Dual Aperture Research Articles

Multistage Depressed Collector With Novel Dual Aperture Electrodes for Space Traveling Wave Tubes

Multistage Depressed Collector With Novel Dual Aperture Electrodes for Space Traveling Wave Tubes

Increasing abdominal aortic aneurysm curvature visibility using 3D dual probe bistatic ultrasound imaging combined with probe translation

High frame rate ultrasound (US) imaging techniques in 3D are promising tools for capturing abdominal aortic aneurysms (AAAs) over time, however, with the limited number of channel-to-element connections current footprints are small, which limits the field of view. Moreover, the maximal steering angle of the ultrasound beams in transmit and the maximal receptance angle in receive are insufficient for capturing the curvy shape of the AAA. Therefore, an approach is needed towards large arrays. In this study, high frame rate bistatic 3D US data (17 Hz) were acquired with two synchronized matrix arrays positioned at different locations (multi-aperture imaging) using a translation stage to simulate what a larger array with limited channel-to-element connections can potentially achieve. Acquisitions were performed along an AAA shaped phantom with different probe tilting angles (0 up to ± 30°). The performance of different multi-aperture configurations was quantified using the generalized contrast-to-noise ratio of the wall and lumen (gCNR). Furthermore, a parametric model of the multi-aperture system was used to estimate in which AAA wall regions the contrast is expected to be high. This was evaluated for AAAs with increasing diameters and curvature. With an eight-aperture 0° probe angle configuration a 69 % increase in field of view was measured in the longitudinal direction compared to the field of view of a single aperture configuration. When increasing the number of apertures from two to eight, the gCNR improved for the upper wall and lower wall by 35 % and 13 % (monostatic) and by 36 % and 13 % (bistatic). Contrast improvements up to 22 % (upper wall) and 12 % (lower wall) are achieved with tilted probe configurations compared to non-tilted configurations. Moreover, with bistatic imaging with tilted probe configurations gCNR improvements up to 4 % (upper wall) and 7 % (lower wall) are achieved compared to monostatic imaging. Furthermore, imaging with a larger inter-probe distance improved the gCNR for a ± 15° probe angle configuration. The gCNR has an expected pattern over time, where the contrast is lower when there is more wall motion (systole) and higher when motion is reduced (diastole). Furthermore, a higher frame rate (45 Hz) yields a lower gCNR, because fewer compound angles are used. The results of the parametric model suggest that a flat array is suitable for imaging AAA shapes with limited curvature, but that it is not suitable for imaging larger AAA shapes with more curvature. According to the model, tilted multi-aperture configurations combined with bistatic imaging can achieve a larger region with high contrast compared to non-tilted configurations. The findings of the model are in agreement with experimental findings. To conclude, this study demonstrates the vast improvements in field of view and AAA wall visibility that a large, sparsely populated 3D array can potentially achieve when imaging AAAs compared to single or dual aperture imaging. In the future, larger arrays, less thermal noise, more steering, and more channel-to-element connections combined with carefully chosen orientations of (sub-) apertures will likely advance 3D imaging of AAAs.

Improved intraoperative identification of close margins in oral squamous cell carcinoma resections using a dual aperture fluorescence ratio approach: first in-human results.

Surgical excision is the main treatment for solid tumors in oral squamous cell carcinomas, where wide local excision (achieving a healthy tissue margin of around the excised tumor) is the goal as it results in reduced local recurrence rates and improved overall survival. No clinical methods are available to assess the complete surgical margin intraoperatively while the patient is still on the operating table; and while recent intraoperative back-bench fluorescence-guided surgery approaches have shown promise for detecting "positive" inadequate margins (), they have had limited success in the detection of "close" inadequate margins (1 to 5mm). Here, a dual aperture fluorescence ratio (dAFR) approach was evaluated as a means of improving detection of close margins. The approach was evaluated on surgical specimens from patients who were administered a tumor-specific fluorescent imaging agent (cetuximab-800CW) prior to surgery. The dAFR approach was compared directly against standard wide-field fluorescence imaging and pathology measurements of margin thickness in specimens from three patients and a total of 12 margin locations (1 positive, 5 close, and 6 clear margins). The area under the receiver operating characteristic curve, representing the ability to detect close compared to clear margins () was found to be 1.0 and 0.57 for dAFR and sAF, respectively. Improvements in dAFR were found to be statistically significant (). These results provide evidence that the dAFR approach potentially improves detection of close surgical margins.

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Correction to: Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Correction to: Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Design and implementation of an electromechanical gear system for optimization of automatic phase-shifting of a Dual Aperture Common-Path Interferometer

In this work, we report experimental results of a proposed gear system for optimization of phase shifts used for extraction of phase between a reference and a test object in a Double Aperture Common Path Interferometer. The electromechanical approach is designed to increase the precision and control of automated transverse translation of a diffraction grating to obtain equidistant displacements, typically carried out manually. Calculations and analytics for the design and operation of the mechanical gear system are presented. The experimental results demonstrate significant error minimizing for equally spaced phase shifts compared to a previously reported implementation of our research group. The proposed system represents a reliable and low-cost implementation to improve the obtaining of suitable interferogram captures for equally spaced phase-shifting interferometry techniques.

Low-Profile Dual-Polarized Double-Layer Microstrip Antenna for 5G and 5G Wi-Fi.

A dual-polarized double-layer microstrip antenna with a metasurface structure is proposed for 5G and 5G Wi-Fi. A total of 4 modified patches are used for the middle layer structure, and 24 square patches are used for the top layer structure. The double-layer design has achieved -10 dB bandwidths of 64.1% (3.13 GHz~6.08 GHz) and 61.1% (3.18 GHz~5.98 GHz). The dual aperture coupling method is adopted, and the measured port isolation is more than 31 dB. A low profile of 0.096λ0 is obtained (λ0 is the wavelength of 4.58 GHz in the air) for a compact design. Broadside radiation patterns have been realized, and the measured peak gains are 11.1 dBi and 11.3 dBi for two polarizations. The antenna structure and E-field distributions are discussed to clarify its working principle. This dual-polarized double-layer antenna can accommodate 5G and 5G Wi-Fi simultaneously, which can be a competitive candidate for 5G communication systems.

Modeling the Daily Variations of the Coronal X-ray Spectral Irradiance with Two Temperatures and Two Emission Measures

The Miniature X-ray Solar Spectrometer (MinXSS-1) CubeSat observed solar X-rays between 0.5 and 10 keV. A two-temperature, two-emission-measure model is fit to each daily averaged spectrum. These daily average temperatures and emission measures are plotted against the corresponding daily solar 10.7 cm radio flux (F10.7) value and a linear correlation is found between each that we call the Schwab Woods Mason (SWM) model. The linear trends show that one can estimate the solar spectrum between 0.5 and 10 keV based on the F10.7 measurement alone. The cooler temperature component of this model represents the quiescent Sun contribution to the spectra and is essentially independent of solar activity, meaning the daily average quiescent Sun is accurately described by a single temperature (1.70 MK) regardless of solar intensity and only the emission measure corresponding to this temperature needs to be adjusted for higher or lower solar intensity. The warmer temperature component is shown to represent active region contributions to the spectra and varies between 5 and 6 MK. The Geostationary Operational Environmental Satellite (GOES) XRS-B data between 1 and 8 Å is used to validate this model and it is found that the ratio between the SWM model irradiance and the GOES XRS-B irradiance is close to unity on average. MinXSS-1 spectra during quiescent solar conditions have very low counts beyond around 3 keV. The SWM model can generate MinXSS-1 or Dual Aperture X-ray Solar Spectrometer spectra at very high spectral resolution and with extended energy ranges to fill in gaps between measurements and extend predictions back to 1947.

Comparison of passive beamformers for isolating cavitation activity originating in the spinal canal

Focused ultrasound application to the spinal cord, through the intact spine, is confounded by the presence of substantial prefocal cavitation, in the posterior soft tissue and musculature. When constructing cavitation images to localize and control intracanal cavitation, the prefocal cavitation zones dwarf the signals from the canal, destructing the localization ability of the imaging inside the sensitive cord tissue—even when conventional phase and amplitude corrections are applied. In this study, multiple beamforming formulations are investigated to mitigate the influence of prefocal cavitation on transvertebral cavitation imaging, while preserving the localization ability in the canal. The performance of a standard delay-and-sum-integrate beamformer (DAS) is compared to delay-multiply-and-sum-integrate beamformer (DMAS), and the DMAS algorithm is tested with a paired multiplicative compounding method (pDMAS) that leverages the dual aperture approach required for transvertebral focused ultrasound sonications. The focal point spread function of the beamformers in passive cavitation images (tint = 7 μs) were 7.9 × 2.2 × 1.3 mm (DAS), 6.9 × 1.7 × 1.1 (DMAS), and 6.5 × 2.9 × 1.7 mm (pDMAS) at 800 kHz. These beamforming approaches are evaluated for localization ability and clinical feasibility through cavitation imaging of prefocal and focal sources with in silico models and ex vivo human vertebrae.

An aberration correction approach for single and dual aperture ultrasound imaging of the abdomen

Abdominal ultrasound image quality is hampered by phase aberration, that is mainly caused by the large speed-of-sound (SoS) differences between fat and muscle tissue in the abdominal wall. The mismatch between the assumed and actual SoS distribution introduces general blurring of the ultrasound images, and acoustic refraction can lead to geometric distortion of the imaged features. Large aperture imaging or dual-transducer imaging can improve abdominal imaging at deep locations by providing increased contrast and resolution. However, aberration effects for large aperture imaging can be even more severe, which limits its full potential. In this study, a model-based aberration correction method for arbitrary acquisition schemes is introduced for delay-and-sum (DAS) beamforming and its performance was analyzed for both single- and dual-transducer ultrasound imaging. The method employs aberration corrected wavefront arrival times, using manually assigned local SoS values. Two wavefront models were compared. The first model is based on a straight ray approximation, and the second model on the Eikonal equation, which is solved by a multi-stencils fast marching method. Their accuracy for abdominal imaging was evaluated in acoustic simulations and phantom experiments involving tissue-mimicking and porcine material with large SoS contrast (∼100 m/s). The lateral resolution was improved by up to 90% in simulations and up to 65% in experiments compared to standard DAS, in which the use of Eikonal beamforming generally outperformed straight ray beamforming. Moreover, geometric distortions were mitigated in multi-aperture imaging, leading to a reduction in position error of around 80%. A study on the sensitivity of the aberration correction to shape and SoS of aberrating layers was performed, showing that even with imperfect segmentations or SoS values, aberration correction still outperforms standard DAS.

A dual aperture (mesoporous and macroporous) system loaded with cell-free fat extract to optimize bone regeneration microenvironment.

Injured bone regeneration requires a systemically and carefully orchestrated series of events involving inflammation, angiogenesis, and osteogenesis. Thus, we designed a multifunctional cell-supporting and drug-retarding dual-pore system: cell-free fat extract (Ceffe)-mesoporous silica nanoparticle (MSN)@poly(lactic-co-glycolic acid) (PLGA) (Ceffe-MSN@PLGA) to mimic the developmental spatial structure, the microenvironment of bone regeneration and integration during injured bone regeneration. In this system, a macroporous scaffold (pore size 200-250 μm) of PLGA is combined with mesoporous MSN (pore size 2-50 nm), aiming at realizing the slow release of Ceffe. Besides, PLGA and MSN are used to recruit the temporary support of cells that are able to degrade simultaneously with bone regeneration and provide space for bone tissue regeneration. And the Ceffe isolated from fresh human adipose tissue has a therapeutic effect in regulating the important functions of early inflammatory cell transformation, neovascularization and eventual osteogenic differentiation. Our results suggest that the mesoporous and macroporous Ceffe-MSN@PLGA system represents a promising strategy to better fit the regeneration of injured bone tissue.

Bandpass filters based on integrated aperture‐ and gap‐coupled discontinuities

An electromagnetic coupling mechanism is discussed for distributed-element aperture- and gap-coupled discontinuities based on rigorous lumped-element equivalent circuit analysis. The two discontinuities are analysed in terms of their transmission poles and transmission zeros for the selectivity enhancement of microwave and or millimetre-wave components. The integration of these two discontinuities is put forward for bandpass filter design. A frequency-dependent lumped-element equivalent circuit is employed to study the behaviour of the two distributed-element discontinuities in the transverse direction. Bandpass filters are characterised based on the dual aperture- and gap-coupled discontinuities integrated within substrate integrated waveguide structures. It is shown that multiple transmission zeros close to transmission poles are realised due to the magnetic and electric field cancelation in the gap-coupled discontinuity, while the aperture-coupled discontinuity contributes to a resonator with a higher quality factor. The integration of both aperture- and gap-coupled discontinuities shows the priority of this kind of microwave resonator in terms of selectivity, size, and upper stopband in comparison with the conventional aperture-coupled one.

Low‐profile wideband dual‐polarized microstrip antenna element for 5G communication

AbstractA low‐profile wideband dual‐polarized microstrip antenna is presented for 5G communication. Using a periodical diamond structure, both low profile and wideband performance have been achieved with high port isolation. Relative bandwidths of 53.4% and 54.0% are obtained for two polarizations with a low profile of 0.047λ0, where λ0 is the free space wavelength at the center frequency of 4.18 GHz. The dual aperture coupling method is adopted for each polarization direction and high‐order modes are stimulated across the passband. The measured port isolation of more than 30 dB is obtained. Unidirectional radiation patterns have been achieved with low cross‐polarization levels. The proposed dual‐polarized microstrip antenna can offer a low‐profile structure and wideband performance, which can be another potential candidate for the 5G communication.

Dual-aperture hologram receiver for visible light communications

To optimize the performance of visible light communication (VLC) systems it is important that a VLC receiver has both a carefully designed field of view (FOV) which excludes light from unwanted directions and optical filtering to block unwanted wavelengths. The new dual-aperture hologram receiver consists of two parallel opaque layers each with a transparent aperture and a volume hologram placed below the second aperture. The dual apertures ensure that only light from specific directions reaches the hologram. The hologram provides wavelength selectivity and additional directivity. Analytical and simulation results show how the FOV of the new dual aperture hologram receiver depends on the dimensions of the aperture structure, and the position and size of the receiver photodiode, and how the optical bandwidth depends on the design of the hologram. Proof of concept experiments confirm the performance of the receiver. Major advantages of the new receiver are its compact structure suitable for incorporation in smartphones and its ease of manufacture.

Internet of Radars: Sensing versus Sending with Joint Radar-Communications

The of Things (IoT) is made up of interconnected devices for exchanging information through sensors and actuators. One of the main physical sensors to understand the environment beyond the visible world is a radar. Basically, radars have always been a military tool to investigate the environment. However, with the developing technology, radars have become more compact and affordable to use in a building, in a car, in a drone, or even in a wristwatch. In the near future, radar-equipped IoT platforms will start to appear increasingly. For each IoT platform, dual use of spectrum with dual aperture is required for sensing and communicating when using conventional approaches. Emissions from the radar and communication circuitries are the main causes of the increase in energy consumption for any radar sensing IoT device. Furthermore, an increasing number of radars cause congested spectrum, and RF convergence between radar and communication systems becomes more likely to present itself. In recent years, numerous research works have proposed using the single waveform for perceiving the environment and sending information. They are often called joint radar-communication' (JRC) systems. As a result of the latest advancements in JRC system designs, radar sensing IoT platforms now can be transformed into an Internet of Radars (IoR). This article is an attempt to introduce a prospective research direction in order to develop the architectures necessary to make the IoR concept possible. In this article, we present a short survey of JRC technologies likely to be used on radar-sensing-capable IoT devices. Then possible application areas, challenges to enable JRC, and future research perspectives are proposed.

Electro-Wetting Liquid Lens With Dual Apertures

We report an electro-wetting liquid lens with dual apertures which consists of internal channel with two variable interfaces and external channel with a plano-concave solid lens. And we use LC cell and Polarizers to achieve switching between internal and external channel. The proposed lens can achieve a large turning range of focal length, and the shortest positive and negative focal length are ~24 mm and ~-16 mm, respectively. Meanwhile, the experimental results show that the angular resolution of the proposed lens can reach to v29". It has potential to be applied in cameras, microscopes and so on.

A spatial-phase-shift-based defect detection shearography system with independent adjustment of shear amount and spatial carrier frequency

Digital shearography has a wide application in defect detection. Phase-shift-technique-based shearography has a higher phase measurement sensitivity than the real-time shearography. This phase shift technique can be divided into temporal phase shift shearography and spatial phase shift shearography. The latter has the advantage of fast detection and can be used in dynamic detection. In a traditional spatial carrier frequency shearography system, shear amount adjustments and spatial carrier frequency are not completely independent. In some shearography systems, shear amount and spatial carrier frequency are adjusted by rotating mirrors. The amounts of rotation required to obtain the appropriate shear amount and spatial carrier frequency are different, thereby reducing the accuracy of detection results. In other shearography systems, although the two adjustments are divided into two parts, using a rotating mirror to obtain the appropriate shear amount will also introduce additional spatial carrier frequency which will also have some influence on the result. This paper introduces a detection method with independently adjusting shear amount and spatial carrier frequency. Shear amount adjustment is achieved by changing the written image of a spatial light modulator (SLM). No additional spatial carrier frequency is introduced. Spatial carrier frequency is only controlled by the relative position between the dual apertures. Experimental results of undamaged and damaged specimens indicate that this system is suitable for detecting the phase distribution of the deformation and internal defects.

Offset Aperture: A Passive Single-Lens Camera for Depth Sensing

Numerous camera sensors have been recently proposed to estimate the depth of objects in the scene. However, many of these sensors either require multiple imaging elements or an active illuminant. In this paper, we propose a new depth camera, termed offset aperture (OA) camera, which provides depth of the scene with a single shot without an active illuminant. The camera is based on a 4-color sensor that senses the infrared (IR) signal along with the visible RGB signals. Separate OAs are used for IR and RGB images. A depth-dependent disparity is generated between the IR and RGB images. There is no disparity across the R, G, and B channel images, which allows the RGB image to be well-aligned. Numerous techniques are used in this work to observe good-quality depth maps and images. Leakage compensation has been proposed to remove crosstalk between the IR and RGB images. A comparison with another 4-color sensor called Dual Aperture camera shows that OA camera provides 88% improvement in depth sensitivity and 45% improvement in color quality, on average. The proposed OA camera can be used for numerous applications including occlusion handling in stereo, selective focus, and night vision. The advantages of the proposed OA camera include competitive image quality, capability of depth extraction, well-aligned RGB images, and small footprint of the camera, which make OA camera a suitable candidate for mobile applications.

Short-lag spatial coherence imaging using minimum variance beamforming on dual apertures

BackgroundShort-lag spatial coherence (SLSC) imaging, a newly proposed ultrasound imaging scheme, can offer a higher lesion detectability than conventional B-mode imaging. It requires a high focusing quality which can be satisfied by the synthetic aperture imaging mode. However, traditional nonadaptive synthesis for the SLSC still offers an unsatisfactory resolution. The spatial coherence estimation on the receive aperture cannot fully utilize the coherence information in two-dimensional (2D) echo data.MethodsTo overcome these drawbacks, an improved SLSC scheme with adaptive synthesis on dual apertures is proposed in this paper. The minimum variance (MV) beamformer is applied in synthesizing both the receiving and transmitting apertures, while the SLSC function is estimated on both apertures as well. In this way, the resolution is enhanced by the MV implementation, while the coherence in dual apertures is fully utilized.ResultsSimulations, phantom experiments, and in vivo studies are conducted to evaluate the performance of the proposed method. Results demonstrate that the proposed method achieves the best performance in terms of the contrast ratio (CR), contrast-to-noise ratio (CNR), and the speckle signal-to-noise ratio (SNR). Specifically, compared with the delay-and-sum (DAS) method, the proposed method achieves 42.5% higher CR, 412.7% higher CNR, and 402.9% higher speckle SNR in simulations. The resolution is also better than the DAS and conventional SLSC beamformers.ConclusionsThe proposed method is a promising technique for improving the SLSC imaging quality and can provide better visualization for medical diagnosis.

Analysis of a dual aperture approach and standing wave suppression pulse sequences for controlled transvertebral focused ultrasound delivery in ex vivo human thoracic vertebrae

Focused ultrasound (FUS), in conjunction with microbubbles (MB), can open the blood-brain barrier to aid therapeutic delivery. Its feasibility for blood-spinal cord barrier opening (BSCBO) has been demonstrated in small animals. Controlled transvertebral delivery of FUS to the human vertebral canal requires low frequencies to penetrate thick vertebral bone. The resulting focal depth of field (DoF) is comparable to the size of the canal, promoting the formation of standing waves (SW) and potentially compromising treatment safety. Through k-Wave simulations and experimental acoustic field scans, a confocal, dual aperture approach was investigated in combination with SW suppressing pulses (linear chirp, short bursts and random phase shift keying (PSK)) to simultaneously reduce DoF and mitigate SWs. Two transducers (470/530 kHz, angle 90°) reduced the DoF by 85% compared to a single transducer (500 kHz). While all modified pulses reduced SWs relative to a 30 cycle sinusoid, short bursts performed significantly better than longer burst methods such as linear chirps (p = 0.03, (59±15) vs (34±11)% reduction). In combination with PSK, short bursts implemented in the dual aperture configuration mitigated SWs, while producing a uniform focal spot. The feasibility of using confocal, dual-aperture FUS to create a controlled focus within ex vivo vertebrae has been demonstrated. Next steps will include investigating MB emissions under short burst, PSK exposures, and characterizing spectral content associated with BSCBO and tissue damage.