bluuebunny/crossref_metadata_2025 huggingface dataset:
Urban morphology as an indicator of solar potential on building facades at high latitudes
Authors: Giorio Martina , Manni Mattia , Kong Gefei , Fan Hongchao , Lobaccaro Gabriele
Published: August 2024

Solar cadastres enable calculating and visualizing solar energy potential data on urban surfaces (i.e., roofs, facades, and ground). At high latitudes, knowing the solar potential of vertical surfaces is important due to the solar geometry (i.e., low sun angle). This study provides insights into correlations between neighbourhood morphology and solar energy potential. It moves from the acquisition of the three-dimensional urban surface mode of Trondheim (Norway) to the estimation of the solar potential on urban surfaces with data post-processing and visualization at the neighbourhood scale. The results show that facades' irradiance spread emphasizes high-density neighbourhoods influence on solar potential.
Development of an Integrated Solar-Biomass Energy System for Near-Zero Energy Buildings: A Technical and Environmental Study
Authors: Karkon Ehsan , Liravi Mohammad , Georges Laurent , Li Jinping , Novakovic Vojislav
Published: August 2024

The present study aims to satisfy the energy demands of a set of Norwegian residential structures with the least carbon dioxide and most renewable energy. Real-time data on building domestic hot water (DHW), heating, and electricity usage is used to plan and expand the renewable energy supply side. PVT panels provide DHW and electricity in the hybrid solar and biomass energy system. Heat is produced by the digester and heat pump. Also used is a twofold effect absorption refrigeration system for cooling. Rule-based regulation manages heat streams and redirects flows on the supply side. We provide the plant's size and execute the dynamic energy simulation. Electricity and biomass expenses determine building heating. The system is then tuned for operational conditions and compared to the design point. PVT may generate over 80% of annual DHW. Summertime radiation is more intense and can be turned into cooling energy, therefore 64.8% of cooling output comes from it. Digester/CC heats 66.55% of the structure, suggesting designers use biomass in winter due to increased energy costs. A parametric analysis shows that increasing PVT duration and tank size affects efficiency and emissions differently. Cost, efficiency, and emission index at TOPSIS are 9.73 $/hr, 36.8%, and 7.75 kg/MWh, according to optimization findings.
Data science skills for the built environment: Lessons learned from a massive open online Python course for construction, architecture, and engineering
Authors: Miller Clayton , Tan Charlene
Published: August 2024

It’s not just the models, techniques, or technologies that improve building performance; the digital skills of built environment professionals also play a significant part. The deluge of data from buildings, intelligent systems, and simulation tools is well-documented, and like other domains, building design, construction, and operations professionals are keen to learn skills like Python scripting that are common to the data science communities. This paper analyzes a massive open online course on the edX platform called Data Science for Construction, Architecture, and Engineering. This course was launched in April 2020, and it combines building science concepts with beginner-level data science skills, such as using Python and the essential libraries of Pandas, Scikit Learn, and Seaborn. This paper presents an analysis of the demographics and geographic data from 18,600 participants and survey results from 126 out of 1,561 verified course users. The survey focused on the experience of course participants and suggestions for improvement. This information can aid other data science educators in developing content to better educate built environment professionals.
Challenges, benefits, and open questions in Data-Driven Commercial Building Cooling Optimization
Authors: Sukhanov Ivan , Volkova Anna , Kose Ahmet , Hani Allan , Petlenkov Eduard
Published: August 2024

The rising demand for building cooling presents a challenge, expected to triple energy usage by 2050. European Parliament targets a 40% reduction in final energy and 42.5% in primary energy by 2030. This paper examines data-driven solutions in Building Management Systems (BMS) for energy-efficient cooling. It outlines challenges, benefits, and open questions in Data-Driven Commercial Building Cooling Optimization. By integrating data-driven techniques with current infrastructure, it proposes sustainable cooling practices. Results indicate potential energy reductions of up to 24%, lower costs, and prolonged system lifespan. This research addresses cooling deficiencies, providing practical, lasting energy efficiency solutions for commercial buildings.
Simulation of the airflow patterns within the surgical microenvironment in operating room
Authors: Harsen Trond Thorgeir , Venås Bård , Fečer Tomáš , Georges Laurent , Bi Yang , Mathisen Hans Martin , Cao Guangyu
Published: August 2024

Maintaining acceptable indoor air quality within operating rooms (ORs) in healthcare facilities is vital to prevent surgical site infections (SSIs). Two prevalent ventilation systems, laminar airflow (LAF) and mixing ventilation (MV), are widely used in ORs for various surgical operations. However, several studies have stated that these systems have slightly different SSI rate controls. Earlier studies discovered the airflow velocity above the surgical incision in LAF-equipped ORs to be twice as high as in MV-equipped ones. In addition, the placement of surgical lamps and different airflow patterns add complexity to the study of the surgical microenvironment. The objective of this study is to characterize the airflow pattern in the surgical microenvironment by computational fluid dynamics (CFD) simulations and experimental measurements in the newly built operating room lab at NTNU. The findings may provide new guidelines for standards development ensuring safer surgeries in healthcare facilities. The research project is called: Reduction of postoperative surgical site infection (POSI) through the development of XR tool. The project is supported by the Norwegian Research Council and Norconsult.
Grey-box modeling of Air Handling Units for Analysis and Virtual Sensing
Authors: Fjerbæk Esben Visby , Smith Kevin Michael , Hviid Christian Anker
Published: August 2024

The optimization of control sequences in air handling units (AHUs) presents a significant opportunity for energy savings within HVAC systems. However, many building owners and operators require quantifiable estimates of potential energy savings before committing to retrofitting control systems. Valid estimates of energy savings require system models that consider capacity and limitations of the AHU, but in existing systems, scarce information hinders such modeling efforts. This lack of information complicates AHU modeling and the assessment of alternative control strategies.

This paper demonstrates an approach that leverages time-series data from a newly constructed Danish AHU, equipped with multiple sensors for temperature, flow, and pressure, to construct a grey-box model of the unit, including component properties.

The estimated parameters for the components are validated against data sheet information, and shows that the estimation procedure is accurate for parameter estimation. To analyze the energy-efficiency of the cooling coil, the model is used to estimate the latent cooling in the cooling coil, as Danish conditions rarely require dehumidification of supply air.
Behavior of the continuum coupling correlation energy in the vicinity of the particle emission threshold - Gamow shell model study
Authors: Linares Fernandez J.P. , Michel N. , Płoszajczak M.
Published: August 2024

The Gamow shell model provides the open quantum system formulation of nuclear shell model. In the coupled-channel representation, Gamow shell model provides the unified theory of nuclear structure and reactions which is well suited for the study of resonances and clustering. In this work, we apply this approach to study the continuum-coupling correlation energy for selected near-threshold states of7Li,7Be, using a translationally invariant Hamiltonian with an effective finite-range two-body interaction.
Intriguing aspects of light baryon resonances
Authors: Khemchandani K. P. , Martínez Torres A. , Kim Sang-Ho , Nam Seung-il , Hosaka A. , Nagahiro H.
Published: August 2024

We discuss that some light baryon resonances exhibit properties which cannot be described when attributing a three-valence quark structure to them. Besides pointing out the hadron resonances which clearly require description beyond the quark model, we focus on the third s11, N∗ state and its decay to final states consisting of the lightest hyperon resonances which have a partial width comparable to that for the decay to πN. Such properties of the mentioned nucleon resonance get manifested in the cross sections and other observables related to processes producing the lightest hyperon resonances. We show that all these findings arise from the strong association of the baryon resonances to the dynamics among the ground-state hadrons.
Photon-photon scattering
Authors: Schubert Christian
Published: August 2024

The existence of photon-photon scattering historically was one of the first non-trivial predictions of QED. However, since the cross section is very small at low energies it was only in 2017 that a direct measurement was achieved in heavy-ion collisions at the LHC. After short reviews of the history of the subject and of the CERN experiment, I discuss the general structure of the four-photon tensor, which also serves as the prototype for all vertices of four gauge bosons. I then come to generalizations from QED to the Standard Model and beyond, in particular to the Born-Infeld theory that has gained some popularity in recent years as an alternative to standard quantum electrodynamics.
Pair creation in electric fields
Authors: Schubert Christian
Published: August 2024

Sauter-Schwinger pair creation in electromagnetic fields is a fundamental prediction of QED and one of the motivations for the present efforts in constructing super-strong lasers. I will give a historical review of the subject, and then focus on two recent developments. The first one is the worldline instanton formalism, a sophisticated version of the WKB approximation that makes it possible to calculate the pair creation rate for complicated field configurations. The second one is an adaptation of the Dirac-Heisenberg-Wigner formalism suitable for a detailed study of the formation of real particles in time and space.
Kinderkrankenpflege in Zeiten der generalistischen Pflegeausbildung
Authors: Weber Jenny
Published: August 2024

Die Pflege von kranken Kindern erfordert spezielle Kenntnisse und Fähigkeiten. In der Vergangenheit erfolgte die Ausbildung der Kinderkrankenpflege in Deutschland separat von der Gesundheits- und Krankenpflege. Doch mit der Einführung der Generalistik hat sich dies geändert. Dieser Artikel beleuchtet die Integration der Kinderkrankenpflege in die generalistische Pflegeausbildung und die Bedeutung des Angebots der Vertiefung in der pädiatrischen Versorgung.
„nestwärme“ – ein innovatives Konzept zur Hospiz- und Palliativversorgung
Authors: Graupner Lara , Gertsen Willi , Himmelsbach Ines
Published: August 2024

In den vergangenen Jahrzehnten hat sich die Hospiz- und Palliativversorgung in Deutschland kontinuierlich weiterentwickelt und auch im Bereich der Kinder- und Jugendversorgung hat sie bedeutende Fortschritte verzeichnet. Dennoch besteht noch keine flächendeckende Sicherstellung der Versorgung. Die Zusammenarbeit zwischen verschiedenen Akteuren gestaltet sich als anspruchsvoll und resultiert in sektoralen Lücken. Vor diesem Hintergrund wurde ein Konzept untersucht, das eine koordinierte überregionale Hospiz- und Palliativversorgung für Kinder und Jugendliche unter einem Dach verspricht.
Einfluss der Spezialisierung auf primäre Erfolgs- sowie Komplikationsrate bei der ERCP. Vorschlag zur Verbesserung der Qualität der ERCP
Authors: Leifeld Ludger , Jakobs Ralf , Frieling Thomas , Denzer Ulrike , Faiss Siegbert , Lenzen Henrike , Lynen Petra , Mayerle Julia , Ockenga Johann , Tappe Ulrich , Terjung Birgit , Wedemeyer Heiner , Albert Jörg ,   für die DGVS
Published: August 2024

Die Endoskopische retrograde Cholangio-Pankreatikografie [ERCP] ist eine komplexe Prozedur mit flacher Lernkurve, die mit den Risiken ernsthafter Komplikationen, wie der Pankreatitis, der Blutung, der Cholangitis und der Perforation einhergeht. So sollte zur präzisen Indikationsstellung der risikoreicheren ERCP auch die Endsonografie angeboten werden. Zahlreiche Faktoren beeinflussen den Erfolg der ERCP. Neben einer strukturierten Ausbildung zum Kompetenzerwerb mit einer Mindestzahl an ERCPs unterschiedlicher Schwierigkeitsgrade, erfordert die Aufrechterhaltung einer guten Qualität der ERCP auch eine regelhafte Mindestanzahl durchgeführter Untersuchungen pro Jahr. Es existiert mittlerweile eine umfangreiche Evidenz, die eine signifikante Korrelation der ERCP-Volumina mit den primären Erfolgsraten, niedrigeren Krankenhausverweildauern, weniger ungewollten Wiederaufnahmen sowie geringeren Komplikationen zeigt. Die Grenzen zur Unterscheidung zwischen Hochvolumen- und Niedrigvolumen-Zentren wurden in den Studien uneinheitlich gewählt, die höchste Evidenz liegt für einen Grenzwert von 200 ERCPs/Jahr vor. Die Frage nach einer Spezialisierung in der ERCP hat einen aktuellen Bezug erhalten durch die derzeitigen Entwicklungen der Krankenhausreform. Hier soll eine Mindestvorhaltezahl für Leistungsgruppen definiert werden. Eine Mindestvorhaltezahl allein wird aber keine gute Behandlungsqualität erreichen können. Im Sinne einer qualitativ hochwertigen Patientenversorgung ist es notwendig, dass die ERCP in der spezialisierten Gastroenterologie angeboten wird, die vor dem Hintergrund der Krankenhausreform in der Leistungsgruppe „Komplexe Gastroenterologie“ zugeordnet wird, die neben einer ausreichenden Anzahl an ERCPs zur Weiterbildung und zum Kompetenzerhalt, einen Rufdienst und komplementäre Verfahren wie die EUS anbieten und die in angemessen erreichbaren Kliniken eingebettet sind, die über die notwendigen Ressourcen zum Komplikationsmanagement verfügen.
Institutionelle und patient*innenbezogene Einflussfaktoren auf die
Häufigkeit von Fixiermaßnahmen auf einer allgemeinpsychiatrischen
Akutstation
Authors: Paetzold Miriam , Kuhr Kathrin , Lehnhardt Fritz-Georg
Published: August 2024

Ziel Valide Kenntnisse über eine Risikostratifizierung sind essenziell für
die Entwicklung präventiver Ansätze zur Reduktion von Zwangsmaßnahmen.

Methodik In dieser retrospektiven, monozentrischen Untersuchung wurden
alle 248 Fixiermaßnahmen an 79 Patient*innen einer universitären
Abteilungspsychiatrie im Jahr 2015 untersucht. Acht institutionelle und sieben
patient*innenbezogene Einflussfaktoren wurden statistisch mittels logistischer
Regressionsanalyse und „matched pairs“ berechnet.

Ergebnisse Eine statistisch signifikant erhöhte Fixierwahrscheinlichkeit
zeigte sich bei den institutionellen Einflussfaktoren für eine geringere Anzahl
Pflegekräfte pro Patient*innen, eine höhere Anzahl gesetzlich untergebrachter
Patient*innen, eine geringere Berufserfahrung der Pflegekräfte, im pflegerischen
Spätdienst, sowie bei den patient*innenbezogenen Einflussfaktoren lediglich für
den Zugangsweg über den Rettungsdienst.

Schlussfolgerung Auf Basis der Ergebnisse werden Möglichkeiten präventiver
organisatorischer Maßnahmen abgeleitet und Voraussetzungen für eine prospektive
Evaluation der komplexen, insbesondere patient*innenbezogenen Einflussfaktoren
auf Zwangsmaßnahmen diskutiert.
Predicting ERCP procedure time – the SWedish Estimation of ERCP Time (SWEET) tool
Authors: Waldthaler Alexander , Warnqvist Anna , Waldthaler Josefine , Vujasinovic Miroslav , Ghorbani Poya , von Seth Erik , Arnelo Urban , Lohr Mathias , Bergquist Annika
Published: August 2024

Background: The duration of an endoscopic retrograde cholangiopancreatography (ERCP) is influenced by a multitude of factors. The aim of this study was to describe the factors influencing ERCP time and to create a tool for preintervention estimation of ERCP time.

Methods: Data from 74 248 ERCPs performed from 2010 to 2019 were extracted from the Swedish National Quality Registry (GallRiks) to identify variables predictive for ERCP time using linear regression analyses and root mean squared error (RMSE) as a loss function. Ten variables were combined to create an estimation tool for ERCP duration. The tool was externally validated using 9472 ERCPs from 2020 to 2021.

Results: Mean (SD) ERCP time was 36.8 (25.3) minutes. Indications with the strongest influence on ERCP time were primary sclerosing cholangitis and chronic pancreatitis. Hilar and intrahepatic biliary strictures and interventions on the pancreatic duct were the anatomic features that most strongly affected ERCP time. The procedure steps with most influence were intraductal endoscopy, lithotripsy, dilation, and papillectomy. Based on these results, we built and validated the Swedish Estimation of ERCP Time (SWEET) tool, which is based on a 10-factor scoring system (e.g. 5 minutes for bile duct cannulation and 15 minutes for pancreatic duct cannulation) and predicted ERCP time with an average difference between actual and predicted duration of 17.5 minutes during external validation.

Conclusions: Based on new insights into the factors affecting ERCP time, we created the SWEET tool, the first specific tool for preintervention estimation of ERCP time, which is easy-to-apply in everyday clinical practice, to guide efficient ERCP scheduling.
Nickel-Catalyzed Radical Hydroalkylative Dearomatization of Indoles with Alkyl Bromides
Authors: Cheng Yuan-Zheng , You Shu-Li , Dai Hao-Tian , Huang Xu-Lun
Published: August 2024

Dearomatization of indole derivatives offers a straightforward approach to accessing the indoline framework. However, highly efficient dearomatization of indoles bearing electron-deficient groups remains underdeveloped. Herein, a nickel-catalyzed intermolecular hydroalkylative dearomatization reaction of indoles with simple alkyl bromides through a single-electron-transfer process is reported. A wide variety of indole derivatives bearing various functional groups were compatible with this protocol and reacted with primary, secondary, or tertiary alkyl bromides to afford a series of indolines in good yields (up to 82%) and with excellent diastereoselectivity (up to >20:1). Notably, a nickel-mediated hydrogen-atom-transfer process was observed when terminal alkyl bromides were employed as the radical precursors, which resulted in branched products.
Iron(III) Triflate and γ-Cyclodextrin-Catalyzed Hydroarylation of Alkenes with 1-Naphthols and 2-Naphthols
Authors: Hu Meng-Xue , Chen Peng , Jiang Yi-Jun , Miao Le-Wei , Shi Jianghuan
Published: August 2024

A Fe(OTf)3 and γ-cyclodextrin-catalyzed hydroarylation of alkenes with 1-naphthols or 2-naphthols is demonstrated. This efficient and general method delivers a wide range of benzylic naphthols from readily available starting materials with high chemo- and regioselectivity in up to 99% yield, with no need for a strong base or additive.
Serendipity as a Driving Force in the Synthesis of Isatins Substituted with Electron-Donating Groups
Authors: Ryabukhin Serhiy V. , Bondarenko Semen S. , Fedorchenko Anatolii M. , Druzhenko Tetiana V. , Melnykov Kostiantyn P. , Volovenko Yulian M. , Volochnyuk Dmytro M.
Published: August 2024

An efficient synthetic procedure for the synthesis of isatins was found after careful analysis of the serendipitous results of the unexpected products obtained by aromatic nucleophilic substitution when it was attempted to introduce 6-fluoroisatins to the classic Pfitzinger reaction. Attentive analysis of these results led to elaborating a methodology for synthesizing electron-enriched isatins, including those with hydroxy-, alkoxy-, alkylthio-, and dialkylamino-substituted aromatic rings. Limitations of the method were established. The reaction conditions were optimized according to the understanding of water’s role. Finally, the classic Pfitzinger reaction procedure was modified to yield the expected 2-substituted 7-fluoroquinoline-4-carboxylic acids.
Fellows of the American Medical Informatics Association (FAMIA): Looking Back and Looking Ahead
Authors: Heermann Langford Laura , Fultz Hollis Kate , Edmunds Margo , McCoy Allison B. , Hall Eric S. , Nielson Jeffrey A. , Rosetti Sarah Collins
Published: August 2024

Background Over the past 30 years, the American Medical Informatics Association (AMIA) has played a pivotal role in fostering a collaborative community for professionals in biomedical and health informatics. As an interdisciplinary association, AMIA brings together individuals with clinical, research, and computer expertise and emphasizes the use of data to enhance biomedical research and clinical work. The need for a recognition program within AMIA, acknowledging applied informatics skills by members, led to the establishment of the Fellows of AMIA (FAMIA) Recognition Program in 2018.

Objectives To outline the evolution of the FAMIA program and shed light on its origins, development, and impact. This report explores factors that led to the establishment of FAMIA, considerations affecting its development, and the objectives FAMIA seeks to achieve within the broader context of AMIA.

Methods The development of FAMIA is examined through a historical lens, encompassing key milestones, discussions, and decisions that shaped the program. Insights into the formation of FAMIA were gathered through discussions within AMIA membership and leadership, including proposals, board-level discussions, and the involvement of key stakeholders. Additionally, the report outlines criteria for FAMIA eligibility and the pathways available for recognition, namely the Certification Pathway and the Long-Term Experience Pathway.

Results The FAMIA program has inducted five classes, totaling 602 fellows. An overview of disciplines, roles, and application pathways for FAMIA members is provided. A comparative analysis with other fellow recognition programs in related fields showcases the unique features and contributions of FAMIA in acknowledging applied informatics.

Conclusion Now in its sixth year, FAMIA acknowledges the growing influence of applied informatics within health information professionals, recognizing individuals with experience, training, and a commitment to the highest level of applied informatics and the science associated with it.
Bounds on the growth of energy for particles on the torus with unbounded time dependent perturbations
Authors: Bambusi Dario
Published: August 2024

We prove a C∞ version of Nekhoroshev theorem for time dependent Hamiltonians in Rd×Td. Precisely, we prove a result showing that for all times the energy of the system is bounded by a constant times ⟨t⟩ɛ. We apply the result to the dynamics of a charged particle in Td subject to a time dependent electromagnetic field.
Microstructural stability and mechanical properties of the as-cast and heat-treated newly developed TiNbCrTa refractory complex concentrated alloy
Authors: Gupta Aman , Shankar Gyan , Pawar Saurabh , Choi Shi-Hoon , Suwas Satyam
Published: August 2024

In this study, a TiNbCrTa refractory complex concentrated alloy (RCCA) was prepared using vacuum arc remelting. The microstructural evolution and mechanical properties of both as-cast and heat-treated RCCA samples were analyzed. Heat treatment (HT) was performed at 800–1200 °C for 1 h in a vacuum-sealed environment. These samples exhibited a formation of Cr2Nb and Cr2Ti Laves phases. A variation in elemental distribution was observed, with interdendritic (ID) regions showing higher fractions of Ti and Cr, while the dendritic regions had a greater concentration of Ta and Nb. Micro-segregation at the IDs was confirmed through energy dispersive x-ray spectroscopy mapping, which inferred the formation of Cr- and Ti-rich phases during HT at 800–1200 °C. High-temperature HT at 1200 °C for 1 h led to the evolution of the hcp omega phase. Prolonged HT at 1200 °C for 96 h resulted in the evolution of a Cr-rich Laves phase (Cr2Ta), which was homogeneously distributed within the microstructure, indicating an unstable microstructure. Furthermore, despite prolonged HT, a variation in the elemental distribution persisted due to the presence of dendritic and ID regions. Electron backscattered diffraction analysis revealed the presence of bcc and hcp phases in the dendritic and ID regions, respectively, of the as-cast and HTed samples. The as-cast samples demonstrated a high compressive strength of approximately 2 GPa. Micro-hardness values increased with the HT temperature up to 1000 °C. Further increases under HT conditions did not significantly reduce the microhardness value, whereas prolonged HT at 1200 °C led to an increase in the microhardness value. Overall, the newly developed TiNbCrTa RCCA exhibited high-strength behavior even after the phase transformation.
Compositional engineering of interfacial charge transfer in van der Waals heterostructures of graphene and transition metal dichalcogenides
Authors: Wen Guanzhao , Fu Shuai , Bonn Mischa , Wang Hai I.
Published: August 2024

Owing to their unique optical and electronic properties, vertical van der Waals heterostructures (vdWHs) have attracted considerable attention in optoelectronic applications, such as photodetection, light harvesting, and light-emitting diodes. To fully harness these properties, it is crucial to understand the interfacial charge transfer (CT) and recombination dynamics across vdWHs. However, the effects of interfacial energetics and defect states on interfacial CT and recombination processes in graphene-transition metal dichalcogenide (Gr-TMD) vdWHs remain debated. Here, we investigate the interfacial CT dynamics in Gr-TMD vdWHs with different chemical compositions (W, Mo, S, and Se) and tunable interfacial energetics. We demonstrate, using ultrafast terahertz spectroscopy, that while the photo-induced electron transfer direction is universal with graphene donating electrons to TMDs, its efficiency is chalcogen-dependent: the CT efficiency of S atom-based vdWHs is 3–5 times higher than that of Se-based vdWHs thanks to the lower Schottky barrier present in S-based vdWHs. In contrast, the electron back transfer process from TMD to Gr, which defines the charge separation time, is transition metal-dependent and dominated by the mid-gap defect level of TMDs: W transition metal-based vdWHs possess extremely long charge separation, well beyond 1 ns, which is significantly longer than Mo-based vdWHs with only 10 s of ps charge separation. This difference can be traced to the much deeper mid-gap defect reported in W-based TMDs compared to Mo-based ones, resulting in modified energetics for the back electron transfer from the trapped states to graphene. Our results shed light on the role of interfacial energetics and defects by tailoring chemical compositions of TMDs on the interfacial CT and recombination dynamics in Gr-TMD vdWHs, which is pivotal for optimizing optoelectronic devices, particularly in the field of photodetection.
Manifold learning-based reduced-order model for full speed flow field
Authors: Li Ruixue , Song Shufang
Published: August 2024

Reduced-order models (ROMs) can effectively balance the accuracy and efficiency of computational fluid dynamics (CFD). The nonlinear flow field characteristics cannot be captured accurately by traditional ROMs, such as proper orthogonal decomposition (POD). Combining isometric mapping (ISOMAP) and local linear embedding (LLE), a novel manifold learning method (ISOMAP-Local LLE) is proposed, performing global and accurate reconstruction of the nonlinear flow field. First, the nonlinear dimensionality reduction is derived by considering the global isometric characteristic and the local reconstruction relationship simultaneously. Then, the local interpolation model is constructed to improve the interpolation accuracy introduced by the global interpolation model. Finally, the flow field reconstruction is accomplished based on the inverse mapping. Furthermore, the criteria of hyperparameters have been established to achieve high-precision prediction. Several examples covering full speed flow field are carried out to demonstrate the accuracy and efficiency of ISOMAP-Local LLE. The proposed manifold learning-based ROM achieves prediction accuracy that surpasses that of other ROMs (such as POD, ISOMAP, LLE, etc.), resulting in significant time cost savings for CFD simulations.
Design of a pilot-scale microwave freeze dryer for in situ neutron imaging
Authors: Hilmer Mathias , Gruber Sebastian , Kis Zoltán , Schulz Michael , Foerst Petra
Published: August 2024

The gentle yet cost-effective drying of sensitive products in the food and pharmaceutical industries is becoming increasingly important. To maintain sensitive ingredients, color, structure, and viability of micro-organisms, often freeze-drying is the only possible way to preserve the product. As many products come in as bulk material, they are dried on heated shelves resulting in poor heat and mass transport through the bed. Resulting in a very time and cost intensive process. Therefore, efforts are being made to improve the mass and heat transport of the process. The outer mass transport through the bulk can be improved by continuous mixing of the pellets, facilitating the removal of water vapor from the condenser. In addition, the issue of limited heat transport can be addressed by using volumetric energy input from microwaves. This process is called dynamic microwave freeze-drying. As dynamic microwave freeze-drying is a combined drying and mixing process, with particle properties continuously changing during drying, it is necessary to gain a more detailed insight into the process. For this purpose, a drier is designed that is capable of in situ neutron imaging, a method sensitive to a material’s hydrogen content. This paper presents the design of a pilot-scale microwave freeze dryer for in situ neutron imaging and shows the first images taken during the dynamic microwave freeze-drying of bulk particles at the Center for Energy Research, Budapest Neutron Center in Budapest, Hungary.
Time-of-flight vs time-of-arrival in neutron spectroscopic measurements for high energy density plasmas
Authors: Grim G. P. , Mitrani J. M. , Chandler G. A. , Hahn K. D. , Jones M. C. , Mannion O. M.
Published: August 2024

The neutron time-of-flight (nToF) diagnostic technique has a lengthy history in Inertial Confinement Fusion (ICF) and High Energy Density (HED) Science experiments. Its initial utility resulted from the simple relationship between the full width half maximum of the fusion peak signal in a distant detector and the burn averaged conditions of an ideal plasma producing the flux [Lehner and Pohl, Z. Phys. 207, 83–104 (1967)]. More recent precision measurements [Gatu-Johnson et al., Phys. Rev. E 94(8), 021202 (2016)] and theoretical studies [Munro, Nucl. Fusion 56, 035001 (2016)] have shown the spectrum to be more subtle and complicated, driving the desire for an absolute calibration of the spectrum to disambiguate plasma dynamics from the conditions producing thermonuclear reactions. In experiments where the neutron production history is not well measured, but the neutron signal is preceded by a concomitant flux of photons, the spectrum can be in situ calibrated using a set of collinear detectors to obtain a true “time-of-flight” measurement. This article presents the motivation and overview of this technique along with estimates of the experimental precision needed to make useful measurements in existing and future nToF systems such as the pulsed power Z-machine located in Albuquerque, NM, at Sandia National Laboratories.
Magnetosonic shock waves in degenerate electron–positron–ion plasma with separated spin densities
Authors: Ahmad Mansoor , Adnan Muhammad , Qamar Anisa
Published: August 2024

This study investigates magnetosonic shock waves in a spin-polarized three-component quantum plasma using the quantum magnetic hydrodynamic model. We explore the influence of spin effects, specifically spin magnetization current and spin pressure, on shock wave behavior. Numerical analysis of the linear dispersion relation under varying parameters such as positron imbalance, spin polarization ratio, plasma beta, quantum diffraction, and magnetic diffusivity reveals differential impacts, with diffusion exerting significant influence on the plasma frequency. Our findings highlight the sensitivity discrepancy between the real and imaginary parts of the dispersion relation. Furthermore, nonlinear behavior of magnetosonic shock waves is examined via the Korteweg–de Vries–Burgers equation, showcasing transitions between oscillatory and monotonic wave patterns based on changes in dimensionless parameters. Notably, we observe the combined effects of spin-up and spin-down positrons with spin-up and spin-down electrons on shock wave dynamics, contributing to a deeper understanding of spin-plasma interactions with implications across various fields.
Double glass transition in polyethylene naphthalate by MDSC, BDS, and TSDC
Authors: Cañadas Juan Carlos , Diego José Antonio , Diez-Berart Sergio , López David Orencio , Mudarra Miguel , Salud Josep , Sellarès Jordi
Published: August 2024

In this work, we present an experimental study of the primary and secondary relaxations of the semi-crystalline polymer polyethylene naphthalate by modulated differential scanning calorimetry, Thermally Stimulated Depolarization Currents (TSDCs), and Broadband Dielectric Spectroscopy (BDS) and how they are affected by physical aging. Three dipolar relaxation modes can be observed: from slowest to fastest: the primary α relaxation, which vitrifies at the glass transition temperature, Tgα, and two secondary relaxations, named β* and β. Modulated differential scanning calorimetry results show how the secondary β* relaxation also vitrifies, giving rise to an additional glass transition at Tgβ* < Tgα. In fact, the α and β* relaxations can be considered as part of a very broad and distributed relaxation. Its main part is the primary α relaxation with a shoulder at the high-frequency region corresponding to a complex secondary β* relaxation. BDS results about β* can be modeled by a main contribution (β3*) and two additional ones (β1* and β2*) with a weaker dielectric strength. TSDC results show that each single mode of the relaxation has its own glass transition temperature and they are compatible with the structure inferred by BDS. This scenario gives rise to an extended glass transition dually centered in the Tgβ* ∼ 305 K and Tgα ∼ 387 K temperatures.
Progress in electron energy modeling for plasma flows and discharges
Authors: Parent Bernard , Rodriguez Fuentes Felipe Martin
Published: August 2024

A novel formulation of the electron energy relaxation terms is presented here, which is applicable to plasma flows and discharges wherein the electron temperature could be higher or lower than the gas temperature. It is demonstrated that the electron energy losses due to inelastic collisions can be expressed as a function of only two species-dependent parameters: the reduced electric field and the reduced electron mobility. This formulation is advantageous over previous ones, being simpler to implement and more accurate when experimental data of the reduced electric field and reduced mobility are available. Curve fits to empirical data of these two properties are outlined here for all important air molecular species. The approach accounts for all inelastic electron energy relaxation processes without needing individual cross sections or rates, reducing potential errors associated with independently handling each process. Several test cases are presented to validate the proposed electron energy source terms including reentry plasma flows for which the electron temperature is less than the gas temperature, as well as discharges in which the electron temperature reaches values in excess of 30 eV. In all cases, the agreement with experimental data is observed to be very good to excellent, significantly surpassing prior electron energy models for plasma flows.
Study on the internal waves induced by a submerged body moving in a continuously stratified fluid
Authors: Chen Xuebin , Du Hui , Xu Jiexin , Cai Shuqun
Published: August 2024

This paper studies the characteristics of internal waves induced by the motion of a submerged body through a combination of experimental and numerical methods. First, by deploying an array of conductivity probes in an experiment, the temporal evolution of the internal wave at the plane of the conductivity probe array is obtained and compared with numerical simulation results based on the Navier–Stokes equations, thereby validating the accuracy of the Computational Fluid Dynamics (CFD) model. Subsequently, utilizing CFD calculations, further exploration is conducted on the spatiotemporal distribution characteristics of the internal wave, encompassing its generation and evolution, velocity field distribution, wake angle, and wave profile features. Finally, the variation of the internal wave with the Froude number (Fr) is investigated, revealing that it varies apparently with Fr, including the wave component, wave mode, wake length, wake angle, wave amplitude, and so on. It is found that when Fr is large, the internal wave converges toward the centerline behind the body, until forming a line. The wave magnitude changes with Fr in four stages, i.e., increasing with Fr from zero in the first stage, reaching a peak and decreasing thereafter in the second stage, then changing little in the third stage, and finally increasing approximately linearly in the fourth stage.
Four-dimensional hemodynamic prediction of abdominal aortic aneurysms following endovascular aneurysm repair combining physics-informed PointNet and quadratic residual networks
Authors: Kang Jiaheng , Li Gaoyang , Che Yue , Cao Xiran , Wan Mingyu , Zhu Jing , Luo Mingyao , Zhang Xuelan
Published: August 2024

Hemodynamic parameters can provide surveillance for the risk of complication of abdominal aortic aneurysms following endovascular aneurysm repair (EVAR). However, obtaining hemodynamic parameters through computational fluid dynamics (CFD) has disadvantages of complex operation and high computational costs. Recently proposed physics-informed neural networks offer novel solutions to solve these issues by leveraging fundamental physical conservation principles of fluid dynamics. Based on cardiovascular point datasets, we further propose an integration algorithm combining physics-informed PointNet and quadratic residual networks (PIPN-QN) that is capable of mapping sparse point clouds to four-dimensional hemodynamic parameters. The implemented workflow includes generating point cloud datasets through CFD simulation and dynamically reproducing the three-dimensional flow field in the spatial and temporal dimensions through deep learning. Compared with physics-informed PointNet (PIPN), the PIPN-QN reduces the mean square error of pressure and wall shear stress by around 32.1% and 33.1% and anticipates hemodynamic parameters in less than 2 s (14 400 times faster than CFD). To address the challenge of big data requirements, we quantify the universal flow field using a reduced number of supervision points, as opposed to the large number of point clouds generated from the CFD simulation. The PIPN-QN can meet the real-time hemodynamic parameters obtained from patients with abdominal aortic aneurysms following EVAR with higher accuracy, faster speed, and lower training costs.
The effect of swirling injector geometry on the flow dynamics of precessing vortex core
Authors: Zhu Jinxiang , Yang Yao , Fang Yuanqi , Wang Gaofeng , Zheng Yao
Published: August 2024

Precessing vortex core (PVC), a typical vortex structure, universally exists in swirling flow fields and originates from the Kelvin–Helmholtz instability of the swirling shear layer. In the combustion chamber, pressure pulsations from PVC might resonantly couple with acoustic modes, leading to thermoacoustic oscillations which is a significant challenge in the development of rocket engines and gas turbines. The present work focuses on the time-averaged and unsteady flow characteristics of different swirling flow fields in the premixed swirling combustor. The PVC observed in the swirlers adopted presents a single helical structure and the PVC frequency is proportional to the incoming flow velocity. Moreover, another low-frequency helical mode located in the downstream region of the flow fields has been identified and categorized as PVC type II to be distinguished with common PVC mode in this study, which originates from the precession of the central recirculation zone. The experimental results further emphasize the effects of the swirling injector geometry on PVC and the low-frequency helical modes. This indicates that as the diameter of the bluff body or the divergence cup angle increases, the energy of the PVC mode decreases while that of the helical mode increases significantly. In addition, the PVC mode would be gradually suppressed as the tail size of the bluff body increases. These results, especially the coexistence of the PVC mode and the low-frequency helical mode, are rarely reported in previous studies, and they may provide an effective guidance for investigating the mechanism and control of thermoacoustic oscillations.
Study on the water transport characteristics during spontaneous imbibition and its impact on gas desorption
Authors: Zhou Aitao , Sun Yongxin , Wang Kai , Wang Zhaofeng , Ma Shujun , Wang Yida , Liang Yuehui
Published: August 2024

During the exploitation of deep coal resources, the gas hazard becomes increasingly significant, severely threatening the high-quality development of the coal industry and the occupational safety and health of miners. Coal seam water injection is underground coal mines' most commonly used dust control measure. Additionally, it is an effective method for preventing localized coal and gas outburst hazards. After injecting water into the coal seam, spontaneous imbibition causes the retained water in the fractures to migrate under capillary action and widely distribute the water within the coal seam, which enhances the wetting degree of the coal by water and the effectiveness of gas prevention. To reveal the migration characteristics of water in the coal during spontaneous imbibition and its impact on gas control, a self-developed gas-bearing coal spontaneous imbibition system was used to conduct isobaric water injection imbibition and gas desorption experiments on gas-bearing coal samples. The results showed that after the water was injected into the coal sample, it migrated from bottom to top under capillary action, resulting in three stages of abrupt, rapid, and gradual changes in the electrical resistivity of different layers of the coal sample over time. The migration distance of water increased with the imbibition time, but the rate of increase gradually decreased. The compaction load increase reduced the coal sample's average pore size, resulting in faster water migration speed. After imbibition, the water content decreased gradually from bottom to top along the axial direction and showed a non-uniform distribution in the radial direction. During imbibition, the water displaced gas within the coal sample, and the amount of gas displaced increased with the imbibition time. Increasing the amount of water injected and the coal sample compacted load can promote water migration within the coal, expanding the wetted area and displacing more gas. After imbibition, due to the displaced gas being released and the water-lock effect, the atmospheric gas desorption amount of the coal sample decreased with an increase in the amount of water injected, following a modified power function relationship. When the amount of water injected into the coal sample was low, increasing the water-injected amount could significantly reduce the gas desorption expansion energy of the coal sample. However, this trend became less apparent as the amount of water injected continued to increase. To improve the effectiveness of coal seam water injection in preventing gas outburst hazards, it is recommended to carry out water injection operations as early as possible to expand the wetted area of the coal seam and to add gas drainage holes to prevent increased coal body outburst tendencies due to local gas pressure rise in the coal seam.
Improved defect-correction algorithms for the Navier–Stokes equations at small viscosity
Authors: Zhang Qi , Huang Pengzhan
Published: August 2024

In this article, based on finite element discretization, we propose some improved defect-correction algorithms for solving the stationary Navier–Stokes equations with small viscosity. The proposed algorithms are mainly inspired by the idea of the grad-div stabilized method and error correction technique. Maintaining the benefit of the usual defect-correction method, the proposed algorithms further improve the ability to solve problems with small viscosity and have a fast convergence rate. Moreover, stability analysis and error estimation of these algorithms are provided under the uniqueness requirement. Finally, some numerical experiments are tested to illustrate the effectiveness of the presented algorithms for small viscosity problem.
Muzzle bubble dynamics characterization of underwater launching
Authors: Sun Zhiqun , Li Qiang , Zhang Xuewei , Qu Pu , Lu Lin
Published: August 2024

To comprehensively understand the dynamic behavior of muzzle bubbles during underwater launching, an emptying process aligned with the muzzle flow characteristics is established and an evaporative condensation mechanism is modeled according to the high temperature and pressure properties of the propellant gas. Utilizing the spherical bubble theory, which comprises the inflation process and evaporative condensation effects, the dynamics of muzzle bubbles and their corresponding pressure waves are investigated. The numerical simulation results well agree with the experimental observations in terms of bubble radius and near-field pressure waves. Furthermore, the influence of two key factors on the bubble dynamics is examined: underwater launching depth and initial muzzle pressures. The results illustrate that the inflation process needs to be accurately described for precise pressure wave predictions. Using the evaporation condensation model, the bubble radius and frequency can be accurately characterized. Moreover, the launching depth influences the free expansion radius and oscillation frequency mostly due to the increase in hydrostatic pressure, which decreases by 33% and increases by 150% in the 1–20 m range, respectively. The initial muzzle pressure affects the initial expansion velocity and initial shock wave mainly due to the increase in the mass flow rate, which increase by 56% and 82% in the 35–65 MPa range, respectively.
High piezoelectric coefficient and thermal stability of BKT-BFPT ceramics with ex situ high depoling temperature at 520 °C
Authors: Zhou Yu , Wen Fei , Mo Xiping , Li Lili , Gao Xiaoyi , Chen Jianguo
Published: August 2024

The in situ and ex situ temperature dependence of dielectric and piezoelectric properties of 0.1(Bi0.5K0.5)TiO3-0.6BiFeO3-0.3PbTiO3 (BKT-BFPT) ceramics were characterized, and related mechanisms were studied. The tetragonal distortion, Curie temperature Tc, depoling temperature Td, and piezoelectric coefficient d33 of BKT-BFPT are 0.06, 545 °C, 520 °C, and 205 pC/N, respectively. The in situ piezoelectric coefficient variation of BKT-BFPT ceramics from room temperature to 280 °C is only 10%, being 1/5 and 1/10 those of 0.36BiScO3-0.34PbTiO3 and Pb(Zr0.52Ti0.48)O3 ceramics. The better dielectric and piezoelectric thermal stabilities are owing to the temperature insensitive domain texture of BFPT-BKT ceramics due to their large lattice distortion. Resistivity results reflected that the higher depoling temperature derived from the ex situ measurement than that from the in situ test results from the high-temperature conductivity.