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•V2O5/PEDOT electrodes reach high steady-state capacity without activation processes.•PEDOT coated V2O5 reaches 380 mA⋅h⋅g−1 at 0.3 A⋅g−1 and 344 mA⋅h⋅g−1 at 1 A⋅g−1.•PEDOT layer ...enhances the properties of the electrode, compared to pristine V2O5.
Vanadium(V) oxide was coated by poly(3,4-ethylenedioxythiophene) (PEDOT) by chemical oxidation of EDOT. The obtained composite (V2O5/PEDOT) was studied as cathode material for aqueous zinc-ion batteries. V2O5/PEDOT electrodes demonstrate excellent electrochemical performance in the (0.3–1.4) V (vs. Zn/Zn2+) potential range in comparison to electrodes based on the pristine V2O5. V2O5/PEDOT material provides high specific capacity 380 mA⋅h⋅g−1 at 0.3 A⋅g−1, improved C-rate capability (274 mA⋅h⋅g−1 and 102 mA⋅h⋅g−1 at 5 A⋅g−1 and 20 A⋅g−1, and better stability during long-term cycling (7% capacity fading during 200 cycles at 5 A⋅g−1).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A search for sub-GeV dark matter production mediated by a new vector boson A′, called a dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in ...an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×1011 electrons on target no evidence of such a process has been found. The most stringent constraints on the A′ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new ...particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a (s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a (s) → γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a (s) decays downstream of the HCAL. This method allows for the probing of the a (s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84 × 10 11 electrons on target, allowing us to set new limits on the a(s)γγ -coupling strength for a (s) masses below 55 MeV.
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•Convection velocities and temperature are determined in evaporating droplets.•Convective flows in water droplets may reduce their heating times several-fold.•Convection velocities ...increase during rapid evaporation of droplet.•The number of vortices in a droplet, size and location mostly depend on heat flux.•The growth of evaporation rate is limited to the droplet surface temperature.
Today, requirements to the resource efficiency of power plants are becoming increasingly stringent, but hardware limitations are still there. The scientific community keeps searching for the ways to intensify heat and mass transfer and phase transitions in many applications of heat and power industry, such as heaters, economizers, cooling towers, heat carriers based on flue gases, water vapors and droplets, superheaters, etc. The answer might be in the potential (or latent) reserves in the energy performance indicators of heat and mass transfer processes. One of the relevant and understudied fields is high-temperature evaporation of droplets of water and water-based emulsions, slurries, and solutions in a gas environment. Using optical methods and cross-correlation software and hardware systems, unparalleled experimental data have been obtained lately on temperature fields as well as heating and evaporation rates of liquid droplets. These experimental data provided the basis for the first models of high-temperature vaporization. However, convective flows in rapidly heated and evaporating water droplets remain unstudied. In this research, we study experimentally the macroscopic laws of convective flows forming in evaporating water droplets exposed to high-temperature (up to 500 °C) heating in a gas environment. We use Planar Laser-Induced Fluorescence and Particle Image Velocimetry for high-speed recording of temperature and velocity of liquids (droplets, films, and aerosols). Series of experiments show how long it normally takes a practically homogeneous temperature field to form in an evaporating water droplet. We also determine how water droplet heating and evaporation rates differ if there are convective flows in a droplet. Average and maximum velocities of these flows are calculated and features of vortex structures are identified, such as their location, dimensions, number, etc. Dependences are obtained of maximum convection velocities in droplets on the temperature and velocity of the incoming heated air flow as well as on the droplet size. The resulting experimental database will help develop advanced models of high-temperature droplet heating and evaporation. The results of the experimental research are processed to determine the dominating processes of heat and mass transfer in the droplets and in their near-surface steam-gas layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
For the first time, the effect of asymmetry of the membrane transport was studied for organic solvents and solutes upon their nanofiltration through the plasma-modified membranes based on ...poly(1-trimethylsilyl-1-propyne) (PTMSP). Plasma treatment is shown to provide a marked hydrophilization of the hydrophobic PTMSP surface (the contact angle of water decreases from 88 down to 20°) and leads to the development of a negative charge of −5.2nC/cm2. The XPS measurements prove the formation of the oxygen-containing groups (Si–O and C–O) due to the surface modification. The AFM images show that the small-scale surface roughness of the plasma-treated PTMSP sample is reduced but the large-scale surface heterogeneities become more pronounced. The modified membranes retain their hydrophilic surface properties even after the nanofiltration tests and 30-day storage under ambient conditions. The results of the filtration tests show that when the membrane is oriented so that its modified layer contacts the feed solution, the membrane permeability for linear alcohols (methanol–propanol) and acetone decreases nearly two times. When the modified membrane surface faces the permeate, the membrane is seen to regain its transport characteristics: the flux becomes equal to that of the unmodified PTMSP. The well-pronounced effect of the transport asymmetry is observed for the solution of the neutral dye Solvent Blue 35 in methanol, ethanol, and acetone. For example, the initial membrane shows the negative retention for the Solvent Blue 35 dye (−16%) upon its filtration from the ethanol solution whereas, for the modified PTMSP membrane, the retention increases up to 17%. Various effects contributing to the asymmetry of the membrane transport characteristics are discussed.
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•Asymmetry of membrane transport was first shown for organic solvent nanofiltration.•One side of PTMSP membranes was modified by direct current glow discharge in air.•Plasma treatment provides marked hydrophilization of hydrophobic PTMSP surface and negative charge.•Depending on membrane orientation, two times difference in solvent flux•Transport and retention asymmetry for solution of neutral dye
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The prevention of physical aging of thin-film composite membranes based on PTMSP by the introduction of porous aromatic framework particles (PAF-11) was studied. A number of the thin-film composite ...(TFC) membranes with a varied thickness of the selective layer of 1.7–6.8 µm were fabricated, and its gas transport properties were monitored during up to 650 days at ambient temperature. Among all studied TFC membranes, TFC/6.8/PAF sample provided better stability of gas permeance by retaining of 0.19, 0.24 and 0.30 from its original values for N2, O2, and CO2, respectively. The best gas permeance for the stabilized aged TFC membrane were 300 (N2), 500 (O2) and 1900 GPU (CO2), and the ideal selectivity of 1.8 and 6.9 for the pair of O2/N2 and CO2/N2, respectively. It was shown that the gas selectivity of stabilized TFC membranes could be varied from 6.7 to 17 for (CO2/N2), and from 1.7 to 2.6 for (O2/N2), by adjustment of the selective layer thickness.
•The effect of porous aromatic framework particles on aging of TFC membranes based on PTMSP was studied.•The performance of TFC membrane was monitored during up to 650 days at ambient temperature.•The aging rate of TFC membranes was mainly determined by the thickness of selective layer.
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•Porous condenser for thermally driven membrane processes was proposed.•Gravity-independent operation of membrane module with porous condenser was proven.•The concept was demonstrated for two ...applications: water desalination and removal of butanol from its solution in water.
New thermally driven processes configuration based on the porous condenser (instead of non-porous cooling plate) and using permeate as a coolant was suggested and successfully proven for two processes: (i) membrane distillation with porous condenser (MD-PC) tested for the desalination of model NaCl solutions of 5–40g/l and (ii) thermopervaporation with porous condenser (TPV-PC) tested for the removal of n-butanol from its 1wt.% aqueous solution. In both cases, the experiments were carried out at different orientations of the membrane module. No noticeable difference for MD-PC and TPV-PC performance, including the worst case scenario for conventional AGMD when the membrane was located horizontally under the air gap, was observed. In addition, in contrast to the conventional AGMD, stable MD-PC, and TPV-PC performance was demonstrated at extremely low air gap width of 0.1–1mm. The water fluxes up to 21kg/m2h and salt rejection higher than 99% were attained for MD-PC, and the total flux of 1kg/m2h for TPV-PC separation of 1wt.% butanol-water mixture was obtained which is comparable with the conventional vacuum PV. Potential applications for the new thermally driven processes such as space and marine can be identified.
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•Novel composite PSf/PTMSP hollow fiber membranes are fabricated.•Ethylene/ethane separation in membrane contactor with aqueous AgNO3 is studied.•Highest ethylene overall permeance ...(83 GPU) at ethylene recovery of 44% is achieved.•Ethylene overall permeance decreases only by 24% during six months of MC operation.•Membrane and liquid phase resistances are significant and comparable.
The novel highly permeable composite membranes with a thin selective layer made of poly(1-trimethylsilyl-1-propyne) (PTMSP) on polysulfone hollow fiber support were proposed for application in gas-liquid membrane contactor for ethylene/ethane separation. The effects of AgNO3 concentration in aqueous absorbent and its velocity on the ethylene mass transfer coefficient were evaluated. High ethylene permeance (83 GPU) at ethylene recovery of 44% was achieved. Six months of membrane contactor operation revealed only 24% drop in the overall mass transfer coefficient. The contributions of membrane and liquid phase to the overall mass transfer resistance were estimated. The contributions were found to be comparable values.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A power counting rule is provided that allows us to obtain upper bounds for the absolute values of Feynman parametric integrands. The rule reflects both the ultraviolet and infrared behaviour taking ...into account that the external momenta are on the mass shell. It gives us the ability to rigorously prove the absolute convergence of the corresponding integrals. The consideration is limited to the case of the quantum electrodynamics Feynman graphs contributing to the lepton magnetic moments and not containing either lepton loops or ultraviolet divergent subgraphs. However, a rigorous mathematical proof is given for all Feynman graphs satisfying these restrictions. The power counting rule is formulated in terms of Hepp's sectors, ultraviolet degrees of divergence and so-called I-closures. The obtained upper bound can not be substantially improved: the illustrative example is provided. The paper provides the first mathematically rigorous treatment of the ultraviolet behaviour together with the on-shell infrared behaviour with some kind of generality. Practical applications of this rule are explained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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