• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.515-526
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• 2009

There are three main production processes in the manufacture of concrete-filled square steel columns. The first process is known as the 'box-type process' or 'four-seam method,' wherein four beams are welded together at the seams. The second is the 'cold-forming process' or 'two-seam method,' wherein the seams of two channel beams are welded together. The third is the 'pressing process' or 'one-seam method,' wherein a circular column is pressed until it becomes a square column. In calculating the production cost for the making of a steel tube, it is very important to consider the welding process to be used and the desiredthickness of the steel tube, such as a square column that was developed under a new method, formed through the four-seam flare welding method at the center of the steel column width, following the L-shape formation. Certain tests were suggested in this study to evaluate the welding amount of concrete-filled square steel columns. With the parameters of the production method of a square steel column, the thickness of the steel square columns, and the welding amount, six specimens were produced. A structural test and finite-element analysis were conducted to assess the behavior of the steel column according to the water pressure inside the steel columns.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.1321-1329
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• 2009

Web technology has allowed the rise of services such as blogs or YouTube that make possible the sharing of opinions, perspectives, and experiences with other users through contents. Online services that promote such sharing of information and communication are known as social media. Recently, the explosive growth of these services displays the carry-over of the natural sociality that all humans possess as social creatures. This study took an exploratory approach in investigating what influential relationships are involved in forming new relationships through sharing and participation, as sharing and participation are core keywords of social media. In order to do this, relationship formations were observed in actual usage environments with the use of the diary study method and in-depth interviews. This study sought to deduce necessary elements in relationship formations and examine the influences of weak ties on participation and sharing.

• Journal of Korean Traditional Oncology
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• v.11 no.1
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• pp.55-63
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• 2006

This study was conducted to investigate angiogenic inhibitory effect of Zingiberis Rhizoma methanol extract using ECV-304 cells and HT1080 fibrosarcoma cells. The viability of ECV-304 was 30% at 50${\mu}g/m{\ell}$ of Zingiberis extract and that of HT1080 was 30% at 100${\mu}g/m{\ell}$. Using the BrdU incorporation assay, Zingiberis inhibited the DNA synthesis of ECV-304 and HT1080 by 70% and 50 % at 200${\mu}g/m{\ell}$. In tube formation assay, at 10${\mu}g/m{\ell}$ of Zingiberis, tube network began to degrade and at higher doses, it was completely destroyed. Zymography demonstrated that Zingiberis extract decreased MMP-9 at 10${\mu}g/m{\ell}$ and higher doses remarkably inhibited the expression of MMP-9. These data indicate that Zingiberis Rhizoma has angiogenic inhibitory effects and shows the possibility of future anti-metastatic drug.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.2
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• pp.1-6
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• 2009

Nuclear power plants (NPP) using Alloy 600 (Ni 75wt%, Cr 15wt%, Fe 10wt%) as a heat exchanger tube of the steam generator (SG) have experienced various corrosion problems by ageing such as pitting, intergranular attack (IGA) and stress corrosion cracking (SCC). In spite of much effort to reduce the material degradations, SCC is still one of important problems to overcome. Especially lead is known to be one of the most deleterious species in the secondary system that cause SCC of the alloy. Even Alloy 690 (Ni 60wt%, Cr 30wt%, Fe 10wt%) as an alternative of Alloy 600 because of outstanding superiority to SCC is also susceptible to leaded environment. An oxide on SG tubing materials such as Alloy 600 and Alloy 690 is formed and modified expanding to complex sludge throughout hideout return (HOR) of various impurities including Pb. Oxide formation and breakdown is requisite for SCC initiation and propagation. Therefore it is expected that an oxide property such as a passivity of an oxide formed on steam generator tubing materials is deeply related to PbSCC and an inhibitor to hinder oxide modification by lead efficiently can be found. In the present work, the SCC susceptibility obtained by using a slow strain rate test (SSRT) in aqueous solutions with and without lead was discussed in view of the oxide property. The oxides formed on Alloy 600 and Alloy 690 in aqueous solutions with and without lead were examined by using a transmission electron microscopy (TEM), an energy dispersive x-ray spectroscopy (EDXS), an x-ray photoelectron spectroscopy (XPS) and an electrochemical impedance spectroscopy (EIS).

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.266-272
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• 2006

Application of power higher than the optimum operation value to an external electrode fluorescent lamps(EEFL) leads to the formation of small holes, called pinholes, which subsequently leads to lamp failure. The pinholes come from the insulating breakdown of the capacitor which is the dielectric layer between an external electrode and glass tube. The power of insulation breakdown is proportional to the electric power applied to the lamp. When a lamp current is low in the glass tube of dielectric constant K, the dielectric field strength of pinholes is about 3K kV/mm. The field strength of insulation breakdown decreases as the lamp current increases.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.362-367
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• 2003

It is shown that the effect of variable parameters on flame structures and NOx emissions in the laminar partially premixed methane-air flames with a co-axial Bunsen burner. Objectives of this paper is to understand the effects of flow variables on NOx emissions and the flame structure with OH chemiluminescence, including reconstructed image by abel inversion processing at each conditions. A fuel flowrate of 200 [cc/min] was fixed and the amount of air was varied from 400 to 1200 [cc/min]. The experimental variables were equivalence ratio(${\Phi}$ fuel split percentage(${\sigma}$ and inner tube recess(x/D). Flow conditions were ranged from $1.36{\sim}4.76$(equivalence ratio), $50{\sim}100$(fuel split percentage) and $0{\sim}20$(inner tube recess). NOx analyzer and ICCD camera with a OH filter were used as a main experimental apparatus. In addition, Abel inversion, which is a kind of tomography and valuable to estimate a two-dimensional structure of co-axial flames from cubical information, was employed for combustion diagnostics. Results from this study indicate that the main effects depend on equivalence ratio and next sigma, x/D for NOx production and OH formation. Throughout Abel inversion, we could affirm the maximum position and the tendency of OH radical intensity by variants at five axial heights above the burner exit.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1508-1515
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• 1992

Between 1975 and 1992, forty five patients with trachea stenosis received tracheoplasty for relief of obstruction. The causes of airway problem are brain contusion[19 cases, 40%], cerebrovascular disease[3 cases, 7%], drug intoxication[8 cases, 18%], psychotic problem[2 cases, 4%], trachea tumor[3 cases, 7%], adult respiratory distress syndrome[9 cases, 20%] and direct trauma[1 case, 2%]. Direct causes of trachea stenosis were complications of tracheostomy[36 cases, 80%], complications of nasotracheal intubation[5 cases, 11%], tumor[3 cases, 6%] and trauma[1 case, 2%]. Thirty one patients underwent the sleeve resection and end-to-end anastomosis. Five patients performed a wedge resection and end-to-end anastomosis. Forteen patients received the Montgomery T-tube for relief of airway obstruction. Four patients have done simple excision of granulation tissue. Two, subglottic stenosis patients were received Rethi procedure[anterior division of cricoid cartilage, wedge partial resection of lower thyroid cartilage and Montgomery T-tube molding] and the other subglottic stenosis patient underwent permanent trachea fenestration. Including cervical flexion in all patients postoperatively, additional surgical techniques for obtain tension-free anastomosis were hyoid bone release technique in two cases, and hilar mobilization, division of inferior pulmonary ligament and mobilization of pulmonary vessel at the pericardium were performed in one case. Cervical approach was used in 39 cases, cervicomediastinal in 12 cases and transthoracic in one case. Complications of tracheoplasty were formation of granulation tissue at the anastomosis site[3 cases], restenosis[9 cases], trachea-innominate artery fistula[2 cases], wound infection[2 cases], separation of anastomosis[2 cases], air leakage[3 cases], injury to a recurrent laryngeal nerve[temporary 8 cases, permanent 2 cases] and hypoxemia[1 case]. Surgical mortality for resection with primary reconstruction was 6.7%, with one death due to postoperative respiratory failure and two deaths due to tracheo-innominate artery fistula.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.259-263
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• 2002

Three different ribbons of amorphous $Til_{1-x}Be_x$ alloys such as $Ti_{0.59}Be_{0.41},\;Ti_{0.61}Be_{0.39}\;and\;Ti_{0.63}Be_{0.37}$ were made by melt-spinning method to be used as brazing filler metals for joining Zircaloy-4 nuclear fuel cladding tubes, and their crystallization behavior as well as microstructure of the brazed zone were examined. The crystallization behavior was investigated in teams of thermal stability, crystallization temperature and activation energy. The crystallization of the $Ti_{1-x}Be_x$ alloys proceeded in two steps by the formation of ${\alpha}$-Ti at a lower temperature and of TiBe at a higher temperature. The crystallization temperature and activation energy of $Ti_{1-x}Be_x$ alloys were higher and larger than those of $Zr_{1-x}Be_x$ alloys and PVD Be. Those resulted thinner joining layer with $Ti_{1-x}Be_x$ alloys, which kept sound thickness of Zircaloy-4 nuclear fuel cladding tubes after brazing. But in the brazed zones made by $Ti_{1-x}Be_x$ filler metals, a little solid-solution layers composed of Zr and Ti were formed toward the Zr cladding tube and Zr was detected in the brazed zones. Microstructure of brazed zone was changed from globular to dentrite with decreasing Be content in the $Ti_{1-x}Be_x$ filler metal.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1775-1780
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• 2003

A continuous flow system has been developed to determine trace Cu(II), Mn(II), Ni(II) and Zn(II) in a large volume of water samples by a solvent sublation technique. The mixed solution of 1,10-phenanthroline(phen) and thiocyanate ion was used as ligands for the formation of their ternary complexes. The continuous system was constructed in this laboratory with a peristaltic pump, a mini shaker, three mixing bottles and a flotation cell by connecting each part with a polyethylene tube. The flotation conditions such as the flow rate of sample solution and the injection rates of ligand, buffer and surfactant solutions have been investigated to obtain the best sublation efficiencies. Each solution flowed into the flotation cell through each polyethylene tube by the peristaltic pumps. The ternary complexes were floated and extracted into MIBK in a flotation cell of 2 L by bubbling a nitrogen gas. The absorbances of extracted analytes in MIBK were directly measured by graphite furnace-AAS. The concentrations of 1,10-phenanthroline and thiocyanate ion were $2.6\;{\times}\;10^{-3}$ M and $2.3\;{\times}\;10^{-2}$ M in the mixed solution, respectively. The pH of sample solution was adjusted to 5.0 with a buffer solution and 1%(m/v) sodium lauryl sulphate solution was added as a surfactant to support the effective flotation of the complexes. The $N_2$ gas was bubbled at 30 mL/min for 90 minutes for 20 L of sample. Reproducible results of less than 10% RSD and recoveries of 80-120% could be obtained in real samples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.291-298
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• 2010

A conventional EGR cooler, which is used in an EGR system of an automobile diesel engine, has a low heat-exchange efficiency. To maximize the heat transfer between the exhaust gas and coolant, dimples are formed on the surface of heat exchange tubes. When designing the dimpled EGR cooler, the net heat transfer areas in the conventional and dimpled tube-type EGR coolers are compared. Structural integrity evaluations are also performed by combining finite element analysis with a homogenization method. Subsequently, the process of manufacturing the dimpled tube, i.e., the formation of dimples, edge bending, center v-notch bending, compression, and plasma welding, is established and carried out. Thus, the dimpled EGR cooler is developed, and its performance is verified.