Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Julie A. Hubbard, Dept. of Psychology. Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Barbara Licht, Florida State University, Dept. of Psychology. Title and description from dissertation home page (viewed Apr. 8, 2004). Includes bibliographical references.

This study examined a first grade, general education teacher's changing practices related to reading intervention for struggling readers as she worked with a group of university researchers to develop and implement a first grade reading instruction model. This study also investigated the following research questions: What changes in a first grade, general education teacher’s reading instructional practices occurred because of a year long university-teacher collaborative relationship in implementing evidence-based reading instruction for struggling students? What were the facilitators and barriers for implementing evidence-based reading practices for struggling readers? Analyses of classroom observations, teacher interviews, intervention validity checklists (IVC's), observations, support team meeting notes, research team meeting notes, field notes, and other forms of documentation provided a view into the process of change of one teacher. / text

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Highway/railroad grade crossings present a danger to vehicular traffic. According to the USDOT Bureau of Transportation Statistics, in 2009, there were 1,887 crashes at highway/rail crossings resulting in 248 fatalities (FRA, 2009). The installation of presignals at grade crossings decreases crashes and fatalities at highway/rail crossings. There are no Federal standards that provide guidance for the installation of presignals. Therefore, current practices do not conform to any set of consistent nationwide standards except for guidelines specified in the MUTCD. These guidelines state that a presignal should be considered where the at-grade highway/rail crossing is located within 50 feet of a signalized intersection. The MUTCD also gives the option of installing a presignal at a distance greater than 50 feet, if an engineering study determines a need; however, no specific guidelines are provided for such studies.This work uses a case study to determine which measures are needed to warrant a presignal and examines if the distance criterion of 50 feet between signalized intersections and highway/rail crossings is adequate. It also explores the need for consistent national standards to provide guidance to practitioners in determining the needs for the installation of such signals.The study finds that distance criterion should not be used as the sole indicator for the installation of a presignal and therefore, engineering studies must be performed in all cases to determine presignal needs. Furthermore, the work concluded that the MUTCD must be modified to provide standards and guidelines that can be used nationwide for systematic quantitative assessment in determining when presignals are warranted near railroad crossings. This study proposes that presignals be installed based on warrants that consist of crash data, queue distance and no gates at the crossing. The proposed modifications include describing presignal types, defining their purpose, developing presignal warrants, and creating guidelines that can be used by practitioners.The changes and revisions recommended by this research work include queue length analysis, signal phasing and timing modifications, and existing intersection infrastructure needs. The resulting warrants and guidelines for presignal installation can be used nationally to provide uniform guidance and recommendations in performing presignal studies.

The analysis of grade crossing safety has long focused on vehicle-train crashes using statistical models based on crash data. The potential crashes generated by vehicle-vehicle rear-end conflicts have often been ignored. The interaction of different traffic attributes on safety performance of a grade crossing is also not well-understood. The primary objective of this thesis is to model the causal relationship of vehicle-vehicle interactions by developing the operation logic of gate-equipped grade crossing using a commercially available microscopic simulation package that models human driver behaviors. The simulation-generated vehicle trajectory data allows detail safety performance analysis on vehicle-vehicle interaction over time as they approach the track. A dual-gate equipped crossing at Kitchener, Ontario is selected as the study area. Initially, logic modifications are made to the simulation package (VISSIM) in order to accurately model the grade crossing segment. A two-step calibration is used in this thesis. Firstly, model input parameters for a signalized intersection from literature are used to model typical car-following behavior along this type of roadway. Secondly, parameters used to model drivers’ decision and reaction when approaching crossing is fine tuned through data collection and calibration. After incorporating all the modifications to the simulation package, validation is undertaken by comparing model-generated speed profiles to on-site observed speed profile. The established model is tested for its safety performance sensitivity through varying three traffic attributes in the simulation: (i) percentage of bus, (ii) total traffic volume, (iii) percentage of cars in the center lane of a 2-lane approach. Four safety performance measures were selected. The overall results indicate that the established model is functional and reliable in modeling grade crossing vehicles interactions at gated crossings. In the absence of a train, vehicles’ reduction in speed in the vicinity of a crossing results in traffic flow turbulence that increases the opportunity for high risk rear-end vehicle interactions. The sensitivity test revealed that the spillback behavior of vehicles due to the stopping behaviors of buses increases risk in the upstream section. Also, overloading of vehicles into the network indeed improves safety as the effect of differential speed diminishes. Among the four selected safety performance measures, DRAC seems to reflect problems with rear-end vehicle interactions in the vicinity of a crossing as a function of the traffic attributes considered in this research.

Current methods of solar-grade silicon (SG-Si) production are energy intensive and costly. The possibility of using metallurgical techniques for refining metallurgical-grade Si (MG-Si) to SG-Si has been investigated. The main steps in the metallurgical refining route include alloying with copper to produce a 50-50wt% Cu-Si alloy, controlled solidification, crushing, and acid leaching. The controlled solidification process involved 5 variations to determine the best process to maximize Si dendrite agglomeration in the sample and produce the purest Si. This was determined by using various techniques, such as: optical imaging, dendrite analysis, EPMA and SEM analysis and ICP analysis. The crushing and acid leaching steps were carried out to remove the unwanted Cu3Si eutectic from the pure Si dendrite phase. Upon completion of the analysis techniques, the optimal cooling method was determined to be the top cooled, 0.5°C/min sample.

Current methods of solar-grade silicon (SG-Si) production are energy intensive and costly. The possibility of using metallurgical techniques for refining metallurgical-grade Si (MG-Si) to SG-Si has been investigated. The main steps in the metallurgical refining route include alloying with copper to produce a 50-50wt% Cu-Si alloy, controlled solidification, crushing, and acid leaching. The controlled solidification process involved 5 variations to determine the best process to maximize Si dendrite agglomeration in the sample and produce the purest Si. This was determined by using various techniques, such as: optical imaging, dendrite analysis, EPMA and SEM analysis and ICP analysis. The crushing and acid leaching steps were carried out to remove the unwanted Cu3Si eutectic from the pure Si dendrite phase. Upon completion of the analysis techniques, the optimal cooling method was determined to be the top cooled, 0.5°C/min sample.