Angular Geometry Research Articles

ISAC‐oriented access point placement in cell‐free mMIMO systems

AbstractIn mobile communication networks for integrated sensing and communication, site planning of access points fundamentally determines both communication quality and sensing performance. This paper aims to tackle the AP placement problem under the setting of cell‐free massive multiple‐input multiple‐output, which represents a promising direction for network architecture evolution. Seeking a balance between the sum‐throughput of communication and the Cramér–Rao lower bound of target sensing, the access points are first pre‐placed by solving a convex optimization and further adjusted with optimal angular geometry. The final step involves employing nearest neighbour projection to refine access point positions in the cell‐free massive multiple‐input multiple‐output system, ensuring alignment with integrated sensing and communication requirements. The numerical results show that the proposed algorithm achieves 90% of the optimal communication sum‐rate and 95% of the optimal target localization accuracy.

Chirally-coupled-ring fibers for arbitrary-order orbital angular momentum mode generation and detection.

A novel chirally-coupled-ring fiber (CCRF) is proposed for efficiently generating and detecting arbitrary-order orbital angular momentum (OAM) modes in ring-core fibers (RCFs). The CCRF comprises inner and outer cores, N angularly uniformly distributed dielectric rods, and a cladding layer. These rods, twisted along the fiber axis between the cores, introduce angular geometry perturbations to manipulate the core modes. Through meticulous theoretical modeling and systematic analysis grounded in coupled-mode theory, we reveal CCRF eigenmodes carrying spin-entangled OAM, elucidate the mode coupling and power transfer in CCRFs, and present the CCRF design principle. Utilizing the full-vector beam propagation method, we carry out a proof-of-principle experimental system to demonstrate the capability of CCRFs in OAM mode manipulation and their feasibility and superiority in system-level applications. Additionally, we generate OAM modes across a wide range of topological charges from ℓ = -8 to ℓ = 8 using CCRFs, with conversion efficiencies from 92.10% to 99.63% and mode purities from 90.28% to 99.48%. Attributed to a coaxial dual-core structure with core-separated geometry perturbations, CCRFs enable flexible manipulation of arbitrary-order OAM modes without altering core geometry parameters, effectively solving design flexibility and compatibility problems in conventional single-core fiber devices. The proposed CCRF holds great promise for fiber-based OAM applications, especially for RCF-based OAM multiplexing communications.

Breaking ground in Ghana: LiDAR for site monitoring and its implications on project delivery

Light Detection and Ranging (LiDAR) has in contemporary times become a popular technology in the developed world, being utilized in city planning and infrastructure development. Documentation on the knowledge of its usage in Ghana is scanty. A major challenge that hinders the effective and timely delivery of infrastructural projects in Ghana is the delay in validating certificates for payment as a result of the use of traditional methods of measurement. This paper analysed the use of LiDAR in Aboragyei dumpsite in comparison with the existing traditional method of measurement, which is both time-consuming and prone to measurement inaccuracies. The objective was to evaluate the level of accuracy in measurement between the two methods. This paper used quasi-experimental designs on LiDAR technology to capture 3D models and extract vertical and horizontal measurements from them within a short period. The findings from the comparative assessment indicated that LiDAR technology speeds up infrastructure projects by enhancing not only procedure productivity but also cross-team communication. The cloud point models generated by LiDAR mapping do not deform when confronted with angular or complex geometry, unlike theodolite. This study makes a strong case for the utilization of LiDAR as a method for measuring vertical and horizontal angles by illuminating the target with laser light and measuring each reflection with a sensor. LiDAR system if adapted for site monitoring in Ghana will help avoid distortions in measuring horizontal and vertical angles and save time. However, a major constraint using it in Ghana was the unstable weather patterns.

Geometric Angles and Gene Expression in Cells for Structural Bone Regeneration.

Geometry and angles play crucial roles in cellular processes; however, its mechanisms of regulation remain unclear. In this study, a series of three dimensional (3D)-printed microfibers with different geometries is constructed using a near-field electrostatic printing technique to investigate the regulatory mechanisms of geometry on stem cell function and bone regeneration. The scaffolds precisely mimicked cell dimensions with high porosity and interoperability. Compared with other spatial topography angles, microfibers with a 90° topology can significantly promote the expression of osteogenic gene proteins in bone marrow-derived mesenchymal stem cells (BMSCs). The effects of different spatial structures on the expression profiles of BMSCs differentiation genes are correlated and validated using microRNA sequencing. Enrichment analysis shows that the 90° microfibers promoted osteogenesis in BMSCs by significantly upregulating miR-222-5p/cbfb/Runx2 expression. The ability of the geometric architecture to promote bone regeneration, as assessed using the cranial defect model, demonstrates that the 90° fiber scaffolds significantly promote new bone regeneration and neovascular neural network formation. This study is the first to elucidate the relationship between angular geometry and cellular gene expression, contributing significantly to the understanding of how geometric architecture can promote stem cell differentiation, proliferation, and function for structural bone regeneration.

Synthesis and Structure of the Dicarboxyl-Terminated Iron(II) Tris-Glyoximates with Linear and Angular Geometry of their Molecules

Template condensation of the chelating α-dioximate ligand synthon—glyoxime and the appropriate cross-linking agent—monofunctionalized boronic (3-carboxyphenylboronic or 4-carboxyphenylboronic) Lewis acid in a boiling nitromethane as a solvent on the iron(II) ion as a matrix afforded the dicarboxyl-terminated iron(II) tris-glyoximates with functionalizing meta- and para-substituents in their apical boron-based aromatic fragments. The composition and structure of these macrobicyclic complexes were confirmed using elemental analysis, UV-vis, 1H and 13C{1H} NMR spectra. Their crystal and molecular structures were obtained by the single crystal X-ray diffraction experiments. Asymmetric units of their crystals contain, besides of a clathrochelate molecule, two solvate molecules, which form hydrogen bonds with its functionalizing carboxyl groups. The C–O bond lengths in these terminal groups and a possibility of localization of hydrogen atoms on the difference Fourier maps clearly demonstrate that the formation of such associates does not include a deprotonation of the macrobicyclic complex and its intracomplex molecules remain neutral. The encapsulated iron(II) ion in their molecules occupies a centre of its FeN6-coordination polyhedron. Its geometry is intermediate between a trigonal prism (TP, the distortion angle φ = 0°) and a trigonal antiprism (TAP, φ = 60°); the values of φ are equal to 17.1 and 18.9°, respectively. Fe–N distances vary from 1.901(2) to 1.924(2) Å, thus suggesting a low-spin diamagnetic state of the encapsulated iron(II) ion. The C=N bonds in the donor oxime groups are shortened, while the С–С bonds in the chelating glyoximate fragments are elongated, as compared with those in their aliphatic analogs. Free rotation of the apical aromatic substituents at the cross-linking boron atoms around the ordinary B–C bonds caused the absence of their coplanarity. The intramolecular distances С···С between the terminal carboxyl groups in the apical cross-linking fragments are equal to 15.693(4) and 17.888(3) Å for the clathrochelate meta- and para-isomers, respectively. The aforementioned rotation allows to achive an angular geometry of the prospective meta-dicarboxyloclathrochelate ligand with a formation of ∠C···Fe···C close to 145° between its terminal O‑donor carboxyl groups. This complex can play a role of both the angular and linear 3D-ligands, while its clathrochelate para-substituted isomer seems to be the prospective linear metalloligand.

Synthesis and Structure of the Dicarboxyl-Terminated Iron(II) Tris-Glyoximates with Linear and Angular Geometry of their Molecules

Synthesis and Structure of the Dicarboxyl-Terminated Iron(II) Tris-Glyoximates with Linear and Angular Geometry of their Molecules

Periocular Biometric Recognition for Masked Faces

Since the outbreak of Coronavirus Disease 2019 (COVID-19), people are recommended to wear facial masks to limit the spread of the virus. Under the circumstances, traditional face recognition technologies cannot achieve satisfactory results. In this paper, we propose a face recognition algorithm that combines the traditional features and deep features of masked faces. For traditional features, we extract Local Binary Pattern (LBP), Scale-Invariant Feature Transform (SIFT) and Histogram of Oriented Gradient (HOG) features from the periocular region, and use the Support Vector Machines (SVM) classifier to perform personal identification. We also propose an improved Convolutional Neural Network (CNN) model Angular Visual Geometry Group Network (A-VGG) to learn deep features. Then we use the decision-level fusion to combine the four features. Comprehensive experiments were carried out on databases of real masked faces and simulated masked faces, including frontal and side faces taken at different angles. Images with motion blur were also tested to evaluate the robustness of the algorithm. Besides, the experiment of matching a masked face with the corresponding full face is accomplished. The experimental results show that the proposed algorithm has state-of-the-art performance in masked face recognition, and the periocular region has rich biological features and high discrimination.

Feasibility of cross-calibrating ocean-color sensors in polar orbit using an intermediary geostationary sensor of reference

A generic methodology is presented to cross-calibrate satellite ocean-color sensors in polar orbitviaan intermediary geostationary sensor of reference. In this study, AHI onboard Hiwamari-8 is used as the intermediary sensor to cross-calibrate SGLI onboard GCOM-C and MODIS onboard Aqua and Terra (MODIS-A and MODIS-T) after system vicarious calibration (SVC). Numerous coincidences were obtained near the Equator using 3 days of imagery, i.e., 11 May 2018, 22 January 2019, and 25 January 2020. Spectral matching to AHI spectral bands was first performed for a wide range of angular geometry, aerosol conditions, and Case 1 waters using a single band or multiple bands of SGLI, MODIS-A and MODIS-T, yielding root mean square differences of 0.1–0.7% in the blue and green and 0.7%–3.7% in the red depending on the band combination. Limited by the inherent AHI instrument noise and the system vicarious calibration of individual polar-orbiting sensors, cross-calibration was only performed for equivalent AHI bands centered on at 471, 510, and 639 nm. Results show that MODIS-A and MODIS-T are accurately cross-calibrated, with cross-calibration ratios differing by 0.1%–0.8% in magnitude. These differences are within or slightly outside the estimated uncertainties of ±0.6% to ±1.0%. In contrast, SGLI shows larger cross-calibration differences, i.e., 1.4%, 3.4%, and 1.1% with MODIS-A and 1.5%, 4.6%, and 1.5% with MODIS-T, respectively. These differences are above uncertainties of ±0.8–1.0% at 471 and 510 nm and within uncertainties of ±2.3% and ±1.9% at 639 nm. Such differences may introduce significant discrepancies between ocean-color products generated from SGLI and MODIS data, although some compensation may occur because different atmospheric correction schemes are used to process SGLI and MODIS imagery, and SVC is based on the selected scheme. Geostationary sensors with ocean color capability have potential to improve the spectral matching and reduce uncertainties, as long as they provide imagery at sufficient cadence over equatorial regions. The methodology is applicable to polar-orbiting optical sensors in general and can be implemented operationally to ensure consistency of products generated by individual sensors in establishing long-term data records for climate studies.

Solid Particle Erosion Behavior on the Outer Surface of Basalt/Epoxy Composite Pipes Produced by the Filament Winding Technique

Basalt/epoxy composite pipes in a [±55]4 winding configuration were produced on CNC filament winding machines (10 N fiber tension and ~11 mm bandwidth). In the experiments, a 34 m/s impact velocity was set using the double-disc method, and five different particle impingement angles (30, 45, 60, 75, and 90°) were used to determine the erosive effect on the outer surfaces of filament wound composite pipes under the influence of 600 μm erodent particles with angular geometry in the test set, complying with the ASTM G76-95 standard. The winding patterns in the lamina (±55 angle-ply laminate region) and zigzag (±55 zigzag region) regions of BFR/EP pipes were determined to have significant effects on solid particle erosion resistance, as evidenced by the SEM images.

Testing of Cutting Tools on a Pneumatic Experimental Device and Evaluation of Cutting Edge Wear Using a Non-Contact 3D Method

This research is focused on the evaluation of cutting edge wear of the delimbing knife by contactless methods. Delimbing knives were tested in an experimental device constructed in our laboratory, which operates on the principle of a forest harvester head. The greatest wear of the cutting edge was manifested in knife no. 1 with a blade angle of ∢ 7°. The research was focused on the wear of delimbing knives made of DIN 58SiCr8/WNr material when changing the angular geometry of the tool and using a constant delimbing speed of 2.0 m.s−1 while delimbing spruce wood of various wood diameters. The Alicona Infinite Focus device, which functions as a non-contact 3D optical device, was used to determine the amount of wear on the cutting edge of the knife. The size of cutting edge wear significantly affects chipless cutting wood, which can be observed in an increase in the cutting force during the delimbing process. The use of harvester technology in forestry is a highly topical issue today. From this point of view, it is necessary to focus on increasing the efficiency and reducing the energy consumption of the machine, which economically benefits its delimbing operation.

The Interface of a Bimaterial Crossed by a Line Force

The 3D deformation of a bimaterial subjected to a dislocation composed of two straight semi‐infinite arms is known when the two arms are placed on each side of the interface. The resolution is possible taking into account an anisotropic elasticity for both media, thanks to the use of the concept of dislocation/force proposed by Belov (1992). By generalizing the analysis of this author, it is possible to solve a similar problem having an angular geometry, but which concerns a line force crossing the interface. For isotropic media, the solution can be formulated explicitly when the two arms are continuous and perpendicular to the interface. A few numerical applications illustrate the calculations for environments with different elastic properties and for different orientations of the two arms.

Possible wobbling motion in multiple chiral doublets

The analysis of mixing ratios δ of the ΔI =1 linking transitions in the chiral and multiple chiral doublet bands with the ideal case are theoretically performed for the first time by employing the quantum particle rotor model. The calculated E2 fraction extracted from the mixing ratio show that the ΔI =1 linking transitions in the lowest and excited chiral doublet bands are of the pure M1 character, while those connecting the excited to lowest chiral doublet bands are of M1/E2 character with a relatively large E2 admixture. The further analysis of the angular momentum geometry and azimuthal plots reveals that the excited chiral doublet bands represents a chiral geometry with a wobbling motion of the core. This provides a possible figure of wobbling motion in multiple chiral doublets.

Sub-surface granular dynamics in the context of oblique, low-velocity impacts into angular granular media

Oblique, low-velocity impacts onto non-terrestrial terrain are regular occurrences during space exploration missions. These are not only a necessary component of landing and sampling maneuvers, but can also be used as impact experiments to reveal characteristics of the interacting surfaces. We conduct two-dimensional discrete simulations to model such impacts into a bed of triangular grains. Finite element method provides the basis for simulation, enabling the angular grain geometry. Our findings re-create the three classes of impact behavior previously noted from experiments: full-stop, rollout, and ricochet (Wright et al., 2020). An application of Set Voronoi tessellation assesses packing fraction at a high resolution, revealing how grains shift relative to each other during an impact event. We also assess how packing fraction at the point of impact influences different impact behavior types. Calculation of Von Mises strain distributions then reveal how grains shift relative to the overall system, leading to the notion of the ‘skin zone’. Intuition would suggest that the region of perturbed grains would grow deeper with higher velocity impacts, results instead show that increasing velocity may evoke a change in the grains’ dissipative response that dispatches energy predominantly laterally from the impact site instead of deeper into the bed. Finally, we consider how sub-surface response could link with impactor dynamics to deepen our understanding of oblique, low-velocity impact events, one day helping to improve mission outcomes.

Halogen Bonding and CO-Ligand Blue-Shift in Hybrid Organic—Organometallic Cocrystals [CpFe(CO)2X] (C2I4) (X = Cl, Br)

This work is focused on the complex interplay of geometry of I⋯X halogen bonds (HaB) and intermolecular interaction energy in two isomorphic cocrystals [CpFe(CO)2X] (C2I4) (X = Cl (1), Br (2)). Their IR-spectroscopic measurements in solid state and solution demonstrate the blue-shift of CO vibration bands, resulting from I⋯X HaB. The reluctance of their iodide congener [CpFe(CO)2I] to form the expected cocrystal [CpFe(CO)2I] (C2I4) is discussed in terms of different molecular electrostatic potential (MEP) of the surface of iodide ligands, as compared with chloride and bromide, which dictate a different angular geometry of HaB around the metal-I and metal-Br/Cl HaB acceptors. This study also suggests C2I4 as a reliable HaB donor coformer for metal-halide HaB acceptors in the crystal engineering of hybrid metal–organic systems.

Long-Range Supramolecular Synthon Isomerism: Insight from a Case Study of Vinylic Tellurium Trihalides Cl(Ph)C=C(Ph)TeX3 (X = Cl, I)

A slight modification of the synthetic procedure resulted in a new (Cc) polymorph of vinylic tellurium-trichloride Z-Cl(Ph)C=C(Ph)TeCl3 (1, β-form) which is stabilized by Te⋯Cl chalcogen bonds, assembling its molecules into the zigzag chains. Such a packing motive is in contrast to the known (Pca21) polymorph of Z-Cl(Ph)C=C(Ph)TeCl3 (1, α-form, CCDC refcode: BESHOW), which is built upon Te⋯π(Ph) chalcogen bonded chains. We noted a similar case of [Te⋯halogen] vs. [Te⋯π(Ph)] supramolecular synthon polymorphism in its triiodide congener Z-Cl(Ph)C=CPh(TeI3) (2, α and β-polymorphic forms). Quantum chemical calculations of the intermolecular interaction and lattice energies for 1α–β and 2α–β supported the assumption that α is thermodynamic while β is a kinetic form. Kinetic forms 1β and 2β are isostructural (Cc), while the thermodynamic forms 1α (Pca21) and 2α (P21/c) are not and feature an unusual example of long-range supramolecular synthon module isomerism. In other words, 1α–2α pairs demonstrate very similarly to isostructural Te⋯πPh ChB stabilized chains, which are further packed differently relative to each other, following different angular geometry of type-I Cl⋯Cl and type-II I⋯I halogen bonding. These structural considerations are backed by quantum chemical calculations that support the proposed hierarchy of primary and secondary supramolecular synthons and the assignment of α and β as thermodynamic and kinetic forms, respectively.

Microscopic investigation on the existence of transverse wobbling under the effect of rotational alignment: The Nd136 case

The even- and odd-spin two-quasiparticle yrast bands in $^{136}\mathrm{Nd}$ are investigated with the triaxial projected shell model, focusing on the possible interpretation as transverse wobbling. With the experimental observables reproduced reasonably, the conditions under which the wobbling approximation is valid are examined via the angular momentum geometry and the configuration components extracted from the microscopic wave functions. The impact of the rotational alignment of the quasiparticles on the scenario of transverse wobbling is emphasized. It turns out that the $n=0$ band of the wobbling candidate is more affected than the $n=1$ one, which tends to go against the decreasing trend of the wobbling energy expected in the transverse case.

Laboratory Investigation on the Stress-Dependent Anisotropic Shear Wave Velocity (Vs) and Coefficient of Lateral Earth Pressure at Rest (K0) of Granular Materials

The stress-dependent K0, Vs, and Vs anisotropy and their correlations with sand for 1D consolidation stress were tested with a custom-designed floating-wall consolidometer-type Bender Element (BE) testing apparatus. K0 of a soil sample was calculated using stress measurements through soil pressure transducers installed at the midsection of the consolidometer. The Vs and Vs anisotropy were measured by the bender elements installed in three orthogonal directions in the consolidometer, i.e., vh, hv, and hh. Granular soils with different sizes and shapes were tested. The effects of the stress level, overconsolidation ratio (OCR), particle size and shape on the Vs anisotropy, and K0 of the granular soils during one-dimensional consolidation were investigated. The laboratory investigations suggested (1) the K0 showed a constant value during loading, while it increased as the OCR increased during unloading, (2) soils with smaller particle sizes, rough surfaces, and angular geometry tended to have a lower value of K0, and vice versa, (3) both the anisotropic stress state and the anisotropic fabric (geometry) could lead to the Vs anisotropy, but the Vs anisotropy was manifested due to the horizontal stress-lock during unloading stage, and (4) the published correlation between Vs and K0 was modified by introducing the influence of the OCR, which could effectively reduce the variation and improve the prediction accuracy. Therefore, the modified correlation could be used as a robust approach to estimate K0 for both normally consolidated and highly overly consolidated granular soils.

Influence of knife geometry on selected factors pertaining to the delimbing process

Cutting mechanisms and the cutting force are the focus of this article. The cutting force can be determined theoretically or mathematically by statistical analysis. In this work, the cutting speed was compared when changing the diameter of the test wood and when using the three types of angular geometry of delimbing knives. Experimental measurements were conducted on a self-designed experimental pneumatic stand. Empirical relationships and values from the scientific literature were used to determine the input parameters. Based on a regression analysis, conclusions were drawn relative to factors affecting the process of delimbing. The angular geometry of the delimbing knife plays a significant role in the delimbing process. The thicker the knife, the higher the energy consumption in the cutting process and the poorer the quality of the cutting surface of the wood. The quality of chipless separation timber was found to depend on the cutting speed, and the optimal speed was 2.0 m s-1.

Experimental investigation of abrasive properties in waterjet machining

Abrasive waterjet (AWJ) machining has proven to be one of the most flexible non-conventional production techniques for difficult-to-machine materials. However, the prediction of process results is challenging since multiple physical processes occur simultaneously. Until now, the use of alternative abrasive material for special applications has received limited attention. In this work, different solid materials of altered shape and mechanical properties were used to analyze the physical phenomena experimentally. A ceramic and a steel abrasive material of either circular or angular geometry were used. The experiments were conducted by AWJ controlled-depth machining on 42CrMo4 steel in various structural modifications regarding the interference of particle interactions. Furthermore the study aims to gain a fundamental understanding of the AWJ erosion process of different abrasive grit for a better prediction and optimization of AWJ machining, in particular for future applications.

Distortions, deviations and alternative facts: reliability in crystallography.

This feature article is derived from the author's presentation of the Lonsdale lecture at the BCA Spring Meeting in 2018. One of the research results for which Kathleen Lonsdale is best known was her 1929 demonstration that the benzene ring in crystalline hexa-methyl-benzene is planar and has essentially hexagonal symmetry, resolving decades of dispute among organic chemists. More recent crystallographic studies of hexa-methyl-benzene have shown that there are actually small deviations from planarity. Such deviations for aromatic compounds may be due to electronic, steric, and/or intermolecular factors. Some substituted benzene molecules display remarkably large deviations, both from a planar ring structure and from regular hexagonal angular geometry around the ring. Starting from this specific connection with Kathleen Lonsdale's research, a number of stories are recounted of structural distortions and deviations from expected results and explanations that have been suggested for them, across a wide range of chemical topics including macrocycles, metal clusters, unusual coordination geometry and isomerism. On the way we find genuine surprises and results that have led to new understanding, but also examples of poor experiments, misinterpretation of data, scientific bias and preconceived ideas, incompetence and even deliberate fraud. Some aspects of structure validation are discussed. While showcasing some interesting research in its own right, this account also serves an educational purpose.