A novel multi-channel porous structure facilitating mass transport towards highly efficient alkaline water electrolysis

An advantageous porous architecture of electrodes is pivotal in significantly enhancing alkaline water electrolysis(AWE)efficiency by optimizing the mass transport mechanisms.This effect becomes even more pronounced when aiming to achieve elevated current densities.Herein,we employed a rapid and scalable laser texturing process to craft novel multi-channel porous electrodes.Particularly,the obtained electrodes exhibit the lowest Tafel slope of 79 mV dec^(-1)(HER)and 49 mV dec^(-1)(OER).As anticipated,the alkaline electrolyzer(AEL)cell incorporating multi-channel porous electrodes(NP-LT30)exhibited a remarkable improvement in cell efficiency,with voltage drops(from 2.28 to 1.97 V)exceeding 300 mV under 1 A cm^(-1),compared to conventional perforated Ni plate electrodes.This enhancement mainly stemmed from the employed multi-channel porous structure,facilitating mass transport and bubble dynamics through an innovative convection mode,surpassing the traditional convection mode.Furthermore,the NP-LT30-based AEL cell demonstrated exceptional durability for 300 h under 1.0 A cm^(-2).This study underscores the capability of the novel multi-channel porous electrodes to expedite mass transport in practical AWE applications.

Controlled thermally-driven mass transport in carbon nanotubes using carbon hoops

Controlling mass transportation using intrinsic mechanisms is a challenging topic in nanotechnology.Herein,we employ molecular dynamics simulations to investigate the mass transport inside carbon nanotubes(CNT)with temperature gradients,specifically the effects of adding a static carbon hoop to the outside of a CNT on the transport of a nanomotor inside the CNT.We reveal that the underlying mechanism is the uneven potential energy created by the hoops,i.e.,the hoop outside the CNT forms potential energy barriers or wells that affect mass transport inside the CNT.This fundamental control of directional mass transportation may lead to promising routes for nanoscale actuation and energy conversion.

Mass and Energy Transportation in Ore-Forming Processes of Sulfide Deposits in Tongling District

Based on dynamics of heat conduction, fluid flow caused by heating and chemical material transport induced by fluid flow, temperature and stream fields of fluid flow in ore-forming processes of Cu-Au sulfide in the Tongling district deposits was modeled and analyzed. It is shown that: (1) Mass and energy flow caused by fluid flow is key problem of kythrothermal ore-forming processes; the heating from magma intruded is basic power for driving fluid flow. (2) occurrence of pluton, different chemical property and porosity of wall rocks and infiltration restrict the specifically field of precipitation for ore-forming material.Therefore, the dissolution and precipitation field for ore-forming material in deposit can be forecasted. (3) Iron and sulfur material comes mostly from sandstone formation of Wutong Group, which contains pyrite and high porosity. The cataclastic dolomite interlayered in sandstone and limestone is a favorable place for ore accumulating. The difference of chemical property between sandstone and dolomite forms a favorable interface for ore-forming processes.

Boosting the Oxygen Reduction Performance of Fe-N-C Catalyst Using Zeolite as an Oxygen Reservoir

Non-precious metal electrocatalysts(such as Fe-N-C materials) for the oxygen(O_(2)) reduction reaction demand a high catalyst loading in fuel cell devices to achieve workable performance. However, the extremely low solubility of O_(2) in water creates severe mass transport resistance in the thick catalyst layer of Fe-N-C catalysts. Here, we introduce silicalite-1 nanocrystals with hydrophobic cavities as sustainable O_(2) reservoirs to overcome the mass transport issue of Fe-N-C catalysts. The extra O_(2) supply to the adjacent catalysts significantly alleviated the negative effects of the severe mass transport resistance. The hybrid catalyst(Fe-N-C@silicalite-1) achieved a higher limiting current density than Fe-N-C in the half-cell test. In the H_(2)-O_(2) and H_2-air proton exchange membrane fuel cells, Fe-N-C@silicalite-1 exhibited a 16.3% and 20.2% increase in peak power density compared with Fe-N-C, respectively. The O_(2)-concentrating additive provides an effective approach for improving the mass transport imposed by the low solubility of O_(2) in water.

Unleashing the Potential of Unidirectional Mechanical Materials: Breakthroughs and Promising Applications

The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively channel mechanical energy and facilitate directed sound propagation, controlled mass transport, and concentration of mechanical energy amidst random motion. This article explores the fundamentals of mechanically one-way materials, their potential applications across various industries, and the economic and environmental considerations related to their production and use.

Mass transport deposits and processes in the north slope of the Xisha Trough,northern South China Sea

Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length （from headwall to termination）. Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and three- dimensional structure model diagram af the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.

Mass Transport in a Thin Layer of Bi-Viscous Mud Under Surface Waves

The mass transport in a thin layer of non-Newtonian bed mud under surface waves is examined with a two-fluid Stokes boundary layer model. The mud is assumed to be a bi-viscous fluid, which tends to resist motion for small-applied stresses, but flows readily when the yield stress is exceeded. Asymptotic expansions suitable for shallow fluid layers are applied, and the second-order solutions for the mass transport induced by surface progressive waves are obtained numerically. It is found that the stronger the non-Newtonian behavior of the mud, the more pronounced intermittency of the flow. Consequently, the mass transport velocity is diminished in magnitude, and can even become negative (i.e., opposite to wave propagation) for a certain range of yield stress.

Lagrangian analysis of the formation and mass transport of compressible vortex rings generated by a shock tube

In order to understand the mass transport and the dynamic genesis associated with a compressible vortex formation,a dynamic analysis of compressible vortex rings (CVRs) generated by shock tubes by using the framework of Lagrangiancoherent structures (LCSs) and finite-time Lyapunov exponents field (FTLE) is performed. Numerical calculation is performed to simulate the evolution of CVRs generated by shock tubes with 70 mm, 100 mm, and 165 mm of the driver sectionat the circumstances of pressure ratio = 3. The formation of CVRs is studied according to FTLE fields. The mass transportduring the formation is obviously seen by the material manifold reveled by FTLE fields. A non-universal formation numberfor the three CVRs is obtained. Then the elliptic LCSs is implemented on three CVRs. Fluid particles separated by ellipticLCSs and ridges of FTLE are traced back to t = 0 to identify the fluid that eventually forms the CVRs. The elliptic LCSsencompass around 60% fluid material of the advected bulk but contain the majority of the circulation of the ring. The otherparts of the ring carrying almost zero circulation advect along with the ring. Combining the ridges of FTLE and the ellipticLCS, the whole CVR can be divided into three distinct dynamic parts: vortex part, entrainment part, and advected part. Inaddition, a criterion based on the vortex part formation is suggested to identify the formation number of CVRs.

Mixed convective heat and mass transfer analysis for peristaltic transport in an asymmetric channel with Soret and Dufour effects

The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.

Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅱ. Residual current and its impact on mass transport in winter

Some observational characteristics of residual current and mass transport in the Hangzhou Bay and the Changjiang Estuary in winter are analyzed. The residual current and its impact on mass transport are simulated with a 3 - D joint model for the Hangzhou Bay and the Changjiang Estuary, in which the impacts of river flux, wind, baroclinic pressure gradient (BPG), background current in the East China Sea and tide (including M2, S2, K1 and O1) are taken into account. Based on there studies, further simulations are made to analyze the dynamical mechanisms of the observational characteristics.

STUDY ON THE CONTROLLED MASS TRANSPORT THROUGH POROUS MEMBRANES

Cryopreservation of cells and tissues (natural or engineered) usually involves complicated protocols for addition and later removal of cryoprotecting agents to avoid osmotic shock and toxicity to cells. The rate of CPA addition and removal is essential to cell survival. In this study, the feasibility of using porous membrane to control the rate of CPA transfer to cell environment is studied, A purpose designed diffusion chamber was fabricated. The effects of membrane characteristics (porosity and effective thickness), temperature, and initial concentration were experimentally studied. A simplified mathematical model was developed, which provides the basis to desire the membrane parameters based on tile experimental measurements.

Mass transport of a mesoscale eddy in the South China Sea identified by a simulated passive tracer

To quantitatively investigate the water mass transport of mesoscale eddies,the mass transport induced by a simulated anticyclonic eddy in the South China Sea was evaluated by using the Regional Ocean Modelling System(ROMS)and a built-in passive tracer module.The results indicate that the eddy can trap and transport 51%of the initial water in the eddy core to 689 km from its origin during its lifetime of 100 days,with a stable loss rate of 6‰per day.During propagation,there is drastic horizontal water exchange between the inside and outside of the eddy.Meanwhile,the vertical mass transport is signifi cant,and 65%of the water initially in the mixed layer of the eddy is eventually detrained into the subsurface.A tracer budget analysis of eddy shows that advection is the dominant dynamic process of transport,while the eff ect of mixing is weak,and horizontal process plays a controlling role.Horizontal and vertical advection exhibit opposite patterns and strongly off set each other.Particularly,a distinct dipole pattern is found in the local velocity fi eld of the eddy,with signifi cant convergence(downwelling)and divergence(upwelling)zones in the anterior and posterior of the eddy,respectively,which is likely related to the driving mechanism of the westward propagation of the eddy.The dipole further induces a vertical overturning cell,through which the surface water in the anterior of the eddy detrains into the subsurface by downwelling and resurface from the posterior of the eddy by upwelling and gradually spreads out of the eddy.The temporal variability in the tracer budget is signifi cant,in which horizontal advection is dominant.The propagation acceleration and temporal derivative of the deformation rate are highly correlated with tracer transport,suggesting the potential eff ect of the temporal instability of eddies on the eddy mass transport.

Seasonal Variations of Terrestrial OC Sources in Aerosols over the East China Sea: The Influence of Long-Range Air Mass Transport

Aerosols represent an important source of terrestrial organic carbon(OC)from the East Asian continent to the China marginal seas,thus their provenance and transport play important roles in the global carbon cycle.Fifty samples of total suspended particle were collected seasonally from the nearshore Huaniao Island(HNI)in East China Sea(ECS)from April 2018 to January 2019;and they were analyzed for total organic carbon(TOC)content and stable carbon isotope(δ^(13)C),as well as terrestrial bio-markers including n-alkanes(C_(20)-C_(33)),n-alkanols(C_(20)-C32)and n-fatty acids(n-FAs,C_(20)-C30),to distinguish the seasonal variabili-ties of terrestrial OC sources and reveal the influence of the long-range air mass transport on these sources.The TOC-δ^(13)C values(range from−27.3‰to−24.3‰)and molecular distributions of terrestrial biomarkers both suggested that terrestrial OC contribu-tions to aerosols had significant seasonal variations.The source indices of terrestrial biomarkers(e.g.,Fossil%=82.8%for n-alkanes)revealed that the fossil fuel OC contributions,including coal burning and vehicular emission,were higher in winter,mainly because of the long-range air mass transport from the north of the East Asian continent.The terrestrial plant OC contributions were higher in summer(e.g.,Wax%=32.4%for n-alkanes),likely due to local vegetation sources from HNI and East Asian continental air masses.Cluster analysis of air mass backward-trajectories clearly showed that transport pathway plays an important role in determining the organic constituents of aerosols in China marginal seas.A comparison of these terrestrial OC contributions from different air mass origins suggested that fossil fuel OC showed less variations among various air mass origins from northern China in winter,while terrestrial plant OC sources from northern and southern China in summer contributed more than that from the air masses transported through the ECS.These results provided a basis for future quantification of terrestrial OC from different origins in marine aerosols,by combining biomarker index and carbon isotopes.

Correlation between impedance spectroscopy and bubble-induced mass transport in the electrochemical reduction of carbon dioxide

In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance.This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide(CO_(2))electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO_(2) depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.

Mass Transport of β-Diketonate Precursors for MOCVD of YBa_2Cu_3O_(7-δ) High T_c Superconducting Thin Films

Mass transport of Y(dpm)2 Ba(dpm)5· OH· 2Ho and Cu (dpm)2 by a carrier gas(argon) was theoretically considered and experimentally studied as a function of the system with operating parameters including temperature, carrier gas flow rate and system pressure. The experimental results are in a good agreement with the theoretical prediction. The mechanism of mass transport of these organometallic precursors and their use for YBCO film stoichiometry control and reproducibility are discussed.

Mass transport model of ions within biofilms under the effect of external field

A mass transport model was developed to predict the transport rate of ions within biofilms, which was experimentally verified using the fluxes of NH4^＋ and Ca^2＋ through the heterotrophic biofilms with the thickness varying from 230 to 1430μm under the effect of external field in the range of-20 V/m to 60 V/m. It is found that the result predicted by the model is in agreement with the experimentally obtained one, with the error less than 5 percent for the thin biofilms. The error increases with the increase of the biofilm thickness. The transport rate of ions caused by electric migration is affected by the charges, field strength, and biofilm thickness and so on.

Dynamic Behavior and Mass Transport in Polyacrylic Acid Gel by Dynamic Light Scattering

Dynamic behaviors on polyacrylic acid (PAA) gels and mass (small molecules) transports in the gels have been studied mainly by dynamic light scattering (DLS). The cross-linking degree (fc), monomer concentration (Cm) and temperature of the gels have significant influences on its dynamic behavior and mass transport in the gels. The increase of fc leads to decrease of the mesh sizes of the gels, thus the obstacle of the gels for mass transport is increased. As a result, small molecular diffusion Dk in the gels is decreased. So even if for small molecules, the Dk also is influenced.

MASS TRANSPORT IN SOLID TUMORS (Ⅰ)──FLUID DYNAMICS

A three-porous-medium model for transvascular exchange and extravascular transport of fluid and macromolecules in a spherical solid tumor is developed. The microvasculature , lymphatics, and tissue space are each treated as a porous medium with the flow of blood. lymph, and interstitial fluid obeying Darcy's law and Starling 's assumption. In this part, the role of interstitial pressure and fluid convection are studited. The analytical soiutions are obtained for foe isolated tumor and the normal-tissue-surrounded tumor respectively. The calculated interstitial pressure profue are consistent with the experimental observation that the elevated interstitial pressure is a major barrier in the penetration of macromolecular drug into tumors. The factors which may reduce the interstitial pressure are analyzed in details.

Classifying Electrolyte Solutions by Comparing Charge and Mass Transport

The conventional classification of electrolyte solutions as“strong”or“weak”accounts for their charge transport properties,but neglects their mass transport properties,and is not readily applicable to highly concentrated solutions.Here,we use the Onsager transport formalism in combination with linear response theory to attain a more general classification taking into account both charge and mass transport properties.To this end,we define a molar mass transport coefficientΛ_(mass),which is related to equilibrium center-of-mass fluctuations of the mobile ions and which is the masstransport analogue of the molar ionic conductivityΛ_(charge).Three classes of electrolyte solution are then distinguished:(i)“Strong electrolytes”with 4Λ_(mass)≈Λ_(charge);(ii)“weak charge transport electrolytes”withΛ_(charge)≪4Λ_(mass);and(iii)“weak mass transport electrolytes”with 4Λ_(mass)≪Λ_(charge).While classes(i)and(ii)encompass the classical“strong”and“weak”electrolytes,respectively,many highly concentrated electrolytes fall into class(iii)and thus exhibit transport properties clearly distinct from classical strong and weak electrolytes.