• Structural Engineering and Mechanics
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• 제60권3호
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• pp.405-412
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• 2016

Bone is a living material with a complex hierarchical structure that gives it remarkable mechanical properties. Bone constantly undergoes mechanical. Its quality and resistance to fracture is constantly changing over time through the process of bone remodeling. Numerical modeling allows the study of the bone mechanical behavior and the prediction of different trauma caused by accidents without expose humans to real tests. The aim of this work is the modeling of the femur fracture under static solicitation to create a numerical model to simulate this element fracture. This modeling will contribute to improve the design of the indoor environment to be better safe for the passengers' transportation means. Results show that vertical loading leads to the femur neck fracture and horizontal loading leads to the fracture of the femur diaphysis. The isotropic consideration of the bone leads to bone fracture by crack propagation but the orthotropic consideration leads to the fragmentation of the bone.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.389-392
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• 2004

It is clinically well known that pre-tension of wires increases the fracture stability in ring or hybrid external fixation. In some cases, additional half pin should be necessary to increase the stability when soft tissue impalement occurs during fixation. In this paper, the fracture stability of a hybrid external fixator system with different pre-tension effects and additional half-pins was analysed using FEM to investigate the effects of these pre-tension and half pin on the system stability quantitatively. 3-D finite element models of five different fixator frames were developed using by beam elements. In axial compression analysis, the fracture stiffness was increased maximally 62％ as the pre-tension increased. In torsion analysis, in the other hand, there is little variations in the fracture stiffness. Additional half pin increased the system stiffness about 200 ％. From the results, proper pre-tension and additional half pin would provide good methods to increase the fracture stability of the hybrid external fixator and provide more surgical options to minimize soft tissue damage at the fracture site.

• Archives of Plastic Surgery
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• 제35권6호
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• pp.675-679
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• 2008

Purpose: In the orbital floor fracture, sensory impairment due to the damage of the infraorbital nerve is one of the most common symptom and complication. In this report, we have the assumption that tailoring of $medpor^{(R)}$ for decompression may have correlations to the damage and regeneration of the nerve. Methods: Among patients who had open reduction for pure orbital floor fracture in our hospital from March 2005 to March 2008, we selected 80 cases. In 40 cases, we inserted tailored $medpor^{(R)}$, and in other 40 cases, non-tailored $medpor^{(R)}$ was inserted. Patient's reports were obtained and analyzed, and the pin-prick test and the 2-point discrimination test on the infraorbital nerve regions were done for testing the sensory impairments. Results: The results show that the patients who adopted sculpture of $medpor^{(R)}$ showed higher tendency of recovery of sensory impairments in the patient's subjective report, static touch sensation, static two point discrimination using. And in postoperative 3 months, there are statistically significant recovery of sensory symptoms, signs and the result of sensory tests. Conclusion: From these results, tailored $medpor^{(R)}$ in reconstruction of orbital wall fracture may improve recovery of sensory impairments for decreasing of compression of infraorbital nerve.

• Archives of Plastic Surgery
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• 제36권1호
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• pp.80-83
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• 2009

Purpose: Isolated hypoglossal nerve palsy is a rare manifestation of various underlying disease. This article presents a rare complication of general anesthesia associated with an surgical procedure on a case of zygomatic fracture. Methods: An 18-year-old female patient was referred to our department by painful swelling on her left zygomatic area after the traffic accident. Left zygomatic complex fracture was identified on the simple x-ray and facial bone CT scan, and the fracture was treated with open reduction and internal fixation under general anesthesia. On the first postoperative day, she complained of difficulty in swallowing solid food, dysarthria and deviated tongue to her right side. There was no abnormal findings on the neurological examination, brain MRI and routine chemistry. She was diagnosed with transient hypoglossal nerve palsy and dexamethasone with multi-vitamins was administrated intravenously for 5 days. Results: The symptoms were completely resolved by the ninth postoperative day and the patient was discharged without any other complications. Conclusion: The hypoglossal(cranial nerve XII)nerve supplies motor innervation to all of the ipsilateral extrinsic and intrinsic tongue muscles. The hypoglossal nerve damage may caused by the compression between the airway and the hyoid bone during the endotracheal intubation, and direct trauma due to excessive pressure or neck extension. We described a rare case of unintended injury to hypoglossal nerve and care must be taken not to cause the hypoglossal nerve damage especially in facial plastic surgery with excessive neck extension under general anesthesia.

• Steel and Composite Structures
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• 제20권4호
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• pp.833-849
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• 2016

Pre-stressing of existing structures using steel cables, FRP cables or FRP laminates has been successfully tried in the past. Retrofitting of beams using pre-stressed laminates does not utilize the full strength of the FRP due to de-bonding of the laminates before the fibre fracture. In the present study attempt has been made to overcome this problem by replacing the FRP laminates by the FRP sheets. In the present paper the effect of initial damage level and pre-stress level on strength, stiffness, cracking behaviour and failure mode of girders retrofitted using pre-stressed CFRP sheets has been studied. The results indicate that rehabilitation of initially damaged girders by bonding pre-stressed CFRP sheets improves the flexural behaviour of beams appreciably. However, it has been observed that with increase in pre-stressing force the load carrying capacity of the girders increases up to a particular level up to which the mode of failure is fibre fracture. Thereafter, the mode of failure shifts from fibre fracture to de-bonding and there is no appreciable increase in load carrying capacity with further increase in pre-stressing force.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2328-2335
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• 2002

A hybrid composite material has many potential usage due to the high specific strength and the resistance to fatigue, when compared to other composite materials such as fiber reinforced plastic(FRP) and metal matrix composite(MMC). However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. In this study, Al 7075 sheets and carbon epoxy preprags were used to fabricate the hybrid composite. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. AE technique was used to clarify the microscopic damage behavior and failure mechanism of A17075/CFRP hybrid composite. It was found that AE paralneters such as AE event, energy and amplitude were effective to evaluate the failure process of Al 7075/CFRP composite. In addition, the relationship between the AE signal and the characteristics of fracture surface using optical microscope was discussed.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.173-178
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• 2002

Fourier transform has been one of the most common tools to study the frequency characteristics of signals. With the Fourier transform alone, it is difficult to tell whether signal's frequency contents evolve in time or not. Except for a few special cases, the frequency contents of most signals encountered in the real world change with time. Time-frequency methods are developed recently to overcome the drawbacks of Fourier transform, which can represent the information of signals in time and frequency at the same time. In this study, heat damage process of a carbon fiber reinforced plastic(CFRP) and glass fiber reinforced plastic(GFRP) under monotonic tensile loading was characterized by acoustic emission. Different kinds of specimens were used to determine the characteristics of Strength and AE signals. Time-frequency analysis methods were employed for the analysis of fracture mechanism in CFRP such as matrix cracking, debonding and fiber fracture.

• 한국해양공학회지
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• 제37권3호
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• pp.111-121
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• 2023

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

• 대한두개안면성형외과학회지
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• 제21권1호
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• pp.7-14
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• 2020

Background: It is difficult to completely fix nasal bone fractures with closed reduction, as it is often accompanied by septal cartilage damage, and this often results in postoperative secondary deformities. Thus, patients are often reluctant to undergo closed reduction surgery. The present study aimed to evaluate aesthetic and functional satisfaction, as well as satisfaction with and complications of closed reduction, according to nasal bone fracture type. Methods: The subjects were patients who underwent closed reduction under general anesthesia from January 2017 to December 2018. Based on the modified Murray classification, patients were classified into five groups according to the fracture site, septal fracture, and deviation. A total of 211 patients were sent a web-based survey on postoperative satisfaction and complications, as well as intention for revision and cosmetic surgery. Sixty-one patients (28.9%) responded. Results: There were no significant differences in aesthetic and functional satisfaction or satisfaction with closed reduction according to the fracture type, site, or severity. Postoperative functional complications developed in 14 of 61 patients (22.95%). With 10 out of 24 (41.67%) patients (p = 0.044), the bilateral fracture with septal fracture or prominent septal deviation type had a higher incidence of complications than the other types. Conclusion: The incidence of complications is higher for bilateral fracture with septal fracture or prominent septal deviation compared to the other nasal bone fracture types. Therefore, long-term follow-up after closed reduction surgery for this fracture type can aid in establishing additional postoperative treatment plans and improving patient satisfaction.

• Computers and Concrete
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• 제33권5호
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• pp.605-619
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• 2024

The increase of reclaimed asphalt pavement (RAP) content in recycled asphalt concrete (RAC) is accompanied by the degradation of low-temperature cracking resistance, which has become an obstacle to the development of RAC. This paper aims to reveal the meso-scale mechanisms of the low-temperature fracture behavior of RAC and provide a theoretical basis for the economical recycling of RAP. For this purpose, micromechanical heterogeneous peridynamic model of RAC was established and validated by comparing three-point bending (TPB) test results against corresponding numerical simulation results of RAC with 50% RAP content. Furthermore, the models with different aggregate shapes (i.e., average aggregates circularity (${\bar{C_r}}=1.00$, 0.75, and 0.50) and RAP content (i.e., 0%, 15%, 30%, 50%, 75%, and 100%) were constructed to investigate the effect of aggregate shape and RAP content on the low-temperature cracking resistance. The results show that peridynamic models can accurately simulate the low-temperature fracture behavior of RAC, with only 2.9% and 13.9% differences from the TPB test in flexural strength and failure strain, respectively. On the meso-scale, the damage in the RAC is mainly controlled by horizontal tensile stress and the stress concentration appears in the interface transition zone (ITZ). Aggregate shape has a significant effect on the low-temperature fracture resistance, i.e., higher aggregate circularity leads to better low-temperature performance. The large number of microcracks generated during the damage evolution process for the peridynamic model with circular aggregates contributes to slowing down the fracture, whereas the severe stress concentration at the corners leads to the fracture of the aggregates with low circularity under lower stress levels. The effect of RAP content below 30% or above 50% is not significant, but a substantial reduction (16.9% in flexural strength and 16.4% in failure strain) is observed between the RAP content of 30% and 50%. This reduction is mainly attributed to the fact that the damage in the ITZ region transfers significantly to the aggregates, especially the RAP aggregates, when the RAP content ranges from 30% to 50%.