• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1881-1882
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• 2008

• Korean Journal of Materials Research
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• v.13 no.7
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• pp.424-428
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• 2003

The microstructure and field emission properties of carbon nanotubes(CNT) grown by Ni-catalytic chemical vapor deposition(CVD) were investigated. CVD-grown CNT had a high density of curved shape with randomly oriented. It was found that an increase in electric field caused an increase in field emission current and field emission sites of CNT. The maximum field emission current density was measured to be 3.6 ㎃/$\textrm{cm}^2$ at 2.5 V/$\mu\textrm{m}$, while the brightness of 56 cd/$\textrm{cm}^2$ was observed for the CNT-grown area of 0.8 $\textrm{cm}^2$ from a phosphor screen. Field emission current at constant electric field gradually decreased initially and then stabilized with time.

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.396-400
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• 2007

LTCC(Low Temperature Co-fired Ceramic) which offers a good performance to produce multilayer structures with electronic circuits and components has emerged as an attractive technology in the electronic packaging industry. In LTCC module fabrication process, the lamination and the sintering are very important processes and affect the electrical characteristics of the final products because the processes change the permittivity of ceramics and the dimension of the circuit patterns which have influences on electronic properties. This paper discusses the influence of lamination pressure and sintering temperature on the permittivity and the dimensional change of LTCC products. In the present investigation, it is shown that the permittivity increases along with increasing of the lamination pressure and the sintering temperature.

• Transactions of Materials Processing
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• v.23 no.8
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• pp.507-512
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• 2014

The objective of the current investigation is to establish techniques in micro pattern forming operations of polymeric circular tubes by using hydrostatic pressing. This method was developed and successfully applied to the micro pattern forming on polymeric plates. The key idea of the new technique is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature of the polymeric substrates. The new process is thought to be a promising micro-pattern fabrication technique for two reasons; first, (hydro-) isostatic pressing ensures a uniform micro-pattern replicating condition regardless of the substrate area and thickness. Second, multiple curved substrates can be patterned at the same time. With the prototype forming machine for the new process, micro prismatic array patterns, 25um in height and 90 degrees in apex angle, were successfully made on the PMMA circular tubes with diameters of 5~40mm. These results show that this process can be also used in the micro pattern forming process on curved plates such as circular tube.

• Advances in pediatric surgery
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• v.13 no.1
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• pp.30-36
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• 2007

Intestinal malrotation is usually asymptomatic and most often is found during abdominal exploration for other surgical diseases. However, a serious complication of intestinal malrotation, midgut volvulus is a true surgical emergency of childhood. The clinical findings, diagnostic procedures, treatment, and prognosis of midgut volvulus were reviewed by a retrospective study. Between 1980 and 2005, 29 patients with midgut volvulus ranging in age from 1 day and 15 years were treated at HanYang University Hospital. Seventy-nine percent of the patients presented before 1 month of age. Midgut volvulus occurred 2 times more frequently in male. The clinical findings were bilious vomiting (96.6 %), irritability (34.5 %), abdominal distention (13.8 %), abdominal pain (10.3 %), and palpable abdominal mass (6.9 %). The diagnosis was made by abdominal simple x-ray (17.2 %), upper gastro-intestinal contrast study (37.9 %), abdominal sonogram (20.7 %), abdominal CT (3.4 %), and abdominal exploration (20.7 %). Among the 29 patients, 5 patients developed gangrene of small intestine due to strangulation and underwent resection of bowel. Two patients died due to sepsis.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.122-123
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• 2014

Measurement of the strength of concrete is an important indicator of the safety of the fresh as well as old concrete structures. It is possible to evaluate the strength of the concrete by means of an ultrasonic velocity method which is a kind of non-destructive inspection method for safety diagnostic evaluation of the building structures with aging. Steel embedded in the concrete and age of the concrete may affect ultrasonic pulse velocity. In order to accurately assess the strength of the concrete, it is necessary to understand rebar embedded in the concrete, steel shapes in various forms which effect ultrasonic pulse velocity. In this study, by measuring the velocity of ultrasonic waves generated when the waves pass through the ultrasonic pulse in a direction perpendicular to the reinforcing bars embedded in concrete, the effect of reinforcing bars on ultrasonic velocity accurately was verified and used to estimate the strength of the concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.129-133
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• 2008

For the construction of Top-Down structures, it is crucial to have a solid connection between prefounded columns and slabs. This paper presents a new construction method for the connection when using a circular Concrete Filled Tube (CFT) as a prefounded column as an alternative to currently using wide flange type columns. The development of shear studded jackets along with a shear band suitable for the circular shape of the column has been made. The details and mechanism of the connection is explained together with the results of experiments which verified the structural integrity of the connection.

• The KSFM Journal of Fluid Machinery
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• v.8 no.5 s.32
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• pp.7-12
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• 2005

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers, the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better break-up of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• The KSFM Journal of Fluid Machinery
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• v.11 no.4
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• pp.52-62
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• 2008

All forecasts of a future energy demand anticipate an increase across the globe. With the increase of energy demand, the emission of $CO_2$ is also likely to increase by at least the same amount because energy supply will be based on fossil fuels, which is more apparent in a number of developing countries. In this context, the Micro Gas Turbine (MGT) is being considered as a promising solution. In order to propose a feasible concept of those technologies such as improving environmental effect and economics, we performed a sensitivity study for a biomass fueled MGT using a simulation model. The study consists of 1) the fundamental modeling using manufacturer's technical specifications, 2) the correction with the experimental data, and 3) the sensitivity study for system parameters. The simulation model was developed by PEPSE-GT 72, commercial steam/gas turbine simulation toolbox.

• The korean journal of orthodontics
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• v.13 no.1
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• pp.7-14
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• 1983

Serial cephalometric roentgenorgams of 40 Korean children (25 males, 15 females) were employed to study the growth changes of the cranial bases. As a result of this study, the following conclusions can be made: 1. The mean size of the cranial bases in males was larger than the females, especially at the age of 13. 2. In both sexes, growth of the cranial bases was seen from 6 to 13 years of age and the growth of the posterior cranial base (S-Ba) was larger than the anterior cranial base (S-N). 3, Variation in the changes of the saddle angle (Ba-S-N) was exhibited with males showing a marked tendency toward a decrease in saddle angle size.