bluuebunny/crossref_metadata_2025 huggingface dataset:
Social media participatory development communication during COVID-19 by Elected Women Representatives (EWR) of Panchayati Raj Institutions (PRI) in India
Authors: Darshan B.M. , Kalyani Suresh
Published: December 2021

Technological advancement has mandated many elected representatives to use social media for socio-political participation, participatory development, and currently to create awareness about COVID-19. Examining the social media usage experiences of elected women Panchayati Raj representatives during the COVID-19 pandemic reveals insights into their efforts towards creating awareness on COVID-19, ease of communication during the pandemic, increased involvement in developmental issues, and the challenges faced by them. The qualitative data that emerged from the in-depth interview are analyzed using Braun and Clarke’s (2006) thematic analysis method. The participants experienced instances of positive outcomes, overcoming the limitations caused by the COVID-19 pandemic and fighting against it. The elected representative become more accountable and sensitive to the development issues arising in their constituency and look for ingenious ways to solve them. Apart from the administrative and Panchayat related activities, social media platforms are also used to extend help and services to the poor and disadvantaged sections of the society during this difficult time. Critical development issues such as water and environment protection are also dealt with effectively through social media platforms.
Wohl einmalige Revisionsindikationen bei autologem Gefäßzugang
Authors: Krönung Gerhard
Published: December 2021

In diesem Beitrag werden seltene, kasuistisch hochinteressante Revisionsindikationen vorgestellt, die zusätzlich das notwendig breite Spektrum der insbesondere autologen Operationstechniken in der Shuntchirurgie eindrücklich belegen.
Risk factors for post-polypectomy bleeding; a retrospective case-control study of a high-volume colonoscopy center
Authors: Eleftheriadis Dimitrios , Imalis Christina , Gerken Guido , Wedemeyer Heiner , Duerig Jan
Published: December 2021

Background and aim Post-polypectomy bleeding (PPB) remains an uncommon although serious complication of colonoscopy. The aim of this study is to determine the PPB-prevalence in a secondary care hospital and its associated risk factors.

Patients and methods We collected data from 581 patients, with the removal of 1593 polyps between August 2017 and August 2019. A univariate binary logistic regression analysis was conducted retrospectively.

Results PPB occurred in only 10 cases, representing 1.7% of patients: immediate in 1.2% and delayed in 0.5%. The number of removed polyps per patient [4.5 (SD 2.59) for hemorrhagic vs. 2.74 (SD 1.98) for non-hemorrhagic group] and the propofol dose [232 mg (SD 93.07) for hemorrhagic vs. 133 mg (SD 57.28) for non-hemorrhagic group] were relevant patient-related risk factors. The polyp-based analysis showed the polyp size [18.4 mm (SD 10.44) for hemorrhagic vs. 4.42 mm (SD 4.29) for non-hemorrhagic group], the morphology [wide-based: OR 24.83 (95 % CI 2.76 – 223.44), pedunculated: OR 56.67 (95 % CI 5.03 – 638.29)], the location at ileocecal valve [OR 20.48, 95 % CI 1.81 – 231.97)], and the polypectomy method [hot snare piecemeal with epinephrine injection: OR 75.38 (95 % CI 7.67 – 741.21)] as significant risk factors for PPB, too.

Conclusions The low rate of PPB confirms the safety of the procedure in non-tertiary, high-volume colonoscopy centers. The number of polyps removed per patient, the polyp size, morphology and location, as well as the sedation dose and the method of polypectomy were shown as relevant risk factors.
Vitamin D 2021 – mehr als nur
Prävention
Authors: Spitz Jörg
Published: December 2021

Vitamin D hat eine überragende Bedeutung für die menschliche
Gesundheit, bei Fertilität und Schwangerschaft, Vorbeugung von akuten
Erkrankungen wie Atemwegsinfekten und insb. in der Prävention
zahlreicher chronischer Erkrankungen. Große Teile der deutschen
Bevölkerung leiden an einem Vitamin-D-Mangel. Gerade Kinder sind oft
unzureichend versorgt, während sich die Situation bei Menschen in der 2.
Lebenshälfte in den letzten Jahren durch Supplementation verbessert hat.
Vitamin D sollte zur Kompensation eines Mangels täglich eingenommen
werden, da freies Cholecalciferol in den ersten 24 Stunden nach Einnahme bes.
gut verfügbar ist.
Genetics Landscape of Nonsyndromic Hearing Loss in Indian Populations
Authors: Ray Manisha , Sarkar Saurav , Sable Mukund Namdev
Published: December 2021

Congenital nonsyndromic hearing loss (NSHL) has been considered as one of the most prevalent chronic disorder in children. It affects the physical and mental conditions of a large children population worldwide. Because of the genetic heterogeneity, the identification of target gene is very challenging. However, gap junction β-2 (GJB2) is taken as the key gene for hearing loss, as its involvement has been reported frequently in NSHL cases. This study aimed to identify the association of GJB2 mutants in different Indian populations based on published studies in Indian population. This will provide clear genetic fundamental of NSHL in Indian biogeography, which would be helpful in the diagnosis process.
The emergence of concentrator photovoltaics for perovskite solar cells
Authors: Sadhukhan Priyabrata , Roy Anurag , Sengupta Payal , Das Sachindranath , Mallick Tapas K. , Nazeeruddin Mohammad Khaja , Sundaram Senthilarasu
Published: December 2021

The emergence of high-efficiency photovoltaic research is undergoing intense study and is technologically desirable to meet sustainable energy and environmental demand. However, every single solar cell has a theoretical power conversion efficiency limit, and, thus, without compromising the cost, the power conversion efficiency enhancement of a solar cell is highly challenging. As a convenient solution, concentrating photovoltaics can focus sunlight onto an extremely high-efficiency solar cell integrating various optics. Concentrating photovoltaics use optical devices that collect and redirect the light toward the smaller photovoltaic cell and reduce the demand for the mined elements required for the solar cell fabrication. The research interest from the photovoltaic community has concentrated on organic-inorganic hybrid halide perovskite absorbers, and nowadays, perovskite solar cells manifest their outstanding contribution among the low-cost photovoltaic technologies. Inevitably, large-area perovskite solar cells suffer a lot with their poor stability, hindering their commercialization pace. Thus, the implementation of concentrating photovoltaic technology in perovskite solar cells demonstrates an inherent advantage using a smaller size solar cell. This review provides an overview of concentrating photovoltaic technology implementation, including their recent research and development portfolio, their economic benefits in combination with inexpensive optical elements and tracking systems, limitations, challenges, and relative scope of the future study, focusing on the emerging perovskite solar cell technology.
Understanding consumer preference for vascular access safety and quality measurement: an international survey
Authors: Schults Jessica , Paterson Rebecca , Kleidon Tricia , Cooke Marie , Ullman Amanda , McNeil Keith , Chopra Vineet , Charles Karina , Ray-Barruel Gillian , Marsh Nicole , Sullivan Clair , Sturgess David J. , Rickard Claire
Published: December 2021

Objectives The aim of this study was to examine patient perceptions regarding vascular access quality measurement. Methods A web-based, cross-sectional survey was performed using a convenience sample of healthcare consumers with vascular access experience, recruited from September 2019 to June 2020. Survey respondents were asked to rate the perceived importance of 50 vascular access data items, including patient demographics, clinical and device characteristics, and insertion, management and complication data. Data were ranked using a five-point Likert scale (1, least important; 5, most important), and are reported as median values. Respondents proposed additional items and explored broader perspectives using free-text responses, which were analysed using inductive thematic analysis. Results In all, 68 consumers completed the survey. Participants were primarily female (82%), aged 40–49 years (29%) and living in Australia or New Zealand (84%). All respondents indicated that measuring the quality of vascular access care was important. Of the 50 items, 37 (74%) were perceived as ‘most important’ (median score 5), with measures of quality (i.e. outcomes and complications) rated highly (e.g. thrombosis and primary blood stream infection). Participants proposed 16 additional items. ‘Gender’ received the lowest perceived importance score (median score 3). Two themes emerged from the qualitative analysis of broader perspectives: (1) measurement of vascular access device complication severity and associated factors; and (2) patient experience. Conclusion Measuring vascular access quality and safety is important to consumers. Outcome and complication measures were rated ‘most important’, with respondents identifying a need for increased monitoring of their overall vascular access journey through the health system. What is known about the topic? The use of vascular access devices is common among hospitalised patients. Quality surveillance is not standardised, with no incorporation of patient preference. What does this paper add? We identify the data items consumers perceive as valuable to measure related to their vascular access journey; most importantly, consumers perceived the collecting of vascular access data as important. What are the implications for practitioners? Health services can use these data to develop platforms to monitor the quality and safety of vascular access care.
Revisited interpretation ofTa’ārof
Authors: Yaqubi Mojde
Published: December 2021

Speech acts used in doingta’ārof(Iranian system of politeness) have been conceptualized in terms of both positive (i.e. sincere or genuine) and negative (i.e. ritual or ostensible) meanings. This study aimed to revisit the interpretation of the negative meaning by concentrating onta’ārof(ritual) offers produced by characters in Iranian films. First, these items were identified and distinguished from their genuine counterparts based on the strategies used in their structures and analysing their contextual features respectively. Then, the researcher proposed a model in which she adopted the notion ofLeech’s (1983)meta-implicature (indirect implicature) to explicate the negative meaning ofta’ārofoffers. She grouped a series of effective factors in working out these meta-implicatures. Finally, a tentative hierarchy of stages for identification and interpretation ofta’ārofoffers in Iranian films were proposed.
Adjectival and verbal agreement in the oral production of early and late bilinguals
Authors: Alarcón Irma
Published: December 2021

Extended oral production has seldom been used to explore adjectival and verbal agreement in L2 Spanish. This study examines oral narrations to compare the agreement behavior, speech rates, and patterns of errors of highly proficient Spanish heritage and L2 learners (early and late bilinguals, respectively), whose L1 is English, with those of native controls. Although both bilingual groups displayed high agreement accuracy scores, only the early bilinguals performed at or close to ceiling. In addition, the L2 learners spoke significantly more slowly than the heritage and native speakers, who displayed similar speech rates. Explanations accounting for the differences in speech rates and agreement accuracy include age of acquisition of Spanish, syntactic distance between a noun and its adjective, and task effects. All of these factors favored the early bilinguals, enhancing their advantages over L2 learners. Findings suggest that the integrated knowledge and automatic access needed for native-like attainment in agreement behavior in extended oral production is more easily achievable by early than by late bilinguals.
Acute exposure to extracellular BTP2 does not inhibit Ca2+ release during EC coupling in intact skeletal muscle fibers
Authors: Wei-LaPierre Lan , Groom Linda , Dirksen Robert T.
Published: December 2021

The inhibitor of store-operated Ca2+ entry (SOCE) BTP2 was reported to inhibit ryanodine receptor Ca2+ leak and electrically evoked Ca2+ release from the sarcoplasmic reticulum when introduced into mechanically skinned muscle fibers. However, it is unclear how effects of intracellular application of a highly lipophilic drug like BTP2 on Ca2+ release during excitation–contraction (EC) coupling compare with extracellular exposure in intact muscle fibers. Here, we address this question by quantifying the effect of short- and long-term exposure to 10 and 20 µM BTP2 on the magnitude and kinetics of electrically evoked Ca2+ release in intact mouse flexor digitorum brevis muscle fibers. Our results demonstrate that neither the magnitude nor the kinetics of electrically evoked Ca2+ release evoked during repetitive electrical stimulation were altered by brief exposure (2 min) to either BTP2 concentration. However, BTP2 did reduce the magnitude of electrically evoked Ca2+ release in intact fibers when applied extracellularly for a prolonged period of time (30 min at 10 µM or 10 min at 20 µM), consistent with slow diffusion of the lipophilic drug across the plasma membrane. Together, these results indicate that the time course and impact of BTP2 on Ca2+ release during EC coupling in skeletal muscle depends strongly on whether the drug is applied intracellularly or extracellularly. Further, these results demonstrate that electrically evoked Ca2+ release in intact muscle fibers is unaltered by extracellular application of 10 µM BTP2 for <25 min, validating this use to assess the role of SOCE in the absence of an effect on EC coupling.
Atomistic effect of laterally and vertically growth shell on physical behaviours of CdSe/CdTe type-II core/crown and core/shell nanoplatelets: tight-binding theory
Authors: Sukkabot Worasak
Published: December 2021

Utilizing the atomistic tight-binding theory, the impact of the lateral and vertical potential confinement by the coated shell on the CdSe/CdTe core/crown and core/shell nanoplatelets (NPLs) is attained. The spatial charge separation and encapsulated shell have a noteworthy impact on the electronic structures and optical properties because of the type-II band profile. The reduced band gaps with the growing laterally and vertically passivated shell thicknesses are due to the quantum confinement phenomena. The optical band gaps adjusted across the visible light are achieved by the shell thickness change. The excitonic binding energies of CdSe/CdTe core/shell NPLs are larger than those of CdSe/CdTe core/crown NPLs. Thanks to the spatial charge separation, a shortening of the oscillation strengths is concomitant with an increase of the radiative lifetimes. Overall, this scientific research underlines the importance of the theoretical understanding and practical control by lateral and vertical confinement of heterostructure NPLs.
Impact of Cr3+ substitution on the nephelauxetic ratio and Racah parameter of Cr-Mn-Zn nanoferrites
Authors: Abdo M A , Sadeq M S
Published: December 2021

For the first time, we present the ligand field splitting (10Dq) nephelauxetic ratio (β), Racah parameter (B) and stability of Cr3+ within Mn–Zn nanoferrite which synthesized using the citrate route. These parameters were determined via optical absorption spectra. The obtained bands in the significance range of optical absorption spectra are wide as well as asymmetric; therefore the deconvolution process becomes a necessary task. The values of 10Dq and B have been estimated from the produced bands. The values of 10Dq are observed to increase from 16366.61 to 16447.37 cm−1 whereas, B values are observed to decrease from 829.81 to 760.80 cm−1 with additional Cr3+ substitution. The increasing 10Dq and decreasing B values, evidence for bonds between Cr3+ ions with their environments became a further covalent (less ionic). Moreover, the values of β are observed to decrease for further Cr3+ substitution. This decrease of β produces less stability between Cr3+ and its ligand. Furthermore, Dq/B values declare that Cr3+ centers are in the low-field sites by a slight tendency towards the high-field sites with further Cr/Fe substitution process. Therefore, it was suggested that Cr3+ substituted Mn–Zn nanoferrites are excellent candidates for diverse optical applications such as a tunable laser.
Effect of Ti incorporation on the electronic structure and optical properties of MoS2 (a first principle study)
Authors: Akhtar Perveen , Khan Muhammad Junaid Iqbal
Published: December 2021

The novelty of the Molybdenum disulfide (MoS2) emerges owing to its opportunity to replace graphene and Si technology. In order to explore the great potential of the MoS2 in current technology, its doping with the titanium (Ti) is performed using the first principle calculations. The exchange and correlation effects are approximated using the Perdew–Burke–Ernzerhof, generalized gradient approximation (PBE-GGA) as employed in the Wien2k code. The Ti atoms substitute the Mo atoms and different concentrations (3.7%, 5.55%, 12.5%) are computationally realized in the current study. A review of the partial density of states (PDOS) and total density of states (TDOS) suggest a remarkable contribution of Ti 3d-states while these dopant states appreciably participate in tuning the electronic properties of Ti doped MoS2 (Ti:MoS2). A blueshift in the absorption spectrum is noticed along with increase in Ti concentrations which leads to its potential uses in the high energy visible optoelectronic applications. Moreover, an increase in dielectric constant and refractive index is observed which further extends the uses of the proposed material (Ti:MoS2) in the fields of photonic, photodetectors, optics, and photosensing applications.
Robustness of multipartite entangled states for fermionic systems under noisy channels in non-inertial frames
Authors: Kim Kwang-Il , Pak Myong Chol , Kim Tae-Hyok , Kim Jong Chol , Ko Yong-Hae , Pak Hak Chol
Published: December 2021

We investigate robustness of bipartite and tripartite entangled states for fermionic systems in non-inertial frames, which are under noisy channels. We consider two Bell states and two Greenberger-Horne-Zeilinger (GHZ) states, which possess initially the same amount of entanglement, respectively. By using genuine multipartite (GM) concurrence, we analytically derive the equations that determine the difference between the robustness of these locally unitarily equivalent states under the amplitude-damping channel. We find that tendency of the robustness for two GHZ states evaluated by using three-tangle τ and GM concurrence as measures of genuine tripartite entanglement is equal to each other. We also find that the robustness of two Bell states is equal to each other under the depolarizing, phase damping and bit flip channels, and that the same is true for two GHZ states.
Freedericksz transition in ferronematic liquid crystal under weak anchoring conditions
Authors: Lahiri T , Pushkar S K , Poddar P
Published: December 2021

Freedericksz effect is investigated theoretically for a ferronematic liquid crystal, which is a colloidal suspension of ferromagnetic nanoparticles in a nematic fluid. Considering a splay type Freedericksz geometry, weak anchoring conditions are assumed at the cell boundaries. The specific nature of this anchoring reveals a rich variety of stable ferronematic phases, which include uniform, distorted and saturated states. Apart from weak anchoring conditions at the cell boundaries, soft planar anchoring is assumed for the mesogenic molecules at the surface of a nanoparticle. The interplay between these two anchoring phenomena along with Frank type elastic theory determine the values of Freedericksz threshold between various ferronematic states. It is found that compared to relatively strong anchoring for the mesogens both at the cell boundaries and at the surface of the nanoparticles, weak anchoring significantly reduces the Freedericksz threshold field. Landau theory is then utilized to understand the nature of transition between different ferronematic states. Based on the phenomenon of segregation effect, these transitions are found to be either first order or second order in nature. The present theory is also extended to non-ferromagnetic nanoparticles and significant reduction in Freedericksz threshold is obtained. Finally, these results are corroborated with experimental findings.
Cell–extracellular matrix dynamics
Authors: Doyle Andrew D , Nazari Shayan S , Yamada Kenneth M
Published: December 2021

The sites of interaction between a cell and its surrounding microenvironment serve as dynamic signaling hubs that regulate cellular adaptations during developmental processes, immune functions, wound healing, cell migration, cancer invasion and metastasis, as well as in many other disease states. For most cell types, these interactions are established by integrin receptors binding directly to extracellular matrix proteins, such as the numerous collagens or fibronectin. For the cell, these points of contact provide vital cues by sampling environmental conditions, both chemical and physical. The overall regulation of this dynamic interaction involves both extracellular and intracellular components and can be highly variable. In this review, we highlight recent advances and hypotheses about the mechanisms and regulation of cell–ECM interactions, from the molecular to the tissue level, with a particular focus on cell migration. We then explore how cancer cell invasion and metastasis are deeply rooted in altered regulation of this vital interaction.
Experimental study of perturbations modeled by a membrane in 2D and 3D boundary layers
Authors: Sadovskii I A , Katasonov M M
Published: December 2021

The work is devoted to experimental studies of the dynamics of the development of perturbations introduced by a membrane under various conditions. The studies were carried out under conditions of a low and moderate degree of free-flow turbulence. It is shown that the impulsive motion of the membrane generates a localized longitudinal structure in the boundary layer, as well as wave packets at its fronts. A circular membrane generates wave packets consisting of forward and oblique waves, while a rectangular membrane generates predominantly forward waves. A moderate degree of turbulence inhibits the development of wave packets at the linear stage and intensifies at the nonlinear stage. The separation of the boundary layer stimulates an increase in the amplitude of the wave packets.
Numerical study of the flow around a circular cylinder with the slip length boundary effect at a critical Reynolds number
Authors: Sentyabov A. , Gavrilov A. , Dekterev A.
Published: December 2021

The paper presents an investigation of the slip length effect on the flow around a circular cylinder at Reynolds number Re = 2.5·105. The study was performed by means of numerical simulation of the flow with the URANS approach based on the k-ω SST model. Calculations show a significant effect of the slip length on the flow patterns. With an increase in the slip length, the drag coefficient noticeably decreases and the pulsations of the lift force reduce. With an increase in the slip length, the separation of the flow from the cylinder is delayed, which significantly affects the flow patterns in the wake behind the cylinder.
Temperature distribution in the three-layered upper mantle beneath a continent
Authors: Kirdyashkin A G , Kirdyashkin A A , Borodin A V , Kolmakov V S
Published: December 2021

Temperature distribution in the upper mantle underneath the continent, as well as temperature distribution in the lower mantle, is obtained. In the continental lithosphere, the solution to the heat transfer equation is obtained in the model of conduction heat transfer with inner heat within the crust. To calculate the temperature distribution in the upper and lower mantle, we use the results of laboratory and theoretical modeling of free convective heat transfer in a horizontal layer heated from below and cooled from above.
Penetration of vertical pulsed jets in crossflow at low velocity ratio
Authors: Dobroselsky K G
Published: December 2021

Using the visualization method, the initial rise and penetration of a circular turbulent pulsed jet into a transverse air flow are studied at the ratio of jet velocities to the transverse flow r = u

j
/u

f
= 0.67–2.33. A comparative assessment of the penetration of a pulsating jet into a transverse flow for frequencies from 0 to 20 Hz is carried out. The cases of both stationary and oscillating jet flows are analyzed. The penetration of a pulsating jet into a transverse flow is shown to be more significant than for a stationary one and depends on an increase in the ratio of velocities and frequency: it increases linearly at a fixed frequency and passes through a minimum at a fixed ratio of velocities.
Flow and heat transfer in the separation region behind a backward-facing step with convergently mounted plates of longitudinal vortex generator
Authors: Terekhov V I , Dyachenko A Yu , Zhdanov V L , Smulsky Ya J , Sharov K A
Published: December 2021

The paper presents the results of an experimental study of the dynamics of separated flow and heat transfer behind a backward-facing step when using longitudinal vortex generators (LVGs) at an angle of -30º at Re = 4000. Longitudinal vortex generators represent a pair of plates with a height of 6 mm, located symmetrically relative to the flow. Along with the average values, the pulsation characteristics of the flow are considered. The thermohydraulic efficiency was estimated by the found dynamic and thermal characteristics.
Heat transfer behind the backward-facing step in the presence of longitudinal vortex generators installed at an angle to each other
Authors: Terekhov V I , Dyachenko A Yu , Zhdanov V L , Smulsky Ya J
Published: December 2021

The paper presents the experimental results on the control of heat transfer enhancement behind the backward-facing step at Re = 4000. The flow is controlled by a pair of longitudinal vortex generators (LVGs) installed at the step edge. The pair of vortex generators (VG) consists of two plates positioned symmetrically relative to the flow. The influence of the height, the angle of VG installation relative to the flow, the distance between VG pairs and the shape of the plate on local and average heat transfer is investigated.
Parametric study of cone angle influence on bubble vortex breakdown onset in laminar conical flow at various swirl numbers
Authors: Skripkin S G
Published: December 2021

The current work studies a swirling laminar viscous pipe flow with a controllable swirl number and varying pipe divergence cone angle. Such flows are widely used in various engineering applications. When a certain level of flow swirl is reached, a phenomenon called vortex breakdown occurs, the characteristics of which depend on the intensity of swirling of the flow and the Reynolds number. However, in addition to these two parameters, an important influence is exerted by the pipe opening angle, which often does not allow generalizing the results obtained in the pipe flow with even slightly different angles. Since experimentally it is quite difficult and expensive to change the pipe angle, especially considering the water as working fluid, this issue could be solved using CFD techniques. Using the design study, 63 different combinations of S and α are considered. The effect of the pipe divergence angle on the position of the bubble vortex breakdown and its properties is demonstrated. It is shown that there is a nonlinear relationship between the position of the bubble breakdown onset and the minimum value of the axial velocity at the axis depending on the opening angle of the cone.
Investigating a pulsating flow in the smooth channel and at the bifurcation section with regard to the popliteal artery hemodynamics
Authors: Molochnikov V M , Mikheev N I , Mikheev A N , Paereliy A A , Goltsman A E
Published: December 2021

Experimental setup is described. Pulsating flow in a smooth channel, and steady and pulsating flows at a bifurcation section simulating the distal end of an artery anastomosis at different flow rates in the main and outflow channels are studied. Indications of laminar-turbulent transition are observed in the near-wall region of the smooth channel. Mechanisms of turbulization of the near-wall region in the pulsating flow are suggested. Vortex flow structure in the bifurcation section is analyzed.
Characteristics of the circular subsonic laminar jets flow with an initial Poiseuille profile
Authors: Lemanov V V , Terekhov V I , Sharov K A , Shumeiko A A
Published: December 2021

In this work, the experimental data are compared with the version of the “strong” jet (Re ≫ 1) of the exact Landau-Squire solution. The experiments were performed for a submerged air jet flowing out of a tube with a diameter of D = 3.2 mm and a length of more than 100D at a Reynolds number equal to Re = 436. The initial conditions in the jet are the Poiseuille velocity profile, the level of velocity pulsations is less than 1%. Measurements were carried out using a hot-wire anemometer. It is shown that satisfactory agreement with theory is achieved at distances from the tube starting from x/D = 5.6 and up to the zone of transition to turbulence (x/D > 35). Turbulence along the jet axis will increase from 1% to 2.5%, while in the mixing layers it increases to 4.7%.
Non-stationary convective heat transfer in an air synthetic impinging jet. Experiment and numerical simulation
Authors: Lemanov V.V. , Pakhomov M.A. , Terekhov V.I. , Travnicek Z.
Published: December 2021

An unsteady local heat transfer in an air synthetic non-steady-state jet impingement onto a flat plate with a variation of the Reynolds number, nozzle-to-plate distance and pulses frequency is experimentally and numerically studied. Measurements of the averaged and pulsating heat transfer at the stagnation point are conducted using a heat flux sensor. The axisymmetric URANS method and the Reynolds stress model are used for numerical simulations. For local values of heat transfer, zones with the maximum instantaneous value of heat flux and heat transfer coefficient are identified. The heat transfer increases at relatively low nozzle-to-plate distances (H/d ≤ 4). The heat transfer decreases at high distance from the orifice and target surface. An increase in the Reynolds number causes reduction of heat transfer.
Quasi-periodic forces and conditionally averaged characteristics of unsteady cavitation flow around a hydrofoil
Authors: Ivashchenko E I , Hrebtov M Yu , Mullyadzhanov R I
Published: December 2021

Large-eddy simulations are performed to investigate the cavitating flow around two dimensional hydrofoil section with angle of attack of 9° and high Reynolds number of 1.3×106. We use the Schnerr-Sauer model for accurate phase transitions modelling. Instantaneous velocity fields are compared successfully with PIV data using the methodology of conditional averaging to take into account only the liquid phase characteristics as in PIV. The presence of two frequencies in a spectrum corresponding to the full and partial cavity detachments is analysed.
Experimental investigation of pressure fields in a single trench dimple
Authors: Yan Lun N , Baranov I N , Terekhov V I , Chokhar I A
Published: December 2021

The paper describes the technique and results of an experimental investigation of the pressure distribution over the surface of an oval trench dimple (OTD). The trench dimple in cross-section is a cylindrical segment on one of the flat channel walls. The experiments were carried out at a constant Reynolds number Re
D
= 3.2 · 104 and variation of the inclination angle relative to the longitudinal axis of the channel in the range φ = 0 – 90°.
Experimental study of flow dynamics of a sweeping jet in a slot channel
Authors: Shestakov M V
Published: December 2021

In recent years, fluidic oscillators have been actively applied as devices for flow control in the field of aero and hydrodynamics. This study aims to investigate the structure of a flow of sweeping jet ejected from a fluidic oscillator into a confined area – slot channel. Dynamics of sweeping jet flow are investigated using the PIV method with high temporal resolution. The effect of the Re number on the sweeping jet oscillation frequency was studied in the range from 1 500 to 8 000. Linear frequency dependence on Re number was obtained. Bounding walls affect the dynamics of sweeping jet flow that leads to a change of average velocity field. For low Re numbers, obtained results are in good agreement with the results of other studies.
Electroplasma processing of medical and biological waste
Authors: Domarov P V , Anshakov A S , Faleev V A
Published: December 2021

The article presents an experimental study of biomedical waste in the form of disposable masks. The study was carried out on a laboratory plasma arc installation with a capacity of 20 kg/h. During the experiments, the most important technological parameters were studied: the composition of the exhaust gases, the dependence of the exhaust gases on the temperature in the chamber of the plasma arc furnace, etc.
Non-equilibrium process of transfer of momentum in medium with relaxation microstructure
Authors: Popov V I , Kuznetsov A V
Published: December 2021

The non-equilibrium process of transfer of the momentum of polymer media with an evolving nonequilibrium relaxation microstructure is considered. For the basic conditions of deformation, the regularities for the structural and dynamic components of the stress tensor with conjugate forces are obtained and analyzed, which are consistent with experiment.
Temperature measurements in a swirling impinging flame by planar laser-induced fluorescence
Authors: Tolstoguzov R. V.
Published: December 2021

This article presents the results of approbation of the method for registering temperature distributions based on the planar laser-induced fluorescence of a hydroxyl radical (OH) when the band (1-0) of the A2Σ+–X2Π system is excited. The thermometry is based on the recording the ratio of the radiation intensity of the band (2-0) and the bands (0-0), (1-1). Numerical modelling of fluorescence spectra is performed using the LASKIN program for the most frequent excitation lines Q2(7), Q1(8), R1(14), P1(2). The temperature field of a swirling flame, impinging on a flat cold surface, for H/d = 1, 2 and 3 calibres (where H is the distance between the jet nozzle and the surface, d is the outlet diameter of the nozzle) is obtained. The results of the work demonstrate that when the transition Q1(8) is excited, the ratio of the intensity of fluorescence signals for the band (2-0) and the bands (0-0), (1-1) provides a high sensitivity to temperature and is not significantly affected by fluorescence quenching. The report also concludes that this method can be implemented using single pulsed laser illumination and is effective for the detecting the position of flow recirculation zones and registering hot heat release zones with the combustion products.
Investigation of service life characteristics of hot cathodes in arc plasmatrons
Authors: Anshakov A S , Aliferov A I , Domarov P V
Published: December 2021

Among the applied challenges associated with the use of electric-arc plasma, the most urgent is the erosion of electrodes in plasmatrons, which determine the continuous operation of an electric-plasma device. Investigation results on the thermal state of hot cathodes and their erosion are presented depending on the main defining parameters, namely geometrical dimensions of electrodes, Joule heating, current of the arc discharge, and the gas medium. The conditions for the minimum specific erosion and long service life of tungsten thermionic cathodes are established experimentally.
Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields
Authors: Severin A S , Timoshevskiy M V , Ilyushin B B , Pervunin K S
Published: December 2021

A new method was developed for statistical analysis of ensembles of instantaneous velocity fields measured by PIV in liquid (continuous phase) to determine the distribution of the vapor phase in cavitating flow. The method is based on two main principles: the absence of tracers used for PIV measurements in vapor, and the statistical independence of individual measurements. This allowed establishing an exponential dependence of repeatability of the vapor phase at a certain point of a cavitating flow. Compliance with this theoretical law was verified using the Pearson chi-square test. All theoretical distributions were divided into several groups depending on the time-averaged local vapor content calculated over the entire ensemble of realizations and the probability of a single event. As a result, dimensions of the stationary part of an attached cavity and the place of detachments of cloud cavities from the hydrofoil surface were determined using the new method of statistical analysis for an unsteady cloud cavitation regime.
The investigation of the height effect of a slit microchannel with a textured wall on its hydrodynamic drag
Authors: Lobasov A S , Minakov A V
Published: December 2021

The numerical investigation of the fluid flow in a slit microchannel with a textured wall was carried out. The effect of the channel height on the hydrodynamic drag coefficient, as well as on the pressure drop in such channel and the effective slip length on the wall for various Reynolds numbers, are presented in the paper. The channel length was 100 µm, and its height was varied from 25 µm to 500 µm. The Reynolds number was varied from 0.1 to 100. The main studied characteristics were compared to the similar ones obtained for a channel with normal walls (no-slip conditions). It was found that the pressure drop in such textured microchannel was lower as compared to a conventional channel for any of its heights and for any Reynolds numbers. The dependences of the relative pressure drop, effective slip length, and drag coefficient on the Reynolds number were obtained for different channel heights. The drag coefficient was described as 20/Re for the average values of the channel height. A correlation that describes the dependence of the friction factor on the Reynolds number for small and large heights of the channel was proposed. The accuracy of the proposed correlation was about 90%.
An experimental study on the subcooled flow boiling pressure drop of R141b in the system of two microchannels
Authors: Shamirzaev A. S.
Published: December 2021

An experimental study of the pressure drop under subcooled flow boiling of the refrigerant R141b in a system with two slotted microchannels was carried out. A copper block with two microchannels 2 mm wide, 0.4 mm deep, and 16 mm long was used as an experimental section for testing. The mass flow rate varied in the range from 1 to 4 g/s, the initial subcooling from 20°C to 50°C. Experimental data show a significant decrease in the pressure drop when the critical heat flux is reached. The experimental data are compared with the model known from the literature. Experimental data show that the occurrence of nucleate boiling incipience at subcooled boiling corresponds to a larger heat flux than that given by the recommended correlation.
Numerical Modelling of Liquid Film Spreading Dynamics over Smooth Vertical Surface under Isothermal Conditions
Authors: Sakhnov A , Volodin O A , Pecherkin N I , Pavlenko A N
Published: December 2021

The paper presents numerical modelling of the liquid film spreading dynamics of the R21 (mol. fraction: 0.9) and R114 refrigerants mixture. We considered an outer flow along a round vertical cylinder at Reynolds number of 104 and various contact angles. The simulation was performed in OpenFOAM software on the basis of the volume of fluid (VOF) method. We have shown that the wetting front deforms at wetting angles of 30 and 50 degrees, and regular jets form. At the same time, it was demonstrated that at the wetting angle of 10 degrees the spreading front has practically a flat shape, but one may see some regular thickenings of the liquid film along the contact line of the front.
Application of the Riemann problem with complex equations of state for modeling three-dimensional flows of real media
Authors: Tenenev V A , Koroleva M R , Chernova A A
Published: December 2021

The paper considers the numerical simulation of spatial flows of real media in safety valves on the basis of the problem of an arbitrary discontinuity breakdown with complex equations of state. The solution is constructed by means of the developed numerical method, which is a modification of the classical scheme by S. K. Godunov and includes various complex equations of state of matter. The Van der Waals equations of state were used to model the flow of real gases, and the Mie-Grüneisen equation was used to describe the flow of a real weakly compressible fluid. It is shown that the proposed numerical schemes allow for modeling fluid and gas dynamic processes in real fluids and gases with shock waves and contact discontinuities and can be used both in areas of classical medium behavior and in areas with non-classical behavior.
Capillary-gravitational waves and storage of liquid CO2 in the oceans
Authors: Derzho O G
Published: December 2021

A theory of capillary-gravitational waves in the transition region between seawater and liquid carbon dioxide in deep oceans is proposed. It is shown that the thickness of the transition layer affects the properties of capillary-gravity waves. The question of the structure and stability of wave disturbances at the interface between seawater and liquefied carbon dioxide is essential for the safe storage of liquefied carbon dioxide in the ocean. This is an important issue on the current agenda in light of global warming.
Nonlinear evolution equation for modeling waves at the boundary of a stratified flow of viscous liquids in an inclined channel
Authors: Arkhipov D G , Khabakhpashov G A
Published: December 2021

The dynamics of perturbations of the interface of a two-layer Poiseuille flow in a flat closed inclined channel is studied. The velocity profiles of wave motion are analytically found neglecting dissipation, dispersion and pumping of perturbations. On the basis of the found solution, a nonlinear evolution integro-differential equation for plane moderately long perturbations of the interface of the liquids is derived. The coefficients of the equation are represented by integrals over the layer thicknesses from functions depending on the stationary flow and perturbation profiles. The equation takes into account viscous dissipation: one of the integrals in this equation corresponds to dissipation in lion-stationary boundary layers, and the other corresponds to the transfer of energy from the flow to the wave. For the case of small flow velocities, the coefficients of the equation are analytically calculated. The equation has also been generalized to the quasi-two-dimensional case when the gradients along the transversal coordinate are small.
Research of pressure pulsations during gas outlet to closed pipe area with liquid and installed disc barrier
Authors: Alekseev M V , Vozhakov I S , Lezhnin S I
Published: December 2021

A numerical simulation of the gas outflow to a closed region filled with liquid with a barrier disk was performed. The calculations were carried out using the VOF method, supplemented by the k-e turbulence model. Calculations were performed for three cases of 100, 200, and 300 mm distances of the disk from the injector with a gas outflow into water and liquid lead. The pulsations of axial pressure on a disk obstacle were investigated. It was found that the maximum pressure during pulsations of the upper gas volume in lead can be greater than the pressure in the gas receiver.
Modeling of nonstationary gas outflow at breaks of subsea gas pipelines
Authors: Lukyanov A A , Alekseev M V
Published: December 2021

Numerical modeling of the outflow of an air jet into water with a guillotine rupture of a pipeline by the VOF method using k-ε and k-ω SST turbulence models was carried out. The calculations were carried out in the axisymmetric approximation. The following phases of the outflow process were calculated: the formation of a large gas bubble at the place of the rupture, its growth, the separation of the bubble from the place of rupture, and the formation of a gas jet behind the bubble. It is shown that the rate of bubble detachment in the calculations by the k-ω SST model is higher than that in the calculation by the k-ε model.
Heat transfer in a centrifugal vortex tube
Authors: Gorelikov E U , Naumov I V , Tsoy M A , Shtern V N
Published: December 2021

The results of an experimental study of the heat flux in a model of a centrifugal vortex apparatus with a lower rotating disk are presented. An experiment considered three cases at a distance between the disks H=R/2 and H=R: “water”, “water-air”, and “water-oil”. Using the colorimetric method, the dependence of the heat flux on Reynolds is shown. The case “water-air” was chosen to evaluate the contribution to heat exchange from the thermocapillary effect (Marangoni) at high Re. For the case of two immiscible liquids of different densities (water-oil), the effect of “centrifugal levitation” is found.
An experimental study of flow boiling heat transfer of zeotropic mixture R32/R134a in a microchannel heat exchanger
Authors: Shamirzaev A. S.
Published: December 2021

This paper presents experimental data on heat transfer of a binary zeotropic mixture of refrigerants R32/R134a in a microchannel heat exchanger with a high specific surface within a range of parameters that is practically important for the development of cooling systems for microelectronics and space technology. The experiments were carried out in a horizontal heat exchanger with one-sided heating of a copper microchannel plate 20x40 mm, containing 21 rectangular microchannels with a cross-section of 335x930 μm, within the range of mass fluxes from 80 to 250 kg/m2s, and at an absolute pressure in the system ranged from 12 to 14 bar. A zeotropic mixture of refrigerants R32/R134a with a molar concentration of the initial mixture of 65%/35% was used as a working fluid. Experimental data were compared with model-based calculations that take into account the influence of changes in the concentrations of components in the liquid and gas phases.
Experience in registration of evaporation of liquid drops on a substrate by the capacitive method
Authors: Kokorin A V , Nazarov A D , Serov A F
Published: December 2021

This paper presents the results of an experimental study of the dynamics of evaporation of nanofluid droplets based on distilled water with a mass concentration of SiO2 nanoparticles of 0.1%, 0.5%, and 7% lying on a metal surface. The drop height was changed over time using original equipment, which is based on an integrated approach to the combined use of capacitive and optical recording methods. The experimental results show that the change in the height of nanofluid droplets with concentrations of 0.1%, 0.5%, and 7% is linear over the main part of the evaporation time interval. A deviation from the linear law is observed at the final stage, at the time interval of complete evaporation. The time for complete evaporation of droplets of nanofluids with a concentration of 0.1% increases by 20%, for droplets with a concentration of 0.5%, it increased by 28% in comparison with the evaporation of droplets of the base liquid. The particle concentration of 7% does not lead to an increase in the evaporation time of droplets in comparison with the evaporation of low concentration droplets. Before the formation of a jelly-like residue of nanoparticles, the evaporation rate of droplets with a particle concentration of 7% is comparable to the evaporation rate of droplets with a concentration of 0.1%.