• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.91-103
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• 2023

This study aims to investigate the dynamic fracture characteristics of rocks and rock-like materials subjected to the Nonex Rock Cracker (NRC), a vapor pressure crushing agent that produces vapor pressure by instantaneously vaporizing a liquid mixture crystallized through the thermite reaction. Furthermore, the study seeks to develop an analytical technique for predicting the fracture pattern. A dynamic fracture test was performed on a PMMA block, an artificial brittle material, using the NRC. High-speed cameras and dynamic pressure gauges were employed to capture the moment of vapor pressure generation and measure the vapor pressure-time history, respectively. The 2-dimensional Dynamic Fracture Process Analysis (2D DFPA) was used to simulate the fracture process caused by the vapor pressure, with the applied pressure determined based on the vapor pressure-time history. The proposed analytical method was used to examine various fracture patterns with respect to granite material and high-performance explosives.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.115.2-115.2
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• 2005

• Steel and Composite Structures
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• v.20 no.4
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• pp.913-930
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• 2016

It is common practice to use Reduced Web Beam Sections (RWBS) in steel moment resisting frames. Perforation of beam web in these members may cause stress and strain concentration around the opening area and facilitate ductile fracture under cyclic loading. This paper presents a numerical study on the cyclic fracture of these structural components. The considered connections are configured as T-shaped assemblies with beams of elongated circular perforations. The failure of specimens under Ultra Low Cycle Fatigue (ULCF) condition is simulated using Cyclic Void Growth Model (CVGM) which is a micromechanics based fracture model. In each model, CVGM fracture index is calculated based on the stress and strain time histories and then models with different opening configurations are compared based on the calculated fracture index. In addition to the global models, sub-models with refined mesh are used to evaluate fracture index around the beam to column weldment. Modeling techniques are validated using data from previous experiments. Results show that as the perforation size increases, opening corners experience greater fracture index. This is while as the opening size increases the maximum observed fracture index at the connection welds decreases. However, the initiation of fracture at connection welds occurs at lower drift angles compared to opening corners. Finally, a probabilistic framework is applied to CVGM in order to account for the uncertainties existing in the prediction of ductile fracture and results are discussed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.284-287
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• 2005

The flow of groundwater in fractured medium is related to the geometric characteristics of the fracture system. And a fracture aperture and a fracture density are considered as important factor concerning the permeability. Data acquisition of the properties of fracture such as aperture and density is so difficult and has uncertainty. We also cannot know the fracture characteristics through the in-situ tests. We usually obtain the fracture information from a ultrasonic scan logging or borehole television indirectly. Using the deduced results, we can make the fracture system and simulate the groundwater flow and solute transport in the crystalline rock. This study aimed to analyze the correlation between the properties of fracture and hydraulic conductivities obtained at the same interval. The properties of fracture are examined by acoustic televiwer and hydraulic conductivities are obtained by constant Pressure injection test. The distributioin of fracture width and fracture frequency shows the log-normal probability plot. And, Results of correlation analysis explain that opened type fractures have proper relation with hydraulic conductivity. But, as though there are semi-opened type fractures or closed type fractures, those have the permeable structure.

• Transactions of Materials Processing
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• v.32 no.2
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• pp.92-99
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• 2023

In this study, shear fracture specimens are designed using finite element analyses for the characterization of ductile fracture criteria of metal sheets. Many recently suggested ductile fracture criteria require experimental fracture data at the shear stress states in the model parameter identification. However, it is challenging to maintain shear stress states in tension-based specimens from the initial yield to the final fracture, and the loading path can be different for the different materials even with the same shear specimen geometries. To account for this issue, two different shear fracture specimens for low ductility/high ductility metal sheets are designed using the sensitivity tests conducted by finite element simulations. Priorly mechanical properties including the Hosford-Coulomb fracture criterion of the aluminum alloy 7075-T6 and DP590 steel sheets are used in the simulations. The results show that shear stress states are well-maintained until the fracture at the fracture initiation points by optimizing the notch geometries of the shear fracture specimens.

• Journal of Chest Surgery
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• v.45 no.4
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• pp.246-250
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• 2012

Background: Although it is rare for the fracture itself to become a life threatening injury in patients suffering from rib fracture, the lives of these patients are occasionally threatened by other associated injuries. Especially, early discovery of patients with rib fracture and intra-abdominal organ injury is extremely important to the prognosis. This study analyzed the link between rib fracture and intra-abdominal injury to achieve improved treatment. Materials and Methods: Among trauma patients that had visited the hospital emergency room from January 2007 to December 2009, a retrospective study was conducted on 453 patients suffering from rib fracture due to blunt trauma. Rib fracture was classified according to location (left, right, and bilateral), and according to level (upper rib fracture [1-2nd rib], middle rib fracture [3-8th rib], and lower rib fracture [9-12th rib]). The researched data was statistically compared and analyzed to investigate the correlation between the location, level, and number of rib fracture and intra-abdominal organ injury. Results: Motor vehicle injury was found to be the most common mechanism of injury with 208 cases (46%). Associated injuries accompanied with rib fracture were generated in 276 cases (61%). Intra-abdominal organ injury was discovered in 97 cases (21%). Liver injury was the most common intra-abdominal injury associated with rib fracture with 39 cases (40%), followed by spleen injury, with 23 cases (23%). Intra-abdominal injury according to level of rib fracture was presented as upper rib fracture in 11 cases (11%), middle rib fracture in 31 cases (32%), and lower rib fracture in 55 cases (57%), thus verifying that intra-abdominal injuries were commonly accompanied in lower rib fractures (p=0.03). In particular, significant increase of intra-abdominal injury was presented in fractures below the 8th rib (p=0.03). The number of intra-abdominal injuries requiring emergency operations was significantly higher in patients with more than 6 rib fractures (p=0.04). Conclusion: Intra-abdominal organ injury is more common in patients with lower rib fracture, especially fractures below the 8th rib. Intra-abdominal organ injuries generated in multiple rib fracture patients with more than 6 fractures significantly higher severity. These cases must be thoroughly inspected and carefully observed as there is possibility of emergency operation.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.13-19
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• 2015

This paper presents a hydraulic fracture propagation model to describe propagation more realistically. In propagating the hydraulic fractures, we have used two criteria: maximum tangential stress to determine the fracture initiation angle and whether a hydraulic fracture intersects a natural fracture. The model was validated for the parameters relevant to fracture propagation, such as initiation angle and crossing ability through natural fracture. In order to check whether a hydraulic fracture crosses a natural fracture, the model results on crossing state excellently matched with the experimental data. In the sensitivity analysis for direction of maximum horizontal stress, frictional coefficient of fracture interface, and natural fracture orientation, the results show that hydraulic fracture intersects natural fracture, and then, propagated suitably with theoretical results according to fracture interaction criterion. In comparison of this model against vertical fracture approach, it was ascertained that there are discrepancies in fracture connectivity and stimulated reservoir volume.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.1
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• pp.1-8
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• 2012

This study is a basic experimental research to apply FRP (Fiber Reinforced Polymer) box members to slabs and girders among various architectural structures, which receive bending stress. We prepared prefabricated FRP member and connected it to an FRP box member as a large cross section before we conducted an experiment in diverse conditions to analyze characteristics of compressive fracture behavior. In this study, we carried out a compressive fracture behavior test according to fillers on the upper part of the FRP box member, loading methods, and connective types and thereby performed a finite element analysis. The comparison of analysis results with test results revealed that rigidity was found to be slightly low, while stress was concentrated on the fracture point of the sample.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.611-623
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• 1998

The delamination fracture of multidirectional carbon-fiber/epoxy laminates under the Mode I condition has been studied using the modified beam analysis for a fracture mechanics approach. It was found that the variation of fracture energy $G_IC$ with increasing length of the propagating crack exhibited a minimum for the pure interlaminar fracture and a maximum for the intraply fracture,i.e. a rising "R-curve", which was strongly affected by the degree of fiber bridging and crack-tip splitting arising in the global delamination. The maximum $G_IC$ value was significantly dependent on such types of delamination as no crack jumping, crack jumping into the adjacent ply and edge-delamination. It was shown also that the value of "effective flexural modulus" estimated from the modified beam analysis increased much with the development of fiber bridging behind the crack tip.ehind the crack tip.

• Journal of Korean Biological Nursing Science
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• v.18 no.4
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• pp.193-202
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• 2016

Purpose: The study was to analyze clinical outcomes and risk factors of for complications associated with the hip fracture surgery in the elderly before and after interdisciplinary treatment. Methods: A retrospective method was used to investigate the general and therapeutic characteristics, frequency of complications and clinical outcomes. The subjects of the study were 553 patients who underwent hip fracture surgery from January, 2009 to December, 2014. Results: The interdisciplinary group was older and less likely to walk independently even before the fracture than a usual care group. The incidence of complications was higher in the interdisciplinary group than the usual care group. The prevalence of complications in both groups was 66.5%. Multivariate logistic regression analysis showsed that the risk factors for complications of hip fracture surgery were as follows: advanced age, stroke, Parkinson disease, time interval from emergency room to operation, pre & post ambulatory status, American Society of Anesthesiologists (ASA) classification quality of postop intensive care unit (ICU) care and foley indwelling. Conclusion: This study has implications in that it recognized the necessity for interdisciplinary treatment and provided the basic base data for nursing intervention of the elderly patients who underwent hip fracture surgery.