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Effectively utilizing deep red to near-infrared (DR-NIR) phosphors to achieve the optimal performance of NIR phosphor-converted white LEDs (DR-NIR pc-wLEDs) is currently a research hotspot. In this study, an optical model of DR-NIR pc-wLEDs with virtual multilayer fluorescent films was established based on the Monte Carlo ray-tracing method. Different gradient distributions of the particles were assigned within the fluorescent film to explore their impact on the optical performance of pc-LEDs. The results show that, for the case with single-type particles, distributing more DR-NIR particles far from the blue LED chip increased the overall radiant power. The distribution of more DR-NIR particles near the chip increased the conversion ratio from blue to DR-NIR light. The ratio of the 707 nm fluorescence emission intensity to the 450 nm excitation light intensity increased from 1:0.51 to 1:0.28. For multiple-type particles, changes in the gradient distribution resulted in dual-nature changes, leading to a deterioration in the color rendering index and an increase in the correlated color temperature, while also improving the DR-NIR band ratio. The reabsorption caused by the partial overlap between the excitation band of the DR-NIR particles and the emission band of the other particles enhanced the radiant power at 707 nm. Distributing DR-NIR phosphor particles closer to the chip effectively amplified this effect. The proposed model and its results provide a solution for the forward design of particle distributions in fluorescent films to improve the luminous performance of DR-NIR pc-wLEDs. [ABSTRACT FROM AUTHOR]

Extreme wettability materials, which can enable high-efficiency oil/water separation, has become a widely discussed topic due to increasingly severe oil pollutions including frequent offshore oil-spills accidents and industrial oily wastewater emission. However, most of existing methods to prepare these materials involved complicated machining processes or dangerous operations, especially the use of corrosive or toxic chemicals. Herein, a novel and environment friendly method including mark electrochemical machining (MECM) and subsequent chemical immersion, was proposed to acquire micropore arrays on Al foil for efficient oil collection from oil/water mixtures. Micro-dimple arrays were generally fabricated by MECM process followed by CuCl2 immersion to make it through. Both simulation and experimental verification were conducted to elucidate how dimple structures varied with machining parameters. The micro-scale rectangular-shaped step-like structures on micropore arrays endowed as-prepared samples with excellent superhydrophibic and underwater superoleophobic properties. Moreover, oils with kinematic viscosities ranging from 0.41 to 74.4 cSt could be separated from water with separation efficiencies above 95%. The superhydrophilic Al foil still showed good durability through repeated oil/water separation tests, and retained its superhydrophilicity even after the storage in water for 120 hours. Therefore, this novel and green method gives researchers new insights into functional materials preparation for practical oil/water separation. [ABSTRACT FROM AUTHOR]

Compared with the single-component metal plate, the stainless steel-carbon steel laminated plate (SCLP) combines the stainless steel layer and the carbon steel layer with a special preparation technique. In order to estimate the bending angle of laminated plates accurately, it is of great significance to establish an analytical model. Based on the temperature gradient mechanism, the temperature distribution equation of the SCLP is established by the piecewise function. Then, the depth of the plastic zone is calculated by the recrystallization temperature according to the temperature distribution along the thickness direction of the SCLP. Moreover, by fitting the yield strength curves of stainless steel and carbon steel, the average compressive stress of the plastic zone is calculated through the integral method. By optimizing the calculation of the plastic depth and the average compressive stress in the plastic zone, the analytical model is established based on mechanical equilibrium equations. The experimental verification shows that the average error of bending angle using the proposed model is 9.95%, while Liu's model is 38.02%. The proposed model provides a calculation method for estimating the bending angle, which contributes to improving the accuracy of the analytical model in laser bending of SCLP. [ABSTRACT FROM AUTHOR]

A morphology investigation of sectional stripes and adhering slag based on the vapor-to-melt ratio is carried out to reveal the effect of material removal proportion on the Nd:YAG laser cutting process. The influences of vapor-to-melt ratio on the morphology of sectional stripes and adhering slag (roughness, stripe width, and slag height) are investigated by the experimental observation and analysis. It is shown that the maximum particle diameter demonstrates the size of the hanging slag nodules, and the average particle diameter reflects the section stripe spacing. At a suitable vapor-to-melt ratio, the stripes with regular morphology and uniform width allow the molten layer to produce spherical particles with smaller diameter and uniform size. The molten pool is superimposed and the material is evenly paved, resulting in a good roughness of the section. Because of the good removal effect, the proportion of the membranous part hanging on the bottom surface is higher than that of the nodular part. Although the slag height is relatively obvious, the microcracks connected inside make the whole adhering slag easier to remove. The control of vapor-to-melt ratio is helpful for reducing the height of adhering slag and the proportion of nodular solidified materials, which has guiding significance for improving the cutting quality of the bottom surface of the plate. [ABSTRACT FROM AUTHOR]

Spontaneous and directional pumpless transportation (SDPT) of subaqueous gas bubbles has great prospects in eliminating destructive gas bubbles in fluid transportation pipes. However, with current technology it is difficult to realize non-buoyancy driven long-distance SDPT. How to realize long-distance SDPT of subaqueous gas bubbles and how to fabricate a surface with the capacity of long-distance SDPT of subaqueous gas bubbles on engineering metals still remain a challenge. Here, a serial wedge-shaped wettability pattern with an exterior surrounding subaqueous superaerophobic region and interior subaqueous superaerophilic region is designed to realize long-distance SDPT of subaqueous gas bubbles. The process is driven by unbalanced surface tension forces; hence, subaqueous gas bubbles can not only be transported on a horizontal and straight pattern, but can also be easily transported on a horizontal and spiral-shaped pattern or on a wave-shaped pattern that is spatially tilted. In addition, a universal method composed of electrochemical etching and laser etching is also proposed to fabricate the serial wedge-shaped wettability pattern on various engineering metal materials including Al, Mg alloy, Ti alloy, and Zn. [ABSTRACT FROM AUTHOR]

Liquid marbles which can be created by encapsulating water droplets using superhydrophobic powders have attracted extensive attention for their various promising application prospects. Cupric stearate coated liquid marbles was created by encapsulating water droplet using cupric stearate powders in a droplet rolling process. Hierarchies of robustness have been constructed which showed that the cupric stearate coated liquid marbles survived on surfaces with different wettabilities and could keep intact after impact, manipulation, transportation and mechanical compression. To evaluate robustness of the liquid marbles in manipulation processes, the mass of superhydrophobic powders per unit area on the surface of liquid marbles (powder surface density) was investigated. Powder surface density was decreased with the increase of water volume in the liquid marble. Moreover, water volume of the liquid marble was adjusted in situ, and the critical powder surface density was obtained via increasing or decreasing water volume of the liquid marble. By analyzing the critical surface density upon rupture or collapse of the liquid marble, the dependence of the critical surface density on the water volume of the liquid marble was predicted, which agrees well with experimental results. [ABSTRACT FROM AUTHOR]

As an appropriate type of foundation for offshore wind turbines (OWTs), wide-shallow composite bucket foundation (WSCBF) is cost-competitive, and it has a unique and special substructure that comprises seven internal rooms arranged in a honeycomb-like structure. In this study, the cyclic behavior of WSCBF for OWTs embedded in saturated clay was investigated using a large-scale model subjected to lateral cyclic loading. The responses of foundation under constant- and various-amplitude cyclic loadings were recorded in terms of displacements, rotations, and bending moments. The variations in stiffness and damping were obtained, and a collaborative bearing mechanical model between the bucket and soil was considered, which was beneficial for improving the stiffness of the whole structure. Accumulative deformation was found to have little effect on the bearing capacity of the foundation. Dynamic analysis in frequency domain was further performed on both moment and rotation data, and the complex, frequency-dependent impedance was also studied. [ABSTRACT FROM AUTHOR]

In order to reveal the relationship between vapor-to-melt ratio and processing quality in pulsed laser cutting of alumina ceramic sheets, experiments are carried out to obtain variations of the vapor-to-melt ratio with laser power, scanning speed, and thickness of ceramic sheet. By the morphological observation and analysis, the influence of the vapor-to-melt ratio on cutting quality is summarized. It is found that the vapor-to-melt ratio is increased with the increase of laser power, while it is decreased with the increase of scanning speed and the increase of sheet thickness. A good processing quality with suitable kerfs' width, better uniformity, and smaller roughness is obtained at a relatively large value of vapor-to-melt ratio. However, the excessive vapor-to-melt ratio will cause the deterioration of cutting stability and quality. Therefore, to meet the requirement, the vapor-to-melt ratio is controlled at around 0.1 to get 250 μm of average kerfs' width and Ra less than 3.2 μm of uniform kerfs. It reveals that the vapor-to-melt ratio is more intuitive to reflect the connection between the forms of material removal and cutting quality in laser processing, which provides an important theoretical and experimental support in the field of precision laser cutting on alumina ceramic sheets. [ABSTRACT FROM AUTHOR]

To study the regular pattern of vapor-to-melt ratio in laser cutting sheet metal, a physical model of vapor-to-melt ratio is developed to demonstrate the material remove forms of vaporization-melt in cutting area and the state of energy and mass flow in the molten layer. Variation of vapor-to-melt ratio with laser power and cutting velocity is obtained by laser cutting of 6063 aluminum alloy sheet. The 0.5-mm sheet thickness is carried out on a JK701H Nd:YAG pulse laser cutting system by simulating under the regression correction of cut radius. Observation on the cut samples with different parameters (65 W, 85 W, 105 W varied with laser power increasing, and 2.2 mm/s, 2.0 mm/s, 1.8 mm/s with decreasing of beam cutting speed) and the calculations show that vapor-to-melt ratio increases (0.595–1.995, 0.672–2.631, 0.787–4.171) with laser power (65 W–110 W) and decreases with cutting velocity (1.8 mm/s–2.4 mm/s). At the same time, the laser cutting quality increases with vapor-to-melt ratio and the decrease with thickness of residual molten layer. The results show good agreement between vapor-to-melt ratio model and experiments. The analysis verifies that this model is feasible and it makes contribution to laser precision cutting. [ABSTRACT FROM PUBLISHER]

High cleaning quality for silicon wafers without damage is a challenge in laser cleaning technologies. Laser cleaning of Al2O3 micro-particles, which are the main contaminants of silicon wafer lapping and polishing solutions used in industry, from silicon wafers was studied for determining laser energy for high efficient particle removal while not causing damage to the wafers. As the cleaning force is generated from laser-energy absorption and conduction of the wafer, heat-conduction model on silicon wafer was developed during laser irradiation using a finer finite element method, from which cleaning force exerting on the particles greater than the adhesion force between the particle and the substrate, but less than the wafer damage energy of laser input was determined. Calculations of the laser energy threshold values for both particle cleaning and wafer damage were conducted for silicon wafers of 200 mm in diameter and 0.2 mm in thickness, and they were found to be about 60 mJ/cm2 and 320 mJ/cm2, respectively. The laser energy threshold model was finally verified experimentally using a KrF Excimer laser and found to be in good agreement with the experimental data. With the cleaning parameters from the model, the cleaning efficiency of as high as 98% has been achieved. [ABSTRACT FROM PUBLISHER]

Gears with a complex curve tooth, such as spiral bevel and hypoid gears, lack an ideal technique for the final finishing process. Pulse electrochemical finishing (PECF) is considered a promising method for surface finishing due to its micro-removal characteristics. A PECF system for spiral bevel gear (SBG) is established according to the generation of SBG tooth surfaces. An SBG (module, 12 mm; number of teeth, 38) is selected as the processing test piece, and mathematical models are developed for analyzing the characteristics of PECF. The influence of the experimental variables, including applied voltage, interelectrode gap, and finishing time, on the total removal thickness and surface roughness is discussed. The calculated values are found to be approximately consistent with the experimental values. The other parameters, including the concentration of electrolyte, tool rotational speed, flow rate of electrolyte, and pulse period, are also studied. Results show that the roughness of the SBG tooth surface is reduced from Rz 7.13 to 4.32 μm. The precision of the SBG is also improved. [ABSTRACT FROM AUTHOR]

Based on the basic platform of BP neural networks, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1–2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indicate that the prediction allowance is controlled less than 5%–8% and can provide a theoretical and experimental basis for industry purpose. [ABSTRACT FROM AUTHOR]

According to ANSYS software and an electron probe experiment, a multi-layer finite element model (FEM) of pulsed laser bending of stainless steel-carbon steel laminated plate (SCLP) including interfaces has been established. Compared with a single-layer stainless steel plate (SLSP), based on a temperature gradient mechanism considering the depth of the plastic zone, the influence of the interfaces and carbon steel layer in the model of the SCLP on the bending angle has been studied by analyzing the distributions of the temperature field, stress field and strain field in the thickness direction. The simulation results show that the temperature of the SCLP in the thickness direction is lower than that of the SLSP due to interfacial thermal resistance of the interface and fast heat conduction of the carbon steel layer, resulting in a smaller depth of the plastic zone of the SCLP defined by the recrystallization temperature. Affected by the temperature distribution, the plastic stress and strain of the SCLP in the plastic zone are smaller than those of the SLSP, leading to a smaller bending angle of the SCLP. When the laser power is 140 W, the scanning speed is 400 mm/min, the defocus distance is 10 mm, and the scanning time is 1, the bending angle of the SCLP is 1.336°, which is smaller than the bending angle 1.760° of the SLSP. The experimental verifications show that the maximum error of the bending angle is 3.74%, which verifies that the model of laser bending is usable and contributes to refining the laser bending mechanism of the SCLP. [ABSTRACT FROM AUTHOR]

Compared with the single-component metal plate, there is a special transition layer on the joint interface between two kinds of materials in the stainless steel-carbon steel laminated plate (SCLP). In order to describe the finite element model of laser bending accurately, it is of great significance to determine material properties of the transition layer. Based on the element distribution, an equivalent method is adopted to calculate thermal conductivity, thermal expansion coefficient, elastic modulus, density, Poisson's ratio, and specific heat capacity of transition layer. The electron probe experiments show that the transition layer is formed by interfacial element diffusion with thickness of 7 μm. Besides, the volume fraction of stainless steel (46.63%) and carbon steel (53.37%) in the transition layer is tested by energy dispersive spectrometer, respectively. Through the equivalent method, a laser bending model of SCLP is simulated by ANSYS software to predict the bending angle under different parameters. The experimental verification shows that the maximum of bending angle errors is 3.74%, which is lower than the maximum 4.93% of errors calculated by the mean value method. The analysis verifies that the laser bending model is feasible and contributes to improving the accuracy of modeling SCLP in the laser bending process. [ABSTRACT FROM AUTHOR]