Surface Protrusions Research Articles

Passive control of cylinder aeolian tone by surface protrusions at low Reynolds number

Aerodynamic noise control is important for various engineering applications, including automobiles. To develop effective control methods for the flow and sound of bluff bodies, flow past a cylinder is usually studied as a simplified problem. In this study, a passive control technique using surface protrusions was developed to suppress the aeolian tone generated by a two-dimensional laminar flow past a circular cylinder. Protrusions were created on the front and rear surfaces of the cylinder using an optimization approach based on the lattice Boltzmann and adjoint methods, allowing the optimization of complex geometries. The computational results revealed that a pair of protrusions on the front surface could stabilize the separated shear layers by fixing the separation points to their tips, whereas a pair of protrusions on the rear surface can stabilize the separated shear layers by interfering with the interaction between the top and bottom shear layers. Consequently, these shapes effectively suppressed the vortex shedding and aeolian tone while decreasing the mean drag. A shape with symmetrical protrusions on the front and rear surfaces reduced the aeolian tone by 3.6 dB.

Experimental evaluation and thermal performance analysis of a twisted tape with dimple configuration in a heat exchanger

This contemporary experiment examines heat transfer and friction factor of liquid (water) going in a double pipe heat exchanger with twisted tape (TT) insert. Effect of twisted tape in DPHE inserts dimple configuration by providing a dimple protrusion surface only on the front face with a hole configuration placed adjacent to it over the tube length of 1500 mm and diverse dimple diameter (D) and dimple diameter-to-depth ratio (D/H) proceeding heat transfer and friction factor(f) characteristics are analysed in this work. Twist ratio for all cases is 5.5 for each twist, range of Reynolds number (Re) 6000–14,000, D of 2, 4, and 6 mm and (D/H) of 1.5, 3 and 4.5. Six twisted tapes with dimples were tested, and their performance was compared to that of twist with plain tube. It is discovered that the Nusselt number is the deviance with respect to Reynolds number of a plain tube (without twisted tape and dimples) with an inner tube diameter of d = 16 mm. It is evident from the plot that there is an increase in the rate of Nusselt number with a subsequent increase in the value of Reynolds number. Through experimental analysis conducted, Therefore, Optimum value for higher Nusselt number is standard for discussion at D/H = 3 for different diameter as it 111 (for Re = 13987) and 58 (for Re = 6180) using D = 4 mm. As a result of the investigation, it is determined that the depth and diameter of the dimple is directly proportional to the friction factor. Therefore, optimum value for lower friction factor is benchmarked for discussion at D/H = 4.5 for different diameter as it 0.1033 (for Re = 13987) and 0.1437 (for Re = 6180).

Investigating the effect of surface protrusions on galloping energy harvesting

This Letter explores the potential effect of implementing different surface protrusions on galloping energy harvesters. Three types of protruded bluff bodies with rectangular, triangular, and elliptical metasurfaces are proposed, and four kinds of surface treatments are deployed to vary their protruded shape. Wind tunnel experiments reveal that adding the protrusions can obviously change the mode of oscillations, and only the backward protrusions can enhance the galloping response. Both the experiments and simulations show that elliptical surface protrusions have the greatest potential to enhance the galloping energy harvesting performance. Specifically, with a backward protruded length of 15 mm, the maximum output power in the experiments is measured to be 0.757 mW, which occurs at 5.1 m/s, and an optimal load resistance of 300 kΩ. In this case, the energy harvester outperforms its counterpart carrying a simple square prism by 157.48%.

Electrically Controlled Liquid Crystal Elastomer Surfaces for Dynamic Wrinkling

Liquid crystal elastomers (LCEs) are becoming increasingly popular as a shape memory material for soft robot actuators that operate in a contractile or flexural mode. There have been previously studies on the use of LCEs for reversible changes in surface topography. However, surface protrusions have typically been limited to the order of 1 μm or depend on light, heat, or electrical stimulation that are difficult to locally control or require relatively high voltage. This article presents a novel operation mode of LCE actuators based on the wrinkling behavior of an LCE‐elastomer bilayer architecture. Embedding a liquid‐metal‐based conductive ink within the LCE enables electrical control of surface wrinkling through Joule heating. The actuator cells can generate wrinkles with amplitudes ranging from 17 to 45 μm within 30 s under an input power of 2 W and a voltage on the order of 1 V. As the bilayer is composed entirely of soft materials, it is highly deformable, flexible, and can be integrated into a multi‐cell array capable of bending on curved surfaces.

Enhanced technique for photochemical nano-polishing of a rough quartz surface: the numerical calculation of profile evolution.

The enhanced technique of quartz surface nano-local etching is considered. The enhancement of an evanescent field above surface protrusions and, as a result, an increase in the rate of quartz nano-local etching, are proposed. The possibility to reduce the amount of etch products filled in rough surface troughs and control the optimal rate of the surface nano-polishing process is achieved. The dependences of the quartz surface profile evolution on the initial values of surface roughness parameters, on the refractive index of the medium containing molecular chlorine and contacting the quartz surface, and on the wavelength of radiation illuminating this surface are shown.

Capsid structure of a fungal dsRNA megabirnavirus reveals its previously unidentified surface architecture.

Rosellinia necatrix megabirnavirus 1-W779 (RnMBV1) is a non-enveloped icosahedral double-stranded (ds)RNA virus that infects the ascomycete fungus Rosellinia necatrix, a causative agent that induces a lethal plant disease white root rot. Herein, we have first resolved the atomic structure of the RnMBV1 capsid at 3.2 Å resolution using cryo-electron microscopy (cryo-EM) single-particle analysis. Compared with other non-enveloped icosahedral dsRNA viruses, the RnMBV1 capsid protein structure exhibits an extra-long C-terminal arm and a surface protrusion domain. In addition, the previously unrecognized crown proteins are identified in a symmetry-expanded cryo-EM model and are present over the 3-fold axes. These exclusive structural features of the RnMBV1 capsid could have been acquired for playing essential roles in transmission and/or particle assembly of the megabirnaviruses. Our findings, therefore, will reinforce the understanding of how the structural and molecular machineries of the megabirnaviruses influence the virulence of the disease-related ascomycete fungus.

Morphological peculiarities of the lithium electrode from the perspective of the Marcus-Hush-Chidsey model

This study employs the kinetics framework of Marcus-Hush-Chidsey (MHC) to investigate the charge transfer at the interface of lithium electrode and electrolyte in lithium(ion)-batteries. The charge-transfer rate constant is evaluated for different facets of lithium, namely (1 0 0), (1 1 0), (1 0 1), and (1 1 1) as a function of surface charge density with the aid of density functional theory (DFT) calculations. The results highlight and quantify the sensitivity of the rate of lithium plating and stripping to the surface orientation, surface charge density, and charge-transfer over-potential. An intrinsic kinetics competition among the different surface orientations is identified together with an asymmetry between the lithium plating and stripping and showcased to influence the deposit morphology and surface protrusions and indentations.

What in particle morphology determines the DLVO interaction energy between hematite particles in electrolyte solutions?

The experimental stability of hematite particles (radius: ∼74 nm) dispersed in solutions of varying salinity deviates considerably from predictions based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. For untreated hematite particles, at pH = 6 and 10, the theoretical values could be matched to the experimental ones by modifying the particle radius used in calculations from 74 to 13 nm. For particles heat-treated at 350 °C for 1 h, the theoretical values at pH = 10 could also be matched to the experimental ones by modifying the particle radius to 7 nm. Atomic force microscopy measurements revealed that the radius of curvature for surface protrusions on the hematite particles was 14 nm on average for the untreated particles at pH = 6 and 10, which almost equals the aforementioned modified particle radius. For the heat-treated hematite particles at pH = 10, the average radius of curvature was 9 nm, which also matched the corresponding modified particle radius. Therefore, we argue that the interaction energy between hematite particles is governed by not the overall particle radius but the curvature radius for surface protrusions. This could account for the discrepancy between theory and experiment regarding the salinity-dependent stability ratio of these particle dispersions.

Effect of magnetic field intensity on the microstructure and abrasion resistance of magnetic electrodeposited Ni–Co–SiC thin films

The purpose of this work is intended to fabricate Ni–Co–SiC thin films on the surface of carbon steel bearing by magnetic electrodeposition (MED) technique. The surface morphology and composition of Ni–Co–SiC thin films were investigated by scanning electron microscope (SEM), energy disperse spectroscopy (EDS), and X-ray diffraction (XRD). The microhardness and frictional coefficient were detected by utilizing microhardness tester and ball-on-desk wear tester. The surface protrusion of Ni–Co–SiC thin films presented first descent and then ascent with the increasing magnetic field intensity. The surface morphology of Ni–Co–SiC thin films obtained at magnetic field intensity of 0.8 T presented more flat and dense than those deposited at magnetic field intensity of 0.4 and 1.2 T. Meanwhile, the highest microhardness of 987.5 Hv and lowest frictional coefficient of 0.75 were also emerged in the Ni–Co–SiC thin films fabricated at magnetic field intensity of 0.8 T. In addition, XRD results indicated the Ni–Co–SiC thin films manufactured at magnetic field intensity of 0.8 T possessed smallest Ni–Co grain size of 15.6 nm. The abrasion loss of M2 thin film was 17.3 mg, while the M1 film processed the largest abrasion loss of 31.5 mg. In addition, the average frictional coefficients of M1, M2 and M3 thin films were 1.04, 0.75 and 0.85, respectively.

Experimental investigation of flow-induced sound of kite lines

In times of increasing importance of renewable energies, airborne wind energy (AWE) systems represent an emerging extension to conventional wind turbines. Many AWE systems use powerful kites to provide tether traction to mechanically unwind the tether, generating electricity on the ground. In addition to the traction tether, a large number of kite lines spanning the kite are moved through the air at high speed. This can produce a loud unpleasant whistling noise on the ground, which is due to a superposition of the aeolian tones of the many different lines. In the present work, differently structured kite lines were investigated in the aeroacoustic wind tunnel with respect to their sound radiation when they were exposed to a flow at up to 34 ms−1 resulting in Re ≦ 7300 and angles of attack (AOA) in the range of 90° ≧ AOA ≧ 45°. It was found that greater surface roughness increases sound radiation while line tension has negligible influence. By weaving a single-helix-shaped protrusion into the sheath of the kite line, the total radiated sound pressure level can be reduced by up to 9 dB. If the line itself has a helical contour, even a reduction of up to 11.5 dB is reachable. For decreasing AOA the noise suppression effect of helical surface protrusions and helical line shape is significantly reduced. The results provide initial guidelines on how to effectively reduce sound radiation from aircraft kites. Further investigations should consider the individual contributions of fluid and structural sounds to the total radiated sound of a flying kite.

Strategy for Regulating Surface Protrusion of Gold Nanoflowers and Their Surface-Enhanced Raman Scattering

Strategy for Regulating Surface Protrusion of Gold Nanoflowers and Their Surface-Enhanced Raman Scattering

Cobalt-rich spinel oxide-based wide angular spectral selective absorber coatings for solar thermal conversion applications

Solar energy conversion technologies attain enormous attention to create more efficient energy production sources to meet the current world's demand. The solar thermal conversion system converts solar energy to heat, and the receiver tube is crucial for achieving high photo-thermal conversion efficiency. The absorber coatings with high solar absorptance at normal and wide incidence angles of solar radiation improve the performance of concentrated and non-concentrated solar thermal systems. To achieve high photo-thermal conversion efficiency in the solar thermal conversion system, a novel spinel structured cobalt-rich transition metal oxide-based absorber coating was developed by a cost-effective wet chemical route. The developed absorber coatings with sub-micron scaled surface protrusions with porous structure (size 0.75 μm) exhibit an excellent spectral selectivity (α/ε = 0.91/0.13). In addition, the coatings show an excellent wide angular solar absorptance of 0.97–0.96 at incidence angles of 10°–40°. Extensive characterization has been carried out to analyze the structural properties of the absorber coatings and correlated to the spectral selectivity and wide angular solar absorptance property. The stability of the absorber coating at 400 °C for 100 h in an open-air atmosphere assessed by the performance criteria (PC) function value of 0.015 indicates the ability of the optimized absorber coatings to employ in solar thermal systems.

Pocket structures of surface protrusions shared among serologically distinct nervous necrosis viruses (NNVs) were predicted in silico to bind to sialylated N-glycans, a host cellular receptor

Nervous necrosis virus (NNV), one of the simplest spherical RNA-viruses, causes high mortality in aquaculture facilities worldwide. In this study, we investigated changes in the infectivity and reactivity of serologically distinct NNVs after treatment with 2.0 M urea, which was used as a means to predict a site or sites on surface protrusions responsible for NNV infection. Antigenicity of NNVs declined significantly after urea treatment but their infectivity was maintained, regardless of serological distinctions. The ability of urea-treated NNVs to be neutralized by antisera was also maintained, regardless of serological distinction. Moreover, weak but reliable cross-neutralizing reactions were observed between serologically distinct NNVs even after urea-treatment. These results suggested that common epitopes resistant to urea-treatment were shared among serologically distinct NNVs. Furthermore, two highly conserved amino-acid stretches among NNVs were revealed, and these stretches surround the pocket structures at the apex of surface protrusions. Molecular docking analysis showed that the pocket structure of surface protrusions was a site for maximally stable binding with the terminal moiety of sialylated N-glycans, a common cellular receptor for serologically distinct NNVs. Based on these results, the pocket structures on surface protrusions of NNVs, appear to be sites responsible for binding to sialylated N-glycans. Contrarily, a red-spotted grouper NNV (RGNNV)-specific MAb, neutralized naïve RGNNV but not the urea-treated RGNNV, suggesting that the epitope for this MAb was not present in the pocket structures. This suggests that disappearance of NNV infectivity due to binding with this MAb was the result of indirect inhibition of binding to the cellular receptor.

Combined Treatment of Parts Produced by Additive Manufacturing Methods for Improving the Surface Quality

To improve the quality of a part manufactured by the additive method, it is necessary to eliminate the porosity and high roughness of its surface, as well as to deposit a coating on it. For this purpose, in the present work, we studied the combined processing in a gas discharge plasma of complex shape parts obtained by the additive manufacturing method, which includes explosive ablation of surface protrusions when voltage pulses are applied to the part immersed in the plasma; polishing with a concentrated beam of fast neutral argon atoms at a large angle of incidence on the surface of the part, and magnetron deposition of a coating on it with assistance by fast argon atoms. Combined processing made it possible to completely get rid of porosity and reduce the surface roughness from Ra ~ 5 µm to Ra ~ 0.05 µm.

Heat flux enhancement by regular surface protrusion in partitioned thermal convection

We investigate the influence of the regular roughness of heated and cooled plates and adiabatic partition boards on the mean heat transport in a square Rayleigh–Bénard (RB) convection enclosure by two-dimensional direct numerical simulations. The roughness is in the form of isothermal protrusions with a rectangular base and triangular tip. The protrusion height varies from 10% to 25% of enclosure height. With increased protrusion height, the large-scale circulation cannot wash out the cavity between two consecutive protrusions. Thus, the overall heat transport of the enclosure impedes. We have inserted the partition boards between two successive protrusions with a gap between the conduction plate and the partition board to wash out the cavity. The partition board height varies from 20% to 99.8% of enclosure height. We have performed the simulations for the range of Rayleigh number 106–108 and at a fixed Prandtl number of 1. The tip of the triangular protrusion acts as an active plume-emitting spot. We observe a single large-scale elliptical roll with counter-rotating corner rolls for small partition board height. With an increase in partition board height, an elliptical large-scale roll breaks down into the number of large-scale rolls horizontally placed one beside the other. Finally, we observe multiple rolls stacked vertically when the partition boards almost touch the conduction walls. Heat flux enhancement strongly depends on large-scale flow structures. We found a maximum heat flux enhancement in protrusion with partitioned RB case approximately up to 4.7 times the classical square RB for an optimal gap between conduction plate and partition board. The maximum heat transport enhancement is due to the strong horizontal flow through the gap between the conduction plate and partition board, which locally reduces the thermal boundary layer's thickness. The interaction between the horizontal jets and the thermal boundary layers enhances heat transport.

Sucrose-based cryoprotective storage of extracellular vesicles

Advancements in extracellular vesicle (EV) studies necessitate the development of optimized storage conditions to ensure preservation of physical and biochemical characteristics. In this study, the most common buffer for EV storage (phosphate-buffered saline/PBS) was compared to a cryoprotective 5% sucrose solution. The size distribution and concentration of EVs from two different sources changed to a greater extent after −80 °C storage in PBS compared to the sucrose solution. Additionally, molecular surface protrusions and transmembrane proteins were more prevalent in EVs stored in the sucrose solution compared to those stored in PBS. This study demonstrates, for the first time, that distinct ring-like molecular complexes and cristae-like folded membranous structures are visible upon EV degradation. Taken together, the size, concentration, molecular surface extensions, and transmembrane proteins of EVs varied substantially based on the buffer used for −80 °C storage, suggesting that biocompatible cryoprotectants, such as sucrose, should be considered for EV studies.

Biohybrid Magnetic Microrobots for Tumor Assassination and Active Tissue Regeneration.

Magnetic microrobots have attracted increasing research interest for diverse biomedical applications, such as targeted therapy and tissue regeneration. However, multifunctional microrobots with complex morphology at the microscale are urgently needed to be fabricated, actively controlled, and functionalized. In this study, the chrysanthemum pollen-derived biohybrid magnetic microrobots (CDBMRs) with spiny protrusion, hollow cavity, and porous surface structure were proposed for tumor assassination and active tissue regeneration. By exquisitely designing the sequential treatment process, CDBMRs were fabricated and the innate morphology of pollen templates was well preserved. Under magnetic field, CDBMR exhibited various individual and collective behaviors. CDBMRs were utilized for synergetic tumor treatment by the combination of magnetically controlled physical assassination and active drug delivery. Meanwhile, CDBMRs showed excellent ability for active cell delivery and tissue regeneration, which was further proved by enhanced osteogenesis ability. By making full use of the natural morphology of pollen grains, the biohybrid microrobots presented a promising strategy for effective tumor therapeutics and tissue regeneration.

In vitro regeneration and its histological characteristics of Dioscorea nipponica Makino

Dioscorea nipponica Makino is an optimal candidate to develop the diosgenin industry in North China. Due to its increasing demand in the medicine industry, it is urgent to apply new biotechnological tools to foster breeds with desirable traits and enhanced secondary metabolite production. The production of useful metabolites by the in vitro cultured rhizomes can be explored successfully for utilization by various food and drug industries. In this study, we reported callus formation and plantlet regeneration of the medicinal plant D. nipponica. Explants of leaves, stem segments and rhizomes of aseptic seedlings were cultured on Murashige and Skoog (MS) medium containing various combinations of auxin and cytokinin to find the optimal PGRs of each type of explant for callus induction and shoot regeneration of D. nipponica. The paraffin section technique was also used to observe of the morphogenesis of callus and adventitious bud. Explants of seeds and rhizomes formed calli at high frequency in all lines we examined. However, the explant of leaves rarely formed callus. Three kinds of callus were detected during the induction phase. Here, we describe three types of callus (Callus I–III) with different structure characteristics. Greenish in color and a nodule-like protrusion surface (Callus type III) were arranged more closely of cells with less interstitial substance, cell differentiation ability stronger than other callus types. The optimum combination was the maximum shoot differentiation frequency of 90% in callus derived from seeds cultured on MS medium with 2.0 mg L−16-BA + 0.2 mg L−1NAA. The shoot differentiation frequency (88.57%) of rhizome-induced callus was obtained by the combination of MS medium supplemented with 3.0 mg L−16-BA + 2.0 mg L−1NAA. 1/2 MS medium plus 0.5 mg L−1NAA resulted in a higher root regeneration frequency of 86.70%. In vitro propagated plantlets with healthy roots were domesticated and transplanted into small plastic pots containing sterile soil rite under greenhouse conditions with 80% survivability. Bud differentiation is mostly of exogenous origin, mostly occurring on the near callus surface. Therefore, it may be surmised that in vitro morphogenesis of D. nipponica is mainly caused by indirect organogenesis (adventitious bud).

Performance Analysis of a Propeller with Surface Protrusions

Performance Analysis of a Propeller with Surface Protrusions

Surface protrusion induced by inter-diffusion on Cu-Sn micro-pillars

With downward scaling of the micro-bumps in three-dimensional integrated circuits, surface inter-diffusion becomes dominant, changing the kinetic path of intermetallic compounds (IMC) formation and causing serious reliability issues. However, an in-depth understanding of the surface inter-diffusion process and the corresponding influence on the formation mechanism of IMC in a micro-bump remain unclear. We conducted annealing at 170 ℃, over 16 h for pillar type Sn/Cu micro-bumps and observed a unique 2-step sidewall Cu3Sn IMC formation phenomenon on the FIB-cut clean surface of the micro-bumps. It is found the two-step sidewall IMC formation is dominated by the surface inter-diffusion of Sn and Cu atoms. Density functional theory calculations reveal that the activation energy barrier of nucleation for sidewall Cu3Sn IMC is about 1/3 of that of sidewall Cu6Sn5 on corresponding interfacial IMC layers, making the formation of sidewall Cu3Sn dominant. Moreover, we proposed a kinetic model that can predict the mean lateral growth rate of the sidewall IMC which may cause fatal short-circuit failure.