Packing Configuration Research Articles

Enlargement of Bandgap and Birefringence in Nonlinear Optical Alkali‐Metal Sulfate Crystals by the Substitution of Asymmetrical Non‐π‐Conjugated Cation

AbstractWide bandgap and large birefringence, as well as strong second harmonic effect, are important but often mutually restraint prerequisites for deep‐ultraviolet (DUV) nonlinear optical (NLO) crystals, a type of photoelectronic materials that play an indispensable role in the DUV laser generation. For the long term, the search for new DUV NLO crystals has focused on the alkali‐metal inorganic acid salts where the variations of anionic groups are considered. Herein, another design strategy is reported, in which the alkali‐metal cations are substituted by the asymmetrical non‐π‐conjugated cations to harmonize the above mutual restrictions. Accordingly, LiN2H5SO4 (LNHSO) crystal is obtained by the substitution of [N2H5]+ for alkali‐metal ions in LiMSO4 (M = Na, K, and Rb). Compared with LiMSO4 (M = Na, K, and Rb), LNHSO exhibits a moderate phase‐matching second‐harmonic generation response (0.6 × KH2PO4), increased birefringence (two to three times that of other sulfates), and the widest bandgap (7.69 eV) among all the reported NLO sulfates. The structural analysis and theoretical calculation reveal that the structural anisotropy, arrangement, and packing configuration of the novel NLO‐active [N2H5]+ cation in LNHSO effectively promotes the optical properties and enlarges the bandgap. This work provides an innovative perspective for the rational design and synthesis of DUV NLO materials with excellent performance.

Active vs. passive isotopic analysis: Insights from urban Beijing field measurements and ammonia source signatures

Active collection methods such as ChemComb Speciation Cartridge samplers (CCSCs) are considered more accurate for determining the isotopic composition of NH3 (i.e., δ15N(NH3)), especially in ambient air. However, it is uncertain whether the difference in δ15N values remains consistent when comparing ALPHA to a lab-verified CCSCs with different filter types (Teflon, cellulose, and glass fiber). Here, we deployed two CCSCs and ALPHA side-by-side to collect ambient NH3 samples and compare their δ15N(NH3) values in urban Beijing during July 2019. Furthermore, NH3 source samples from urban traffic and livestock waste were collected using the ALPHA sampler under different scenarios, including various sampling locations, and sampling intervals to assess their representativeness. The results showed that NH3 concentrations measured by ALPHA were 27.6% and 8.5% lower than the concentrations measured by CCSCs A and B, respectively. CCSCs A showed lower δ15N(NH3) values (−16.4 ± 8.0‰) compared to CCSCs B, whereas the δ15N(NH3) values obtained from ALPHA (−23.9 ± 7.7‰) were not significantly different from CCSCs A. This variation in δ15N(NH3) values was attributed to reduced isotopic fractionation (31.5 ± 22.9‰) caused by decreased NH3 volatilization using Teflon and cellulose filter pack configurations. Moreover, this study revealed a consistent 15.1‰ lower δ15N(NH3) value with ALPHA compared to CCSCs B, when Teflon and glass fiber filter pack configurations were used for daily sampling. Additionally, this study revealed that ALPHA sampler might reach saturation when used for longer sampling durations, in contrast to shorter intervals of 8–12 h specifically for livestock waste. This saturation led to positive δ15N(NH3) values (2.9 ± 0.4‰), which were significantly higher compared to samples collected within the 8–12 h range. Further studies should conduct co-located measurements using both passive and active methods, enabling more accurate comparisons of sampling techniques at each location and ensuring representative samples for source apportionment studies.

Granular convergence as an iterated local map.

Granular convergence is a property of a granular pack as it is repeatedly sheared in a cyclic, quasistatic fashion, as the packing configuration changes via discrete events. Under suitable conditions the set of microscopic configurations encountered converges to a periodic sequence after sufficient shear cycles. Prior work modeled this evolution as the iteration of a pre-determined, random map from a set of discrete configurations into itself. Iterating such a map from a random starting point leads to similar periodic repetition. This work explores the effect of restricting the randomness of such maps in order to account for the local nature of the discrete events. The number of cycles needed for convergence shows similar statistical behavior to that of numerical granular experiments. The number of cycles in a repeating period behaves only qualitatively like these granular studies.

(Invited) Making Stacks of Nitrogenated Polycyclic Aromatic Hydrocarbons with Hydrogen Bonds

Architectures constituted of stacked aromatics play a crucial role in the development of function in biomacromolecules. Recreating this feature on synthetic systems would not only allow understanding and reproducing biological functions but also developing new functions. For instance, the performance of organic field-effect transistors, light-emitting diodes, and solar cells critically depends on the charge transport efficiency of stacks of organic semiconductors. Among different packing configurations, lamellar π-stacking has been identified as an optimal configuration for electronic transport, because of the efficient intermolecular electronic coupling.Nitrogenated polycyclic aromatic hydrocarbons and nanographenes have attracted considerable attention in recent years. Besides the effect of nitrogen doping on the electronic structure, sp2 nitrogens can be engaged in hydrogen bonding interactions as acceptors. We have developed the synthesis of novel architectures constituted of stacked nitrogenated polycyclic aromatic hydrocarbons held together by hydrogen bonds, which include new families of pseudorotaxanes, rotaxanes, foldamers and supramolecular polymers. The synthesis and self-assembling properties of these systems will be discussed together with their charge transporting properties.

Influence of packing configuration and flow rate on the performance of a forced draft wet cooling tower

Influence of packing configuration and flow rate on the performance of a forced draft wet cooling tower

A multi-scale study of 3D printed Co-Al2O3 catalyst monoliths versus spheres

This study demonstrates the characteristics of two model packing configurations: 3D printed (3DP) catalyst monoliths on the one hand, and their conventional counterparts, packed beds of spheres, on the other. Cobalt deposited on alumina is selected as a convenient model system for this work, due to its wide spread use in many catalytic reactions. 3DP constructs were produced from alumina powder impregnated with cobalt nitrate while the alumina spheres were directly impregnated with the same cobalt nitrate precursor. The form of the catalyst, the impregnation process, as well as the thermal history, were found to have a significant effect on the resulting cobalt phases. Probing the catalyst bodies in situ by XRD-CT indicated that the level of dispersion of identified Co phases (Co3O4 reduced to CoO) across the support is maintained under reduction conditions. The packed bed of spheres exhibits a non-uniform distribution of cobalt phases, including a core-shell morphology with an average crystallite size of 10–14 nm across the sphere, while the 3DP monolith exhibits a uniform distribution of cobalt phases with an average crystallite size of 5–12 nm upon reduction from Co3O4 to CoO. Computational Fluid Dynamics (CFD) modelling was carried out to develop digital twins and assess the effect of the geometry of both configurations on the pressure drop and velocity profiles. Finally, the activity of both Cobalt-based catalyst geometries was assessed in terms of their conversion, selectivity and turn over frequencies under model multiphase (selective oxidation) reaction conditions, which showed that the desired 3D printed monolithic geometries can offer distinct advantages to the reactor design.

Charging performance of structured packed-bed latent thermal energy storage unit with phase change material capsules

A mathematical model of the charging process for a structured packed-bed latent thermal energy storage unit with phase change material capsules is established. The thermal-hydrodynamic characteristics of the unit are investigated. The impacts of the heat transfer fluid inlet velocity, heat transfer fluid inlet temperature, initial temperature of the latent thermal energy storage unit, and diameters of the phase change material capsules are analyzed. The charging performance of a scaled-up latent thermal energy storage unit is studied. The numerical results indicate that the structured packing configuration of the structured packed-bed latent thermal energy storage unit influences the periodic flow characteristics of the latent thermal energy storage unit. The melting behaviors in each phase change material capsule are synchronous due to the excellent heat transfer capacity of the latent thermal energy storage unit. With the increasing initial temperature of the latent thermal energy storage unit, the duration of the charging process varies little, but the total heat storage capacity of the unit decreases. The decreasing diameter of the phase change material capsule significantly shortens the charging process of the latent thermal energy storage unit. The total heat storage capacities of the latent thermal energy storage unit with different phase change material capsule diameters are nearly the same. The heat storage capacity of the phase change material unit can be easily scaled up by adding more phase change material capsules and extending the phase change material capsule zone. The scale-up of the structured packed-bed latent thermal energy storage unit does not affect the charging time of the latent thermal energy storage unit.

Structural analyses of silk fibroins based on the structures of oligoalanine, and periodic oligopeptides of L‐alanine and glycine using x‐ray diffraction and 13C solid‐state NMR methods

AbstractThe structures of (A)12, (AAAG)7, (AAG)10, (AG)15, and (AGG)10 were determined using x‐ray diffraction and 13C sold‐state NMR methods after different solvent treatments to obtain knowledge about the structural changes of silk fibroins (SFs) from Samia cynthia ricini (S.c.ricini) and Bombyx mori (B. mori). Three solvent treatments were performed: precipitation from dialysis of LiSCN (LiSCN/Dialysis) or LiBr (LiBr/Dialysis) aqueous solutions, and drying from formic acid (FA) or trifluoroacetic acid (TFA) solutions. (AAAG)7 and (AAG)10 as models of S.c.ricini SF, formed antiparallel β‐sheet structure with staggered packing configuration and did not change after LiSCN/Dialysis or LiBr/Dialysis and FA treatments. (AGG)10 formed 31 helix structure and did not change with these solvent treatments either. On the other hand, (AG)15 as model of B. mori SF formed Silk I (type II β‐turn) structure after LiBr/Dialysis treatment and Silk II (lamellar packing) structure after FA treatment. Especially, B. mori SF seems useful for biomaterials.

Thermal Treatment of Trichloroethene by Electrical Resistance Heating: Visualization of Gas Production in Coarse Layers

The effective implementation of in situ thermal treatment (ISTT) technologies requires understanding of gas production and migration in heterogenous media. However, investigations of the effects of high permeability contrast on gas formation, accumulation, and migration, as well as its potential effect on the redistribution of dense non-aqueous phase liquid (DNAPL), are relatively rare. In this study, electrical resistance heating (ERH) experiments were conducted in a thin sand-packed cell to simulate common yet not well-studied scenarios encountered during ISTT applications, such as coarse lenses surrounded by finer material. Two packing configurations were employed: 2 mm glass beads surrounded by 20/30 silica sand and 20/30 silica sand overlaying 40/50 silica sand. Each experiment contained an emplaced pool of trichloroethene (TCE) within the coarse material. If permeable material or pathways were present between the coarse lens and the upper cell boundary, the gas migrated along these pathways, and local DNAPL redistribution was limited to near the top of the pool before it vaporized. In contrast, if the coarse material was surrounded by finer material and contained a sufficient volume of DNAPL, the gas accumulated inside the coarse lens leading to DNAPL displacement from the lens. For five selected DNAPLs, this volume was estimated to be 0.1% to 0.5% of the total pore volume of the coarse material. The conceptual model developed in this study improves our understanding of this common geological scenario, demonstrating the importance of considering both lower- and higher-permeability material and their effects on multiphase flow during co-boiling, as well as the design of gas extraction systems during ISTT applications.

Study of Strain-rate Effect in Two-dimensional Biaxial Test on Granular Material using Discrete Element Method

Numerical study to investigate the effect of various strain rates on global friction angle in the sand has been performed. Granular material behavior is influenced by several factors, among others: pack configuration, grain macro and micro roughness, confinement pressure, loading rate, etc. Sand is a granular material composed of discrete particles that the most refined microscopic techniques are needed to study its mechanical properties. In Indonesia, research related to the Discrete Element Method is still very limited. The two-dimensional discrete element method is capable to calculate the motion and interparticle contacts of large number of small particles, and each particle is modeled as a rigid circular element. The study started with the validation of the DEM model using YADE. Particles with a local friction angle of 35° are arranged in a closed rectangular box (frictionless wall). The number of particles used in this model validation simulation is 1000 sphere-type particles with monodisperse particle gradations. The simulation was done by a drained biaxial test with confinement stress of 100 kPa, thereafter varying strain rate are applied. Based on the deviatoric stress–axial strain curve from YADE, the result can be depicted on the Mohr circle to obtain the value of the global friction angle. It is found that the different value of strain rate affects its global friction angle. Increasing the value of the strain rate can increase the material global friction angle, which increases the strain rate from 1% to 5%, 10%, 25%, and 50% will increase its global friction angle by 5%, 5%, 14%, and 18%, respectively.

New lower bounds for optimal horoball packing density in hyperbolic n-space for 6 le n le 9

Koszul type Coxeter simplex tilings exist in hyperbolic n-space mathbb {H}^n up to n = 9, and their horoball packings achieve the highest known regular ball packing densities for n = 3, 4, 5. In this paper we determine the optimal horoball packing densities of Koszul simplex tilings in dimensions 6 le n le 9, which give new lower bounds for optimal packing density in each dimension. The symmetries of the packings are given by Coxeter simplex groups, and a parameter related to the Busemann function gives an isometry invariant description of different optimal horoball packing configurations.

C60 adsorption on defective Si (1 0 0) surface having one missed dimer from atomic simulations at electrical level

The adsorption geometry and electronic information of C60 onto reconstructed Si (100) surface having two types of missed dimers were investigated from self-consistent charge density functional tight-binding (SCC-DFTB) simulations. The C60 molecular orientation being relative to the defective Si surface, bonding form, and the number and distribution of dimers in the silicon surface, greatly affect the packing configurations in the C60/Si (100) systems. Charge-difference density and Mulliken populations analysis indicated that C60 was chemically bound to the silicon substrate by C-Si covalent bonds and the bond energy of short CSi covalent bonds is higher than others. The different adsorption configurations of C60/Si systems have different chemical potentials, implying their various applications in the redox reactivity.

Design of lithium‐ion battery packs for two‐wheeled electric vehicles

AbstractThe design of lithium‐ion battery pack to meet the power requirements of two‐wheeled electric bikes for Indian conditions is studied here. Theoretical calculations are performed based on the technical data collected from various resources in India. In particular, the two‐wheeled “Activa 6G” vehicle is considered for the analysis. Based on the numerical analysis, a relation between cell parameters such as: C‐rate, voltage, capacity, pack configuration, and vehicle dynamics parameters like: weight of the vehicle, payload, travel range per charge, and energy consumption, has been established. Commercial cylindrical cells, namely: 18650, 21 700, and 26 650 are used in all the calculations. The corresponding battery packs are designed considering a range of 100 km. Furthermore, simulations are performed to understand the voltage‐discharge characteristics, state of charge and variation of cell concentration with respect to time as the battery discharges. The studies are extended to analyze the battery thermal management to estimate the degradation and heat generation rate, and hence, the optimum operating parameters, that is, optimal electrode thicknesses and particle size to enhance the endurance. Based on the degradation and heat generation profiles, the life of the battery pack made of 26 650 cells is found to be better as compared to the battery packs made of 18 650 and 21 700 cells. Furthermore, the analysis is extended for battery packs made of 26 650 cells in four different configurations, considering air and mineral oil as the cooling fluids to estimate the maximum temperature and hence degradation characteristics. Tapered configuration is found to be the best configuration among the four, yielding lowest maximum temperature and capacity fading. On the other hand, when mineral oil is used as the cooling fluid in rectangular configuration, the maximum operating temperature is found to be reduced by 4.49 K. However, usage of mineral oil adds to the periodic maintenance and replacement costs.

Revealing the Key Packing Features Determining the Stability of Peptide Bilayer Membrane.

Short surfactant-like amphiphilic peptide, A3K, resembling a surfactant with a hydrophobic tail (A3) and a polar headgroup (K), is experimentally determined to form a membrane. Although the peptides are known to exist as β-strands, the exact packing architecture stabilizing the membrane is unknown. Earlier simulation studies have reported successful packing configurations through trial and error. In this work, we present a systematic protocol to identify the best peptide configurations for different packing patterns. The influence of stacking peptides in square and hexagonal packing geometry with the neighboring peptides in parallel and antiparallel orientations was explored. The best peptide configurations were determined from the free energy of bringing 2-4 peptides together as a bundle that can be stacked into a membrane. The stability of the assembled bilayer membrane was further investigated through molecular dynamics simulation. The role of peptide tilting, interpeptide distance, the nature and the extent of interactions, and the conformational degrees of freedom on the stability of the membrane is discussed. The consistency with the experimental findings suggests hexagonal antiparallel as the most relevant molecular architecture.

Investigation on the Performance of CO2 Absorption in Ceramic Hollow-Fiber Gas/Liquid Membrane Contactors.

The absorption efficiencies of CO2 in ceramic hollow-fiber membrane contactors using monoethanolamine (MEA) absorbent under both cocurrent- and countercurrent-flow operations were investigated theoretically and experimentally; various MEA absorbent flow rates, CO2 feed flow rates, and inlet CO2 concentrations were used as parameters. Theoretical predictions of the CO2 absorption flux were analyzed by developing the mathematical formulations based on Happel's free surface model in terms of mass transfer resistances in series. The experiments of the CO2 absorption were conducted by using alumina (Al2O3) hollow-fiber membranes to confirm the accuracy of the theoretical predictions. The simplified expression of the Sherwood number was formulated to calculate the mass transfer coefficient of the CO2 absorption incorporating experimental data. The data were obtained numerically using the fourth-order Runge-Kutta method to predict the concentration distribution and absorption rate enhancement under various fiber packing configurations accomplished by the CO2/N2 stream passing through the fiber cells. The operations of the hollow-fiber membrane contactor encapsulating N = 7 fiber cells and N = 19 fiber cells of different packing densities were fabricated in this work to examine the device performance. The accuracy derivation between experimental results and theoretical predictions for cocurrent- and countercurrent-flow operations were 1.31×10-2≤E≤4.35×10-2 and 3.90×10-3≤E≤2.43×10-2, respectively. A maximum of 965.5% CO2 absorption rate enhancement was found in the module with embedding multiple fiber cells compared with that in the device with inserting single-fiber cell. Implementing more fiber cells offers an inexpensive method of improving the absorption efficiency, and thus the operations of the ceramic hollow-fiber membrane contactor with implementing more fiber cells propose a low-priced design to improve the absorption rate enhancement. The higher overall CO2 absorption rate was achieved in countercurrent-flow operations than that in cocurrent-flow operations.

Physical models of notochord cell packing reveal how tension ratios determine morphometry

The physical and geometric aspects of notochords are investigated using a model of finite-length notochords, with interior vacuolated cells arranged in two common packing configurations, and sheath modeled as homogeneous and thin. The key ratios governing packing patterns and eccentricity are number of cells per unit length λ and cell tension ratio Γ. By analyzing simulations that vary Γ and total number of cells N, we find that eccentricity, λ, and internal pressure approach consistent asymptotic values away from the tapering ends, as N increases. The length of the tapering ends is quantified as a function of Γ and pattern. Formulas are derived for geometric ratios, pressure, and energy as functions of Γ and pattern. These observations on the relationship between mechanics, geometry, and pattern provide a framework for further work which may provide insight into the roles of mechanosensing and pressure-volume regulation in the notochord.

Detection of inhomogeneities in serially connected lithium-ion batteries

Serially connected batteries present a cell-to-cell variation in their electrochemical behavior that tends to increase over the lifetime. The decision for the best circular economy option for aged or defective battery packs – i.e., repair, remanufacturing, or recycling – requires comprehensive testing, analysis, and an according data basis. Remanufacturing of battery packs refers to the replacement of individual (sub-)modules or cells which are defective or show a diverging aging behavior to the rest of the battery units. A detection algorithm is required to decide if a significant inhomogeneity in a serial connection of batteries is present. For this reason, virtual battery packs are built based on the measurement of 12 individual batteries of the same type. Cell-to-cell variations are determined at the begin of life and a novel representation for the quantitative and qualitative analysis is given. This work extracts impedance-based features of different serial battery pack configurations through a novel comparative analysis approach. The features are extracted from Bode and Nyquist plots and the real and imaginary parts of the impedance itself. The detectability is analyzed depending on the number of cells and the underlying effects are discussed. A detailed sensitivity analysis is carried out for the most promising features, in which the influence of the cell-to-cell variations, the aging condition, and the aging mechanism are analyzed. The feature that shows the highest sensitivity, the so called low-frequency minimum, is able to detect single outliers within a high number of serially connected cells.

Improved Heat Transfer in Guar Gel Composites Reinforced with Randomly Distributed Glass Microspheres

Improved heat transfer in composites consisting of guar gel matrix and randomly distributed glass microspheres is extensively studied to predict the effective thermal conductivity of composites using the finite element method. In the study, the proper and probabilistic three-dimensional random distribution of microspheres in the continuous matrix is automatically generated by a simple and efficient random sequential adsorption algorithm which is developed by considering the correlation of three factors including particle size, number of particles, and particle volume fraction controlling the geometric configuration of random packing. Then the dependences of the effective thermal conductivity of composite materials on some important factors are investigated numerically, including the particle volume fraction, the particle spatial distribution, the number of particles, the nonuniformity of particle size, the particle dispersion morphology and the thermal conductivity contrast between particle and matrix. The related numerical results are compared with theoretical predictions and available experimental results to assess the validity of the numerical model. These results can provide good guidance for the design of advanced microsphere reinforced composite materials.

DFTB investigations of structures and electron states for a decahedron Ti7 cluster on graphene on electrical level

We performed self-consistent charge density functional tight binding simulations to investigate the interactions between a decahedron Ti 7 cluster and graphene. Different adsorption behaviors of the cluster on perfect and defective graphene are characterized by adsorption energy, chemical potential, HOMO-LUMO energy gap, charge density differences, Mulliken populations on atoms, and molecular orbitals on HOMO and LUMO energy levels. Simulation results show that relatively contacting orientations of the cluster and graphene as well as adsorption positions greatly affect adsorption's packing configurations. The defective graphene improves high possibility for strongly binding the metal cluster. Apparent charge transfer occurs from the cluster to graphene for the adsorption on defective graphene. The molecular orbitals on the HOMO and LUMO energy levels present differences for different adsorption configurations. • A decahedron Ti 7 cluster and graphene • Different adsorption behaviors of the cluster on perfect and defective graphene • Adsorption energy, chemical potential, HOMO-LUMO energy gap • Charge density differences, Mulliken populations on atoms, and molecular orbitals on HOMO and LUMO energy levels

Correlations of lithium-ion battery parameter variations and connected configurations on pack statistics

Battery cell-to-cell parameter variations and connected configurations jointly affect pack performance. Knowledge of the quantitative correlations of lithium-ion battery parameter variations and connected configurations on pack statistics is crucial for understanding and improving the pack performance in the automotive industry. From a statistical perspective, this study theoretically developed analytical correlations to analyze the impact of the statistics (mean and standard deviation) of cell-level parameters (capacity and resistance) and connected configurations on module/pack statistical performance under a random sampling scenario. These correlations are applied to various cell-to-cell parameter variations and module/pack configurations and are verified by Monte Carlo simulations. The results demonstrate that cell-to-cell variations have a negative effect on the statistical performance of modules, especially series mean capacity. Meanwhile, parallel and series configurations can dramatically reduce the variation in module-level parameters, and the variations in parallel or series modules with four cells are 50% of those of cell-to-cell. Therefore, parallel configurations can effectively compensate for the loss of mean capacity caused by series configuration so that the pack with parallel modules connected in series has the capacity advantages compared to that of the pack with series modules connected in parallel, but their resistance statistics are the same. The correlations developed in this study provide important guidance for battery screening and the selection of pack configuration and equalization topology, thereby giving critical information for optimizing pack performance from the cell level to the pack level.