Asymmetric Array Research Articles

Volumetric photoacoustic imaging with symmetric spatial resolution in transverse plane from the asymmetric array using a virtual-transducer concept

Volumetric photoacoustic imaging based on the one-dimensional array has shown increasing applications for its low cost and convenient integration. However, due to the asymmetric angular detection aperture, the image obtained from such arrays faces challenges of asymmetric spatial resolution and artifacts. To address these issues, a virtual-transducer-based approach is proposed to achieve a volumetric image with symmetric resolution and low artifacts. By considering the asymmetric array as a symmetrical spherical-focused virtual transducer, the method ensures a symmetric angular detection aperture. The entire image reconstruction is then based on the equivalent symmetric data. Simulation and phantom experiment demonstrate excellent symmetric resolution and low artifact performance. The ratio of the average intensity between targets and artifacts is suppressed up to 25.09 dB. The in vivo experiment validates the biomedical practicability of the proposed method. This approach exhibits a general value and holds significant promise for low-cost, convenient, and high-quality volumetric photoacoustic imaging in biomedical applications.

Multi-Asymmetric Irradiation Method Using a Ring Array to Obtain an Emission-Capable LED Beam Power Effect to Observe Cancer Removal Status in a Surgical Microscope.

The light emitting diodes (LEDs) used in surgical fluorescence microscopes have weak power, to induce fluorescence emission. The LED induces fluorescence emission throughout a lesion due to its large beam width; however, the beam irradiation intensity is not uniform within the beam width, resulting in a fluorescence emission induction difference. To overcome this problem, this study proposes an asymmetric irradiation array for supplying power uniformly throughout the beam width of the LED and increasing the intensity of the LED. To increase the irradiation power of the LEDs, a multi-asymmetric irradiation method with a ring-type array structure was used. The LED consisted of eight rings, and the space between the LEDs, the placement position, and the placement angle were analyzed to devise an experimental method using 3D printing technology. To test the irradiation power of the LED, the working distance (WD) between the LED and target was 30 cm. The bias voltage of the LED for irradiating the light source was 5.0 V and the measured power was 4.63 mW. The brightness (lux) was 1153 lx. Consequently, the LED satisfied the fluorescence emission induction conditions. The diameter of the LED-irradiated area was 9.5 cm. Therefore, this LED could be used to observe fluorescent emission-guided lesions. This study maximized the advantages of LEDs with optimal conditions for fluorescence emission by increasing the beam width, irradiation area, and energy efficiency, using a small number of LEDs at the maximum WD. The proposed method, optimized for fluorescence expression-induced surgery, can be made available at clinical sites by mass producing them through semiconductor processes.

Enantioselective Target Transport-Mediated Nanozyme Decomposition for the Identification of Reducing Enantiomers in Asymmetric Nanochannel Arrays.

Enantioselective identification of chiral molecules is regarded as one of the key issues in biological and medical sciences because of their configuration-dependent effects on biological systems. In this study, we developed an electrochemical platform based on a tandem recognition-reaction zone design in TiO2 nanochannels for the specific recognition of reducing enantiomers. In this system, MIL-125(Ti) Ti-metal-organic frameworks, in situ grown in TiO2 nanochannels, provided a homochiral recognition environment via postmodification with l-tartaric acid (l-TA); MnO2 nanosheets possessing both glucose oxidase (GOD)- and peroxidase (POD)-mimicking activities served as the target-reactive zone at the end of the nanochannels. The use of penicillamine (Pen) enantiomers as model-reducing targets facilitated the passage of d-Pen through the homochiral recognition zone, owing to its lower affinity with l-TA. The passed Pen molecules reached the responsive zone and induced a target concentration-dependent MnO2 disassembly. Such target recognition event impaired the cascade GOD- and POD-like activities of MnO2. Combining the enantioselectivity of the recognition nanochannels with the cascade enzyme-like activity of MnO2 toward glucose and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate), the quantitative identification of l- and d-Pen was achieved through the changes in transmembrane ionic current induced by the generated charged products. This recognition-reaction zone design paves an effective way for developing a promising electrochemical platform for the identification of reducing enantiomers with improved selectivity and sensitivity.

Development of novel Cuckoo search optimization-based controller for partially shaded Photovoltaic system

Among the list of reliability issues in Photovoltaic (PV) systems, partial shading is one of the crucial issues that affect the row current creating a wide range of current differences between rows these results in reduced output power and panel life span by creating hotspots. It also creates difficulty in tracking the power, because of multiple hotspot peaks obtainable in PV and IV (Current-Voltage) curves. Physical relocation of panels during shade occurrence is not an encouraging solution because of rooftop solar and domestic PV systems, where the area for PV installation is a ceiling. The optimization-based controller is retrofitted for the electrical relocation of panels. It is developed based on the Cuckoo Search Algorithm (CSA), which aims to reduce the row current difference with a minimum reposition of panels as constraints. For the 9*9 PV arrangement, the row current ranges from 3.747 A to 8.424 A. It is reduced and almost made zero. Hence, the Fill factor raises from 38.073 to 51.707%. The power output is enhanced by about 20%. To prove the algorithm’s novelty a shading case for 4*3 asymmetric array arrangement is also considered for simulation studies. The proposed system proves to be economically beneficent for PV users. The performance of CSA is compared with PSO, Skyscraper, and SuDoKu. An economic analysis is carried out that adds the PV efficiency value to the proposed CSA algorithm. The real-time experimental validation holds good for 3*3 solar array agreement with theoretically simulated results.

Construction of asymmetric orthogonal arrays of high strength via generator matrix

Asymmetric orthogonal arrays are very useful in theoretical studies and practical applications. However, it is difficult to construct such designs of high strength. In this article, we use the generator matrix method to obtain some asymmetric orthogonal arrays of strength three. Then we combine it with the general (further) replacement procedure to get more general asymmetric orthogonal arrays of high strength.

The symmetry-induced numerosity illusion depends on visual attention

Symmetry is an important and strong cue we rely on to organize the visual world. Although it is at the basis of objects segmentation in a visual scene, it can sometimes bias our perception. When asked to discriminate numerical quantities between symmetric and asymmetric arrays, individuals tend to underestimate the number of items in the symmetric stimuli. The reason for this underestimation is currently unknown. In this study we investigated whether the symmetry-induced numerosity underestimation depends on perceptual grouping mechanisms by depriving attentional resources. Twenty-six adults judged the numerosity of dot arrays arranged symmetrically or randomly, while ignoring a visual distractor (single task) or while simultaneously judging its color and orientation (dual-task). Diverting attention to the concurrent color–orientation conjunction task halved the symmetry-induced numerosity underestimation. Taken together these results showed that the bias in numerosity perception of symmetric arrays depends—at least partially—on attentional resources and suggested that it might originate from the recruitment of attentional dependent incremental grouping mechanisms.

Terahertz asymmetric metallic hole arrays with polarization-independent quasi-bound states in the continuum for membrane sensing.

Resonances with both high-quality factor and polarization-independent characteristics are highly desirable for terahertz (THz) sensing. Here, THz sensors based on asymmetric metallic hole arrays (AMHAs) are experimentally demonstrated. Such sensors consisting of four-hole arrays support polarization-independent quasi-bound states in the continuum (BICs). The induced quasi-BIC presents a quality factor exceeding 2000, which enables enhanced sensing for thin membranes. Results show that the frequency shift is 97.5 GHz for the 25-µm thick polyimide (PI), corresponding to a sensitivity of 147.7 GHz/RIU. The sensing performance strongly relates to the enhanced field originating from sharp quasi-BICs. A maximum field enhancement of 15.88 in contrast to the incident field is achieved. When the PI thickness is large than the decay length of enhanced fields, the interaction strength of field-PI becomes weak, resulting in a saturation effect for the shift of quasi-BICs. The proposed sensor possessing polarization-independent quasi-BICs has great potential for practical sensing applications in real-time chemical and biomolecular.

Dual-band circularly polarized asymmetric dipole array antenna for GPS L1 and L2 bands

A dual-band, circularly polarized (CP) asymmetric dipole array antenna for Global Positioning System (GPS) applications with a wide beam is presented in this paper. The proposed antenna comprises two different-sized printed crossed dipoles with integrated baluns fed by an asymmetric feeding network to achieve dual-band functionality. Using two branch-line couplers with different dimensions in the feeding network performs Right-Hand Circular Polarization (RHCP) operation at GPS L1 and L2 bands. According to the experiments, the proposed antenna has wide impedance bandwidths of 24.82% (1139.5–1462.4 MHz) and 14.82% (1500.4–1740.5 MHz), and 3 dB Axial-Ratio (AR) bandwidth of 37.4% (1132.3–1653.2 MHz) to cover the GPS L1 and L2 bands. Furthermore, at 1227 MHz frequency, the antenna has a gain of 4.65 dBic, and a 3 dB AR beamwidth of 148.2° facing the sky. Also, at 1575 MHz frequency, a gain of 5.25 dBic and a 3 dB AR beamwidth of 139.3° are achieved.

Broadband, angle-dependent optical characterization of asymmetric self-assembled nanohole arrays in silver

Plasmonic nanostructured materials made of nanohole arrays in metal are significant plasmonic devices exhibiting resonances and strong electromagnetic confinement in the visible and near-infrared range. As such, they have been proposed for use in many applications such as biosensing and communications. In this work, we introduce the asymmetry in nanoholes, and investigate its influence on the electromagnetic response by means of broadband experimental characterization and numerical simulations. As a low-cost fabrication process, we use nanosphere lithography, combined with tilted silver evaporation, to obtain a 2D hexagonal array of asymmetric nanoholes in Ag. Our experimental set-up is based on a laser, widely tunable in the near-infrared range, with precise polarization control in the input and in the output. We next resolve the circular polarization degree of the transmitted light when the nanohole array is excited with linear polarization. We attribute the disbalance of left and right transmitted light to the asymmetry of the nanohole, which we support by numerical simulations. We believe that the optimization of such simple plasmonic geometry could lead to multifunctional flat-optic devices.

Asymmetric electrodes for droplet directional actuation by a square wave on an open surface

The large-scale electrowetting-on-dielectric (EWOD) digital microfluidic platforms always require complex electrode-addressing schemes and high-cost fabrication methods of dielectric and hydrophobic layers. Hence, the voltage polarity-dependent electrowetting was used to actuate droplets with asymmetric printed circuit board (PCB) electrodes on an open slippery liquid-infused porous surface (SLIPS) chip. The V-shaped, convex-shaped, and curve-shaped coplanar asymmetric electrode arrays were designed to achieve the directional motion of a droplet by a square wave voltage signal. The operation ranges of voltage amplitude and frequency for continuously actuating a 10 µl droplet were obtained on the three asymmetric electrode arrays. Our results found that the curve-shaped electrode array has a broader voltage operation range than the other two for continuous pumping of a 10 µl droplet. It is because the droplet has a long effective width of contact line with the front curve-shaped electrode and does not overlap with the rear electrode during the movement. Meanwhile, a reconfigurable convex-shaped electrode structure was also proposed to achieve bidirectional actuation of a droplet by controlling the square wave voltage. This work provides a low-cost, straightforward electrode-addressing scheme for designing digital microfluidic devices.

Influence of topography on the optical performances of a Fresnel linear asymmetrical concentrator array: The case of the eLLO solar power plant

Solar field orientation and inclination are variables that significantly influence the optical performance over the year of Linear Fresnel Collector (LFC). The usual field configuration is a flat north-south (NS) orientation, however, the future development of the LFC sector, for example for solar heat for industry, could more often impose the land choice and therefore the solar field configuration. To study the influence of such configuration on a solar field optical performance, a ray-tracing model was used to evaluate the LFC optical performance for each solar position and a consistent methodology was developed to evaluate the solar position in the module reference system. This method allows studying the optical performance of any LFC array configuration. The paper first looks separately at the influence of orientation and tilt imposed by the topography of the eLLO project, then focuses on the eLLO solar power plant case study. The results of eLLO's solar line simulation showed an increase of 1.6% in annual absorbed energy compared to NS implementation, which is the best orientation for the localization. In conclusion, the design and implementation of modular LFC array can be adapted to a wide range of terrains and can even take advantage of this constraint.

Blind study site assessment of shear-wave velocity at Kumamoto City, Japan, using direct-fitting SPAC methods

The study used data acquired by the ESG6 Blind Prediction Step BP1 Working Group for purposes of facilitating a comparison of interpretation methods for obtaining shear-wave velocity profiles (Vs) from array observations of microtremor (passive seismic) noise. This work uses the direct-fitting MMSPAC method and the krSPAC method on passive seismic data supplied from four seven-station nested triangular arrays with apertures ranging from 1 to 962 m, located within Kumamoto City, Japan. The data allow a useful frequency range of 38 Hz down to 0.3 Hz, giving depth sensitivities from 2 m to > 1000 m. Results are presented as a seven-layer model which has time-averaged shear wave velocities for top 30 m and 300 m of Vs30 = 189 m/s and Vs300 = 584 m/s, respectively. HVSR spectra show two significant peaks at 1.2 and 0.35 Hz which are indicative of major Vs contrasts at depths 26 m and 750 m. The MMSPAC method (and its krSPAC variant) also proved viable on one asymmetric array where four of the seven stations were corrupted by incoherent low-frequency noise. Indications of a lateral variation in Vs could be detected due to the non-concentric geometry of the four arrays, and also from variations in HVSR spectra at stations of the largest array. Further analysis in step 4 of the blind trials, making use of geological data and a Preferred model supplied to participants, showed apparent discrepancies between the Preferred and our BP1 model for the upper 40 m where a supplied PS log appears to be inconsistent with geological data and the blind BP1 model. At low frequencies 0.5–2.5 Hz dispersion data and the BP1 model suggest that use of the Rayleigh effective mode is superior to use of the fundamental mode in deducing the Vs model at depths below 100 m. The method of direct fitting of model and observed SPAC spectra used in MMSPAC also enabled the use of a bandwidth 0.5–38 Hz for interpretation, which is a wider bandwidth than that achieved by other participants for use of passive seismic data alone.Graphical

Novel Shade Dispersion Techniques for Reconfiguration of Partially Shaded Photovoltaic Arrays

The photovoltaic (PV) arrays are inevitably subjected to partial shading (PS) conditions that highly limit the output. To mitigate these effects, various reconfiguration procedures have been executed by the researchers. However, many of these procedures fail to disperse the shade effectively over the entire array and hence there is a dire need for such an efficient reconfiguration technique. This paper explores Knight’s Tour Magic square (KTM) and Doubly Even-order Magic square (DEM) techniques which effectively disperse the shadow by reconfiguring the array without altering the electrical connections. To examine the superiority of the proposed techniques, their performance has been compared with conventional total-cross-tied, existing odd-even and odd-even-prime configurations of a symmetric 8 × 8 and asymmetric 4 × 3 PV arrays. Further, the applicability of the proposed techniques is proved by analysing the system with eight performance parameters such as global maximum power, power mismatch, percentage losses, efficiency, fill factor, capacity factor, array yield, and performance ratio under 20 distinct PS patterns. The power enhancement in GMP using the KTM and DEM approaches are nearly 42.67%, 17.87%, 16.24%, 8.04% for asymmetric arrays, and 26.43%, 25.38%, 25.09%, 15.61%, 10.63%, for the symmetric arrays. Finally, a comprehensive economic analysis is also performed, and it is observed that there is a significant augmentation in the number of units and the revenue generated by employing the proposed techniques.

An ultra-high figure of merit refractive index sensor with Mie lattice resonance of a toroidal dipole in an all-dielectric metasurface array in the near-infrared

Recently, improvement of the sensing performance of refractive index sensors using the weak far-field radiation and strong local field enhancement properties of toroidal dipole resonances has been intensively studied. Transmission/reflection spectra with significant narrow linewidth resonance have a vital effect in improving the sensing performance. However, a narrower linewidth always leads to smaller modulation depth of the resonance, which hinders the sensing performance to be improved for experiments. In this paper, we design an ultrathin all-dielectric asymmetric X-type metasurface array, where an extremely narrow linewidth and high modulation depth of transmission resonance in the near-infrared have been demonstrated with Mie lattice resonance formed by the coupling of the toroidal dipole with Rayleigh anomalous diffraction. With optimized structure parameters, a transmission dip with a full width at half-maximum as narrow as 0.061 nm and a modulation depth as high as 99.24% are achieved at a wavelength of 943.33 nm with a corresponding Q factor of 15464. According to the analysis of the displacement current distributions and the scattered powers in the far field at the resonant and nonresonant wavelengths, it is confirmed that the narrow linewidth resonance originates from the coupling of the toroidal dipole with Rayleigh anomalous diffraction. A sensitivity and a figure of merit of 321 nm RIU−1 and 5262 RIU−1 are numerically demonstrated respectively for a refractive index sensor based on the all-dielectric asymmetric X-type metasurface array.

Time-Switching Symmetric Transmitter Array to Increase Sweet Region for Far-Field Wireless Power Transmission Under Receiver Rotation and Location Variation

For wireless power transfer using linear-polarized transmitter (TX) and receiver antennas, the rotation and movement of receiving antenna cause received power variation. The received power pattern is proposed to describe the received power variation from a specific TX antenna under receiver rotation. By placing the peak of the received power pattern of additional TX antennas in null directions of the previous TX antenna, received power variation due to rotation can be compensated. With symmetrically placed TX antennas, the power variation due to location variation can be compensated. This article proposes a time-switching symmetric transmitting array combining both techniques to increase the sweet region for far-field wireless power transfer under rotation and location variation. A sweet region is an area in the 2-D case or volume in the 3-D case, which is defined as an area or a volume inside the TX array that can get guaranteed minimum received power under rotation. The received power calculation using the Friis equation with short dipole antenna pattern shows that a symmetric TX array can achieve a larger sweet region than an asymmetric TX array under the same total transmitted power. The efficiency for the receiver at the origin is 1/2 at the 2-D case and 1/3 at the 3-D case. In the experiment, a linear-polarized TX array at 915 MHz with monopole receiver antenna and power detector is used as the receiver to measure received power under rotation and location variation. Measurement results at 2-D and 3-D cases confirm the received power level predicted by calculation using the Friis equation. The power budget calculation for wirelessly powering a sensor module attached on a bee inside a beehive using the proposed 3-D TX array shows that it is feasible to deliver sufficient power to the sensor module regardless of the orientation and location of the bee inside the beehive.

Low-Concentration Biological Sample Detection Using an Asymmetric Split Resonator Terahertz Metamaterial

A simple and efficient THz metamaterial based on an asymmetric double split square array resonator was designed and fabricated. The sensitivity and Q value of the metamaterial sensor were theoretically analyzed to be 278 GHz/RIU and 11, respectively. Three typical biological samples with different concentrations were measured to validate the sensitivity of the THz metamaterial. For the bovine serum albumin (BSA) protein solution, the lowest detectable concentration (LDC) can reach to 1 μM, which is comparable to most recent reports. For the Staphylococcus aureus bacteria, the LDC is 1 × 103 cells/mL, and for the K-citrate solution, the LDC is 0.1 mM. Our studies indicate that the THz metamaterial may be effectively applied in the low-concentration detection of biological samples.

A Flexible, High-Voltage (>100V) Generating Device Based on Zebra-Like Asymmetrical Photovoltaic Cascade.

The mutual conversion between light and electricity lies at the heart of optoelectronic and photonic applications. Maximization of the photoelectric conversion is a long-term goal that can be pursued via the fabrication of devices with ad-hoc architectures. In this framework, it is of utter importance to harvest and transform light irradiation into high electric potential inspecific area for driving functional dielectrics that respond to pure electric field. Here, a nano-fabrication technology has been devised featuring double self-alignment that is applied to construct zebra-like asymmetric heterojunction arrays. Such nanostructured composite, which covers a surface area of 5×4mm2 and contains 500 periodic repeating units, is capable of photo generating voltages as high as 140V on a flexible substrate. This approach represents a leap over the traditional functionalization process based on simply embedding materials into devices by demonstrating the disruptive potential of integrating oriented nanoscale device components into meta-material.

Modular thermoelectric generation arrays reconfiguration under heterogeneous temperature distribution via improved cooperation search algorithm: Modelling, design and HIL validation

• ICSA based modular TEG arrays reconfiguration is presented. • Enhanced exploration operator and discretization are incorporated into ICSA. • Solution optimization program reduces possible unnecessary switching actions. • Feasibility of the proposed method are validated under two TEG arrays. • An RTLAB platform based real-time hardware-in-the-loop test has been carried out. • Maximum output power is increased by 146.45 W under asymmetric TEG array. This paper innovatively proposes a modular thermoelectric generation (TEG) arrays reconfiguration technique based on an improved cooperation search algorithm (ICSA), which aims to mitigate the troublesome effects of heterogeneous temperature distribution (HTD) conditions and fully exploit their power generation potential. Firstly, the original TEG array is divided into three blocks, upon which only two switch matrices are required to implement various reconfiguration, while its number of switches and construction costs can be significantly reduced. Secondly, the ratio of output power and voltage range (namely voltage imbalance factor (VIF)) between TEG columns is regarded as a fitness function to simultaneously maximize output power and minimize voltage imbalance. Furthermore, in order to solve this model, ICSA is designed to effectively and efficiently seek the global optimum. Meanwhile, three traditional discrete meta-heuristic algorithms are employed for comparison (e.g., genetic algorithm (GA), particle swarm optimization (PSO), and simulated annealing (SA) algorithm). Besides, to validate the problem formulation and solver design, both symmetric ( 15 × 15 ) and asymmetric ( 15 × 20 ) TEG arrays are tested under three typical HTD conditions, i.e., outer, centre, and random. Lastly, simulation results on MATLAB verify that ICSA can rapidly smooth the output power curves and dramatically enhance generation efficiency of TEG arrays. Specifically, the maximum output power can be increased at most by 93.77 W with a decrease of 164.02 V of VIF under symmetric case, and 146.45 W with a decrease of 111.92 V of VIF under asymmetric scenario, respectively.

Directional transport behaviour of droplets on the surfaces with asymmetric slanted cone arrays

Directional transport behaviour of droplets on the surfaces with asymmetric slanted cone arrays

A Dimension-Independent Array Relocation (DIAR) Approach for Partial Shading Losses Minimization in Asymmetrical Photovoltaic Arrays

A Dimension-Independent Array Relocation (DIAR) Approach for Partial Shading Losses Minimization in Asymmetrical Photovoltaic Arrays