• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 41
  • 9
  • 7
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 80
  • 80
  • 25
  • 21
  • 14
  • 13
  • 12
  • 12
  • 11
  • 10
  • 9
  • 9
  • 8
  • 8
  • 8
  • 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.
41

Optimization and reaction kinetics of the production of biodiesel from castor oil via sodium methoxide-catalyzed methanolysis

Crymble, Scott David 01 May 2010 (has links)
This paper studies castor oil’s potential as a biodiesel feedstock. Base-catalyzed transesterification batch reactions were conducted at various experimental conditions while measuring the concentration of the reaction components over time. A gas chromatograph with a flame-ionization detector analyzed these samples. A factorial design of experiments was used to determine how conversion was affected by reaction temperature, sodium methoxide concentration, and ratio of methanol to oil. Conversion was maximized (0.9964) at 30 °C, 0.5% catalyst, and 9:1 molar ratio. The concentration data were used to study the reaction kinetics. Modeling the reaction as three equilibria yielded six rate constants. These values indicate that castor oil transesterifies faster than soybean oil. The fuel properties were determined by ASTM D 6751. Viscosity was excessively high, but specifications were met for the remaining tests. Despite the promising yield and kinetics of the reaction, the fuel viscosity limits castor oil’s viability as a biodiesel feedstock.
42

Komparace koncepcí elektromobility v České republice, Francii a USA / Comparison of electromobility conceptions in the Czech republic, France and USA

Kovalová, Lucie January 2010 (has links)
A quarter of CO2 emissions in the European Union currently comes from transport, which causes a significant deterioration of air quality. Therefore, it contributes to the deterioration of the health of people living in these areas. The number of cars on the roads continues to increase globally, and with them the increase in CO2 emissions. Alternative fuel in various forms began appearing on the market. Electric cars, with their emission-free operation, are trying to find their place here. Their wider use, especially in densely populated cities, could help people to a cleaner environment. Currently, there are some technical and economic problems with a wider introduction of electric vehicles. Technology and an associated high cost of storage of the necessary power are the main challenges. Nonetheless, experts believe that electric cars have future. Each country approaches the development of electromobility in a different manner.
43

Analýza významu LPG jako alternativního paliva v osobní automobilové dopravě v České republice / Analysis of the importance of LPG as an alternative fuel for the vehicular transport in the Czech Republic

Klusoňová, Petra January 2010 (has links)
The main goal of this economic paper is to analyse the importance of LPG as an alternative fuel for the vehicular transport in the Czech Republic and to simplify the decision of potential applicants about the conversion of a car engine to run on LPG. At first this text briefly describes the main kinds of alternative fuels. Then the text focuses on LPG itself that is defined and described including its application in the past and at present. The next section of this paper is concentrated on the individual decision about the conversion of his car engine to run on LPG and the main attention will be focused on the environmental, economic, technical and institutional aspects of this conversion. Then the text compares LPG and CNG because CNG could be considered to be the main competitor of LPG in the field of alternative fuels. At the conclusion the paper summarizes the discovered facts and tries to predict future use of LPG as an alternative fuel in the Czech Republic.
44

CHEMISTRY – PERFORMANCE CORRELATIONS IN ALTERNATIVE AVIATION FUELS TOWARDS A SUSTAINABLE FUTURE

Petr Vozka (6796532) 16 August 2019 (has links)
<div>Determination of the chemical composition of liquid transportation fuels emerged as a novel and important field of study after the introduction of advanced analytical instruments, which are capable of very detailed chemical analyses of complex mixtures. Aviation fuels make up a crucial portion of liquid transportation fuels. There are several significant challenges in the field of aviation fuels, including the development of optimal analytical methods for the determination of the chemical compositions of the fuels, fuel properties measurements, and correlations between fuel properties and chemical composition. This dissertation explores possible correlations between fuel chemical composition and its properties and proposes novel approaches. First, a detailed description of a method for the determination of the detailed chemical composition of all middle distillate fuels (diesel and aviation fuels) is presented. Second, the density was correlated to fuel composition. Additionally, the approach of measuring the density, the hydrogen content, and the carbon content via a GC×GC-FID was introduced. Lastly, it was discovered that minute differences in chemical composition can influence fuel properties. This finding is described in the last chapter, where three HEFA samples were investigated. </div>
45

Podmínky implementace ekologicky šetrných technologií na trhu automobilů v ČR / Conditions for implementation of alternative fuel technologies in passenger cars on the Czech market

Holeček, Petr January 2010 (has links)
The thesis topic is creating conditions for successful implementation of alternative fuel technologies in passenger cars on the Czech market. Its goal is to develop a comprehensive concept of proposed measures that would create demand for alternative powertrain. It analyzes current situation of the environmental-friendly vehicles market and examines reasons why consumers have not been purposefully searching for these cars so far. The thesis consists of several coherent blocks. The first one deals with general aspects of innovations and development, energy resources, climate protection and car fleet in the Czech Republic. The second part focuses on new alternative technologies from the viewpoint of energy resources and examines the offer on the local market. The third section includes a consumer research focused on information related to potential customers' preferences and compares economic efficiency and costs of selected technologies. The final part presents proposed ways of accomplishing the main goal, while special attention is given to specific recommendations, which would help to create demand and facilitate promotion among consumers.
46

Produção de híbridos de Eucalyptus grandis x E. urophylla em plantios adensados no sudoeste goiano / Hybrid production Eucalyptus grandis x E. urophylla in plantations dense in southwest goiano

Martins, William Rodrigues 01 March 2016 (has links)
Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-21T11:00:40Z No. of bitstreams: 2 Dissertação - William Rodrigues Martins - 2016.pdf: 595784 bytes, checksum: 3a2ef59ef753e50f8bafcc9b780fa57f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-21T11:01:10Z (GMT) No. of bitstreams: 2 Dissertação - William Rodrigues Martins - 2016.pdf: 595784 bytes, checksum: 3a2ef59ef753e50f8bafcc9b780fa57f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-21T11:01:10Z (GMT). No. of bitstreams: 2 Dissertação - William Rodrigues Martins - 2016.pdf: 595784 bytes, checksum: 3a2ef59ef753e50f8bafcc9b780fa57f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-01 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The objective of this work was to verify the volumetric production per area, the growth in height and diameter at breast height (DBH) in hybrid of Eucalyptus urophylla x E. grandis W. Hill., in reduced different planting spacings in southwest Goiás. The work was implemented in the Experimental Farm of the Federal University of Goiás, Regional Jataí (UFG / REJ), town of Jataí-GO, following the assumptions of completely randomized design, with three hybrids, two treatments for hybrid treatments and three replications, totaling 18 plots with 50 seedlings per plot. The hybrids were AEC1528, I144 and GG100 and the evaluated spacings were 3.0 m x 0.5 m and 3.0 m x 1.0 m. At 33 months of age tree were collected for the volume analysis, growth in height and diameter. The spacing of 3.0 m x 0.5 m in energy forests, affect the individual growth for both diameter and height, as to volume. The differentiation of hybrids was in height and production, where I144 hybrid gained greater prominence. The greatest expression in volume production, for wood with bark, not bark and bark volume was observed for 3.0 m x 0.5 m spacing. / Objetivou-se com este trabalho verificar a produção volumétrica por unidade de área, o crescimento em altura e diâmetro a altura do peito (DAP) em povoamentos de híbridos de Eucalyptus urophylla x E. grandis W. Hill., em diferentes espaçamentos reduzidos de plantio no sudoeste goiano. O trabalho foi implantado na Fazenda Experimental da Universidade Federal de Goiás, Regional Jataí (UFG/REJ), Município de Jataí-GO, seguindo os pressupostos do delineamento inteiramente casualizado, com seis tratamentos, e três repetições, totalizando 18 parcelas, com plantio de 50 mudas por parcela. Os híbridos avaliados foram o AEC1528, I144 e GG100 e os espaçamentos avaliados foram 3,0 m x 0,5 m e 3,0 m x 1,0 m. Assim observou-se aos 33 meses de idade que os crescimentos em diâmetro e altura são diretamente afetados pelo adensamento das plantas, e consequentemente com a redução da área útil disponível para cada planta. Os espaçamentos de 3,0 m x 0,5 em florestas energéticas afetam o incremento individual, tanto para diâmetro e altura, quanto para volume. A diferenciação dos híbridos ocorreu para o incremento em altura e produção, onde o híbrido I144 destacou-se. A maior expressão na produção volumétrica, para a madeira com casca, sem casca e o volume de casca foi observada para o espaçamento 3,0 m x 0,5 m.
47

Feasibility and emissions of compression ignition engines fueled with waste vegetable oil [electronic resource] / by Morgan H. Crawford.

Crawford, Morgan H. January 2003 (has links)
Title from PDF of title page. / Document formatted into pages; contains 39 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Research and experience has shown that vegetable oil can be processed, by transesterification, into a useable fuel for compression ignition engines. Earlier research examined using straight vegetable oil as a fuel, but found it to cause detrimental engine problems. Trial and error has shown that heating the vegetable oil prior to injection, is a viable option. A diesel vehicle engine was operated for over 188 hours or approximately 7,000 miles, using waste cooking oil as fuel. The longevity of the vehicle engine was limited by an undetermined engine failure. Using stationary testing, with no engine load and various power settings, engine emissions of several engines operating on waste cooking oil were compared to emissions from two other fuels, diesel and Biodiesel, and found to be very positive. Waste vegetable oil (WVO) had lower overall emissions than diesel and lower levels of nitrogen species than Biodiesel. / ABSTRACT: Agricultural yield predictions estimate that currently only 5% and at most 20% of all diesel fuel needs can be met with vegetable oil. Currently WVO is a disposal problem. It is primarily used as a feedstock. / ABSTRACT: WVO is not a commodity and has disposal fees associated with it. If WVO is used as a fuel, it would not only provide another source for disposal, but it may also increase the value of WVO making it a commodity instead of a disposal burden. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.
48

Model for marketing liquefied petroleum gas in Nigeria: Warri as a case study / Nonekuone Jolomi

Nonekuone, Jolomi January 2008 (has links)
Despite the huge national energy resources, many Nigerians do not have access to high quality, modern energy services. For those with access, energy supply lacks reliability, especially in the case of liquefied petroleum gas (LPG). Hence this research considers the possibility of enhancing the household use of LPG. It analyzes the factors affecting the current demand and supply. Salient features of the LPG supply and distribution system were also discussed. On the basis of the existing situation, barriers of increasing LPG use, in particular, the problems regarding affordability, priCing, government poliCies, safety, transportation and distribution were analyzed and identified statistically using the chi-square statistical method as a tool. Finally, on the basis of the challenges identified, suggestions and recommendations were made regarding the policies through which the problems could be overcome. Furthermore, a model was developed and tested for an effective marketing strategy of LPG in Warri Nigeria. ii / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.
49

Model for marketing liquefied petroleum gas in Nigeria: Warri as a case study / Nonekuone Jolomi

Nonekuone, Jolomi January 2008 (has links)
Despite the huge national energy resources, many Nigerians do not have access to high quality, modern energy services. For those with access, energy supply lacks reliability, especially in the case of liquefied petroleum gas (LPG). Hence this research considers the possibility of enhancing the household use of LPG. It analyzes the factors affecting the current demand and supply. Salient features of the LPG supply and distribution system were also discussed. On the basis of the existing situation, barriers of increasing LPG use, in particular, the problems regarding affordability, priCing, government poliCies, safety, transportation and distribution were analyzed and identified statistically using the chi-square statistical method as a tool. Finally, on the basis of the challenges identified, suggestions and recommendations were made regarding the policies through which the problems could be overcome. Furthermore, a model was developed and tested for an effective marketing strategy of LPG in Warri Nigeria. ii / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.
50

A model and optimization of alternative fuel vehicle fleet composition with triple bottom line concerns

Zullo, Johnathon 06 July 2012 (has links)
Alternative fuel types and technologies are increasingly being advocated for transportation needs to ameliorate concerns around energy security, climate change, and fuel cost. Each fuel type has unique advantages and disadvantages for cost structure and emissions. Meanwhile, corporate fleet customers are often making more sustainable choices of vehicle type due to public perception and other influencing factors. The sustainability of these vehicles can be viewed from a triple bottom line perspective of financial, environmental, and societal implications. However, there is currently a lack of organized knowledge that would allow a decision-maker to elect the appropriate vehicle type beyond lifecycle cost and carbon emissions. The simplification of the impact of fuel type choice disregards issues that are emerging in prominence around water consumption and public health. Water consumption is of particular importance to investigate as fuel types that have reduced carbon emissions are often more water intensive. This thesis develops a tool that examines these issues through modeling to provide a more holistic lifecycle view of a prospective fleet's impact. The choice of vehicle type then can be optimized by utility theory preference elicitation of the different customer desires. Various scenarios of corporate preference and fleet specifications are explored to provide case studies that exemplify the complexity of the decision process. Each potential scenario has its own characteristics that cannot be optimally fulfilled by an overarching fuel type but rather should be thoroughly examined individually to understand the true consequences.

Page generated in 0.1427 seconds