• Journal of Digital Convergence
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• v.20 no.3
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• pp.507-516
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• 2022

The purpose of this study was to examine the factors influencing on the smartphone usage time according to the happiness perceived by adolescents. This study underwent the approval procedure for using the raw data of the 13th (2017) Adolescents' Health Behavior Online Survey through the homepage of Korea Centers for Disease Control and Prevention and selected 54,603 persons of 12-18 age groups as subjects of the study. The analysis was performed after generating a complex sample plan file by assigning weights using the IBM SPSS 23.0 program. There were significant differences in general characteristics and physical & psychological characteristics according to the use of the smartphone in the happy group and the unhappy group (p<.05). And there was a statistically significant difference in factors affecting smartphone usage time between the group of adolescents who perceived as happy and the group who perceived themselves as unhappy. It is necessary to improve the quality of life by increasing the level of happiness through the correct use of smartphones among adolescents.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.128-133
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• 2024

Although antisolvent-assisted crystallization is one of the promising processes to produce high-quality perovskite films, general antisolvents such as chlorobenzene (CB) have toxic and volatile properties. In addition, CB is not suitable to control the crystallization of perovskite in the atmospheric air. In this work, isopropyl acetate (IA) is used as an eco-friendly antisolvent to demonstrate air-processed perovskite solar cells, and ethyl-4-cyanocinnamate (E4CN) with a cyano group, carbonyl group, and aromatic ring is introduced in IA to improve the performance and stability of devices. Defects at the surface and grain boundaries of the perovskite layer, such as un-coordinated Pb²⁺ and iodine, can be decreased resulting from the interaction of E4CN and perovskite, and thus reduced recombination and enhanced carrier transport can be expected. As a result, the perovskite device with E4CN achieves a high maximum power conversion efficiency (PCE) of 18.89% and outstanding stability, maintaining 60% of the initial efficiency for 300 h in the air without any encapsulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.400-406
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• 2024

Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.

• Progress in Medical Physics
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• v.11 no.2
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• pp.123-130
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• 2000

The performance of an electrometer directly affects on the accuracy and precision in radiation dosimetry. This study is to list of the quality control for maintaining performance and to perform evaluation tests of an electrometer. Performance tests selected include proper polarizing voltages, warm-up and equalization time, leakages, long-term stability, linearity, and effect of ambient conditions. An electrometer connected with a rigid stem ionization chamber was evaluated with a Strontium-90 check device. Bias voltage was measured directly on the input socket. Equalization time is the time required for reaching threshold of charged state after the power is on or the bias voltage is changed. Pre- and post-signal leakages are defined as the accumulation of signal with no exposure and after exposure, respectively. Over three months period, the electrometer's long-term stability was measured by comparison of the temperature-pressure corrected readings. Linearity was expressed as the deviation of readings from multiple short exposures from one continuous exposure. Effect of ambient conditions was expressed as the zero drift of the electrometer over 17-34$^{\circ}C$ temperature ranges. For two nominal values, 300 and 500 volts, measured voltages were lower by 2.5 and 5.8%, respectively. The warm-up time, 20 minutes, was longer than the lamp time by 9 minutes and the equalization time was less than 1 minute. Without exposure, the zero-drift was 0.002 scale-unit in 15 minutes and the leakage after 10 minutes exposure was minimal. The IQ-4 was stable over 99.4% for three-month periods. Deviation from the linearity was 0.9% for measurement scale, 0.000-9.991. Over 17-34$^{\circ}C$ temperature range, the zero-drift was minimal, less than 0.2%. For a clinically-used electrometer, a list for the basic peformance evaluations is proposed. By running this program, the measurement error using an electrometer can be reduced and in turn the improvement in accuracy and precision of radiation dosimetry can be achieved.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.6
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• pp.531-548
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• 2006

The purpose of this study was to investigate the biomechanical, histologic findings of distracted regenerate and TMJ response in modified distraction osteogenesis (DO) technique combined with compression force as biomechanical stimulation method which has been suggested in 2002, and developed thereafter by authors. This study was performed with two experiments. First experiment was designed to explore the optimal ratio of compression force versus distraction force for the new DO technique. Second experiment was planned to evaluate the reaction of TMJ tissue, especially condyle, disc after application of the DO technique with compression force. Total 52 New Zealand adult male-rabbits with 3.0kg body weight were used for the study. For the first study, 30 adult male-rabbits underwent osteotomy at one side of mandibular body and a external distraction device was applied on each rabbit with same manner. In the control group of 10 rabbits, final 8 mm of distraction with 1 mm rate per day was done with conventional DO technique after 5 latency days. For the experimental group of 20 rabbits, a compression force with 1 mm rate per day was added to the distracted mandible on 3-latency day after over-distraction (over-lengthening). As the amount of the rate of compression versus distraction, experimental subgroup I (10 rabbits) was set up as 2 mm compression versus 10 mm distraction (1/5) and experimental subgroup II (10 rabbits) was set up as 3 mm compression versus 11 mm distraction (about 1/3). All 30 rabbits were set up to obtain final 8 mm distraction and sacrificed on postoperative 55 day to analysis on biomechanical, and histologic findings of the bone regenerates. For second study, 22 adult male-rabbits were used to evaluate TMJ response after the DO method application with compression force. In the control group, 10 rabbits was used to be performed with conventional DO method, on the other hand, in a experimental group of 10 rabbits, 10 mm distraction with 2 mm compression (1/5 ratio) was done. The remaining 2 rabbits served as the normal control group. Histomorphologic examinations on both condyle, histological studies on condyle, disc were done at 1, 2, 3, 4, 7 weeks after distraction force application. The results were as follows: 1. On the bone density findings, the experimental group II (force ratio - 1/3) showed higher bone density than the other experimental group (force ratio - 1/5) and control group (control group - $0,2906\;g/cm^2$, experimental group I - $0.2961\;g/cm^2$, experimental group II - $0.3328\;g/cm^2$). 2. In the histologic findings, more rapid bone maturation like as wide lamellar bone site, more trabeculae formation was observed in two experimental groups compared to the conventional DO control group. 3. In morphologic findings of condyle, there were no differences of size and architecture in the condyle in the control and experimental groups. 4. In histologic findings of condyles, there were thicker fiberous and proliferative layers in experimental group than those of control group until 2 weeks after distraction with compression force. But, no differences were seen between two groups on 3, 4, 7 weeks after compression. 5. In histologic findings of disc, more collagen contents in extracellular matrix, more regular fiber bundles, and less elastin fibers were seen in experimental group than control group until 2 weeks after distraction with compression. But, no differences were seen between two groups on 3, 4, 7 weeks after distraction with compression. From this study, we could identify that the new distraction osteogenesis technique with compression stimulation might improve the quality of bone regeneration. The no remarkable differences on TMJ response between control and experimental groups were seen and TMJ tissues were recovered similarly to normal TMJ condition after 3 weeks.

• Journal of radiological science and technology
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• v.18 no.2
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• pp.87-102
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• 1995

The education of radiologic technology began in the regular institute of higher education in Korea in 1963. Up to now from then, our education to bring up the radiologic technologists has developed greatly in quality and quantity, and now departments of radio-technology are founded in the 16 junior colleges in March, 1995. This study was done to verify the necessity and propriety to reform the education system of radiologic technology which was run as two or three year system of college curriculum for 32 years since 1963, and to search for the method to reform in the future. We got the following results from this research. 1. In the survey, on the desirable education year for radiologic technologists, 63.9 % of professors of department of radio-technology and 63.0 % of radiologic technologists chose the 4 year system, 27.9 % of professors and 34.6 % of radiologic technologists chose the 4 year system added to graduate school. 2. In the survey, on the future development of radiologic equipments and technique, 67.2 % of professors of department of radiologic technology and 86.4 % of radiologic technologists have a view of "revolutional development". Also, on the future tasks or roles of radiologic technologists 95.1% of professors and 94.9% of radiologic technologists have a view that "They will increase". 3. On the necessity of extension of education year to 4 years from 3 years, the factor is that development of medical technique and machinery and tools, advance of qualification of radiologic technologists, enlargement and specialization of the business of the radiologic technologists, ballance of education year with other medical sciences, international competitive power and cooperation of radiologic technology, and education continuation of the graduates of department of radiologic technology. 4. They suggested that in the 4 year curriculum of department of radiologic technology, clinical medicine, quality control of radiation and radiologic equipment, related subjects to the radiologic application and computer application should be enforced and clinical practice should be extended more. 5. On the device to found the 4 year college curriculum of radiologic technology, they suggested that first, 4 year curriculum should be founded through the variety of educational year, secondly, department of radiologic technology should be founded in the 4 year health sciences college, thirdly, educational continuation of the radiologic technologists should be systematized on the basis of life-long education.

• Korean Security Journal
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• no.15
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• pp.243-264
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• 2008

Recently the private security industry is showing rapid growth compared with the different types of industry. However, it is not prepared the device for the system to verify the professional qualification of the security guards. To protect individual life and property, body and security guards have to be qualified professionally. For it the role of professional qualification systems is emphasized. The problem of the certification of the qualification about the security guard to play the role to protect a body / life of the individual and property are the part to need necessarily as the quality problem of the individual and the trust of the people. The settlement of the qualification system which is such system can induce the development of the security industry with social trust. The certified security certification is needed and how to control the security quality to get better service to the clients. The professional qualification system to be carrying out with America and Japan is fixed through the cooperation of the business world and steady research for the qualification system plan, these are giving the trial of the qualification system of a security of Korea full of the suggestion. This study will do this to the basis which a necessity about the qualification system of the security man emphasis and considerate professional qualification system concerning the private security development plan around the Bodyguard Qualifying Examination which are carried out at twice by the Korea Security Association and the Korean Institute of Security. In summary to meet the social demand professional qualification for the security guards will be drawn from the analyses of civil security qualification systems.

• Journal of the Korea Computer Industry Society
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• v.8 no.2
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• pp.107-112
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• 2007

Laser wave length can have evaporation effect by absorption because outer skin or tissue of focus is consisted of water almost though absorption of water occurs more than 90% almost in formation thickness of very thin floor. Can operate outer skin, steam by floor and correct incision of formation is available. Suture surgical operation is available to vein or lymph system and surgical operation region can dry and see as eye and radish bleeding surgical operation is available. Specially, stability of tube both end output about pulse by weight very, this research can cause various curative effect because can reduce bulk and control easily current wave style of medical laser using electric power conversion device of high frequency way. If introduce ZVS (Zero Voltage Switching) or ZVZCS (Zero Voltage and Zero Current Switching), is more profitable because can reduce switching damage. Because electric power department of proposed medical laser can do stable soft-switching in wide subordinate extent introducing ZVZCS technique by the first help and control department composes microcontroller, output current waveform user have free form make Result that experiment because design and manufacture, brought result that improve of 20% than existing equipment, and will be bought to get into superior result if supplement as systematic late.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.183-184
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• 2013

Two main MBE growth techniques have been used: plasma-assisted MBE (PA-MBE), which utilizes a rf plasma to supply active nitrogen, and ammonia MBE, in which nitrogen is supplied by pyrolysis of NH3 on the sample surface during growth. PA-MBE is typically performed under metal-rich growth conditions, which results in the formation of gallium droplets on the sample surface and a narrow range of conditions for optimal growth. In contrast, high-quality GaN films can be grown by ammonia MBE under an excess nitrogen flux, which in principle should result in improved device uniformity due to the elimination of droplets and wider range of stable growth conditions. A drawback of ammonia MBE, on the other hand, is a serious memory effect of NH3 condensed on the cryo-panels and the vicinity of heaters, which ruins the control of critical growth stages, i.e. the native oxide desorption and the surface reconstruction, and the accurate control of V/III ratio, especially in the initial stage of seed layer growth. In this paper, we demonstrate that the reliable and reproducible growth of GaN on Si (110) substrates is successfully achieved by combining two MBE growth technologies using rf plasma and ammonia and setting a proper growth protocol. Samples were grown in a MBE system equipped with both a nitrogen rf plasma source (SVT) and an ammonia source. The ammonia gas purity was ＞99.9999% and further purified by using a getter filter. The custom-made injector designed to focus the ammonia flux onto the substrate was used for the gas delivery, while aluminum and gallium were provided via conventional effusion cells. The growth sequence to minimize the residual ammonia and subsequent memory effects is the following: (1) Native oxides are desorbed at $750^{\circ}C$ (Fig. (a) for [$1^-10$] and [001] azimuth) (2) 40 nm thick AlN is first grown using nitrogen rf plasma source at $900^{\circ}C$ nder the optimized condition to maintain the layer by layer growth of AlN buffer layer and slightly Al-rich condition. (Fig. (b)) (3) After switching to ammonia source, GaN growth is initiated with different V/III ratio and temperature conditions. A streaky RHEED pattern with an appearance of a weak ($2{\times}2$) reconstruction characteristic of Ga-polarity is observed all along the growth of subsequent GaN layer under optimized conditions. (Fig. (c)) The structural properties as well as dislocation densities as a function of growth conditions have been investigated using symmetrical and asymmetrical x-ray rocking curves. The electrical characteristics as a function of buffer and GaN layer growth conditions as well as the growth sequence will be also discussed. Figure: (a) RHEED pattern after oxide desorption (b) after 40 nm thick AlN growth using nitrogen rf plasma source and (c) after 600 nm thick GaN growth using ammonia source for (upper) [110] and (lower) [001] azimuth.

• Journal of Acupuncture Research
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• v.27 no.1
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• pp.1-10
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• 2010

Objectives : The mechanical properties of Korean electric cupping systems are studied via experimental measurements. The study aimed at establishing the fundamentals of industrialization and systemization of oriental medicine device industry, as well as improving the quality of life for many Koreans. Methods : We reviewed the studies on traditional cupping as well as modern one to fine necessary factors for electric cupping systems. To characterize the mechanical properties of Korean electric cupping systems, we measured the pressure characteristics of commercially available electric cupping system by using an automatic pressure acquisition system and a standard cup. The pumping capability was checked at 40 seconds, and the stability of the suction cup was checked at 600 seconds. We also acquired the noise level of each system in clinical setting. To check the portability of each system, we also measured its physical dimensions. We scrutinized system manuals provided by the system manufacturers. Results : It took less than 5 second to reach the pressure if the connection between the air hose and the vacuum valve of the cupping system was secure. Pressure diminished to no more than 10% for 600s for all systems. Noise levels were 55~70 dB. Increase in pressure was too fast to control for a designated vacuum level except for one product. Conclusions : The Pumping ability of the systems is impressive and reliable. Pressure retention ability of each cup is quite reliable and reproducible. Therefore, their mechanical performances were worthy of recommendation. Some of them had noise level higher than 60 dB and they were bothersome. It was also suggested that the control for low to middle pressure needed to be accomplished by the cupping system.