Many engineering applications make use of fiber assemblies under compression. Unfortunately, this compression behavior is difficult to predict, due to nonlinear compliance, hysteresis, and anelasticity. The main objective of this research is to develop an algorithm which is capable of incorporating the microscale features of the fiber network into macroscopic scale applications, particularly the modeling of contact mechanics in multibody systems. In micromechanical approaches, the response of a fiber assembly to an external force is related to the response of basic fiber units as well as the interactions between these units, i.e. the mechanical properties of the constituent fibers and the architecture of the assembly will both have a significant influence on the overall response of the assembly to compressive load schemes. Probabilistic and statistical principles are used to construct the structure of the uniformly-distributed random network. Different micromechanical approaches in modeling felt, as a nonwoven fiber assembly with unique mechanical properties, are explored to gain insight into the key mechanisms that influence its compressive response. Based on the deformation processes and techniques in estimating the number of fiber contacts, three micromechanical models are introduced: (1) constitutive equations for micromechanics of three-dimensional fiberwebs under small strains, in which elongation of the fibers is the key deformation mechanism, adapted for large deformation ranges; (2) micromechanical model based on the rate theory of granular media, in which bending and torsion of fibers are the predominant elemental deformations used to calculate compliances of a particular contact; and (3) a mechanistic model developed using the general deformation theory of the fiber networks with fiber bending at the micro level and a binomial distribution of fiber contacts. A well-established mechanistic model, based on fiber-to-fiber friction at the micro level, is presented for predicting the hysteresis in compression behavior of wool fiberwebs. A novel algorithm is introduced to incorporate a hysteretic micromechanical model - a combination of the mechanistic model with microstructural fiber bending, which uses a binomial distribution of the number of fiber-to-fiber contacts, and the friction-based hysteresis idea - into the contact mechanics of multibody simulations with felt-lined interacting bodies. Considering the realistic case in which a portion of fibers slides, the fiber network can be treated as two subnetworks: one from the fibers with non-sliding contact points, responsible for the elastic response of the network, and the other consisting of fibers that slide, generating irreversible hysteresis phenomenon in the fiberweb compression. A parameter identification is performed to minimize the error between the micromechanical model and the elastic part of the loading-unloading experimental data for felt, then contribution of friction was added to the obtained mechanistic compression-recovery curves. The theoretical framework for constructing a mechanistic multibody dynamic model of a vertical piano action is developed, and its general validity is established using a prototype model. Dynamic equations of motion are derived symbolically for the piano action using a graph-theoretic formulation. The model fidelity is increased by including hammer-string interaction, backcheck wire and hammer shank flexibility, a sophisticated key pivot model, nonlinear models of bridle strap and butt spring, and a novel mathematical contact model. The developed nonlinear hysteretic micromechanical model is used for the hammer-string interaction to affirm the reliability and applicability of the model in general multibody dynamic simulations. In addition, dynamic modeling of a flexible hub-beam system with an eccentric tip mass including nonlinear hysteretic contact is studied. The model represents the mechanical finger of an actuator for a piano key. Achieving a desired finger-key contact force profile that replicates that of a real pianist's finger requires dynamic and vibration analysis of the actuator device. The governing differential equations for the dynamic behavior of the system are derived using Euler-Bernoulli beam theory along with Lagrange's method. To discretize the distributed parameter flexible beam in the model, the finite element method is utilized. Excessive vibration due to the arm flexibility and also the rigid-body oscillations of the arm, especially during the period of key-felt contact, is eliminated utilizing a simple grounded rotational dashpot and a grounded rotational dashpot with a one-sided relation. The effect on vibration behavior attributed to these additional components is demonstrated using the simulated model.

SMA belongs to a class of so-called “smart materials” which possess properties that can be controlled by application of various types of stimuli – stress, temperature, electric field or magnetic field. In particular, SMA is a smart material which undergoes a temperature- or stress-dependent phase transformation giving it the property of remembering its original shape. Once deformed (up to a certain recoverable strain), SMA returns to its original shape upon heating. In this thesis, a study of SMA models and techniques to improve the performance of SMA actuators was carried out. In general, an SMA model is required for 3 main purposes: simulation, analysis and for model-based hysteresis compensation. In this work, the reduced-order form of John Shaw’s partial-differential equation model is chosen for implementation and simulation. The reduced-order form is used because its simpler structure makes it more useful for real-time control applications. The parameters were estimated for the John Shaw model followed by its implementation in MATLAB. From the view of control applications, a limitation of the John Shaw model is the inability to reproduce the so-called ‘minor loop behavior’ which is observed when the material is subject to cycling resulting in incomplete phase transformations. Modeling minor loop behavior is particularly important in closed-loop strain (or position) control applications since achieving a specific target strain between the two (load-dependent) extremes requires partial phase transformation. Herein, the governing equations are modified to include minor loop behavior. This behavior was tested using damped signals which would be expected to trigger minor loops in the actual SMA and reasonable match is observed from the simulations. The use of SMA actuators is limited by the relatively slow response time compared to other smart materials. The conventional current saturation (CS) scheme limits the maximum current into the wire at the manufacturer-specified safe current values in order to protect the wire from damage due to overheating. However, this is a conservative limit on the maximum current and hence, the response is artificially slowed. In order to improve the response time, a model-based temperature saturation (MBTS) scheme was developed, in which current is saturated based on model-predicted temperature. The MBTS scheme allows much higher currents to be applied to the wire, while ensuring that the wire is not damaged. Based on simulations using the reduced-order John Shaw model, it is observed that better tracking occurs using the MBTS scheme in the actuation scheme as compared to the CS scheme.

The performance of Thin Membrane Surface (TMS) highways is largely controlled by the strength of the subgrade soil which in turn is a function of the soil suction (Fredlund and Morgenstern, 1977). Thermal conductivity suction sensors can be used to indirectly measure in situ matric suction. <p>Thirty two (32) thermal conductivity sensors were installed under Thin Membrane Surface (TMS) in two highway locations; namely, Bethune and Torquay, Saskatchewan, in September 2000. The sensors were installed beneath the pavement, shoulder and side-slope to monitor matric suction and temperature changes with time. The monitoring system at Bethune was damaged after two years of operation. The thermal conductivity sensors at Torquay all appear to have been working well and data are still being collected.<p>Other attempts had been made in the past to use thermal conductivity sensors for field suction measurement, but all were terminated within a short period of time due to limitations associated with the equipment. The long-term suction measurement at the Torquay site is unique and provides valuable field data. <p>This research project presents and interprets the long-term matric suction measurements made between the years 2000 to 2005 at the Torquay site and from 2000 to 2002 at the Bethune site. To help in the interpretation of the data, a site investigation was undertaken along with a laboratory testing program that included the measurement of Soil-Water Characteristic Curves (SWCC). As well, a limited laboratory study was undertaken on several new thermal conductivity matric suction sensors. <p>The matric suction readings in the field showed a direct relationship to rainfall and regional evaporation conditions at the test sites. At the Bethune and Torquay test sites, the changes in matric suctions appeared to be mainly due to the movement of moisture through the edge of the road. Relatively constant equilibrium suctions were encountered under the driving-lanes. Conversely, matric suctions under the side-slopes were found to vary considerably with time and depth. Matric suctions under the driving-lanes ranged from 20 to 60 kPa throughout the years. Matric suctions on the side-slopes changed from 100 to 1500 kPa over the years. <p>The greatest variation of soil suctions occurred in the month of April from location to location in the subgrade. The soil suctions became less variable in June while larger variations again occurred from July to October. <p>The matric suction measurements obtained from the thermal conductivity sensors showed a general agreement with the values estimated using the soil-water characteristic curves, SWCC, measured in the laboratory.

In this study we use PDMS thin films to fabricate of multi-domain surface. PDMS gets the characteristic of good physical properties and chemical, not only low surface free energy, flexible, also has low toxicity, low cost and can protect our environment. We used the DI water that was dropped on the PDMS thin film surface and became stable to explore the wettability of the surface, and we had a discussion about when liquid crystal dropped on the PDMS thin film surface. Then we also observe the phenomenon that was liquid crystal will shift a little distance and we used the optical image to analyze our device.

The objective of this thesis is to provide a reliable and effective iron loss estimation scheme for the electromagnetic steel products in the design and on-line operation stages. To investigate the possible performance of electromagnetic steel products, proper iron loss information of the products that are constructed by different steels is one of the key concerns. Along with the various power electronic device applications and iron core structures, the magnetic fluxes flowing through the machine cores will be non-uniform and include harmonic terms. Unless excessive computation efforts in expensive software tools are performed, large discrepancies will be exhibited the estimated and actual values of machine iron losses. To overcome these drawbacks, a rational machine iron loss estimation scheme is proposed. By adopting the iterative magnetic equivalent circuits and the nonlinear magnetic characteristics of the electromagnetic steels, the preliminary operational flux information in the machine is first obtained, and then a numerical Epstein Frame test circuit with magnetizing inductance modeled by Preisach model is applied. With appropriate circuit input voltages devised from preliminary information, the detailed hysteresis inner-loop characteristics resulting from product structures and magnetization harmonics can be properly modeled. Based on the circuit results, the iron losses of electric machines with any operation can be rationally evaluated, and a valuable reference in machine designing can be provided.

The dynamic response and bifurcations of a harmonic oscillator with a hysteretic restoring force and sinusoidal excitation are investigated. A multilinear model of hysteresis is presented. A hybrid system approach is used to formulate and study the problem. A novel method for obtaining exact transient and steady state response of the system is discussed. Simple periodic orbits of the system are analyzed using the KBM method and an analytic criterion for existence of bound and unbound resonance is derived. Results of KBM analysis are compared with those from numerical simulations. Stability and bifurcations of higher period orbits are studied using Poincar´e maps. The Poincar´e map for the system is constructed by composing the corresponding maps for the individual subsystems of the hybrid system. The novelty of this work lies in a.) the study of a multilinear model of hysteresis, and, b.) developing a methodology for obtaining the exact transient and steady state response of the system.

It is well known that the Preisach model is useful to approximate the effect of hysteresis behavior in smart materials, such as piezoactuators and Shape Memory Alloy(SMA) wire actuators. For tracking control, many researchers estimate a Preisach model and then compute its inverse model for hysteresis compensation. However, the inverse of its hysteresis behavior also shows hysteresis behavior. From this idea, the inverse model with Kransnoselskii-Pokrovskii(KP) model, a developed version of Preisach model, can be used directly for SMA position control and avoid the inverse operation. Also, we propose another method for the tracking control by approximating the inverse model using an orthogonal polynomial network. To estimate and update the weight parameters in both inverse models, a gradient-based learning algorithm is used. Finally, for the SMA position control, PID controller, adaptive controllers with KP model and adaptive nonlinear inverse model controller are compared experimentally.

Ion-sensitive field effect transistors (ISFET's) have many advantages than the conventional ion selective electrode. Small size, fast response and compatible with conventional IC technologies were the most important advantages. The general structure of ISFET was the same with MOSFET, but the main difference is that the metal gate in MOSFET was replaced by reference electrode/electrolyte/insulator(ionic sensor membrane) structure in ISFET. The insulator surface will suffer the change of potential as the is sample immersed into electrolyte, by which, we can measure the pH or other ionic concentration. In this thesis the amorphous lead titanate (a-PbTiO3) thin film was prepared by sol-gel method to be the sensor gate of ISFET. The lead titanate thin films were deposited on SiO2(1000&#x00C5;)/p-Si substrates, and the EIS structure was obtained. The flat-band voltage(£GVBF) can be shifted by C-V measurement. The optimum conditions were found that the firing temperature was about 4000C and thin film thickness was about 0.5

The sol-gel-derived lead titanate (PbTiO3) membrane has been successfully applied as a novel pH-sensing layer to form the PbTiO3 gate ISFET (ion-sensitive field-effect transistor). There exhibit the excellent quasi-Nernstian response of 55-58 mV/pH, good surface adsorption and anticorrosion characteristics via the capacitance- voltage measurement of the electrolyte-insulator-semiconductor structure. At a specific pH concentration, the output and transfer characteristics of the PbTiO3 gate ISFET are very similar to the behaviours of MOSFETs (metal-oxide-semiconductor field-effect transistors), and the pH-ISFET model can be derived by the modified MOSFET model. As it operated in the nonsaturation region, there exhibits a linear pH response of about 55-58 mV/pH. Simultaneously, there exhibit the stable response time of 2-4 minutes, the drift of 0.5-1 mV/h, the hysteresis of 3-5 mV and the reduction rate of about ¡V10 mV/pH-day. On the other hand, as it operated in the saturation region, the pH responses and linearity can be controlled by adjusting the VGS values, e.g. the absolute pH response of 4.2, 24.8 and 31.3 uA/pH and the correlation coefficients of 0.9491, 0.9995 and 0.9996 at VGS= 1, 3 and 5 V can be obtained, respectively. Besides, the PbTiO3 gate ISFET has been modified by doping the Mg2+ and La3+ impurities into the PbTiO3 membrane. As a result, the former is a great benefit to improve the pH-sensing characteristics, which exhibits the pH response of 58-59 mV/pH, the drift of below 0.4 mV/h, the hysteresis of 1-3 mV and the reduction rate of -0.2 mV/pH-day. Finally, a digital pH meter has been successfully developed.

People for long term exposed to an air-conditioned but highly humid environment are vulnerable to hyper-sensitivity or asthma triggered by fungi or dust mites. This thesis aims to develop a high-linearity and low-hysteresis capacitive relative humidity (RH) microsensor to more precisely accommodate the humidity of living spaces. To reduce the hysteresis and enhance the linearity, this research uses not only one polyimide (PI) thin film as a humidity sensing layer but also utilizes another PI thin film as a protecting layer of the top electrodes. To improve further the RH sensitivity and responding speed, interlacing out-of-plane electrodes are designed in the RH microsensor. The main processing steps of the RH sensor developed in this study involve at least five photolithographic and four thin film deposition processes. The influences of sensing area, number of electrode pairs and testing temperature on the sensitivity and sensing linearity of humidity microsensors were investigated. Based on the measurement results, the sensitivity apparently increase as well as the sensing area (2 mm ¡Ñ 2 mm: 0.12 pF/%RH, 3 mm ¡Ñ 3 mm: 0.48 pF/%RH, 5 mm ¡Ñ 5 mm: 1.09 pF/%RH), and decrease with the number of electrode pairs (40 pairs: 0.51 pF/%RH, 20 pairs: 0.4 pF/%RH) and increase with the testing temperature. The thesis has demonstrated that the capacitance of the RH sensor vary from the relative humidity with a very linear relationship (linearity: 98.8%~99.99%) over the range of 30~70%RH. Finally, to increase effectively the surface area and to reduce further the hysteresis, three-dimensional (3D) moisture entrances and exits were designed and a very low hysteresis value (0.5%RH) can be achieved.