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Found 6327 publications
Studying the Relation of the Residual Stresses in the Ballast Layer to the Elastic Wave Propagation
Publication Name: Transportation Infrastructure Geotechnology
Publication Date: 2023-12-01
Volume: 10
Issue: 6
Page Range: 962-987
Description:
During track construction or ballast bed maintenance, ballast layer compaction quality plays an essential role in the following track irregularity accumulation, its lifecycle, and maintenance costs. The ballast compaction process is characterized by its compaction and the accumulation of the stressed state. The elastic wave propagation methods are an effective way for the identification of the ballast bed compaction properties. The paper presents the theoretical and experimental studies of the ballast consolidation under the vibration loading of the sleeper. The practical laboratory study is given by the 1:2.5 scaled physical model of one sleeper and the corresponding ballast layer box. The measurements of ballast pressure and deformations under the vibration loading in the ballast layer and the photogrammetric recording of the ballast flow are carried out. The measurements demonstrate the accumulation of the residual stresses under the ballast layer. Furthermore, the measurements of elastic wave time of flight (ToF) using the shakers under the sleeper and acceleration sensors under the ballast show the substantial increase of the ToF velocities after the tamping process. Moreover, the distribution of the velocities along the sleeper is spatially inhomogeneous. The numeric simulation using the discrete element method (DEM) of the tamping and the testing processes proves the inhomogeneous wave propagation effect. The modeling shows that the main reason for the wave propagation inhomogeneity is the accumulated residual stress distribution and the minor one – the compaction density. Additionally, a method for identifying wave velocity spatial distribution is developed by wave tracing the inhomogeneous medium. The procedures allow ballast identification in the zones outside the shakers.
Open Access: Yes
A physics-based reduced order model for urban air pollution prediction
Publication Name: Computer Methods in Applied Mechanics and Engineering
Publication Date: 2023-12-01
Volume: 417
Issue: Unknown
Page Range: Unknown
Description:
This article presents an innovative approach for developing an efficient reduced-order model to study the dispersion of urban air pollutants. The need for real-time air quality monitoring has become increasingly important, given the rise in pollutant emissions due to urbanization and its adverse effects on human health. The proposed methodology involves solving the linear advection–diffusion problem, where the solution of the Reynolds-averaged Navier–Stokes (RANS) equations gives the convective field. At the same time, the source term consists of an empirical time series. However, the computational requirements of this approach, including microscale spatial resolution, repeated evaluation, and low time scale, necessitate the use of high-performance computing facilities, which can be a bottleneck for real-time monitoring. To address this challenge, a problem-specific methodology was developed that leverages a data-driven approach based on Proper Orthogonal Decomposition with regression (POD-R) coupled with Galerkin projection (POD-G) endorsed with the discrete empirical interpolation method (DEIM). The proposed method employs a feedforward Neural Network (NN) to non-intrusively retrieve the reduced-order convective operator required for online evaluation. The numerical framework was validated on synthetic emissions and real wind measurements. The results demonstrate that the proposed approach significantly reduces the computational burden of the traditional approach and is suitable for real-time air quality monitoring. Overall, the study advances the field of reduced order modeling and highlights the potential of data-driven approaches in environmental modeling and large-scale simulations.
Open Access: Yes
Extending the TPTool MATLAB toolbox with LMI based observer and disturbance rejection design
Publication Name: Results in Control and Optimization
Publication Date: 2023-12-01
Volume: 13
Issue: Unknown
Page Range: Unknown
Description:
Present paper demonstrates the extensions of MATLAB TPtool toolbox. The toolbox does not include the LMI based observer and disturbance rejection design. Thus, the suggested extensions include the observer and H∞ based disturbance rejection LMI conditions for TP models. Furthermore this toolbox contains obsolete algorithms. Therefore, in this paper, the recommended algorithms are presented. Showing the proposed design method is based on a nonlinear dynamic system; modified TP model of the TORA example is used. Thus, the detailed observer and controller design, the disturbance rejection design are presented with LMI stability conditions through the HOSVD based method in the PDC framework.
Open Access: Yes
The Effect of Drying of Glycerol-Plasticized Starch upon Its Dielectric Relaxation Dynamics and Charge Transport
Publication Name: Journal of Polymers and the Environment
Publication Date: 2023-12-01
Volume: 31
Issue: 12
Page Range: 5389-5400
Description:
Carbohydrate polymers are promising materials for an eco-friendly future due to their biodegradability and abundance in nature. However, due to their molecular characteristics and hydrophilicity, are often complicated to be investigated via spectroscopic methods. Thermoplastic starch plasticized by glycerol was prepared through melt processing conditions using twin screw extruder. Here we show how the presence of water molecules affects the dielectric response and charge transport dynamics over broad frequency (10−1 to 107 Hz) and temperature (− 140 to 150 oC) ranges. Overall, 7 dielectric processes were observed and differentiation between electronic and ionic conductivities was achieved. Two segmental relaxation processes were observed for each sample, ascribed to the starch-rich and glycerol-rich phases. Although the timescales of the two segmental relaxations were found different, both arise from the same temperature, giving thus an alternative explanation on what is reported in the literature. The origin of the σ-relaxation was attributed to hydrogen ions and was found to be proportional to the ionic conductivity according to the Barton, Nakajima and Namikawa relation. The presence of water molecules was found to enhance the ionic conductivity, indicating that water contributes charge carriers when compared to the dried sample. Graphical Abstract: [Figure not available: see fulltext.]
Open Access: Yes
Kibble–Zurek scaling due to environment temperature quench in the transverse field Ising model
Publication Name: Scientific Reports
Publication Date: 2023-12-01
Volume: 13
Issue: 1
Page Range: Unknown
Description:
The Kibble–Zurek mechanism describes defect production due to non-adiabatic passage through a critical point. Here we study its variant from ramping the environment temperature to a critical point. We find that the defect density scales as τ-dν or τ-d/z for thermal or quantum critical points, respectively, in terms of the usual critical exponents and 1 / τ the speed of the drive. Both scalings describe reduced defect density compared to conventional Kibble–Zurek mechanism, which stems from the enhanced relaxation due to bath-system interaction. Ramping to the quantum critical point is investigated by studying the Lindblad equation for the transverse field Ising chain in the presence of thermalizing bath, with couplings to environment obeying detailed balance, confirming the predicted scaling. The von-Neumann or the system-bath entanglement entropy follows the same scaling. Our results are generalized to a large class of dissipative systems with power-law energy dependent bath spectral densities as well.
Open Access: Yes
Getting the priorities straight: resource use, emissions, impacts, avoidable/unavoidable waste
Publication Name: Clean Technologies and Environmental Policy
Publication Date: 2023-12-01
Volume: 25
Issue: 10
Page Range: 3129-3130
Description:
No description provided
Open Access: Yes
How Organizations Lose Their Way: Unethical Behavior and Moral Disengagement in Complex Organizational Context
Publication Name: Business and Professional Ethics Journal
Publication Date: 2023-12-01
Volume: 42
Issue: 1
Page Range: 109-137
Description:
Unethical behavior in organizations has garnered more and more attention in the last decades but most of the scholarly work has used a static approach relying on methodological individualism and a mechanistic worldview when studying this topic. The process of moral disengagement and organizational culture have been linked to the prevalence of unethical behavior earlier, but this paper uses a complexity-informed systems perspective to explore the dynamic relationship of these concepts and aims to improve our understanding of the often unnoticeable, step-by-step process through which organizational cultures can become conducive to unethical behavior. Organizations are conceptualized as complex adaptive systems in which transformative and stabilizing processes based on feedback loops take place continuously. It is discussed how these processes can lead to a phase transition driving organizations towards a state where unethical behavior is the general norm. The process is illustrated through real-life examples.
Open Access: Yes
Molecular-phylogenetic analyses of Ixodes species from South Africa suggest an African origin of bird-associated exophilic ticks (subgenus Trichotoixodes)
Publication Name: Parasites and Vectors
Publication Date: 2023-12-01
Volume: 16
Issue: 1
Page Range: Unknown
Description:
Background: Among hard ticks (Acari: Ixodidae), the genus Ixodes comprises the highest number of species, which in turn are most numerous in the Afrotropical zoogeographic region. In South Africa extensive morphological studies have been performed on Ixodes species but only few reports included molecular analyses. Methods: In this study, 58 Ixodes spp. ticks, collected from ten mammalian and eight avian host species in South Africa, were molecularly and phylogenetically analyzed. In addition, a newly collected sample of the Palearctic Ixodes trianguliceps was included in the analyses. Results: Among the ticks from South Africa, 11 species were identified morphologically. The majority of ticks from mammals represented the Ixodes pilosus group with two species (n = 20), followed by ticks resembling Ixodes rubicundus (n = 18) and Ixodes alluaudi (n = 3). In addition, single specimens of Ixodes rhabdomysae, Ixodes ugandanus, Ixodes nairobiensis and Ixodes simplex were also found. Considering bird-infesting ticks, Ixodes theilerae (n = 7), Ixodes uriae (n = 4) and ticks most similar to Ixodes daveyi (provisionally named I. cf. daveyi, n = 2) were identified. Molecular analyses confirmed two species in the I. pilosus group and a new species (I. cf. rubicundus) closely related to I. rubicundus sensu stricto. Phylogenetic trees based on concatenated mitochondrial or mitochondrial and nuclear gene sequences indicated that the subgenus Afrixodes forms a monophyletic clade with bird-associated exophilic ticks (subgenus Trichotoixodes). Ixodes trianguliceps clustered separately whereas I. alluaudi with their morphologically assigned subgenus, Exopalpiger. Conclusions: Phylogenetic analyses shed new lights on the relationships of Ixodes subgenera when including multiple sequences from subgenus Afrixodes and African as well as Palearctic species of subgenera Trichotoixodes and Exopalpiger. Subgenera Afrixodes and bird-associated Trichotoixodes share common ancestry, suggesting that the latter might have also originated in Africa. Regarding the subgenus Exopalpiger, I. alluaudi is properly assigned as it clusters among different Australian Ixodes, whereas I. trianguliceps should be excluded. Graphical Abstract: [Figure not available: see fulltext.].
Open Access: Yes
A 4-year study of bovine reproductive hormones that are induced by pharmaceuticals and appear as steroid estrogenic pollutants in the resulting slurry, using in vitro and instrumental analytical methods
Publication Name: Environmental Science and Pollution Research International
Publication Date: 2023-12-01
Volume: 30
Issue: 60
Page Range: 125596-125608
Description:
The main objective of the research was to study the environmental "price" of the large-scale, milk production from a rarely known perspective, from the mapping of the estrogenic footprint (the amount of oestrus-inducer hormonal products, and the generated endoestrogens) in the resulting slurry in a dairy cow farm. These micropollutants are endocrine-disrupting chemicals (EDCs) and can be dangerous to the normal reproductive functions even at ng/kg concentration. One of them, 17ß-estradiol, has a 20,000 times stronger estrogenic effect than bisphenol-A, a widely known EDC of industrial origin. While most studies on EDCs are short-term and/or laboratory based, this study is longitudinal and field-based. We sampled the slurry pool on a quarterly basis between 2017 and 2020. Our purpose was testing the estrogenic effects using a dual approach. As an effect-based, holistic method, we developed and used the YES (yeast estrogen screen) test employing the genetically modified Saccharomyces cerevisiae BJ3505 strain which contains human estrogenic receptor. For testing exact molecules, UHPLC-FLD was used. Our study points out that slurry contains a growing amount of EDCs with the risk of penetrating into the soil, crops and the food chain. Considering the Green Chemistry concept, the most benign ways to prevent of the pollution of the slurry is choosing appropriate oestrus-inducing veterinary pharmaceuticals (OIVPs) and the separation of the solid and liquid parts with adequate treatment methods. To our knowledge, this is the first paper on the adaptation of the YES test for medicine and slurry samples, extending its applicability. The adapted YES test turned out to be a sensitive, robust and reliable method for testing samples with potential estrogenic effect. Our dual approach was successful in evaluating the estrogenic effect of the slurry samples.
Open Access: Yes
