An experimental study of the effects of double-diffusive convention processes during the solification of binary alloys

Experiments were conducted to show the effects of thermal and geometric boundary conditions on the liquid pool of a binary alloy system which is undergoing phase change, solidification. Transparent analogue solutions were selected for study and experimental apparatus were designed and built. Thermal distribution and concentration data were collected and analysed for the melt pool of various selected geometries and boundary conditions of the systems under study. The data indicate-that characteristic flows develop for both Hypereutectic and Hypoeutectic concentration levels and that the development of macrosegregation and microsegregation defects in continuous casting materials can be minimised by the adjustment of the process variables.

An experimental study of micro-end-milling operations

Cutting tools less than 2mm diameter can be considered as micro-tool. Microtools are used in variety of applications where precision and accuracy are indispensable. In micro-machining operations, a small amount of material is removed and very small cutting forces are created. The small cross sectional area of the micro-tools drastically reduces their strength and makes their useful life short and unpredictable; so cutting parameters should be selected carefully to avoid premature tool breakage. The main objective of this study is to develop new techniques to select the optimal cutting conditions with minimum number of experiments and to evaluate the tool wear in machining operations. Several experimental setups were prepared and used to investigate the characteristics of cutting force and AE signals during the micro-end-milling of different materials including steel, aluminum and graphite electrodes. The proposed optimal cutting condition selection method required fewer experiments than conventional approaches and avoided premature tool breakage. The developed tool wear monitoring technique estimated the used tool life with ±10% accuracy from the machining data collected during the end-milling of non-metal materials.

The development of rubrics to measure undergraduate students' global awareness and global perspective: A validity study

Higher education institutions across the United States have developed global learning initiatives to support student achievement of global awareness and global perspective, but assessment options for these outcomes are extremely limited. A review of research for a global learning initiative at a large, Hispanic-serving, urban, public, research university in South Florida found a lack of instruments designed to measure global awareness and global perspective in the context of an authentic performance assessment. This quasi-experimental study explored the development of two rubrics for the global learning initiative and the extent to which evidence supported the rubrics' validity and reliability. One holistic rubric was developed to measure students' global awareness and the second to measure their global perspective. The study utilized a pretest/posttest nonequivalent group design. Multiple linear regression was used to ascertain the rubrics' ability to discern and compare average learning gains of undergraduate students enrolled in two global learning courses and students enrolled in two non-global learning courses. Parallel pretest/posttest forms of the performance task required students to respond to two open-ended questions, aligned with the learning outcomes, concerning a complex case narrative. Trained faculty raters read responses and used the rubrics to measure students' global awareness and perspective. Reliability was tested by calculating the rates of agreement among raters. Evidence supported the finding that the global awareness and global perspective rubrics yielded scores that were highly reliable measures of students' development of these learning outcomes. Chi-square tests of frequency found significant rates of inter-rater agreement exceeding the study's .80 minimum requirement. Evidence also supported the finding that the rubrics yielded scores that were valid measures of students' global awareness and global perspective. Regression analyses found little evidence of main effects; however, post hoc analyses revealed a significant interaction between global awareness pretest scores and the treatment, the global learning course. Significant interaction was also found between global perspective pretest scores and the treatment. These crossover interactions supported the finding that the global awareness and global perspective rubrics could be used to detect learning differences between the treatment and control groups as well as differences within the treatment group.