Effect of Grain Size on Scratch Interactions and Material Removal in Alumina

Dramatic effects of scratch interactions on material removal are observed in alumina. A series of parallel scratches are made in aluminas with different grain sizes to investigate the influence of scratch interactions on the material removal process in abrasive machining. The separation distance between the two scratches and the normal load are varied and subsurface microfracture and damage modes are examined to assess the mechanisms of material removal. A very small amount of material is removed when the separation distance between the two parallel scratches is large or when the two scratches completely overlap. However, at intermediate distances the volume of material removed increases dramatically as a result of the interactions between the two scratches. The maximum amount of material removed and the corresponding distance between the two scratches are found to depend strongly on the grain size and the load. Observations of surface and subsurface damage reveal that grain dislodgement is the predominant mechanism of material removal, irrespective of the grain size. The relation between grain size, scratch interactions, and the material removal process in grinding and abrasive machining of ceramics is discussed in terms of the short-crack toughness of ceramics.     

Modelling an imperfect debugging phenomenon in software reliability

Several Software Reliability Growth Models (SRGMs) have been developed in the literature assuming the debugging process to be perfect and thus implying that there is one-to-one correspondence between the number of failures observed and errors removed. However, in reality it is possible that the error which is supposed to have been removed may cause a failure again. It may be due to the spawning of a new error because of imperfect debugging. If such a phenomenon exists then the Software Reliability Growth is S-shaped. In this paper, we develop a model which can describe imperfect debugging process and has the inbuilt flexibility of capturing a wide class of growth curves. Earlier attempts of modelling such a process were able to capture only a particular curve. In other words, if a failure observation phenomenon is exponential then the error removal is again modelled by an exponential growth curve. Applicability of the model has been shown on several data sets obtained from different software development projects.     

Memory Fault Modeling Trends: A Case Study

In recent years, embedded memories are the fastest growing segment of system on chip. They therefore have a major impact on the overall Defect per Million (DPM). Further, the shrinking technologies and processes introduce new defects that cause previously unknown faults; such faults have to be understood and modeled in order to design appropriate test techniques that can reduce the DPM level. This paper discusses a new memory fault class, namely dynamic faults, based on industrial test results; it defines the concept of dynamic faults based on the fault primitive concept. It further shows the importance of dynamic faults for the new memory technologies and introduces a systematic way for modeling them. It concludes that current and future SRAM products need to consider testability for dynamic faults or leave substantial DPM on the table, and sets a direction for further research.     

Design of a commercial solar-powered greenhouse

A completely solar-powered greenhouse complex has been designed for climate controlled food production in hot, humid environments. The concept uses passive design features to provide irrigation water from saline water sources. This paper discusses the overall system concept and the solar still subsystem which has been designed to provide a continuous fresh water supply. While incorporating many innovative features, the use of proven technologies and passive design results in a system that should compete economically with current, more traditional designs.     

Wear mechanisms of boundary-lubricated surfaces

Examination of steel specimens tested under boundary lubrication conditions indicates the existence of three distinct processes which lead to wear particle formation: deformation and fracture of original machining marks; deformation and fracture of edges of plowing tracks; delamination. Deformation and fracture of original machining marks and the raised edges of the plowing furrows generate wear particles which are 1–15 μm in the largest dimension. The process of delamination, however, generates particles that are 100 μm wide. The formation of these large wear particles coincides with a high rate of wear and scuffing failure.     

Influence of Al2O3 support on the thermal decomposition of ammonium metavanadate

The thermal decomposition of ammonium metavanadate (AMV) supported on aluminium oxide was investigated using differential thermal analysis, thermogravimetry, infrared and X-ray diffraction techniques. The results obtained revealed that the decomposition of AMV supported on alumina proceeded in three decomposition stages. Alumina was found to enhance only the decomposition of the intermediate ammonium hexavanadate to produce V₂O₅. In addition, the values of activation energies of the various decomposition stages were accompanied by a significant decrease on decreasing the concentration of AMV. The infrared spectra indicated that the band corresponds to the surface site V=O strongly affected by the presence of Al₂O₃. Finally, an interaction between Al₂O₃ and V₂O₅ occurred at 660 °C giving well-crystallized AlVO₄.     

Egyptian Mango Juice. Experiment on Storage Experience

In this study processed mango juice was packed in four types of containers and stored at different temperatures for 16 weeks through which furfural level determination and organoleptic assessment were conducted. The experiment revealed an evident relationship to exist among furfural level, storage temperature and type of packing material. Furfural level failed to closely parallel flavour difference; therefore it could be regarded as one of the features concomitant juice aging rather than accepted as a satisfactory criterion of off flavour. The study relates flavour deterioration to the changes in the lipid fraction of the juice.     

Bioavailability of Eight Brands of Ampicillin Capsules

An in vivo absorption study was performed in a crossover fashion on 6 healthy volunteers (4 males and 2 females) to compare the bioavailability of 8 brands of ampicillin capsules. Absorption was assessed by a urinary excretion method in which the drug was assayed chemically. Statistical analysis of the results was carried out to evaluate the significance of differences between brands and between subjects. Results of the analysis of variance indicated no significant differences between the tested brands of ampicillin capsules. However, significant differences between brand A and brand B were found on using the student t-test. A significant intersubject variation was also found between the volunteers participated in the present study.     

Thermodynamic comparisons of methods for producing hot gases

We present a thermodynamic comparison of combustion processes for the production of high-temperature gases (2000–3100 °K) from methane. We compare:

1. (1) CH₄---O₂ mixtures, with oxygen added either in the gaseous or the liquid state,

2. (2) CH₄-enriched air systems, with enrichment by removal of gaseous nitrogen from air,

3. (3) CH₄-enriched air systems, with enrichment achieved by adding either pure gaseous or pure liquid oxygen to air, and

4. (4) CH₄-air electrically augmented systems, in which enriched air is produced in an air-separation plant and electrical augmentation is produced by applying strong electric fields between electrodes immersed in the flame gases.

Comparisons involve energy costing.