The objective of this investigation was to determine the sensitivity of three selected input parameters in the operational control of continuous bottan-fed thickeners used for the treatment of coal refuse slurries. The three variable paramenters were "Feed Flow Rate," "Feed pH," and "Feed Solids Concentration." These three input parameters were studied under three polymeric conditions. The X-ray analysis of underflow refuse samples from two coal preparation plants showed that the samples contained clays of various types. Kaolinite type clay was chosen as the feed material in this investigation. The static settling tests on the kaolinite-water suspensions using polymers showed that slurries with 5.0% or less feed solids concentration could be separated by all the polymeric conditions (cationic, anionic, and cationic-anionic). The continous solid-liquid separation in the laboratory thickener showed that a 3.0% feed solids was the maximum feed solids concentration that could be used in the continuous thickener operation with the same polymeric conditions. The minimum feed solids concentration was 1.0% solids. The feed pH ranged from 5.0 to 10.0, and the feed flow rate ranged from 915 to 2275 ml/min. The collective determination of the most and least sensitive variables was based on an experimental design procedure, employing Response Surface Methodology (RSM), to develop mathematical models for the thickener control. The three polymeric conditions used were, cationic polymer, anionic polymer, and a combination of cationic-anionic polymer. For each polymeric condition, two mathematical models were developed: one for overflow response, the other for underflow response. The formation of small flocs by the cationic polymer produced a sludge bed which prevented the particles from escaping into the overflow. The movement of the sludge bed was rapid. To prevent the bed from passing a pre-determined height, the underflow pump was "on" during most of the experimental time. This situation brought a low solids underflow, but the desired quality of the overflow was reasonably good. The anionic polymer did not produce a good overflow, because neutralization of the surface charges did not occur and a sludge bed never formed. This condition left the underflow pump "off" at all times, except when samples were to be withdrawn for the analysis. Overflow was the worst quality compared to the other polymeric conditions. The underflow quality was better than the underflow of the cationic tests, and almost as good as the underflow with the combination polymer. The use of the combination cationic-anionic polymer produced large floes immediately, because of the surface charge neutralization and bridging action that occurred. The time allowed for this action was longer for low to medium flow rates, producing larger flocs which settled and prevented the formation of a sludge bed. However, the desired quality of overflow and underflow remained good. For the majority of the runs with combination polymer, the underflow pump was "off" at all times, except when samples were withdrawn for the analysis. The overflow and underflow quality was the best desired quality for the combination polymer when compared to the results obtained utilizing the cationic and the anionic polymers separately. The input variables were used to develop six mathematical models. With the aid of the models, contour plots of the main responses were generated; that is, the "suspended solids in the overflow" and the "percent solids in the underflow." The plots gave regions of the best thickener performance within the wide variations of the three mentioned input variables. The plots would allow an operator to control and/or adjust any of the three variables to achieve optimum conditions. The combination polymers produced the best desired quality of overflow and underflow. For this polymeric condition, changes in the feed solids concentration was the most sensitive factor in the maintenance of the overflow quality, and the feed pH was the most sensitive factor for the maintenance of the underflow quality. The role of the feed flow rate for the maintenance of both overflow and underflow quality was proved to be moderate. / Ph. D.

There is increasing recognition of an impending shortage of educational leaders to fill vacant administrative positions. Consequently, interest in finding ways to support, guide, and retain novice principals has emerged. Mentoring is a popular and effective means of transferring knowledge from an experienced principal to a newly appointed one. Little attention, however, has been given to the process of formal administrative mentorships and how they can be shaped to meet the varied needs of new school principals. The purpose of this study was to explore the personal experiences of novice and veteran principals and the underpinnings of the formal administrative mentoring program in one local school district in Virginia. Seventeen principals were interviewed as participants in this case study. The study was implemented through the use of qualitative research methods of inquiry, including interviews with an administrator of the mentoring program, in-depth interviews with principals, and examination of available documents. This research presents the perspectives of both novice and veteran principals regarding the extent to which their formal mentoring experiences helped them. The data that emerged from this study demonstrated that the formal administrative mentoring experience provided the participants with a greater clarity of role, developed their understanding of the organization, thus facilitating their socialization into it, and helped with diminishing their feelings of isolation. The participants reported that mentoring helped increase their understanding of three major roles of the contemporary principal: (a) instructional leader; (b) school visionary; and (c) team builder. According to the novices, mentors helped them learn how to integrate into the school system through interaction with their communities and how to negotiate their needs within the school division. Novice principals' responses reflected ambivalence about this particular area of their mentoring experience and the help it afforded, however; their responses appeared to be related to their years of experience and the positions they had previously held in the division. Mentees and mentors alike reported that mentoring helped reduce their feelings of isolation through the development of camaraderie with one another as well as a network of colleagues. Most of the participants in the study reflected overall positive perceptions related to their formal administrative mentoring experiences. / Ed. D.

Perovskite solar cells have attracted much attention both in research and industrial domains. An unprecedented progress in development of hybrid perovskite solar cells (HPSCs) has been seen in past few years. The power conversion efficiencies of HPSCs has been improved from 3.8% to 24.2% in less than a decade, rivaling that of silicon solar cells which currently dominate the solar cell market. Hybrid perovskite materials have exceptional opto-electrical properties and can be processed using cost-effective solution-based methods. In contrast, fabrication of silicon solar cells requires high-vacuum, high-temperature, and energy intensive processes. The combination of excellent opto-electrical properties and cost-effective manufacturing makes hybrid perovskite a winning candidate for solar cells. As power conversion efficiencies of HPSCs improves beyond that of the established solar cell technology and their long-term stability increases, one of the crucial hurdles in the path to commercialization remaining to be adequately addressed is the cost-effective scalable fabrication. Spin-coating is the prevailing method for fabrication of HPSCs in laboratories. However, this technique is limited to small areas and results in excessive material waste. Two types of scalable manufacturing methods have been successfully demonstrated to fabricate HPSCs: (i) meniscus-assisted coating such as doctor-blade coating and slot-die coating; and (ii) dispersed deposition based on the coalescence of individual droplets, such as inkjet printing and spray coating. Electrospray printing belongs to the second category with advantages of high material utilization rate and patterning capability along with the scalability and roll-to-roll compatibility. In Chapter 3 of this dissertation, electrospray printing process is described for manufacturing of HPSCs in ambient conditions below 150 C. All three functional layers were printed using electrospray printing including perovskite layer, electron transport layer, and hole transport layer. Strategies for successful electrospray printing of HPSCs include formulation of the precursor inks with solvents of low vapor pressures, judicial choice of droplet flight time, and tailoring the wetting property of the substrate to suppress coffee ring effects. Implementation of these strategies leads to pin-hole free, low surface roughness, and uniform perovskite layer, hole transport layer and electron transport layer. The power conversion efficiency of the all electrospray printed device reached up to 15.0%, which is among the highest to date for fully printed HPSCs. The most efficient HPSCs rely on gold and organic hole-transport materials (HTMs) for achieving high performance. Gold is also chosen for its high stability. Unfortunately, the high price of gold and high-vacuum along with high-temperature processing requirements for gold film is not suitable for the large-scale fabrication of HPSCs. Carbon is a cheap alternative electrode material which is inert to hybrid perovskite layer. Due to the ambipolar transport property of hybrid perovskite, perovskite itself can act as a hole conductor, and the extra hole transport layer can be left out. Carbon films prepared by doctor-blade coating method have been reported as the top electrode in HPSCs. The efficiencies of these devices suffer from the poor interface between the doctor-blade coated carbon and the underlying perovskite layer. In Chapter 4, electrospray printing was applied for the fabrication of carbon films and by optimizing the working distance during electrospray printing, the interface between carbon and the underlying perovskite layer was greatly improved compared to the doctor-blade coated carbon film. The resulting HPSCs based on the electrospray printed carbon electrode achieved higher efficiency than that based on doctor-blade method and remarkably, this performance is close to that of gold based devices. In Chapter 5, preliminary results are provided on the laser annealing of hybrid perovskite films to further advance their scalable manufacturing. All layers of HPSCs require thermal annealing at temperature over 150 C for about half an hour or longer. The time-consuming conventional thermal annealing complicates the fabrication process and is not suitable for continuous production. High temperature over150 C is also not compatible with flexible substrates such as PET. Laser annealing is a promising method for overcoming these issues. It has several other advantages including compatibility with continuous roll-to-roll printing, minimal influence on non-radiated surrounding area, and rapid processing. Laser annealing can be integrated with the electrospray process to realize the continuous fabrication of hybrid perovskite film. Rapid laser annealing process with optimized power density and scanning pattern is demonstrated here for annealing perovskite films. The resulting hybrid perovskite film is highly-crystalline and pin-hole free, similar to that obtained from conventional thermal annealing. / Doctor of Philosophy / Hybrid perovskite solar cell (HPSC) is a promising low-cost and high efficiency photovoltaic technology. One of the big challenges for it to be commercially competitive is scalable fabrication method. This dissertation focuses on developing electrospray printing technology for HPSCs. This is a scalable method with high material usage rate that naturally lead to large scale fabrication of HPSCs. Electrospray printing parameter space was systematically studied and optimized to synthesize high-quality perovskite films and other functional layers including hole transport layer and electron transport layer. All electrospray printed high-efficiency perovskite solar cell devices were successfully demonstrated under the ambient condition and low temperature. Another achievement of this thesis is the electrospray printing of carbon film to replace the costly gold electrode in perovskite solar cells. Laser annealing technique is demonstrated for HPSCs, which is compatible with continuous fabrication and integrates easily with electrospray printing.

The purpose of this study was to determine how well current students and graduates of principal preparation program cohorts in one large school district in the Mid-Atlantic perceived their program was preparing them, or has prepared them, to be school-based administrators. Current cohort students and graduates were studied to determine their perceptions regarding how well their principal preparation program prepared them to be school-based administrators as well as how well they believed their program was aligned with the current (2015) Professional Standards for Educational Leaders (PSELs). To ascertain if any significant differences appeared in the data, a two-tailed t test was used to compare participant groups (graduates with administrative positions and graduates without administrative positions) and an ANOVA was used to compare universities. Statistical analysis revealed that graduates with administrative positions perceived they were better prepared to be school-based administrators than graduates without administrative positions on most of the current PSELs. Additionally, graduates with school-based administrative positions believed their programs were better aligned the current PSELs than graduates without administrative positions. Furthermore, graduates and current students perceived that one of the universities under study did not prepare them as well and was not as well aligned as the other two universities under study based on some of the current PSELs. Focus group discussions revealed that significant differences in the data may be due to different administrative experiences/internships, curriculum, professors, and personal responsibility. A document review indicated that the standards taught were, in general, not well aligned with the current PSELs. / Doctor of Education / This study sought to determine the perceptions of preparedness of current students and graduates of principal preparation program cohorts in one large school district in the MidAtlantic. Additionally, this study sought to determine how well current students and graduates believed their programs were aligned with current Professional Standards for Educational Leaders (PSELs). A review of accreditation documents revealed that the standards taught in the principal preparation programs were not, in general, aligned with the current PSELs. A survey of current students and graduates of three principal preparation cohorts in the school district under study indicated that graduates with school-based administrative positions (principals, assistant principals, associate principals, deans) perceived they were better prepared than graduates without school-based administrative positions. Furthermore, graduates with school-based administrative positions indicated their programs were more aligned to the PSELs than did graduates without administrative positions. When comparing universities, current students and graduates perceived that one of the universities under study did not perform as well as the other two universities regarding perceptions of preparedness and PSEL alignment on some of the PSELs. A focus group determined that the possible reasons for the differences in the data were due to administrative experiences/internships, curriculum, professors, and personal responsibility. This study is significant because it informs the universities and school district of any perceived programmatic strengths and weakness. The school district and universities may want to gather more data to improve their program effectiveness.

This study presents a qualitative analysis of principals' perceptions of the relationship among principal preparation programs, professional development and instructional leadership confidence in one urban school division in Virginia. Levine (2005) argued that the principal has a salient effect on the instructional programs within schools, and the preparation and professional development of the principal affects the degree to which they maintain and improve instruction. To examine principal perceptions on feelings of confidence toward instructional leadership, four research questions were investigated: What are principals' perceptions concerning the instructional confidence needed to lead schools in one school division? What are principals' perceptions regarding the coursework undertaken in their preparation program and the associated confidence developed for instructional leadership in one school division? What are principal perceptions concerning post-graduate professional development and the associated confidence developed for instructional leadership in one school division? What type of additional training do principals believe would enhance their confidence toward instructional leadership in one school division? The researcher sought to ascertain principal perceptions concerning the construct, instructional leadership efficacy, based on their academic training and professional development. The findings were as follows: a) interviewed principals in one urban school division described instructional leadership efficacy in terms of one's capacity to provide instructional leadership and one's know how to foster home-school relations; b) interviewed principals in one urban school division believe that the principal must act as an instructional leader to facilitate learning in the building; c) interviewed principals from one urban school division reported that the course of greatest significance to instructional leadership was school law; d) interviewed principals from one urban school division were unable to identify the most beneficial professional development in terms of that which is needed to be the instructional leader; e) there was no recommendation for specific coursework in the principal preparation program that was supported by the majority of the interviewed principals. / Ed. D.

My dissertation is comprised of two manuscripts on preparing educators to address the needs of students with disabilities. The first manuscript is a systematic review of 23 empirical studies published over the last two decades, addressing how traditional teacher preparation programs prepared preservice educators to learn about teaching students with disabilities in inclusive settings. A conceptual model was developed to synthesize the findings. Better outcomes in dispositions, knowledge, and skills were associated with preservice educators placements in inclusive classrooms where supportive supervising teachers modeled effective collaboration and provided opportunities for developing specific teaching skills. Although student disability type and teacher education program type are not directly related to preparation, researchers suggest that they mediate preservice educators' dispositions. The second manuscript examines the demographic, preparation, and school poverty level of a nationally representative sample of 51,340 early career special educators and the extent to which more and less preparation predicted their perceived preparedness for eight instructional practices. Data analyses included descriptive statistics, cross tabulations, and multiple linear regression. Findings indicated that more preparation significantly predicted educators' feelings of preparedness as they began teaching. The majority of educators with more preparation entered teaching through traditional routes while those who were less prepared tended to enter through alternative routes. Additionally, the majority of all educators felt least prepared to use student data to inform instruction and most prepared to differentiate instruction. Implications for education policy, teacher preparation, and future research are considered in both manuscripts. / Ph. D.

Student teaching is arguably the most beneficial aspect of teacher preparation programs. The student teaching experience is shaped by several key components. One of the most important, yet least well defined component is the cooperating center at which a student teacher will gain his or her experiences. Very little research has been published regarding the characteristics of good cooperating centers for agricultural education. This study was designed to create a list of the key elements of cooperating centers for agricultural education student teachers. Qualitative research was conducted within the population of cooperating teachers and first-year teachers of agricultural education employed in the Commonwealth of Virginia. Two nominal groups were conducted on October 15, 1998, each having ten participants. One group was comprised of ten cooperating teachers and the other of ten first-year agricultural education teachers. The responses from these participants were used to create a prioritized list of the characteristics of cooperating centers that they felt were most important for a successful student teaching experience. / Master of Science

A special wafer bonding method called the Silicon Direct Bonding technique is used to study the bonding of unipolar (n-type, <100> oriented) silicon wafers. The primary objective of this thesis project is to find an optimum surface preparation technique for subsequent silicon wafer bonding. Wafer cleaning and treatment methods are investigated to understand the correlation between a high quality wafer surface and the resulting high quality electrical conduction at the interface. Accordingly, in this project, a preference for hydrophobic (less polar Si-OH surface) wafers is given to ensure a minimized amount of oxide layer on the surface. Several key factors that govern the quality of the wafer surfaces, such as the degree of hydrophobicity, HF etching time, composition of HF etching solution and Dr water rinse, are examined with ellipsometric and XPS measurements. An HF etching followed by a sputter etching has been selected to pre-treat the wafer surfaces for bonding. A maximum allowable air exposure time (35 second) is also found which would allow bonding without significant re-growth of the oxide layer. Bonding is performed under vacuum with a special mechanical fixture and the resulting structures from a subsequent heat treatment process are examined with crack propagation testing. Bond strength after annealing is sufficient to withstand a pull test, however, with a 3 point bend testing, the crack propagated horizontally at the interface. / Master of Science

Yes / Purpose The purpose of this paper is to explore the impact of factors such as attention, preparation, participation, feedback and engagement on the student learning performance. Design/methodology/approach Students of an undergraduate business course of a British university took part in the survey. The survey questionnaire was distributed to students during the revision week of the course and a total of 61 valid responses were gathered from them. The linear regression analysis using statistical package for the social sciences was performed to analyse the data. Findings The results indicated the significant relationships for all six hypotheses. The model explains variance of 43.2 per cent in learning performance, which indicates that independent constructs contribute significantly on the research model's performance. Research limitations/implications First, the sample only provides the students' views about the use of clickers in the classroom setting. Second, the sample size for the gathered data is small. Third, the variance explained by the research model is reasonably moderate and hence can be improved further. Originality/value This is the first study to explore the impact of factors such as attention, preparation, participation, feedback and engagement on the student learning performance in the UK educational setting.

This study investigates how four urban school districts, serving low socioeconomic status (SES) student populations, define, prepare teachers for, and implement integration of computer technology into the K-12 classroom in response to a Virginia state mandate. Factors influencing computer integration into the curriculum were also studied. Semi-structured interviews were conducted with 50 educators representing 2 state-level administrators, 12 district level-administrators, 8 school-level administrators, 23 classroom teachers, and 5 school-level technology specialists. Interviews were supplemented by classroom observations, teacher lesson plans, and district technology plans to provide data for an in-depth, multi-case study. Based on the access provided, one to two weeks were spent in each setting conducting interviews and recording the availability and use of computer technology in the classroom and its integration into instruction. All four districts met the mandate as stated and used similar definitions of integration and approaches to teacher preparation and implementation. Results indicate, however, that computer technology use within these schools is still confined primarily to laboratory settings and that students' technology experiences are not directly integrated into daily classroom instruction or lesson planning. Leadership, planning, funding, access to resources, time, training, and support were identified as factors when integrating technology into daily instruction. The mandate required a level of accountability, which served as a device to encourage and motivate more reluctant users of computer technology to gain necessary technical skills and adopt technology as a tool to support instruction. Response to the mandate has (1) increased dialogue between administrators, support staff, and teachers regarding technology and its integration; (2) provided an impetus for districts to use funds to purchase computers and other technology resources; and (3) provided an impetus for districts to begin to look at and monitor, if not evaluate teachers' use of technology for instruction. / Ph. D.