► Increasing HTF inlet parameters can improve PCTES performance. ► The inlet parameters restrict each other for the rated solar collector. ► The PCTES performance can be effectively enhanced by ...enhanced tubes. ► The pressure drops caused by the enhanced tubes could almost be neglected.
Based on enthalpy method, numerical studies were performed for high temperature molten salt phase change thermal energy storage (PCTES) unit used in a dish solar thermal power generation system. Firstly, the effects of the heat transfer fluid (HTF) inlet temperature and velocity on the PCTES performance were examined. The results show that although increasing the HTF inlet velocity or temperature can enhance the melting rate of the phase change material (PCM) and improve the performance of the PCTES unit, the two parameters will restrict each other for the fixed solar collector heat output. Then three enhanced tubes were adopted to improve the PCTES performance, which are dimpled tube, cone-finned tube and helically-finned tube respectively. The effects of the enhanced tubes on the PCM melting rate, solid–liquid interface, TES capacity, TES efficiency and HTF outlet temperature were discussed. The results show that compared with the smooth tube, all of the three enhanced tubes could improve the PCM melting rate. At the same working conditions, the melting time is 437.92min for the smooth tube, 350.75min for dimpled tube which is reduced about 19.9% and 320.25min for cone-finned tube which is reduced about 26.9% and 302.75min for helically-finned tube reduced about 30.7%. As a conclusion, the thermal performance of PCTES unit can be effectively enhanced by using enhanced tube instead of smooth tube. Although, the HTF pressure drops for the enhanced tubes are also larger than that of the smooth tube, the largest pressure drop (1476.2Pa) is still very lower compared with the working pressure (MPa magnitude) of the dish solar generation system. So, the pressure drops caused by the enhanced tubes could almost be neglected.
Pure Cu was deformed at different strain rates and temperatures, i.e. with different Zener–Hollomon parameters (
Z) ranging within ln
Z
=
22–66, to investigate the effect of
Z on its microstructures ...and mechanical properties. It was found that deformation twinning occurs when ln
Z exceeds 30, and the number of twins increases at higher
Z. The average twin/matrix lamellar thickness is independent of
Z, being around 50
nm. Deformation-induced grain refinement is enhanced at higher
Z, and the mean transverse grain size drops from 320 to 66
nm when ln
Z increases from 22 to 66. The grain refinement is dominated by dislocation activities in low-
Z processes, while deformation twinning plays a dominant role in high-
Z deformation. An obvious increment in yield strength from 390 to 610
MPa was found in deformed Cu with increasing Z, owing to the significant grain refinement as well as the strengthening from nanoscale deformation twins.
► Based on the unstable solar radiation, a model was established for phase change process under unsteady boundary. ► The PCM melting time decreases with the initial inlet temperature increase under ...the same average inlet temperature. ► The melting time reduces about 51.9% with the initial inlet temperature increase from 30°C to 90°C. ► The melting time decreases with the initial inlet mass flow rate increase under the same average inlet mass flow rate. ► The melting time reduces about 36.5% with the initial inlet mass flow rate increase from 2.0
×
10
−4
kg/s to 8.0
×
10
−4
kg/s.
Due to the solar radiation intensity variation over time, the outlet temperature or mass flow rate of heat transfer fluid (HTF) presents non-steady-state characteristics for solar collector. So, in the phase change thermal energy storage (PCTES) unit which is connected to solar collector, the phase change process occurs under the non-steady-state inlet boundary condition. In present paper, regarding the non-steady-state boundary, based on enthalpy method, a two dimensional physical and mathematical model for a shell-and-tube PCTES unit was established and the simulation code was self-developed. The effects of the non-steady-state inlet condition of HTF on the thermal performance of the PCTES unit were numerically analyzed. The results show that when the average HTF inlet temperature in an hour is fixed at a constant value, the melting time (time required for PCM completely melting) decreases with the increase of initial inlet temperature. When the initial inlet temperature increases from 30
°C to 90
°C, the melting time will decrease from 42.75
min to 20.58
min. However, the total TES capacity in an hour reduces from 338.9
kJ/kg to 211.5
kJ/kg. When the average inlet mass flow rate in an hour is fixed at a constant value, with the initial HTF inlet mass flow rate increasing, the melting time of PCM decreases. The initial inlet mass flow rate increasing from 2.0
×
10
−4
kg/s to 8.0
×
10
−4
kg/s will lead to the melting time decreasing from 37.42
min to 23.75
min and the TES capacity of PCM increasing from 265.8
kJ/kg to 273.8
kJ/kg. Under all the studied cases, the heat flux on the tube surface increases at first, until it reaches a maximum then it decreases over time. And the larger the initial inlet temperature or mass flow rate, the earlier the maximum value appearance and the larger the maximum value.
Fecal microbiota transplantation (FMT) is effective in treating recurrent Clostridium difficile infection (CDI). Bacterial colonization in recipients after FMT has been studied, but little is known ...about the role of the gut fungal community, or mycobiota. Here, we show evidence of gut fungal dysbiosis in CDI, and that donor-derived fungal colonization in recipients is associated with FMT response. CDI is accompanied by over-representation of Candida albicans and decreased fungal diversity, richness, and evenness. Cure after FMT is associated with increased colonization of donor-derived fungal taxa in recipients. Recipients of successful FMT ("responders") display, after FMT, a high relative abundance of Saccharomyces and Aspergillus, whereas "nonresponders" and individuals treated with antibiotics display a dominant presence of Candida. High abundance of C. albicans in donor stool also correlates with reduced FMT efficacy. Furthermore, C. albicans reduces FMT efficacy in a mouse model of CDI, while antifungal treatment reestablishes its efficacy, supporting a potential causal relationship between gut fungal dysbiosis and FMT outcome.
Abstract
Using the observations of the high-energy detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 from 2017 to 2020, we search for hard X-ray tails in the X-ray ...spectra in ∼30–200 keV. The hard X-ray tails are found throughout the
Z
-track on the hardness–intensity diagram, and the detected hard X-ray tails become hard and weak from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra of Insight-HXMT between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows a high-energy cutoff, implying a hot corona in it, but the high-energy cutoff is not seen in the hard X-ray spectrum of Sco X-1. From fitting the broadband spectrum of Sco X-1 in ∼2–200 keV, it is proposed that the hard X-ray tails in the HB and NB can be explained by the overall Comptonization COMPTB model, suggesting that the hard X-ray tails could have resulted from the Comptonization of the photons from the neutron star (NS) surface by the thermal electrons in the region between the NS and the disk and the energetic electrons in the freefall toward the NS in the converging flow onto the NS. However, this model cannot be responsible for the hard X-ray tails in the FB. Further study on the FB hard X-ray tails is needed.
To evaluate the prevalence, awareness, treatment and control of hypertension and its risk factors in Dehui City of Jilin Province in China. The study was performed among 3778 subjects (male=1787) in ...Dehui City, Jilin Province of China. The subjects completed a standard questionnaire, biochemical tests and physical examinations. Logistic regression analyses were used to identify risk factors for hypertension. The prevalence of hypertension was 41.00% in this area. The awareness, treatment and the control of hypertension were 21.82, 15.56 and 1.10%, respectively, with city areas being significantly higher than rural areas. Significant risk factors for hypertension included age, sex, central obesity, alcohol consumption, family history of hypertension, dyslipidemia, education level and type of work. Further analysis showed that diabetes for urban participants and cigarette smoking for rural participants were risk factors but were not statistically significant at the multi-variate level. The prevalence of hypertension in Dehui Ctiy of Jilin Province is higher than in other areas of China. In addition, rates of awareness and treatment of the condition are much lower than in other populations, with the control rate only 1.10%.
ObjectiveAlthough COVID-19 is primarily a respiratory illness, there is mounting evidence suggesting that the GI tract is involved in this disease. We investigated whether the gut microbiome is ...linked to disease severity in patients with COVID-19, and whether perturbations in microbiome composition, if any, resolve with clearance of the SARS-CoV-2 virus.MethodsIn this two-hospital cohort study, we obtained blood, stool and patient records from 100 patients with laboratory-confirmed SARS-CoV-2 infection. Serial stool samples were collected from 27 of the 100 patients up to 30 days after clearance of SARS-CoV-2. Gut microbiome compositions were characterised by shotgun sequencing total DNA extracted from stools. Concentrations of inflammatory cytokines and blood markers were measured from plasma.ResultsGut microbiome composition was significantly altered in patients with COVID-19 compared with non-COVID-19 individuals irrespective of whether patients had received medication (p<0.01). Several gut commensals with known immunomodulatory potential such as Faecalibacterium prausnitzii, Eubacterium rectale and bifidobacteria were underrepresented in patients and remained low in samples collected up to 30 days after disease resolution. Moreover, this perturbed composition exhibited stratification with disease severity concordant with elevated concentrations of inflammatory cytokines and blood markers such as C reactive protein, lactate dehydrogenase, aspartate aminotransferase and gamma-glutamyl transferase.ConclusionAssociations between gut microbiota composition, levels of cytokines and inflammatory markers in patients with COVID-19 suggest that the gut microbiome is involved in the magnitude of COVID-19 severity possibly via modulating host immune responses. Furthermore, the gut microbiota dysbiosis after disease resolution could contribute to persistent symptoms, highlighting a need to understand how gut microorganisms are involved in inflammation and COVID-19.
AbstractFour shear-critical RC shear walls were tested under a tension-bending-shear load to replicate seismic behavior of the bottom shear wall in high-rise buildings. The axial tension ratio ranged ...from 0 to 0.5 and the aspect ratio was 1.06. The shear compression failure mode was observed for each specimen, characterized by the formation of an inclined crack at 45° and direct strut action. The shear displacement was a dominant deformation component throughout the loading history. When the axial tension force increased from 0 to 1,293 kN, the ultimate drift ratio increased from 0.90% to 2.38%, while shear capacity linearly decreased from 1,507 to 895 kN. The load–displacement curve showed a significant pinching effect and strength degradation effect. In addition, this paper reports an innovative experimental method to obtain shear resistance of transverse reinforcement (Vs) based on the plasticity theory and strain measuring result. Test results using this method show that not all horizontal distributed rebar yield simultaneously at the ultimate capacity. The US code-specified shear strength contribution of horizontal distributed rebar was found to be unsafe for each test specimen. Finally, a database of RC shear walls subject to combined tension-bending-shear load was established to evaluate shear strength formulas in design codes. The comparison showed the Chinese code predicted spuriously higher tension-shear capacity, while the US code predicted conservative capacity. Based on the developed database, a simplified design formula is proposed with adequate safety concerns and accuracy.
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