• 한국재료학회지
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• 제5권2호
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• pp.191-196
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• 1995

비정질 PEEK 필름의 self-bonding강도는 접합시의 공정변수(시간, 온도, 그리고 압력)와 밀접한 관계가 있다. 본 연구에서는 이러한 공정변수의 효과를 규명하기 위하여 각기 다른 접합조건하에서 개발된 시편들의 self-bonding강도를 single lap-shear test를 통하여 측정된 각각의 전단 응력(shear strength)으로 나타내었다. 개발된 self-bonding강도는 접합온도가 증가함에 따라 증가하였으며, 접합시간의 1/4승에 일차함수적으로 비례증가하였다. 접합공정 중의 압력의 효과는 단지 초기 접합단계인 wetting에 기여하였을 뿐 self-bonding강도 자체에는 거의 영향을 미치지 않는 것으로 사려되었다. 결론적으로 비정질 PEEK 필름의 self-bonding현상은 현장에서의 실제 접합공정에서 어떠한 접착재료의 사용없이도 모재와 같은 강도를 개발하는데 무한한 가능성이 있는 것으로 판단되었다.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1367-1379
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• 2020

The small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity control in SMSFR by using innovative systems, including burnable poisons and optimized control rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of control rods. Two optimized control rod designs with rare earth oxides (Eu₂O₃ and Gd₂O₃) and moderators are compared to the conventional design with natural boron carbide (B₄C). The optimized designs show improved neutronic and safety performance.

• Journal of Radiation Protection and Research
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• 제29권1호
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• pp.41-48
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• 2004

A safety assessment code, called SAGE (Safety Assessment Groundwater Evaluation), has been developed to describe post-closure radionuclide releases and potential radiological doses for low- and intermediate-level radioactive waste (LILW) disposal in an engineered vault facility in Korea. The conceptual model implemented in the code is focused on the release of radionuclide from a gradually degrading engineered barrier system to an underlying unsaturated zone, thence to a saturated groundwater zone. The radionuclide transport equations are solved by spatially discretizing the disposal system into a series of compartments. Mass transfer between compartments is by diffusion/dispersion and advection. In all compartments, radionuclides ate decayed either as a single-member chain or as multi-member chains. The biosphere is represented as a set of steady-state, radionuclide-specific pathway dose conversion factors that are multiplied by the appropriate release rate from the far field for each pathway. The code has the capability to treat input parameters either deterministically or probabilistically. Parameter input is achieved through a user-friendly Graphical User Interface. An application is presented, which is compared against safety assessment results from the other computer codes, to benchmark the reliability of system-level conceptual modeling of the code.

• 천문학회지
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• 제29권spc1호
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• pp.169-170
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• 1996

In the past, it. was very difficult to distinguish thermal and non-thermal emission. Broadbent et a1. (1989) has developed a new technique with the help of the IRAS 60 micron emission. The distribution of non-thermal or synchrotron emission in the Galactic disk has been modeled from the 408 MHz all sky survey of Haslam et a1. (1982) after removal of the thermal component.. At. 408 MHz, t.here is very little absorption in the interstellar medium and the distribution along the line-of-sight. is inferred mainly from its presumed relationship to other tracers of spiral structure via a. number of fitted parameters. But. at lower frequencies, free-free absorption becomes important and can give some direct. information on the line of sight. distribution. We have modeled the thermal electron density according to the spiral arm models and the distribution of ionized hydrogen in the Galactic plane by Lockman (1976) and Cersosimo et. al. (1989) and have made predictions to compare with the surveys of Dwarakanath et al. (1990) at. 34.5 MHz and .Jones and Finlay (1974) at 29.9 MHz. The result confirms that the absorption model of the synchrotron emissivity in the Galactic plane is broadly corrected and illustrates the potential of the absorption technique.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제23권1호
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• pp.110-114
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• 2020

Gastric xanthoma is frequently an incidental finding on upper endoscopy in adults. Gastric xanthomas (GX) can be mistaken for malignancies and warrant prompt histologic diagnosis. The underlying etiology is not fully understood; however, it has been linked to Helicobacter pylori gastritis and gastric cancer. GX in the pediatric population is largely unreported in the literature. Because of the relative rarity, documentation with case reports are essential to provide as much data as possible to see if there is a correlation between GX and malignant potential in the pediatric population. Our group is reporting two cases, a 10-year-old male and a 7-year-old male, both who presented with chronic dysphagia, upper abdominal pain, nausea, vomiting, and loss of appetite. Upper endoscopies for both patients revealed small polypoid lesions located in the antrum with foamy histiocytes on histology, leading to the diagnosis of gastric xanthoma.

• Interaction and multiscale mechanics
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• 제2권3호
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• pp.223-233
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• 2009

This paper presents a new nonlocal stress variational principle approach for the transverse free vibration of an Euler-Bernoulli cantilever nanobeam with an initial axial tension at its free end. The effects of a nanoscale at molecular level unavailable in classical mechanics are investigated and discussed. A sixth-order partial differential governing equation for transverse free vibration is derived via variational principle with nonlocal elastic stress field theory. Analytical solutions for natural frequencies and transverse vibration modes are determined by applying a numerical analysis. Examples conclude that nonlocal stress effect tends to significantly increase stiffness and natural frequencies of a nanobeam. The relationship between natural frequency and nanoscale is also presented and its significance on stiffness enhancement with respect to the classical elasticity theory is discussed in detail. The effect of an initial axial tension, which also tends to enhance the nanobeam stiffness, is also concluded. The model and approach show potential extension to studies in carbon nanotube and the new result is useful for future comparison.

• Advances in Traditional Medicine
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• 제3권2호
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• pp.90-99
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• 2003

There are several data in the literature indicating a great variety of pharmacological activities of Polypodium genus, which exhibit antiinflammatory and immunomodulatory activities. Since one of our main interests is to obtain natural immunoregulatory agents devoid of pharmacological adverse effects, we used flow cytometry analysis to highlight relative contributions of a water-soluble fraction of different concentrations of Polypodium rhizome extracts on lymphocyte subpopulations, NK and LAK activity. To measure their potential immunoregulatory activity a T cell proliferation assay in response to phytohemaglutinin (PHA) and mixed lymphocyte reactions were chosen. As a confirmatory bioassay we studied the effect of our extracts on CD45RO and CD95 antigen expressions. The results indicate that CD95 expression dramatically increases after peripheral blood lymphocyte activation and treatment with Polypodium leucotomus, cambricum and vulgare extracts, suggesting a powerful intrinsic pro-apoptotic effect.

• 한국지하수토양환경학회지:지하수토양환경
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• 제15권2호
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• pp.40-46
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• 2010

In this study, microwave irradiation, which is reflected by metals, was used to reduce the amount of sewage sludge, and the results were used to verify solubilization efficiency and determine optimum operation conditions. Biogas production and methane content of the gas under optimized conditions were measured with the biochemical methane potential (BMP) test. The sludge was taken from a thickened sludge tank at J sewage treatment plant (JSTP) in Seoul, Korea. For the experiments, 50 mL of sludge was filled in vessels and the vessels were irradiated with the power of 500, 600, 700, and 800W for 2~5 min. In addition, Fe powder was added by 0.01, 0.05, and 0.1 g to compare the efficiency with and without Fe powder. The results confirmed that solubilization efficiency was higher in the presence of Fe powder. The optimum conditions of 0.01 g addition of Fe powder with 800W irradiation for 5 min, yielded nearly 22.95% higher solubilization efficiency than without Fe powder. The BMP tests were carried out using sludge obtained from the experiments carried out under the optimum conditions. As a result, sludge subjected by 800W with 0.01 g of Fe powder for 5 min displayed the highest level of gas production and methane content. Through this study, it could be confirmed that solubilization efficiency increased by addition of Fe powder.

• Asian-Australasian Journal of Animal Sciences
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• 제21권9호
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• pp.1324-1329
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• 2008

This study was conducted to evaluate the potential of the transformed Lactobacillus reuteri Pg4 (T-Pg4) harboring the ${\beta}$-glucanase gene as a poultry probiotic. The probiotic properties of the T-Pg4 strain were evaluated in vitro by their adherence capability and acid and bile salt tolerance, and were evaluated in vivo by their survival and adhesion in the gastrointestinal tract (GIT) of specific-pathogen-free (SPF) chickens. The results showed that the T-Pg4 strain exhibited resistance to acidic conditions and contact with bile salt, and adhered efficiently to the crop and intestinal epithelial cells of chickens in vitro. The T-Pg4 strain also could survive and colonize the gastrointestinal epithelium of the experimental SPF chickens in vivo. In addition, radial enzyme diffusion was used to demonstrate that the Lactobacillus spp. randomly isolated from the GIT of the SPF chickens fed T-Pg4 possessed ${\beta}$-glucanase secretion capability. These findings have demonstrated that the transformed L. reuteri Pg4 survives transit through the stomach and intestine, and may secrete ${\beta}$-glucanase in the chicken GIT. Therefore, it is suggested that this organism could be used as a multifunctional poultry probiotic.

• Asian-Australasian Journal of Animal Sciences
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• 제14권11호
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• pp.1580-1584
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• 2001

A study was conducted to estimate the nutritive value of some selected acacia forages using palatability index, in sacco degradability and in vitro gas production characteristics. Ten wethers (mean wt. $18{\pm}3.5kg$) were offered Acacia tortilis, Acacia nilotica, Acacia mellifera, Acacia brevispica, Acacia Senegal and Leucaena leucocephala (control) using a cafeteria system to determine the species preference by the animals. The acacia species were rich in nitrogen and showed variable palatability pattern. Significant (p<0.05) differences in relative palatability index (RPI) were detected among the species with the following ranking: brevispica > leucaena > mellifera > tortilis > Senegal > nilotica. Acacia nilotica appeared to be of low relative palatability with RPI of 24% and this was attributed to relatively high phenolic concentrations. The DM potential degradability (B) and rate of degradation (c) of the species were significantly (p<0.05) different, ranging from 40.1 to 59.1% and 0.0285 to 0.0794/h respectively. Acacia species had moderate levels of rumen undegradable protein, much higher than that in leucaena. In vitro gas production results indicated the effect of polyphenolic compounds on the fermentation rate, with lower gas production recorded from A. nilotica and tortilis. Based on RPI, A. brevispica and mellifera were superior to the rest and comparable to L. leucocephala. Long-term feeding trials are required with the superior species when used as protein supplements to poor quality diets.