DEM

O Departamento de Engenharia Mecânica do IST acumula a experiência de várias décadas de empenhamento em actividades de ensino, investigação e desenvolvimento. A diversidade de competências intrínsecas a um corpo docente próprio qualificado e constituído quase integralmente por titulares do grau de doutor (cerca de 90 doutores) associadas à qualidade e variedade dos equipamentos experimentais que se encontram instalados nos seus laboratórios conferem ao actual Departamento de Engenharia Mecânica do IST a excelência indispensável a um ensino de elevada qualidade.


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Artigo Científico

24 Fevereiro 2015, 15:15 - Jorge Manuel Fontes Coelho

Teixeira, A.P., Guedes Soares, C., Chen, N.Z. e Wang, G., 

Uncertainty analysis of load combination factors for global longitudinal bending moments of double hull tankers”,

Journal of Ship Research, Vol. 57(1), 2013, da autoria de Professores do DEM (Área Cientifica de Engenharia e Arquitetura Naval), foi distinguido como “Significant Paper of 2013” pela Society of Naval Architects and Marine Engineers (SNAME).O "Journal of Ship Research" é uma das revistas de maior prestigio científico a nível mundial em Engenharia Naval.


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Mechanical Aspects of Natural and Reconstructed Hearing

2 Março 2015, 11:06 - Jorge Manuel Fontes Coelho

Dr. Albrecht Eiber

Institute of Engineering and Computational Mechanics, University of Stuttgart, Germany
e-mail: Albrecht.Eiber@itm.uni-stuttgart.de
 
Local:  Sala de reuniões do Departamento de Engenharia Mecânica; Pavilhão de Mecânica III
Data:   5 de Março de 2015
Hora:  11:30 Horas
 
Informações:  
Prof. Jorge  Ambrósio, Dept. de Engenharia Mecânica, 21 8419044.
Prof. Miguel Silva, Dept. Engª Mecânica, 21 8417024
Prof. Paulo  Fernandes, Dept. Engª Mecânica, 21 8417925
 
Biographic Highlights:
Scientic Background: description and simulation of dynamical systems. Area of research since 25 years: Dynamics of Hearing; Academic Director of Mechanical Engineering until 2015; Long term research cooperation with otosurgeons.
 
Summary:
To achieve good hearing results after surgical reconstruction is a most challenging task for otosurgeons. For that it is helpful to know about the mathematical background of the complex mechanical processes in the middle ear and the cochlea. First, the frequency dependent transfer behavior of sound through the middle ear to the basilar membrane in terms of dynamical transfer behavior with natural frequencies and vibrational modes is discussed based on mechanical computer models. With such models the effects of diseases like otosclerosis or partial malleus head fixation can be studied. For the surgeon, they facilitate the appropriate choice of passive or active implants to reconstruct damaged hearing and allow the optimization of surgical procedures.
The sound transfer in physiological range of sound intensity can be described with linearized models whereas large quasistatic pressure variations or internal preloads must be treated by fully nonlinear descriptions. In case of reconstructions, such preloads can be intrinsic, e.g. due to implant coupling or scar tissue and may lead to a distorted sound transfer. The reconstruction with various types of passive prostheses is considered. They may differ in material, the points of attachment and in the mechanical principle of coupling them to the natural structures. Particularly, the vibrational behavior and the principle how the implant is attached to the bones or membranes determines the quality of sound transfer as well as the handling and safety of application. Different coupling principles like plastic crimping, elastic clips or shape memory alloys (Nitinol) are discussed concerning contact forces, application forces and damping of the interface layers.
Active implants offer an amplification of sound and therefore feed-back effects may occur. The implants have to be classified according to their driving principle (piezoelectric or magnetic coils) and the fixation of the actuator´s base (free floating or skull coupled). Again, the coupling interface between actuator and ossicles or round window membrane plays the crucial role for the sound transfer. The particular properties and advantages of the different configurations are discussed.
Introducing a CI-electrode into the inner ear for an electrical stimulation, the hydrodynamics of inner ear fluid is changed. Important issues of the altered travelling waves of the basilar membrane are the surgical modifications at the round window, the creation of a third window, the stiffness of the oval window and the vibrational behavior of the CI-electrode itself. These facts become important when a combined stimulation is in focus, e.g. natural excitation of lower frequencies utilizing a residual hearing and an additional electrical stimulation of the higher frequencies. Appropriate measures are addressed to asses a reconstruction. For a detailed judgment, the entire system of natural ear with particular disease and the implant with actuator, amplifier and microphone has to be taken into account. Here, the mechanical aspects are considered from the clinical point of view.

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