This master's thesis is engaged in development of new sanding units for a specific type of rail vehicle. Sanding in rail transport is application of most commonly silica sand into wheel-rail contact. Thanks to its reliability it is still the most widely used method for removing contaminants and improving adhesion in that contact. Sanding devices were developed in cooperation with corporation, which deals with production of rail transport equipment, among other things. The most important part of sanding device is sand dispenser. Dispensers were experimentally developed at the test station in the cooperating corporation. Dispensers were tested for utilization conditions on the locomotive of the train and conditions for trams and light rail vehicles. Furthermore, sand boxes have been designed for specific type of rail vehicle and new type of sand discharge tube, which directs sand directly into wheel-rail contact was designed too.

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Text in Afrikaans / In hierdie studie word 'n bydrae tot die beskrywing van 'n resente periode in die Afrikaanse prosageskiedenis, naamlik die dekade 1980-1989, aangepak. Die terme ''Tagtiger" en "tagtigerskrywer" word bespreek en gedefinieer. Negentien skrywers word aan die hand van vyf kanoniseringsmeganismes as belangrike Afrikaanse tagtigerprosaskrywers geidentifiseer. Hierdie skrywers en hulle 51 prosatekste wat tussen 1980-1989 gepubliseer is, word dan deur Vanheste (1981) se vier gei"dentifiseerde literatuursosiologiese aandagsvelde naamlik die outeur, die literere werk, die literere kanaal en die leser ondersoek ten einde die posisie van die gekose skrywers m.b.t. maatskappy en skrywerskap, enkele samebindende aspekte in die proefgroep se tagtigerprosatekste, die funksionering van die literere kanaal t.o.v. hierdie tekste en die resepsie daarvan te bepaal. Met behulp van vraelyste aan die proefgroep is hul houdings t.o.v. 'n aantal aktuele aangeleenthede ondersoek. Ses onderskeidende kategoriee in die proefgroep se tekste, naamlik politiek en betrokkenheid; realisme; grens- en geweldliteratuur; postmodernisme; homoerotiek en goeie gewilde prosa word aangedui. Die posisie van verskillende "hekwagters" in die literere kanaal, saam met die invloed van sensuur op die proefgroep, die rol van die Afrikaanse Skrywersgilde en die "little magazines" wat publikasiegeleenthede vir die jong skrywers gebied het, ontvang aandag. J.C.Kannemeyer as geskiedskrywer en 'n verskeidenheid resensente se waarde-oordele word nagegaan. Aan die hand van Vanheste se literatuursosiologiese kommunikasiemodel, gekombineer met sy (aangepaste) analisemodel, word etlike sosiale werklikhede in Alexander Strachan se 'n Wereld sander grense dan onder die loep geneem. Die ondersoekterrein van die literatuursosiologie dek s6 'n wye veld dat heelwat interessante aspekte noodwendig agterwee moes bly. Resepsiestudies van lesers gedurende die tagtigerdekade was nie moontlik nie en 'n resepsiestudie kon ongelukkig eers vyf jaar na die tagtigerdekade uitgevoer word. Die gevolgtrekking waartoe in hierdie studie gekom word, is dat, hoewel waarskynlik nie op dieselfde betekenisvlak as die term "Sestigers" nie, daar wel van ooreenkomste in die werk van Afrikaanse tagtigerskrywers gepraat kan word. Samehang word ook aangedui tussen die sosiale omwereld en die tagtigertekste wat daarbinne tot stand gekom het, veral met betrekking tot tematiese en stilistiese keuses. Terselfdertyd het die literere werke van hierdie dekade 'n invloed uitgeoefen op die omwereld waarbinne dit verskyn het / This study attempts to make a contribution to the description of a recent period in Afrikaans Prose History, namely the decade 1980-1989. The term writer of the Eighties is defined and discussed. Nineteen writers have been identified as important Afrikaans Eighties writers with the aid of five canonization mechanisms. These writers and their 51 prosa texts published between 1980-1989 are then investigated by means of Vanheste's four identified attention areas in the sociology of literature, namely the author, the literary work, the literary channel as well as the reader. Questionnairs have been used to investigate the attitude of the trial group with regards to a number of current affairs. Six distinguishing categories have been identified in the texts of the trial group namely politics, realism, border and violence literature, postmodernism, homo-erotics and popular prose. The position of different gate-keepers in the literary channel, together with the influence of censorship on the trial group, the role of the "Afrikaanse Skrywersgilde" and the "little magazines", together with publication opportunities offered to these young writers, have enjoyed attention. J.C.Kannemeyer as historian, together with the critics as readers of the trial group's texts are investigated. The manipulation of a few social realities in Alexander Strachan's 'n Wereld sander grense is investigated in terms of Vanheste's communication model of literary sociology, combined with his (adapted) analysis model. The field of investigation of the sociology of literary covers such a wide field that numerous interesting aspects had to be omitted. Reception studies during the decade of the eighties were not possible and could, unfortunately, only be done five years after the decade of the eighties. The conclusion of this study is that, although not at quite the same level of significance as the term "Sixties", one could still find similarities in the works of Afrikaans writers from the Eighties decade. Cohesion between the social world and the texts of the Vll eighties have evolved from it, especially with regards to thematic and stilistic choices. At the same time, the literary works of this decade have contributed to the social world in which they were published / Afrikaans & Theory of Literature / D. Litt. et Phil. (Afrikaans)

Knowledge of offspring production (recruitment) is fundamental to understanding and forecasting the dynamics of a population. In this thesis, I focus on two demographic characteristics of fish stocks that are important to recruitment: population density and age structure. First, populations produce more recruits at low density, but quantifying this response has proven difficult. Using data from hundreds of populations of walleye (Sander vitreus), an economically important freshwater fish, I demonstrate that the growing-degree-day metric (a temperature index) is better than age at explaining variation in density-dependent growth and maturity both within and among populations. I then incorporate multi-lake measures of density-dependent life history change into a temperature-based biphasic model of growth and reproduction to predict sustainable rates of mortality for walleye throughout most of their range. Second, the age (or size) structure of a population may also affect recruitment because of positive effects of maternal age on offspring production and survival; however, evidence for these ‘maternal influences’ on recruitment is limited. Using both an analytical model and a meta-analysis of stock-recruitment data from 25 species of exploited marine fish, I show that (i) maximum reproductive rate increased with the mean age of adults in a population, and (ii) the importance of age structure increased with a species’ longevity. I then demonstrate a similar effect of maternal influences on reproductive rate in a detailed study of Lake Erie walleye. By highlighting the importance of fisheries-induced demographic change to recruitment, this thesis provides insight into past and present failures. However, it also demonstrates clearly the benefits of proactive management strategies that (i) identify and respect the limits of exploitation, (ii) protect from exploitation reproductively valuable individuals—principles that apply generally to any freshwater, marine, or terrestrial species that is of recreational, commercial, or conservation value.

Knowledge of offspring production (recruitment) is fundamental to understanding and forecasting the dynamics of a population. In this thesis, I focus on two demographic characteristics of fish stocks that are important to recruitment: population density and age structure. First, populations produce more recruits at low density, but quantifying this response has proven difficult. Using data from hundreds of populations of walleye (Sander vitreus), an economically important freshwater fish, I demonstrate that the growing-degree-day metric (a temperature index) is better than age at explaining variation in density-dependent growth and maturity both within and among populations. I then incorporate multi-lake measures of density-dependent life history change into a temperature-based biphasic model of growth and reproduction to predict sustainable rates of mortality for walleye throughout most of their range. Second, the age (or size) structure of a population may also affect recruitment because of positive effects of maternal age on offspring production and survival; however, evidence for these ‘maternal influences’ on recruitment is limited. Using both an analytical model and a meta-analysis of stock-recruitment data from 25 species of exploited marine fish, I show that (i) maximum reproductive rate increased with the mean age of adults in a population, and (ii) the importance of age structure increased with a species’ longevity. I then demonstrate a similar effect of maternal influences on reproductive rate in a detailed study of Lake Erie walleye. By highlighting the importance of fisheries-induced demographic change to recruitment, this thesis provides insight into past and present failures. However, it also demonstrates clearly the benefits of proactive management strategies that (i) identify and respect the limits of exploitation, (ii) protect from exploitation reproductively valuable individuals—principles that apply generally to any freshwater, marine, or terrestrial species that is of recreational, commercial, or conservation value.

Text in Afrikaans / In hierdie studie word 'n bydrae tot die beskrywing van 'n resente periode in die Afrikaanse prosageskiedenis, naamlik die dekade 1980-1989, aangepak. Die terme ''Tagtiger" en "tagtigerskrywer" word bespreek en gedefinieer. Negentien skrywers word aan die hand van vyf kanoniseringsmeganismes as belangrike Afrikaanse tagtigerprosaskrywers geidentifiseer. Hierdie skrywers en hulle 51 prosatekste wat tussen 1980-1989 gepubliseer is, word dan deur Vanheste (1981) se vier gei"dentifiseerde literatuursosiologiese aandagsvelde naamlik die outeur, die literere werk, die literere kanaal en die leser ondersoek ten einde die posisie van die gekose skrywers m.b.t. maatskappy en skrywerskap, enkele samebindende aspekte in die proefgroep se tagtigerprosatekste, die funksionering van die literere kanaal t.o.v. hierdie tekste en die resepsie daarvan te bepaal. Met behulp van vraelyste aan die proefgroep is hul houdings t.o.v. 'n aantal aktuele aangeleenthede ondersoek. Ses onderskeidende kategoriee in die proefgroep se tekste, naamlik politiek en betrokkenheid; realisme; grens- en geweldliteratuur; postmodernisme; homoerotiek en goeie gewilde prosa word aangedui. Die posisie van verskillende "hekwagters" in die literere kanaal, saam met die invloed van sensuur op die proefgroep, die rol van die Afrikaanse Skrywersgilde en die "little magazines" wat publikasiegeleenthede vir die jong skrywers gebied het, ontvang aandag. J.C.Kannemeyer as geskiedskrywer en 'n verskeidenheid resensente se waarde-oordele word nagegaan. Aan die hand van Vanheste se literatuursosiologiese kommunikasiemodel, gekombineer met sy (aangepaste) analisemodel, word etlike sosiale werklikhede in Alexander Strachan se 'n Wereld sander grense dan onder die loep geneem. Die ondersoekterrein van die literatuursosiologie dek s6 'n wye veld dat heelwat interessante aspekte noodwendig agterwee moes bly. Resepsiestudies van lesers gedurende die tagtigerdekade was nie moontlik nie en 'n resepsiestudie kon ongelukkig eers vyf jaar na die tagtigerdekade uitgevoer word. Die gevolgtrekking waartoe in hierdie studie gekom word, is dat, hoewel waarskynlik nie op dieselfde betekenisvlak as die term "Sestigers" nie, daar wel van ooreenkomste in die werk van Afrikaanse tagtigerskrywers gepraat kan word. Samehang word ook aangedui tussen die sosiale omwereld en die tagtigertekste wat daarbinne tot stand gekom het, veral met betrekking tot tematiese en stilistiese keuses. Terselfdertyd het die literere werke van hierdie dekade 'n invloed uitgeoefen op die omwereld waarbinne dit verskyn het / This study attempts to make a contribution to the description of a recent period in Afrikaans Prose History, namely the decade 1980-1989. The term writer of the Eighties is defined and discussed. Nineteen writers have been identified as important Afrikaans Eighties writers with the aid of five canonization mechanisms. These writers and their 51 prosa texts published between 1980-1989 are then investigated by means of Vanheste's four identified attention areas in the sociology of literature, namely the author, the literary work, the literary channel as well as the reader. Questionnairs have been used to investigate the attitude of the trial group with regards to a number of current affairs. Six distinguishing categories have been identified in the texts of the trial group namely politics, realism, border and violence literature, postmodernism, homo-erotics and popular prose. The position of different gate-keepers in the literary channel, together with the influence of censorship on the trial group, the role of the "Afrikaanse Skrywersgilde" and the "little magazines", together with publication opportunities offered to these young writers, have enjoyed attention. J.C.Kannemeyer as historian, together with the critics as readers of the trial group's texts are investigated. The manipulation of a few social realities in Alexander Strachan's 'n Wereld sander grense is investigated in terms of Vanheste's communication model of literary sociology, combined with his (adapted) analysis model. The field of investigation of the sociology of literary covers such a wide field that numerous interesting aspects had to be omitted. Reception studies during the decade of the eighties were not possible and could, unfortunately, only be done five years after the decade of the eighties. The conclusion of this study is that, although not at quite the same level of significance as the term "Sixties", one could still find similarities in the works of Afrikaans writers from the Eighties decade. Cohesion between the social world and the texts of the Vll eighties have evolved from it, especially with regards to thematic and stilistic choices. At the same time, the literary works of this decade have contributed to the social world in which they were published / Afrikaans and Theory of Literature / D. Litt. et Phil. (Afrikaans)

No description available.