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Multi-element analysis of archaeological limestone artifacts: A data-level matrix correction approach
No full textElemental analysis of carbonate-rich heritage materials is often subject to strong matrix effects caused by high calcium content, which can lead to systematic underestimation of some major and trace elements, including rare earth elements (REEs), by ICP-OES and ICP-MS. This study develops a practical analytical strategy tailored to archaeological limestone artifacts, combining microwave-assisted digestion with a data-level, element-specific matrix correction based on certified reference materials (CRMs). Concentrations obtained by external calibration were empirically adjusted using correction factors derived from the ratio of standard addition to external calibration results for the CRMs NIST 1d and NCS DC 73306. This approach brought all determined element concentrations into statistical agreement with the certified values. The workflow was applied to 69 limestone figurines from the Emecik Apollo Sanctuary (Türkiye) that were previously attributed to Cypriot sources. After matrix correction, multivariate statistical analysis of the major, trace, and REE data identified three distinct geochemical clusters, consistent with the exploitation of at least three Cypriot limestone formations. The method is minimally destructive, time- and cost-efficient, and suitable for large archaeological assemblages, providing more accurate compositional data that support reliable provenance interpretations and establish a solid geochemical basis for reconstructing raw material procurement strategies for limestone votive figurines in the ancient Eastern Mediterranean
Computational modeling of viscoelastic snap-through in mechanical metamaterials
No full textMechanical metamaterials are architected solids whose macroscopic response is governed primarily by geometry rather than composition. Instability-induced metamaterials form a crucial subclass within this group, harnessing mechanical instabilities to achieve programmable deformations. Moreover, these materials are often made up of rubberlike materials which undergo large deformations and exhibit dissipative behavior due primarily to viscoelastic effects. Although hyperelastic constitutive models do not fully capture the observed rate-dependent dissipative response, periodic porous metamaterials are often modeled within the framework of finite elasticity. Therefore, it is essential to extend hyperelastic approaches towards viscoelastic formulations within the geometrically non-linear setting. To this end, we employ the theory of finite viscoelasticity to consider the rate-dependent dissipative response of elastomeric metamaterials with a periodic porous structure. Similar to their response predicted by finite elasticity, the instability due to geometrical non-linearity under compression leading to pattern transformation is also observed with finite viscoelasticity models. As opposed to elasticity, however, the energy dissipation caused by the intrinsic material response varies because of the snap-through response at different rates of loading as the body of the metamaterial includes heterogeneity. To the best of the authors’ knowledge, the viscoelastic snap-through response of a biholar metamaterial under compression and in the presence of lateral confinement has not been studied before. Therefore, this study aims to fill this gap through the finite element analysis of the viscoelastic snap-through response of a periodic porous metamaterial with biholar architectures under lateral confinement and vertical compression
High-Performance Multilevel Inverter Integrated DVR for Comprehensive Power Quality Improvement in Power Systems
No full textThis paper proposes a dynamic voltage restorer (DVR) based on a new three-phase multilevel inverter (MLI). An integral component of DVRs is the power electronic converter. At medium-to-high voltage levels, MLIs are the ideal converters for DVR applications because lower voltage-rated switches are used to generate high voltages, thus minimizing power losses. The proposed three-phase MLI generates 15 levels of load voltage per phase, using a reduced component count: eight lower-rated semiconductor power switches, four primary DC voltage sources, two auxiliary DC sources, and eight driver circuits per phase. Additionally, each phase features a low-frequency transformer with voltage-boosting and galvanic isolation capabilities. The switching sequence of the proposed MLI is simpler to execute using fundamental frequency control; this methodology provides reduced switching stress and reduced switching losses as merits. Structurally, the proposed MLI is less complex and thus scalable. The proposed DVR, based on three-phase MLI, efficiently offsets power quality problems such as voltage swell, voltage sags, and harmonics for balanced and unbalanced loads. The operational performance of the proposed DVR-MLI is verified by a simulation, using PSCAD software and an experimental prototype
Recurrence Quantification Analysis for Group Eye Tracking Data
No full textTraditional eye tracking methodologies have largely focused on single-user data. The study of multi-user dynamics and social interaction requires a novel analysis framework, partially addressed in current research. In this study, we introduce Group Eye Tracking (GET) as a framework for simultaneously collecting and analyzing eye movement data from multiple participants to reveal group-level patterns of visual dynamics. We use a custom application, which synchronously records eye movements from multiple users performing tasks on separate computers, and a custom R package implementing Recurrence Quantification Analysis (RQA) for examining time-series recurrences of visual dynamics. By quantifying how eye movement patterns recur and align among group members, we potentially provide indicators of cognitive states in collaborative decision-making, within real-time group interactions. The resulting measures can also provide information about the role of task parameters, interface layouts, and team performance. This approach demonstrates how GET can serve for developing next-generation augmented cognition systems by integrating advanced analytics and real-time adaptivity by the analysis of collective task outcomes
Stochastic dynamics of postural sway modeled by double Ornstein Uhlenbeck process
No full textAbstract: The study examines center-of-pressure dynamics in the anteroposterior direction (CoPx). It is assumed that CoPx dynamics involve two dynamical processes during quiet stance. The first process describes fast postural corrections around the given equilibrium. The second process describes slowly changing equilibrium point which is assumed to be controlled by higher nervous system. We proposed a novel system of coupled stochastic differential equations, double Ornstein-Uhlenbeck process (dOU), where two processes are described in terms of two Ornstein-Uhlenbeck processes (OU). Specifically, the equilibrium point of the fast postural correction OU process is controlled by the slowly evolving equilibrium point OU process. We derived closed forms of correlation and the power spectral density (PSD) functions of the processes. We conducted experiments with three repetitions from eight healthy subjects at four different sensory conditions on rigid and compliant surfaces. We optimized four model parameters in frequency domain by comparing averaged PSD estimates of experimental data and analytical PSD functions at each sensory combination. We found that mean reversion rate of the first OU governing postural reflexes around a given equilibrium, was significantly higher on the rigid surface. Consequently, the dynamics of postural sway on rigid surface were predominantly captured by a single OU. Contrarily, on compliant surface, approached the second OU’s mean reversion rate,, and we observed a significant increase in its volatility,. Findings suggest that two-level CoPx dynamics become more pronounced under the compliant surface. We showed that dOU is capable of capturing bounded diffusive characteristics of CoPx dynamics
Impacts of timing of nitrogen addition on Chardonnay fermentations sequentially inoculated with Metschnikowia pulcherrima and Saccharomyces cerevisiae
No full textSequential inoculation of Metschnikowia pulcherrima and Saccharomyces cerevisiae has been shown to produce wines containing less alcohol. However, the inoculation creates competition between these yeasts for scarce nutrients such as amino acids and ammonia. This study examined impacts of the timing of nitrogen addition (1, 3, or 5 days after M. pulcherrima inoculation) on fermentation kinetics, yeast assimilable nitrogen (YAN) consumption, and formation of by-products, including ethanol. After adjusting 28 ˚Brix, M. pulcherrima P01A016 on day 0 and S. cerevisiae Lalvin NBC™ on day 4 were inoculated into Chardonnay must with or without YAN supplementation. Most wines reached dryness by day 31, except for those without the supplementation. YAN addition on day 5 significantly reduced fermentation duration by 20 % while producing higher concentrations of glycerol (10.5 g/L). Wines that reached dryness with sequential inoculation had similar alcohol content to those inoculated with only S. cerevisiae (15.5–16.1 % versus 16.3 % v/v). Regardless of timing, YAN supplementation supported sequential inoculation for fermenting Chardonnay wines to dryness. Furthermore, the timing of nitrogen addition had a significant impact on fermentation duration and glycerol synthesis, but it did not significantly affect alcohol reduction. The timing of nitrogen addition may be used to shorten fermentation time and enhance glycerol production in the wine industry
An LLM-driven framework for automatic curriculum learning to enhance generalization in open-ended reinforcement learning
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Engineering Nanoparticles for Biomedical Applications: From Theory to Experiments and Modeling
No full textThis chapter explores the crystallization-driven synthesis of nanoparticles, emphasizing the critical roles of thermodynamics and kinetics in determining crystal size, size distribution, and morphology. Crystallization is a bottom-up approach widely employed in nanomaterial fabrication and proceeds via crystal nucleation and subsequent growth. The chapter begins by outlining Classical Nucleation Theory (CNT), highlighting the influence of supersaturation, temperature, and interfacial energy on the activation energy barrier and nucleation rate. The discussion extends to phase stability and transformations, underscoring the prevalence of metastable phases and the implications of Ostwald's rule of stages. Growth mechanisms, categorized into diffusion- and surface reaction-controlled, are described with reference to models like LaMer's and further examined in the context of Ostwald ripening and particle-based assembly. A central theme of the chapter is the control of particle characteristics through modulation of crystallization parameters. The chapter details strategies for tuning nucleation and growth, such as burst nucleation, seeding, and the use of additives or spatial confinement to regulate size and uniformity. Morphology control is discussed through the lens of internal crystal structure and external growth conditions, including the influence of supersaturation, pH, and selective facet binding. Finally, practical examples of spherical and anisotropic nanoparticles, including iron oxide, gold, and polymeric systems, demonstrate how synthesis techniques and reaction parameters can be tailored to produce nanomaterials with desired structural features. By integrating theoretical insights with experimental case studies, this chapter offers a comprehensive framework for understanding and engineering nanoparticle formation via crystallization
The Impact of Vision Problems on Households' Incomes: Evidence From the 2019 and 2022 Rounds of the Turkey Health Survey
No full textVision problems reduce individuals' quality of life, and they also reduce their productivity as workers and consequently decrease their incomes. Most vision problems can be corrected with properly fitted eyeglasses, but many people with vision problems do not have such eyeglasses. There is very little research to date on the impact of vision problems on workers' productivity, and no studies at a national scale. This paper addresses this gap by estimating the impact of vision problems on the probability of working and on the household incomes of workers, using a nationally representative survey from Turkey. Estimates indicate that vision problems reduce the employed population by 2.1% and the income of those who are employed by 1.4%. Combined, the overall impact of vision problems is to reduce household income by 3.5%