Single Structural Parameter Research Articles

3-Bit coded metasurface for linear and circular polarized vortex beam broadband modulation based on dual-frequency multistage resonance

A metasurface design scheme is proposed based on reflective double vertical U-shaped resonators. Compared to planar resonators with the same parameters, vertical meta-atom can excite magnetic dipole resonance and quaternary resonance respectively at low and high frequency to achieve stable wideband phase shift and unique free regulation. Vertical meta-atoms can be applied as 3-bit coding elements in linearly polarized (LP) and circularly polarized (CP) states with bandwidths of 0.7–1.1 THZ and 0.55–1.5 THZ, respectively. At the same time, as a half-wave plate, the deflection conversion rate is 95%, the relative bandwidth is 69%, and the operating Angle is 80°. In order to verify the application capability of the designed meta-atom, the excitation and separation of multi-stage vortex beams are performed in the wide frequency range of LP and CP using the coded convolutional addition method. The designed meta-atom only needs to regulate a single structural parameter to fully satisfy the requirements of 3-Bit broadband coding under LP and CP incidence, so it has multi-type polarization wave universality and ultra-wide working bandwidth. Meanwhile, the method can be effectively applied to optical band and microwave band.

Synthesis, crystal growth, structural, optical, and laser damage threshold characterizations on 2-amino-4,6-di­methyl­pyrimidinium hydrogen sulfate single crystal for nonlinear optical applications

2-Amino-4,6-di­methyl­pyrimidinium hydrogen sulfate (2AMPHS) organic single crystal was successfully grown by slow evaporation solution technique (SEST) for the first time. A good transparent 2AMPHS single crystal with dimensions of 5 mm × 5 mm × 2 mm was grown after a 25-day growth period. The 2AMPHS single crystals structural parameters were confirmed and well matched with the reported values. The good crystalline nature of 2AMPHS crystal was characterised using SXRD, PXRD, UV–Visible NIR, laser damage threshold, and third harmonic generation (THG). The optical property of 2AMPHS crystal was investigated by UV–visible-NIR analysis. Laser damage threshold analysis was performed with an Nd: YAG laser, and the laser wavelength is 1064 nm. The third harmonic generation study was analysed by a Z-scan study. The He-Ne laser source with a wavelength of 632.8 nm has used for Z-scan analysis.

Parameterized complexity of multiwinner determination: more effort towards fixed-parameter tractability

We study the parameterized complexity of winner determination problems for three prevalent k-committee selection rules, namely the minimax approval voting (MAV), the proportional approval voting (PAV), and the Chamberlin–Courant’s approval voting (CCAV). It is known that these problems are computationally hard. Although they have been studied from the parameterized complexity point of view with respect to several natural parameters, many of them turned out to be W[1]-hard or W[2]-hard. Aiming at obtaining plentiful fixed-parameter algorithms, we revisit these problems by considering more natural single parameters, combined parameters, and structural parameters.

Gains from trade liberalization with flexible extensive margin adjustment

We propose a sufficient statistic to measure the ex-post welfare gains from trade in CES models featuring any productivity distribution and any pattern of selection into production and exporting. This statistic is based on a single data moment, the change in the market share of continuing domestic producers, and a single structural parameter, the elasticity of substitution between products. We apply our statistic to measure Canada's gains from the Canada-US Free Trade Agreement using data on observed firm selection. We find that welfare gains can substantially deviate from welfare estimates implied by formulas that assume a constant extensive margin trade elasticity.

Relationship between compressive strength and pore structure of tailings ball concrete

To study the relationship between compressive strength and pore structure of concrete under chloride and sulfate dry–wet cycles, chloride dry–wet cycle tests, sulfate dry–wet cycle tests and cube compressive strength tests were conducted for normal concrete (C) and tailings ball concrete (T) with erosion ages of 30, 60, 90, 120, 150 and 180 days. A Rapidair 457 concrete pore structure analyser was used to obtain pore structure characteristic parameters to calculate the fractal dimension and investigate the influence of erosion environment and materials on macroscopic properties and pore structure, the connection between compressive strength, pore structure and fractal dimension, and the most relevant pore structure parameters, based on the most sensitive pore size theory, to derive a multifactor compressive strength model. The results show a better compressive strength of C than T for late chloride erosion and a better compressive strength of T than C for late sulfate attack, as well as much higher correlation between the most relevant pore structure parameters and compressive strength than between a single pore structure parameter and compressive strength. The multifactor compressive strength model is consistent with the experimental results and well describes the quantitative relationship between compressive strength and pore structure under chloride and sulfate attack.

The evolution of the rheological behavior of hydrating cement systems: Combining constitutive modeling with rheometry, calorimetry and mechanical analyses

The prediction of the time-dependent rheological behavior of concrete is a challenging task of crucial importance to many applications in the construction industry. In particular, the advent of 3D concrete printing (3DCP) highlighted the importance of a more comprehensive understanding of the rheological behavior of cement systems undergoing hydration reactions. In this research, a recently proposed constitutive model is used to describe the evolution of the time-dependent rheological behavior of a cement system employed in 3DCP applications. The model is based on a single structure parameter that describes the instantaneous structuring level of the material's structure, considering both reversible and irreversible effects simultaneously. To validate the model, constant shear rate experiments are carried out and the flow curve of the fresh cement system is constructed from thixotropic equilibrium data observed before the hydration effects become significant. Then, stress ramps are performed to verify that the model can predict the time-dependent rheological behavior of a given cement system subjected to different dynamics. The main contribution of this work is the implementation of model parameters obtained directly from experiments. Calorimetric and mechanical tests were carried out with real samples, rather than just relying on fitted rheological data or estimates from literature. In comparison to other models found in the literature, this work improves the connection with real experimental quantities, providing supporting evidence for the model. The model is improved to better describe the hydration effects on the time-dependent rheological behavior of concrete by generalizing the irreversible progress function to account for different early-age and long-term hydration effects. It is shown that good agreement between experiments and model predictions can be achieved, which can impact the way 3D concrete printing applications are designed nowadays.

Inverse Design of Metamaterials via Deep Learning for Electromagnetically Induced Transparency

The physical limitations of metamaterial structures cannot be solved under the conditions of high time cost and complex algorithms in metamaterial inverse engineering in the past. This paper proposes limiting the value range of metamaterial structural parameters through a single structural parameter acquisition method (SSPAM) for the first time, which will meet the expected values of our predictions and obtain high-quality and effective data in a relatively short time. This is the first attempt to use this method to solve the problem of physical limitations in the inverse design of metamaterials effectively. Furthermore, it is a further improvement of inverse design, enhances the reliability of metamaterial inverse design once again, and realizes the idea of on-demand design. The mean squared error of our best deep learning model is 0.00075 and 0.00026 in the training set and validation set, respectively, and 3.0×10−5 in the test set. We input three specific points of the EIT spectrum into our optimal model to predict the corresponding EIT structural parameters inversely, verified by numerical simulation calculation, and obtained satisfactory results. This work can provide new ideas and methods for the inverse design of metamaterials for other models.

Defining the scope for altering rice leaf anatomy to improve photosynthesis: a modelling approach.

Leaf structure plays an important role in photosynthesis. However, the causal relationship and the quantitative importance of any single structural parameter to the overall photosynthetic performance of a leaf remains open to debate. In this paper, we report on a mechanistic model, eLeaf, which successfully captures rice leaf photosynthetic performance under varying environmental conditions of light and CO2 . We developed a 3D reaction-diffusion model for leaf photosynthesis parameterised using a range of imaging data and biochemical measurements from plants grown under ambient and elevated CO2 and then interrogated the model to quantify the importance of these elements. The model successfully captured leaf-level photosynthetic performance in rice. Photosynthetic metabolism underpinned the majority of the increased carbon assimilation rate observed under elevated CO2 levels, with a range of structural elements making positive and negative contributions. Mesophyll porosity could be varied without any major outcome on photosynthetic performance, providing a theoretical underpinning for experimental data. eLeaf allows quantitative analysis of the influence of morphological and biochemical properties on leaf photosynthesis. The analysis highlights a degree of leaf structural plasticity with respect to photosynthesis of significance in the context of attempts to improve crop photosynthesis.

Study on Characteristics Optimization of Combustion and Fuel Injection of Marine Diesel Engine

The emission requirements of diesel engines are becoming increasingly strict and reducing emissions has become the key technology. In view of this development trend, the influence law of fuel injection on emission is studied in this paper. Numerical studies were performed to analyze the structural parameters of fuel injection system on combustion and emission characteristics of marine diesel engines. The numerical modelling was validated based on single-cylinder diesel engine tests and fuel injection tests. After investigating the single structural parameters on the fuel injection characteristics, the orthogonal method was used to design the double-parameter structural optimization scheme of the fuel injection system. There are 22 optimized cases selected to further investigate using the CFD method by visualizing scalar distributions in cylinder, which was helpful to explain the reason of pollutant formation. Comprehensively comparing the performance of each fuel injection system’s structural optimization scheme, moderate reduction of the discharge valve chamber volume and high-pressure tubing diameter would increase injection mass, along with faster injection rate and boosted injection pressure, leading to reduced Sauter mean diameter (SMD). Considering pollutant emission characteristics as well as economic and power concerns, case D6 with spray angle enlarging 5° showed best performance. Compared with the original condition, there was no NO deterioration and large reduction of soot emission by 65.4%, along with fuel consumption being lowered by 2.18% and more indicated power, by 2.21%. Therefore, reasonable optimization of spray angle can improve power, economy and emission performance simultaneously.

Experimental and theoretical studies on new 2-amino-6-methylpyridinium 2,4-dihydroxybenzoate monohydrate organic single crystal for second order nonlinear optical applications

In this new work, 2-amino-6-methylpyridinium 2,4-dihydroxybenzoate monohydrate (2A6MDH) organic single crystal was grown by slow evaporation method. The grown 2A6MDH single crystal structural parameters were examined by using a single crystal X-ray diffraction technique. It revealed that the grown 2A6MDH crystal belongs to a monoclinic crystal system with a P1n1 non-centrosymmetric space group. The functional groups of the entire vibrational bands of grown 2A6MDH complex were identified using FT-IR and 1H NMR spectral analysis. The optical parameters such as cut-off wavelength, transmittance percentage, band gap energy, and excitation, emission value of the 2A6MDH crystal were studied by UV-Visible and photoluminescence analyses. TG-DSC analysis was carried out on the grown 2A6MDH crystal to understand its thermal properties. Micro hardness analysis ensures the mechanical strength of the as-grown crystal. The nonlinear optical property of 2A6MDH crystal was evidenced from the second harmonic generation (SHG) analysis. Density functional theory (DFT) was computed by the Gaussian 09 program using the basis set of B3LYP/6-311++G (d,P) to find out the molecular geometry, frontier molecular orbital energies, molecular electrostatic potential (MEP), Mulliken charge analysis, natural bond orbital (NBO) analysis and first-order hyperpolarizability of the grown 2A6MDH crystal.

Numerical Simulation and Experimental Study on Magnetorheological Fluid Seals With Flexible Pole Pieces

Magnetorheological fluid seal and brush seal are successful sealing forms. To address problems such as pole pieces colliding with spindles, precise sealing clearance in magnetic fluid seals, and inevitable leakage in brush seals, this article combines the advantages of magnetic fluid seal and brush seal and proposes a magnetorheological fluid seal with flexible pole pieces. The magnetic field of the seal was estimated using the finite-element method and the seal capacity was studied in theory. Single structural parameters of the seal that affect sealing capacity such as the relative permeability and thickness were discussed. The combined effects of various structural parameters were analyzed. The results show that an increase in the relative permeability and length of the flexible pole pieces leads to the enhancement of the seal capacity. The thickness of the flexible magnetic pole piece and the magnetic part of the flap and coating are inversely proportional to the sealing pressure value. The experimentally obtained seal capacity agrees with the value calculated through the simulation. This article presents a structure of the magnetorheological fluid seal and comparative results of the seal capacity obtained from both experimental studies and numerical simulation calculations.

Parametric dependence of bound states in the continuum in periodic structures: Vectorial cases

A periodic structure sandwiched between two homogeneous media can support bound states in the continuum (BICs) that are valuable for many applications. It is known that generic BICs in periodic structures with an up-down mirror symmetry and an in-plane inversion symmetry are robust with respect to structural perturbations that preserve these two symmetries. For two-dimensional (2D) structures with one periodic direction and the up-down mirror symmetry (without the in-plane inversion symmetry), it was recently established that some scalar BICs can be found by tuning a single structural parameter. In this paper, we analyze vectorial BICs in such 2D structures, and show that a typical vectorial BIC with nonzero wave numbers in both the translationally invariant and the periodic directions can only be found by tuning two structural parameters. Using an all-order perturbation method, we prove that such a vectorial BIC exists as a curve in the 3D space of three generic parameters. Our theory is validated by numerical examples involving periodic arrays of dielectric cylinders. The numerical results also illustrate the conservation of topological charge when structural parameters are varied, if both BICs and circularly polarized states are included. Our study reveals a fundamental property of BICs in periodic structure and provides a systematical approach for finding BICs in structures with less symmetry.

Spin-decoupled metasurface for broadband and pixel-saving polarization rotation and wavefront control.

In this paper, a strategy to achieve a simultaneous wavefront shaping and polarization rotation, without compromising the number of pixels and energy efficiency as well as having broadband operation range, is proposed. This strategy is based on the application of a spin-decoupled phase metasurface composed by only one set of metal-insulator-metal (MIM) umbrella-shaped chiral unit cells. Quasi-non-dispersive and spin-decoupled phase shift can be achieved simply by changing single structural parameter of the structure. By further merging the Pancharatnam-Berry (PB) geometric phase, conversion of an incident LP light beam into right- and left-handed circularly polarized reflected beams with similar amplitudes, desired phase profiles and controlled phase retardation on a nanoscale is enabled with high efficiency. Based on the proposed strategy, a polarization-insensitive hologram generator with control optical activity, and a multiple ring vortex beam generator are realized. The results obtained in this work provide a simple and pixel-saving approach to the design of integratable and multitasking devices combining polarization manipulation and wavefront shaping functions, such as vectorial holographic generators, multifocal metalenses, and multichannel vector beam generators.

On the molecular basis of H2O/DMSO eutectic mixtures by using phenol compounds as molecular sensors: a combined NMR and DFT study.

NMR and DFT studies of phenol compounds as molecular sensors were carried out to investigate H2O/DMSO eutectic mixtures at a molecular level. The experimental 1H NMR chemical shifts of the OH groups, δexp(OH), of phenol, paracoumaric acid, and vanillic acid show maximum deshielding and, thus, hydrogen bond interactions in the range of mole fractions 0.20 < χ(DMSO) < 0.33. In the mole fractions χ(DMSO) < 0.2, a progressive decrease in δexp(OH) was observed which demonstrates a decrease in hydrogen bond interactions at infinite dilution in H2O, despite the increase in the number of available hydrogen bond acceptor and donor sites. DFT calculated δcalc(OH) of minimum energy solvation clusters were shown to be in reasonable agreement with the pattern in experimental δexp(OH) data. The chemical shift deshielding and, thus, increased hydrogen bond interactions in the natural product + DMSO + nH2O (n = 2, 3) solvation clusters, relative to complexes in DMSO or H2O solutions, cannot be attributed to a single structural parameter of the cooperative interactions between H2O and DMSO molecules with the phenol OH groups of the natural products. The minimum energy conformers of phenol compounds + 2H2O + DMSO complexes are in excellent agreement with a recent low temperature neutron diffraction experiment of 3D2O + DMSO and demonstrate a general structural motif of solvation complexes. The combined use of 1H NMR and DFT studies with emphasis on δ(OH) of phenol compounds, as molecular sensors, can provide an effective method for the study of solute-solvent interactions at the atomic level.

Research on volume prediction of single tree canopy based on three-dimensional (3D) LiDAR and clustering segmentation

ABSTRACT Canopy volume information of fruit trees is a very important biological parameter, which is of great significance to predict the yield of fruit trees, estimate the application amount of pesticides and fertilizers. This study proposes a novel volume prediction method of single tree canopy based on the three-dimensional (3D) Light Detection and Ranging (LiDAR) point cloud. The method involves several steps, mainly including point cloud pre-processing, spatial clustering segmentation based on K-dimensional tree (KD tree), acquisition of single tree structural parameters, calculation of tree canopy volume based on multiple regression analysis. This study tests the performance of the proposed method with a collected data set of Begonia forest. The average error and standard deviation between the predicted and manually measured heights to the canopy are 0.038 m and 0.030 m, respectively. As to the diameter of the trunk, the average error and standard deviation are 0.013 m and 0.008 m, respectively. The coefficient of determination (R 2) of the proposed canopy volume prediction method is 0.8610, and the F test result is significant. High correlation is found between the predicted canopy volumes and the R 2 value is 0.8223. The experimental results verify the validity of the proposed method. The research can provide a stable and accurate technical reference for the statistics on forest biomass.

Parametric dependence of bound states in the continuum on periodic structures

Bound states in the continuum (BICs) have some unusual properties and important applications in photonics. A periodic structure sandwiched between two homogeneous media is the most popular platform for observing BICs and realizing their applications. Existing studies on BICs assume the periodic structure has a ${C}_{2}$ rotational symmetry about the axis perpendicular to the periodic layer. It is known that all BICs turn to resonant states with finite quality factors if the periodic structure is perturbed by a generic perturbation breaking the ${C}_{2}$ symmetry, and a typical BIC continues to exist if the perturbation keeps the ${C}_{2}$ symmetry. We study how typical BICs depend on generic structural parameters. For a class of BICs with one opening radiation channel, we show that in the plane of two generic parameters, the BICs exist continuously as a curve. Consequently, BICs can exist on periodic structures without the ${C}_{2}$ symmetry, and they can be found by tuning a single structural parameter. The result is established analytically by a perturbation theory with two independent perturbations and validated by numerical examples. Our study reveals a much larger family for BICs on periodic structures, and provides new opportunities for future applications.

Effect of Structural Parameters on the Relative Contact Area for Ideal, Anisotropic, and Correlated Random Roughness

The relative contact area between an initially flat, adhesion- and frictionless, linearly elastic body and a variety of rough, rigid counterbodies is studied using Green's function molecular dynamics. The indenter's height profiles range from ideal random roughness through roughness with a moderate amount of correlation to periodically repeated, single-asperity indenters having perfect phase coherence. At small reduced pressures, p* := p/(E*/g) << 1, sufficiently large systems are consistent with a linear aC = kappa p* relation. Here, p is the pressure, E* is the contact modulus, g the root-mean-square height gradient, and kappa a unitless proportionality coefficient. However, the parameter g must be evaluated over the real contact area for the linear relation to hold if the random roughness is correlated or the interfacial dimension reduced. No single unitless structural parameter--- including the Nayak parameter--- correlates in a significant fashion with kappa.

Toward accurate prediction of amino acid derivatives structure and energetics from DFT: glycine conformers and their interconversions.

This work provides the accurate reference data for structural and energetic properties relevant for computational studies of amino acids and polypeptides. Glycine due to its small size allows for detailed theoretical explorations of its whole conformational space. The reference energies are computed at the CCSD(T)/CBS+CV level on the best estimated geometries of all local minima and the transition states. For the minima, we complete the set of reference structures reported in Phys. Chem. Chem. Phys., 2013, 15, 10094, by determining the CCSD(T)/(CBS+CV)MP2 quality geometries for the two highest energy conformers VIIp/tcc and VIIIn/gtc. These data stand as the reference to asses reliability and accuracy of less expensive computational models, with particular focus on dispersion-corrected hybrid and double-hybrid DFT approaches, considering several basis sets of double- and triple-ζ quality. Based on results for minima the B2LYP-D3(BJ)/aug-cc-pVTZ level is set as the reference for transition states geometries. Considering accuracy of both single point energies and structural parameters B2PLYP(-D3BJ) and DSDPBEP86 in conjunction with aug-cc-pVTZ basis set can be recommended for reference studies of amino-acids and small poly-peptides, while B3LYP(-D3(BJ)) shown to be the most robust from considered hybrid DFT approaches. Graphical abstract TOC: Benchmarking DFT for amino acid analogues: highly accurate characterization of energies and structures from full glycine conformational space.

Phase transition in the high-order nonideal mixing model

We extend the existing second-order nonideal mixing model, which only formally allows for the second-order phase transition, into the fourth-order. The Landau theory reveals that both first- and second-order phase transitions may exist in this higher-order model. Moreover, we show that a single structural parameter determines whether the phase transition abruptly switches between first- and second- orders. We note, it provides an explanation of either appearance or absence of the liquid-liquid critical point in the liquid-liquid phase transition on debate.

Lattice Expansion in Optimally Doped Manganese Oxide: An Effective Structural Parameter for Enhanced Thermochemical Water Splitting

Earth abundant transition-metal oxides have attracted broad interest for thermochemical production of renewable fuels and other gaseous commodities. Despite progress, a major challenge remains in achieving fast and reversible redox kinetics as well as large oxygen exchange capacities. Here, we present insights on the optimal doping of manganese oxide nanocrystals for their efficient and stable utilization as redox material for thermochemical water splitting. The detailed investigation of the evolution of the material properties over a broad range of possible Ce-Mn compounds reveals a single key structural parameter affecting the thermochemical performance. We observe that the expansion of the MnO lattice is essential for activating its reduction from oxide to carbide and thus for H2O splitting during its subsequent reoxidation. This is optimally achieved for a very narrow window of dopant concentration peaking at 3% Ce content, which provides the largest distortion of the manganese oxide crystal lattice. In contrast, smaller or higher Ce amounts of 1 and 5%, respectively, result in significantly smaller lattice expansions either due to an insufficient dopant amount or to the segregation of Ce in large CeO2 domains. We use these findings to propose a mechanism for the enhancement of the redox kinetics of this metal oxide, which may provide guidance for the design of a family of future materials for thermochemistry.