Film Shape Research Articles

Real-time observation of the precursor film for low viscosity liquids spreading on solid substrates by a customized differential laser interference microscopy.

While static wettability is well treated with Young's equation via its static contact angle, theoretical analyses for wetting dynamics are not yet reaching consensus due to a singularity of the spreading forces worked at the vapor/liquid/solid contact line. One plausible explanation to overcome the singularity problem is that there is a so-called precursor film spreading outside the apparent contact line. After its first finding in 1919, many researchers have attempted to visualize its shape. However, because its length and thickness are as small as micrometer and nanometer-order, respectively, its visualization stillremains a challenging issue especially for low-viscosity liquids. In the present study, we developed a differential laser interference microscope, which has a thickness resolution of approximately 2nm at the best, and applied it to the wetting front of 10 cSt of silicone oil spreading on a silicon wafer with an almost constant spreading velocity. As a result, the precursor film of 14µm long and 108nm thick was clearly visualized. While the macro contact line has a finite advancing contact angle of 4.0°, the gradient of the precursor film surface gradually decreased and converged to ~ 0.1° at the micro-contact angle. The shape of the precursor film was independent of the time after the dropping for the range of 600s ± 10%, which is consistent to theoretical estimation. The present study demonstrated that our interferometer simultaneously achieved nanometer thickness resolutions, micrometer in-plane spatial resolution, and at least a millisecond temporal resolution with a simple optical setup.

Comprehensive evaluation of copper vanadate (α-CuV2O6) for use as a photoanode material for photoelectrochemical water splitting

This study is an initial account of solution-based spray pyrolysis-produced n-type copper vanadate (CuV2O6) thin film photoanodes. CuV2O6 photoelectrodes have been tested for their ability to oxidize water in aqueous (pH 6.8) solutions using photoelectrochemical (PEC) tests. The band edge positions, band gap energy, photocurrent generation, flat band potential, chemical make-up, chemical stability, charge carrier transit, and O2 production faradic efficiency are a few of the physical and photophysical features measured and described. According to the findings, CuV2O6 possesses a satisfactory bandgap of 1.9 eV and appropriate band locations that allow for the use of visible light for overall solar water splitting. Under AM1.5 simulated sunlight, the maximum photocurrent density recorded is 0.18 mA cm− 2 at 1.23 VRHE with Na2SO3 acting as a hole scavenger. As evidenced by film shape, surface compositions before and after the PEC measurements, and outstanding structural and compositional stability throughout the oxygen evolution reaction (OER), the CuV2O6 photoelectrodes performed well. CuV2O6 photoanodes also exhibit almost a unit faradic efficiency for the oxidation of water. The overall photoelectrochemical efficiency, however, is constrained by the photogenerated charge carriers' weak mobility (∼8 ×10−3 cm2 V−1 s−1), short lifetime (∼20 ns), and limited hole diffusion length (∼20.4 nm), according to time-resolved microwave conductivity (TRMC) tests. Based on the current findings, this study offers new insight into building enhanced high-quality CuV2O6 photoanodes by methodically clarifying numerous important physical and photoelectrochemical characteristics for the photooxidation of water.

Semi-empirical model for the liquid fuel film formed by an oblique jet impinging on a curved wall

The operating conditions and the properties of the liquid have great effects on the shape and size of the liquid film and eventually affect the efficiencies of the atomization of alternative fuels, liquid jet impingement cooling, and equipment cleaning processes. The shape and size of the liquid film are dominated by the distance from the stagnation point to the liquid film edge(rmax). In this study, after deducing the thickness profile and the theoretical rather than the numerical solution of the initial velocity profile of the liquid film, a set of semi-empirical models about the shape, size of the liquid film, and the width of the raised zone formed by an oblique jet impinging on curved walls have been developed. In order to validate the theoretical model, a corresponding experiment has been developed, in which the jet velocities, impingement angles, liquid viscosity, surface tension, and radius of curvature have been included. The comparisons showed the theoretical results are in good agreement with the experimental data. The error for the location of the inner and outer border lines are less than 14.9% and 13.5%, respectively, except for the location in the upstream part of the film. And the effects of jet velocity, impingement angle, surface tension, dynamic viscosity, and radius of curvature were also theoretically discussed. The outer border line of the liquid film is dominated by the impingement angle and the impingement velocity, which affect the rmax exponentially and linearly, respectively. And the liquid viscosity and surface tension coefficient also affect the rmax approximately linearly. But the effects of the liquid viscosity and surface tension coefficient on the rmax are much less than the impingement velocity. The radius of curvature has little effect on the outer border lines and width of the raised zone when gravity is ignored.

Optoelectrical Properties of Hexamine Doped-Methylammonium Lead Iodide Perovskite under Different Grain-Shape Crystallinity.

The crystallinity properties of perovskite influence their optoelectrical performance in solar cell applications. We optimized the grain shape and crystallinity of perovskite film by annealing treatment from 130 to 170 °C under high humidity (relative humidity of 70%). We found that the grain size, grain interface, and grain morphology of the perovskite are optimized when the sample was annealed at 150 °C for 1 h in the air. At this condition, the perovskite film is composed of 250 nm crystalline shape grain and compact inter-grain structure with an invincible grain interface. Perovskite solar cells device analysis indicated that the device fabricated using the samples annealed at 150 °C produced the highest power conversion efficiency, namely 17.77%. The open circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) of the device are as high as 1.05 V, 22.27 mA/cm2, and 0.76, respectively. Optoelectrical dynamic analysis using transient photoluminescence and electrochemical impedance spectroscopies reveals that (i) carrier lifetime in the champion device can be up to 25 ns, which is almost double the carrier lifetime of the sample annealed at 130 °C. (ii) The interfacial charge transfer resistance is low in the champion device, i.e., ~20 Ω, which has a crystalline grain morphology, enabling active photocurrent extraction. Perovskite's behavior under annealing treatment in high humidity conditions can be a guide for the industrialization of perovskite solar cells.

Finely Tuned Molecular Packing Realized by a New Rhodanine-Based Acceptor Enabling Excellent Additive-Free Small- and Large-Area Organic Photovoltaic Devices Approaching 19 and 12.20% Efficiencies.

A new nonfullerene acceptor (NFA), BTA-ERh, was synthesized and integrated into a PM6:Y7:PC71BM ternary system to regulate the blend film morphology for enhanced device performance. Due to BTA-ERh's good miscibility with host active blend films, an optimized film morphology was obtained with appropriate phase separation and fine-tuning of film crystallinity, which ultimately resulted in efficient exciton dissociation, charge transport, lower recombination loss, and decreased trap-state density. The resulting additive-free quaternary devices achieved a remarkable efficiency of 18.90%, with a high voltage, fill factor, and current density of 0.87 V, 76.32%, and 28.60 mA cm-2, respectively. By adding less of a new small molecule with high crystallinity, the favorable nanomorphology shape of blend films containing NFAs might be adjusted. Consequently, this strategy can enhance photovoltaic device performance for cutting-edge NFA-based organic solar cells (OSCs). In contrast, the additive-free OSCs exhibited good operational stability. More importantly, large-area modules with the quaternary device showed a remarkable efficiency of 12.20%, with an area as high as 55 cm2 (substrate size, 100 cm2) in an air atmosphere via D-bar coating. These results highlight the enormous research potential for a multicomponent strategy for future additive-free OSC applications.

Low-RCS UWB Planar Monopole Array Antenna Based on the Optimized Design of the Conductor Layers

Using an optimized design of combining traditional copper (Cu) film and novel phase transition film vanadium dioxide (VO2), this communication proposes an ultrawideband (UWB) planar monopole array antenna with excellent stealth performance. The VO2 film exhibits two controllable phases: one with low conductivity of less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{3}$ </tex-math></inline-formula> S/m and the other with high conductivity of more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{6}$ </tex-math></inline-formula> S/m. Since VO2 has lower conductivity than Cu, antenna designs using this material will have lower radiating efficiency as a tradeoff for reducing the radar cross Section (RCS). To optimize this tradeoff, careful antenna shape design, and an innovative combination of using VO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}+$ </tex-math></inline-formula> Cu films, the RCS can be reduced in a UWB without significantly decreasing the gain of the array antenna. In this work, Cu is applied in the regions supporting high current density, while phase transition VO2 film is used in areas supporting lower current density. Both the shape and size of the VO2 film are optimized. Compared with the all-Cu film counterpart, the realized gain of the VO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}+$ </tex-math></inline-formula> Cu hybrid film array antenna is decreased only by an average of 0.4 dBi, maintaining the same radiation pattern in the working band of 6–9 GHz, while the monostatic RCS is reduced by about 9 dB on average across the UWB of 4–11 GHz.

Enhancing the output performance of ZnO nanosheet based piezoelectric nanogenerator by molar ratio modifications

The current work shows how the molar ratio of zinc nitrate and hexamethylenetetramine (HMTA) affects the output performance of a ZnO nanosheet-based piezoelectric nanogenerator. ZnO nanosheets were synthesized at three different molar concentrations of HMTA with fixed zinc nitrate hexahydrate concentration (1:1, 1:2, and 1:3). The shape, crystallinity, chemical composition, and photoluminescence properties of ZnO nanosheet films were further studied. The increased concentration of HMTA in solution results in larger and thinner nanosheets. In addition, three piezoelectric nanogenerators were fabricated using these ZnO nanosheet films deposited on two sides of an aluminum foil. The larger ZnO nanosheet film-based nanogenerator (PENG3) produced an enhanced output voltage than the smaller ZnO nanosheet film-based nanogenerator (PENG1) with an average output voltage of ∼423 mV and an average short-circuit current of ∼0.697 µA, respectively. The output voltage of PENG3 was enhanced by 1.55 times and short-circuit current by 1.34 times compared to the PENG1 device. PENG3 has an instantaneous output power of about 0.2277 mW/m2 at a load resistance of 250 kΩ. The photoluminescence study also confirmed that this could be used as a suitable UV light sensor. In addition, these highly porous nanosheets can also be used for photovoltaic materials in DSSC applications.

Abundance, characteristics, and ecological risks of microplastics in the riverbed sediments around Dhaka city

Microplastic (MP) pollution has become an escalating problem in Bangladesh due to its rapid urbanization, economic growth, and excessive use of plastics; however, data on MP pollution from fresh water resources in this country are limited. This study investigated microplastics pollution in riverbed sediments in the peripheral rivers of Dhaka, the capital of Bangladesh. Twenty-eight sediment samples were collected from the selected stations of the Buriganga, Turag, and Balu Rivers. Density separation and wet-peroxidation methods were employed to extract MP particles. Attenuated total reflectance-Fourier transform infrared spectroscopy was used to identify the polymers. The results indicated a medium-level abundance of MPs in riverbed sediment in comparison with the findings of other studies in freshwater sediments worldwide. Film shape, white and transparent color, and large-size (1–5 mm) MPs were dominant in the riverbed sediment. The most abundant polymers were polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). Pollution load index (PLI) values greater than 1 were observed, indicating that all sampling sites were polluted with MPs. An assessment of ecological risks, using the abundance, polymer types, and toxicity of MPs in the sediment samples, suggested a medium to very high ecological risk of MP pollution of the rivers. The increased abundance of MPs and the presence of highly hazardous polymers, namely; polyurethane, acrylonitrile butadiene styrene, polyvinyl chloride, epoxy resin, and polyphenylene sulfide, were associated with higher ecological risks. Scanning electron microscopy (SEM) analysis indicated that the MPs were subjected to weathering actions, reducing the size of MPs, which caused additional potential ecological hazards in these river ecosystems. This investigation provides baseline information on MP pollution in riverine freshwater ecosystems for further in-depth studies of risk assessment and developing strategies for controlling MP pollution in Bangladesh.

Mangrove and microplastic pollution: A case study from a small island (Mauritius)

Marine sediments have been demonstrated to be a long-term sinks for microplastics and their contamination in mangrove sediment are of no exception with relatively scarce information available globally. This work aimed to determine the prevalence of microplastics in two natural mangrove forests of a small island developing state, Mauritius, with emphasis on the proximity of human settlement and anthropogenic activities. Sediments were collected in triplicates monthly from October to December 2018 at Ferney (remote site) and Mahebourg (populated site) in three tidal zones: seaward (Z1), middle (Z2) and landward zone (Z3). Microplastics retrieved were classified in terms of shape and size classes. Results showed the presence of microplastics in all sediment samples with average abundance of 107.4 ± 76.42 particles kg −1 at Ferney and 140.2 ± 85.38 particles kg −1 at Mahebourg. Average microplastics abundance was highest in the ZI and Z3 tidal zones and least in Z2 at Ferney and Mahebourg respectively. Majority of microplastics recovered were in the size class 800–1000 μm and 1000–2000 μm, and in the fragment and film shape that may be derived from the fragmentation of larger plastic debris. This study is an important baseline for mangrove protection as it provides a better understanding of microplastics pollution status and information for future planning of management strategies on a local and regional scale.

Interaction between the oil droplet in water and wetted wall: Force model and motion law

To investigate the force model and motion law of oil droplets in water near the wetted wall, oil droplets with R1 = 0.29–0.62 mm and oil films with R2 = 1–6 mm are solved numerically. In addition to buoyancy, flow resistance, and added mass force, the film-induced force triggered by the wetted wall constraint is also introduced into the force model. The drainage process is described using the Stokes–Reynolds equation, and the Young–Laplace equation is used to calculate the pressure within the water film. The results show that the force model can be coupled with the Stokes–Reynolds–Young–Laplace model equation to better describe the drainage dynamics near the wetted wall. The pressure distribution law is closely related to the shape of the water film, especially when the oil–water interface is in the shape of a dimple, which can lead to the formation of negative pressure zones within the water film. The maximum pressure first grows in an exponential, then logarithmic pattern and eventually approaches the equivalent Laplace pressure. Around the critical size, the direction of the film-induced force changes and the form of action switches between driving and drag forces. The film-induced force's dominant effect is strongest when the curvature radius of the oil film is comparable to the droplet size.

Prediction model of volume average diameter and analysis of atomization characteristics in electrostatic atomization minimum quantity lubrication

Minimum quantity lubrication (MQL) is a relatively efficient and clean alternative to flooding workpiece machining. Electrostatic atomization has the merits of small droplet diameter, high uniformity of droplet size, and strong coating, hence its superiority to pneumatic atomization. However, as the current research hotspot, the influence of jet parameters and electrical parameters on the average diameter of droplets is not clear. First, by observing the shape of the liquid film at the nozzle outlet, the influence law of air pressure and voltage on liquid film thickness (h) and transverse and longitudinal fluctuations are determined. Then, the mathematical model of charged droplet volume average diameter (VAD) is constructed based on three dimensions of the liquid film, namely its thickness, transverse wavelength (λh), and longitudinal wavelength (λz). The model results under different working conditions are obtained by numerical simulation. Comparisons of the model results with the experimental VAD of the droplet confirm the error of the mathematical model to be less than 10%. The droplet diameter distribution span value Rosin-Rammler distribution span (R.S) and percentage concentrations of PM10 (particle size of less than 10 µm)/PM2.5 (particle size of less than 2.5 µm) under different working conditions are further analyzed. The results show that electrostatic atomization not only reduces the diameter distribution span of atomized droplets but also significantly inhibits the formation of PM10 and PM2.5 fine-suspension droplets. When the air pressure is 0.3 MPa, and the voltage is 40 kV, the percentage concentrations of PM10 and PM2.5 can be reduced by 80.72% and 92.05%, respectively, compared with that under the pure pneumatic atomization condition at 0.3 MPa.

Experimental Investigation of Discharge Phenomena in Electrochemical Discharge Machining Process

Electrochemical discharge machining (ECDM) is a promising non-traditional processing technology used to machine non-conductive materials, such as glass and ceramic, based on the evoked electrochemical discharge phenomena around the tool electrode. The discharge in ECDM is a key factor that affects the removal of material. Moreover, the discharge current is an important indicator reflecting the discharge state. However, the discharge characteristics remain an open topic for debate and require further investigation. There is still confusion regarding the distinction of the discharge current from the electrochemical reaction current in ECDM. In this study, high-speed imaging technology was applied to the investigation of the discharge characteristics. By comparing the captured discharge images with the corresponding discharge current, the discharge can be classified into three types. The observations of the discharge effect on the gas film indicate that a force was exerted on the gas film during the discharge process and the shape of the gas film was changed by the force. In addition, the energies released by different types of discharge were calculated according to the voltage and current waveforms. The discharge frequency was found to increase with the increase in applied voltage and the frequency of the second type of discharge was approximately equal to that of the third type when the applied voltage was higher than 40 V.

Regulating surface morphology and thermochromic properties of VO2 films by Cu-Ag bimetallic nanoparticles

For decades, the synchronous improvements of solar modulation ability (ΔTsol) and luminous transmittance (Tlum) has always been a challenge for VO2-based smart windows. In this research, Cu-Ag bimetallic nanoparticles (Cu-Ag NPs) were embedded into VO2/VO2 bilayer films by pulsed laser deposition. The effects of Cu-Ag NPs on crystal quality, surface morphology and optical properties of VO2 film were investigated. The results showed that the intensity of localized surface plasmon resonance (LSPR) effect could be adjusted by changing the number of laser pulses during Cu-Ag NPs deposition process. SEM and EDS characterization further suggested that Cu-Ag NPs preferred to nucleate at the "concave" formed by several VO2 grains. Compared with VO2/VO2 bilayer film (ΔTsol = 8.1%, Tlum = 40.0%), VO2/Cu-Ag NPs/VO2 composite film showed excellent energy saving performance, the ΔTsol and Tlum were further improved to 10.6% and 55.7%, respectively. In addition, the finite-difference time-domain simulations revealed that the improvements of thermochromic properties could be attributed to the LSPR effect induced by the unevenly distributed VO2 nanoparticles. The results in this work confirmed that the existence of the irregular Cu-Ag NPs could both improve the crystallinity and regulate the grain shape of VO2 films, which is an effective way to enhance the performance of VO2 smart windows.

Depolymerization of robust polyetheretherketone to regenerate monomer units using sulfur reagents

Super engineering plastics, high-performance thermoplastic resins such as polyetheretherketone, and polyphenylene sulfide have been utilized in industries, owing to their high thermal stability and mechanical strength. However, their robustness hinders their depolymerization to produce monomers and low-weight molecules. Presently, chemical recycling for most super engineering plastics remains relatively unexplored. Herein, we report the depolymerization of insoluble polyetheretherketone using sulfur nucleophiles via carbon–oxygen bond cleavages to form benzophenone dithiolate and hydroquinone. Treatment with organic halides converted only the former products to afford various dithiofunctionalized benzophenones. The depolymerization proceeded as a solid–liquid reaction in the initial phase. Therefore, this method was not affected by the shape of polyetheretherketone, e.g., pellets or films. Moreover, this depolymerization method was applicable to carbon- or glass fiber-enforced polyetheretherketone material. The depolymerized product, dithiofunctionalized benzophenones, could be converted into diiodobenzophenone, which was applicable to the polymerization.

Improvement of performance of CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite solar cells by polyvinylidene fluoride additive

&lt;sec&gt;Recently, the power conversion efficiency (PCE) of organic-inorganic hybrid perovskite solar cells has been enhanced rapidly from 3.8% to 25.8%, which is a top research topic in the field of photovoltaic power generation. However, the preparation of the hybrid perovskite solar cells has high environmental requirements, and the absorber layer is easily caused by the environmental influence and decomposition, resulting in the degradation of device performance. The all-inorganic CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite material has good stability, can be prepared directly in air, and is more economical, showing great potential applications. However, the PCE of all-inorganic CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite solar cells is not high, and at this stage, there is still much room for exploring high-quality controllable preparation of CsPbBr&lt;sub&gt;3&lt;/sub&gt; films. In this paper, we aim to prepare efficient and stable CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite solar cells with additive engineering.&lt;/sec&gt;&lt;sec&gt;Polymer is one of the most effective additives in perovskite solar cells. The use of polymer additive in perovskite layer can improve the shape-form, structure, and band gap of the film, thus improving the quality of perovskite film. Polyvinylidene fluoride (PVDF) is a cheap polymer with hydrophobic F ions and long flexible polymer chains, and can be used to prepare efficient and stable perovskite solar cells.&lt;/sec&gt;&lt;sec&gt;In this paper, CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite films are prepared by multi-part spin-coating method. PVDF with enriched hydrophobic F is added into the PbBr&lt;sub&gt;2&lt;/sub&gt; precursor solution as an additive to adjust the crystalline quality of the perovskite film, and the effects of PVDF on the growth process and device performance of the perovskite film are systematically studied. The results show that the PVDF can be used as a template to promote the growth of perovskite crystals, improve the crystal structure and film shape, thus reducing the defect density and charge recombination, and increasing the PCE of the device to 8.17%. The original efficiency of more than 90% can be maintained after 1400 h of storage under unencapsulated condition. Finally, high-efficiency, stable and low-cost CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite solar cells are obtained, which is important in further expanding the optimized design ideas of CsPbBr&lt;sub&gt;3&lt;/sub&gt; perovskite solar cells. The PVDF can form hydrogen bonds with perovskite or interact with lead ions to improve the structural stability of perovskite, and the F ions in PVDF can improve the moisture stability of perovskite layers.&lt;/sec&gt;

Computing the area-minimizing surface by the Allen-Cahn equation with the fixed boundary

&lt;abstract&gt;&lt;p&gt;The Allen-Cahn equation is a famous nonlinear reaction-diffusion equation used to study geometric motion and minimal hypersurfaces. This link has been scrutinized to construct minimal surfaces for many years. The shape of soap film is very interesting, and it can stimulate mathematical inspirations since it explains curvatures and equilibrium shapes in nature. There are many interesting ways to create area-minimizing surfaces with the boundaries, called frame boundaries. However, dealing with surface's ends (boundaries) numerically is not easy for constructing surfaces. This paper presents a mathematical formulation and numerical construction of area-minimizing surfaces, also known as minimal surfaces. We use differential geometry knowledge for numerical verification. The proposed numerical scheme involves fixed frame boundary conditions in the Laplacian operator. We treat the Laplacian with the constraint implicitly and explicitly solve the nonlinear free energy term. This approach ensures stable and efficient construction of area-minimizing surfaces with frame boundaries. In the numerical aspect, we suggest the construction of minimal surfaces by illustrating two classical examples, which are Scherk's minimal surface and catenoid. Both examples have the frame boundaries. Scherk's first surface is a doubly periodic, complete and properly embedded one with parallel ends. The catenoid is formed between two coaxial circular rings and is classified mathematically as the only properly embedded minimal surface with two ends and finite curvature. To be specific, we deal with two different frame boundaries, right angle frame and round frame boundaries, via two examples, Scherk's surface and catenoid.&lt;/p&gt;&lt;/abstract&gt;

The influence of shape and matrix size on the mechanical properties of the 2D epoxy thin film by Monte Carlo simulation method

In this paper, we studied the effect of the 2D epoxy thin films’ shape with equilateral triangle and square structures, and matrix size Lx × Ly of (10 × 9), (20 × 19), (30 × 29), and (40 × 39) with equilateral triangle structure and (10 × 10), (20 × 20), (30 × 30), and (40 × 40) with the square structure on their mechanical properties [such as strain (ɛ), stress (σ), Young stress (E), and shear strain (G)] by using the Monte Carlo simulation method. The results show that when the shape of the 2D epoxy thin film is changed from an equilateral triangle structure to a square structure, the values of σ, E, and G decreased sharply. In addition, when the matrix size is increased from (10 × 9) to (20 × 19), (30 × 29), and (40 × 39) with an equilateral triangle structure and from (10 × 10) to (20 × 20), (30 × 30), and (40 × 40) with a square structure, σ slightly increased, but E and G decreased slightly. These results prove that the influence of structure shape on the mechanical properties of the 2D epoxy thin film is very large. The strain stress on the epoxy 2D thin film with an equilateral triangle structure and with a matrix size of (30 × 29) has a value of σ = 63.3 MPa. This result is consistent with the experimental result that σ of bulk epoxy has the maximum value of σmax = 64.76 MPa. The results are the basis for experimental research in future studies on practical applications of epoxy-thin films. In these cases, when thin films with equilateral triangle structures are used in biomedical fields, high stresses are required (such as replacement material for adaxial onion epidermis and fibrin and collagen with low stress).

Particulate flow modelling in a spiral separator by using the Eulerian multi-fluid VOF approach

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator, and thus a Eulerian multi-fluid volume of fluid (VOF) model was first proposed to describe the particulate flow in spiral separators. In order to improve the applicability of the model in the high solid concentration system, the Bagnold effect was incorporated into the modelling framework. The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature. Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model, and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature. Furthermore, the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator. When the Bagnold lift force model was considered, predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data. In the initial development stage, the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force. Thus, a better predicted vertical stratification between quartz and hematite particles was obtained, which provided favorable conditions for subsequent radial segregation.

Development of a hybrid Lagrange–Euler transition model for the film formation and dynamics of an impinging liquid spray

This paper proposes a hybrid Lagrange–Euler transition model that fully describes the injection and film formation process with different transition sub-models to balance accuracy and efficiency under the incompressible framework for spray cooling of electric machines. When the liquid phase is far away from a wall or film, a Lagrange discrete particle modeling method is employed to track liquid phase motion, which then transforms into a Eulerian droplet when a particle is close to a wall or film. Thereafter, the volume-of-fluid (VOF) method is adopted to simulate the processes of impingement, wall film formation, and dynamics. The transition model is implemented with the CONVERGE code package and validated against several available experimental data ranging from single droplets to spray impingement. The results indicate that the hybrid Lagrange–Euler transition model exhibits excellent mass and momentum conservation under different mesh resolution conditions and can well reproduce film formation and dynamics behaviors. In addition, detailed comparisons between the transition model and particle-based thin film modeling (TFM) are made for wall film formed by spray impingement. The transition model predicts a smaller film area and a better film shape than the TFM model compared to the measurements. Overall, the transition model coupled with the VOF method shows a higher sensitivity to mesh resolution, whereas the TFM model is more easily affected by semi-empirical splash models.

From Freedom Dreams to Boomer Nostalgia

During the 1980s, media images of white boomer nostalgia were often accompanied by 1960s Motown songs due to the popularity of the hit film The Big Chill as well as advertising and licensing strategies inspired by it. In previous decades, however, Motown was used to dramatize onscreen representations of Black male film characters’ emotional experiences of aspiration and resilience. This article explores how 1960s Motown songs came to be employed in two motion pictures—Nothing But a Man and Cooley High—to represent particular notions of everyday Black life, and then provides an industrial backdrop for why such cinematic uses of Motown came to effectively be replaced by invocations of white nostalgia. By analyzing the uses of Motown music within film narratives and the industrial conditions through which such licensing took place, this study goes beyond the formal analysis of film music in order to demonstrate how the act of licensing popular songs for film participates in the making of songs’ social, cultural, and political meanings. In so doing, this article shows how the material conditions of licensing music for film shape what and whose experiences of popular music are able to be represented onscreen.