Hemispherical Pattern Research Articles

Design of a multi‐function global navigation satellite system and 5G cellular antenna structure for automotive applications using characteristic mode analysis

AbstractThis paper illustrates a single antenna structure that simultaneously satisfies the antenna requirement for 5G cellular and global navigation satellite systems (GNSS). The antenna has a linearly polarised omnidirectional radiation for the newly defined 5G sub‐6 GHz cellular bands in the 617–5000 MHz frequency range. In contrast, a right‐hand circular polarisation (RHCP) with a hemispherical radiation pattern at the GNSS L1 has a frequency range of 1559–1606 MHz. This multi‐function antenna would provide a simplified product design and better space utilisation, particularly suitable for flat antenna modules and automotive. The primary concept involves employing a planar inverted F antenna structure to generate radiation modes for cellular bands and incorporate U‐slot on the top plate to generate the GNSS radiation modes. The design methodology utilises the characteristic mode analysis tool to tune the desired radiation characteristic mode at the intended frequency range for each function. The antenna was fabricated, and the performance was evaluated on a 1‐m ground plane. The GNSS RHCP gain measures 5 dBc at boresight, with an axial ratio below 2 dB across the L1 bands, while the cellular gain maintains an excellent return loss and omnidirectional radiation pattern performance across the cellular bands.

Individual prediction of hemispheric similarity of functional connectivity during normal aging.

In the aging process of normal people, the functional activity pattern of brain is in constant change, and the change of brain runs through the whole life cycle, which plays a crucial role in the track of individual development. In recent years, some studies had been carried out on the brain functional activity pattern during individual aging process from different perspectives, which provided an opportunity for the problem we want to study. In this study, we used the resting-state functional magnetic resonance imaging (rs-fMRI) data from Cambridge Center for Aging and Neuroscience (Cam-CAN) database with large sample and long lifespan, and computed the functional connectivity (FC) values for each individual. Based on these values, the hemispheric similarity of functional connectivity (HSFC) obtained by Pearson correlation was used as the starting point of this study. We evaluated the ability of individual recognition of HSFC in the process of aging, as well as the variation trend with aging process. The results showed that HSFC could be used to identify individuals effectively, and it could reflect the change rule in the process of aging. In addition, we observed a series of results at the sub-module level and find that the recognition rate in the sub-module was different from each other, as well as the trend with age. Finally, as a validation, we repeated the main results by human brainnetome atlas (BNA) template and without global signal regression, found that had a good robustness. This also provides a new clue to hemispherical change patterns during normal aging.

A Search for Large‐Scale Variations in the Fine‐Scale Structure of Earth's Inner Core

AbstractA hemispherical pattern in inner core attenuation (Q) has been observed from the apparent Q of inner core transmitted waves (PKPDF). How the elastic scattering (QSC) originating from kilometer‐scale inner core heterogeneities relates to large‐scale apparent Q variations remains elusive. Such inner core scattered (ICS) energy is characterized by emergent, long‐lasting, high‐frequency (1–4 Hz) coda immediately following pre‐critical reflections (PKiKP) from the inner core boundary (ICB). In this study, we develop a framework to systematically investigate ICS and examine its hemispherical pattern using data from two arrays that sample opposing sides of the Pacific quasi‐hemispherical boundary. We use all the viable data from earthquakes (Mw ≥ 5.8) within the past 2–3 decades recorded at distances of 50°–75° by YKA and ILAR—small‐aperture (∼10–20 km) seismic arrays situated in northwestern North America. Two independent waveform stripping methods are applied to extract ICS from the background energy, and various stacks are performed to identify ICS and its spatial pattern. We found that individual beams lacking clear evidence of PKiKP coda waves reveal ICS characteristics when stacked together, implying that ICS is ubiquitous. We used a modified phonon‐based simulation to reinforce the idea that ICS is primarily created by volumetric heterogeneity within the inner core as opposed to ICB topography. With simplified two‐layer ICS models, our results suggest that ICS within the eastern quasi‐hemisphere is slightly stronger than in the western quasi‐hemisphere, although intra‐hemispherical variations are as significant, and our sampling is limited to patches of the northern hemisphere.

Dual-Band Phased Array 5G Mobile-Phone Antenna with Switchable and Hemispherical Beam Pattern Coverage for MIMO-Diversity Communications

A new design of dual-band antenna array with 3D-coverage beam steering characteristic for millimeter-wave (MM-Wave) communications is proposed in this manuscript. The antenna covers frequency bands of 18 GHz and 28 GHz. Its configuration contains three subarrays of patch radiators along the edge area of the smart phone printed circuit board (PCB). Each sub-array contains eight elements of dual-band patch antennas with C-shaped slots. The resonant frequencies of the single element radiator can be adjusted by tuning the sizes of the embedded C-shaped slot and the main patch radiator. The beam-steerable antenna is designed on an N9000 PTFE dielectric. In order to achieve high gain beams and also for covering wider beam-steering area, each sub-array is deployed in different top-sides of the PCB with a dimension of 55××110 mm22. Using three uniform linear eight element sub-arrays, hemispherical beam pattern coverages can be achieved. The proposed antenna provides good performances in terms of gain, radiation and total efficiencies, and beam steering properties which make it suitable for use in the fifthgeneration (5G) mobile-phone platforms.

Optimization and characterization of electrochemical protein Imprinting on hemispherical porous gold patterns for the detection of trypsin

In this study, protein-imprinted sensors with thin bulk films were electrochemically fabricated on gold-coated quartz crystal electrodes with hemispherical porous gold patterns for detecting trypsin (Trp). The gold patterns were electrodeposited on a polystyrene colloidal monolayer and then rinsed using toluene. For Trp imprinting on the gold patterned electrodes, a thin layer with a poly(o-phenylenediamine) and Trp protein was formed using a cyclic voltammetry method under optimized conditions. In addition, a two-dimensional molecularly imprinted polymer (2D-MIP) film was prepared on a planar gold electrode under the same conditions to compare to the dependence of Trp selective recognition on three-dimensional (3D) thin MIP structure, and each corresponding nonimprinted polymer film were constructed by electropolymerization, in the absence of Trp template, to compare molecular imprinting effects. The sensing properties of Trp imprinted sensors were investigated using electrochemical, such as cyclic voltammetry and electrochemical impedance spectroscopy, and microgravimetric methods to confirm the sensitivity and selectivity of MIP films. The 3D-MIP films demonstrated a higher imprinting factor (3.51) in 48-μg/mL of Trp concentration than the 2D-MIP film, and the limit of detection was calculated to be 70.9-ng/mL. In addition, the films exhibited higher electrochemical sensing responses due to increased Trp recognition by the effective molecular imprinting over a larger surface area. Thus, the construction of 3D-MIP films for the protein imprinting could provide excellent specificity, faster kinetics, and higher sensitivity for detecting macromolecular proteins than 2D-MIP films.

Microstructural Features of Freezing and Thawing-Creep Damages for Concrete Mixed with Fly Ash

The macroscopic morphology characteristics, pore structure characteristics, and microfracture morphology of concrete with fly ash subjected to the freeze-thaw-creep effect were analyzed via scanning electron microscopy (SEM). The results revealed that the macrosection of a specimen subjected to freeze-thaw cycling evolves from a regular to an irregular morphology in which the degree of fragmentation increases. Four specimen pore structure types characterized by single holes, nonconnected hole clusters, connected hole clusters, and fly ash holes, respectively, were identified. The microfracture morphology of the concrete was found to include five types of brittle fractures—river, step, cascade, hemispherical, and irregular patterns—and two types of ductile fractures—dimple and peak forest patterns. Two sets of experiments in which (1) the fly ash content ( m = 35 % ) was kept constant and the number of freeze-thaw cycles increased, and (2) the number of freeze-thaw cycles ( n = 120 ) was kept constant, and the fly ash content was increased were carried out. In both cases, the number of connected hole clusters increased and a surrounding skeleton structure with a needle filamentous or flaky appearance was produced. In addition, the degree of deterioration of the pore structure increased and the fracture features changed from brittle to ductile.

Compact S-band and X-band antennas for CubeSats

This paper presents compact S-band and X-band antenna products dedicated to CubeSat applications and their radio frequency performances. The S-band antenna covers simultaneously the 2.025–2.110 GHz telecommand and the 2.2–2.29 GHz telemetry band. It has a hemispherical radiation pattern with superior gain and lower axial ratio values at low elevation angles compared to other S-band antennas on the market. On the other side, the X-band antenna is optimized for payload TM at the frequencies 8.025–8.4 GHz. The antenna gain is higher than 10 dBi over ± 10° in all planes and the axial ratio is excellent. Both antennas are smaller than a 1 U surface and have unequalled RF performances. All processes and materials have strong space heritage and benefit from the Cnesadvanced label. These antennas are thus perfectly suited for professional CubeSat missions with high level of performance and reliability.

Foldable All‐Textile Cavity‐Backed Slot Antennas for Personal UWB Localization

AbstractAn all‐textile multimoded cavity‐backed slot antenna has been designed and fabricated for body‐worn impulse radio ultra‐wideband (IR‐UWB) operation in the 3,744–4,742.4 MHz frequency band, thereby covering Channels 2 and 3 of the IEEE 802.15.4a standard. Its light weight, mechanical flexibility, and small footprint of 35 mm 56 mm facilitate integration into textile for radio communication equipment for first aid responders, personal locator beacons, and equipment for localization and medical monitoring of children or the elderly. The antenna features a stable radiation pattern and reflection coefficient in diverse operating conditions such as in free space, when subject to diverse bending radii and when deployed on the torso or upper right arm of a test person. The high isolation toward the wearer's body originates from the antenna's hemispherical radiation pattern with a 3 dB beamwidth of and a front‐to‐back ratio higher than 11 dB over the entire band. Moreover, the antenna exhibits a measured maximum gain higher than 6.3 dBi and a radiation efficiency over %. In addition, orientation‐specific pulse distortion introduced by the antenna element is analyzed by means of the System Fidelity Factor (SFF). The SFF of the communication link between two instances of this antenna is higher than 94% for all directions within the antenna's 3 dB beamwidth. This easily wearable and deployable antenna is suitable to support IR‐UWB localization with an accuracy in the order of 5 cm.

Multi-scale surface patterning to tune friction under mixed lubricated conditions

It is well accepted that the tribological performance of surfaces can be directly correlated with their energy efficiency and lifetime. Consequently, surface patterning has gained great attention to manipulate friction and wear under dry and lubricated conditions in the last 2 decades. Inspired by multi-scale surfaces found in nature, direct laser interference patterning (finer cross-pattern) and hot micro-coining (coarser hemispherical patterns) were used to create multi-scale patterns on stainless steel substrates. Using a ball-on-disk set-up, the running-in behavior and the maximum oil film lifetime were characterized for all single- and multi-scale patterns under mixed lubrication. Compared to the polished reference, all patterned surfaces helped to prolong the oil film lifetime. Synergetic effects induced by multi-scale patterns were observed leading to the best performance of the sample combining deep micro-coined patterns (intermediate area density) with the additional laser pattern. As a result of the additional hydrodynamic pressure generated by the finer laser pattern and the oil reservoir effect as well as the entrapment of wear particles induced by the coarser micro-coined pattern, the oil film lifetime was extended by a factor of 200 (200 times).

Moisture seepage in asphalt mixture using X-ray imaging technology

Understanding moisture flow in asphalt mixtures is the first step in analyzing moisture-induced damage caused by moisture in pavements. However, the precise quantities of the dynamic movements of wetting fronts and their relationship with the internal structures of asphalt mixtures are yet to be determined. The aims of this study are (1) to quantify the dynamic movements of wetting fronts in asphalt mixtures with X-ray computed tomography (X-ray CT) and (2) to investigate the effects of internal structures of asphalt structures on seepage characteristics. In this study, purified water and three types of asphalt mixtures were used as liquid and pavement materials, respectively. We initially applied sensitivity analysis to determine optimal experimental condition and then performed X-ray CT to balance scanning time and measurement precision in the capture of microscale moisture distribution. The characteristics of moisture seepage, including wetting front, seepage velocity, and initial inertial region, were quantified by tracing the flow at different moments. At a fixed infiltration rate, all the local seepage velocities decreased in power function over time, suggesting the existence of unsteady flow during the seepage. The initial inertia of water droplet had a stronger influence on the vertical migration than in the horizontal migration. This result indicated that the hemispherical shape transport pattern shifted to a trapezoidal shape with the increase of penetration time. Water droplets were easily broken, and water was prone to spread in horizontal direction owing to the decrease in void size, thereby consequently resulting in the directional distribution of the initial inertial region. These findings contribute to the understanding of dynamic moisture movement on the micro-scale of asphalt mixtures and provide an effective opportunity to reveal the evolutionary path of moisture-induced damage in asphalt pavement.

Morphology evolution of self-organized porous structures in silicon surface

Abstract We have investigated the morphology evolution of silicon surface by laser irradiation. A pulsed ns-laser interaction with silicon in aqueous medium can produce self-organized microporous concave cell array structure without any chemicals and auxiliary equipment. Low radiant power was applied to the photo-induced non-thermal silicon surface modification. At the early stage, hemispherical patterns of 2 ∼ 3 µm were formed, maintaining a constant distance from each other without merging. Due to the thermal properties of water, subsurface heating proceeds under the silicon surface. The molten surface leads to the surface modulation to form subsided areas or expansions by nucleation and coalescence, resulting in the formation of a concave cone-shaped porous surface with a diameter of 10 ∼ 20 µm. The AFM reveals that the hierarchical hemispherical structures of two different scales are progressing simultaneously from the early stage.

A New Approach on HCI Extracting Conscious Jaw Movements Based on EEG Signals Using Machine Learnings.

Machine computer interfaces (MCI) are assistive technologies enabling paralyzed peoples to control and communicate their environments. This study aims to discover and represents a new approach on MCI using left/right motions of voluntary jaw movements stored in electroencephalogram (EEG). It extracts brain electrical activities on EEG produced by voluntary jaw movements and converts these activities to machine control commands. Jaw-operated machine computer interface is a new way of MCI entitled as jaw machine interface (JMI) provides new functionality for paralyzed people to assist available environmental devices using their jaw motions. In this article, root mean square (RMS) and standard deviation (STD) features of signals are extracted and hemispherical pattern changes are computed and compared as offline analysis approach. A statistical algorithm, principle component analysis (PCA), is used to reduce high dimensional data and two types of machine learning algorithms which are linear discriminant analysis (LDA) and support vector machine (SVM) incorporating k-fold cross validation technique are employed to identify pattern changes by utilizing the features of horizontal jaw movements stored in EEG.

Detection of small scale heterogeneities at the Inner Core Boundary

The hemispherical pattern of seismic velocities in the uppermost inner core has been described at the global scale in many studies. In this paper, we investigate shorter scale heterogeneities in the vicinity of the Inner Core Boundary (ICB) using differential travel time and amplitude measurements between the pair of core phases PKP(DF) and PKiKP. Seismic events occurring close to Sumatra and recorded at USArray stations in the distance range 132–142° are used to investigate the velocity and attenuation structure at the ICB and in the uppermost 100 km of the inner core beneath Eastern Russia.In this distance range, PKP(DF) and PKiKP are difficult to separate due to their proximity in travel time. We present a new method based on the envelope of the seismic signal to identify them, following which we measure differential travel time residuals and amplitude ratios by comparison with synthetics computed using the Direct Solution Method, which allows us to take into account the correct phase shift of the PKiKP. We found that, in our region of study, the compressional velocity is slower in the uppermost inner core than the AK135 model. However, the sampled region is located in the Eastern hemisphere generally considered as faster and more attenuating than the AK135 model. This suggests significant regional departures from the simple hemispherical pattern reported in the literature.We also deduce from the amplitude ratios that the attenuation is stronger than the global average at the top of the inner core in this region, as expected from its location in the eastern hemisphere. Our results confirm the presence of a low attenuation zone at the top of the inner core, followed by a highly attenuating layer centered around 35 km depth in the inner core, as found in the eastern hemisphere in previous studies. This zone is however thinner (15 km) and more attenuating, Qα reaching values less than 50.

Nanotribological Properties of Nanotextured Ni-Co Coating Surface Measured with AFM Colloidal Probe Technique

Surface-texturing is a useful method of modifying surface frictional performance. A simple, novel, easily-controlled method was used to fabricate different kinds of textures on an Ni-Co coating surface. The nanotribological properties were characterised by atomic force microscope (AFM) with a colloidal probe. The results showed that, compared to the original Ni-Co coating surface, the nanotextured surface can adjust the surface friction forces. The half-elliptic patterns have better tribological properties than hemispherical patterns. Therefore, both laser energy and laser scanning speed will influence the friction performances of Ni-Co coating surfaces.

Performance of leading artifact removal algorithms assessed across microwave breast imaging prototype scan configurations

Microwave imaging is a promising imaging modality for the detection of early-stage breast cancer. One of the most important signal processing components of microwave radar-based breast imaging is early-stage artifact removal. Several artifact removal algorithms have been reported in the literature. However, the neighbourhood-based skin subtraction and hybrid artifact removal algorithms have shown particularly promising results in different realistic 3D breast phantoms. For the first time in this paper, both algorithms have been evaluated and compared using the scan approaches of the most common microwave breast imaging prototype systems. The tests include 3D numerical as well as experimental breast phantoms scanned with hemispherical, cylindrical and adaptive scanning patterns. The efficacy of both algorithms has been evaluated across a range of appropriate performance metrics.

Design of Panel Pattern Array in LED Flat Light for Improvement of Illuminance

A pattern array integrated on the front panel of a LED flat light was designed to improve the illuminance. Various pattern shapes were fabricated, including square pillar, hexagonal pillar, circular pillar, and hemispheres. Among them, the hemispherical pattern shape showed the highest improvement in the illuminance of the LED flat light due to a decrease in the total internal reflection of light. Using both a ray-tracing simulation and an experiment with a hardware fabrication, the optimal conditions in the pattern size of the hemispherical pattern array for the maximum improvement of the illuminance were investigated.

RELATIONSHIPS BETWEEN FLUID VORTICITY, KINETIC HELICITY, AND MAGNETIC FIELD ON SMALL-SCALES (QUIET-NETWORK) ON THE SUN

ABSTRACT We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.

Source Geometry Optimization for Hemispherical Radiation Pattern Coverage

Single beam patterns radiated by linear sources degrade as their maxima points toward endfire direction. Different source geometries are, therefore, to be investigated and compared to achieve better angular coverage. We choose to perform this by analyzing the characteristics of the linear operator connecting the current source to the far field in a simplified two-dimensional (2-D) geometry through its singular value decomposition (SVD). Two indexes are introduced and found useful to achieve geometry optimization. First, the case of continuous sources is examined and then the results are extended to discrete (array) sources. It is found that, while the best solution is a conformal semicircumference source, linear sources arranged at angles provide nearly identical single beam patterns pointing in different directions to provide a hemispherical coverage.

Imaging the inner core under Africa and Europe

The inner core under Africa is thought to be a region where the nature of inner core texture changes: from the strongly anisotropic ‘western’ part of the inner core to the weakly anisotropic, or isotropic ‘eastern’ part of the inner core. Additionally, observations of a difference in isotropic velocity between the two hemispheres have been made. A very large new dataset of simultaneous PKPdf and PKPbc observations, on which differential travel times have been measured, is used to examine the upper 360km of the inner core under Europe, Africa and the surrounding oceans. Inversion of the differential travel time data for laterally varying inner core anisotropy reveals that inner core anisotropy is stronger under central Africa and the Atlantic Ocean than under the western Indian Ocean. No hemispherical pattern is present in Voigt isotropic velocities, indicating that the variation in anisotropy is due to differing degrees of crystal alignment in the inner core, not material differences. When anisotropy is permitted to change with depth, the upper east-most part of the study region shows weaker anisotropy than the central and western regions. When depth dependence in the inner core is neglected the hemisphere boundary is better represented as a line at 40°E than one at 10°E, however, it is apparent that the variation of anisotropy as a function of depth means that one line of longitude cannot truly separate the more and less anisotropic regions of the inner core. The anisotropy observed in the part of the inner core under Africa which lies in the ‘western’ hemisphere is much weaker than that under central America, showing that the western hemisphere is not uniformly anisotropic. As the region of low anisotropy spans a significant depth extent, it is likely that heterogeneous heat fluxes in the core, which may cause variations in inner core anisotropy, have persisted for several hundred million years.

Effect of lithographically designed structures on the caffeine sensing properties of surface imprinted films.

In this study, molecularly imprinted films with concave and convex hemispherical patterns were fabricated using soft lithography and photopolymerization, and their dynamic sensing properties were compared using the gravimetric detection of caffeine.