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  • Articles  (45)
  • Hindawi  (32)
  • Dessau-Roßlau : Umweltbundesamt  (13)
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  • Articles  (45)
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  • 1
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    Urban environmental protection international : stock-taking and outlook ; final report (2021)
    Dessau-Roßlau : Umweltbundesamt
    Details
    Publication Date: 2022-02-18
    Description: The aim of this study is to contribute to a learning process about innovative and successful approaches to overcoming problems and challenges of urban environmental protection. To this end, a detailed overview of the importance of environmental challenges, political priorities and successful solutions in selected countries and cities is given. Based on this, the study analyzes specific success factors and discusses the extent to which these can be transferred and replicated to other cities. Finally, recommendations are made for cities, countries and the international community on how environmental protection at the urban level can be further strengthened. The role of German cities and institutions will also be discussed. The case studies analyzed include Belo Horizonte in Brazil, Moscow in Russia, Kochi in India, Beijing in China, Cape Town in South Africa and Jakarta in Indonesia. These cities were selected because they have already implemented successful policies, measures and other initiatives in the past. For each city, the study analyzes relevant policy documents in order to present the respective challenges and political priorities. The analysis aims to understand the effectiveness of the plans and instruments taking into account the national political environment. Despite the cross-sectoral approach, the analysis of each case study focuses on specific sectors in order to produce well-founded results. The success factors that are worked out based on this sectoral analysis are placed in a holistic context in order to be able to make generalizable statements about success factors.
    Keywords: ddc:320
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: report , doc-type:report
    Format: application/pdf
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  • 2
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    Assessment of Combustor Working Environments (2013)
    Hindawi
    Details
    Publication Date: 2013-03-07
    Description: In order to assess the remaining life of gas turbine critical components, it is vital to accurately define the aerothermodynamic working environments and service histories. As a part of a major multidisciplinary collaboration program, a benchmark modeling on a practical gas turbine combustor is successfully carried out, and the two-phase, steady, turbulent, compressible, reacting flow fields at both cruise and takeoff are obtained. The results show the complicated flow features inside the combustor. The airflow over each flow element of the combustor can or liner is not evenly distributed, and considerable variations, ±25%, around the average values, are observed. It is more important to note that the temperatures at the combustor can and cooling wiggle strips vary significantly, which can significantly affect fatigue life of engine critical components. The present study suggests that to develop an adequate aerothermodynamics tool, it is necessary to carry out a further systematic study, including validation of numerical results, simulations at typical engine operating conditions, and development of simple correlations between engine operating conditions and component working environments. As an ultimate goal, the cost and time of gas turbine engine fleet management must be significantly reduced.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Hindawi
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  • 3
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    Assessment of Combustor Working Environments (2012)
    Hindawi
    Details
    Publication Date: 2012-01-01
    Description: In order to assess the remaining life of gas turbine critical components, it is vital to accurately define the aerothermodynamic working environments and service histories. As a part of a major multidisciplinary collaboration program, a benchmark modeling on a practical gas turbine combustor is successfully carried out, and the two-phase, steady, turbulent, compressible, reacting flow fields at both cruise and takeoff are obtained. The results show the complicated flow features inside the combustor. The airflow over each flow element of the combustor can or liner is not evenly distributed, and considerable variations, ±25%, around the average values, are observed. It is more important to note that the temperatures at the combustor can and cooling wiggle strips vary significantly, which can significantly affect fatigue life of engine critical components. The present study suggests that to develop an adequate aerothermodynamics tool, it is necessary to carry out a further systematic study, including validation of numerical results, simulations at typical engine operating conditions, and development of simple correlations between engine operating conditions and component working environments. As an ultimate goal, the cost and time of gas turbine engine fleet management must be significantly reduced.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Hindawi
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  • 4
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    Combined Effects of Thermal Radiation and Nanoparticles on Free Convection Flow and Heat Transfer of Casson Fluid over a Vertical Plate (2018)
    Hindawi
    Details
    Publication Date: 2018
    Description: The influences of thermal radiation and nanoparticles on free convection flow and heat transfer of Casson nanofluids over a vertical plate are investigated. The governing systems of nonlinear partial differential equations of the flow and heat transfer processes are converted to systems of nonlinear ordinary differential equations through similarity transformations. The resulting systems of fully coupled nonlinear ordinary differential equations are solved using the differential transformation method with Padé-approximant technique. The accuracies of the developed analytical methods are verified by comparing their results with the results of past works as presented in the literature. Thereafter, the analytical solutions are used to investigate the effects of thermal radiation, Prandtl number, nanoparticle volume fraction, shape, and type on the flow and heat transfer behaviour of various nanofluids over the flat plate. It is observed that both the velocity and temperature of the nanofluid as well as the viscous and thermal boundary layers increase with increase in the thermal radiation parameter. The velocity of the nanofluid decreases and the temperature of the nanofluid increase, respectively, as the Prandtl number and volume fraction of the nanoparticles in the base fluid increase. The decrease in velocity and increase in temperature are highest in lamina-shaped nanoparticle and followed by platelet-, cylinder-, brick-, and sphere-shaped nanoparticles, respectively. Using a common base fluid to all the nanoparticle types, it is established that the decrease in velocity and increase in temperature are highest in TiO2 and followed by CuO, Al2O3, and SWCNT nanoparticles, in that order. It is hoped that the present study will enhance the understanding of free convection boundary layer problems of Casson fluid under the influences of thermal radiation and nanoparticles as applied in various engineering processes.
    Print ISSN: 1687-806X
    Electronic ISSN: 1687-8078
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Hindawi
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  • 5
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    Combined Effects of Thermal Radiation and Nanoparticles on Free Convection Flow and Heat Transfer of Casson Fluid over a Vertical Plate (2018)
    Hindawi
    Details
    Publication Date: 2018-09-03
    Description: The influences of thermal radiation and nanoparticles on free convection flow and heat transfer of Casson nanofluids over a vertical plate are investigated. The governing systems of nonlinear partial differential equations of the flow and heat transfer processes are converted to systems of nonlinear ordinary differential equations through similarity transformations. The resulting systems of fully coupled nonlinear ordinary differential equations are solved using the differential transformation method with Padé-approximant technique. The accuracies of the developed analytical methods are verified by comparing their results with the results of past works as presented in the literature. Thereafter, the analytical solutions are used to investigate the effects of thermal radiation, Prandtl number, nanoparticle volume fraction, shape, and type on the flow and heat transfer behaviour of various nanofluids over the flat plate. It is observed that both the velocity and temperature of the nanofluid as well as the viscous and thermal boundary layers increase with increase in the thermal radiation parameter. The velocity of the nanofluid decreases and the temperature of the nanofluid increase, respectively, as the Prandtl number and volume fraction of the nanoparticles in the base fluid increase. The decrease in velocity and increase in temperature are highest in lamina-shaped nanoparticle and followed by platelet-, cylinder-, brick-, and sphere-shaped nanoparticles, respectively. Using a common base fluid to all the nanoparticle types, it is established that the decrease in velocity and increase in temperature are highest in TiO2 and followed by CuO, Al2O3, and SWCNT nanoparticles, in that order. It is hoped that the present study will enhance the understanding of free convection boundary layer problems of Casson fluid under the influences of thermal radiation and nanoparticles as applied in various engineering processes.
    Print ISSN: 1687-806X
    Electronic ISSN: 1687-8078
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Hindawi
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  • 6
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    Formulation of the Settling Velocity of Small Particles Initially Situated inside an Inclined Vortex (2016)
    Hindawi
    Details
    Publication Date: 2016-03-21
    Description: Both the estimation of the time that small heavy particles remain inside a 3D vortex and the estimation of the average settling velocity of those particles are some important features in many practical situations. Previous works focused on the case of a horizontal 2D vortex. In this paper, we simulate the dynamics of heavy particles initially situated inside a three-dimensional vortex obtaining a formula for their average settling velocity. In a previous paper we obtained the trajectories of the particles and a formula that provides the time that they need to escape, . This work simulates and analyses the escape process, and its main result is the obtaining, from numerical simulation, of a theoretical formulation of the average settling velocity and its relationship with the elapsed time. We prove that the permanence time is of the order of (with particle diameter) and that the average settling velocity is of the order of for sufficiently small particles. Some applications of the settling velocity formula developed in this work would be the design of mixture devices, the design of particle separation devices, and the prediction of the settling of pollutant particles, seeds, and pollen.
    Print ISSN: 1687-806X
    Electronic ISSN: 1687-8078
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 7
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    Formulation of the Settling Velocity of Small Particles Initially Situated inside an Inclined Vortex (2016)
    Hindawi
    Details
    Publication Date: 2016-01-01
    Description: Both the estimation of the time that small heavy particles remain inside a 3D vortex and the estimation of the average settling velocity of those particles are some important features in many practical situations. Previous works focused on the case of a horizontal 2D vortex. In this paper, we simulate the dynamics of heavy particles initially situated inside a three-dimensional vortex obtaining a formula for their average settling velocity. In a previous paper we obtained the trajectories of the particles and a formula that provides the time that they need to escape,Te⁎. This work simulates and analyses the escape process, and its main result is the obtaining, from numerical simulation, of a theoretical formulation of the average settling velocityVz⁎and its relationship with the elapsed time. We prove that the permanence time is of the order ofdp⁎-10(withdp⁎particle diameter) and that the average settling velocity is of the order ofTe⁎-1/5for sufficiently small particles. Some applications of the settling velocity formula developed in this work would be the design of mixture devices, the design of particle separation devices, and the prediction of the settling of pollutant particles, seeds, and pollen.
    Print ISSN: 1687-806X
    Electronic ISSN: 1687-8078
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Hindawi
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  • 8
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    Development of Pogo Pin-Based Holding and Release Mechanism for Deployable Solar Panel of CubeSat (2019)
    Hindawi
    Details
    Publication Date: 2019
    Description: CubeSats are revolutionary to the space industry and are transforming space exploration which enables the next generation of scientists and engineers to complete all phases of space missions. Deployable solar panels have been widely used for the generation of enough power in CubeSats due to their limited volume area for solar cell integration. In general, the cable cutting release mechanism have been used in 1U-3U small satellites because of its simplicity and low cost. However, this mechanism has a low constraint force and is unable to apply constraints along the in-plane and out-of-plane directions. In this study, for the improvement of the conventional cable cutting mechanism, a spring-loaded pogo pin-based nichrome burn wire holding and release mechanism (HRM) was proposed and fabricated. The pogo pin constitutes an immensely attractive function for the holding and release mechanism of solar panels because it works as an electrical interface to provide power, a separation spring to initiate the reaction force to deploy the panels, and a status switch to determine deployments. In addition, the proposed mechanism guarantees the loading capability along the in-plane and out-of-plane directions of solar panels, the synchronous release of multiple panels, and a handling simplicity that differentiates it from the conventional mechanism. The design feasibility, structural safety, and reliability of the mechanism were verified through functionality tests and launch and on-orbit environmental tests. The proposed pogo pin-based holding and release mechanism would be equally applicable for other CubeSat deployable appendages.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
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    Development of Pogo Pin-Based Holding and Release Mechanism for Deployable Solar Panel of CubeSat (2019)
    Hindawi
    Details
    Publication Date: 2019-05-05
    Description: CubeSats are revolutionary to the space industry and are transforming space exploration which enables the next generation of scientists and engineers to complete all phases of space missions. Deployable solar panels have been widely used for the generation of enough power in CubeSats due to their limited volume area for solar cell integration. In general, the cable cutting release mechanism have been used in 1U-3U small satellites because of its simplicity and low cost. However, this mechanism has a low constraint force and is unable to apply constraints along the in-plane and out-of-plane directions. In this study, for the improvement of the conventional cable cutting mechanism, a spring-loaded pogo pin-based nichrome burn wire holding and release mechanism (HRM) was proposed and fabricated. The pogo pin constitutes an immensely attractive function for the holding and release mechanism of solar panels because it works as an electrical interface to provide power, a separation spring to initiate the reaction force to deploy the panels, and a status switch to determine deployments. In addition, the proposed mechanism guarantees the loading capability along the in-plane and out-of-plane directions of solar panels, the synchronous release of multiple panels, and a handling simplicity that differentiates it from the conventional mechanism. The design feasibility, structural safety, and reliability of the mechanism were verified through functionality tests and launch and on-orbit environmental tests. The proposed pogo pin-based holding and release mechanism would be equally applicable for other CubeSat deployable appendages.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Hindawi
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  • 10
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    Structural Design and Impact Analysis of Deployable Habitat Modules (2018)
    Hindawi
    Details
    Publication Date: 2018
    Description: Space-deployable habitat modules provide artificial habitable environments for astronauts and will be widely used for the construction of future space stations and lunar habitats. A novel structural design concept of space-deployable habitat modules consisting of flexible composite shells and deployable trusses has been proposed. Geometric relationships of deployable trusses based on two types of scissor elements were formulated. Flexible composite shells of space habitat modules were designed, and a nonlinear FEA model using ANSYS software was described. Considering folding efficiencies, stiffness, and strength of the structures, the influences of design parameters were analyzed and the final design scheme of space-deployable habitat modules was determined. After detailing the structural designs, low-speed impact dynamic responses between the structures and a stainless steel cylinder were simulated. The analysis results show that dynamic responses are only significant at the point of low-speed impact. The works will provide technical supports for structural designs and engineering applications of space-deployable habitat modules.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Hindawi
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