• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.4
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• pp.43-49
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• 2014

This experimental study has been conducted to scrutinize the effects of an ultrasonic standing wave (USW) on the propagating velocity and structure of methane/air premixed flame. Propagating flame was caught by high-speed Schlieren photography, and the variation of flame-behavior was analyzed in detail. It is revealed that horizontal splitting in burnt zone is resulted by the USW, and the flame propagation velocity is augmented due to the strengthened chemical reaction. Evolutionary feature of the flame perturbed by USW, maintaining a pseudo-symmetry of top and bottom flame-front about the propagation axis tends to be free from buoyancy effect.

• Composites Research
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• v.28 no.6
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• pp.389-394
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• 2015

The sound absorption coefficient and sound transmission loss of graphite intercalation compound (GIC) included epoxy composites were investigated. Epoxy resin was infused into the expanded GIC and the impedance tube method was employed to measure the sound absorption coefficient and sound transmission loss. Scanning electron microscopy photographs showed uniform distribution of the GIC in the epoxy matrix. The surface density of epoxy/GIC (20 wt%) composites decreased about 56% compared to that of pure epoxy. The sound absorption coefficient of composites increased about 3 times at the frequency range of 500~1000 Hz compared to the pure epoxy. The sound transmission loss of composites decreased with increasing the GIC content and it is attributed to the increase of pores in the composites.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.490-493
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• 2000

Mesiodens are supernumerary teeth in the region of the maxillary central incisors, a condition which can lead to disorders of the dentition. Their presence may lead to disorders, such as delay in eruption of permanent teeth, development of dentigerous cysts, resorption of adjacent roots and eruption of a supernumerary tooth into nasal cavity. The optimal time for surgical intervention is controversial. Early diagnosis is important so as to enable good prognosis. Diagnosis primarily depends on x-ray films. Panorama film, occlusal film, periapical film have been used for detection of mesiodens. But, all of them have disadvantages. $SCANORA^{(R)}$ is a multimodal radiology system which utilizes the principles of narrow beam radiology and spiral tomography. Pre-programmed imaging procedure are provided for many dental situations An optional personal computer can be connected into the unit to help design the examination. We report two cases diagnosed by $SCANORA^{(R)}$. When compared with tube shift technique, it is simple and exact method of detecting mesiodens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1741-1751
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• 2004

It is commonly requested that the steam generator tubes wall-thinned in excess of 40% should be plugged. However, the plugging criterion is known to be too conservative for some locations and types of defects and its application is limited to a single crack in spite of the fact that the occurrence of multiple through-wall cracks is more common in general. The objective of this research is to propose the optimum failure prediction models for two adjacent through-wall cracks in steam generator tubes. The conservatism of the present plugging criteria was reviewed using the existing failure prediction models for a single crack, and six new failure prediction models for multiple through-wall cracks have been introduced. Then, in order to determine the optimum ones among these new local or global failure prediction models, a series of plastic collapse tests and corresponding finite element analyses for two adjacent through-wall cracks in thin plate were carried out. Thereby, the reaction force model, plastic zone contact model and COD (Crack-Opening Displacement) base model were selected as the optimum ones for assessment of steam generator tubes with multiple through-wall cracks. The selected optimum failure prediction models, finally, were used to estimate the coalescence pressure of two adjacent through-wall cracks in steam generator tubes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.22-29
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• 2002

The conventional neon transformer systems are very bulky and heavy because it consist of leakage type transformers made of silicon steel plates. In addition, it has problems in noise by a neon transformer and in possibilities of fire and electrical shock when neon tubes are destroyed. A protection circuit is designed for all types of neon transformer loaded with one or more neon tubes. Whenever the neon tube fails to be started up, comes to the life end, encounters faults with open-circuits at the output terminals of the neon transformer, the protection circuit will be initiated to avoid more critical hazards. The input of the transformer is automatically cut off when the abnormal condition occurs, preventing waste of no-load power. To improve such problems, in this paper, a new type of neon power supply systems for neon tube is designed and implemented using inverter type circuits and a newly designed lightweight transformer. In the developed neon transformer system, a 60［Hz］power input is converted to 20［KHz］high frequency using half-wave inverters, thereby the transformer reduces its size by 1/5 in volume and 1/10 in weight.

• Journal of radiological science and technology
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• v.31 no.2
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• pp.109-114
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• 2008

There is a standard shoulder oblique method (Grashey method) available to view the shoulder joint. This method projects AP view of the shoulder joint so that the Humerus head's subuxation or joint degeneration can be easily visualized. However, in this view, the patients, with supine or sitting or erect position, have to keep their body obliquely. Whereas, the patients who are not well or operated, usually feel very uncomfortable to keep their body in this position and hence, we need other persons' help and much efforts will be needed to get the good quality shoulder joint view. Therefore, we thought of examining a method which shows the joint well by angling the tube to Medio-Lateral direction and without keeping the patients' one side upward in supine position. For this study, total 15 subjects with no history of neurological or psychiatric illness, were recruited for examinations. They consisted of 9 males and 6 females. Statistic group analysis was performed with ANOVA test. Scores of the evaluation of the experts were $1.10{\pm}0.54$ at $25^{\circ}$, $2.50{\pm}0.50$ at 30^{\circ}$, $2.85{\pm}0.36$ at $35^{\circ}$ and $2.33{\pm}0.47$ at $40^{\circ}$, respectively, and they were significant(p<0.05, Table 1). Joint space of the Humerus head and Scapula were well distinguished at $35^{\circ}$, $30^{\circ}$ and $40^{\circ}$ with the almost same score. However, the degree of distortion at $40^{\circ}$ was more severe than that at $30^{\circ}$. Ultimately, $30-35^{\circ}$ views were shown to yield good quality shoulder oblique images. In conclusion, this method may be very useful for the patients who are uncomfortable and for the emergency patients. In order to get similar or comparable view, the same X-tube angle is recommended to be used before and after the operation. Therefore, we hope that this new angled method seems to be efficient.

• Journal of Radiation Protection and Research
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• v.35 no.1
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• pp.21-25
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• 2010

Burnup of spent fuel should be determined accurately for the safety control of spent fuel. Especially, it is necessary to measure the burnup profile along the nuclear fuel axis. In the present work, an ionization chamber was designed and fabricated to measure the gamma ray profile inside the guide tube of spent fuel. The ionization chamber was composed of three parts; induction part, gas-inlet part, and sensor part. The sensor part had two electrodes; cathode and anode. A guide electrode was considered in the ionization chamber design to make the ionization chamber to be inserted easily into the guide tube. Pure gas (argon and xenon) was inserted into the ionization chamber, and the leakage current and saturation curve were measured to determine the operation characteristics of the ionization chamber. The gamma ray radiation was also measured in relatively high dose environment. The gamma ray profile of the spent fuel will be measured with the ionization chamber.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.62-69
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• 2020

This study examined Internet discourse on inter-regional co-prosperity. In particular, the study is interested in the co-prosperity between the Daegu-Gyeongbuk regions. The Internet discourse was searched through a set of four keywords: co-prosperity, economy, business attraction, and cultural tourism. The study also conducted sentiment analysis of YouTube comments to determine how the Internet responds to co-prosperity topics. The findings of the analysis are as follows. First, Internet discourse related to co-prosperity has evolved from abstract concepts to concrete cooperative measures and policy contents. Second, the discussion of co-prosperity has moved from outside help or support to self-sustaining innate motivation. Finally, YouTube sentiment analysis showed that if co-prosperity efforts between regions are promoted through concrete policy contents, it becomes easier to gain positive responses from citizens and lead a positive policy drive. In this regard, a study on Internet discourse is a useful means to detect citizens' response to inter-regional co-prosperity.

• Restorative Dentistry and Endodontics
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• v.30 no.4
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• pp.344-351
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• 2005

This study compared the microshear bond strength $({\mu}SBS)$ to end and side of enamel rod bonded by four adhesives including two total etch adhesives and two self-etch adhesives. Crown segments of extracted human molars were cut mesiodistally. The outer buccal or lingual surface was used as specimens cutting the ends of enamel rods, and inner slabs used as specimens cutting the sides of enamel rods. They were assigned to four groups by used adhesives: Group 1 (All-Bond 2), Group 2 (Single Bond), Group 3 (Tyrian SPE/One-Step Plus), Group 4 (Adper Prompt L-Pop). After each adhesive was applied to enamel surface, three composite cylinders were adhered to it of each specimen using Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to ${\mu}SBS$ testing with a crosshead speed of 1 mm/minute. The results of this study were as follows: 1. The $({\mu}SBS)$ of Group 2 $(16.50\pm2.31 MPa)$ and Group 4 $(15.83\pm2.33 MPa)$ to the end of enamel prism was significantly higher than that of Group 1 $(11.93\pm2.25 MPa)$ and Group 3 $(11.97\pm2.05 MPa)$ (p<0.05). 2. The $({\mu}SBS)$ of Group 2 $(13.43\pm2.93 MPa)$ to the side of enamel prism was significantly higher than that of Group 1 $(8.64\pm1.53 MPa)$, Group 3 $(9.69\pm1.80 MPa)$, and Group 4 $(10.56 \pm1.75 MPa)$ (p<0.05), 3. The mean $({\mu}SBS)$ to the end of enamel rod was significantly higher than that to the side of enamel rod in all group (p<0.05).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.519-529
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• 2009

Fiber reinforced composite materials have various advantages in mechanical and chemical aspects. Not only high fatigue and chemical resistance, but also high specific strength and stiffness are attained, and therefore, damping characteristics are beneficial to marine piles. Since piles used for marine structures are subjected to compression and bending as well, detailed research is necessary. Current study examine the mechanical behavior under flexural and/or compressive loads using concrete filled fiber reinforced plastic composite piles, which include large size diameter. 25 pile specimens which have various size of diameters and lengths were fabricated using hand lay-up or filament winding method to see the effect of fabrication method. The inner diameters of test specimens ranged from 165 mm to 600 mm, and the lengths of test specimens ranged from 1,350 mm to 8,000 mm. The strengths of the fill-in concrete were 27 and 40 MPa. Fiber volumes used in circumferential and axial directions are varied in order to see the difference. For some tubes, spiral inner grooves were fabricated to reduce shear deformation between concrete and tube. It was observed that the piles made using filament winding method showed higher flexural stiffness than those made using hand lay-up. The flexural stiffness of piles decreases from the early loading stage, and this phenomenon does not disappear even when the inner spiral grooves were introduced. It means that the relative shear deformation between the concrete and tube wasn't able to be removed.