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In this study, the influence of ceramic shield characteristics, including thickness and geometry, on the transmission spectrum and electron density measurements of a ceramic shield cutoff probe (CSC) was investigated to measure high-density or process plasma. Through electromagnetic simulations and circuit modeling, we examined the measurement characteristics of the CSC based on different ceramic shield geometries. When the ceramic shield is sufficiently thin, it does not affect the CSC wave transmission characteristics. However, for a thick ceramic shield, a cutoff frequency shift of up to 3% toward the lower side can occur. This shift is attributed to the electrical properties of the ceramic material, which can function as a parasitic capacitor. In addition, when fabricating a CSC, depending on the shape of the ceramic shield or the method used to couple it with the CSC body, a cutoff frequency shift can occur toward the lower side. The simulation results were validated through experiments, revealing a cutoff frequency shift toward the lower side of up to 18.0% in the simulations and up to 11.6% in the experiments. The findings of this study could assist in high-density or processing plasma measurements using cutoff probes. [ABSTRACT FROM AUTHOR]

It is important to understand the dynamics of red blood cells (RBCs) in blood flow. This requires the formulation of coarse-grained RBC models that reproduce the hydrodynamic properties of blood accurately. One of the models that successfully reproduces the rheology and morphology of blood has been proposed by Fedosov et al. [Comput. Methods Appl. Mech. Eng. 199, 1937-1948 (2010)]. The proposed RBC model contains several parameters whose values are determined by either various experiments or physical requirements. In this study, we developed a new method of determining parameter values precisely from the fluctuations of the RBC membrane. Specifically, we studied the relationship between the spectra of the fluctuations and model parameters. Characteristic peaks were observed in the spectra, whose peak frequencies were dependent on the parameter values. In addition, we investigated the spectra of the radius of gyration. We identified the peaks originating from the spring potential and the volume-conserving potential appearing in the spectra. These results lead to the precise experimental determination of the parameters used in the RBC model., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

Mobility spectrum analysis (MSA) is a process of recovering the spectrum of carrier mobilities in an electronic material from a magnetic-field-dependent Hall measurement. This paper first presents a set of useful general properties of MSA that are true for all MSA methods. One such property is that Hall data can be classified as either "physical," with at least one spectrum of carrier mobilities that exactly fits the data, or "unphysical," where no mobility spectra exactly fit the data and the analysis must find approximate solutions. Almost all experimental Hall data collected at seven or more magnetic fields are slightly unphysical. The closest approximate solution for such unphysical data is always a set of discrete-carrier mobilities. A new method for multicarrier MSA is presented to display the likely properties of the discrete carriers as two-dimensional spectra vs both mobility and carrier density instead of one-dimensional spectra vs only mobility, as in previous methods. Measurement uncertainties are included as a fundamental part of the analysis so that the user can easily view the resultant uncertainty in the derived carrier properties. A separate method is also presented for reliably determining a smooth, high-entropy spectrum of carrier mobilities, which is constructed as the maximum-entropy linear combination of discrete-carrier solutions to the Hall data. An example using calculated Hall data corresponding to acoustic phonon scattering shows that the technique could potentially be used to measure the continuous mobility distributions that result from different scattering mechanisms. [ABSTRACT FROM AUTHOR]

We present an integral density method for calculating the multifractal dimension spectrum for nucleon distribution in atomic nuclei. This method is then applied to analyze the non-uniformity of density distribution in several typical types of nuclear matter distributions, including the Woods-Saxon distribution, halo structure, and tetrahedral α clustering. The subsequent discussion provides a comprehensive and detailed exploration of the results obtained. The multifractal dimension spectrum shows a remarkable sensitivity to the density distribution, establishing it as a simple and novel tool for studying the distribution of nucleons in nuclear multibody systems., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

A method to perform spectrum analysis on low power signals between 0.1 and 10 THz is proposed. It utilizes a nanoscale antiferromagnetic tunnel junction (ATJ) that produces an oscillating tunneling anisotropic magnetoresistance, whose frequency is dependent on the magnitude of an evanescent spin current. It is first shown that the ATJ oscillation frequency can be tuned linearly with time. Then, it is shown that the ATJ output is highly dependent on matching conditions that are highly dependent on the dimensions of the dielectric tunneling barrier. Spectrum analysis can be performed by using an appropriately designed ATJ, whose frequency is driven to increase linearly with time, a low pass filter, and a matched filter. This method of THz spectrum analysis, if realized in the experiment, will allow miniaturized electronics to rapidly analyze low power signals with a simple algorithm. It is also found by simulation and analytical theories that for an ATJ with a 0.09 μ m 2 footprint, spectrum analysis can be performed over a 0.25 THz bandwidth in just 25 ns on signals that are at the Johnson–Nyquist thermal noise floor. [ABSTRACT FROM AUTHOR]

In this study, two individual dam-break induced surge impact pressure datasets are analyzed using the Hilbert–Huang transform method, which is capable of adaptively decomposing the impulsive, oscillatory, and quasi-steady pressure components from the measured raw pressure data. Time-frequency characteristics of these three pressure components are analyzed. Applying the empirical mode decomposition method, the intrinsic mode function (IMF) series extract the local periodic features, including the impulsive and oscillatory pressures, whereas the non-periodic residual series reveal the general variation characteristics of the surge impact pressure, i.e., the quasi-steady pressure. Subsequently, the Hilbert spectrum analysis is conducted to the individual IMF series. The impulsive pressure components are found to be high-frequency (over 5 Hz in this study), and the oscillatory pressure components have frequency ranging from 20 to 60 Hz. It is confirmed that the quasi-steady pressure contributes the dominant amount of the total surge impact energy in both the bottom impact zone and the upper outer zone on the wall. The impulsive pressure-induced instantaneous energy is large in the bottom impact zone shortly after the impact, whereas the oscillatory pressures only lead to a small local instantaneous energy peak. In addition, the impulsive pressure impulses are calculated, which are more test-stable than those of peak pressures. These findings indicate that impulsive pressures induced by surge impact can be rather destructive, especially near the toe of the structure, thus deserve particular attention in the safe design of coastal structures. [ABSTRACT FROM AUTHOR]

A detailed consideration of the discrete mobility-spectrum analysis (DMSA) method and its application to transport studies in HgCdTe is given. First, a brief review of the methods of the analysis of field dependences of the Hall coefficient and conductivity in HgCdTe-based structures with a multi-carrier mobility spectrum is presented. The advantages and drawbacks of these methods, which include original mobility-spectrum analysis by Beck and Anderson, multi-carrier fitting and iterative approach by Dziuba and Górska, and the later developments of these techniques, are considered. The properties of the envelope of the mobility spectrum are analyzed, and the specifics of DMSA are presented. Analysis of some magnetic-field B dependences of conductivity tensor components σxx(B) and σxy(B) presented in the literature is performed with DMSA, and the results are compared to those obtained with other methods. [ABSTRACT FROM AUTHOR]

A high-resolution absorption spectrum of the S1–S0 transition of free-base phthalocyanine was observed and analyzed with improved reliability. The spectrum, with a partially resolved rotational structure, was obtained by using the buffer-gas cooling technique and a single-mode tunable laser. Our new analysis reveals that the S 1 ← S 0 0 0 0 band belongs to the a-type transition, where the electronic transition moment aligns parallel to the NH–HN direction, allowing the assignment of the S1 state to 1B3u. These results agree with a prior study using supersonic expansion and are well supported by theoretical calculations. Interestingly, the rotational constant B in the S1 state, which is often smaller than that in the ground state for typical molecules, was found to be slightly larger than that in the S01Ag state. This suggests a change in the character of π bonds with the electronic excitation. [ABSTRACT FROM AUTHOR]

It is known that rare-earth-based pyrochlore oxide may accommodate the well-defined two-in-two-out spin ice state with its tetrahedral unit. Low-energy excitation is argued to favor the highly concerned monopole state which attracts essential attention. However, such an excitation cannot be directly tracked and imaged using advanced characterizations, raising challenges to our understanding of the physics of monopoles. In this work, we propose an improved two-dimensional artificial spin ice structure on the Shastry–Sutherland lattice to restore the degeneracy of realistic pyrochlore systems. Such a structure avoids the deficiency of inequivalent nearest and next-nearest exchanges in the planar quadrate unit, which, however, is equivalent to the tetrahedral unit of realistic pyrochlore oxides. Therefore, this spin ice model restores state degeneracy that is lost in conventional planar artificial spin ice structures, representing an improved simulator of real spin ice systems. Our careful investigations of such improved structures reveal the rich physics of spin ice excitations, including the phase diagram, which allows different ordered phases and interesting critical phase transitions between spin ice phase I and phase II. Energy spectrum analysis suggests that restoration of state degeneracy substantially reduces monopole excitation energy, resulting in a striking monopole emergency at the critical point. Furthermore, the emergent spin dimer phase in this improved model allows high-density monopole excitations and exhibits high-correlated monopole fluid states. [ABSTRACT FROM AUTHOR]

The (sub-)millimeter wave spectrum of the non-rigid CH2OH radical is investigated both experimentally and theoretically. Ab initio calculations are carried out to quantitatively characterize its potential energy surface as a function of the two large amplitude ∠H1COH and ∠H2COH dihedral angles. It is shown that the radical displays a large amplitude torsional-like motion of its CH2 group with respect to the OH group. The rotation–torsion levels computed with the help of a 4D Hamiltonian accounting for this torsional-like motion and for the overall rotation exhibit a tunneling splitting, in agreement with recent experimental investigations, and a strong rotational dependence of this tunneling splitting on the rotational quantum number Ka due to the rotation–torsion Coriolis coupling. Based on an internal axis method approach, a fitting Hamiltonian accounting for tunneling effects and for the fine and hyperfine structure is built and applied to the fitting of the new (sub)-millimeter wave transitions measured in this work along with previously available high-resolution data. 778 frequencies and wavenumbers are reproduced with a unitless standard deviation of 0.79 using 27 parameters. The N = 0 tunneling splitting, which could not be determined unambiguously in the previous high-resolution investigations, is determined based on its rotational dependence. [ABSTRACT FROM AUTHOR]

We present structural models for three different amyloid fibril polymorphs prepared from amylin20-29 (sequence SNNFGAILSS) and amyloid-β25-35 (Aβ25-35) (sequence GSNKGAIIGLM) peptides. These models are based on the amide C=O bond and Ramachandran ψ-dihedral angle data from Raman spectroscopy, which were used as structural constraints to guide molecular dynamics (MD) simulations. The resulting structural models indicate that the basic structural motif of amylin20-29 and Aβ25-35 fibrils is extended β-strands. Our data indicate that amylin20-29 forms both antiparallel and parallel β-sheet fibril polymorphs, while Aβ25-35 forms a parallel β-sheet fibril structure. Overall, our work lays the foundation for using Raman spectroscopy in conjunction with MD simulations to determine detailed molecular-level structural models of amyloid fibrils in a manner that complements gold-standard techniques, such as solid-state nuclear magnetic resonance and cryogenic electron microscopy., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

This study explores the effects of bubble distribution parameters on the noise spectrum of bubble clusters through direct numerical simulations across volume fractions from 0.005% to 40%. Three types of bubble cluster distributions were analyzed: layered (uniformly sized bubbles with layered positioning), random (uniformly sized bubbles with random positioning), and lognormal (log-normally distributed bubble sizes with random positioning). Using the Ffowcs Williams–Hawkings (FW–H) method, we evaluated the sound pressure levels of the clusters. We found that the arrangement of bubble positions has little impact on the collapse times of bubble clusters. At volume fractions greater than 0.5%, bubble size also shows minimal effect on collapse times. However, when the volume fraction is less than 0.5%, the collapse times gradually approach the collapse time of the largest bubble in the cluster in a free field. Noise spectrum analyses showed that the arrangement of bubble positions significantly influences the noise spectra within the volume fraction range of 0.5%–25%, but has minimal impact outside this range. Importantly, the distribution of bubble sizes shows negligible effects on the noise spectrum, demonstrated by the nearly identical sound pressure level octave decay rates for random and lognormal clusters at the same volume fractions. This consistency can be mathematically described by the fitting formula: decay rate (dB/octave) = 18.192 × α − 0.047 −16.264. These findings enhance our understanding of the noise spectrum across varied bubble cluster distributions and provide new insights into the mechanisms of cavitation noise. [ABSTRACT FROM AUTHOR]

The gas-phase rotational spectrum from 8 to 750 GHz and the high-resolution infrared (IR) spectrum of pyridazine (o-C4H4N2) have been analyzed for the ground and four lowest-energy vibrationally excited states. A combined global fit of the rotational and IR data has been obtained using a sextic, centrifugally distorted-rotor Hamiltonian with Coriolis coupling between appropriate states. Coriolis coupling has been addressed in the two lowest-energy coupled dyads (ν16, ν13 and ν24, ν9). Utilizing the Coriolis coupling between the vibrational states of each dyad and the analysis of the IR spectrum for ν16 and ν9, we have determined precise band origins for each of these fundamental states: ν16 (B1) = 361.213 292 7 (17) cm−1, ν13 (A2) = 361.284 082 4 (17) cm−1, ν24 (B2) = 618.969 096 (26) cm−1, and ν9 (A1) = 664.723 378 4 (27) cm−1. Notably, the energy separation in the ν16-ν13 Coriolis-coupled dyad is one of the smallest spectroscopically measured energy separations between vibrational states: 2122.222 (72) MHz or 0.070 789 7 (24) cm−1. Despite ν13 being IR inactive and ν24 having an impractically low-intensity IR intensity, the band origins of all four vibrational states were measured, showcasing the power of combining the data provided by millimeter-wave and high-resolution IR spectra. Additionally, the spectra of pyridazine-dx isotopologues generated for a previous semi-experimental equilibrium structure (reSE) determination allowed us to analyze the two lowest-energy vibrational states of pyridazine for all nine pyridazine-dx isotopologues. Coriolis-coupling terms have been measured for analogous vibrational states across seven isotopologues, both enabling their comparison and providing a new benchmark for computational chemistry. [ABSTRACT FROM AUTHOR]

We investigated the effect of the sheath around the probe tips on the transmission spectrum of a cutoff probe using an electromagnetic simulation and a circuit model. Our results show that the width of the sheath can change the transmission spectrum, which can affect the absolute value of the electron density. In a real-world cutoff probe structure, this effect may become apparent in a low-density plasma or when a high bias voltage is applied to the plasma. The key factor is capacitance, which contains the sheath component. In the case of a low-density plasma, the change in the sheath capacitance of the sheath region contributes to the shift in the resonant frequency. For thick sheath widths, at least a 5% discrepancy can occur between the actual plasma frequency and the measurement owing to variations in the capacitance, particularly the sheath components surrounding the probe. We expect that this study will facilitate reduction in the measurement error and uncertainty in microwave cutoff probe measurements, particularly when applied to low-density plasma measurements. [ABSTRACT FROM AUTHOR]

A flat-cutoff sensor installed on the chamber wall or chuck allows precise measurement of the plasma density in real time, even with a wafer placed on the sensor. However, a few studies have been conducted on the measurement characteristics in an environment where a wafer containing a metal layer is placed on a sensor. In this study, we investigated the effect of wafers containing metal layers on flat-cutoff sensor measurements using circuit models and experiments. The metal layer in the wafer shifts the cutoff frequency up to four times higher, and the degree of shift depends on the plasma density. The relationship between the shift in the cutoff frequency and plasma density can be interpreted as the ratio of the plasma inductance to that of the metal layer from the circuit model of the flat-cutoff sensor. The calculation results were verified experimentally using wafers containing Al and Ti metal layers. As a result, measurement was found to be possible even when a wafer containing a metal layer was placed on a flat-cutoff sensor, and these results can improve the measurement accuracy of the flat-cutoff sensor for the real-time plasma measurement. [ABSTRACT FROM AUTHOR]

A powerful method for mobility spectrum analysis is presented, based on Bryan’s maximum entropy algorithm. The Bayesian analysis central to Bryan’s algorithm ensures that we avoid overfitting of data, resulting in a physically reasonable solution. The algorithm is fast, and allows the analysis of large quantities of data, removing the bias of data selection inherent in all previous techniques. Existing mobility spectrum analysis systems are reviewed, and the performance of the Bryan’s algorithm mobility spectrum (BAMS) approach is demonstrated using synthetic data sets. Analysis of experimental data is briefly discussed. We find that BAMS performs well compared to existing mobility spectrum methods.© 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Accurate and stable wind power prediction is the basis of wind energy planning, dispatching, and control in the generation and conversion of the wind power generation industry. A new nonlinear hybrid model, singular spectrum analysis (SSA)-temporal neural network (TCN) is proposed to improve the accuracy of wind power sequence prediction. This method introduces SSA, which decomposes the original wind power sequence into four parts: trend, primary detail components, secondary detail components, and noise. The experiment is conducted under the three conditions of no noise removal, only noise removal, and decomposing original sequences without noise into several components to verify that SSA does help improve the model performance. Moreover, this paper adopts a new TCN network instead of the current most advanced Long Short-Term Memory (LSTM) network. It has a longer actual memory range and is better able to cope with the gradient disappearance. In order to study the advancement of the TCN, the experimental part also includes the performance comparison between the TCN and the LSTM network, as well as the ablation experiment of the TCN. Finally, multi-step prediction is conducted to further demonstrate the fitting ability of the TCN, SSA-TCN, and LSTM network. The results show that (a) the SSA-TCN has the best predictive performance among the involved models; (b) SSA can significantly improve the prediction accuracy; (c) the performance of the TCN is better than that of the LSTM network because of the extended causal convolution structure of the TCN and the residual blocks. [ABSTRACT FROM AUTHOR]

Two-dimensional infrared Raman spectroscopy is a powerful technique for studying the structure and interaction in molecular and biological systems. Here, we present a new implementation of the simulation of the two-dimensional infrared Raman signals. The implementation builds on the numerical integration of the Schrödinger equation approach. It combines the prediction of dynamics from molecular dynamics with a map-based approach for obtaining Hamiltonian trajectories and response function calculations. The new implementation is tested on the amide-I region for two proteins, where one is dominated by α-helices and the other by β-sheets. We find that the predicted spectra agree well with experimental observations. We further find that the two-dimensional infrared Raman spectra at least of the studied proteins are much less sensitive to the laser polarization used compared to conventional two-dimensional infrared experiments. The present implementation and findings pave the way for future applications for the interpretation of two-dimensional infrared Raman spectra.

In this study, we consider the connection of the hydrodynamic force with vortex shedding behind a stationary sphere in an unbounded fluid at several Reynolds numbers, covering the range of critical transition from plane-symmetric to non-symmetric flow. A principal spectrum analysis (PSA) is employed/proposed to obtain the spectral representation (SR) modes for each time-varying force coefficient; this enables us to identify (i) one single characteristic frequency at R e = 300 , 350, and 380, i.e., the fast frequency f V S which represents the frequency of vortex shedding and (ii) two characteristic frequencies at R e = 390 , 400, and 420: one is the first fast frequency f 1 = f V S , representing the frequency of vortex shedding, and the other is the second fast frequency f 2 , representing the frequency of side oscillations of the vortex flow in the transverse flow direction. In the situations of the latter set of Reynolds numbers, the SR modes indicate that not only the strength but also the phase of shed vortex varies slightly at each successive vortex shedding, and most notably, we have identified rotation of the vorticity pattern in the near wake about the central axis. The PSA-SR mode analysis reveals that these three vortex activities all co-operate at the integer multiples of the greatest common-divisor of the two characteristic frequencies ( f 1 , f 2 ). In other words, the intricate subtlety of vortex shedding behind a stationary sphere can well be uncovered through the PSA-SR mode analysis for establishing the close connections between the force coefficients and the vorticity activities behind the sphere. The present work represents a sequel to our previous study: A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds numbers [Lu et al., "A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds number," Phys. Fluids 35(5), 053606 (2023)], where we initially proposed the PSA-SR analysis to establish the connections between the force coefficients and the vortex shedding of the circular cylinder under pre-, sub-, and normal synchronization. [ABSTRACT FROM AUTHOR]

Presents information pertaining to an improved quantitative mobility spectrum analysis (i-QMSA) involving the magnetic-field-dependent Hall characterization, while determining the free electron and hole densities and mobilities. What the mixed-conduction effects frequently exert; Introduction of the empirical procedures for manipulating the mobility spectra; Application of a fully automated computer implementation of the improved QMSA.

The D5Π–X5Δ (0,0) band of vanadium hydride at 654 nm has been recorded by laser excitation spectroscopy and represents the first analyzed spectrum of VH in the gas phase. The molecules were generated using a hollow cathode discharge source, with laser-induced fluorescence detected via the D5Π–A5Π (0,0) transition. All five main (ΔΩ = ΔΛ) subbands were observed as well as several satellite ones, which together create a rather complex and overlapped spectrum covering the region 15 180–15 500 cm−1. The D5Π state displays the effects of three strong local perturbations, which are likely caused by interactions with high vibrational levels of the B5Σ− and c3Σ− states, identified in a previous multiconfigurational self-consistent field study by Koseki et al. [J. Phys. Chem. A 108, 4707 (2004)]. Molecular constants describing the X5Δ, A5Π, and D5Π states were determined in three separate least-squares fits using effective Hamiltonians written in a Hund's case (a) basis. The fine structure of the ground state is found to be consistent with its assignment as a σπ2δ, 5Δ electronic state. The fitted values of its first-order spin–orbit and rotational constants in the ground state are A = 36.5378 15 c m − 1 and B = 5.7579(13) cm−1, the latter of which yields a bond length of R 0 = 1.7212 2 Å. This experimental value is in good agreement with previous computational studies of the molecule and fits well within the overall trend of decreasing bond length across the series of 3d transition metal monohydrides. [ABSTRACT FROM AUTHOR]

Examines free electron and hole densities and mobilities in semiconductors with the use of an optimized quantitative mobility spectrum analysis (QMSA) technique. Resistivities and Hall coefficients at different temperature ranges; Electron and hole QMSA spectra corresponding to the conductivity tensor components.

To study the initiation and development of interfacial electrical damage in multi-layer dielectrics, an aging test of 3-layer polyimide films was conducted under pulsed voltage with a repetitive frequency of 500 Hz and a maximal amplitude of 30 kV. The variation in the damage morphology with the number of applied pulses was analyzed by a statistical method. The circuit current and partial discharge at different aging stages was measured, and the Fourier transform infrared spectrum analysis results of the aged and unaged sample regions were compared. The results demonstrate that the partial discharge in the dielectric interface gap, which is unavoidable in manufacturing, is the main cause of damage. It initiates from the interface and grows into the interior of the dielectric with the application of pulses. When there are no macroscopic defects on dielectric films, damage presents a punctiform morphology. The damage process can be divided into the following three stages: surface roughening damage, steady growth stage of damage points, and pre-breakdown stage. Differing from dielectrics without macroscopic defects, dielectrics with original void defects present transverse dendritic damage channels that initiate from the edge of the defect. [ABSTRACT FROM AUTHOR]

Exploring very-large-scale motions (VLSMs) in open channel flows (OCFs) is crucial for comprehensively understanding material transport and energy exchange. While previous studies focused on OCFs in ideal flumes with simple boundaries, this paper presents large eddy simulation (LES) results on the existence and scale characteristics of VLSMs in complex river morphologies with the Minjiang River in southwestern China as a case study. This research demonstrates that the OpenFOAM-based LES model is capable of accurately reconstructing the time-averaged flow field and providing instantaneous velocity data that capture VLSMs with sufficient resolution. Spectrum analysis of the streamwise fluctuating velocity shows that VLSMs are present in the straight segment of the river, with streamwise wavelengths approximately (16–22) times the water depth but are absent in the bend and confluence segments due to the suppression by secondary currents. This article validates the effectiveness of LES in examining the characteristics of VLSMs in natural rivers, thereby laying a good foundation for further studies on the impacts of such structures on sediment transport and pollutant dispersion. [ABSTRACT FROM AUTHOR]

The Mg-42Zn-7Y alloy, which contains an icosahedral quasicrystalline phase, was prepared using a conventional solidification process. The fracture toughness of this quasicrystalline phase in the Mg-42Zn-7Y alloy was nondestructively detected using in situ tensile and indentation techniques. The alloy exhibited a tensile strength of 99.17 MPa and an elongation of 3.9%. Microscopic observation and energy spectrum analysis confirmed the high-contrast lamellar structure as the quasicrystalline phase. Ultimately, under cyclic loading during indentation, the fracture toughness of the quasicrystalline phase was determined to be 35.08 MPa m0.5. The findings of the present study provided an effective basis for the determination of the fracture toughness of the quasicrystalline phase. [ABSTRACT FROM AUTHOR]

As one of the popular coherent Raman scattering techniques, stimulated Raman scattering (SRS) has made significant progress in recent years, especially in label-free biological imaging. Polarization provides an additional degree of freedom to manipulate the SRS process. In previous studies, only linearly polarized SRS was fully investigated, in which both pump and Stokes laser fields are linearly polarized. Here, we theoretically analyzed the SRS process excited by two circularly polarized laser fields and then experimentally demonstrated it by taking a spherical symmetric CH 4  molecule as a model system. The experimental results are in good agreement with the theoretical ones. It is shown that circularly polarized SRS (CP-SRS) has unique characteristics different from linear polarization. When the handedness of circular polarization states of two laser fields is the same, CP-SRS further suppresses the depolarized vibrational band while keeping the polarized band almost unaffected. On the other hand, when the handedness is opposite, CP-SRS enhances the depolarized band while suppressing the polarized band. Therefore, the CP-SRS not only allows us to resolve the symmetry of vibrational modes but also can enhance vibrational contrast based on symmetry selectivity by suppressing or enhancing the signal from a specific vibrational mode. These results will have potential applications in improving chemical selectivity and imaging contrast as well as spectral resolution SRS microscopy. In addition, the CP-SRS has the ability to determine the depolarization ratio ρ and identify the overlapping Raman bands.

It is shown that applying isotropic quantitative mobility analysis to anisotropic materials can lead to drastic qualitative errors, even in the case of modest anisotropy. The procedure may provide not only wrong values for carrier mobilities and concentrations but even a wrong number of carrier species. [ABSTRACT FROM AUTHOR]

Stick-spectrum expressions for electronic two-dimensional (2D) photon-echo (PE) signal of a generic multi-level system are presented and employed to interrelate oscillations in individual peaks of 2D PE signal and the underlying properties (eigenstates and coherent dynamics) of excitonic or vibronic systems. When focusing on the identification of the origin of oscillations in the rephasing part of 2D PE it is found, in particular, that multiple frequencies in the evolution of the individual peaks do not necessarily directly reflect the underlying system dynamics. They may originate from the excited-state absorption contribution to the signal, or arise due to multi-level vibrational structure of the electronic ground state, and represent a superposition of system frequencies, while the latter may evolve independently. The analytical stick-spectrum predictions are verified and illustrated by numerical calculations of 2D PE signals of an excitonic trimer and of a displaced harmonic oscillator with unequal vibrational frequencies in the two electronic states. The excitonic trimer is the smallest excitonic oligomer where excited-state absorption may represent a superposition of excited-state coherences and significantly influence the phase of the observed oscillations. The displaced oscillator is used to distinguish between the frequencies of the ground-state and of the excited-state manifolds, and to demonstrate how the location of a cross peak in 2D pattern of the PE signal "predetermines" its oscillatory behavior. Although the considered models are kept as simple as possible for clarity, the stick-spectrum analysis provides a solid general basis for interpretation of oscillatory signatures in electronic 2D PE signals of much more complex systems with multi-level character of the electronic states. [ABSTRACT FROM AUTHOR]

Searching for efficient surface-enhanced Raman scattering (SERS) substrates remains a challenge. In this study, we used metal-organic chemical vapor deposition to directly grow a pitted a-plane GaN thin film, subsequently covered by a thin Au layer (∼25 nm), for use as a SERS substrate, without the need for any additional etching or lithography process. The SERS substrate containing these micrometer-sized pits provided a low limit of detection (∼10 -9 M) for Rhodamine 6G (R6G), with a high enhancement factor (4.27 × 10 8 ) relative to normal Raman spectroscopy. Furthermore, Raman spectral mapping indicated that most of the R6G molecules were concentrated in the pits, enhancing the localization of the probe molecules for further analysis. The same molecular localization phenomenon was also effective for polar methylene blue but not for nonpolar paraffin. The molecular aggregation became more ambiguous upon increasing the thickness of the Au layer, suggesting that the polarity of the Ga and N atoms in the pits was responsible for the efficient aggregation of the polar R6G molecules, which could be potentially beneficial for biomedical detection.

Fluidized beds are favored for their high efficiency in material and heat exchange. However, a limited understanding of two-phase flow dynamics leads to the construction of larger equipment and makes precise control of fluidized beds challenging. Since it is challenging to eliminate the impact of signal noise in experiments, which arises from the inconsistency of particles and measurement methods, a square fluidized bed model has been established for numerical analysis of the chaotic characteristics of two-phase flow. The bubble distribution in the fluidized bed was observed more clearly, the bubble behavior was combined with the chaotic parameters, and the two flow states and the chaotic state were analyzed comprehensively. The results show that the bubbles present a regular arrangement parallel to the diagonal in the early stage of bubbling. At the same time, smooth reconstructed attractors are observed. The increase in fluidization wind speed will make the attractors rough until collapse. The bubbling bed experiences bifurcation into chaos as the fluidization wind speed increases, and we can see this process through the pressure signal. The system state cannot be distinguished by correlation dimension or K-entropy alone. Comprehensive consideration of a variety of chaotic features can be used as a method to identify two-phase flow chaotic states. The method used in this paper combines bubble behavior, pressure signal, power spectrum analysis, phase space reconstruction, correlation dimension, and Kolmogorov entropy to distinguish the state of the fluidized bed more accurately. [ABSTRACT FROM AUTHOR]

The nonlinear theory of radial correlation reflectometry (RCR) predicts that the cross correlation function of a signal follows a Gaussian distribution with a cutoff separation, where the correlation length is determined by both the turbulence amplitude and its radial correlation length. In contrast, phase spectrum analysis provides information solely on the turbulence amplitude. This work describes the possibility of applying both signal analysis methods and demonstrates that turbulence amplitude and radial correlation length can be simultaneously measured using RCR diagnostics in the nonlinear regime. [ABSTRACT FROM AUTHOR]