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Efeito do tipo de óleo básico no desempenho tribológico de dialquilditiocarbamato de molibdênio como aditivo para lubrificantes automotivos. / Effect of the base oil on the tribological behaviour of molybdenum dialkyldithiocarbamate as automotive lubricants additive.Trindade, Eduardo Dominguez 14 March 2014 (has links)
A otimização da formulação do óleo lubrificante empregado em motores de combustão interna é uma importante maneira de se reduzir o atrito e assim aumentar a eficiência energética. É também uma forma de assegurar proteção ao sistema, mantendo a taxa de desgaste em um nível adequado. O óleo de motor é uma mistura de óleos básicos selecionados com aditivos, entre os quais podem ser encontrados os modificadores de atrito, que são compostos com capacidade de aderir às superfícies metálicas, proporcionando melhoria da lubrificação em condições mista e limítrofe. O dialquilditiocarbamato de molibdênio (MoDTC) está entre os mais importantes redutores de atrito empregados em óleos lubrificantes. Ésteres sintéticos podem ser usados como óleos básicos em algumas formulações. Visto que ésteres são mais polares que hidrocarbonetos, essas moléculas podem atuar modificando propriedades do óleo na região próxima à superfície metálica. Podem também interferir com filmes adsorvidos, limitando sua efetividade. O objetivo do trabalho é a comparação dos efeitos do MoDTC em diferentes misturas contendo hidrocarboneto e éster. Para isso, formulações lubrificantes contendo uma polialfaolefina, um diéster e um aditivo à base de MoDTC foram preparadas, caracterizadas e ensaiadas em tribômetro oscilatório SRV usando configuração esfera-disco. Foram empregadas esferas de aço AISI 52100 e discos de aço AISI H13. Foi estudada a influência da variação da temperatura e da força normal aplicada. Empregando-se mistura de hidrocarboneto e éster como lubrificante, o aumento da temperatura causou leve aumento do coeficiente de atrito. Em ausência de MoDTC, a presença de éster aumentou a capacidade de suportação de carga das formulações. Os testes com óleos contendo MoDTC foram marcados pela ocorrência de dois fenômenos: ativação e depleção do aditivo. Estes fenômenos se mostraram dependentes da carga normal e da composição do óleo. O efeito de redução do atrito pelo MoDTC tende a ser menos duradouro com óleos mais ricos em éster e em condições de carregamento mais severo. O comportamento tribológico do éster em mistura com polialfaolefina, medido através do coeficiente de atrito, seguiu a isoterma de adsorção de Frumkin, com alguma atração entre as moléculas do éster, e energia livre da ordem de -4 kJ/mol, típica de fisissorção. Óleos envelhecidos artificialmente foram testados e não apresentaram diferenças significativas com relação aos mesmos óleos novos. A adição de etanol aos óleos envelhecidos causou uma leve diminuição no coeficiente de atrito a 40 °C; tal efeito não foi perceptível em temperaturas mais altas, provavelmente devido à perda por evaporação do álcool. / The optimization of the lubricant oil formulation used in internal combustion engines is an important way of reducing friction, thus increasing energetic efficiency. It is also a way of protecting the system, maintaining wear rate in an adequate level. The engine oil is a blend of selected base oils with additives, amongst which are the friction modifiers substances able to adhere to the metal surfaces, thus providing better lubrication at the mixed and boundary regimes. Molybdenum dialkyldithiocarbamate (MoDTC) is amongst the most important friction reducers used in lubricant oils. Synthetic esters may be employed as base oils in some formulations as well. Given that esters are more polar than hydrocarbons, these molecules can actuate by modifying oil properties in the near-surface region. They can also interfere with adsorbed films, preventing their effectiveness. The objective of this work is the comparison of the effects of MoDTC in different mixtures containing hydrocarbon and ester. With this aim, lubricating formulations containing a polyalphaolefin, a diester and a MoDTC-based additive were prepared, characterized and tested in a reciprocating SRV tribometer using ball-on-disc configuration. AISI 52100 steel balls and AISI H13 steel discs were employed. The influences of the temperature and of the normal load were both studied. Employing a mixture of hydrocarbon and ester as lubricant, a higher temperature caused a slightly higher coefficient of friction in the lubricant free of additive. In the absence of MoDTC, the ester increased the load-carrying capacity of the lubricant formulations. Tests with MoDTC-containing oils were characterized by two phenomena: activation and depletion of the additive. These phenomena showed to be dependent on the normal load and on the oil composition. The MoDTC friction reducing effect tends to be less sustainable with higher ester concentrations and at higher loads. The tribological behavior of the ester in the presence of polyalphaolefin, as measured by the coefficient of friction, followed the Frumkin adsorption isotherm, with some attraction between ester molecules, and free energy in the order of -4 kJ/mol, typical of physisorption. Artificially aged oils were tested and did not show differences when compared with the results of the fresh oils. Adding ethanol to the aged oils caused a slightly reduction in the coefficient of friction at 40 °C, but this effect was not observed at higher temperatures, probably due to evaporation loss of the alcohol.
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Efeito do tipo de óleo básico no desempenho tribológico de dialquilditiocarbamato de molibdênio como aditivo para lubrificantes automotivos. / Effect of the base oil on the tribological behaviour of molybdenum dialkyldithiocarbamate as automotive lubricants additive.Eduardo Dominguez Trindade 14 March 2014 (has links)
A otimização da formulação do óleo lubrificante empregado em motores de combustão interna é uma importante maneira de se reduzir o atrito e assim aumentar a eficiência energética. É também uma forma de assegurar proteção ao sistema, mantendo a taxa de desgaste em um nível adequado. O óleo de motor é uma mistura de óleos básicos selecionados com aditivos, entre os quais podem ser encontrados os modificadores de atrito, que são compostos com capacidade de aderir às superfícies metálicas, proporcionando melhoria da lubrificação em condições mista e limítrofe. O dialquilditiocarbamato de molibdênio (MoDTC) está entre os mais importantes redutores de atrito empregados em óleos lubrificantes. Ésteres sintéticos podem ser usados como óleos básicos em algumas formulações. Visto que ésteres são mais polares que hidrocarbonetos, essas moléculas podem atuar modificando propriedades do óleo na região próxima à superfície metálica. Podem também interferir com filmes adsorvidos, limitando sua efetividade. O objetivo do trabalho é a comparação dos efeitos do MoDTC em diferentes misturas contendo hidrocarboneto e éster. Para isso, formulações lubrificantes contendo uma polialfaolefina, um diéster e um aditivo à base de MoDTC foram preparadas, caracterizadas e ensaiadas em tribômetro oscilatório SRV usando configuração esfera-disco. Foram empregadas esferas de aço AISI 52100 e discos de aço AISI H13. Foi estudada a influência da variação da temperatura e da força normal aplicada. Empregando-se mistura de hidrocarboneto e éster como lubrificante, o aumento da temperatura causou leve aumento do coeficiente de atrito. Em ausência de MoDTC, a presença de éster aumentou a capacidade de suportação de carga das formulações. Os testes com óleos contendo MoDTC foram marcados pela ocorrência de dois fenômenos: ativação e depleção do aditivo. Estes fenômenos se mostraram dependentes da carga normal e da composição do óleo. O efeito de redução do atrito pelo MoDTC tende a ser menos duradouro com óleos mais ricos em éster e em condições de carregamento mais severo. O comportamento tribológico do éster em mistura com polialfaolefina, medido através do coeficiente de atrito, seguiu a isoterma de adsorção de Frumkin, com alguma atração entre as moléculas do éster, e energia livre da ordem de -4 kJ/mol, típica de fisissorção. Óleos envelhecidos artificialmente foram testados e não apresentaram diferenças significativas com relação aos mesmos óleos novos. A adição de etanol aos óleos envelhecidos causou uma leve diminuição no coeficiente de atrito a 40 °C; tal efeito não foi perceptível em temperaturas mais altas, provavelmente devido à perda por evaporação do álcool. / The optimization of the lubricant oil formulation used in internal combustion engines is an important way of reducing friction, thus increasing energetic efficiency. It is also a way of protecting the system, maintaining wear rate in an adequate level. The engine oil is a blend of selected base oils with additives, amongst which are the friction modifiers substances able to adhere to the metal surfaces, thus providing better lubrication at the mixed and boundary regimes. Molybdenum dialkyldithiocarbamate (MoDTC) is amongst the most important friction reducers used in lubricant oils. Synthetic esters may be employed as base oils in some formulations as well. Given that esters are more polar than hydrocarbons, these molecules can actuate by modifying oil properties in the near-surface region. They can also interfere with adsorbed films, preventing their effectiveness. The objective of this work is the comparison of the effects of MoDTC in different mixtures containing hydrocarbon and ester. With this aim, lubricating formulations containing a polyalphaolefin, a diester and a MoDTC-based additive were prepared, characterized and tested in a reciprocating SRV tribometer using ball-on-disc configuration. AISI 52100 steel balls and AISI H13 steel discs were employed. The influences of the temperature and of the normal load were both studied. Employing a mixture of hydrocarbon and ester as lubricant, a higher temperature caused a slightly higher coefficient of friction in the lubricant free of additive. In the absence of MoDTC, the ester increased the load-carrying capacity of the lubricant formulations. Tests with MoDTC-containing oils were characterized by two phenomena: activation and depletion of the additive. These phenomena showed to be dependent on the normal load and on the oil composition. The MoDTC friction reducing effect tends to be less sustainable with higher ester concentrations and at higher loads. The tribological behavior of the ester in the presence of polyalphaolefin, as measured by the coefficient of friction, followed the Frumkin adsorption isotherm, with some attraction between ester molecules, and free energy in the order of -4 kJ/mol, typical of physisorption. Artificially aged oils were tested and did not show differences when compared with the results of the fresh oils. Adding ethanol to the aged oils caused a slightly reduction in the coefficient of friction at 40 °C, but this effect was not observed at higher temperatures, probably due to evaporation loss of the alcohol.
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DYSLEXIA, AWARENESS AND DISCRIMINATORY POTENTIAL : Perceptions of dyslexia among teachers in primary schools in PrishtinaJusufi, Qefsere January 2014 (has links)
Background The most common reading disability is dyslexia. This reading disability encompasses various symptoms such as poor spelling outcomes, reading fluency and difficulties in expressing oneself. Failur to diagnose children coping with dyslexia is a potential risk of discrimination and social exclusion. Aim The aim of this Master thesis is to explore if the primary school teachers in Prishtina are conscious of the term dyslexia. This provides a better understanding of teacher’s perceptions about dyslexia and to which extent they are aware of it. An additional purpose is to investigate teachers’ awareness of their responsibilities to provide equal opportunities for these children. Method A qualitative research, using an open-ended and semi-structured questionnaire had been utilized to collect data about teacher’s awareness and knowledge concerning dyslexia and its issues. The texts provided by the surveys were subjected to thematic analysis. Result The results of the presented qualitative research helped to understand the awareness of the primary teachers in Prishtina concerning the term dyslexia. The findings showed that most of the teachers heard about dyslexia, but demonstrated clear misconceptions of what dyslexia is. Even though the majority of teachers had misconception of dyslexia, more than half of them considered their role as very important to provide equal opportunities for children coping with dyslexia. Conclusion One of the significant findings to emerge from this thesis is that the primary teacher's of Prishtina have misconceptions about dyslexia. The results of this study support the idea that due to the lack of knowledge among teachers about dyslexia, children coping with dyslexia might be at risk of discrimination and exclusion comparing to other children.
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Mobilitätsverhalten potentieller Radfahrer in DresdenManteufel, Rico 01 October 2015 (has links) (PDF)
Before the German reunification, Dresden was a city of motorized traffic and cyclist were rare. But in the 90's began a change of transport policy and cycling became more important. This Master Thesis wants to show the current standing of cycling in Dresden. Thats why the results of the "SrV"-study should be analysed with regard to potential cyclists and their journeys. As methods were used a descriptive analysis and the linear discriminant analysis, both used at a personal and journey-specific level of data. As a result, Dresden have to do much more to become a good "cycling-city", so the bike-level wasn't really high in the year 2013. Instead the car is still the mostly used transport vehicle and the proportion in the Modal-Split is only slowly sinking. But this study shows typical characteritics of cyclists and cycling journays of Dresden, so there is a basis to get more people involved to cycle and become a more eco-friendly city.
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Analyse des Pkw-Besitzes in Haushalten der 25 großen SrV-VergleichsstädteLins, Stefan 28 December 2018 (has links)
Climate change, increasing fine dust, changes in values and the accessibility of Carsharing are well discussed topics nowadays in combination with the vehicle ownerships in German households. This paper aims to characterize the vehicle ownership and to evaluate their effects. National and international literature discusses the vehicle ownership in different ways like car ownership as status symbol or the variable ‘vehicle ownership’ as a mediating variable. Basis of this analysis is a survey called ‘SrV - Mobilität in Städten’. The used data contains information about households in the 25 ‘großen SrV-Vergleichsstädte’. This information is available on different levels, which means that the information is available in separate datafiles for levels of ways, persons and households. The basis level for this analysis should be the household level. To get this level it is necessary to aggregate the information. As a result, we get several socioeconomic and alternative specific variables which must be investigated with descriptive and correlation methods in order to prove their suitability for the binary logit model. This model allows it to evaluate metric, nominal and categoric variables with the aim to find characteristics about vehicle ownership. Some results are for example that the vehicle ownership is more probable in households with more persons than in single-person households. Furthermore, the income and missing accessibility of alternatives have a positive effect on vehicle ownership. In addition, this model offers the possibility to predict the vehicle ownership in households. An interesting result is, that some variables have another effect than assumed. These results were compared with the findings of other papers. As a result, one can find some parallel and additional structures.:Abbildungsverzeichnis VII
Tabellenverzeichnis IX
Abkürzungsverzeichnis XI
Symbolverzeichnis XIII
1 Einleitung 1
2 Literaturübersicht 3
3 Methodik 5
3.1 Deskriptive Analyse 5
3.1.1 Lage- und Streumaße 5
3.1.2 Zusammenhangsmaße 5
3.2 Binäre logistische Regression 7
3.2.1 Allgemeines 7
3.2.2 Modellformulierung 8
3.2.3 Schätzung der logistischen Regressionsfunktion 9
3.2.4 Prüfung des Gesamtmodells 10
3.2.5 Prüfung der Merkmalsvariablen 13
3.2.6 Residuen-Analyse 14
3.2.7 Interpretation der Regressionskoeffizienten 15
4 Daten 17
4.1 Datensatz 17
4.2 Aufbereitung der Daten 17
4.2.1 Zusammenhänge in der Multilevelstruktur 18
4.2.2 Wegedaten 18
4.2.3 Personendaten 19
4.2.4 Haushaltsdatei 20
4.3 Datengrundlage 21
5 Deskriptive Analyse 23
5.1 Vorgehen 23
5.2 Streu- und Lagemaße für kardinal skalierte und klassierte Variablen 23
5.2.1 Alternativenspezifische Variablen 23
5.2.2 Sozioökonomische Variablen 27
5.3 Korrelation zwischen den metrischen Variablen 29
5.4 Relative Häufigkeiten kategorialer Variablen 29
5.4.1 Höchste Schulausbildung im Haushalt 30
5.4.2 Höchste Berufsausbildung im Haushalt 30
5.4.3 Geschlecht 30
5.4.4 Altersklassen 31
5.4.5 Erwerbstätigkeit 32
5.5 Nominale Variablen 32
5.6 Beurteilung der Variablen anhand des korrigierten Kontingenzkoeffizienten nach Pearson 34
6 Binäres Logit-Modell 35
6.1 Schätzung der Regressionskoeffizienten 35
6.2 Prüfung des Gesamtmodells 37
6.2.1 Informationskriterien und Log-Likelihood-Wert 37
6.2.2 Likelihood-Ratio-Test 37
6.2.3 Pseudo-R2-Statistiken 37
6.2.4 Klassifizierung neuer Elemente 38
6.2.5 ROC-Kurve 38
6.3 Prüfung der Merkmalsvariablen 39
6.4 Residuen-Analyse 39
6.5 Interpretation und Diskussion der Regressionskoeffizienten 40
6.5.1 Metrische Variablen 40
6.5.2 Nominale Variablen 41
6.5.3 Kategoriale Variablen 42
6.5.4 Konfidenzintervalle 44
7 Fazit 45
8 Diskussion und Literatur 47
9 Kritische Würdigung und Ausblick 49
Anhang XVII
Danksagung XXXI / In Zeiten des Klimawandels, erhöhten Feinstaubwerten, geänderten sozialen Wertevorstellungen und der Verfügbarkeit von Carsharing rückt der Pkw-Besitz in Haushalten immer wieder in den Fokus der Berichterstattung. Das Ziel dieser Arbeit ist es, Charakteristika zu finden, die den Pkw-Besitz beschreiben, und deren Wirkungen zu beurteilen. Der Besitz eines Pkws wird in der Literatur auf verschiedene Weise im Hinblick auf die Bedeutung als intervenierende Variable oder als Statussymbol untersucht. Als Grundlage dienen die Daten aus der Umfrage ‚SrV - Mobilität in Städten‘, wobei die Ergebnisse der 25 großen SrV-Vergleichsstädte verwendet werden. Diese Daten besitzen eine sogenannte Multilevelstruktur, das heißt, dass die Daten auf Wegeebene, Personenebene und Haushaltsebene separat vorliegen, wodurch eine Aggregation auf das Haushaltsniveau erforderlich wird. Der sich daraus ergebende Datensatz mit sozioökonomischen und alternativenspezifischen Variablen wird mithilfe deskriptiver Methoden sowie mit Zusammenhangsmaßen auf die Eignung als Variablen für die Anwendung des binären Logit-Modells untersucht, um aussagekräftige Ergebnisse generieren zu können. Mithilfe dieses Modells werden kardinale, kategoriale sowie nominale Variablen betrachtet und bewertet. Daraus lässt sich beispielsweise ableiten, dass der Pkw-Besitz in Haushalten mit zunehmender Personenzahl wahrscheinlicher ist, als bei Singlehaushalten. Auch das Einkommen und der fehlende Zugang zu Alternativen hat einen positiven Einfluss auf den Pkw-Besitz. Das Modell kann neben der Bestimmung der Eigenschaften dazu beitragen, den Pkw-Besitz in Haushalten zu prognostizieren.
Interessant dabei ist, dass nicht alle Variablen die erwartete Wirkung entfalten. Die gefundenen Ergebnisse des Modells werden mit Erkenntnissen aus der Literatur verglichen, woraus sich einige Parallelen und Ergänzungen ergeben.:Abbildungsverzeichnis VII
Tabellenverzeichnis IX
Abkürzungsverzeichnis XI
Symbolverzeichnis XIII
1 Einleitung 1
2 Literaturübersicht 3
3 Methodik 5
3.1 Deskriptive Analyse 5
3.1.1 Lage- und Streumaße 5
3.1.2 Zusammenhangsmaße 5
3.2 Binäre logistische Regression 7
3.2.1 Allgemeines 7
3.2.2 Modellformulierung 8
3.2.3 Schätzung der logistischen Regressionsfunktion 9
3.2.4 Prüfung des Gesamtmodells 10
3.2.5 Prüfung der Merkmalsvariablen 13
3.2.6 Residuen-Analyse 14
3.2.7 Interpretation der Regressionskoeffizienten 15
4 Daten 17
4.1 Datensatz 17
4.2 Aufbereitung der Daten 17
4.2.1 Zusammenhänge in der Multilevelstruktur 18
4.2.2 Wegedaten 18
4.2.3 Personendaten 19
4.2.4 Haushaltsdatei 20
4.3 Datengrundlage 21
5 Deskriptive Analyse 23
5.1 Vorgehen 23
5.2 Streu- und Lagemaße für kardinal skalierte und klassierte Variablen 23
5.2.1 Alternativenspezifische Variablen 23
5.2.2 Sozioökonomische Variablen 27
5.3 Korrelation zwischen den metrischen Variablen 29
5.4 Relative Häufigkeiten kategorialer Variablen 29
5.4.1 Höchste Schulausbildung im Haushalt 30
5.4.2 Höchste Berufsausbildung im Haushalt 30
5.4.3 Geschlecht 30
5.4.4 Altersklassen 31
5.4.5 Erwerbstätigkeit 32
5.5 Nominale Variablen 32
5.6 Beurteilung der Variablen anhand des korrigierten Kontingenzkoeffizienten nach Pearson 34
6 Binäres Logit-Modell 35
6.1 Schätzung der Regressionskoeffizienten 35
6.2 Prüfung des Gesamtmodells 37
6.2.1 Informationskriterien und Log-Likelihood-Wert 37
6.2.2 Likelihood-Ratio-Test 37
6.2.3 Pseudo-R2-Statistiken 37
6.2.4 Klassifizierung neuer Elemente 38
6.2.5 ROC-Kurve 38
6.3 Prüfung der Merkmalsvariablen 39
6.4 Residuen-Analyse 39
6.5 Interpretation und Diskussion der Regressionskoeffizienten 40
6.5.1 Metrische Variablen 40
6.5.2 Nominale Variablen 41
6.5.3 Kategoriale Variablen 42
6.5.4 Konfidenzintervalle 44
7 Fazit 45
8 Diskussion und Literatur 47
9 Kritische Würdigung und Ausblick 49
Anhang XVII
Danksagung XXXI
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Evaluation verschiedener Imputationsverfahren zur Aufbereitung großer Datenbestände am Beispiel der SrV-Studie von 2013Meister, Romy 09 March 2016 (has links) (PDF)
Missing values are a serious problem in surveys. The literature suggests to replace these with realistic values using imputation methods. This master thesis examines four different imputation techniques concerning their ability for handling missing data. Therefore, mean imputation, conditional mean imputation, Expectation-Maximization algorithm and Markov-Chain-Monte-Carlo method are presented. In addition, the three first mentioned methods were simulated by using a large real data set. To analyse the quality of these techniques a metric variable of the original data set was chosen to generate some missing values considering different percentages of missingness and common missing data mechanism. After the replacement of the simulated missing values, several statistical parameters, like quantiles, arithmetic mean and variance of all completed data sets were calculated in order to compare them with the parameters from the original data set. The results, that have been established by empiric data analysis, show that the Expectation-Maximization algorithm estimates all considered statistical parameters of the complete data set far better than the other analysed imputation methods, although the assumption of a multivariate normal distribution could not be achieved. It is found, that the mean as well as the conditional mean imputation produce statistically significant estimator for the arithmetic mean under the supposition of missing completely at random, whereas other parameters as the variance do not show the estimated effects. Generally, the accuracy of all estimators from the three imputation methods decreases with increasing percentage of missingness. The results lead to the conclusion that the Expectation-Maximization algorithm should be preferred over the mean and the conditional mean imputation.
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Klassifizierung junger Erwachsener anhand ihres Mobilitätsverhaltens – Eine empirische Analyse der großen SrV-VergleichsstädteChutsch, Bastian 30 September 2015 (has links) (PDF)
Die vorliegende Arbeit untersucht das Mobilitätsverhalten junger Erwachsener. Dies ist von besonderer Relevanz, da die heutige jüngere Generation die Mobilität der Zukunft prägen wird. Aus jenem Grund ist es von eminenter Bedeutung, dass diese Altersklasse intensiv und über einen längeren Zeitraum betrachtet wird, um Veränderungen in deren Verkehrsmittelwahlverhalten zu erkennen. Weiterhin beeinflussen neben den mobilitätsspezifischen Einflüssen auch soziodemografische Entwicklungen das genannte Verhalten, welche sowohl identifiziert, als auch bzgl. der Einflussstärke ausgewertet werden müssen.
Ein Vergleich diverser Studien zeigt jedoch, dass die Altersklasse der jungen Erwachsenen eine noch relativ unerforschte Gruppe darstellt. Zudem besteht im Hinblick auf die Altersabgrenzung in der Literatur Uneinigkeit. Daraus ergibt sich die zentrale Frage dieser Arbeit, inwieweit sich die Gruppe der jungen Erwachsenen im Mobilitätsverhalten unterscheidet und ob es somit sinnvoll ist eine differenziertere Betrachtung vorzunehmen. Nach intensiver Recherche wurde hier die Altersspanne der jungen Erwachsenen wie folgt definiert: Personen zwischen 18 und 35 Jahren.
Als Datengrundlage dieser empirischen Analyse wurden die großen SrV-Vergleichsstädte von 2013 herangezogen. Der Datensatz jener Stadtgruppe bezieht sich auf deutsche Großstädte mit mind. 100.000 Einwohnern. Mithilfe einer Clusteranalyse konnte zunächst eine Struktur im Datensatz aufgedeckt werden, wonach die 18-21-, 22-26- und 27-35-Jährigen homogene Cluster bilden. Diese Cluster wurden anschließend deskriptiv analysiert. Hierbei sind deutliche Unterschiede im Verkehrsmittelwahlverhalten festzustellen. Der MIV-Anteil steigt z. B. mit zunehmendem Alter an, wohingegen beim ÖPV ein entgegengesetztes Verhalten zu erkennen ist. Die Fahrradnutzung ist wiederum konstant und mit steigendem Alter werden mehr Wege zu Fuß zurückgelegt. Weiterhin werden die einzelnen Gruppen u. a. durch unterschiedliche Lebensumstände sowie neue Kommunikationstechnologie beeinflusst. Abschließend wurde eine Diskriminanzanalyse durchgeführt, um ein Modell zur Gruppentrennung der drei gebildeten Cluster zu entwickeln. Das resultierende Modell beinhaltet jeweils drei soziodemografische und mobilitätsspezifische Variablen und trennt die Gruppen sehr gut. Darüber hinaus wurden die Elemente eines Kontrolldatensatzes ähnlich optimal eingeordnet, wodurch die Anwendbarkeit dieses Modells bestätigt werden konnte.
Die Analyse des Mobilitätsverhaltens der jungen Erwachsenen hat somit ergeben, dass es sich hierbei um eine heterogene Altersklasse handelt. Aus diesem Grund scheint es sinnvoll jene Zielgruppe bei zukünftigen Untersuchungen differenzierter zu betrachten und die ermittelten Cluster zu berücksichtigen.
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Recent administrative reform in VietnamHai, Peter Nguyen Van, n/a January 1994 (has links)
Since the introduction in 1986 of Doi Moi program, a Vietnamese form of
Perestroika, which was designed partly to reduce the role of state bureaucracy
in the system, major economic reforms have been carried out in the Socialist Republic of Vietnam (SRV). However, while Vietnam's economic reforms
have generated considerable interest, its limited political reforms, especially in
the area of public administration, have not been a central concern among
political scientists, historians and researchers. In their efforts to revitalise the
state bureaucracy, reformers in Vietnam now recognise the importance of well
qualified bureaucrats, and they inevitably have to face the old issue of how best
to attract, motivate, train and retain public servants for a better government.
This paper, based on the search through the maze of official documents in
Vietnamese language, describes the SRV's political institutions, provides an
overview of Vietnam's administrative system against the backdrop of the
country's economic and political reforms, highlighting institutional interactions
induced by reform imperatives, discusses recent administrative reforms
emanating from the amended 1992 Constitution, and evaluates the effectiveness
of current administrative reform strategies. Comments will also be made on
. The roles and functions of central agencies in Vietnam
. Policy making processes and paradigms
. The 'emerging' dichotomy between policy and administration
. The 'ministerial department' a la Vietnamienne
. Machinery of government changes
. Human resource management initiatives
. The 'career service' nature of the Vietnamese public service, and,
. Central versus provincial governments.
Vietnamese Public Service is an important question and worthy of investigation
because of the increasingly close bilateral relationship between Australia and
Vietnam. Many Australian investors who have often been annoyed by
unnecessary delays caused by bureaucratic red tape and corruption, are now
keen to learn more about the policy making style of Vietnamese bureaucrats.
Vietnam still displays many deliberate trappings of a country run in a highly
centralist fashion. Its reorganisation strategy of the state's administrative
system will continue to bear the socialist imprints. Dr David Marr of the
Australian National University contends that layer upon layer of bureaucratic
influence, from Chinese Neo-Confucian to French Third Republic to Soviet
Stalinist, can be seen in Vietnam today. This paper argues that Vietnam's
political and cultural legacies will continue to exercise significant influence, as
they have in the past, on its public service's structures, strategies and ethics.
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Mobilitätsanalysen für die Region Dresden (BMBF-Leitprojekt intermobil Region Dresden ; Schlussbericht - Band 2)Ahrens, G.-A., Ließke, F., Wittwer, R. 09 May 2005 (has links) (PDF)
Der vorliegende Band 2 des Schlussberichtes "Mobilitätsanalysen für die Region Dresden" ordnet sich in das Teilprojekt AP 700 "Projektevaluation/ Wirkungsanalysen" ein. Es stellt die Ergebnisse umfangreicher Mobilitätsanalysen für das räumliche Untersuchungsgebiet von intermobil dar, die von der TU Dresden unter Nutzung des Systems repräsentativer Verkehrsbefragungen (SrV) durchgeführt worden sind. Sie bildeten eine wesentliche Grundlage der im AP 700 durchzuführenden Wirkungsanalyse, insbesondere im Hinblick auf die Abschätzung langfristig zu erwartender Wirkungen. Die gewonnenen Erkenntnisse haben darüber hinaus grundsätzliche Bedeutung für ein besseres Verständnis der komplexen Fragen von Verkehrs- und Mobilitätsentwicklung in der Region Dresden. (Dresden, im Dezember 2004 / Prof. Dr.-Ing. habil. Dr. h. c. H. Strobel - Projektleiter TU Dresden)
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Evaluating the repeatability of friction and wear testing on a lubricant with dispersed hexagonal-boron nitride nanoparticlesBenadé, Howard P. January 2015 (has links)
The SRV test rig was used to evaluate the friction and wear properties of a lubricant in a laboratory setup. Normally, the coefficient of friction and the amount of wear that occurred are measured while the wear scar surface is also evaluated. Special attention was paid to factors that affect the repeatability.
The test fluid was subjected to a friction and wear test on the SRV test rig in order to determine what factors affect the repeatability of the coefficient of friction, the amount of wear that occurred and the wear scar appearance. The test fluid used was based on rapeseed oil and white mineral oil. The fluid also contained an extreme pressure additive in the form of sulphurised ester. This was also compared for the same test fluid with dispersed hexagonal-boron nitride (h-BN) nanoparticles.
The standard test method as described by ASTM D 6425, was used as test method. Instead of the standard temperature, the block temperature was increased to 100 °C in order to simulate harsher operating environments. The load was set at 200 N
It was found that:
The rapid load increase from 50 to 200 N at the end of the running-in period (as described in the standard test method) caused poor repeatability. The test was modified with a more gradual load application for the duration of the running-in period (30 N/min), which resulted in improvement in the repeatability of the tests conducted.
The moisture content in the atmosphere also affected the repeatability of the friction and wear tests. This was most likely due to the formation of a corrosion layer that involves water and by keeping the relative humidity constant, a further improvement in the repeatability was observed. The addition of the h-BN nanoparticles resulted in an improvement of the repeatability of the coefficient of friction (COF), wear scar surface (WSS) and wear scar volume (WSV), since the wear scar surfaces indicated that the particles remove the corrosion layers. This could have led to more consistent wear surfaces for the duration of the test.
The particles also influenced the corrosion layer formation. For both fluids, Raman spectroscopy indicated that greigite (Fe3S4) and goethite (α-FeOOH) were found on the surface, while additional corrosion products were found on the wear scar surface for the test fluid with dispersed particles. These compounds were melanterite (FeSO4.7H2O) and rozenite (FeSO4.4H2O). All these corrosion products were most likely formed due to the reaction of iron from the specimens with sulphurised esters in the test fluid. / Dissertation (MEng)--University of Pretoria, 2015. / tm2015 / Chemical Engineering / MEng / Unrestricted
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