10 resultados para Design of Experiments and Sample Surveys
em Brock University, Canada
Resumo:
A new Ultra-High Vacuum (UHV) reflectance spectrometer was successfully designed, making use of a Janis Industries ST-400 sample cryostat, IR Labs bolometer, and Briiker IFS 66 v/S spectrometer. Two of the noteworthy features include an in situ gold evaporator and internal reference path, both of which allow for the experiment to progress with a completely undisturbed sample position. As tested, the system was designed to operate between 4.2 K and 325 K over a frequency range of 60 - 670 cm~^. This frequency range can easily be extended through the addition of appUcable detectors. Tests were performed on SrTiOa, a highly ionic incipient ferroelectric insulator with a well known reflectance. The presence and temperatmre dependence of the lowest frequency "soft" mode were measured, as was the presence of the other two infrared modes. During the structural phase transition from cubic to tetragonal perovskite, the splitting of the second phonon mode was also observed. All of the collected data indicate good agreement with previous measurements, with a minor discrepency between the actual and recorded sample temperatures.
Resumo:
Fermi patches in quasi-two dimensional charge density waves (CDW) have not described the connection to superconductivity (SC) according to theory adequately at this point in time. The connection between CDW and SC in the quasi-two dimensional material CuxTiSe2 is an interesting one which might reveal mechanisms in unconventional superconductors. A previous Brock graduate student grew crystals of CuxTiSe2. The precise doping of the samples was not known. In order to determine the doping parameter x in CuxTiSe2, a sensitive resistivity measurement system was necessary. A new resistivity measurement system was designed and implemented utilizing an Infrared Labs HDL-10 He3 cryostat. By comparing with data from the literature, doping of two samples was investigated using the new measurement system and a Quantum Design Magnetic Property Measurement System (MPMS). Methods for determining the doping revealed that the old resistivity system would not be able to determine the CDW transition temperature of highly doped samples or doping for elongated samples due to electronic noise. Doping in one sample was found to be between x=0.06 and x=0.065. Values of doping in the second sample had a discrepancy but could be explained by incorrect sample orientation.
Resumo:
The perovskite crystal structure is host to many different materials from insulating to superconducting providing a diverse range of intrinsic character and complexity. A better fundamental description of these materials in terms of their electronic, optical and magnetic properties undoubtedly precedes an effective realization of their application potential. SmTiOa, a distorted perovskite has a strongly localized electronic structure and undergoes an antiferromagnetic transition at 50 K in its nominally stoichiometric form. Sr2Ru04 is a layered perovskite superconductor (ie. Tc % 1 K) bearing the same structure as the high-tem|>erature superconductor La2_xSrrCu04. Polarized reflectance measurements were carried out on both of these materials revealing several interesting features in the far-infrared range of the spectrum. In the case of SmTiOa, although insulating, evidence indicates the presence of a finite background optical conductivity. As the temperature is lowered through the ordering temperature a resonance feature appears to narrow and strengthen near 120 cm~^ A nearby phonon mode appears to also couple to this magnetic transition as revealed by a growing asymmetry in the optica] conductivity. Experiments on a doped sample with a greater itinerant character and lower Neel temperature = 40 K also indicate the presence of this strongly temperature dependent mode even at twice the ordering temperature. Although the mode appears to be sensitive to the magnetic transition it is unclear whether a magnon assignment is appropriate. At very least, evidence suggests an interesting interaction between magnetic and electronic excitations. Although Sr2Ru04 is highly anisotropic it is metallic in three-dimensions at low temperatures and reveals its coherent transport in an inter-plane Drude-like component to the highest temperatures measured (ie. 90 K). An extended Drude analysis is used to probe the frequency dependent scattering character revealing a peak in both the mass enhancement and scattering rate near 80 cm~* and 100 cm~* respectively. All of these experimental observations appear relatively consistent with a Fermi-liquid picture of charge transport. To supplement the optical measurements a resistivity station was set up with an event driven object oriented user interface. The program controls a Keithley Current Source, HP Nano-Voltmeter and Switching Unit as well as a LakeShore Temperature Controller in order to obtain a plot of the Resistivity as a function of temperature. The system allows for resistivity measurements ranging from 4 K to 290 K using an external probe or between 0.4 K to 295 K using a Helium - 3 Cryostat. Several materials of known resistivity have confirmed the system to be robust and capable of measuring metallic samples distinguishing features of several fiQ-cm.
Resumo:
ADeweyan (1916) democratic theoty ofeducation called for the participation ofall citizens in deliberating important educational issues to improve overall student learning. Thus, the move to include parents in educational decision making can be considered to be rooted in democratic principles. To gain greater insight into the issue ofparent involvement in educational decision making, one elementary school was studied and a triangulization method was employed in an attempt to clarify the important issues surrolUlding the move to include parents in the governance ofschools. The three methods to gain information included surveys, interviews, and documentation ofsignificant school events and related work. All ofthe parents and teachers ofthe school were surveyed, 10 parents and 6teachers were interviewed, and related school events were recorded. The survey design was modeled on the Parent Involvement Questionnaire (PIQ) created and reported on by Chavkin and Williams (1987). The results ofthe surveys were used as a guide for the interview questions. An interview outline was developed based on Seidman's (1991) open-ended approach and Patton's (1980) standardized open-ended interview style in which parents and teachers were asked about their experiences and opinions on anmnber ofparent involvement issues. Parents and teachers in this school indicated agreater interest in becoming more aware ofeducational issues such as school budget and school discipline policies. Although the parents indicated agreater interest in school matters and the teachers indicated awillingness to include parents in school matters, both the parents and teachers in this study perceived the role ofthe parent as advisory, not decision making. It was concluded that to ensure ameaningful and functional role for parellts as tlleir p811icipatioll ill educational matters evolves, SCllools must have a clear vision ofthe primary goal ofall schools, namely, to foster and nourish democratic citizens for ademocratic society (Glickman, 1993). Furthennore, intentional practices such as Purkey's (ad) 5-P Relay approach, based on a democratic theory and practice of education, will have to be employed in order to give parents an authentic voice in educational matters and provide an avenue for parents to acquire the necessary skills and lmowledge needed to do so. As schools, school boards, and the Ministry ofEducation implement parent involvement guidelines and policies, developmental needs ofeach school need to be considered to ensure the employment ofdemocratic practices not authoritarian mandates. Parent interest and involvement, at whatever level, should be an important element in the overall move to make schools part ofthe democratic society they were meant to be.
Resumo:
The purpose of this project was to identify in a subject group of engineers and technicians (N = 62) a preferred mode of representation for facilitating correct recall of information from complex graphics. The modes of representation were black and white (b&w) block, b&w icon, color block, and color icon. The researcher's test instrument included twelve complex graphics (six b&w and six color - three per mode). Each graphics presentation was followed by two multiple-choice questions. Recall performance was better using b&w block mode graphics and color icon mode graphics. A standardized test, the Group Embedded Figures Test (GEFT) was used to identify a cognitive style preference (field dependence). Although engineers and technicians in the sample were strongly field-independent, they were not significantly more field-independent than the normative group in the Witkin, Oltman, Raskin, and Karp study (1971). Tests were also employed to look for any significant difference in cognitive style preference due to gender. None was found. Implications from the project results for the design of visuals and their use in technical training are discussed.
Resumo:
This study sought to compare the results of the Motivation Assessment Scale (MAS; Durand & Crimmins, 1988), Questions About Behavior Function Scale (QABF; Matson & Vollmer, 1996) and Functional Analysis Screening Tool (FAST; Iwata & Deleon, 1996), when completed by parent informants in a sample of children and youth with autism spectrum disorders (ASD) who display challenging behaviour. Results indicated that there was low agreement between the functional hypotheses derived from each of three measures. In addition, correlations between functionally analogous scales were substantially lower than expected, while correlations between non-analogous subscales were stronger than anticipated. As indicated by this study, clinicians choosing to use FBA questionnaires to assess behavioural function, may not obtain accurate functional hypotheses, potentially resulting in ineffective intervention plans. The current study underscores the caution that must be taken when asking parents to complete these questionnaires to determine the function(s) of challenging behaviour for children/youth with ASD.
Resumo:
The study purpose was to examine differences between competitive and recreational weight trainers on indices of motivation, goals and behaviour. Data was collected from a purposive sample of competitive (n = 177; Mage = 30.86; SDage = 11.35) and recreational (n = 196; Mage = 21.97; SDage = 6.05) weight trainers using a cross-sectional, non-experimental design. Participants completed the Behavioural Regulation in Exercise Questionnaire-2R, Exercise Motivations Inventory-2, assessment of weight training behaviour and demographic questions. Multivariate analyses of variance indicated higher endorsement of autonomous motives and mostly intrinsically-oriented goals, while independent samples t-tests indicated higher frequency of weight training behaviour among the competitive weight trainers. Group differences were independent of demographic factors. Findings suggest that autonomous motives and intrinsic goals may not be undermined by competition among competitive weight trainers. This study also provides support for the utility of organismic integration theory and goal contents theory in examining strength-based exercise.
Resumo:
Mobile augmented reality applications are increasingly utilized as a medium for enhancing learning and engagement in history education. Although these digital devices facilitate learning through immersive and appealing experiences, their design should be driven by theories of learning and instruction. We provide an overview of an evidence-based approach to optimize the development of mobile augmented reality applications that teaches students about history. Our research aims to evaluate and model the impacts of design parameters towards learning and engagement. The research program is interdisciplinary in that we apply techniques derived from design-based experiments and educational data mining. We outline the methodological and analytical techniques as well as discuss the implications of the anticipated findings.
Resumo:
Mobile augmented reality applications are increasingly utilized as a medium for enhancing learning and engagement in history education. Although these digital devices facilitate learning through immersive and appealing experiences, their design should be driven by theories of learning and instruction. We provide an overview of an evidence-based approach to optimize the development of mobile augmented reality applications that teaches students about history. Our research aims to evaluate and model the impacts of design parameters towards learning and engagement. The research program is interdisciplinary in that we apply techniques derived from design-based experiments and educational data mining. We outline the methodological and analytical techniques as well as discuss the implications of the anticipated findings.
Resumo:
Voucher #7 from the Engineer Department of Port Dalhousie and Thorold Railway Extension to W.G. Thompson accompanied by an abstract of vouchers and summaries of account paid by W.G. Thompson for surveys, Jan. 31, 1857.