Variable Spacing Research Articles

Microscale Electrical Resistivity Measurements to Investigate Particle Distribution.

The functional performance of a particulate thin film depends greatly on the particle distribution that forms during drying. In situ methods for monitoring the impact of different processing parameters on the distribution of particles currently require expensive and specialized equipment. This work addresses this gap by miniaturizing a geophysical prospecting method to thin-film applications. In this method, four-electrode resistivity measurements at variable probe spacing detect changes in the vertical particle concentration profile. A heuristic colloidal drying model describes the particle distribution during drying in terms of the relative effects of Brownian diffusion, sedimentation, and evaporation. For sedimentation- and evaporation-dominated drying, the film is modeled as two stratified layers of different concentrations. Solving this model simultaneously alongside Laplace's equation for electrostatic resistance identifies the parameters necessary to distinguish between diffusion-, sedimentation-, and evaporation-dominated drying. For resistive particles in a conductive solvent, simulations predict that the normalized thickness of the top layer, δt/H0, must exceed a critical value to distinguish between different drying regimes. The heuristic model results are validated theoretically by comparison to a physics-based drying model. Model predictions are experimentally validated by fabricating a custom microlithography four-line probe device and measuring the transient resistance of systems for which the drying mechanism is known. This work offers a low-cost and in situ method to identify drying mechanisms and extract physical parameters that better characterize the processing-structure-function relationships for many coatings.

The Heisenberg-RIXS instrument at the European XFEL.

Resonant inelastic X-ray scattering (RIXS) is an ideal X-ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core-hole lifetime energy broadening. Also, in pump-probe experiments the interaction time is made very short by the same core-hole lifetime. RIXS is very photon hungry so it takes great advantage from high-repetition-rate pulsed X-ray sources like the European XFEL. The Heisenberg RIXS instrument is designed for RIXS experiments in the soft X-ray range with energy resolution approaching the Fourier and the Heisenberg limits. It is based on a spherical grating with variable line spacing and a position-sensitive 2D detector. Initially, two gratings were installed to adequately cover the whole photon energy range. With optimized spot size on the sample and small pixel detector the energy resolution can be better than 40 meV (90 meV) at any photon energy below 1000 eV with the high-resolution (high-transmission) grating. At the SCS instrument of the European XFEL the spectrometer can be easily positioned thanks to air pads on a high-quality floor, allowing the scattering angle to be continuously adjusted over the 65-145° range. It can be coupled to two different sample interaction chambers, one for liquid jets and one for solids, each state-of-the-art equipped and compatible for optical laser pumping in collinear geometry. The measured performances, in terms of energy resolution and count rate on the detector, closely match design expectations. The Heisenberg RIXS instrument has been open to public users since the summer of 2022.

Reasonable layout range of lower mining roadways in the close and variable interval coal seams mining: a case study.

In the context of close-distance coal seam mining, the stress transfer mechanism following the extraction of the upper coal seam is crucial for the layout of roadways in the lower coal seam. This study utilizes ground-penetrating radar (GPR) to analyze the stability and plastic zone extent of residual coal pillars after upper seam extraction. A theoretical model for the stress distribution of multiple goaves and coal pillars was established. Based on a case study with variable inter-seam spacing, the stress distribution and transfer mechanisms of the floor were analyzed. The results indicate that during the transition from the center of the coal pillar to the goaf, stress concentration initially decreases significantly and then gradually returns to the original rock stress, forming a distinct stress gradient distribution. As the depth of the floor strata increases, the weight of the overlying strata is more evidently transferred through the coal pillars to the goaf. Finally, a reasonable layout range for the lower seam mining roadways under different inter-seam spacings is proposed, providing a reference for optimizing roadway layout in similar geological conditions.

Mass and Heat Exchange in Rotating Compressor Cavities With Variable Cob Separation

Abstract Next generation aeroengines will operate at ever-increasing pressure ratios with smaller cores, where the control of blade-tip clearances across the flight cycle is an emerging design challenge. Such clearances are affected by the thermal expansion of the compressor disks that hold the blades, where acute thermal stresses govern operating life. The cavities formed by corotating disks feature a heated shroud at high radius and cooler cobs at low radius. A three-dimensional, unsteady and unstable flow structure is induced by destabilizing buoyancy forces. The radial distribution of disk temperature is driven by a conjugate heat transfer at Grashof numbers of order 1013. Such flows are further influenced by the heat and mass exchange with an axial throughflow of cooling air at low radius, where the interaction depends on the Rossby number and separation of the disk cobs. This paper is the first to study the effect of cob separation ratio on mass and heat exchange for compressor cavities. A model is developed to predict the cavity-throughflow interaction, and disk and fluid-core temperatures. The judicious use of a physics-based methodology provides reliable, reduced-order solutions to the complex conjugate problem, thereby making it appropriate for practical engine thermo-mechanical design. The model is validated by detailed experimental measurements using the Bath Compressor Cavity Rig, where variable disk cob spacings were investigated over a range of engine-representative conditions. The unsteady pressure measurements collected in the frame of reference of the rotating disks reveal new insight into the fundamentally aperiodic nature of the flow structure. This new understanding of heat transfer informs an expedient reduced-order model and enables more efficient design of future high pressure-ratio aeroengines.

Odd-Even Law Mediated Supramolecular Chirality of Luminescent Dipeptides for Chiroptical Energy Transfer.

Inherent luminescent short peptides essentially provide opportunities to rationally manipulate supramolecular chirality and chiral luminescence. Herein, a facile protocol to construct a series of naphthalimide-appended dipeptides is reported that show ultrasound wave-activated supramolecular chirality regulated by odd-even law. Naphthalimide luminophores are conjugated to the dipeptide skeleton with variable alkyl spacers. The presence of tyrosine interferes the kinetic aggregation into achiral nanoparticles without chirality transfer to supramolecular scale. However, ultrasound treatment initiates the nanoparticle-to-helix transition accompanied with the appeared chiral optics, including Cotton effect and circularly polarized luminescence (CPL). The supramolecular chiral parameters, including handedness of helices and chiroptical behaviors, follow the odd-even law of alkyl spacers in dipeptides bearing non-substituted naphthalimides. The amine-substitution boosted the quantum yields of dipeptide whereas no odd-even effect. The two types of dipeptides constituted ideal energy transfer pairs that enable the efficient energy transfer as well as the transportation of odd-even law to dipeptides containing substituted naphthalimides. This work sheds light on the construction of luminescent dipeptides with applications in precise control over chirality transportation and chiral luminescence.

Grade control drillhole spacing and mining selectivity determination using high resolution simulations applied on distinctly heterogeneous open pit mines

The grade control drillhole spacing and mining selectivity decisions are typically made using the resource model estimated from exploration and infill drilling data. Once production starts, large quantities of grade control data are collected to delineate ore and waste boundaries for ore control. In this work, a grade control drillhole spacing and mining selectivity optimization workflow is presented which allows the practitioner to use site specific knowledge to determine the most profitable ore control mining scenario. The densely gridded production data is used to simulate a ground truth block model from which scenarios of variable drillhole spacing and selectivity are evaluated against their corresponding costs to determine the maximum profit scenario. Eleven mining scenarios are evaluated using year production data from three distinctly heterogeneous mine with drillhole spacing and mining selectivity varying from 3 × 3 × 3 m (27 m3) to 30 × 30 × 15 m (13,500 m3). The profit differences from the optimum scenario varied by millions of dollars (1–8%) against the next best case depending on the heterogeneity of the deposit. Practitioners could apply this workflow to inform grade control drillhole spacing and mining selectivity decisions for different domains within the mine or multiple pits especially if distinctly heterogeneous volumes exist.

Resilience enhancement of power distribution system using fixed and mobile emergency generators based on deep reinforcement learning

Growing extreme weather-related events have increased the need for a resilient emergency response in the Power Distribution Systems (PDSs). This paper proposes a novel restoration scheme that involves forming Micro-Grids (MGs) and dispatching Mobile Emergency Generators (MEGs) between them. Due to the PDS variability and extensive decision space, conventional model-based approaches aren't suitable for implementing the proposed scheme. Therefore, a model-free framework is designed to control the restoration process. The proposed problem is formulated as a Markov Decision Process (MDP) considering uncertainties associated with load profile, and renewable resources. Deep Q-Network (DQN), a fundamental algorithm in Deep Reinforcement Learning (DRL), is employed to solve the proposed MDP model. DQN algorithm can learn optimal control strategy by interacting with the simulated environment at the training phase and then deploy the learned policy in a real-world application. The main objective of the designed DQN model is to maximize the restored loads and ensure a high level of post-restoration reliability for Critical Loads (CLs). MATLAB software is considered as the simulated environment to perform power flow calculation and MEGs routing. The efficiency and applicability of the proposed method are evaluated by conducting experiments on the modified IEEE 13-bus, 37-bus, and 123-bus networks.

Wide-range angle sensing based on mixed variable line spacing gratings

Variable line spacing (VLS) gratings are core components in spatial spectrum and synchrotron radiation facilities due to their merits of self-focusing, aberration correction, and flat focal field. However, optimal design and fabrication of VLS gratings are still required for matching various applications. Scratch-induced selective wet etching has been proven as a robust way for fabricating various nanostructures because of its simplicity, flexibility, and controllability. In this paper, we proposed convenient and maskless methods to fabricate VLS grating based on scratch-induced selective wet etching. During the etching, key factors, including normal load for the scratching, etching time, and types of etchants, were investigated systematically toward optimizing the process. The shapes including sidewall angle and the bottom curvature of the grating elements can be controlled by adjusting the normal load, etching time and/or etching etchants. It is found that the VLS gratings present a wide-range sensing for angle detection based on the reflection spectrum. Furthermore, combining transferring process, the VLS master gratings could be replicated on polydimethylsiloxane (PDMS) surface, which showed great optical performance. This work opened new light to some extent for the application of angle sensing and structural color showing.

Multi deep learning-based stochastic microstructure reconstruction and high-fidelity micromechanics simulation of time-dependent ceramic matrix composite response

A multi deep learning-based framework is developed for efficient, automated microstructure reconstruction and generation of stochastic representative volume elements (SRVEs) with periodic boundary conditions (PBCs) for accurate modeling of ceramic matrix composite (CMC) response. The methodology comprises a convolutional neural network coupled with regression layers to act as a vanilla regression network for semantic segmentation of the microstructure, allowing accurate characterization of the phases and their distributions at the microscale. Scanning electron microscope and confocal microscope are used to obtain C/SiNC and SiC/SiNC CMCs micrographs for vanilla regression testing. Microstructure variability in terms of fiber volume fraction and porosity are quantified through the output regression layer, ensuring accurate representation of material variability in SRVE construction. Generative adversarial network (GAN) and its variants are designed to produce high-fidelity SRVE, spanning CMCs microstructure variability space. A circular padding algorithm is developed to generate SRVEs with PBCs during training of GANs. The accuracy of the generated SRVEs is established through micromechanics simulations, where an efficient formulation of the high-fidelity generalized methods of cells (HFGMC) approach is used to compute the effective mechanical properties. An iterative algorithm is implemented in the HFGMC solver to simulate time-dependent deformation of SiC/SiNC subjected to creep loading conditions.

Investigating the Influence of Seasonal Variability and Urban Green Spaces on Ambient Air Quality in an Urban Environment

Investigating the Influence of Seasonal Variability and Urban Green Spaces on Ambient Air Quality in an Urban Environment

Bionic design of thin-walled bilinear tubes with excellent crashworthiness inspired by glass sponge structures

In order to enhance energy absorption, this study draws inspiration from the diagonal bilinear robust square lattice structure found in deep-sea glass sponges, proposing a design for thin-walled structures with superior folding capabilities and high strength-to-weight ratio. Firstly, the crashworthiness of bionic glass sponge tube (BGSTO) is compared with that of equal-wall-thickness equal-mass four-X tube through both experiments and simulations, and it is obtained that the specific energy absorption of BGSTO is increased by 78.64%. And the crashworthiness of BGSTO is also most significant compared to that of multicellular tubes with the similar number of crystalline cells. Additionally, we found that the double-line spacing of the glass sponge can be freely adjusted without changing the material amount. Therefore, based on BGSTO, we designed two other double-line structures, BGSTA and BGSTB. Then with equal wall thickness and mass as a prerequisite, this study proceeds to design and compare the energy absorption properties of three bilinear thin-walled tubes in both axial and lateral cases. The deformation modes and crashworthiness of the three types of tubes with variable bilinear spacing (βO/A/B ) are comparatively analysed. The improved complex proportional assessment (COPRAS) synthesis decision is used to obtain that BGSTO exhibits superior crashworthiness over the remaining two kinds of tubes. Finally, a surrogate model is established to perform multi-objective optimization on the optimal bilinear configuration BGSTO selected by the COPRAS method.

Compression-induced crossovers for the ground state of classical dipole lattices on a Möbius strip.

We explore the ground-state properties of a lattice of classical dipoles spanned on the surface of a Möbius strip. The dipole equilibrium configurations depend significantly on the geometrical parameters of the Möbius strip, as well as on the lattice dimensions. As a result of the variable dipole spacing on the curved surface of the Möbius strip, the ground state can consist of multiple domains with different dipole orientations which are separated by domain-wall-like boundaries. We analyze in particular the dependence of the ground-state dipole configuration on the width of the Möbius strip and highlight two crossovers in the ground state that can be correspondingly tuned. A first crossover changes the dipole lattice from a phase which resists compression to a phase that favors it. The second crossover leads to an exchange of the topological properties of the two involved domains. We conclude with a brief summary and an outlook on more complex topologically intricate surfaces.

Effect of Sinusoidal Fiber Waviness on Non-Linear Dynamic Performance of Laminated Composite Plates with Variable Fiber Spacing

This study investigated influence of varying waviness characteristics of fiber, represented by path amplitude Δ and different numbers of half sine waves k , on the elastic-plastic dynamic behaviour of laminated composite plates with variable fiber spacing. The analysis was based on the equations for action of constant axial dynamic loading and two-dimensional layered approach with classical first order shear deformation theory with five degrees of freedom per node, and it was performed with FORTRAN 94 programming language. Von-Karman’s assumptions were used for the discretization of the laminated plates to include geometric nonlinearity for nine-node Lagrangian isoperimetric quadrilateral elements. Complete bond between the layers was assumed with no delamination, which was based on first-order shear deformation theory. The Newmark implicit time integration method and Newton-Raphson iteration were simultaneously used to solve the nonlinear governing equation in conjunction. It was proven in the research that the nonlinear performance of the laminated composite plate was affected by the studied waviness parameters Δ and k , and also by the variable distribution pattern selected for this study.

Synchronization of delayed stochastic reaction–diffusion Hopfield neural networks via sliding mode control

Synchronization of stochastic reaction–diffusion Hopfield neural networks with s-delays via sliding mode control is investigated in this article. To begin with, we choose suitable functional space for state variables, then the system is transformed into a functional differential equation in an infinite-dimensional Hilbert space by using appropriate functional analysis technique. Based on above preliminary preparation, sliding mode control (SMC) is constructed to drive the error trajectory into the designed switching surface. Specifically, the switching surface is constructed as linear combination of state variables, which is related to control gains. Then novel SMC law is designed which involving delay, reaction diffusion term, and reaching law. Furthermore, the criterion of mean-square exponential synchronization for stochastic delayed reaction–diffusion Hopfield neural networks with s-delays is given in the form of matrix form. This criterion is less restrictive and easy to check in computer. Meanwhile, a different novel Lyapunov–Krasovskii functional (LKF) mixed with Itô’s formula, Young inequality, Hanalay inequality is employed in this proof procedure. At last, a numerical example is presented to validate the availability of theoretical result. The simulation is based on the finite difference method, and numerical result coincides with the theoretical result proposed.

Contrasting patterns of 5S rDNA repeats in European and Asian ecotypes of greater duckweed, Spirodela polyrhiza (Lemnaceae).

Ribosomal DNA (rDNA) contains highly conserved, specifically organized sequences encoding ribosomal RNAs (rRNAs) separated by variable non-transcribed intergenic spacers (NTSs) and is abundant in eukaryotic genomes. These characteristics make the rDNA an informative molecular target to study genome organization, molecular evolution, and phylogenetics. In this study, we characterized the 5S rDNA repeats in the greater duckweed Spiroldela polyrhiza, a species known for its small size, rapid growth, highly conserved genome organization, and low mutation rate. Sequence analysis of at least 12 individually cloned PCR fragments containing the 5S rDNA units for each of six ecotypes that originated from Europe (Ukraine) and Asia (China) revealed two distinct types of 5S rDNA repeats containing NTSs of different lengths and nucleotide compositions. The shorter 5S rDNA repeat units had a highly homogeneous 400-bp NTS, with few ecotype- or region-specific single-nucleotide polymorphisms (SNPs). The longer 5S rDNA units had NTSs of 1056-1084 bp with characteristic intra- and inter-genomic variants due to specific SNPs and insertions/deletions of 4-15-bp DNA elements. We also detected significant variability in the ratio of short/long 5S rDNA variants between ecotypes of S. polyrhiza. The contrasting dynamics of the two types of 5S rDNA units, combined with the unusually low repeat copy number (for plants) in S. polyrhiza (46-220 copies per genome), shows that this species could serve as an excellent model for examining the mechanisms of concerted evolution and functional significance of rDNA variability.

Effect of Spacing and Different Levels of Phosphorus on Growth and Yield of Malepatan-1 Variety of Cowpea (Vigna unguiculata (Linn.) Walp.) in Dang District, Nepal

The simplest strategy to boost cowpea production is to have an optimum fertilizer level and spacing. The study was performed to assess the effect of variable row spacing and phosphorus (P) levels on the growth and yield of cowpeas. The experiment was carried out using a split-plot design with three planting geometry as the main plot (15 cm × 30 cm, 30 cm × 30 cm, and 45 cm × 30 cm) and three P levels as subplots (20, 40, and 60 kg/ha), each replicated three times. The result demonstrated that P had a significant effect on the number of pods per plant at 100 days after sowing (DAS), pod length at 85 and 100 DAS, and yield of fresh pods. However, P did not significantly impact plant height or number of pods per plant at 70 and 85 DAS. The highest fresh pod yield (1.05 t/ha) and pod length at 85 and 100 DAS (20.33 and 21.16 cm, respectively) were observed at 60 kg/ha P level. Similarly, the highest number of pods per plant at 100 DAS (8.3) was recorded at a P level of 40 kg/ha, which was comparable to that obtained at a P level of 60 kg/ha (8.1). Also, the spacing showed a nonsignificant effect on any of the studied parameters, except for the number of branches per plant at 30 DAS. The 45 cm × 30 cm spacing resulted in the highest number of branches per plant at this stage (2.4).

Formation of Ediacaran stromatolitic cherts through a combination of biogenic and abiotic processes: New insights from the Bohemian Massif

Stromatolites are remarkable organosedimentary laminated structures that grow gradually through time due to the activity of microorganisms, mostly algae and cyanobacteria. The appearance of stromatolites in formations as old as ∼ 3.7 Ga represents the earliest macroscopic traces of life on Earth. Yet, the biogenic origin of some presumed stromatolites has been questioned as abiotic processes (e.g., fluid precipitation, diagenesis and metamorphism) can also be responsible for the formation of stromatolite-like textures. This is especially true in case of pervasively silicified stromatolites (stromatolitic cherts) that have rarely been reported from Neoproterozoic successions. Here, we present a detailed study of the Ediacaran stromatolitic cherts from the Blovice accretionary complex (Bohemian Massif) that combines petrography, trace element and Si–O isotopic compositions and Raman spectroscopy of organic matter to decipher the complex processes leading to their formation and evaluate the biogenicity of their precursor. Textural evidence (i.e. the presence of pseudomorphs after carbonate/evaporate and micro-ooids, variable thickness and spacing of organic-rich laminae) as well as trace element/isotopic compositions argue for a multi-stage formation of stromatolitic cherts. The primary carbonaceous stromatolitic precursors first formed in shallow-water lagoons with variable salinity at seamount slopes, were then fragmented by surface processes (erosion, mass wasting), and finally silicified by low-temperature hydrothermal fluids. The primary biogenic character of stromatolitic textures is evidenced by the non-equidistant alternation of dark (organic matter-rich) and light laminae with markedly different oxygen isotopic compositions reflecting probably seasonal cycles during stromatolite deposition, enrichment of bio-essential elements (e.g., Cu, Zn, Co and Mn) in dark laminae, and Raman spectra of organic matter indicative for variably matured kerogens. The presence of late-stage diagenetic modifications might be related to subsequent burial and low-grade metamorphism of stromatolitic cherts within the accretionary wedge.

Thermal history inversion from thermochronometric data and complementary information: New methods and recommended practices

Thermal history inverse modeling has become one of the primary platforms for interpreting thermochronometric data. This paper introduces new features in the HeFTy software, and compares them with both earlier HeFTy versions and other programs. The approach for combining multiple goodness-of-fit tests into a single probability has been changed to Fisher's method, improving both statistical accuracy and ease of plain-language interpretation. The mechanism and guidelines for setting up Monte Carlo inverse modeling in HeFTy are reviewed, with particular attention to the role of allowing complex but geologically realistic time-temperature (t-T) paths. A new implementation of the controlled random search algorithm for paths with variable time spacing greatly accelerates finding solutions that fit the data while trying to also map the solution space as effectively as an unbiased Monte Carlo approach, so as to avoid providing an unrealistic impression of resolving power. A new time-depth (t-Z) modeling mode uses a 1-D thermal model to make a first-order conversion between depth and temperature, with depth change corresponding to erosion or deposition at the Earth surface. This mode approximates the thermal buffering effects of the crust, and allows temperature relationships between samples and the Earth surface to evolve in a physically appropriate fashion. These improvements enable multi-sample modeling along an elevation transect, including testing and constraining the timing of deformation, expressed as tilting, and topography development. In most cases, adding geological constraints during the modeling process is crucial for achieving meaningful results, as the resolving power of the thermochronometric data alone is usually limited, and the best-fitting results are not necessarily geologically realistic. A crucial step in interpreting any modeling result is to ascertain how the data and assumptions, including those embedded in the software, lead to the outcome obtained. These principles are illustrated using recent examples of modeling thermal histories associated with the Great Unconformity.

Performance analysis of a complex superstructure-foundation-subsoil interaction system due to variable pile spacing

Performance analysis of a complex superstructure-foundation-subsoil interaction system due to variable pile spacing

Investigation of interference effect on hexagonal plan-shaped high-rise building under wind excitation

ABSTRACT This paper represents a detailed investigation of tall hexagonal buildings in the presence of a similar type of single-interfering buildings and double-interfering buildings. The building models are analysed using CFD in ANSYS CFX module. The k-ε turbulence model is used to carry out the numerical simulations. For two buildings case (single interfering building), the wind incidence angles (WIA) vary from 0° to 90° at an interval of 15° and from 90° to 360° at an interval of 30°. The variable spacing of 200 mm, 300 mm, 500 mm and 800 mm has been kept apart for two building case. For the three building case (double interfering buildings), the orientation of the interfering buildings kept varying from 15° to 90° with a regular interval of 15°. The variable spacing between the principal building and interfering buildings is kept 300 mm and 500 mm apart. The model height for both cases is 500 mm in 1:300 length scale. The variation of interference factors for both pressure and force coefficients are evaluated and graphically represented to investigate the hexagonal building model. The interference Factor is found to be minimum at 90° WIA in each of the faces irrespective of spacing between buildings.