5,852 research outputs found
Multiphase gas in the circumgalactic medium: relative role of and density fluctuations
We perform a suite of simulations with realistic gravity and thermal balance
in shells to quantify the role of the ratio of cooling time to the free-fall
time () and the amplitude of density perturbations
() in the production of multiphase gas in the circumgalactic
medium (CGM). Previous idealized simulations, focussing on small amplitude
perturbations in the intracluster medium (ICM), found that cold gas can
condense out of the hot ICM in global thermal balance when the background
. Recent observations suggest the presence
of cold gas even when the background profiles have somewhat large values of
. This partly motivates a better understanding of
additional factors such as large density perturbations that can enhance the
propensity for cooling and condensation even when the background is high. Such large density contrasts can be seeded by
galaxy wakes or dense cosmological filaments. From our simulations, we
introduce a condensation curve in the - min space, that defines the threshold for condensation of
multiphase gas in the CGM. We show that this condensation curve corresponds to
applied to the overdense
blob instead of the background for which can be
higher. We also study the modification in the condensation curve by varying
entropy stratification. Steeper (positive) entropy gradients shift the
condensation curve to higher amplitudes of perturbations (i.e., make
condensation difficult). A constant entropy core, applicable to the CGM in
smaller halos, shows condensation over a larger range of radii as compared to
the steeper entropy profiles in the ICM.Comment: 17 pages, 14 figures, 2 tables, the version accepted in MNRA
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Self-Sorting Microscale Compartmentalized Block Copolypeptide Hydrogels
Multicomponent interpenetrating network hydrogels possessing enhanced mechanical stiffness compared to their individual components were prepared via physical mixing of diblock copolypeptides that assemble by either hydrophobic association or polyion complexation in aqueous media. Optical microscopy analysis of fluorescent-probe-labeled multicomponent hydrogels revealed that the diblock copolypeptide components rapidly and spontaneously self-sort to form distinct hydrogel networks that interpenetrate at micron length scales. These materials represent a class of microscale compartmentalized hydrogels composed of degradable, cell-compatible components, which possess rapid self-healing properties and independently tunable domains for downstream applications in biology and additive manufacturing
Liquid gating elastomeric porous system with dynamically controllable gas/liquid transport
【Abstract】The development of membrane technology is central to fields ranging from resource harvesting to medicine, but the existing designs are unable to handle the complex sorting of multiphase substances required for many systems.
Especially, the dynamic multiphase transport and separation under a steady-state applied pressure have great
benefits for membrane science, but have not been realized at present. Moreover, the incorporation of precisely
dynamic control with avoidance of contamination of membranes remains elusive. We show a versatile strategy
for creating elastomeric microporous membrane-based systems that can finely control and dynamically modulate
the sorting of a wide range of gasesandliquids underasteady-stateapplied pressure,nearlyeliminate fouling,and
can be easily applied over many size scales, pressures, and environments. Experiments and theoretical calculation
demonstrate the stability of our system and the tunability of the critical pressure. Dynamic transport of gas and
liquid can be achieved through our gating interfacial design and the controllable pores’ deformation without
changing the applied pressure. Therefore, we believe that this system will bring new opportunities for many applications, such as gas-involved chemical reactions, fuel cells, multiphase separation, multiphase flow, multiphase microreactors, colloidal particle synthesis, and sizing nano/microparticles.This work was supported by the National Natural Science
Foundation of China (grant no. 21673197), the Young Overseas High-level Talents Introduction
Plan, the 111 Project (grant no. B16029).
研究工作得到国家自然科学基金委(项目批准号:21673197)和厦门大学校长基金(项目批准号:20720170050)等资助与支持
The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics
The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future
Multiphase Stirred Tank Bioreactors – New Geometrical Concepts and Scale‐up Approaches
Mainly with respect to biotechnological cases, current developments in the field of impeller geometries and findings for multistage configurations with a specific view on aerated stirred tanks are reviewed. Although often the first choice, in the given case the 6‐straight blade disc turbine is usually not the best option. Furthermore, quantities usable for scale‐up, specifically applicable in this field are discussed. Only quantities taking local conditions into account appear to be able to actually compare different stirrer types and scales.DFG, 56091768, TRR 63: Integrierte chemische Prozesse in flüssigen MehrphasensystemenDFG, 315464571, Interaktion der mechanischen Beanspruchung und der Produktivität von biologischen Agglomeraten in RührfermenternDFG, 256647858, Stoffübergang von aufsteigenden Blasen in reagierenden FlüssigphasenTU Berlin, Open-Access-Mittel - 201
Petrophysical and rock physics analyses for characterization of complex sands in deepwater Niger delta, Nigeria
Characterization of complex sand reservoirs in deepwater of Niger Delta was carried out through petrophysical and rock physics evaluation of well log data from three wells. Petrophysical analysis to determine clay volume, porosity, lithologies and hydrocarbon saturation were made. Rock physics was studied in velocity-porosity plane to analyze the influence of depositional and diagenetic features on the reservoirs. Cross-plots of different elastic parameters, using linear regression and cluster analysis, were generated for lithologic and fluid fill identification and to differentiate between the hydrocarbon bearing sands, brine sands and shale. Variance attribute was extracted on seismic time slice in order to image the complex sand distribution in the area. Three reservoirs of turbidite origin were identified within the upper fan to lower fan area. Petrophysical results revealed gas bearing reservoir units with less than 20% shale volume and porosity of 25-31%. Lambda-Mu-Rho (LMR) cross-plots for the reservoirs show gas saturated data cloud and trend. Ratio-Difference (R-D) cluster analysis of elastic rock properties shows a distinct trend and data cloud that represents lithofacies units and fluid fills. The study concludes that the reservoirs simulated contact cement and friable models with properties that ranged from highly porous, well sorted and poorly consolidated sand to fairly sorted and highly cemented sands. The results provide a model that increases the possibility of finding reservoir sand, while mitigating the risk involved in finding hydrocarbons
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