Surface Orientation Research Articles

Recent advances of selected passive heat transfer intensification methods for phase change material-based latent heat energy storage units: A review

The following article overviews recent studies regarding heat transfer enhancement methods, explicitly focusing on fins and coils utilization, in phase change material-based latent heat thermal energy storage systems. It discusses the influence of various geometrical and material parameters on the melting and solidification processes, as well as the orientation of the heat transfer surface within the storage tank. Additionally, the article examines the use of a range of phase change materials regarding their melting temperature. Results show that there are research gaps regarding a few ranges of phase change materials of certain previously studied melting points. This paper's main goal was to detect possible research gaps within the phase change studies field. It should be highlighted that a vast amount of numerical studies of both finned and coiled geometries is in need of experimental verification. More than 62% of analyzed studies were performed numerically, while only 37% were performed experimentally. What is more, there were only a few studies concerning experimental investigations for melting temperatures higher than 60 °C. Furthermore, the majority of experimental as well as numerical studies were concerned only with melting phenomena. This paper also advocates for more standardized studies regarding coil geometries using non-dimensional parameters.

Multiple Magnetic Topological Phases in the van der Waals Crystal Mn(Bi,Sb)4Se7.

Magnetic topological materials have drawn markedly attention recently due to the strong coupling of their novel topological properties and magnetic configurations. In particular, the MnBi2Te4/(Bi2Te3)n family highlights the researches of multiple magnetic topological materials. Via first-principles calculations, we predict that Mn(Bi, Sb)4Se7, the close relatives of MnBi2Te4/(Bi2Te3)n family, are topological nontrivival in both antiferromagnetic and ferromagnetic configurations. In the antiferromagnetic ground state, Mn(Bi, Sb)4Se7 are simultaneously topological insulators and axion insulators. Massless Dirac surface states emerge on the surfaces parallel to the z axis. In ferromagnetic phases, they are axion insulators. Particularly, when the magnetization direction is along the x axis, they are also topological crystalline insulators. Mirror-symmetry-protected gapless surface states exist on the mirror-invariant surfaces. Hence, the behaviors of surface states are strongly dependent on the magnetization directions and surface orientations. Our work provides more opportunities for the study of magnetic topological physics.

Large 1-systems of curves in nonorientable surfaces

A longstanding avenue of research in orientable surface topology is to create and enumerate collections of curves in surfaces with certain intersection properties. We look for similar collections of curves in non-orientable surfaces. A surface is non-orientable if and only if it contains a Mobius band. We generalize a construction of Malestein-Rivin-Theran to non-orientable surfaces to exhibit a lower bound for the maximum number of curves that pairwise intersect 0 or 1 times in a generic non-orientable surface.

First-principles study on effects of X (Ta, Ti, and W) on the nitriding behavior of γ′-Ni3Al in Ni-based superalloys: From the surface adsorption and diffusion of nitrogen

The role of X (Ta, Ti, and W) doping in affecting the adsorption and diffusion behavior of nitrogen at Ni3Al(110) and Ni3Al(111) surfaces was studied based on first-principles calculations to understand the nitriding mechanism of γ′-Ni3Al in Ni-based superalloys. The calculated results show that the substituting of X atom on the 1st-layer (top layer) Al site could enhance the adsorption ability of N on Ni3Al surface, especially on Ni3Al(111), owing to the stronger bonding strength between N and X atoms. For comparison, the effect of the X atom on the adsorption behavior of nitrogen is not significant when it is doped in the 2nd-layer or 3rd-layer. Nitrogen diffusion into the Ni3Al surfaces as the rate-determining step of nitriding is calculated based on the climbing image nudged elastic band (CI-NEB) method. The doping of Ti could significantly decrease the energy barriers of N penetration into γ′-Ni3Al surface, regardless of surface orientation, which contributes to promoting the nitriding process of γ′ phase. The strongest strengthening effect of Ti explains the experimental results that γ′-Ni3Al contains Ti element having a great nitriding behavior in Ni-based superalloys. Our results can provide an in-depth insight into the diffusion mechanism of nitriding γ′-Ni3Al phase in Ni-based superalloys.

Structural characterization of AlN thin films grown on sapphire by atomic layer deposition

In this article, two sets of AlN thin films were produced on sapphire wafers with diverse surface orientations (C-, M-, R-, and A-) via atomic layer deposition. Various material characterization techniques were applied to investigate the morphological, structural, and optical properties of the AlN films, including atomic force microscope (AFM), X-ray diffraction, Raman scattering, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible spectrophotometer (UV–vis). The AFM results reveal that all AlN films are uniformly covered on the sapphire substrate, with no pinholes or cracks. Raman scattering spectroscopy indicates that the AlN thin films deposited on A-plane and M-plane sapphire substrates have low defect concentration. According to XPS results, the surface chemical state and element ratios of the AlN films produced on sapphire substrates with varied surface orientations are constant. The results of UV–vis transmission measurements show that the AlN film on M-plane sapphire substrate has the highest transmittance.

The effect of surface treatment and orientation on fatigue crack growth rate and residual stress distribution of wire arc additively manufactured low carbon steel components

The directed energy deposition (DED) processes, such as laser metal deposition or Wire Arc Additive Manufacturing (WAAM), are gradually becoming the preferred method for fabrication of large-scale components using metal additive manufacturing (AM) technology. In this work, the possibility of fatigue life enhancement in WAAM built low carbon steel components, by means of rolling and laser shock peening surface treatment techniques, was investigated. A series of fatigue crack propagation tests were performed on surface treated ER70S-6 and ER100S-1 WAAM built specimens, and the results were analysed and compared with the untreated materials tested under the same loading conditions. The obtained results were interpreted in terms of the sensitivity of the cracking behaviour to the specimen orientation and extraction location. Furthermore, the residual stress profiles were measured, before and after applying the surface treatment techniques, and the effects of locked-in residual stresses on the fatigue performance of WAAM built components were discussed. Finally, a detailed texture analysis was performed on the surface treated and untreated regions of both WAAM built materials considered in this work. The obtained results from this study provide an insight into the advantages and disadvantages of various surface treatment techniques for fatigue life enhancement of WAAM built components with the view to extend the application of this advanced manufacturing technology to a wider range of industrial applications.

Morphological and Ultrastructural Collagen Defects: Impact and Implications in Dentinogenesis Imperfecta.

Collagen is the building block for the extracellular matrix in bone, teeth and other fibrous tissues. Osteogenesis imperfecta (OI), or brittle bone disease, is a heritable disorder that results from defective collagen synthesis or metabolism, resulting in bone fragility. The dental manifestation of OI is dentinogenesis imperfecta (DI), a genetic disorder that affects dentin structure and clinical appearance, with a characteristic feature of greyish-brown discolouration. The aim of this study was to conduct a systematic review to identify and/or define any ultrastructural changes in dentinal collagen in DI. Established databases were searched: Cochrane Library, OVID Embase, OVID Medline and PubMed/Medline. Search strategies included: Collagen Ultrastructure, DI and OI. Inclusion criteria were studies written in English, published after 1990, that examined human dental collagen of teeth affected by DI. A Cochrane data extraction form was modified and used for data collection. The final dataset included seventeen studies published from 1993 to 2021. The most prevalent findings on collagen in DI teeth were increased coarse collagen fibres and decreased fibre quantity. Additional findings included changes to fibre orientation (i.e., random to parallel) and differences to the fibre organisation (i.e., regular to irregular). Ultrastructural defects and anomalies included uncoiled collagen fibres and increased D-banding periodicity. Studies in collagen structure in DI reported changes to the surface topography, quantity, organisation and orientation of the fibres. Moreover, ultrastructural defects such as the packing/coiling and D-banding of the fibrils, as well as differences in the presence of other collagens are also noted. Taken together, this study provides an understanding of the changes in collagen and its impact on clinical translation, paving the way for innovative treatments in dental treatment.

Ultrasonic wave propagation in randomly layered heterogeneous media

This article considers the propagation of high frequency elastic waves in a layered material. Each layer is locally anisotropic and the layer thicknesses and slowness surface orientations are modelled by a (Markovian) process. This work is important in deepening our understanding of the ultrasonic non-destructive testing of carbon fibre reinforced polymer (CFRP) composites and polycrystalline materials. The paper focuses on monochromatic shear waves propagating in two-dimensional ((x1,x3) plane) heterogeneous media. The displacement is in the x2 direction and the model focuses on the reflection and transmission of the wave at layer interfaces. The rotation of the slowness surface in each layer lies in the (x1,x2) plane and varies with the wave propagation direction (x3) only. Expressions for the local and global coefficients for the reflected and transmitted wave amplitudes are derived and shown to satisfy energy conservation. The resulting stochastic differential equations lead to a self-adjoint infinitesimal generator which can be used to produce a Fokker–Planck equation to study the probability distribution of the transmission coefficient. Explicit expressions for the moments of the probability distributions of the power transmission and reflection coefficients are then derived. The dependency of the mean and standard deviation of the power transmission coefficient on the depth of wave penetration, the localisation length, and the direction of wave propagation is then reported.

Insight into Surface Electronic Effects on Pd Nanostructures as Efficient Electrocatalysts.

Although the unique properties of nanomaterials have endowed enzyme-mimic catalysts with broad applications, the development of catalysts still relies on trial-and-error strategies without predictive indicators. Surface electronic structures have rarely been studied in enzyme-mimic catalysts. Herein, we present a platform for understanding the impact of surface electronic structures on electrocatalysis toward H2O2 decomposition, using the Pd icosahedra (Pd ico), Pd octahedra (Pd oct) and Pd cubic nanocrystals as electrocatalysts. The electronic properties on Pd were modulated with a correlation of surface orientation. We revealed the relationship between the electronic properties and electrocatalytic performance, in which the surface electron accumulation can boost the electrocatalytic activity of the enzyme-mimic catalysts. As a result, the Pd icodimer exhibits the highest electrocatalytic and sensing efficiency. This work offers new perspectives for the investigation of structure-activity relationships and provides an effective knob for utilizing the surface electronic structures to boost the catalytic performance for enzyme-mimics.

Diffusion of Sn donors in β-Ga2O3

Diffusion of the n-type dopant Sn in β-Ga2O3 is studied using secondary-ion mass spectrometry combined with hybrid functional calculations. The diffusion of Sn from a Sn-doped bulk substrate with surface orientation (001) into an epitaxial layer is observed after heat treatments in the temperature range of 1050–1250 °C. Calculated formation energies of Sn-related and intrinsic defects show that the migration of Sn is mediated by Ga vacancies (VGa) through the formation and dissociation of intermittent mobile VGaSnGa complexes. The evolution of the Sn concentration vs depth profiles after heat treatments can be well described by a reaction–diffusion model. Using model parameters guided by the hybrid functional calculations, we extract a VGaSnGa complex migration barrier of 3.0 ± 0.4 eV with a diffusion coefficient of 2 × 10−1 cm2/s. The extracted migration barrier is consistent with our theoretical predictions using the nudged elastic band method, which shows migration barriers of 3.42, 3.15, and 3.37 eV for the [100], [010], and [001] directions, respectively.

Roughening of two-dimensional interfaces in nonequilibrium phase-separated systems.

I show that nonequilibrium two-dimensional interfaces between three-dimensional phase separated fluids exhibit a peculiar "sublogarithmic" roughness. Specifically, an interface of lateral extent L will fluctuate vertically (i.e., normal to the mean surface orientation) a typical rms distance w≡sqrt[〈|h(r,t)|^{2}〉]∝[ln(L/a)]^{1/3} [where a is a microscopic length, and h(r,t) is the height of the interface at two-dimensional position r at time t]. In contrast, the roughness of equilibrium two-dimensional interfaces between three-dimensional fluids, obeys w∝[ln(L/a)]^{1/2}. The exponent 1/3 for the active case is exact. In addition, the characteristic timescales τ(L) in the active case scale according to τ(L)∝L^{3}[ln(L/a)]^{1/3}, in contrast to the simple τ(L)∝L^{3} scaling found in equilibrium systems with conserved densities and no fluid flow.

Effect of Power on Structural and Mechanical Properties of DC Magnetron Sputtered Cr Coatings

Cr coatings were deposited on the surface of PCrNi1MoA steel by DC magnetron sputtering. The effects of power (100~250 W) on the structure and mechanical properties of the coating were systematically studied. The results show that all Cr coatings have strong (110) preferred orientation and anisotropic surface morphology, and the cross sections are columnar structures. With the increase in power, the deposition rate increases linearly, the surface roughness and grain size increase gradually, and the nanomechanical properties decrease first and then increase slightly. At 100 W, the columnar grain of the coating is compact and continuous, and the wear resistance and plastic deformation resistance are the best, with the highest binding force of 27.04 N. At 200 W, due to grain growth and tensile stress, internal defects increase, and mechanical properties are poor. The combination of coating and substrates is not tight enough, and it is easy to fall off and fail under the action of external force. When the power reaches 250 W, the higher bombardment rate helps the coating release stress, and reduce porosity.

Toward Understanding the Formation of Coke during the MCS Reaction: A Theoretical Approach

In the Müller–Rochow process, where CH3Cl reacts with silicon to form methylchlorosilanes, copper is used as a catalyst. To provide insight into mechanisms leading to coke formation in the process, the interactions and decomposition of CH3Cl with four different surface orientations of copper were investigated by means of density functional theory. CH3Cl adsorbs weakly on the different surfaces, and decomposition occurs preferentially by splitting the C–Cl bond, leaving CH3 and Cl on the surface. Dehydrogenation of CH3 can be considered as a key step toward coke formation as the presence of CH2 can lead to C–C bond coupling or further dehydrogenation. All surfaces investigated, Cu(100), Cu(111), Cu(410) and Cu(221), show that CH2 formation is thermodynamically favorable relative to gaseous CH3Cl, and the path with lowest energy barriers is found for the Cu(410) surface.

A remark on Schottky representations and Reidemeister torsion

The present paper establishes a formula of Reidemeister torsion for Schottky representations. The theoretical results are applied to 3-manifolds with boundary consisting orientable surfaces with genus at least 2.

Investigating the robustness of the AlignRT InBore™ co-calibration process and determining the overall tracking errors

ObjectiveTo determine the overall tracking errors inherent to the co-calibration procedure of AlignRT InBore™’s (Vision RT Ltd., London, UK) ceiling-mounted and ring-mounted cameras. MethodsExtrinsic calibration errors related to the mismatch between ceiling and InBore cameras’ isocentres and treatment isocentre were determined using MV images and the SRS package and compared to traditional plate-based error. Next, using a realistic anthropomorphic female phantom, intrinsic calibration errors were determined while varying source-skin distance (80 to 100 cm), breast board inclination (0° to 12.5°), room lighting conditions (0 to 258 lx), skin colour (dark, white and natural skin colour), and pod occlusion. ResultsMV images of the cube proved plate-based calibration to suffer from large errors especially in the vertical direction (up to 2 mm). Intrinsic calibration errors were considerably lower. Indeed, RTD values of ceiling and InBore cameras showed little variability with isocentre depth (within 1.0 mm/0.4°), surface orientation and breast board inclination (within 0.7 mm/0.3°), changing lighting conditions (within 0.1 mm/0.2°), skin colour/tone (within 0.3 mm/0.3°) and camera pod occlusion (within 0.3 mm/0.2°). ConclusionThe use of MV-images proved critical to maintain co-calibrating errors of ceiling and InBore cameras to Halcyon’s treatment isocentre below 1 mm.

Performance Evaluation of State-of-the-Art Texture Feature Extraction Techniques on Medical Imagery Tasks

Interpreting medical images is certainly a complex task which requires extensive knowledge [1]. According to Computer Aided Diagnosis (CAD) serves as a second opinion that will help radiologists in diagnosis and on the other hand Content-based Image Retrieval uses visual content to help users browse, search and retrieve similar medical images from a database based on the user’s interest [2-4]. The competency of the CBMIR system depends on feature extraction methods [5]. The textural features are very important to determine the content of a medical image. Textural features provide scenic depth, the spatial distribution of tonal variation, and surface orientation [6]. Therefore, this study seeks to compare and evaluate some of the hand-crafted texture feature extraction techniques in CBMIR. This is to help those concerned in enhancing CBIR systems to make informed decisions concerning the selection of the best textural feature extraction techniques. Since there is no clear indication of which of the various texture feature extraction techniques is best suited for a given performance metric when considering which of the techniques to choose for a particular study in CBMIR systems. The objective of this work, therefore, is to comparatively evaluate the performance of the following texture feature extraction techniques; Local Binary Pattern (LBP), Gabor Filter, Gray-Level Co-occurrence Matrix (GLCM), Haralick Descriptor, Features from Accelerated Segment Test (FAST) and Features from Accelerated Segment Test and Binary Robust Independent Elementary Features (FAST &BRIEF) using the metrics; precision, recall, f1-score, mean squared error (MSE), accuracy and time. These techniques are coupled with specific similarity measure to obtain results. The results showed that LBP, Haralick Descriptor, FAST, and GLCM had the best results in terms of (Precision and Accuracy), Time, F1-Score, and Recall respectively. LBP had 82.05% and 88.23% scores for precision and accuracy respectively. The following scores represent the performance of the Haralick descriptor, FAST, and GLCM models respectively; 0.88s, 38.7%, and 44.82%. These test scores are obtained from datasets ranging from 1k-10.5k. Aside from LBP outperforming the other 5 models mentioned, it still outperformed the following proposed models ' [7]’, ‘Tamura texture feature and wavelet transform combined with Hausdorff distance - [8]’, ‘ [9]’ in terms of (precision, accuracy, and recall) and (precision and recall) respectively and probably f1-score (since f1-score is the weighted average of precision and recall). It is believed that an ensemble of LBP, Haralick descriptors, and Support Vector Machine (SVM) can represent a robust system for both medical image retrieval and classification.

Warping caused by surface elasticity in a nanowire under torsion

By combining molecular statics simulations and continuum mechanics-based modeling, we show in this paper that the torsion of a $\ensuremath{\langle}001\ensuremath{\rangle}$ single-crystal copper nanowire with a circular cross section gives rise to a warp, i.e., to a displacement field along the wire axis that renders the cross section nonplanar. This behavior, which is in apparent contradiction with what is predicted by continuum mechanics for an isotropic cylinder, can be well explained if we take into account the elastic response of the wire lateral surface. The latter is characterized by the anisotropy of the surface elastic constants and, more specifically in the case of torsion, by the surface shear constant ${C}_{44}^{S}$ whose strength as a function of the local orientation of the lateral surface is estimated independently from atomistic calculations on slabs presenting different vicinal surfaces. The solution of the torsion problem is then obtained by adopting a semi-inverse method in the framework of the finite strain theory in linear elasticity with Gurtin-Murdoch boundary conditions linking surface stress and bulk stress. It is shown that such an approach is well suited to explain quantitatively the warp obtained in our atomistic simulations and to prove the preponderant role played by the surface elastic constant ${C}_{44}^{S}$.

Effect of the annealing temperature on structural, morphological, and nonlinear optical properties of TeO2 thin films used for efficient THz generation.

This paper reports the effect of annealing on T e O 2 films deposited using the thermal evaporation technique. T e O 2 films of 120 nm thickness were grown on a glass substrate at room temperature (RT) and annealed at 400°C and 450°C. The structure of the film and the influence of the annealing temperature on the crystalline phase change were examined using the X-ray diffraction method. Optical properties such as transmittance, absorbance, complex refractive index, and energy bandgap were determined between ultraviolet-visible to terahertz (THz) range. These films have a direct allowed transition with the optical energy bandgap of 3.66, 3.64, and 3.54 eV at as-deposited temperatures (RTs) of 400°C and 450°C. The effect of the annealing temperature on the morphology and surface roughness of the films was investigated using atomic force microscopy. The nonlinear optical parameters, which are the refractive index and absorption coefficients, were calculated using THz time domain spectroscopy. The microstructure variation of the T e O 2 films in terms of surface orientation plays an important role in understanding the change in the nonlinear optical properties of the films. Finally, these films were subjected to 800 nm wavelength of 50 fs pulse duration obtained from a Ti:sapphire amplifier at a 1 kHz repetition rate for efficient THz generation. The power of incidence of the laser beam was tuned at a range between 75 and 105 mW; the highest power of the generated THz signal was of the order of 210 nW for 450°C annealed film with respect to the incident power of 105 mW. The conversion efficiency was found to be ∼0.22×10-5 %, which is 2.025 times more than the film annealed at 400°C.

Visualization of Surface Charge Carrier Diffusion Lengths in Different Perovskite Crystal Orientations Using 4D Electron Imaging

AbstractUnderstanding charge carrier dynamics on the surface of materials at the nanometer and femtosecond scales is one of the key elements to optimizing the performance of light‐conversion devices, including solar cells. Unfortunately, most of the pump‐probe characterization techniques are surface‐insensitive and obtain information from the bulk due to the large penetration depth of the pulses. However, ultrafast scanning electron microscopy (USEM) is superior in visualizing carrier dynamics at the surface with high spatial‐temporal resolution. Here, the authors successfully used USEM to uncover the tremendous effect of surface orientations and termination on the charge carrier of MAPbI3 perovskite single crystals. Time‐resolved secondary electrons snapshots and density functional theory calculations clearly demonstrate that charge carrier diffusion, surface trap density, surface work function, and carrier concentration are strongly facet‐dependent. The results display a diffusion length of 22 micrometers within 6.0 nanoseconds along (001) orientation. While (100) facet forms defect states that prevent carrier diffusion and shows an increase in the surface work function leading to dark contrast and fast charge carrier recombination. These findings provide a new key component to optimizing the surface of perovskites, thus paving the way for even more efficient and stable solar‐cell devices based on perovskite single crystals.

Harmonic representatives in homology over arbitrary fields

We introduce a notion of harmonic chain for chain complexes over fields of positive characteristic. A list of conditions for when a Hodge decomposition theorem holds in this setting is given and we apply this theory to finite CW complexes. An explicit construction of the harmonic chain within a homology class is described when applicable. We show how the coefficients of usual discrete harmonic chains due to Eckmann can be reduced to localizations of the integers, allowing us to compare classical harmonicity with the notion introduced here. We focus on applications throughout, including CW decompositions of orientable surfaces and examples of spaces arising from sampled data sets.