Technique for experimental determination of radiation interchange factors in solar wavelengths

Process obtains solar heating data which support analytical design. Process yields quantitative information on local solar exposure of models which are geometrically and reflectively similar to prototypes under study. Models are tested in a shirtsleeve environment

Proving Termination of Graph Transformation Systems using Weighted Type Graphs over Semirings

We introduce techniques for proving uniform termination of graph transformation systems, based on matrix interpretations for string rewriting. We generalize this technique by adapting it to graph rewriting instead of string rewriting and by generalizing to ordered semirings. In this way we obtain a framework which includes the tropical and arctic type graphs introduced in a previous paper and a new variant of arithmetic type graphs. These type graphs can be used to assign weights to graphs and to show that these weights decrease in every rewriting step in order to prove termination. We present an example involving counters and discuss the implementation in the tool Grez

Vanwaar die kragtige invloed van die optrede en prediking van Jesus?

No Abstract

Selective laser sintering of stearic acid-coated alumina ceramic

The purpose of this research is to develop a process that will enable a Selective Laser Sintering (SLS) machine to create geometrically complex green parts of various sizes that become strong, dense ceramic parts after sintering. This will be applicable to SLS systems already operational in industry, and may offer a more cost-effective, more time-efficient method for producing high-temperature ceramic rapid prototype parts. Alumina was the chosen ceramic for the developmental stage of this research. Fine alumina powder (average particle size of 0.4 µm) was coated with stearic acid, which served as a binder. Green parts were made from this powder using low temperature, low laser power SLS processes. The green strength of parts produced in this research was sufficient for safe transport and to survive the binder burnout process to remove the organic binder. The average final density of fully sintered parts was 88% of the theoretical density for alumina (3.96 g/cm³), and the average flexural strength of fully sintered flexural test bars was 255 MPa. The sintered parts have an average surface roughness of approximately 7.6 µm without any finishing processes such as grinding or polishing. No infiltration, compaction, or post-processing other than binder burnout/sintering is required to achieve these results. Holes of diameters less than 1 mm and holes with multiple bends have consistently been produced in Al₂O₃ parts of various thickness and height. Average dimensional variances are approximately 0.12 mm for hole diameters and 0.25x0.27x0.21 mm for the length, width, and height of flexural strength bars, respectively. Features of green parts produced in this research include sharp corners, crisp lines, flat surfaces, complex holes, slots, and overhangs --Abstract, page iii