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Studying thin film damping in a micro-beam resonator based on non-classical theories

Acta Mechanica Sinica 2016年第3期32卷 369-379页

作者： mina ghanbari Siamak Hossainpour Ghader Rezazadeh Mechanical Engineering Department Sahand University of Technology Mechanical Engineering Department Faculty of Engineering Urmia University

In this paper, a mathematical model is presented for studying thin film damping of the surrounding fluid in an in-plane oscillating micro-beam resonator. The proposed model for this study is made up of a clamped-clamped micro-beam bound between two fixed layers. The microgap between the micro-beam and fixed layers is filled with air. As classical theories are not properly capable of predicting the size dependence behaviors of the micro-beam,and also behavior of micro-scale fluid media, hence in the presented model, equation of motion governing longitudinal displacement of the micro-beam has been extracted based on non-local elasticity theory. Furthermore, the fluid field has been modeled based on micro-polar theory. These coupled equations have been simplified using Newton-Laplace and continuity equations. After transforming to non-dimensional form and linearizing, the equations have been discretized and solved simultaneously using a Galerkin-based reduced order model. Considering slip boundary conditions and applying a complex frequency approach, the equivalent damping ratio and quality factor of the micro-beam resonator have been obtained. The obtained values for the quality factor have been compared to those based on classical theories. We have shown that applying non-classical theories underestimate the values of the quality factor obtained based on classical theo-ries. The effects of geometrical parameters of the micro-beam and micro-scale fluid field on the quality factor of the resonator have also been investigated.

关键词： Thin film damping micro-electromechanical systems(MEMS) Micro-polar theory

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Enhancement of Periodontal Healing by Application of a Novel Ointment Compared with Hyaluronic Acid, Histological Observation in Animal Model

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Modern Research in Inflammation 2014年第3期3卷 71-81页

作者： ghanbari Habiboallah Zakeri Mahdi Saghravanian Nasroallah Zakeri Massoud Baradaran Nasseri Ehsan Zareian Jahromi mina Sardari Kamran Department of Oral and Maxillofacial Pathology School of Dentistry and Maxillofacial Diseases Research Center Mashhad University of Medical Sciences Mashhad Iran Department of Periodontics School of Dentistry and Dental Research Center Mashhad University of Medical Sciences Mashhad Iran School of Dentistry Mashhad University of Medical Science Mashhad Iran School of Dentistry Shahed University Tehran Iran School of Veterinary Medicine Ferdowsi University of Mashhad Mashhad Iran

Objectives:?The early healing of the periodontal wound in oral cavity may be critical to the treatment outcome. Thus, we made a novel ointment based on natural constituents that our recent investigation suggested a positive therapeutic effects on gingival wounds. The present study was conducted to evaluate the role of this novel biomaterial on periodontal wound healing including soft as well as hard tissue. Materials and Methods: Experimental periodontitis was induced by wire tied around the cement-enamel junction of I2, P1, P3?and M1?in six adult, healthy beagle dogs. After 3 months, mucoperiostal flap elevated and root surfaced was thoroughly scaled and planed. Randomly, three materials including our ointment with two different ratios including materials A and B and hyluronic acid were applied topically and then the flaps were repositioned and sutured. Three dogs at day 7 and the three remaining ones two weeks post-surgery were sacrificed and histological changes were monitored. Results: The result of this study showed that the local applications of this novel ointment promoted the healing process particularly fibroblast proliferation and collagen density remarkably in comparison with hyaluronic acid and control group. Besides, histological finding of our material revealed that in general terms had all the hallmarks of complete healing two weeks post operatively. Conclusion: Our novel material appeared to have outstanding effect on periodontal wound healing which can improve the periodontal healing consequences and provide better strength of periodontal wound flap. From a clinical standpoint, it could play an important role for better repair in diabetic patients who frequently present difficulties in mucosal and cutanous wound healing.

关键词： Anti-Inflammatory Healing Hyaluronic Acid Ghee Periodontal Flap Surgery Animal Model

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