• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.503-509
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• 2011

ECC is a micro-mechanically designed cementitious composite which exhibits tightly controlled crack width and strain hardening behavior in uniaxial tension while using a moderate amount of reinforcing fiber, typically less than 2% fiber volume fraction. Recently, a variety of applications of this material ranging from repair and retrofit of structures, cast-in-place structures, to precast structural elements requiring high ductility are developed. In the present study, a retrofitting method using ECC reinforced with high strength rebar was proposed to enhance load-carrying capacity and crack control performance of deteriorated reinforced concrete (RC) beams. Six beam specimens were designed and tested under a four-point loading setup. The flexural test revealed that load-carrying capacity and crack control performance were significantly enhanced by the use of ECC and high strength rebar. This result will be useful for practical field applications of the proposed retrofitting method.

• Composites Research
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• v.15 no.2
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• pp.32-39
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• 2002

This study focused on the introduction of processing procedure for microcapsules loaded with the healing agent and then microcapsules with the healing agent were manufactured by experiments. The DCPD (dicyclopentadiene) was used for the healing agent and the shell of microcapsules was consisted of urea-formaldehyde resin. The magnitude and the site distribution of microcapsules were measured by a particle size analyzer using laser diffraction technique. Thermal analysis was conducted by using a DSC fur the healing agent, microcapsules without the healing agent, and microcapsules with the healing agent. Also thermal stability was investigated by using a TGA under continuous and isothermal heating conditions far the healing agent, microcapsules without the healing agent, microcapsules with the healing agent. According to the results. microcapsules with the healing agent were verified to be so thermally stable that the healing agent could not evaporate until the shell of microcapsules were burned.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.269-272
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• 2008

This paper reports on the cracking mitigation and flexural behavior experimentally observed in concrete prisms layered with strain-hardening cement composites (SHCCs) which is micro-mechanically designed cement composite and exhibits pseudo tensile strain-hardening behavior accompanied by multiple cracking while using a moderate amount of fiber, typically less than 2 percent in term of fiber volume fraction. In this study, SHCC is reinforced with 1.3 percent polyvinyl alcohol (PVA) and 0.20 percent polyethylene (PE) in volume fraction. Tests were conducted using $100{\times}100{\times}400mm$ long prisms supported over a simply supported span of 350mm. The four point load was applied using MTS servo control machine. The thickness patched with SHCC is the main variable for this study. Experimental study shows that when subject to monotonic flexural loading, the SHCC layered repair system showed 2.7 - 4.2 times increased load carrying capacity, and mitigated cracking damage of concrete beams layered with SHCC compared with plain concrete beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.411-418
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• 2012

In this study, behavior of unpatched and patched cylindrical shells with through-wall cracks has been estimated using numerical experiments, and patching effect of them has been investigated according to various patching parameters. To show credibility of numerical models considered, two ways such as h- and p-methods have been adopted. Also, domain integral method and virtual crack extension method have been considered to calculate energy release rates based on linear elastic fracture mechanics. For examples, the unpatched cylindrical shells with circumferential cracks under remote tension have firstly been analyzed to show the validity of finite element modeling with h-method or p-method, and then the results have been compared with literature values published. Next, the sensitive analysis of patch repaired problems in terms of thickness of patch and adhesive, shear modulus of adhesive, composite material type of patch, crack length, etc. has been carried out.

• Computers and Concrete
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• v.19 no.3
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• pp.233-241
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• 2017

During the last two decades, CFRP have been extensively used for repair and rehabilitation of existing structures as well as in new construction applications. For rehabilitation purposes CFRP are currently used to increase the load and the energy absorption capacities and also the shear strength of concrete columns. Thus, the effect of CFRP confinement on the strength and deformation capacity of concrete columns has been extensively studied. However, the majority of such studies consider empirical relationships based on correlation analysis due to the fact that until today there is no general law describing such a hugely complex phenomenon. Moreover, these studies have been focused on the performance of circular cross section columns and the data available for square or rectangular cross sections are still scarce. Therefore, the existing relationships may not be sufficiently accurate to provide satisfactory results. That is why intelligent models with the ability to learn from examples can and must be tested, trying to evaluate their accuracy for composite compressive strength prediction. In this study the forecasting of wrapped CFRP confined concrete strength was carried out using different Data Mining techniques to predict CFRP confined concrete compressive strength taking into account the specimens' cross section: circular or rectangular. Based on the results obtained, CFRP confined concrete compressive strength can be accurately predicted for circular cross sections using SVM with five and six input parameters without spending too much time. The results for rectangular sections were not as good as those obtained for circular sections. It seems that the prediction can only be obtained with reasonable accuracy for certain values of the lateral confinement coefficient due to less efficiency of lateral confinement for rectangular cross sections.

• Archives of Reconstructive Microsurgery
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• v.1 no.1
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• pp.24-30
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• 1992

Tendocutaneous free flap transfer has been usually used to treat troublesome wounds, which had extensive defect of skin and tendons, since Daniel and Taylor had reported successful free flap transfer in 1973. Among the numerous types of free flap, the dorsalis pedis flap, which could include superficial peroneal nerve, extensor tendon and second metatarsus, was widely used as composite free flap. The authors analysed 13 cases of tendocutaneous free flap transfer from dorsum of the foot which were operated at Korea University Hospital from March 1981 to August 1991. The results were as follows: 1. The average size of these flaps was $53.7cm^2$(mazimum $82cm^2$, minimum $30cm^2)$, the average number and length of tendons were 2.9(maximum, 5, minimum 1), and 9.2cm (maximum 17cm, minimum 5cm). 2. The survival rate of flaps was 100%, and functional results by Dargan's criteria were 4 in excellent, 4 good, 3 fair and 2 poor. 3. The delayed healing on donor site could prevented by the meticulous skin graft and repair of extensor retinaculum. 4. The cases of electrical burn were more worse than the traumatic cases in functional results.

• Steel and Composite Structures
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• v.8 no.1
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• pp.1-18
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• 2008

Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. In addition, axial forces will be induced with temperature increasing and play an important role on the behaviour of the restrained beam. The factors influencing the behavior of a restrained beam subjected to fire include the stiffness of axial and rotational restraints, the load type on the beam and the distribution of temperature in the cross-section of the beam, etc. In this paper, a simplified model is proposed to analyze the performance of restrained steel beams in fire condition. Based on an assumption of the deflection curve of the beam, the axial force, together with the strain and stress distributions in the beam, can be determined. By integrating the stress, the combined moment and force in the cross-section of the beam can be obtained. Then, through substituting the moment and axial force into the equilibrium equation, the behavior of the restrained beam in fire condition can be worked out. Furthermore, for the safety evaluation and repair after a fire, the behaviour of restrained beams during cooling should be understood. For a restrained beam experiencing very high temperatures, the strength of the steel will recover when temperature decreases, but the contraction force, which is produced by thermal contraction, will aggravate the tensile stresses in the beam. In this paper, the behaviour of the restrained beam in cooling phase is analyzed, and the effect of the contraction force is discussed.

• Archives of Plastic Surgery
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• v.36 no.1
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• pp.46-50
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• 2009

Purpose: Finger injury by green onion cutting machine is one of the common hand injuries in the kitchen. It has a unique feature: there are multiple parellel laceration 3 - 5 mm wide. There are two directions of injuries(vertical, oblique). It may involve bone, tendon, nerve, and vessel injuries. We discuss its management and the long - term progress. Methods: We have treated six patients from 2003 to 2007. We carried out low tension approximation with thin suture materials to avoid ischemia and performed the additional operation as nail bed repair, tenorrhaphy, open reduction, vessel anastomosis, and composite graft. We reviewed the record of initial injury and collected the follow - up record. Results: They were all middle aged - women who had worked in the kitchen. Right hand was dominent over left hand. The ratio of the directions was 3 : 3 (vertical : oblique). They were all competely healed although there were three atrophy, four hyperesthesia, and one nail deformity. Conclusion: Finger injury by green onion cutting machine is a unique pattern of laceration with various accompanied injuries. It may look like a severe form of injury, but in most cases have relatively favorable progress. We have to perform careful examination of accompanied injuries and carry out the proper management. First and foremost, the user especially in the middle aged women should be warned to be careful in handling this risky machine.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.489-497
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• 2003

Bridge has to be long-spanned and of simple structure, considering the social environment. As a result of this trend in bridge construction, it is important for the sake of economical efficiency to improve the structural system and increase the life cycle of a bridge. To attain these goals in constructing a steel bridge, the detail analyses based on real structure must be performed. In the steel structure bridge, the parts that are a main focus of interest are the diaphragm and the vertical bracing of the steel box girder support. This study observed the behavior of the diaphragms on the bearings of a closed section steel box girder bridge support, as dead load was increased. Stress variation of the support diaphragms in a steel box girder was considered, and both experimental test and structural analyses were performed to verify the behavior of a composite steel box girder bridge under repair or maintenance.

• Journal of Chest Surgery
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• v.40 no.3 s.272
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• pp.225-227
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• 2007

The aortic inclusion technique is frequently used in the original Bentall's procedure for the control of excessive postoperative bleeding. Although this procedure has improved the outcome of patients with aortic root disease, there is a high incidence of both early and late complications, including coronary artery stenosis, kinking or pseudoaneurysm formation at the coronary suture lines. Pseudoaneurysm of the ascending aorta is a relatively rare, but fatal complication, which occurs after wrap-inclusion composite graft replacement. Herein, the case of a 45-year-old female, who developed a perigraft aortic pseudoaneurysm 10 years after a Bentall's procedure (wrap-inclusion technique), but was successfully managed using the Cabrol's method, is reported.