• The Journal of Engineering Geology
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• v.26 no.4
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• pp.485-495
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• 2016

To reinforce and improve the soft ground under a breakwater while using materials efficiently, the replacement ratio and leaving periods of surcharge load are optimized probabilistically. The results of Bayesian updating of the random variables using prior information decrease uncertainty by up to 39.8%, and using prior information with more samples results in a sharp decrease in uncertainty. Replacement ratios of 15%-40% are analyzed using First Order Reliability Method and Monte Carlo simulation to optimize the replacement ratio. The results show that replacement ratios of 20% and 25% are acceptable at the column jet grouting area and the granular compaction pile area, respectively. Life cycle costs are also compared to optimize the replacement ratios within allowable ranges. The results show that a range of 20%-30% is the most economical during the total life cycle. This means that initial construction cost, maintenance cost and failure loss cost are minimized during total life cycle. Probabilistic analysis for leaving periods of shows that three months acceptable. Design optimization with respect to life cycle cost is important to minimize maintenance costs and retain the performance of the structures for the required period. Therefore, more case studies that consider the maintenance costs of soil structures are necessary to establish relevant design codes.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.34-39
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• 2017

Typical flow regime of overflow at barrier or weir constructed in mid and small streams becomes as the submerged flow during most flood events. One of major causes of barrier failure has been reported as the levee-scour near the conjuction node between barrier and levee. However, most related design guidelines in Korea have not mentioned about the protection of levee around barrier or weir in detail. Furthermore, most previous researches have focused on the flow characteristics of overflow around several types of weirs but they did not have considered the material properties of levee itself. In this study, local scour near barrier was investigated with different material properties of levee under the submerged overflow condition which is assumed to reenact a flood event. Based on results from Fritz et al. and Mavis et al., a theoretical formula was also proposed in initial stage of laboratory experiments. And hydraulic experiments were carried out for the verification of the proposed formula. Levee was installed in the prismetic trapezoidal open channel and most parts were made of concrete except for movable section in which scour was expected to occur for the efficiency of experimental procedure. Each compaction of movable section in levee was followed by the basis of the KS F 2312. Further, after performing the experiments to find the optimum water content for each sediment, the specific amount of water was injected before flowing water. The difference between the proposed theoretical formula and experiment results was not much but considerable, which might be caused by the effect of compaction. For theoretical approach, it seemed that the formula did not take into account the compaction of levee, thus the correction coefficient for levee compaction determined in the literature was considered. Finally, the formula for the length of scour around barrier or weir was proposed, which can be useful to predict a levee in the reference design of revetment in mid and small streams. As shortly future study, scour length of levee around barrier or weir under different flow conditions such as perfect overflow condition will be studied and it will be able to contribute to suggest the design formula or criteria under all overflow conditions near barrier or weir.

• Korean Journal of Head & Neck Oncology
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• v.16 no.2
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• pp.172-176
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• 2000

Objectives: To improve local control and reduce toxicity, 3-D conformal radiotherapy was used as a boost the primary tumor site following fractionated radiotherapy in patients with nasopharyngeal carcinoma. Materials and Methods: Eight patients with previously untreated nasopharyngeal carcinomas were treated with 3-D conformal radiotherapy following fractionated radiotherapy from September 1998 to April 2000. All patients had biopsy confirmation of disease before radiation therapy. Stages were II in 1, III in 5, and IV in 2. Two patients received cisplatin based chemotherapy in addition to radiation therapy; induction chemotherapy in 1, concurrent chemoradiation in 1. 3-D conformal radiotherapy delivered using 6MV Linac as a boost(range 25.2-28.8Gy, median 25.7Gy) following conventionally fractionated radiotherapy(range 50.4Gy). Average total dose ranged from 75.6-79.2Gy(median 76Gy). Follow-up time was 4-21 months(median 9.6 months). Results: Seven of 8 patients were evaluated radiologically within 3 months after completion of radiation therapy. All 7 patients were seen complete remission. One of 7 patients had distant metastasis after 5 months and local failure after 7 months. The tree interval of local recurrence was ranged from 4 - 21 months(median 10.2 months). One patient without radiological evaluation got complete remission clinically. Treatment related toxicity was grade 1-3 xerostomia, dysphagia, and mucositis. During 3-D conformal radiotherapy, there was no aggravation of any toxicity. Conclusion: Although the number of patients was small and follow-up period was short, 3-D conformal radiotherapy following conventional radiotherapy improved tumor control and dose escalation without increased toxicity. Survival and late toxicity should be evaluated through long term follow-up. In addition, it is necessary to confirm the benefits of 3-D conformal radiotherapy in nasopharyngeal carcinoma with randomized trial.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.406-418
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• 2020

When developing weapons systems, it is important to implement the functions and performance of equipment suitable for development purposes, but it is very important to ensure that the equipment is capable of operating without any vacuum with reliability after development. Therefore, various activities are carried out to enhance reliability of equipment. Reliability is enhanced by using high-specification parts in development, reliability verification through analysis, and testing using development prototypes to reinforce and improve the parts that are lacking in equipment. However, recently, development schedules are shortened due to rapidly changing external conditions and technologies, and there are cases where sufficient reliability growth activities were not carried out due to problems such as cost. Examples are projects that perform reliability activities only in analytical methods (reliability, FMECA). In this paper, analyzing and testing methods for analysis and testing were carried out on the same equipment through FMECA and super-accelerated life test, the contents of reliability growth activity were derived, the results of design change/review were accordingly compared, the differences between the two methods were analyzed, and measures were proposed to strengthen reliable growth activities. It was concluded that reliable growth activities through analysis from the beginning of development and reliable growth activities through testing should be carried out at the completion of initial prototype production.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.474-482
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• 2020

To ensure the safe operation of offshore plants, a system is needed for evaluating the equipment performance and for monitoring the results. Currently, owing to the operating environments of of shore plants situated far from the land, measurement data must be periodically stored in storage devices and carried on the land for evaluating the equipment performance. Consequently, it is difficult to prevent equipment failure because the performance evaluation cycle is long. Furthermore, until the next performance evaluation is conducted, it is difficult to determine the equipment's degree of performance degradation. Hence, it is necessary to install an onboard equipment performance monitoring system within the offshore plant. In this study, to evaluate and visualize the results of equipment performance within an offshore plant, a database was designed as the initial step towards the development of an equipment performance monitoring system. The tag data of major equipment were selected and analyzed. Furthermore, in order to store and manage the data measured in real time within the offshore plant, a database was developed for the onboard equipment performance monitoring system.

• Journal of Yeungnam Medical Science
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• v.14 no.2
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• pp.393-398
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• 1997

An accurate early diagnosis of congenital midgut malrotation is essential to prevention of catastrophic effects of volvulus. To evaluate the usefulness of radiologic examinations in diagnosing intestinal malrotation, we retrospectively analyzed radiologic findings and operation records of 17 intestinal malrotation patients, who were radiologically diagnosed. The age range of the patients studied were from 1day to 12years. The presenting symptoms were vomiting, vomiting with abdominal pain, abdominal distention, diarrhea and failure to thrive. The viewpoints of this analysis were the location of duodeno-jejunal flexure on barium meal and cecal location on barium enema. Sixteen of 17 patients, who were radiologically diagnosed, were surgically proven, but one patient with annular pancreas was false positive. In the case of 3 surgically proved patients, malrotation was suspected on barium meal prior to the barium enema, but final diagnosis was determined on barium enema examination. We concluded that a barium enema should be performed on all children with suspected malrotation where the initial upper gastro-intestinal study was normal or suspicious on account of the small incidence of false positive and false negative barium meals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.579-584
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• 2017

The damper oil seal of a high-speed railway vehicle is made from nitrile butadiene rubber (NBR) in order to prevent lubricant from leaking into the damper and to stop harmful contaminants from entering the external environment while in service. Oil leakage through the seal primarily occurs from fatigue failure of the damper. Cumulative damage of the seal occurs due to the contact force between the rod and the rubber during movement due to track irregularities and cants, among other factors. Thus, the design of the oil seal should minimize the maximum principal strain at weak points. In this study, the optimal cross section of the damper oil seal was found using the multi-island genetic algorithm method to improve the durability of the damper. The optimal shape of the oil seal was derived using process automation and design optimization software. Nonlinear material properties for finite element analysis (FEA) of the rubber were determined by Marlow's model. The nonlinear FEA confirmed that the maximum principal strain at the oil leakage point was decreased 24% between the initial design and the optimum design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.537-544
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• 2017

An experimental study was carried out to investigate the characteristics of the propagation distance of a flood wave considering the levee failure speed in a flat inundation area. The Ritter solution for one dimensional flow was considered to formulate the experimental results and a representative form with coefficients of k and m, which consider the three dimensional flow characteristics, was applied. The experiments showed that the propagation velocity of the wave front in the inundation area was influenced by the levee breach speed as well as the initial water level, which is a significant variable representing the flood wave behavior. In addition, coefficients k and m are not constants, but variables that vary with levee breach speed. An empirical formula was also suggested using the experimental results in the form of the relationships between k and m. In this study, a large-scale experiment for flood inundation was carried out to examine the behavior of flooding in the inundated area and the relationships between the levee breach speed and wave-front propagation velocity were suggested based on the experimental results. These research results are expected to be used as the baseline data to draw a flow inundation map, establish an emergency action plan, and verify the two-dimensional numerical model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1227-1240
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• 2014

Abandoned mines often cause environmental problems, such as alteration of landscape, metal contamination, and landslides due to a heavy rainfall. Geotechnical and rheological tests were performed on waste materials corrected from Imgi waste rock dump, located in Busan Metropolitan City. Debris flow mobility was examined with the help of 1-D BING model which was often simulated in both subaerial and subaqueous environments. To determine flow curve, we used a vane-penetrated rheometer. The shear stress (${\tau}$)-shear rate (${\dot{\gamma}}$) and viscosity(${\eta}$)-shear rate (${\dot{\gamma}}$) relationships were plotted using a shear stress control mode. Well-known rheological models, such as Bingham, bilinear, Herschel-Bulkley, Power-law, and Papanastasiou concepts, were compared to the rheological data. From the test results, we found that the tested waste materials exhibited a typical shear shinning behavior in ${\tau}$-${\dot{\gamma}}$ and and ${\eta}$-${\dot{\gamma}}$ plots, but the Bingham behavior is often observed when the water contents increased. The test results show that experimental data are in good agreement with rheological models in the post-failure stage during shearing. Based on the rheological properties (i.e., Bingham yield stress and viscosity as a function of the volumetric concentration of sediment) of waste materials, initial flowing shape (5 m, 10 m, and 15 m) and yield stress (100 Pa, 200 Pa, 300 Pa, and 500 Pa) were input to simulate the debris flow motion. As a result, the runout distance and front velocity of debris flow are in inverse propositional to yield stress. In particular, when the yield stress is less than 500 Pa, most of failed masses can flow into the stream, resulting in a water contamination.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.4
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• pp.330-333
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• 2009

Alveolar bone resorption after extraction impairs the necessary bone volume and complicates the case for implant surgery and aesthetic implant prosthesis. Immediate implant surgery after extraction decreases the number of surgical procedures and the duration of treatment, while allowing minimum alveolar bone resorption and preserving the residual bone volume. Although immediate implant holds many advantages such as preservation of hard and soft tissue around the extraction socket, greater implant survival rate and higher patient satisfaction, various complications and high failure rate are discouraging factors for the clinicians. In this case report, severe alveolar bone resorption with soft tissue changes were predicted after the extraction of prolonged retained deciduous incisors and impacted maxillary canines and thus decided on immediate implant procedure. Immediate implant surgery after extraction was carried out with minimal bone reduction and tapered wide-neck implant to establish initial stability. Simultaneous bone graft was done by filling the defect area with iliac cancellous bone with additional onlay-type bone graft and absorbable membrane on the labial bone for upper lip support. A stable and esthetic result was obtained with shortened treatment period.