Digital computer study of nuclear reactor thermal transients during startup of 60-kWe Brayton power conversion system

A digital computer study was made of reactor thermal transients during startup of the Brayton power conversion loop of a 60-kWe reactor Brayton power system. A startup procedure requiring the least Brayton system complication was tried first; this procedure caused violations of design limits on key reactor variables. Several modifications of this procedure were then found which caused no design limit violations. These modifications involved: (1) using a slower rate of increase in gas flow; (2) increasing the initial reactor power level to make the reactor respond faster; and (3) appropriate reactor control drum manipulation during the startup transient

Measurement of Thermal Conductivity of Foods in Situ by aNon-Steady State Method

An improved line heat source thermal conductivity probe was designed to simplify the construction and extend the life of thermal conductivity probes for use in the determination of thermal properties of foods. The probe was designed with the thermocouple on the outside of a cylindrical heater instead of being placed inside a hypodermic needle as used by most researchers in the literature. The utility of the apparatus was checked by measuring the thermal conductivity of food samples with varying conditions of moisture content and at different ambient temperatures. Linearity of temperature versus logarithm of time was obtained after 8 to 10 minutes (r2 = 0.985)

Critical thinking in the context of group learning: A qualitative study of postgraduate accounting and finance students' perceptions

Critical thinking has been seen as the foundation of Western university education (Barnett, 1997). Today, educators and industry constantly emphasise the importance of acquiring critical thinking by students and graduates. One of the possible ways to facilitate critical thinking in students’ learning is group learning. The aim of this qualitative study grounded in Constructivism is to work towards an understanding of critical thinking in the context of group learning. The research objectives are concerning with the postgraduate accounting and finance students’ perceptions and experiences within and between students in this constructivist model of learning. The sample was composed of twenty students who enrolled in a Fundamentals of Financial Management (FFM) Module of the MSc Accounting and Finance. Students were required to participate in group learning and engaged in critical thinking to complete the group assignment. The primary data collection method was in-depth semi-structured interviews and the supportive method was students’ individual reflection reports. The study particularly interested in their perceptions and responses in relation to critical thinking and group learning.This study used Interpretative Phenomenological Analysis (IPA) as the guide for data analysis. Student profiles were created in order to understand their perceptions and experiences according to their voices rather than the researcher’s. This study adopted two approaches to generate the findings. First, it considers the significant variations of the ways students described and revealed the perceptions and responses in the context of group learning. At this stage, the study identified presents findings which include students’ stance, perceptions, orientations to group learning, motivation and critical responses. Second, it used matrices to identify potential relationship between the identified findings at the first stage. This research identified there were both congruent and incongruent relationship between the findings. In other words, it revealed that group learning provided a complex environment for learning and engagement with critical thinking. Students brought with them particular stance, perceptions, orientations, and motivation that appeared to predispose them to engage in particular ways within the group. Hence, the congruent and incongruent relationship will make sense only after considering students as ‘the person who learn’ (Javis, 2006).This study concluded that students should take central role to engage in critical thinking and learning. This study also concluded that group learning provide the social contextual conditions for critical thinking to take place. However, it must be employed with students in mind. With these in mind, the implications and recommendations for pedagogy were made for the policy makers and educators. Limitations of the research were reported and a number of recommendations for future research were offered in relation to critical thinking and group learning. The study seeks to make a unique contribution to the research of critical thinking and group learning and illuminates the teaching and learning pedagogical practices in HE and AE. Its conclusion will be of value to policy makers and educators in advancing knowledge of critical thinking and group learning in HE and professional accounting education

A stirling engine computer model for performance calculations

To support the development of the Stirling engine as a possible alternative to the automobile spark-ignition engine, the thermodynamic characteristics of the Stirling engine were analyzed and modeled on a computer. The modeling techniques used are presented. The performance of an existing rhombic-drive Stirling engine was simulated by use of this computer program, and some typical results are presented. Engine tests are planned in order to evaluate this model

Tinigible Body Macrophages in Regulation of Germinal Center Reactions

Tingible body macrophages (TBM), long thought simply as scavengers of apoptotic lymphocytes, are located in the unique microenvironment of germinal centers in close proximity to antigen-retaining follicular dendritic cells (FDC). Observations that TBM endocytose FDC-iccosomal (immune-complex coated bodies) antigen suggested that TBM might present this antigen and help regulate the germinal center reaction. To test for antigen presentation, the ovalbumin (OVA)-specific TH hybridoma, 3DO-54.8, which produces IL-2 on receiving effective presentation of OVA, were used as responders to OVA-bearing TBM. Results showed that OVA-bearing TBM failed to induce IL-2 production. Furthermore, addition of TBM to IL- 2-inducing positive controls (B cells) not only failed to augment IL-2 production, but rather TBM significantly (55-90%) reduced B-cell induction of IL-2. We found that TBM were rich in prostaglandin by comparison with other nongerminal center lymph node macrophages and that addition of indomethacin to the cultures reversed the inhibitory effect of TBM. Depletion of TBM from enriched preparations, prior to addition to positive control cultures, also abrogated the inhibitory effect on IL-2 production. These data support the concept that TBM, within the unique microenvironment of germinal centers, may be specialized to downregulate the germinal center reaction