Spherical Hole Research Articles

A new strategy for efficient light management in inverted perovskite solar cell

The light management is of vital importance for development of efficient inverted perovskite solar cells (PSCs), which could maximize the light trapping and minimize optical loss. Herein, a novelly-designed, functional spherical NiO hole transporting layer (HTL) is reported for the first time to effectively increase light utilization and the final photocurrent of inverted MAPbI3 PSCs. Experimental and theoretical results indicate that such hollow NiO HTLs improves optical field distribution and light harvesting efficiency. This contributes to realize the better light utilization and higher photocurrent of over 24 mA cm−2, which is one of the highest reported values for NiO-based MAPbI3 PSCs. Besides, the synergistic Cu doping strategy was further employed to ensure the enhanced hole extraction and suppressed recombination loss. Eventually, this hollow Cu:NiOx PSCs feature desirable efficiency over 20%, along with the improved open-circuit voltage and low hysteresis. This work demonstrates the necessity of light management and unveils a simple approach for achieving efficient inverted NiO-based devices.

Production of diesel–biodiesel–water fuel nanoemulsions using three-dimensional printed rotor–stator hydrodynamic cavitation

This study aimed to produce a diesel–biodiesel–water fuel nanoemulsion using a rotor–stator hydrodynamic cavitation reactor (HCR). The continuous nanoemulsion fuel process comprised a cylindrical rotor with spherical holes on its surface, with the distance from the center to the center of each fixed hole. A continuous HCR was used to optimize the production of diesel–biodiesel–water emulsion fuel using response surface methodology (RSM) with a 4-factor central composite design (CCD). The independent variables of the hole diameter (3–7 mm), hole depth (2–10 mm), rotor speed (1000–5000 rpm), and flow rate of coarse emulsion fuel (5–25 L/h) were optimized to obtain the droplet size of diesel–biodiesel–water emulsion fuel. The selected conditions consisted of 42 vol% diesel, 50 vol% biodiesel, 2 vol% water, 3 vol% Span80, and 3 vol% Tween80 (D42B50W2S3T3 blend). The results showed that the nanoemulsion fuel can remain stable for over 90 d at a mean droplet size of 257.6 nm under the optimized condition of 5.8 mm hole diameter, 6.4 mm hole depth, and 4011 rpm rotor speed at a 11.8 L/h flow rate of coarse emulsion fuel. Finally, diesel, biodiesel, and nanoemulsion fuel were employed as fuels to study exhaust emissions, the exhaust gas temperature (EGT) and fuel consumption (FC) at engine speeds ranging from 1100 to 2300 rpm without engine load. The findings indicated that the nitrogen oxides (NOx) gas, the most concerning gas among the emission gases, of the D42B50W2S3T3 blend was significantly decreased by 60.4% and 57.53% when the values were compared to those of diesel and biodiesel at the highest engine speed of 2300 rpm. However, the carbon monoxide (CO) emissions of the nanoemulsion fuel were higher at 42.97% and 78.81% than those of diesel and biodiesel at engine speeds of 2300 rpm, respectively. At the maximum engine speed of 2300 rpm, the EGT of the nanoemulsion fuel was 1.94 and 2.68% lower than those of diesel and biodiesel, respectively. The FC of the nanoemulsion fuel was 0.48 kg/h, which was 3.32% lower than that of biodiesel and 18.18% higher than that of diesel at the maximum engine speed.

THE FORMULAS OF AN ACOUSTIC CHANNEL OF AN ANGLE DUAL PROBES OF LONGITUDINAL WAVES FOR VARIOUS MODELS OF REFLECTORS IN A FAR FIELD

Formulas of acoustic channels of an angle dual probes of longitudinal waves for several models of reflectors – a spherical hole, a notch, an infinite strip, a round flat bottom hole etc. in a far field are given, allowing to carry out calculations of signals at change of position of probes on a surface of the control concerning reflectors. For reflectors as lateral side drilled hole and spherical hole definition of an angle of probe and an angle of a direction on a point of reflection in a plane of the control is carried out by the decision of system from two transcendental equations. In formulas of acoustic channels for angle reflectors at the account of easing of longitudinal waves at their reflection from flat surfaces method of prof. I. N. Ermolov is used.

Eigenvalues approach on thermo-elastic diffusions problem for an infinite material containing spherical holes

In this article, the thermoelastic diffusion interaction in an unbounded medium containing spherical holes in the context Green-Naghdi model of type III are studied. The inner surface of hole is taken to be tractions free and due to an exponent of the decayed heat flux. The Laplace transforms techniques are used. The eigenvalues approaches are adopted for the solutions of applications for infinite media with a spherical hole. The numerical results for the concentration, the displacement, the chemical potential, the temperature, and the stress are presented analytical and graphically.

Multi-fractional-differential operators for a thermo-elastic magnetic response in an unbounded solid with a spherical hole via the DPL model

<abstract> <p>The current research aims to investigate thermodynamic responses to thermal media based on a modified mathematical model in the field of thermoelasticity. In this context, it was considered to present a new model with a fractional time derivative that includes Caputo-Fabrizio and Atangana-Baleanu fractional differential operators within the framework of the two-phase delay model. The proposed mathematical model is employed to examine the problem of an unbounded material with a spherical hole experiencing a reduced moving heat flow on its inner surface. The problem is solved analytically within the modified space utilizing the Laplace transform as the solution mechanism. An arithmetic inversion of the Laplace transform was performed and presented visually and tabularly for the studied distributions. In the tables, specific comparisons are introduced to evaluate the influences of different fractional operators and thermal properties on the response of all the fields examined.</p> </abstract>

The Influences of the Hyperbolic Two-Temperatures Theory on Waves Propagation in a Semiconductor Material Containing Spherical Cavity

This article focuses on the study of redial displacement, the carrier density, the conductive and thermodynamic temperatures and the stresses in a semiconductor medium with a spherical hole. This study deals with photo-thermoelastic interactions in a semiconductor material containing a spherical cavity. The new hyperbolic theory of two temperatures with one-time delay is used. The internal surface of the cavity is constrained and the density of carriers is photogenerated by a heat flux at the exponentially decreasing pulse boundaries. The analytical solutions by the eigenvalues approach under the Laplace transformation approaches are used to obtain the solution of the problem and the inversion of the Laplace transformations is performed numerically. Numerical results for semiconductor materials are presented graphically and discussed to show the variations of physical quantities under the present model.

Evolution mechanism of surface morphology and internal hole defect of 18Ni300 maraging steel fabricated by selective laser melting

The performance of the selective laser melting (SLM) parts was critically affected by the surface quality and internal defects that are closely related to process parameters. An in-depth understanding of the relationship between the formation and evolution of surface and internal defects and process parameters is needed to achieve defect-free and high-performance SLM parts. In this study, the influencing mechanism of laser power, scanning speed, hatch spacing and layer thickness on melt pool morphology, surface quality and internal hole defect of SLMed 18Ni300 maraging steel was investigated. The thermal and physical behaviour and instability of the molten pool, as well as the formation and distribution behaviour of internal hole defects, were also analyzed and discussed. Recoil pressure, the insufficient overlap between tracks and remelting between layers, Plateau-Rayleigh instability and material aggregation caused by the Marangoni effect were characterized as the main factors closely related to molten pool morphology and surface quality. Within the selected parameters in this study, the obtained surface roughness and tensile strength range from 9.08–26.40 μm and 544.14–1246.24 MPa, respectively. The internal defect changes from irregular lack-of-fusion at low energy density to the keyhole-included spherical hole at high energy density. In addition, the volumetric energy density (VED) has a certain limitation in predicting surface quality and mechanical properties due to the complex physical characteristics of the molten pool.

Influence of Alloying Elements on the Mechanical Properties of Anodized Aluminum and on the Adhesion of Copper Metallization.

The active development of the power electronics market and a constant increase in the prices of components require new materials and approaches, including a power module packaging technology. The use of aluminum instead of copper in the power module baseplate is an interesting and promising solution. The insulated metal baseplate is one of the most extensively developed technologies nowadays. The object of this study is an insulated metal substrate based on anodized aluminum. The main goal of the article is the comparison of copper topology adhesion to an anodized aluminum oxide layer formed on different aluminum alloys with aluminum content of at least 99.3 wt %. Peel test and pull-off adhesions showed a twofold difference for both aluminum alloys. The high ordered defect-free anodized alumina formed on alloys with copper content of 0.06 wt % had a mean pull-off adhesion of 27 N/mm2 and hardness of 489 HV. In the case of the alloy with copper content of around 0.15 wt %, it had hardness of 295 HV and a mean pull-off adhesion of 12 N/mm2. The results of our microstructure investigation showed that anodized alumina based on alloys with copper content of around 0.15 wt % is fragile due to spherical holes. Summing up the results, it can be concluded that not all initial impurities are critical for anodized alumina, but some, specifically copper, dramatically decreased the mechanical properties of anodized alumina.

Topological sensitivity analysis revisited for time-harmonic wave scattering problems. Part II: recursive computations by the boundary integral equation method

PurposeThe purpose of this paper is to revisit the recursive computation of closed-form expressions for the topological derivative of shape functionals in the context of time-harmonic acoustic waves scattering by sound-soft (Dirichlet condition), sound-hard (Neumann condition) and isotropic inclusions (transmission conditions).Design/methodology/approachThe elliptic boundary value problems in the singularly perturbed domains are equivalently reduced to couples of boundary integral equations with unknown densities given by boundary traces. In the case of circular or spherical holes, the spectral Fourier and Mie series expansions of the potential operators are used to derive the first-order term in the asymptotic expansion of the boundary traces for the solution to the two- and three-dimensional perturbed problems.FindingsAs the shape gradients of shape functionals are expressed in terms of boundary integrals involving the boundary traces of the state and the associated adjoint field, then the topological gradient formulae follow readily.Originality/valueThe authors exhibit singular perturbation asymptotics that can be reused in the derivation of the topological gradient function in the iterated numerical solution of any shape optimization or imaging problem relying on time-harmonic acoustic waves propagation. When coupled with converging Gauss−Newton iterations for the search of optimal boundary parametrizations, it generates fully automatic algorithms.

A study on thermoelastic interactions in fiber-reinforced mediums containing spherical cavities

This research pertains to the evaluation of thermoelastic interactions in fiber-reinforced material with spherical cavities. In the context of Green–Naghdi model (GNIII), the numerical solutions are obtained with the use of the finite element scheme. The discretization of the structure is done by the finite element method where the element is quadratic. The internal surface of the spherical hole is loaded by a uniform step in temperature. The results are graphically presented to show the effects in the absence and presence of reinforcement.

Topological sensitivity analysis revisited for time-harmonic wave scattering problems. Part I: the free space case

PurposeIn this paper, the authors revisit the computation of closed-form expressions of the topological indicator function for a one step imaging algorithm of two- and three-dimensional sound-soft (Dirichlet condition), sound-hard (Neumann condition) and isotropic inclusions (transmission conditions) in the free space.Design/methodology/approachFrom the addition theorem for translated harmonics, explicit expressions of the scattered waves by infinitesimal circular (and spherical) holes subject to an incident plane wave or a compactly supported distribution of point sources are available. Then the authors derive the first-order term in the asymptotic expansion of the Dirichlet and Neumann traces and their surface derivatives on the boundary of the singular medium perturbation.FindingsAs the shape gradient of shape functionals are expressed in terms of boundary integrals involving the boundary traces of the state and the associated adjoint field, then the topological gradient formulae follow readily.Originality/valueThe authors exhibit singular perturbation asymptotics that can be reused in the derivation of the topological gradient function that generates initial guesses in the iterated numerical solution of any shape optimization problem or imaging problems relying on time-harmonic acoustic wave propagation.

Microstructure tailoring of Ti–15Mo alloy fabricated by selective laser melting with high strength and ductility

In this study, selective laser melting (SLM) of Ti–15Mo alloy was systematically investigated, especially in its densification, microstructure and mechanical properties. At low scanning speed, the formation of spherical holes are mainly due to gas porosity brought about by residual gases. At high scanning speed, the lack of fusion (LOF) defects are presented because of the insufficient energy density, which is very detrimental to the ductility. Owing to the difference of the temperature gradient, the transition from the cellular crystals to equiaxed crystals has been observed in XY plane while the XZ plane are mainly consist of columnar crystals which are radiating along the edge of the molten pool. As a result of the retention of a reasonable level of ω phase, high dislocation density, finer grains, the twinning-induced plasticity (TWIP) and the changes of texture orientation, the Ti–15Mo samples processed by the SLM achieve a greater combination of high tensile strength of 840.41 MPa and a high elongation of 32.37%, which are higher than those reported so far. The twins become denser and thicker with increasing strain, and the average of twin widths with various strains were calculated to 7 μm at strain of 10%, 4 μm at strain of 15% and 2 μm at strain of 20%.

Dinosaur taphonomy of the Jurassic Shishugou Formation (Northern Junggar Basin, NW China) – insights from bioerosional trace fossils on bone

Bioerosional trace fossils can offer invaluable insights into taphonomic processes, ecosystem dynamics and environmental conditions that are not obtainable by other lines of evidence. Here, we describe the first invertebrate trace fossils on dinosaur bone from the Upper Jurassic Shishugou Formation of the northeastern Junggar Basin. The traces occur as spherical holes in the bone, closely resembling boreholes attributed to either indeterminate insects or dermestid beetles and thus they are here likewise ascribed to feeding and/or pupation by necrophagous insects. Such bioerosional trace fossils have several taphonomical and palaeoecological implications for they are only inflicted on subaerially exposed tissues and preferentially when carcasses are desiccated. We, therefore, conclude that the dinosaur carcass was exposed for at least several weeks under a semi-arid and seasonal climate before it was buried by sediment. This supports the general palaeoclimatological and paleoenvironmental reconstructions for the Shishugou Formation from sedimentological data. Moreover, this is the first evidence for invertebrate–vertebrate interactions from the Late Jurassic of Asia, offering a novel glimpse into the diverse biotic relationships of this ancient Jurassic ecosystem.

Two-stage continuous production process for fatty acid methyl ester from high FFA crude palm oil using rotor-stator hydrocavitation

Two-stage continuous production process for fatty acid methyl ester (FAME) from crude palm oil was performed using the rotor–stator hydrocavitation reactor. The novel ABS filament printed rotor having spherical holes on the surface of the rotor which is an efficient, fast and cost-effective procedure, was installed in the stainless steel stator of hydrosonic reactor. The 3D printed hydrosonic reactor was used to treat the FFA-rich in MCPO by esterification and followed by transesterification to produce the methyl ester. The optimum conditions of both esterification and transesterification processes were determined using the response surface methodology (RSM). For the 1st step esterification, the conditions of methanol 17.7 vol%, sulfuric acid 2.9 vol%, 3000 rpm rotor speed, hole’s diameter and depth 4 and 6 mm, and 25 L/h MCPO, were used for decreasing the FFA from 11.456 to 1.028 wt%. For the 2nd step, transesterification was employed with the optimal condition of 28.6 vol% methanol, 6.2 g/L of potassium hydroxide, 3000 rpm rotor speed, the dimension of the spherical holes on the rotor’s surface having diameter of 6.4 mm and 6.2 mm in depth, and esterified oil flow rate 25 L/h, for producing the methyl ester to over 99.163 wt%. Moreover, the purified biodiesel yields and the average energy consumption for the entire two-stage continuous process between hydrosonic and ultrasonic clamp reactors were compared. The results of purified methyl ester clearly indicate that the methyl esters of 99.163 wt% and 97.814 wt% were achieved from hydrosonic and ultrasonic clamp reactors, respectively, under the same optimized conditions. The maximum yields of purified biodiesel were 97.51 vol% and 88.69 vol% using hydrosonic and ultrasonic clamp reactors, respectively. The average energy consumption for the entire continuous two-stage process for both hydrosonic and ultrasonic clamp reactors were 0.049 and 0.056 kW h/L, respectively. For practical industrial processes, stainless steel rotors inside the stator was manufactured by CNC machine, which was also verified under the optimum conditions. The results showed that 1.07 wt% FFA and 99.221 wt% methyl ester of were obtained from first step and second step, respectively.

Shape and Temperature Expansion of Free Volume Holes in Some Cured Polybutadiene-Polyisoprene Rubber Blends.

The free volume fraction of a macromolecular structure can be assessed theoretically by using a suitable model; however, it can also be evaluated from experimental data obtained from dilatometry and positron annihilation lifetime spectra. In this second case, a regular geometry of the sub-nanometric cavities forming the free volume has to be assumed, although in fact they are irregularly shaped. The most popular approach is to guess spherical holes, which implies an isotropic growth of these last with temperature. In this work, we compared the free volume fraction, as obtained from experiments in a set of polybutadiene and polyisoprene cured rubbers and their blends, with the analogous quantity expected by using the lattice-hole model. The results allowed us to obtain insights on the approximate shape of the holes. Indeed, a cylindrical flattened geometry of the cavities produced a better agreement with the theory than the spherical shape. Furthermore, the best fit was obtained for holes that expanded preferentially in the radial direction, with a consequent decrease of the aspect ratio with temperature.

Generalized thermo-elastic interaction in a fiber-reinforcedmaterial with spherical holes

In this paper, a mathematical model is used to the evaluation of thermoelastic interactions in fiber-reinforced material with a spherical cavity. With the goal of establishing the generalized thermoelastic model with thermal relaxation time are exploited. inner surface of the spherical cavity is tractions free and loaded by the uniform step in temperature. The finite element scheme is used to get the problem numerical solutions. The numerical results have been discussed graphically to show the impacts of the presence and the absence of reinforcement.

Continuous acid-catalyzed esterification using a 3D printed rotor–stator hydrodynamic cavitation reactor reduces free fatty acid content in mixed crude palm oil

Free fatty acid (FFA) content in FFA-rich mixed crude palm oil (MCPO) was reduced through a continuous esterification process. The reaction conditions were optimized, the yield purified esterified oil was determined, and the average total electricity consumption of the entire process was evaluated. The key component of this study was the cost-effective, 3D-printed rotor that was installed in a continuous rotor–stator hydrodynamic reactor. The surface of the rotor was designed with spherical holes where the center-to-center distance between them was fixed. Response surface methodology (RSM) using central composite design (CCD) was employed to analyze the design of experiments (DOE) and optimize FFA-content reduction. The optimized conditions were 17.7 vol% methanol, 2.9 vol% sulfuric acid, a 3000 rpm rotor speed, and surface holes measuring 4 mm in diameter and 6 mm in depth. The experimental results showed that the FFA content in MCPO was reduced from 11.456 to 1.028 wt% upon esterification under these optimal conditions. The maximum yield of esterified oil from the phase separation step was 96.07 vol%, and that of the purified esterified oil was 91.27 vol%. The average total energy consumed by this hydrodynamic cavitation reactor to produce this esterified oil was 0.0264 kW h/L. This 3D printed rotor–stator reactor is a promising, novel reactor technology for producing biodiesel from FFA-rich oils.

Systematic study of pasta nuclei in neutron stars with families of the empirical nuclear equations of state

The structures of pasta nuclei in the crust of a neutron star are investigated systematically by using a family of the equations of state (EOSs) of nuclear matter within the framework of the Thomas-Fermi theory. This EOS family is given as a function of the incompressibility K 0 of symmetric nuclear matter and the parameter L that characterizes the density dependence of the symmetry energy. The remaining saturation parameters are chosen so that the masses and radii of stable nuclei calculated within the framework are consistent with the empirical values. The structure of a neutron-rich nucleus is determined by the local pressure balance of asymmetric nuclear matter, which is mainly controlled by L and K 0. With this EOS family, we calculate the structure of pasta nuclei in the crust of a neutron star, and examine its (K 0, L) dependence. It is found that the existence of pasta nuclei is mainly determined by L. For sufficiently small L, as the matter density increases, the shape of the nuclei changes from sphere to cylinder, slab, cylindrical hole and spherical hole successively. For larger L, this sequence of the shape change may end before reaching spherical hole. All the pasta shape can exist for L ≤ 70 MeV, while no pasta shape appears for L ≥ 110 MeV. The density width of each pasta phase, the energy and volume fraction at the onset of each pasta phase have a clear correlation with L while the onset density also has an appreciable Ko dependence.

Amorphous silica wastes for reusing in highly porous ceramics

AbstractThe paper analyzes a solution in green manufacturing of foamed or cellular ceramics. The objective of this study was to determine the technical solution for rice husk ash and “tales” of mixed glass cullet reusing based on the specific properties of these materials for creation of spherical holes inside ceramic using the process of coalescence of cellular glass. The paper reports on experimental results obtained from the production of lightweight cellular glass granules produced using glass cullet and rice husk ash. Lightweight cellular glass granules were mixed with clay, pressed and fired in air at 920°C. Clay sintering and the formation of ceramic were followed with the coalescence of cellular structure of glass granules and with the formation of spherical hollows inside the matrix. Density and strength of the fired ceramic bodies were determined. It is observed that the lightweight ceramics with density 900 ÷ 920 kg/m3 possess a compressive strength of about 5 MPa that is acceptable for bricks or tiles manufacture. The utilization of amorphous silica waste for lightweight ceramics manufacture helps in reducing waste disposal concerns and costs associated, and also transforms the waste into an alternative raw material with added value, moreover making the final product cheap.

Numerical analysis of mechanical behaviour of lattice and porous structures

Lattice and porous structures have attracted attention in scientific literature due to the development of 3D printers that facilitate their manufacturing. A thorough understanding of the mechanical behaviour of these structures is necessary. In this work, several lattice and porous structures are analysed using the finite element method. Eleven configurations have been studied using periodic boundary conditions, in order to numerically estimate their elastic mechanical properties (Young’s modulus, shear modulus and Poisson’s ratio) as a function of the structure porosity. In addition, a tensile fracture test has been modelled to analyse the predicted fracture pattern as well as the stress-strain curve for each structure. It is shown that structures based on spherical holes distributions lead to stiffer structures in tensile and shear conditions. The distribution of cavities has a strong influence on the mechanical behaviour. The square distribution improves stiffness, while the hexagonal distribution improves the shear modulus. Random distributions clearly decrease the stiffness and strength of the structure, although the damage in these structures is more progressive. Therefore, this work provides a comparative study to assess the influence of the lattice topological structure on some mechanical properties of interest in structural engineering, as a function of porosity.