可穿戴设备是近几年发展最快的电子产品之一，但是目前电池寿命仍然不够长、换电池代价高等问题制约进一步发展。为解决该问题，本文提出一种可拉伸式压电振动能量采集器，通过转化肢体运动的能量直接为设备的供能。该器件由柔性衬底、压电铁磁性悬臂梁以及磁铁组成。当衬底被拉伸，悬臂梁从磁铁上分离，进入高频振动发电状态；当衬底从拉伸状态恢复，悬臂梁被磁铁吸引，再次高频发电。本工作先建立器件 3D 模型，用 COMSOL 结构力学得到的前三阶模态阵型，并和解析计算结果进行对比，阵型函数很相近。采用压电设备和 AC/DC 电路模块进行多物理场耦合：在特征值研究中，分析两次高频振动发电的固有频率和模态；在瞬态研究中，分析器件位移、电压等时域结果，采用对电压求积分的后处理办法计算平均发电效率；还对不同 AC/DC 电阻负载进行参数扫描，找到匹配电阻最大化发电效率。同时采用 AC/DC 无电流磁场模块 ...
Using Perturbation Force Analysis for the Design of a Levitronc: an Application of Magnetic Levitation
Z. De Grève[1,2], C.Versèle, and J.Lobry
Faculty of Engineering, Mons, Belgium
Belgian Fund for Research, F.R.S./FNRS, ResearchFellow, Belgium
The Levitron offers an interesting demonstration of natural magnetic levitation using permanent magnets. It is composed by a small magnetized top and a circular magnetized base with a hole on its center. The top is placed in an area where magnetic field configuration and gyroscopic torques allow the existence of a locus of stable equilibrium. In this paper, we intend to dimension and realize a ...
E. Zanchini, and T. Terlizzese
Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, Università di Bologna, Bologna, Italy
The results of two thermal response tests recently performed on two vertical borehole heat exchangers (BHEs) are presented. The BHEs have the same cross section and a depth of 100 m and 120 m respectively. The evaluation of the thermal properties of the ground and grout are performed by a finite-element simulation method, developed through the software package COMSOL Multiphysics 3.4.
INFN/LNL, Laboratori Nazionali di Legnaro, Legnaro, Italy
Many scientific instruments are based on high vacuum equipment with a gas pressure maintained in the order of 1 Pa or below. The gas flow in the low pressure limit, called the molecular flow regime, is a case of transport with zero viscosity. The ability to solve an integral equation on the boundary with finite elements methods allows us to find the gas densities and flows in the ...
Extraction of Phenolic Compound from Grape Fruit. A Comparison Between a 3D FEM Model and Experimental Results
E. Madieta, I. Zouid, R. Siret, and F. Jourjon
Laboratoire GRAPPE, ESA, Angers, France
Fresh fruits and vegetables are gaining importance in the human diet because they contain many beneficial compounds. Among these compounds, phenols are of vital importance due to their antioxidant properties. It is well evident from previous researches that the skin of red grapes is considered a good source of phenols. The aim of this work is to simulate the extraction procedure of phenols in ...
Kurt Lund Consulting, Del Mar, California, USA
A kernel of grain is modeled as an isothermal sphere, with descriptive differential equations scaled or rendered into non-dimensional form, where moisture transfer is governed by internal diffusivity, not by surface conditions. The time dependent problem is solved with COMSOL and the average non-dimensional moisture content and its time-rate of change are obtained; by regression, these numerical ...
Senior Materials Scientist, NASA Marshall Space Flight Center
A scientific hypothesis states that cryogenic trapped water is just under the surface of lunar soil at the poles in permanently shadowed craters. Microwave energy can be used to efficiently extract this water from permafrost. COMSOL permits calculation of the heating of simulated lunar soil using measured temperature dependent dielectric properties. Calculations at different microwave ...
Experimentally Matched Finite Element Modeling of Thermally Actuated SOI MEMS Micro-Grippers Using COMSOL Multiphysics
M. Guvench, and J. Crosby
University of Southern Maine, Gorham, Maine, USA
In “Micro-Electro-Mechanical-Systems” shortly known as MEMS, one of the most important and effective principle of creating transduction of electrical power to displacement force is thermal expansion. A slim beam of MEMS material, typically Silicon, is heated by the application of electrical current via Joule heating; it expands and creates motion. In the design of many MEMS devices ...
S. De Paolis, F. Lionetto, and A. Maffezzoli
Department of Innovation Engineering, University of Salento, Lecce, Italy
Finite element analysis has been used to model the ultrasonic wave propagation both in a custom made transducer and in the tested polymer sample. The model consists of acoustic (passive elements) and electroacoustic (active elements) transmission lines. The simulation of the acoustic propagation accounts for the interaction between the transducer and the materials in the buffer rods, and the ...
P. Lamy-Bracq and C. Coulouarn
Nexter Munitions, Tarbes, France
A solidification process of casting explosives in shell is studied in this paper. An enthalpy method approach is used to model the solidification process. Both the thermal and mechanical effects are taken into account. An ALE (Arbitrary Lagrangian-Eulerian) method is used to represent the physical deformation due to solidification. Results from the model are verified against experimental ...