• Korean Journal of Metals and Materials
• /
• v.49 no.1
• /
• pp.85-91
• /
• 2011

Alnico magnets can be used as magnetic bearings for the precise electric power measuring instruments such as watt-hour meters because they have high remanence ($B_r$), relatively high maximum energy product ($(BH)_{max}$), and excellent temperature stability. In this study, Alnico composite magnets were fabricated by appropriately mixing alnico alloy powders with epoxy resin and binder. The Alnico powders mixed with epoxy resin and a hardening agent with a mixing ratio of 96:4 were pressed and then cured to be a toroid-type ring magnet with an outer diameter (${\Phi}_{out}$) of 15 mm, an inner diameter (${\Phi}_{in}$) of 6.5 mm and a thickness (t) of 2.5 mm, respectively. The magnetic properties of the Alnico ring magnets were varied with the mixing ratio of Alnico powders that possess different average particle sizes. The Alnico ring magnet prepared by mixing 5 wt% of $50{\mu}m$ (small size) powder, 15~20 wt% of $150{\mu}m$ (medium size) powder, and 75~80 wt% of $300{\mu}m$ (large size) powder showed the best magnetic properties (remanent induction, coercive force, maximum energy product, and surface flux density). In addition, measurements of temperature and moisture characteristics for the Alnico ring magnets showed that the surface flux densities of the N and S poles decreased little and the repulsive distance between the magnets decreased as small as 0.05 mm after 10 days.

• Wind and Structures
• /
• v.32 no.3
• /
• pp.227-238
• /
• 2021

This study analyzed the pressure patterns and local pressure of tall buildings with corner modifications (recessed and chamfered corner) using wind tunnel tests and proper orthogonal decomposition (POD). POD can distinguish pressure patterns by POD mode and more dominant pressure patterns can be found according to the order of POD modes. Results show that both recessed and chamfered corners effectively reduced wind-induced responses. Additionally, unique effects were observed depending on the ratio of corner modification. Tall building models with recessed corners showed fluctuations in the approaching wind flow in the first POD mode and vortex shedding effects in the second POD mode. With large corner modification, energy distribution became small in the first POD mode, which shows that the effect of the first POD mode reduced. Among building models with chamfered corners, vortex shedding effects appeared in the first POD mode, except for the model with the highest ratio of corner modifications. The POD confirmed that both recessed and chamfered corners play a role in reducing vortex shedding effects, and the normalized power spectral density peak value of modes showing vortex shedding was smaller than that of the building model with a square section. Vortex shedding effects were observed on the front corner surfaces resulting from corner modification, as with the side surface. For buildings with recessed corners, the local pressure on corner surfaces was larger than that of side surfaces. Moreover, the average wind pressure was effectively reduced to 88.42% and 92.40% in RE1 on the windward surface and CH1 on the side surface, respectively.

• Nuclear Engineering and Technology
• /
• v.56 no.1
• /
• pp.78-91
• /
• 2024

Double steel plate concrete composite shear wall (SCSW) has been widely utilized in nuclear power plants and high-rise structures, and its shear connectors have a substantial impact on the seismic performance of SCSW. Therefore, in this study, the mechanical properties of SCSW with angle stiffening ribs as shear connections were parametrically examined for the reactor containment structure of nuclear power plants. The axial compression ratio of the SCSW, the spacing of the angle stiffening rib arrangement and the thickness of the angle stiffening rib steel plate were selected as the study parameters. Four finite element models were constructed by using the finite element program named ABAQUS to verify the experimental results of our team, and 13 finite element models were established to investigate the selected three parameters. Thus, the shear capacity, deformation capacity, ductility and energy dissipation capacity of SCSW were determined. The research results show that: compared with studs, using stiffened ribs as shear connectors can significantly enhance the mechanical properties of SCSW; When the axial compression ratio is 0.3-0.4, the seismic performance of SCSW can be maximized; with the lowering of stiffener gap, the shear bearing capacity is greatly enhanced, and when the gap is lowered to a specific distance, the shear bearing capacity has no major affect; in addition, increasing the thickness of stiffeners can significantly increase the shear capacity, ductility and energy dissipation capacity of SCSW. With the rise in the thickness of angle stiffening ribs, the improvement rate of each mechanical property index slows down. Finally, the shear bearing capacity calculation formula of SCSW with angle stiffening ribs as shear connectors is derived. The average error between the theoretical calculation formula and the finite element calculation results is 8% demonstrating that the theoretical formula is reliable. This study can provide reference for the design of SCSW.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.96-101
• /
• 2012

An experimental study was conducted to investigate the performance of a concentrating photovoltaic cell (CPV) against temperature. It is know that a high efficiency of a CPV can be achieved only with proper cell temperature as well as high concentration ratio (CR). This study is concerned with appropriate cooling condition for a liquid-convection cooler for the best performance of a specific CPV. A series of experiments was conducted in a range of cell temperatures as a result of varying cooling conditions, while the concentration ratio was 390 and the solar irradiation flux was higher than 900 $W/m^2$ in outdoor environment. The CPV had a planar dimension of 10 by 10 mm. A Fresnel lens was used as a concentrator, of which the dimension was 221 mm(W) ${\times}$ 221 mm(L) ${\times}$ 3 mm(t) and the transmissivity was known to be 0.8. The cooler was attached to the bottom side of the CPV and had a contact area of 21 mm(W) ${\times}$ 26 mm(L), which was identical to the size of the base plate of the CPV. The coolant temperature was controlled by an isothermal bath and the flow rate was controlled and measured by a flowmeter. The experimental results showed that the average of power efficiency of the CPV decreased from 28.6 % to 24.7 % as the cell temperature increased from $36^{\circ}C$ to $97^{\circ}C$. An appropriate cooling method of a CPV might increase the power conversion efficiency by about 4% for the same concentration ratio. Discussion is included from the viewpoint of the combined efficiency in addition to the power efficiency.

• Journal of Radiation Protection and Research
• /
• v.32 no.4
• /
• pp.178-183
• /
• 2007

Neutrons are high LET (linear energy transfer) radiation and cause more damage to the target cells than x-rays or gamma rays. The damage from neutrons is generally considered fatal to a cell and neutrons have a greater tendency to cause cell death through direct interaction on DNA. We performed experiments to measure growth delay ratio and oxygen enhancement ratio (OER) in mouse model system. We inoculated EMT-6 cells to the right hind leg of BALB-c mouse and X-rays and neutron beams were given when the average volume of tumors reached $200-300mm^3$. We irradiated 0, 11, 15.4 Gy of X-ray and 0, 5, 7 Gy of fast neutron beam at normoxic and hypoxic condition. The volume of tumors was measured 3 times per week. In x-ray experiment, growth delay ratio was 1.34 with 11 Gy and 1.33 with 15.4 Gy in normoxic condition compared to in hypoxic condition, respectively. In neutron experiment, growth delay ratio was 0.94 with 5 Gy and 0.98 with 7 Gy, respectively. The OER of neutron beam was 0.97. The neutron beam was more effective than X-ray in the control of hypoxic tumors.

• Korean Journal of Community Nutrition
• /
• v.1 no.1
• /
• pp.61-70
• /
• 1996

Correlations of adolescents' blood pressure with dietary factors and blood or urinary electrolytes were investigated in this study. Through the screening for blood pressures of 960 middle school students aged 13-16 years, 30 students with the mean value of SBP and DBP above 96th percentile(high blood pressure group) and the other 30 with the mean blood pressure between 48th and 52th percentiles(normal blood pressure group) were selected as the subjects. SBP/DBP of the high and talc normal blood pressure groups were $141.8{\pm}9.0$ / $83.6{\pm}5.1$ mmHg and $116.4{\pm}3.5$ / $69.8{\pm}3.7 mmHg$, respectively. The average values of age, weight, height, BMI, degree of relative crude physical activity, and family income were not different between two groups. Among nutrients for which intakes were determined by 24 hour-recall and expressed as percent RDA, intakes of total and animal calcium were lower in the high blood pressure group compared to the normal, and were negatively correlated with both SBP and DBP even when the effects of related general and other dietary factors were excluded. Whereas energy, total, animal and vegetable protein, total and animal lipid, and riboflavin were higher in intake in the high blood pressure group than in fille normal, and they were in positive correlations with SBP and/or DBP. Vitamin A and ascorbic acid intakes were also negatively correlated with DBP, though ascorbic acid intake was not different between two groups. High blood pressure group preferred higher concentration of thin rice gruel than normal group and talc preferred salt concentrations was ill positive correlation with SBP. Serum and urinary levels of Ca, Mg, Ca/Mg ratio, Na, K and Na/K ratio did not show any differences between two groups. However serum Ca/Mg retio was in negative and se겨m Mg was ill positive correlations with SBP, and urinary Na excretion was negatively correlated with SBP. Calcium intake showed negative correlation with serum Ha and Na/K ratio. Our data indicated that dietary intake of Ca, energy, protein, lipid, vitamin A and C as well as salt preference were associated with blood pressure in adolescents. It might be assumed that Ca lowered blood pressure by increasing serum Ca/Mg ratio and decreasing serum Ca/K ratio though urinary excretion of Na.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.1
• /
• pp.71-77
• /
• 2019

Recently, most of the pile foundations have been applied as a method to transfer the heavy load of the structure to the ground with high bearing capacity. In this study, the pile-cap behavior between foundation and hollow-head precast reinforced concrete(HPC) pile reinforced with longitudinal rebar and filling concrete was experimentally evaluated depending on the cyclic load and reinforcement ratio. As the drift ratio increases, it was found that the cracks pattern and fracture behavior of two types of pile-cap specimens according to the reinforcement ratio were evaluated to be similar. As the reinforcement ratio increases by 1.77 times, the BS-H25 specimen increases the maximum load by 1.47 times compared to the BS-H19 specimen. However, the ductility ratio of positive and negative was decreased by 76% and 70% respectively. After the yielding of the pile-cap reinforcing rebars, the positive and negative stiffness of the all specimens were decreased by a range from 66% to 71% and a range from 54% to 57% respectively, and the average stiffness of BS-H25 specimen is 13% higher than that of BS-H19 specimen. The cumulative dissipated energy capacity of BS-H19 and BS-H25 specimen under ultimate load state is 5.5 times and 6.6 times higher than that of service load state.

• Journal of the East Asian Society of Dietary Life
• /
• v.13 no.4
• /
• pp.267-283
• /
• 2003

This study reviewed the prisoners' dietary lift status under the world panics and Japanese food shortage based on the data of the 1920~1930's prisons' main dish supplies in Chosun, Shinchu boys' prison in Taiwan, Franue correction center in France and Moabit detention house in Germany. 1. The status of main dish food supply of Chosun prisons in 1920~1930's was as follows: 1) Meals were provided with 12 rates depending on the working activities. There were big differences in energy supply between 1$^{st}$ rate of 6045.0 ㎉ in the Mockpo prison and 12$^{th}$ rate of 1855.8 ㎉ in the Masan prison in accordance with the grain supply ratio and the diet rates. 2) The average ratio of energy provided with protein, fat and carbohydrate(PFC ratio) was 20.0: 20.2: 59.8. The supplies of protein and fat were relatively high because main dish was mostly composed of soybean. The soybean was used in 20 ~60％ of main dish in prisons except Gaesung. 3) It was estimated that PFC ratio(8.3: 8.1 : 83.6) in Gaesung boys' prison was not appropriate for growing boys because the soybean supply was low. 2. The overall comparison of nutrition supply of prisons in Chosun, Taiwan, France and Germany was as follows: 1) The daily supplies of energy in Keongsung prison was 3966.5 ㎉, of which the PFC ratio was 18.9: 16.6: 64.5. This showed that the PFC ratio seemed to be balanced, even though the total amount of energy is too high and the ratios of protein and fat were somewhat high and somewhat low, respectively. 2) The main dish of the Taiwan boys' prison was provided with 6 rates and the side dish in the from of weekly cycle menu. The energy intakes from 1$^{st}$ rate of 2862.9 ㎉ to 6$^{th}$ rate of 1388.9 ㎉ were not quite enough for growing boys. It was estimated that the amounts of protein and fat taken were small but the quality was not that bad because animal protein such as protein small fish and fried tofu were supplied. 3) In the French Frenue correction center and the German Moabit detention house, the daily total amounts of energy were 2771.3 ㎉ and 2678.7 ㎉, respectively, which was estimated as appropriate compared with standard energy amount of 3000 ㎉ at that time and the current energy RDA of 2500 ㎉ for adult. The ratio of PFC was 16.2: 12.0: 71.8 in Frenue correction center and 12.4: 14.3: 73.3 in Moabit detention house, which showed that the amount of fat was slightly lacked. From this study, it was suggested that the prisons in Chosun and Taiwan under the Japanese rule and European prisons after the world panic were making an efforts to supply prisoners the appropriate amount of energy. The only question remains is that this data may be from only the food supply plan not from the data the prisoners took in real.eal.

• Korean Journal of Community Nutrition
• /
• v.2 no.3
• /
• pp.305-318
• /
• 1997

This study was aimed at evaluating the nutritional status of Korean lactating women, who were attending peripheral community clinics in low-income areas, by anthropometric measurement, estimating dietary intakes and analyzing the contents of breast milk components, serum lipid content and fatty acid composition. Regarding anghropometric measurements, maternal circumferences decreased significantly at the trunk but not at the limbs. The skinfold thickness on all regions had the tendency to decrease during lactation. It was found that intakes of energy, protein, lipid and carbohydrates were desirable while calcium, zinc, copper and vitamin A were low and sodium was excessive. The energy $\%$of fat was 22.41$\%$of the total energy which is higher than the RDA for adults but it is proper for lactating women, but energy $\%$ from each fatty acid was usually low and an intake ratio of $\omega$6/$\omega$3 fatty acids was desirable. Accordingly, it is thought that dietary fat intake was balanced in quality. Concentrations of the nutrients in matured human milk showed the same range as that reported form different regions with the exception of calcium and magnesium which were relatively low. Serum lipid contents were decreased with the time postpartum and the average serum lipid content of lactating women were similar to the normal range of adults. Serum polyunsaturated fatty acids. especially $\omega$6 fatty acids have gradually increased with the time postpartum, but the composition were not greatly influenced by dietary intakes.

• Journal of Radiation Protection and Research
• /
• v.41 no.2
• /
• pp.179-183
• /
• 2016

Background: As an important detecting device, TLD is a widely used in the radiation monitoring. It is essential for us to study the property of detecting element. The aim of this study is to calculate the thermo-luminescence efficiency of TL elements. Materials and Methods: A batch of thermo-luminescence elements were irradiated by the filtered X-ray beams of average energies in the range 40-200 kVp, 662 keV $^{137}Cs$ gamma rays and then the amounts of lights were measured by the TL reader. The deposition energies in elements were calculated by theory formula and Monte Carlo simulation. The unit absorbed dose in elements by photons with different energies corresponding to the amounts of lights was calculated, which is called the thermo luminescent efficiency (${\eta}^{(E)}$). Because of the amounts of lights can be calculated by the absorbed dose in elements multiply ${\eta}^{(E)}$, the ${\eta}^{(E)}$ can be calculated by the experimental data (the amounts of lights) divided by absorbed dose. Results and Discussion: The deviation of simulation results compared with theoretical calculation results were less than 5%, so the absorbed dose in elements was calculated by simulation results in here. The change range of ${\eta}^{(E)}$ value, relative to 662 keV $^{137}Cs$ gamma rays, is about 30% in the energy range of 33 keV to 662 keV, is in accordance by the comparison with relevant foreign literatures. Conclusion: The ${\eta}^{(E)}$ values can be used for updating the amounts of lights that are got by the direct ratio assumed relations with deposition energy in TL elements, which can largely reduce the error of calculation results of the amounts of lights. These data can be used for the design of individual dosimeter which used TLD-2000 thermo-luminescence elements, also have a certain reference value for manufacturer to improve the energy-response performance of TL elements by formulation adjustment.