• Journal of Electrical Engineering and Technology
• /
• v.6 no.4
• /
• pp.539-542
• /
• 2011

Thin-film transistors (TFTs) are fabricated using an amorphous indium gallium zinc oxide (a-IGZO) channel layer by rf-magnetron sputtering. Oxygen partial pressure significantly changed the transfer characteristics of a-IGZO TFTs. Measurements performed on a-IGZO TFT show the change of threshold voltage in the transistor channel layer and electrical properties with varying $O_2$ ratios. The device performance is significantly affected by adjusting the $O_2$ ratio. This ratio is closely related with the modulation generation by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• Journal of the Korean Society of Safety
• /
• v.19 no.4 s.68
• /
• pp.20-24
• /
• 2004

Antifatigue failure technology take an important the part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel and improving the fatigue strength on surface. Therefore in this paper the effect of compressive residual stress by shot peening on fatigue crack growth characteristics in stress ratio(R=0.1, 0.3, 0.6)was investigated with considering fracture mechanics. There is difference between shot peening specimen and unpeening specimen. Fatigue crack growth rate of shot peening specimen was lower than that of unpeening specimen. Fatigue lift shows more improvement in the shot peening material than in the unpeening material. And compressive residual stress of surface on the shot peening processed operate resistance force of fatigue crack propagation. That is the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation.

• Journal of Navigation and Port Research
• /
• v.32 no.9
• /
• pp.729-736
• /
• 2008

Very often has it happened that Korean flag ships were detained due to the defect of the ship itself at the port they are entering into by the system of Port State Control(PSC). It does matter because the high detention ratio of Korean ships causes to increase the survey ratio of Korean ships by PSC countries, which increases overall operating costs of Korean shipping companies. Therefore Korean government should take tougher action on the detention of Korean ships. The study uses 946 inspections to formulate the model of identifying PSC-weak ships by logistic regression analysis.

• International Journal of Advanced Culture Technology
• /
• v.7 no.2
• /
• pp.218-226
• /
• 2019

In modern society, people live in an environment with artificial or natural noise. Especially, the sound that corresponds to the artificial noise makes the noise itself and affects each other because many people live and work in the city. Sounds are generated by the activities and causes of various people, such as construction sites, aircraft, production machinery, or road traffic. These sounds are essential elements in human life and are recognized and judged by human auditory organs. Noise is a sound that you do not want to hear by subjective evaluation, and it is a loud sound that gives hearing damage or a sound that causes physical and mental harm. In this study, we introduce the method of stimulating the human hearing by finger vibration and explain the advantages of the proposed method in various kinds of a noise environment. And how to improve the sound quality to improve efficiency. In this paper, we propose a method to prevent the loss of hearing loss and the transmission of sound information based on proper signal to noise ratio when using portable IT equipment in various noise environments.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.6
• /
• pp.659-666
• /
• 2015

In this paper, various influence factors on the impact-echo test which is an effective method in characterizing defects such as such as the delamination in the concrete structures were studied. The side to thickness ratio(a/h), the relative position of impacting and sensing points over the delamination that have great effects on the flexural and impact-echo(thickness) modes were investigated and examined by the parametric finite element analysis. As a result, the flexural modes dominate in the case of a/h > 2 and the thickness mode was more evident when a/h < 2. With regard to the relative position of impact source and sensing point to the defect, the flexural modes dominate even when either the loading or sensing point was over the delamination defect. However, the thickness mode prevails when both the impacting and sensing points are over the solid region beyond the delamination area.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.18 no.4
• /
• pp.271-277
• /
• 1998

Nondestructive method can include both testing itself and analysis or evaluation of the testing results. Although vast amount of testing can be accomplished in a fairly short amount of time due to the advancement of electronic technology. it is really difficult matter to identify whether the indication found during testing corresponds to be a real defect. Thus, in ultrasonic testing, advanced digital signal processing techniques have been widely studied in order to identify the shape of the defect during testing, and one of the signal processing techniques, synthetic aperture focusing technique(SAFT) was tried for holes machined in carbon steel plate in this study. Result showed that signal to noise ratio has been improved considerably compared to the result from original RF signals.

• Journal of Periodontal and Implant Science
• /
• v.38 no.sup2
• /
• pp.273-298
• /
• 2008

Purpose: The aim of this review is to introduce a novel bone-graft material for hard-tissue regeneration based on the calcium phosphate glass(CPG). Materials and Methods: CPG was synthesized by melting and subsequent quenching process in the system of CaO-$CaF_2-P_2O_5$-MgO-ZnO having a much lower Ca/P ratio than that of conventional calcium phosphates such as HA or TCP. The biodegradability and bioactivity were performed. Effects on the proliferation, calcification and mineralization of osteoblast-like cells were examined in vitro. Influence in new bone and cementum formations was investigated in vivo using calvarial defects of Sprague-Dawley rats as well as 1-wall intrabony defect of beagle dogs. The application to the tissue-engineered macroporous scaffold and in vitro and in vivo tests was explored. Results: The extent of dissolution decreased with increasing Ca/P ratio. Exposure to either simulated body fluid or fetal bovine serum caused precipitation on the surface. The calcification and mineralization of osteoblast-like cells were enhanced by CPG. CPG promoted new bone and cementum formation in the calvarial defect of Sprague-Dawley rats after 8 weeks. The macroporous scaffolds can be fabricated with $500{\sim}800{\mu}m$ of pore size and a three-dimensionally interconnected open pore system. The stem cells were seeded continuously proliferated in CPG scaffold. Extracellular matrix and the osteocalcin were observed at the $2^{nd}$ days and $4^{th}$ week. A significant difference in new bone and cementum formations was observed in vivo (p<0.05). Conclusion: The novel calcium phosphate glass may play an integral role as potential biomaterial for regeneration of new bone and cementum.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.181-181
• /
• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• Journal of Chest Surgery
• /
• v.22 no.4
• /
• pp.620-629
• /
• 1989

A clinical analysis of 138 cases of ventricular septal defect operated on from 1983 to June 1988 at the department of Thoracic and Cardiovascular Surgery, School of Medicine, Chung-nam National University was done. The following results were obtained. 1. The VSD were 27.6 % and 41.0 % respectively of 500 open heart surgery cases and 334 congenital heart disease. 2. The range of age when the VSD was repaired was 3 months to 45 years, the mean age was 10.4 years and the 53.6 % of patients were under 7 years. The sex ratio was 6:4 in males favor. 3. The two common symptoms were frequent upper respiratory infection and dyspnea whose frequency was 62.5 % and 58.7% respectively. 4. 52% of the patients was below 25 percentile of the standard body weight. 5. The most common chest PA findings were cardiomegaly and increased pulmonary vascularity. 6. On anatomical classification, perimembranous type was most common [65.5%], subpulmonary arterial type was 27.6 %, perimembranous plus subpulmonary arterial type was 3.4 % multiple VSD was 0.8 % and LV-RA defect was 2.6 %. 7. Associated cardiac anomalies were founded in 39 cases [35.5 %] and PDA and aortic valve prolapse were most common associated anomalies and extracardiac anomalies were founded in 6.7 % of patients. 8. Mean extracorporeal circulation time was 68 min. and mean aortic cross-clamping time was 42 min. 9. The postoperative complications developed in 26 % of patients and the most common one was minor wound infection. 10. Right bundle branch block developed in 54.8% of the patients who had right ventriculotomy, 40.0% of the patients who had right atriotomy and 10.5% of the patients who had pulmonary arteriotomy. 11. The overall operative mortality was 5.1 % and the operative mortality of the patients who body weigh under 10 Kg was 23.8%.

• Journal of Chest Surgery
• /
• v.26 no.8
• /
• pp.591-594
• /
• 1993

To clarify the apparent hypoplasia of the descending aorta in infants with atrioventricular septal defect[AVSD] patients, we reviewed the catheterization data and angiograms of 34 consecutive patients with AVSD less than 1 year of age who underwent repair at our institution since 1985. We compared them to 10 patients with Atrial Septal Defect[ASD] and 10 patients with Ventricular Septal Defect[VSD] who were matched for age, size and Qp/Qs. The Descending Aorta Index [DAI] of the AVSD group was not different from the VSD or ASD groups, [147.9$\pm$ 34.8 mm2/m2 versus 158.6$\pm$ 31.5 mm2/m2 and 153.2$\pm$ 43.1 mm2/m2].However, the Pulmonary Artery Index [PAI] of the AVSD group was significantly larger than the other groups [684.3$\pm$ 170.7 mm2/m2 versus 454.1$\pm$ 109.1 mm2/m2 and 534.9$\pm$ 148.4 mm2/m2][p<0.05], as was the ratio of PAI/DAI in the AVSD group [4.99$\pm$ 1.77 versus 2.89$\pm$ 0.81 and 3.6$\pm$ 0.92][p<0.05]. Despite similar Qp/Qs ratios, both the mean PA pressure and the Rp/Rs in the AVSD group was higher than the VSD and ASD groups: 43.1$\pm$ 15.6 mmHg versus 29$\pm$ 11.6 mmHg and 24$\pm$ 18.1 mmHg [p<0.05], and 0.27$\pm$ 0.22 versus 0.14$\pm$ 0.03 and 0.11$\pm$ 0.05 [p<0.05] respectively. The apparent hypoplasia of the descending aorta in infants with AVSD is an illusion created by the abnormally large pulmonary arteries, which are significantly larger than in patients with ASDs or VSDs.