Mechanisms of thyristor turn-on wore studied. An attempt was made to relate the ‘on’ plasma spreading velocity to the small signal current gain value of the n-p-n transistor section of the thyristor. The extent to which the thyristor turns on initially largely affects the speed of turning-on the device. A model is proposed to calculate the initial turned-on area of thyristors.

M.A. (Afrikaans) / In this epic poem, Raka, N.P. van Wyk Louw made abundant use of prepositions. A linguistic analysis of these preposition structures explains and reveals the nature of this syntactic category in Afrikaans. From this it is evident that prepositions are vital in accomplishing cohesion in the text. Cognitive linguistics argue that syntactic organisation and semantics cannot stand independently from each other. Therefore the meaning of 'n phrase of expression cannot be reduced to an objective categorization of the situation that is being described. Against this background it is evident that structures conveying meaning are expressed through prepositions and prepositional structures. Certain semantic values and meaning structures of prepositions in RAKA are dealt with to help clarify some implied cognitive dimensions. A closer analysis shows that the preposition structures in RAKA represent intricate syntactic patterns. The semantic values of prepositions in RAKA are categorized through image schemas in terms of space Qncluding place, perspective and proximity), time, movement, part-whole, reason and cause, as well as manner and means. Finally it is indicated how the epic structures can be made more explicable by image schemas. Through the use of prepositions in the language, aspects of the epic, namely characterization, time and spatial placing are endorsed. Progression, in terms or epic movement is supported through the use of prepositions that specifically imply space and movement. It is therefore apparent that although the research was approached from a linguistic angle, it also contributes to literary analysis.

D.Phil. (Afrikaans-Nederlands) / Please refer to full text to view abstract

M.A. (Afrikaans en Nederlands) / Please refer to full text to view abstract

<p> An approximate model has been developed for the p-n-p lateral segmented transistor, and used to characterize the behaviour of the common-emitter dc current gain to the collector segment when the control segment is set to arbitrary voltage levels. The model is a development of the type introduced by Ebers and Moll. </p> <p> The dc current gain is found to be a sensitive function of the control segment voltage, and for changes in this voltage level of the order of± 200mV, it can be made to vary between two limiting values which are dependent on device geometry. A number of applications for this device have been suggested, particularly where an a.g.c. function or controlled current source requirement are needed. </p> <p> An analytic expression has been obtained for the controlled hFE in terms of the control segment voltage and the device parameters, using an approximate analogue for the device geometry. The results have been found to describe the behaviour for a family of p-n-p lateral transistors, having circular geometry with different segment periphery ratios, within the limits of the approximations and experimental errors. </p> / Thesis / Master of Engineering (MEngr)

No description available.

Text in Afrikaans with abstracts in Afrikaans and English. / Hierdie verhandeling handel oor die radiodramas van N.P. van Wyk Louw se afhanklikheid van die gesproke woord en die gebruik van ouditiewe middele ter ondersteuning daarvan. In radiodramas soos Dias, Kruger breek die pad oop en die eerste voortrek, is die gesproke woord hoofsaaklik as betekenisdraer gebruik. Gaandeweg word byklanke in Blomme vir die winter aangewend en in Die vonnis speel musiek n strukturerende rol by die opbou van die handeling. In Die held en Lewenslyn eksperimenteer Louw met radiotegniese moontlikhede ten einde die ouditiwiteit en verbeelde visualiteit te verhoog. In Dagboek van n soldaat word die byklank soms oorheersend, maar in sy laaste radiodrama, Die val van n regvaardige man, keer hy weer terug na die uitsluitlike krag van die woord. Die aanwending van dramatiese tegnieke, sowel as aktuele temas, komplekse karakterisering en die vooropstel van die idee, dra alles by tot die "toneelmatigheid" van sy radiodramas. / This dissertation deals ·with the radio dramas of N.P. van Wyk Louw, describes its dependence on the spoken word and the use of acoustical forms to reinforce the dialogue. Louw uses the spoken word as the prime bearer of meaning in Dias, Kruger breek die pad oop and Die eerste voortrek. Gradually he makes use of sound-effects in Blornme vir die winter and music plays a structural role in the action in Die vonnis. In Die held and Lewenslyn technical possibilities increase the auditory effect and imagined visuality. Sometimes the sound-effects dominate in Dagboek van n soldaat, but in his lastradio drama, Die val van n regvaardige man, Louw returns to the exclusive force of the spoken word. Louw's use of dramatical techniques, together with actual themes, complex characterization and the bringing forth of the idea, is responsible for the radio dramas being "fit for the stage". / Afrikaans and Theory of Literature / M.A. (Afrikaans en Nederlands)

In recent years there is an increasing awareness of the importance of chiral phosphorus ligands in transition metal organometallic chemistry because of the utility of such complexes in homogeneous catalytic reactions. This thesis deals with synthetic, spectroscopic and X-ray crystallographic studies on ruthenium complexes of chiral and achiral P-N-P type ligands, known as "diphosphazanes", with emphasis on ruthenium carbonyl clusters. Several ruthenium carbonyl clusters have been synthesized and characterized by elemental analyses, ER and NMR (lH, nC and 3lP) spectroscopic data. In several instances, the molecular structures of the clusters have been confirmed by single crystal X-ray diffraction studies. Chapter 1 provides a brief overview of various types of chiral phosphorus ligands and general synthetic routes to diphosphazanes. A brief review of the transition metal chemistry of diphosphazanes and diphosphazane chalcogenides (published since 1994) is presented A review of the literature on the carbonyl clusters of the group-8 transition metals (Fe, Ru, Os) bearing mono- and diphosphines is also included in this chapter The scope and aim of the present investigation is outlined at the end of this chapter. Chapter 2 provides the results obtained in the present investigation and a detailed discussion of the spectroscopic and crystallographic data. The essential feature of the work is summarized at the end of the chapter. Chapter 3 gives a detailed account of the experimental procedure for the synthesis of the compounds and spectroscopic and analytical measurements. The experimental details of X-ray structure determination are also given in this chapter. To save space, the coordinates of the H-atoms and the calculated and observed structure factor tables are not included. In some cases, reference to CCDC deposition number is included. The references of the literature are compiled at the end of the thesis and are indicated in the text by appropriate numbers appearing as superscripts. The compounds synthesized in the present study are represented by bold Arabic numerals and are listed in Appendix I. The abbreviations employed in the thesis conform to those generally used in Chemical Abstracts.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-03-08T14:08:25Z No. of bitstreams: 1 PGCS17MA161.pdf: 277204 bytes, checksum: 295ae0923cdfa15e00efc516619613f4 (MD5) / Made available in DSpace on 2018-03-08T14:08:25Z (GMT). No. of bitstreams: 1 PGCS17MA161.pdf: 277204 bytes, checksum: 295ae0923cdfa15e00efc516619613f4 (MD5) Previous issue date: 2016-12-21 / Capes / The revegetation of degraded areas is a fundamental recovery strategy to improve the physical and chemical attributes of the soils, besides providing through the vegetation cover, the necessary protection to reduce the loss of sediments due to water erosion. The present work had the objective of evaluating the revegetation of a degraded area that originated a slope with soil de - tailing within the CAV / UDESC Agroveterinary Sciences Center, from isolated and intercropping of summer forage species in association with organic / mineral fertilization And mineral fertilization. The experimental design was in randomized blocks with subdivided plots, with 9 treatments and 4 replications. The main treatments were arranged in the subplots, being: isolated cultivation of Brachiaria decumbens, isolated Crotalaria spectabilis cultivation, and intercropped Brachiaria + Crotalaria intercrop. The secondary treatments were arranged in the plots, and they refer to fertilization, they are: fertilization with bed of aviary supplemented with mineral fertilization, mineral fertilization (N-P-K) and without fertilization (control). At the beginning and at the end of the experiment, soil samples were collected to verify the changes in their chemical attributes. In the chemical analyzes were determined the pH and the contents of N, P, K, Ca, Mg, Al, Organic matter and organic C. The soil was previously scarified and the pH corrected in all plots, as a result of soil chemical analysis. The fertilizations followed the recommendations of the CQFS (2004) and were applied in the subplots. The sowing was in line with spacing of 20cm between rows, totaling 5 rows per subplot. Plant samples were collected from the three central lines of each subplot. The accumulation of fresh and dry mass of the aerial part and the nutrient contents were determined: nitrogen, phosphorus and potassium (N, P, K, Ca and Mg) present in the dry matter. The results were submitted to analysis of variance and comparison of means by Fisher DMS test, at a significance level of 5%. The isolated cultivation of brachiaria and consortium showed the highest production of biomass and dry mass of aerial part. Crotalaria presented the highest concentrations of N, P, Ca, and Mg in plant tissue. The contents of K in the plant tissue showed interaction between fertilization and species, and the fertilization effect was significant for brachiaria and consortium, which accumulated the highest levels in the plots without fertilization (control). Crotalaria and consortium presented the highest concentrations of K in the fertilized plots with bed of birds and crotalaria had the highest concentration in the plots fertilized with mineral fertilizer (N-P-K). It was verified that the revegetation of the degraded area, associated to liming and fertilization, improved some soil chemical attributes, such as: elevation of pH, increase of Mg, K, P, organic matter and organic carbon; And Al reduction. However, it was not possible to determine differences in terms of improvement of soil chemical conditions related to organic fertilization / A revegetação de áreas degradadas é uma estratégia de recuperação fundamental para melhorar os atributos físicos e químicos dos solos, além de fornecer através da cobertura vegetal, a proteção necessária para diminuir a perda de sedimentos por erosão hídrica. O presente trabalho teve por objetivo avaliar a revegetação de uma área degradada que originou um talude com solo decapeado dentro do Centro de Ciências Agroveterinárias CAV/UDESC, a partir do cultivo isolado e consorciado de espécies forrageiras de verão, em associação com adubação orgânica/mineral e adubação mineral. O delineamento experimental utilizado foi em blocos casualizados com parcelas subdivididas, com 9 tratamentos e 4 repetições. Os tratamentos principais foram dispostos nas subparcelas, sendo eles: cultivo isolado de capim-braquiária (Brachiaria decumbens), cultivo isolado de crotalária (Crotalaria spectabilis) e cultivo consorciado capim-braquiária + crotalária. Os tratamentos secundários foram dispostos nas parcelas, e referem-se à adubação, são eles: adubação com cama de aviário complementada com adubação mineral, adubação mineral (N-P-K) e sem adubação (testemunha). No início e ao final do experimento foram efetuadas coletas de solo para verificar as alterações ocorridas nos seus atributos químicos. Nas análises químicas foram determinados o pH e os teores de N, P, K, Ca, Mg, Al, Matéria orgânica e C orgânico. O solo foi previamente escarificado e o pH corrigido em todas as parcelas, conforme resultado da análise química do solo. As adubações seguiram as recomendações do CQFS (2004) e foram aplicadas nas subparcelas. A semeadura foi em linha com espaçamento de 20cm entrelinhas, totalizando 5 linhas por subparcela. As amostras de plantas foram coletadas das três linhas centrais de cada subparcela. Foi determinado o acúmulo de massas fresca e seca da parte aérea e os teores de nutrientes: nitrogênio, fósforo e potássio (N, P, K, Ca e Mg) presentes na matéria seca. Os resultados foram submetidos à análise de variância e comparação de médias por teste de DMS de Fisher, ao nível de significância de 5%. O cultivo isolado de braquiária e consórcio apresentaram a maior produção de biomassa e de massa seca de parte aérea. A crotalária apresentou as maiores concentrações de N, P, Ca, e Mg no tecido vegetal. Os teores de K no tecido vegetal apresentaram interação entre adubação x espécie, sendo que o efeito adubação foi significativo para braquiária e consórcio que acumularam os maiores teores nas parcelas sem adubação (testemunha). Crotalária e consórcio apresentaram as maiores concentrações de K nas parcelas adubadas com cama de aves e crotalária teve a maior concentração nas parcelas adubadas com fertilizante mineral (N-P-K). Verificou-se que a revegetação da área degradada, associada a calagem e a adubação, melhorou alguns atributos químicos do solo, como: elevação do pH, aumento dos teores de Mg, K, P, matéria orgânica e carbono orgânico; e redução Al. Contudo, não foi possível determinar diferenças em termo de melhoria das condições químicas do solo, relativas a adubação orgânica

Ce mémoire porte sur l’accès simple et peu coûteux à de nouveaux ligands ferrocéniques aminés et aminophosphinés et leur coordination avec des métaux de transition pour des applications en catalyse homogène.Des métallo-ligands aminés flexibles ont été obtenus et caractérisés après amination réductrice du 1,1’-diformylferrocène. D’autres ligands (N,N) rigides ont été isolés au départ du précurseur du 1,1’-di-tert-butyl-3,3’-diformylferrocène. Des aza-ferrocénophanes ont également été facilement préparés avec ces deux précurseurs carbonylés. Lors de la coordination de ces ligands avec le palladium, un palladacycle original a été isolé et caractérisé par diffraction de rayons X.Des ligands ferrocéniques (N,P) ont été obtenus par trois méthodes: i) ortholithiation de ligands ferrocéniques aminés suivie d’un ajout de chlorophosphine, ii) amination réductrice des ferrocènes formylés substitués ou non en présence d’amine portant une fonction phosphine, iii) substitution directe du ferrocène dilithié par des chlorophosphines comportant un hétérocycle azoté. Leur coordination avec du palladium et du platine a été étudiée. Ces métallo-ligands hybrides ont été impliqués dans des réactions de chlorures d’aryle avec des acides arylboroniques (couplage de Suzuki), ainsi que dans la réaction de Sonogashira avec le couplage de bromures et de chlorures d’aryle avec le phénylacétylène / This thesis focuses on simple and inexpensive access to new amino and aminophosphine ferrocenyl ligands and their coordination with transition metals for applications in homogeneous catalysis.Flexible amine metallo-ligands were obtained and characterized after reductive amination of 1,1'-diformylferrocene. Other rigid (N,N) ligands were isolated starting from the precursor 1,1'-di-tert-butyl-3, 3'-diformylferrocene. Aza-ferrocenophanes were also easily prepared with these two formyl precursors. During the coordination of these ligands with palladium, a stable and original palladacycle was isolated and characterized by DRX.(N,P) ferrocenyl ligands were obtained by three methods: i) ortholithiation of aminoferrocenyl ligands followed by addition of chlorophosphines, ii) reductive amination of substituted or not formylferrocene in the presence of amine bearing a phosphine function, iii) direct substitution of dilithiated ferrocene by chlorophosphines with a nitrogen-containing heterocycle. Their coordination with palladium and platinum has been studied. These hybrid metallo-ligands have been implicated in the reactions of aryl chlorides to arylboronic acids (Suzuki cross-coupling), as well as in the Sonogashira reaction involving of coupling aryl bromides and chlorides to phenylacetylene