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RISS 인기검색어
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- 저자 : Ebrahim Safari (검색결과 2 건)
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Is Facet Tropism Associated with Increased Risk of Disc Herniation in the Lumbar Spine?
Hassan Ghandhari,Ebrahim Ameri,Habib Hasani,Mir Bahram Safari,Ali Tabrizi 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.3
Study Design: Retrospective case control study. Purpose: In current study, we compared the incidence of facet tropism (FT) in patients with lumbar disc herniation and normal controls. Overview of Literature: It has been suggested that FT can be associated with increased risk of lumbar disc herniation. Methods: A total of 66 and 63 patients with L4/L5 and L5/S1 disc herniation, respectively, were evaluated in the present study. The control group comprised 61 normal subjects. Facet joint angle was measured using axial magnetic resonance images. The FT was defined as a difference of >10° between the right and left facet joints. The incidence of FT was compared between patients and controls. We also investigated the relationship between facet orientation (sagittal or coronal) and side of disc herniation. Results: The incidence of FT at the L4/L5 level was significantly higher in patients with disc herniation (48.5% vs. 26.2%, p =0.01), while it was found to be the same at the L5/S1 level in patients and controls (50.8% vs. 36%, p =0.098). Among the 64 patients with FT, intervertebral disc herniation occurred significantly toward the more sagittally oriented facet joint in 41 patients (p <0.05). Conclusions: FT is associated with increased risk of L4/L5 intervertebral disc herniation, but not at the L5/S1 level. In addition, disc herniation occurred toward the more sagittally oriented facet joint.
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Thermal and stress analyses in an end-pumped Nd:YAG slab laser using finite element method
Mina Babaei Bavil,Ebrahim Safari 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8
The increasing application on high laser power in industries required studies in the portion of pump radiation absorbed by laser mediathat exchanges to heat. Heat may cause thermal stress, stress birefringence and thermal lens effects. These effects can destroy the opticalproperties of the laser medium, decrease the beam quality and may lead to medium break. In this paper, the thermal and stress analyses ofcontinuous and pulsed end-pumped Nd:YAG slab laser are studied using finite element method. Heat deposited in the slab is removed bycooling water, flowing on the largest faces of the slab, which surrounds the active media. The temperature and stress distributions of theend-pumped Nd:YAG slab are defined by coupled field methods in the ANSYS commercial finite element software. The value of maximumtemperature and stress in the slab which is affected by an end-pumping are calculated. Finally the maximum pump-power rangewhich can be applied to the slab is determined using the limit of maximum stress in the slab. The analyses are done in from transient tosteady-state regimes for continuous pumping. Results show that deposited heat due to the pulsed pumping acts like a mechanical impact.
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