engineering properties of bottom ash, especially the particle breakage, to recycle that. Bottom ash was crushed by impact method according to compaction energy and then compared with or original sample and crushed it in terms of particle size distribution and characteristics of strength. In result, after crushed it, particle finer was increased, especially 2~0.85 mm size, than original. It was displayed a tendency that internal friction of crushed sample was decreased but cohesion of it was not. Therefore, it is important to investigate the engineering properties of bottom ash in terms of the particle breakage to use construction materials for various field.