936 research outputs found
Generalized Impedance Boundary Conditions for Strongly Absorbing Obstacles: the full Wave Equations
This paper is devoted to the study of the generalized impedance boundary
conditions (GIBCs) for a strongly absorbing obstacle in the {\bf time} regime
in two and three dimensions. The GIBCs in the time domain are heuristically
derived from the corresponding conditions in the time harmonic regime. The
latters are frequency dependent except the one of order 0; hence the formers
are non-local in time in general. The error estimates in the time regime can be
derived from the ones in the time harmonic regime when the frequency dependence
is well-controlled. This idea is originally due to Nguyen and Vogelius in
\cite{NguyenVogelius2} for the cloaking context. In this paper, we present the
analysis to the GIBCs of orders 0 and 1. To implement the ideas in
\cite{NguyenVogelius2}, we revise and extend the work of Haddar, Joly, and
Nguyen in \cite{HJNg1}, where the GIBCs were investigated for a fixed frequency
in three dimensions. Even though we heavily follow the strategy in
\cite{NguyenVogelius2}, our analysis on the stability contains new ingredients
and ideas. First, instead of considering the difference between solutions of
the exact model and the approximate model, we consider the difference between
their derivatives in time. This simple idea helps us to avoid the machinery
used in \cite{NguyenVogelius2} concerning the integrability with respect to
frequency in the low frequency regime. Second, in the high frequency regime,
the Morawetz multiplier technique used in \cite{NguyenVogelius2} does not fit
directly in our setting. Our proof makes use of a result by H\"ormander in
\cite{Hor}. Another important part of the analysis in this paper is the
well-posedness in the time domain for the approximate problems imposed with
GIBCs on the boundary of the obstacle, which are non-local in time
Effect of the green-emitting CaF2:Ce3+,Tb3+ phosphor particles’ size on color rendering index and color quality scale of the in-cup packaging multichip white LEDs
In this paper, we investigate the effect of the green-emitting CaF2:Ce (3+), Tb (3+) phosphor particle's size on the color rendering index (CRI) and the color quality scale (CQS) of the in-cup packaging multichip white LEDs (MCW-LEDs). For this purpose, 7000K and 8500K in-cup packaging MCW-LEDs is simulated by the commercial software Light Tools. Moreover, scattering process in the phosphor layers is investigated by using Mie Theory with Mat Lab software. Finally, the research results show that the green-emitting CaF2: Ce (3+), Tb (3+) phosphor's size crucially influences on the CRI and CQS. From that point of view, CaF2: Ce (3+), Tb (3+) can be proposed as a potential practical direction for manufacturing the in-cup packaging phosphor WLEDs.Web of Science13235134
Combined effects of a simulated marine heatwave and an algal toxin on a tropical marine aquaculture fish cobia (Rachycentron canadum)
Ongoing global warming is one of the major challenges for the development of aquaculture in the tropical regions where species are already cultured in the water temperature close to their upper physiological thresholds. Furthermore, warming can trigger blooms of toxic algae, yet we do not know how extreme warming such as a marine heatwave (MHW) and algal toxins may affect marine aquaculture species. To address this issue, we investigated the effects of a simulated MHW in combination with exposure to trans-4-trans-decadienal (PUA), a diatom-derived toxin, on survival, growth, development and biochemical composition of cobia larvae and juveniles. Cobia larvae were exposed for 48 hr to one of two temperatures (29 vs. 34°C) and two PUA treatments (0 vs. 0.5 µM). Surviving larvae from each treatment were divided into two subsets: three replicates were used for the feeding test and five replicates were used for the recovery test in a non-contaminated environment at the respective temperatures of 29 or 34°C. Survival of cobia larvae was reduced by 16% in either MHW or PUA, but it dropped by 60% when both stressors were present, indicating a synergistic effect. MHW, but not PUA, reduced the feeding of cobia larvae. PUA had no delayed effects on growth rate and biochemical composition of the fish. MHW strongly reduced specific growth rate, body protein and lipid contents in cobia. Our results provide the first empirical evidence of how MHW and toxic algae may interact and challenge cobia and marine aquaculture production in tropical countries.publishedVersio
Enabling relay selection in non-orthogonal multiple access networks: direct and relaying mode
In this paper, we consider downlink non-orthogonal multiple access (NOMA) in which the relay selection (RS) scheme is enabled for cooperative networks. In particular, we investigate impact of the number of relays on system performance in term of outage probability. The main factors affecting on cooperative NOMA performance are fixed power allocations coefficients and the number of relay. This paper also indicate performance gap of the outage probabilities among two users the context of NOMA. To exhibit the exactness of derived formula, we match related results between simulation and analytical methods. Numerical results confirms that cooperative NOMA networks benefit from increasing the number of relay
Seeing the world from its words: All-embracing Transformers for fingerprint-based indoor localization
In this paper, we present all-embracing Transformers (AaTs) that are capable of deftly manipulating attention mechanism for Received Signal Strength (RSS) fingerprints in order to invigorate localizing performance. Since most machine learning models applied to the RSS modality do not possess any attention mechanism, they can merely capture superficial representations. Moreover, compared to textual and visual modalities, the RSS modality is inherently notorious for its sensitivity to environmental dynamics. Such adversities inhibit their access to subtle but distinct representations that characterize the corresponding location, ultimately resulting in significant degradation in the testing phase. In contrast, a major appeal of AaTs is the ability to focus exclusively on relevant anchors in RSS sequences, allowing full rein to the exploitation of subtle and distinct representations for specific locations. This also facilitates disregarding redundant clues formed by noisy ambient conditions, thus enhancing accuracy in localization. Apart from that, explicitly resolving the representation collapse (i.e., none-informative or homogeneous features, and gradient vanishing) can further invigorate the self-attention process in transformer blocks, by which subtle but distinct representations to specific locations are radically captured with ease. For that purpose, we first enhance our proposed model with two sub-constraints, namely covariance and variance losses at the Anchor2Vec. The proposed constraints are automatically mediated with the primary task towards a novel multi-task learning manner. In an advanced manner, we present further the ultimate in design with a few simple tweaks carefully crafted for transformer encoder blocks. This effort aims to promote representation augmentation via stabilizing the inflow of gradients to these blocks. Thus, the problems of representation collapse in regular Transformers can be tackled. To evaluate our AaTs, we compare the models with the state-of-the-art (SoTA) methods on three benchmark indoor localization datasets. The experimental results confirm our hypothesis and show that our proposed models could deliver much higher and more stable accuracy
GUNNEL: Guided Mixup Augmentation and Multi-View Fusion for Aquatic Animal Segmentation
Recent years have witnessed great advances in object segmentation research.
In addition to generic objects, aquatic animals have attracted research
attention. Deep learning-based methods are widely used for aquatic animal
segmentation and have achieved promising performance. However, there is a lack
of challenging datasets for benchmarking. In this work, we build a new dataset
dubbed "Aquatic Animal Species." We also devise a novel GUided mixup
augmeNtatioN and multi-viEw fusion for aquatic animaL segmentation (GUNNEL)
that leverages the advantages of multiple view segmentation models to
effectively segment aquatic animals and improves the training performance by
synthesizing hard samples. Extensive experiments demonstrated the superiority
of our proposed framework over existing state-of-the-art instance segmentation
methods
On the solutions of universal differential equation by noncommutative Picard-Vessiot theory
Basing on Picard-Vessiot theory of noncommutative differential equations and
algebraic combinatorics on noncommutative formal series with holomorphic
coefficients, various recursive constructions of sequences of grouplike series
converging to solutions of universal differential equation are proposed. Basing
on monoidal factorizations, these constructions intensively use diagonal series
and various pairs of bases in duality, in concatenation-shuffle bialgebra and
in a Loday's generalized bialgebra. As applications, the unique solution,
satisfying asymptotic conditions, of Knizhnik-Zamolodchikov equations is
provided by d\'evissage
On The Global Renormalization and Regularization of Several Complex Variable Zeta Functions by Computer
This review concerns the resolution of a special case of
Knizhnik-Zamolodchikov equations () using our recent results on
combinatorial aspects of zeta functions on several variables and software on
noncommutative symbolic computations. In particular, we describe the actual
solution of leading to the unique noncommutative series, ,
so-called Drinfel'd associator (or Drinfel'd series). Non-trivial expressions
for series with rational coefficients, satisfying the same properties with
, are also explicitly provided due to the algebraic structure and
the singularity analysis of the polylogarithms and harmonic sums
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