Critical Point Model Research Articles

Composition-dependent optical, dielectric and d-orbital electron characteristic of high-throughput horizontal composition gradient Li1-xMgxTi2O4 combinatorial film

The unique physical properties of LiTi2O4 and MgTi2O4 attracted extensive research interest in various fields, including new type batteries and high-temperature superconductors. However, the intricate mechanism governing the d-orbital electron within this system still awaits further excavation. Herein, we employed the combinatorial laser molecular beam epitaxy technique to fabricate a high-quality composition-spread Li1-xMgxTi2O4 film and evaluated its structure, composition, surface morphology and phonon modes by X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and Raman scattering spectroscopy. The optical constants and dielectric properties of diverse microregions with varying Li/Mg content over a wide spectral range (189–1658 nm) were measured nondestructively using spectroscopic ellipsometry, revealing the composition-dependent optical properties of Li1-xMgxTi2O4. By fitting the second derivative spectra (d2ε/dE2) using the standard critical point model, five transitions within the detected spectral range were observed. Combining previous analyses and first-principles calculation, we attribute the critical points to crystal field (CF) transition 4A2 →4T1 originating from the spin state of tetrahedral Li/Mg ions, the binding of Ti-related pairs and electron transitions between O-2p to Ti-3d orbits. This exploration of the precise structure of the d-metal band provides a positive reference for the regulation and application of relevant devices.

Relative variation between γ coordinate and the potential of the Bohr Hamiltonian producing X(4) from Z(4)

In this paper, four degree of freedom γ-rigid solutions of the Bohr Hamiltonian at γ 0 = π/6 are obtained. The relative variation between γ and the potential of the Hamiltonian is employed to retrieve X(4) from Z(4). γ is varied in the interval 0 ≤ γ 0 ≤ π/6 while the potential minimum, β 0, is varied in the interval 0 ≤ β 0 ≤ ∞ . Very small value of β 0 yields Z(4) while a large value of β 0 produces X(4) and SU(3) is realized at β 0 ≈ ∞ . The solutions at γ 0 = 0 correspond to X(4) while the solutions at γ 0 = π/6 yield Z(4): a dynamic link between Z(4) and X(4) critical point symmetries (CPSs) has been provided. The fact that γ and β 0 of the potential play the same role in the dynamical link between Z(4) and X(4) shows that β 0 also measures the departure from axial symmetry to other shapes as γ does. In the experimental realization of the model, the conformation of 192Pt and 194Pt isotopes to the present Z(4) model shows that the present model can be employed in the description of triaxial rotors and γ-soft isotopes. 194Pt is shown to be the best choice for triaxial rigid rotor candidacy. 130Xe, a critical point isotope, which belongs to the class of γ-soft nuclei, reproduces this present model very well in all the states. Consequently, this present model can serve as a critical point model. 40,0 − β 0 distribution for Z(4) and X(4) candidate isotopes shows a significant interval between the two models where the T(4) CPS lies.

An expansion effect based pseudo-boiling critical point model for supercritical CO<sub>2</sub>

Heat transfer deterioration (HTD) is one of the important issues in the study of supercritical fluid (SCF) heat transfer. However, when the SCF crosses the pseudo-critical point, the none-quilibrium process occurs in liquid, so SCF is very complicated. Recently, the existence of SCF pseudo-boiling on a macro scale has sparked controversy. There is still no unified understanding of the mechanism of gas-like and liquid-like transition affecting heat transfer. In this work, it is assumed that SCF has a macroscopic phenomenon similar to subcritical flow boiling. By analogy with subcritical boiling heat transfer, a boiling critical point model is proposed to describe the HTD in supercritical CO<sub>2</sub>. Our study reveals that the HTD caused by pseudo-boiling only occurs under large temperature gradient, which makes the superheated liquid-like layer cover the wall, and the gas-like and liquid-like may present different distribution forms, thus changing the heat transfer characteristics. When the wall temperature is higher than the pseudo-critical temperature and the enthalpy of the fluid layer covering the wall exceeds a certain value, the HTD may occur. The proposed theoretical model can explain the experimental results well, and the prediction accuracy of heat transfer correlation considering pseudo-boiling is greatly improved. In this work, the connection between supercritical heat transfer and subcritical heat transfer is established theoretically, which provides a new idea for studying the deterioration of SCF heat transfer, thus enriching the theory of supercritical heat transfer.

3D face recognition algorithm based on deep Laplacian pyramid under the normalization of epidemic control

Under the normalization of epidemic control in COVID-19, it is essential to realize fast and high-precision face recognition without feeling for epidemic prevention and control. This paper proposes an innovative Laplacian pyramid algorithm for deep 3D face recognition, which can be used in public. Through multi-mode fusion, dense 3D alignment and multi-scale residual fusion are ensured. Firstly, the 2D to 3D structure representation method is used to fully correlate the information of crucial points, and dense alignment modeling is carried out. Then, based on the 3D critical point model, a five-layer Laplacian depth network is constructed. High-precision recognition can be achieved by multi-scale and multi-modal mapping and reconstruction of 3D face depth images. Finally, in the training process, the multi-scale residual weight is embedded into the loss function to improve the network’s performance. In addition, to achieve high real-time performance, our network is designed in an end-to-end cascade. While ensuring the accuracy of identification, it guarantees personnel screening under the normalization of epidemic control. This ensures fast and high-precision face recognition and establishes a 3D face database. This method is adaptable and robust in harsh, low light, and noise environments. Moreover, it can complete face reconstruction and recognize various skin colors and postures.

Anisotropic dielectric function, direction dependent bandgap energy, band order, and indirect to direct gap crossover in α-(AlxGa1−x)2O3 (≤x≤1)

Mueller matrix spectroscopic ellipsometry is applied to determine anisotropic optical properties for a set of single-crystal rhombohedral structure α-(AlxGa1−x)2O3 thin films (0 ≤ x ≤ 1). Samples are grown by plasma-assisted molecular beam epitaxy on m-plane sapphire. A critical-point model is used to render a spectroscopic model dielectric function tensor and to determine direct electronic band-to-band transition parameters, including the direction dependent two lowest-photon energy band-to-band transitions associated with the anisotropic bandgap. We obtain the composition dependence of the direction dependent two lowest band-to-band transitions with separate bandgap bowing parameters associated with the perpendicular (bEg,⊥ = 1.31 eV) and parallel (bEg,|| = 1.61 eV) electric field polarization to the lattice c direction. Our density functional theory calculations indicate a transition from indirect to direct characteristics between α-Ga2O3 and α-Al2O3, respectively, and we identify a switch in band order where the lowest band-to-band transition occurs with polarization perpendicular to c in α-Ga2O3 whereas for α-Al2O3 the lowest transition occurs with polarization parallel to c. We estimate that the change in band order occurs at approximately 40% Al content. Additionally, the characteristic of the lowest energy critical point transition for polarization parallel to c changes from M1 type in α-Ga2O3 to M0 type van Hove singularity in α-Al2O3.

Optical property and pseudogap study of FeSe thin films on different substrates

Among Fe-based superconductors, β-FeSe has received a lot of attention from researchers because it has unique and complex physical properties under the simplest crystal structure. In this paper, FeSe films were prepared on CaF2, LiF, and SrTiO3 substrates by pulsed laser deposition (PLD) technique with the same growth parameters. The superconducting transition temperatures of the samples were tested at 11.44 K, 10.91 K, and 5.4 K, respectively, by applying electrodes on the surface of the films. We used X-ray diffraction (XRD) and atomic force microscopy (AFM) to obtain the crystal structure and roughness of the samples, respectively. Two phonons (A1g, B1g) of different samples were found in the Raman spectra, indicating that different strain effects were introduced by the substrates. In order to accurately reflect the properties of FeSe films, a dispersion model with Lorentz + Drude oscillations was established. The physical properties such as complex refractive index and scattering rate were analyzed by spectroscopic ellipsometry (SE) inversion. Meanwhile, we adopted the standard critical point (SCP) model to fit the second derivatives of the imaginary part of the dielectric function and calculate the transition energy. In combination with the first-principles calculation based on density functional theory (DFT), the physical origin of the transition peaks was obtained. On this basis, we propose a new method to acquire the FeSe pseudogap by making the difference between the two transition energies observed by SE. The experimental result indicates that pseudogap of FeSe film is negatively correlated with the superconducting transition temperature. This work can offer a new perspective for the prediction of the superconductivity of FeSe and a reference for the application of FeSe on different substrates.

Origin of the anomalous properties in supercooled water based on experimental probing inside “no-man's land”

Austen Angell conducted pioneering work that opened up the field of supercooled water by observing the temperature dependent divergence of the thermodynamic response functions. Many different scenarios have been proposed as the origin of the anomalous properties and now it has become possible to test the various hypotheses in experimental studies of bulk supercooled water at conditions where ice crystallization becomes extremely rapid. Through the usage of x-ray lasers, ultrafast measurements could be conducted, as the sample is rapidly brought to the extreme conditions on time scales preceding ice formation. In particular the experimental observation of the existence of a liquid-liquid transition at positive pressure, one phase behavior at atmospheric conditions at temperatures down to 228 K, and the existence of maxima in several properties at 230 K indicative of a Widom line, are only consistent with the proposed liquid-liquid critical point model as the origin of the anomalous properties. • Unexpected behavior of the heat capacity started the field of supercooled water. • Experimental exploration of no-man's land tests hypotheses. • The liquid-liquid transition and critical point scenario consistent with the data.

Crop damage, economic losses, and the economic damage threshold for northern corn leaf blight

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum (E. turcicum), is one of the most common maize (Zea mays L.) diseases worldwide. To determine the crop damage and economic losses caused by NCLB and propose economic damage thresholds (EDTs), 16 field experiments were performed for seven crop seasons (2010–11 to 2016–17) during different naturally occurring outbreaks of NCLB in central-northern Córdoba province, Argentina. NCLB severity gradients were generated by applying different fungicides and doses at different growth stages to seven susceptible (S) and nine moderately susceptible (MS) hybrids. Plots were arranged in a completely randomized block design with four replications. Severity was evaluated at the R4 growth stage by estimating the percentage of leaves affected; and grain yield in kg ha−1 per plot was also estimated. A critical-point yield model was fitted with NCLB severity and the EDT and the action damage threshold (ADT) were calculated. The management regime generated disease gradients with severities ranging between 3.2 and 33.1. There was a statistically significant negative correlation between severity and yield (R2 = 0.52; p = 0.001). On average, for each percentage point increase, in NCLB severity, 20.15 kg t−1 of yield were lost; MS and S hybrids were 23.88 kg t−1 and 15.21 kg t−1, respectively. The mean EDT was 1.09% of severity and the mean ADT was 0.88%. Furthermore, the mean economic losses were 243.6 USD ha−1 [122.0–353.2]. The generated information can play a role in optimizing the use of fungicides for NCLB control, reducing disease control costs, and protecting the ecological environment of farmlands.

Near-bandgap optical properties of Al1−x In x N thin films grown on a c-plane freestanding GaN substrate

We investigated the relationship between the optical constants and localized states near the band-edge in high-quality crystalline Al1−x In x N alloys, with an indium content x ranging from 0.12 to 0.22, grown on a c-plane freestanding GaN substrate. Optical constants were obtained by spectroscopic ellipsometry. The tanΨ and cosΔ spectra were fitted by the Adachi’s critical-point (AC) model. The effects of the near-band-edge localized states on the optical constants were characterized by the spectral broadening factor γ, which was obtained by the AC model. The γ increased with increasing x and this tendency also confirmed by the γ obtained by the photoluminescence excitation (PLE). The bandgap energies obtained by the AC model agree well with those obtained by the PLE. It is suggested that the indium-related near-band-edge localized states cause the spectral broadening of the refractive index and extinction coefficient spectra in Al1−x In x N alloys.

Grain boundary segregation transitions and critical phenomena in binary regular solutions: A systematics of complexion diagrams with universal characters

A systematics of grain boundary (GB) segregation transitions and critical phenomena has been derived to expand the classical GB segregation theory. Using twist GBs as an example, this study uncovers when GB layering vs. prewetting transitions should occur and how they are related to one another. Moreover, a novel descriptor, normalized segregation strength (ϕseg), is introduced. It can represent several factors that control GB segregation, including strain and bond energies, as well as misorientation for small-angle GBs (in a mean-field approximation), which had to be treated separately in prior models. In a strong segregation system with a large ϕseg, first-order layering transitions occur at low temperatures and become continuous above GB roughing temperatures. With reducing ϕseg, the layering transitions gradually merge and finally lump into prewetting transitions without quantized layer numbers, akin to Cahn's critical-point wetting model. Furthermore, GB complexion diagrams with universal characters are constructed as the GB counterpart to the classical exemplar of Pelton-Thompson regular-solution binary bulk phase diagrams.

수산물 산지위판장의 HACCP 모델 개발

An auction house at the place of origin is the endpoint of the production stage of fishery products and the starting point of the distribution stage. It plays a key role in the distribution of fishery products as large quantities of the product are collected here, and it is where the price is determined. The primary sanitation management in the auction house may affect the freshness and quality of the products for subsequent distribution and processing. Nevertheless, this aspect is mostly neglected. In addition, the current laws are ineffective as the announced sanitation management standards are not presented in a specific and obvious manner, and thus, they are rarely utilized in the field. Therefore, this study aims to develop a hazard analysis and critical control points model for an auction house at the place of origin, which is a food safety management system with considerable recognition and reliability, to ensure that high-quality and safe fishery products are supplied to the consumer.

Ellipsometric study of the optical properties of TlInSeS layered crystal

TlInSeS optical properties at photon energy ranges from 0.96 to 5.06 eV have been determined by means of variable-angle spectroscopic ellipsometry (VASE). This energy range contains the fundamental band gap. The measured pseudo-dielectric ε(E) spectrum depicts different peaks. The spectrum is analyzed with reference of two inter-band transitions models that postulated for crystal semiconductors, explicitly, critical point parabolic band (CPPB) and standard critical-point (SCP) models. It is noted that both dielectric function models illustrates the plausible agreement with the experiment ε(E) spectra. The optical properties of the present sample as extension coefficient refractive index absorption coefficient and the normal-reflectance, are investigated. The elemental composition of TlInSeS system has been confirmed by means of Energy Dispersive X-ray fluorescence spectrometer (EDXRF).

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry

Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid-liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.

Analysis of the optical constants and bandgap energy in Al1-x In x N alloys grown on a c-plane freestanding GaN substrate by using spectroscopic ellipsometry

The optical constants and bandgap energy (E g) of semiconductors, characterized by spectroscopic ellipsometry (SE), are highly affected by the applied model dielectric function (MDF). In this study, we investigated the optical constants and E g in low indium content (x) Al1-x In x N alloys grown on a c-plane freestanding GaN substrate by using SE, and their applied MDF dependence was investigated. The tanΨ and cosΔ spectra, in a photon energy range of 1.5–5.0 eV, of high-quality crystalline Al1-x In x N alloys were well fitted by Adachi’s critical-point (ACP) model. The ACP model exhibited better spectral fitting results than did the Tauc–Lorentz model, which has often been adopted for Al1-x In x N alloys. The accuracy of the E g values obtained by the ACP model was confirmed by optical reflectance measurements. It is suggested that the ACP model is a suitable MDF for recent high-quality crystalline Al1-x In x N alloys as well as other III-nitride semiconductors.

A critical-point yield model to appraise the damage caused to soybean by white-mold

A model to estimate the damage caused by white mold to soybean yield from experimental field data gathered during the summer season of 2009-10 was generated. Six soybean cultivars were grown on six sites of the Cerrados region, resulting in a total of nine separate experiments. The gradient of disease intensity (plant stem incidence) and yield was generated through the application of different fungicides and rates three times over the course of the season. The disease incidence in plant stems was evaluated at the R1, R5.2 and R5.5 growing stages. Manual harvest at the physiological ripening stage was followed by grain drying, threshing, and cleaning. Finally, grain yield was estimated in kg/ha, and regression analysis was performed. Nine linear equations representing the damage function were generated. The mean damage function was y = - 6.7 x + 1,000, where y represents grain yield normalized to 1,000 kg/ha and x represents WM incidence in plants. To appraise the damage caused by various disease intensities, these models should first be validated. Damage coefficients may be used to determine the level of economic damage.

Controlling of Microbial Hazards for Potato Chips manufacturing through Food Safety Management System (ISO 22000)

Food safety is a fundamental public health concern, and achieving a safe supply poses major challenges for organization involved in the food chain, so numbers of foodborne hazards must be properly analyzed, assessed and managed to meet growing and increasingly complex sets of global food chain. Proper implementation of food hygiene principle across the food chain in conjunction with hazards analysis and critical control points system will ensure food safety. In this study, Microbiological hazards were controlled for two fried potato chips production lines, processing & packaging for each line starting from raw materials receiving, storage…etc, where microbiolgical tests were carried out at all stages of product production on raw materials received, water used in the manufacturing process, microbiological swabs were taken from the equipment and surfaces of the processing and packaging lines as well as the hands of the workers, in short the stages of potato chips production are as follows: Potatoes receiving & storage ==> Washing ==> Peeling ==> Manual sorting ==> slicing ==> washing and remove starch ==> Frying ==> Optical & Manual sorting ==> Seasoning ==> Packaging and print coding ==> Palletizing. Based on actual conditions in the plant a specific Hazard analysis and critical control point (HACCP) model has been developed to ensure safe product, reduce and support the traditional inspection and quality procedure of fried potato chips product through food safety management system ( FSMS-ISO 22000), the prerequisite programs (PRPs), operational prerequisite programs (OPRPs), critical control point (CCP), critical limits, preventive, monitoring procedures and corrective actions have been designed in this HACCP plan.

Comprehensive Study on Numerical Aspects of Modified Lorentz Model-Based Dispersive FDTD Formulations

Finite-difference time domain (FDTD) has been widely used to analyze electromagnetic wave interaction with dispersive media. It is of great necessity to incorporate a dispersion model into FDTD formulation for electromagnetic wave analysis of dispersive media. Recently, it was reported that the modified Lorentz model can cover Debye, Drude, Lorentz, critical point, and quadratic complex rational function models. In this work, it is illustrated that the modified Lorentz model can also cover the complex-conjugate pole-residue model which is one of the most popular dispersion models. Modified Lorentz-based dispersive FDTD has not been thoroughly studied, especially for numerical aspects. In this work, we investigate auxiliary differential equation (ADE)-FDTD formulations for the modified Lorentz model based on electric flux density (D), current (J), or polarization (P). We perform a comprehensive study on memory requirement, the number of arithmetic operations, numerical stability, and numerical permittivity for the above three ADE-FDTD formulations. In addition, the bilinear transformation (BT) is incorporated into modified Lorentz-based FDTD formulations and it will be shown that the utilization of the BT can lead to better performance in terms of numerical stability and numerical accuracy. Numerical examples are used to demonstrate our work.

Electronic and optical properties of layered chalcogenide FeIn2Se4

We investigated the spectral-dependent dielectric function and temperature-dependent bandgap energy of layered chalcogenide FeIn2Se4 crystals. The critical-point energy and Lorentzian broadening were analyzed by fitting second-derivative spectra using the standard critical point model. The temperature effect of the bandgap energy was analyzed based on an analytical model considering both thermal lattice expansion and electron–phonon interactions. We also extensively analyzed the temperature dependence of absorption tails and identified their possible origins. The dielectric functions and absorption coefficient in the photon-energy range of 0.75–4.75 eV were obtained. The results also showed that optical phonon modes associated with the electron–phonon interactions could be closely related to the average phonon energy.

Study the optical properties of Pr2CuO4 thin films with different Tc0 via spectroscopic ellipsometry

In this work, we primarily present spectroscopic ellipsometry (SE) study on Pr2CuO4 (PCO) thin films, a parent compound of electron-doped cuprate superconductors. The c-aixs orientation films with various superconducting transition temperature Tc0 were prepared by a chemical method, which are single phase and good crystallinity verified by x-ray diffraction. The imaginary part of dielectric function (εi) of PCO was investigated by SE using a four-layer optical model in the photon energy range from 1.55 to 4.13 eV. Through fitting the second derivative spectra of εi via critical point model, we find that the charge-transfer gap exists in PCO system and, more importantly, this gap has a negative relationship with Tc0. This viewpoint demonstrates that the charge-transfer gap would merge together with the electrons doping in PCO and opens a door to understand the nature of cuprate superconductors.

Information Transfer by Near-Infrared Surface-Plasmon-Polariton Waves on Silver/Silicon Interfaces

Electronic interconnections restrict the operating speed of microelectronic chips as semiconductor devices shrink. As surface-plasmon-polariton (SPP) waves are localized, signal delay and crosstalk may be reduced by the use of optical interconnections based on SPP waves. With this motivation, time-domain Maxwell equations were numerically solved to investigate the transport of information by an amplitude-modulated carrier SPP wave guided by a planar silicon/silver interface in the near-infrared spectral regime. The critical-point model was used for the permittivity of silicon and the Drude model for that of silver. The signal can travel long distances without significant loss of fidelity, as quantified by the Pearson and concordance correlation coefficients. The signal is partially reflected and partially transmitted without significant loss of fidelity, when silicon is terminated by air; however, no transmission occurs when silicon is terminated by silver. The fidelity of the transmitted signal in the forward direction rises when both silicon and silver are terminated by air. Thus, signals can possibly be transferred by SPP waves over several tens of micrometers in microelectronic chips.