196746 research outputs found
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Waste Heat Recovery and Exergy-Based Comparison of a Conventional and a Novel Fuel Cell Integrated Gas Turbine Hybrid Configuration
No full textIn conventional gas-turbine cycles, a significant amount of heat is generated and gets unutilized, which results in lower thermal efficiency and higher exergy destruction. In this study, the available waste heat from the gas-turbine has been examined, considering the promising ways to utilize this waste heat. By integrating a waste heat recovery system, these losses can be overcome, and its exergy destruction can be minimized, and results in higher thermal efficiency. For this, a novel comparison has been made between simple gas-turbine without waste heat recovery, recuperated gas-turbine with single-stage recovery, and a solid oxide fuel cell recuperated gas-turbine with double-stage waste heat recovery hybrid system in terms of energy, exergy efficiency and exergy destruction. Using MATLAB, a detailed thermodynamic modelling has been done. The finding shows that a two-stage waste heat recovery system helps in reducing the temperature gradient at the inlet of fuel-cell, which makes the system more stable. At a pressure ratio of 10 and turbine inlet temperature 1250 K, maximum energy and exergy efficiency have been achieved for the proposed hybrid system, i.e., 65.33% and 61.639%, respectively. The waste heat recovery for recuperated gas-turbine is 119.462 kW, and for solid oxide fuel cell gas-turbine, is 1153.885 kW
Controlling the microbial competition between hydrogenotrophic methanogens and homoacetogens using mass transfer and thermodynamic constraints
No full textThe reduction of CO2 allows the synthesis of platform molecules for the chemical and energy industry. Anaerobic microbial consortia contain homoacetogenic microorganisms (HAC) capable of reducing CO2 to acetate. However, one of the obstacles to their use is the understanding and management of their functional diversity. In particular, managing the competition between HAC and hydrogenotrophic methanogens (HM) that convert CO2 into methane is crucial to selectively produce acetate.This study contributes to bring new knowledge on the competition between HAC and HM. This microbial competition is encountered in numerous anaerobic systems, and it is necessary to know how to manage it. In this sense, mass transfer between the gas phase where the substrates are located, and the liquid phase which contains the microbial catalysts, as well as kinetic and thermodynamic aspects of biological reactions have been integrated in this work. The microbial competition between HM and HAC was studied in successive batches. The effect of temperature between 25 °C and 35 °C was investigated, as well as different states of mass transfer limitation in the system.A clear effect of temperature between 25 °C and 35 °C on the outcome of the competition between HM and HAC was highlighted, as well as the effect of mass transfer limitation. Enrichment of Acetobacterium homoacetogens and elimination of hydrogenotrophic methanogens was possible at 25 °C without mass transfer limitation. Acetate product selectivity was of 100% by the end of the enrichment period in successive batches. On the contrary, under mass transfer limitation, and/or at 35 °C, Methanobacterium hydrogenotrophic methanogens were promoted with 100% of methane selectivity by the end of the enrichment. This study contributes to identify specific process parameters influencing the selection of HAC over HM and should help in the design of experiments depending on the target product from H2/CO2. Furthermore, the results obtained could be applied to continuous acetate producing systems, at a larger scale, and they can also be useful in other gas fermentation systems and processes.</p
Luminescence dating of anthropogenic deposits from Tall Zarʿa in the Jordan Valley
No full textThis study uses quartz-based optically stimulated luminescence dating to determine when a massive fortification wall (W11186) was constructed in the archaeological site of Tall Zarʿa in the Jordan Valley. A total of 11 samples of sediments were taken from a trench on the north side of the wall (extramuros). The extracted quartz grains had good luminescence characteristics and were identified as well bleached by comparison with feldspar infrared-stimulated luminescence (IRSL) ages. The optical ages showed that the deposition against the wall occurred in two different periods. The first was around 3.20 ± 0.07 ka ago (Iron Age), and the second was around 2.28 ± 0.08 ka (Hellenistic period). Human activity was evident because of the intermixing of cultural material with the presumed naturally deposited units.</p
A hybrid study of a 4-stage compressed solar distiller based on experimental, computational and deep learning methods
No full textIn the present study, a hybrid technique is employed to demonstrate the thermal performance of a 4-stage compressed solar distiller with hydrophilic evaporators (CSDHE) regarding the role of natural convection in the air gap domain. Initially, the test is conducted under simulated solar radiation of 2.13 W·m−2 over 5400 s. A thermodynamic model incorporating diffusion is developed for the next step to analyze internal transient temperatures. In the third step, a 3D single-phase natural convection model of the CSDHE is simulated to achieve the research objectives. Based on experimental, thermal modeling, and computational results, a dual deep neural network is developed to predict the thermal behavior of the system and the variation of convection heat transfer coefficient for different air gap thicknesses over 10,000 s. The experimental results revealed a distilled water production rate of 3.806 kg·m−2h−1 with a gained output ratio (GOR) of 112 %. Moreover, the findings demonstrate that conduction accounts for 84.23 % of total heat transfer, while convection accounts for 6.36 % during 5400 s. We also found that, by employing a convolutional neural network (CNN) and directly harvesting data from pre-defined contours, the hybrid training dataset for deep forward neural network (DFNN) is trained 28.35 % faster than conventional methods.</p
Fabrication and characterization of food-grade pea protein-ascorbic acid nanoparticles-stabilized Pickering emulsion
No full textIn this study, modified pea proteins (PP) were prepared by heat treatment, ultrasound, adjusting the pH to 9, and the addition of ascorbic acid (AA) to stabilize the Pickering emulsion (PE) with a 50% volume fraction of corn oil. The solubility of PP after different treatments was higher in all treatments than in the native state. FTIR and SDS-PAGE results confirmed that a covalent bond (Maillard reaction) was formed between PP and AA, which occurred more strongly in the heat-treated suspensions. The nanoparticles produced from ultrasonication of PP and the PP/AA complexes were able to stabilize the emulsion with a high volume fraction of oil as novel Pickering emulsifiers. In ultrasonicated PP and PP/AA complexes, the reduction of interfacial tension and particle size and increase of contact angle caused a significant improvement in the physical stability of the PE, which can be the result of regular placement of protein particles at the water-oil interface. The treatment corresponds to highly stable PE, heat-treated PP in the presence of AA in alkaline conditions (HPP.AA.pH), increased the contact angle of PP from ∼ 42 to 77, and decreased interfacial tension from ∼ 25 to 14. These PEs showed high physical and oxidative stability. According to CLSM images, the type of PE was oil in water, and PP particles surrounded the oil droplets. The results of this research could be effective in developing PP-based low-fat formulations with improved oxidative stability by utilizing different treatments, including ultrasonic treatment and/or complex formation between PP and AA
Novel light-sheet scattering microscopy for voxel-wise validation of 3D-fibre orientations in murine white matter
No full textThis work develops a novel 3D validation technique that reveals the white matter orientation with micron resolution in cleared murine brains. Light-sheet elastic scattering microscopy (LSSM) can be used to exploit the scattering signal exhibited by white matter fibres, which is dependent on their orientation. The rotation and imaging of the sample yield a scattering profile, which corresponds to that of infinitely long cylinders. Our work combines two orthogonal acquisitions to voxel-wise reconstruct 3D-fibre orientations in large brain volumes. LSSM could be the definitive validation method for diffusion MRI orientation methods
Does window/door opening behaviour during summer affect the bedroom environment and sleep quality in a high-density sub-tropical city
No full textTo investigate the effects of window and/or door opening on sleep quality, a two-week field intervention study was performed in 50 bedrooms in the summer in a high-density city (Shanghai). Each participant slept as they did normally in their own bedroom during the first week and changed the state of windows or doors from open to closed or vice versa in the second week. Their bedroom environment and sleep quality were objectively measured. Available data from 256 person-nights in which the intervention was effective were used for analysis of window or door manipulation. The indoor carbon dioxide (CO2) concentrations were lower and the air temperatures and PM2.5 concentrations were higher when windows were open. The perceived air freshness and noise intensity were both higher and the duration of REM-sleep (Rapid Eye Movement sleep) was lower in this condition. No significant differences were found in other sleep quality indexes. These results suggest that in a high-density city, the increased indoor temperature, PM2.5 concentration as well as noise caused by opening windows may disturb sleep and offset the positive effects of improving the ventilation. Thus, window opening should not be recommended as a universal way of achieving bedroom ventilation to promote sleep. Affordable retrofit solutions for bedroom ventilation should take these aspects into account
A benchmark for Monte Carlo simulations in gamma-ray spectrometry Part II:True coincidence summing correction factors
No full textThe goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage
UAV-borne near-surface geophysics:Application of electromagnetic and magnetic sensor systems for surveying archaeological structures and anthropogenic metal contaminants.
No full textIntegrated biogas upgrading and medium-chain fatty acids production for more efficient resource recovery
No full textThe conversion of carbon dioxide (CO2) from biogas into medium-chain fatty acids (MCFAs) represents an eco-friendly resource recovery approach to reduce dependence on fossil fuels and combat global climate change. This study presented the novel concept of integrated resource recovery by coupling biogas upgrading and MCFAs production for the first time. Initially, the impact of different initial ethanol concentrations on chain elongation was examined, determining that an ethanol concentration of 160 mmol/L maximized MCFAs yield at 45.7 mmol/L. Subsequently, using this optimal ethanol supply, the integrated strategy was implemented by connecting two bioreactors in series and maintaining continuous operation for 160-day. The results were noteworthy: upgraded bio-methane purity reached 97.6 %, MCFAs production rate and carbon-flow distribution reached 24.5 mmol/L d-1 and 76.1 %, respectively. In summary, these promising outcomes pioneer a resource recovery approach, enabling the high-value utilization of biogas and the conversion of CO2 into valuable bio-chemicals