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Detailed first-principle models of grinding processes, while very satisfactory for simulation purposes, are not well suited for the development of control schemes due to their high level of complexity. In this study, a low-order model describing the time evolution of the particle distribution in a few size intervals is proposed. Using a maximum-likelihood approach, the model is identified and its...
Iterative ultrasonic computed tomography (UCT) based on ray theory uses the initial straight line paths to iterate that will lead to error diffusion. In this paper, we focus on the application of industrial flaw detection via UCT, in which the material to be detected is often a collection of a background area and a small amount of defect areas. An effective two-step algorithm is developed to reduce...
The recent advances in thin-film thermoelectric (TE) materials have created opportunities for on-chip cooling and energy-harvesting with heat-fluxes >100W/cm2. However, it remains unclear how effective these materials are in the context of realistic microprocessor floorplan and workloads. Moreover, these TE materials suffer from contact parasitics that can significantly impact their performance...
This document details the design, implementation and analysis of a clamped-clamped capacitively-coupled beam resonator with a high Q-factor [>10000] in the VHF band [30-300MHz]. The document also draws a parallel between simulation results and theoretical results of key performance metrics of the design.
We study free vibrations of a circular AT-cut quartz resonator using the two-dimensional scalar differential equation by Tiersten and Smythe in conjunction with COMSOL. Resonant frequencies and mode shapes are obtained and compared with available experimental results as well as available analytical solutions of the scalar equation. The accuracy of various analytical solutions is examined.
In this paper, we report on a dielectric study of a series of composite systems based upon a polystyrene matrix (έm ∼2.7) containing dispersed particles of lead zirconate titanate (PZT) and barium titanate (BaTiO3) (in both cases, έp ∼1000). These components were chosen to give a high dielectric contrast within the system and, because polystyrene is readily etched using permanganic reagents, the size...
This paper derives an explicit dispersion equation of SH waves propagating along the interface between a piezoelectric (PE) and a piezomagnetic (PM) half-space. It is assumed that the interface has a magneto-electro-elastic imperfect bonding. A general linear spring model, considering the spring constants of mechanical, electric and magnetic fields, simultaneously considering the coupled spring constants...
We study the horizontal shear (SH) wave problem propagating in a functionally graded piezoelectric material (FGPM) layered structure to compare the Wentzel-Kramers-Brillouin (WKB) method with the power series method. We establish coupled governing equations on the basis of elastodynamics theory. Both the WKB and power series methods are employed to solve the second-order variation coefficient equations...
The objective of this work is to use the Finite Element Method (FEM) to simulate the performance of a PVDF transducer array to measure temperature gradients through the determination of phase shifts, i.e. time shifts of the waveform of the echo due to a change in the speed of propagation of ultrasound as a result of a change in temperature, they can be interpreted as phase shifts in the frequency...
The electric stress control is important for improving insulation performance and upgrading design of power devices. In recent years, the technique of applying field grading material (FGM) is proposed for the designs of cable accessories and machine insulation, but fewer applications in HV bushing realm. In this paper, modeling of electric stress control in a simplified HV wall bushing is presented...
Smoke environment is a common condition during the fire-fighting operation, and the change of lighting's illuminating effect in the smoke environment is the issue concerned by fire department and lighting manufacturer. According to this issue, a development on lighting's smoke penetrability performance test device was conducted, and by this device an illumination change test was made for three types...
A thermo chromic materials named Salicylaldehyde ethanolamine Schiff base was synthesized with ethanolamine and salicylaldehayde derivative in the medium of ethanol, and was characterized by means of UV-Vis absorption, GCMS. The reaction kinetics of Schiff base production was investigated through UV-Vis absorption spectra, and also the thermochromism of Schiff Base Condensed from ethanolamine and...
Firstly, the theoretical model of polystyrene external thermal insulation material fires under conditions of window fire was put forward, the equations that calculate the important characteristic parameters of these fires such as the spread height, spread rate and ignition time were derived, and the relevant analyses were preliminarily made. Secondly, on the basis of theoretical analyses, the medium...
Flexure-based mechanisms like compliant actuation system embed complex dynamics which will reduces the control bandwidth and limit their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The free vibration signals of the hinge in three different damping configurations are measured...
This paper presents the modeling of thrust force in microdrilling processes of five commonly used alloys (titanium-based, tungsten-based, aluminum-based and invar). The process was carried out by peck drilling and the influence of five parameters (drill diameter, cutting speed, feed rate, one-step feed length and total drilling length) on the behavior of the thrust force was considered. A fuzzy system...
This paper experimentally explores thin film micro-contact pairs of Au-Au, Au-Ru and Au-RuO2 through the utilization of thin-film contact resistance and spreading resistance theory. Contacts of various combinations of material pairs, including evaporated Au lower planar contact and sputtered Au, Ru or Au-RuO2 upper hemispherical contact were fabricated and their performance monitored through many...
In earlier work it was recommended that accelerated tests, using elevated currents, be used to evaluate the performance of contact designs using materials that may be susceptible to electro-migration. This is necessary since it was found in earlier work that the type of self-diffusion in some cases had a major impact on time to failure. Since the type of diffusion is generally not known in advance,...
A novel prospective way of continuous surface heating of steel work-pieces by a laser beam is modelled. The process is supplemented with pre-heating and post-heating of the heated parts by a classic inductor in order to avoid unacceptably high temperature gradients and subsequent mechanical stresses in the processed material. Its continuous mathematical model is solved numerically in 3D in the hard-coupled...
A model is developed to determine the peak current required to weld large area closed contacts with ‘n’ points of contact when passing short duration, high fault currents. The model also predicts the threshold welding current for parallel contact structures used to carry large currents in high current switching devices. The model considers: (1) the total contact resistance of the closed contacts by...
The present paper describes the strategies used to compile and teach an Informatics course developed during last years at Tallinn University of Technology. The strategy is based on the main principles of blended learning and the analysis of the results of experiments with students from different faculties. Various tests were carried out to identify students' levels of knowledge and preferences in...
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