Theoretical Reference Data Research Articles

Numerical parameters study on seismic performance of short replaceable link with perforated web: Bearing capacity and overstrength

This study builds on experimental research of replaceable links with perforated web by using finite element software to develop a finite element model (FEM) of the link. The model’s reliability and accuracy were confirmed by comparing its results with experimental data. The simulation results closely match the experimental hysteresis curves, demonstrating the model's accuracy. Additionally, the simulations effectively replicated the observed failure modes, confirming the model's reliability and practical relevance. Building on this, 22 different finite element models were developed to investigate the impact of various parameters on link performance, including the shape and size of web openings, the number of openings, flange weakening depth, and link length ratio. The analysis revealed that links with circular or elliptical web openings have higher overstrength coefficients than other shapes. Additionally, as the link length ratio and flange weakening depth decrease, the overstrength coefficient tends to increase. These findings offer valuable theoretical insights and reference data for designing and optimizing replaceable link with perforated web.

Hydrophilic Chain Length for Octylphenol Polyoxyethylene Ether Adsorption at the n-Hexadecane-Water Interface: Theoretical and Experimental Study.

With the advancement of technologies for developing tight and shale reservoirs, nonionic surfactants have garnered significant attention due to their remarkable properties. The structure of these surfactants plays a crucial role in determining the characteristics of the oil-water interface, particularly influencing emulsification behavior and crude oil recovery. This study investigates the effect of varying the number of hydrophilic polar groups (n = 10, 20, 30, 50) in octylphenol polyoxyethylene ether (OP-n) on its adsorption behavior at the n-hexadecane-water interface using molecular dynamics simulation. The impact of these variations on interfacial properties was further analyzed through measurements of interfacial tension and observations of emulsion droplet morphology. The study results indicate that variations in the number of hydrophilic polar groups significantly affect interfacial properties. Increasing the number of hydrophilic polar groups led to a notable increase in the thickness of the n-hexadecane or water phase, as well as the thickness of the water or oil layer and the surfactant layer. Moreover, when the number of hydrophilic polar groups reached 20, the OP-n molecules exhibited a more curled conformation at the interface, enhancing their ability to encapsulate water and resulting in a decrease in the diffusion coefficient of the molecules in each phase. Additionally, interfacial tension was found to be positively correlated with the number of hydrophilic polar groups and remained unchanged beyond a certain emulsion diameter. This study provides a theoretical basis and reference data for optimizing surfactant structures to improve crude oil recovery.

Effect of low degree succinylation on properties of enzyme-induced casein hydrogel

This study examines the impact of succinic anhydride (SA) modification (0–9 %) on the gel properties of casein. Upon succinylation, the surface hydrophobicity (H0) of casein initially increased before decreasing, achieving its peak at a degree of succinylation of 5.22 ± 0.16 %. The α-helix content rose to 14.13 ± 2.60 %, and the -OH peak shifted towards lower wavenumbers, suggesting enhanced hydrogen bonding within intra/intermolecular structures. The storage modulus in the rheological test escalated from 2160.11 Pa to 5047.60 Pa, and SEM analysis revealed that the optimally succinylated casein gel formed a denser and more stable gel network structure. Moreover, succinylated casein hydrogels demonstrated superior texture properties, swelling ability, and thermal stability. Molecular dynamics simulation (MD) results suggest that SA preferentially binds to LYS27 and LYS28 of β-casein via hydrogen bonds and amide bonds, respectively. The interaction between modified proteins is primarily governed by hydrogen bonds, aligning with FT-IR findings. PCA analysis identified a positive correlation between the ordered structure and gel performance. This research offers theoretical insights and reference data for modulating casein hydrogel properties through succinylation.

Fundamental physicochemical properties, intermolecular interactions and CO2 absorption properties of binary mixed solutions of monoethanolamine + diethylenetriamine

This work presents experimental data on the density (ρ), viscosity (η), and surface tension (γ) of monoethanolamine (MEA), diethylenetriamine (DETA), and their binary mixed solutions across 298.15–318.15 K. Using these physicochemical data, the work also explored properties like excess molar volume (VmE) and viscosity deviation (Δη) of the solutions. The experimental results were modeled using the Jouyban-Acree model, McAllister four-body model, and Redlich-Kister (R-K) equation. The application of these parametric models confirmed strong intermolecular interactions (The length (1.911 Å) and energy (HF value: −2237.54 kJ/mol and Des: −21.61 kJ/mol) of hydrogen bond) within the MEA + DETA binary mixed solutions. Spectroscopic analyses, including Raman and nuclear magnetic resonance hydrogen spectroscopy, revealed the presence of intermolecular hydrogen bonding (OH⋯N(H2)) in the MEA + DETA binary mixed solutions. Lastly, the CO2 absorption capacity of the solutions was experimentally studied, providing a theoretical foundation and reference data for future experiments and process design of CO2 capture.

Effect and Mechanism of Root Characteristics of Different Rice Varieties on Methane Emissions

Methane (CH4), which is an important component of the greenhouse gases from paddy ecosystems, is a major contributor to climate change. CH4 emissions from paddy ecosystems are closely related to the rice root system; however, how the rice root system affects CH4 emissions remains unclear. We conducted a field experiment in 2023 at the Heping Irrigation District Rice Irrigation Experiment Station in Qing’an County, Heilongjiang Province. The field experiment used five local rice varieties with similar fertility periods to observe rice root morphology and physiology indexes, CH4 emission fluxes, and cumulative CH4 emissions. A structural equation model (SEM) was established to investigate the effects of root characteristics on the CH4 emissions from rice and understand the potential mechanisms of these effects. The results showed that the seasonal patterns of CH4 emission fluxes were similar in different rice varieties, and that, during the tillering to heading–flowering stages, the cumulative CH4 emissions accounted for 89.8–92.6% of the total cumulative CH4 emissions of rice. Significant negative correlations were observed between CH4 emission fluxes and root volume, root dry weight, root oxidation activity (ROA), and root radial oxygen loss (ROL) (r = −0.839, −0.885, −0.401 and −0.934, p < 0.05), while there were significant positive correlations between root diameter; malic acid, citric acid, and succinic acid contents; and CH4 emission fluxes (r = 0.407, 0.753, 0.797, and 0.685, p < 0.05). The SEM showed that CH4 emission fluxes were directly influenced by ROL and organic acid contents, while the other root indicators had indirect effects by modulating ROL and organic acid contents. ROL and root volume had the largest total effect, indicating that ROL and root volume were the most significant root physiological and morphological indicators affecting CH4 emission fluxes. This study provides theoretical support and reference data for achieving sustainable agricultural development in the black soil region of Northeast China.

Unraveling proton-coupled electron transfer in cofactor-free oxidase- and oxygenase-catalyzed oxygen activation: a theoretical view.

Oxygen plays a crucial role in the metabolic processes of non-anaerobic organisms. However, a detailed understanding of how triplet oxygen participates in the enzymatic oxidation of organic compounds involved in life processes is still lacking. It is noteworthy that recent studies have found that cofactor-free oxidase- and oxygenase-catalyzed oxygen activation occurs through proton-coupled electron transfer (PCET), which is significantly different from the previously proposed single electron transfer (SET) mechanism. Herein, we summarize the recent advances in the general mechanism of catalytic activation reactions of triplet oxygen by these enzymes. We believe that this review not only helps in providing a deep understanding of the processes involved in oxygen metabolism in organisms but also provides valuable theoretical reference data for designing more efficient enzyme mutants for treating diseases and handling environmental pollution in the future.

Study on Electrochemical Behavior of Oxidized Pyrite in Alkaline Electrolyte

Nowadays, refractory gold ore production around the world accounts for about 30% of total gold production, and the low leaching rate of such gold concentrate seriously limits the efficient utilization of gold resources. The alkaline preoxidation process can improve the leaching rate of this kind of gold deposit and has good development and application prospects. Therefore, it is of great significance to study the oxidation and dissolution behavior of pyrite in an alkaline environment. In this paper, the oxidation process of gold-bearing pyrite in an alkaline electrolyte was studied using electrochemical techniques, and the oxidation products of a pyrite electrode in an alkaline solution were characterized using XPS, SEM, and other analytical methods. The results show that the optimum pH for pyrite electrochemical oxidative dissolution is about 12, and the oxidation potential of pyrite should be above 0.8 V. In the process of alkaline oxidative dissolution of pyrite, part of the S element enters the electrolyte in the forms of Sx2−, S2O32−, SO32−, and SO42−, and a small amount of the S element is adsorbed on the surface of the electrode in the form of S0 and becomes a part of the passive layer. The Fe element is adsorbed on the surface of the electrode in the forms of Fe(OH)2, Fe2O3, and Fe2(SO4)3, which become the main components of the passivation layer. This study provides a theoretical basis and reference data for the chemical preoxidation treatment of gold-bearing sulfide ores.

Analytic hierarchy process-based life cycle assessment of the renewable energy production by orchard residual biomass-fueled direct-fired power generation system

Orchard residues (OR), primarily consists of pruned fruit tree branches (PFTB), serve as a significant biomass source in China and many other countries. In this study, we established a comprehensive life cycle assessment (LCA) model for PFTB-based BDP (PFTB-BDP) using LCA and the analytic hierarchy process (AHP). The model was employed to evaluate the environmental impacts (EIs), abiotic depletion (AD), and comprehensive performance of PFTB-BDP. Our findings revealed that the comprehensive performance index (COPI) of PFTB-BDP ranged from 0.005 to 0.019 (person·year)/MWh. EIs exerted a more significant influence on comprehensive performance compared to AD, with the impact strength of EIs following the order of local > equal > regional > global. The maximum COPI value of PFTB-BDP amounted to 48.72% of the minimum COPI value of a coal-fired power generation (CP) system, demonstrating the superiority of PFTB-BDP over CP. The comprehensive performance of PFTB-BDP was most sensitive to total solid waste (SW) (−21.79%–17.89%) and the raw material consumption rate (−13.01%–11.58%). The outcomes of this study provide a crucial theoretical foundation and reference data for PFTB-BDP research.

Inter-Species and Inter-Organ Differences in Stable C and N Isotope Signatures of Macrophytes from the Largest Freshwater Lake in China

Macrophytes play important roles in shallow aquatic ecosystems. Stable isotope signatures of macrophytes indicate the environmental conditions and macrophyte contributions to food webs. However, macrophyte isotope signatures have been studied less than isotope signatures of other organisms. We determined the stable C and N isotope signatures of 10 aquatic plant species from Poyang Lake wetland (Wucheng, Yongxiu County) and Nanji wetland (Nanjishan, Xinjian County) in Jiangxi Province, which are Chinese national nature reserves, among different seasons. The isotope signatures for different species and seasons were significantly different. The dominant macrophyte species were Potamogeton malaianus and Nymphoides peltatum. The isotope signatures for different organs of these two species were determined. Both δ13C and δ15N values were higher for P. malaianus than for N. peltatum stems, roots and leaves, and δ13C varied less for N. peltatum than for P. malaianus organs. The δ13C and δ15N values for P. malaianus organs increased in the order roots<stems<leaves. δ13C values for N. peltatum organs decreased in the order roots>stems>leaves, and δ15N values for N. peltatum organs increased in the order roots<stems<leaves. The stable C and N isotope signatures for P. malaianus and N. peltatum may be controlled by various factors including macrophyte life history, external sources of C/N, and the amount of water in the wetland. These results provided a theoretical reference and experimental data support for detecting the flow trend of C & N elements and environment changes in the lake by the δ13C and δ15N values of euhydrophytes.

Development of Cistanche deserticola Fermented Juice and Its Repair Effect on Ethanol-Induced WRL68 Cell Damage

Cistanche deserticola is a valuable Chinese herb, but traditional dry processing causes the loss of active substances. This study developed Cistanche deserticola fermented juice (CFJ) using lactic acid bacteria and optimized the fermentation process to achieve the maximum active substance content and taste. More interestingly, superoxide dismutase (SOD) activity was increased during fermentation, and CFJ exerted a reparative effect on ethanol-induced cell damage. SOD activity reached 603.26 U/mL when the ratios in the total inoculum volume of Lactobacillus reuteri, Lactococcus pentosus, Streptococcus thermophilus, Bifidobacterium animalis, Lactobacillus casei, and Lactobacillus acidophilus were 31.74%, 15.71%, 17.45%, 11.65%, 9.56%, and 13.89%, respectively. Further, the optimal fermentation conditions for CFJ were determined using a response surface methodology. More importantly, CFJ promoted the proliferation of WRL68 cells, and CFJ exerted an obvious reparative effect on ethanol-treated cells, in which the cell survival rate increased to 120.35 ± 0.77% (p < 0.05). The underlying mechanism might have been that CFJ reduced the MDA content in damaged cells from 1.36 nmol/mg prot to 0.88 nmol/mg prot and increased GSH-Px and SOD activities by 48% and 72%, respectively. This study provides a theoretical basis and reference data for the fermentation of C. deserticola and its hepatoprotective activity.

Assessing the Accuracy of Tailored Coupled Cluster Methods Corrected by Electronic Wave Functions of Polynomial Cost.

Tailored coupled cluster theory represents a computationally inexpensive way to describe static and dynamical electron correlation effects. In this work, we scrutinize the performance of various coupled cluster methods tailored by electronic wave functions of polynomial cost. Specifically, we focus on frozen-pair coupled cluster (fpCC) methods, which are tailored by pair-coupled cluster doubles (pCCD), and coupled cluster theory tailored by matrix product state wave functions optimized by the density matrix renormalization group (DMRG) algorithm. As test system, we selected a set of various small- and medium-sized molecules containing diatomics (N2, F2, C2, CN+, CO, BN, BO+, and Cr2) and molecules (ammonia, ethylene, cyclobutadiene, benzene, hydrogen chains, rings, and cuboids) for which the conventional single-reference coupled cluster singles and doubles (CCSD) method is not able to produce accurate results for spectroscopic constants, potential energy surfaces, and barrier heights. Most importantly, DMRG-tailored and pCCD-tailored approaches yield similar errors in spectroscopic constants and potential energy surfaces compared to accurate theoretical and/or experimental reference data. Although fpCC methods provide a reliable description for the dissociation pathway of molecules featuring single and quadruple bonds, they fail in the description of triple or hextuple bond-breaking processes or avoided crossing regions.

Implicit Solvation Methods for Catalysis at Electrified Interfaces.

Implicit solvation is an effective, highly coarse-grained approach in atomic-scale simulations to account for a surrounding liquid electrolyte on the level of a continuous polarizable medium. Originating in molecular chemistry with finite solutes, implicit solvation techniques are now increasingly used in the context of first-principles modeling of electrochemistry and electrocatalysis at extended (often metallic) electrodes. The prevalent ansatz to model the latter electrodes and the reactive surface chemistry at them through slabs in periodic boundary condition supercells brings its specific challenges. Foremost this concerns the difficulty of describing the entire double layer forming at the electrified solid–liquid interface (SLI) within supercell sizes tractable by commonly employed density functional theory (DFT). We review liquid solvation methodology from this specific application angle, highlighting in particular its use in the widespread ab initio thermodynamics approach to surface catalysis. Notably, implicit solvation can be employed to mimic a polarization of the electrode’s electronic density under the applied potential and the concomitant capacitive charging of the entire double layer beyond the limitations of the employed DFT supercell. Most critical for continuing advances of this effective methodology for the SLI context is the lack of pertinent (experimental or high-level theoretical) reference data needed for parametrization.

Simulation of the plasticizing behavior of composite modified double-base (CMDB) propellant in grooved calendar based on adaptive grid technology

The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base (CMDB) propellant. Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process. To improve the accuracy of the simulation results, material parameters and model structure were corrected based on actual conditions, and adaptive grid technology was applied in the local mesh refinement. In addition, the rheological behavior, motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps, rotational rates and temperatures of two rollers. The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet. Compared with the gap, the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging. Meanwhile, under the synergistic effect of contact heat transfer as well as convective heat exchange, heat accumulated near the outlet and diffused along the reflux movement, which led to the countercurrent heat dissipation behavior of CMDB propellant slurry. The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored, which provided theoretical guidance and reference data for the optimization of calendering process conditions. Based on the simulation results, the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.

Characterization of ABS + W and ABS + Bi 3D printing filaments attenuation for different photon beams

3D printing techniques and materials have become widely available in the last couple of decades and remains a hot topic of study as new materials can lead to new applications. This study aims to evaluate the attenuation behaviour of GMASS over photon beams ranging from 29.7 up to 661.7keV, comparing with pure ABS and using theoretical data of pure lead as reference. It was used the transmission method to obtain experimental attenuation coefficients to all materials and theoretical data. HVL and TVL calculations were also performed. Results show that ABS+W has higher attenuation than ABS+Bi and pure ABS. Using the lead theoretical reference data it can be concluded that although ABS+Bi and ABS+W attenuates less than pure lead, the 3D printing filaments can be used to create shielding tolls depending on radiation energy and application.

Understanding molecular motion mechanism of phase change materials in mesoporous MCM-41

Abstract Although nanoporous shape-stabilized composite phase change materials (PCMs) could efficiently address the leakage issue of pure PCMs during the solid-liquid phase transition process, numerous experiments have verified that the thermophysical parameters of the nanoporous shape-stabilized composite PCMs are significantly different from those of macroscopic bulk PCMs due to the nanoconfinement effects. However, macroscopic experimental data cannot directly reflect the microscopic interaction mechanisms in composite PCMs. Herein, to systematically understand the molecular motion mechanisms of PCMs with different functional groups (octadecane, octadecylamine, octadecanol and stearic acid) confined in the mesoporous MCM-41, we utilize molecular dynamics to simulate the spatial distribution and motion states of surface adsorbed PCMs molecules. This study aims to systematically reveal the interaction mechanisms between mesoporous MCM-41 and surface adsorbed PCMs at the molecular and atomic levels, thus providing constructive theoretical guidance and reference data for the targeted design and preparation of high-performance MCM-41-based composite PCMs.

Extended tight‐binding quantum chemistry methods

AbstractThis review covers a family of atomistic, mostly quantum chemistry (QC) based semiempirical methods for the fast and reasonably accurate description of large molecules in gas and condensed phase. The theory is derived from a density functional (DFT) perturbation expansion of the electron density in fluctuation terms to various orders similar to the original density functional tight binding model. The term “eXtended” in their name (xTB) emphasizes the parameter availability for almost the entire periodic table of elements (Z ≤ 86) and improvements of the underlying theory regarding, for example, the atomic orbital basis set, the level of multipole approximation and the treatment of the important electrostatic and dispersion interactions. A common feature of most members is their consistent parameterization on accurate gas phase theoretical reference data for geometries, vibrational frequencies and noncovalent interactions, which are the primary properties of interest in typical applications to systems composed of up to a few thousand atoms. Further specialized versions were developed for the description of electronic spectra and corresponding response properties. Besides a provided common theoretical background with some important implementation details in the efficient and free xtb program, various benchmarks for structural and thermochemical properties including (transition‐)metal systems are discussed. The review is completed by recent extensions of the model to the force‐field (FF) level as well as its application to solids under periodic boundary conditions. The general applicability together with the excellent cost‐accuracy ratio and the high robustness make the xTB family of methods very attractive for various fields of computer‐aided chemical research.This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Electronic Structure Theory > Semiempirical Electronic Structure Methods Software > Quantum Chemistry

Variations in stable carbon isotopes in different components of aquatic macrophytes from Taihu Lake, China

Understanding the fractionation mechanism and factors controlling carbon isotopes (δ13C) in macrophytes is significant for studying the biogeochemical carbon cycle and changes in nutrients within lakes. However, whether the environmental implications of δ13C are different in the different components (α-cellulose, holocellulose and whole sample) of macrophytes is unclear. In this paper, the δ13C composition of different macrophytes tissue components in Taihu Lake was analysed on spatial and temporal scales. The effects of aquatic environmental variables on the δ13C values of macrophytes were also explored. The results showed that emergent plants have the most negative stable carbon isotope signals, with a mean value (±SD) of −27.85‰ ± 0.95‰. Submerged macrophytes have large variations with significantly more positive δ13C values (−15.19‰ ± 3.08‰). The δ13C values of floating-leaved plants (−25.32‰ ± 1.02‰) fall between those of the two groups above. In the one-way analysis of variance (ANOVA), the different components (α-cellulose, holocellulose and whole sample) of δ13C exhibited significant differences (p-value <0.01) among the three groups of macrophytes. However, there was no significant seasonal difference in the δ13C of macrophytes. In addition, the δ13C of macrophytes in rivers were lighter than those in lakes. Correlation analyses indicated that the water pH was the main factor affecting δ13C variability in macrophytes. The δ13C values of α-cellulose showed stronger sensitivity to environmental variation than did those of the whole samples and holocellulose. Hence, it is necessary to extract α-cellulose when using the δ13C of aquatic macrophytes to study the changes in lake ecological environments. These results provided a theoretical reference and experimental data support for a modern process of using δ13C in macrophytes for palaeoenvironmental changes.

Thermal Wave Scattering and Temperature Concentration around the Opening in Platinum–Rhodium Leaky Plates

Based on the non-Fourier heat conduction wave model, the thermal wave scattering near the opening in the platinum–rhodium glass fiber leaky plate structure is studied by using complex function method and conformal mapping method, and the general solution of the thermal wave scattering problem is given. The boundary condition of the open surface is adiabatic. The influence of the geometrical and physical parameters of the leaky plate on the temperature distribution in the plate is analyzed, and the numerical results of the temperature concentration are given. This study can provide theoretical basis and reference data for the design and optimization of the opening structure of platinum–rhodium glass fiber leaky plate.

Optimizing genotype-environment-management interactions to ensure silage maize production in the Chinese Maize Belt

Grain maize production exceeds the demand for grain maize in China. Methods for harvesting good-quality silage maize urgently need a theoretical basis and reference data in order to ensure its benefits to farmers. However, research on silage maize is limited, and very few studies have focused on its energetic value and quality. Here, we calibrated the CERES-Maize model for 24 cultivars with 93 field experiments and then performed a long-term (1980-2017) simulation to optimize genotype-environment-management (G-E-M) interactions in the 4 main agroecological zones across China. We found that CERES-Maize could reproduce the growth and development of maize well under various management and weather conditions with a phenology bias of &lt;5 d and biomass relative root mean square error values of &lt;5%. The simulated results showed that sowing long-growth-cycle cultivars approximately 10 d in advance could yield good-quality silage. The optimal sowing dates (from late May to July) and harvest dates (from early October to mid-November) gradually became later from north to south. A high-energy yield was expected when sowing at an early date and/or with late-maturing cultivars. We found that Northeast China and the North China Plain were potential silage maize growing areas, although these areas experienced a medium or even high frost risk. Southwestern maize experienced a low risk level, but the low soil fertility limited the attainable yield. The results of this paper provide information for designing an optimal G×E×M strategy to ensure silage maize production in the Chinese Maize Belt.

Full-Dimensional Photodynamics of Bistable Proton Transfer Switches

Abstract Excited-state intramolecular proton transfers (ESIPT) are one of the fastest reactions in chemistry (&lt;100 fs) which – among other features like high photostability – makes them an important reaction class for molecular switches. ESIPTs can be coupled with double bond rotation/isomerization, so that molecules can act as “molecular cranes”, facilitating long-range proton transfer. A versatile model system is 7-hydroxy-4-methylquinoline-8-carbaldehyde (HMQCA): it features two proton-accepting sites, two stable ground-state isomers and should allow for easy derivatization. There is also experimental and theoretical reference data available, however, only for static properties, e.g. ground-state IR spectra or potential energy surface scans. In this contribution we show the results of full-dimensional surface-hopping molecular dynamics (MD) of HMQCA after photo-excitation, employing semiempirical quantum mechanics coupled to floating-occupation configuration interaction. The results support the potential of HMQCA as prototype system for directed proton transport by ESIPT.