• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.21-30
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• 2008

The fuel cell generation convert fuel source, and gas directly to electricity in an electro-chemical process. Unlike traditional and conventional turbine engines, the process of fuel cell generation do not burn the fuel and run pistons or shafts, and it has not revolutionary machine, so have fewer efficiency losses, low emissions and no noisy moving parts. A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space constraints. In this system, the fuel cell itself is nearly small-sized by other components of the system such as the fuel reformer and power inverter. So, the fuel cell energy's stationary fuel cells produce reliable electrical power for commercial and industrial companies as well as utilities. In this paper, a fuel cell system has been modeled using PSCAD/EMTDC to analyze its electric signals and characteristics. Also the power quality of the fuel cell system has been evaluated and the problems which can be occurred during its operation have been studied by modeling it more detailed. Particularly, we have placed great importance on its power quality and signal characteristics when it is connected with a power grid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.987-994
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• 2015

This study examines how single-person household expenditure patterns are different with respect to age and income groups using Tobit model. The expenditure data of the national household survey from 2006 to 2012 were used. The results show that income elasticities of all items are greater than 1 except for food & beverage, housing, water, electricity & gas, and Communication. Income elasticities are significantly different among consuming items. Additionally the income elasticities are also different between various age and income groups of single-person households. Therefore governments and businesses have to take this into account when devising their policies or strategies regarding single-person households. Especially, businesses need to adopt a strategy targeted at single-person households with high income and buying power such as unmarried professional people. As the number of single-person household increases the proportion of expenditures on necessities such as beverage, food, and energy is expected to decrease while that on services increases. Consequently policy responses are required to prepare for the expansion of service industries such as health, hospital, and housekeeping services.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1126-1139
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• 2014

World is experiencing abnormal weather caused by urbanization and industrialization increasing greenhouse gas and one of these phenomenon domestically happening is flood and drought. The increase of green-house gases is due to urbanization and industrialization acceleration which are causing abnormal climate changes such as the El Nino and a La Nina phenomenon. It is expected that there will be many difficulties in water management, especially considering the topography and seasonal circumstances in Korea. Unlike in the past, a variety of water conservation initiatives have been undertaken like the river-management flow and water capacity expansion projects. To meet the increasing demand for water resources, new environmentally-friendly small and medium-sized dams have been built. Therefore, the development of a new paradigm for water resources management is essential. This study shows that additional security is needed for potential water resources through diversion tunnels and is very important to consider for future water supplies and situations. Using RCP 6.0 and RCP 8.5 in representative concentration pathway climate change scenario, specific hydrologic data of study basin was produced to analyze past observed basin rainfall tendency which showed both scenario 5%~9% range increase in rainfall. Through sensitivity analysis using objective function, population in highest goodness was 1000 and cross rate was 80%. In conclusion, it is expected that the results from this study will help to make long-term and stable water supply plans by using the potential water resource evaluation model which was applied in this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.329-329
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• 2007

Photoconductive poly crystalline lead oxide coated on amorphous thin film transistor (TFT) arrays is the best candidate for direct digital x-ray detector for medical imaging. Thicker films with lessening density often show lower x-ray induced charge generation and collection becomes less efficient. In this work, we present a new methodology used for the high density deposition of PbO. We investigate the structural properties of the films using X-ray diffraction and electron microscopy experiments. The film coatings of approximately $200\;{\mu}m$ thickness were deposited on $2"{\times}2"$ conductive-coated glass substrates for measurements of dark current and x-ray sensitivity. The lead oxide (PbO) films of $200\;{\mu}m$ thickness were deposited on glass substrates using a wet coating process in room temperature. The influence of post-deposition annealing on the characteristics of the lead oxide films was investigated in detail. X-ray diffraction and scanning electron microscopy, and atomic force microscopy have been employed to obtain information on the morphology and crystallization of the films. Also we measured dark current, x-ray sensitivity and linearity for investigation of the electrical characteristics of films. It was found that the annealing conditions strongly affect the electrical properties of the films. The x-ray induced output charges of films annealed in oxygen gas increases dramatically with increasing annealing temperatures up to $500^{\circ}C$ but then drops for higher temperature anneals. Consequently, the more we increase the annealing temperatures, the better density and film quality of the lead oxide. Analysis of this data suggests that incorporation and decomposition reactions of oxygen can be controlled to change the detection properties of the lead oxide film significantly. Post-deposition thermal annealing is also used for densely film. The PbO films that are grown by new methodology exhibit good morphology of high density structure and provide less than $10\;pA/mm^2$ dark currents as they show saturation in gain (at approximate fields of $4\;V/{\mu}m$). The ability to operate at low voltage gives adequate dark currents for most applications and allows voltage electronics designs.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.146-160
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• 2017

$CO_2$ sequestration for alleviating global warming is a hot issue in the world. In this study, TOUGH2 and FLAC3D were combined for analyzing the hyro-mechanical coupling behaviors expected in $CO_2$ sequestration and applied it to Sleipner project carried out in Norway. In the analysis, the influence of pore pressure on in situ stress was considered and the influence of caprock permeability on hydro-mechanical behaviors was analyzed. In the condition of constant injection rate, pressure and saturation at the injection well, liquid and gas saturation in rock, major and minor stress variations with time and distance from the injection well, and horizontal and vertical displacements after injection could be investigated. The major principal stress was quickly increased in the early stage and then slowly decreased to a stable value, which was higher than the initial value. In contrast, the minor principal stress returned to initial value after some increase in the early stage. Surface upheaval was steadily increased and it was up to 15mm in 2 years after injection. When the caprock's permeability was changed from $3e-15m^2{\sim}3e-18m^2$, it was found that the injection well pressure and surface upheaval were inversely propotional to the permeability.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.73-82
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• 2016

PURPOSES: The national highways and expressways in Korea constitute a total length of 17,951 km. Of this total length of pavement, the asphalt pavement has significantly deteriorated, having been in service for over 10 years. Currently, hot in-place recycling (HIR) is used as the rehabilitation method for the distressed asphalt pavement. The deteriorated pavement becomes over-heated, however, owing to uncontrolled heating capacity during the pre-heating process of HIR in the field. METHODS: In order to determine the appropriate heating method and capacity of the pre-heater at the HIR process, the heating temperature of asphalt pavement is numerically simulated with the finite element software ABAQUS. Furthermore, the heating transfer effects are simulated in order to determine the inner temperature as a function of the heating system (IR and wire). This temperature is ascertained at $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$, and $800^{\circ}C$ from a slab asphalt specimen prepared in the laboratory. The inner temperature of this specimen is measured at the surface and five different depths (1 cm, 2 cm, 3 cm, 4 cm, and 5 cm) by using a data logger. RESULTS: The numerical simulation results of the asphalt pavement heating temperature indicate that this temperature is extremely sensitive to increases in the heating temperature. Moreover, after 10 min of heating, the pavement temperature is 36%~38% and 8%~10% of the target temperature at depths of 25 mm and 50 mm, respectively, from the surface. Therefore, in order to achieve the target temperature at a depth of 50 mm in the slab asphalt specimen, greater heating is required of the IR system compared to that of the gas. CONCLUSIONS : Numerical simulation, via the finite element method, can be readily used to analyze the appropriate heating method and theoretical basis of the HIR method. The IR system would provide the best heating method and capacity of HIR heating processes in the field.

• Journal of Chest Surgery
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• v.27 no.2
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• pp.99-113
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• 1994

Pentastarch is a new synthetic hydroxyethyl starch similar to hetastarch. We report on the clinical comparisons the clinical efficacy and safety of 10% pentastarch in prime solutions for CPB in cardiac operations with that of 20% serum albumin. During CPB, group P [n = 20] received 500ml of 10% pentastarch and group A [n = 20] received 100ml of 20% albumin in prime solutions The postoperative time of ICU stay in group P and the day and amount of chest drain, hospital stay in group A were longer [p<0.05]. Fresh whole blood and PRBC were added only in group A and a higher amount of hartman solution was added in group A during CPB [p<0.05]. Prothrombin time was prolonged preoperatively and 2 days postoperatively in group A and 7 days postoperatively in group P [p<0.05] but there were no significant differences in bleeding time or fibrinogen level. Platelet count was higher immediately postoperatively in group A and preoperatively and 1, 2, and 7 days postoperatively in group P [p<0.05].Total protein and albumin level were higher 1 day postoperatively in group A and 2 and 7 days postoperatively in group P [p<0.05]. BUN was increased 2 days postoperatively in group A and Cr was increased 1 day postoperatively in group P [p<0.05]. CPK was higher preoperatively and 1, 2, and 7 days postoperatively in group A and plasma hemoglobin level was also higher 2 and 7 days postoperatively in group A [p<0.05]. There were no significant differences in arterial blood gas analysis but higher pO2 and lower pCO2 levels were maintained in group P and ejection fraction was higher 7 days postoperatively in group P [p<0.05]. Both groups were improved postoperatively in NYHA class and the hemodynamic parameters such as MAP, CO, CI, SV, LVSWI were well maintained in group P [p<0.05]. The amount of blood products used was higher in group A and urine output was higher immediately postoperatively in group A and 1, 2 days postoperatively in group P and the chest output was higher in group A. The complications were developed in 7 patients in group A and 5 patients in group P and mortality was not present in both groups.In conclusion, 10% pentastarch is as safe and effective as 20% albumin in prime solutions for cardiopulmonary bypass in cardiac operations.

• Journal of Trauma and Injury
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• v.21 no.1
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• pp.46-52
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• 2008

Purpose: This study was to evaluate the effect of arterial embolization on survival in patients with pelvic bone fractures and arterial bleeding. Methods: From January 2001 to December 2007, in all, 18 patients with pelvic bone fractures that had been treated with interventional arterial embolization were included in this retrospective study. The Injury Severity Score (ISS), the Revised Trauma Score (RTS), the initial hemodynamic status, the blood gas analysis, blood transfusion data, and mortality were the main outcome measurements. Results: Pelvic bone fractures were classified into lateral compression (LC), antero-posterior compression (APC), vertical shear (VS), and combined (CM) type according to the Young-Burgess classification. The Survivor group included 11 patients (61.1%), and the non-survivor group included 7 patients (38.9%). The mean ages for the survivor and the non-survivor groups were 40.0 and 45.6 years (p=0.517). The types of pelvic bone fractures were LC 11 (61.1%), APC 6 (33.3%), and VS 1 (5.6%): LC 7 (63.6%), and APC 4 (36.4%) in the survivor group and LC 4 (57.1%), APC 2 (28.6%), and VS 1 (14.3%) in the non-survivor group. The internal iliac artery was the predominant injured vessel among both the survivors (n = 5, 45.5%) and the non-survivors (n = 4, 57.1%). No differences in initial blood pressures, ISS, and RTS existed between the two groups, but the arterial pH was lower in the non-survivor group (pH 7.09 (${\pm}0.20$) vs 7.30 (${\pm}0.08$), p=0.018). The number of transfused 24-hour units of packed RBC was greater in the non-survivor group ($24.1{\pm}12.5$ vs $14.4{\pm}6.8$, p=0.046). Conclusion: No differences in initial blood pressure and trauma scores existed between survivors and non-survivors with pelvic bone fractures, who had been treated with arterial embolization, but arterial pH was lower the in non-survivors.

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.456-460
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• 2011

Recently, the size of currently-researched components and devices reduces nano-scale. Thus, it is important and emphasizes the analyses of physical properties in nano scale. Especially, the mechanical properties are not over micro-scale components but nano-scale components with different characteristics that has been reported. However, most analytical methods for currently studying in nano-scale are related to spectroscopy and electronics, affected the limitation of viewing size that these methods give only average information. In this research, the representative nanotribology analyses, nano-indenter study the physical and mechanical properties of W-N thin film for nano region and nano depth within nano-scale that the thickness of W-N diffusion barrier has less than tens of nanometers. The Scanning probe microscopy (SPM) study the surface image. From these results, the hardness of W-N thin film underneath the nano-surface decreased from 57.67 GPa to 9.1 GPa according to the increase of nitrogen gas flow. The elastic modulus of W-N thin film underneath the nano-surface also decreased from 575.53 GPa to 178.1 GPa.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.244-250
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• 1999

MOCVD TiN films were prepared from a new TiN precursor, tetrakis(etylmethylamino)titanium (TEMAT) and ammonia. Deposition of TiN films from a single precursor, TEMA T yielded the growth rates of $70 to 1050\AA$/min, depending on the deposition temperature. Furthermore, the excellent bottom coverage of -90% over $0.35\mu\textrm{m}$ contacts was obtained at $275^{\circ}C$. The addition of ammonia to TEMA T lowered the resistivity of as- deposited TiN film to ~ $800\mu\omega-cm$ from $3500~6000\mu\omega-cm$ and improved the stability of TiN film in air. Examination of the films by Auger electron spectroscopy(AES) showed that the oxygen and carbon contents decreased with the addition of ammonia. However, increasing ammonia flow rate decreased the bottom coverage of TiN films over $0.5\mu\textrm{m}$ contacts, probably due to the high sticking coefficient of intermediate species produced from the gas phase reaction of TEMA T and ammonia. Based on the byproduct gases detected by the quadrupole mass spectrometer (QMS), the transammination reaction was proposed to be responsible for TiN deposition. In addition, XPS analysis revealed that the carbon in the films made from TEMA T and ammonia was metallic carbon, suggesting that $\beta$-hydrogen activation process occurs competitively with the transammination reaction.