| 1. |
- Liu, G.Q., et al.
(författare)
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Naphthenic acid corrosion characteristic and corrosion product film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum gas oil
- 2016
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Ingår i: Corrosion Engineering, Science and Technology. - 1478-422X .- 1743-2782. ; 51:6, s. 445-454
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Tidskriftsartikel (refereegranskat)abstract
- Although naphthenic acid corrosion (NAC) has been studied for many years, the mechanism of NAC is not fully understood. The objective of this paper is to study high-temperature NAC in secondary vacuum gas oil of an industrial crude oil vacuum distillation tower. A high-temperature autoclave was applied to conduct high-temperature corrosion test to investigate NAC behaviour of carbon steel and Cr5Mo low alloy steel at different sulphur contents and total acid numbers (TAN). The result shows that the corrosion rate of carbon steel and low alloy steel is high at low TAN and high TAN while it keeps at a low value at medium TAN. Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr7S8 film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN which are strange and different from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward.
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| 2. |
- Liu, X. H., et al.
(författare)
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High-temperature X-ray diffraction studies on polyamide6/clay nanocomposites upon annealing
- 2002
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Ingår i: Polymer Bulletin. - : Springer Science and Business Media LLC. - 0170-0839 .- 1436-2449. ; 48:05-apr, s. 381-387
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Tidskriftsartikel (refereegranskat)abstract
- The influence of nanodispersed clay on the alpha crystalline structure of polyamide 6 (PA6) was examined in-situ with X-ray diffraction (XRD) between room temperature and melting. In pure PA6 upon annealing the alpha crystalline phase was substituted by an unstable pseudohexagonal phase at 150degreesC, then it transformed into a new stable crystalline structure - high temperature alpha' phase above the transition temperature. However, in PA6/clay nanocomposite (PA6CN), the alpha phase did not present crystalline phase transition on heating. The increase in the annealing temperature only led to continuous intensity variation. The different behaviors were caused by the confined spaces formed by silicate layers, which constrained the mobility of the polymer chains in-between.
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| 3. |
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| 4. |
- Wang, Q.Z., et al.
(författare)
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The flattened Brazilian disc specimen used for testing elastic modulus, tensile strength and fracture toughness of brittle rocks : analytical and numerical results
- 2004
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 41:2, s. 245-253
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Tidskriftsartikel (refereegranskat)abstract
- The flattened Brazilian disc specimen is proposed for determination of the elastic modulus E, tensile strength sigma (sub t) and opening mode fracture toughness K (sub IC) for brittle rocks in just one test. This paper is concerned with the theoretical analysis as well as analytical and numerical results for the formulas. According to the results of stress analysis and Griffith's strength criteria, in order to guarantee crack initiation at the centre of the specimen, which is considered to be crucial for the test validity, the loading angle corresponding to the flat end width must be greater than a critical value (2alpha > or =20 degrees ). The analysis shows that, based on the recorded complete load-displacement curve of the specimen (the curve should include the "fluctuation" section after the maximum load), E can be determined by the slope of the section before the maximum load, sigma (sub t) by the maximum load, and K (sub IC) by the local minimum load immediately subsequent to the maximum load. The relevant formulas for the calculation of E, sigma (sub t) , K (sub IC) are obtained, and the key coefficients in these formulas are calibrated by finite-element analysis. In addition, some approximate closed-form formulas based on elasticity are provided, and their accuracy is shown to be adequate by comparison with the finite-element results.
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| 5. |
- Zhang, L., et al.
(författare)
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A nearly end-to-end deep learning approach to fault diagnosis of wind turbine gearboxes under nonstationary conditions
- 2023
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Ingår i: Engineering applications of artificial intelligence. - : Elsevier Ltd. - 0952-1976 .- 1873-6769. ; 119
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Tidskriftsartikel (refereegranskat)abstract
- Fault diagnosis of wind turbine gearboxes is crucial in ensuring wind farms’ reliability and safety. However, nonstationary working conditions, such as load change or speed regulation, may result in an accuracy deterioration of many existing fault diagnosis approaches. To overcome the issue, this research proposes a nearly end-to-end deep learning approach to fault diagnosis of wind turbine gearboxes using vibration signals. Concretely, we adopt Empirical Mode Decomposition (EMD) to decompose vibration signals into a series of Intrinsic Mode Functions (IMFs). Then, the multi-channel IMFs are fed into a 1D Convolutional Neural Network (CNN) for automatic feature learning and fault classification. Since EMD is a signal processing technique requiring no prior knowledge, the model architecture can be viewed as nearly end-to-end. The proposed approach was validated in a real-world dataset; it proved deep learning models have an overwhelming advantage in representation capacity over traditional shallow models. It also demonstrated that the introduction of EMD as a preprocessing step improves both the training efficiency and the generalization ability of a deep model, thus leading to a better fault diagnosis efficacy under variable working conditions.
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| 6. |
- Zhang, Zhibo, et al.
(författare)
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Application and Challenge of Ionic Liquids as Co-solvent for Electro-enzymatic Conversion of CO2 to Methanol
- 2021
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Ingår i: Proceedings of the Chinese Society of Electrical Engineering. - : Chinese Society for Electrical Engineering. - 0258-8013. ; 41:11, s. 3657-3665
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Tidskriftsartikel (refereegranskat)abstract
- Utilization of carbon dioxide (CO2) has attracted great research interests, because CO2 is both a typical greenhouse gas and renewable carbon resource. This review mainly summarized and reviewed the research work linked to the challenges in the enzymatic conversion of CO2, such as NADH regeneration and low CO2 conversion efficiency. Based on the summary on the electro-enzymatic conversion of CO2, ionic liquids for the enzymatic conversion of CO2, and ionic liquids for the electrochemical conversion of CO2, we suggested applying ionic liquids as co-solvent in the enzymatic conversion of CO2 to methanol and coupling it with the reduction of NAD+ to NADH by electrocatalysis, providing a novel pathway for producing methanol from CO2.
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| 7. |
- Lethuillier, A., et al.
(författare)
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Cometary dust analogues for physics experiments
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 515:3, s. 3420-3438
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Tidskriftsartikel (refereegranskat)abstract
- The CoPhyLab (Cometary Physics Laboratory) project is designed to study the physics of comets through a series of earth-based experiments. For these experiments, a dust analogue was created with physical properties comparable to those of the non-volatile dust found on comets. This ‘CoPhyLab dust’ is planned to be mixed with water and CO2 ice and placed under cometary conditions in vacuum chambers to study the physical processes taking place on the nuclei of comets. In order to develop this dust analogue, we mixed two components representative for the non-volatile materials present in cometary nuclei. We chose silica dust as a representative for the mineral phase and charcoal for the organic phase, which also acts as a darkening agent. In this paper, we provide an overview of known cometary analogues before presenting measurements of eight physical properties of different mixtures of the two materials and a comparison of these measurements with known cometary values. The physical properties of interest are particle size, density, gas permeability, spectrophotometry, and mechanical, thermal, and electrical properties. We found that the analogue dust that matches the highest number of physical properties of cometary materials consists of a mixture of either 60 per cent/40 per cent or 70 per cent/30 per cent of silica dust/charcoal by mass. These best-fit dust analogue will be used in future CoPhyLab experiments.
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| 8. |
- Li, Fangfang, et al.
(författare)
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Combination of CO2 electrochemical reduction and biomass gasification for producing methanol : A techno-economic assessment
- 2024
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Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 307
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Tidskriftsartikel (refereegranskat)abstract
- Combining CO2 electrochemical reduction (CO2R) and biomass gasification for producing methanol (CH3OH) is a promising option to increase the carbon efficiency, reduce total production cost (TPC), and realize the utilization of byproducts of CO2R system, but its viability has not been studied. In this work, systematic techno-economic assessments for the processes that combined CO2R to produce CO/syngas/CH3OH with biomass gasification were conducted and compared to stand-alone biomass gasification and CO2R processes, to identify the benefits and analyze the commercialization potential of different pathways under current and future conditions. The results demonstrated that the process that combined biomass gasification with CO2R to CO represents a viable pathway with a competitive TPC of 0.39 €/kg-CH3OH under the current condition. For all the combined cases, electricity usage for CO2R accounts for 36–76% of total operating cost, which plays a key role for TPC. Sensitivity analysis confirmed that the process that combined biomass gasification with CO2R to CO is sensitive to the price of electricity, while both CO2R performance and prices of stack and electricity are important for the processes that combined with CO2R to syngas/CH3OH.
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| 9. |
- Zhang, Z., et al.
(författare)
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Electromagnetic wave-based analysis of laser–particle interactions in directed energy deposition additive manufacturing
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- A modified heat-source model based on electromagnetic wave theory was proposed to investigate the interactions between powder particles and a laser beam, considering the spatial distribution of particles inside the beam. The absorption of energy by these particles in laser directed energy deposition additive manufacturing was calculated using the proposed model, which was validated experimentally. Both numerical model and experiment were used to study the effects of powder velocities on the temperature variations in the additive manufacturing process. Results indicate that the direct heat transfer from the laser to a target can be increased if the size distribution is wider; it also increases with the velocity of the particles. However, with the increase of powder-flow rate, the rate of mass transfer decreases the heat transfer. Melt-pool depth in melting and re-melting processes can therefore be controlled by varying these parameters.
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| 10. |
- Zhang, Z.X., et al.
(författare)
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A feasibility study on controlling ground vibrations caused by blasts in Malmberget underground mine
- 2010
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Ingår i: Fragblast. - : Informa UK Limited. - 1385-514X .- 1744-4977. ; 8:1, s. 3-21
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Tidskriftsartikel (refereegranskat)abstract
- In order to control or reduce the ground vibrations caused by underground blasts in Malmberget mine, a number of blast tests were carried out during production blasts and a series of single shot waveforms were obtained. Then the single shot waveforms from the same ring or different rings were analysed and compared with each other. The results showed that the single shots are reproducible, meaning that the ground vibrations caused by underground blasts can be controlled by means of the interference of the vibration waveforms measured. Finally, a formal test using electronic detonators and employing an optimum delay time of 8 ms was done in production. The test for an 11-borehole ring shows that the maximum vertical ground vibrations are reduced to the maximum vertical vibrations of a single shot. Particularly, the total vibration history for the 11-borehole-ring blast is shortened to about 200 ms over a velocity of 2 mm/s. However, the total vibration history of a normal production blast of 11-borehole ring is always 1400 ms over a velocity of 2 mm/s, namely the total vibration time of a production blast can be reduced to one seventh of that of the common production blasts by using the vibration control method. This indicates that the vibration control method introduced in the paper is feasible for underground mining blasts.
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