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  • Zardari, Muhammad Auchar, et al. (författare)
  • Numerical Analysis of Staged Construction of an Upstream Tailings Dam
  • 2014
  • Ingår i: Proceedings of 1st National Conference on Civil Engineering (NCCE 2013-14) : (Modern Trends and Advancements). - Quest Nawabshah, Pakistan : Department of Civil Engineering, Quest Nawabshah, Pakistan. ; s. 150-160
  • Konferensbidrag (refereegranskat)abstract
    • A case study is presented in this paper which describes finite element analysis of staged construction of the upstream tailings dam Aitik, located in north of Sweden. The purpose of the study is to evaluate stability of the dam for current and future raisings and to strengthen the dam with optimum volume of rockfill banks on the downstream side when stability of the dam is not satisfactory during a construction stage. The finite element method was utilized to model the consolidation process and stability of the dam during the staged construction. The study has shown that stability of the dam during raisings was reduced due to build-up of excess pore pressures. Therefore, the dam was strengthened with rockfill banks on the downstream side to carry out the construction of the dam at a planned rate of raising. An optimization analysis was performed in order to reduce the volume of the rockfill necessary for stabilizing the dam. With the use of the finite element based optimization approach discussed in this paper, stability of the dams during staged construction can be enhanced by utilizing a minimum volume of rockfill banks.
  • Zardari, Muhammad Auchar (författare)
  • Stability of tailings dams focus on numerical modelling
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Upstream tailings dams may experience slope stability problems when the rate of raising is too fast. Tailings consolidate slowly due to low hydraulic conductivity. The excess pore pressures can build up due to accelerated rate of raising. The cumulative increase in excess pore pressures due to successive raisings can endanger slope stability of a tailings dam. The stability of a tailings dam is closely related to the consolidation process. The consolidation process and associated stability of an upstream tailings dam during staged construction was modelled with the finite element program PLAXIS. The analysis indicated that the stability of the dam reduced during raising due to increase of excess pore pressures. The safety of the dam was improved by adding rockfill banks on the downstream side. The volume of the rockfill banks was minimized with an optimization technique. This technique involves (i) construction of a rockfill bank on the downstream side when the factor of safety is less than a permissible limit, (ii) utilization of a minimum volume of the rockfill that is necessary to stabilize the slope. This technique can be practicable when the rate of raising is moderate, and partial consolidation occurs between consecutive raisings. Numerical analysis was also performed on a curved embankment of an upstream tailings dam in order to investigate the possible risk of hydraulic fracturing and internal erosion in a corner of the dam. The analysis showed that low compressive stresses occurred above the phreatic level, near the zones of filter and rockfill banks. These zones contain coarse material, and are, therefore, not susceptible to hydraulic fracturing and internal erosion. An increase in the radius of the corner is suggested in order to prevent large reductions in compressive stresses that may occur due to future raisings. Presently the curved dam section is stable. However, an additional rockfill bank on the downstream side will be required for future raisings. Static liquefaction is considered as a common cause of disastrous flow failures of tailings dams. These flow failures can be predicted with numerical modelling using suitable constitutive models. In this context, some constitutive models capable of simulating static liquefaction behaviour of loose saturated sands are reviewed. It is generally concluded that the finite element method can be a helpful tool for modelling stability of tailings dams.
  • Zarshenas, Mohammad, et al. (författare)
  • Molecular Dynamics Simulations of Hydrocarbon Film Growth from Acetylene Monomers and Radicals : Effect of Substrate Temperature
  • 2018
  • Ingår i: The Journal of Physical Chemistry C. - American Chemical Society (ACS). - 1932-7447. ; 122:27, s. 15252-15263
  • Tidskriftsartikel (refereegranskat)abstract
    • In an attempt to rationalize the mechanisms occurring during plasma polymerization of acetylene, classical molecular dynamics (MD) computer simulations investigating the deposition and reaction of a mixed gas of acetylene molecules and radicals on the Ag(111) substrate were performed for a wide range of substrate temperatures. Prior to that, this article establishes a methodology for film deposition and identifies the appropriate potentials for hydrocarbons by comparison with electronic calculations using the density functional theory (DFT). Based on this preliminary study, simulations of films growth are carried out at different temperatures using the REBO potential. Our results show that the rates of creation of new C-C and C-H bonds are higher at the beginning of the film growth when the substrate is still exposed, than when it is covered with polymeric chains, and these initial reaction rates are proportional to temperature. The analysis of the hybridization of carbon atoms in the films shows that the substrate temperature increase leads to the formation of coatings containing more carbon atoms in the sp2 and sp3 configurations and less in the sp configuration with sp2 becoming dominant at high temperatures. We establish a polymerization-connectivity formalism that describes the structural transformation of the film during the deposition on the basis of each atom hybridization and bonding. Within this formalism the evolution of the polymerization and the connection character of the polymers is observed and discussed.
  • Zaslavsky, Arkady, et al. (författare)
  • Aiding wireless intrusion detection and response with context-awareness
  • 2004
  • Ingår i: M-business 2004 : the next waves - major opportunities and the essential lessons ; the Third International Mobile Business Conference (ICMB) ; July 12 - 13, 2004, Roosevelt Hotel, NYC. - New York : Institute for Technology and Enterprise, Polytechnic University. - 918902533
  • Konferensbidrag (refereegranskat)
  • Zaslavsky, Arkady, et al. (författare)
  • Context-aware mobile medical emergency management decision support system for safe transportation
  • 2009
  • Ingår i: 2009 International Conference on DSS : Reflecting on Yesterday, Assessing Today, Envisioning Tomorrow.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Management of safe and successful large-scale events requires detailed careful planning and complex system-wide decision making . However, research into medical emergency knowledge management for just-in-time decision support in mass gatherings lags behind the needs of the community. Unforeseen circumstances, dynamic changes in the environment, various unexpected impact factors require immediate real-time adequate response that can be achieved mainly through context-aware, intelligent and cost-efficient functionality of the systemContext-awareness relates to building an appropriate and relevant model of the surrounding environment (Zaslavsky, 2002). Road system, traffic accidents, congestion, knowledge of individual vehicles, as well as emergency vehicles are all important part of such a model. Context includes information about road infrastructure, data gathered from sensor networks, and other sources of context.We propose to combine mobile communication technologies with pervasive computing techniques which will facilitate and enable effective context-aware decision support for medical emergency management in mass gatherings while ensuring road safety. For example, some intelligent transportation systems can be added to the underlying infrastructure for timecritical decision making in emergency situations. We aim to develop and test a prototype mobile decision support system for improving transportation safety during medical emergency in mass gatherings. The prototype will utilise the medical emergency management ontology, which was developed based on extensive review of the relevant literature and with consultation with industry (Sujanto, et al, 2007).We will report on the project, which capitalizes on smart information use and will be of great benefit to making better transportation decisions in mass gatherings emergency management. This research will result in gaining a clearer understanding of the nature and requirements of road safety in medical emergency during mass gathering events. We propose to build and test a mobile real time decision support tool for improving efficiency of transportation decisions. Such tools will strengthen ability to manage potential health- related hazards in real-time and on the move.ReferencesSujanto, F., Ceglowski, A., Burstein, F., and Churilov, L. (2008). 'An integrated framework for comprehensive collaborative emergency management'. In P. Zarate, J. P. Belaud, G. Camilleri & F. Ravat (Eds.), Collaborative Decision Making: Perspectives and Challenges (pp. 127-138). Amsterdam, Netherlands: IOS Press.Zaslavsky A (2002) Adaptability and Interfaces: Key to Efficient Pervasive Computing, NSF Workshop series on Context-Aware Mobile Database Management, Brown University, Providence, 24-25 Jan, 2002
  • Zaslavsky, Arkady (författare)
  • Mobile agents: can they assist with context awareness?
  • 2004
  • Ingår i: Proceedings : 2004 IEEE International Conference on Mobile Data Management : 19 - 22 January 2004, Berkeley, California. - Los Alamitos, Calif : IEEE Computer Society Press. - 0-7695-2070-7 ; s. 304-305
  • Konferensbidrag (refereegranskat)abstract
    • This position paper argues that the mobile agents paradigm is a useful and important technology enabling pervasive and ubiquitous computing. Context awareness drives adaptability of pervasive computing systems. It is asserted that mobile agents capable of discovering, extracting, interpreting and validating context will make significant contribution to increasing efficiency, flexibility and feasibility of pervasive computing systems.
  • Zaslavsky, Arkady, et al. (författare)
  • Mobile computing overview and current status
  • 1998
  • Ingår i: Journal of Research and Practice in Information Technology. - 1443-458X. ; 30:2, s. 42-52
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years, mobile computing has become the focus of vigorous research efforts in various areas of computer science and engineering. These areas include wireless networking, distributed systems, operating systems, - distributed databases, software engineering, applications development, just to name a few. This paper introduces the conceptual overview of mobile computing, its achievements, challenges and opportunities. The current status and ongoing research projects in mobile computing worldwide are detailed. This paper also discusses the two Australian workshops on mobile computing, databases and applications held in 1996 and 1997
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