<p> Statistical analysis of panel count data is an important topic to a number of applied fields including biology, engineering, econometrics, medicine, and public health. Panel count data include observations on subjects over multiple time points where the response variable is a count or recurrent event process when only the numbers of events occurring between observation time points are available. The choice of method for analyzing panel count data usually depends on the relationship between the observation times and the response variable and questions of interest. Most of the previous research was done when the observation times are fixed. If the observation times are random, the data structure becomes more challenging since the observation times for individual subjects vary in addition to the incompleteness of observations. The model-based approach was used to deal with such data. However, this method relies on extra assumptions on the observation scheme and thus is restrictive in practice. In this dissertation, we discuss the problem of multi-sample nonparametric comparison of counting processes with panel count data, which arise naturally when recurrent events are considered. For the problem considered, we develop some new nonparametric tests.</p> <p> First, we construct a class of nonparametric test statistics based on the integrated weighted differences between the estimated mean functions of the count processes, where the isotonic regression estimate is used for the mean functions. The asymptotic distributions of the proposed statistics are derived and their finite-sample properties are examined through Monte Carlo simulations. A panel count data from a cancer study is analyzed and presented as an illustrative example.</p> <p>As shown through Monte Carlo simulations, the nonparametric maximum likelihood estimator (NPMLE) of the mean function is more efficient than the nonparametric maximum pseudo-likelihood estimator (NPMPLE). However, no nonparametric tests have been discussed in the literature for panel count data based on the NPMLE since the NPMLE is more complicated both theoretically and computationally. It is, therefore, particularly important to develop nonparametric tests based on the NPMLE for panel count data.</p> <p> In the second part of the dissertation, we focus on the situation when treatment indicators can be regarded as independent and identically distributed random variables and propose a nonparametric test in this case using the maximum likelihood estimator. The asymptotic property of the test statistic is derived. Simulation studies are carried out which suggest that the proposed method works well for practical situations, and is more powerful than the existing tests based on the NPMPLEs of the mean functions.</p> <p>In the third part of the dissertation, we consider more general situations. We construct a class of nonparametric tests based on the accumulated weighted differences between the rates of increase of the estimated mean functions of the counting processes over observation times, where the nonparametric maximum likelihood approach is used to estimate the mean functions instead of the nonparametric maximum pseudolikelihood. The asymptotic distributions of the proposed statistics are derived and their finite-sample properties are evaluated by means of Monte Carlo simulations. The simulation results show that the proposed methods work quite well and the tests based on NPMLE are more powerful than those based on NPMPLE. Two real data sets are analyzed and presented as illustrative examples.</p> <p>The last part of the dissertation discusses a special type of panel count data, namely, current status or case 1 interval-censored data. Such data often occur in tumorigenicity experiments. For nonparametric two-sample comparison based on censored or interval-censored data, most of the existing methods have focused on testing the hypothesis that specifies the two population distributions to be identical under the assumption that observation or censoring times have the same distribution. We consider the nonparametric Behrens-Fisher hypothesis (NBFH) under this settings. For this purpose, we study the asymptotic property of the nonparametric maximum likelihood estimator of the probability that an observation from the first distribution exceeds an observation from the second distribution. A nonparametric test for the NBFH is proposed and the asymptotic normality of the proposed test is established. The method is evaluated using simulation studies and illustrated by a set of real data from a tumorigenicity experiment.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Solar Cells of at least 10% conversion efficiency were fabricated from silicon wafers of one inch diameter and the same processing procedure was applied to wafers of three inch diameter. Four of the three inch diameter solar cells were affixed to a galvanized steel plate and hooked in a parallel configuration to make a solar cell panel. A piece of special plastic was placed over the solar cells on the panel and hermetically sealed to protect the solar cells from the environment which in time would degrade the performance of the solar cells. </p> / Thesis / Master of Engineering (MEngr)

No description available.

No description available.

Traditionally, underwater vehicles have been using propellers for locomotion but they are not only inefficient but generate large acoustic signature. Researchers have taken inspiration from efficient swimmers like fish to address the issue with alternate propulsion mechanism. Mostly, research on fish locomotion involved studying a foil tethered to a fixed point inside uniform flow. A major drawback of such study is that neither it resembles a freely swimming fish nor it takes into consideration the dynamics of moving fish on propulsive forces. Hence, in our current study, we focus on comparing the performance of a free swimming fin over tethered fin both experimentally and numerically. Experimentally, we focus on the oscillatory form of locomotion where the caudal fin pitches to generate necessary thrust as seen in boxfish. We intend to investigate the Caudal fin kinematics and its physical properties on locomotion performance. To better understand, we build an automated robo-physical model that swims in a circular path so as to carry extensive experiments. We focus on understanding the effect of flexibility, shape and thickness of caudal fin on performance. Currently, we have studied three different flexibility and for each flexibility, we studied three different shape. We found there must be an optimal flexibility for minimising the Cost of Transport (COT). We also propose that the steady forward speed linearly varies with tail tip velocity. Furthermore, we investigated the effect of thickness of fin and considered uniform and tapered fin with equal area moment of inertia. Numerically, we investigated the effect of phase offset between heave and pitch motion on the performance of a freely swimming fin and compared that to a tethered fin. A freely-swimming fin self propels and moves with steady speed while a tethered fin remains stationary and actuates under uniform flow. We model the fin as a rigid body undergoing prescribed motion in an inviscid fluid and solved for coupled interaction using panel method. We show the effect of phase offset for optimum performance and found a significant difference between tethered and freely swimming fin. / M.S. / Underwater vehicles use propeller based mechanism but they are inefficient and generate noise. Researchers have taken inspiration from nature to replace propellers with efficient propulsion mechanism. In the current study, we design a robotic model to understand the effect of various kinematic and physical properties of tail fin on performance. Our research is unique from past study in the aspect that most research involved studying performance using a robotic model fixed at its position which does not resemble a freely-swimming fish. Hence, in our current study, we focus on comparing the performance of our freely swimming model with tethered fin. The robot has one degree of freedom and can pitch its tail to generate thrust. We intend to investigate the tail fin kinematics and its physical properties on locomotion performance. We focus on understanding the effect of flexibility, shape and thickness of fin on performance. Currently, we have studied three different flexibility and for each flexibility, we studied three different shape. We showed there exists an optimal flexibility for maximising efficiency. For any fin undergoing combined pitch and heave motion, there exists a phase offset between them which will maximise the performance. Researchers have tried to understand its impact using both experiment and numerical simulation. In the current study, we study the impact of phase offset between pitch and heave for a freely-swimming fin and compare that to a fixed fin. A freely-swimming fin self propels and moves with steady speed while a tethered fin remains stationary and actuates under uniform flow. We show the effect of phase offset for optimum performance and found a significant difference between tethered and freely swimming fin.

A current trend in residential construction is the use of prefabricated wall panels. It is important to carefully establish how panels will be stacked, because an optimal sequence will improve productivity and reduce the possibility of worker injury. Mathematical models and heuristics are proposed for solving the panel stacking problem without consideration of interference. Dissertation work includes a mathematical model of the corresponding panel stacking problems in which the goal is to minimize total weighted panel move distance concurrent with certain construction assumptions. The heuristic method was provided to establish how each panel would be stacked and gave the drop-off location of each stack. The heuristic method was found to be able to reduce the total weighted panel move distance and ensure connectivity was always maintained, meanwhile, interference could also be avoided. In terms of solution speed, the heuristic method can solve real size problems in less than one second. Solutions to such problems can increase productivity. Three improvements to the only known existing panel stacking algorithm with consideration of interference were proposed. The computational results indicate the proposed algorithm performed better than existing algorithm in all experimental cases. Improvement on panel move distance ranged from 1.35-47.93%, and improvement on interfering panels ranged from 20-100%. The proposed algorithm can solve non-rectangular cases (not possible with existing algorithm) and was compared with an experienced panel designer and commercial software. When compared to the proposed algorithm, total weighted panel move distance increased 0.10-85.52% and 0.77-136.23%, respectively, for the panel designer and software. While connectivity was 100% for all cases with the proposed algorithm (the algorithm ensures connectivity is always maintained), it ranged from 69.56-86.95% and 73.33-90.91%, however, for the panel designer and software respectively. Finally, the proposed algorithm can solve the interfering panels in the last stack: this cannot be done with the existing algorithm. Because prefabricated wall panels are typically large and cumbersome to work with, there is a significant probability of worker injury. It is important to carefully establish how each panel will be handled by workers. This is typically the responsibility of field construction foreman, but such personnel are often ill-equipped to make such decisions. An alternative, proactive approach is to establish how each panel will be handled in advance, such that overall ergonomic consequences can be properly considered. This dissertation presents mathematical models of the corresponding construction task scheduling and worker assignment problems, where the goal is to minimize total project completion time (subject to worker quantity constraints) and assign tasks to workers as evenly as possible. The solution of such problems can help residential construction managers better plan construction by establishing the ergonomic impact associated with a given construction plan. A heuristic was also developed to solve large problems by balancing workload between workers. The heuristic was found to be able to provide near-optimal solutions, and can solve large problems in less than one second. / Ph. D.

A series of composite panels were fabricated by resin transfer molding (RTM), varying materials and process conditions. Reinforcements used included a fiberglass woven material, and AS-4 carbon in both sized and unsized plain weave fabrics. Vinyl ester, epoxy, and cyanate ester resins were pressure injected into these fabrics. The epoxy panels were processed with varying injection temperatures and pressures. A density-based technique was used to measure the fiber volume fraction and void content of the composite panels. Optical photomicrographs were used to verify the accuracy of the void calculations. Mechanical tests included compression strength, inplane and interlaminar shear strengths, and impact. Compression after impact tests were performed and compared to undamaged compression strengths. The compression, inplane shear, and interlaminar shear strengths of the epoxy composites were higher than the vinyl ester composites. Similarly, cyanate ester systems with similar reinforcements outperformed the epoxy composites in these tests. In impact testing, the graphite fabric/ epoxy resin composite retained the lowest portion of original strength after impact. The cyante esters retained the most strength, but vinyl ester composites suffered less damage. Vinyl ester composites made with unsized carbon fibers performed better in interlaminar shear, and in impact tests, than those with sized fibers. The variation of injection temperature had little effect on either void content or strength of the epoxy composites. Increases in injection pressure did produce a higher void content in epoxy laminates, but no significant change in strength was observed. / Master of Science

Cellular core structures are the state-of-the-art technology for light weight structures in the aerospace industry. In an aerospace product, sandwich panels with cellular core represent the primary structural component as a given aerospace product may contain a large number of sandwich panels. This reveals the necessity of understanding the mechanical behavior of the cellular core and the impact of that behavior on the overall structural behavior of the sandwich panel, and hence the final aerospace product. As the final aerospace product must go through multiple qualification tests to achieve a final structure that is capable of withstanding all environments possible, analyzing the structure prior to testing is very important to avoid any possible failures and to ensure that the final design is indeed capable of withstanding the loads. To date, due to the lack of full understanding of the mechanical behavior of cellular cores and hence the sandwich panels, there still remains a significant lack of analytical capability to predict the proper behavior of the final product and failures may still occur even with significant effort spent on pre-test analyses. Analyzing cellular core to calculate the equivalent material properties of this type of structure is the only way to properly design the core for sandwich enhanced stiffness to weight ratio of the sandwich panels. A detailed literature review is first conducted to access the current state of development of this research area based on experiment and analysis. Then, one of the recently developed homogenization schemes is chosen to investigate the mechanical behavior of heavy, non-corrugated square cellular core with a potential application in marine structures. The mechanical behavior of the square cellular core is then calculated by applying the displacement approach to a representative unit cell finite element model. The mechanical behavior is then incorporated into sandwich panel finite element model and in an in-house code to test the predicted mechanical properties by comparing the center-of-panel displacement from all analyses to that of a highly detailed model. The research is then expanded to cover three cellular core shapes, hexagonal cores made of corrugated sheets, square cores made of corrugated sheets, and triangular cores. The expansion covers five different cell sizes and twenty one different core densities for each of the core shapes considering light cellular cores for space applications, for a total of 315 detailed studies. The accuracy of the calculated properties for all three core shapes is checked against highly detailed finite element models of sandwich panels. Formulas are then developed to calculate the mechanical properties of the three shapes of cellular cores studied for any core density and any of the five cell sizes. An error analysis is then performed to understand the quality of the predicted equivalent properties considering the panel size to cell size ratio as well as the facesheet thickness to core thickness ratio. The research finally expanded to understand the effect of buckling of the unit cell on the equivalent mechanical property of the cellular core. This part of the research is meant to address the impact of the local buckling that may occur due to impact of any type during the manufacturing, handling or assembly of the sandwich panels. The variation of the equivalent mechanical properties with the increase in transverse compression load, until the first folding of the unit cell is complete, is calculated for each of the three core shapes under investigation. / Ph. D.

The Radiant Heating markets - especially, the hydronic segment - are growing rapidly in North America due to homeowners' increasing demand for comfort and the steady rise in residential construction. Radiant systems are promising technologies for energy saving in commercial and residential building sectors together with improving occupant thermal comfort. Such a technology is different from the more standard all-air systems and thus can be termed Space Conditioning. However, the thermal performance of radiant systems in buildings has not been fully understood and accounted for. This is primarily due to lack of any standard testing mechanism. The central thrust of this paper is to experimentally investigate questions relating to thermal performance of radiant systems, thus also contribute towards evolving a new standard for testing mechanisms. Products from 12 different radiant floor systems were chosen from the market. Having defined each with similar control parameters such as flow rate, supply water temperature and similar design parameters like size, insulation etc., they are separately tested in a well insulated test setup. Experiments on the time variations for each test floor were performed at supply water temperatures ranging between 100F – 140F with a 10F increment at each stage. Having gathered data through the Data Acquisition System (DAS), the data is analyzed and compared between all systems. The paper concludes by providing recommendations for experimentally testing thermal energy performance, thermal uniformity and thermal stability of radiant floor heating technology. / Master of Science

Photovoltaics panel (PV) integration with the utility grid has been installed throughout the globe. The fault-monitoring technology for photovoltaics (PV) panels is a method to save energy production losses and become a key contributor to overall cost reduction in variable operating costs for photovoltaics systems. PV researchers today explore factors such as reducing utility energy bills and CO2 emissions, grid voltage stability, peak demand shaving, supply of electric power off-grid areas, and many more. The technology discussed is easy to incorporate, requires no additional hardware, doesn't alter the system’s stability, is implemented at a steady state point, and is helpful to record changes in PV cell operation from forward bias to reverse bias state. PV panel AC impedance can be used as an early-stage fault indicator. Also, comparing AC impedance magnitude and phase at maximum power point (MPP) or near MPP can help identify the nature of the fault in a PV system. The focus of the thesis is proposing the fault detection of 300 W PV panels using online AC impedance measurement, utilizing existing panel-level power optimizers and microinverters in a PV system to actively perturb small signals into the PV panel and compute its small signal impedance. The technology is incorporated in a power optimizer with C2000 MCU and helps identify hot spot faults and short circuit faults in a 300 W rooftop PV panel. Multiple PV panel faults scenarios such as hot spot faults, short circuit faults, junction box faults, and capacitor faults are investigated to deduct further the effectiveness of the online impedance measurement using a small signal. This thesis’s focus areas are, first, modeling the PV panel and power converter and incorporating fault scenarios to identify the fault indicators. Secondly, measuring PV panel impedance under normal and faulty conditions using an equipment-based offline technique. Lastly, measuring PV panel impedance under normal and faulty conditions using a power optimizer. / M.S. / A Photovoltaics panel is a series and parallel combination of many photovoltaics cells to generate electricity from sunlight via a photoelectric process. The fault-monitoring technology for photovoltaics (PV) panels is a method to save energy production losses and become a key contributor to overall cost reduction in variable operating costs for photovoltaics systems. The PV panel, over a period of time, can degrade with fluctuations in temperature and weather. Photovoltaics panel (PV) integration with the utility grid has been installed throughout the globe. PV researchers today explore factors such as reducing utility energy bills and CO2 emissions, grid voltage stability, peak demand shaving, supply of electric power off-grid areas, and many more. The technology discussed is easy to incorporate, requires no additional hardware, doesn't alter the system’s stability, is implemented at a steady state point, and is helpful to record changes in PV cell operation from forward bias to reverse bias state. A PV panel operating at maximum power point (MPP) generates direct current (DC) and maintains a stable voltage across the PV panel load. A small signal injection in PV panel current or voltage is an addition of a sinusoidal signal with an amplitude of 10 % to the operating point of PV panel voltage or current and frequency sweep between 10 Hz to 200 kHz. The PV panel's AC impedance is measured under small signal injection and can be used as an early-stage fault indicator. Also, comparing AC impedance magnitude and phase at maximum power point (MPP) or near MPP can help identify the nature of the fault in a PV system. The focus of the thesis is proposing the fault detection of PV panels using online AC impedance measurement and utilizing existing panel-level power optimizers and microinverters in a PV system to actively perturb small signals into the PV panel and compute its small signal impedance. The technology is incorporated in a power optimizer with C2000 MCU and helps identify hot spot faults and short circuit faults in a 300 W rooftop PV panel. This thesis’s focus areas are, modeling the PV panel and power converter and incorporating fault scenarios to identify the fault indicators. Multiple PV panel faults scenarios such as hot spot fault, short circuit fault, junction box fault, and capacitor fault are investigated to further deduct the effectiveness of the online impedance measurement using a small signal. Secondly, measuring PV panel impedance under normal and faulty conditions using an equipment-based offline technique. Lastly, measuring PV panel impedance under normal and faulty conditions using a power optimizer.