Band Decomposition Research Articles

Study of silicon surface layers modified by hydrogen plasma immersion ion implantation and oxidation

We report a study of p-Si(100) surface layers modified by plasma immersion ion implantation (PIII) and dry oxidation. This is expected to allow one to engineer near-surface layers with different thicknesses and levels of amorphization. Hydrogen ions were introduced into a shallow near-surface Si region through PIII with energy of 2 keV and doses ranging from 1013 ion/cm2 to 1015 ion/cm2. The implanted Si surface was subjected to oxidation in dry oxygen atmosphere at temperatures ranging from 700 °C to 800 °C. The optical and structural properties of the modified Si layers were studied in detail by spectroscopic ellipsometry (SE) in the IR spectral range of 300 – 4000 cm−1. The surface morphology was examined by atomic force microscopy (AFM) imaging at different scales and by fractal analysis. Through decomposition of the main Si-O bands into Gaussian peaks, different Si oxidation states were identified, suggesting non-stoichiometric oxide layer composition.

Second-order large time step wave adding scheme for hyperbolic conservation laws

This paper constructs a second-order large time step wave adding scheme (LTS-WA2) for hyperbolic conservation laws. Based on the first-order large time step wave adding scheme (LTS-WA1), a piece-wise linear reconstruction with limiter is performed on the solutions, and the band decomposition and band adding is complemented (into the discontinuity decomposition and wave adding), then the scheme is extended to second-order. The manufacture of the new scheme is simplified and written uniformly. Theoretical analyses are made for scalar cases. Numerical experiments give 11 tests which involve 1D scalar equations, 1D, 2D and 3D Euler equations. Computations show that the new scheme maintains high resolution and low dissipation of the original scheme at large CFL number, and also improves the problem of low resolution of the original scheme for rarefaction wave and contact discontinuity at small CFL number (roughly less than 2). Accuracy order is analyzed theoretically and validated using tests of 1D linear equation and 2D Burgers equation. CPU time is also compared with traditional second-order (Harten-TVD) scheme, showing that LTS-WA2 is more cost effective.

Stacking-dependent excitonic properties of bilayer blue phosphorene

Ab initio calculations in the framework of many-body perturbation theory (MBPT) are performed to calculate the electronic and optical properties of monolayer and bilayer blue phosphorene with different stacking configurations. It is found that the stacking configuration of bilayer blue phosphorene strongly affects the electronic band gap of the material. By solving the Bethe-Salpeter equation (BSE) on top of the ${G}_{0}{W}_{0}$ calculation, the binding energies, spectral positions, and band decomposition of excitons of monolayer and bilayer configurations are investigated. The most prominent two excitonic peaks of bilayers are examined in detail. Our calculations show that different stacking configurations lead to distinct interlayer interaction characteristics which lead to substantial change in the optical spectrum of bilayer blue phosphorene. Mostly intralayer and mixed interlayer excitons with quite high binding energies are obtained in bilayer blue phosphorene. Our results show that excitonic properties of ultrathin materials play an important role in tuning and improving the optoelectronic performance of two-dimensional materials.

PH-dependent cell\u2013cell interactions in the green alga Chara

Characean internodal cells develop alternating patterns of acid and alkaline zones along their surface in order to facilitate uptake of carbon required for photosynthesis. In this study, we used a pH-indicating membrane dye, 4-heptadecylumbiliferone, to study the kinetics of alkaline band formation and decomposition. The differences in growth/decay kinetics suggested that growth occurred as an active, autocatalytic process, whereas decomposition was due to diffusion. We further investigated mutual interactions between internodal cells and found that their alignment parallel to each other induced matching of the pH banding patterns, which was mirrored by chloroplast activity. In non-aligned cells, the lowered photosynthetic activity was noted upon a rise of the external pH, suggesting that the matching of pH bands was due to a local elevation of membrane conductance by the high pH of the alkaline zones of neighboured cells. Finally, we show that the altered pH banding pattern caused the reorganization of the cortical cytoplasm. Complex plasma membrane elaborations (charasomes) were degraded via endocytosis, and mitochondria were moved away from the cortex when a previously acid region became alkaline and vice versa. Our data show that characean internodal cells react flexibly to environmental cues, including those originating from neighboured cells.

ANALYSIS OF THE SEPARATION METHODS OF OPTICAL SPECTRA FOR INDIVIDUAL COMPONENTS

A comparative analysis of various methods for the decomposition of broad bands into individual components has been carried out. It is shown that the most universal are the methods of modulation spectroscopy and direct differentiation of conventional spectral characteristics, which, unlike the widely used Alentsev-Fock method, are applicable to spectra of any type (luminescence, transmission, absorption, etc.). The features and capabilities of the direct differentiation method are used to identify the structure in the emission spectra and transmission of ZnSe <Al> single-crystal substrates.

Comment on “Learning To Read Spectra: Teaching Decomposition with Excel in a Scientific Writing Course”

Recently a useful paper by Muelleman and Glaser was published in this Journal demonstrating how Microsoft Excel can be applied for band decomposition in IR and UV–Vis spectroscopy. With this communication, I intend to update the provided information, stressing the physical meaning of the results and defining some of the terms used.

Teager Energy Entropy Ratio of Wavelet Packet Transform and Its Application in Bearing Fault Diagnosis.

Kurtogram can adaptively select the resonant frequency band, and then the characteristic fault frequency can be obtained by analyzing the selected band. However, the kurtogram is easily affected by random impulses and noise. In recent years, improvements to kurtogram have been concentrated on two aspects: (a) the decomposition method of the frequency band; and (b) the selection index of the optimal frequency band. In this article, a new method called Teager Energy Entropy Ratio Gram (TEERgram) is proposed. The TEER algorithm takes the wavelet packet transform (WPT) as the signal frequency band decomposition method, which can adaptively segment the frequency band and control the noise. At the same time, Teager Energy Entropy Ratio (TEER) is proposed as a computing index for wavelet packet subbands. WPT has better decomposition properties than traditional finite impulse response (FIR) filtering and Fourier decomposition in the kurtogram algorithm. At the same time, TEER has better performance than the envelope spectrum or even the square envelope spectrum. Therefore, the TEERgram method can accurately identify the resonant frequency band under strong background noise. The effectiveness of the proposed method is verified by simulation and experimental analysis.

Spectroscopic studies of fly ash-based geopolymers

In the present work fly-ash based geopolymers with different contents of alkali-activator and water were prepared. Alkali-activation was conducted with sodium hydroxide (NaOH) at the SiO2/Na2O molar ratio of 3, 4, and 5. Water content was at the ratio of 30, 40, and 50wt% in respect to the weight of the fly ash. Structural and microstructural characterization (FT-IR spectroscopy, 29Si and 27Al MAS NMR, X-ray diffraction, SEM) of the specimens as well as compressive strength and apparent density measurements were carried out.The obtained geopolymers are mainly amorphous due to the presence of disordered aluminosilicate phases. However, hydroxysodalite have been identified as a crystalline product of geopolymerization. The major band in the mid-infrared spectra (at about 1000cm−1) is related to SiO(Si,Al) asymmetric stretching vibrations and is an indicator of the geopolymeric network formation. Several component bands in this region can be noticed after the decomposition process. Decomposition of band at 1450cm−1 (vibrations of CO bonds in bicarbonate group) has been also conducted. Higher NaOH content favors carbonation, inasmuch as the intensity of the band then increases. Both water and alkaline activator contents have an influence on compressive strength and microstructure of the obtained fly-ash based geopolymers.

Spectral band decomposition combined with nonlinear models: application to indoor formaldehyde concentration forecasting

This paper proposes a new approach for forecasting continuous indoor air quality time series and in particular the concentration of a common air pollutant in offices like formaldehyde. Forecasting is achieved through the combination of the spectral band decomposition using fast Fourier transform and nonlinear time series modeling. Two nonlinear models have been tested: a threshold autoregressive (TAR) model and a Chaos dynamics-based modeling. This study shows the benefit of the Fourier decomposition coupled with nonlinear modeling of each extracted component, compared to forecasting applied directly on the raw data. Both TAR and Chaos dynamics models are able to reproduce nonlinearities, with slightly better performance in the case of the second model. These hybrid models provide good performance on forecast time horizon up to 12 h ahead.

Local Structure of Li+ in Concentrated Ethylene Carbonate Solutions Studied by Low-Frequency Raman Scattering and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods.

Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+···TFSA-, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+···TFSA- ion pair were observed at ν = 168-177 and 202-224 cm-1, respectively. Detailed structural properties of solvated Li+ and Li+···TFSA- contact ion pair were derived from the least-squares fitting analysis of first-order difference function, ΔLi(Q), between neutron scattering cross sections observed for 6Li/7Li isotopically substituted 10 and 25 mol % *LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+···O(EC) distance and Li+···O(EC)═C(EC) bond angle are determined to be 1.90 ± 0.01 Å and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC solution, the average solvation number of Li+ decreases to ca. 3 and ca. 1.5. TFSA- are directly contacted to Li+. These results agree well with the results of band decomposition analyses of isotropic Raman spectra for intramolecular vibrational modes of both EC and TFSA-.

HEART MURMURS DETECTION AND CHARACTERIZATION USING WAVELET ANALYSIS WITH RENYI ENTROPY

Phonocardiogram signals (PCGs) represent a nonstationary signal due to their complicated production. Also, during the registration they may be added with different noise and pathological murmurs. Indeed, in real situation, the heart sound signal (HSs) may present some abnormal murmur characterizing a variety of heart diseases. This work deals with the segmentation of pathological PCGs based on the Discrete Wavelet Transform (DWT) which permits signal decomposition in different frequency bands. After the decomposition step, we estimate the Renyi Entropy (RE) of the detail coefficients. Then, we apply a threshold allowing detecting the murmur of the PCGs. After the detection, we characterize the results in time–frequency domain in order to extract some features such as frequency band, peak frequency and time duration of the abnormal murmur. The validation of the method is evaluated and proved using some pathological PCGs such as: Early Aortic Stenosis (EAS), Late Aortic Stenosis (LAS), Mitral Regurgitation (MR), Aortic Regurgitation (AR), Opening Snap (OS) and Pulmonary Stenosis (PS). The method presents good results in terms of the detection and the characterization of the main components and the abnormal murmurs associated with some valves disease.

Optimal Frequency Bands for Modeling the Coupling of Structure-Borne to Underwater Sound of a Surface Vessel

In this paper, we present a method for investigating the coupling of structure-borne sound (SBS) and underwater sound (UWS) of ships based on a decomposition in optimal frequency bands. The coupling is modeled by a linear regression model for sequences of spectral power, integrated over frequency intervals and moving time windows. As part of this analysis, a novel approach to detecting frequency intervals that bear particular relevance for the relationship between SBS and UWS is introduced. Regression models are regularized by a maximum-significance constraint. Cross correlations between UWS regressands and SBS regressors seem to be promising as quantitative measures for describing the coupling between SBS and UWS time series. The method is evaluated with experimental data recorded simultaneously from fixed SBS sensors onboard the research vessel R/V PLANET and from a freely drifting buoy system during an open-sea experiment north of the Outer Hebrides, Scotland, in 2011.

Partial duality and closed 2-cell embeddings

In 2009 Chmutov introduced the idea of partial duality for embeddings of graphs in surfaces. We discuss some alternative descriptions of partial duality, which demonstrate the symmetry between vertices and faces. One is in terms of band decompositions, and the other is in terms of the gem (graph-encoded map) representation of an embedding. We then use these to investigate when a partial dual is a closed 2-cell embedding, in which every face is bounded by a cycle in the graph. We obtain a necessary and sufficient condition for a partial dual to be closed 2-cell, and also a sufficient condition for no partial dual to be closed 2-cell.

Intelligent Transient Overvoltages Location in Distribution Systems Using Wavelet Packet Decomposition and General Regression Neural Networks

Overvoltages are the main causes of damages and accidents in electric power grids. The traditional approach is to install some static protection devices that are passive and cannot identify the overvoltage types or locate where the overvoltage event occurs. In recent years, with the development of smart grids, some online overvoltage monitoring systems have been developed. However, the approaches to data processing still need further development. A novel technique for identification and location of overvoltages in power distribution systems is proposed, which uses capacitor bank energization overvoltages (CBOVs) and ground fault temporary overvoltages (TOVs) as the study cases. The wavelet packet decomposition (WPD) theory is used for frequency band decomposition, and a general regression neural network (GRNN) is used in identification and location. Simulation results based on real-world power distribution systems show that the method is accurate and fast.

PROGRAMMABLE PARALLEL FBD SIGMA DELTA ADC RECONSTRUCTION STAGE DESIGN FOR SOFTWARE DEFINED RADIO RECEIVER

Today’s bottleneck of signal processing in multistandard software defined radio (SDR) receiver is the analog-to-digital converter (ADC). Therefore, the authors present in this paper the design and simulation results of a programmable parallel frequency band decomposition (FBD) architecture for ADC. The designed parallel architecture is composed of six parallel branches based on discrete-time (DT) 4th order sigma delta modulators using single-bit quantizers. Each branch processes a sub-bandwidth of the received signal. Only needed branches are selected according to the chosen standard. The parallel sigma delta modulators’ outputs are handled by a demodulation-based digital reconstruction stage in order to provide the FBD sigma delta-based ADC output signal. The digital reconstruction stage differs from one communication standard to another. In this paper, its design is discussed for the UMTS use case. The objective is to propose a digital reconstruction design with optimized complexity. In fact, the authors propose a comparative study between some configurations of demodulation, decimation and filtering processes. Technical choices and simulation results are discussed. For UMTS use case, the proposed FBD sigma delta-based ADC architecture ensures a computed signal-to-noise ratio (SNR) over 74 dB.

In-situ micro-FTIR spectroscopic observation on the hydration process of Poria cocos

In Poria cocos, triterpene compound and polysaccharides are the main compositions. The heteropolysaccharide was identified as a linear chain of β-(1→3)-d-glucan, which has the strong water absorbing capacity. In order to investigate the effect of water on the structure of Poria cocos, which belongs to a kind of Polyporaceae, the Micro-Fourier transform infrared spectroscopy (micro-FTIR) technique has been employed with the ambient relative humidity (RH) increasing. The gained IR spectra are measured and analyzed in detail. Because of strong overlaps between some bands, the differential spectra and band decompositions have been applied to analyze the structural change. IR spectra show the transformation of hydrogen bonds with the RH. The blue shift of the CH2 bending vibration from 1417 to 1424cm−1 with the increase in RH means that the hydrogen bonds are formed between CH2 groups and water molecules at lower RH and some transferred to weak hydrogen bonds. The further study suggests that the C1OH, C2OH, and C3OH groups from polysaccharide bond formed C1OH⋯H2O, C2OH⋯H2O, and C3OH⋯H2O steady modes, respectively, with water molecules.

The effect of bulky groups on the electro-optic coefficient [formula omitted] of a pyridine-donor nonlinear optical chromophore

The effect of bulky groups attached to pyridine-donor chromophores on the electro-optic coefficient r33 of host-guest polymers was measured by modulation ellipsometry. Overall, the experimental results indicated no significant beneficial effect of the bulky groups on r33. The maximum r33 achieved was just under 6pm/V for the plain chromophore, compared with the expected 20pm/V based on the molecular properties. Decomposition of the chromophore absorption band revealed significant aggregation, with the monomer fraction estimated to be marginally less than 1/3 for all chromophores studied. We attribute the lower achieved r33 values to increased molecular aggregation.

Effect of GeO2 content on structural and spectroscopic properties of antimony glasses doped with Sm3+ ions

Antimony-based glasses with different germanium oxide content doped with Sm3+ ions have been developed. On the basis of decomposition of absorption bands (FTIR) in the mid infrared region, was determined that antimony and germanium ions are the glass-forming ions, setting up the lattice of fabricated glasses. The effect of GeO2/Sb2O3 ratio in fabricated glass doped with samarium ions on thermal, structural and luminescent properties was also investigated. Characteristic bright reddish-orange luminescence from the 4G5/2 state to the lower lying levels 6HJ with J = 5/2, 7/2, 9/2 and 11/2 with maximum intensity at the wavelength of 603 nm originating from 4G5/2 → 6H7/2 transition was observed. The asymmetry nature of molecular structure around samarium ion have been determined from intensity ratio between 4G5/2 → 6H9/2 (ED) and 4G5/2 → 6H5/2 (MD) transitions. An introduction of GeO2 to the antimony glass results in the increasing of 4G5/2 lifetime and decreasing of the orange-to-red intensity ratio, which is are related to reduction of non-briding oxygens.

A Hybrid Fast WOC (wavelet Otsu curvelet) Algorithm for Stem Cell Image Segmentation

This paper mainly concentrates on image segmentation using Wavelet, otsu and Curvelet algorithm. The existing Chan Vese model becomes complex in determining multiple images simultaneously in varying intensities. In order to increase the detection performance the WOC (wavelet Otsu curvelet) algorithm is proposed. Due to high directionality and anisotropic nature of the curvelet transform, it gives better performance at the edges and it is also applied for multi-scale edge enhancement. Wavelet transform is well suited for multi resolution. Wavelet and curvelet transforms are incorporated for sub band decomposition of frequency coefficients. Otsu algorithm has a novel approach for segmentation where thresholding is done using histogram analysis. This in turn reduces the segmentation complexity and hence the new algorithm is termed as Hybrid fast WOC algorithm.

Mixed baseband architecture based on FBD ΣΔ–based ADC for multistandard receivers

<p>This paper presents the design and simulation results of a novel mixed baseband stage for a frequency band decomposition (FBD) analog-to-digital converter (ADC) in a multistandard receiver. The proposed FBD-based ADC architecture is flexible with programmable parallel branches composed of discrete time (DT) 4<sup>th</sup> order single-bit Sigma-Delta modulators. The mixed baseband architecture uses a single non-programmable anti-aliasing filter (AAF) avoiding the use of an automatic gain control (AGC) circuit. System level analysis proved that the proposed FBD architecture satisfies design specifications of the software defined radio (SDR) receiver. In this paper, the authors focus on the Butterworth AAF filter design for a multistandard receiver. Besides, theoretical analysis of the reconstruction stage for UMTS test case is discussed. It leads to a complicated system of equations and high digital filter orders. To reduce the digital reconstruction stage complexity, the authors propose an optimized digital reconstruction stage architecture design. The demodulation-based digital reconstruction stage using two decimation stages has been implemented using MATLAB/SIMULINK. Technical choices and performances are discussed. The computed signal-to-noise ratio (SNR) of the MATLAB/SIMULINK FBD ADC model is equal to at least 75 dB which satisfies the dynamic range required for UMTS signals. Next to hardware implementation with quantized filters coefficients, the authors implemented their proposition in VHDL in a SysGen environment. The measured SNR of the hardware implementation is equal to 74.08 dB which satisfies the required dynamic range of UMTS signals.</p>