• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.399-407
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• 2010

The flexural behaviors of two types of beam members exposed to freeze-thaw cycles were evaluated. This study aims to examine the effect of freeze-thaw cycles on the behavior characteristics of reinforced concrete (RC) beams. For the purpose, a part of the beam specimens were damaged until yielding of tension reinforcement was reached, before they were exposed to 150 and 300 cycles of freeze-thaw. Cyclic tests, as well as monotonic tests, were conducted to evaluate the stiffness degradation characteristics when same cycle is repeated. The material tests showed that relative dynamic modulus of concrete exposed to 300 cycles of freeze-thaw moderately decreased to 86.8% of normal concrete, indicating that concrete used in this study has good durability against freeze and thaw damage. The results of monotonic tests showed reduction of flexural strength, ductility and stiffness of the beam specimens exposed to freeze-thaw cycles compared with those of the control speciments. In particular, BDF13 specimens, which had been subjected to artificial cracking damage, did not showed enough flexural strength to satisfy nominal moment required by current concrete structure design code. In the monotonic tests results, BF75 specimens exposed to freeze-thaw cycles showed 10% or more cyclic stiffness degradation. Therefore, it was thought that deformation of concrete in compression have to be considered in design process of members under cyclic load, such as seismic device.

• The Korean Journal of Financial Management
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• v.24 no.1
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• pp.149-182
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• 2007

This study examines the determinants of the long-run stock price performance of the firms that granted stock options between 1997 and 2002. We divide the sample into the firms run by the owner and those run by the professional manager. If the primary reason for granting stock options is reduction of the agency costs between the manager and shareholders, the effect of stock options is likely to be more pronounced in the firms run by the professional manager. We find that the long-run abnormal returns of the firms run by the professional manager are negatively associated with the shareholdings by the manager and the book-to-market value and are positively associated with the earnings growth and the size of the outstanding stock options. In contrast, the long-run abnormal returns of the firms run by the owner are negatively associated with the cash flows rate and the sales growth rate and are positively associated with the firm size. This is consistent with the argument that the agency costs arising from the conflicts between the manager and shareholders are an important determinant of the post-stock option granting long-run stock price performance only in the firms run by the professional manager. The results also suggest that stock options in the firms run by the owner are likely to be used for the purposes such as additional compensation, a signaling device, a means that reduce the agency costs within firms.

• Journal of Radiation Protection and Research
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• v.34 no.1
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• pp.31-36
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• 2009

The purpose of this study is to measure the tube voltage, the tube current/volume, exposure time and exposure dose of diagnostic X-ray unit in each doctor offices, hospitals and general hospitals for evaluating the performance of such device, to learn the method and technology of its measurement and to suggest its importance. Research subjects were total 30 X-ray units and divided into groups of 10 X-ray units each. The tube voltage, the tube current/volume, exposure time and exposure dose were measured using percentage average error, and then reproducibility of exposure dose was measured through calculating coefficient of variation. The results are like followings; The tube voltage correctness examination showed that incongruent devices among total 30 X-ray units were 5 devices (16.7%). The tube current correctness examination showed that incongruent X-ray units were 3 devices (10.0%). The tube current volume correctness examination showed that incongruent X-ray units were 4 devices (13.3%). Finally, according to exposure time correctness examination, incongruent X-ray units were 5 devices (16.7%) and according to reproducibility examination of exposure dose, incongruent X-ray units were 7 devices (23.3%). Above results showed serious problem in performance management based on management regulation of diagnostic X-ray unit; it means that regular checkout and safety management are required, and as doing so, patients will be able to receive good quality of medical service by the reduction of radiation exposure time, image quality administration, unnecessary retake and etc. Therefore, this study suggests that the performance of diagnostic X-ray units should be checked regularly.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.88-96
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• 2017

Purpose: The purpose of this study is to assess the relationship between the time spent designing custom abutments and repeated learning using dental implant computer aided design (CAD) software. Materials and Methods: The design of customized abutments was performed four stages using the 3DS CAD software and the EXO CAD software, and measured repeatedly three times by each stage. Learning effect by repetition was presented with the learning curve, and the significance of the reduction in the total time and the time at each stage spent on designing was evaluated using the Friedman test and the Wilcoxon signed rank test. The difference in the design time between groups was analyzed using the repeated measure two-way ANOVA. Statistical analysis was performed using the SPSS statistics software (P < 0.05). Results: Repeated learning of the customized abutment design displayed a significant difference according to the number of repetition and the stage (P < 0.001). The difference in the time spent designing was found to be significant (P < 0.001), and that between the CAD software programs was also significant (P = 0.006). Conclusion: Repeated learning of CAD software shortened the time spent designing. While less design time on average was spent with the 3DS CAD than with the EXO CAD, the EXO CAD showed better results in terms of learning rate according to learning effect.

• Information Systems Review
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• v.8 no.1
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• pp.1-24
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• 2006

Now, the Korean footwear industry needs the concrete enhancement of its competitive edge for regaining of its previous well known reputation. For this purpose, this study emphasizes the cooperation between the members through the supply chain of Korean footwear industry, as a c-SCM(Collaborative Supply Chain Management) by aid of information system. The key issue will be how well to coordinate operations flow not only through internal process stages, but also through entire external supply chain stages. In other words, the target goal must be the system optimization through the entire supply chain beyond the local optimization of internal supply chain process. We, at first, analyze the traditional structure of supply chain in Korean footwear industry and find out critical problems, and then, we develop the collaborative information framework in conjunction with several collaborative process modules. The suggested collaborative production & supply planning system was designed for sharing information and it is based on ebXML(electronic business eXtensible Markup Language) framework. In this way, the enhancement of the efficiency and competitiveness can be expected through the synergy effect of coordination of information and material flow, the reduction of lead times, and production costs.

• Archives of Plastic Surgery
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• v.37 no.3
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• pp.227-232
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• 2010

Purpose: Continuous irrigation method is an important step in managing wound infection. V.A.C. devices have been used in intractable wounds for reducing discharge, improving local blood flow, and promoting healthy granulation tissue. We expect synergistic effects of reduced infection and more satisfactory, accelerated wound healing when using both methods simultaneously. This study evaluated continuous irrigation combined with V.A.C. appliance for treatment of infected chronic wounds. Methods: We reviewed data from 17 patients with infected intractable chronic wounds. V.A.C. device (Group A) was used in 9 patients, and V.A.C. with antibiotics irrigation (Group B) was used in 8 patients. We placed Mepitel$^{(R)}$ on the surface of wound and placed an irrigation and aspiration tube on each side. A sponge was placed on the Mepitel$^{(R)}$ and covered with film dressing. The wound was irrigated continuously with mixed antibiotics solution at the speed of 200 cc/hr and aspirated through the wall suction at the pressure of -125 mmHg. V.A.C. applied time, wound culture and wound size were compared between the two groups. Results: No complication were seen in two groups. Compared with Group A, in the Group B, V.A.C. applied time was shortened from 32.7 days to 25.6 days and showed efficacy in the reduction rate of wound size. No statistical differences were shown in bacterial reversion. Conclusion: V.A.C. appliance with continuous irrigation is an effective new method of managing infected chronic wounds and useful to reduce treatment duration and decrease wound size. Moreover it could be applied more widely to infected wound.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.545-551
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• 1998

The Radio communication by existing SSB, VHF, etc. in a coast station and a base station for military affairs is still used to a very important the device of information delivery or transmitting and receiving by the remote controller to using to the exclusive cable for a equipment established at a long distance. When a number of consumer to connected and operated by a number of transceiver is essential for a circuit controller of ICS, in KOREA, is devoted by import to considerable quantity because of to be delayed development of this field. This Paper has been realized to optimal algorithm and designing of a circuit connection controller by multi-processor to pre-stage for the development of ICS. The H/W is composed able to remote control to circuit connector with the several slave processor and a processor for master, and this has taken possible through without any obstacle to communication circuits of a control signal by FSK system. The S/W make possible monitoring for communication condition of other circuits by means of a serial communication system by the multi-processing. This paper has been studied for connecting to a circuits wished to rapidly and precisely by the full application to a interrupt technique. A technique to control by remote to a number of transceiver is a way increasing to application for a frequency resource of the limited MF/SF, VHF and the existing radio communication technique. According to, this paper will achieve to be the reduction of energy & equipment and multiplicity of information delivery in the general communication and disposal to rapid and exact for the important communication as distress, urgency and safety on the sea.

• Journal of Korean Foot and Ankle Society
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• v.24 no.2
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• pp.81-86
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• 2020

Purpose: Ankle fractures with dislocations and pilon fractures at the distal tibia are usually associated with soft tissue damage caused by high-energy damage. Recently, a two-stage operation to perform internal fixation after the application of external fixation devices for stabilizing soft tissues has been accepted as the treatment of choice. This paper reports the clinical result of these injuries treated with threaded trans-calcaneal pin external fixation devices. Materials and Methods: Thirty-three patients diagnosed with ankle fractures with dislocations or tibial pilon fractures without open wounds. They underwent surgical treatment with threaded trans-calcaneal pin external fixation from January 2008 to February were enrolled in this study. This study evaluated the visual analogue scale (VAS), foot function index (FFI), and Olerud & Molander score as well as whether complications occurred. Results: The average VAS showed a meaningful decrease (p<0.001) from 7.4 before surgery to 2.6 after application of the external fixation device, and 1.4 at 12 months after surgery. The FFI also decreased significantly from 84.3 preoperatively to 20.3 at 12 months postoperatively (p<0.001). The Olerud & Molander score averaged 71.4 points, showing good clinical results. Complete bone union was observed in all patients. One patient each underwent debridement due to wound necrosis and infection in the pin insertion site. At the final follow-up, seven patients had posttraumatic ankle joint arthritis, according to a radiological examination. Conclusion: Manual reduction and external fixation using a threaded trans-calcaneal pin is a suitable surgical technique that is easy to perform and shows good clinical outcomes in stabilizing soft tissue damage in fractures and dislocations of ankle fracture or tibia pilon fractures in foot and ankle injury.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.334-334
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• 2013

In the past decade, the infrared detectors based on intersubband transition in quantum dots (QDs) have attracted much attention due to lower dark currents and increased lifetimes, which are in turn due a three-dimensional confinement and a reduction of scattering, respectively. In parallel, focal plane array development for infrared imaging has proceeded from the first to third generations (linear arrays, 2D arrays for staring systems, and large format with enhanced capabilities, respectively). For a step further towards the next generation of FPAs, it is envisioned that a two-dimensional metal hole array (2D-MHA) structures will improve the FPA structure by enhancing the coupling to photodetectors via local field engineering, and will enable wavelength filtering. In regard to the improved performance at certain wavelengths, it is worth pointing out the structural difference between previous 2D-MHA integrated front-illuminated single pixel devices and back-illuminated devices. Apart from the pixel linear dimension, it is a distinct difference that there is a metal cladding (composed of a number of metals for ohmic contact and the read-out integrated circuit hybridization) in the FPA between the heavily doped gallium arsenide used as the contact layer and the ROIC; on the contrary, the front-illuminated single pixel device consists of two heavily doped contact layers separated by the QD-absorber on a semi-infinite GaAs substrate. This paper is focused on analyzing the impact of a two dimensional metal hole array structure integrated to the back-illuminated quantum dots-in-a-well (DWELL) infrared photodetectors. The metal hole array consisting of subwavelength-circular holes penetrating gold layer (2DAu-CHA) provides the enhanced responsivity of DWELL infrared photodetector at certain wavelengths. The performance of 2D-Au-CHA is investigated by calculating the absorption of active layer in the DWELL structure using a finite integration technique. Simulation results show the enhanced electric fields (thereby increasing the absorption in the active layer) resulting from a surface plasmon, a guided mode, and Fabry-Perot resonances. Simulation method accomplished in this paper provides a generalized approach to optimize the design of any type of couplers integrated to infrared photodetectors.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1205-1214
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• 2005

This study was carried out to investigate the emission characteristics of volatile metals(Hg, As, Se) and semi volatile metals such as Pb from small and medium size municipal solid waste incinerators(MSWIs). The concentrations of Hg, Pb, As and Se in emission gas from small size waste incinerators were higher than those of medium size waste incinerators. This is probably due to less air pollutant control devices and high emission gas temperature of the small size waste incinerators relative to the medium size waste incinerators. Emission gas temperature from small and medium size waste incinerators were divided into 2 groups. The first group was about $100^{\circ}C$ and the second roup in the range of $400{\sim}700^{\circ}C$. The concentrations of emission gas at the second group were Hg $70.43\;{\mu}g/Sm^3$, Pb $0.94\;{\mu}g/Sm^3$, As $9.83\;{\mu}g/Sm^3$ and Se $5.05\;{\mu}g/Sm^3$. The concentrations of Hg, Pb, As and Se at the first group were lower than those found at the second group. Besides, the removal efficiencies of Hg in medium size waste incinerators were $55.2{\sim}95.9%$. Emission gas temperature reduction from waste heat boiler(WHB) contribute to control of Hg. Based on above results, we postulate that the temperature of flue gas should play a very important role in volatile metal control in small and medium size MSWIs. In order to improve the volatile metals removal efficiency, the temperature of cooling system must be controlled and the air pollution control device should be operated properly.