The advancement of photonics technologies depends on synthesis of novel materials and processes for device fabrication. The characterization techniques of the optical, electrical and magnetic properties of the synthesized materials and devices, by non-contact, non-invasive and nondestructive methods plays a significant role in development of new photonics technologies. The research reported in this thesis focuses on two such aspects of photonic materials characterization: Magneto-Optic characterization and Spectroscopic Ellipsometry. The theoretical and experimental basis of these two techniques, and experimental data analysis are presented in two parts. In Part 1, the changes in magneto-optic parameters of FePT PS-P2VP block copolymer nanocomposites with increasing concentrations of FePt nanoparticles in the block copolymer are analyzed. We present the results of change in MO anisotropy factor with the wt% of FePt and try to analyze these changes with further experimentation. Part 2 presents the results of spectroscopic ellipsometry of group III-IV multilayered thin film materials to give their precise thicknesses and optical constants. Both these techniques are unique ways to understand novel material characteristics for future use in device development.

The geometry of surfaces of rotation in three dimensional Euclidean space has been studied widely. The rotational surfaces in three dimensional Euclidean space are generated by rotating an arbitrary curve about an arbitrary axis. Moreover, the geodesics on surfaces of rotation in three dimension Euclidean space have been considered and discovered. Clairaut's [1713-1765] theorem describes the geodesics on surfaces of rotation and provides a result which is very helpful in understanding all geodesics on these surfaces. On the other hand, the Minkowski spaces have shorter history. In 1908 Minkowski [1864-1909] gave his talk on four dimensional real vector space, with asymmetric form of signature (+,+,+,-). In this space there are different types of vectors/axes (space-like- time-like and null) as well as different types of curves (space-like- time-like and null). This thesis considers the different types of axes of rotations, then creates three different types of surfaces of rotation in three dimensional Minkowski space, and generates Clairaut's theorem to each type of these surfaces, it also explains the analogy between three dimensional Euclidean and Minkowskian spaces. Moreover, this thesis produces different types of surfaces of rotation in four dimensional Minkowski spaces. It also generalises Clairaut's theorem for these surfaces of rotations in four dimensional Minkowski space. Then we see how Clairaut's theorem characterization carries over to three dimensional and four dimensional Minkowski spaces.

Fertility-building crops (FBCs) offer the opportunity to alleviate the costs of inorganic fertiliser by providing an alternative supply of available nitrogen (N) in soils. A survey of relevant literature reviewed the types of FBCs, their nitrogen accumulation potentials, residue characteristics, and subsequent release patterns. It also identified a paucity of data concerning the response of different species to UK climatic, soil, and management conditions. In order to investigate these relationships further pot and field trials were established in 2007 at the Royal Agricultural College, Cirencester (SP 00481 01382) and at Coates Manor Farm (SO 98473 00402) on Sherborne series (typical Cotswold) soils, to investigate the biology and morphology of FBCs potentially suitable for short term fertility-building, their accumulation of N under field conditions, and its subsequent recovery within test crops. Data so obtained was used as a verification and refinement tool for the FBC model (Cuttle et al, 2003), a simple, commercially applicable, rotation-based model which can be applied to both organic and conventional production systems. Nine leguminous and two non-leguminous FBC treatments were established in April 2007 by straight sowing, followed by mulching at the conclusion of the nitrogen accumulation phase and by undersowing in spring barley (Hordeum sativum). The recovery test crops (winter and spring wheat Triticum aestivum L.) were established in September 2007 and March 2008. All FBCs established successfully. Above-ground dry matter (DM) yield and residue quality (C:N ratio) of FBCs varied significantly (P<0.05) between crops and cropping regimes with a significant correlation (r2=0.418) between DM yields and C:N ratios. FBCs and cropping regimes had significant effects (P<0.001 and P<0.05 respectively) on potential mineralisable nitrogen (PMN) levels in the soil and on the grain yields of winter and spring wheat test crops. Straight sown Lupinus albus, Trifolium pratense, Trifolium repens and a legume mixture resulted in higher winter wheat grain yields. However, the opportunity cost associated with straight sowing (i.e. the gross margin foregone from a spring barley crop) meant that the rotation would probably not be viable economically. Undersown Medicago lupulina, Vicia villosa, T. pratense, T. repens and the legume mixture gave worthwhile yield increases in spring wheat without incurring a yield penalty in the spring barley cover crop. Following enhancement and using actual data from the trials, the FBC model (Cuttle et al, 2003) provided encouraging predictions (R>0.6) for soil mineral nitrogen (SMN) and key parameters were identified for future use. It was concluded that FBCs established for short term soil fertility building could provide a worthwhile enhancement of soil N levels and grain yields in a conventional arable rotation, particularly in spring wheat following FBCs undersown in spring barley. It was also concluded that the FBC model (Cuttle et al, 2003), following further enhancement, and using additional data from these and other similar trials, could provide reasonably accurate estimates of SMN to aid more precise applications of N fertiliser in the future.

Thesis (MAgricAdmin)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Crop rotation present a possible alternative to wheat mono culture production in the Middle Swartland region where farming circumstances became increasingly more difficult since 1996 due to decreasing profit margins. Crop rotation as such presents a number of advantages like higher yield for wheat within the system and reduced inputs costs mainly due to cuts in fertilizers, herbicides and pesticides. Crop rotation trials are currently undertaken at the Langgewens experimental farm in which canola and lupines are used in rotation with wheat while medics and medic/clover mixtures are used as pasture crops in rotation with wheat. The trials is scheduled to run over a period of 20 years, a study of the possible financial effect crop rotation might have on the typical farm can be of some importance to decision makers in the wheat industry. Due to a lack in reliable information the knowledge of a multi disciplinary panel of experts were use to obtain information concerning certain aspects of crop rotation. The expected profitability could thus be determined. To be able to determine the expected financial implications on farm level a typical farm model was developed with the help of the panel of experts. The typical farm of 630 ha was used for the model. The expected profitability and financial implications of the implementation of the eight different crop rotation systems on such a typical farm were estimated making use of long term budgets. The dispersion of rainfall over time was identified as the single most influential factor on the yields of the different crops in the region and was taken into account determining the profitability of the systems over time. The period used for the calculations were thus divided into good, average or poor rainfall years. The IRR (internal rate of return) was used as financial criteria in calculating the expected profitability of the different / AFRIKAANSE OPSOMMING: Wisselbou bied 'n moontlike alternatief vir koringmonokultuurverbouing in die Middel Swartland waar boerdery omstandighede sedert 1996 toenemend moeiliker word weens dalende winsmarges. Wisselbou as sulks bied verskeie voordele ten opsigte van verhoogde opbrengste vir veral koring wat in die wisselboustelsel voorkom, sowel as insetbesparings ten opsigte van hoofsaaklik bemesting en spuitprogramme. Wisselbouproewe word tans op Langgewens Proefplaas onderneem om wisselboustelsels waarin kanola en lupien as wisselbougraangewasse en medies en medics/klawer kombinasies as wisselbouweidingsgewasse saam met koring ondersoek word. Die proef is geskeduleer om oor 'n 20 jaar tydperk uitgevoer te word, maar 'n voortydige finansiële ontleding van die verwagte effek wat wisselbou vir die tipiese plaas kan inhou, kan waardevol wees vir besluitnemers in die betrokke bedryf Weens 'n tekort aan toepaslike betroubare inligting is van 'n multidissiplinêre span van kundiges gebruik gemaak om inligting ten opsigte van sekere aspekte van wisselbou te genereer. So kan die verwagte winsgewendheid van die geïdentifiseerde wisselboustelsels bepaal word. Ten einde die finansiële implikasies van gewaswisselbou relatief tot koringmonokultuurverbouing op plaasvlak te ondersoek, is van 'n tipiese plaasmodel gebruik gemaak wat met behulp van die paneel kundiges ontwikkel is. 'n Tipiese plaas van 630 ha is gebruik as ontledingsmodel. Die verwagte winsgewendheid en finansiële implikasies van die implementering van eik van agt verskillende wisselboustelsels is beraam deur middel van langtermyn begrotings. Reënval en reënvalverspreiding is geïdentifiseer as die faktore wat die grootste invloed op die opbrengs prestasie van gewasse in die betrokke omgewing uitoefen en is in ag geneem met die beraming van die finansiële prestasie van die stelsels oor die langtermyn. Die berekeningstermyn is gevolglik ingedeel in goeie, gemiddelde en swak reënvaljare ten einde die invloed van reënval op die opbrengste van die verskillende gewasse in ag te neem. Die lOK (interne opbrengskoers van kapitaal) is gebruik as finansiële maatstaf vir die meet van die winsgewendheid van eike wisselboustelsel, soos geïmplementeer op die tipiese plaas. Wisselboustelsels met kanola en lupien saam met koring toon goeie finansiële resultate, terwyl stelsels met weidingsgewasse en koring oor die algemeen meer winsgewend vertoon as koringmonokultuur.Na verwagting behoort die stelsel waar koring en medics/klawennengsel afgewissel word, die beste te vaar ten opsigte van winsgewendheid.

Stars with spectral type `A' (also called A-type stars or just A-stars) are bright intermediate mass stars (∼1.5-2.5 M⊙) that make up ∼1% of stars within 25 parsecs, and ∼20% of the brightest stars in the night sky (V < 3 mag). Most A-stars rotate rapidly with rotational velocities that range from ∼100 to ∼200 km/s in most cases, but can exceed 300 km/s. Such rapid rotation not only causes a star's observed properties (flux, temperature, and radius) to be inclination dependent, but also changes how the star evolves both chemically and structurally. Herein we conduct an interferometric survey of nearby A-stars using the CHARA Array. The long baselines of this optical/infrared interferometer enable us to measure the angular sizes of stars as small as ∼0.2 mas, and directly map the oblate shapes of rotationally distorted stars. This in turn allows us to more accurately determine their photospheric properties and estimate their ages and masses by comparing to evolution models that account for rotation. To facilitate this survey, we construct a census of all 232 A-stars within 50 parsecs (the 50PASS) and from that construct a sample of A-stars (the OSESNA) that lend themselves to interferometric observations with the CHARA Array (i.e., are in the northern hemisphere and have no known, bright, and nearby companions - 108 stars in total). The observations are interpreted by constructing a physical model of a rapidly rotating star from which we generate both photometric and interferometric model observations for comparison with actual observations. The stellar properties of the best fitting model are then compared to the MESA evolution models to estimate an age and a mass. To validate this physical model and the adopted MESA code, we first determine the ages of seven members of the Ursa Major moving group, which are expected to be coeval. With the exception of one star with questionable membership, these stars show a 1-σ spread in age of 56 Myr. This agreement validates our technique and provides a new estimate of the age for the group of 414 ± 23 Myr. We apply this validated technique to the directly-imaged `planet' host star κ Andromedae and determine its age to be 47+27-40 Myr. This implies the companion has a mass of 22+8-9 MJup and is thus more likely a brown dwarf than a giant planet. In total, we present new age and mass estimates for 55 nearby A-stars including six members of the Hyades open cluster, five stars with the λ Boötis chemical peculiarity, nine stars which have an infrared excess, possibly from a debris disk, and nine pulsating stars.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008.

No description available.

Nous présentons une étude expérimentale du "spin-up" et "spin-down" en présence d'une stratification linéaire sur un fond plat. Deux comportements très différents ont été mis en évidence selon la valeur du nombre de Burger, une mesure de l'importance relative de la stratification et des effets de Coriolis. Pour des nombres de Burger supérieurs à un, l'écoulement est remarquablement axisymétrique en dehors des couches limites, et aucune instabilité n'est observée malgré le grand nombre de Reynolds. Le confinement de la circulation secondaire du à la stratification est bien décrit par la théorie de Walin (1969), qui omet la viscosité. Cependant, le "spin-up" non-uniforme de l'intérieur provoque des gradients verticaux d'écoulement sensiblesaux effets visqueux. En conséquence, la comparaison avec la théorie montre un taux plus rapide de décroissance de l'écoulement azimutal.On propose une prise en compte simplifié de la diffusion verticale de quantité de movement dans la solution analytique de Walin. Aux temps courts, l'écoulement initial est correctement décrit par l'addition d'effets diffusifs visqueux, mais l'écart entre la théorie et les mesures persiste pour des temps intermédiaires. Pour des nombres de Burger inférieurs à un, le comportement de l'écoulement est très différent. La pénétration plus profonde de la circulation secondaire réduit notamment les gradients verticaux devitesse. La décroissance de la vitesse azimutale est presque verticalement uniforme et le développement des perturbations non-axisymmetriques est observé. Le déclin initial est bien décrit par la solution analytique. Cependant, la décroissance expérimentale est plus faible que la prédiction théorique pour des temps plus longs. L'écart correspond à l'apparition d'une instabilité. Cerésultat est en contradiction avec Smirnov et al. (2005), qui affirment que la formation de tourbillons à grande échelle fournit un mécanisme supplémentaire pour transporter le moment angulaire des frontières vers l'intérieur. En revanche, le transport radial de quantité de movement des couches limites latérales vers l'intérieur expliquerait la plus forte décroissance expérimentale aux temps longs. Le modèle classique d'Eady est cohérent avec les structures expérimentales observées. En considérant une dérivation de ce modèle par Smirnov et al. (2005), ainsi que des conditions initiales pertinentes, nous trouvons une estimation raisonnable du taux de croissance de l'instabilité, ce qui n'aurait pas été le cas avec la théorieclassique d'Eady. Ainsi, le mécanisme de l'instabilité barocline est l'explication la plus plausible pour l'existence d'une instabilité à grand nombre d'onde dans les processus de "spin-up" et "spin-down".

The aim of this report is to investigate the ductile performance of concrete tilt-up panels reinforced with cold-drawn mesh to improve the current seismic assessment procedure. The commercial impact of the project was also investigated. Engineering Advisory Group (EAG) guidelines state that a crack in a panel under face loading may be sufficient to fracture the mesh. The comments made by EAG regarding the performance of cold-drawn mesh may be interpreted as suggesting that assessment of such panels be conducted with a ductility of 1.0. Observations of tilt-up panel performance following the Christchurch earthquakes suggest that a ductility higher than μ=1.0 is likely to be appropriate for the response of panels to out-of-plane loading. An experimental test frame was designed to subject ten tilt-panel specimens to a cyclic quasi-static loading protocol. Rotation ductility, calculated from the force-displacement response from the test specimens, was found to range between 2.9 and 5.8. Correlation between tensile tests on 663L mesh, and data collected from instrumentation during testing confirmed that the mesh behaves as un-bonded over the pitch length of 150mm. Recommendation: Based on a moment-rotation assessment approach with an un-bonded length equal to the pitch of the mesh, a rotation ductility of μ=2.5 appears to be appropriate for the seismic assessment of panels reinforced with cold-drawn mesh.

No description available.