We present a method of ozonation to form the rear-side passivation layers of crystalline silicon PERC cells. In the method, a thin aluminum film was deposited on the back surface of a silicon wafer ...and then was oxidized into an aluminum oxide layer by gaseous ozone. Lifetimes of the wafers with such passivation layers proved to be increased with respect to those untreated, and the resultant PERC cells showed a performance improvement compared with standard cells with full back surface fields.
Due to its absorption properties in atmosphere, the mid-infrared (mid-IR) region has gained interest for its potential to provide high data capacity in free-space optical (FSO) communications. Here, ...we experimentally demonstrate wavelength-division-multiplexing (WDM) and mode-division-multiplexing (MDM) in a ~0.5 m mid-IR FSO link. We multiplex three ~3.4 μm wavelengths (3.396 μm, 3.397 μm, and 3.398 μm) on a single polarization, with each wavelength carrying two orbital-angular-momentum (OAM) beams. As each beam carries 50-Gbit/s quadrature-phase-shift-keying data, a total capacity of 300 Gbit/s is achieved. The WDM channels are generated and detected in the near-IR (C-band). They are converted to mid-IR and converted back to C-band through the difference frequency generation nonlinear processes. We estimate that the system penalties at a bit error rate near the forward error correction threshold include the following: (i) the wavelength conversions induce ~2 dB optical signal-to-noise ratio (OSNR) penalty, (ii) WDM induces ~1 dB OSNR penalty, and (iii) MDM induces ~0.5 dB OSNR penalty. These results show the potential of using multiplexing to achieve a ~30X increase in data capacity for a mid-IR FSO link.
Direct foaming from solids is the most efficient method to fabricate porous materials. However, the ideal foaming fails to prepare aerogel of nanoparticles because the plasticity of their solids is ...denied by the overwhelming interface interactions. Here, we invent a hydroplastic foaming method to directly convert graphene oxide solids into aerogel bulks and microarrays, replacing the prevalent freezing method. The water intercalation plasticizes graphene oxide solids and enables direct foaming instead of catastrophic fragmentation. The bubble formation follows a general crystallization rule and allows nanometer-precision control of cellular wall thickness down to 8 nm. Bubble clustering generates hyperboloid structures with seamless basal connection and renders graphene aerogels with ultrarobust mechanical stability against extreme deformations. We exploit graphene aerogel to fabricate tactile microarray sensors with ultrasensitivity and ultrastability, achieving a high accuracy (80%) in artificially intelligent touch identification that outperforms human fingers (30%).
Flexible electronics with continuous monitoring ability a extensively preferred in various medical applications. In this work, a flexible pressure sensor based on porous graphene (PG) is proposed for ...continuous cardiovascular status monitoring. The whole sensor is fabricated in situ by ink printing technology, which grants it the potential for large-scale manufacture. Moreover, to enhance its long-term usage ability, a polyethylene terephthalate/polyethylene vinylacetate (PET/EVA)-laminated film is employed to protect the sensor from unexpected shear forces on the skin surface. The sensor exhibits great sensitivity (53.99/MPa), high resolution (less than 0.3 kPa), wide detecting range (0.3 kPa to 1 MPa), desirable robustness, and excellent repeatability (1000 cycles). With the assistance of the proposed pressure sensor, vital cardiovascular conditions can be accurately monitored, including heart rate, respiration rate, pulse wave velocity, and blood pressure. Compared to other sensors based on self-supporting 2D materials, this sensor can endure more complex environments and has enormous application potential for the medical community.
We explore the use of orbital-angular-momentum (OAM)-multiplexing to increase the capacity of free-space data transmission to moving platforms, with an added potential benefit of decreasing the ...probability of data intercept. Specifically, we experimentally demonstrate and characterize the performance of an OAM-multiplexed, free-space optical (FSO) communications link between a ground transmitter and a ground receiver via a moving unmanned-aerial-vehicle (UAV). We achieve a total capacity of 80 Gbit/s up to 100-m-roundtrip link by multiplexing 2 OAM beams, each carrying a 40-Gbit/s quadrature-phase-shift-keying (QPSK) signal. Moreover, we investigate for static, hovering, and moving conditions the effects of channel impairments, including: misalignments, propeller-induced airflows, power loss, intermodal crosstalk, and system bit error rate (BER). We find the following: (a) when the UAV hovers in the air, the power on the desired mode fluctuates by 2.1 dB, while the crosstalk to the other mode is -19 dB below the power on the desired mode; and (b) when the UAV moves in the air, the power fluctuation on the desired mode increases to 4.3 dB and the crosstalk to the other mode increases to -10 dB. Furthermore, the channel crosstalk decreases with an increase in OAM mode spacing.
The use of optical interconnects has burgeoned as a promising technology that can address the limits of data transfer for future high-performance silicon chips. Recent pushes to enhance optical ...communication have focused on developing wavelength-division multiplexing technology, and new dimensions of data transfer will be paramount to fulfill the ever-growing need for speed. Here we demonstrate an integrated multi-dimensional communication scheme that combines wavelength- and mode- multiplexing on a silicon photonic circuit. Using foundry-compatible photonic inverse design and spectrally flattened microcombs, we demonstrate a 1.12-Tb/s natively error-free data transmission throughout a silicon nanophotonic waveguide. Furthermore, we implement inverse-designed surface-normal couplers to enable multimode optical transmission between separate silicon chips throughout a multimode-matched fibre. All the inverse-designed devices comply with the process design rules for standard silicon photonic foundries. Our approach is inherently scalable to a multiplicative enhancement over the state of the art silicon photonic transmitters.
In this paper, we review high-capacity underwater optical communications using orbital angular momentum (OAM)-based spatial division multiplexing. We discuss methods to generate and detect blue–green ...optical data-carrying OAM beams as well as various underwater effects, including attenuation, scattering, current, and thermal gradients on OAM beams. Attention is also given to the system performance of high-capacity underwater optical communication links using OAM-based space division multiplexing. The paper closes with a discussion of a digital signal processing (DSP) algorithm to mitigate the inter-mode crosstalk caused by thermal gradients.
•Underwater optical communications using OAM multiplexing is reviewed.•Methods to generate/detect blue–green OAM beams is discussed.•OAM beams may be degraded under various underwater effects.•System performance of OAM-based underwater optical communications is discussed.•Algorithm to mitigate crosstalk caused by thermal gradients is discussed.
With the introduction of earth observation satellites, the classification technology through high-definition remote sensing images appeared. After decades of evolution, the land cover classification ...method in high-definition satellite maps has been gradually improved. Recently, high-definition remote sensing maps have been applied to land cover classification. Nowadays, classification methods using high-definition maps have these following problems: First, traditional land cover classification methods cannot process the rich details in high-definition maps. Second, there are different acquisition conditions in the maps of different regions, which leads to distortion, deformation and illumination blur of remote sensing images. Third, existing methods are unable to provide a good generalization performance. To address these issues, a dual-branch parallel network structure is proposed, called Sgformer, to improve performance of Transformer in the context of high-definition remote sensing maps. The network enhances perceptual learning with convolution operators that extract local features and a self-attention module that captures global representations. Local information and global representations with semantic divergence are fused through a feature coupling module. At last, a decoder is designed to maximize the preservation of local features and global representations, and to better recover high- definition feature maps. The results of semantic segmentation experiments show that the methodology in this study has higher accuracy than other methodologies.
To evaluate the midterm clinical and angiographic outcomes after pipeline embolization device (PED) placement for treatment of intracranial aneurysms.
This prospective nonrandomized multicenter study ...was approved by the review boards of all involved centers; informed consent was obtained. Patients (143 patients, 178 aneurysms) with unruptured saccular or fusiform aneurysms or recurrent aneurysms after previous treatment were included and observed angiographically for up to 18 months and clinically for up to 3 years. Study endpoints included complete aneurysm occlusion; neurologic complications within 30 days and up to 3 years; clinical outcome of cranial nerve palsy after PED placement; angiographic evidence of occlusion or stenosis of parent artery and that of occlusion of covered side branches at 6, 12, and 18 months; and clinical and computed tomographic evidence of perforator infarction.
There were five (3.5%) cases of periprocedural death or major stroke (modified Rankin Scale mRS > 3) (95% confidence interval CI: 1.3%, 8.4%), including two posttreatment delayed ruptures, two intracerebral hemorrhages, and one thromboembolism. Five (3.5%) patients had minor neurologic complications within 30 days (mRS = 1) (95% CI: 1.3%, 8.4%), including transient ischemic attack (n = 2), small cerebral infarction (n = 2), and cranial nerve palsy (n = 1). Beyond 30 days, there was one fatal intracerebral hemorrhage and one transient ischemic attack. Ten of 13 patients (95% CI: 46%, 93.8%) completely recovered from symptoms of cranial nerve palsy within a median of 3.5 months. Angiographic results at 18 months revealed a complete aneurysm occlusion rate of 84% (49 of 58; 95% CI: 72.1%, 92.2%), with no cases of parent artery occlusion, parent artery stenosis (<50%) in three patients, and occlusion of a covered side branch in two cases (posterior communicating arteries). Perforator infarction did not occur.
PED placement is a reasonably safe and effective treatment for intracranial aneurysms. The treatment is promising for aneurysms of unfavorable morphologic features, such as wide neck, large size, fusiform morphology, incorporation of side branches, and posttreatment recanalization, and should be considered a first choice for treating unruptured aneurysms and recurrent aneurysms after previous treatments.
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120422/-/DC1.
Abstract
Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest. In terms of changes in time, OAM can be manifest at a given ...distance in different forms, including: (1) a Gaussian-like beam dot that revolves around a central axis, and (2) a Laguerre-Gaussian (
$$LG_{\ell ,p}$$
L
G
ℓ
,
p
) beam with a helical phasefront rotating around its own beam center. Here we explore the generation of dynamic spatiotemporal beams that combine these two forms of orbital-angular-momenta by coherently adding multiple frequency comb lines. Each line carries a superposition of multiple
$$LG_{\ell ,p}$$
L
G
ℓ
,
p
modes such that each line is composed of a different
$$\ell$$
ℓ
value and multiple
p
values. We simulate the generated beams and find that the following can be achieved: (a) mode purity up to 99%, and (b) control of the helical phasefront from 2
π
-6
π
and the revolving speed from 0.2–0.6 THz. This approach might be useful for generating spatiotemporal beams with even more sophisticated dynamic properties.
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