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| 3. |
- Davoodi, Ali, et al.
(författare)
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Developing an AFM-Based SECM system; Instrumental setup, SECM simulation, characterization, and calibration
- 2008
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 155:8, s. C474-C485
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Tidskriftsartikel (refereegranskat)abstract
- An integrated atomic force microscopy/scanning electrochemical microscopy (AFM/SECM) system was developed as an in situ local electrochemical probing technique. It consists of a dual-mode probe acting as an AFM cantilever and SECM microelectrode to simultaneously obtain the topography and electrochemical current map of the same area. Two types of probes with different geometries were used. The scan velocity and concentration profile of the redox mediator during the scan were simulated, using the equations of convection-diffusion mass transport coupled with continuity and momentum in three dimensions under steady-state and transient conditions. The temporal and spatial resolutions of the probes were investigated. It was found that, during a normal scan rate (around 1 Hz), the effect of convective transport is negligible and the SECM lateral resolution depends on the geometrical parameters. With favorable geometry, a probe with a Pt microelectrode of 1 mu m diameter can distinguish two active sites with a distance of at least 3-4 mu m. The paper also reports experiments for characterization and calibration of the AFM/SECM system. Concurrent AFM and SECM images obtained on a gold band calibration sample verify the high-resolution capability of the SECM of one or a few micrometers with optimized conditions.
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| 4. |
- Abolhasani, Hasanali, et al.
(författare)
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Development of self-healable acrylic water-based environmental-friendly coating as an alternative to chromates coatings
- 2023
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Ingår i: Progress in organic coatings. - : Elsevier B.V.. - 0300-9440 .- 1873-331X. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- In this study, different coating systems, including solvent-based epoxy and water-based acrylic resins, were evaluated for their potential as an alternative to chromate coatings in order to avoid Cr(VI) toxic hazards. The resins were used as either pigment-free coatings or were formulated with 20-wt% zinc/aluminum pigments. The coatings were subsequently applied on galvanized ST12 steel plates and their corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) evaluations. The effect of the binder and pigment type on the impact resistance of two different polymeric coatings was also evaluated. The results of impact tests revealed completely peeled film from the substrate for epoxy coatings. However, under the same experimental conditions, very few small cracks were created in water-based acrylic coatings for both pigmented and pigment-free cases. In addition, some other parameters such as drying time and coating cost were taken into account to select a good alternative to chromate coatings. The results of this work can facilitate the introduction of an inexpensive environmentally friendly acrylic coating as a promising self-healing alternative to chromate coating.
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| 5. |
- Davoodi, Ali, 1984, et al.
(författare)
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Analysis of Screening Performance using Discrete Element Modeling
- 2017
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Ingår i: Proceedings of the Conference in Minerals Engineering. ; 2017
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Konferensbidrag (refereegranskat)abstract
- Screening is an important process in size classification of granular materials. It is a complex process due to the collision between particles and also a number of different operational parameters that effect the screening process. The aim of this paper is to evaluate screening performance in one of the LKAB crushing platforms. In this work an industrial vibration screen has been simulated by using Discrete Element Method (DEM). The simulations were validated with data from experiments and the screening performance has been analyzed by changing the parameters such as feeding rate. The result shows that DEM simulation is an effective tool for understanding the process of screening and because of the contact model between individual particles and particles and geometries the result is comparable with real process. It is shown that by increasing the feeding rate to 100 ton/h the screening efficiency can be improved by 20 percent.
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| 6. |
- Davoodi, Ali, 1984, et al.
(författare)
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Application of the Discrete Element Method to Study the Effects of Stream Characteristics on Screening Performance
- 2019
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Screening is a key operation in a crushing plant that ensures adequate product quality of aggregates in mineral processing. The screening process can be divided into the two sub-processes of stratification and passage. The stratification process is affected by the relative difference between various properties, such as particle shape, size distribution, and material density. The discrete element method (DEM) is a suitable method for analyzing the interactions between individual particles and between particles and a screen deck in a controlled environment. The main benefit of using the DEM for simulating the screening process is that this method enables the tracking of individual particles in the material flow, and all of the collisions between particles and between particles and boundaries. This paper presents how different particle densities and flowrates affect material stratification and, in turn, the screening performance. The results of this study show that higher density particles have a higher probability of passage because of their higher stratification rate, which increases the probability that a particle will contact the screen deck during the process.
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| 7. |
- Davoodi, Ali, 1984, et al.
(författare)
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DEM Modelling and Simulation of Banana Screen Classification Efficiency
- 2015
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Ingår i: Minerals Engineering. - 0892-6875.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Banana screens are popular and frequently used in minerals processing. The screens are characterized by a high separation capacity and low maintenance need. The operation of screening usually takes place after crushing operation. The banana screens have multiple panels with variable slope which enables the feed material to flow rapidly resulting in a high screening rate. The difference between banana screens and other screens is that in banana screens the screen cut size varies with the changing slope of the decks. There are a number of factors affecting the screening operation; the deck panel slope progression, screen deck material, aperture shape, vibrational motion, open area, thickness of deck, feed rate and material properties.The aim of this paper is to simulate the screening performance by using the Discrete Element Method (DEM) and to analyse different motions that affect screening operation efficiency. Three decks with different slopes have been used and two different motions, linear and elliptical, have been evaluated at one feed rate. Figure 1 shows the overview of DEM simulation of screening process. Design of Experiment (DoE) has been used to evaluate the factors that control the value of parameters. The results show that the classification efficiency can be evaluated by conventional comparison between the feed particle size distribution and each of the product streams. The resolution of the model also enables the calculation of a critical efficiency criteria position along the screen deck. This position can be used to define a screening robustness factor. The passage probability and stratification behaviour can also be evaluated.
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| 8. |
- Davoodi, Ali, 1984
(författare)
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DEM Modelling of Vibratory Screens
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden, about 100 million tons of aggregate is used for road, railway, and concrete every year. Crushing is the main process for producing aggregate material in different fractions. The production process is divided into two sub-processes: comminution or size reduction and classification. The vibratory screen is one of the separation machines used to make a final separation to produce the products based on a grade or a size range. In an industry where logistics plays an important role, the transport of unnecessary materials can be costly and it is therefore critical to screen these materials before transporting them. Industrial vibratory screens are costly and also have a substantial effect on the quality of the final product. Therefore, selecting the correct vibratory screen for the crushing plant at the outset results in a better return on investment and better quality products. The main aim of this research is to understand the screening process in different conditions such as different particle size distribution (PSD) and different feed rates. The first step towards achieving the screening model is to understand the influence of different machine parameters and material properties in the screening performance. Some of these parameters have been studied in this research, such as the motion type, the material of the screen media, and the aperture shape. The Discrete Element Method (DEM) has been used to study these parameters with the idea that by using DEM simulation the particle-to-particle and particle-to-geometry interaction can be studied in a way that is impossible to achieve by real experiments. The study results show that some of the factors have a greater influence on screening, such as the effect of the motion type for the different slope of the deck. Elliptical motion is more efficient compared to linear motion. Also, the aperture shape in different parts of the screen deck has a different effect when using a single-layer or multi-layer material in the feeding point. The result of this research needs further investigation to study the effect of the interaction between different factors before achieving the complete screen model. Another achievement of this research work is to investigate the validation of DEM modelling in screening performance by using a laboratory-scale vibratory screen.
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| 9. |
- Davoodi, Ali, 1984, et al.
(författare)
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DEM simulation of banana screen performance
- 2015
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Ingår i: Proceedings, ;Minerals Engineerings Conference Physical Separation 2015 June 11-12...
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Banana screening is an important size classification component. The screens are characterized by a high capacity for separation. The operation of screening usually takes place after crushing operation. The shape of the banana screens causes the feed material to flow rapidly and the result will be faster screening rate. The difference between banana screens and other screens is that in banana screens the screen cut size varies with the changing slope of the decks. There are number of factors that affect screening operation like inclination of discharge, open area, thickness of deck and feed rate.The aim of this paper is to simulate the screener deck with the help of DEM Simulation and to analyze different parameters that affect screener operation efficiency and optimizing the screener so that it has the best performance during the wear life of the screen media. The one deck banana screen are simulated, the result show when the value of deck thickness and deck slope increase the probability of particles passage through the apertures will be decrease.
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| 10. |
- Davoodi, Ali, 1984
(författare)
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Discrete Element Modelling and Simulation of Vibratory Screens
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden about 85 million tonnes aggregate is used for road, railway and concrete every year. Crushing is the main process for producing the aggregate material in different fractions. The crushing process is divided into two sub-processes; comminution and separation. The vibratory screen is one of the separation machines used to make a final separation to produce the products based on a grade or a size range. In an industry where logistics play an important role, the transport of unnecessary materials can be costly and it therefore becomes critical to screen these materials before transporting them. Industrial vibratory screens are costly and also have a substantial effect on the quality of the final product. Therefore, selecting the correct vibratory screen from the beginning for the crushing plant results in a better return on investment and better quality products. The main hypothesis of this research is to find the screen model and to understand the screening process in different conditions such as different particle size distribution (PSD) and different feed rate. The first step towards achieving the screening model is to understand the influence of different machine parameters and material properties in screening performance. Some of these parameters have been studied in this research such as motion type, the material of the screen deck and the aperture shape. Discreet Element Method (DEM) has been used to study those parameters with the idea that by using DEM simulation the interaction of particle to particle and particle to geometry can be studied in a way which is difficult to attain by real experiments. The study results show some of these factors have a larger influence on screening such as a effect of motion type for different slope of deck. The elliptical motion is more efficient compared to linear motion. And also, the aperture shape in different parts of the screen deck has a different effect based on single layer material or multiple layer material in the feeding point. The result of this research needs further investigation in order to study the effect of interaction between different factors before achieving the complete screen model.
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