Single Adjustable Parameter Research Articles

Mathematical modeling of fermentation from glucose, xylose, and food waste of clostridia sp. strain BOH3 for the production of ABE solvents and hydrogen

In this study we develop a robust, structured dynamic model of ABE and hydrogen production using Clostridium BOH3 strain. The model represents simultaneous fermentation of glucose and xylose, and concurrent saccharification and fermentation when grown on a variety of complex feedstocks, using only a single adjustable parameter. The model simulations were developed and validated with experimental data of BOH3 fermentations from the literature. Sugar consumption and ABE production dynamics are successfully predicted at different glucose to xylose ratios, and from hydrolyzed lignocellulose, representative of horticultural waste. Butanol and hydrogen production are in close agreement with the experimental data in simulations with rice starch and food waste as substrates. The sensitivity analysis highlights the important roles of xylose transport and xylose kinase on the xylose consumption and butanol formation, in accordance with experimental findings on how these enzymes enable the efficient xylose utilization by BOH3.

Role of Coulomb interaction in elastic pion-proton scattering from holography

Differential cross sections of the elastic pion-proton scattering are investigated at very small momentum transfer in a holographic QCD model, considering both the strong and Coulomb interaction in the Regge regime. The strong interaction is described by the Pomeron and Reggeon exchange, and the Coulomb interaction is characterized by the one photon exchange. The two interactions are linked through an interference term and we only need to determine a single adjustable parameter involved in this term. As to the parameters for the strong interaction, we can utilize the values determined in the previous studies. The differential cross sections can be predicted without any additional parameters, and it is shown that our predictions are consistent with the experimental data. We explicitly show the momentum transfer dependence for the interference effect. The energy dependence of the contribution ratios for each component is also discussed. Published by the American Physical Society 2024

Elastic proton–neutron and antiproton–neutron scattering in holographic QCD

The total and differential cross sections of the elastic proton–neutron and antiproton–neutron scattering are studied in a holographic QCD model, focusing on the Regge regime. Taking into account the Pomeron and Reggeon exchange, which are described by the Reggeized spin-2 glueball and vector meson propagator respectively, those cross sections are obtained. It is presented that the currently available experimental data of the total cross sections can be well described within the model. Once a single adjustable parameter is determined with the total cross section data, the differential cross sections can be calculated without any additional parameters. Although the available differential cross section data are limited, it is found that our predictions are consistent with those.

Multi-Instant Gain-Scheduling Fuzzy Observer of Discrete-Time Takagi-Sugeno Systems and Its Application: An Efficient Balanced Matrix Approach.

The problem of relaxed state estimation of discrete-time Takagi-Sugeno fuzzy systems is studied by constructing a novel multi-instant gain-scheduling fuzzy observer. First, a multi-instant gain-scheduling mechanism with a single adjustable parameter is given for the first time in order to produce more reasonable switch modes over previous results reported in recent literature. Second, for every switch mode, a batch of specified observer gain matrices is determined by developing an efficient balanced matrix approach so that the updated values of adjacent normalized fuzzy weighting functions can be flexibly exploited. Since the implied information of each specific switch mode is capable of being absorbed and utilized more thoroughly by the aid of the refined higher-order balanced matrices, the conservatism can be prominently reduced at the price of consuming extra computational burden within the allowable range. Finally, two benchmark examples are provided to test and verify the progressiveness of our proposed approach.

A multiscale approach to coupled nuclear and electronic dynamics. II. Exact and approximated evaluation of nonradiative transition rates.

This work follows a companion article, which will be referred to as Paper I [Campeggio et al., J. Chem. Phys. 158, 244104 (2023)] in which a quantum-stochastic Liouville equation for the description of the quantum-classical dynamics of a molecule in a dissipative bath has been formulated in curvilinear internal coordinates. In such an approach, the coordinates of the system are separated into three subsets: the quantum coordinates, the classical relevant nuclear degrees of freedom, and the classical irrelevant (bath) coordinates. The equation has been derived in natural internal coordinates, which are bond lengths, bond angles, and dihedral angles. The resulting equation needs to be parameterized. In particular, one needs to compute the potential energy surfaces, the friction tensor, and the rate constants for the nonradiative jumps among the quantum states. While standard methods exist for the calculation of energy and dissipative properties, an efficient evaluation of the transition rates needs to be developed. In this paper, an approximated treatment is introduced, which leads to a simple explicit formula with a single adjustable parameter. Such an approximated expression is compared with the exact calculation of transition rates obtained via molecular dynamics simulations. To make such a comparison possible, a simple sandbox system has been used, with two quantum states and a single internal coordinate (together with its conjugate momentum). Results show that the adjustable parameter, which is an effective decoherence time, can be parameterized from the effective relaxation times of the autocorrelation functions of the conjugated momenta of the relevant nuclear coordinates.

Plasma Dynamics-Based Modeling and Analysis of Partial Discharge in Voids Inside Insulation of Power Transformer

Partial discharge (PD) modeling in voids is being studied; earlier, however, most studies considered a simplified model with many adjustable parameters. In this article, a comprehensive comparative study is being done with possible void shapes in transformer insulation using a modified drift-diffusion model with single adjustable free parameter of the electron generation rate and considering the secondary ionization process. In simulation studies, plasma-dynamics-based models are used to better understand PD activity inside voids. A drift-diffusion model is used for investigating the PD phenomena inside air-filled voids of commonly found geometries, namely, cylindrical, spherical, and ellipsoidal, bounded by different insulating materials in power transformers. The model is applicable for all void shapes and material of insulation. PD inception field, residual field, space charge density, and other electrical properties are obtained, and all the possible parameters are incorporated in the model thus improving its accuracy. In this article, the effect of void shape and insulation material on the PD activity is obtained. The inception electric field at which the discharge initiates is found to be lowest in case of spherical void resulting in easy formation of plasma discharge. This study thus uncovers the physical mechanism of PD inside insulation thus helping in maintenance and optimum design of transformer insulation.

Machine-learning-based monitoring and optimization of processing parameters in 3D printing

ABSTRACT Additive manufacturing (AM), commonly known as 3D printing, is a rapidly growing technology. Guaranteeing the quality and mechanical strength of printed parts is an active research area. Most of the existing methods adopt open-loop-like Machine Learning (ML) algorithms that can be used only for predicting properties of printed parts without any quality assuring mechanism. Some closed-loop approaches, on the other hand, consider a single adjustable processing parameter to monitor the properties of a printed part. This work proposes both open-loop and closed-loop ML models and integrates them to monitor the effects of processing parameters on the quality of printed parts. By using experimental 3D printing data, an open-loop classification model formulates the relationship between processing parameters and printed part properties. Then, a closed-loop control algorithm that combines open-loop ML models and a fuzzy inference system is constructed to generate optimized processing parameters for better printed part properties. The proposed system realizes the application of a closed-loop control system to AM.

Elastic pion-proton and pion-pion scattering at high energies in holographic QCD

The total and differential cross sections of high energy pion-proton and pion-pion scattering are investigated in a holographic QCD model, focusing on the Regge regime in which the Pomeron exchange gives the dominant contribution to those cross sections. The Pomeron is described by the Reggeized spin-2 particle propagator, and the hadron-Pomeron couplings are given by gravitational form factors of the hadrons, which are obtained from the bottom-up AdS/QCD models. Since the parameters, which characterize the Pomeron trajectory, have been determined in a preceding study of the proton-proton scattering, the pion-proton cross sections can be expressed with a single adjustable parameter. Once this parameter is determined by the experimental data of the pion-proton total cross section, its differential cross section and the pion-pion cross sections can be calculated without any additional parameter. Although the currently available data are limited, it is found that our calculation is consistent with those. Our predictions are explicitly shown, and the present model can be tested at the future experimental facilities.

Experiments and Modeling of Flow-Enhanced Nucleation in LLDPE.

A computational and experimental framework for quantifying flow-enhanced nucleation (FEN) in polymers is presented and demonstrated for an industrial-grade linear low-density polyethylene (LLDPE). Experimentally, kinetic measurements of isothermal crystallization were performed by using fast-scanning calorimetry (FSC) for melts that were presheared at various strain rates. The effect of shear on the average conformation tensor of the melt was modeled with the discrete slip-link model (DSM). The conformation tensor was then related to the acceleration in nucleation kinetics by using an expression previously validated with nonequilibrium molecular dynamics (NEMD). The expression is based on the nematic order tensor of Kuhn segments, which can be obtained from the conformation tensor of entanglement strands. The single adjustable parameter of the model was determined by fitting to the experimental FSC data. This expression accurately describes FEN for the LLDPE, representing a significant advancement toward the development of a fully integrated processing model for crystallizable polymers.

Parametric visco-hyperelastic constitutive modeling of functionally graded 3D printed polymers

Grayscale masked vat photopolymerization (MSLA) 3D printing enables the fabrication of graded structures from a single material, overcoming a major limitation of vat photopolymerization methods. Two main parameters affecting the curing of the resin in vat photopolymerization , and thus the resulting material properties, are the exposure time per layer and the intensity of the ultraviolet light, which can be regulated in terms of the grayscale value of the mask. Here, the concept of grayscale MSLA is extended by combining these two easily adjustable parameters into a single parameter, which we call the grayscale exposure. Then, a parametric visco-hyperelastic constitutive model is formulated for the strain rate-dependent behavior of the resulting material in finite deformations, which depends on the grayscale exposure. Hyperbolic tangent functions are utilized to express the dependency of the material coefficients in terms of grayscale exposure. The advantage of expressing the material model in terms of grayscale exposure is not only the reduction of design parameters from two to one, but also the fact that the printing time can be reduced through the correlation of exposure time and grayscale. Furthermore, the grayscale exposure values are verified through a comparison of different couples of grayscale and exposure time. Finally, the constitutive model is validated against further experimental results, showing a good agreement. In summary, the main contributions of this manuscript are the systematic investigation of the correlation of process parameters with rate-dependent mechanical properties, the unification of light intensity and layer printing time into the grayscale exposure as a single adjustable design parameter, as well as the development of a parametric visco-hyperelastic constitutive model and its experimental identification and verification.

Structural model for amorphous aluminosilicates.

An analytical model is developed for the composition-dependent structure of the amorphous aluminosilicate materials (M2O)x(Al2O3)y(SiO2)1-x-y and (MO)x(Al2O3)y(SiO2)1-x-y, where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1. The model is based on a simple set of reactions and contains a single adjustable parameter p (0 ≤ p ≤ 1). The latter is found from 27Al solid-state nuclear magnetic resonance (NMR) experiments in the regime where R = x/y ≥ 1, aided by new experiments on the magnesium and zinc aluminosilicate systems. The parameter p decreases linearly as the cation field strength of M+ or M2+ increases, as per the observation previously made for the degree of aluminum avoidance [Lee et al., J. Phys. Chem. C 120, 737 (2016)]. The results indicate that as the cation field strength increases, there are less fourfold coordinated aluminum atoms to contribute toward the glass network, and Al-O-Al bonds become more prevalent in a progressive breakdown of Loewenstein's aluminum avoidance rule. The model gives a good account of the composition-dependent fraction of non-bridging oxygen (NBO) atoms for R ≥ 1, as assessed from the results obtained from solid-state NMR experiments. An extension of the model to (M2O3)x(Al2O3)y(SiO2)1-x-y glasses leads, however, to an excess of NBO atoms, the proportion of which can be reduced by invoking network-forming fivefold coordinated Al atoms and/or oxygen triclusters. The model provides a benchmark for predicting the structure-related properties of aluminosilicate materials and a starting point for predicting the evolution in the structure of these materials under the extreme conditions encountered in the Earth's interior or in processes such as sharp-contact loading.

Phonon-assisted excitonic absorption in diamond

The phonon-assisted optical transitions of excitons in intrinsic diamond have been investigated theoretically and experimentally. Excellent agreement is indicated between absorption spectra measured and calculated based on the phonon coupling strengths from first-principles calculations using just a single adjustable parameter. Temperature shift and broadening are incorporated via a pseudo-Voigt function analysis developed for the derivative of the experimental absorption spectra. The absorption coefficients of excitons in discrete and continuum states are separated and contributions from different phonon modes are discussed, which enable theoretical derivation of the exceptionally high phonon-assisted radiative rate of excitons in diamond among indirect-gap semiconductors. This study expands the applicability of the second-order perturbation theory involving electron-phonon interactions in materials important for future photonics and power electronics.

Data Analysis for Electrolyte Systems: A Method Illustrated on Alkali Halides in Water

In the recent years, the need to improve the thermodynamic models, particularly making them more precise and predictable for complex systems, has increased [Hendriks, E. Industrial Requirements for Thermodynamics and Transport Properties. Ind. Eng. Chem. Res. 2010, 49, 11131 11141 and Kontogeorgis, G. Industrial Requirements for Thermodynamic and Transport Properties. Ind. Eng. Chem. Res. 2021, 60, 4987 5013]. The complexity of electrolyte systems is due to the strong interactions between ions, the hydration forces that take place during salt dissociation, and the physical forces at high concentrations of solute. Consequently, the existing thermodynamic electrolyte models show some limitations and are far from being completely optimized for industrial simulations. Thermodynamics based on electrolyte mixtures and mixed solvents requires further development and research [Poling, B. E. The Properties of Gases and Liquids, 5th ed.; McGraw-Hill Education, 2001].The EleTher Joint Industrial Project (JIP) aims at promoting research in this field. A practical workflow is under development where the first stage consists in analyzing the data. The present work is part of this larger scope and presents a strategy to analyze the internal and external consistency of experimental data for electrolyte mixtures. The focus is on alkali halide salts in water. Internal consistency allows testing the quality of data by confronting them to each other and using the thermodynamic relationships between these data. For that purpose, the data are confronted with a model that was initially optimized and the deviations are analyzed. For this purpose, the electrolyte non-random two-liquid (eNRTL) thermodynamic model was selected. Some deviations are attributed to the model inadequacy (high temperature or high molalities). Others are to be attributed to data inconsistencies. On the other hand, the objective of external consistency is to evaluate the consistency between different systems of the same family. The Bromley model is used for this purpose, as it contains a single adjustable parameter. Investigating the trend of this parameter with type of compound or with temperature may provide valuable information regarding the underlying physics, in addition to identifying outliers.

Quadrupole-mediated dielectric response and the charge-asymmetric solvation of ions in water.

Treating water as a linearly responding dielectric continuum on molecular length scales allows very simple estimates of the solvation structure and thermodynamics for charged and polar solutes. While this approach can successfully account for basic length and energy scales of ion solvation, computer simulations indicate not only its quantitative inaccuracies but also its inability to capture some basic and important aspects of microscopic polarization response. Here, we consider one such shortcoming, a failure to distinguish the solvation thermodynamics of cations from that of otherwise-identical anions, and we pursue a simple, physically inspired modification of the dielectric continuum model to address it. The adaptation is motivated by analyzing the orientational response of an isolated water molecule whose dipole is rigidly constrained. Its free energy suggests a Hamiltonian for dipole fluctuations that accounts implicitly for the influence of higher-order multipole moments while respecting constraints of molecular geometry. We propose a field theory with the suggested form, whose nonlinear response breaks the charge symmetry of ion solvation. An approximate variational solution of this theory, with a single adjustable parameter, yields solvation free energies that agree closely with simulation results over a considerable range of solute size and charge.

Solid–liquid–liquid phase envelopes from temperature-scanned refractive index data

Abstract A novel method for estimating the upper critical solution temperature (UCST) of N,N-diethyl-m-toluamide (DEET)-polyethylene systems was developed. It was validated using data for the dimethylacetamide (DMA)-alkane systems which showed that refractive index mixing rules, linear in volume fraction, can accurately predict mixture composition for amide-alkane systems. Furthermore, rescaling the composition descriptor with a single adjustable parameter proved adequate to address any asymmetry when modeling the DMA-alkane phase envelopes. This allowed the translation of measured refractive index cooling trajectories of DEET-alkane systems into phase diagrams and facilitated the estimation of the UCST values by fitting the data with an adjusted composition descriptor model. For both the DEET- and DMA-alkane systems, linear behavior of UCST values in either the Flory–Huggins critical interaction parameter, or the alkane critical temperature, with increasing alkane molar mass is evident. The UCST values for polymer diluent systems were estimated by extrapolation using these two complimentary approaches. For the DEET-polyethylene system, values of 183.4 and 180.1 °C respectively were obtained. Both estimates are significantly higher than the melting temperature range of polyethylene. Initial liquid–liquid phase separation is therefore likely to be responsible for the previously reported microporous microstructure of materials formed from this binary system.

Direct Osmotic Pressure Measurements in Articular Cartilage Demonstrate Nonideal and Concentration-Dependent Phenomena.

The osmotic pressure in articular cartilage serves an important mechanical function in healthy tissue. Its magnitude is thought to play a role in advancing osteoarthritis. The aims of this study were to: (1) isolate and quantify the magnitude of cartilage swelling pressure in situ; and (2) identify the effect of salt concentration on material parameters. Confined compression stress-relaxation testing was performed on 18 immature bovine and six mature human cartilage samples in solutions of varying osmolarities. Direct measurements of osmotic pressure revealed nonideal and concentration-dependent osmotic behavior, with magnitudes approximately 1/3 those predicted by ideal Donnan law. A modified Donnan constitutive behavior was able to capture the aggregate behavior of all samples with a single adjustable parameter. Results of curve-fitting transient stress-relaxation data with triphasic theory in febio demonstrated concentration-dependent material properties. The aggregate modulus HA increased threefold as the external concentration decreased from hypertonic 2 M to hypotonic 0.001 M NaCl (bovine: HA=0.420±0.109 MPa to 1.266±0.438 MPa; human: HA=0.499±0.208 MPa to 1.597±0.455 MPa), within a triphasic theory inclusive of osmotic effects. This study provides a novel and simple analytical model for cartilage osmotic pressure which may be used in computational simulations, validated with direct in situ measurements. A key finding is the simultaneous existence of Donnan osmotic and Poisson-Boltzmann electrostatic interactions within cartilage.

Alpha decay of heavy and super heavy nuclei with a generalized electrostatic potential

Half-lives of α decay for Z≥ 84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented by a Hulthen potential. For favored decays, the model has a single adjustable parameter associated with the screening of the electrostatic potential. The description of half lives for unfavored decays requires an additional hindrance term. A good agreement with experimental data is obtained in all considered cases. The evolution of the screening parameter for each nucleus revealed its dependence on shell filling. The model is also used for theoretical predictions on a few nuclei with uncertain or incomplete decay information.

Quantitative theory of triplet pairing in the unconventional superconductor LaNiGa2

The exceptionally low-symmetry crystal structures of the time-reversal symmetry breaking superconductors LaNiC$_2$ and LaNiGa$_2$ lead to an internally-antisymmetric non-unitary triplet (INT) state as the only possibility compatible with experiments. We argue that this state has a distinct signature: a double-peak structure in the Density of States (DOS) which resolves in the spin channel in a particular way. We construct a detailed model of LaNiGa$_2$ capturing its electronic band structure and magnetic properties ab initio. The pairing mechanism is described via a single adjustable parameter. The latter is fixed by the critical temperature $T_c$ allowing parameter-free predictions. We compute the electronic specific heat and find excellent agreement with experiment. The size of the ordered moment in the superconducting state is compatible with zero-field muon spin relaxation experiments and the predicted spin-resolved DOS suggests the spin-splitting is within the reach of present experimental technology.

EFFECT OF NON-HOMOGENEOUS LIQUID DISTRIBUTION ON EFFICIENCY OF STRUCTURED PACKING MATERIALS

Uneven liquid distribution (maldistribution) is a recurrent problem in the design and operation of packed towers, regardless of the type of packing. Using a simple but rigorous analysis it can be shown that the effect of liquid maldistribution on holdup is highly nonlinear and has cascading effects on liquid residence times and mass transfer rates. A statistical liquid film thickness description is used to characterize liquid distribution on corrugated structural packing. The distribution has a single adjustable parameter, the volume average variance of the distribution.

Glass transition temperature from the chemical structure of conjugated polymers

The glass transition temperature (Tg) is a key property that dictates the applicability of conjugated polymers. The Tg demarks the transition into a brittle glassy state, making its accurate prediction for conjugated polymers crucial for the design of soft, stretchable, or flexible electronics. Here we show that a single adjustable parameter can be used to build a relationship between the Tg and the molecular structure of 32 semiflexible (mostly conjugated) polymers that differ drastically in aromatic backbone and alkyl side chain chemistry. An effective mobility value, ζ, is calculated using an assigned atomic mobility value within each repeat unit. The only adjustable parameter in the calculation of ζ is the ratio of mobility between conjugated and non-conjugated atoms. We show that ζ correlates strongly to the Tg, and that this simple method predicts the Tg with a root-mean-square error of 13 °C for conjugated polymers with alkyl side chains.