25 research outputs found

    The effects of supercritical CO2 on the seepage characteristics and microstructure of water-bearing bituminous coal at in-situ stress conditions

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    CO2 geological storage (CGS) is considered to be an important technology for achieving carbon peak and carbon neutralization goals. Injecting CO2 into deep unminable coal seams can achieve both CGS and enhance coalbed methane (ECBM) production. Therefore, the deep unminable coal seams are considered as promising geological reservoirs. CO2 exists in a supercritical CO2 (ScCO2) when it was injected into deep unminable coal seams. The injection of ScCO2 can induce changes in the seepage characteristics and microstructure of deep water-bearing coal seams. In this study, typical bituminous coal from Shenmu, Shanxi Province was used to investigate the effects of ScCO2 on seepage characteristics, pore characteristics, and mineral composition through experiments such as seepage tests, low-temperature liquid nitrogen adsorption, and X-ray diffraction (XRD). The results indicate that ScCO2 treatment of dry and saturated coal samples caused a significant increase in clay mineral content due to the dissolution of carbonates, leading to the conversion of adsorption pores to seepage pores and an improvement in seepage pore connectivity. Therefore, the Brunauer-Emmett-Teller (BET) specific surface area and pore volume of the two coal samples both decreased after ScCO2 treatment. Moreover, the permeability of dry and saturated coal samples increased by 191.53% and 231.71% at 10 MPa effective stress respectively. In semi-saturated coal samples, a large amount of dolomite dissolved, leading to the precipitation of Ca2+ and CO32- to form calcite. This caused pore throats to clog and macropores to divide. The results show that the pore volume and average pore size of coal samples decrease, while the specific surface area increases after ScCO2 treatment, providing more space for gas adsorption. However, the pore changes also reduced the permeability of the coal samples by 32.21% and 7.72% at effective stresses of 3 MPa and 10 MPa, respectively. The results enhance our understanding of carbon sequestration through ScCO2 injection into water-bearing bituminous coal seams

    Particle-hole asymmetric superconducting coherence peaks in overdoped cuprates

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    To elucidate the superconductor to metal transition at the end of superconducting dome, the overdoped regime has stepped onto the center stage of cuprate research recently. Here, we use scanning tunneling microscopy to investigate the atomic-scale electronic structure of overdoped trilayer Bi-2223 and bilayer Bi-2212 cuprates. At low energies the spectroscopic maps are well described by dispersive quasiparticle interference patterns. However, as the bias increases to the superconducting coherence peak energy, a virtually non-dispersive pattern with sqrt(2)*sqrt(2) periodicity emerges. Remarkably, the position of the coherence peaks exhibits evident particle-hole asymmetry which also modulates with the same period. We propose that this is an extreme quasiparticle interference phenomenon, caused by pairing-breaking scattering between flat anti-nodal Bogoliubov bands, which is ultimately responsible for the superconductor to metal transition.Comment: 15 pages, 4 figure

    Feel data: Public data visualization as a medium to motivate data donation

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    In our everyday activities, trackers and IoT devices are recording an increasing amount of data in the wild. It is believed that incorporating these data will contribute to more inclusive products and services as well as stimulate designers' creativity. As a result of the General Data Protection Regulation, users can now access their data and take the control of its usage. Under such circumstances, one can freely donate personal data for research purposes. Moreover, users have the opportunity to utilize their data more efficiently and to be aware of the importance of their privacy. This project is about exploring how an effective public data visualization could be designed to encourage more people to donate personal data at the very beginning of the data collection process, with a limit on the amount of data that may be manipulated. Students who are not experts in data visualization are the target audience. And the brightspace platform is chosen since it is the simplest and most convenient way for students to receive faculty notifications. As data visualization outcomes and people's willingness to donate data vary depending on the type of data, according to the research insights, this project focuses exclusively on public photo visualizations. A series of two design iterations was conducted in order to leverage the intrinsic motivation of students to donate photos of their home working environment to be used for research purposes. This project explores motivation from the perspective of self-determination theory, and proposes criteria and design directions for designing photo visualizations for behavior change purpose. In this study, the author identified five fundamental needs, including autonomy, competence, connectedness, purpose, and stimulation in order to evaluate data visualization's effects on the intimate data donation experience. Autonomy: Donors should feel free to choose the type of photos they want to donate. Their photos can also be used to express themselves creatively. Competence: Users should feel their photos are needed for the visualization. Relatedness: Users could feel connected with the visualization platform as they explored or interacted with it. Additionally, they believe they could build relationships by donating photos. Purpose: Users believe that donating their photos is meaningful to themselves or to researchers who require them. Stimulation: The way to ask for their donation is novel. And the entire experience with this visualization platform is enjoyable and interesting.Through the study of three types of photo visualization, it was discovered that whether the visualization is explanation dominant or exploration dominant has an impact on users' willingness and results in varying types of photo donations. Further, design directions for effective self-determined public photo visualization in terms of information, function, and visual form were synthesized as a starting point for more future data visualization projects to motivate autonomous data donation behavior.Design for Interactio

    Quick Decision-Making for Close-Boiling Distillation Schemes

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    Separating close-boiling components using distillation is very common in industry. Considering the higher capital and energy intensity of the task, schematic selection of optimal distillation strategies becomes a significant decision of both industrial and methodological importance. In this sense, this paper introduces a reliable shortcut method of simplicity and robustness for optimizing the target of total annualized cost (TAC). In detail, selective analyses are carried out among four schematic candidates for three close-boiling systems. The schemes are conventional distillation column, mechanical vapor recompression (MVR), double-effect distillation, and distillation with a recycle process. The mixtures to be separated are methyltrichlorosilane/dimethylchlorosilane, methylcyclopentane/cyclohexane, and isobutanol/<i>n</i>-butanol. After the first round evaluation, hydraulic calculations through rigorous simulations are worked out to size the equipment, which is necessary for TAC analyses. In the second round comparison, MVR stands out to be a more attractive option for close-boiling separations than other configurations

    Effect of Different Compatibilizers on the Properties of Poly (Lactic Acid)/Poly (Butylene Adipate-Co-Terephthalate) Blends Prepared under Intense Shear Flow Field

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    In this report, poly(lactic acid) (PLA) and Poly(butylene adipate-co-terephthalate) (PBAT) with three kinds of compatibilizers were melt blended under intensive shear flow. A self-made parallel three-screw extruder was developed to generate such flow during the process. Mechanical properties, chemical reactions among PLA, PBAT and compatibilizers, rheological behavior and morphology were investigated. The mechanical tests showed that the notched impact strength of super-tough composite with 10 wt% EGMA is about 20 times than that of pure PLA. The Fourier transform infrared spectroscopy (FT-IR) results showed that the epoxy functional groups or maleic anhydride functional groups of KT-20, KT-915 and EGMA reacted with the hydroxyl groups of PLA or PBAT macromolecules, resulting in a bridge of PLA and PBAT. About rheological properties, the tan &delta;&mdash;angular frequency curves and the &eta;&rsquo;&rsquo;- &eta;&rsquo; curves confirmed the chemical reactions mentioned above and indicated better compatibility of &eta;&rsquo;&rsquo;- &eta;&rsquo; between PLA and PBAT, respectively. Meanwhile, the loss modulus and storage modulus&mdash;angular frequency curves demonstrated the discrepancy of different compatibilizer components. In particular, from scanning electron microscopy (SEM) images, it can be seen that the phase size and dispersion uniformity of PBAT adjusted by compatibilizer, corresponding to better compatibility that is described in the &eta;&rsquo;&rsquo;- &eta;&rsquo; curves. The approach for producing super-tough PLA/PBAT/compatibilizer by intensive shear flow provides a viable direction for further improving PLA performance

    Research on Rotary Parts Vibration Suppression Based on Coaxiality Measurement and Unbalance Constraint

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    To suppress the vibration of rotary parts, this paper established an unbalanced vibration response control model of rotary parts based on rotating axis coordinate system. This model considered the stacking transformation of geometric parameter errors and mass parameter errors of single stage rotor. First of all, the centroid transfer model based on the actual rotation axis was established, and the unbalanced excitation force vector of each stage of the rotor was studied. Secondly, the unbalanced excitation force vector of each stage of the rotor is substituted into the model of assembly vibration control based on the double constraints optimization strategy. Finally, the simulation analysis and the vibration experiment of three-stage rotor stacking assembly is carried out. The results show that the vibration of the engine rotor can be effectively suppressed by adjusting the assembly phase of the rotors, and the vibration amplitude of the combined rotor assembled by the double constraint optimization assembly strategy is 22.5% less than the vibration amplitude assembled by the direct assembly strategy. Besides, the coaxiality and the unbalance are reduced by 44.1% and 78.4%, which fully shows the advantages of the double constraint optimization assembly strategy