Optimum Aperture Research Articles

High-Resolution Imaging: An Approach by Compensating Absorption and Dispersion in Prestack Time Migration With Effective Q Estimation and Fresnel Zone Identification Based on Deep Learning

We have developed a migration scheme that can compensate absorption and dispersion with effective Q estimation and Fresnel zone identification based on deep learning. We use the U-Net neural network technology in deep learning to automatically identify Fresnel zones from compensated migrated dip-angle gathers and obtain the optimal aperture for migration, avoiding the tedious task of manually modifying the boundaries of Fresnel zones. Instead of the interval Q factor, we used an effective Q parameter to compensate absorption and dispersion. The effective Q is estimated using VSP well data and surface seismic velocity data. The proposed scheme can be incorporated into conventional seismic data processing workflow. A field data set was employed to validate the proposed scheme. Higher resolution imaging results with low noise levels are obtained.

Effects of multi-orifice plate with different geometric parameters on flow distribution of plenum chamber for ventilation duct systems

Plenum chambers are common devices used for flow and pressure equalization in ventilation and air conditioning systems. Aiming for reducing energy consumption and improving ventilation performance, the optimal cross-sectional aspect ratio (W/H) and length (L) of the single-path unlined rectangular plenum chamber is obtained through the authors’ preliminary research. In this study, based on the analysis of interior flow characteristics of single-path plenum chamber, it is shown that the traditional chamber configuration commonly used in engineering is not an ideal structure that can achieve uniform flow distribution. The multi-orifice plate is proposed to add inside chamber to improve flow uniformity. Under the two typical design schemes of W/H=1/1 and 5/1, the effect of multi-orifice plate with different geometric parameters on flow distribution of plenum chamber is investigated, and the optimal installation position and aperture rate of orifice plate is proposed. The optimized aperture ratio is designed to be 30% for both the two typical chamber configurations. When W/H=1/1, it is recommended to install the multi-orifice plate at the position of y/L=0.1, as for W/H=5/1, the y/L=0.3 is preferred. Besides, the fluid equalizing effect of the plenum chamber with multi-orifice plate is verified under four commonly used air ducts specifications in engineering.

Golomb Patterns, Astrophysics, and Citizen Science Games

This paper presents an online citizen science game called “Game and Repository for Aperture Solutions and Patterns (GRASP).” GRASP is uniquely tailored to an important task of designing a small-aperture antenna array by leveraging a mathematical structure called a Golomb pattern. In this application of GRASP, an optimal aperture pattern leads to space images of desired spectral resolution observed with the least-cost antenna aperture array via interferometry imaging techniques. Finding near optimal Golomb patterns is computationally very hard. GRASP citizen scientists are tasked with finding (near-)optimal Golomb patterns by selecting cells on a grid that obey the rules of the game, ensuring Golomb properties to be satisfied. They can also submit known Golomb solutions with their citations, display existing solutions in GRASP repository, and employ GRASP solutions for non-redundant aperture design of the interferometry and radar applications. In this paper, we introduce the concept of Golomb patterns, and present current design and framework of our citizen science platform GRASP as a means to solve, store, and display such patterns, as well as the motivation behind our work. In particular, we discuss the application of Golomb patterns in astrophysics’ inteferometry missions for small-aperture antenna array design.

Exploiting the full potential of the advanced two-hexapole corrector for STEM exemplified at 60kV

Ultimate resolution in scanning transmission electron microscopy (STEM) with state-of-the-art aberration correctors requires careful tuning of the experimental parameters. The optimum aperture semi-angle depends on the chosen high tension, the chromatic aberration and the energy width of the source as well as on potentially limiting intrinsic residual aberrations. In this paper we derive simple expressions and criteria for choosing the aperture semi-angle and for counterbalancing the intrinsic sixth-order three-lobe aberration of two-hexapole aberration correctors by means of the fourth-order three-lobe aberration. It is noteworthy that for such an optimally adjusted electron probe the so-called flat area of the Ronchigram is explicitly not maximized. The above considerations are validated by experiments with a CEOS ASCOR in a C-FEG-equipped JEOL NEOARM operated at 60 kV. Sub-Angstrom resolution is demonstrated for a Si[112] single crystal as well as for a single-layered MoS2 crystalline film. Lattice reflections of 73 pm for silicon and 93 pm for molybdenum disulfide are visible in the Fourier transform of the images, respectively. Moreover, single sulfur vacancies can be clearly identified in the MoS2.

Near-Field Bessel-Gauss Antenna for Nonmetal Internal Defects Detection

A radial line slot array (RLSA) is proposed for Bessel-Gauss beam generation with a narrow main beamwidth and low sidelobe characteristics for nonmetallic internal defects detection. Owing to the radial attenuation factor of Gaussian function, the sidelobe level of Bessel-Gauss beam can be suppressed. By accurately adjusting the slot position and size of the RLSA, the optimum aperture field distribution can be synthesized to generate the near-field Bessel-Gauss beam based on the projection method. The simulated/measured results have shown that the maximum nondiffraction distance of 70 mm/70 mm and the null-null beam width of the Bessel-Gauss main beam of 30 mm/30 mm are achieved at the operating frequency of 12.5 GHz/12.5 GHz, while low sidelobe levels (<−18.14 dB/−18.07 dB) are generated. Compared to other antennas for microwave nondestructive testing, the proposed RLSA has merits of low sidelobes, large E-field depth and narrow main beam; therefore, it can improve the detection performance in terms of sensitivity and depth, which can be widely, used for nonmetal internal defects detection applications.

Ground-based corner cube retroreflector optimal design for the geolocation validation of satellite photon counting lidar.

The corner cube retroreflector (CCR) can be applied in the on-orbit geolocation validation of satellite photon counting lidar, which provides insight into the fidelity of laser footprint geolocation on the ground. A novel parameter optimization method, to the best of our knowledge, is proposed to enhance the performance of the CCR. Based on the velocity aberration effect of the satellite and the far-field diffraction pattern (FFDP) of the CCR, a mathematical model with respect to the received energy and design parameters of the CCR, including the aperture, the dihedral angle errors (DAE), and the curvature radius of the front face (CROF), is derived. We can achieve the optimal design parameters of the CCR through searching for the locations of the maximal and uniform FFDP on the circumference of the aberration position. We resolve the optimal aperture, the DAE, and the CROF of the CCR as 14.3 mm, 2.4 in., and 6000 m for the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) lidar. The received energy derived from the derived parameters has a significant improvement of around 26 times compared with the CCR parameters employed in the ICESat-2. The results demonstrate that the proposed algorithm is effective, and the regression models of the optimal aperture and DAE for different satellite altitudes are conveniently employed in the design of the CCR for the geolocation validation of satellite photon counting lidar.

Modeling evaluation on solid-liquid mixing characteristics in a dislocated guide impeller stirred tank

Abstract The solid-liquid mixing characteristics in a stirred tank with pitched blade impellers, dislocated impellers, and dislocated guide impellers were investigated through using CFD simulation. The effects of impeller speed, impeller type, aperture ratio, aperture length, solid particle diameter and initial solid holdup on the homogeneity degree in the solid-liquid mixing process were investigated. As expected, the solid particle suspension quality was increased with an increase in impeller speed. The dislocated impeller could reduce the accumulation of solid particles and improve the cloud height compared with pitched blade impeller under the same power consumption. The dislocated guide impeller could enhance the solid particles suspension quality on the basis of dislocated impeller, and the optimum aperture ratio and aperture length of dislocated guide impeller were 12.25% and 7 mm, respectively, in the solid-liquid mixing process. Smaller solid particle diameter and lower initial solid holdup led to higher homogeneity degree of solid-liquid mixing system. The dislocated guide impeller could increase solid particle integrated velocity and enhance turbulent intensity of solid-liquid two-phase compared with pitched blade impeller and dislocated impeller under the same power consumption.

Lateral resolution limit of laser Doppler vibrometer microscopes for the measurement of surface acoustic waves

The lateral or transverse resolution of single-point interferometers for vibration measurement is especially critical for microelectromechanical systems (MEMS) vibrating up to the gigahertz range. In this regime, the acoustic wavelengths are typically in the range of the size of the laser focus. Thus, a successful vibration measurement requires distinct knowledge about the lateral resolution limit and its dependencies with instrumentation parameters. In this paper, we derive an analytic approximation formula, which allows for estimation of the systematic measurement deviation of the vibration amplitude and, thus, a definition of the lateral resolution limit of single-point interferometers for vibration measurement. Further, a compensation and an optimum numerical aperture are proposed the reduce the measurement deviation. For this, the model includes a laser-interferometer microscope of Mach-Zehnder type with Gaussian laser beams considering the Gouy effect and wavefront curvature. As a measurement scenario, an unidirectional surface acoustic wave (SAW) is regarded. The theoretic findings have been validated in the experiment with a representative vibration measurement on a SAW filter at 433,{mathrm {MHz}} with our heterodyne laser-Doppler interferometer with offset-locked semiconductor lasers. The provided formulas help instrument designers and users to choose suitable instrument parameters, especially the numerical aperture of the utilized microscope objective.

Design of Maximum-Gain Dielectric Lens Antenna via Phase Center Analysis

In this work, a method is presented to maximize the gain of millimeter-wave (mm-wave) lens antennas using phase center analysis. This analysis is required when the underlying radiator antenna is not a point source, especially for the cases of arrays. Commonly, for designing a lens antenna, the lens is simply positioned on top of antenna radiator, which is may not always provide the optimum gain and aperture efficiency. A solution is proposed, where the lens will be placed at a distance calculated using the phase center analysis to produce the maximum gain from the lens-antenna systems. A mm-wave microstrip antenna array is designed, and the proposed method is applied for the gain enhancement. Simulation results show that the proposed scheme obtains around 25% gain enhancement compared to the traditional method.

Proposal of moire-free aerial display based on the LED panel and apertured retro-reflector

We have realized a novel optical system to form a large aerial image in front of a full-color LED panel that is covered with retro-reflector. The retro-reflector has square apertures through which lights from the LED pixels pass. Our optical system is based on aerial imaging by retro-reflection (AIRR). The aerial image formed with AIRR is visible over a wide viewing angle without using 3D glasses. To reduce the system volume, a beam splitter is placed parallelly in front of the LED panel covered with the retro-reflector. Because the apertured retro-reflector is placed on the LED panel, no moire occurs between the apertures in the retro-reflector and black regions on the LED panel. We have analytically clarified the optimal aperture ratio in the proposed optical system to increase the luminance of the aerial image. Furthermore, we have developed a prototype for experimental confirmation of our optical system and measured of the luminance intensity of the aerial images. Consequently, we have confirmed measured results are consistent with our analysis. Showing aerial signage in front of an LED panel reduces the foot space, which is suitable for the installation of a large-scale aerial display for advertisement and exhibitions.

Overexpression of MdATG8i improves water use efficiency in transgenic apple by modulating photosynthesis, osmotic balance, and autophagic activity under moderate water deficit

Water deficit is one of the major limiting factors for apple (Malus domestica) production on the Loess Plateau, a major apple cultivation area in China. The identification of genes related to the regulation of water use efficiency (WUE) is a crucial aspect of crop breeding programs. As a conserved degradation and recycling mechanism in eukaryotes, autophagy has been reported to participate in various stress responses. However, the relationship between autophagy and WUE regulation has not been explored. We have shown that a crucial autophagy protein in apple, MdATG8i, plays a role in improving salt tolerance. Here, we explored its biological function in response to long-term moderate drought stress. The results showed that MdATG8i-overexpressing (MdATG8i-OE) apple plants exhibited higher WUE than wild-type (WT) plants under long-term moderate drought conditions. Plant WUE can be increased by improving photosynthetic efficiency. Osmoregulation plays a critical role in plant stress resistance and adaptation. Under long-term drought conditions, the photosynthetic capacity and accumulation of sugar and amino acids were higher in MdATG8i-OE plants than in WT plants. The increased photosynthetic capacity in the OE plants could be attributed to their ability to maintain optimal stomatal aperture, organized chloroplasts, and strong antioxidant activity. MdATG8i overexpression also promoted autophagic activity, which was likely related to the changes described above. In summary, our results demonstrate that MdATG8i-OE apple lines exhibited higher WUE than WT under long-term moderate drought conditions because they maintained robust photosynthesis, effective osmotic adjustment processes, and strong autophagic activity.

Analysis of shielding effectiveness by optimizing aperture dimensions of a rectangular enclosure with genetic algorithm

Electromagnetic compatibility (EMC) has now become a substantial challenge more than any other time sincethe number of electric vehicles (EV) increased rapidly. The electric driving system in an EV consists of power electroniccomponents supplied by high voltage battery source. They are both source and victim of potential electromagneticinterference (EMI) since fast switching process occurs inside them. Electromagnetic shielding provides a significantprotection against EMI for any electrical and electronic components inside the vehicle. In this paper, analysis of shieldingeffectiveness (SE) by optimizing aperture dimensions of a rectangular enclosure is investigated. Realistic dimensions of theshielding enclosure of an inverter component are employed. An optimization methodology based on genetic algorithm(GA) is carried out and applied to an SE analytical model. It is aimed to keep the total aperture area as large aspossible inside a particular dimension range while improving SE of the enclosure compared with the reference level.Obtained optimization results are presented by indicating optimum aperture length and width which satisfy both EMCand dimension requirements. Finally, it is concluded that through the optimization methodology designed in this study,the SE of the enclosure is raised from a poor level to an average one while providing larger aperture area.

Optimal Aperture and Digital Speckle Optimization in Digital Image Correlation

Digital image correlation (DIC) method is a non-interference and non-contact full-field optical measurement technology. DIC’s measurement accuracy is largely determined by the image acquisition system and the quality of the speckle pattern. Although the optimal speckle pattern has been designed theoretically, the optimization process does not consider the influence of the imaging system. Furthermore, the optimal aperture has not been yield. The objective of this paper is to improve the measurement accuracy through optimization of aperture and speckle pattern. In this paper, speckle images with different apertures and different speckle generation parameters were captured, and the corresponding measurement errors were evaluated. (1) The influence of aperture and the optimization of speckle are independent of each other. The optimal speckle generation parameters (speckle size and density) are determined experimentally, which turn out to be consistent with existing theoretical models. (2) The optimal aperture is 5.6, because excessively large F-number causes the loss of high-frequency information and excessively small F-number leads to significant lens aberrations, both of which will reduce the measurement accuracy. The optimal aperture and speckle generation parameters (speckle diameter and density) are found and proved to be uncorrelated through actual experiments in practical conditions. These results provide experimental basis for the selection of parameters in actual engineering applications.

Impact of Aperture Shape Controller on Knowledge-based VMAT Planning of Prostate Cancer

Knowledge-based planning (KBP) has disadvantages of high monitor unit (MU) and complex multi-leaf collimator (MLC) motion. We investigated the optimal aperture shape controller (ASC) level for the KBP to reduce these factors in volumetric modulated arc therapy (VMAT) for prostate cancer. The KBP model was created based on 51 clinical plans (CPs) of patients who underwent the VMAT for prostate cancer. Another 10 CPs were selected randomly, and the KBPs with/without ASC, changed stepwise from very low (KBP-VL) to very high (KBP-VH), were performed with a single auto-optimization. The parameters of dose-volume histograms (DVHs) and MLC performance metrics were evaluated. We obtained the modulation complexity score for VMAT (MCSv), closed leaf score (CLS), small aperture score (SAS), leaf travel (LT), and total MU. The ASC did not affect the DVH parameters negatively. The following comparisons of MLC performance were obtained (KBP vs. KBP-VL vs. KBP-VH, respectively): 0.25 vs. 0.27 vs. 0.30 (MCSv), 0.19 vs. 0.18 vs. 0.16 (CLS), 0.50 vs. 0.45 vs. 0.40 (SAS10 mm), 0.73 vs. 0.68 vs. 0.63 (SAS20 mm), 768.35 mm vs. 671.50 mm vs. 551.32 mm (LT), and 672.87 vs. 642.36 vs. 607.59 (MU). There were significant differences between KBP and KBP-VH for MCSv and LT (p<0.05). The KBP using an ASC set to the very high level could reduce the complexity of MLC motion significantly more without deterioration of the DVH parameters compared with the KBP in VMAT for prostate cancer.

Comparative Performance Assessment of 300 MW Solar‐Coal Hybrid Power Generation System Under Different Integration Mechanisms

Solar−coal hybrid power generation (SCHPG) system is one of the interesting solutions for solar power generation. This research aims to find a more viable integration mechanism of solar energy into a coal‐fired thermal power plant in terms of techno‐economic and ecology perspective. Performance of the 300 MW SCHPG system in the nominal and part‐load condition is analyzed under three different integration mechanisms. Numerical simulation of 300 MW SCHPG system is investigated under four different cases using a thermal balance approach. Operation modes of fuel‐saving (FS) and power‐boosting (PB) are considered for each case. Among the proposed cases, Case 4 is obtained as a good operation performance, which is recommended as the main case. The solar energy in Case 4 is used for evaporating feedwater and steam superheating, and steam reheating. Results show that the optimal aperture area of the heliostat solar field is 330 330 m2, and the minimum levelized cost of electricity is 0.1847 USD kWh−1. In Case 4, thermal efficiency is increased by 7.19% with standard coal consumption reduced by 45.3 g kWh−1 compared to a reference power plant. In the SCHPG system, coal consumption is reduced by 26.8 tons h−1 in FS mode, whereas power output is increased 30 MW h−1 in PB mode.

First systematic high-precision survey of bright supernovae

Rapid variability before and near the maximum brightness of supernovae has the potential to provide a better understanding of nearly every aspect of supernovae, from the physics of the explosion up to their progenitors and the circumstellar environment. Thanks to modern time-domain optical surveys, which are discovering supernovae in the early stage of their evolution, we have the unique opportunity to capture their intraday behavior before maximum. We present high-cadence photometric monitoring (on the order of seconds-minutes) of the optical light curves of three Type Ia and two Type II SNe over several nights before and near maximum light, using the fast imagers available on the 2.3 m Aristarchos telescope at Helmos Observatory and the 1.2 m telescope at Kryoneri Observatory in Greece. We applied differential aperture photometry techniques using optimal apertures and we present reconstructed light curves after implementing a seeing correction and the Trend Filtering Algorithm (TFA, Kovács et al. 2005, MNRAS, 356, 557). TFA yielded the best results, achieving a typical precision between 0.01 and 0.04 mag. We did not detect significant bumps with amplitudes greater than 0.05 mag in any of the SNe targets in the VR-, R-, and I-bands light curves obtained. We measured the intraday slope for each light curve, which ranges between −0.37−0.36 mag day−1 in broadband VR, −0.19−0.31 mag day−1 in R band, and −0.13−0.10 mag day−1 in I band. We used SNe light curve fitting templates for SN 2018gv, SN 2018hgc and SN 2018hhn to photometrically classify the light curves and to calculate the time of maximum. We provide values for the maximum of SN 2018zd after applying a low-order polynomial fit and SN 2018hhn for the first time. We conclude that optimal aperture photometry in combination with TFA provides the highest-precision light curves for SNe that are relatively well separated from the centers of their host galaxies. This work aims to inspire the use of ground-based, high-cadence and high-precision photometry to study SNe with the purpose of revealing clues and properties of the explosion environment of both core-collapse and Type Ia supernovae, the explosion mechanisms, binary star interaction and progenitor channels. We suggest monitoring early supernovae light curves in hotter (bluer) bands with a cadence of hours as a promising way of investigating the post-explosion photometric behavior of the progenitor stars.

An analytical model for particle-geogrid aperture interaction

The shear strength of geogrid-reinforced ballast is often dependent on the aperture size of geogrids and the nominal size of ballast. This paper presents a theoretical analysis based on probabilistic mechanics of how aperture size affects the interaction between particles and geogrid. Unlike past literature, in this study, the properties of the particle size distribution is analysed using a Weibull distribution. The probability of grain interlock is proposed to describe the interactive mechanisms between particles and geogrids based on the relative particle size, which is defined as the ratio of particle size to aperture size. The mathematical model is calibrated by a set of large-scale direct shear tests with almost single-size (highly uniform) ballast aggregates, and then validated by independent set of data taken from both literature and current study. The study concludes that more uniform particle size distribution increases the probability of grain interlock at the optimum aperture size but decreases it at non-optimum aperture sizes.

Cylindrical Vector Beams for Wireless Power Transfer

This article investigates wireless power transfer in the Fresnel zone using cylindrical vector beams. First, a generalized coupling coefficient between two circular apertures in the Fresnel zone is derived. From the generalized coupling coefficient, explicit coupling coefficients between two circular (focused or unfocused) apertures supporting Gaussian, Bessel-Gaussian, and Laguerre-Gaussian beams are found in closed form. The analytically derived coupling coefficients and corresponding efficiencies are compared with those obtained through numerical integration of the reaction integral, as well as the results of a commercial electromagnetic solver. Then, it is demonstrated that a finite aperture, which supports a cylindrically apodized Bessel beam, is close to the optimal illumination. Also, it is shown that Bessel beams have a higher coupling coefficient than conventional Gaussian beams. Finally, the optimal aperture illumination is found numerically by constructing an aperture field from a summation of Bessel beams with different axicon angles. That is, the complex amplitude of each Bessel beam is found that maximizes coupling between the two apertures. The optimal illumination radiates a magnetic field equal to the complex conjugate of the receiver aperture's electric field. This observation agrees with those for optimal illumination in the context of a confocal optical resonator.

Computational fluid dynamics simulation of solid-liquid suspension characteristics in a stirred tank with punched circle package impellers

Abstract Solid-liquid suspension characteristics in a stirred tank with four pitched-blade impellers, circle package impellers, and punched circle package impellers were studied via computational fluid dynamics (CFD) simulation. A classical Eulerian-Eulerian approach coupled with the standard k-ε turbulence model was adopted to simulate the solid-liquid two-phase turbulent flow. The effects of impeller speed, power consumption, impeller type, aperture size/ratio, solid particle diameter and liquid viscosity on the solid particle suspension quality were investigated. Results showed that the solid particle suspension quality was improved with an increment in the impeller speed. Punched circle package impeller could reduce the just suspension speed and improve the level of homogeneity for solid-liquid mixing process on the basis of four pitched-blade impeller and circle package impeller. The optimum aperture ratio and aperture diameter were 11.8% and 8 mm, respectively, for solid particles suspension process in this work. Smaller particle diameter led to smaller settling velocity and higher solid particle suspension quality. More viscous liquid was easier for sustaining the solid particles in suspension state. Meanwhile, punched circle package impeller can reduce the power consumption compared with four pitched-blade impeller and circle package impeller at the same impeller speed, and enhance the solid integrated velocity, turbulent kinetic energy, and turbulent kinetic energy dissipation rate of solid-liquid mixing system at the same power consumption.

EXPERIMENTAL INVESTIGATION OF A CONCEPT WAVE ENERGY CONVERTER FOR HARNESSING LOW AMPLITUDE SEA WAVES

This paper presents the results from experimental validation of numerical simulation of a concept wave energy converter for low amplitude sea waves. The device was conceived to contain a wave amplifying device (WAD) to magnify the wave height of incident waves while point absorber buoy(s) efficiently harness the wave energy for electricity production. The validation results show that the optimum aperture angle for the WAD is 45±2 degree, and wave height magnification of 170% is possible. The optimal buoy shape for the device was confirmed as concave wedge buoy. The combination of the two in a single device shall make economical the harnessing of low amplitude waves.