Location Of Aperture Research Articles

5G Radiation Source Location Based on Passive Virtual Aperture Technology by Single-Satellite

With the development of 5th-Generation Mobile Communication (5G) technology and the deployment of low-Earth orbit satellites, using satellites to locate 5G radiation sources is of great significance in commerce and the military as an important task of integrated sensing and communication. Recently, passive virtual aperture technology has been introduced into passive location to improve accuracy, but the existing method, using matched filters to search the Doppler information to realize the location, has the disadvantages of high complexity and poor range resolution. In this paper, an improved 5G radiation source location based on a virtual aperture is proposed, which uses the improved Golden Section search-fractional Fourier algorithm (GSS-FRFT) to improve the existing passive virtual aperture location methods. First, the received signals are coherently accumulated to convert the time gain into spatial gain, and the subcarrier phase information is extracted by Fast Fourier Transform based on the 5G signal characteristics to obtain the azimuth signal. Then, an improved high-order GSS-FRFT algorithm is proposed to analyze the Doppler information, and signal focusing and satellite ephemeris data are used to estimate the effective velocity and solve the radiation source location. The simulation results show that the proposed method can improve the location accuracy compared with other single-satellite location methods and has high resolution, high accuracy and low complexity compared with the existing passive virtual aperture location method.

Technical Note: Impact of Linear Array Transducer Doppler Aperture Location on Spectral Peak Velocity Measurements - A Phantom Study

ObjectiveUltrasound beams sometimes need to be steered from the edge of linear array transducers to reach the sample volume with a desired Doppler angle in vascular exams. This phantom study aims to evaluate the impact of apertures located at the array edge on peak velocity (PV) measurements. MethodsThree ultrasound scanner systems equipped with eight transducers from 3 major ultrasound vendors were tested using a flow phantom with a horizontal tube. Five spectral Doppler measurements with the aperture positioned at one edge of the array and 5 with the aperture at the center of the array were obtained using all available scanner-transducer combinations while maintaining all scan parameters and the sample volume in the same tube location. Differences in PVs between center and edge apertures were compared across 4 constant flow rates. ResultsThe averaged PVs for all phantom flow rates ranged from 24.4 cm/s to 138.2 cm/s from the array center. The averaged PVs from the center aperture were significantly greater than the corresponding measurements from the edge aperture for each flow rate (all p < 0.001). The relative PV differences ranged from 6.7% to 19.4% across all transducers and flow rates. ConclusionSignificantly lower PVs were consistently shown with the Doppler beam aperture at the array edge compared to center among all tested systems. This may be due to a narrower aperture width, shifted central axis, and less intrinsic spectral broadening error at the array edge. Controlling variations in Doppler aperture location is important in clinical applications which depend on consistent velocity measurements.

SLPA-Net: A Real-Time Recognition Network for Intelligent Stomata Localization and Phenotypic Analysis.

Plant stomatal phenotype traits play an important role in improving crop water use efficiency, stress resistance and yield. However, at present, the acquisition of phenotype traits mainly relies on manual measurement, which is time-consuming and laborious. In order to obtain high-throughput stomatal phenotype traits, we proposed a real-time recognition network SLPA-Net for stomata localization and phenotypic analysis. After locating and identifying stomatal density data, ellipse fitting is used to automatically obtain phenotype data such as apertures. Aiming at the problems of small stomata and high similarity to background, we introduced ECANet to improve the accuracy of stoma and aperture location. In order to effectively alleviate the unbalance problem in bounding box regression, we replaced the Loss function with a more effective Focal EIoU Loss. The experimental results show that SLPA-Net has excellent performance in the migration generalization and robustness of stomata and apertures detection and identification, as well as the correlation between stomata phenotype data obtained and artificial data.

ФОТОННА ІНТЕГРАЛЬНА СХЕМА ТА ЇЇ КАЛІБРУВАННЯ

The article proposes a new structure of a photonic integrated circuit for multiplying vector signals by a matrix. The architecture and principles of operation of modern photonic integrated circuits according to the given classification are briefly described. The proposed system consists of three layers, which includes a radiating, receiving and intermediate block with apertures. The connection of the photonic integrated circuit to the necessary electrical circuit for the investigation of the output signals of the photonic integrated circuit is described. With the help of the electrical circuit, we can monitor and control the input signals on each waveguide of the radiating unit, and track the change of the output signals that have passed through the system and fixed at the output of each waveguide. In the course of the study, we develop graphs of the levels of input and output signals of the system. With the help of which we represent the system errors and the change of signals, which makes it possible to calibrate the system. Calibration of the photonic integrated circuit is carried out by calibrating all electrical elements of the radiation and the receiving unit. In the emitting unit, it is necessary to select the same LEDs according to their characteristics, and with the help of variable resistors, which are connected to each pair of LEDs, calibrate the LED to the same brightness. We control the uniformity of brightness with the help of an IR camera. To calibrate the receiving unit, we fix the shadow noise and enter the reference coefficients for each receiver. After all the units were configured, the system was tested. A block with a specific aperture location was created, and the output signal was removed. Based on the results of the study, we proved that the system calibration is correct and that the system is operational.

Time-Domain Analysis of the Impact of Advanced Building Construction Materials on the Propagation of Lightning Electromagnetic Field and Its Mitigation Using Nanoforging

The comprehension of the propagation characteristics of lightning electromagnetic field (LEMF) is essential to inspect the impact of nearby lightning strike and its coupling effect on different systems and equipment. Undeniably, the presence of building structures alters LEMF reaching any point of installation of critical equipment. In this regard, this article attempts a complete time-domain analysis of the influence of building structures on LEMF propagation at near and far striking distance. The influence of aperture location on structures with respect to the direction of LEMF propagation is quantified first ever. The LEMF penetration capability of novel constructional materials, namely carbon nanotube (CNT)-forged concrete and glass fiber-reinforced gypsum, is compared to that of concrete, and surface charge estimation methodology is adopted for the first time to quantify the plausible LEMF shielding performance. It is observed that the presence of apertures influences the LEMF distribution, but their location has inconsequential effect. Among the materials, CNT-forged concrete offers nearly 2 dB of electric field attenuation and 10 dB in energy penetration due to LEMF, quantifying the field mitigation effect due to nanoforging. Experimental study confirms better shielding performance of nanocompounded concrete. For magnetic field, the presence of apertures and the type of construction material do not deliver a sizable effect.

Deep Learning-Based System for Preoperative Safety Management in Cataract Surgery

An artificial intelligence-based system was implemented for preoperative safety management in cataract surgery, including facial recognition, laterality (right and left eye) confirmation, and intraocular lens (IOL) parameter verification. A deep-learning model was constructed with a face identification development kit for facial recognition, the You Only Look Once Version 3 (YOLOv3) algorithm for laterality confirmation, and the Visual Geometry Group-16 (VGG-16) for IOL parameter verification. In 171 patients who were undergoing phacoemulsification and IOL implantation, a mobile device (iPad mini, Apple Inc.) camera was used to capture patients’ faces, location of surgical drape aperture, and IOL parameter descriptions on the packages, which were then checked with the information stored in the referral database. The authentication rates on the first attempt and after repeated attempts were 92.0% and 96.3% for facial recognition, 82.5% and 98.2% for laterality confirmation, and 67.4% and 88.9% for IOL parameter verification, respectively. After authentication, both the false rejection rate and the false acceptance rate were 0% for all three parameters. An artificial intelligence-based system for preoperative safety management was implemented in real cataract surgery with a passable authentication rate and very high accuracy.

Arthroscopic-Assisted Toggle Rod Stabilization in Canine Coxofemoral Luxation: A Cadaveric Study.

The aim of this study was to describe an arthroscopic-assisted technique for coxofemoral toggle rod placement, and to report on the feasibility, drill tunnel trajectory and accuracy of tunnel aperture location using this method. Cadaveric pilot study. Eight coxofemoral joints. Craniodorsal coxofemoral joint luxations were artificially created. A simulated open hip reduction and stabilization with a toggle rod were performed through a limited arthrotomy under arthroscopic guidance. Computed tomography scans were performed to evaluate drill hole trajectory across the femoral neck, and joints were disarticulated and photographed. Digital imaging software was used to determine the percent overlap of the drill hole apertures relative to the origin and insertion of the round ligament on the acetabulum and fovea. The exit point of the tunnel was entirely within the fovea capitis in five of eight femurs, three of eight femoral drill apertures were only partially within the target area. Of the eight acetabular bone tunnels examined, all were centred occupying the acetabular fossa. Coxofemoral toggle rod placement can be performed under arthroscopic guidance through a limited arthrotomy. Comparable femoral tunnel accuracy with the standard open technique should be achieved with the current method prior to its clinical use.

Comparing the Use of Flexible and Rigid Reaming Systems Through an Anteromedial Portal for Femoral Tunnel Creation During Anterior Cruciate Ligament Reconstruction: A Systematic Review.

Background:Recent studies have suggested that femoral tunnel drilling during anterior cruciate ligament (ACL) reconstruction (ACLR) with the use of a flexible reaming system through a standard anteromedial portal (AM-FR) may result in a different tunnel geometry compared with a rigid reamer through an accessory anteromedial portal with hyperflexion (AM-RR).Purpose:To summarize radiologic, anatomic, and clinical outcomes from available studies that directly compared the use of AM-FR versus AM-RR for independent femoral tunnel creation during ACLR.Study Design:Systematic review; Level of evidence, 4.Methods:A literature search was performed using the MEDLINE (PubMed) and Web of Science databases to identify all studies that directly compared radiologic, anatomic, and clinical outcomes between the use of AM-FR and AM-RR. The literature search, data recording, and methodological quality assessment was performed by 2 independent reviewers. The outcomes analyzed included resultant ACL graft positioning and graft bending angle; femoral tunnel positioning, aperture morphology, length, and widening; posterior wall breakage; and distance from various posterolateral knee structures.Results:A total of 13 studies met the eligibility criteria for inclusion. There was no difference in femoral tunnel aperture location between techniques. There were conflicting findings among studies regarding which technique resulted in a more acute graft bending angle. One study reported greater femoral tunnel widening upon follow-up with the use of AM-FR. AM-FR produced longer and more anteverted femoral tunnels than did AM-RR. The difference in tunnel length was significant and more prominent in lesser degrees of knee flexion. With AM-FR, femoral tunnels were farther from the lateral collateral ligament and peroneal nerve, and 1 of 5 studies had fewer reports of posterior wall breakage. There has been no literature comparing the clinical or functional outcomes of these techniques.Conclusion:Although no clinical studies exist comparing AM-FR and AM-RR for femoral tunnel creation during ACLR, both systems allow for reproducible positioning of an anatomic femoral tunnel aperture. The use of AM-FR results in longer and more anteverted femoral tunnels than using AM-RR, with exit points on the lateral femur that are different but safe. Surgeons should be aware of the technical differences with each method; however, further study is needed to identify any clinically important difference that results.

Numerical study of effects of device design on drug delivery efficiency for an active dry powder inhaler

Active dry powder inhalers (DPIs) actuated by low air volume provide distinct advantages for delivering aerosols to patients with poor respiratory capacity. This work aims to investigate the effects of piercing aperture location and inlet flow rate on device-emptying, and to identify the mechanism of particle deposition in a realistic mouth-throat (MT) region. Computational fluid dynamics (CFD) is employed to predict dispersion parameters that measure turbulence intensity, and mono-sized particles are tracked by the discrete phase model (DPM). Results show that the piercing aperture location and the inlet flow rate both have significant impacts on device emptying. Strong correlations have been established between the emitted dose and flow field parameters. The pattern and distribution of the deposited particles in the realistic MT region are highly sensitive to particle size, flow rate and reservoir length. This work provides profound insights into the performance of the active DPIs and an additional perspective on device design.

Principles of the exposure natural lighting modeling of premises

It’s well known that a criterion of estimating the varying natural lighting is exposure equal to the product of light intensity by its duration. Here we have made studies into the exposure in the room depending on the orientation of a light aperture and its location in space. The exposure has been considered by the example of three identical office rooms with the same light apertures oriented north, west and south and having three positions – vertical, inclined and horizontal. To calculate the annual exposure we made use of the well-known software package VELUX Daylight Visualizer 2. For convenience of analyzing the exposure there was introduced the concept of the natural exposure coefficient (NEC) which is a ratio between the exposure in the room and a simultaneous value of the outer exposure. Our studies have shown that exposure is an effective criterion to assess the indoor natural lighting in time. The existing system of estimating energy consumption in lighting buildings with the help of a simultaneous lighting is rough and does not take into account such factors as orientation of light apertures by the sides of the horizon and their location in space. The use of exposure let us improve the method of calculating energy consumption in lighting premises taking into account the light aperture location in space and their as orientation by the sides of the horizon. The numerical experiment performed has given a predicted result, namely, the most power-consuming room is the north-oriented one with the vertical light aperture and the least power-consuming room is the one with the horizontal light aperture. The room with the inclined light aperture has average energy consumption.

Investigation of Parameters Affecting the Level of Perforated Conductive Enclosure Protection Against HEMP Radiation Using FDDM

One of the best methods to protect electronic circuits against high-altitude electromagnetic pulse (HEMP) is using a metallic shield enclosure, which usually has apertures and slots for venting and passing power and data cables. In this article, we investigate the effect of the rise time of HEMP-like pulses on time-domain shielding effectiveness (TD-SE). The rise time of the electromagnetic pulse is one of the essential characteristics that depend on the mechanism of pulse production in pulse generators. Since the dimensions and location of aperture, the wall thickness of enclosure, and the enclosure dimension are important factors in coupling the electromagnetic pulse with circuits inside the enclosure shield, the effect of these factors on TD-SE will be checked. Finite difference delay modeling (FDDM) is used as a new method in the computation of transient field in perforated metallic enclosure and SE. Results of FDDM is verified by comparing with finite integration technique (FIT) method results (CST-Microwave Studio).

The distance between the tibial tunnel aperture and meniscal root attachment is correlated with meniscal healing status following transtibial pullout repair for medial meniscus posterior root tear

BackgroundTo investigate the relationship between tibial tunnel aperture location and postoperative meniscal healing. MethodsWe enrolled 25 patients (20 women and five men, mean age: 62.5 years) who underwent transtibial pullout repair for medial meniscus (MM) posterior root repair. The expected MM posterior root attachment center (AC) and tibial tunnel center (TC) were identified using three-dimensional computed tomography, and the minimum AC–TC distance was calculated. The meniscal healing status following transtibial pullout repair was assessed by second-look arthroscopy (mean postoperative period: 15 months) using a previously reported scoring system (meniscal healing score; range: 0–10). The association between AC–TC distance and meniscal healing score was investigated using univariate linear regression models. The optimal AC–TC distance cut-off for improved MM healing score (≥7) was determined using receiver operating characteristic analysis. ResultsThe AC–TC distance and meniscal healing score were significantly associated (y = −0.42x + 9.48, R2 = 0.342; P = 0.002), with the optimum AC–TC distance being 5.8 mm. This cut-off had a sensitivity of 100% and specificity of 53%. ConclusionsThis study demonstrates that AC–TC distance is significantly correlated with postoperative meniscal healing. Anatomical repair within 5.8 mm of the AC may result in improved meniscal healing.

Radiologic analysis of the location, shape and size of the external aperture of the carotid canal in children

This retrospective computed tomography (CT) study was aimed to assess the growth dynamic of the external aperture of the carotid canal (EACC) in children aged between 1 and 20years. Two hundred patients (sex 100 females/100 males, average age 10.50 ± 5.77years) with good head CT image quality were included in this study. CT images of the patients were used to obtain data related to the location, shape and dimension of EACC. EACC shapes were identified as oval shaped, round shaped, and tear-drop shaped in 58.3% (233 sides), 24% (96 sides) and 17.8% (71 sides), respectively. EACC length, disEACC-MSP (distance between EACC and midsagittal plane), and EACC width did not change from the prepubescence period; while, the disEACC-SC (distance between EACC and supramastoid crest) seemed to reach adult size in the postpubescence period. Linear functions for EACC length and width were calculated as: y = 5.453 + 0.091 × years, and y = 5.398 + 0.059 × years, respectively. The regression equations of the measured parameters representing the growth dynamic of EACC in children can be helpful to estimate its size, location and angulation, which suggest that the dimension and distances to certain anatomical landmarks seemed to reach adult size in different developmental periods. In this context, the findings of this study may seem to emphasize the importance of preoperative radiological evaluation on skull base, related to EACC, for multidisciplinary surgeon teams during childhood surgeries in terms of patients' positioning, and the selection of appropriate surgical approach.

Coded Aperture Optimization in Spatial Spectral Compressive Spectral Imagers

The spatial spectral compressive spectral imager (SSCSI) is a recently proposed optical architecture, where the spatial-spectral coding of a scene is jointly realized by a binary ON-OFF mask and a dispersive element. The quality of the recovered hyperspectral scene in SSCSI depends on various parameters, such as the coded aperture location with respect to the sensor, the coded aperture and detector pitch sizes, and the diffraction introduced by the grating. Given these parameters, the sensing matrix of the imager is largely dependent on the coded aperture structure and characteristics. As such, its optimization is critical to maximizing the quality of the recovered scene. In this article, an algorithm that optimizes the coded aperture patterns for SSCSI is derived. The final structure of such patterns turns out to be directly linked to the coded aperture position measured from the sensor. It is also shown that the optimal coded apertures in SSCSI adhere to green-blue noise spectral characteristics, where the degree of green spectral components depends on the location of the coded aperture with respect to the sensor. Simulations under different conditions are presented to demonstrate the underlying concepts.

Excitation of Guided Waves on a Lossless Dielectric Slab by an E-Polarized Complex Source Point Beam

A lossless slab excited by an E-polarized two-dimensional (2-D) complex source point (CSP) beam is studied analytically. Such a source, unlike a Gaussian beam, satisfies exactly the Helmholtz equation and radiation condition, without paraxial approximation or formulation incompleteness. The guided-waves fields as well as the scattered fields in the regions above and below the slab are determined; in turn, the corresponding powers are directly calculated. Numerical results on the variations of these quantities with respect to the slab electrical thickness, the beam angle of incidence, the source aperture size and location are presented. Substantial power transfer from the finite directive source into each of the slab’s guided waves is recorded especially in the case of near-grazing beam illumination. Such a finding may inspire further theoretical and experimental efforts towards numerous research directions like non-invasive sensing, wireless optical tagging and energy teleportation.

Analysis of Impact of Conic Aperture in Differentially Pumped Chamber

The paper focuses on the simulation of medium dynamics in the environmental scanning electron microscope. In particular, the paper examines the conical aperture location effect in the differentially pumped chamber and the width of the pumping channel in this chamber. The solution is based on the Taylor-Maccoll theory about the impact of the shock wave and was obtained by the use of continuum and finite volume methods in the ANSYS Fluent system.

Comparison of Graft Length Changes During Knee Motion Among 5 Different Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction Approaches: A Biomechanical Study.

Background:In several anatomic single-bundle anterior cruciate ligament (ACL) reconstruction (ASB-ACLR) procedures, the femoral and tibial tunnel apertures are created at different locations within the native ACL attachment area.Hypothesis:Graft length changes during knee motion will be different among ASB-ACLR procedures with different femoral and tibial tunnel aperture locations.Study Design:Controlled laboratory study.Methods:A total of 12 cadaveric knees were used in this study. In each knee, 4 and 3 thin tunnels were created within the ACL attachment area on the femur and the tibia, respectively. Using 1 of 5 different combinations of femoral and tibial tunnel aperture location, 5 ASB-ACLRs were performed on each knee. In each reconstruction approach, a strong thread was used in place of the tendon graft, and the tibial graft end was tethered to a custom-made isometric positioner at 0° of knee flexion, with an approximately 12-N load applied to the thread. Then, each specimen underwent 5 cycles of knee flexion-extension motion in a range between 0° and 120°, and graft length changes were determined for each SB-ACLR approach.Results:The length changes of the graft were significantly different among the 5 ASB-ACLRs. The maximum length change values of the 3 grafts that were implanted between the femoral and tibial centers of the posterolateral bundle attachments or implanted into the femoral tunnel created at the center of the fanlike extension fiber attachment were significantly greater than those of the graft implanted between the centers of the anteromedial bundle attachments (P < .0001) and of the graft implanted between the centers of the whole ACL attachments (P < .0001).Conclusion:The length changes of the graft during knee motion were significantly different among the 5 ASB-ACLR approaches, even though all of the tunnel apertures were created within the femoral and tibial attachments of the native ACL.Clinical Relevance:The grafts in the first 3 graft locations may be so relaxed during knee flexion that they cannot resist anterior drawer loads exerted on the tibia.

Gamma-ray modulation properties of tungsten coded apertures for a novel mixed-field imaging system

An investigation into the gamma-ray modulation properties of a tungsten coded aperture, whose design is based on the mathematical principles of Modified Uniformly Redundant Arrays (MURA), has been performed. Due to the small size of the individual cells, the aperture was built using additive manufacturing methods. The gamma-ray field was produced by a 137Cs radioactive isotope at Lancaster University, U.K. An organic plastic scintillator sample, which is capable of pulse shape discrimination, has been used to detect the gamma-ray field modulated by a tungsten aperture. Prior to the investigation of the aperture modulation properties, energy calibration of the scintillator was performed. Its pulse shape discrimination capabilities were verified using a 252Cf fission source. In this study, each of 169 coded aperture cells was investigated by collimating the modulated gamma-ray field of 137Cs through a 25.4 mm thick lead supporting plate. The supporting plate has one opening in the centre, of the same dimensions as the single aperture cell, i.e. 2.5 mm × 2.5 mm. The number of pulses detected for every aperture location were recorded in an array. The array was subsequently used to create a two-dimensional image of the source, which was encoded through the coded aperture pattern. Finally, the image was decoded using deconvolution techniques to reveal the actual source location. The new results obtained in this study indicate that sufficient gamma-ray modulation properties of the aperture can be determined, despite the relatively small footprint and thickness of the coded aperture.

Low-cost Gaussian beam profiling with circular irises and apertures.

The fundamental Gaussian TEM00 mode is the most common mode of propagation within various optical devices, modules, and systems. Beam profilers are widely used in accurately ascertaining the cross-sectional irradiance profile of a TEM00 mode for free-space optical communication systems as well as tracking beam evolution when propagating within optical submodules. We demonstrate beam profiling methods that use low-cost, off-the-shelf, widely available circular apertures such as circular irises and spatial filters. In order to demonstrate beam profiling with any circular aperture, we first derive exact analytical expressions for power transmittance of the TEM00 mode through a decentered circular aperture and then use this mathematical derivation to estimate the irradiance profile of a Gaussian beam by 1)fixing the location of a circular aperture and changing its radius, and 2)scanning the entire area of the beam profile by translating a circular aperture of a fixed radius across the region of interest. This method is fast and easily reproducible and simply puts to use circular irises/circular spatial filters, which are commonly available in most optical laboratories. Consequently, the proposed method provides cheap and convenient means to estimate the profile of a Gaussian beam with simple optical components. Our experimental results demonstrate a performance that is comparable to a standard knife-edge-based estimate of beam profile. Moreover, a strong agreement with presented theory validates the analytical expressions derived in this paper.

Steeper posterior tibial slope correlates with greater tibial tunnel widening after anterior cruciate ligament reconstruction.

To investigate the correlation between posterior tibial slope (PTS) and tibial tunnel widening after anterior cruciate ligament reconstruction (ACL-R). Twenty-five patients underwent anatomic single-bundle ACL-R using quadriceps tendon autograft. Six months after surgery, each patient underwent high-resolution computed tomography (CT). Tibial tunnel aperture location was evaluated using a grid method. Medial and lateral PTS (°) was measured based on a previously described method. To evaluate tibial tunnel widening, cross-sectional area (CSA) of the tibial tunnel beneath the aperture was measured using CT axial slice. Nominal elliptical area was calculated using the diameter of a dilator during the surgery and the angle between the axial slice and the tunnel axis. Percentage of tunnel widening (%) was determined by dividing the CSA by the nominal area. Pearson correlation coefficient was used to explore the association between medial/lateral PTS and tibial tunnel widening (P < 0.05). Location of tibial tunnel aperture was 29.8 ± 6.3% in anterior-posterior direction, and 45.7 ± 2.1% in medial-lateral direction. Medial and lateral PTS were 3.7° ± 2.5° and 4.9° ± 2.4° respectively. Tibial tunnel widening was 97.2 ± 20.3%. Tibial tunnel widening was correlated with medial PTS (r = 0.558, P = 0.004) and lateral PTS (r = 0.431, P = 0.031). Steeper medial and lateral PTS correlated with greater tibial tunnel widening. The clinical relevance is that surgeons should be aware that PTS may affect tibial tunnel widening after ACL-R. Thus, subjects with steeper PTS may need to be more carefully followed to see if there is greater tibial tunnel widening, which might be important especially in revision ACL-R. III.