• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.1
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• pp.21-26
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• 2017

Failure of high-voltage transmission line, which is responsible for large-scale power transmission, can be reason for system voltage instability. There are many methods to prevent voltage instability like adjustment of equipment, the generator voltage setting, and load shedding. Among them, the load shedding, have a problem of economic loss and cascading effect to power system. Therefore, the execution of load shedding, amount and timing is very important. Conventionally, the load shedding setting is decided by the preformed simulation. Now, it is possible to monitor the power system in real time by the appearance of PMU(Phasor Measurement Unit). By this reason, some of research is performed about decentralized load shedding. The characteristics of the load can impact to amount and timing of decentralized load shedding. Especially, it is necessary to consider the influence of the induction motor loads. This paper review recent topic about under voltage load shedding and compare with decentralized load shedding scheme with conventional load shedding scheme. And simulations show the effectiveness of proposed method in resolving the delayed voltage recovery in the Korean Power System.

• International conference on construction engineering and project management
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• 2007.03a
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• pp.160-168
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• 2007

Conflicts of interest and independent agenda of the parties brought together for implementation of a construction project often leads to dispute in Contract and claim situations. Construction Industry is notorious for claim that is managed on its arising and there lacks an endeavor to minimize the breeding grounds through efficient planning and alignment to purpose, of all contract-documents. There failure of a concerted effort entails wastage of resources, delayed completion of facilities and stained relationships of parties when collide in mistrust in contract to win over the other. There needs a focus on the claim breeding issue and establish an effective mechanism to deal with disputes in urgency. Claim occurs mostly during the construction phase. But the seeds of claim and nutrients essential for development are contained in the contract documentation and the information supplied or not in pre-contract phase. Opportunity to prevent nutrients for seed of Claim comes to an end once tender-documents are finalized, the contract is awarded and established or not a mechanism for dealing with claim situation. The processes presented here would help in minimizing the breeding grounds and emergence of disputes during progression of works and dealing with eventualities in forceful manners for finding a resolution most effectively in relevant time.

• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.363-371
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• 2016

PURPOSE. On maxillofacial tumor patients, oral implant placement prior to postoperative radiotherapy can shorten the period of prosthetic reconstruction. There is still lack of research on effects of post-implant radiotherapy such as healing process or loading time, which is important for prosthodontic treatment planning. Therefore, this study evaluated the effects of post-implant local irradiation on the osseointegration of implants during different healing stages. MATERIALS AND METHODS. Custom-made implants were placed bilaterally on maxillary posterior edentulous area 4 weeks after extraction of the maxillary first molars in Forty-eight Sprague-Dawley rats. Experimental group (exp.) received radiation after implant surgery and the other group (control) didn't. Each group was divided into three sub-groups according to the healing time (2, 4, and 8 week) from implant placement. The exp. group 1, 2 received 15-Gy radiation 1 day after implant placement (immediate irradiation). The exp. group 3 received 15-Gy radiation 4 weeks after implant placement (delayed irradiation). RESULTS. The bone mineral density (BMD) was significantly lower in the immediate irradiation groups. BMD was similar in the delayed irradiation group and the control group. The irradiated groups exhibited a lower bone-to-implant contact ratio, although the difference was not statistically significant. The irradiated groups also exhibited a significantly lower bone volume and higher empty lacuna count than the control groups. No implant failure due to local irradiation was found in this study. CONCLUSION. Within the limits of this study, the timing of local irradiation critically influences the bone healing mechanism, which is related to loading time of prostheses.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.5
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• pp.284-293
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• 2013

Purpose: For reconstruction of craniomaxillofacial defects caused by tumor, trauma, infection etc, free flap transplantation with microvascular surgery is a very useful method. Thrombus formation at the anastomosis site is the major cause of graft failure. 4-Hexylresorcinol (4-HR) is generally known as an antiseptic and antiparasitic agent. This study was conducted in order to evaluate the effect of 4-HR on blood coagulation in vitro. In addition, we investigated thrombus formation and endothelial repair of an injured vessel in an animal model. Methods: In the in vitro experiment, we compared blood coagulation time between the 4-HR treated group and normal blood. Thirty rats were used for in vivo animal experiments. After exposure of the right femoral vein, a micro vessel clamp was placed and the femoral vein was intentionally cut. Microvascular anastomosis was performed on all rats using 10-0 nylon under microscopy. The animals were divided into two groups. In the experimental group (n=15), 4-HR (250 mg/kg) mixed with olive oil (10 mL/kg) was administered per os daily. Animals in the control group (n=15) were given olive oil only. The animals were sacrificed at three days, seven days, and fourteen days after surgery and rat femoral vein samples were taken. Vascular patency and thrombus formation were investigated just before sacrifice. Histologic analysis was performed under a microscope. Results: Results of an in vitro blood coagulation test showed that coagulation time was delayed in the 4-HR treated group. The results obtained from an in vivo 4-HR administered rat model showed that the patency of all experimental groups was better at thirty minutes, seven days, and fourteen days after microvascular anastomosis than that of the control group at seven and fourteen days after anastomosis, and the amount of thrombus in the experimental groups was much less than that of the control group. Endothelial repair was observed in the histologic analysis. Conclusion: Findings of this study demonstrated that blood coagulation was delayed in the vitro 4-HR treated group. In addition, good vascular patency, anti-thrombotic effect, and repair of venous endothelial cells were observed in the vivo 4-HR administered rat group.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.545-555
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• 2011

Presently, The Regular Block System(Automatic, Interlocking block system) is usually used during the operation of block section. However, In case that the regular block system fails because of the failure of the fixed signals and block equipment or in case of the unexpected emergency which should drive on the single line due to the accidents in the double line section or the repair work of the single line, the Substitute Block System to use the driving permission license(mapping ticket and paper) is used. In case of the operation of the opposite line and the temporary one line, the safety gets worse and the SBS may cause the fatal accidents such as a head-on & a rear-end collision. Also, the unmanned railroad stations has recently increased owing to the effective operation of the stations, for it is difficult to execute the SBS in their absence. As a result, the increase of the operation time made the train delayed. Being on the rise of these problems, in this study, we analyzed the problems and difficulties of the SBS on one line which is lacking stability and safety and on the sections combined between maned and unmaned railroad stations. And we proposed the suitable method in KORAIL referring to the examples of European & Japan railways lately. According to the passing of the high tech time, If the new SBS equipped with stability and safety is executed, it will contribute to the effective operation of trains and the satisfaction of KORAIL customers in the future.

• Journal of the Korea society of information convergence
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• v.1 no.1
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• pp.33-40
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• 2008

When performing a software development project, the most important thing is building a result with planned quality within development period. Particularly, if the project is delayed or has no good quality in the case of the content software development project which is sensitive to the release time and quality, it is immediately connected to the failure of the whole project. Extreme programming is a methodology that divides the development cycle into smaller units for reducing the risk factor of the project in which the development period is important. In this paper, we suggest the expanded extreme programming which can consider the development period and quality at the same time for content software development environment. The suggested methods are documentation mechanism that is upcoming during the development project and multiple role model which is extended from pair programming method.

• Archives of Reconstructive Microsurgery
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• v.16 no.2
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• pp.119-124
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• 2007

Purpose: We reconstructed the skin defect of lower legs exposing muscles, tendons and bone with fasciocutaneous sural artery flap and report our cases. Materials and Methods: Between March 2005 and September 2006, 8 cases of skin defect were reconstructed with fasciocutaneous sural artery flap. Defect site were 4 case of ankle and foot and 4 cases of lower leg. The average defect size was $4{\times}4\;cm^2$. There were 5 men and 3 women and mean age was 52.2 years. We evaluated the viability of flap, postoperative complication, healing time, patient's satisfaction. Results: There was no flap failure in 8 cases. But recurrent discharge in 2 cases was healed through several times adequate debridement and delayed suture without complication. Flap edema may be due to venous congestion was healed through leg elevation and use of low molecular weight heparin. Mean time to heal the skin defect was 4 weeks. No infection and recurrence in follow up period. Cosmetic results as judged by patients were that 5 cases are good and 3 cases are fair. Conclusion: Sural artery flap is good treatment method among the numerous methods in the cases of skin defect, with soft tissue exposed, which is not covered with debridment and skin graft. Sural artery flap is useful method for the skin defect of lower legs because it is simple procedure, has constant blood supply and relatively good cosmetic effect.

• Archives of Reconstructive Microsurgery
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• v.17 no.2
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• pp.115-119
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• 2008

Purpose: We reconstructed the skin defect of hands exposing tendons and/or bone with distally based ulnar artery flap and report our cases. Materials and Methods: Between March 2005 and September 2007, 6 cases of skin defect were reconstructed with distally based ulnar artery flap. Defect site were 5 cases of hand dorsal side and 1 case of hand volar side. The average defect size was $3{\times}3\;cm^2$. There were 4 men and 2 women and mean age was 55.5 years. We evaluated the viability of flap, postoperaive complication, healing time, patient's satisfaction. Results: There was no flap failure in 6 cases. But 1 case with recurrent discharge was healed with several times adequate debridement and delayed suture. 1 case with flap edema which might be due to venous congestion was healed with hand elevation and use of low molecular weight heparin. Mean time to heal the skin defect was 4 weeks. No infection and recurrence was found in follow up period. Cosmetic results as judged by patients were that 3 cases are good and 3 cases are fair. Conclusion: Distally based ulnar artery flap is good treatment method among the numerous methods in the cases of skin defect, with soft tissue exposed, which is not covered with debridment and skin graft. Distally based ulnar artery flap is useful method for the skin defect of hands because it is simple procedure, has constant blood supply and relatively good cosmetic effect.

• Journal of Intelligence and Information Systems
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• v.27 no.1
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• pp.177-190
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• 2021

Due to the development of the fourth industrial revolution technology, efforts are being made to improve areas that humans cannot handle by utilizing artificial intelligence techniques such as machine learning. Although on-demand production companies also want to reduce corporate risks such as delays in delivery by predicting total production time for orders, they are having difficulty predicting this because the total production time is all different for each order. The Theory of Constraints (TOC) theory was developed to find the least efficient areas to increase order throughput and reduce order total cost, but failed to provide a forecast of total production time. Order production varies from order to order due to various customer needs, so the total production time of individual orders can be measured postmortem, but it is difficult to predict in advance. The total measured production time of existing orders is also different, which has limitations that cannot be used as standard time. As a result, experienced managers rely on persimmons rather than on the use of the system, while inexperienced managers use simple management indicators (e.g., 60 days total production time for raw materials, 90 days total production time for steel plates, etc.). Too fast work instructions based on imperfections or indicators cause congestion, which leads to productivity degradation, and too late leads to increased production costs or failure to meet delivery dates due to emergency processing. Failure to meet the deadline will result in compensation for delayed compensation or adversely affect business and collection sectors. In this study, to address these problems, an entity that operates an order production system seeks to find a machine learning model that estimates the total production time of new orders. It uses orders, production, and process performance for materials used for machine learning. We compared and analyzed OLS, GLM Gamma, Extra Trees, and Random Forest algorithms as the best algorithms for estimating total production time and present the results.

• Journal of the Korean Orthopaedic Association
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• v.53 no.6
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• pp.505-512
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• 2018

Purpose: Many reconstruction methods have been attempted after an en-bloc resection of the proximal humerus. In particular, the introduction of reverse shoulder arthroplasty (RSA) has made a breakthrough in the functional recovery of the shoulder. Nevertheless, RSA has limitations when the humeral bone stock loss is significant. In addition, it is unclear if RSA is effective in patients showing failure with non-operative treatment of a proximal humeral tumor. Materials and Methods: A reconstruction was performed using an overlapping allograft-RSA composite for 11 patients with a failed proximal humeral construct. Delayed RSA was performed on 6 patients with failed non-operative treatment. The pre- and postoperative Musculoskeletal Tumor Society (MSTS) score and the complications were addressed. Results: Overlapping allograft-RSA composite afforded a stable construct in 11 failed proximal humeral reconstructions and the patient's chief complaints were resolved. The mean time to the union of overlapped allograft-host junction was 5.5 months. Average preoperative MSTS score of 20.3 point increased to 25.7 point, postoperatively. Four of the six patients who had RSA within 4 years from the index operation showed arm elevation of more than $90^{\circ}$ whereas the remaining 5 patients showed some disability. The complications include one case each of dislocation and aseptic infection, which were resolved by changing the polyethylene liner and scar revision, respectively. None of the 6 patients who underwent delayed RSA after the failure of non-operative treatment showed arm elevation more than $90^{\circ}$. Conclusion: An overlapping allograft-RSA composite is a simple and reliable reconstructive modality in patients with massive bone loss. In patients with metastatic cancer necessitating a surgical resection at presentation, early conversion to RSA is recommended to secure functional recovery.