bluuebunny/crossref_metadata_2025 huggingface dataset:
Körperliche Aktivität während Corona bei
Beschäftigten im Homeoffice
Authors: Walle Oliver
Published: December 2021

Hintergrund Bewegungsmangel gehört zu den führenden
Risikofaktoren für gesundheitliche Probleme, weshalb allgemeine
Empfehlungen von mindestens 150 Minuten pro Woche moderater oder 75 Minuten
intensiver körperlicher Aktivität sprechen. Bereits vor der
Corona-Pandemie zeigte sich in nationalen und internationalen Untersuchungen ein
unzureichendes Bewegungsverhalten der Menschen; in den Untersuchungsgruppen traf
dies teilweise sogar auf über 50% der Proband*innen zu.
Infolge der Pandemie kam es aufgrund des Infektionsschutzes und der damit
einhergehenden Kontaktbeschränkungen zur verstärkten
Homeoffice-Tätigkeit. Dies führte zu einer veränderten
Arbeits- und Lebenssituation und demnach auch zu einem veränderten
Gesundheitsverhalten. In der vorliegenden Studie wurde daher den Fragen
nachgegangen, welche Auswirkungen die Homeoffice-Tätigkeit auf die
körperliche Aktivität der Beschäftigten hatte, welche
Faktoren dabei eine Rolle spielten und welche Erkenntnisse sich für die
Betriebliche Gesundheitsförderung (BGF) ableiten lassen.

Methodik Im Juni 2021 wurde eine Online-Befragung durchgeführt
unter Verwendung des GPAQ-Fragebogens (GPAQ=Global Physical Activity
Questionnaire) der World Health Organization (WHO) sowie ergänzender
Fragen zu Veränderungen des Bewegungs- und Sitzverhaltens und deren
Gründen, zu Aktivitätsbeispielen und Wünschen
für Maßnahmen. Die Auswertung erfolgte für den
GPAQ-Fragebogen auf Basis der WHO-Leitlinie und anschließender
deskriptiver Kennwerte und Häufigkeiten. Die weiteren Variablen wurden
primär mit Häufigkeitsverteilungen sowie Freitextantworten nach
der Methode der qualitativen Datenanalyse (QDA) ausgewertet.

Ergebnisse An der Befragung nahmen 193 Beschäftigte
unterschiedlicher Unternehmen und Branchen teil, davon konnten 183
gültige Datensätze für eine Aktivitätsauswertung
herangezogen werden. 25% wiesen ein geringes, 51% ein moderates
und 24% ein hohes Aktivitätsniveau auf, die durchschnittlichen
Sitzzeiten lagen bei 8,9 Stunden pro Tag. Es zeigte sich sowohl eine
Erhöhung des Aktivitätsverhaltens bei einigen während
der Pandemie als auch eine Verringerung bei anderen. Insgesamt war in Bezug auf
die Sitzzeiten eine deutliche Zunahme zu erkennen. Die qualitativen Daten zeigen
Gründe für die Veränderungen im Bewegungsverhalten auf,
zugleich werden Möglichkeiten zur Förderung der
körperlichen Aktivität genannt.

Schlussfolgerungen Die Studie liefert Erkenntnisse zu den Auswirkungen der
Homeoffice-Tätigkeit während der Corona-Pandemie. Zugleich
werden Potenziale für die BGF im Homeoffice deutlich.
PflegeAufwandBemessungsAssessment in der DIAlyse
Authors: Eikelmann Matthias , von Gliszczynski Anika
Published: December 2021

Wie bereits in einem Artikel 1 beschrieben, arbeitet der fnb e. V. an einem Assessmentinstrument für die Bemessung des Pflegeaufwandes von Patienten mit Nierenersatzverfahren. Grundlage dafür ist eine Unterteilung in behandlungsspezifischen und pflegerischen Aufwand der Patienten an der Dialyse.
Methodische Verfahren: Von der Frage zur Antwort
Authors: Mehrholz Jan , Kerlen-Petri Katharina
Published: December 2021

Kennen Sie das? Sie behandeln eine Schwangere und wissen nicht, warum Ihre Behandlung der Frau nicht hilft. Jan Mehrholz erläutert auf dieser Seite, wie Sie eine Antwort darauf finden können, und erörtert, welche Studien für welche Fragen geeignet sind.
Gesund im Mund – frühkindliche Karies verhindern
Authors: Wagner Yvonne
Published: December 2021

Die frühkindliche Karies ist eine besonders schwerwiegende Form der Karies, die unbehandelt innerhalb kürzester Zeit zur gesamten Zerstörung des Milchgebisses führen kann. In Deutschland sind bereits 13,7 % der Dreijährigen betroffen. Die Verabreichung zucker- und säurehaltiger Getränke mit der Saugerflasche in Zusammenhang mit der Vernachlässigung der Mundhygiene sind die Hauptrisikofaktoren für die Entstehung. Die Folgen reichen weit über die Mundgesundheit hinaus und beeinträchtigen die gesunde Entwicklung und Lebensqualität der Kinder. Kinderärzte betreuen die Familien bei den Vorsorgeuntersuchungen regelmäßig, können die Zahngesundheit der Kinder einschätzen und die Eltern im Rahmen der U5 bis U9 an den Zahnarzt verweisen. Die Chance besteht darin, die Familien zur Durchführung einer täglichen, sorgfältigen Mundhygiene und zuckerrestriktiven Ernährung zu motivieren.
Corona-Pandemie und Dialyse
Authors: von Gregory Ulrike
Published: December 2021

Seit Frühjahr 2020 hält das Corona-Virus SARS-CoV-2 die Welt in Atem und hat das Leben aller Menschen verändert. Seitenlange Infektionsschutzgesetze, Abstandsregeln und Kontaktbeschränkungen bestimmen das Leben der Menschen auch in Deutschland. Dieser Beitrag setzt sich mit der Frage auseinander, wie diese neuen Regeln und Verbote das Leben der Dialysepatienten beeinflussen. Haben diese über Jahre bis Jahrzehnte chronisch kranken Patienten unter diesen Herausforderungen zu leiden oder gibt es auch positive Aspekte und konnten sie daraus etwas gewinnen? Mittels einer Befragung von 93 Patienten, die im Februar 2021 stattfand, sollte herausgefunden werden, welche Veränderungen oder Einschränkungen die Patienten für sich wahrnehmen.
60 Jahre Deutsche Gesellschaft für Luft- und Raumfahrtmedizin (DGLRM e. V.)
Authors: Harsch Viktor , Pippig Torsten M.
Published: December 2021

Die Deutsche Gesellschaft für Luft- und Raumfahrtmedizin e. V. (DGLRM, zunächst DGLM) wurde am 1. Dezember 1961 in München gegründet. Ihren Vorsitz übernahm der Beschleunigungsphysiologe Professor Dr. med. Heinz von Diringshofen (1900–1967) 1.
Warum Weltraumtourismus?
Authors: Ullrich Oliver , Dové Natalie
Published: December 2021

Als Sir Richard Branson am 11. Juli 2021 mit der VSS Unity von Virgin Galactic und am 20. Juli 2021 Jeff Bezos mit der New Shepard von Blue Origin erfolgreiche suborbitale Raumflüge absolvierten, liefen die Kommentarspalten der Medien heiß. Es war von „Milliardärsspielzeug“ und „galaktischen Größenwahn“ die Rede. Tatsächlich löste die Inszenierung dieser ersten kommerziellen Suborbitalflüge Abwehrreflexe aus, denn sie erscheinen als nur „Superreichen“ zugängliche elitäre und nutzlose Ressourcenverschwendung. Wagt man aber einen weiteren Blick, sieht die Sache ganz anders aus.
25. Symposium des AKTX-Pflege e. V.
Authors: Marks Lara , Pohl Marei
Published: December 2021

Auch in diesem Jahr hat der Arbeitskreis Transplantationspflege (AKTX-Pflege e. V.) das jährliche 25. Symposium des AKTX-Pflege e. V. am 7. und 8. Oktober 2021 ausgerichtet. Wie bereits in den zurückliegenden Jahren, geschah dies in guter Kooperation zusammen mit der Deutschen Transplantationsgesellschaft (DTG), welche ihre Jahrestagung ebenfalls im Oktober veranstaltete.
Strategischer Patientenlufttransport im EATC – aktuelle und künftige Herausforderungen
Authors: Limpricht Eberhard
Published: December 2021

Die gesicherte Verfügbarkeit von militärischen Luftfahrzeugen zum weltweiten, qualifizierten Patientenlufttransport (Strategic Aeromedical Evacuation – StratAE) stellt auch zukünftig eine unverzichtbare Voraussetzung für den Einsatz von Streitkräften dar. Der Einsatz militärischer StratAE-Mittel ist darüber hinaus in manchen Fällen die einzige Möglichkeit, um auch erkrankte oder verletzte Zivilpatienten unter erschwerten Bedingungen aus aller Welt zur medizinischen Behandlung ins Heimatland zu holen.
Das Nicht-Pseudogen HLA‑J ist ein neuer prognostischer Marker für das Ansprechen auf Therapie und das Überleben bei Brustkrebs
Authors: Würfel Franziska M. , Wirtz Ralph M. , Winterhalter Christoph , Taffurelli Mario , Santini Donatella , Mandrioli Anna , Veltrup Elke , Rübner Matthias , Fasching Peter A. , Würfel Wolfgang , Zamagni Claudio
Published: December 2021

Humane Leukozyten-Antigene (HLA) sind Proteine auf der Zelloberfläche, die essenziell für die Immunzellinteraktion sind. HLA‑G ist für seine hohe immunosuppressive Wirkung sowie als potenzieller prädikativer Marker für Brustkrebs bekannt. Dagegen ist kaum etwas über HLA‑J und seine immunosuppressiven, prognostischen und prädiktiven Eigenschaften bekannt, da es basierend auf In-silico-Sequenzanalysen als „Pseudogen“ interpretiert wurde. Die Expression von HLA‑J, ESR1, ERBB2, KRT5 und KRT20 mRNA wurde in 29 frisch gefrorenen Brustkrebsbiopsien analysiert und mit den klinisch-pathologischen Daten von Patientinnen, welche mit neoadjuvanter Chemotherapie behandelt wurden, verglichen. Die mRNA-Expression wurde mit genspezifischen TaqMan-basierten Primer/Probe-Sets analysiert und auf Calmodulin 2 normalisiert. Alle Gewebeproben von Patientinnen mit Brustkrebs exprimierten HLA‑J, und der HLA‑J-mRNA-Spiegel war nach NACT oft erhöht. In den Brustkrebsstanzbiopsien war die HLA-J-mRNA-Expression signifikant mit der Überexpression von ESR1-mRNA (Spearmans ρ 0,5679; p = 0,0090) und KRT5-mRNA (Spearmans ρ 0,6121; p = 0,0041) assoziiert und dominierte im Luminal-B-Subtyp. Die Kaplan-Meier-Analyse zeigte, dass ein Anstieg der HLA-J-mRNA-Expression nach NACT mit einem schlechteren progressionsfreien Überleben einhergeht (p = 0,0096), womöglich als Gegenreaktion des Tumorgewebes, um eine Eliminierung durch tumorinfiltrierende Lymphozyten, welche durch eine NACT induziert wurden, zu verhindern. Diese Gegenreaktion ist mit einer schlechteren Prognose assoziiert. Soweit uns bekannt, handelt es sich hierbei um die erste Studie, die HLA-J als neuen prädiktiven Marker im Brustkrebs identifiziert hat und möglicherweise zur Immunevasion beiträgt.
The Efficiency of a Learning Software Compared to e-Books in Dental Education
Authors: Luhrenberg Philipp , Rahimi-Nedjat Roman Kia , Sagheb Kawe , Sagheb Keyvan , Al-Nawas Bilal
Published: December 2021

Objectives Due to time-consuming curricular and extracurricular activities, students in dentistry and medicine can profit from efficient learning strategies. One strategy could be the preparation with individually designed educational software that embed different multimedia sources. The aim of this study was to determine the efficiency of such a program compared with an e-book similar to a traditional textbook.

Materials and Methods Dentistry students of the Johannes Gutenberg-University of Mainz passed an entrance multiple-choice test on the topic of odontogenic tumors and were then randomized into two groups. Afterward, both groups had 14 days to study on the topic of odontogenic tumors either with a learning software or an e-book. A final exam was then taken and the two groups were compared.

Statistical Analysis A least significant difference post hoc analysis comparing the group average values was performed. The level of significance was p <0.05.

Results Seventy-one students took part in the study. While students from the first and second clinical semester showed significantly better results and improvements with the e-book, an opposite effect was observed in students from the third and fifth clinical semester with significantly better results and improvements with the software.

Conclusion Depending on the clinical experience and knowledge, a multimedia educational software can help students in dentistry to enhance efficiency in the preparation for exams.
Microendoscopic Decompression for Lumbar Spinal Stenosis Associated with Adjacent Segment Disease following Lumbar Fusion Surgery: 5-year Follow-up of a Retrospective Case Series
Authors: Murata Shizumasa , Minamide Akihito , Nakagawa Yukihiro , Iwasaki Hiroshi , Taneichi Hiroshi , Schoenfeld Andrew J. , Simpson Andrew K. , Yamada Hiroshi
Published: December 2021

Background and Study Aims Surgical treatment options for lumbar spinal stenosis (LSS) based on adjacent segment disease (ASD) after spinal fusion typically involve decompression, with or without fusion, of the adjacent segment. The clinical benefits of microendoscopic decompression for LSS based on ASD have not yet been fully elucidated. We aimed to investigate the clinical results of microendoscopic spinal decompression surgery for LSS based on ASD.

Patients and Methods From 2011 to 2014, consecutive patients who underwent microendoscopic spinal decompression without fusion for LSS based on ASD were enrolled. Data of 32 patients (17 men and 15 women, with a mean age of 70.5 years) were reviewed. Japanese Orthopaedic Association score and low back pain/leg pain visual analog scale score were utilized to measure neurologic and axial pain outcomes, respectively. Additionally, after the surgeries, we analyzed the magnetic resonance imaging (MRI), computed tomography (CT) scans, or radiographs to identify any new instabilities of the decompressed segments or progression of ASD adjacent to the decompressed segments.

Results The Japanese Orthopaedic Association recovery rate at the 5-year postoperative visit was 49.2%. The visual analog scale scores for low back pain and leg pain were significantly improved. The minimum clinically important difference for leg pain (decrease by ≥24 mm) and clinically important difference for low back pain (decrease by ≥38 mm) were achieved in 84% (27/32) and 72% (23/32) of cases, respectively. Regarding new instability after microendoscopic decompression, no cases had apparent spinal instability at the decompression segment and adjacent segment to the decompressed segment.

Conclusions Microendoscopic spinal decompression is an effective treatment alternative for patients with LSS caused by ASD. The ability to perform neural decompression while maintaining key stabilizing structures minimizes subsequent clinical instability. The substantial clinical and economic benefits of this approach may make it a favorable alternative to performing concurrent fusion in many patients.
Preoperative Thrombocytosis is Not Associated with Overall Survival in 309 Glioblastoma Patients
Authors: Marx Sascha , Altmann Robert , Baschin Marcel , Paland Heiko , Rauch Bernhard , Kohlmann Thomas , Schroeder Henry W. S.
Published: December 2021

Background In recent years, a correlation of thrombocytosis and a worse prognosis was shown for many solid cancers, including glioblastoma multiforme (GBM).

Methods A retrospective review was performed for all patients with a histologically proven and first-diagnosed GBM between 2005 and 2015 in our department. Clinical and paraclinical parameters were acquired from patient documentation and structured for subsequent data analysis. The association of potential risk factors with overall survival was assessed using the Kaplan–Meier survival analysis and Cox regression.

Results The present study includes 309 patients first diagnosed with primary GBM. Our analyses validate well-known risk factors of a decreased overall survival such as higher patient age, a larger preoperative tumor volume, Karnofsky performance status, extent of resection, tumor localization, and adjuvant treatment. However, no correlation was observed between a preoperative thrombocytosis, the mean platelet volume, leucocyte count, activated partial thromboplastin time (apTT), fibrinogen level, and acetylsalicylic acid 100 co-medication. Patients with preoperative hemoglobin below 7.5 mmol/L had decreased overall survival.

Conclusion The present study, enrolling the largest numbers of patients assessing this topic to date, did not find any association between a preoperative thrombocytosis and overall survival in 309 patients with GBM.
Techno-economic performances of future concentrating solar power plants in Australia
Authors: Boretti Alberto , Castelletto Stefania
Published: December 2021

The prediction of the techno-economic performances of future concentrated solar power (CSP) solar tower (ST) with thermal energy storage (TES) plants is challenging. Nevertheless, this information is fundamental to energy policymakers. This work aims to fill the knowledge gap regarding estimations of costs, amount, and quality of electricity produced by these plants over their lifetime. Every estimate should be based on real-world data of actual costs incurred to build and maintain constructed plants, and their actual electricity production, sampled with high frequency, to be reliable. Here we discuss as the available information is insufficient. There has been so far very limited transparency on the real cost and performance of CSP plants built and operated worldwide, and in the very few cases where data has been made public, for example, Crescent Dunes in the United States, costs have been much higher than expected, while annual average capacity factors have been much less. Important statistical parameters such as the standard deviation of the capacity factor with high-frequency sampling have never been provided. We conclude as the techno-economic performances of these plants are therefore unpredictable with accuracy until a significant number of plants will be built and operated, their costs and operating parameters will be shared, and their delivered techno-economic performances will be compared to the modeled values, finally permitting validation of the techno-economic analysis tools.
Study on the influence of different soil parameters on the modal response of gravity retaining wall slope
Authors: Chen Li , Zhang Yachao , Yang Zhongyong , Li Qian , Han Linfeng
Published: December 2021

In this paper, the vibration characteristics of gravity retaining wall slope are studied. Using the M language of MATLAB, the finite element calculation program is compiled to calculate the frequency and characteristic values of the structure, and the first three modes of the structure are drawn. By analyzing and calculating the different parameters of soil behind the wall, the influence of different elastic moduli of soil and Poisson’s ratio on the vibration characteristics of the slope is studied, and the conclusion is further verified by an elastic time history analysis. The results show that the change of soil elastic modulus has an obvious effect on the vibration characteristics of the structural system, while the change of Poisson’s ratio has no obvious effect on the vibration characteristics of the structural system.
Automatic lexical collocate extraction for corpus-based ontology building and refinement
Authors: Fernández-Martínez Nicolás José , Felices-Lago Ángel Miguel
Published: December 2021

Traditional corpus-based methods rely on manual inspection and extraction of lexical collocates in the study of selection preferences, which is a very costly, labor-intensive, and time-consuming task. Devising automatic methods for lexical collocate extraction becomes necessary to handle this task and the immensity of corpora available. With a view to leveraging the Sketch Engine platform and in-built corpora, we propose a working prototype of a Lexical Collocate Extractor (LeCoExt) command-line tool that mines lexical collocates from all types of verbs according to their syntactic constituents and Collocate Frequency Score (CFS). This might be the first tool that performs comprehensive corpus-based studies of the selection preferences of individual or groups of verbs exploiting the capabilities offered by Sketch Engine. This tool might facilitate the task of extracting rich lexico-semantic knowledge from diverse corpora in a few seconds and at a click away. We test its performance for ontology building and refinement departing from a previous detailed analysis of stealing verbs carried out by Fernández-Martínez & Faber (2020). We show how the proposed tool is used to extract conceptual-cognitive knowledge from the THEFT scenario and implement it into FunGramKB Core Ontology through the creation and modification of theft-related conceptual units.
Effects of task repetition with written corrective feedback on the knowledge and written accuracy of learners with different
prior knowledge of the structure
Authors: Khezrlou Sima
Published: December 2021

Previous task repetition studies have largely overlooked the second language learners’ development of linguistic knowledge
as well as written accuracy. Furthermore, sufficient attention has not been paid to the role of written corrective feedback (WCF) in task
repetition to reinforce attention to form. Moreover, studies exploring task repetition effects on learners with different prior knowledge of
the target structure are rare. This study attempted to bridge these lacunas. Seventy-nine upper-intermediate learners in Iran were divided
into four groups: task repetition with no feedback (TR), task repetition with metalinguistic feedback (TR+M), task repetition with direct
feedback (TR+D), and task repetition with mixed direct metalinguistic feedback (TR+DM). All groups performed an error correction test that
measured explicit knowledge, an elicited imitation test that tapped automatized explicit knowledge, and a picture-cued written production
test that measured written accuracy. Participants performed a dictogloss task and received WCF before repeating the same task. Subsequently,
they performed another dictogloss task with different content. Results revealed that the +Prior Knowledge learners in the TR+DM group gained
explicit knowledge and proved slightly better than the TR+D regarding written accuracy. None of the groups, however, could develop
automatized explicit knowledge.
The phase transition of polyamide 6 with pre-stretching process at different temperatures
Authors: Cai Ziqing , Ye Jinqiao , Zhang Yunfan , Nie Danli , Jianglin Ouyang
Published: December 2021

The temperature and strain fields are two key factors in the regulation of fibrous aggregate structure. In this paper, plate specimens of polyamide 6 were prepared by compression molding method. The oriented polyamide 6 plates were systematically analyzed from aspects of mechanical properties, thermal properties, crystal structure and crystal morphology. The maximum tensile strength and elastic modulus of polyamide 6 plate appeared at 120 °C. The stretching process induced the formation of a more thermal stable α-form crystals. With the increase of stretching temperature, α-form crystals transformed into γ-form crystals gradually. The crystal chips transformed into fibrils during the stretching process. The structural evolution model of materials under the temperature and strain fields was established.
FAST Continuum Mapping of the SNR VRO 42.05.01
Authors: Xiao Li , Zhu Ming , Sun Xiao-Hui , Jiang Peng , Sun Chun
Published: December 2021

The relativistic electrons rotate in the enhanced magnetic field of the supernova remnants and emit the synchrotron radio emission. We aim to use the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to obtain a sensitive continuum map of the supernova remnant VRO 42.05.01 (G166.0+4.3) at 1240 MHz. The 500 MHz bandwidth is divided into low and high-frequency bands centered at 1085 and 1383 MHz to investigate the spectral index variations within the remnant, together with the Effelsberg 2695 MHz data. We obtained an integrated flux density of 6.2 ± 0.4 Jy at 1240 MHz for VRO 42.05.01, consistent with previous results. The spectral index found from temperature-temperature plot (TT-plot) between 1240 and 2695 MHz agrees with previous values from 408 MHz up to 5 GHz. The three-band spectral index distribution shows a clear flatter value of α ∼ −0.33 in the shell region and steeper index of α = −0.36 to −0.54 in the wing region. The flatter spectral index in the shell region could be attributed to a second-order Fermi process in the turbulent medium in the vicinity of the shock and/or a higher compression ratio of shock and a high post-shock density than that in elsewhere.
Effect of coherent structures on convective heat transfer in a swirling impinging jet
Authors: Lobasov A S
Published: December 2021

The present paper reports on the detailed investigation of the flow dynamics and unsteady heat transfer in an impinging jet in regimes with high swirl and vortex breakdown. A combination of the time-resolved stereoscopic PIV, time-resolved PLIF and high-speed IR-thermometry methods is used. Two cases of distances between the jet nozzle and impingement surface are considered, H = d and H = 2d. The Reynolds number is fixed as Re = 5000. The temperature distribution in the flow has a maximum on the jet axis near the surface in the region of the central recirculation zone. The data are processed using the POD method to extract coherent flow structures and quantify temperature fluctuations on the impact surface. The helical vortex structure in the case of H = d influences heat transfer between the swirling jet and the surface, the temperature fluctuations on the surface reach 0.05 degrees.
Adjoint shape optimization of a duct for a wall jet film cooling setup
Authors: Kozyulin N N , Bobrov M S , Hrebtov M Y
Published: December 2021

The paper presents the results of optimization of the geometric parameters of the simplified wall jet cooling system using a modified Adjoint Shape optimization method for algebraic systems of equations (Discrete Adjoint Optimization). The modification consists in using a linearized discrete system of equations with the replacement of derivatives by their finite-volume approximations. The jet flowed through a duct and out from a nozzle. The duct was inclined at an angle of 35 degrees to the cooled wall. The mean velocity ratio between the jet and the main flow was set to 2. The total heat flux on the cooled wall was taken as a cost function. The problem was considered in a two-dimensional stationary turbulent formulation (RANS). As a result of optimization, the shape of the duct changed significantly, affecting the flow inside it. The optimization led to the disappearance of the recirculation zone and reattaching of the jet to the cooled wall. As a result of the optimization performed, the heat flux at the wall increased by 20%.
Experimental study of heat transfer of impinging swirling jets and jets with chevrons
Authors: Nebuchinov A S
Published: December 2021

The aim of this work is to study the effect of different forms of passive change in the shape of the flow on the intensity of heat transfer in the impact jet. In this work, a cycle of experiments was performed to investigate an axisymmetric jet flowing normally onto a heated surface. The jet was located both in natural conditions and during swirling of the flow (S = 0.4; 0.7; 1.0). It is shown that the intensity of heat transfer on a heated target in the case of a chevrons jet has little effect on the character, but significantly intensifies heat transfer. In the case of a swirling jet, the intensity distribution on the wall changes its character and locally increases at small distances between the nozzle and the heater.
Experimental study of the heat transfer of two parallel impinging jets
Authors: Philippov M V , Chokhar I A , Terekhov V V , Terekhov V I
Published: December 2021

Local and integral characteristics of heat transfer are obtained at varying the Reynolds number Re = 5500, 11000, the distance between the jets y/D = 1.8, and the distance from the jets to the surface z/D = 0.5-10 for the system of two identical impinging jets. It is found in experiments that the effect of an adjacent jet leads to enhancement of local heat transfer at large distances between the nozzles and the barrier. It is also shown that an increase in the Re number increases integral heat transfer, and, at the same time, weakens the inter-jet interaction. The paper analyzes the scenarios of the behavior of local and integral heat transfer depending on the geometric and flow parameters of the system of two circular turbulent jets.
A study and comparison of the modes of diffusion combustion of hydrogen and methane at their outflow from the annular nozzle together with the flow of supplied air from the coaxially located circular nozzle
Authors: Tambovtsev A S , Kozlov V V , Litvinenko M V , Litvinenko Yu A , Shmakov A G
Published: December 2021

The article presents qualitative data on the study of the process of diffusion combustion during the outflow of a gas jet from a nozzle apparatus with a certain arrangement of nozzles. The nozzle apparatus is a round nozzle with a straight channel and a coaxially located annular slot. In the experiments, hydrogen or methane was supplied through an annular slot, and the air was supplied through a central circular micro nozzle. The main features of the diffusion combustion of hydrogen and methane during the outflow from the nozzle apparatus are revealed and a qualitative comparison of the processes is carried out. In both cases, at the initial stage, laminar combustion is observed near the nozzle exit and a breakthrough of the flame front occurs with the release of an incombustible mixture of combustible gas and air. At a high flow rate, the flame separates from the nozzle exit. The fundamental difference is that hydrogen exhibits significantly better combustion stabilization characteristics at the nozzle exit.
Simulation of thermal processes of shaft plasma furnace for waste gasification
Authors: Anshakov A S , Faleev V.A. , Domarov P V
Published: December 2021

Mathematical modeling of a part of a mine plasma electric furnace for waste gasification is presented. In model calculations, the study of the effect of additional resistive heating as an in-furnace process of drying waste was carried out. In the course of modeling, the electrical resistance of the waste at natural moisture was taken into account. A study was carried out to identify the uniform release of energy inside the waste batch in the drying zone with different connections of the electrodes and the type of current.
Combustion of kerosene sprayed with a jet of superheated steam
Authors: Kopyev E P , Anufriev I S , Mukhina M A , Sadkin I S
Published: December 2021

In the present work, the effect of forced air supply on the combustion process of liquid hydrocarbons was studied using diesel fuel as an example. The content of the flame intermediate components and temperature distribution along the flame symmetry axis were studied using an atmospheric burner in which liquid fuel is atomized by a steam jet. The gas composition of equilibrium combustion products and heat release were also investigated. The influence of the excess air ratio in the combustion chamber of the burner device on the thermal and environmental characteristics was shown.
Investigation of the characteristics of an electric arc plasmatron with variable geometry electrodes
Authors: Faleev V.A. , Bikeev R.A. , Domarov P.V.
Published: December 2021

The study of the electric arc plasmatron was carried out. The energy characteristics of the plasmatron, thermal efficiency and current-voltage characteristics were experimentally investigated. The comparison of the energy characteristics with the plasmatron having no changing geometry of the electrodes was carried out.
Calculation of evaporation length of a liquid bridge flowing between inclined hot tubes
Authors: Geshev P I
Published: December 2021

The bridge consists of liquid held by surface tension forces between two inclined tubes in an LNG heat exchanger. The shape of the bridge is calculated by the hydrostatic equation, which is reduced to a nonlinear integral equation and resolved by the Newton method. The velocity and temperature fields in the bridge are described by the Navier-Stokes and energy equations, respectively. They are reduced to the boundary integral equations and calculated by the method of boundary elements. Heat transfer coefficient is calculated for evaporating bridge and the length of total bridge evaporation is estimated.
Experimental study of the effect of various surfactants on the wave characteristics of the film flow
Authors: Guzanov V V , Bobylev A V , Kvon A Z
Published: December 2021

In this paper we present the results of experimental investigation of the effect of ionic surfactants (sodium dodecyl sulfate and cetrimonium bromide) at various concentrations on the vertical film flow in the range of Reynolds numbers 10 < Re < 50. The laser-induced fluorescence technique was used for instant film thickness measurements. The results are compared with data obtained for non-ionic Triton X-100. For all surfactants the rivulets formation and the dumping of wave motion are observed. The difference in the action of ionic and non-ionic surfactants on wave motion is revealed. Such deviations indicate that for ionic surfactants the surface tension relaxation process (at least in the case of film flows) is not fully described by diffusion processes, but has a more complex nature.
Automatically hemodynamic analysis of AAA from CT images based on deep learning and CFD approaches
Authors: Fedotova Y V , Epifanov R UI , Karpenko A A , Mullyadzhanov R I
Published: December 2021

Abdominal aortic aneurysm is a serious disease which course is accompanied by the development of health complications and often leads to patient death due to aortic rupture. One of the powerful methods to estimate the risk of rupture is three-dimensional patient-specific hemodynamic analysis. In this study, we develop a software tool based on deep learning and CFD methods to perform automated computational hemodynamics with patient-specific geometry reconstructed from computed tomography images.
Heat transfer enhancement at evaporation and boiling of liquid on capillary-porous surfaces created by 3D printing
Authors: Volodin O A , Pecherkin N I , Pavlenko A N
Published: December 2021

The paper presents the results of experiments on measuring heat transfer in laminar-wave films of R114/R21 refrigerant mixture flowing down a vertical plate (70 × 80 mm). The experiments were carried out on the saturation line at a pressure of 2 bar. To enhance heat transfer, a porous copper coating with a flat layer thickness of 400 μm and a porosity of 45% was applied to the heat-transfer surface by 3D printing. The effectiveness of the application of the technique used for the heat transfer enhancement is demonstrated: an increase in the boiling heat transfer coefficient is obtained up to three times in comparison with the reference smooth surface, as well as two-fold increase in heat transfer coefficient in the evaporation regime. Based on the obtained experimental results and analysis of the research data of other authors, the geometric structure of promising multiscale porous enhancing coating is proposed for further research.
Parameters of temperature disturbance triggering the propagation of the quench front on an extremely overheated surface
Authors: Starodubtseva I P , Pavlenko A N
Published: December 2021

The results of computational experiments simulating the triggering of the quench front propagation on the superheated vertically oriented metal plates are presented. The plates are quenched by a gravitationally flowing down liquid nitrogen film. The temperature of the test samples at the beginning of the process was higher than the critical temperature and the Leidenfrost temperature, which means that direct long-term liquid-solid contact is impossible. For this reason, the front is initially motionless. As a result of numerical simulation, a dynamic pattern of the quench front propagation on a high-temperature surface was obtained. Analysis of the results allowed to find the realistic values of heat sink into the cooling medium, as well as the parameters of the local temperature disturbance, its spatial extent and amplitude, at which the conditions are created for triggering the process of quench front propagation on the high-temperature surface. Direct comparison of the numerical simulations results with experimental data on the velocity, geometry of the quench front and on the dynamical pattern of the process confirmed the reliability of the results obtained.
Effect of the distance between the micro/nanostructures on pool boiling heat transfer with water on a copper heater
Authors: Vladimirov V Yu , Khmel S Ya
Published: December 2021

Copper heaters were made. On the surface of these heaters the arrays of micrococoons were synthesized from silicon oxide (SiOx) nanowires with different concentrations of micro/nanostructures and hence different average distances between them. Boiling curves were obtained for these samples and it was found that heat transfer enhancement during boiling occurs on them in comparison with a smooth copper surface. It was shown that the effect increases with decreasing concentration of micro/nanostructures and reaches a maximum for microrelief with an approximate concentration of microstructures equal to unity per square micron. It was found that surfaces with micrococoons are sufficiently stable and suitable for enhancing heat transfer during boiling.
Experimental study of heat transfer during boiling in a thin layer of liquid on surfaces with structured porous coatings
Authors: Shvetsov D A , Pavlenko A N , Brester A E , Zhukov V I
Published: December 2021

The paper presents the results of the study of evaporation and boiling in a thin horizontal layer of liquid on microstructured surfaces in a wide range of changes in pressure. It is found that the thermal conductivity of materials of microstructured surfaces significantly affects the mechanism of steam removal from the pores and circulation of liquid along the heat transfer surface. It is determined that the pressure change leads to three regimes of heat transfer: evaporation, transition regime, and bubble boiling. The lowest values of the heat transfer coefficients and CHF were obtained in the transition regime; the highest ones were obtained in the bubble regime on both surfaces. Due to the higher thermal conductivity, the higher heat transfer coefficients and CHF were obtained on the bronze coating than on stainless steel over the entire pressure range.
Effect of fluoropolymer spots on pool boiling heat transfer
Authors: Vladimirov V Yu , Khmel S Ya , Safonov A I , Semionov V V , Chinnov E A
Published: December 2021

In this paper, the investigation of pool boiling heat transfer on biphilic micro/nanostructured surfaces is presented. An array of micrococoons from silicon oxide nanowires was synthesized on the surface of a copper heater using the gas-jet electron beam plasma chemical vapor deposition method. The biphilic properties of the surface were achieved by applying fluoropolymer spots by hot wire chemical vapor deposition. Technology of creating biphilic surfaces was developed and boiling curves were obtained for used samples. The advantages of using a biphilic surface to enhance heat transfer were demonstrated in comparison with a smooth surface and a micro-nanostructured surface without local hydrophobic fluoropolymer regions. This technology can be applied to enhance boiling heat transfer.
Hollow cathode gun for electron beam annealing
Authors: Konstantinov V O , Shchukin V G
Published: December 2021

An electron gun with a hollow cathode was tuned to be used in electron beam annealing. Electron beams with an energy of 1 keV and a current of 100 mA were obtained. It is shown that the diameter of the electron beam varies in the range from 7 to 5 mm, while the specific power is from 2·105 to 2·104 W/m2. Such electron beams have a soft, non-destructive effect on the surface and are suitable for electron beam annealing of various films.
Improving the efficiency of carousel wind turbine using aerodynamic shield
Authors: Serov A F , Mamonov V N , Nazarov A D , Miskiv N B
Published: December 2021

The problem of increasing the efficiency of using the oncoming air flow for a wind wheel with a vertical axis of rotation, which is a mechanical drive of the wind heat generator, is considered. It is proposed to increase the efficiency of the device by installing an aerodynamic shield for the air flow oncoming the wind wheel. Such a shield is a cylindrical body in which a heat generator is placed. The shield creates an effect of confuser, leading to an increase in the speed and, consequently, in the kinetic energy of the air flow acting on the rotor blades. It is shown experimentally that the presence of an aerodynamic shield under the conditions of the experiments carried out at an incoming air flow velocity of ~ 1 m/s leads to a practical doubling of the wind wheel torque.
Study of dispersed composition of spray during atomization of water-fuel emulsion with a superheated steam jet
Authors: Shadrin E Yu , Kopyev E P
Published: December 2021

Using the method of direct shadow photography the dispersed composition of fuel spray was studied when water-fuel emulsion is sprayed with the superheater steam jet. For emulsions with a mass water content of 5 and 10%, the characteristic droplet size in the flow is 1–2 μm and sufficient for effective combustion.
The unsteady swirling jet in a model of radial burner
Authors: Litvinov I V , Gorelikov E U , Shtork S I
Published: December 2021

The experimental study of an isothermal swirl flow with the formation of a precessing vortex core in the radial swirler upon non-confinement and confinement conditions is carried out. Velocity profiles are obtained with varying Re and guide vane angle, changing the swirl number S. Four acoustic sensors and LDA system are used to measure Strouhal number as the function of the integral swirl number in the range from 0.5 <S <0.8. It is shown that the unsteady flow with PVC effect significantly changes upon non-confinement and confinement conditions.
Numerical simulation of pulsed planar evaporation into background gas based on direct Monte Carlo simulation and solution of the BGK model kinetic equation
Authors: Morozov A A , Titarev V A
Published: December 2021

A numerical study of the planar gas expansion under pulsed evaporation into the background gas is carried out. The chosen conditions are typical for nanosecond laser deposition of thin films and nanostructure synthesis, with the saturated gas pressure at the surface of 5.4 MPa and the background pressure of 50 and 500 Pa. The problem is solved based on the direct simulation Monte Carlo method and direct numerical solution of the BGK model kinetic equation. A generally good agreement was obtained for all computed macroscopic quantities, with the exception of the higher density peak in the compressed layer and a wider shock front in the background gas for the BGK model.
Molecular diffusion in gases and liquids
Authors: Kharlamov G V
Published: December 2021

The diffusion coefficients in gases and liquids calculated by the molecular dynamics method with the use of the hard absolutely rough elastic spheres model are compared with those calculated using the Lennard-Jones potential. It is shown that dependences of reduced diffusion coefficients on density are similar, but differ numerically for different intermolecular interaction models. The simulation results have been compared with the experimental data on the diffusion in gaseous and liquid argon and in liquid benzene.
Numerical investigation of energy transfer efficiency from microwave radiation to plasma in a cylindrical resonant cavity
Authors: Hrebtov M Y , Bobrov M S
Published: December 2021

The paper presents a simplified numerical model of the hydrogen plasma generation process in a microwave resonant cavity. The model assumes electroneutrality and the prescribed electron temperature of the plasma, thus significantly reducing the computational cost. This allows for the parametric study in a wide range of operating pressures end electric field magnitudes (at a frequency of 2.45GHz). The prescribed model allows finding the effective range of operating pressures for the plasma generation. At low pressures, the collision rate is too low to effectively absorb all the emitted energy while at high pressures the electron conductivity drops which also reduces the absorption efficiency.
Experimental Achievements in Mini- and Micro- Channel Cooling
Authors: Pukhovoy M. V. , Bykovskaya E. F. , Kabov O. A.
Published: December 2021

There are a significant number of cooling techniques for micro- and mini-sized devices. One of them is mini-channel cooling. In this review, a large amount of experimental work on mini-channel cooling by various liquids is conceptually considered, in which the threshold in the removal of specific heat flux of >1 MW/m2 has been reached. A comparison of mini-channel cooling with other cooling techniques is performed. It was established that 1) micro-channel cooling has practically no thermophysical advantages over macro- or mini-channel one; 2) single-phase cooling in mini-channels gives comparable results compared to two-phase cooling; 3) only a small set of conceptual techniques allows the mini-channel heat exchanger to overcome the limit of 10 MW/m2 or to reach the heat transfer coefficient larger than 0.2 MW/(m2*K).
Heat capacity of Inconel 617 alloy
Authors: Samoshkin D A , Agazhanov A Sh , Stankus S V
Published: December 2021

In the present article, the heat capacity of Inconel 617, one of the most promising superalloys, was investigated. The measurements were carried out in the temperature range from 300 to 1270 K of the solid state. The method of differential scanning calorimetry was applied using DSC 404 F1 Pegasus calorimeter. The estimated error of the received data was 2-4% depending on the temperature. The fitting equations for the temperature dependences of the heat capacity and the reference table of recommended values have been received for use in various engineering and scientific tasks.
Non-contact heat transfer models identification for laser hyperthermia of semi-transparent materials
Authors: Semenov D S , Nenarokomov A V
Published: December 2021

The identification of mathematical models of heat transfer traditionally involves the installation of temperature sensors inside the sample under study and registration of the response to external thermal effects. In cases where the use of contact methods for measuring temperature is impossible, it is necessary to develop new approaches to determining the unknown thermophysical and radiation-optical characteristics. Laser hyperthermia of superficial tissues is one such case. The paper proposes a method for identifying a model of one-dimensional unsteady heating of a semitransparent sample using non-contact thermometry. A feature of the physical process under consideration is the possibility of its discretization. Due to this, a two-stage iterative procedure for solving the inverse heat transfer problem was formulated. The implementation of the proposed algorithm using software made it possible to carry out a computational experiment. The results showed the effectiveness of this approach. The presented method can be used in the development of means for monitoring and regulating the laser hyperthermia procedure.
Development of unsteady boundary layers on the generatrices of a vertical silicon rod heated by electric current in the mode of conjugate radiation-convective heat transfer
Authors: Mitina A. V. , Berdnikov V. S. , Mitin K. A.
Published: December 2021

The nonstationary conjugate radiation-convective heat transfer of a single silicon rod heated by an electric current with the surrounding gas medium is studied numerically in the axisymmetric formulation by the finite element method. The calculations were carried out at the Prandtl number Pr = 0.68, and the range of the Grashof number, determined by the temperature difference and the radius of the rod 9 703 ≤ Gr ≤ 261 977. It is shown that after a short incubation period, a circulation flow is formed. As a result, a significantly inhomogeneous temperature field in the longitudinal direction is formed in a silicon rod heated by an electric current. As the Grashof number increases, the inhomogeneity of the longitudinal distribution of the temperature field increases.
Laminar-turbulent transitions during thermal gravitational-capillary convection in horizontal liquid layers heated from below
Authors: Berdnikov V S , Grishkov V A , Mikhailov A V , Ryabov V O
Published: December 2021

The evolution of the spatial form of the flow versus the Rayleigh number in layers with two rigid horizontal boundaries and layers with a free surface is experimentally investigated depending on the Rayleigh and Marangoni numbers. The experiments were carried out with layers of ethyl alcohol and water. A thermal imager was used to measure temperature fields on free surfaces of liquids.