This work is mainly focused upon the analytical examination of the physical and mechanical response of plastics undergoing an induced scratch deformation caused by a semi-spherical scratch tip under a linearly increasing normal load. Evaluation of the scratch deformations in this study was based upon visual and optical observations and upon observations of failure and fracture mechanisms as well as Electron Microscopy examinations. In the first section of this study an effort was made to correlate the scratch resistance observed in Polypropylene (PP) thin sheets with material properties, such as molecular weight and surface crystallinity. In the second section of this work the scratch behavior of epoxy nanocomposites was examined and a conclusion was made based upon the effects of the addition of nano-additives with various natures into the epoxy matrix. Furthermore, a region of the scratch path prior to the onset of scratch visibility known as the mar region, which was an obscure area of deformation on a microscopic scale, was thoroughly investigated for the epoxy systems and various conclusions were made based upon those results. Finally, based on these findings and previous studies, it was shown that failure and fracture mechanisms of polymeric materials under scratch deformations are dependent on the type and physical nature of the material, whereas brittle and ductile materials show various behaviors under the specified conditions. Based on the failure mechanism which the material exhibits subsequent to the scratch deformation process and the physical and mechanical characteristics of the material, several factors were shown to effect the materials ability to scratch resistance.

In this thesis, the feasibility of inverse evaluation of piezoelectric parameters by using piezoelectric beam¡¦s natural frequencies is presented. Generally, all the piezoelectric parameters are not measured simultaneously. In other words, the interactive effects between the piezoelectricity and strain are not all included. The piezoelectric beam¡¦s natural frequencies are analyzed by the inverse evaluation of piezoelectric parameters associated with the optimization algorithm. The dynamic model for piezoelectric beam is proposed by using Hamilton¡¦s principle in this study. The corresponding eigenvalue problems of different piezoelectric beams are formulated and solved by employing differential quadrature method (DQM). The genetic optimization algorithm is employed to optimize all piezoelectric parameters from the measured natural frequencies. Optimization of piezoelectric parameters of piezoelectric beam under the boundary conditions of fix-fix ends and fix-free ends are investigated. The robustness of program is also demonstrated through several numerical examples. The results demonstrate the method of this study applied to determine piezoelectric parameters by using natural frequencies is feasible and practicable.

In the region of the harmonic parameter analysis, we often use the Fast Fourier Transform (FFT) to get the character of the signal, but due to the limit conditions of the FFT, the analysis results will appear some error effects, these error effects are: Aliasing effect¡BLeakage effect and Picket-fence effect. When the error effects appear, we can not get the harmonic parameter accurate. For the purpose of getting accuracy harmonic parameters, In this paper proposes, we will introduce the analysis method of FFT and it's limit conditions, then will based on FFT to develop an accuracy formula to find the harmonic parameter fast and accurately. This method will be divided into three parts. First, we will discuss the effect of harmonic to spectrum. Second, we will discuss the parameter calculation with no interfere. Third, we will rid interfere of the harmonic for getting accuracy harmonic parameter. Finally, we will analysis the actual signal to prove the ability of this method, and raise the future research direction for the successor.

Proefschrift Universiteit van Amsterdam. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Class of 2005 Abstract / Objectives: Doses of vancomycin are frequently estimated using various predictor formulas aiming for trough concentrations between 5 and 15 mg/L and peak concentrations between 25 and 40 mg/L.1 There is however, some controversy about the relationship between vancomycin concentrations and therapeutic response. This project compares the ability of several methods to estimate serum concentrations of vancomycin. Methods: This project was a retrospective look at 243 patient records, the patients were given vancomycin and later had at least one concentration measured. Data collected while the patient was being treated was used in the nine predictor models to determine which model would best predict actual concentrations. The methods compared were Moellering, Matzke, Lake-Peterson, Rodvold, Abbott, Birt, Burton, Ambrose, and Bauer. Results: There were 188 patients included in the analysis, 97 males and 91 women. The method with the least bias (+ 1.0) was the Rodvold method using the actual body weight. None of the models were very precise, with most around 10 (high of 12.83, and a low of 9.35). The r- values for all the models were also low, none of the models had an r- value greater than 0.5. The Lake-Peterson method predicted within 20% and 50% the most often; the Ambrose method the least often within 50%, and both Ambrose and Bauer the least often within 20%. The Lake-Peterson method predicted concentrations within plus or minus 2.5 and 5.0 mg/L of measured concentrations most frequently. The Ambrose method predicted concentrations within plus or minus 2.5 mg/L of measured the least often; Burton and Rodvold the least often within 5.0 mg/L of measured. Implications: With the best model only accurate (defined as ± 20%) less than 25 percent of the time, there is too much error to make a good decision on dose and interval without the feedback of measured serum concentrations. The models may be a good starting point as which dose and interval to choose, but they are not a substitute for measuring steady state concentrations.

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An experimental investigation was made involving the synthesis of nepheline (NaAlSiO4) under varying conditions of temperature and water pressure 2022-2130 for each synthesized charge was obtained using x-ray diffraction methods. It was found that the results of the individual runs provided an erratic lattice parameter variation with temperature in the range 500 to 800 degrees Celsius. However, a least squares curve indicates that no change in lattice parameters in the low-nepheline polymorph occurs with temperature of formation, for 95 percent probability. / Thesis / Master of Science (MS)

Sex steroids influence the storing of fat, and differences in the distribution of fat are a typical secondary sexual characteristic. Androgens act on fatty tissues in males either directly through stimulation of the androgen receptor or indirectly through aromatization of the estrogen receptor. Androgens can be classified as aromatizable or non-aromatizable. Testosterone (T) is the main aromatizable androgen, while its metabolite dihydrotestosterone (DHT) is a non-aromatizable androgen that acts only through the androgen receptor. It is precisely this difference in having activity only through the androgen receptor that has given rise to the hypothesis concerning the differing effects of DHT and T on body composition, with DHT possibly being responsible for male-type fat distribution. As part of my post-graduate studies we analyzed the dependence serum levels of T and DHT on age, as well as changes in their ratio with age. Further, we sought relationships between aromatizable and non-aromatizable androgens and metabolic and anthropometric parameters. We also focused on following any changes in steroidogenesis in obese males. We showed that before puberty the dominant androgen is rather DHT than T, that the fDHT/fT ratio during the life of adult males is constant, and that there is no evidence of a reversal...

Maize is the third most important cereal crop in the world and many subsistence farmers are practicing intercropping of it with legumes due to land scarcity and in order to enhance production. Intercropping system is being practiced in may areas of South Africa mainly in the Limpopo province. The objective of the study was to evaluate the crop responses to intercropping maize with different growth length cowpea cultivars. The effects of intercropping on weed growth, maize and cowpea growth and yield components were investigated. The experiment was conducted during the 2005/06 and 2006/07 seasons at Bethlehem and Potchefstroom. Treatments were: maize sole, maize+PAN311 (short duration cowpea cultivar), maize+Glenda (medium duration cowpea cultivar), maize+Agrinawa (long duration cowpea cultivar) and sole plots of all cowpea varieties. Each plot was divided into two weed levels where all the plots were kept weed free for one month after planting, after which one half was left weedy and the other half weed free. Weed sampling was done within each weed treatment. Intercropping reduced maize LAI and plant height while time to physiological maturity was also reduced by weed infestation, especially under drier and warmer environments. Glenda and Agrinawa intercrops produced more nodules per plant under cooler and wetter conditions. Agrinawa produced the highest leaf and total DMY under sole crop conditions and this was significantly reduced by weed infestation. Different growth duration cultivars did not differ in their N2-binding abilities. Maize intercropping, especially with Glenda and Agrinawa, significantly reduced weed biomass. Maize sole crop under zero weeds had high grain yield compared to intercropping. PAN311 and Glenda sole crops under zero weeds produced higher yields under dry and warmer conditions, and cooler and wetter conditions, respectively, compared to intercropping. High cowpea grain yields were strongly correlated to more seeds per pod and larger pod lengths and number of pods per plant especially for Glenda. No intercropping advantage compared to sole cropping was observed (total LER < 1). This implies that maize and cowpeas must rather be planted as sole crops for better yields under wetter and cooler, and warmer and drier conditions. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

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