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The present problem addressed the transient behavior of convective heat and mass transfer characteristics across a curved surface under the influence of exothermic catalytic chemical reactions. The governing non-linear mathematical model wastransformed into a convenient form with the help of a primitive variable formulation. The final primitive formed model wassolved numerically by applying the finite difference method. The analysis of the above said computed numerical data in terms of oscillatory heat transfer, skin friction, and oscillatory mass transfer for various emerging parameters, such as the mixed convection parameter λT, modified mixed convection parameter λc, index parameter n, activation energy parameter E, exothermicparameter β, temperature relative parameter γ, chemical reaction parameter λ, and Schmidt number Sc is plotted in graphical form. An excellent agreement is depicted for oscillatory heat transfer behavior at the large value of activation energy E. The amplitude of heat transfer and prominent fluctuating response in mass transfer with a certain height is found at each value of the index parameter n with a good alteration. An increase in the activation energy led to an increase in the surface temperature, which yielded more transient heat transfer in the above-said mechanism. The main novelty of the current study is that first, we ensured the numerical results for the steady state heat and fluid flow and then these obtained results wereused in the unsteady part to obtain numerical results for the transient behavior of the heat and mass transfer mechanism.

In this paper, a measurement correction method is proposed to correct the error of the irradiation reflection method when measuring the emissivity of curved surface targets. First, by introducing an angle parameter related to the target surface shape, the formulas of emissivity measurements for curved surface targets under various types of radiation sources were obtained. Then, the variation law of these emissivity measurement formulas was analyzed, the concept of the measurement correction factor was proposed, and then a unified correction measurement formula was obtained. Finally, a scene of measuring the emissivity of a curved surface target based on the irradiation reflection method was simulated. Different target emissivities and different distances between the radiation source and target were set, and the errors between the measured and corrected emissivities were compared. The results revealed that the proposed method could effectively correct the error caused by the curvature of the target surface when measuring its emissivity by the irradiation reflection method. This is of great significance to expanding the application scope of the irradiation reflection method and improving the measurement accuracy.

Zusammenfassung Die optische Vermessung gekrümmter Oberflächen erfolgt meist über problemspezifische Messverfahren und Algorithmen zur 3D-Rekonstruktion, die an die optischen Eigenschaften der zu untersuchenden Oberfläche angepasst sind. In diesem Artikel wird ein Verfahren zur 3D-Rekonstruktion von Freiformflächen vorgestellt, das das Oberflächenrelief in einem telezentrischen Strahlengang mit einer telezentrischen Abbildungsoptik und einer koaxialen telezentrischen Beleuchtung erfasst. Die untersuchte Oberfläche des Prüflings kann dabei texturiert oder untexturiert und transparent, spiegelnd oder diffus sein. Die Oberfläche wird dabei nicht direkt vermessen, sondern mittels darauf aufgebrachter retroreflektierender Marker rekonstruiert. Da zwischen den Markern keine Messwerte vorliegen, können nur Oberflächen rekonstruiert werden, die eine örtliche Glattheit aufweisen. Mit einem Verfahren für monokulares Stereo werden aus einer Bildserie simultan sowohl die Kameraposen als auch die 3D-Koordinaten der Reflexionsmarker berechnet. Die sonst übliche Kalibrierung der extrinsischen Kameraparameter entfällt. Anschließend wird eine parametrische B-Spline-Oberfläche gefittet, aus der sowohl das Oberflächenrelief als auch die Oberflächennormalen berechnet werden können.

The heat and mass transfer of the unsteady flow of a micropolar fluid over a curved stretching surface was considered in this study. The Brownian motion and thermophoresis effects were explored in this analysis. The effects of suction/injection cases on the curved surface were discussed. Under flow assumptions, a mathematical model was designed employing boundary layer approximations using partial differential equations. A suitable transformation was developed using the lie symmetry method. Partial differential equations were transformed into ordinary differential equations by suitable transformations. The dimensionless system was elucidated through a numerical technique, namely bvp4c. The involved physical parameters’ influences are described in the form of graphs as well as numerical results in the form of tables. Our current work is helpful in the engineering and industrial fields. The unsteadiness parameter increases which Nusselt number at increased but concentrations declined. The thermophoresis parameter increases when increasing the Nusselt number because the small number of nanoparticles enhances the heat transfer rate. The temperature profile declined due to increasing values of unsteadiness parameter for both cases of suction and injection cases.

This study investigates the flow of heat and mass transport of an incompressible MHD Cross fluid over a nonlinear curved stretching sheet. Heat transport incorporates viscous dissipation, radiative flux, and surface heating, whereas the fluid concentration is distressed with the first-order chemical reaction. A radially varying applied magnetic field is considered to examine the effect of Lorentz force and Ohmic heating. The rheology of the fluid is theoretically modeled and constitute a novel work for the completeness of shear thinning and thickening fluids over curved structure. Similarity method is utilized to reduce the governing system of PDE’s into ODE’s. Numerical computation through Runge-Kutta fourth order with shooting technique is implemented by the first initialized higher-order system into the first ODEs. The behaviors of the flow quantities—velocity, temperature, and concentration—are graphically analyzed against the parameters, including radius of curvature, fluid rheology, radiation, and rate of reactions. The numerical results are validated in comparison with the published results. Studies of Newtonian fluids on flat and curved surfaces are the special cases of this work. The results are useful in material processing and polymer dynamics involving stretchable materials.

Vicinal surfaces exhibiting arrays of atomic steps are frequently investigated due to their diverse physical-chemical properties and their use as growth templates. However, surfaces featuring steps with a large number of low-coordinated kink-atoms have been widely ignored, despite their higher potential for chemistry and catalysis. Here, the equilibrium structure and the electronic states of vicinal Ag(111) surfaces with densely kinked steps are investigated in a systematic way using a curved crystal. With scanning tunneling microscopy we observe an exceptional structural homogeneity of this class of vicinals, reflected in the smooth probability distribution of terrace sizes at all vicinal angles. This allows us to observe, first, a subtle evolution of the terrace-size distribution as a function of the terrace-width that challenges statistical models of step lattices, and second, lattice fluctuations around resonant modes of surface states. As shown in angle resolved photoemission experiments, surface states undergo stronger scattering by fully-kinked step-edges, which triggers the full depletion of the two-dimensional band at surfaces with relatively small vicinal angles., We acknowledge the financial support from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. MAT2016-78293-C6 and Severo Ochoa No. SEV-2013-0295), the Basque Government (Grant No. IT-621-13), the regional Government of Aragon (RASMIA project), the CERCA Programme/Generalitat de Catalunya, and the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA194/16 TNSI).

The catalytic oxidation of CO on transition metals, such as Pt, is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with O. However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. Analysis of C and O core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature., We acknowledge financial support from the Spanish Ministry of Science and Innovation (Grants MAT-2017-88374-P, PID2019-107338RB-C63, PID2019-107338RB-C66), the Basque Government (Grants IT-1255-19, IT-1246-19), the Knut and Alice Wallenberg foundation (DNR KAW 2015.0058 „Atomistic Design of new Catalysts“) and the Swedish Research Council (DNR 349-2011-6491 „Catalysis on the atomic scale“).

The study of new design methods targeted to minimize the use of materials is a theme of great relevance nowadays; structural designers pursue structural solutions characterized by efficiency, sustainability and optimization. Funicular systems adopt the “right” shape in accordance with the applied load and are ideally able to act without introducing bending. In this work an effective and easy-to-read method to study and quantify the funicularity is presented and applied to structural shells obtained using form finding, and analyzed under different static loads. In order to formulate the new method, the classical funicularity concept has been extended and the definition of Relaxed Funicularity (R-Funicularity) introduced. The parameter used to define the funicularity is the eccentricity and a structural shell is called R-Funicular when the eccentricity is included into an admissibility interval.

This paper examines the impact of hybrid nanoparticles on the stagnation point flow towards a curved surface. Silica (SiO2) and alumina (Al2O3) nanoparticles are added into water to form SiO2-Al2O3/water hybrid nanofluid. Both buoyancy-opposing and -assisting flows are considered. The governing partial differential equations are reduced to a set of ordinary differential equations, before being coded in MATLAB software to obtain the numerical solutions. Findings show that the solutions are not unique, where two solutions are obtained, for both buoyancy-assisting and -opposing flow cases. The local Nusselt number increases in the presence of the hybrid nanoparticles. The temporal stability analysis shows that only one of the solutions is stable over time.

Energy harvesting properties of PVDF layers partially covered on double-curved shallow shells are studied. Firstly, the analytical expressions of voltage on the PVDF layers induced by shell vibration are derived; then the contribution to the voltage from vibrations in different directions is explored and also the effect of geometric parameters is analyzed. The results obtained theoretically indicate that: (1) The PVDF layers used on curved surface possess higher energy harvesting capabilities than those used on planar surface. (2) With the decreasing of radius of the shell, the energy harvesting capability of the PVDF layers is improved. (3) The energy harvesting ability of the laminated PVDF layers is better than that of single layer when laminated layers are connected in series mode. To validate the analytical results, energy harvesting experiments of PVDF layers on a straight beam and a curved beam are carried out comparatively. The voltage induced by vibration of the curved beam is much higher than that produced by the straight beam and the energy harvesting rate of PVDF layers on the curved beam is more rapidly than that on the straight beam. Furthermore, the voltage on the laminated PVDF layers in series connection is almost the summation of the voltages of PVDF layers which work separately. The results obtained experimentally are in agreement with those obtained analytically.

The heat transfer and flow characteristics of air jet impingement on a curved surface are investigated with computational fluid dynamics (CFD) approach. The first applied model is a one-equation SGS model for large eddy simulation (LES) and the second one is the SST-SAS hybrid RANS-LES. These models are utilized to study the flow physics in impinging process on a curved surface for different jet-to-surface (h/B) distances at two Reynolds numbers namely, 2960 and 4740 based on the jet exit velocity (Ue) and the hydraulic diameter (2B). The predictions are compared with the experimental data in the literature and also the results from RANS k-e model. Comparisons show that both models can produce relatively good results. However, one-equation model (OEM) produced more accurate results especially at impingement region at lower jet-to-surface distances. In terms of heat transfer, the OEM also predicted better at different jet-to-surface spacings. It is also observed that both models show similar performance at higher h/B ratios.

Nanoimprint lithography (NIL) is a micro/nanoscale patterning technology on thermoplastic polymer films, and has been widely used to fabricate functional micro/nanoscale patterns. NIL was also used to develop micro/nanoscale patterns on curved surfaces by employing flexible polymer stamps or micropatterned metal molds with macroscopic curvatures. In this study, two-step ultrasonic forming was used to develop micropatterns on a curved surface out of a flat metal stamp, by connecting ultrasonic imprinting and stretching processes. Ultrasonic imprinting was used to replicate functional micropatterns on a flat polymer film, using a flat ultrasonic horn and micropatterned metal stamps with prism and dot micropatterns. An ultrasonic stretching process was then used to form a curvature on the patterned film using a curved ultrasonic horn and a soft mold insert, to avoid damage to the pre-developed micropatterns. The ultrasonic horn was designed to have three different tip radii, and the resulting forming depth and curvature formation were investigated experimentally. As a result, three different curved surfaces containing two different micropatterns were obtained. The developed curved films containing micropatterns were then evaluated optically, and showed different optical diffusion and illumination characteristics according to the film curvature and micropattern type. These results indicate that the proposed technology can extend the functionality of conventional micropatterned products by imposing appropriate curvatures.

Laser cladding on curved surfaces is essential in industrial applications for restoration and remanufacturing of high-value parts. This study investigated the influence of different factors on clad width, clad height, and dilution rate in curved surface laser cladding with curved path. Mathematical models were developed using central composite designs to predict these geometric characteristics by controlling laser power, scanning speed, gas flow, and altering the outside radius of the cylindrical substrate. Analysis of variance and response surface methodology indicated that clad width increased with increasing laser power and reducing scanning speed. Clad height positively correlated to laser power and negatively correlated to the outside radius of the cylindrical substrate. Increasing the laser power while decreasing the scanning speed led to an increase in dilution rate. Afterwards, the geometric characteristics of the clad were improved by optimizing these factors with the target to maximize clad width and height as well as to minimize dilution rate. The difference between model predictions and experimental validations for clad width, clad height, and dilution rate were 3.485%, 3.863%, and 6.566%, respectively. The predicted accuracy was verified with these models, and they were able to provide theoretical guidance to predict and control the geometric characteristics of curved surface laser cladding with a curved path.

A smart climbing hold with variable inclination of the grip surface was developed, instrumented with two triaxial force transducers. The inclination of the cylindrical grip surface was varied by adding 10mm panels to the wall, thereby confining the surface to larger inclinations. The difficulty of gripping the hold with variable surface inclination was reflected in the vertical and horizontal forces, which decreased as the inclination increased, and in the increasing angle of the average force vector.

International audience; A technique based on infrared thermography is used to determine the convective heat transfer on a flat plate on which either a single circular air jet or a row of jets impinged. The flat plate is heated using the thin-foil technique, which enables one to impose different convective heat fluxes. For each flux, a temperature distribution is recorded using a thermographic camera. After that, local heat transfers and local adiabatic temperatures are determined by means of a linear regression method. Parameters that are made to vary include jet injection temperature, the Reynolds number, spacing between adjacent jet, and the distance between the flat plate and jets orifices. In each case, two configurations are investigated: one with and the other without semi-confinement. Results show the independence of heat transfer coefficients and effectiveness from the jet injection temperature within the range studied. The influence of confinement on heat transfer coefficient is weak, but it has a great impact on effectiveness.

In engineering systems, features such as textures or patterns on curved surfaces are common. In addition, such features, in many cases, are required to have shapes that are conformal to the underlying surfaces. To address the fabrication challenge in building such conformal features on curved surfaces, a newly developed additive manufacturing (AM) process named computer numerically controlled (CNC) accumulation is investigated by integrating multiple tools and multiple axis motions. Based on a fiber optical cable and a light source, a CNC accumulation tool can have multi-axis motion, which is beneficial in building conformal features on curved surfaces. To address high resolution requirement, the use of multiple accumulation tools with different curing sizes, powers, and shapes is explored. The tool path planning methods for given cylindrical and spherical surfaces are discussed. Multiple test cases have been performed based on a developed prototype system. The experimental results illustrate the capability of the newly developed AM process and its potential use in fabricating conformal features on given curved surfaces.