Facet Planes Research Articles

A simple model for faceted topographies at normal faults based on an extended stream-power law

Abstract. Mountain fronts at normal faults are often faceted in the sense that they contain strikingly planar surface elements that follow the surface trace of the fault. Since the dip angle of the facets is typically much lower than the dip angle of the fault, it is clear that the facets are not just the exhumed footwall but have been eroded considerably. It has also been shown that a constant erosion rate in combination with a constant rate of displacement can explain the occurrence of planar facets. Quantitatively, however, the formation of faceted topographies is still not fully understood. In this study, the shared stream-power model for fluvial erosion and sediment transport is used in combination with a recently published extension for hillslopes. As a major theoretical result, it is found that the ratio of the tangents of the facet angle and the dip angle of the fault as well as the ratio of the baseline length and horizontal width of perfect triangular facets mainly depend on the ratio of the horizontal rate of displacement and the hillslope erodibility. Numerical simulations reveal that horizontal displacement is crucial for the formation of triangular facets. For vertical faults, facets are rather multiangular and much longer than wide. While the sizes of individual facets vary strongly, the average size is controlled by the ratio of hillslope erodibility and fluvial erodibility.

Conic sections in ferroelectric nematics: Experiments and mathematical modeling

The domain structure of a fluid ferroelectric nematic is dramatically different from the domain structure of solid ferroelectrics since it is not restricted by rectilinear crystallographic axes and planar surface facets. We demonstrate that thin films of a ferroelectric nematic seeded by colloidal inclusions produce domain walls (DWs) in the shape of conics such as a parabola. These conics reduce the bound charge within the domains and at the DWs. An adequate description of the domain structures requires one to analyze the electrostatic energy, which is a challenging task. Instead, we demonstrate that a good approximation to the experimentally observed polydomain textures is obtained when the divergence of spontaneous polarization—which causes the bound charge—is heavily penalized by assuming that the elastic constant of splay in the Oseen-Frank energy is much larger than those for twist and bend. The model takes advantage of the fact that the polarization vector is essentially parallel to the nematic director throughout the sample. Published by the American Physical Society 2024

Structures and migrations of interfaces between β precipitates and α′ matrix in a Ti-2.6 wt% Mo alloy

While the precipitation of α (hcp) from β (bcc) in various Ti alloys has been investigated in great detail, less is known about the precipitation of β from α. This study conducts a systematic investigation of structures and migrations of interfaces between β precipitates and α′ matrix in a Ti-2.6 wt% Mo alloy. Utilizing conventional and high-resolution transmission electron microscopy (TEM), assisted with molecular dynamics and generalized O-element analysis approaches, we unveil the dislocation and atomic structures of three typical portions of the interface surrounding a β precipitate, i.e., the habit plane, the side facet, and the end face. The habit plane of β precipitates contains two sets of dislocations with Burgers vectors b1=[21¯1¯3]α/6|[11¯1]β/2 and b4=[21¯1¯3¯]α/6|[111¯]β/2, in contrast to the single set of b1 dislocations previously found on the habit plane of α laths precipitated from β matrix in various Ti alloys. Interface migrations during shrinkage of β precipitates are characterized via in-situ TEM, showing that both the habit plane and side facet migrate through the lateral motion of nanometer-high growth ledges. The dislocation structures of various growth ledges were obtained through generalized O-element calculations, suggesting a potential non-conservative dislocation trajectory as semicoherent growth ledges sweep across the interface.

Programmable multi-stability of curved-crease origami structures with travelling folds

Multi-stable structures capable of rapid switching among different stable states have seen applications in various fields such as energy absorption, mechanical computing, and soft actuators. Curved-crease origami, which naturally involves simultaneous deformation of creases and facets, shows great potential in the development of multi-stable structures. However, upon loading, existing curved-crease origami structures tend to follow the same deformation mode as in the curved surface formation process which involves facets elastic bending, flattening, and reverse bending, thus leading to only two stable states. To achieve multi-stability, here we propose a series of curved-crease origami structures composed of planar facets and curved ones. Through a combination of experiments, numerical simulations, and analytical modelling, we demonstrate that the planar facets forming a Sarrus linkage guide the deformation mode of the curved ones, leading to the initiation and propagation of travelling folds in the curved facets. By transforming the travelling folds at specific positions into actual creases, we can achieve multiple stable states in a single structure. In addition, the number and positions of the stable states, as well as the initial peak force, can be programmed by varying the geometric parameters. Consequently, this work opens a new pathway for the development of generic multi-stable structures with programmable mechanical properties.

How caged motion in the contact layer enhances thermal tunneling across a liquid/solid interface

Ever more powerful and densely packed chips for applications like cryptocurrency mining and artificial intelligence generate such enormous heat fluxes that designers are pivoting from gas to liquid cooling to forestall damage from thermal runaway. Even with optimal flow patterns, however, the intrinsic thermal boundary resistance at the liquid/solid (L/S) interface poses an additional source of thermal impedance. There is a lingering misconception in the field that the higher the liquid contact density, the more frequent the L/S collision rate and the smaller the thermal slip length. Here we present an insightful counterexample based on nonequilibrium molecular dynamics simulations of a simple liquid confined between two face centered cubic crystals at different temperatures aligned with the [001], [011] or [111] facet plane. Measurements of various static and dynamic quantities of the contact layer reveal the ways in which long-range order, anisotropy of the L/S potential, and correlated motion act to reduce thermal boundary resistance. Systems with the smallest thermal slip length exhibit two distinct features: 2D caged motion with stringlike alignment of liquid particles, unlike that observed in glassy systems, and larger nonergodicity parameter with shorter, not longer, caging times. This trapping and release mechanism suggests a paradigm for the design of L/S interfaces to maximize thermal exchange across a classical L/S interface. Published by the American Physical Society 2024

Faceting effect on magnetism in manganese ferrites nanoparticles

Manganese ferrite (MnFe2O4) stands out among multifunctional spinel ferrites for its attractive magnetic properties, high chemical stability and excellent biocompatibility, which are essential prerequisites for effective performance in various applications, including biomedical. However, very little work has been carried out on the ideal reaction conditions to obtain nanoparticles with high performance in terms of magnetization correlated to facet engineering. This study reports the synthesis of MnFe2O4 nanoparticles by a thermal decomposition process, controlling the decomposition temperature and the ligand/precursor ratio. Indeed, with a decomposition temperature of manganese stearate maintained at 270 °C and a ligand/precursor ratio equal to 2, superparamagnetic behavior and significantly high saturation magnetization were obtained from monodisperse nanoparticles of cubic shape and approximately 7 nm in size. Combining magnetic measurements with Monte Carlo simulations demonstrated that this behavior is attributed to the shape anisotropy of cubic nanoparticles, which favors the orientation of the magnetic moment along planar facets with low surface anisotropy. The strong influence of this faceting on the nanomagnetism of ferrite based on MnFe2O4 should open new avenues for numerous applications, particularly in biomedical imaging.

Synthesis of Molybdenum Oxide Nanofibers with Multiple Surface Facets Via Electropsinning Followed by Rapid Thermal Treatment

A MoO3 nanofiber prepared by electrospinning and subsequent heat treatment is attracting significant attention due to its structural advantages. Vibrant studies are being conducted to control its morphology and diameter to improve its properties. In this study, we demonstrated the synthesis of α-MoO3 nanofibers with multiple surface facets by controlling the heating rate and temperature in the heat treatment step for removing polymer and crystallizing MoO3 from the electrospun polymer/precursor nanofibers. The analysis results show that the faster heating rate and higher heat treatment temperature in the thermal treatment process are more favorable for forming a shape in which particles with facet planes are connected. Finally, we observed the morphological change according to the heat treatment time to confirm the effect of the heat treatment conditions on the shape of MoO3 and interpreted the results in terms of nucleation and crystal growth.

CVT grown CuSe single crystals: Unveiling photodetection advancements and thermoelectric promise

Over the past few decades, transition metal chalcogenides garnered global recognition for their noteworthy contributions to the modeling and engineering of electronic, optoelectronic, and thermoelectric devices to improve overall device performance. In the current investigation, the first ever growth of CuSe single crystals is achieved utilizing the chemical vapor transport technique with iodine serving as a transporting medium. The ascertainment of the hexagonal unit cell configuration in the grown CuSe crystals with the P63/mmc space group is substantiated via powder X-ray diffraction examination. The micro-surface characteristics exhibited planar facets outlined by layer boundaries, signifying crystal development through a mechanism reliant on layer growth. The direct optical bandgap of 1⋅64 eV for CuSe single crystals is unveiled by optical reflectance spectrum, demonstrating its aptitude for incorporation into photodetectors. The Raman spectrum manifested a prominent peak at 259 cm−1, aligning to Ag1 vibrational mode. The exploration of temperature-induced fluctuations in the power factor and figure of merit unveiled a progressive increase with rising temperatures. The optimal ZT parameter for the CuSe single crystals attains 0⋅058 at 523 K. The thermogravimetric patterns of CuSe single crystals exhibited singular step decomposition, exemplified by an average weight reduction of 25⋅49 % across the temperature spectrum from ambient to 813 K. The current−voltage (I–V) features of the fabricated CuSe single crystal photodetector are assessed under biasing voltage set at 20 mV at ambient temperature. Under a bias voltage of 20 mV and a polychromatic light intensity of 50 mW/cm2, the achieved responsivity is 4335⋅57 μA/W and a detectivity of 135 × 106 Jones. The photoresponse and thermoelectric examination of CuSe crystals alludes to their potential utility in innovative applications on the horizon.

Vicinal (111) surfaces at Si solid-liquid interface during unidirectional solidification

The solid-liquid interfaces of silicon grains have been observed by an in-situ system. Two silicon seeds having different crystallographic orientations (as ⟨100⟩, ⟨110⟩, and ⟨111⟩) along the growth direction were placed side by side in a silica crucible for the direct comparison of interface behavior during the melt-growth process. Experimental evidence proved the existence of flat {111} surfaces at different grain orientations during crystallization. The difference in the interface positions of the two grains was used to calculate the undercooling of the {111} surfaces. The growth rate-undercooling relationship was linear in all experiments, showing that the observed flat surfaces were planes vicinal to {111} facets, growing through a step flow mode. The terrace length was constant but different from one experiment to another. Therefore, this work indicates that it is crucial to consider the vicinal surface kinetics in the analysis of Si facet planes and grooves during the melt-growth process.

Rockfall Analysis from UAV-Based Photogrammetry and 3D Models of a Cliff Area

The application of Unmanned Aerial Vehicles (UAVs), commonly known as drones, in geological, geomorphological, and geotechnical studies has gained significant attention due to their versatility and capability to capture high-resolution data from challenging terrains. This research uses drone-based high-resolution photogrammetry to assess the geomechanical properties and rockfall potential of several rock scarps within a wide area of 50 ha. Traditional methods for evaluating geomechanical parameters on rock scarps involve time-consuming field surveys and measurements, which can be hazardous in steep and rugged environments. By contrast, drone photogrammetry offers a safer and more efficient approach, allowing for the creation of detailed 3D models of a cliff area. These models provide valuable insights into the topography, geological structures, and potential failure mechanisms. This research processed the acquired drone imagery using advanced geospatial software to generate accurate orthophotos and digital elevation models. These outputs analysed the key factors contributing to rockfall triggering, including identifying discontinuities, joint orientations, kinematic analysis of failures, and fracturing frequency. More than 8.9 × 107 facets, representing discontinuity planes, were recognised and analysed for the kinematic failure modes, showing that direct toppling is the most abundant rockfall type, followed by planar sliding and flexural toppling. Three different fracturation grades were also identified based on the number of planar facets recognised on rock surfaces. The approach used in this research contributes to the ongoing development of fast, practical, low-cost, and non-invasive techniques for geomechanical assessment on vertical rock scarps. In particular, the results show the effectiveness of drone-based photogrammetry for rapidly collecting comprehensive geomechanical data valid to recognise the prone areas to rockfalls in vast regions.

Spallation damage of tungsten heavy alloy under shock loading

In this study, plate-impact experiments are conducted using tungsten heavy alloy (WHA) to obtain the free-surface velocity profiles under shock stress of 6–23 GPa. By analyzing the velocity wave profile, it is demonstrated that the spall strength is weakly dependent on the peak stress. The microstructure of the recovered WHA is well characterized and it’s observed that intergranular fracture and cleavage are the primary fracture mechanisms. Deformation twins are sparsely distributed near the cleavage crack. The existence of twin boundary not only affects crack propagation but also regulates the crack path and reinitiates the cleavage propagation direction on the twin boundary. The macroscopic cleavage facet planes are detected to be {100}, {110} and {111} at all shock stress.

IPR-VINS: Real-time monocular visual-inertial SLAM with implicit plane optimization

SLAM typically involves updating numerous landmarks to reconstruct scenes rather than generating a topological depiction of the actual environment. Planar features, prevalent in structured environments, can contribute to the development of more nuanced yet less cumbersome maps. The incorporation of fusions between feature points and planar facets gives rise to new discrepancies that must be meticulously addressed. To prevent the uncontrolled expansion of planar boundaries, a robust technique for boundary extraction is offered. Scene planes are fused using the boundary function, ensuring stable feature extraction and planar association. To leverage limited computational resources effectively, a streamlined back-end framework is constructed. Finally, factors are fine-tuned at a consistent scale, which not only elevates locational accuracy but also diminishes computational complexity. To reduce systematic errors, plane prior information is assimilated into global optimization. Compared with VINS-Mono, the average Absolute Trajectory Error of the proposed method on EuRoC is reduced by 44%.

Regional distribution prevalence of heterotopic ossification in the elbow joint: a 3D study of patients after surgery for traumatic elbow injury

BackgroundHeterotopic ossification (HO) is a common complication after elbow fracture surgery and can lead to severe upper extremity disability. The radiographic localization of postoperative HO has been reported previously. However, there is no literature examining the distribution of postoperative HO at the three-dimensional (3D) level. This study aimed to investigate 1) the distribution characteristics of postoperative HO and 2) the possible risk factors affecting the severity of postoperative HO at a 3D level. MethodsA retrospective review was conducted of patients who presented to our institution with HO secondary to elbow fracture between 13 January 2020 and 16 February 2023. CT scans of 56 elbows before elbow release surgery were reconstructed in three dimensions (3D). HO was identified using density thresholds combined with manual identification and segmentation. The elbow joint and HO were divided into six regions according to three planes: the transepicondylar plane (TEP), the lateral ridge of the trochlear plane (LTP), and the radiocapitellar joint and coronoid facet plane (RCP). The differences in the volume of regional HO associated with different initial injuries were analyzed. ResultsPostoperative HO was predominantly present in the medial aspect of the capsule in 52 patients (93%), in the lateral aspect of the capsule in 45 patients (80%), in the medial supracondylar in 32 patients (57%), and in the lateral supracondylar, radial head, and ulnar region in the same number of 28 patients (50%). The median and interquartile range (IQR) volume of total postoperative HO was 1683 (777∼4894) mm3. The median and IQR volume of regional postoperative HO were: 584 (121∼1454) mm3 at medial aspect of capsule, 207 (5∼568) mm3 at lateral aspect of capsule, 25 (0∼449) mm3 at medial supracondylar, 1 (0∼288) at lateral supracondylar, 2 (0∼478) at proximal radius and 7 (0∼203) mm3 at the proximal ulna. In the subgroups with Injury Severity Score (ISS) >or= 16, Gustilo–Anderson II, normal uric acid levels, elevated alkaline phosphatase (ALP), and Body Mass Index (BMI) >or= 24, the median HO volume exceeds that of the respective control groups. ConclusionThe medial aspect of the capsule was the area with the highest frequency and median volume of postoperative HO among all initial elbow injury types. Patients with higher Gustilo-Anderson grade, ISS, ALP or BMI had higher median volume of postoperative HO.

Coalescence behavior of size-selected gold and tantalum nanoclusters under electron beam irradiation: insights into nano-welding mechanisms.

The emerging technique of nano-welding (NW) via precisely regulating the fusion of nanoclusters (NCs) in nanotechnology has attracted significant attention for its innovative approach. Employing the gas-phase condensation cluster source with a lateral time-of-flight (TOF) mass-selector, size-selected gold (Au), and tantalum (Ta) NCs were prepared. This study explores the coalescence behavior of size-selected Au and Ta NCs under electron beam irradiation, aiming to investigate the related mechanism governing the welding process. Intrinsically driven by the reduction of excess surface energy, electron beam induces atomic thermal migration, fostering sintering neck growth at cluster interfaces. During this process, atomic diffusion and recrystallization enable NCs to alter shape while retaining stable facet planes. Aberration-corrected scanning transmission electron microscopy (AC-STEM) showcases the formation of single or polycrystalline sintered clusters, during which some lattice distortions can be eliminated. Interestingly, oxidized Ta clusters experience knock-on damage caused by elastic scattering of electron beams, partially deoxidizing them. Additionally, electron-phonon inelastic scattering transforms oxidized Ta clusters from amorphous to crystalline structures. Moreover, the quantum size effect and surface effect of NCs facilitate the surpassing of miscibility limits during Au-Ta heterogeneous welding processes. This investigation bridges the gap between fundamental research on cluster materials and their practical applications.

Research on the localized lightfield features of metallic nano-cone-tip optical antenna via investigating near-field lightwave and correlated net-charge distribution

In this paper, the near-field lightwave characteristics of an arrayed silicon nano-cone-tip optical antenna (NOA) covered by a common metal film, which can be viewed as a featured quasi quantum dot (QD), are carefully investigated. A dipole net-charge distribution closely correlated with the surface lightwaves excited over the antennas by incident lasers with a central wavelength of 633 nm, is clearly observed. An obvious Coulomb-like blockade from the apex apparently influencing the net-charge converging over the surface of NOA, is verified, which can also be predicted by the simulations according to surface standing waves across the apex node. The antinodes of the surface net-charge instantaneous distribution are already pushed away from the normal location owing to the apex Coulomb-like blockade, so as to present a distorted waveform different from traditional standing wave modes. The tip proximity effect leading to a relatively weak net-charge converging over surrounding planar facet and adjacent NOAs, is also discovered.

Heat Transfer in Gold Interfaces Capped with Thiolated Polyethylene Glycol: A Molecular Dynamics Study.

Reverse nonequilibrium molecular dynamics simulations were used to study heat transport in solvated gold interfaces which have been functionalized with a low-molecular weight thiolated polyethylene glycol (PEG). The gold interfaces studied included (111), (110), and (100) facets as well as spherical nanoparticles with radii of 10 and 20 Å. The embedded atom model (EAM) and the polarizable density-readjusted embedded atom model (DR-EAM) were implemented to determine the effect of metal polarizability on heat transport properties. We find that the interfacial thermal conductance values for thiolated PEG-capped interfaces are higher than those for pristine gold interfaces. Hydrogen bonding between the thiolated PEG and solvent differs between planar facets and the nanospheres, suggesting one mechanism for enhanced transfer of energy, while the covalent gold sulfur bond appears to create the largest barrier to thermal conduction. Through analysis of vibrational power spectra, we find an enhanced population at low-frequency heat-carrying modes for the nanospheres, which may also explain the higher mean interfacial thermal conductance (G) value.

Is There a Critical Dorsal Lunate Facet Size in Distal Radius Fractures That Leads to Dorsal Carpal Subluxation? A Biomechanical Study of the Dorsal Critical Corner

Intra-articular distal radius fractures are common and can be associated with carpal instability. Failure to address articular fragments linked to maintaining carpal stability can lead to radiocarpal subluxation or dislocation. The purpose of this study was to evaluate the size of a dorsal osteotomy in the dorsal/volar plane of the lunate facet that leads to dorsal carpal subluxation. Dorsal lunate facet fractures were simulated twice in each of nine fresh-frozen cadavers. After completing a partial dorsal osteotomy in the radial/ulnar plane between the scaphoid and lunate facets, an osteotomy in the dorsal/volar plane was completed. Using a cutting jig, first an estimated 5-mm osteotomy, and then a 10-mm osteotomy (from the dorsal rim of the distal radius) were completed. The wrist was mounted in a custom jig and loaded with 100 N. Displacement of the lunate in the dorsal/volar plane compared with displacement in an intact specimen was evaluated and used to assess carpal subluxation. Lunate translation was 0 mm ± 0 mm in the intact state. The 5-mm osteotomy averaged 29% of the distal radius dorsal lunate facet in the dorsal/volar plane, and lunate translation was 0.7 mm ± 1.7 mm. The 10-mm osteotomy averaged 54% of the dorsal lunate facet in the dorsal/volar plane, and lunate translation was 2.8 mm ± 2.6 mm. Assuming a linear relationship from the osteotomies created, an osteotomy of an estimated ≥40% of the distal radius in the dorsal to volar plane resulted in substantial dorsal subluxation, although this specific osteotomy was not assessed in our study. Sequentially increased dorsal osteotomies of the dorsal lunate facet result in increased dorsal carpal subluxation. Distal radius fractures that include >40% of the "dorsal critical corner" are at risk for dorsal carpal subluxation and may require supplementary fixation.

PowerRTF: Power Diagram based Restricted Tangent Face for Surface Remeshing

AbstractTriangular meshes of superior quality are important for geometric processing in practical applications. Existing approximative CVT‐based remeshing methodology uses planar polygonal facets to fit the original surface, simplifying the computational complexity. However, they usually do not consider surface curvature. Topological errors and outliers can also occur in the close sheet surface remeshing, resulting in wrong meshes. With this regard, we present a novel method named PowerRTF, an extension of the restricted tangent face (RTF) in conjunction with the power diagram, to better approximate the original surface with curvature adaption. The idea is to introduce a weight property to each sample point and compute the power diagram on the tangent face to produce area‐controlled polygonal facets. Based on this, we impose the variable‐capacity constraint and centroid constraint to the PowerRTF, providing the trade‐off between mesh quality and computational efficiency. Moreover, we apply a normal verification‐based inverse side point culling method to address the topological errors and outliers in close sheet surface remeshing. Our method independently computes and optimizes the PowerRTF per sample point, which is efficiently implemented in parallel on the GPU. Experimental results demonstrate the effectiveness, flexibility, and efficiency of our method.

Sensing of Magnetic-Field Gradients with Nanodiamonds on Optical Glass-Fiber Facets.

We demonstrate a photonic sensor of the magnetic field and its gradients with remote readout. The sensor is based on optically detected magnetic resonance (ODMR) in nanodiamonds with nitrogen-vacancy color centers that are covalently attached as a thin film on one facet of an optical fiber bundle. By measuring ODMR signals from a group of individual fibers in an ∼0.5-mm-wide imaging bundle, differences of local magnetic field strengths and magnetic field gradients are determined across the plane of the bundle facet. The measured gradients are created by direct electric currents flowing in a wire placed near the nanodiamond film. The measurement enabled the determination of the net magnetic field corresponding to various current directions and their corresponding magnetic field gradients. This demonstration opens up a perspective for compact fiber-based endoscopy, with additional avenues for remote and sensitive magnetic field detection with submicrometer spatial resolution under ambient conditions.

Solvent and A-Site Cation Control Preferred Crystallographic Orientation in Bromine-Based Perovskite Thin Films.

Preferred crystallographic orientation in polycrystalline films is desirable for efficient charge carrier transport in metal halide perovskites and semiconductors. However, the mechanisms that determine the preferred orientation of halide perovskites are still not well understood. In this work, we investigate crystallographic orientation in lead bromide perovskites. We show that the solvent of the precursor solution and organic A-site cation strongly affect the preferred orientation of the deposited perovskite thin films. Specifically, we show that the solvent, dimethylsulfoxide, influences the early stages of crystallization and induces preferred orientation in the deposited films by preventing colloidal particle interactions. Additionally, the methylammonium A-site cation induces a higher degree of preferred orientation than the formamidinium counterpart. We use density functional theory to show that the lower surface energy of the (100) plane facets in methylammonium-based perovskites, compared to the (110) planes, is the reason for the higher degree of preferred orientation. In contrast, the surface energy of the (100) and (110) facets is similar for formamidinium-based perovskites, leading to lower degree of preferred orientation. Furthermore, we show that different A-site cations do not significantly affect ion diffusion in bromine-based perovskite solar cells but impact ion density and accumulation, leading to increased hysteresis. Our work highlights the interplay between the solvent and organic A-site cation which determine crystallographic orientation and plays a critical role in the electronic properties and ionic migration of solar cells.