Insulator-to-metal temperature phase transition Vanadium Dioxide (VO2) can enable radiative property switching in the mid- to far-infrared wavelengths. With computational optimization of grating ...arrangement and layer thickness parameters, we identify a monolithic high-performance turn-down thermal emittance coating of no more than 2 μm thick, consisting of a VO2 sub-wavelength nanowire grating array on an index-matched Fabry-Perot dielectric thin film on an additional absorbing VO2 sublayer. The working principles of this optimized VO2 structure are its gradient refractive index allowing high through-coating transmittance in the cold state, and its near-unity emissivity from semi-metal-insulator-metal plasmonic coupling in the hot state. This anisotropic patterned structure also considers performance over polarized incident light. A survey of other Fabry-Perot cavity materials with refractive index matching points to higher turn-down performances given an optimal VO2 nanowire volume filling ratio. With 24-hour solar and environmental analysis in comparison to other VO2 metasurfaces and multilayers, this coating enables responsive passive radiative cooling at high temperatures exceeding transition. This nano/micro-patterned coating could potentially impact self-cooling of the solar cells, batteries, and electrical devices where risk presents at high temperatures.
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We consider using gradient descent to minimize the nonconvex function \(f(X)=\phi(XX^{T})\) over an \(n\times r\) factor matrix \(X\), in which \(\phi\) is an underlying smooth convex cost function ...defined over \(n\times n\) matrices. While only a second-order stationary point \(X\) can be provably found in reasonable time, if \(X\) is additionally rank deficient, then its rank deficiency certifies it as being globally optimal. This way of certifying global optimality necessarily requires the search rank \(r\) of the current iterate \(X\) to be overparameterized with respect to the rank \(r^{\star}\) of the global minimizer \(X^{\star}\). Unfortunately, overparameterization significantly slows down the convergence of gradient descent, from a linear rate with \(r=r^{\star}\) to a sublinear rate when \(r>r^{\star}\), even when \(\phi\) is strongly convex. In this paper, we propose an inexpensive preconditioner that restores the convergence rate of gradient descent back to linear in the overparameterized case, while also making it agnostic to possible ill-conditioning in the global minimizer \(X^{\star}\).
While it is nearly effortless for humans to quickly assess the perceptual similarity between two images, the underlying processes are thought to be quite complex. Despite this, the most widely used ...perceptual metrics today, such as PSNR and SSIM, are simple, shallow functions, and fail to account for many nuances of human perception. Recently, the deep learning community has found that features of the VGG network trained on ImageNet classification has been remarkably useful as a training loss for image synthesis. But how perceptual are these so-called "perceptual losses"? What elements are critical for their success? To answer these questions, we introduce a new dataset of human perceptual similarity judgments. We systematically evaluate deep features across different architectures and tasks and compare them with classic metrics. We find that deep features outperform all previous metrics by large margins on our dataset. More surprisingly, this result is not restricted to ImageNet-trained VGG features, but holds across different deep architectures and levels of supervision (supervised, self-supervised, or even unsupervised). Our results suggest that perceptual similarity is an emergent property shared across deep visual representations.
Clique tree conversion solves large-scale semidefinite programs by splitting an
n
×
n
matrix variable into up to
n
smaller matrix variables, each representing a principal submatrix of up to
ω
×
ω
. ...Its fundamental weakness is the need to introduce
overlap constraints
that enforce agreement between different matrix variables, because these can result in dense coupling. In this paper, we show that by dualizing the clique tree conversion, the coupling due to the overlap constraints is guaranteed to be sparse over dense blocks, with a block sparsity pattern that coincides with the adjacency matrix of a tree. We consider two classes of semidefinite programs with favorable sparsity patterns that encompass the MAXCUT and MAX
k
-CUT relaxations, the Lovasz Theta problem, and the AC optimal power flow relaxation. Assuming that
ω
≪
n
, we prove that the per-iteration cost of an interior-point method is
linear
O
(
n
) time and memory, so an
ϵ
-accurate and
ϵ
-feasible iterate is obtained after
O
(
n
log
(
1
/
ϵ
)
)
iterations in
near-linear
O
(
n
1.5
log
(
1
/
ϵ
)
)
time. We confirm our theoretical insights with numerical results on semidefinite programs as large as
n
=
13
,
659
.
Plasmonic and phase transition has been blended to gain the infrared radiative switching which is tunable with temperature or voltage supply. This is applied via vanadium dioxide, tungsten trioxide, ...and molybdenum trioxide as transition metal oxides (TMO). The metallic phase at high temperature or colored state contributes in magnetic polariton (MP) excitation, producing broad absorptance. The TMO-based sub-layer is integrated underneath the grating fully supporting MP resonance. In contrast, this underlayer leads to producing the narrowband absorptance originated from concept of zero contrast grating (ZCG). The zero gradient in refractive index at the output plane of the grating cause transmission of light in broad wavelength range. With introduction of reflective silver underlayer, those transmitted through the grating are reflected back. However, there exists the near-zero narrowband transmission peaks in ZCG. This undergoes transformation to narrowband absorptance. In addition, another absorptance peak can be induced due to phonon modes at insulating phase. The MP resonance at metallic phase is characterized with inductor-capacitor (LC) circuit and the narrowband absorptance peaks are characterized with phase shift from the Fabry-Perot round trip (FP-RT) eigenequation from high contrast grating (HCG). The work expands the usage of transition metal oxides in infrared region with larger contrast.
Edge-Aware Point Set Resampling HUI HUANG; SHIHAO WU; MINGLUN GONG ...
ACM transactions on graphics,
2013, 2013-01-00, 20130101, Letnik:
32, Številka:
1
Journal Article
Recenzirano
Points acquired by laser scanners are not intrinsically equipped with normals, which are essential to surface reconstruction and point set rendering using surfels. Normal estimation is notoriously ...sensitive to noise. Near sharp features, the computation of noise-free normals becomes even more challenging due to the inherent undersampling problem at edge singularities. As a result, common edge-aware consolidation techniques such as bilateral smoothing may still produce erroneous normals near the edges. We propose a resampling approach to process a noisy and possibly outlier-ridden point set in an edge-aware manner. Our key idea is to first resample away from the edges so that reliable normals can be computed at the samples, and then based on reliable data, we progressively resample the point set while approaching the edge singularities. We demonstrate that our Edge-Aware Resampling (EAR) algorithm is capable of producing consolidated point sets with noise-free normals and clean preservation of sharp features. We also show that EAR leads to improved performance of edge-aware reconstruction methods and point set rendering techniques.
Due to the negative coefficient of thermal expansion of graphene, temperature changes of graphene-coated photonic surfaces could induce resonant mode shifts in diffractive optical absorptance and ...emission. This study focuses on the modification of optical properties through folding, or “origami,” of graphene covering a plasmonic metal channel grating. This work is especially critical to understanding tailored deep plasmon emission from geometrically-modulated conducting sheets such as graphene. Conformational changes in graphene on gratings are found to tailor cavity resonance emission and plasmonic oscillations such as magnetic polaritons (MPs) and surface plasmon polaritons (SPPs), respectively. Up to 46% reduction in radiative absorptance was observed through retarded MP. Excited SPP modes can increase narrowband absorptance of 0.5 through folding of graphene. Tailoring of optical absorptance can be used for applications such as photodetectors and thermal emitters.
A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariant, BA.2.86, has emerged and spread to numerous countries worldwide, raising alarm because its spike protein contains 34 ...additional mutations compared with its BA.2 predecessor
. We examined its antigenicity using human sera and monoclonal antibodies (mAbs). Reassuringly, BA.2.86 was no more resistant to human sera than the currently dominant XBB.1.5 and EG.5.1, indicating that the new subvariant would not have a growth advantage in this regard. Importantly, sera from people who had XBB breakthrough infection exhibited robust neutralizing activity against all viruses tested, suggesting that upcoming XBB.1.5 monovalent vaccines could confer added protection. Although BA.2.86 showed greater resistance to mAbs to subdomain 1 (SD1) and receptor-binding domain (RBD) class 2 and 3 epitopes, it was more sensitive to mAbs to class 1 and 4/1 epitopes in the 'inner face' of the RBD that is exposed only when this domain is in the 'up' position. We also identified six new spike mutations that mediate antibody resistance, including E554K that threatens SD1 mAbs in clinical development. The BA.2.86 spike also had a remarkably high receptor affinity. The ultimate trajectory of this new SARS-CoV-2 variant will soon be revealed by continuing surveillance, but its worldwide spread is worrisome.
Excitation of surface plasmon polaritons helps to increase the near-field heat flux by orders of magnitude beyond the limit governed by Stefan–Boltzmann law. However, the photon tunneling probability ...is rather low, except for modes satisfying the resonance condition of surface plasmon polaritons. Broadband hyperbolic metamaterials can broaden the frequency region for the enhancement of near-field heat transfer, but can hardly maintain a high tunneling probability for large wavevectors since no resonances are excited to overcome the inherent exponential decay. In this letter, perfect photon tunneling with near-unity probability across broad frequency and k-space region is demonstrated based on the hybridization of graphene plasmons and hyperbolic modes. As a result, the near-field heat transfer coefficient between doped-silicon-nanowire hyperbolic metamaterials can be further improved several fold when covered by a graphene sheet, approaching to a theoretical limit.
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