• Tuberculosis and Respiratory Diseases
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• 제71권1호
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• pp.59-61
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• 2011

Obstructive Fibrinous Tracheal Pseudomenbrane (OFTP) is a rarely known but potentially fatal complication of endotracheal intubation. Sudden respiratory failure shortly after extubation is not infrequent in the ICU. However, these cases are commonly diagnosed as laryngospasm, retention of secretion or laryngeal edema. A 68-year-old woman presented with a 6-day history of progressive dyspnea. She had undergone invasive ventilator care for 24 hours. The patient was discharged from the hospital with improvement after having an extubation. However, after 3 days she revisited the emergency department with progressive dyspnea. The patient was diagnosed with OFTP from the results of chest CT and bronchoscopy. This is the first case studied in detail using CT images, pulmonary function test, and bronchoscopy.

• Wind and Structures
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• 제28권6호
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• pp.389-404
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• 2019

In coastal regions, it is common to witness significant damages on low-rise buildings caused by hurricanes and other extreme wind events. These damages start at high pressure zones or weak building components, and then cascade to other building parts. The state-of-the-art in experimental and numerical aerodynamic load evaluation is to assume buildings with intact envelopes where wind acts only on the external walls and correct for internal pressure through separate aerodynamic studies. This approach fails to explain the effect of openings on (i) the external pressure, (ii) internal partition walls; and (iii) the load sharing between internal and external walls. During extreme events, non-structural components (e.g., windows, doors or rooftiles) could fail allowing the wind flow to enter the building, which can subject the internal walls to lateral loads that potentially can exceed their load capacities. Internal walls are typically designed for lower capacities compared to external walls. In the present work, an anticipated damage development scenario is modelled for a four-story building with a stepped gable roof. LES is used to examine the change in the internal and external wind flows for different level of assumed damages (starting from an intact building up to a case with failure in most windows and doors are observed). This study demonstrates that damages in non-structural components can increase the wind risk on the structural elements due to changes in the loading patterns. It also highlights the load sharing mechanisms in low rise buildings.

• Structural Engineering and Mechanics
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• 제39권3호
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• pp.427-447
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• 2011

The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.

• 대한기계학회논문집A
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• 제37권1호
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• pp.83-88
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• 2013

연쇄붕괴는 충격이나 폭발 등의 비정상 하중에 의하여 구조물의 하중 전달요소가 제거됨으로써 구조물의 일부 또는 전체가 연쇄적으로 붕괴되는 형상을 말한다. 예상외의 하중이 기둥부재에 작용할 경우, 좌굴이 발생하며 내력저하가 급격히 진행되어 붕괴에까지 이르게 된다. 하지만 좌굴 후 에너지를 흡수할 수 있는 잔존내력이 충분하면 붕괴를 막을 수 있다. 따라서, 구조물이 최종 붕괴상태에 도달되는 전 과정에 대한 기둥부재의 하중-변형관계를 명확히 파악할 필요가 있다. 본 논문에서는 비선형유한요소해석을 실시하여 H 형 강재기둥의 단부 구속조건이 고정일 경우 잔존내력의 변화추이를 파악하였다. 또한, 처짐이론을 기반으로 이론식을 도출하여 해석값과의 적합성을 검토하였다.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.381-394
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• 2019

If an alternative path would not be considered for redistribution of loads, local failure in structures will be followed by a progressive collapse. When a vertical load-bearing element of a steel structure fails, the beams connected to it will lose their support. Accordingly, an increase in span's length adds to the internal forces in beams. The mentioned increasing load in beams leads to amplifying the moments there, and likewise in their corresponding connections. Since it is not possible to reinforce all the elements of the structure against this phenomenon, it seems rational to use other technics like specified strengthened connections. In this study, a novel connection is suggested to handle the stated phenomenon which is introduced as a passive connection. This connection enables the structure to tolerate the added loads after failing of the vertical element. To that end, two experimental models were constructed and thereafter tested in half-scale, one-story, double-bay, and bolted connections in three-dimensional spaces. This experimental study has been conducted to compare the ductility and strength of a frame that has ordinary rigid connections with a frame containing a novel passive connection. At last, parametric studies have been implemented to optimize the dimensions of the passive connection. Results show that the load-bearing capacity of the frame increased up to 75 percent. Also, a significant decrease in the displacement of the node wherein the column is removed was observed compared to the ordinary moment resisting frame with the same loads.

• Computers and Concrete
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• 제21권2호
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• pp.189-197
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• 2018

A discrete element approach is used to investigate the effects of confining stress on the shear behaviour of joint's bridge area. A punch-through shear test is used to model the concrete cracks under different shear and confining stresses. Assuming a plane strain condition, special rectangular models are prepared with dimension of $75mm{\times}100mm$. Within the specimen model and near its four corners, four equally spaced vertical notches of the same depths are provided so that the central portion of the model remains intact. The lengths of notches are 35 mm. and these models are sequentially subjected to different confining pressures ranging from 2.5 to 15 MPa. The axial load is applied to the punch through the central portion of the model. This testing and models show that the failure process is mostly governed by the confining pressure. The shear strengths of the specimens are related to the fracture pattern and failure mechanism of the discontinuities. The shear behaviour of discontinuities is related to the number of induced shear bands which are increased by increasing the confining pressure while the cracks propagation lengths are decreased. The failure stress and the crack initiation stress both are increased due to confining pressure increase. As a whole, the mechanisms of brittle shear failure changes to that of the progressive failure by increasing the confining pressure.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3199-3210
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• 1996

The buckling and postbuckling behaviors were sutdied analytically and experimentally for stiffened laminated composite panels under compression loading. The panels with I-, blade, -and hat-shapeed stiffeners were investigated. In the analysis, the stiffened panels were anlyzed using the nonlinear finite element method combined with an improved arc-length method. The progressive failure analysis was done by adopting the maximum stress criterion and complete unloading failure model. The effects of the fiber angles were investigated on the buckling and postbuckling behaviors. In the experiment, the web and the lower cap of each stiffener were formed by the continuous lay-up of the skin for cocuring the stiffened panels. Therefore, the separation between stiffener and skin was not found in the junction part even after postbuckling ultimate load and the stiffened panels had excellent postbuckling load carrying capacity. A shadow moire thchnique was used to monitor the out-of-plane deformations of the panels. The piezoelectric films were attached to the panels to get the failure characteristics of the panel. The analytical results on the buckling load, postbuckling ultimate load, and failure pattern showed good agreement with the experimental results.

• Journal of Korean Neurosurgical Society
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• 제50권2호
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• pp.99-102
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• 2011

Objective : The purpose of this retrospective study was to evaluate the outcome of gamma knife radiosurgery (GKRS) and/or whole brain radiation therapy (WBRT) for the treatment of small cell lung carcinoma (SCLC) metastasis to the brain. Methods : From 2000 to 2010, 50 patients underwent GKRS for metastatic brain lesions originating from SCLC. Among these patients, 11 received prophylactic cranial irradiation (PCI) before the development of metastatic lesions (PCI group), and GKRS was performed as an initial treatment for newly diagnosed lesions in 12 patients who had not received PCI (primary GKRS group). In addition, GKRS was performed as a salvage treatment for progressive lesions after WBRT in 27 patients (salvage GKRS group). The medical records and imaging data of all patients were retrospectively analyzed. Results : The overall survival of the 50 patients was 20.8 months (range 1-53) after the diagnosis of primary tumor and 12.0 months (range 1-47) after the development of cerebral metastasis. Median survival after GKRS was 4.8 months (range 1-15) in the PCI group, 4.6 months (range 0-18) in the primary GKRS group, and 7.6 months (range 0-33) in the salvage GKRS group. Further treatment for progressive lesions after GKRS was necessary in 15 patients, after a mean interval of 3.8 months. Causes of death were systemic organ failure in 15 patients, deterioration of neurological state in 13 patients, and unknown or combined causes in 16 patients. The local control rate of the lesions treated with GKRS was 76.4% (decreased in 13 patients and stable in 16 patients at the final imaging follow-up (mean 5.60 months). Conclusion : GKRS is an effective local treatment for brain metastasis from SCLC both as an initial treatment for newly diagnosed lesions after PCI and as a salvage treatment for recurrent or progressive lesions. However, the survival benefit is not significant because most patients die of systemic multi-organ failure with a short life expectancy.

• Geomechanics and Engineering
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• 제20권5호
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• pp.399-410
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• 2020

Cavities often develop behind the vault during the construction of double-arch tunnels, generally in the form of various defects. The study evaluates the impact of cavities behind the vault on the mechanical and failure behaviors of double-arch tunnels. Cavities of the same sizes are introduced at the vault and the shoulder close to the central wall of double-arch tunnels. Physical model tests are performed to investigate the liner stress variation, the earth pressure distribution and the process of progressive failure. Results reveal that the presence of cavities behind the liner causes the re-distribution of the earth pressure and induces stress concentration near the boundaries of cavities, which results in the bending moments in the liner inside the cavity to reverse sign from compression to tension. The liner near the invert becomes the weak region and stress concentration points are created in the outer fiber of the liner at the bottom of the sidewall and central wall. It is suggested that grouting into the foundation soils and backfilling injection should be carried out to ensure the tunnel safety. Changes in the location of cavities significantly impact the failure pattern of the liner close to the vault, e.g., cracks appear in the outer fiber of the liner inside the cavity when a cavity is located at the shoulder close to the central wall, which is different from the case that the cavity locates at the vault, whereas changes in the location of cavities have a little influence on the liner at the bottom of the double-arch tunnels.

• Journal of Acupuncture Research
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• 제31권3호
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• pp.67-73
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• 2014

Objectives : Amyotrophic lateral sclerosis(ALS) is a progressive neurodegenerative disorder characterized by a selective death of motor neuron, leading to respiratory insufficiency. The purpose of this study was to assess the long term respiratory management of ALS patient with respiratory failure. Methods : One ALS patient applying a non-invasive BIPAP ventilator as well as Korean medical treatment such as acupuncture, pharmacopuncture and herbal medicine was measured on $SpO_2$, $EtCO_2$, Vte(expiratorytidalvolume) for 2 years 7 months. Results : The $SpO_2$, $EtCO_2$ of ALS patient were maintained in the normal range for 2 years 7 months. The Vte of ALS patient also wasn't worse in this study. Conclusions : In this study, the long term respiration management, combined administration of Korean medical treatment and non-invasive BIPAP ventilator, could be effective in ALS patient with respiratory failure.