Aperture Pattern Research Articles

The roughness of fracture surfaces and its scale dependence – a methodological study based on natural fractures in sandstones from Southern Germany

The study of groundwater flow in fractured aquifers is an important part of hydrogeology. Main parameters that influence the flow rate and velocity in fractures are their number and connectivity but especially their opening width (aperture). The roughness of fractures also has an important influence, as it locally modifies both aperture and flow patterns. However, it is seldom measured, not fully understood and, therefore, often not included into calculations. The present study focuses on methodological aspects and investigates the roughness and composition of weathered fracture surfaces from Triassic Bunter Sandstone samples from Southern Germany. Such weathered surfaces have received little attention so far. For the first time, different mechanical and optical methods were used and compared. Results show a clear scale dependency, indicating a fractal, self-affine nature, despite several different methods being used. This confirms that all methods provide useful data. .

Noninvasive holographic imaging through dynamically scattering media.

We present a noninvasive method for quantitative phase imaging through dynamically scattering media. A complex amplitude object, illuminated with coherent light, is captured through a dynamically scattering medium and a variable coded aperture, without the need for interferometric measurements or imaging optics. The complex amplitude of the object is computationally retrieved from intensity images that use multiple coded aperture patterns, employing a stochastic gradient descent algorithm. We demonstrate the proposed method both numerically and experimentally.

Imaging performance of wide-field X-ray Transient Localization Experiment onboard microsatellite KOYOH

We designed a flight model of the wide field X-ray imager on board the microsatKOYOH, referred to as T-LEX, and investigated its imaging performancethrough laboratory beam tests. T-LEX employs the coded mask method, whereinthe aperture pattern of the mask was selected and fabricated from 50,000 patternsusing a Monte Carlo approach. Utilizing the obtained mask along with a siliconstrip detector, we examined the angular response by varying the incidentangle with a stage during X-ray irradiation. The resulting angular responseexhibited deviations from the design values, yet it confirmed that the targetedposition accuracy of 15 arcminutes is maintained across a range from -20deg to+20deg with the best fit calibrated model.

Impact of stress-driven crack growth on the emergence of anomalous transport in critically connected natural fracture networks

We study the role of in-situ stresses in fluid flow and mass transport through a two-dimensional fractured rock. The fracture network is based on a real outcrop with a connectivity state around the percolation threshold. We simulate stress-dependent fracture propagation and deformation using a geomechanics model based on the hybrid finite-discrete element method. The hydrodynamic transport through the deformed rock mass is then modeled based on particle tracking simulations. By exploring various scenarios of different stress ratios and orientations, we systematically analyzed how the superimposed multiple geomechanical processes (i.e., compression-induced closure, shear-induced dilation, and stress-induced propagation) control the aperture patterns, flow fields, and transport behaviors of the fracture network. Our results show that an increased stress ratio tends to promote fracture shear dilation and thus enhance flow channelization, resulting in an anomalously early arrival of solute transport. Furthermore, the increased differential stress attempts to drive the growth of wing cracks that bridge pre-existing fractures and form new flow pathways. We observe a qualitative transformation of the flow structure from a disconnected to a connected regime accompanied by a significant alteration of its overall transport properties. This phenomenon is attributed to the superimposed effect of stress-driven crack propagation and shear-induced fracture dilation. By quantitative parameter analyses of global flow and transport properties, we further found that the breakthrough time median of particles is well correlated with the equivalent permeability of the fractured rock when the effect of new cracks is removed. However, this correlation is greatly reduced when fracture propagation is considered; instead, the breakthrough time shows a good correlation with mean tortuosity. Our findings have important implications for the strategy design of geothermal production and waste disposal in critically connected fractured geological media under various stress conditions.

Numerical Investigation of Diffraction Patterns of Small Size Apertures Using Light Sources From Xuv to The Visible Region: Simulation for The Small Size Structures

In the present work, a computer simulation program generates Fresnel diffraction patterns from small-size apertures using illumination wavelengths from extreme ultraviolet (XUV) to the visible region suggesting that it can be used to model a wide range of experimental setups. By being able to simulate diffraction patterns for such a broad range of wavelengths, the program can be used to investigate the effects of varying wavelengths and aperture size on the resulting pattern. By using a computer simulation program that can generate Fresnel diffraction patterns across a wide range of wavelengths, one can explore how different wavelengths of light interact with various aperture sizes. This allows one to investigate the effects of changing these parameters on the resulting diffraction pattern. The computer simulation program generating Fresnel diffraction patterns from square apertures by using the illumination wavelength sources from XUV to the visible region has been studied. Changing the aperture-screen distance, the illumination wavelength, and the aperture size provides a clear transition of diffraction patterns from the Fresnel to the Fraunhofer region. The diffraction patterns obtained by the Fresnel integral method have been compared with that simulated by the Fraunhofer calculation. There is a good agreement between the results. The structural similarity index (SSI) exhibits that comparing the diffraction images produced with both approaches agree.

Optimal Amplitude–Density Synthesis of Linear Aperiodic Arrays

New deterministic procedures for the design of linear aperiodic arrays are described which permit exploiting, in a combined way, both the positions and the excitation amplitudes of the array elements obtaining a pattern which optimally fits, in terms of a weighted L2 norm, the pattern of a reference linear continuous aperture. A first numerical procedure is based on alternating optimization of positions and amplitudes by means of closed-form convex projectors. Sufficient conditions for the solution to be optimal are established. A second numerical procedure is based on a domino-like sequential determination of the unknowns which can be iterated to convergence. Additionally, analytical asymptotic expressions for the optimal inter-element spacing and amplitude are derived by means of variational techniques. The optimal asymptotic inter-element spacing is demonstrated to be proportional to the reference tapering to the power (-2/3) while the optimal asymptotic array amplitude is proportional to the reference tapering to the power (1/3). For aperiodic arrays with equiamplitude excitation it is proved that the optimal inter-element spacing is proportional to the reference tapering to the power (-1). Based on these asymptotic dependencies, closed-form analytical solutions are obtained for amplitudes and positions of the elements. Several numerical results confirm the effectiveness and accuracy of the new procedures.

Evaluation of Open-Graded Aggregates Stabilized with a Multi-Axial Geogrid Using a Large-Scale Triaxial Test Set-Up

Geogrids are commonly used in paved and unpaved roadways to stabilize base and subbase layers by laterally restraining movements of unbound aggregates under applied wheel loading, often referred to as interlocking. The geogrid-aggregate interlock is a function of the match between the geogrid aperture size and geometry and the grain size and shape characteristics of the stabilized aggregates. Open-graded coarse aggregates (OGA) are commonly used as an alternative to dense-graded materials in permeable base/subbase applications as well as in railway ballast to facilitate drainage. This paper describes an experimental study recently conducted to investigate the repeated load-deformation behavior of a geogrid-stabilized OGA material in large-scale triaxial testing. Two multi-axial geogrids with the same aperture patterns but different aperture sizes were tested. The aperture patterns include different sizes of hexagonal, trapezoidal, and triangular openings. The multi-axial geogrid with the larger apertures better matched the OGA material properties to provide a reduction in permanent deformation in the test specimen. The improved interlocking and the related local stiffness enhancement were successfully quantified using embedded shear wave transducers termed bender elements. To stabilize aggregates with relatively uniform grain sizes, for example, AASHTO No. 57 stone studied here and railroad ballast, the ratio between the aperture size and a representative particle size (i.e., D90) served as a good indicator of the effectiveness of the geogrid. The findings of this experimental study therefore provided valuable information on the governing properties and mechanisms that play a role in geogrid-aggregate interaction with multi-axial geogrids.

Contrast-Enhanced Ultrasound with Optimized Aperture Patterns and Bubble Segmentation Based on Echo Phase.

Amplitude modulation (AM) suppresses tissue signals and detects microbubble signals in contrast-enhanced ultrasound (CEUS) and is often implemented with checkerboard apertures. However, possible crosstalk between transmitting and non-transmitting array elements may compromise tissue suppression in AM. Using AM aperture patterns other than the conventional checkerboard approach (one on, one off) may reduce the degree of crosstalk and increase the contrast-to-tissue-ratio (CTR) compared with conventional AM. Furthermore, previous studies have reported that the phase difference between the echoes in AM pulsing sequences may be used to segment tissue and microbubbles and improve tissue signal suppression and the CTR of CEUS images. However, the CTR of the image produced by alternative AM aperture patterns and the effect of segmentation approach on these alternative apertures have not been investigated. We evaluated a number of AM aperture patterns to find an optimal AM aperture pattern that provides the highest CTR. We found that the aperture that uses alternating groups of two elements, AM2, had the highest CTR for the probe evaluated. In addition, a segmentation technique based on echo phase differences (between the full and half-pulses, ΔΦAM, between the complementary half-pulses, ΔΦhalf, and the maximum of the two ΔΦmax) was also considered in the AM aperture optimization process. The segmentation approach increases the CTR by about 25 dB for all apertures. Finally, AM2 segmented with ΔΦmax had a 7-dB higher CTR in a flow phantom and a 6-dB higher contrast in a perfused pig liver than conventional AM segmented with ΔΦAM, and it is the optimal transmit aperture design.

POLLEN MORPHOLOGY OF SOME PLANTS FROM THE GYZMEIDAN MUD VOLCANO (REPUBLIC OF AZERBAIJAN)

The aim of this study was to assess the influence of unfavorable conditions of the mud volcano on the morphological features of pollen. Using light, scanning and transmission electron microscopes, the morphology of pollen of 20 species from 14 families of dicotyledonous plants growing on the Gyzmeidan mud volcano (Shamakhi) in the Republic of Azerbaijan has been studied. According to the aperture patterns of the pollen grains in the studied species, there are 5 pollen types: 3-colpate (Brassicaceae, Convolvulaceae, Fabaceae (Hedysarum sericeum), Lamiaceae, Linaceae), 3-colporate (Asteraceae, Cistaceae, Clusiaceae, Euphorbiaceae, Fabaceae, Rosaceae), stepanocolporate (Polygalaceae), heteroaperturate (Boraginaceae), pantoporate (Ranunculaceae).No significant deviations of the main morphological features of pollen (shape, outline, size of pollen grains, type and number of apertures, exine sculpture, thickness and ultrastructure of the sporoderm) were found. Most of the studied species have a low percentage of deformed, underdeveloped, morphologically sterile, and atypical pollen grains. The number of deformed pollen grains differs between taxa. It can vary from single grains (most of the studied samples) to 56% in Potentilla pedata. However, its plants from the mud volcano produce less deformed pollen than the control ones (88%). This is most likely a feature of the taxon, rather than the influence of growing conditions.

Time-Division Multiplexing Light Field Display with Learned Coded Aperture.

Conventional stereoscopic displays suffer from vergence-accommodation conflict and cause visual fatigue. Integral-imaging-based displays resolve the problem by directly projecting the sub-aperture views of a light field into the eyes using a microlens array or a similar structure. However, such displays have an inherent trade-off between angular and spatial resolutions. In this paper, we propose a novel coded time-division multiplexing technique that projects encoded sub-aperture views to the eyes of a viewer with correct cues for vergence-accommodation reflex. Given sparse light field sub-aperture views, our pipeline can provide a perception of high-resolution refocused images with minimal aliasing by jointly optimizing the sub-aperture views for display and the coded aperture pattern. This is achieved via deep learning in an end-to-end fashion by simulating light transport and image formation with Fourier optics. To our knowledge, this work is among the first that optimize the light field display pipeline with deep learning. We verify our idea with objective image quality metrics (PSNR, SSIM, and LPIPS) and perform an extensive study on various customizable design variables in our display pipeline. Experimental results show that light fields displayed using the proposed technique indeed have higher quality than that of baseline display designs.

A Dual-Modality Volumetric Gamma-Ray Imager for Near-Field Applications

There is an ever-growing need for instrumentation that provides both high-resolution and sensitive volumetric gamma-ray imaging capabilities across a wide range of photon energies in the near field. Such a technology is particularly critical to the fields of emergency response and contamination remediation, nuclear security and safeguards, and nuclear medicine. We aim to meet this technological demand by proposing a proof-of-principle prototype that has both volumetric coded aperture and Compton imaging capabilities in the near field. This article provides a detailed discussion of the coded aperture design and pattern optimization. We also evaluate the performances of the coded aperture and Compton imagers in terms of spatial resolution and sensitivity. The system exhibits a lateral resolution in full-width at half-maximum (FWHM) as good as 4.5 mm in the coded aperture mode and 2.1 mm in the Compton mode. Furthermore, the coded aperture and Compton modalities provide sensitivities on the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-1}$ </tex-math></inline-formula> for energies below a few hundred keV and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$ </tex-math></inline-formula> for energies above a few hundred keV, respectively. We further demonstrate the imaging capabilities of the system by presenting 3-D reconstructions of near-field sources of various shapes and energies. To our knowledge, these results are the first demonstration of both volumetric coded aperture and Compton imaging in the near field via a single detection system.

Quality assurance of scanned proton beams at different gantry angles using an ionization chamber array in a rotational phantom

PurposeTo implement a single set-up monthly QA procedure for 9 different beam parameters at different gantry angles and evaluate its clinical implementation over a 12 month period. MethodsWe developed a QA procedure using an array detector (PTW Octavius 1500XDR) embedded in a rotational unit (PTW Octavius 4D) at our proton facility. With a single set-up we can monitor field central axis position, field symmetry, field size, flatness, penumbrae, output, spot size, spot position and range at different gantry angles (AAPM TG 224). The set-up is irradiated with homogenous 2D fields with dynamic aperture and spot patterns at five gantry angles. A modular top is used to check the range consistency. Absolute γ analysis were performed to compare measured dose distributions to calculated dose. All other parameters are directly extracted from the measurements. Additionally, the sensitivity of the set-up to small changes in beam parameters were compared to the Lynx detector (IBA). ResultsOver a 12 month period, output, symmetry, and flatness were within ± 2 %; FWHM, spot positions, penumbra widths, and central axis fields were within ± 1 mm. Range differences were all within 1/2 of the energy spacing (±0.6 MeV) relative to baseline. Most (2 %, 2 mm) γ-analysis showed agreement scores higher than 90 %. The sensitivity is comparable to the Lynx detector and measurement time is reduced by 40 %. ConclusionThe time-efficient monthly QA procedure that we developed can accurately be used to measure a large range of beam parameters at different gantry angles, within the TG 224 AAPM recommendations.

Pollen Diversity of Sri Ram Narayan Khedia Government Degree College Banswada, Kamareddy District, Telangana State, India

The present paper study on the study of pollen diversity of 31 plants from various gardens of Sri Ram Narayana Khedia Government Degree College Banswada, Kamareddy district, Telangana state, India. These plants some are medicinal, ornamental and tree members. The pollens of these plants have diversity of morphological characters viz., symmetry, shape, polarity, aperture patterns and sculpture. In the present study, a total of 31 plant species belongs to 19 families. The plants with Spheroidal shape pollen Catharanthus roseus, Lantana camara, Bougainvillea spectabilis, Tridax procumbens, Pseuderanthamum, Ixora coccinea, Jasminum sambac, Hibiscus rosa-sinensis, Pulmeria alba, Euphorbia heterophylla, Cynodon dactylon, Ghompherna celosioides, Hibiscus syriacus, Tecomaria capensis, Turnera ulmifolia, Punica grantum , Cleome gynandra, Oxalis dilenii, Nerium oleander, Ghompherna globosa, Datura stramonium, Jatropa integrerrima, Cyanthillium cinereum, Delonix regia, Tecoma stans . The plants with Symmetrical pollen is Parthenium hysterophorus. The plant with Irregular pollen shape is Callaindra. The plants with Cylindric pollen shape Bauhinia racemosa, Crossandra infundibuliformis. The plant with Boat shaped pollen is Hymencallis littoralis, are repotted. This plant species diversity record which is helps to the identification of Indian pollen flora.

Theoretical simulation on Fraunhofer diffraction of arbitrarily shaped aperture

The diffraction refers to the phenomenon that when light encounters an obstacle during propagation, it will deviate from the original propagation path and propagate behind the obstacle. In the study of diffraction and the relevant, we often encounter the questions about the prediction or estimation on the diffraction patterns of apertures with various shapes. Yet the specially designed optical experiment is very time consuming and laborious for this simple purpose. In this paper, the laser far-field diffraction is studied based on Kirchhoff diffraction theory. The intensity distribution is described by using a two-dimensional matrix and then the mathematical representations of the diffraction pattern of arbitrary aperture are provided. Visualization of calculated data is achieved by computer programming, and high-precision diffraction patterns are obtained. The above theoretical analysis method presented in this paper has higher universality. When the calculation infinitesimals are small enough and the computer graphics display function is sufficient, the diffraction pattern with high resolution can be obtained efficiently compared with the experiment.

DEAP1 encodes a fasciclin-like arabinogalactan protein required for male fertility in rice.

Arabinogalactan proteins (AGPs) are widely distributed in plant cells. Fasciclin-like AGPs (FLAs) belong to a subclass of AGPs that play important roles in plant growth and development. However, little is known about the biological functions of rice FLA. Herein, we report the identification of a male-sterile mutant of DEFECTIVE EXINE AND APERTURE PATTERNING1 (DEAP1) in rice. The deap1 mutant anthers produced aberrant pollen grains with defective exine formation and a flattened aperture annulus and exhibited slightly delayed tapetum degradation. DEAP1 encodes a plasma membrane-associated member of group III plant FLAs and is specifically and temporally expressed in reproductive cells and the tapetum layer during male development. Gene expression studies revealed reduced transcript accumulation of genes related to exine formation, aperture patterning, and tapetum development in deap1 mutants. Moreover, DEAP1 may interact with two rice D6 PROTEIN KINASE-LIKE3s (OsD6PKL3s), homologs of a known Arabidopsis aperture protein, to affect rice pollen aperture development. Our findings suggested that DEAP1 is involved in male reproductive development and may affect exine formation and aperture patterning, thereby providing new insights into the molecular functions of plant FLAs in male fertility.

Rock Fracture Response Exposed to Hydraulic Fracturing: Insight into the Effect of Injection Rate on Aperture Pattern

Injection rate is critical to hydraulic fracturing operation, especially to the hydraulic fracture aperture, which affects the proppant and methane migration. In this study, hydraulic fracturing experiments were carried out on shale specimens to investigate the influence of injection rate on hydraulic fracture aperture. According to the experimental results, when the injection rate increases, the average aperture of hydraulic fracture shows a significant linear increase. For different injection rate, the average aperture of stimulated natural fracture is always slightly greater than that of newly opened fracture. Compared with a low injection rate, the fracture apertures induced by the largest injection rate are evenly distributed in more intervals and approximately conform to the normal distribution. The research results can provide a theoretical basis for enhancing the fracture conductivity of hydraulic fracturing in shale reservoirs.

Contiguous perfect coded aperture patterns with high throughput.

A method is described that mosaics linear uniformly redundant arrays and modified uniformly redundant arrays onto a square lattice to create coded aperture patterns of approximately 50% throughput that are contiguous, whereby every opaque element in the aperture is joined to at least one other opaque element. Parameters required to create these perfect high-throughput contiguous apertures for all coded aperture unit pattern orders of up to 300 elements are presented. The apertures presented increase significantly the number of known contiguous apertures in dimensions forbidden to the known patterns and that have the same imaging quality as uniformly redundant arrays and modified uniformly redundant arrays while having imaging quality superior to other known self-supporting apertures. The effect of supporting the weaker areas of these contiguous apertures is investigated. Contiguous apertures are of interest for coded aperture systems that require extra rigidity or use active collimation.

A Review of the Developmental Processes and Selective Pressures Shaping Aperture Pattern in Angiosperms.

Pollen grains of flowering plants display a fascinating diversity of forms. The observed diversity is determined by the developmental mechanisms involved in the establishment of pollen morphological features. Pollen grains are generally surrounded by an extremely resistant wall displaying apertures that play a key role in reproduction, being the places at which pollen tube growth is initiated. Aperture number, structure, and position (collectively termed ‘aperture pattern’) are determined during microsporogenesis, which is the earliest step of pollen ontogeny. Here, we review current knowledge about aperture pattern developmental mechanisms and adaptive significance with respect to plant reproduction and how advances in these fields shed light on our understanding of aperture pattern evolution in angiosperms.

A new subspecies of &lt;i&gt;Ruthenica filograna&lt;/i&gt;(Pulmonata: Clausiliidae) from Croatia

A new subspecies of land snails of the clausiliid genus Ruthenica has been found on the territory of Republic of Croatia. Illustrated description is presented. New subspecies differs from others in shell shape, semi-apostrophic aperture and sculpture pattern.

Golomb Patterns, Astrophysics, and Citizen Science Games

This paper presents an online citizen science game called &#x201C;Game and Repository for Aperture Solutions and Patterns (GRASP).&#x201D; 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&#x2019; inteferometry missions for small-aperture antenna array design.