• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.361-361
• /
• 2011

Cu(InGa)(SeS2) (CIGS) thin film solar cells have recently reached an efficiency of 20%. Recent studies suggest a double graded band gap structure of the CIGS absorber layer to be a key issue in the production of high efficiency thin film solar cell using by sputtering process method. In this study, Cu(InGa)(SeS2) absorbers were manufactured by selenization and surfulization, we have deposited CIG precusor by sputtering and Se layer by evaporation before selenization. The objective of this study is to find out surfulization effects to improve Voc and to compare with non-surfulization Cu(InGa)Se2 absorbers. Even if we didn't analysis Ga depth profile of Cu(InGa)(SeS2) absorbers, we confirmed increasing of Eg and Voc through surlization process. In non-surfulization Cu(InGa)Se2 absorbers, Eg and Voc are 0.96eV and 0.48V. Whereas Eg and Voc of Cu(InGa)(SeS2) absorbers are 1.16eV and 0.57V. And the efficiency of 9.58% was achieved on 0.57cm2 sized SLG substrate. In this study, we will be discussed to improve Eg and Voc through surfulization and the other method without H2S. gas.

• Nuclear Engineering and Technology
• /
• v.28 no.1
• /
• pp.17-26
• /
• 1996

The in-reactor fuel rod support conditions against the fretting wear-induced damage can be evaluated by residual spacer grid spring deflection or rod-to-grid gap. In order to evaluate the impact of fuel design parameters on the fretting wear-induced damage, a simulation methodology of the in-reactor fuel rod supporting conditions as a function of burnup has been developed and implemented in the GRIDFORCE program. The simulation methodology takes into account cladding creep rate, initial spring deflection, initial spring force, and spring force relaxation rate as the key fuel design parameters affecting the in-reactor fuel rod supporting conditions. Based on the parametric studies on these key parameters, it is found that the initial spring deflection, the spring force relaxation rate and cladding creepdown rate are in the order of the impact on the in-reactor fuel rod supporting conditions. Application of this simulation methodology to the fretting wear-induced failure experienced in a commercial plant indicates that this methodology can be utilized as an effective tool in evaluating the capability of newly developed cladding materials and/or new spacer grid designs against the fretting wear-induced damage.

• Restorative Dentistry and Endodontics
• /
• v.37 no.1
• /
• pp.41-49
• /
• 2012

Objectives: The internal adaptation of composite restorations with or without resin modified glass ionomer cement (RMGIC) was analyzed non-destructively using Microcomputed tomography (micro-CT). Materials and Methods: Thirty intact human teeth were used. The specimens were divided into 3 groups. In the control group, the cavities were etched with 10% phosphoric acid for 15 sec. Composite resin was filled into the cavity without adhesive. In group 1, light cured glass ionomer cement (GIC, Fuji II LC, GC) was applied as a base. The cavities were then etched, bonded, light cured and filled with composites. In group 2, the cavities were then etched, bonded, light cured and filled with composites without base application. They were immersed in a 25% silver nitrate solution. Micro-CT was performed before and after mechanical loading. One-way ANOVA with Duncan analysis was used to compare the internal adaptation between the groups before or after loading. A paired t-test was used to compare internal adaptation before and after mechanical loading. All statistical inferences were made within the 95% confidence interval. Results: The silver nitrate solution successfully penetrated into the dentinal tubules from the pulp spaces, and infiltrated into the gap between restoration and pulpal floor. Group 2 showed a lower adaptation than the control group and group 1 (p < 0.05). There was no significant difference between the control group and group 1. For all groups, there was a significant difference between before and after mechanical loading (p < 0.05). Conclusions: The internal adaptation before and after loading was better when composites were bonded to tooth using adhesive than composites based with RMGIC.

• The Journal of the Convergence on Culture Technology
• /
• v.6 no.2
• /
• pp.529-534
• /
• 2020

The development of civilization is in line with evolution of cities and transportation technology caused by industrialization. Up to now, a city has been developed owing to transportation cost reduction and needs for land utilization as a limited core business district. Continuous increase of urban population density has accompanied by lots of problems socioeconomically such as rise of land value, traffic congestion, gap between the rich and poor, air pollution, etc. Those issues are difficult to be solved in existing city ecosystem. However, a clue for solving the problems could be found in there. The design of Seoul mid-night bus route was from analysis of movement of people in the rural area by using ICT so that a city ecosystem should be firstly analyzed for solving rural issues. If the cause of those is found, big data platform construction is required to raise the life quality of citizen and the problems could be solved. Big data should be located in the middle of the platform connected with every element of city based on ICT for real-time collection, analysis and application. This paper addresses construction of big data platform and its application for sustainable smart city.

• Journal of Digital Convergence
• /
• v.7 no.1
• /
• pp.157-164
• /
• 2009

This research focuses on entrepreneurial orientation(EO) of technology spin-offs as they are expected to reduce the gap between their technology and the market. Entrepreneurial orientation is an organizational activity or process that redistributes or combines resources in an innovative way and takes risk to create new values. It helps improve the level of organizational innovation to deal with uncertainty. An empirical study was performed to analyze the EO of spin-offs established by members of university faculties and research institutes in Korea. Antecedent variables to EO are hypothesized to include public policy for university faculty members and researchers at research institutes, the relationship with incubating organizations, and the level of social networking with other firms. The EO and technological performance relationships are also hypothesized. Data from a total of 121 spin-off organizations were collected and a series of multiple regressions were performed. The performance variable included both technological performance, such as the number of newly marketed products and new technology and subjective performance, such as the level of satisfaction with sales amount and profitability. Several important conclusions were drawn from this study. First, while government policy is not related to EO, the policy of a university or a research institute has a significant effect on the level of innovativeness. Second, a high percentage of human resources applied at the incubating organization results in a negative effect on risk taking. The level of cooperation with the incubating organization too is not related to Entrepreneurial Orientation. Third, the intensity of cooperative networking with other firms has a significant effect on risk-taking. Network relationship with government related organizations is not related to Entrepreneurial Orientation. This study analyzes the importance and role of policy of the university and research institute and networking with other firms to improve EO. It also suggests that a high composition of human resources at the incubating organization has a negative relationship with EO.

• The korean journal of orthodontics
• /
• v.24 no.2
• /
• pp.479-508
• /
• 1994

This study was designed to investigate the reciprocal movement which was derived form application of active torque in ideal archwire by computer-aided three-dimensional finite element analysis of maxillary teeth and surrounding periodontal ligament composed of 2617 elements and 3725 nodes. Ideal archwire model was also made using the beam elements and the contact between the wire and the bracket slot was made using the gap element. In this study non-linear elastic behaviors of contact between the wire and the bracket slot were considered on. We put the active torque between the lateral and cenral incisor and between the second premolar and the first molar with/without cinch-back. The results were expressed by quantitative and visible ways. The findings of this study were as follows: 1. Reciprocal actions to active torque were complex system consisting of a combination of counter-torque, bucco-lingual linear displacement and tipping, rotation of the teeth, occluso-gingival linear displacement. 2. When active anterior crown labial torque was applied, crown labial tippings of the lateral were the greatest, and those of the central incisor was the next, Crown lingual tippings of the canine and the first premolar, mesial rotations and extrusion of the lateral and distal rotations and intrusion of the canine occurred. When anterior torque with the cinch-back was applied, amount of crown labial tippings of the lateral and central incisor were reduced. Amount of crown lingual tipping of the canine and the first premolar were increased. Mesial tippings and mesial rotations of the second molar occurred. 3. When active posterior crown lingual torque was applied, crown lingual tippings of the first moalr were the greatest, and crown labial tippings of the second premolar and the first premolar were the next, the crown lingual tipping of the second molar were a little. Mesial rotations of the second premolar occurred but those of the first premolar didn't occurred.

• Imaging Science in Dentistry
• /
• v.32 no.4
• /
• pp.201-206
• /
• 2002

Purpose : To evaluate the radiographic change of operation sites after orthognathic surgery using the digital image processing and fractal analysis. Materials and Methods : A series of panoramic radiographs of thirty-five randomly selected patients who had undergone mandibular orthognathic surgery (bilateral sagittal split ramus osteotomy) without clinical complication for osseous healing, were taken. The panoramic radiographs of each selected patient were taken at pre-operation (stage 0), 1 or 2 days after operation (stage 1), 1 month after operation (stage 2), 6 months after operation (stage 3), and 12 months after operation (stage 4). The radiographs were digitized at 600 dpi, 8 bit, and 256 gray levels. The region of interest, centered on the bony gap area of the operation site, was selected and the fractal dimension was calculated by using the tile-counting method. The mean values and standard deviations of fractal dimension for each stage were calculated and the differences among stage 0, 1, 2, 3, and 4 were evaluated through repeated measures of the ANOVA and paired t-test. Results : The mean values and standard deviations of the fractal dimensions obtained from stage 0, 1, 2, 3, and 4 were 1.658±0.048, 1.580±0.050, 1.607±0.046, 1.624±0.049, and 1.641 ±0.061, respectively. The fractal dimensions from stage 1 to stage 4 were shown to have a tendency to increase (p < 0.05). Conclusion: The tendency of the fractal dimesion to increase relative to healing time may be a useful means of evaluating post-operative bony healing of the osteotomy site.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3D
• /
• pp.477-487
• /
• 2011

The modified repeat-sales model is employed in this study in order to identify differentiating impacts of time-varying accessibility characteristics on housing price. The results demonstrate that accessibility measures have very differential impacts on housing price over time. The improvement of accessibility through newly built facilities and apartment complex has either increased or decreased housing price. For example, the new subway line 9 has positive impact on housing price nearby, therefore price gap between subway access area and the other parts has been increased. The impact of the wide area facilities such as shopping center and hospital are decreased because they can be used more easily by the new subway line before. However, the small service area facility such as elementary school doesn't lose their impact even though subway accessibility extremely increased. The results imply that new facilities in existing residential site can affect not only housing price but also the other facilities' impact of housing price.

• Proceedings of the KSMRM Conference
• /
• 2002.11a
• /
• pp.111-111
• /
• 2002

Purpose： This study is to compare the distinct brain activation between implicit and explicit memory retrieval tasks using a non-invasive blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging(fMRI). Materials ＆ Methods： We studied seven right-handed, healthy volunteers aged 21-25 years(mean；22 years) were scanned under a 1.5T Signa Horizon Echospeed MR imager(GE Medical Systems, Milwaukee, U.S.A.). During the implicit and explicit memory retrieval tasks of previously teamed words under the conceptual processing, we acquired fMRI data using gradient-echo EPI with 50ms TE, 3000ms TR, 26cm${\times}$26cm field-of-view, 128${\times}$128 matrix, and ten slices(6mm slice thickness, 1 mm gap) parallel to the AC-PC(anterior commissure and posterior commissure) line. By using the program of statistical parametric mapping(SPM99), functional activation maps were reconstructed and quantified.

• Journal of the Ergonomics Society of Korea
• /
• v.34 no.1
• /
• pp.11-18
• /
• 2015

Objective: The aim of this study was to understand the effects of phone weight on the typing performance and muscle recruitment in the neck and upper extremity while typing a text message with dominant hand. The iPhone4 and iPhone5 were compared due to their 28-gram differences in weight. Background: Too much use of a cellular phone can lead the musculoskeletal disorders in the upper extremity. Phone makers tend to make their new models bigger, lighter, faster and smarter. Method: Fourteen healthy volunteers without any history of neuromuscular disorders or ongoing pain who used their smartphone more than one year were recruited. A 112g phone (iPhone5) and a 142g phone (iPhone4) were used for typing the lyric of the Korean national anthem with their dominant hand. Typing duration, the typing error, the perceived fatigue, and preference was investigated. Muscle recruitment and the resting gap of neck (middle trapezius and levator scapula), shoulder (infraspinatus and mid deltoid), elbow (biceps brachii and brachioradialis), thumb (extensor and abductor policis brevis) were collected using surface electromyography. Typing error was counted and typing speed was calculated in characters per min. The data were analyzed using a paired t-test and chi-square (${\chi}^2$) analysis for the effects of phone weight on the typing performance parameters and muscle recruitment. Results: Typing text message with iPhone5 took longer but had less muscle recruitment in brachioradialis, and extensor policis brevis muscles. Lighter weight of iPhone5 made biceps brachii to rest less without increasing the mean %EMG. Conclusion/Application: Findings of this study can be valuable information for phone designers to develop more productive device and for smartphone users to prevent the musculoskeletal disorders in the upper extremities.