• Nuclear Engineering and Technology
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• v.37 no.4
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• pp.363-374
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• 2005

A heterogeneous thorium-based Kyung Hee Thorium Fuel (KTF) assembly design was assessed for application in the APR-1400 to study the feasibility of using thorium fuel in a conventional pressurized water reactor (PWR). Thermal hydraulic safety was examined for the thorium-based APR-1400 core, focusing on the Departure from Nucleate Boiling Ratio (DNBR) and Large Break Loss of Coolant Accident (LBLOCA) analysis. To satisfy the minimum DNBR (MDNBR) safety limit condition, MDNBR>1.3, a new grid design was adopted, that enabled grids in the seed and blanket assemblies to have different loss coefficients to the coolant flow. The fuel radius of the blanket was enlarged to increase the mass flow rate in the seed channel. Under transient conditions, the MDNBR values for the Beginning of Cycle (BOC), Middle of Cycle (MOC), and End of Cycle (EOC) were 1.367, 1.465, and 1.554, respectively, despite the high power tilt across the seed and blanket. Anticipated transient for the DNBR analysis were simulated at conditions of $112\%$ over-power, $95\%$ flow rate, and $2^{\circ}C$ higher inlet temperature. The maximum peak cladding temperature (PCT) was 1,173K for the severe accident condition of the LBLOCA, while the limit condition was 1,477K. The proliferation resistance potential of the thorium-based core was found to be much higher than that of the conventional $UO_2$ fuel core, $25\%$ larger in Bare Critical Mass (BCM), $60\%$ larger in Spontaneous Neutron Source (SNS), and $155\%$ larger in Thermal Generation (TG) rate; however, the radio-toxicity of the spent fuel was higher than that of $UO_2$ fuel, making it more environmentally unfriendly due to its high burnup rate.

• Journal of the Korean Society of Combustion
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• v.15 no.1
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• pp.43-49
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• 2010

Co-combustion of syngas in an existing boiler can be one of the options for replacing conventional fossil fuel with alternative fuels such as waste and biomass. This study is aimed to investigate effects of syngas cocombustion on combustion characteristics and boiler efficiency. An experimental study was performed for a pilot-scale furnace with 4 oil burners. Tests were conducted with mixture-gas as a co-combustion fuel and heavy oil as a main fuel. The mixture-gas was composed of 15% CO, 7% $H_2$, 3% $CH_4$ and 75% $N_2$ for simulating syngas from air-blown gasification. And LHV of the mixture-gas was 890 kcal/$Nm^3$. Temperature distribution in the furnace and flue gas composition were measured for various heat replacement ratio by the mixture gas. Heat loss through the wall was also carried out through heat & mass balance calculation, in order to obtain informations related to boiler efficiency. Experimental results show that similar temperature distribution and flue gas composition can be obtained for the range of 0~20% heat replacement by syngas. NOx concentration is slightly decreased for higher heat replacement by the syngas because fuel NOx is decreased in the case. Meanwhile, heat loss is a bit decreased for higher heat replacement by the syngas, which implies that boiler efficiency can be a bit decreased when syngas co-combustion is applied to a boiler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1071-1074
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• 2006

The frequency response functions and loss factors, $\eta$, of structurally hollowed, rectangular, metal cantilever beams have been measured in bending vibrations within low strain amplitudes. The beams were heat treated or fined with aluminum to vary the material conditions. The measured frequency response functions at the end of the cantilevered beam were processed to calculate the structural damping ratios. The results showed that the modal frequencies and damping ratios of heat treated beam are increased due to the increase of beam rigidity with the predictions of the classical beam theory. When the beams are fined with aluminum, however, the frequencies are decreased due to the increase of mass, while the damping ratios are increased. As the agreement between measurement and classical theory is good, the performance of a beam with heat treated or fined with dissimilar material can be duplicated, for industrial and most practical purposes, by the theory developed for an internally damped homogeneous beam.

• Corrosion Science and Technology
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• v.21 no.2
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• pp.147-157
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• 2022

Electrochemical characteristics and damage behavior of 6061-T6 aluminum alloy used as a battery housing material for electric vehicles were investigated in solution simulating the acid rain environment with chloride concentrations. Potentiodynamic polarization test was performed to analyze electrochemical characteristics. Damage behavior was analyzed through Tafel analysis, measurement of damage area, weight loss, and surface observation. Results described that corrosion current density was increased rapidly when chloride concentration excceded 600 PPM, and it was increased about 7.7 times in the case of 1000 PPM compared with 0 PPM. Potentiodynamic polarization experiment revealed that corrosion damage area and mass loss of specimen increased with chloride concentrations. When chloride concentration was further increased, the corrosion damage area extended to the entire surface. To determine damage tendency of pitting corrosion according to chloride concentration, the ratio of damage depth to width was calculated. It was found that the damage tendency decreased with chloride concentrations. Thus, 6061-T6 aluminum alloy damage becomes larger in the width direction than in the depth direction when a small amount of chloride is contained in an acid rain environment.

• Fire Science and Engineering
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• v.15 no.3
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• pp.36-43
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• 2001

Several types of widely used interior upholsteries including wallpaper, veneer board and floor cover, were selected to be evaluated by using the method of NES 713 text. Test results indicates that a fire with retardant wallpaper release a large amount of toxic gases when constantly exposed to a fire source. When evaluated in terms of the masses of released gases, the release of Carbon monoxide appears the highest in case of wallpaper fire, while the ratio of CO/Mass loss appears the highest in case of floor cover fire. Therefore, it can be concluded that, a large amount of toxic gas will release from a floor cover fire with even a small quantity of fuel.

• Journal of KSNVE
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• v.1 no.2
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• pp.121-128
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• 1991

In order to use viscoelastic materials efficiently for noise and vibration control, or th qualify newly developed materials, knowledge of the Young' s modulus and loss factor is essemtial. These material properties, the so-called complex Young' s modulus, are frequently treated as dynamic charicteristics because of their dependence upon the frequency. Many techniques have been developed and verified for measuring complex Young' s modulus of viscoelastic materials. Among them, the impedance method is preferable in order to obtain the frequency information in detail. In this method, a cylindrical or prismatic specimen is excited into longitudinal harmonic vibration at one end, the other being fixed, and the resulting force is measured at the driving or fixed end. The amplitude ratio of the two signals and phase angle between them are then used to compute the material properties using various mathematical models. In this paper, the impedance method is investigated theoretically and experimentally. A way to determine the specimen geometry which is most appropriate for the identification of complex Young' s modulus using the lumped mass model is presented and discussed. Then experimental results supporting the theoretical predictions are presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.6
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• pp.550-560
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• 2000

In order to minimize compression power and analyze the cause of exergy loss for a dry ice production cycle with 3-stage compression, the variation of compression power was investigated and the exergy analysis was peformed for the cycle. In this cycle, $CO_2$, is used both as a refrigerant and as a raw material for dry ice. The behavior of compression power and irreversibility in the cycle were examined as a function of intermediate pressure. From this result, the conditions for the minimum compression power were obtained in terms of the first stage or the third stage pressure. In addition, the irreversibilities for the cycle were investigated with respect to the efficiency of compressor. Result shows that the optimum pressure is not consistent with the conventional pressure obtained from the equal-pressure-ratio assumption. This is mainly due to the change in mass flow rate of the intermediate stage compressor by the flash gas evaporation from the flash drums. Most important is that the present exergy analysis enabled us to find bad performance components for the cycle and informed us of methods to improve the cycle performance.

• Analytical Science and Technology
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• v.36 no.5
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• pp.205-215
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• 2023

In the present study, an analytical method was proposed for detecting trifluralin in aquatic products at trace concentrations. The method employed QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) and gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) as the sample preparation and measurement, respectively. The effect of the aqueous phase volume used in the QuEChERS was demonstrated, and the ratio of 10:10 (mL) between water and acetonitrile phase was used for 5 g of sample. Besides, dSPE using C18 and primary-secondary amine (PSA) was applied to remove the potential interferences from the food matrices, indicating no remarkable analyte loss. The linear range was built up from 0.50 ㎍ L^-1 to 3.0 ㎍ L^-1 (R² = 0.9993). Other criteria, i.e., repeatability (RSD_r = 0.86-1.96 %), reproducibility (RSD_R = 1.09-2.01 %), and recovery (over 90 %), were in accordance with Appendix F of AOAC (2016) for method performance. Although no trifluralin was detected for the commercial samples (fish, shrimp, and breaded shrimp), the spiked samples performed favorable recoveries and precision.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.4
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• pp.367-373
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• 1993

A 4-week energy balance study was conducted to estimate the energy expenditure (EE) of 7 high school age girl, 15 to 16 year age, by measurement of energy intakes and changes in body energy (BE) content (intake/balance technique), keeping their normal living pattern and eating behavior. Gross energy intake (GE) and fecal energy (FE) loss was measured by bomb calorimetry. Urinary energy (UE) loss was calculated from nitrogen excreted. Fat mass (FM) was determined from body density estimated from skinfold thickness. Mean constitutional ratio of carbohydrate, protein and fat for the total energy intake was 70.1$\pm$1.8%, 12.2$\pm$0.7% and 17.7$\pm$2.0%, respectively, Fecal energy loss was 2.8% proportion of the gross energy intake. Mean daily metabolizable energy estimated by subtract fecal and urinary energy loss was 2022 $\pm$ 50㎉. Total body energy change estimated from body composition change over 28days was increased 2400 $\pm$ 950㎉ . Mean daily energy expenditure was 1958$\pm$87㎉ (39$\pm$2㎉ /kg of body weight).

• The Journal of Korean Medicine
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• v.32 no.6
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• pp.30-40
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• 2011

Objectives: The purpose of this study was to determine whether gocho (苦椒) extract mesotherapy can effectively reduce weight and abdominal fat in obese patients. Methods: Forty obese participants were recruited and randomly assigned to two groups. Five participants dropped out voluntarily during the course of the study and four men were excluded from the analysis to avoid gender bias. Results are presented on a total of thirty-one women. Over an eight-week period, the treatment group (n=13) received gocho (苦椒) extract injections (100mcg/3cc) in the abdominal skin, twice per week; the control group (n=18) received normal saline injections (3cc). A mixed lidocaine and prilocaine cream (2.5%/2.5% EMLA cream) was applied before the injection. At baseline and 8 weeks, body weight, body-mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), abdominal fat, energy expenditure, and questionnaires (eating attitudes and physical activity) were evaluated in both groups. Results: Reductions in body weight (p<0.005), BMI, and WC (p<0.05) were greater in the treatment group. WHR, total fat area, and visceral fat area decreased only in the treatment group (p<0.05). Resting metabolic rate (RMR) change was correlated with weight loss only in the control group (r=-0.498, p<0.05). Before and after the treatment, there were no significant differences between the two groups in questionnaire variables (p>0.05). Conclusion: his study suggests that abdominal gocho (苦椒) extract mesotherapy might be an effective way to promote weight and abdominal fat loss in obese Korean women.