• Transactions of Materials Processing
• /
• v.12 no.4
• /
• pp.290-295
• /
• 2003

High temperature deformation behavior and prediction of final microstructure after forming of Ti-6Al-4V alloy were investigated in this study. Equiaxed and Widmanstatten microstructures of Ti-6Al-4V alloys were prepared as initial microstructures and compression tests were performed to obtain the flow curves at high temperatures (700∼110$0^{\circ}C$) and various strain rates (10$^{-4}$ ∼10$^2$/s). From the results of compression test, strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equation. To predict the final microstructure after farming, finite element analysis was performed considering the microstructural parameters such as grain size and volume fraction of second phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.11
• /
• pp.681-684
• /
• 2016

This research was carried out experiments of variety IGBTs for industrial inverter and electric vehicle. The devices for this paper were planar gate IGBT, trench gate IGBT and dual gate IGBT and we designed using same design and process parameters. As a result of experiments, the electrical characteristics of planar gate IGBT were 1,459 V of breakdown voltage, 4.04 V of threshold voltage and 4.7 V of on-state voltage drop. And the electrical characteristics of trench gate IGBT were 1,473 V of breakdown voltage, 4.11 V of threshold voltage and 3.17 V of on-state voltage drop. Lastly, the electrical characteristics of dual gate IGBT were 1,467 V of breakdown voltage, 4.14 V of threshold voltage and 3.08V of on-state voltage drop. We almost knew that the trench gate IGBT was superior to dual gate IGBT in terms of breakdown voltage. On the other hand, the dual gate IGBT was better than the trench gate IGBT in terms of on state voltage drop.

• Journal of Chest Surgery
• /
• v.14 no.3
• /
• pp.235-240
• /
• 1981

A total of 102 patients who had an Open Heart Surgery from April 1976 to July 1981 were reviewed. 55 paeitnts were congenital heart disease and 47 patients were acquired heart disease. Among SS patients of congenital heart disease, 18 T 0 F, 18 V S D, 8 A S D, and each one case of l\ulcorner 0 R V, Truncus arteriosus, Ebstein anomaly, Single ventricle, P D A, P 5, A S D + P 5, E C D, V 5 D + P D A, A - P window, D C R V were noted respectively. In 47 patients of acquired heart disease and one Ebstein patient, 46 prosthetic values were implanted: 17 had M V R, 4 had A V R, 2 had M V R + A V R, and 4 had M V R + T V R and one T V R. The operative mortality was 8.S% in acquired heart disease and 17% in congenital heart disease. The follow up period was between 6 months and 6 years. There were 3 cases of late mortality in acquired heart disease and one case in congenital heart disease.

• 전자공학회논문지 IE
• /
• v.48 no.4
• /
• pp.13-18
• /
• 2011

In this paper, we have examined electrical characteristics of LDO regulator according to the process variation using a 1 ${\mu}m$ 20 V high voltage CMOS process. The electrical analysis of LDO regulator have been performed with three kind of SPICE parameter sets (Typ : typical, FF : fast, SS : slow) by process variation which cause change of SPICE parameter such as threshold voltage and effective channel length of MOS devices. From simulation results, we confirmed that in case of SS type SPICE parameter set, the LDO regulator has 3.6 mV/V line regulation, 0.4 mV/mA load regulation and 0.86 ${\mu}s$ output voltage settling time. And in case of Typ type SPICE parameter set, the LDO regulatorhas 4.2 mV/V line regulation, 0.44 mV/mA load regulation and 0.62 ${\mu}s$ output voltage settling time. Finally, in the FF type SPICE parameter set, the LDO regulator has 7.0 mV/V line regulation, 0.56 mV/mA load regulation and 0.27 ${\mu}s$ output voltage settling time.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.3
• /
• pp.225-233
• /
• 2007

To verify which loop regions of 18S rRNA gene are suitable as species-specific genetic markers in ciliates, we analyzed the genetic variation of 18S rRNA gene among 9 Euplotes species (Hypotrichia : Ciliophora). In our result, no inter-specific variation was detected from V1, V3 and V5 regions, and the length of V7 and V8 are 44 bp and 79 bp, respectively, which are too short to make genetic marker. In contrast, V2 and V4 may be good candidate segments of species-specific diagnostic molecular markers because these two regions are most variable ($1.75{\sim}20.61%$) and showed good inter-specific phylogeny. Furthermore, the sequences of V2 and V4 are 123 bp and 306 bp, respectively in length which are enough to make species-specific marker.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.4
• /
• pp.278-283
• /
• 2002

The response of electrocardiogram(ECG) of Nile tilapia, Oreochromis niloticus [Linnaeus] was studied to the electric stimulus which was given to a certain part of body The experiments were performed in such a way that three levels of electric stimulus (20, 30, 40 Vp ； 10 msec) were given to fishes with electrode inserted into their bodies and then their ECGs were recorded continuously for 60 minutes in the water temperature of 16~18$^{\circ}C$ The results of the experiments were divided by day and night, and then were analyzed by experimental conditions as follows; 1. Nile tilapia reached a stable condition within 3 minutes after the electrode inserted into their bodies during anesthesia. In stable condition, the heart rates average was 45.8 beat/min during daytime and 45.0 beat/min at night. The action potentials average was 1.76 $mutextrm{V}$during daytime and 1.75 $mutextrm{V}$ at night. 2. The heart rates average by three levels of electric stimulus were \circled1 In the stimulus condition, the heart rates were 34.9 beat/min during daytime and 33.4 beat/min at night for the 20 Vp level, 36.8 bea/min during daytime and 36.0 beat/min at night for the 30 Vp level, and 38.0 beat/min during daytime and 36.4 beat/min at night for the 40Vp level. \circled2 In the recovery condition, the action potentials were 45.5 beat/min during daytime an 45.1 beat/min at night for the 20Vp level, 47.9 beat/min during daytime and 49.0 beat/min at night for the 30Vp level, and 51.4 beat/min during daytime and 50.7 beat/min at night for the 40Vp level 3. The action potentials average by three levels of electric stimulus were, \circled1 In the stimulus condition, action potentials were 2.54 $mutextrm{V}$ during daytime and 2.39 $mutextrm{V}$ at night for the 20 Vp level, 3.30 $mutextrm{V}$ during daytime and 2.30 $mutextrm{V}$ at night for the 30 Vp level and 6.05 $mutextrm{V}$ during daytime and 3.23 $mutextrm{V}$ at night for the 40 Vp level. \circled2 In the recovery condition, action potentials were 1.92 $mutextrm{V}$ during daytime and 1.95 $mutextrm{V}$ at night for the 20 Vp level and 2.78 $mutextrm{V}$ during daytime and 2.21 $mutextrm{V}$ at night for the 30Vp level and 3.6 0 $mutextrm{V}$ during daytime and 2.98 $mutextrm{V}$ at night for the 40 Vp level.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.9 no.2
• /
• pp.139-146
• /
• 2006

Purpose: Human astrovirus (HAstV) is known to be an important etiologic agent of acute gastroenteritis in infants worldwide. However, the prevalence of HAstV infection varies according to geographic region and patient age. The purpose of our study was to investigate the incidence of HAstV infection among hospitalized children at a tertiary hospital in Seoul. Methods: Fecal samples were collected from hospitalized children up to five years of age with acute gastroenteritis. A total of 812 fecal samples were collected from hospitalized children with acute gastroenteritis between February 2004 and January 2005. Fecal specimens were screened for rotavirus, enteric adenovirus and norovirus by enzyme immunoassay (EIA) or reverse transcriptase polymerase chain reaction (RT-PCR). HAstV positive samples were characterized by RT-PCR. Results: Rotavirus was detected in 16.9% (138/812), norovirus in 11.6% (94/812), and adenovirus in 4.0% (33/812) of the study population. HAstV was detected in 4.0% (33/812) samples by RT-PCR. The age distribution of HAstV positive patients was as follows: <12 month old, 82.0% (27/33); 1~2 years old, 6.0% (2/33); 2~5 years old, 12.0% (4/33). The seasonal distribution of HAstV positive samples was as follows; April (3), May (5), June (4), August (12), September (4), October (2), November (2), and December (1). The peak rate of HAstV infection was observed during the summer season, 2004. A mixed infection of viral agents was confirmed in 2.7% (22 /812) of the study population, most commonly with rotavirus and norovirus, and with rotavirus and HAstV. Genotype 1 was the predominant type (91%, 20/22) and genotype 8 was detected in two cases. Conclusion: The prevalence of HAstV infection was 4.0% in hospitalized children with acute gastroenteritis, and was especially high in infants. HAstV can be considered as an important etiologic agent of gastroenteritis in children.

• Journal of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.19-26
• /
• 1986

A titanium oxide thin films were prepared by air oxidation and vapour oxidation and a $TiO_2$ single crystal was reduced by heating in an argon atmosphere. All the electrode characteristics of the Ti$O_{2-x}$, thin films are not different from those of slightly reduced single crystal rutile. In cyclic voltammogram of oxygen containing electrolyte solution at Ti$O_{2-x}$ electrodes, cathodic peaks were observed at between -0.8V and -1.0V vs. SCE. The cathodic current near 0V vs. SCE in saturated solution with nitrogen was observed to be greater than in saturated solution with air. The chronoamperogram was represented by the equation of i = $i_0e^{-kt}$, when the rate constant k was represented by the equation of k =$k_0{[H^+]}^nexp(A{\eta}+E_a/RT)$ The values of activation energy $E_a $were found to be 4.6~4.8kcal/mole in overpotential range of 0.035∼0.145 V and 1.6kcal/mole in overpotential range of 0.2∼0.5V. The values of n and A were found to be 0. 1 and 5.4~5.6/V in range of 0.035~0.145V, and in range of 0.2~0.5V, to be 0.04 and 1.3/V, respectively. This can be interpreted as an totally irreversible reduction of oxygen.

• Journal of the Chungcheong Mathematical Society
• /
• v.30 no.4
• /
• pp.423-433
• /
• 2017

We introduce the concepts of double strongly (r, s)(u, v)-semiopen sets, double strongly (r, s)(u, v)-semiclosed sets and double pairwise strongly (r, s)(u, v)-semicontinuous mappings in double bitopological spaces and investigate some of their characteristic properties.

• Journal of the Korean Magnetics Society
• /
• v.21 no.6
• /
• pp.198-203
• /
• 2011

The electronic structure of ferrimagnetic spinel oxide of $FeV_2O_4$ has been investigated by employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). The Fe 2p and V 2p XAS spectra show that the valence states of Fe and V ions are ${\sim}Fe^{2.3+}$ mixed-valent states and ${\sim}V^{3+}$ states, respectively. In Fe 2p XMCD spectra, finite XMCD signals are observed for divalent $Fe^{2+}$ states only, but not for $Fe^{3+}$ states. This finding indicates that the magnetic moments of $Fe^{2+}$ ions are ordered ferromagnetically but that those of $Fe^{3+}$ ions are cancelled, implying that $Fe^{2+}$ ions play an important role in determining magnetic properties of $FeV_2O_4$.