• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3006-3013
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• 2015

Flat tube heat exchangers can improve the thermal performance significantly compared with round tube heat exchangers. For proper design of flat tube heat exchangers, one should know the tubeside heat transfer coefficients. In this study, convective boiling heat transfer coefficients of R-410A were obtained in a flat extruded aluminum tube with $D_h=1.41mm$. The test range covered mass flux from 200 to $600kg/m^2s$, heat flux from 5 to $15kW/m^2$ and saturation temperature from $5^{\circ}C$ to $15^{\circ}C$. The heat transfer coefficient curve shows a decreasing trend after a certain quality(critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique 'cross-over' of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kaew-On et al. correlations reasonably predicted the present data.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.7-13
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• 1998

In this study, for the safety performance of LNG storage tank, the fracture toughness in X-grooved weld HAZ(heat-affected zone) of $9\%$ Ni steel was evaluated qualitatively and quantitatively, and the relation with the change in microstructure was analyzed. The toughness assessment was peformed through the modified CTOD test proposed for thick weldment with X-groove. Additionally, microstructures of HAZ were evaluated by OM, SEM and XRD. From the results, HAZ toughness of SMA(shielded metal arc)-welded $9\%$ Ni steel decreased as the evaluated region approached the fusion line. The decrease in toughness was apparently caused by the increase in the fraction of coarse-grained zone within HAZ. On the other hand, toughness drop with decreasing test temperature in F.L.(fusion line) ${\~}$F.L.+3mm was larger than that in F.L.+5mm${\~}$F.L.+7mm region due to the fact that in the former regions, retained austenite had poor stability.

• Journal of the Korean Child Neurology Society
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• v.26 no.4
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• pp.240-245
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• 2018

Purpose: Early prediction of prognosis of children resuscitated from cardiac arrest is a major challenge. We investigated the utility of electroencephalography (EEG) and laboratory studies for predicting of neurologic outcome in children resuscitated from cardiac arrest. Methods: We retrospectively analyzed medical records of patients who were resuscitated from cardiac arrest from 2006 to 2015 at the Gil Medical Center. Patients aged one month to 18 years were included. EEG analysis included background scoring, reactivity and seizure burden. EEG background was classified score 0 (normal/organized), score 1 (slow and disorganized), score 2 (discontinuous or burst suppression), and score 3 (suppressed and featureless). Neurologic outcome was evaluated by Pediatric Cerebral Performance Category (PCPC) at least 6 months after cardiac arrest. Results: Total 26 patients were evaluated. Nine patients showed good neurologic outcome (PCPC 1, 2, 3) and 17 patients showed poor neurologic outcome (PCPC 4, 5, 6). Patients of poor neurologic outcome group showed EEG background score 3 in 88.2%, whereas 44.4% in patients of good neurologic outcome group (P=0.028). Electrographic ictal discharges except non-convulsive status epilepticus were presented in 44.4% of good neurologic outcome group and 5.9% of poor neurologic outcome group (P=0.034). Ammonia and lactate levels were higher and pH levels were lower in poor outcome group than good neurologic outcome group. Conclusion: Suppressed and featureless EEG background is associated with poor neurologic outcome and electrographic seizures are associated with good neurologic outcome.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1061-1070
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• 2023

Over the last few years, lead-free inorganic metal perovskites have gained impressive ground in empowering satellites in space exploration owing to their material stability and performance evolution under extreme space environments. The present work has examined the versatility of eight such perovskites as space radiation shielding materials by computing their photon, charged particles and neutron interaction parameters. Photon interaction parameters were calculated for a wide energy range using PAGEX software. The ranges of heavy charged particles (H, He, C, N, O, Ne, Mg, Si and Fe ions) in these perovskites were estimated using SRIM software in the energy range 1 keV-10 GeV, and that of electrons was computed using ESTAR NIST software in the energy range 0.01 MeV-1 GeV. Further, the macroscopic fast neutron removal cross-sections were also calculated to estimate the neutron shielding efficiencies. The examined shielding parameters of the perovskites varied depending on the radiation type and energy. Among the selected perovskites, Cs₂TiI₆ and Ba₂AgIO₆ displayed superior photon attenuation properties. A 3.5 cm thick Ba₂AgIO₆-based shield could reduce the incident radiation intensity to half its initial value, a thickness even lesser than that of Pb-glass. Besides, CsSnBr₃ and La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ displayed the highest and lowest range values, respectively, for all heavy charged particles. Ba₂AgIO₆ showed electron stopping power (on par with Kovar) better than that of other examined materials. Interestingly, La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ demonstrated neutron removal cross-section values greater than that of standard neutron shielding materials - aluminium and polyethylene. On the whole, the present study not only demonstrates the employment prospects of eco-friendly perovskites for shielding space radiations but also suggests future prospects for research in this direction.

• Korean Journal of Poultry Science
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• v.12 no.2
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• pp.89-95
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• 1985

Two experiments were undertaken to study the growth promoting effect of Spiramycin and Virginiamycin at the level of 5ppm each. In the first experiment, 180 day - old male broiler chickens (Maniker parent stock) were divided into 18 groups of 10 birds each. Six groups were placed on one of the three experimental diets (Nonmedicated control, Spiramycin supplemented diet and Virginiamycin supplemented diet). Basal diet of Experiment 1 contained 21.9% crude protein and 3159kcal /kg diet. Second experiment employed same treatments as were used in the Experiment 1. Ninety male and 90 female day-old broiler chickens(Maniker commercial) were grouped by 10 birds of sane sex in each and assigned to 3${\times}$2 factorial design. Basal diet of Experiment 2 contained 19.95% crude protein and 2931kcal/kg diet. Chicks were fed for six weeks in battery with raised floor and kept further for metabolic trials. The results of feeding trials showed that there were no statistically significant differences between treatments in weight gain, feed intake, feed efficiency and mortality. However, birds fed Antibiotic B supplemented diet grew approximately 3% more than the control in Experiment 1 and than those fed Antibiotic A supplemented diet in Experiment 2. Feed efficiency was also improved by supplementing Antibiotic B in both experiments. There were significant(P〈0.01) differences between sexes in growth rate, feed intake and feed efficiency. Birds fed Antibiotic B supplemented diet of Experiment 1 showed significantly (P〈0.01) greater availability for crude fat than those fed other diets. Birds fed Antiobiotic A supplemented diet in Experiment 1 showed significantly (P〈0.05) lower availability of crude fiber than those of other treatments. Weight of small intestine of birds fed Antibiotic B tended to be heavier than those fed other diets.

• Korean Journal of Agricultural Science
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• v.49 no.2
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• pp.175-184
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• 2022

The present study investigated the neuroprotective effects of Coreopsis lanceolate extract against hydrogen-peroxide (H₂O₂)-induced oxidative damage and cell death in pheochromocytoma 12 (PC12) cells. Reactive oxygen species (ROS), 2,2'-azinobis (3-ethylbebzothiazoloine-6-sulfonic acid) diammonium salt, and 1,1-diphenyl-2-picrrylhydrazyl radical scavenging activities, as well as the expression levels of proteins associated with oxidative damage and cell death were investigated. According to the results, C. lanceolate extract exhibited inhibitory activity against intracellular ROS generation and cell-damaging effects induced by hydroxyl radicals in a dose-dependent manner. Total phenolic and flavonoid contents were 22.3 mg·g^-1 gallic acid equivalent and 16.2 mg·g^-1 catechin equivalent, respectively. Additionally, a high-performance liquid chromatography (HPLC) assay based on the internal standard method used to detect phenolic compounds. The phenolic compounds identified in C. lanceolata extract contained (+)-catechin hydrate (5.0 ± 0.0 mg·g^-1), ferulic acid (1.6 ± 0.0 mg·g^-1), chlorogenic acid (1.5 ± 0.0 mg·g^-1), caffeic acid (1.2 ± 0.0 mg·g-1), naringin (0.9 ± 0.0 mg·g^-1), and p-coumaric acid (0.5 ± 0.0 mg·g^-1). C. lanceolata extract attenuated pro-apoptotic Bax expression levels and enhanced the expression levels of anti-apoptotic Bcl-2, caspase-3, and caspase-9 proteins. Therefore, C. lanceolata is a potential source of materials with neuroprotective properties against neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.803-811
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• 2024

Nuclear accidents such as Fukushima Daiichi have highlighted the potential of passive safety systems to replace or complement active safety systems as part of the overall prevention and/or mitigation strategies. In addition, passive systems are key features of Small Modular Reactors (SMRs), for which they are becoming almost unavoidable and are part of the basic design of many reactors available in today's nuclear market. Nevertheless, their potential to significantly increase the safety of nuclear power plants still needs to be strengthened, in particular the ability of computer codes to determine their performance and reliability in industrial applications and support the safety demonstration. The PASTELS project (September 2020-February 2024), funded by the European Commission "Euratom H2020" programme, is devoted to the study of passive systems relying on natural circulation. The project focuses on two types, namely the SAfety COndenser (SACO) for the evacuation of the core residual power and the Containment Wall Condenser (CWC) for the reduction of heat and pressure in the containment vessel in case of accident. A specific design for each of these systems is being investigated in the project. Firstly, a straight vertical pool type of SACO has been implemented on the Framatome's PKL loop at Erlangen. It represents a tube bundle type heat exchanger that transfers heat from the secondary circuit to the water pool in which it is immersed by condensing the vapour generated in the steam generator. Secondly, the project relies on the CWC installed on the PASI test loop at LUT University in Finland. This facility reproduces the thermal-hydraulic behaviour of a Passive Containment Cooling System (PCCS) mainly composed of a CWC, a heat exchanger in the containment vessel connected to a water tank at atmospheric pressure outside the vessel which represents the ultimate heat sink. Several activities are carried out within the framework of the project. Different tests are conducted on these integral test facilities to produce new and relevant experimental data allowing to better characterize the physical behaviours and the performances of these systems for various thermo-hydraulic conditions. These test programmes are simulated by different codes acting at different scales, mainly system and CFD codes. New "system/CFD" coupling approaches are also considered to evaluate their potential to benefit both from the accuracy of CFD in regions where local 3D effects are dominant and system codes whose computational speed, robustness and general level of physical validation are particularly appreciated in industrial studies. In parallel, the project includes the study of single and two-phase natural circulation loops through a bibliographical study and the simulations of the PERSEO and HERO-2 experimental facilities. After a synthetic presentation of the project and its objectives, this article provides the reader with findings related to the physical analysis of the test results obtained on the PKL and PASI installations as well an overall evaluation of the capability of the different numerical tools to simulate passive systems.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.106-113
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• 2024

Understanding the tritium release and retention behavior of candidate tritium breeder materials is crucial for breeder blanket design. Recently, a melt spraying process was developed to prepare Li₄SiO₄ pebbles, which were subsequently subjected to the in-pile tritium production and extraction platform in China Mianyang Research Reactor (CMRR) to investigate their in-situ tritium release behavior and irradiation performance. The results demonstrate that HT is the main tritium release form, and adding hydrogen to the purge gas reduces tritium retention while increasing the HT percent in the purge gas. Post-irradiation experiments reveal that the irradiated pebbles darken in color and their grains swell, but the mechanical properties remain largely unchanged. It is concluded that the tritium residence time of Li₄SiO₄ made by melt spraying method at 467 ℃ is approximately 23.34 h. High-density Li₄SiO₄ pebbles exhibit tritium release at relatively low temperatures (<600 ℃) that is mainly controlled by bulk diffusion. The diffusion coefficient at 525 ℃ and 550 ℃ is 1.19 × 10^-11 cm²/s and 5.34 × 10^-11 cm²/s, respectively, with corresponding tritium residence times of 21.3 hours and 4.7 hours.

• Korean Journal of Poultry Science
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• v.33 no.3
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• pp.225-231
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• 2006

To investigate the effect of feeding rare earth (RE) on the performance of breeder hens a feeding trial with sixteen thousands of 158 day old Ross broiler breeder hens was conducted for thirty weeks. A mixture of RE- chlorides containing mainly La, Ce, and Pr was mixed into corn-soy based diet at two levels, 300 and 600 mg/kg, All the hens were housed in flat layer houses and the ratio of male to female was maintained at one to ten. Dietary supplementation of the of RE at a level of 300 mg/kg made the hens reach egg production peak higher by about 6% and earlier by about two weeks. As a result, it made higher hatchable egg production by 3.5%. It also reduced dramatically the mortality of both male and female breeders(P<0.05). Egg weight was slightly increased but egg qualify was not much influenced by dietary supplementation of RE. Egg albumin hight and Haugh unit were significantly improved while egg shell thickness, egg breaking strength and yolk color were similar to those of the control. Experimental results appeared to show a good possibility that egg fertility and hatchability were improved by feeding RE. Dietary supplementation of RE at a level of 300 mg/kg should be acceptable but not the 600 mg/kg level for breeder hens. Further studies on the effect of RE on egg fertility and hatchability appears to be necessary.

• Korean Journal of Food Science and Technology
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• v.50 no.5
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• pp.517-527
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• 2018

The current study investigated in vitro anti-diabetic and neuroprotective effects of the ethyl acetate fraction in Actinidia arguta sprouts (EFAS), on $H_2O_2$ and high glucose-induced cytotoxicity in human neuroblastoma MC-IXC cells. EFAS had high total phenolic and total flavonoid contents. An assessment of 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity of EFAS, as well as its potential for inhibiting malondialdehyde production, indicated that EFAS may possess significant antioxidant properties. EFAS exerted inhibitory effects on ${\alpha}-glucosidase$ via glycemic regulation which forms advanced glycation end products. In addition, EFAS exhibited significant acetylcholinesterase inhibitory effects. Moreover, EFAS displayed protective effects against $H_2O_2$ and high glucose-induced cell death, and inhibited the generation of reactive oxygen species in MC-IXC cells. Finally, the main physiological compound of EFAS was identified via high performance liquid chromatography as a rutin.