bluuebunny/crossref_metadata_2025 huggingface dataset:
Unravelling microbiome changes in aerobic granular sludge saline wastewater treatment using a slow stepwise salt increase strategy
Authors: Paulo Ana M. S. , Salazar Oihane , Costa Joana , Mesquita Daniela P. , Ferreira Eugénio C. , Castro Paula M. L. , Amorim Catarina L.
Published: October 2024

A gradual stepwise salt increase strategy applied to an AGS system proved vital for maintaining process stability and performance. This strategy promoted the persistence of key microbes, especially those crucial for nutrient removal.
Uncertainty of the white dwarf astrophysical gravitational wave background
Authors: Hofman Sophie , Nelemans Gijs
Published: October 2024

Context. The astrophysical gravitational wave background (AGWB) is a stochastic gravitational wave (GW) signal emitted by different populations of in-spiralling binary systems containing compact objects throughout the Universe. In the frequency range between 10−4 and 10−1 hertz (Hz), it will be detected by future space-based gravitational wave detectors, such as Laser Interferometer Space Antenna (LISA). In a recent work, we concluded that the white dwarf (WD) contribution to the AGWB dominates that of black holes (BHs) and neutron stars (NSs).

Aims. We aim to investigate the uncertainties of the WD AGWB that arise from the use of different stellar metallicities, star formation rate density (SFRD) models, and binary evolution models.

Methods. We used the code we previously developed to determine the WD component of the AGWB. We used a metallicity-dependent SFRD based on an earlier work to construct five different SFRD models. We used four different population models based on a range of common-envelope treatments and six different metallicities for each model.

Results. For all possible combinations, the WD component of the AGWB is dominant over other populations of compact objects. The effects of metallicity and population model are less significant than the effect of a (metallicity dependent) SFRD model. We find a range of about a factor of 5 in the level of the WD AGWB around a value of ΩWD = 4 × 10−12 at 1 mHz and a shape that is weakly dependent on the model.

Conclusions. We find the uncertainty for the WD component of the AGWB to be about a factor of 5. We note that there are other uncertainties that have an effect on this signal as well. We discuss whether the turnover of the WD AGWB at 10 mHz will be detectable by LISA and find it to be likely. We confirm our previous findings asserting that the WD component of the AGWB dominates over other populations, in particular, BHs.
Propagation of untwisting solar jets from the low-beta corona into the super-Alfvénic wind: Testing a solar origin scenario for switchbacks
Authors: Touresse J. , Pariat E. , Froment C. , Aslanyan V. , Wyper P. F. , Seyfritz L.
Published: October 2024

Context. Parker Solar Probe’s (PSP) discovery of the prevalence of switchbacks (SBs), localised magnetic deflections in the nascent solar wind, has sparked interest in uncovering their origins. A prominent theory suggests these SBs originate in the lower corona through magnetic reconnection processes, closely linked to solar jet phenomena. Jets are impulsive phenomena, observed at various scales in different solar atmosphere layers, associated with the release of magnetic twist and helicity.

Aims. This study examines whether self-consistent jets can form and propagate into the super-Alfvénic wind, assesses the impact of different Parker solar wind profiles on jet dynamics, and determines if jet-induced magnetic untwisting waves display signatures typical of SBs.

Methods. We employed parametric 3D numerical magnetohydrodynamics (MHD) simulations using the Adaptively Refined Magnetohydrodynamics Solver (ARMS) code to model the self-consistent generation of solar jets. Our study focuses on the propagation of solar jets in distinct atmospheric plasma β and Alfvén velocity profiles, including a Parker solar wind. We explored the influence of different atmospheric properties thanks to analysis techniques such as radius-time diagrams and synthetic in situ velocity and magnetic field measurements, akin to those observed by PSP or Solar Orbiter.

Results. Our findings demonstrate that self-consistent coronal jets can form and then propagate into the super-Alfvénic wind. Notable structures such as the leading Alfvénic wave and trailing dense-jet region were consistently observed across different plasma β atmospheres. The jet propagation dynamics are significantly influenced by atmospheric variations, with changes in Alfvén velocity profiles affecting the group velocity and propagation ratio of the leading and trailing structures. U-loops, which are prevalent at jet onset, do not persist in the low-β corona but magnetic untwisting waves associated with jets exhibit SB-like signatures. However, full-reversal SBs were not observed.

Conclusions. These findings may explain the absence of full reversal SBs in the sub-Alfvénic wind and illustrate the propagation of magnetic deflections through jet-like events, shedding light on possible SB formation processes.
Towards an active semi-anechoic room: simulations and first measurements
Authors: Pinhède Cédric , Boulandet Romain , Friot Emmanuel , Allado Mark R. , Côté Renaud , Herzog Philippe
Published: October 2024

Semi-anechoic rooms are used for the acoustic characterisation of noise sources. They involve heavy infrastructures and thick absorbent lining. The aim of this work is to demonstrate a less expensive alternative by complementing a thin passive coating with an active technology. Previous work has achieved the active reduction of the pressure scattered by the reflective wall of a semi-anechoic room, in the 80–200 Hz frequency band. This work validated an innovative approach allowing to control the scattered pressure throughout the measurement volume, using a setup located over its periphery. This paper extends a previous presentation at Forum Acusticum dealing with the active control of the low-frequency reflections on the walls and ceiling of a semi-anechoic room [Pinhède et al., Forum Acusticum 2023, Torino, Italy, 11–15 September, 2023, https://doi.org/10.61782/fa.2023.0399]. We describe the design principles and the 2D semi-analytical and 3D finite element simulations of the control system that help optimise parameters such as the transducers number and locations. A full-scale demonstrator has been built to validate the control strategy. Acoustics measurements, which have been used to characterise the room acoustics and to update the simulation parameters are also presented and compared to an updated numerical model.
The theory of complexity and construction management: An analysis of perception and impact on the construction industry in Brazil and Bolivia
Authors: Ochoa Walter Antonio Abujder , Málaga Moisés Alejandro Sánchez , Rojas Michael Diego Lizarazu , Arce Angela Gabriela Torrico , Neto Alfredo Iarozinski
Published: October 2024

The theory of complexity derived from systems theory emphasizes complex systems and their dynamic interactions with their environment. In this sense, in project management, this theory offers invaluable perspectives, where systems involve diverse components working towards a common objective. The construction sector is facing challenges in managing project complexity, and effective strategies are required to ensure success. While projects are often perceived as predictable, the reality of construction complexity demands a shift in perspective. Currently, the linear view of construction processes is being challenged, advocating for recognizing projects as nonlinear and dynamic phenomena. This study aims to explore the application of complexity theory in construction project management, focusing on differences in complexity perception between Cochabamba and the Metropolitan Region of Curitiba. Discriminant Analysis does not reveal a significant disparity in complexity perception between the two regions, with variables such as uncertainty about the subsoil having the most influence on complexity perception.
Enhancing Wind Turbine Performance using Computational Fluid Dynamics
Authors: Sravanthi Jajimoggala , Kumari D. Radha , Punia Ankit , Jugran Sudhir , Kumar Suresh , Kundra Danish , Chaturvedi Rishabh , Alabdeli Haider
Published: October 2024

This study explores the potential of Computational Fluid Dynamics (CFD) to enhance wind turbine performance by analyzing fluid flow and aerodynamic behavior. By applying CFD simulations to optimize blade designs and predict wake interactions, significant improvements in turbine efficiency and power output were achieved. The study focuses on the effects of different blade geometries, wind speeds, and turbulence models. Results show a 15% increase in aerodynamic efficiency through optimized blade angles, with a 10% reduction in turbulence-induced losses. This research provides insights into using CFD to improve turbine design and performance, making wind energy more efficient and sustainable.
Predictive Modeling of Energy Consumption in Smart Grids using Artificial Neural Networks
Authors: Tkachenko Vladimir , Saxena Anil Kumar , Nimmagadda Babu , Dhawan Aashim , Mundher adnan Myasar , Kumar Manish , Singh Sarpal Sumeet , Shukla Aasheesh , Chandra Mouli Kathi
Published: October 2024

This study delves into the ground-breaking applications of optical fiber grids for material analysis. In it, we look at the correlation between light intensity and temperature, analyze the material composition, and conduct a comprehensive examination into sensor calibration. Optical fiber grids are quite accurate in detecting changes in temperature and refractive index, as shown by the calibration results, which showed an outstanding average accuracy of 98%. The grids were able to distinguish between different materials with an average accuracy of 96%, according to the material composition research. The correct identification of a polymer sample with 45% polyethylene and 55% polypropylene demonstrated this. Also, the grids were able to properly react to changing temperatures since there was a strong linear relationship between light intensity and temperature (92 percent explanatory power). Taken together, the findings highlight optical fiber grids’ versatility and reliability, showing how they might revolutionize material research across several industries.
Sustainable Production of Hydrogen from Biomass using Pyrolysis
Authors: Abbas Haider Mohammed , subbarayudu Yerragudipadu , Chandna Manisha , Dhall Himanshu , Nijhawan Ginni , Madan Praney , Singh Pankaj Kumar , KrishnaBhargavi Y.
Published: October 2024

This study uses biomass to produce hydrogen from biomass via pyrolysis to meet renewable energy demand and reduce environmental effect. Pyrolysis revealed substantial variations in cellulose, hemicellulose, and lignin content in biomass samples. Pyrolysis was tested with different biomass compositions, with Catalyst D converting hydrogen at 80%. Biomass 4 produced the most hydrogen at 120 g/L. Catalyst D was the most sustainable, with 1.8 kWh/kg energy usage, 0.05 kg/kg trash, and 0.15 kg/kg CO2 emissions, according to an environmental impact evaluation. The percentage change study highlighted Catalyst D’s significant pyrolysis performance and environmental sustainability gains. These results show that green biomass may increase biomass-to-hydrogen production efficiency and sustainability, advancing clean energy technology and a more sustainable energy future.
Analysis of the Thermal Regime of a Residential Building Premises after an Emergency Shutdown of the Heating System
Authors: Vafaeva Khristina Maksudovna , Karpov Denis Fedorovich , Pavlov Mikhail Vasilyevich , Ismailov Aleksei Marlenovich , Gupta Tannmay , Seshappa Angadi , Taneja Madhur , Joshi Abhishek , Rao Gundavarapu Mallikarjuna , Tiwari Deepak Kumar
Published: October 2024

Maintaining favorable microclimatic conditions in a residential dwelling is directly related to the stable operation of the heating system. An emergency shutdown of the heating system, especially in the winter season, can lead to serious negative consequences: disruption of thermal comfort for people in the residential building, rupture of pipelines and heating devices, flooding of adjacent premises, etc. Thus, the issue of predicting the thermal regime of a residential dwelling after the termination of heat supply is of practical relevance. The object of study: Residential premises in buildings. Subject of study: Patterns of change in the temperature of the indoor air (in dimensional and dimensionless forms), the rate of temperature drop, and the loss of thermal energy during an emergency shutdown of the heating system. Objective of the study: To forecast the thermal regime of a room in a residential building after an emergency shutdown of the heating system. Research methods: Classical theory of thermal stability of building enclosures; theory of regular thermal regime, according to which the temperature field at all points of the cooled body (in this case, the heating system) changes in the same way, obeying the exponential law; software computer calculations. Research results: In a room of a residential building, the indoor air temperature will reach the dew point (12.5 ℃) within 8 hours 42 minutes after an emergency shutdown of the heating system and zero value - after 23 hours 42 minutes. Based on the conducted scientific research, it can be stated that the thermal storage capacity of external enclosures, due to their design features, plays a primary role in preserving the thermal regime of a residential dwelling after the heating system is turned off.
High energy and average power solid-state UV laser for industrial applications
Authors: Bruel N. , Casagrande O. , Derycke C. , Tiago T. , Bihel A. , Caradec F. , Simon-Boisson C. , Besaucele H.
Published: October 2024

High energy and average power solid-state UV laser involves several challenges to manage degradation due to UV radiations. Recent results achieved in this direction are presented.
A contribution for dismantling of nuclear facilities: a functional pattern for dismantling operations and indicators design and management
Authors: Chapurlat Vincent
Published: October 2024

Optimizing nuclear installation decommissioning and dismantling operations is an ongoing quest. Faced with the complexity of this activity, Model Based System Engineering promotes relevant principles and modeling techniques. It motivated the definition of a functional generic pattern model of the waste package production line and the decommissioning of the facility. It proposes a global and generic functional architecture of such a system aiming to reduce the level of the pollutant. This pattern is coupled with a process of logistics. Six functions are combined to define this functional pattern. The application of this pattern model to a case of waste recovery in a pit shows the relevance of the model-based system engineering approach, reducing the weight of the history in the development of scenarios by optimizing the control means for nuclear safety and product quality.
Uncertainty-aware estimation of inverter field efficiency using Bayesian neural networks in solar photovoltaic plants
Authors: Guerra Gerardo , Mercadé Ruiz Pau , Anamiati Gaetana , Landberg Lars
Published: October 2024

Solar inverters are one of the most important components in a Photovoltaic plant. Their main function is to convert the DC power produced by the solar modules into AC power that can be injected into the grid. Although inverter efficiency has reached exceptionally high values, thanks to recent technological advancements, it is typically measured at dedicated laboratories under strict testing conditions, which makes its validation after deployment extremely challenging, both from a logistic and financial point of view. This paper presents a methodology for the calculation of inverter field efficiency based on Bayesian neural networks. The goal of the neural network is to model inverter efficiency and its variance as a function of the inverter's operational state. Results show that an optimised Bayesian neural network can effectively model inverter efficiency with small reconstruction errors and negligible bias. Furthermore, the model has been proven useful to replicate the calculation of the European efficiency along with a full uncertainty characterisation.
Hierarchical data synchronous interaction in nonlinear complex systems
Authors: Yuan Lufeng , Gao Shijie , He Xin , Liu Changnian , Ren Xilei , Fan Zhichao
Published: October 2024

Nonlinear complex systems are widely used in various industries, and the complexity and dynamism of the systems pose enormous challenges to data synchronization and interaction. This study proposes a method based on signal synchronization for data synchronization and interaction in nonlinear complex systems. The synchronization interaction path of data was analyzed, and signals were used as the carrier for data synchronization. The data synchronization interaction was carried out by combining the main synchronization signal and the auxiliary synchronization signal. Furthermore, mean filtering was introduced for signal filtering, and the main synchronization process was divided into two parts: coarse and fine tuning. The experimental results showed that the main synchronization frequency deviation of the research method was 303 Hz when the main synchronization completion rate was 100% in a −15 dB signal-to-noise ratio environment. In the analysis of data synchronization success rate, the research method achieved a highest success rate of 99.7% when the data transmission density was 50 pieces per minute. The experiment shows that the research method can effectively improve the quality and efficiency of data synchronization and interaction in nonlinear complex systems.
Does Marriage Still Make a Difference in Infant Health?
Authors: Yan Ji
Published: October 2024

Although a vast literature examines the effects of family structure on school-aged children, adolescents and adults, less attention has been paid to infants. We use a longitudinal sample to disentangle the marriage effects from unobserved fixed characteristics of the mother and various observed confounders. Results from standard cross-sectional regressions tend to overstate the marriage premium. The within-mother analysis shows marriage leads to a small increase in birth weight but still fairly large declines in the risks of low birth weight and small for gestational age. Abstaining from smoking and having early prenatal care help explain how marriage improves infant health.
Performance prediction of IPMC modified with SiO2-SGO based on backpropagation neural network
Authors: Zhai Zhengxin , Tian Aifen , Zhang Xinrong , Du Huiling , Wang Yaping
Published: October 2024

Ionic polymer–metal composites (IPMCs) constitute a new type of artificial muscle material that is commonly used in bionic soft robots and medical devices because of its small driving voltage and considerable deformation. However, IPMCs are limited by performance issues such as low output force and small operating time away from water. Silicon dioxide sulfonated graphene (SiO2-SGO) particles are often used to improve the performance of polymer membranes because of their hydrophilicity and high chemical stability. Reported here is the addition of SiO2-SGO particles prepared by in situ hydrolysis to perfluorosulfonic acid in order to improve the IPMC properties. Also, a predictive model was constructed based on a backpropagation neural network, with the SiO2-SGO doping amount and the IPMC excitation voltage in the input layer and the driving displacement in the output layer. The results show that the IPMC prepared with 1.0 wt. % doping content performed the best, with a maximum output displacement of 47.7 mm. The correlation coefficient (R2) was 0.9842 and the mean square error was 0.000 370 73, which show that the predictive model has high predictive accuracy and is suitable for predicting the performance of the SiO2-SGO-modified IPMC.
Super-resolution microscopy by grating and deep neural network
Authors: Liu Xingyu , Zhang Zongyan , Yang Songlin , Jiang Wenli , Yu Jiang , Fang Wenjing , Zhang Jia-Yu , Ye Yong-Hong
Published: October 2024

In this study, a novel optical super-resolution imaging technique, grating and deep neural network assisted super-resolution microscopy, is proposed. The technique utilizes a sub-wavelength grating, placed between the sample and the microscope objective, to convert the evanescent waves of a sample surface into propagating waves, allowing more high spatial-frequency information of the sample to be detected in the far field. Then, the far-field image of the sample is captured and trained end-to-end with a customized deep neural network model to heuristically reconstruct a clear image of the sample with structural features smaller than λ/3. Compared with the existing super-resolution imaging techniques, the proposed technique has the advantages of label-free, large field of view, one-time direct imaging, and white light illumination and observation in an atmospheric environment. Moreover, it has the flexibility to replace raster and network rendering components according to specific inspection requirements to meet diverse application scenarios.
Analytical calculation of the kinetic q factor and resonant response of toroidally confined plasmas
Authors: Antonenas Y. , Anastassiou G. , Kominis Y.
Published: October 2024

Symmetry-breaking perturbations in axisymmetric toroidal plasma configurations have a drastic impact on particle, energy, and momentum transport in fusion devices, thereby affecting their confinement properties. The perturbative modes strongly affect particles with specific kinetic characteristics through resonant mode–particle interactions. In this work, we present an analytical calculation of the kinetic q factor, enabling the identification of particles with kinetic properties that meet the resonant conditions. This allows us to predict the locations and structures of the corresponding resonant island chains, as well as the existence of transport barriers in the particle phase space. The analytical results, derived for the case of a large aspect ratio configuration, are systematically compared to numerical simulations, and their domain of validity is thoroughly investigated and explained. Our findings demonstrate that calculating the kinetic q factor and its dependence on both particle and magnetic field characteristics provides a valuable tool for understanding and predicting the resonant plasma response to non-axisymmetric perturbations. Moreover, this approach can be semi-analytically applied to generic realistic experimental equilibria, offering a low-computational-cost method for scenario investigations under various multi-scale perturbative modes.
Neuroevolution machine learning potential to study high temperature deformation of entropy-stabilized oxide MgNiCoCuZnO5
Authors: Timalsina B. , Nguyen H. G. , Esfarjani K.
Published: October 2024

Entropy stabilized oxide of MgNiCoCuZnO5, also known as J14, is a material of active research interest due to a high degree of lattice distortion and tunability. Lattice distortion in J14 plays a crucial role in understanding the elastic constants and lattice thermal conductivity within the single-phase crystal. In this work, a neuroevolution machine learning potential (NEP) is developed for J14, and its accuracy has been compared to density functional theory calculations. The training errors for energy, force, and virial are 5.60 meV/atom, 97.90 meV/Å, and 45.67 meV/atom, respectively. Employing NEP potential, lattice distortion, and elastic constants is studied up to 900 K. In agreement with experimental findings, this study shows that the average lattice distortion of oxygen atoms is relatively higher than that of all transition metals in entropy-stabilized oxide. The observed distortion saturation in the J14 arises from the competing effects of minimum site distortion, which increases with increasing temperature due to enhanced thermal vibrations, and maximum site distortion, which decreases with increasing temperature. Furthermore, a series of molecular dynamics simulations up to 900 K are performed to study the stress–strain behavior. The elastic constants, bulk modulus, and ultimate tensile strength obtained from these simulations indicate a linear decrease in these properties with temperature, as J14 becomes softer owing to thermal effects. Finally, to gain some insight into thermal transport in these materials, with the so-developed NEP potential, and using non-equilibrium molecular dynamics simulations, we study the lattice thermal conductivity (κ) of the ternary compound MgNiO2 as a function of temperature. It is found that κ decreases from 4.25 W m−1 K−1 at room temperature to 3.5 W m−1 K−1 at 900 K. This suppression is attributed to the stronger scattering of low-frequency modes at higher temperatures.
The interplay of excitonic delocalization and vibrational localization in optical lineshapes: A variational polaron approach
Authors: Reppert Mike , Dutta Rajesh , Slipchenko Lyudmila
Published: October 2024

The dynamics of molecular excitonic systems are complicated by a competition between electronic coupling (which drives delocalization) and vibrational-electronic (vibronic) interactions (which tend to encourage electronic localization). A particular challenge of molecular systems is that they typically possess a large number of independent vibrations, with frequencies often spanning the entire spectrum of relevant electronic energy gaps. Recent spectroscopic observations and numerical simulations on a water-soluble chlorophyll-binding protein (WSCP) reveal a transition between two regimes of vibronic behavior, a Redfield-like regime in which low-frequency vibrations respond to a delocalized excitonic state, and a Förster-like regime where high-frequency vibrations act as incoherent excitations on individual pigments. Although numerical simulations can reproduce these effects, there is a need for a simple, systematic theory that accurately describes the smooth transition between these two regimes in experimental spectra. Here we address this challenge by generalizing the variational polaron transform approach of [Bloemsma et al., Chem. Phys. 481, 250 (2016)] to include arbitrary bath densities for systems with or without symmetry. We benchmark this theory against both numerical matrix-diagonalization methods and experimental 77 K fluorescence spectra for two WSCP variants, obtaining quite satisfactory agreement in both cases. We apply this theory to offer an explanation for the large loss in apparent electronic coupling in the WSCP Q57K mutant and to examine the likely impact of the interplay between excitonic delocalization and vibrational localization on vibrational sideband shapes and apparent coupling strengths in high-resolution optical spectra for chlorophyll-protein complexes such as WSCP.
Understanding the effect of physical aging on slip dynamics in soft-glassy materials using pure elongation flow
Authors: Chaudhary Ishu , Kaushal Manish
Published: October 2024

Slip over a solid surface is a very common occurrence in industrial scale transport and the processing of complex fluids. The knowledge of slip also plays a huge role in the correct estimation of rheological properties. In this work, we have studied the slip dynamics in a model soft-glassy material that exhibits physical aging, wherein the structure evolves gradually toward a more solid-like character via rearrangement of constituents. More precisely, we have investigated the impact of physical aging on slip associated with pure elongation flow of the material. We have allowed the sample to age over different waiting times, followed by the sample being deformed slowly in elongation mode by pulling the top plate to achieve a pure elongation flow. Normal force as a function of gap has been recorded during such pure elongation. These normal force–gap curves demonstrated a remarkable gap-waiting time superposition, manifesting the strong signature of self-similarity in the pure elongation flow of the soft-glassy system. We have adopted a slip layer model, which predicted these normal force–gap flow curves remarkably well. Such prediction also rendered slip layer thickness as a function of waiting time, using which we have explained the intriguing self-similar nature of normal force–gap dependence. Finally, we have established a relationship between the slip layer thickness and the age-dependent bulk rheological properties. We have provided a possible physical reasoning to explain this link between the physical aging-driven state of material and the slip dynamics.
Adaptive resolution force probe simulations: Coarse graining in the ideal gas approximation
Authors: Oestereich Marco , Gauss Jürgen , Diezemann Gregor
Published: October 2024

The unfolding of molecular complexes or biomolecules under the influence of external mechanical forces can routinely be simulated with atomistic resolution. To obtain a match of the characteristic time scales with those of experimental force spectroscopy, often coarse graining procedures are employed. Here, building on a previous study, we apply the adaptive resolution scheme (AdResS) to force probe molecular dynamics (FPMD) simulations using two model systems as examples: One system is the previously investigated calix[4]arene dimer that shows reversible one-step unfolding, and the other example is provided by a small peptide, a β-alanine octamer in methanol solvent. The mechanical unfolding of this peptide proceeds via a metastable intermediate and, therefore, represents a first step toward a complex unfolding pathway. We show that the average number of native contacts serves as a robust order parameter for the forced unfolding of this small peptide. In addition to increasing the complexity of the relevant conformational changes, we study the impact of the methodology used for coarse graining. Apart from the iterative Boltzmann inversion method, we apply an ideal gas approximation, and therefore, we replace the solvent by a non-interacting system of spherical particles. In all cases, we find excellent agreement between the results of FPMD simulations performed fully atomistically and those of the AdResS simulations also in the case of fast pulling. This holds for all details of the unfolding pathways, such as the distributions of the characteristic forces and also the sequence of hydrogen-bond opening in case of the β-alanine octamer. Therefore, the methodology is very well suited to simulate the mechanical unfolding of systems of experimental relevance.
Tip region vortices control based on cutback squealers in a high-loading axial turbine
Authors: Chen Kailai , Zhang Weihao , Wang Yufan , Huang Dongming
Published: October 2024

The evolution of tip region vortices has a significant influence on the aerodynamic performance of the turbine. Most studies on squealer tip optimization focused on enhancing the blockage effect of the vortices inside the clearance but had limited effect on controlling the vortices outside the clearance. In this paper, both the vortices inside and outside the clearance are controlled based on the trailing edge suction side cutback in a non-cooled turbine. The results indicate that inside the clearance, the scraping vortex plays a crucial role in reducing leakage. The cutback enhances the strength of the scraping vortex, thereby expanding the effective blockage range. While outside the clearance, the tip leakage vortex breakdown exacerbates its dissipation effects, leading to a significant loss downstream of the blade. The cutback injects greater fluid momentum into the tip leakage vortex, leading to increased mixing loss between leakage jet and mainstream. Concurrently, this also inhibits the tip leakage vortex breakdown, resulting in a notable reduction in its dissipation loss. The combined impact effectively controls the total leakage loss. It has been demonstrated that there exists an optimal cutback length for the suction side squealer rim at the trailing edge, which can be determined by setting the cutback opening at the initiation of the tip leakage vortex breakdown. The aforementioned effects of the cutbacks are prominently observed under different operating conditions, which indicates that the cutbacks possess good applicability in a certain range. This offers valuable guidance for tip region vortices control and squealer tip optimization.
Free movement of a near-wall particle in fluid of comparable density
Authors: Jolley Ellen M. , Smith Frank T.
Published: October 2024

The fundamental problem of nonlinear interaction between a freely moving particle and surrounding fluid flow is investigated for a density ratio of order unity, with potential applications to biomedical, environmental, and aerodynamic configurations. The interaction takes place near a fixed wall, with the particle being relatively thin. A mathematical model is presented, showing the fluid pressure forces to be dominant over the mass-acceleration effects in the particle motion (in contrast with previous analyses). The added mass due to the fluid motion, thus, greatly exceeds the body mass. Numerical simulations and asymptotic analysis reveal a range of possible particle motions. The main properties emerging are: (a) the distinction between collisions with the wall and fly-away responses; (b) the time scales involved in such behaviors; (c) the pressures and velocities induced at collision; (d) the occurrence of flow reversal in certain cases; and (e) the results being independent of the particle mass and moment of inertia as well as independent of the density ratio provided that the ratio is of order unity (0–7, say) or only slightly larger (8–30, say).
Simplified approach to estimate Lorenz number using experimental Seebeck coefficient for non-parabolic band
Authors: Kumar Ankit
Published: October 2024

Reducing lattice thermal conductivity (κL) is one of the most effective ways for improving thermoelectric properties. However, the extraction of κL from the total measured thermal conductivity can be misleading if the Lorenz (L) number is not estimated correctly. κL is obtained using the Wiedemann–Franz law, which estimates the electronic part of thermal conductivity κe = L σT, where σ and T are electrical conductivity and temperature, respectively. κL is then estimated as κL = κT − L σT. For metallic systems, the Lorenz number has a universal value of 2.44 × 10 −8 WΩ K−2 (degenerate limit), but for non-degenerate semiconductors, the value can deviate significantly for acoustic phonon scattering, the most common scattering mechanism for thermoelectric materials above room temperature. Up until now, L is estimated by solving a series of equations derived from Boltzmann transport equations. For the single parabolic band (SPB) model, an equation was proposed to estimate L directly from the experimental Seebeck coefficient. However, using the SPB model will lead to an overestimation of L in the case of low bandgap semiconductors, which results in an underestimation of κL, sometimes even negative κL. In this article, we propose a simpler equation to estimate L for a non-parabolic band. The experimental Seebeck coefficient, bandgap (Eg), and temperature (T) are the main inputs to the equation, which nearly eliminates the need for solving multiple Fermi integrals besides giving accurate values of L.
Prospects for rank-reduced CCSD(T) in the context of high-accuracy thermochemistry
Authors: Zhao Tingting , Thorpe James H. , Matthews Devin A.
Published: October 2024

Obtaining sub-chemical accuracy (1 kJ mol−1) for reaction energies of medium-sized gas-phase molecules is a longstanding challenge in the field of thermochemical modeling. The perturbative triples correction to coupled-cluster single double triple [CCSD(T)] constitutes an important component of all high-accuracy composite model chemistries that obtain this accuracy but can be a roadblock in the calculation of medium to large systems due to its O(N7) scaling, particularly in HEAT-like model chemistries that eschew separation of core and valence correlation. This study extends the work of Lesiuk [J. Chem. Phys. 156, 064103 (2022)] with new approximate methods and assesses the accuracy of five different approximations of (T) in the context of a subset of molecules selected from the W4-17 dataset. It is demonstrated that all of these approximate methods can achieve sub-0.1 kJ mol−1 accuracy with respect to canonical, density-fitted (T) contributions with a modest number of projectors. The approximation labeled Z̃T appears to offer the best trade-off between cost and accuracy and shows significant promise in an order-of-magnitude reduction in the computational cost of the CCSD(T) component of high-accuracy model chemistries.
Numerical study of rotating cavitation and pressure pulsations in a centrifugal pump impeller
Authors: Wu Yuhan , Xiang Chun , Mou Jiegang , Qian Heng , Duan Zhenhua , Zhang Sanxia , Zhou Peijian
Published: October 2024

To investigate the variations in the flow field of centrifugal pumps with different cavitation numbers, this study utilized the shear stress transport k–ω turbulence model and Zwart–Gerber–Belamri cavitation model to examine the correlation between stall vortices and cavitation flow. The findings indicate that cavitation consistently coincides with the formation of stall vortices, and the distribution of cavitation mirrors the pattern of stall vortex structure. Cavitation tends to develop and aggregate around stall vortices, obstructing a significant portion of inlet areas within the flow channel. As the cavitation number decreases, both the area and intensity of stall vortices increase. For cavitations margins σ = 0.41, 0.23, and 0.15, we observed propagation frequencies of stall vortices at fs = 2.7, 1.8, and 0.9 Hz respectively, as these frequencies decrease relative to impeller movement until reaching near-stationary states. The pressure pulsations in various flow channels exhibit distinct phase differences; smaller cavity numbers result in larger phase disparities along with a gradual reduction in pressure pulsation amplitude. These discoveries present effective strategies for controlling and reducing both cavity formation and pressure fluctuations within centrifugal pumps, thereby enhancing overall stability.
Relation between bubble behaviors in spray sheet and bubbly flow inside an air-induction fan nozzle: A visualization study
Authors: Gong Chen , Li Dongyang , Yan Shifeng , Kang Can , Ding Kejin
Published: October 2024

The present study aims to elucidate the relationship between bubble behaviors in the spray sheet and internal bubbly flow of the air-induction nozzle. An experimental work was performed using the visualization technique. Effects of the air inlet position and spray pressure were investigated. The results show that compared with the bubbles inside the air-induction nozzle, bubbles in the spray sheet have smaller volume but larger average diameter. Disturbance propagates in the horizontal air-inlet segment. When the air inlet position shifts toward the nozzle outlet, overall bubble volume inside the nozzle decreases by about 56%, while in the spray sheet, the bubble volume decreases by about 77%. Bubble breakup causes a decrease in overall bubble volume as bubbles travel from the inner flow passage of the nozzle to the environment. The coalescence and compression of bubbles induce the increase in average bubble diameter. When the spray pressure increases from 0.1 to 0.3 MPa, both the total bubble volume and average bubble diameter increase.
The time history of dynamic response of permeable asphalt mixture pavement based on PFC2D
Authors: Zhang Xingmei , Guo Xiangyu , Yang Datian
Published: October 2024

To investigate the dynamic response of permeable asphalt mixture pavements, a discrete element model was developed using PFC2D under the coupling of seepage and stress fields. This study examines the excess pore water pressure and dynamic behavior of permeable asphalt mixture pavements under the coupling of seepage and stress fields. The findings indicate that the excess pore water pressure amplifies compressive strain and stress at the base of the permeable asphalt mixture over time, while exhibiting alternating positive and negative fluctuations as a roller traverses the pavement.
Aerosol deposition on face masks in an open environment during inhalation
Authors: Lee Y. J. , Moon M. W. , Chung S. , Kim S. J.
Published: October 2024

The aerodynamics of aerosols and their deposition on face masks play a critical role in determining the effectiveness of respiratory protection. While existing studies have focused on the risks associated with aerosol dispersion during exhalation, little attention has been paid to aerosol aerodynamics in an open environment, where aerosols can circumvent masks, during inhalation. This is because mask performance has primarily been evaluated by the particle filtration efficiency in closed pipe setups, which do not account for the aerodynamics of aerosols around the wearer's face. In this study, we conduct experiments in an open environment to investigate the aerosol flow around a face mask and the aerosol deposition under varying inhalation pressures. Our results indicate that an aerosol flow near a mask surface behaves like a viscous flow, stagnating within the range of human inhalation. Within this range, we find that the amount of aerosol deposited can be predicted by modifying existing aerodynamics theory. Using a theoretical model, a critical inhalation pressure is identified at which water aerosols begin to penetrate through a mask. Finally, we propose the aerosol circumvention efficiency as a new metric to assess mask performance in open environments by taking into account the effects of aerosol circumvention.
Research of scale effect on propeller bearing force of a four-screw ship in oblique flow
Authors: Sun Shuai , Qin Taotao , Li Xiang
Published: October 2024

To study the scale effect on propeller bearing forces in oblique flow, the propeller bearing forces of a fully appended four-screw ship that refers to a vessel propelled by four propellers are calculated and investigated. The findings reveal that scale effects in wake fields lead to an increase in the axial velocity of the propeller disk in the full-scale ship compared to the model, influenced by boundary layer flow. Moreover, asymmetric differences in the impact of oblique flow on the leeward and windward sides result in varied effects of positive and negative drift angles on the wakefield. The disparity in wake fields between inside and outside disks exacerbates unbalanced load distribution, with time-averaged loads showing an increase with drift angle for both propellers at full scale. Additionally, pronounced scale effects lead to variations in blade loads between model and full scale, with drift angles shifting the locations of single-blade load extremums. Unsteady bearing force components exhibit periodic fluctuations, with larger amplitudes at the blade passage frequency for the model scale propeller compared to the full scale, particularly evident under negative drift angles. The aforementioned findings can provide theoretical guidance for load balancing and vibration reduction of the four-screw ships.
Impact of peripheral venoarterial extracorporeal membrane oxygenation support for heart failure on systemic hemodynamics and aortic blood flow
Authors: Li Da , Li Xuanyu , Xia Yingjie , Weng ChengXin , Liang Fuyou
Published: October 2024

Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is an advanced temporary life support system for patients with refractory cardiogenic shock or severe cardiopulmonary failure. However, the reperfusion of oxygenated blood into the arterial system via a peripheral artery will induce substantial hemodynamic changes that might contribute to the development of complications. In this study, we developed two types of computational models to quantify the hemodynamic changes induced by the peripheral VA-ECMO support for systolic heart failure (HF) of various severities. One was a lumped-parameter model used for exploring the optimal workload of extracorporeal membrane oxygenation (ECMO) for a specific severity of HF, whereas the other one was a geometrical multiscale model capable of simulating the detailed flow field in the aorta while accounting for the hemodynamic coupling of VA-ECMO with the cardiovascular system. Numerical results revealed that the retrograde transmission of ECMO-supplied blood flow toward the heart not only considerably inhibited cardiac output but also induced marked flow disturbance and regionally high or oscillatory wall shear stress (WSS) in the aorta that may increase the risk of thrombosis and vascular dysfunction. The major characteristics of flow disturbance and spatial distribution of abnormal WSS were codetermined by the cardiac function and workload of ECMO while less influenced by the morphology of aorta. These findings emphasized the importance of tuning the workload of ECMO based on patient-specific cardiac function to balance the amount of blood oxygenation support by ECMO against the risk of complications associated with hemodynamic abnormalities.
Concentration calculation model for calibration of non-dispersive infrared gas detection system
Authors: Kim Kum-Dong , Song Kil-Song , Hwang Hyon-Ung , Choe Chol-Min , Im Song-Jin , Pae Ji-Song , Ri Chol-Song , Ho Kum-Song
Published: October 2024

Non-dispersive infrared (NDIR) gas detection systems have been extensively used for gas monitoring because they are considered the simplest approach with moderate sensitivity and fast response. Concentration calculation models for calibration are particularly important in NDIR gas detection systems because of the nonlinear relationship between the output voltage ratio and concentration. We propose a concentration calculation model with two fitting parameters for non-dispersive infrared gas detection systems, accounting for the fact that not all IR radiation that impinges upon the detector is absorbed by the gas and for the saturation effects in absorption peaks leading to the nonlinear relationship. Despite the small number of fitting parameters of the proposed concentration calculation model, it presents high quality curve fitting to experimental data. The performance of the proposed model is compared to that of other concentration calculation models.
Efficiency high-order discontinuous Galerkin method for low speeds flows with time-derivative preconditioning
Authors: Jia Ruqian , Yan Jia , Niu Zhenyu , Yang Xiaoquan
Published: October 2024

A local preconditioning high-order discontinuous Galerkin (DG) method is introduced to enhance the efficiency and accuracy of the density-based approach for low-speed flows. The method is based on the time-derivative preconditioning technique typically employed in finite volume methods. Traditional approximation methods that only precondition low-order derivatives lead to incompatibility of the equations. To extend the preconditioning technique to the DG method, we employ an analytic preconditioning mass matrix derived from the DG formulation of the preconditioned Navier–Stokes equations. Modified numerical flux functions and a self-adaptive local velocity truncation parameter are employed for DG systems with preconditioning. We demonstrate the efficiency and accuracy of the preconditioned DG method using explicit and implicit schemes for steady flows and a dual-time scheme for unsteady flows. The method has been implemented and used to compute a variety of flow problems, including inviscid and laminar flows, utilizing various degrees of polynomial approximations. Computations with and without preconditioning are performed to analyze the influence of spatial discretization on the accuracy and convergence of the DG solutions at low Mach numbers. Numerical results underscore the enhanced accuracy and convergence properties of the proposed method for low-speed flows, indicating significant performance improvements over traditional methods.