• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.70-73
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• 2003

Although there has been an upcoming recognition in the repairing reinforcement and remodeling of currently existing buildings with a regard to economic and resource saving effects of buildings roughly exposed to the open air for a long-term period, followed by a number of problems with the construction business operations that support economy-oriented projects within the limits of their short-term period durability, it is true that reasonable decisions of concrete performance are insufficient owing to the lack of proper history management for those existing buildings. This research attempted to comparatively analyze the compression strength together with investigation of carbonization depth and alkali concentration according to the passage of years on the subjects of aged buildings, and to provide basic data for remodeling and/or reconstruction of future construction structures by indirectly estimating durability lifetime expectancy according to carbonization phenomenon.

• Journal of Korean Physical Therapy Science
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• v.5 no.2
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• pp.595-602
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• 1998

The purpose of this study was to investigate the effect of sequential intermittent pneumatic compression in patients with lymphedema who were hospitalized for three days at Samsung Medical Center. Thirty-three subjects with lymphedema was selected by physician referral. A selection of the patients was made according to the following criteria : 1) no known metastases, 2) no infection after the a difference of at least 10% in the volumes of edematous limb. All patients were treated with the Lympha-Press(Model 103-A). Circumferential limb mesurements was done before and after a 3-day treatment period. As a result of sequential intermittent pneumatic compression therapy. All extremity showed a decrease in circumferential measurements with the maximal reduction occurring at the wrist(55.75 %) for the upper extremities and at the lower 1/3 of calf (40.61%) for the lower extremities. Upper extremity arm was reduced by 42.1% and lower extremity leg by 33.61%. In contrast with this, the proximal levels of arm patients and leg showed comparatively poor reduction than distal levels. Almost 44.44% of arm patients and 5.26% of leg patients experienced significant reduction(> 50%) after compression therapy. These data clearly indicates that Sequential Intermittent Pneumatic Compression Therapy was effective treatment for reducing of extremity volume in patients with lymphedema. but this was variable degree and dependent on the amount of pre-existing lymphedema. Other factors such as duration of edema, etiology, previous history of radiology, age did not appear to influence the extend of improvement. Further sutdies will be necessary to determine long term benefit of this therapy.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.61-74
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• 2011

This is a fundamental research on use as fill material of lightweight waste such as bottom ash and tire shred. We carried out the test for particle size distribution, specific gravity, density, shear strength, permeability and vertical compression settlement, considering water content change and temperature effect of several waste materials. Bottom ash, which is lighter than soils, has similar permeability and particle size distribution to those of weathered soils. But permeability may differ depending on the particle size distribution. The shear strength aspect of bottom ash and tire shred mixed materials are similar to that of natural fill materials. In the 1-D vertical compression settlement test, we could be assured that bottom ash and tire shred mixed materials showed similar compression settlement to that of sand under actual vertical stress. Furthermore, materials including bottom ash showed smaller compression settlement than that of weathered soils in the long-term settlement test under wetting and freezing-thawing condition.

• Smart Structures and Systems
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• v.19 no.3
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• pp.269-277
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• 2017

Recently, there has been significant interest in structural health monitoring for civil engineering applications. In this research, a specially designed tendon, proposed by embedding FBG sensors into the center king cable of a 7-wire strand tendon, was applied for long-term health monitoring of tensile forces on a ground anchor. To make temperature independent sensors, the effective temperature compensation of FBG sensors must be considered. The temperature sensitivity coefficient ${\beta}^{\prime}$ of the FBG sensors embedded tendon was successfully determined to be $2.0{\times}10^{-5}^{\circ}C^{-1}$ through calibrated tests in both a model rock body and a laboratory heat chamber. Furthermore, the obtained result for ${\beta}^{\prime}$ was formally verified through the ground temperature measurement test, expectedly. As a result, the ground temperature measured by a thermometer showed good agreement compared to that measured by the proposed FBG sensor, which was calibrated considering to the temperature sensitivity coefficient ${\beta}^{\prime}$. Finally, four prototype ground anchors including two tension ground anchors and two compression ground anchors made by replacing a tendon with the proposed smart tendon were installed into an actual slope at the Yeosu site. Tensile forces, after temperature compensation was taken into account using the verified temperature sensitivity coefficient ${\beta}^{\prime}$ and ground temperature obtained from the Korean Meteorological Administration (KMA) have been monitored for over one year, and the results were very consistent to those measured from the load cell, interestingly.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.43-50
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• 2012

In this research, the value of consolidation index was investigated. The range of the investigated standard deviation was analyzed and the deviation based settlement was calculated. Also, the compression index, which is the effect of the uncertainty in the ground was analyzed using the flimsy ground construction method. The settlement behavior in each embankment compaction stage was analyzed by applying the precompression load method, drainage expediting method, and displacement method through numerical analysis. In addition to the above, the settlement behavior was studied by analyzing the Piled Raft method which is stable for long term settlement. As a result, the final settlement amount based on average analysis results was that the settlement based on each of the average interpretation value, mean value of the maximum and minimum value and average compression index was different. The result of the comparison shows the difference in variation coefficient by the difference in time. Amongst them, the Piled Raft method shows the most consistent variation coefficient regardless of time and it also was least affected by the compression index of uncertainty.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.597-609
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• 2020

Accident Tolerant Fuels have been widely studied since the Fukushima-Daiichi accident in 2011 as one of the options on how to further enhance the safety of nuclear power plants. Deposition of protective coatings on nuclear fuel claddings has been considered as a near-term concept that will reduce the high-temperature oxidation rate and enhance accidental tolerance of the cladding while providing additional benefits during normal operation and transients. This study focuses on experimental testing of Zr-based alloys coated with Cr-based coatings using Physical Vapour Deposition. The results of long-term corrosion tests, as well as tests simulating postulated accidents, are presented. Zr-1%Nb alloy used as nuclear fuel cladding serves as a substrate and Cr, CrN, Cr_xN_y layers are deposited by unbalanced magnetron sputtering and reactive magnetron sputtering. The deposition procedures are optimized in order to improve coating properties. Coated as well as reference uncoated samples were experimentally tested. The presented results include standard long-term corrosion tests at 360℃ in WWER water chemistry, burst (creep) tests and mainly single and double-sided high-temperature steam oxidation tests between 1000 and 1400℃ related to postulated Loss-of-coolant accident and Design extension conditions. Coated and reference samples were characterized pre- and post-testing using mechanical testing (microhardness, ring compression test), Thermal Evolved Gas Analysis analysis (hydrogen, oxygen concentration), optical microscopy, scanning electron microscopy (EDS, WDS, EBSD) and X-ray diffraction.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.85-97
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• 2005

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exist concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependent deformation characteristics of geosynthetic reinforced soil under sustained and/or repeated loads were investigated using a series of plane strain compression tests on geogrid reinforced weathered granite soil specimens. The results indicate that sustained or repeated loads can yield appreciable magnitudes of residual deformations, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1287-1296
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• 2007

Recently, the high speed railway comes into the spotlight as the important and convenient traffic infrastructure. In Korea, Kyung-Bu high speed train service began in about 400km section at 2004, and the Ho-Nam high speed railway will be constructed by 2017. The high speed train will run with a design maximum speed of 300-350km/hr. Since the trains are operated at high speed, the differential settlement of subgrade under the rail is able to cause a fatal disaster. Therefore, the differential settlement of the embankment must be controlled with the greatest care. Furthermore, the characteristics and causes of settlements which occurred under construction and post-construction should be investigated. A considerable number of studies have been conducted on the settlement of the natural ground over the past several decades. But little attention has been given to the compression settlement of the embankment. The long-term settlement of compacted fills embankments is greatly influenced by the post-construction wetting. This is called 'hydro collapse' or 'wetting collapse'. In spite of little study for this wetting collapse problem, it has been recognized that the compressibility of compacted sands, gravels and rockfills exhibit low compressibility at low pressures, but there can be significant compression at high pressures due to grain crushing by several researchers(Marachi et al. 1969, Nobari and Duncan 1972, Noorany et al. 1994, Houston et al. 1993, Wu 2004). The characteristics of compression of fill materials depend on a number of factors such as soil/rock type, as-compacted moisture, density, stress level and wetting condition. Because of the complexity of these factors, it is not easy to predict quantitatively the amount of compression without extensive tests. Therefore, in this research I carried out the wetting collapse tests, with focusing in various soil/rock type, stress levels, wetting condition more closely.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.19-26
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• 2012

Recently the world has been suffering from difficulties related to the demand and supply of energy due to the democratic movements sweeping across the Middle East. Consequently, many have turned their attention to never-developed extreme regions such as the polar lands or deep sea, which contain many underground resources. This research investigated the strength and initial elastic modulus values of eternally frozen ground through a uniaxial compression test and indirect tensile test using frozen artificial soil specimens. To ensure accurate test results, a sandymud mixture of standard Jumunjin sand and kaolinite (20% in weight) was used for the specimens in these laboratory tests. Specimen were prepared by varying the water content ratio (7%, 15%, and 20%). Then, the variation in the strength value, depending on the water content, was observed. This research also established three kinds of environments under freezing temperatures of $-5^{\circ}C$, $-10^{\circ}C$, and $-15^{\circ}C$. Then, the variation in the strength value was observed, depending on the freezing environment. In addition, the tests divided the loading rate into 6 phases and observed the variation in the stress-strain ratio, depending on the loading rate. The test data showed that a lower freezing temperature resulted in a larger strength value. An increase in the ice content in the specimen with the increase in the water content ratio influenced the strength value of the specimen. A faster load rate had a greater influence on the uniaxial compression and indirect tensile strengths of a frozen specimen and produced a different strength engineering property through the initial tangential modulus of elasticity. Finally, the long-term strength under a constant water content ratio and freezing temperature was checked by producing stress-strain ratio curves depending on the loading rate.

• Journal of Korean Neurosurgical Society
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• v.45 no.6
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• pp.369-374
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• 2009

Objective : Percutaneous vertebroplasty (VP) can provide immediate stabilization in pathologic fractures of spinal tumors. However, long term follow-up data in cases of pathologic fractures are lacking. The authors report follow-up results of VP in 185 pathologic fractures of 102 spinal tumor patients. Methods : Percutaneous VP was performed at 185 vertebral bodies of 102 patients from 2001 to 2007. Retrospective analysis was done with medical records and radiological data. The change of visual analogue score (VAS), vertebral body (VB) height and kyphotic angle were measured preoperatively and on postoperative one day and at 3, 6, and 12 months. Results : The patients were composed of metastatic spine tumors (81%) and multiple myeloma (19%). Involved spinal segments were between T6 and L5. Mean follow-up period was 12.2 months. VAS for back pain was 8.24 preoperatively, 3.59 (postoperative one day), 4.08 (three months) and 5.22 (one year). VB compression ratio changed from 21.33% preoperatively to 13.82% (postoperative one day), 14.36% (three month), and 16.04% (one year). Kyphotic angle changed from $15.35^{\circ}$ preoperatively to $12.03^{\circ}$ (postoperative one day), $13.64^{\circ}$ (three month), and $15.61^{\circ}$ (one year). Conclusion : Immediate pain relief was definite after VP in pathologic compression fracture of osteolytic spinal disease. Although VAS was slightly increased on one year follow-up, VP effect was maintained without significant change. These results indicate that VP could be a safe and effective procedure as a palliative treatment of the spinal tumor patients.