Polar Arrays Research Articles

Reversible Manipulation of Polar Topologies in Oxide Ferroelectrics via Electric Fields.

Polar topologies show great potentials in memories and other nano-micro devices. To integrate with silicon conducting circuits, it is vital to understand the dynamic evolution and the transformation of different domain configurations under external stimulus. Here in situ transmission electron microscopy is performed and the electrically controlled creation and annihilation of large-scale polar flux-closure array from typical c/a domains in PbTiO3/SrTiO3 bilayers is directly observed. It is found that the transformation is reversible after removal of external electric fields. Increasing external electric fields on (PbTiO3/SrTiO3)5 multilayered films, it is further found that the flux-closure domains are nucleated and propagated via the steps of first the formation of new c domains and then connection with neighboring c domains. The transition from a/c domains to flux-closure arrays under electric fields is collaborated with evaluating energy variations by phase-field simulations in which the electrostatic energy plays an important role. These results demonstrate the polar topologies can be reversibly manipulated by external stimuli, which sheds light on further understanding the dynamics behavior of polar topologies and helps for future nanoelectric applications.

Quasi-2D and 3D phase-field simulation studies of polar vortex domain structures for high-density domain engineering

Phase-field simulations were performed on the polar vortex array structure appearing in the SrTiO3/PbTiO3/SrTiO3 heterostructure to investigate the Kittel law relationship (w ∝ d1/2) between the vortex array period (w) and the PbTiO3 ferroelectric layer thickness (d). Quasi-two-dimensional simulation results show that the equilibrium period can be determined from the relationship between the size of the simulation box and the total free energy density and that the obtained period obeys the Kittel law. However, three-dimensional simulation results show that the polar vortex arrays are not homogeneous in the direction perpendicular to the vortex plane. In the pure vortex state, no obvious correlation exists between the simulation size and energy because of the dislocations caused by the vortex period mismatch. However, in the mixed state with ferroelectric a1/a2, the vortex domains exhibit equilibrium periods that satisfy the Kittel law relationship because of the confinement effect caused by phase separation. Further study of the confined vortex domains in these mixed states and the vortex domains of finite size due to mismatched dislocations are expected to enable domain engineering of higher domain densities.

A Ground Penetrating Radar Array Antenna Designed for Small Targets Detection

Abstract The detection of small targets, especially those made of non-metallic materials, presents significant challenges due to their small size and the difficulty of being detected by traditional metal detectors. Additionally, environmental factors and soil conditions further complicate their detection. Traditional Ground Penetrating Radar (GPR) operate with a single-line detection method, resulting in a low number of scan lines and inefficient detection. This approach makes it difficult to generate slice images and can lead to high missed detection. A miniaturized GPR array antenna suitable for handheld and unmanned platforms has been developed. Utilizing a planar dipole antenna with multiple resistive and capacitive loading, a horizontal oblique polarization array comprising five transmitters and six receivers has been constructed, achieving dual-reception from a single transmission across ten channels, significantly improving upon the limitations of single antenna systems in terms of data volume and sampling interval. Experimental tests demonstrate that the designed system can successfully detect the echo signals of metallic and non-metallic small targets like buried up to 20 cm deep in typical soil conditions, and generate clear slice images, proving its capability for high-resolution imaging detection of shallow buried small targets.

Bidirectional Vectorial Holography Using Bi-Layer Metasurfaces and Its Application to Optical Encryption.

The field of optical systems with asymmetric responses has grown significantly due to their various potential applications. Janus metasurfaces are noteworthy for their ability to control light asymmetrically at the pixel level within thin films. However, previous demonstrations are restricted to the partial control of asymmetric transmission for a limited set of input polarizations, focusing primarily on scalar functionalities. Here, optical bi-layer metasurfaces that achieve a fully generalized form of asymmetric transmission for any input polarization are presented. The designs owe much to the theoretical model of asymmetric transmission in reciprocal systems, which elucidates the relationship between front- and back-side Jones matrices in general cases. This model reveals a fundamental correlation between the polarization-direction channels of opposing sides. To circumvent this constraint, partitioning the transmission space is utilizedto realize four distinct vector functionalities within the target volume. As a proof of concept, polarization-direction-multiplexed Janus vectorial holograms generating four vectorial holographic images are experimentally demonstrated. When integrated with computational vector polarizer arrays, this approach enables optical encryption with a high level of obscurity. The proposedmathematical framework and novel material systems for generalized asymmetric transmission may pave the way for applications such as optical computation, sensing, and imaging.

Compact antenna device for receiving glonas signals in frequency ranges L1 and L2

Problem statement. The article presents the material on the development of compact antenna devices designed to receive GLONASS signals in the frequency ranges L1 and L2. The basic requirements for the design and characteristics of compact antenna devices designed to receive GLONASS signals are described. Aspects of the fundamentals of the design of a compact 25x25x7.5 mm dual-frequency three-layer patch antenna, where the third layer (bottom board) is a power amplifier, which has not been used before, are discussed. Simulation results of the developed compact antenna device are presented and recommendations for the power amplifier are given. Objective. To develop a compact dual-frequency patch antenna with circular polarization, providing a high level of reception of GLONASS signals in the frequency bands L1 and L2, which includes a power amplifier. Results. On the basis of methods of electrodynamic modeling, computational methods of technical electrodynamics, methods of full-scale experimental measurements of antenna characteristics and methods of computer processing of data of full-scale experimental measurements, a compact antenna device with circular polarization is developed, providing reception of GLONASS signals in frequency ranges L1 and L2. The developed compact antenna device is made on the basis of a three-layer patch antenna, having one common point of voltage supply and located in a dielectric case on a metal base, where each layer is a printed circuit board. The upper printed circuit board provides reception of GLONASS signals in frequency ranges L2, the middle board provides reception of GLONASS signals in frequency ranges L1, the lower board - power amplifier significantly increases the gain in radiation of the compact antenna device. The use of this development for the reception of GLONASS signals in the frequency ranges L1 and L2, including as part of the antenna array, will provide significantly more space for placement of payloads, due to its small mass and dimensions. Practical significance consists in providing a high level of reception of signals of the network radio navigation satellite system GLONASS in frequency ranges L1 and L2, designed for global operational navigation of ground mobile objects. The developed compact antenna device with circular polarization and antenna arrays based on it can be used for electronic warfare and can also be used for civilian purposes.

High-Gain Circularly Polarized Array Antenna Based on High-Order Mode ESIC for 5G Millimeter-Wave Application

High-Gain Circularly Polarized Array Antenna Based on High-Order Mode ESIC for 5G Millimeter-Wave Application

Parallelization of Curved Inertial Microfluidic Channels to Increase the Throughput of Simultaneous Microparticle Separation and Washing

The rising global need for clean water highlights the importance of efficient sample preparation methods to separate and wash various contaminants such as microparticles. Microfluidic methods for these purposes have emerged but they mostly deliver either separation or washing, with very low throughputs. Here, we investigate parallelization of a curved-channel particle separation and washing device in order to increase its throughput for sample preparation. A curved microchannel applies inertial forces to focus larger 10 µm microparticles at the inner wall of the channel and separate them from smaller 5 µm microparticles at the outer wall. At the same time, Dean flow recirculation is used to exchange the carrier solution of the large microparticles to a clean buffer (washing). We increased the number of curved channels in a stepwise manner from two to four to eight channels in two different arraying designs, i.e., rectangular and polar arrays. We examined efficient separation of target 10 µm particles from 5 µm particles, while transferring the larger microparticles into a clean buffer. Dean flow recirculation studies demonstrated that the rectangular arrayed device performs better, providing solution exchange efficiencies of more than 96% on average as compared to 89% for the polar array device. Our 8-curve rectangular array device provided a particle separation efficiency of 98.93 ± 0.91%, while maintaining a sample purity of 92.83 ± 1.47% at a high working flow rate of 12.8 mL/min. Moreover, the target particles were transferred into a clean buffer with a solution exchange efficiency of 96.81 ± 0.54% in our 8-curve device. Compared to the literature, our in-plane parallelization design of curved microchannels resulted in a 13-fold increase in the working flow rate of the setup while maintaining a very high performance in particle separation and washing. Our microfluidic device offers the potential to enhance the throughput and the separation and washing efficiencies in applications for biological and environmental samples.

Spatial modulation strategy for construction of artificial polar skyrmion arrays in ferroelectrics

Spatial modulation strategy for construction of artificial polar skyrmion arrays in ferroelectrics

CheB localizes to polar receptor arrays during repellent adaptation.

Adaptation of the response to stimuli is a fundamental process for all organisms. Here, we show that the adaptation enzyme CheB methylesterase of Escherichia coli assembles to the ON state receptor array after exposure to the repellent l-isoleucine and dissociates from the array after adaptation is complete. The duration of increased CheB localization and the time of highly clockwise-biased flagellar rotation were similar and depended on the strength of the stimulus. The increase in CheB at the receptor array and the decrease in cytoplasmic CheB were both ~100 molecules, which represents 15 to 20% of the total cellular content of CheB. We confirmed that the main binding site for CheB in the ON state array is the P2 domain of phosphorylated CheA, with a second minor site being the carboxyl-terminal pentapeptide of the serine chemoreceptor. Thus, we have been able to quantify the regulation of the signal output of the receptor array by the intracellular dynamics of an adaptation enzyme.

Stabilization and control of weakly correlated polar skyrmions in ferroelectric thin films

In recent years, polar topological textures like skyrmions and vortices in ferroelectric superlattices and multilayers have received extensive attention. However, the polar topological textures in these systems suffer strong interactions and are difficult to be manipulated as individual elements, limiting their application prospects in storage and logic devices. Here, via phase field simulations, we demonstrate domain engineering as a feasible strategy to create diverse weakly correlated polar topological texture arrays in single-layer tetragonal ferroelectric thin films, including Néel-type skyrmions with positive/negative topological charges and Bloch-type skyrmions with different chirality. We calculate the stability phase diagram and reveal the evolution characteristics of these polar topological textures under local electric and mechanical stimuli. We realize local erasing and writing of single Néel- and Bloch-type skyrmions, as well as deterministic chirality control of single Bloch-type skyrmion, confirming the weak correlation of the polar skyrmions. Our study therefore demonstrates domain engineering as an effective strategy for stabilizing weakly correlated polar topological textures, which extends the existence system of polar topological textures and paves a new way for the design of storage and logic devices based on polar topological textures.

Experimental characterisation of rotor noise in tandem configuration

This paper presents a comprehensive investigation into the noise radiation characteristics of two rotors in a tandem configuration. Through an extensive experimental campaign, the study explores the effect of the separation distance between two rotors on the noise directivity patterns, spectral characteristics and temporal features of the radiated noise under both hovering and edge-wise flight conditions. The directivity patterns of the overall sound pressure level obtained from the polar and side arrays demonstrate a dependence on the separation distance and advance ratio. Spectral characteristics elucidate the influence of separation distance on tonal and broadband energy content. While the high-frequency broadband noise increases for both hovering and edge-wise flight similarly, the low-frequency broadband energy strongly depends on the advance ratio and the rotor separation distance. The results reveal a distinct envelope in the design space, where the radiated broadband noise for tandem configurations can be minimized, offering potential insights for noise reduction strategies. Additionally, the wavelet analysis for tandem configurations reveals that the emitted noise at the first and second blade passing frequency is strongly intermittent with amplitude modulation, which shall be considered for annoyance perception.

Structural behaviour of asymptotic geodesic hybrid timber gridshells

Asymptotic geodesic gridshells are a novel structural system that is fabricated from straight and flat planks. The planks are elastically bent and twisted around their slender dimension to achieve the desired geometry, while the tall dimension creates structural stiffness. This system combines the geometric features of asymptotic and geodesic curves to create a hybrid tri-hex network on doubly curved surfaces, and provides a stable grid to resist its self-weight and external loads. To comprehensively explore the structural capabilities of asymptotic geodesic gridshells, a full-scale timber gridshell prototype was designed and built. Loading tests, including local and one shell asymmetrical loading, were carried out to examine the structural behaviour of the gridshell. A nonlinear finite-element model was developed and subsequently validated using experimental data. The evaluation of the timber gridshell revealed its high performance under uniformly distributed loads, and the simulation indicated a viable live load capacity of 7.0 kN/m². In a parametric study, the influence of the polar array layout, the joint rotation stiffness, and the support condition on the structural performance of the hybrid gridshell are analysed. Parameters influencing the achievable span are discussed regarding strength, stiffness and buckling behaviour for future design considerations.

Contrasting packing modes for tubular assemblies in chlorosomes

The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ß ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c.

Sub-micron pixel polarization-sensitive photodetector based on silicon nanowire

Silicon nanowire is a potential candidate to be used as polarization-sensitive material, but the relative mechanism of polarization response must be carried out. Herein, a sub-micron metal-single silicon nanowire-metal photodetector exhibits polarization-sensitive characteristics with an anisotropic photocurrent ratio of 1.59 at 780 nm, an excellent responsivity of 24.58 mA/W, and a high detectivity of 8.88 × 109 Jones at 980 nm. The underlying principle of optical anisotropy in silicon nanowire is attributed to resonance enhancement verified by polarizing light microscopy and simulation. Furthermore, Stokes parameter measurements and imaging are all demonstrated by detecting the characteristics of linearly polarized light and imaging the polarizer array, respectively. Given the maturity of silicon processing, the sub-micron linearly polarized light detection proposed in this study lays the groundwork for achieving highly integrated, simplified processes, and cost-effective on-chip polarization-sensitive optical chips in the future.

Novel indices representing heterogeneous distributions of myocardial perfusion imaging

IntroductionHeterogeneous distribution in myocardial perfusion images (MPI) obtained by scintigraphy is often observed in cardiac diseases with normal myocardial perfusion. However, quantitative assessments of such heterogeneity have not been established. We hypothesized that the heterogeneity in MPI can be quantitatively evaluated through histogram analysis, calculating the standard deviation (SD), the 95% bandwidth (BW95%), and entropy.MethodsWe examined resting 99mTc-MIBI images in 20 healthy subjects and 29 patients with cardiac disease who had none or very-mild reduced myocardial perfusion evaluated as a low summed rest score (0 to 4, the range of the studied healthy subjects). Two nuclear medicine specialists blindly divided them into two groups: non-heterogeneity or heterogeneity group, based solely on their visual assessments of heterogeneity on splash and polar maps generated from single-photon emission computed tomography (SPECT) images. The %uptake was determined by dividing the tracer count of each pixel by the tracer count of the pixel with the highest value in the LV myocardium. SD, BW95%, and entropy from histogram patterns were analyzed from the polar map data array of each %uptake. We investigated whether heterogeneity could be assessed using SD, BW95, and entropy in two groups classified by visual assessments. Additionally, we evaluated the area under the curve (AUC) to identify heterogeneity in the receiver operating characteristic curve analysis.ResultsBased solely on visual assessments, 11 (22%) and 38 (78%) cases were classified into the non-heterogeneity and heterogeneity groups, respectively. The non-heterogeneity group consisted of only healthy subjects, and all patients with cardiac disease were classified into the heterogeneity group. The cases in the heterogeneity group had significantly higher values of heterogeneity indices (SD, BW95%, and entropy) in %uptake than those in the non-heterogeneity group (p < 0.05 for all). The AUCs of the heterogeneity indices were sufficiently high (AUCs > 0.90 for all) in distinguishing cases with visually heterogeneous distribution or patients with cardiac disease.ConclusionsHeterogeneity in MPI can be evaluated using SD, BW95%, and entropy through histogram analysis. These novel indices may help identify patients with subtle myocardial changes, even in images that show preserved perfusion (345/350).

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

A Dual-Band and Dual Circularly Polarized Wide-Angle Scanning Array Antenna With Single-Feed Elements at K-/Ka-Bands

A Dual-Band and Dual Circularly Polarized Wide-Angle Scanning Array Antenna With Single-Feed Elements at K-/Ka-Bands

Time-Altitude Variation of 30-Second-Update Full Volume Scan Data for Summer Convective Storms Observed With X-Band Dual Polarized Phased Array Weather Radar

Time-Altitude Variation of 30-Second-Update Full Volume Scan Data for Summer Convective Storms Observed With X-Band Dual Polarized Phased Array Weather Radar

Polar topological superdomain arrays in PMN-PT crystals engineered via a voltage-free method

Domain engineering is an active field of research that aims to enhance the functional properties of ferroelectric materials for various applications. This work presents a voltage-free method for fabricating topological superdomain arrays in 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) crystals. During the cooling process from high-temperature paraelectric phase to room temperature ferroelectric phase, the out-of-plane polarization of PMN-28PT crystals in contact with aluminum can be fully regulated downward, attributed to the difference in the work function of aluminum and PMN-28PT. In conjunction further with photolithography and ultraviolet light illumination, it is easy to obtain periodic strip domain structures with alternating up and down polarization. Moreover, this method can also control in-plane polarization, resulting in a large-scale central divergent/convergent topological superdomain array. These findings provide insights into ferroelectric domain engineering and have implications for the development of electromechanical, piezoelectronic, and photonic devices.

Robust high-order polarization arrays via vectorial spatial-coherence engineering

Robust high-order polarization arrays via vectorial spatial-coherence engineering