Hussain M. Al-Qahtani

Modeling the Electrostatic Deflection of a MEMS Multilayers Based Actuator

An actuator comprised of a rigid substrate and two parallel clamped-clamped microbeams is modeled under the influence of electrostatic loading. The problem is considered under the context of nonlinear Eulers mechanics, where the actuating system is described by coupled integrodifferential equations with relevant boundary conditions. Galerkin-based discretization is utilized to obtain a reduced-order model, which is solved numerically. Actuators with different gap sizes between electrode and beams are investigated. The obtained results are compared to simulations gotten by the finite-element commercial software ANSYS.

Influence of squeeze-film damping on the dynamic behavior of a curved micro-beam

A fixed–fixed curved micro-beam resonator under the influence of harmonic electrostatic field is considered. Due to the presence of incompressible fluid between the micro-beams and the electrode, a squeeze-film damping affects the dynamic behavior of the resonator. The combined effect of curved geometry and fluid squeeze-film damping is investigated for micro-beams with concave and convex geometries. A reduced-order model is obtained through the application of Galerkin discretization on a coupled fluid–structure system composed of the nonlinear Euler–Bernoulli beam equation and Burgdorfer’s model for the neighboring fluid. The dynamic behavior is assessed by investigating the influence of squeeze-film damping on the linear and nonlinear frequency response and the maximum resonant deflection of curved up and curved down micro-beams.

Laser Pulse Heating of Surfaces and Thermal Stress Analysis

PREFACE.- ACKNOWLEDGEMENTS.- INTRODUCTION.- EQUILIBRIUM LASER PULSE HEATING AND THERMAL STRESS ANALYSIS.- INTRODUCTION.- STEP INPUT LASER PULSE HEATING.- STRESS FREE BOUNDARY AT THE SURFACE.- STRESS CONTINUITY BOUNDARY AT THE SURFACE.- TIME EXPONENTIALLY VARYING LASER PULSE HEATING.- STRESS FREE BOUNDARY AT THE SURFACE.- STRESS FREE BOUNDARY AND CONVECTION AT THE SURFACE.- STRESS BOUNDARY AT THE SURFACE.- ENTROPY ANALYSIS DUE TO THERMAL STRESS FIELD.- FINDINGS AND DISCUSSIONS.- STEP INPUT PULSE HEATING.- TIME EXPONENTIALLY VARYING LASER PULSE HEATING.- ENTROPY ANALYSIS DUE TO THERMAL STRESS FIELD.- ANALYTICAL SOLUTION OF CATTANEO AND THERMAL STRESS EQUATIONS.- INTRODUCTION.- SURFACE HEAT SOURCE CONSIDERATION.- STEP INPUT PULSE HEATING.- EXPONENTIAL PULSE HEATING.- VOLUMETRIC SOURCE CONSIDERATION.- STEP INPUT PULSE HEATING.- EXPONENTIAL PULSE HEATING.- ENTROPY ANALYSIS.- FINDINGS AND DISCUSSION.- SURFACE HEAT SOURCE CONSIDERATION.- VOLUMETRIC HEAT SOURCE CONSIDERATION.- ENTROPY GENERATION RATE.- ANALYTICAL TREATMENT OF HYPERBOLIC EQUATIONS FOR STRESS ANALYSIS.- INTRODUCTION.- FORMULATION OF ENERGY TRANSPORT IN METALLIC SUBSTRATES AT MICROSCOPIC LEVEL.- THERMAL STRESS FIELD: CONSIDERATION OF SURFACE AND VOLUMETRIC SOURCES.- SURFACE HEAT SOURCE CONSIDERATION.- VOLUMETRIC HEAT SOURCE CONSIDERATION.- THERMAL STRESS FIELD: TWO-DIMENSIONAL CONSIDERATION.- FINDINGS AND DISCUSSIONS.- SURFACE HEAT SOURCE CONSIDERATION.- VOLUMETRIC HEAT SOURCE CONSIDERATION.- TWO-DIMENSIONAL ANALYSIS.- CONCLUDING REMARKS.- EQUILIBRIUM HEATING.- CATTANEO HEATING MODEL AND THERMAL STRESSES.- NON-EQUILIBRIUM HEATING.

Roll-to-Roll Microcontact Printing of Flexible Aluminum Substrates Using Octadecylphosphonic Acid (ODPA)

Soft-lithography, or the printing of self-assembling molecular inks at micro or sub-micron scale holds the promise of large-scale surface patterning for a variety of applications. One key to the ultimate utility of this concept is continuous roll-to-roll printing on lost-cost flexible substrates. Accordingly, this paper discusses the basic processes involved in roll-to-roll printing of octadecylphosphonic acid (ODPA) on aluminum-coated PET substrates using novel cylindrical stamps cast from PDMS. In addition to printing, visualization of the pattern is achieved through controlled condensation of water vapor and by a post-printing acid etch. By using a roll-to-roll configuration, along with continuous stamps and measurements that can permit real-time online quality monitoring, this method represents a significant step forward in making soft lithography a commercially viable process.Copyright

Design and Development of Instrumentation and Data Acquisition for a Photovoltaic Driven Community Scale RO Desalination System and its Performance Studies

This work is related to the design and development of instrumentation, data acquisition and graphical user interface of Photovoltaic driven Reverse Osmosis system for monitoring and performance evaluation purposes. Installed PV system comprises of 12 PV panels, trackers, batteries and inverter whereas RO system is equipped with pre filters, pumps, energy recovery devices and filtration membranes. Proper instrumentation is carried out in PV system to measure the irradiation, temperatures, voltage and current at various points. Moreover various sensors are used to measure the pressures, flows, salinities at RO unit. Signal conditioning circuits are designed to adjust sensor output signals for computer interface. A simple moving average filter is used to suppress the measurement noise. The experimental investigation of PVRO system is carried out by using LabVIEW interface capabilities. The developed system reveals and stores the pronounced impact of measured variables on the PV output power and specific energy consumption of the RO filtration system. The online data display in multi-scale window frame is very informative for system operation and analysis. During the experimental run of PVRO system using the developed DAQ system, the PV system generated 7.5kWh of energy during the whole day operation. Feed water having 7100ppm salinity and its flow rate was set to 850 lit/hour by adjusting the RPM of the high pressure pump. Clean water flow rate is recorded to be at 465 lit/hour having salinity of 115 ppm during the RO operation. Specific energy consumption of RO system comes out to be 2.083kWh/m3 for 7100ppm salinity of feed water.Copyright

Equilibrium Laser Pulse Heating and Thermal Stress Analysis

When the heating duration becomes greater than the thermalization time of the substrate material, equilibrium heating takes place in the laser irradiated region. In this case, the classical Fourier heating law governs the energy transport. Although the heating process is complicated, some useful assumptions enable to obtain the closed form solution for temperature and stress fields. Since the analytical solution provides the functional relation between the dependent variable and the independent parameters, it provides better physical insight into the heating problem than that of the numerical analysis. In this chapter, equilibrium heating of solid surfaces heated by a laser beam is considered. The closed form solution for the resulting temperature and stress fields are presented for various heating situations. The study also covers the phase change taking place at the irradiated region during the laser treatment process.

Analytical Treatment of Hyperbolic Equations for Stress Analysis

Laser ultra-short pulse heating of metallic surfaces causes the hyperbolic behavior of energy transport in the heated region. The consideration of the parabolic nature of the non-equilibrium heating situation fails to formulate the correct heating process. Although heating duration is ultra-short, material response to the heating pulse is not limited to only heat transfer and the mechanical response of the heated surface also becomes important. Consequently, mechanical response of the surface under ultra-short thermal loading becomes critical in terms of the generation of the high stress levels. In this chapter, hyperbolic behavior of heat transfer is introduced in the laser heated region. The closed for solutions for the temperature and stress fields are obtained for various heating situations. Two-dimensional effect of heating on temperature rise is also considered for nano-scale applications.

Analytical Solution of Cattaneo and Thermal Stress Equations

Laser short pulse heating of metallic surfaces initiates non-equilibrium energy transport in the irradiated region. In this case, thermal separation of electron and lattice sub-systems takes place. The thermal communication of these sub-systems occurs through the collisional process and the electrons transfer some of their excess energy during this process. Although electron temperature attains significantly high values due to the energy gain from the irradiated field through absorption, lattice site temperature remains low. Since the heated region is limited within a small volume, temperature gradients remain high across the irradiated region despite the attainment of low temperature field. Consequently, high temperature gradients cause the development of high thermal stress field in the small region. This limits the practical applications of the laser treatment process at microscopic scales. In this chapter, heat transfer at micro-scale is formulated and temperature field is presented analytically. The closed for solutions for the temperature and stress fields are obtained for various heating situations.

Modeling and Placement of Thermopiezoelectro-Magnetic Materials

There has been a vast interest in the general coupled field analysis of thermopiezoelectro-magnetic materials under which smart piezoelectric, thermopiezoelectric and magnetostrictive materials can be studied. The smart materials are often bonded as thin films on host structures for the purpose of sensing and/or actuation. It is well-known that the placement of sensors and actuators is important in order to obtain the appropriate sensor input and to provide the adequate actuation power. This study aims at modeling the important phenomenon of thermopiezoelectro-magnetism suitable for beam and/or plate type-host structures. The thermopiezoelectro-magnetic materials are modeled using the finite element method and the resulting equations are used for decision making on the best placement of the smart actuators on various host structures.