High Mass Ratio Research Articles

Comparison of Ashes Produced in a Biomass Moving Grate Boiler by Wood Chips and Sewage Sludge

One option to fight global warming is to convert our use of fossil energy into renewables such as biomass energy. However, the forest preservation and the quality of the ambient air are also two major issues. Therefore, the use of biomass waste without any supplementary emissions could represent a part of the solution. In this study, two fuels were considered for a 200 kW moving grate boiler. A multicyclone and a bag filter were fitted on the boiler. The first fuel consisted of classical wood chips whereas the second was a mixture of wood chips with sewage sludge. This second fuel presented a high ashes mass ratio compared to wood chips. The aim was to verify the possibility to burn this kind of fuel without any modification of the installation. The first relevant result is that the conventional pollutants, i.e., CO and NOx, remained under the emissions limits even with the sewage sludge combustion. The Total Suspended Particles emissions at the exhaust were always under 5.4 mg·Nm−3 dry based corrected at 6% of O2, which is low with respect to the standard limitation. The majority of the ashes remained on the combustion room. However, with both fuels, about 5% of ashes mass remained in the heat exchanger. Nevertheless, the heat exchanger was more clogged with the second fuel, which produced five time more ashes. This may lead to a yield loss. Thus, sewage sludge can be used in a wood boiler without any issue if an automatic exchanger sweep is fitted on the installation.

Diurnal Variation of Chemical Characteristics and Source Identification of Fine Particles in the Kaohsiung Harbor

This study investigated the diurnal and monthly variation of fine particle (PM2.5) concentrations and its chemical characteristics and source identification in the Kaohsiung Harbor. Three sites located in the harbor areas were selected for simultaneously sampling 12-h PM2.5 in four months with consecutive seven days in each month. Water-soluble ions (WSIs), metallic elements, carbons, anhydrosugars, and organic acids in PM2.5 were analyzed to characterize their chemical fingerprints and monthly variation. Field sampling and chemical analysis of PM2.5 showed that significant diurnal and monthly variations of PM2.5’s mass concentration and chemical composition were observed in the Kaohsiung Harbor. Prevailing wind direction highly influences the mass concentrations and chemical characteristics of PM2.5 in the port areas. PM2.5 was dominated by WSIs with the abundance of secondary inorganic aerosols (SIAs). Crustal elements dominated the metallic content of PM2.5, but trace elements mainly originated from anthropogenic sources. The V/Ni ratios of PM2.5 in the Kaohsiung Harbor were generally higher than 2.0. Organic carbon (OC) was superior to elemental carbon (EC) in PM2.5 with the dominance of secondary OC (SOC). High concentration of levoglucosan (levo) was observed in spring due to nearby biomass burning. Additionally, high mass ratios of malonic and succinic acids (M/S) in PM2.5 indicated the potential formation of SOAs. Results obtained from chemical mass balanced (CMB) receptor modeling showed that the major sources of PM2.5 resolved in the Kaohsiung Harbor were mobile sources, ship emissions and oil-fired boilers, steel plants, secondary aerosols, sea salt spray, and fugitive dust. Primary PM2.5 emitted from ship traffics accounted for 20.8% of PM2.5.

Excitation of gravitational wave modes by a center-of-mass velocity of the source

Most gravitational wave (GW) sources are moving relative to us. This motion is often closely related to the environment of the source and can thus provide crucial information about the formation of the source and its host. Recently, LIGO and Virgo detected for the first time the subdominant modes of GWs. We show that a motion of the center of mass of the source can affect these modes, where the effect is proportional to the velocity of the source. The effect on the GW modes in turn affects the overall frequency of the GW, thus leading to a phase shift. We study the impact of this effect on LIGO/Virgo detections and show that it is detectable for sources with high mass ratios and inclinations. This effect breaks the degeneracy between the mass and Doppler shift in GW observations and opens a new possibility of detecting the motion of a GW source even for constant velocities.

High Mass-Ratio Binary Population in Open Clusters: Segregation of Early Type Binaries and an Increasing Binary Fraction with Mass

Abstract Binary stars play a vital role in astrophysical research, as a good fraction of stars are in binaries. Binary fraction (BF) is known to change with stellar mass in the Galactic field, but such studies in clusters require binary identification and membership information. Here, we estimate the total and spectral-type high-mass-ratio (HMR) BF (f 0.6) in 23 open clusters using unresolved binaries in color–magnitude diagrams using Gaia DR2 data. We introduce the segregation index (   ) parameter to trace mass segregation of HMR (total and mass) binaries and the reference population. This study finds that in open clusters, (1) HMR BF for the mass range 0.4–3.6 M ⊙ (early M to late B-type stars) has a range of 0.12–0.38 with a peak at 0.12–0.20; (2) older clusters have a relatively higher HMR BF; (3) the mass-ratio distribution is unlikely to be a flat distribution and BF (total) ∼(1.5–2.5) × f 0.6; (4) a decreasing BF (total) from late B to K-type stars, in agreement with the Galactic field stars; (5) older clusters show radial segregation of HMR binaries; (6) B-type and A–F type HMR binaries show radial segregation in some young clusters suggesting a primordial origin. This study will constrain the initial conditions and identify the major mechanisms that regulate binary formation in clusters. Primordial segregation of HMR binaries could result from massive clumps spatially segregated in the collapse phase of the molecular cloud.

Hybrid polymer/lipid vesicle synthesis: Association between cationic liposomes and lipoplexes with chondroitin sulfate

The association of cationic carriers with different anionic mucoadhesive biopolymers has been widely explored as an alternative to improve their delivery routes and specific targeting. This work presents a complete analysis of the association between chondroitin sulfate (CS) and cationic liposomes (CLs)/lipoplex (CL-pDNA). In this study, plasmid DNA (pDNA) was used as a genetic cargo for association with carriers. Firstly, we measured the stoichiometry of pseudo complexes and evaluated their colloidal properties, structural and morphological characteristics. Optimized CL-pDNA lipoplexes (positive z-potential) and CL-CS / CL-pDNA-CS (negative z-potential with CS mass ratio of 9% (w/w)) were further studied in detail. Small-angle X-ray scattering analysis and cryo-transmission electron microscopy micrographs revealed that the electrostatic interaction between CS and CL / CL-pDNA easily reorganized the lipid bilayers resulting in nanoscale uni/multilamellar vesicles. A high CS mass ratio (9% (w/w)) led to the reassembly of liposomal structure, wherein the pDNA was easily exchanged for CS chains, forming more than 50% of dense multilamellar vesicles. This data evidenced that the association between CS and CLs is not a conventional coating process since it generates complex and hybrid structures. We believe that these obtained colloidal data may be used in the future to investigate polymer-tailored nanocarriers and their production process. In brief, the colloidal study of hybrid structures may open interesting perspectives for developing novel carriers for drug and gene delivery applications.

(Invited) A Novel Electrochemical Recycling Method for Rare Earth Metals from Scrap Magnets Using Molten Salt Electrolysis and Alloy Diaphragms

Today, rare earths (RE) are indispensable as industrial materials all over the world. At the same time, the world is facing a shortage of rare earth resources and a sharp rise in rare earth prices. In order to alleviate this situation and establish a more sustainable use of RE metals, it is necessary to develop a simple, inexpensive, and environmentally friendly process for the recovery and separation of RE metals. In particular, the recovery of RE from Nd-Fe-B magnet scraps is very important because a large amount of magnet scraps are expected to be disposed of from EVs and HEVs in 10 years. For use in EVs and HEVs, Dy must be added to Nd-Fe-B magnets in order to maintain strong magnetic properties even at temperatures above 473 K. Therefore, the recovery and separation of Dy and Nd, which is generally difficult, is required for the new recycling process.With this background, we proposed a process for the separation and recovery of RE metals from magnet scraps using molten salt and alloy diaphragms (Figure 1) [1-4, 6-11]. The proposal was based on our previous finding that certain RE metals can be rapidly alloyed and de-alloyed with iron group (IG) metals in molten salt by electrochemical methods [5].As a candidate molten salt, we used LiCl-KCl eutectic melt at 723 K. We first investigated the electrochemical formation of Dy-Ni, Nd-Ni, and Dy-Nd-Ni alloys in the molten salts containing DyCl3, NdCl3, and DyCl3-NdCl3, respectively, and achieved a high separation mass ratio of Dy/Nd = 72 in the alloy samples [6]. As a next step, we demonstrated the selective permeation of Dy through the alloy diaphragm using a primitive-type electrolytic cell [7]. Recently, we further investigated the selective permeation of Dy through an alloy diaphragm made of RENi2 [8].Considering that molten fluorides such as LiF-REF3 and LiF-CaF2-REF3 are used for smelting RE metals, we also investigated the electrochemical formation of Dy-Ni, Nd-Ni, and Dy-Nd-Ni alloys in LiF-CaF2 eutectic melts containing DyF3, NdF3, and DyF3-NdF3, respectively, at 1123 K [2-4]. The results showed that the Dy/Nd ratio in Dy-Nd-Ni alloys has a potential dependence. The highest value of Dy/Nd was 5.6, which is lower than the value obtained for the LiCl-KCl melt [2].We originally focused on RE-Ni alloy, which has both high alloy formation rate and high Dy/Nd separation rate, and started to investigate it as an alloy diaphragm. However, RE-Ni alloy is not suitable for long-term use because of its brittleness and low durability. In order to develop a more durable alloy diaphragm, iron-group alloys such as Ni-Cr, Ni-Mo, and Ni-Cr-Mo alloys were selected as candidates for the base material [9,10]. Since Cr and Mo are difficult to alloy with RE elements, these components are expected to reinforce the mechanical strength of the alloy diaphragm. The shear stress measurements of the Dy-alloyed samples showed that the Ni-Cr-Mo alloy is the most suitable base material to improve mechanical strength [10]. We are also investigating the use of liquid alloys as another candidate for the diaphragm material [11].AcknowledgementA part of this study was conducted as commission research with the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Comparative study of the damping performance of concentrated masses and particle dampers based on cantilever beams

This paper investigates the damping performance of the main structure with a concentrated mass and particle dampers at different particle filling rates and sinusoidal sweep amplitudes under the same mass ratio by means of a controlled experiment, with the concentrated mass and particle dampers attached to the free end of the cantilever beam. As the order increases, the effect becomes progressively weaker. For cantilevered beam structures, a reasonable design with only a small mass ratio of particle dampers can effectively suppress the vibration of the first order. For the second- and third-order bending vibration, particle dampers with high mass ratios show a better damping effect, and when the strength of the excitation reaches a certain value, the damping performance of the particle dampers is basically better than that of the concentrated mass under the same conditions. The reason for this is that particle damping not only dampens the vibration by tuning the mass but also dissipates the energy of the main structure by means of collisions, impacts, and friction between the particles or between the particles and the damper cavity.

Turbulence and its connection to episodic accretion in binary YSOs

ABSTRACT We report signatures of episodic accretion in young stellar objects (YSOs) that emerge in protobinary configurations in a gravoturbulent gas collapse. We find in most of these protobinary systems strong accretion bursts between the two companions with a recurrence time-scale of about 1 kyr. The accretion rate on to the secondary star typically exceeds that on to the primary with a peak value of 2 × 10−2 M⊙ yr−1 for the former and 6 × 10−3 M⊙ yr−1 for the latter. We propose that the secondary companion, which remains more active in its episodes of accretion bursts, especially for the gas cores with subsonic velocity dispersion, may provide observational opportunities to find traces of episodic accretion in the surrounding gas of the embedded YSOs that are in a binary configuration. Also, protostars evolving as single objects in the same environment show fewer accretion bursts and all together a more steady mass growth history. The prestellar cores with subsonic velocity dispersion exhibit an order of magnitude more intense accretion bursts than in the case of cores with supersonic velocity dispersions. The latter shows the formation of some of the protobinaries in which the primary acts as a more actively accreting companion. This can support these binaries to become systems of extreme mass ratio. Moreover, the YSOs in binary configurations with small semimajor axis a ≈ 50 au and high mass ratio q > 0.7 support phases of intense episodic accretion. The eccentricity, however, seems to play no significant role in the occurrence of accretion bursts.

Effects of pressure decay on Non-Methane Volatile Organic Compounds (NMVOC) species distribution in domestic aerosol sprays with LPG propellants

Conventional aerosols sprays contain different Volatile Organic Compounds (VOC). These organic compounds have different properties and can have detrimental impact on air quality. This study investigated the spray performance and variation of the types of Non-Methane VOCs (NMVOCs) expelled over the life of pressurised aerosol spray can. Three types of aerosol sprays – hair sprays, deodorants, and antiperspirants were selected from the solvent-based cosmetic products. Mass Ratio (MR) of solvent (ethanol) to propellant (LPG) for all the products was analysed at pressure decay sequences of 4, 3, 2, and 1.5 bar. It was found that the MR in hair sprays expelled was significantly higher than that of antiperspirants and body sprays by 53% and 54% respectively at 4 bar. As the pressure depleted, however, the antiperspirant and body sprays’ MR decreased while that of the hair spray increased. At the lower pressures (2 bar), the hair spray had the highest MR and antiperspirant had the lowest. This finding is important in evaluating the performance of the delivery pathways of aerosol spray products and will provide insight into the effective design of atomisers with alternative “green” propellants like compressed air replacing LPG as the primary propellant in spray products.

Black hole–neutron star binary mergers: the imprint of tidal deformations and debris

The increase in the sensitivity of gravitational wave (GW) interferometers will bring additional detections of binary black hole (BBH) and double neutron star (NS) mergers. It will also very likely add many merger events of BH–NS binaries. Distinguishing mixed binaries from BBHs mergers for high mass ratios could be challenging because in this situation the NS coalesces with the BH without experiencing significant disruption. To investigate the transition of mixed binary mergers into those behaving more like BBH coalescences, we present results from merger simulations for different mass ratios. We show how the degree of deformation and disruption of the NS impacts the inspiral and merger dynamics, the properties of the final BH, the accretion disk formed from the circularization of the tidal debris, the GWs, and the strain spectrum and mismatches. The results also show the effectiveness of the initial data method that generalizes the Bowen–York initial data for BH punctures to the case of binaries with NS companions.

Synergistic effects from co-pyrolysis of lignocellulosic biomass with low-rank coal: A perspective based on the interaction of organic components

A methodological approach towards synergistic effects from co-pyrolysis of lignocellulosic biomass with low-rank coal was proposed. The main maceral group from low-rank coal and primary organic components from biomass were selected to investigate the interaction of organic components. Thermal behavior and kinetic analysis on the co-pyrolysis of cellulose with acid-washed low-rank coal/vitrinite/inertinite were explored via TGA combined with iso-conversional method. The results indicated that the maceral group from low-rank coal showed different synergistic effects on the pyrolysis parameters and product distribution. The synergistic effect of vitrinite on the yield of volatile was closely related to its mass ratio. Positive and negative synergistic effects were observed when the mass ratio of vitrinite was 25% and 75%, respectively. Inertinite inhibited the formation of volatiles during co-pyrolysis and overall exhibited a negative synergy. No obvious synergy was observed for acid-washed low-rank coal when the heating was 10 °C·min−1 and 20 °C·min−1, while positive synergistic effects were found at a high mass ratio and heating rate. The integrative action of maceral groups played a significant role during the co-pyrolysis process.

Turbulent flame propagation of polymethylmethacrylate particle clouds in an O2/N2 atmosphere

The combustion of solid particle clouds is extensively used in many engineering areas. However, experimental data describing the turbulent flame propagation behavior and the combustion mechanism of solid particle clouds have remained limited. In this work, the combustion of polymethylmethacrylate (PMMA) particle clouds was studied by employing a unique fan-stirred constant-volume chamber. For the quasi-monodispersed particle clouds, the flame propagation velocity increased with the increase in the turbulence intensity and the decrease in the quasi-monodispersed particle size. However, the particle concentration had little effect on the flame propagation velocity, which is unique in a turbulent flow field. The consistency of the results between the current study of PMMA particle clouds and the previous study for coal particle clouds showed that the heterogeneous combustion of char particles had little effect on the turbulent flame propagation velocity of the solid particle clouds. Further, two types of quasi-monodispersed particles were mixed to study how the interactions between small and large (polydispersed) particles affect turbulent flame propagation. We found that the turbulent flame propagation velocity had a nonlinear relationship with the mass ratio of small particles (J-shaped curve). The turbulent flame propagation velocity slightly increased with low mass ratio of small particles, while it sharply increased with high mass ratio of small particles. Increasing the turbulence intensity and decreasing the primary particle (large particle) size can advance the starting point of the sharp increase. These unique features were explained by a mechanism considering the polydispersed interparticle interaction proposed by the authors. In the combustion of turbulent polydispersed particle clouds, the particle–particle agglomeration and the agglomeration break-up in the turbulent flow field affect turbulent flame propagation. To the best of our knowledge, this is the first report on the fundamental spherical turbulent flame propagation phenomenon and the mechanism of solid particle cloud combustion considering the polydispersed interparticle interactions.

Dynamical ejecta synchrotron emission as a possible contributor to the changing behaviour of GRB170817A afterglow

ABSTRACT Over the past 3 yr, the fading non-thermal emission from the GW170817 remained generally consistent with the afterglow powered by synchrotron radiation produced by the interaction of the structured jet with the ambient medium. Recent observations by Hajela et al. indicate the change in temporal and spectral behaviour in the X-ray band. We show that the new observations are compatible with the emergence of a new component due to non-thermal emission from the fast tail of the dynamical ejecta of ab-initio binary neutron star merger simulations. This provides a new avenue to constrain binary parameters. Specifically, we find that equal mass models with soft equations of state (EOSs) and high-mass ratio models with stiff EOSs are disfavoured as they typically predict afterglows that peak too early to explain the recent observations. Moderate stiffness and mass ratio models, instead, tend to be in good overall agreement with the data.

Effect of mass ratio on flow-induced vibration of a trapezoidal cylinder at low Reynolds numbers

A numerical study of the effect of the mass ratio (M*) on the flow-induced vibration of a trapezoidal cylinder at low Reynolds numbers (Re = 60–250) is presented. The response characteristics are divided into three classes with varying mass ratios (2, 5, 10, 20, 30, 50, and 100): (1) class I for low mass ratios (M* = 2), (2) class II for medium mass ratios (5 ≤ M* < 30), and (3) class III for high mass ratios (M* ≥ 30). In class I, for the vortex-induced vibration (VIV) regime, only one peak of maximum amplitude is observed at low Re (∼70). For the galloping regime, a double rise-up for amplitudes is observed, and the mean transverse displacements become positive at higher Re and increase rapidly. In class II, the double rise-up for amplitudes appears at both the VIV and galloping regimes, and the double lock-in is also found for oscillation frequency ratios. In class III, the double rise-up disappears in the VIV and galloping regimes at all considered Re. The onset Re of the galloping regime is much higher (Re > 200), and the peak amplitudes and ranges of lock-in in VIV become much smaller with an increase in M*. Among these three classes, similar distinctions are also observed in the hydrodynamic forces. In terms of X–Y trajectories, three types are found in class I, while there are only two and one in classes II and III, respectively. Wake structures are also investigated for these classes.

Collisional Growth and Fragmentation of Dust Aggregates with Low Mass Ratios. I. Critical Collision Velocity for Water Ice

Abstract We investigated fundamental processes of collisional sticking and fragmentation of dust aggregates by carrying out N-body simulations of submicron-sized icy dust monomers. We examined the conditions for collisional growth of two colliding dust aggregates in a wide range of the mass ratio 1–64. We found that the mass transfer from a larger dust aggregate to a smaller one is a dominant process in collisions with a mass ratio of 2–30 and an impact velocity of ≈30–170 m s−1. As a result, the critical velocity, v fra, for fragmentation of the largest body is considerably reduced for such unequal-mass collisions; v fra of collisions with a mass ratio of 3 is about half of that obtained from equal-mass collisions. The impact velocity is generally higher for collisions between dust aggregates with higher mass ratios because of the difference between the radial drift velocities in the typical condition of protoplanetary disks (PPDs). Therefore, the reduced v fra for unequal-mass collisions would delay growth of dust grains in the inner region of PPDs.

Inter-comparison of chemical characteristics and source apportionment of PM2.5 at two harbors in the Philippines and Taiwan

This study inter-compared the concentration and chemical characteristics of PM2.5 at two harbors in East Asia, and identified the potential sources of PM2.5 and their contribution. Two sites located at the Kaohsiung (Taiwan) and Manila (the Philippines) Harbors were selected for simultaneous sampling of PM2.5 in four seasons. The sampling of 24-h PM2.5 was conducted for continuous seven days in each season. Water-soluble ions, metallic elements, carbonaceous content, anhydrosugars, and organic acids in PM2.5 were analyzed to characterize their chemical fingerprints. Receptor modeling and trajectory simulation were further applied to resolve the source apportionment of PM2.5. The results indicated that the Kaohsiung Harbor was highly influenced by long-range transport (LRT) of polluted air masses from Northeast Asia, while the Manila Harbor was mainly influenced by local emissions. Secondary inorganic aerosols were the most abundant ions in PM2.5. Crustal elements dominated the metallic content of PM2.5, but trace elements were mainly originated from anthropogenic sources. Higher concentrations of organic carbon (OC) than elemental carbon (EC) was found in PM2.5, with secondary OC (SOC) dominant to the former. Levoglucosan in PM2.5 at the Manila Harbor were superior to those at the Kaohsiung Harbor due to biomass burning surrounding the Manila Harbor. Additionally, high mass ratios of malonic and succinic acids (M/S) in PM2.5 indicated the formation of SOAs. Overall, the ambient air quality of Manila Harbor was more polluted than Kaohsiung Harbor. The Kaohsiung Harbor was more severely affected by LRT of polluted air masses from Northeast Asia, while those toward the Manila Harbor came from the oceans. The major sources resolved by CMB and PMF models at the Kaohsiung Harbor were secondary aerosols, ironworks, incinerators, oceanic spray, and ship emissions, while those at the Manila Harbor were secondary aerosols, soil dust, biomass burning, ship emissions, and oceanic spray.

Performance enhancement of air conditioner in hot climate by condenser cooling with cool air generated by direct evaporative cooling

This research studied the direct evaporative cooling technique for generating cool air in hot–dry and hot–humid climates. For direct evaporative cooling, three parameters affected the air temperature: feedwater temperature, wet-bulb temperature, and mass ratio of feedwater to circulating air were investigated. When the feedwater temperature was lower than the wet-bulb temperature, in a hot-humid climate, an increase in the mass ratio of feedwater to the circulating air decreased the outlet air temperature. Conversely, if the feedwater temperature was higher than the wet-bulb temperature, in a hot-dry climate, a decrease in the mass ratio was needed to reduce the air temperature. The cooled air obtained could be used for condenser cooling of air-conditioner for performance enhancement. According to a 1 TR air conditioner simulation, lower feedwater temperature resulted in higher energy efficiency ratio. High mass ratio, thus, was recommended in the hot-humid climate area whereas less mass ratio was preferable for the hot-dry climate area. The energy efficiency ratios of the unit with direct evaporative cooling for hot–dry and hot–humid climates ranged from 3.40 to 4.22 and 3.30 to 3.94, respectively, compared to 3.01 for the normal unit. The payback period for the unit with direct evaporative cooling in case of Chiang Mai (hot-humid climate) was around 2.87 year.

A taxonomy of black-hole binary spin precession and nutation

Binary black holes with misaligned spins will generically induce both precession and nutation of the orbital angular momentum $\bf{L}$ about the total angular momentum $\bf{J}$. These phenomena modulate the phase and amplitude of the gravitational waves emitted as the binary inspirals to merger. We introduce a "taxonomy" of binary black-hole spin precession that encompasses all the known phenomenology, then present five new phenomenological parameters that describe generic precession and constitute potential building blocks for future gravitational waveform models. These are the precession amplitude $\langle\theta_L\rangle$, the precession frequency $\langle \Omega_L\rangle$, the nutation amplitude $\Delta\theta_L$, the nutation frequency $\omega$, and the precession-frequency variation $\Delta\Omega_L$. We investigate the evolution of these five parameters during the inspiral and explore their statistical properties for sources with isotropic spins. In particular, we find that nutation of $\bf{L}$ is most prominent for binaries with high spins ($\chi \gtrsim 0.5$) and moderate mass ratios ($q \sim 0.6$).

Vortex-Induced Vibrations of Two Degrees-of-Freedom Sprung Cylinder With a Rotational Nonlinear Energy Sink: A Numerical Investigation

Abstract Vortex-induced vibration (VIV) is a common fluid–structure interaction phenomenon in the field of wind engineering and marine engineering. The large-amplitude VIV has a marked impact on the slender structure in fluids, at times even destructive. To study how the VIV can be controlled, the dynamics of a rigid cylinder attached to a rotational nonlinear energy sink (R-NES) is investigated in this paper. This is done using a two degrees-of-freedom (2DOF) Van der Pol wake oscillator model adapted to consider a coupled vibration in cross-flow and streamwise directions. The governing equation of R-NES is coupled to the wake oscillator model; hence, a flow-cylinder–NES coupled system is established. While exploring the dynamics of the cylinders with different mass ratios under the action of R-NES, it was found that the R-NES delivers better performance in suppressing the VIV of a cylinder with high mass ratios than that of a low mass ratios cylinder. The effect of the distinct parameters of R-NES on VIV response was also systematically investigated in this study. The results indicate that higher mass parameter β and rotation radius r̂ can lead to improved performance, while the effect of the damping parameter ξ is complex and appears to be linked to the mass ratio of the column structure.

Spray-deposited thin-film composite MOFs membranes for dyes removal

Fabrication of thin-film composite metal-organic frameworks (MOFs) membranes (TFCMMs) has great potential to broaden the application scale due to excellent properties of MOFs, such as adjustable pore structure, high surface area, and uniform pore size. However, there are still some limitations on the TFCMMs such as low MOFs mass ratio and poor compatibility. Here, a simplistic “spray deposition cum post-stabilization (SDS)” technique is proposed to precisely fabricate compact thin-films of different MOFs including ZIF-L, UiO-66-NH2, and MIL-101-NH2 on porous substrates. The SDS strategy can fix various MOFs via crosslinking reaction between the aryl chloride groups of trimesoyl chloride and the amino groups of polyethyleneimine or MOFs in the functional layer, leading to durable TFCMMs with good compatibility and high MOFs mass ratio. The resulting membranes also show high water permeance and excellent dye rejection (99.2% for methyl blue and 97.5% for metanil yellow) as compared to the traditional polyamide membrane.