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Andrej Lotrič Mihael Sekavčnik Igor Kuštrin Mitja Mori 《International Journal of Hydrogen Energy》2021,46(16):10143-10160
We present the results of a life-cycle assessment (LCA) for the manufacturing and end-of-life (EoL) phases of the following fuel-cell and hydrogen (FCH) technologies: alkaline water electrolyser (AWE), polymer-electrolyte-membrane water electrolyser (PEMWE), high-temperature (HT) and low-temperature (LT) polymer-electrolyte-membrane fuel cells (PEMFCs), together with the balance-of-plant components. New life-cycle inventories (LCIs), i.e., material inputs for the AWE, PEMWE and HT PEMFC are developed, whereas the existing LCI for the LT PEMFC is adopted from a previous EU-funded project. The LCA models for all four FCH technologies are created by modelling the manufacturing phase, followed by defining the EoL strategies and processes used and finally by assessing the effects of the EoL approach using environmental indicators. The effects are analysed with a stepwise approach, where the CML2001 assessment method is used to evaluate the environmental impacts. The results show that the environmental impacts of the manufacturing phase can be substantially reduced by using the proposed EoL strategies (i.e., recycled materials being used in the manufacturing phase and replacing some of the virgin materials). To point out the importance of critical materials (in this case, the platinum-group metals or PGMs) and their recycling strategies, further analyses were made. By comparing the EoL phase with and without the recycling of PGMs, an increase in the environmental impacts is observed, which is much greater in the case of both fuel-cell systems, because they contain a larger quantity of PGMs. 相似文献
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Mihael Mohor
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Ale vigelj Gorazd Kandus Markus Werner 《International Journal of Satellite Communications and Networking》2002,20(2):97-120
This paper addresses the performance evaluation of adaptive routing algorithms in non‐geostationary packet‐switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network‐uniform source/destination distribution model and a uniform source–destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri‐like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Bostjan Jurisevic Karl Kuzman Mihael Junkar 《The International Journal of Advanced Manufacturing Technology》2006,31(1-2):18-23
This exploratory paper aims to introduce a high-speed Water Jet (WJ) as a tool for die-less Incremental Sheet Metal Forming (ISMF). First experiments indicate that in the case of Water Jet Incremental Sheet Metal Forming (WJISMF) the forming time, energy efficiency and forming accuracy are rather poor compared to ISMF with a rigid tool. However, the proposed technology brings higher process flexibility and better tools to workpiece interface conditions. For a better process characterization, the relative jet diameter is introduced, which is defined as the ratio between the WJ diameter and the blank thickness. Relevant process parameters are identified and technological windows are phenomenological defined, shoving that WJISMF can be applied as a complementary solution to ISMF with a rigid tool. 相似文献
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Joško Valentinčič Mihael Junkar 《The International Journal of Advanced Manufacturing Technology》2006,28(3-4):294-301
To achieve high removal rate and low electrode wear in sinking electrical discharge machining process (EDM), rough machining
parameters have to be selected according to the size of the eroding surface. In general, the size of the eroding surface varies
according to the depth of the machining. Thus, it has to be determined on-line. This paper shows that the electric current
signal in the gap depends on the size of the eroding surface. The significance of the process attributes of the electric current
signal is established by inductive machine learning and the general decision rules are derived. The size of the eroding surface
can be detected on-line by monitoring and evaluating the electric current signal in the gap. 相似文献
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Kambiz Mehrabi Mihael Brun?ko Albert C. Kneissl Miodrag ?oli? Dragoslav Stamenkovi? Janko Fer?ec Ivan An?el Rebeka Rudolf 《Metals and Materials International》2012,18(3):413-417
NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-K?? radiation at room temperature. 相似文献
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Bioaccumulation of mercury in benthic communities of a river ecosystem affected by mercury mining 总被引:3,自引:0,他引:3
Zizek S Horvat M Gibicar D Fajon V Toman MJ 《The Science of the total environment》2007,377(2-3):407-415
The presence of mercury in the river Idrijca (Slovenia) is mainly due to 500 years of mercury mining in this region. In order to understand the cycling of mercury in the Idrijca ecosystem it is crucial to investigate the role of biota. This study is part of an ongoing investigation of mercury biogeochemistry in the river Idrijca, focusing on the accumulation and speciation of mercury in the lower levels of the food chain, namely filamentous algae, periphyton and macroinvertebrates. Mercury analysis and speciation in the biota and in water were performed during the spring, summer and autumn seasons at four locations on the river, representing different degrees of mercury contamination. Total (THg) and methyl mercury (MeHg) were measured. The results showed that the highest THg concentrations in biota correlate well with THg levels in sediments and water. The level of MeHg is spatially and seasonally variable, showing higher values at the most contaminated sites during the summer and autumn periods. The percentage of Hg as MeHg increases with the trophic level from water (0.1-0.8%), algae (0.5-1.3%), periphyton (1.6-8.8%) to macroinvertebrates (0.1-100%), which indicates active transformation, accumulation and magnification of mercury in the benthic organism of this heavily contaminated torrential river. 相似文献
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Zorka Novak Pintarič Mihael Kasaš Zdravko Kravanja 《American Institute of Chemical Engineers》2013,59(8):2862-2871
A solution strategy for designing flexible process flow sheets with a large number of uncertain parameters is presented. The basic mathematical formulation is a two‐stage stochastic program transformed into its multi‐scenario deterministic equivalent. The main feature of the proposed approach is a tremendous reduction in scenarios to a smaller number of those critical ones. This reduction is achieved through simple sensitivity analyses that identify those uncertain parameters that are critical for feasibility and those that are involved in a stochastic approximation of the objective value. Through the application of this strategy, it is possible to solve the problems with several tens or even hundred uncertain parameters, assuming weak interactions between them. Feasible designs are obtained for a fixed degree of flexibility, while the expected objective function is approximated fairly well. The strategy is applied to two flow sheet examples. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2862–2871, 2013 相似文献
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Introduction of laminated supporting tools in water jet incremental sheet metal forming 总被引:1,自引:1,他引:0
Bostjan Jurisevic Viktor Sajn Franc Kosel Mihael Junkar 《The International Journal of Advanced Manufacturing Technology》2008,37(5-6):496-503
This contribution presents the introduction of laminated supporting tools in water jet incremental sheet metal forming (WJISMF)
process. In WJISMF the main tool is a high-velocity water jet (WJ) instead of a rigid tool. The influence of the main tool
trajectory on the forming outcome in WJISMF is observed and optimized in order to reduce the forming time and improve the
product quality. Laminated tools are fabricated with abrasive water jet (AWJ) machining from aluminium plates of different
thicknesses. The parts formed in this investigation are measured with a coordinate measuring machine (CMM) and results are
compared by means of forming time, parts symmetry and achieved geometry, which is defined with the supporting tool. 相似文献