Particle Damping with Granular Materials for Multi Degree of Freedom System

A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF) structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF) system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range

Effectiveness of Electroconvulsive Therapy for Depression and Cotard’s Syndrome in a Patient with Frontotemporal Lobe Dementia

In the field of psychogeriatrics, the differential diagnosis of depression and dementia, as well as the treatment of depression and comorbid dementia, is an important issue. In this paper, the authors present the case of a 72-year-old woman with Cotard’s syndrome and frontotemporal dementia (FTD) who was admitted to a psychiatric hospital with delusions of negation accompanied by depressive symptoms. Pharmacotherapy over a 2-year hospitalization was unsuccessful, and she was subsequently transferred to our university hospital. A total of 18 sessions of electroconvulsive therapy released her from psychomotor inhibition, appetite loss, and Cotard’s delusions. The indication for electroconvulsive therapy in patients with dementia is discussed