• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 137
  • 2
  • 2
  • Tagged with
  • 141
  • 128
  • 125
  • 32
  • 28
  • 24
  • 14
  • 14
  • 14
  • 14
  • 14
  • 8
  • 8
  • 8
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Rückhaltung von in der Trinkwasseraufbereitung relevanten organischen Spurenstoffen durch Nanofiltrationsmembranen - Rejection of organic trace substances relevant for drinking water treatment by nanofiltration

Berg, Peter 18 February 2003 (has links)
Organic trace substances including pesticides are becoming more important in the drinking water treatment. Nanofiltration for drinking water treatment is mainly used for softening and the removal of humic substances. Recently nanofiltration is sometimes used also for the removal of organic trace substances. The mechanism of the trace substance transport through Nanofiltration membranes is widely unknown. Therefor it is not possible to predict pesticiderejections. Thus one focus of this thesis is the investigation of the rejection of organic trace substances through nanofiltration membranes. By measuring diffusion constants of several electrical uncharged pesticides it could be shown that the size of the molecules is a contributing factor. Due to attached water molecules it is not possible to calculate this "effective" molecule size by molecule modelling programs. To investigat the steric effects the rejection dependent of pH was investigated because the membrane pore size distribution depends on pH. The oppositional behaviour of the rejection and the permeability underlines the steric influence on rejection as well as a mathematical model. With electric charged organic trace substances the electrostatic interactions between the membrane surface and the organic molecule dominates the transport mechanism.
112

Erziehung und die Vernunft der Gefühle : Gefühlserziehung - Möglichkeit, Notwendigkeit, Relevanz? - Education and the Rationality of Emotions : Education of Feelings - Possibility, Necessity, Relevance?

Krimm, Barbara Mechthild 19 February 2003 (has links)
With regard to the question what is constitutional for the human being: the ability to think rationally or the ability to develop emotions, this examination aims to clarify the role of feelings in human life. The analysis of important psychological theories of emotions concerning the development of the varieties of emotions shows that on the basis of a genetical disposition to establish emotions the generating of specific emotions in specific situations has to be learned. In addition to that it can be made clear that decisions depend on the combination of rational and emotional processes.
113

'Die Vernichtung der Menschheit hat begonnen': Zivilisationskritik im Spätwerk von Günter Grass / The destruction of mankind has started : criticism of civilisation in Günter Grass' later work

Schulz, Markus 01 March 2005 (has links)
In the 80s and 90s of the 20th century Günter Grass treated the various chances of a sudden extinction of mankind for instance the decline by overpopulation and nuclear destruction. So the study deals with five main aspects to show Grass' own criticism of civilisation. The thesis at hand shall be a contribution to describe the significance of these various topics concerning Grass' prose, essayistic works and statements during the last 25 years.
114

Development and characterisation of a portable direct methanol fuel cell stack

Oedegaard, Anders 01 March 2006 (has links)
This thesis deals with the development and characterisation of a portable direct methanol fuel cell stack. In addition, calculations of the transport of methanol and water in the membrane are compared with experimentally determined values. It also includes investigations of the behaviour of single-cells and some of its components, as the anode gas diffusion layer and the anode flow-field. For the addition of methanol to the anode feed loop, a passive concept based on a permeable tube was developed and verified by both experiments and simulations.
115

Druckwechseladsorption als Wasserstoffreinigungsverfahren fuer Brennstoffzellen-Systeme im kleinen Leistungsbereich / Pressure Swing Adsorption as hydrogen purification process for small scale fuel cell systems

Walter, Michael 05 March 2004 (has links)
Fuel cells are high efficient energy production systems producing heat and electrical power. Especially PEM fuel cells (Polymeric Electrolyte Membrane) require pure hydrogen for operation. Hydrogen is produced e.g. by reforming of hydrocarbons like natural gas or ethanol. During the production of hydrogen carbon monoxide is formed. CO is a harmful poison for the platinum catalsyst of the fuel cell electrodes. Therefore hydrogen has to be purified. The goal of this work was to develop a pressure swing adsorption for small scale fuel cell systems. The hydrogen to be purified is produced by reforming bio-ethanol. The PSA is designed for a quite low adsorption pressure of 7 bar and a small thermal hydrogen power for fuel cell systems in a range of 1 kW electrical. For the design of the PSA a simplified method of calculating the bed height of the adsorbers was developed. Most scientists working in the field of pressure swing adsorption use mathematical models of breakthrough curves for PSA calculations. But these models can only be solved numerically. The results of these simulations are approved by performing test at lab-scale PSA. Main focus on the tests is set to the breakthrough time and the shape of the breakthrough curves. The calculation method developed in this work is also verified by test. But no breakthrough curves were taken up and no breakthrough time of the unwished gas component (CO) was measured. Only the hydrogen quality and the hydrogen recovery rate even after several adsorption cycles were the dominating criteria for the approval of the calculation model. The PSA tests showed that the required hydrogen quality (less than 10 ppmv CO in hydrogen) for PEM-fuel cells was reached even after a 20 adsorption cycles (one cycle lasted 12 minutes with 3 minutes adsorption). The tests were performed on several days in series without changing the adsorbents or purging them for a longer time.
116

Comme un roman policier: Daniel Pennacs Malaussène-Serie als eine Spielart des Kriminalromans - Like a thriller: Daniel Pennac's Malaussène-Saga as a variation of crime novel

Janssen, Sabine 25 March 2003 (has links)
The doctoral thesis 'Comme un roman policier: Daniel Pennacs Malaussène-Serie als Spielart des Kriminalromans' delivers a thorough analysis of a popular French series consisting of five novels which are rooted in crime literature. The contemporary French author Daniel Pennac makes a playful use of elements characteristic both of the detective novel als well as the thriller. Aspects of the analysis include the structure of the novels, techniques of narration, depiction of society, methods of detection and use of language. Based on René Girard's scapegoat-theory Pennac creates the tragicomic hero of Benjamin Malaussène. Besides the exceptional protagonist, the rest of the Malaussène-universe can be divided into a 'good' in-group and a 'bad' out-group. Pennac draws rough sketches of the characters by using stereotypes and the inversion of stereotypes. By these means Pennac reveals by which absurd and paradoxical mechanisms the contemporary Western society often works. Concerning the detection, the author does not stick to traditional methods, but extents the intruments of knowledge to the supernatural. Theses variations of detective novel and thriller regarding the contents are presented in an elaborated and metaphorical style which furthermore contains innumerable reflections on language and literature. The thesis concludes with a classification of Pennac's Malaussène-Saga within the frame of modern French as well as crime literature.
117

Herstellung und Bewertung der Umformbarkeit von reibrührgeschweißten Tailored Blanks aus Aluminiumlegierungen / Production and formability analysis of friction stir welded aluminium tailored blanks

Sheikhi, Shahram 06 April 2006 (has links)
Friction Stir Welding (FSW) offers an attractive alternative to conventional fusion welding processes because of the excellent properties (particularly ductility), reproducibility, robustness, and surface finished obtained with FSW. However, questions have been raised regarding the productivity of FSW against fusion welding methods. TWBs from the aluminum alloys 5754-H22 and 6181-T4 with different gauges (1 to 2 mm) are produced and tested. Welding speeds up to 10 m/min have been systematically investigated. The welds produced have been subjected to microstructural analysis, mechanical testing and formability analysis.
118

Untersuchungen zum Anwendungsbereich und zur Steigerung der Nachweisempfindlichkeit eines Partikelmassenspektrometers (PMS) - Study of the applicability and the improvement of the detection sensitivity of a particle mass spectrometer (PMS)

Strecker, Marc Gerd Dieter 07 June 2004 (has links)
In the present work the applicability and the improvement of the detection sensitivity of a particle mass spectrometer (PMS) were studied. The PMS was originally used by Hospital and Roth for the investigation of the growth of soot-particles produced in combustion processes. It consists of a molecular beam sampling system and a high vacuum chamber which contains the necessary measurement instrumentation for the in-situ particle sizing.<p><p>Three reactors were employed to investigate the applicability: a low-pressure flame reactor, a microwave reactor and a spark reactor. The reactors are different in respect of the energy transfer into the reactive gases and the bulk material respectively. The flame reactor was used to produce well-known soot particles as reference particles for the experiments related to the improvement of the detection sensitivity of the PMS. Soot-, Silver-, Carbon-, Siliconoxide-, Tinoxide and Nickel- Nanoparticles were produced. The results have shown that the applicability of the PMS could be extended and be applied to particles generated in the microwave reactor as well as in the spark reactor.<p><p>Neutral charged Soot- and Tinoxid-Nanoparticles which were produced in the flame reactor were charged by electron impact ionisation in the high vacuum chamber of the PMS. The charging effect increases with decreasing amount of charged particles in the aerosol. Thus, in the case of neutral or weakly charged aerosols the particles could be characterised with the PMS leading to a further extension of the application range.<p><p>A new detector was developed to improve the detection sensitivity of the PMS. The detector consists of a secondary electron multiplier (SEM) and an external conversion dynode. The dynode was set to a high electrical potential. Thus, the particles were accelerated to a velocity which is sufficient to release secondary electrons or ions from the dynode after the impaction of the particles with the surface of the dynode. Afterwards these secondary electrons and ions respectively were amplified by the SEM. In comparison with the conventional detector, a Faraday-Cup, an increase of the signals of about 10<sup>5</sup> was achieved with this new detector.
119

Sicherung der Wettbewerbsfähigkeit klein- und mittelständischer Unternehmen (KMU) durch qualifikatorische Anpassung der Belegschaft in Phasen der Reorganisation - Company Competitiveness of small and medium sized companies (SME) in Change Management Processes through further training in industry.

Stuhldreier, Jens 05 June 2003 (has links)
An improved utilization of potentials, tapping into new markets, maintaining competitiveness: These are the goals if the responsible echelons in a company decide on measures to reorganize operations. The key factor in this process of restructuring remains the human element. As a rule, SMEs are ideally suited for a sucessfull restructuring. Main advantages in contrast to large corporations: Their operations are not overly complicated, the staff is small enough to build up informal ties, the information network is closely-knit, and decisions are made faster than in large companies. The key question in Change Mangement processes is: Under which conditions are further training offers prepared to ensure the sustainable employabilty of the employess?
120

Zur Verrechtlichung in der Weiterbildung:Untersuchungen über historische und aktuelle Problemlagen der Kodifizierung / Codification and Legislation of Adult Education: Inquiry on Historical Developments and Current Discussions

Kasper, Heinz Peter 13 June 2006 (has links)
Lifelong Learning as a strategy for individuals to ensure employability and to strengthen their knowledge and skills raises questions regarding the state of the system of adult education and the governments responsibility as necessary conditions for a broad participation. The German discussion has frequently shown demands for a constitutional and codified integration of adult education into the general public educational system. Under the perspective of the increasing importance of Lifelong Learning the history of adult education especially has shown that a non-functional educational infrastructure results from low public responsiveness and a lack in legal regulations. Rather than promoting equal opportunities for every citizen the system of adult education in Germany leads to more inequality, Lifelong Learning as a concept detached from public strategies increases social selections instead of compensating them. Consequently, the author analyses public options and public duties referring to a law that rules an incomplete market. The results of the analysis confirm that even if there is no constitutionally guaranteed civil right for a public support of adult education public policy should take care for this section of our educational system and should integrate adult education as a fundamental right shown by a specific legislation.

Page generated in 0.0302 seconds