Miracle-dz/UniFAR-FTUs huggingface dataset:
Subspace Clustering Constrained Sparse NMF for Hyperspectral Unmixing

As one of the most important information of hyperspectral images (HSI), spatial information is usually simulated with the similarity among pixels to enhance the unmixing performance of nonnegative matrix factorization (NMF). Nevertheless, the similarity is generally calculated based on the Euclidean distance between pairwise pixels, which is sensitive to noise and fails in capturing subspace information of hyperspectral data. In addition, it is independent of the NMF framework. In this article, we propose a novel unmixing method called subspace clustering constrained sparse NMF (SC-NMF) for hyperspectral unmixing to more accurately extract endmembers and correspond abundances. First, the nonnegative subspace clustering is embedded into the NMF framework to learn a similar graph, which takes full advantage of the characteristics of the reconstructed data itself to extract the spatial correlation of pixels for unmixing. It is noteworthy that the similar graph and NMF will be simultaneously updated. Second, to mitigate the influence of noise in HSI, only the $k$ largest values are retained in each self-expression vector. Finally, we use the idea of subspace clustering to extract endmembers by linearly combining of all pixels in spectral subspace, aiming at giving a reasonable physical significance to the endmembers. We evaluate the proposed SC-NMF on both synthetic and real hyperspectral data, and experimental results demonstrate that the proposed method is effective and superior by comparing with the state-of-the-art methods.
The Impact of Local Oscillator Frequency Jitter and Laser Linewidth to Ultra High Baud Rate Coherent Systems

Through theoretical analysis and simulation, we investigate the system impact due to a sinusoidal jitter tone and the resultant local oscillator (LO) laser linewidth requirement in ultra-high baud rate and long distance coherent optical systems. We also carried out experiments in 64 Gbaud, dual-polarization (DP)-16 QAM systems to verify the theoretical analysis and simulation. We have also obtained a jitter interference tolerance mask to qualify LO lasers. A jitter tone with a frequency lower than ∼1 MHz has a higher tolerance since it generally causes constant frequency or phase shift, which can be tracked by a receiver DSP. For a jitter tone with a frequency higher than ∼1 MHz, the tolerance becomes much tighter since the tone will affect laser lineshape and induce equalizer-enhanced phase noise (EEPN). Consequently, a jitter tone in the higher frequency region could severely affect the system performance. Theoretical analysis and numerical result illustrate that EVM<sup>2</sup> due to the effect of laser linewidth and a sinusoidal jitter tone is proportional to the weighted sum of <inline-formula><tex-math notation="LaTeX">$[ \Delta \nu \times B_{s}\times \text{L}] $</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$[ \Delta f_{pp}\times B_{s}\times \text{L}] ^{2}$</tex-math></inline-formula>, where Δν is the laser linewidth, <inline-formula><tex-math notation="LaTeX">$B_{s}$</tex-math></inline-formula> is the baud rate, <inline-formula><tex-math notation="LaTeX">$\Delta f_{pp}$</tex-math></inline-formula> is the laser peak-to-peak frequency deviation due to a sinusoidal jitter tone, and <italic>L</italic> is the fiber transmission length. This result is applicable for all orders of QAM constellations. The implication to future 100 Gbaud and beyond systems is delineated.
Wave condensation with weak disorder versus beam self-cleaning in multimode fibers

Classical nonlinear waves exhibit a phenomenon of condensation that results from the natural irreversible process of thermalization toward the Rayleigh-Jeans equilibrium spectrum. Wave condensation originates in the divergence of the thermodynamic equilibrium Rayleigh-Jeans distribution, which is responsible for the macroscopic population of the fundamental mode of the system. Several recent experiments revealed a remarkable phenomenon of spatial organization of an optical beam that propagates through a graded-index multimode optical fiber (MMF), a phenomenon termed beam self-cleaning. Our aim in this article is to provide some physical insight into the mechanism underlying optical beam self-cleaning through the analysis of wave condensation in the presence of structural disorder inherent to MMFs. We consider experiments of beam self-cleaning where long pulses are injected and populate many modes of a 10-20m MMF, for which the dominant contribution of disorder originates from polarization random fluctuations (weak disorder). On the basis of the wave turbulence theory, we derive nonequilibrium kinetic equations describing the random waves in a regime where disorder dominates nonlinear effects. The theory reveals that the presence of a conservative weak disorder introduces an effective dissipation in the system, which is shown to inhibit wave condensation in the usual continuous wave turbulence approach. On the other hand, the experiments of beam-cleaning are described by a discrete wave turbulence approach, where the effective dissipation induced by disorder modifies the regularization of wave resonances, which leads to an acceleration of condensation that can explain the effect of beam self-cleaning. By considering different models of weak disorder in MMFs, we show that a model where the modes experience a partially correlated noise is sufficient to accelerate the thermalization, whereas a fully mode-correlated noise does not lead to a dissipation-induced acceleration of condensation. The simulations are in quantitative agreement with the theory, and evidence an effect of beam-cleaning even in a regime of moderate weak disorder. At the leading order linear regime, random mode coupling among degenerate modes (strong disorder) can enforce thermalization and condensation. The analysis also reveals that the effect of beam cleaning is characterized by a partial repolarization as a natural consequence of the condensation process. In addition, the discrete wave turbulence approach explains why optical beam self-cleaning has not been observed in step-index multimode fibers.
Fuzzy Sampled-Data Control for DFIG-Based Wind Turbine With Stochastic Actuator Failures

The stabilization of fault-tolerant control problem for the doubly fed induction generator (DFIG)-based wind turbine (WT) model has been investigated with stochastic actuator faults by incorporating a Takagi–Sugeno (T–S) fuzzy technique. To depict such stochastic actuator faults, the proposed model is incorporated with Markovian switching parameters for denoting various faulty modes. Besides, a novel fault-tolerant fuzzy switching control with sampled-data (SD) inputs has also been employed for eliminating the stochastic faults so that the stabilization of the system and an optimal ${\mathsf {H}}_{\infty }$ level could be ensured simultaneously. Furthermore, the stability conditions are derived by employing fuzzy Lyapunov–Krasovskii functionals (LKFs), whose matrices are membership dependent functions. Finally, the proposed control method for the stabilization problem is validated through a numerical simulation performed on the DFIG-based WT model.
Grid criteria for numerical simulation of hypersonic aerothermodynamics in transition regime

Grid is an important factor in numerical simulation of hypersonic aerothermodynamics. This paper introduces three criteria for determining grid size in the transition flow regime when using the computational fluid dynamics (CFD) method or the direct simulation Monte Carlo (DSMC) method. The numerical relationship between these three criteria sizes is deduced according to the one-dimensional fluid theory. Then, the relationship is verified using the CFD method to simulate the flow around a two-dimensional cylinder. At the same time, the dependence of simulation accuracy on grid size in the CFD and DSMC methods is studied and the mechanism is given. The result shows that the simulation accuracy of heat flux especially depends on the normal grid size next to surfaces, where the $Re_{\mathit{cell},w}$ criterion and the $\unicode[STIX]{x1D706}_{w}$ criterion based on local parameters are applicable and equivalent, while the $Re_{\mathit{cell},\infty }$ criterion based on the free-stream parameter is only applicable under the assumption of constant viscosity coefficient and constant temperature wall conditions. On the other hand, the trend of the heat flux changing with grid size obtained by CFD and DSMC is exactly the opposite. Therefore, the grid size must be strictly satisfied with the grid criteria when comparing CFD with DSMC and even the hybrid DSMC with Navier–Stokes method.
Hydrodynamic and control optimization for a heaving point absorber wave energy converter

The thesis aims at studying the non-linear performance of a designed 1/50 scale point absorber wave energy converter (PAWEC) in heave motion. In particular, designs of the PAWEC geometry and control strategy are considered to optimize the power capture. Experimental and computational uid dynamics (CFD) data are provided to evaluate the studies. Speci cally, this thesis can be summarized into four parts. Firstly, a numerical wave tank (NWT) is constructed in a commercial CFD package ANSYS/LS-DYNA. The main objective associated with the NWT is to closely reproduce the physical wave-PAWEC interactions. To achieve this, physical experimental data from two speci ed WECs are provided to verify the capability of the NWT. One of the devices is the PAWEC designed at University of Hull. Free decay, excitation force and water splashing tests, etc., are conducted. As a result, the developed NWT is validated to be capable of representing the non-linear behaviors of the PAWEC compared with the costly physical experiments. The second part focuses on investigating the extent to which the non-linear hydrodynamic characteristics of the PAWEC need to be considered. By comparing with the CFD data from a series of tests, a non-linear mathematical modeling involving a quadratic viscous term is veri ed. The results show that the non-linear PAWEC behavior for the conditions of large oscillations (e.g., near resonance or at a large wave heights) can only be predicted realistically by considering a correct viscous effect. This study highlights that the linear counterpart derived from potential ow code ANSYS/AQWA fails to describe the PAWEC behavior and would mislead the control strategy and power take-o (PTO) designs. Additionally, the results show that the viscous damping is signi cantly larger than the inviscid radiation damping for the at-bottom cylindrical heaving PAWEC.
Using multisource data and the V-I-S model in assessing the urban expansion of Riyadh city, Saudi Arabia

ABSTRACT This paper examines the application of remote sensing, based on the Vegetation-Impervious surface-Soil (V-I-S) model and spatial metrics, in an urban analysis for promoting sustainability and understanding urban growth theory. In order to improve the accuracy of land-cover classification, spectral angle mapping (SAM), spectral mixture analysis (SMA) and band ratioing were applied on satellite images for land-cover classification and comparison of the discrimination efficiency of these techniques. For the SMA, subsets of the Landsat (2, 3, 4, 5, and 7) and ASTER (1, 2, and 3N) images were selected. After endmember extraction and purification, the Bayesian probability of each component was computed and used for spectral unmixing. The classified images of different years were compared to analyze the changes in land-use and spatial pattern using V-I-S, a form of percentage of landscape (PLAND) and annualized urban sprawl index (AUSI). The result indicates that the performance of band ratioing (69% accuracy) is not as good as that of SAM (75%) and SMA (86%) in discriminating between vegetation and agricultural land. It is concluded from the land-use analysis that the growth dynamics substantiate the urban theory of diffusion and coalescence and urban growth management strategies have not been completely successful.
Real-Time Shading with Phong BRDF Model

Bu makalede, goruntu tabanli isiklandirma altinda izotropik Iki Yonlu Yansima Dagilim Fonksiyonlari (BRDFs) olusturmak icin gercek zamanli yeni bir BRDF isiklandirma ara yuzu onermekteyiz. Onerdigimiz BRDF isiklandirma arayuzu kullanicilarin Phong BRDF modelinin parametrelerini degistirerek yeni BRDF’ler olusturmasina musaade etmektedir. BRDF isiklandirma arayuzumuzun implementasyonu Shadertoy araciligiyla programlanabilir grafik donanimindan faydalanmaktadir ve cevresel isiklandirma altinda bir objenin uzerinde malzemenin gercek zamanli olarak gosterimini saglamaktadir.
Ultrathin and durable open metamaterials for simultaneous ventilation and sound reduction

We report an ultrathin and durable open metamaterial capable of both fluid passage and noise insulation at low frequencies. The proposed open metamaterial, denoted as the perforated and constrained acoustic metamaterial (PCAM), contains a large orifice in each unit cell. An impedance-based model was established to investigate the working mechanism and acoustic performances of the PCAM and was then verified by measurements in a sound impedance tube. With only a thickness of 1.5 mm (0.19% of wavelength), a PCAM sample exhibits a sound transmission loss of 20 dB at 430 Hz. This high-efficiency soundproof feature under the ventilation condition is attributed to the interferences of the two wave fields between the orifice area and the plate area in the near-field. The PCAM may have potential applications in limited spaces requiring high-efficiency ventilation and long-time service.We report an ultrathin and durable open metamaterial capable of both fluid passage and noise insulation at low frequencies. The proposed open metamaterial, denoted as the perforated and constrained acoustic metamaterial (PCAM), contains a large orifice in each unit cell. An impedance-based model was established to investigate the working mechanism and acoustic performances of the PCAM and was then verified by measurements in a sound impedance tube. With only a thickness of 1.5 mm (0.19% of wavelength), a PCAM sample exhibits a sound transmission loss of 20 dB at 430 Hz. This high-efficiency soundproof feature under the ventilation condition is attributed to the interferences of the two wave fields between the orifice area and the plate area in the near-field. The PCAM may have potential applications in limited spaces requiring high-efficiency ventilation and long-time service.
Statistical Convolutional Neural Network for Land-Cover Classification From SAR Images

Synthetic aperture radar (SAR) images inherently present random and complex spatial patterns, which makes the land-cover classification from SAR images a challenging task. A convolutional neural network (CNN) has been applied to the land-cover classification. However, the statistical properties of an SAR image have not yet been explicitly considered by CNN for feature extraction. To address this problem, this letter presents a statistical CNN (SCNN) for land-cover classification from SAR images, which enables the representation of learning and statistical analysis to be implemented with a unified framework. In the proposed SCNN, the distribution of mid-level primitive features, extracted by representation learning, is characterized by their first- and second-order statistics. These statistics are used to fit the land-cover representations, which encode the statistical properties of the SAR image in the feature space. Experiments on the TerraSAR-X data demonstrate that the SCNN is effective and efficient for the land-cover classification from SAR images.
Broadband, Integrated, Micron-Scale, All-Optical Si3N4/VO2 Modulators with pJ Switching Energy

All-optical, non-resonant, in-plane Si<inf>3</inf>N<inf>4</inf>/VO<inf>2</inf> modulators offering 6.4 pJ switching energy, 1.68 dB/μm extinction ratio, and 4 μm length are demonstrated. This is obtained with broadband control (800-1000 nm) and signal (1500-1600 nm) wavelengths.
A novel impedance source fed H-type flying capacitor multilevel inverter

In this paper, simulation using MATLAB/SIMULINK is performed withbipolar triangular fixed amplitude multi-carrier Phase Disposition (PD)PWM strategy with sine wave, Third Harmonic Injection, 60 degree Pulse Width Modulation and stepped wave reference for the chosen impedance Source based H-Type flying capacitor Multilevel Inverter (ISBH-Type FCMLI). The root means square value of the fundamental component and Total Harmonic Distortion of the output voltage which are the most important performance indices for the chosen inverter topologies are evaluated presented and compared for various references through duty ratios. From the simulation results it is observed that for various references the THD is almost similar but the root mean square value in terms of voltage is more for THI, 60 degree PWM and stepped wave reference with phase disposition strategy. The results are obtained for ma (amplitude modulation index) < 1 (under amplitude modulation index), ma=1 (normal amplitude modulation index) and ma > 1 (over amplitude modulation index).
On Finite-Duration Convergent Attracting Laws

This article concerns studies on finite-time systems (FTSs), which are expected for high-level system synthesis. An FTS usually obeys an attracting law (AL), under which the dynamics of the FTS is governed. This article probes into the analysis of finite-duration convergence of the power-rate ALs, and especially on the estimation for the bound of their settling time functions, without selecting the transition state to be one. It is shown that the settling time is a function of the initial state, and the value of the function varies with the initial state. The existence of the upper bound of the function assures that the duration over which the settling time varies is finite with respect to the initial state. The estimate depends on the transition state, revealing that the bound on the settling time cannot be determined by a certain value, as different transition states are chosen. The optimal transition state in certain sense is acquired in this article, and the comparison is made between the existing estimation and the optimal one. Furthermore, we concern ourselves with the two-phase AL (TPAL) also without fixing the transition state, for which we are able to give an accurate bound of its settling time function. To illustrate the usefulness of the TPAL, we present a finite-duration learning control approach which utilizes the merits of the exiting control methods in coping with both time-varying parametric and nonparametric uncertainties.
On the differences between helicity and chirality

The optical helicity and the optical chirality are two quantities that are used to describe chiral electromagnetic fields. In a monochromatic field, the two quantities are proportional to one another, and the distinction between the two is therefore largely unimportant. However, in a polychromatic field, no such proportionality holds. This paper explicitly examines both the helicity and chirality densities in various polychromatic fields: the superposition of two circularly polarised plane-waves of different frequencies, a chirped pulse of circularly polarised light, and an ‘optical centrifuge’ consisting of two oppositely chirped circularly polarised beams of opposite handedness. Even in the simplest case, there can be significant qualitative differences between the two quantities—they may have opposite signs, or one may be zero while the other is not. The origin of these differences lies in the different frequency scaling of the two quantities, which is made relevant by the presence of multiple frequency components in the fields.
A new unified input‐to‐state stability criterion for impulsive stochastic delay systems with Markovian switching

In this paper, the problems of the input‐to‐state stability (ISS), the integral input‐to‐state stability (iISS), the stochastic input‐to‐state stability (SISS) and the eλt(λ>0)‐weighted input‐to‐state stability (eλt‐ISS) are investigated for nonlinear time‐varying impulsive stochastic delay systems with Markovian switching. We propose one unified criterion for the stabilizing impulse and the destabilizing impulse to guarantee the ISS, iISS, SISS and eλt‐ISS for such systems. We verify that when the upper bound of the average impulsive interval is given, the stabilizing impulsive effect can stabilize the systems without ISS. We also show that the destabilizing impulsive signal with a given lower bound of the average impulsive interval can preserve the ISS of the systems. In addition, one criterion for guaranteeing the ISS of nonlinear time‐varying stochastic hybrid systems under no impulsive effect is derived. Two examples including one coupled dynamic systems model subject to external random perturbation of the continuous input and impulsive input disturbances are provided to illustrate the effectiveness of the theoretic results developed.
Preface to the papers on ‘Credit risk modelling’

Publisher Rights Statement: This is the peer reviewed version of the following article: Crook, J, Bellotti, T, Mues, C & Fuertes, A 2019, 'Preface to the papers on ‘Credit risk modelling’', Journal of the Royal Statistical Society: Series A, vol. 182, no. 4, pp. 1139-1142, which has been published in final form at https://doi.org/10.1111/rssa.v182. 4 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Effects of high intensity interval exercise versus steady state exercise with similar energy expenditures on Epoc

The purpose of the study was to determine whether steady state exercise (SSE) or high intensity interval exercise (HIIE) would better improve energy expenditure (EE) during 90 minutes of excess post exercise oxygen consumption (EPOC) while attempting to match EE between both exercise protocols. We also wanted to examine physiological changes during post exercise measurements, which included VO2, RER, VE and HR. Twelve males aged between 19 and 24 were assigned to the SSE and HIIE conditions. A VO2max and a 30s-all-out sprint set at 150% of maximum workload was performed on a cycling ergometer interspersed by 5 minutes to ensure sufficient recovery time. Participants randomly completed SSE or HIIE followed by 90 minutes of EPOC. A gross efficiency (GE) of 18% was used in order to best quantify the anaerobic attributable EE during the HIIE in order to estimate total EE. Our results indicate that the HIIE expended less EE than SSE and from our pre-test EE estimations (p<0.05). With that being said, HIIE was able to generate a greater EE during EPOC in comparison to SSE, while utilizing more grams of fat during post exercise measurements (p<0.05). There was no significant difference between both protocols when adding exercise and EPOC EE. Physiological markers such as VO2 (L.min-1), VE (L.min-1) and HR were significantly greater in HIIE during EPOC. To conclude, our findings indicate that HIIE is a time efficient workout able to expend more EE, utilize more fat and have greater physiological responses during EPOC when compared to SSE.
Normalized Hierarchical SVM

We present improved methods of using structured SVMs in a large-scale hierarchical classification problem, that is when labels are leaves, or sets of leaves, in a tree or a DAG. We examine the need to normalize both the regularization and the margin and show how doing so significantly improves performance, including allowing achieving state-of-the-art results where unnormalized structured SVMs do not perform better than flat models. We also describe a further extension of hierarchical SVMs that highlight the connection between hierarchical SVMs and matrix factorization models.