• Resources Recycling
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• v.12 no.5
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• pp.42-49
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• 2003

Characteristics of reduction and carbidization for hematite ore with a wide size range have been investigated at high temperature(590∼64$0^{\circ}C$) under $H_2$ and $H_2$-CO gas mixtures. The apparent activation energy for reduction of hematite ore with H2 gas was found to be 20 kJ/mol. The weight loss by reduction was about 28% md the weight gain by carbidization was about 5%. The measured values of weight change were compared with those calculated from equation (3) & (5) and fairly good agreement was obtained. The rate of carbidization was increased with an decrease in temperature, particle diameter and gas ratio($H_2$/ CO). The free carbon was increased with decrease in gas ratio($H_2$/ CO). The rate of carbidization was increased with mixing of $H_2$ gas but this effect was not proportional to fraction of $H_2$ gas. It was also found that the rate of carbidization was the maximum in the $H_2$ gas fraction of 0.5. It is considered that $H_2$ plays a part as a catalyst for formation of iron carbide($Fe_3$C).

• Journal of Power Electronics
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• v.11 no.4
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• pp.408-417
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• 2011

The plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. The PHEV battery would be recharged from the power grid at home or at work and would thus allow for a reduction in the overall fuel consumption. This paper proposes an integrated power electronics interface for PHEVs, which consists of a novel Eight-Switch Inverter (ESI) and an interleaved DC/DC converter, in order to reduce the cost, the mass and the size of the power electronics unit (PEU) with high performance at any operating mode. In the proposed configuration, a novel Eight-Switch Inverter (ESI) is able to function as a bidirectional single-phase AC/DC battery charger/ vehicle to grid (V2G) and to transfer electrical energy between the DC-link (connected to the battery) and the electric traction system as DC/AC inverter. In addition, a bidirectional-interleaved DC/DC converter with dual-loop controller is proposed for interfacing the ESI to a low-voltage battery pack in order to minimize the ripple of the battery current and to improve the efficiency of the DC system with lower inductor size. To validate the performance of the proposed configuration, the indirect field-oriented control (IFOC) based on particle swarm optimization (PSO) is proposed to optimize the efficiency of the AC drive system in PHEVs. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point, where the PSO is applied to evaluate the optimal flux. Moreover, an improved AC/DC controller based Proportional-Resonant Control (PRC) is proposed in order to reduce the THD of the input current in charger/V2G modes. The proposed configuration is analyzed and its performance is validated using simulated results obtained in MATLAB/ SIMULINK. Furthermore, it is experimentally validated with results obtained from the prototypes that have been developed and built in the laboratory based on TMS320F2808 DSP.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.822-828
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• 2002

Fabrication and electrical characterization of R. F. High-power unit capacitors were investigated to study on condition of fabrication processing for R. F. High-power unit capacitor and electrical characteristics according to addition of $ZrO_2$. The unit capacitors were fabricated using tape casting. The optimum mixture ratio of dielectrics and mixing binder for the slurry fabrication was 57.5∼60.0: 42.5∼40.0 wt%. The slurry viscosity was 4000∼5000 cps and casting state of green tape fabricated using these slurry was excellent. Optimum stacking was made by 200 kg/$cm^2$ pressure with 80$^{\circ}C$ heating. $ZrO_2$ was added to improve the electrical characteristics of unit capacitor, especially breakdown characteristics. The dielectric constant and loss factor of the unit condenser having different $ZrO_2$ amounts was not changed in the addition range of 1 to 5 wt%. Also, dielectric constant was not changed in the frequency range of 10 to 500 kHz. It was found that characteristics of resistance voltage was improved through the formation of $CaZrO_3$ and the reduction of particle size as about 3wt% $ZrO_2$ was added.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.4
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• pp.433-441
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• 2024

This study aims to prevent freezing of existing domestic buildings by developing an energy storage mortar with increased energy efficiency that can reduce the increase in carbon emissions and maintenance costs due to external energy use due to heat wires in civil engineering and buildings with embedded heat wires. I suggest. Research has focused on incorporating phase change materials (PCMs) into common cement composites to provide latent heat performance. However, concrete mixed with phase change materials shows problems such as leakage of phase change materials, decreased strength, and insufficient thermal performance. To overcome this problem, we encapsulate phase change materials using microcapsules and mix them into cement composites to minimize strength loss and leakage, and use multi-walled carbon nanotubes and silica fume to minimize the strength reduction of concrete. A heat storage cement composite was developed. When high-efficiency heat storage cement was used as a replacement for ordinary cement composite in an environment where heat wires were buried, the effect was shown to reduce energy by about 42 %, and compared to a cement composite containing only PCM, the compressive strength and bending strength were 18 % and 23 %, respectively. was improved and its effectiveness was proven.

• Journal of Nutrition and Health
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• v.31 no.9
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• pp.1446-1456
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• 1998

Bones are important parts in sustaining the shape of the body, but they are also metabolic organs which undergo bone remodeling by constant bone resorption and formation. Osteoporosis, the typical metabolic bone disease, is characterized by a reduction in bone mineral density (BMD). Women more than men are at risk fir osteoporosis-related fractures, especially in the lumbar spine, wrist, and hip region. Risk of fracture depends on one's BMD, which open determined by the peak bone mass value achieved at skeletal maturity and followed by subsequent age-and menopause-related bone loss. Genetic and environmental factors are known to play a key role in bone metabolism and diet is considered as one of the important environmental factors. The purpose of the present study was to assess the status of BMD and bone mineral content(BMC) to clarify the relationships between dietary intakes and the risk of osteoporosis in adult women in Taegu. Subjects were 130 healthy females in between 20 and 69 years of age. BMD and BMC of the lumbar spine(venebrae L2-4) of the subjects were measured by dual energy X-ray absorptiometry. The average age of the subjects was 47.4${\pm}$11.7 years old, the average weight was 57.2${\pm}$8.4kg, the average age of menarche was 16.6${\pm}$1.9 years old and the average age of menopause was 48.4${\pm}$5.3 years old. The nutrient intakes of the subjects measured by the convenient method were generally lower than the level of RDA. The result of nutrient intake assessed has shown that the average energy intake was 1701${\pm}$316kca1 which is 85.1% of the RDA and the average calcium intake was 485.4${\pm}$172.3mg which is 69.3% of the RDA. The intakes of protein, vitamin A, vitamin B$_1$, niacin were greater than the RDA, whereas the remaining nutrient intakes were lower than the RDA. The average BMD of the subjects was shown to be 1.06${\pm}$1.09g/$\textrm{cm}^2$. The highest BMD of 1.24${\pm}$0.14g/$\textrm{cm}^2$ was noticed in the subjects of 30s compared to 20s, 40s, 50s, 60s. The BMD values were compared by the relative body weight(R3W) of the menopause subjects, and it was found that the underweight group had significant lower BMB while the rest of the groups did not have any differences in BMD. The most strongly correlated nutrient with BMD among the menopause subjects appeared to be calcium. The women whose Ca intakes were higher than 500mg showed the significantly higher BMD than those with Ca intakes lower than 500mg. This study suggests that the most effective way to prevent osteoporosis and to reduce the incidences of fractures seems to be minimizing bone loss through the adequate intake of calcium as well as avoiding underweight, especially in menopausal women. (Korean J Nutrition 31(9) . 1446-1456, 1998)

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.276-284
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• 1993

The ABB-CE System-80 reactor power cutback system(RPCS) is designed to enable continuous operation of the reactor without trip in the events of the loss of one of the two main feedwater pumps and loss of load, and thus improves plant availability in a cost effective manner. In this study expansion of RPCS has been investigated for continuous reactor operation without trip in the event of an inward control element assembly(CEA) deviation including a single rod drop. Under the expanded function of RPCS the control system will provide a rapid core power reduction on demand by releasing CEAs to drop into the core and reduce the turbine power, if necessary, to follow the reactor power variation. This design feature which is included as the new design features to be incorporated in the ABB-CE System-80+ meets the EPRI advanced light water reactor(ALWR) requirements. For this study core analysis models of System-80+ have been developed to simulate the nuclear steam supply system(NSSS) response as well as the RPCS initiation of rapid CEA insertion. The results of this study demonstrate that the reactor trip can be avoided in the event of inward CEA deviation including a single rod drop by the RPCS initiation and thus the plant availability and capacity factor would be increased.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.11a
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• pp.51-55
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• 2003

The thermal behavior of NiFe$_2$O$_4$ prepared by a solid-state reaction was investigated for H$_2$ generation by the thermochemical cycle. The reduction of NiFe$_2$O$_4$ started from 800 $^{\circ}C$, and the weight loss was 0.2-0.3 wt％ up to 1000 $^{\circ}C$. At this reaction, NiFe$_2$O$_4$ was reduced by release of oxygen bonded with the Fe$^3$ion in the B site of NiFe$_2$O$_4$. In the $H_2O$ decomposition reaction, H$_2$ was generated by oxidation of reduced NiFe$_2$O$_4$. The crystal structure of NiFe$_2$O$_4$ for redox reaction maintained spinel structure. Then, NiFe$_2$O$_4$ is excellent material in the thermochemical cyclic reaction due to release oxygen at low temperature for the reduction reaction and produce H$_2$ maintaining crystal structure for redox reaction.

• Journal of the Korean Dietetic Association
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• v.15 no.2
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• pp.179-187
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• 2009

In this study, we examined whether the glycemic index (GI) values of boiled white rice (GI=86) and boiled white rice mixed with grains (GI=58) could influence the total energy intake and satiety rate of a rice-based diet. Thirty adult females participated in this study, in which they ate boiled white rice, or boiled white rice mixed with grains, along with side dishes for lunch, and then ate the same white rice diet for dinner in the lab once a week for 2 weeks. There was no significant difference in the visual analogue scales for taste between the two diets. Although there were no differences between the subjects' energy intakes for side dishes, the total energy consumed from the boiled white rice mixed with grains diet (520.5 kcal) was significantly (p<0.001) lower than that consumed from the boiled white rice diet (560.2 kcal). For dinner, the subjects consumed significantly (p<0.001) lower calories when they had eaten the boiled white rice mixed with grains diet for lunch as compared to the boiled white rice diet. In addition, the subjects reported significantly (p<0.01, p<0.001) higher satiety rates after consuming the boiled white rice mixed with grains diet compared to the boiled white rice diet, despite consuming lower calories. In conclusion, these results indicate that consuming low GI rice such as boiled white rice mixed with grains substituted for boiled white rice, may be a useful strategy for weight loss and weight management since individuals will consume less energy without experiencing a reduction in satiety.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.185-192
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• 2010

The chemical-looping combustion(CLC) has advantages of no energy loss for separation of $CO_2$ without $NO_x$ formation. This CLC system consists of oxidation and reduction reactors where metal oxides particles are circulating through these two reactors. In the present study, the reaction kinetic equations of iron oxide oxygen carriers supported on bentonite have been determined by the shrinking core model. Based on the reactivity data, design values of solid circulation rate and solids inventory were determined for the rector. Two types of interconnected fluidized bed systems were designed for CLC application, one system consists of a riser and a bubbling fluidized bed, and the other one has a riser and two bubbling fluidized beds. Solid circulation rates were varied to about $30kg/m^2s$ by aeration into a loop-seal. Solid circulation rate increases with increasing aeration velocity and it increases further with an auxiliary gas flow into the loop-seal. As solid circulation rate is increased, solid hold up in the riser increases. A typical gas leakage from the riser to the fluidized bed is found to be less than 1%.

• Journal of Nutrition and Health
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• v.30 no.2
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• pp.155-169
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• 1997

This study investigated the effect of weight control by using the commercial appetite suppressant ((-)-hydroxycitric acid(HCA) formula) and nutrition education on 72 obese women over a period of 8 weeks. During the study it conducted nutritional education for women to control their weight, thus analyzed their changes in anthropometric variables. All obese women were randomized in a double-blind method to consume either HCA(HCA group : experimental group) or placebo(placebo group : control group). Two groups were also divided randomly into 2 groups combined with commercial formula diet in 1 meal a day(HD group and PD group : HCA + gormula diet and placebo + formula diet) or not(HO group and conducted with 4 groups(HD, HO, PD, and PO group). All subjects were assigned to consume 800-1500kcal/d balanced diet which is 500kcal less than their usual energy requirement. To evaluate the effect of the weight control program, weight, percent of body fat, waist and hip circumferences, and 5 skinfold thickness were measured up to 5 times in all obese women. The mean weight of the subjects at the onset of the study was 76.5$\pm$10.6kg. The mean body mass index(BMI) wa 30.1$\pm$3.8 and it was in the upper 5 percentile of mean BMI of Korean women. At the end of the program, mean weight loss was 3.5kg after 2 weeks(p<0.001), and 5.8kg after 4 weeks(p<0.001). The waist, hip ratio(WHR) and skinfold thickness measurements of biceps, triceps, subscapular, suprailiac and abdominum showed significant reduction over the entire study period(p<0.05). These outcome were evaluated by effect of nutritional education and counselling. The reduction of % of body fat was significantly different among the 4 groups. Women who administrated HCA demonstrated more change in weight, BMI than the placebo group. There was also significant reduction in body composition (% of body fat, WHR, and skinfold thickness) than the other groups. The HD group which was administrated HCA combined with formula diet was more decreased than other groups. It showed that this program using commercial HCA and formula diet induced not only a change in weight but also a change in body composition. The outcome of this study suggests that HCA has a more effctive change on weight control which is carried out with nutritional education and counselling.