| 1. |
- Ahmadi, R., et al.
(författare)
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Rapid determination of Bond rod-mill work index by modeling the grinding kinetics
- 2013
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 24:1, s. 441-445
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Tidskriftsartikel (refereegranskat)abstract
- Generally, Bond work index is a common method for selecting comminution equipment as well as estimation of grinding efficiency and calculating required power. In the current research, a simple, fast and accurate procedure is introduced to find the rod-mill work index based on the conventional Bond work index. The grinding experiments were carried out on four typical samples of iron, copper, manganese and lead–zinc ore with three test-sieves in specified time periods and aimed to shortening the procedure. Furthermore, the grinding kinetics and mass balance equations were applied to model the standard Bond rod-mill work index. For comparing the standard Bond rod-mill work index and the new modeled method, work index (Wi) and produced fine particles in a cycle (Gi) for the four samples determined. The performed paired Student’s t-test results indicated that the Standard Deviation for Gi and Wi obtained by the shortened method are respectively 0.50 and 0.58 in respect of traditional Bond method.
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| 2. |
- Karim, M.R., et al.
(författare)
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Modelling of Maintenance Data
- 2016
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Ingår i: Current Trends in Reliability, Availability, Maintainability and Safety. - Cham : Encyclopedia of Global Archaeology/Springer Verlag. - 9783319235967 - 9783319235974 ; , s. 409-424
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Konferensbidrag (refereegranskat)abstract
- The modelling of maintenance data starts with the black-box approach (where the model selection is based solely on the maintenance data) and then through the grey-box approach for proper analysis (where one can gain insights to build better models). These models allow for more effective maintenance of the object. This paper deals with the grey-box approach to modelling. It discusses the process of modelling and illustrates this through a real case study
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| 3. |
- Lopes, Julio C.O., et al.
(författare)
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Optmization In Performance-Based Logistics Contracts
- 2017
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Ingår i: Proceedings of MPMM 2016. - Luleå : Luleå tekniska universitet. - 9789175838410 ; , s. 133-138
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Konferensbidrag (refereegranskat)abstract
- Performance-based Logistics (PBL) contracts require metrics and methodologies set in a systemic way to provide readiness for the warfighter at reasonable costs. There must be a clever and verifiable connection of metrics in order to access and analyze data and to deliver sound and consistent inputs for the entire support system to accomplish its goals. A system of incentives and penalties usually takes place and suggests functions to be maximized and/or minimized in a multi-criterion and highly integrated environment. This study deals with the optimization of the entire setup of Performance-Based Logistics contracts and is limited to a preliminary study in a simple scenario that has showed a promises results. A mixed method, using both the Ɛ-Constraint and Goal Programming is proposed to model the case. Results indicate that metrics used for reliability, maintainability, availability and supportability (RAMS) and costs can be optimized simultaneously for clever contracts.
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| 4. |
- Muniruzzaman, Muhammad, et al.
(författare)
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Weathering of unsaturated waste rocks from Kevitsa and Hitura mines : Pilot-scale lysimeter experiments and reactive transport modeling
- 2021
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Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental understanding of hydrogeochemical processes leading to toxic drainage in mining environments is of utmost importance to predict the impact of mining activities in waste facilities and to design effective measures for the mitigation of environmental risk. This study investigates the weathering behavior of different types of mine waste rocks, with considerably different mineralogical and textural properties, by performing long-term (> 3 years) pilot-scale lysimeter experiments combined with multiphase and multicomponent reactive transport modeling. The experiments were carried out in a series of five lysimeter setups, packed with unsaturated waste rocks collected from the Kevitsa and Hitura mine sites in Finland, under the influence of outdoor atmospheric conditions. We focus on the temporal dynamics of the waste rock effluents’ chemistry showing remarkably different compositions in different experiments. The low-sulfide containing Kevitsa pyroxene and Hitura serpentinite waste rocks lead to alkaline drainage, characterized by higher pH (up to 9.5) and lower dissolved constituents (e.g., up to 420 mg/L SO4, 89 μg/L Ni). In contrast, the effluents from the Hitura mica schist waste rocks, which have relatively higher sulfide abundance, show characteristics of acidic drainage with lower pH (∼4.3) and orders of magnitude higher aqueous concentrations (e.g., up to 3100 mg/L SO4, 130 mg/L Ni). The results also show that the presence of a higher fraction of finer particles leads to a faster dissolution rate and thus relatively higher drainage concentrations. The experimental results were quantitatively interpreted with multiphase and multicomponent reactive transport modeling, which allowed capturing the complex dynamic trends and the concentration levels observed in the effluents of the different pilot-scale lysimeters.
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| 5. |
- Murthy, D.N.P, et al.
(författare)
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Data management in maintenance outsourcing
- 2015
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Ingår i: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 142, s. 100-110
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Tidskriftsartikel (refereegranskat)abstract
- Most businesses view maintenance as tasks carried out by technicians and the data collected is mostly cost related. There is a growing trend towards outsourcing of maintenance and the data collection issues are not addressed properly in most maintenance service contracts. Effective maintenance management requires proper data management - data collection and analysis for decision-making. This requires a proper framework and when maintenance is outsourced it raises several issues and challenges. The paper develops a framework for data management when maintenance is outsourced and looks at a real case study that highlights the need for proper data management.
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| 6. |
- Parsaei, S., et al.
(författare)
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Effect of test-caused degradation on the unavailability of standby safety components
- 2024
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Ingår i: Nuclear engineering and technology. - : Elsevier. - 1738-5733 .- 2234-358X. ; 56:2, s. 526-535
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a safety-critical standby component unavailability model that contains aging effects caused by the elapsed time from installation, component degradation due to surveillance tests, and imperfect maintenance actions. An application of the model to a Motor-Operated Valve and a Motor-Driven Pump involved in the HPIS of a VVER/1000-V446 nuclear power plant is demonstrated and compared with other existing models at component and system levels. In addition, the effects of different unavailability models are reflected in the NPP's risk criterion, i.e., core damage frequency, over five maintenance periods. The results show that, compared with other models that do not simultaneously consider the full effects of degradation and maintenance impacts, the proposed model realistically evaluates the unavailabilities of the safety-related components and the involved systems as a plant age function. Therefore, it can effectively reflect the age-dependent CDF impact of a given testing and maintenance policy in a specified time horizon.
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