Spectral Property Research Articles

Trajectory planning for semilinear time-fractional reaction-diffusion systems under Robin boundary conditions

This paper describes how to design flatness-based distributed feedforward controllers for the solution of the trajectory planning problem of semilinear time-fractional reaction-diffusion systems (TFRDSs), where the first-order time derivative of conventional reaction-diffusion system is extended to a Caputo fractional derivative of order α ϵ (0,1]. To this end, an implicit system variable and control input parametrization is determined based on the spectral property of system operator with respect to a basic output and its fractional-order derivatives. The convergence of the parametrizations is guaranteed by restricting the basic output to some certain Gevrey classes. With these, we propose two approaches on solving the trajectory planning problem within a prescribed finite time interval. A simulation example is finally included to illustrate our results.

Mixed samarium valences effect in Faraday rotation glasses: Structure, optical, magnetic and magneto-optical properties

Sm2+ ions are attractive in high density memory applications due to its spectral hole burning property. In this study, for the first time, the influence of mixed valence states of Sm ions to magnetic and magneto optical property of diamagnetic glasses were studied. The chemical valence states of Sm and their modification on glass structure, optical absorption, luminescence, magnetic and Faraday rotation performances were characterized using X-ray Photoelectron Spectroscopy (XPS), X-Ray diffraction, Ultraviolet-visible (UV–Vis), Fourier Transform Infrared (FT-IR), Raman spectra and vibrating-sample magnetization (VSM) measurements, respectively. Characteristic emission peaks due to 5D0→7F0 and 5D0→7F1 transitions of Sm2+ and 5G5/2→6H7/2, 5G5/2→6H9/2 transitions of Sm3+ ions were detected in luminescence spectra, indicating the reduction of Sm3+ to Sm2+. XPS analysis on Sm3d core-level spectra demonstrated the co-existence of Sm2+ and Sm3+ and their evolution was Sm2O3 content-dependent. Optical absorption of 6H5/2→4G5/2, 6F11/2,6F9/2,6F7/2,6F5/2 transitions of Sm3+ ions were observed in UV–VIS spectra, however, the absorption peaks of Sm2+ were covered by the stronger absorption of Pb2+ and Bi3+ ions in the UV region. The refractive index, optical cutoff wavelength and band gap of glasses were changed by the incorporation of highly polarizable Sm ions. Due to the different magnetic ordering of Sm2+ and Sm3+ions, glass doped with 1%Sm2O3 presented diamagnetic nature while glasses doped with higher Sm2O3 exhibited paramagnetic behavior, and the Faraday rotation property also was greatly influenced by magnetization susceptibility. 1%Sm2O3 doped glasses presented the strongest magnetization and biggest Verdet constant of 0.1886 min/G.cm at 633 nm. Several influence factors to Verdet constant such as non-bridging oxygen structure, wavelength, refractive index, magnetic susceptibility and temperature were discussed.

Multimedia utilization of non-computerized disguised voice and acoustic similarity measurement

In this paper, an identification of a speaker for multimedia application under non-electronically disguised voice is performed. In non-electronically disguised voice under physical variation of speech, it is a difficult task to identify the speaker in speech signal processing application area. Due to changes in the frequency spectrum of the speech signal during non- electronic disguising, some methods like Mel-frequency cepstrum coefficients (MFCC), delta Mel-frequency cepstrum coefficients (ΔMFCC) and double delta Mel-frequency cepstrum coefficients (ΔΔMFCC) are used to specify the frequencies spectral property. A new algorithm developed, based on acoustic feature extraction by MFCC technique of text-dependent speech signal of all speaker’s and changed their speech by six physical variation methods. The acoustic features which include the correlation coefficients and the mean value are extracted by the MFCC, ΔMFCC and ΔΔMFCC feature extraction method. Thereafter, different classifiers based on feature extraction are used to classify the non-electronically disguised voice and normal voice.

The codopant assisted tunable photoluminescence and highly efficient CW lasers in Nd3+:SrF2 crystal

Generally, the well shielded f orbitals made the f-f transition of lanthanides be non-tunable and sharp lines. In the work, the spectral property of Nd3+:SrF2 crystal codoped with R3+ (R3+ = Y3+, La3+, Gd3+) were investigated. The results show that with no loss of crystal structure integrity, the photoluminescence were tuned by the codopants in large scale, and altered significantly with the codopant species and concentrations, which strongly indicates that the f-f transitions could be modulated and tuned rather than the general considerations, and the codopants prefer to work as local lattice structure regulators. At the viewpoint, the designing of new lanthanide-doped laser crystals through the local structure modulation was suggested. With help of the codopant, a quasi-single-center system of Nd3+,Y3+:SrF2 and Nd3+,Gd3+:SrF2 were obtained, and the peak emission cross section, lifetime, linewidth and quantum yields were manipulated to be about 5 × 10−20 cm2, 350 μs, 20 nm and 90%, respectively. The highly improved CW lasing efficiency and output power agreed well with the spectral properties. The modified photoluminescence parameters show that Nd3+,R3+:SrF2 crystal with high thermal conductivity were very promising candidate for generation of high repetition rate ultrashort 1 μm lasers.

Quasi-regular representations of discrete groups and associated $C^*$-algebras

Let G be a countable group. We introduce several equivalence relations on the set Sub(G) of subgroups of G, defined by properties of the quasi-regular representations λ G/H associated to H ∈ Sub(G) and compare them to the relation of G-conjugacy of subgroups. We define a class Sub sg (G) of subgroups (these are subgroups with a certain spectral gap property) and show that they are rigid, in the sense that the equivalence class of H ∈ Sub sg (G) for any one of the above equivalence relations coincides with the G-conjugacy class of H. Next, we introduce a second class Sub w−par (G) of subgroups (these are subgroups which are weakly parabolic in some sense) and we establish results concerning the ideal structure of the C

Study on the broad spectral absorption property of monolayer MoS2 based on hybrid structures

The poor light absorption property in monolayer MoS2 limits its applications such as in photonics, optoelectronics and energy utilizations. Here, we propose a hybrid structure, consisting of a Fabry-Perot (F-P) cavity, plasmonic silver (Ag) gratings and an Ag/Al2O3/Al gap-plasmon resonator, to improve the light absorption of monolayer MoS2 in the wavelength region from 400 to 700 nm. We theoretically investigate the spectral absorption of monolayer MoS2 placed on top of different hybrid structures by FDTD simulations. The simulation results show that monolayer MoS2 in the MoS2/Ag grating/Al2O3/Al structure can absorb about 27.6% of the incident solar light integrated from 400 to 700 nm. The absorption peaks can be tuned in a wide spectral range by changing the geometrical parameters of the structure. We further design Ag gratings with interlaced stripes to enhance the absorption from 500 to 700 nm. The proposed structures in this study also can be applied to other two-dimensional semiconductors to achieve strong absorption in the visible spectral region.

On Synchronous, Asynchronous, and Randomized Best-Response Schemes for Stochastic Nash Games

In this paper, we consider a stochastic Nash game in which each player minimizes a parameterized expectation-valued convex objective function. In deterministic regimes, proximal best-response (BR) schemes have been shown to be convergent under a suitable spectral property associated with the proximal BR map. However, a direct application of this scheme to stochastic settings requires obtaining exact solutions to stochastic optimization problems at each iteration. Instead, we propose an inexact generalization of this scheme in which an inexact solution to the BR problem is computed in an expected-value sense via a stochastic approximation (SA) scheme. On the basis of this framework, we present three inexact BR schemes: (i) First, we propose a synchronous inexact BR scheme where all players simultaneously update their strategies. (ii) Second, we extend this to a randomized setting where a subset of players is randomly chosen to update their strategies while the other players keep their strategies invariant. (iii) Third, we propose an asynchronous scheme, where each player chooses its update frequency while using outdated rival-specific data in updating its strategy. Under a suitable contractive property on the proximal BR map, we proceed to derive almost sure convergence of the iterates to the Nash equilibrium (NE) for (i) and (ii) and mean convergence for (i)–(iii). In addition, we show that for (i)–(iii), the generated iterates converge to the unique equilibrium in mean at a linear rate with a prescribed constant rather than a sublinear rate. Finally, we establish the overall iteration complexity of the scheme in terms of projected stochastic gradient (SG) steps for computing an [Formula: see text]-NE2 (or [Formula: see text]-NE∞) and note that in all settings, the iteration complexity is [Formula: see text], where [Formula: see text] in the context of (i), and c > 0 represents the positive cost of randomization in (ii) and asynchronicity and delay in (iii). Notably, in the synchronous regime, we achieve a near-optimal rate from the standpoint of solving stochastic convex optimization problems by SA schemes. The schemes are further extended to settings where players solve two-stage stochastic Nash games with linear and quadratic recourse. Finally, preliminary numerics developed on a multiportfolio investment problem and a two-stage capacity expansion game support the rate and complexity statements.

Analytic Solution of a Delay Differential Equation Arising in Cost Functionals for Systems With Distributed Delays

The solvability of a delay differential equation arising in the construction of quadratic cost functionals, i.e. Lyapunov functionals, for a linear time-delay system with a constant and a distributed delay is investigated. We present a delay-free auxiliary ordinary differential equation system with algebraically coupled split-boundary conditions, that characterizes the solutions of the delay differential equation and is used for solution synthesis. A spectral property of the time-delay system yields a necessary and sufficient condition for existence and uniqueness of solutions to the auxiliary system, equivalently the delay differential equation. The result is a tractable analytic solution framework to the delay differential equation.

The inverse eigenvalue problem of a graph: Multiplicities and minors

The inverse eigenvalue problem of a given graph G is to determine all possible spectra of real symmetric matrices whose off-diagonal entries are governed by the adjacencies in G. Barrett et al. introduced the Strong Spectral Property (SSP) and the Strong Multiplicity Property (SMP) in [Generalizations of the Strong Arnold Property and the minimum number of distinct eigenvalues of a graph. Electron. J. Combin., 2017]. In that paper it was shown that if a graph has a matrix with the SSP (or the SMP) then a supergraph has a matrix with the same spectrum (or ordered multiplicity list) augmented with simple eigenvalues if necessary, that is, subgraph monotonicity. In this paper we extend this to a form of minor monotonicity, with restrictions on where the new eigenvalues appear. These ideas are applied to solve the inverse eigenvalue problem for all graphs of order five, and to characterize forbidden minors of graphs having at most one multiple eigenvalue.

Structural and electronic properties of nanosize semiconductor CeSin0/− (n = 4–20) material: A double-hybrid density functional theory investigation

Structural evolution model, HOMO-LUMO gap, relative stability, magnetic moment and spectral property of nanosize CeSin0/− (n = 4–20) semiconductor material were performed by employing double-hybrid density functional scheme. Optimized geometries for CeSin displayed that the most stable structure is Ce-substituted for a Si in the ground state of Sin+1 with n ≤ 17; Ce atom as linker connects two small silicon subclusters with n = 17–19; and Ce atom is encapsulated into cage-like Si framework with ≥20. For anion, the most stable structure of CeSin− is Ce-linked configuration with n = 8–18 excluded n = 9, and Ce atom is encapsulated into cage-like motif with n = 19–20. The spectral information was reported. The 4f electron of Ce atom in CeSin0/− does not participate in bonding, resulting the total magnetic moments of neutral and anionic CeSin0/− clusters are 2 and 1 μB, respectively. HOMO-LUMO gap, relative stability and chemical bonding analyses revealed that encapsulated configuration of CeSi20− is a “magic” cluster.

Effects of deposition temperature on optical properties of MgF2 over-coated Al mirrors in the VUV**Project supported by the West Light Foundation of the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 61805247).

Both long-term environmental durability and high reflectance of protected-Al mirrors are of great importance for developing the optical instruments in the vacuum ultraviolet (VUV) applications. In this paper, the dependence of spectral property and environmental durability of MgF2 over-coated Al mirrors using a 3-step method on deposition temperature of the outermost MgF2 layer are investigated in detail. Optics (reflectance), structure (surface morphology and crystalline), and environmental durability (humidity test) are characterized and discussed. The results show that both optical and moisture-resistant properties of MgF2 over-coated Al mirrors are dependent on MgF2 deposition temperature, and the optimal deposition temperature for the outermost MgF2 layer should be between 250 °C and 300 °C for MgF2 over-coated Al mirrors to have both reasonably high reflectance in the VUV spectral range and high moisture resistance for long lifetime applications.

Determination of the bruise degree for cherry using Vis-NIR reflection spectroscopy coupled with multivariate analysis.

Determination and classification of the bruise degree for cherry can improve consumer satisfaction with cherry quality and enhance the industry’s competiveness and profitability. In this study, visible and near infrared (Vis-NIR) reflection spectroscopy was used for identifying bruise degree of cherry in 350–2500 nm. Sampling spectral data were extracted from normal, slight and severe bruise samples. Principal component analysis (PCA) was implemented to determine the first few principal components (PCs) for cluster analysis among samples. Optimal wavelengths were selected by loadings of PCs from PCA and successive projection algorithm (SPA) method, respectively. Afterwards, these optimal wavelengths were empolyed to establish the classification models as inputs of least square-support vector machine (LS-SVM). Better performance for qualitative discrimination of the bruise degree for cherry was emerged in LS-SVM model based on five optimal wavelengths (603, 633, 679, 1083, and 1803 nm) selected directly by SPA, which showed acceptable results with the classification accuracy of 93.3%. Confusion matrix illustrated misclassification generally occurred in normal and slight bruise samples. Furthermore, the latent relation between spectral property of cherries in varying bruise degree and its firmness and soluble solids content (SSC) was analyzed. The result showed both colour, firmness and SSC were consistent with the Vis-NIR reflectance of cherries. Overall, this study revealed that Vis-NIR reflection spectroscopy integrated with multivariate analysis can be used as a rapid, intact method to determine the bruise degree of cherry, laying a foundation for cherry sorting and postharvest quality control.

Luminescence property, energy transfer and thermal stability of Sr6Ca4(PO4)6F2:Ce3+, Tb3+, Sm3+ for white light emitting diodes

Series of Sr6Ca4(PO4)6F2:Ce3+, Tb3+, Sm3+ are prepared by a high temperature solid state method. Ce3+, Tb3+ or Sm3+ single-doped Sr6Ca4(PO4)6F2 can produce blue, green and red emission under ultraviolet excitation, respectively. However, the emission intensities of Tb3+ and Sm3+ are relatively weak due to their forbidden transition. In order to achieve white light, the spectral property and decay curves of Sr6Ca4(PO4)6F2:Ce3+/Tb3+/Sm3+ are measured, not only the energy transfer of Ce3+-Tb3+, Ce3+-Sm3+ and Tb3+-Sm3+ was demonstrated, importantly, but also the single-phase white emitting phosphor Sr6Ca4(PO4)6F2:0.14Ce3+, 0.07Tb3+,0.13Sm3+ was obtained by the energy transfer.

Spectral property of SrLaAlO4 by 350 MeV 56Fe21+ ion beam irradiation

SrLaAlO4 materials irradiated with 350 MeV 56Fe21+ ions have been studied by Raman spectroscopy, Potoluminescence (PL) spectra and X-ray diffraction (XRD). A wide luminous band appeared after 56Fe21+irons irradiation; and it increase with irradiation dose. The PL peaks intensity of SrLaAlO4 crystal increased rapidly; and the peaks intensity reached the maximum threshold dose at 5 × 1010 ions/cm2. A series of relatively sharp emission peaks are caused by the transition from 2Eg to 4A2g at the spectrum of 1.82eV–2.14eV. In the oxide fluorescent material, the high level excitation transitions (4A2g → 2T2g) are parity and spin forbidden. The peaks caused by the 4A2g → 2T2g transitions is not clearly observed in many fluoride phosphors; while, after high-energy 56Fe21+ ion irradiation, the parity and spin-forbidden transitions have been observed at 2.25eV–2.48eV. It was found that the spin forbidden transition was allowed to somewhat extent due to the lattice vibration; and, the spin orbital coupling caused by mixing 4A2, 2E, 2T2 and 4T2 states.

Scenarios of local spectral property and multifunctional spin selecting for a triple quantum dot molecule: How do the bonding and antibonding orbitals contribute to the spin currents?

Molecular electronic device is considered as a promising candidate for next generation electronic component, where the basic challenge involves understanding the charge and spin transports through molecular objects. In this paper, with the help of the sophisticated numerical renormalization group technique, we study theoretically the spin selective transport in a parallel triple quantum dot molecular device pierced by a local magnetic field along z axis. Based on simplified parameters of real molecular system, we find such device acts as a multifunctional spin selector when the inter-molecule tunneling couplings are asymmetric, including two 100% polarized spin-up summits, and one 100% spin-down summit in the linear conductance. We show in detail the local density of states for the bonding and anti-boding orbitals, and attribute the spin selection to the orbital polarized Coulomb blockade effect. We demonstrate our numerical results are consistent with those estimated by the analytical techniques, including the Friedel sum rule and the energy level crossings of the isolated orbitals.

Compressive spectral imaging system for soil classification with three-dimensional convolutional neural network.

Compressive spectral imaging systems have promising applications in the field of object classification. However, for soil classification problem, conventional methods addressing this specific task often fail to produce satisfying results due to the tradeoff between the invariance and discrepancy of each soil. In this paper, we explore a liquid crystal tunable filters (LCTF)-based system and propose a three-dimensional convolutional neural network (3D-CNN) for soil classification. We first obtain a set of soil compressive measurements via a low spatial resolution detector, and soil hyperspectral images are reconstructed with improved resolution in spatial as well as spectral domains by a compressive sensing (CS) method. Furthermore, different from previous spectral-based object classification methods restricted to extract features from each type independently, on account of the potential of spectral property on individual solid, our method proposes to apply the principal component analysis(PCA) to achieve a dimensionality reduction in the spectral domain. Then, we explore a differential perception model for flexible feature extraction, and finally introduce a 3D-CNN framework to solve the multi-soil classification problem. Experimental results demonstrate that our algorithm not only is able to accelerate the ability of feature discriminability but also performs against conventional soil classification methods.

Synthesis, characterization, spectral property, Hirshfeld surface analysis and TD/DFT calculations of 2, 6-disubstituted benzobisoxazoles

An effective and clean aerobic oxidative method for the synthesis of 2,6-disubstituted benzobisoxazole using the free radical catalysis was obtained. 2, 6-Di(pyridin-4-yl)-benzo[1,2-d:4,5-d']bisoxazole was synthesized and characterized by 1H and 13C NMR spectroscopy, elemental analysis, UV–vis and emission spectroscopy, as well as by single-crystal X-ray crystallography. In the crystal structure, a self-assembled two-dimensional (2-D) layer supramolecular frameworks is formed with the help of intermolecular hydrogen bonds and π···π stacking interactions. On the basis of experimental results, a plausible reaction mechanism of 2,2′-disubstituted benzoxdiazoles with 4-methoxy-TEMPO as the catalyst is proposed. To obtain more insights into the structure and bonding, DFT calculations were performed. The obtained calculation results were compared with the X-ray diffraction data. The electronic transitions and spectral features of 5a and 5b were discussed by TD-DFT calculations. In addition, the noncovalent interactions among compounds have been also analyzed using Hirshfeld surface analysis.

Nondegeneracy, Morse Index and Orbital Stability of the KP-I Lump Solution

Using Backlund transformation, we analyze the spectral property of the KP-I lump solution. It is proved that the lump is nondegenerate and its Morse index equals one. As a consequence, we show that it is orbitally stable.

15N-NMR spectroscopic studies and investigation of spectral data property relationships of proton pump inhibitors

Isolation of a novel triterpene from the Essential oil of fresh leaves of Chromolaena odorata and its in-vitro cytotoxic activity against HepG2 cancer cell line Velliangiri Prabhu and Subban Ravi

Spectrally entangled biphoton state of cascade emissions from a Doppler-broadened atomic ensemble

We theoretically investigate the spectral property of biphoton state from the cascade emissions from a Doppler-broadened atomic ensemble. This biphoton state is spontaneously created in the four-wave-mixing process. The upper transition of the emissions lies in telecom bandwidth, which prevails in fiber-based quantum communication for low-loss transmission. We obtain the spectral function of the biphoton state in terms of superradiant decay rates of the lower transition, excitation pulse durations, and temperature of the medium. We quantify their frequency entanglement by Schmidt decomposition and find that more entangled source can be generated with longer excitation pulses, enhanced decay rates, and significant Doppler broadening. A minimally entangled biphoton source can also be located at some optimal temperature of the atoms. By tuning these parameters, this biphoton source allows spectral shaping of continuous frequency entanglement, which is useful in multimode long-distance quantum communication.