Angular Region Research Articles

Primary rainbow and Airy minima in 12C + 12C elastic scattering with families of non-monotonic potentials*

The experimental differential cross section of the 12C + 12C elastic scattering over a wide laboratory energy scale 25 ⩽ E lab ⩽ 360 MeV are analyzed within the framework of the optical model (OM) using non-monotonic (NM) nucleus–nucleus potential. The real parts of the NM potentials are derived from the energy density functional (EDF) formalism with the sudden approximation embodying the Pauli exclusion principle and the imaginary parts are taken as phenomenology. The diffractive and the refractive scattering with Airy structures in the whole angular region of the 12C + 12C elastic scattering in the above mentioned energy range are found profoundly successful in OM with the NM nucleus–nucleus potentials in five of different potential families. All the families at lower energies converge at 240 MeV to the unique potential family starting with the EDF potential. This, in conjunction with our recent findings for the 16O + 16O system in Islam et al (2021 J. Phys. G 48 075109), not only verifies the Goldberg criterion for elimination of discrete potential ambiguities for NM potentials, but also establishes that this leads uniquely to the EDF family. The 90° excitation function is also successfully reproduced with extension using NM potentials. The near- and far-side (N/F) decomposition of total elastic scattering amplitude has also been studied using our NM potentials.

Next-to-leading non-global logarithms in QCD

Non-global logarithms arise from the sensitivity of collider observables to soft radiation in limited angular regions of phase space. Their resummation to next-to-leading logarithmic (NLL) order has been a long standing problem and its solution is relevant in the context of precision all-order calculations in a wide variety of collider processes and observables. In this article, we consider observables sensitive only to soft radiation, characterised by the absence of Sudakov double logarithms, and we derive a set of integro-differential equations that describes the resummation of NLL soft corrections in the planar, large-Nc limit. The resulting set of evolution equations is derived in dimensional regularisation and we additionally provide a formulation that is manifestly finite in four space-time dimensions. The latter is suitable for a numerical integration and can be generalised to treat other infrared-safe observables sensitive solely to soft wide-angle radiation. We use the developed formalism to carry out a fixed-order calculation to mathcal{O}left({alpha}_s^2right) in full colour for both the transverse energy and energy distribution in the interjet region between two cone jets in e+e− collisions. We find that the expansion of the resummed cross section correctly reproduces the logarithmic structure of the full QCD result.

The generalized Wiener-Hopf equations for wave motion in angular regions: electromagnetic application.

In this work, we introduce a general method to deduce spectral functional equations and, thus, the generalized Wiener–Hopf equations (GWHEs) for wave motion in angular regions filled by arbitrary linear homogeneous media and illuminated by sources localized at infinity with application to electromagnetics. The functional equations are obtained by solving vector differential equations of first order that model the problem. The application of the boundary conditions to the functional equations yields GWHEs for practical problems. This paper shows the general theory and the validity of GWHEs in the context of electromagnetic applications with respect to the current literature. Extension to scattering problems by wedges in arbitrarily linear media in different physics will be presented in future works.

In-band RCS reduction antennas using an EBG surface

AbstractThe paper has proposed a multilayer, polarization rotation featured, low radar cross-section (RCS) antenna using electromagnetic band-gap (EBG)-based frequency selective surface (FSS) at 8.25 GHz. Cross-shaped EBG unit cells offer zero reflection phase and −25 dB reflection magnitude at 8.25 GHz. The FSS layer consists of eight cross-shaped EBG unit cells sandwiched between two substrates to offer high absorptivity at the desired band. The circular patch antenna resonating at 8.25 GHz is placed on the top substrate having a lower dielectric constant. Four circular-shaped patches are etched at the four corners of the top layer and are coupled with two feed lines which are aligned 90° to each other at the bottom layer and interconnected diagonally to achieve polarization rotation. The proposed antenna offers a gain of 6.72 dB and an in-band RCS of −21.4 dBsm. Incident energy is backscattered into eight directions separated by angle ϕ = 45°. The proposed antenna has the RCS reduction band of 7.7–9.4 GHz. It offers normalized polarization rotation ratio more than 0.8 within the −40° to 40° angular region at the frequency band 8–8.5 GHz. The measured result using the fabricated prototype agrees well with the simulated one.

Active flap control with the trailing edge flap hinge moment as a sensor: using it to estimate local blade inflow conditions and to reduce extreme blade loads and deflections

Abstract. Active trailing edge flaps are a promising technology that can potentially enable further increases in wind turbine sizes without the disproportionate increase in loads, thus reducing the cost of wind energy even further. Extreme loads and critical deflections of the blade are design-driving issues that can effectively be reduced by flaps. In this paper, we consider the flap hinge moment as a local input sensor for a simple flap controller that reduces extreme loads and critical deflections of the DTU 10 MW Reference Wind Turbine blade. We present a model to calculate the unsteady flap hinge moment that can be used in aeroelastic simulations in the time domain. This model is used to develop an observer that estimates the local angle of attack and relative wind velocity of a blade section based on local sensor information including the flap hinge moment of the blade section. For steady wind conditions that include yawed inflow and wind shear, the observer is able to estimate the local inflow conditions with errors in the mean angle of attack below 0.2∘ and mean relative wind speed errors below 0.4 %. For fully turbulent wind conditions, the observer is able to estimate the low-frequency content of the local angle of attack and relative velocity even when it is lacking information on the incoming turbulent wind. We include this observer as part of a simple flap controller to reduce extreme loads and critical deflections of the blade. The flap controller's performance is tested in load simulations of the reference turbine with active flaps according to the IEC 61400-1 power production with extreme turbulence group. We used the lifting line free vortex wake method to calculate the aerodynamic loads. Results show a reduction of the maximum out-of-plane and resulting blade root bending moments of 8 % and 7.6 %, respectively, when compared to a baseline case without flaps. The critical blade tip deflection is reduced by 7.1 %. Furthermore, a sector load analysis considering extreme loading in all load directions shows a reduction of the extreme resulting bending moment in an angular region covering 30∘ around the positive out-of-plane blade root bending moment. Further analysis reveals that a fast reaction time of the flap system proves to be critical for its performance. This is achieved with the use of local sensors as input for the flap controller. A larger reduction potential of the system is identified but not reached mainly because of a combination of challenging controller objectives and the simple controller architecture.

Cortical Structural Connectivity Alterations and Potential Pathogenesis in Mid-Stage Sporadic Parkinson's Disease.

Many clinical symptoms of sporadic Parkinson’s disease (sPD) cannot be completely explained by a lesion of the simple typical extrapyramidal circuit between the striatum and substantia nigra. Therefore, this study aimed to explore the new potential damaged pathogenesis of other brain regions associated with the multiple and complex clinical symptoms of sPD through magnetic resonance imaging (MRI). A total of 65 patients with mid-stage sPD and 35 healthy controls were recruited in this study. Cortical structural connectivity was assessed by seed-based analysis using the vertex-based morphology of MRI. Seven different clusters in the brain regions of cortical thickness thinning derived from the regression analysis using brain size as covariates between sPD and control were selected as seeds. Results showed that the significant alteration of cortical structural connectivity mainly occurred in the bilateral frontal orbital, opercular, triangular, precentral, rectus, supplementary-motor, temporal pole, angular, Heschl, parietal, supramarginal, postcentral, precuneus, occipital, lingual, cuneus, Rolandic-opercular, cingulum, parahippocampal, calcarine, olfactory, insula, paracentral-lobule, and fusiform regions at the mid-stage of sPD. These findings suggested that the extensive alteration of cortical structural connectivity is one of possible pathogenesis resulting in the multiple and complex clinical symptoms in sPD.

Modification of Critical Current Density Anisotropy in High-Tc Superconductors by Using Heavy-Ion Irradiations

The critical current density Jc, which is a maximum value of zero-resistivity current density, is required to exhibit not only larger value but also lower anisotropy in a magnetic field B for applications of high-Tc superconductors. Heavy-ion irradiation introduces nanometer-scale irradiation tracks, i.e., columnar defects (CDs) into high-Tc superconducting materials, which can modify both the absolute value and the anisotropy of Jc in a controlled manner: the unique structures of CDs, which significantly affect the Jc properties, are engineered by adjusting the irradiation conditions such as the irradiation energy and the incident direction. This paper reviews the modifications of the Jc anisotropy in high-Tc superconductors using CDs installed by heavy-ion irradiations. The direction-dispersion of CDs, which is tuned by the combination of the plural irradiation directions, can provide a variety of the magnetic field angular variations of Jc in high-Tc superconductors: CDs crossing at ±θi relative to the c-axis of YBa2Cu3Oy films induce a broad peak of Jc centered at B || c for θi < ±45°, whereas the crossing angle of θi ≥ ±45° cause not a Jc peak centered at B || c but two peaks of Jc at the irradiation angles. The anisotropy of Jc can also modified by tuning the continuity of CDs: short segmented CDs formed by heavy-ion irradiation with relatively low energy are more effective to improve Jc in a wide magnetic field angular region. The modifications of the Jc anisotropy are discussed on the basis of both structures of CDs and flux line structures depending on the magnetic field directions.

Investigations on structural, optical, and impedance spectroscopy studies of titanium dioxide nanoparticles

This article explains a novel synthesis for producing titanium dioxide (TiO2) nanoparticles by a sol-gel technique using titanium tetraisopropoxide as a titanium source. The synthesized nanoparticles were analyzed using many measurements like X-ray diffraction (XRD), HRTEM, absorption UV spectroscopy, FTIR, and ac impedance spectroscopy. X-ray peaks were used to calculate the crystallite size and lattice strain by Williamson–Hall method. Crystallite size calculated from x-ray diffraction using the Scherrer equation gives an approximate size and cannot be used for measurements. TiO2 nanoparticles are found to possess a tetragonal structure with a crystalline size around 12 nm. Particle size was confirmed by HRTEM images. The optical studies response for the nanoparticles showed the possible visible absorption peaks for TiO2 nanoparticles are 323 nm. Bandgap energy (Eg) of the TiO2 nanoparticle calculated from UV visible absorption spectra is discussed, and the bandgap is 3.14 eV. FTIR spectra showed vibration bands of the Ti-O network. AC Conductivity properties of TiO2 nanoparticles are studied in the frequency range 1 to 8 MHz at varying temperatures. The conductivity of the TiO2 nanoparticle is found to be constant in the low angular frequency region. Dielectric parameters were analyzed at different temperatures and frequencies.
 
 KEY WORDS: Conductivity, Dielectric, Nanoparticles, Titanium dioxide, Structural studies
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 151-160.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.13

Nonreciprocal absorber with a narrow band of angular polarization sensitive regions based on a quasi-periodic structure

In the quasi-periodic structure (QPS) containing InSb, a nonreciprocal absorber with a narrow band of angular polarization sensitive regions is studied. Due to the effective role of the antireflection layers (ALs), the effective impedance of the overall structure matches the vacuum wave impedance. Benefiting from the special absorption structure, an absorption band will be created in the photonic bandgap. The results of the investigation show that, with the same parameters, the QPS has a larger frequency bandwidth than the periodic structure and, if the incident frequency of the electromagnetic wave is the same, the former has a larger angular selective range. The degrees of polarization separation and nonreciprocal ability of the presented QPS can be regulated by temperature and magnetic induction intensity. Consequently, the proposed QPS can provide a new basis for the development of polarization separators and nonreciprocal devices.

Diagnosis of cylindrical projections and analysis of suitability for the territorial area of South America

Cartographic Projection can be defined as the mathematical relationship between the position of a model of the terrestrial surface and the flat surface. Cylindrical projections are employed around the world, taking into consideration their properties and special characteristics. The purpose of this study was to identify the cartographic projection that best represents South America terrestrial surface, focusing mainly on the area of the continent, determined by the South American Defense Council. Initially, the projections were selected based on a bibliographic review. Subsequently, a suitability judgment was made for South America applying Tissot Indicatrix, Isolines of Maximum Angular Distortion and Region of Acceptable Distortion. Finally, an assumption was drawn up among the best results. The study control was performed using the software Flex Projector and ArcGIS 10.1, computational resources of great use in Cartography. The study provided a clear, simple and objective understanding of how different projections behave. The motivation comes from the insufficiency of detailed information and applied to the choice of map projection in regions of large areas.

Using Functional Connectivity to Examine the Correlation between Mirror Neuron Network and Autistic Traits in a Typically Developing Sample: A fNIRS Study.

Mirror neuron network (MNN) is associated with one’s ability to recognize and interpret others’ actions and emotions and has a crucial role in cognition, perception, and social interaction. MNN connectivity and its relation to social attributes, such as autistic traits have not been thoroughly examined. This study aimed to investigate functional connectivity in the MNN and assess relationship between MNN connectivity and subclinical autistic traits in neurotypical adults. Hemodynamic responses, including oxy- and deoxy-hemoglobin were measured in the central and parietal cortex of 30 healthy participants using a 24-channel functional Near-Infrared spectroscopy (fNIRS) system during a live action-observation and action-execution task. Functional connectivity was derived from oxy-hemoglobin data. Connections with significantly greater connectivity in both tasks were assigned to MNN connectivity. Correlation between connectivity and autistic traits were performed using Pearson correlation. Connections within the right precentral, right supramarginal, left inferior parietal, left postcentral, and between left supramarginal-left angular regions were identified as MNN connections. In addition, individuals with higher subclinical autistic traits present higher connectivity in both action-execution and action-observation conditions. Positive correlation between MNN connectivity and subclinical autistic traits can be used in future studies to investigate MNN in a developing population with autism spectrum disorder.

Enhancement of polarization purity in square dielectric resonator antenna using coaxial feed with metal strip loading for point-to-point communication applications

In this paper, a simple technique to enhance the polarization purity in a square dielectric resonator antenna (SDRA) using metal strip loading on the probe feed is presented for point-to-point communication applications. Coaxial feed placed at the commonly used offset location adjacent to the DRA has been studied in this regard. Cross polarized (XP) fields scattered from the feed into the air are found to be one of the reasons behind the deterioration of polarization purity in SDRA. When a thin metal strip is loaded on the probe feed using liquid solder to control these XP fields, the measured result shows an XP isolation of 47 dB at the boresight, 42 dB and 29 dB at the angular region of ±30°in the E-plane and H-plane, respectively. The proposed technique helps to overcome many unavoidable fabrication errors associated with complex machining and drilling processes involved in contemporary DRA designs for XP suppression. The proposed SDRA design offering good XP isolation performance and simple fabrication technique is highly suitable for low cost and high precision applications.

Robust wideband adaptive beamforming based on covariance matrix reconstruction in the spatial‐frequency domain

Without the response variation constraint, the main-lobe responses of wideband beamforming usually vary with the frequencies of interest, and the beam pointing may deviate from the incident angle of the desired signal. If the interference-plus-noise covariance matrix (INCM) is directly replaced by the sample covariance matrix, the desired signal in the sample data may result in self-null problem, which can lead to the degradation of the performance of wideband beamformers. Through frequency division, a novel wideband adaptive beamforming is proposed by reconstructing the INCM and solving the convex optimisation problem. Using fast Fourier transform (FFT), the time-domain samples are transformed into the frequency field, and the covariance matrix of each subband can be obtained from the frequency-domain data. In the spatial-frequency domain, the INCM and signal-plus-noise covariance matrix can be respectively reconstructed by integrating the stacked steering vector and the Capon spatial spectrum over the corresponding angular region. Then, we establish the optimisation criteria, that is, minimising the output interference-plus-noise power, minimising the main-lobe spatial response variation, and constraining the response deviation of the desired signal. A novel convex optimisation model can be established, and then the weight coefficients for time-domain wideband beamforming can be obtained by solving the optimisation problem. The simulation and experimental results demonstrate that the proposed beamformer can provide better performance compared with other tested beamformers and maintain good robustness in various applications.

Excitation energy and angular momentum dependence of the nuclear level density parameter around A≈110

Neutron kinetic energy spectra in coincidence with low-energy $\ensuremath{\gamma}$-ray multiplicities have been measured around $A\ensuremath{\approx}110$ in the $^{16}\mathrm{O}+^{93}\mathrm{Nb}$ and $^{20}\mathrm{Ne}+^{93}\mathrm{Nb}$ reactions in a compound nuclear excitation energy range of $\ensuremath{\approx}90--140$ MeV. The excitation energy (temperature) dependence and the angular momentum (spin) dependence of the inverse level density parameter $k$ have been investigated by comparing the experimental data with statistical Hauser-Feshbach calculations. In contrast to the available systematic in this mass region, the inverse level density parameter showed an appreciable increase as a function of the excitation energy. The extracted $k$ values at different angular momentum regions, corresponding to different $\ensuremath{\gamma}$ multiplicities, also showed an overall increase with the average nuclear spins. The experimental results have been compared with a microscopic statistical-model calculation and found to be in reasonable agreement with the data. The results provide useful information to understand the variation of nuclear level density at high temperature and spins.

X-ray diffraction by surface acoustic waves

The possibilities are presented of X-ray diffraction methods for studying the propagation of surface acoustic waves (SAWs) in solids, including diffraction under total external reflection conditions and Bragg diffraction, using acoustically modulated X-ray multilayer mirrors and crystals. SAW propagation was studied using both meridional and sagittal diffraction geometries where the SAW wavevectors and X-ray photons are collinear or perpendicular, respectively. SAW propagation in a crystal leads to sinusoidal modulation of the crystal lattice and the appearance of diffraction satellites on the rocking curve. The intensities and angular positions of these diffraction satellites are determined by the SAW wavelength, amplitude and attenuation. Therefore, diffraction methods allow the analysis of the SAW propagation process and determination of SAW parameters. The influence of X-ray energy on diffraction by acoustically modulated crystals is studied for the first time. It is shown that changes in the X-ray energy can change the angular region where diffraction satellites exist under conditions of total external reflection. By contrast, in the Bragg diffraction region changes in the X-ray photon energy lead to changes in the X-ray penetration depth into the crystal and redistribution of the diffracted intensity among diffraction satellites, but do not change the angular divergence between diffraction satellites on the rocking curve. It is also shown that, in X-ray diffraction on acoustically modulated crystals on a number of successive reflections, a decrease in interplanar spacing leads to an increase in the number of diffraction satellites and a redistribution of diffracted radiation between them.

Simulated reflectance above snow constrained by airborne measurements of solar radiation: implications for the snow grain morphology in the Arctic

Abstract. Accurate knowledge of the reflectance from snow/ice-covered surfaces is of fundamental importance for the retrieval of snow parameters and atmospheric constituents from space-based and airborne observations. In this paper, we simulate the reflectance in a snow–atmosphere system, using the phenomenological radiative transfer model SCIATRAN, and compare the results with that of airborne measurements. To minimize the differences between measurements and simulation, we determine and employ the key atmospheric and surface parameters, such as snow grain morphologies (or habits). First, we report on a sensitivity study. This addresses the requirement for adequate a priori knowledge about snow models and ancillary information about the atmosphere. For this aim, we use the well-validated phenomenological radiative transfer model, SCIATRAN. Second, we present and apply a two-stage snow grain morphology (i.e., size and shape of ice crystals in the snow) retrieval algorithm. We then describe the use of this new retrieval for estimating the most representative snow model, using different types of snow morphologies, for the airborne observation conditions performed by NASA's Cloud Absorption Radiometer (CAR). Third, we present a comprehensive comparison of the simulated reflectance (using retrieved snow grain size and shape and independent atmospheric data) with that from airborne CAR measurements in the visible (0.670 µm) and near infrared (NIR; 0.870 and 1.6 µm) wavelength range. The results of this comparison are used to assess the quality and accuracy of the radiative transfer model in the simulation of the reflectance in a coupled snow–atmosphere system. Assuming that the snow layer consists of ice crystals with aggregates of eight column ice habit and having an effective radius of ∼99 µm, we find that, for a surface covered by old snow, the Pearson correlation coefficient, R, between measurements and simulations is 0.98 (R2∼0.96). For freshly fallen snow, assuming that the snow layer consists of the aggregate of five plates ice habit with an effective radius of ∼83 µm and having surface inhomogeneity, the correlation is ∼0.97 (R2∼0.94) in the infrared and 0.88 (R2∼0.77) in the visible wavelengths. The largest differences between simulated and measured values are observed in the glint area (i.e., in the angular regions of specular and near-specular reflection), with relative azimuth angles <±40∘ in the forward-scattering direction. The absolute difference between the modeled results and measurements in off-glint regions, with a viewing zenith angle of less than 50∘, is generally small ∼±0.025 and does not exceed ±0.05. These results will help to improve the calculation of snow surface reflectance and relevant assumptions in the snow–atmosphere system algorithms (e.g., aerosol optical thickness retrieval algorithms in the polar regions).

Structural Analysis of Extruded Fiber Components of Orange Pulp

X-ray diffractograms, optic and electronic microscopy were used to study the structural changes on extruded orange pulp using a Brabender® laboratory single-screw extruder (GNF 1014/2, 20:1, L/D). The results showed that most of the cellulose would be in the amorphous state, with small crystalline areas in the angular region of 2θ = 14.5°. The evaluated extrusion conditions did not affect the crystallinity of the raw cellulose, maintaining the size of the crystalline regions in the angular region of 2θ = 22.5°. Neutral detergent solubilized the crystalline areas of potassium citrate and cellulose, formed during the extrusion process. However, these conditions did not affect the crystallinity of the raw cellulose. In addition, no change was observed in the crystallinity of pectin. The electron microphotographs allowed for the estimation of the heterogeneity of orange pulp and assessment of the difference of resistance between the walls of the buds and juice vesicles. Thus, it was demonstrated that during the extrusion process most of the porosity and the cellular structure of the endocarp remained unaltered.

Sonic-supersonic Solutions to a Mixed-type Boundary Value Problem for the Two-Dimensional Full Euler Equations

We are concerned with the sonic-supersonic structures extracted from the transonic flow problems in gas dynamics. A local classical supersonic solution for the two-dimensional steady full Euler equations is established in an angular region bounded by the sonic curve and the characteristic curve. In order to overcome the challenges caused by the coupling of nonlinearity and degeneracy at the corner point, we develop a new iteration pattern to show the convergence of the iterative sequence generated by the Euler equations in terms of a partial hodograph coordinate system. The pattern developed here will be useful for studying the degenerate mixed-type boundary value problems for other related nonlinear hyperbolic systems.

Two cases of lesser omentum infarction with suggestive findings in esophagogastroduodenoscopy

We report two cases of lesser omentum infarction with suggestive findings in esophagogastroduodenoscopy (EGD). Both patients were admitted to our hospital who presented with upper abdominal pain accompanied by signs of peritoneal irritation. EGD was performed to rule out gastroduodenal ulcer. No mucosal erythema and ulceration were observed, but we observed two signs suggesting lesser omentum infarction. First, EGD showed a submucosal tumor-like mass at the angular region of the lesser curvature of the stomach in both patients. Second, one of the patients exhibited great tenderness at the site of the tumor when this was depressed by biopsy forceps. We diagnosed the two patients with lesser omentum infarction from the results of abdominal computed tomography, abdominal ultrasonography, and EGD. Conservative management was applied;the patients received analgesic drugs and gradually became asymptomatic. Lesser omentum infarction presents with abdominal pain and sometimes signs of peritoneal irritation, and almost all cases can be successfully managed with conservative treatment. Diagnosing the disease carefully and precisely is essential. We report suggestive findings in EGD, which can assist in the diagnosis of lesser omentum infarction.

In vitro comparison of commercial and ultrafine-grained titanium osteosynthesis miniplates used on mandibular fractures.

Implants called miniplates, with different geometries, are used for the treatment of a fractured or diseased mandible. Generally, Ti-based miniplates in various quantities and with various geometries are fixed into the bone tissue according to the location and shape of the fracture by embedding. The aim of this study was to increase the strength of the material used in the production of miniplates by means of the equal-channel angular pressing (ECAP) treatment, and to provide a highrigidity fixation system with fewer miniplates. In this study, the ECAP method, which is one of the methods of severe plastic deformation, was applied at 4 passes at 300°C in route Bc to increase the strength of pure Ti. Then, miniplates were produced with 2 different geometries (regular and long) and 2 different properties of the Ti material (untreated and ECAP-treated). The produced miniplates were placed in the fracture line formed in the angular region of an artificial, synthetic-bone mandible. The 2-point and 3-point bending and torsion tests were conducted on these fixation systems. As a result, after the ECAP process, the yield and tensile strength of pure Ti increased by 65%, while elongation decreased by 13%. After the ECAP process, the grain size of the material was reduced from 110 μm to 200 nm. This study showed that the fixation system became more rigid due to using ECAP-treated miniplates, and this ensured lesser displacement of the fixation system.