Continue reading »]]> Due to their high torque-to-loss ratio, permanent magnet synchronous machines PMSM) have received increasing attention in automotive applications over the past decade. Because of this unique characteristics, many applications have utilized PMSM. In addition to high efficiency, quiet operation of the machines is desirable in automotive, naval and military applications. In order to operate at high efficiency quietly, the torque pulsation or torque ripple needs to be monitored and mitigated accurately. Magnitude of the torque ripple is influenced by the magnetic design cogging torque) and excitation, and the pattern of ripple is affected by the machines geometry stator slots). Field reconstruction method FRM) has been presented and used in this thesis. FRM introduces the reconstruction of the electromagnetic fields due to the phase currents using basis functions and using one single magnetostatic solution from FEA. The implementation of field reconstruction method based on finite element analysis FRM based on FEA) is performed Matlab/simulink program. Principally, the FRM needs the three-phase stator currents and rotor position of the machine. Next, to accurately calculate torque pulsation, the tangential and normal components of magnetic field, need to be computed. As a result, FRM can correctly calculate the torque of PMSM. In experience, the investigation shows that FRM can accurately calculate the torque pulsation or cogging torque under both balanced and unbalanced operations. Furthermore, the FRM can confirm the effect of torque ripple originated from the geometry of PMSM. In fact, a 12 stator slots PMSM was studied, and the calculation was done by FRM. The resultant torque calculated by FRM shows the accurate calculation of the torque. The experimental results show that FRM can accurately predict the torque.

Continue reading »]]> Flexible reflectors are used for a number of applications in space, including resource monitoring, weather analysis, hazard assessment, reconnaissance, and imaging. With the rapid advances in deployable membrane and mesh antenna technologies, the feasibility of developing large, lightweight reflectors has greatly improved, though high-precision surface control is needed in order to achieve the required surface accuracy. The purpose of this research is to advance the state of the art by implementing high-precision surface control on a flexible reflector using PVDF actuators, as well as introducing methods to overcome real world problems that can develop when implementing this technology. To facilitate the design and analysis of a reflector/actuator system, a theoretical model is derived. The reflector is modeled as a thin, shallow, spherical cap, and the system is solved using a Ritz method with Fourier-Bessel series expansion. PVDF surface actuators are modeled using the same method and are assumed to be perfectly bonded to the reflector surface. The model can be quickly modified in order to accommodate different actuator locations. Surface errors comparable to those the reflector would experience in space are modeled, including “W-error” caused by the inflation of the reflector and the error experienced from temperature changes as the reflector circles the earth. Experimental results show that while the analytical reflector model is generally correct, due to idiosyncrasies in the reflector it should not be used for online control. Therefore, a methodology is proposed for online system identification for use with an online control law. Using the PVDF actuators, surface control is executed using a least squares control law, where photogrammetry is used to determine the out-of-plane displacement at designated points on the surface. Least squares can be used because of the quasi-static nature of the surface error. While there is a time dependence in the temperature profile, the rate of change is very low, so that at any moment in time the surface error can be assumed to be static. Using the least squares control, it is shown that on a theoretical 35 meter space reflector with the surface fully covered by PVDF actuators, the error resulting from a 40 K temperature change on the entire surface of the reflector can be controlled to within the desired tolerances. When the surface cannot be fully covered with actuators, optimal placement of the available actuators must be considered. First, when focusing solely on the constraint on the number of possible actuators, optimal placement of the actuators is found using a genetic algorithm. In order to facilitate the convergence of the algorithm, a symmetric constraint is applied and is shown to reduce the required time to find the optimum, while having a negligible impact on the final result. Next, a constraint on how many independent power supplies are available is added. A new method to determine the optimal grouping of actuators to power supplies is derived, called the En Masse Elimination EME) method. This method can determine the global optimal solution without having to exhaustively search every possible grouping combination. A number of improvements to the EME method are given which increase the speed of the algorithm as well as enable the EME algorithm to be used online during dynamically changing error conditions. Finally, the EME method is experimentally validated using a single pinned-pinned beam. Using a beam rather than a reflector reduces the complexity of the problem while still showing the functionality of the EME algorithm. Experimental data show that the EME algorithm is able to quickly and accurately find the global optimal actuator grouping.

Continue reading »]]> In Mobile Ad Hoc NETworks MANETs) autonomous nodes act both as traffic originators and forwarders to form a multi-hop network. Out-of-range nodes are reachable through a process called routing, which is a challenging task due to the constraints of bandwidth and battery power. Stateless location-based routing schemes have been proposed to avoid complex route discovery and maintenance, whereby nodes make routing decisions based solely on the knowledge of their location, the location of their neighbors, and the location of the destination. Natural routing schemes based on these prerequisites suffer from problems like local maxima or loops. We mitigate those problems by proposing randomized routing algorithms, which outperform others in terms of the packet delivery ratio and throughput. The prerequisite for location-based routing is knowing the location of a node. Location information is more widely useful anyway for location-aware applications like security, health care, robotics, navigation etc. Locating a node indoors remains a challenging problem due to the unavailability of GPS signals under the roof. For this goal we choose the RSS Received Signal Strength) as the relevant attribute of the signal due to its minimal requirements on the RF technology of the requisite modules. Then profiling based localization is considered that does not rely on any channel model range-based) or the connectivity information range-free), but rather exploits the context of a node to infer that information into the estimation. We propose a RSS profiling based indoor localization system, dubbed LEMON, based on low-cost low-power wireless devices that offers better accuracy than other RSS-based schemes. We then propose a simple RSS scaling trick to further improve the accuracy of LEMON. Furthermore, we study the effect of the node orientation, the number and the arrangement of the infrastructure nodes and the profiled samples, leading us to further insights about what can be effective node placement and profiling. We also consider alternate formulations of the localization problem, as a Bayesian network model as well as formulated in a combinatorial fashion. Then performance of different localization methods is compared and again LEMON ensures better accuracy. An effective room localization algorithm is developed, and both single and multiple channels are used to test its performance. Furthermore, a set of two-step localization algorithms is designed to make the LEMON robust in the presence of noisy RSS and faulty device behavior.

Continue reading »]]> The elucidation of learning and memory and of the pathophysiology of Parkinsons Disease PD), Muscular Dystrophy MD), and severe episodic depression are important goals driving contemporary neuroscience. However, this research and the development of long-term neuroprostheses for treating disorders of the human nervous system have been hindered by the unavailability of low-impedance, high resolution, solid-state electrodes In this research, we created the Polypyrrole-coated Vertically Aligned Carbon Nanofiber Microbrush Array Ppy-coated VACNF MBA) and electrodes constructed from single 30 nm diameter multi-walled carbon nanotubes sMWNT Electrode). These novel devices achieve the important goals of preventing washout of cellular constituents, eliciting electrical activity without electrolyzing water, concentrating the electric field, and localization of endogenic signal sources. Furthermore, these probes can potentially be used for high spatial resolution electrophysiology. We show for the first time the application of Ppy-coated VACNF MBA and sMWNT Electrodes to electrophysiological stimulation, recording, and whole cell voltage clamp of electrically active cells. Compared to Tungsten Wire Electrodes, a platinum metal electrode array MEA), and an As-grown VACNF MBA, the Ppy-coated VACNF MBA effects the highest stimulation efficiency. Importantly, the Ppy-coated VACNF MBA is the first reported neuroelectrical device that is able to elicit bioelectrical activity with excitation voltages that eliminate electrolysis which is potentially toxic to cells. The sMWNT electrode is the first reported nanoscale solid-state electrode capable of intracellular and extracellular electrophysiological probing. With respect to a glass micropipette electrode, the sMWNT electrode provides higher spatial resolution, effects higher stimulation efficiency in extracellular and intracellular excitation applications, detects field potentials with higher SNR, and displays lower error voltages in whole cell voltage clamp improving accuracy. We discovered that, in addition to electrode impedance, electrode geometry, and placement are design parameters that influence the performance of electrophysiological probes. Multi-sMWNT electrode architectures achieve enhanced extracellular stimulation efficiency and SNR, signal source localization, electric field concentration, and whole tissue bioimpedance monitoring. These novel findings underscore the feasibility of incorporating sMWNT electrodes and Ppy-coated VACNF electrodes into future neuroprosthetic devices for therapy of diseases such as PD, AD, and depression.

Continue reading »]]> Deep Brain Simulation (DBS) has received attention in the scientific community for its potential to suppress epileptic seizures. To date, DBS has only achieved marginal positive results. We believe that a highly complex possibly chaotic (HPC) biologically inspired stimulation is superior to periodic stimulation. Using Radial Basis Functions (RBFs), we modeled interictal and postictal time series based on electroencephalograms (EEGs) of rat hippocampus slices while under low Mg2＋/high K＋. We then compared the RBF based interictal and postictal stimulations to the periodic stimulation using a Cognitive Rhythm Generator (CRG) model for spontaneous Seizure-Like Events (SLEs). What resulted was a significant improvement in seizure suppression with the HPC stimulators at lower gains as opposed to the periodic signal. This suggests that the use of biologically inspired HPC stimulators will achieve better results while confining the stimulation to a narrow region of the brain.

Continue reading »]]> Retaining wall systems are widely used throughout seismically active areas like California. They represent key elements of important constructed facilities and their potential damage is connected with significant physical and economic consequences. While their design for static applications has been practiced by many sectors, their seismic design has not been extensively developed with a lack of accurate guidelines in the excisting design codes. The current study aims at the investigation of the dynamic response of freeway retaining walls that are used in highways of California and have been designed based on the existing Caltrans specifications and tools. The seismic response of those walls is a very complex phenomenon as it depends on the soil-retaining wall-earthquake interaction. The response becomes even more complex with the addition of a sound wall at the top of the retaining wall.The development of rigorous numerical models in order to capture the dynamic response of the wall as well as the factors that contribute to the failure of the sound wall is the main objective of this work. First, one set of numerical models was developed in order to validate a full scale test on two retaining walls designed according to Caltrans specifications and secondly, another set of models was developed in order to analyze parametrically the effect of the triad soil-retaining wall-earthquake to the system and contribution of sound wall. Main observation from the results of the analysis is that the dynamic response of such a retaining system is the combined result of many factors such as the predominant frequency of the excitation and the eigenfrequency of the structure.

Continue reading »]]> With advances in drug research, the use of biological therapeutics is becoming a reality. Unfortunately, methods for processing and delivering these fragile macromolecules often limit their therapeutic potential. For this dissertation, we explore the aerosolization of macromolecules by way of electrohydrodynamic atomization (EHDA) and how this method can be used to process and deliver therapeutics. EHDA employs a high voltage to break a column of liquid into drops. It was unknown if or how the residual charge left of the resulting droplets would affect lung cells. An in vitro experiment was conducted to spray aerosolized DNA, by way of EHDA, onto human derived lungs cells to test for immunogenic and toxic effects. The lung cells displayed no immunogenic or toxic response to the DNA or high voltage. Previous researchers have used EHDA to aerosolize proteins with mixed results. This work sets forth a simplified thermodynamic theory and provides recommendations to pharmaceutical companies on how to design more stable protein formulations for aerosol processing or delivery. Finally, a new method of producing liposomes was created. It constructs the liposome one layer at a time. The inside of the liposome is sprayed by EHDA, with the lipid and drug in solution together. As the sprayed monolayer passes through a pool containing a solution of lipid in water, the second part of the bilayer attaches to the inner layer creating a complete bilayer liposome.

Continue reading »]]> Silica-aluminas, silicates, and aluminosilites zeolites) have been widely used as heterogeneous catalysts and supports, because compared to homogeneous catalysts, their solid-acid properties are often desirable for selectivity and separation reasons. However, despite decades of use, much remains unknown with regard to the molecular origins of their acidities and how they may be controlled. For zeolites, although the molecular origins of their acidities are known, the molecular interactions that direct the formation of crystalline frameworks are poorly understood, limiting the structures and compositions, and thus acid and/or adsorption properties, which can be obtained. The molecular origins of acidity of silica-aluminas, on the other hand, remain heavily debated, prohibiting predictive control of their acid properties. A greater understanding of the local compositions and structures of solid acid sites is required to develop predictive syntheses of solid acid catalysts or supports with tunable catalytic and/or adsorption properties. Advanced nuclear magnetic resonance NMR) techniques, in conjunction with X-ray diffraction XRD) and infrared IR) spectroscopy, provide insights on the local compositions, structures, and interactions among the various components of silicates, aluminosilicates, and silica-aluminas. For example, the roles of structure-directing and mineralizing agents and their interactions with silicate species during zeolite synthesis can be determined using one- and two-dimensional NMR techniques. Such interactions provide insight on zeolite nucleation and subsequent crystallization that are expected to aid in the development of new predictive synthesis protocols for zeolites with tunable surface properties. For amorphous silica-aluminas, the combination of probe molecule adsorption, catalytic testing, and NMR and IR characterization is vital for determining the molecular origins of their surface acidities. Adsorption of basic probe molecules, in conjunction with NMR and IR spectroscopy, allow for the compositions, structures, strengths, and distributions of surface acid sites on silica-aluminas to be determined. Such detailed understanding of acid sites is used to establish correlations among the Bronsted and Lewis acidities as well as correlations between the bulk and chemical properties of silica-aluminas. Ultimately, the used of advanced spectroscopic techniques has allowed for greater understanding of solid acidity, which can be used to aid in the development of new solid acid catalysts and supports.

Continue reading »]]> A new Evolving-Confirmed process ECP) is introduced that utilizes construction loads for more accurate baseline condition estimations in medium or large civil structures. The structural response, measured during construction, serves as the ECP input to estimate the initially undamaged state, or baseline condition of the structure. Parameters are estimated and evolved over a sequence of construction stages until they satisfy a specified convergence criterion. The ECP is tested in a case study of a three-span continuous bridge, where construction data is generated using a Monte Carlo simulation. The process is also tested on a small scale structure in a laboratory setting with scaled loads comparable to full scale testing. To allow for further expansion of the ECP, a new bilinear approach is developed to estimate the parameters of a member that exhibits a bilinear force-response relationship. It was derived following the classic error minimization technique of the least squares method. The bilinear functions minimize the residual error of a complete data set with the force-displacement relationship in an optimization procedure. To evaluate the effectiveness of the new procedure, laboratory experiments were performed on determinate and indeterminate beams. Results of the testing of the ECP and bilinear approach demonstrated them to be valid estimators of structural member stiffnesses. The case study and laboratory tests showed the ECP to be an effective estimator of baseline conditions of medium and large civil structures. Additionally, the ECP was shown to be more accurate than a standard truck load in estimating baseline conditions, when equivalent measurement noise was present. The bilinear approach was shown to be capable of estimating bilinear stiffnesses of members by sufficiently estimating the section modulus and moment of inertia of a beam of changing stiffness.

Continue reading »]]> The Laser/Water-Jet (LWJ) hybrid machining system, introduced and developed by the Iowa State University’s Laboratory for Lasers, MEMS, and Nanotechnology, was applied to overcome the major deficiencies associated with current EDM and laser machining techniques for shaping Polycrystalline Cubic Boron Nitride (PCBN) cutting tools from the blanks. For PCBN, the purpose of water in LWJ is twofold: phase transformation and thermal shock. Previously LWJ was used to perform straight line cuts on various materials including PCBN. In this work, a further investigation of an understanding of the action of water and two-dimensional contour cutting of PCBN was carried out. The role played by water in LWJ was compared with that of other fluids (argon, nitrogen, oxygen, and air) to illustrate the effectiveness of water in the controlled fracture mechanism of PCBN. In addition, a two-dimensional contour cutting of PCBN using LWJ was investigated by changing the crack direction to 60, 108, 120, 135 degrees and following a curve with 1 mm radius in accordance with the standard PCBN tool shapes. The phase transition and the cut quality were investigated using Raman spectroscopy, Scanning Electron Microscopy (SEM), and optical profilometer. Results indicated that water is the best medium to control the phase transition and apply the controlled fracture mechanism for PCBN. Also, it was shown that successful cuts were made with obtuse angles in contrast to acute angles. A preliminary qualitative model was presented to explain the observed experimental results.