bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppression of background emission for efficient single-photon generation in micropillar cavities
Authors: Wang Bi-Ying , Häyrynen Teppo , Vannucci Luca , Jacobsen Martin Arentoft , Lu Chao-Yang , Gregersen Niels
Published: March 2021

We optimize the efficiency of a quantum-dot-based micropillar single-photon source by minimizing the spontaneous emission into unwanted background modes. We perform a numerical investigation of the background emission, where we identify a semi-periodic enhancement with the diameter. At these peaks of the background emission, the efficiency is reduced by ∼20%, and we show how this reduction can be avoided simply by choosing a diameter away from the peaks. Finally, we analyze the discrepancy between the Purcell factor estimated from experimental lifetime measurements and the true Purcell factor.
Suppressive effect of Ni–Sn internal electrode at the anode on the leakage current degradation of BaTiO3-based multilayer ceramic capacitors
Authors: Suzuki Shoichiro , Yamaguchi Shinichi , Doi Akitaka , Shiota Akihiro , Iwaji Naoki , Abe Shunsuke , Matsuda Makoto , Nakamura Tomoyuki , Sano Harunobu
Published: March 2021

As the BaTiO3 dielectric layer of multi-layer ceramic capacitors (MLCCs) becomes thinner, the problem of leakage current degradation arises. In this study, the leakage current degradation was investigated for the cases when the Ni–Sn internal electrode was placed at either the anode or the cathode. The MLCCs with the Ni–Sn internal electrode at the anode suppressed the leakage current degradation with time significantly better than that at the cathode. The leakage current types for the degraded MLCCs were tunnel and Schottky or Poole–Frenkel for the Ni and Ni–Sn internal electrodes, respectively. High-resolution scanning transmission electron microscopy revealed an interface layer with a high Sn concentration at the interface between the Ni–Sn internal electrode and BaTiO3. Therefore, the interface of the electrode at the anode plays an important role in the leakage current degradation of MLCCs with time.
Photochromism and influence of point defect charge states on optical absorption in aluminum nitride (AlN)
Authors: Gamov Ivan , Hartmann Carsten , Straubinger Thomas , Bickermann Matthias
Published: March 2021

In this work, we study the absorption properties of AlN in the range of 1.5–5.5 eV, as well as the metastable change in absorption induced by ultraviolet (UV) irradiation (photochromism). We also study the restoration of the initial state under the action of the irradiation of 2–4 eV or elevated temperatures. UV irradiation results in a decrease of the absorption coefficient from 110 to 55 cm−1 at 4.7 eV, while in the visible range, the absorption coefficient increases from values below 5 to ∼35 cm−1. Measurements with two linear polarizations, E ∥ c and E ⊥ c, provide the determination of several different absorption bands at 2.6, 2.8, 3.4, 4.0, 4.5, and 4.8 eV. The bands at 2.6 and 3.4 eV identify the defect levels near the valence band, while the band peaking at 2.8 eV is related to the conduction band. Photochromism allows for controlling the absorption of light in two related spectral ranges, because the decrease of UV absorption and increase of visible absorption are related to switching the charge state of the same defects.
Simulation of indoor harmful gas dispersion and airflow using three-dimensional lattice Boltzmann method based large-eddy simulation
Authors: Li Chengwu , Zhao Yuechao , He Yonghang , Luo Kai Hong , Li Yingjun
Published: March 2021

The lattice Boltzmann method (LBM) and large-eddy simulation (LES) are combined with a scalar subgrid-scale model to simulate the indoor air velocity field and harmful gas dispersion. The LBM-LES model is validated by comparing its results with published experimental and numerical simulation results. Taking a simplified chemical building as the scenario, the relative ventilation efficiency is evaluated based on the maximum harmful gas concentration, and configurations with centralized and distributed harmful gas sources with both mixing ventilation (MV) and displacement ventilation (DV) systems are considered. According to the results, if the density of the harmful gas is less than the air density, the DV system is more efficient than the MV system. The DV system is more stable than the MV system under fluctuating relative ventilation efficiency due to changes in the distance between the ventilation vents and in the distance between the centralized gas sources and the exhaust air vent.
On the approximating criteria of parabolic asperities for measured surface profiles
Authors: Zhu Linbo , Chen Jian , Sun Yanhui
Published: March 2021

Surface description is fundamental in mechanical contact analysis. In this paper, some of the most common approaches for roughness description are first briefly described. Some models for approximating a real rough profile with parabolas that guarantee the preservation of some specific characteristics are presented. The specimens of aluminum alloy with different surface roughnesses are prepared and measured. A data analysis program is developed to identify the measured profile with quadratic functions for different approximating criteria. Based on this, the effect of the approximating criterion and the sampling interval on the surface roughness parameters and the mechanical parameters is then presented and compared. The results show that the surface roughness Ra, asperity height H, and peak radii R increase with increasing surface roughnesses for different approximating criteria. The same root mean square approximating criterion is more suitable for calculating the surface roughness Ra. The asperity height H and peak radii R increase with increasing sampling intervals for all roughnesses, while the trend is opposite for the surface roughness Ra. The sampling interval has little effect on these parameters, especially for smoother surfaces.
Review of Scientific Instruments New Products
Authors: Mandelis Andreas
Published: March 2021

In order to supplement manufacturers’ information, this department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials which supersede earlier data or suggest new research applications.
Implementing a hip fracture registry and financial incentive program to enhance best practice in hip fracture care in Western Australia
Authors: Seymour Hannah , Pulido Diana Fajardo , Ling Amanda , Mitchell Rebecca
Published: March 2021

Hip fracture is a common injury in older adults that causes significant morbidity and mortality. Older adults who sustain a hip fracture are at a higher risk of institutionalisation, reduced mobility and subsequent falls and, consequently, have increased rates of morbidity and mortality. Quality improvement strategies that address gaps in hip fracture care are needed to ensure best practice and improve health outcomes for older adults. This case study describes the development of a state-based hip fracture registry and incentive payment scheme in Western Australia (WA), which were designed to drive quality improvement. The registry monitored best practice in hip fracture care criteria across three tertiary hospitals in WA, and the incentive program provided premium payments to these hospitals for meeting six criteria in best practice clinical quality. The fracture registry commenced in 2011, and by 2014 all participating hospitals were eligible for payments. From 2014 to 2016, the proportion of patients who were operated on within 36 hours increased from 60% to 79%. This case study illustrates how a hip fracture registry in conjunction with small premium payments improved well-described process measures in hip fracture care. What is known about the topic? Hip fracture is a common among older adults, usually resulting from a fall. International clinical quality registries have been shown to help drive quality improvements in patient care processes and outcomes. What does this paper add? This paper adds an Australian perspective to the existing literature on the efficacy of hip fracture clinical quality registries. It offers an example of how a Western Australian hip fracture registry with an associated incentive payment program drove clinical care and process change to improve care provision and patient outcomes. What are the implications for practitioners? This case study suggests regular monitoring and reporting on hip fracture care processes and patient outcomes can lead to improvements in both of these measures. Because incentive payments may have contributed to the best practice improvements noted in this case study, practitioners involved in designing future monitoring and reporting programs should consider the merits of incorporating financial incentives.
Overdispersion in COVID-19 increases the effectiveness of limiting nonrepetitive contacts for transmission control
Authors: Sneppen Kim , Nielsen Bjarke Frost , Taylor Robert J. , Simonsen Lone
Published: March 2021

Significance

Evidence indicates that superspreading plays a dominant role in COVID-19 transmission, so that a small fraction of infected people causes a large proportion of new COVID-19 cases. We developed an agent-based model that simulates a superspreading disease moving through a society with networks of both repeated contacts and nonrepeated, random contacts. The results indicate that superspreading is the virus’ Achilles’ heel: Reducing random contacts—such as those that occur at sporting events, restaurants, bars, and the like—can control the outbreak at population scales.
Conductance selectivity of Na
+
across the K
+
channel via Na
+
trapped in a tortuous trajectory
Authors: Mita Kenichiro , Sumikama Takashi , Iwamoto Masayuki , Matsuki Yuka , Shigemi Kenji , Oiki Shigetoshi
Published: March 2021

Significance

Ion selectivity is a fundamental property of ion channels. Potassium channels exhibit an unusual selectivity, allowing passage of larger K
+
ions (ionic radius of 1.3 Å) over smaller Na
+
ions (1.0 Å); the mechanism underlying the small ion rejecting selectivity remains unknown. Here, we applied Na
+
as a probe for examining the pore of a prototypical potassium channel and found slight Na
+
conduction across the pore. Na
+
traced a tortuous trajectory in the narrow pore, with multiple Na
+
ions trapped here and there, leading to slow elution. Contrarily, K
+
passed straight, with three ions moving together rapidly. Na
+
and K
+
take different paths and interactions in the pore, which creates dramatic contrast in the conduction rates of Na
+
and K
+
.
Novel insights into sarcomere regulatory systems control of cardiac thin filament activation
Authors: Solís Christopher , Solaro R. John
Published: March 2021

Our review focuses on sarcomere regulatory mechanisms with a discussion of cardiac-specific modifications to the three-state model of thin filament activation from a blocked to closed to open state. We discuss modulation of these thin filament transitions by Ca2+, by crossbridge interactions, and by thick filament–associated proteins, cardiac myosin–binding protein C (cMyBP-C), cardiac regulatory light chain (cRLC), and titin. Emerging evidence supports the idea that the cooperative activation of the thin filaments despite a single Ca2+ triggering regulatory site on troponin C (cTnC) cannot be considered in isolation of other functional domains of the sarcomere. We discuss long- and short-range interactions among these domains with the regulatory units of thin filaments, including proteins at the barbed end at the Z-disc and the pointed end near the M-band. Important to these discussions is the ever-increasing understanding of the role of cMyBP-C, cRLC, and titin filaments. Detailed knowledge of these control processes is critical to the understanding of mechanisms sustaining physiological cardiac state with varying hemodynamic load, to better defining genetic and acquired cardiac disorders, and to developing targets for therapies at the level of the sarcomeres.
Quantum oscillator as a minimization problem
Authors: D’Eliseo Maurizio M
Published: March 2021

The ground state of the linear harmonic oscillator is the solution to a minimization problem, and this opens up two new ways to completely solve Schrödinger’s time-independent equation. The first exploits systematic patterns that emerge from a formal relationship between two different integral representations of the energy. A remarkable invariant form of the ground-state probability-density equation under specific conditions is the leading principle of the second procedure, where a uniform notation for all mathematical object involved facilitates calculations and generates useful schemes to quickly deduce the main functional relationships of the problem. We believe these procedures may represent useful educational alternatives to standard treatments that address this fundamental problem.
Preparation of aligned nanofibers using parallel inductive-plates assisted electrospinning
Authors: Su Shijie , Liang Junsheng , Xu Shuangchao , Li Xiaojian , Xin Wenwen , Wang Zizhu , Wang Dazhi
Published: March 2021

Electrospinning is a simple, cost-effective, and versatile technique for fabrication of nanofibers. However, nanofibers obtained from the conventional electrospinning are typically disordered, which seriously limits their application. In this work, we present a novel and facile technique to obtain aligned nanofibers with high efficiency by using parallel inductive-plates assisted electrospinning (PIES). In this new electrospinning setup, the electrostatic spinneret is contained in a pair of parallel inductive-plates, which can change the shape and direction of the electric field line during the electrospinning so as to control the flight trajectory and spatial alignment of the spinning nanofibers. This electrospinning setup can divide the electric field line into two parts which are respectively directed to the edge of the upper and lower inductive-plates. Then the nanofibers move along the electric field line, suspend and align between the parallel inductive-plates. Finally, the well aligned nanofibers could be easily transferred onto other substrates for further characterizations and applications. The aligned nanofibers with an average diameter of 469 ± 115 nm and a length as long as 140 mm were successfully achieved by using PIES technique. Moreover, nanofiber arrays with different cross angles and three-dimensional films formed by the aligned nanofibers were also facilely obtained. The novel PIES developed in this work has been proved to be a facile, cost-effective and promising approach to prepare aligned nanofibers for a wide range of applications.
Novel application of Poincaré analysis to detect and quantify exercise oscillatory ventilation
Authors: Welch Ryan , Kolbe John , Lardenoye Mandy , Ellyett Kevin
Published: March 2021

Objective. Exercise oscillatory ventilation (EOV) is frequently observed in individuals with cardiac disease. Assessment of EOV relies on pattern recognition and this subjectivity and lack of quantification limits the widespread clinical use of EOV as a prognostic marker. Poincaré analysis quantifies the short (SD1) and long-term (SD2) variability of a signal and may provide an alternative means to identify and quantify unstable exercise breathing patterns. This study aimed to determine if Poincaré analysis can distinguish between the breathing patterns of healthy control subjects and individuals being assessed for heart transplantation with and without EOV. Approach. Thirty-nine subjects performed a cardiopulmonary exercise test as part of heart transplant assessment and were subjectively classified into two groups according to the presence of EOV: non-EOV (n = 19) and EOV (n = 20). The control group (n = 24) consisted of healthy adults. Poincaré analysis (SD1 and SD2) was performed for minute ventilation (

V
̇

E) and tidal volume (VT) normalized to forced vital capacity (

V
̇

En
and

V
̇

Tn
), and breathing frequency (BF) for breath-by-breath data over the 10–15 ml · min−1 · kg−1

V
̇

O2
range. Main results. Poincaré analysis showed similar exercise ventilatory responses between the non-EOV and control group. BF was found to discriminate between subjects with stable and unstable ventilation. BF SD1 was significantly higher in the EOV group compared to the non-EOV (7.9 versus 4.6, p < 0.01) and control (7.9 versus 4.2, p < 0.01) groups. The EOV group had significantly greater BF SD2 compared to the non-EOV (5.7 versus 3.5, p < 0.01) and control (5.7 versus 3.5, p < 0.01) groups. Significance. We demonstrated that this novel application of Poincaré analysis can objectively distinguish and quantify unstable from stable breathing patterns during exercise. In subjects being assessed for heart transplantation the presence of EOV is associated with greater BF variability. Poincaré analysis provides an objective measure to identify and quantify EOV. Summary at a glance. As EOV may indicate abnormal ventilatory control, there is a need for an objective measure to identify and quantify unstable from stable ventilation during exercise. We developed a method of quantifying BF variation by the application of Poincaré analysis and demonstrated higher than normal variability of BF in subjects being assessed for heart transplantation who demonstrated EOV.
KMAG: KPLO Magnetometer Payload
Authors: Lee Hyojeong , Jin Ho , Jeong Byungwook , Lee Seungah , Lee Seongwhan , Baek Seul-Min , Shin Jehyuck , Lee Jung-Kyu , Park Hyeonhu , Kim Khan-Hyuk , Son Derac
Published: March 2021

Kplo-MAGnetometer (KMAG) is one of the scientific instruments of Korea Pathfinder Lunar Orbiter (KPLO) set to be launched in 2022. Its objectives are magnetic field investigation and technical demonstration near the surface of the Moon. Specifically, it will investigate the lithospheric magnetism of the Moon and measure the electromagnetic wave properties near the lunar surface. It consists of three fluxgate magnetometers on a 1.2 m long boom, which is relatively shorter than the boom used in other missions. The three magnetometers are included for scientific measurements, redundancy checks, and multi-sensor technical investigation. The magnetometers and an inner Anisotropic Magneto-Resistive sensor perform simultaneous sampling to correct for the magnetic field interference caused by the spacecraft. The fully integrated flight model assembly showed that the magnetometer noise level was less than 30 pT Hz−1/2 at 1 Hz and stability was within ±0.2 nT at the 10 Hz sampling rate. This paper describes the configuration and performance of the KMAG using the multi-sensing method. KPLO, THEMIS-ARTEMIS spacecraft, and Commercial Lunar Payload Service modules will be in their operational phase simultaneously. Therefore, the KMAG will be able to contribute to multi-site in-situ measurements of the lunar magnetic field. We expect that the KMAG will provide an up-to-date lunar observation data set and an opportunity to perform the multi-sensor observation.
Entanglement generation and protection for two atoms in the presence of two parallel mirrors
Authors: Ye Yuhong , Yu Hongwei , Hu Jiawei
Published: March 2021

We study, in the framework of open quantum systems, the entanglement generation of two atoms in between two parallel mirrors in a thermal bath of quantum scalar fields. We find that the presence of mirrors plays an important role in entanglement generation and protection. The entanglement dynamics is crucially dependent on the geometric configurations of the two-atom system with respect to the mirrors, and the ranges of temperature and interatomic separation within which entanglement can be generated are significantly changed compared with those in a free space. In particular, when the atomic transition wavelength is larger than twice the distance between the two mirrors, the atoms behave as if they were isolated from the environment and the entanglement can persist in the steady state if the atoms are initially entangled and no entanglement can be created if they are initially separable, no matter how the atoms are placed with respect to the mirrors and to each other. This is in sharp contrast to the fact that in a free space, steady-state entanglement is possible only when the two atoms are placed extremely close to each other, while in the presence of one mirror, it is possible when the two atoms placed extremely close to the mirror.
Exploring effects of tensor force and its strength via neutron drops *
Authors: Wang Zhiheng , Naito Tomoya , Liang Haozhao , Long Wen Hui
Published: March 2021

The tensor-force effects on the evolution of spin-orbit splittings in neutron drops are investigated within the framework of the relativistic Hartree-Fock theory. For a fair comparison on the pure mean-field level, the results of the relativistic Brueckner-Hartree-Fock calculation with the Bonn A interaction are adopted as meta-data. Through a quantitative analysis, we certify that the

-pseudovector (

-PV) coupling affects the evolutionary trend through the embedded tensor force. The strength of the tensor force is explored by enlarging the strength

of the

-PV coupling. It is found that weakening the density dependence of

is slightly better than enlarging it with a factor. We thus provide a semiquantitative support for the renormalization persistency of the tensor force within the framework of density functional theory. This will serve as important guidance for further development of relativistic effective interactions with particular focus on the tensor force.
The moment generating function of pairwise velocity in the context of redshift space distortion
Authors: Zhao Jing-Wei , Chen Jun-De
Published: March 2021

We study the connections between the pairwise velocity moment generating function G(k
∥, r) and redshift space distortion (RSD) modeling. Here k
∥ is the Fourier wavevector parallel to the line of sight, and r is the pair separation vector. We demonstrate its usage by two examples. (1) Besides the known relations between G and the RSD power spectrum (and the correlation function), we propose a new RSD statistics Ps
(k
∥,r
⊥) whose connection to G is convenient to evaluate numerically. (2) We then develop a fast method to numerically evaluate G, and apply it to a high resolution N-body simulation. We find that G (ln G) shows complicated dependence on k
∥ beyond the linear and quadratic dependencies. This not only shows inaccuracy in some existing models and identifies sources of inaccuracy but also provides possible ways of improving the RSD modeling. Consequently, more comprehensive investigations on G are needed to fully explore the usage of G in RSD modeling.
Are pulsar giant pulses induced by re-emission of cyclotron resonance absorption?
Authors: Lu Ji-Guang , Wang Wei-Yang , Peng Bo , Xu Ren-Xin
Published: March 2021

It is conjectured that coherent re-emission of cyclotron resonance absorption could result in pulsar giant pulses. This conjecture seems reasonable as it can naturally explain the distribution of pulsars with giant pulses on theP-P˙diagram.
An HI intensity mapping survey with a Phased Array Feed
Authors: Li Lin-Cheng , Staveley-Smith Lister , Rhee Jonghwan
Published: March 2021

We report results from a neutral hydrogen (H i) intensity mapping survey conducted with a Phased Array Feed (PAF) on the Parkes telescope. The survey was designed to cover ∼ 380 deg2 over the redshift range 0.3 < z < 1 (a volume of ∼ 1.5 Gpc3) in four fields covered by the WiggleZ Dark Energy Survey. The results presented here target a narrow redshift range of 0.73 < z < 0.78 where the effect of radio frequency interference (RFI) was less problematic. The data reduction and simulation pipeline was described, with an emphasis on flagging of RFI and correction for signal loss in the data reduction process, particularly due to the foreground subtraction methodology. A cross-correlation signal was detected between the H i intensity maps and the WiggleZ redshift data, with a mean amplitude of ⟨ΔT
b
δ
opt⟩ = 1.32 ± 0.42 mK (statistical errors only). A future Parkes cryogenic PAF is expected to detect the cross-correlation signal with higher accuracy than previously possible and allow measurement of the cosmic H i density at redshifts up to unity.
He-shell flashes on the surface of oxygen-neon white dwarfs
Authors: Guo Yunlang , Liu Dongdong , Wu Chengyuan , Wang Bo
Published: March 2021

Accretion induced collapse (AIC) may be responsible for the formation of some interesting neutron star binaries (e.g., millisecond pulsars, intermediate-mass binary pulsars, etc). It has been suggested that oxygen-neon white dwarfs (ONe WDs) can increase their mass to the Chandrasekhar limit by multiple He-shell flashes, leading to AIC events. However, the properties of He-shell flashes on the surface of ONe WDs are still not well understood. In this article, we aim to study He-shell flashes on the surface of ONe WDs in a systematic approach. We investigated the long-term evolution of ONe WDs accreting He-rich materialwith various constantmass-accretion rates by time-dependent calculationswith the stellar evolution codeModules for Experiments in Stellar Astrophysics (MESA), in which the initial ONeWD masses range from 1.1 to 1.35 M
⊙. We found that the mass-retention efficiency increases with the ONe WD mass and the mass-accretion rate, whereas both the nova cycle duration and the ignition mass decrease with the ONe WD mass and the mass-accretion rate. We also present the nuclear products in different accretion scenarios. The results presented in this article can be used in the future binary population synthesis studies of AIC events.
Indium–gallium–zinc–oxide thin-film transistors: Materials, devices, and applications
Authors: Zhu Ying , He Yongli , Jiang Shanshan , Zhu Li , Chen Chunsheng , Wan Qing
Published: March 2021

Since the invention of amorphous indium–gallium–zinc–oxide (IGZO) based thin-film transistors (TFTs) by Hideo Hosono in 2004, investigations on the topic of IGZO TFTs have been rapidly expanded thanks to their high electrical performance, large-area uniformity, and low processing temperature. This article reviews the recent progress and major trends in the field of IGZO-based TFTs. After a brief introduction of the history of IGZO and the main advantages of IGZO-based TFTs, an overview of IGZO materials and IGZO-based TFTs is given. In this part, IGZO material electron travelling orbitals and deposition methods are introduced, and the specific device structures and electrical performance are also presented. Afterwards, the recent advances of IGZO-based TFT applications are summarized, including flat panel display drivers, novel sensors, and emerging neuromorphic systems. In particular, the realization of flexible electronic systems is discussed. The last part of this review consists of the conclusions and gives an outlook over the field with a prediction for the future.
Cluster mathematical model for conjugate thermal processes of the isothermal bodies system in the fluid flow
Authors: Madera A G
Published: March 2021

There has been developed a cluster mathematical modelling method for non-stationary thermal processes, occurring in complex technical system structures, which thermal models represent a system of clusters. Each cluster has a core, combining the heat-emitting elements that fall into the said cluster, a shell of the cluster, and a fluid, flowing through the cluster. The state of the thermal process in each cluster at any specific time is characterized by three state variables, namely, by the temperatures of the core, the temperatures of the shell and the ambient temperature. At that, the elements of each cluster (core, shell, fluid flow) exchange heat with each other and the elements of the adjacent clusters. As opposed to existing methods, the cluster method allows modelling thermal processes that occur in complex technical systems, taking into account non-uniform temperature distribution in the fluid flow, conjugate nature of heat transfer between the fluid flow, the cores and the shells of the clusters. The mathematical model, describing state variables of thermal processes in the cluster thermal model, represents a system of block matrix differential equations with matrix and vector blocks, corresponding to the respective clusters of the thermal model. The solution of equations of the mathematical model is the values of the state variables of the thermal processes in the clusters. The methodology of the application of the cluster method is shown on the example of a real technical system.
Heat exchange at the boiling of ozone-safe refrigerants and their oil-freon mixtures
Authors: Ovsyannik A V , Arshukov A I , Kovalchuk P A
Published: March 2021

The object of research is the processes of heat and mass transfer during phase transitions of ozone-safe refrigerants and their oil-freon mixtures on smooth finned and capillary-porous heat-transfer surfaces of industrial heat exchange apparatuses.

The purpose and objectives of the research was theoretical and experimental research of processes of heat transfer in developed bubble boiling of ozone friendly refrigerant and oil-refrigerant mixtures on smooth and developed surfaces of heat exchange by establishing relationships to determine the coeffi-cients of heat transfer and influence of the various factors that determine the intensity of heat transfer at phase transitions in devices of refrigeration, heat pump systems and air conditioning systems; the estab-lishment of the mechanism of heat transfer processes during evaporation of oil-refrigerant mixtures. De-velopment of practical recommendations for the calculation and design of high-efficiency heat exchange equipment, reducing the material consumption and weight and size indicators of heat exchangers. Development and implementation of improved performance vaporizers and condensers for refrigeration, heat pump installations and air conditioning systems.

For the first time, experimental studies of heat exchange processes during the boiling of refriger-ants and their oil-freon mixtures on various surfaces in a wide range of thermal loads (2,9…100,8 kW / m2). Graphic dependences of the heat transfer intensity on the operating parameters of the boiling process and other characteristics are obtained.

The results of the work are implemented in the technological process of VESA LLC and in the educational process of Sukhoi state technical University for lectures on the disciplines “heat and mass Transfer” and “Industrial heat and mass transfer processes and installations”.

The results obtained can be used in the development and creation of highly efficient evaporative heat ex-changers.
Detecting chaos in time series
Authors: Gerasimov D N , Morgunova S B
Published: March 2021

The method to detect the chaotic nature of a time series is proposed. The algorithm works well for known chaotic systems like the Lorenz attractor.
Experiments of superfluid helium flow in a channel with a monodisperse backfill
Authors: Puzina Yu Yu , Kryukov A P , Korolyov P V , Yachevskiy I A
Published: March 2021

The experimental data on the superfluid helium flow in a U-shaped channel filled with a monodisperse backfill at a certain length is considered in this paper. The entire channel is immersed in a volume of superfluid helium. A flat heater is located in one end of the channel. When the heat load is applied, a vapor plug is formed in the channel. The column of superfluid helium begins to fluctuate in size with a constant amplitude and frequency. On the basis of the video recording of experiments, the dependence of the coordinate of the interfacial surface on time was plotted, and a qualitative analysis of heat and mass transfer processes is performed.
Gradient heat flux measurement in study of condensation at inner surface of the tube
Authors: Sapozhnikov S Z , Mityakov V Y , Babich A Y , Zainullina E R
Published: March 2021

To study heat transfer during water steam condensation in the pipe, experiments were carried out with a steam supply from the top pipe edge with the gradient heatmetry. The results which allowed us to apply the new method for non-classical problem have shown compliance with literature data. When the pipe is inclined, the distribution of heat flux per unit area on the inner surface becomes asymmetric, that’s why it is necessary to measure local heat flux in some points there. The distribution of local heat transfer coefficients on the inner surface of the pipe at different angles of inclination is obtained. The heat flux decreases in the lower part of the pipe section, which corresponds to increasing of the condensate film thickness in this area.
Effect of the horseshoe-shaped vortex on heat transfer in vicinity of the leading edge of a cylinder immersed in the turbulent free convection boundary layer on a vertical plate
Authors: Chumakov Yu S , Smirnov E M , Levchenya A M , Panov D O
Published: March 2021

Measurement data obtained with a thermo-resistance (wolfram-wire) probe for fluctuating temperature field in the front of a finite-height adiabatic circular cylinder disturbing the turbulent free convection boundary layer on a heated vertical flat plate are presented. The measurements were focused on detection of the effects attributed to action of the horseshoe-shaped vortex structures developing in the flow separation zone upstream of the obstacle. It is shown that near-wall air temperature gradients at some measurement positions are dramatically higher, if compared with profiles measured far away from the obstacle. It points in particular to highly intensified heat transfer in the flow region under study. The experimental mean temperature profiles are compared with results of previous RANS- and LES-based numerical studies performed by the authors under conditions that were close to those adopted in the experiments. It is shown that the LES-predicted temperature distributions are in a good accordance with the experimental results. The steady-state solution obtained with the RANS approach partially overpredicts the deformation of the temperature field attributed to action of the horseshoe-shaped vortices, which are substantially unsteady in the reality.
Comparative analysis of energy efficiency of ballast tank anti-freezing systems
Authors: Bagaev D V , Syraleva M N , Kudinovich I V
Published: March 2021

Choosing the best way to deal with the internal icing of ballast tanks is the important task of the designing Arctic vessels. To prevent excessive ice formation in the ballast tank, various methods are used, the main of which are: heating the water and increasing of the water circulation intensity inside the tank (air and steam bubbling, forced water circulation). The report presents qualitative assessment of the heating method and air bubbling system and investigation of energy efficiency of anti-freezing systems.
Numerical investigation of hydrodynamic processes in combustion chamber with an intensified fluidized bed
Authors: Babakhodjaev R P , Mirzaev D A
Published: March 2021

A gas suspension fluidized bed is reviewed, as an intensified fluidized bed, where the principles of classical spouted and fluidized beds are used together. A physical model of the process is presented. The working chamber consists of horizontally arranged sections, with spouted bed of gas suspension in the lower section and fluidized bed here in the upper section. Moreover, the lower section has a geometric shape in the form of a truncated regular pyramid. The basic formulas of mathematical modeling and the results of a numerical investigation of the hydrodynamics of a combustion chamber with an intensified fluidized bed are presented. The resulting mathematical model solved by the fourth-order Runge-Kutta method in the Matlab software environment. The graphs of changes in the velocity of gases and solid particles, pressure loss of a gas suspension depending on the height of the working chamber and the angle between the vertical axis and the side faces of the lower part of the section are obtained. Also obtained graphs characterizing the rise time of solid particles in height and their residence time in sections of the working chamber.
Separation of heat transfer mechanisms in porous refractory thermal insulation materials
Authors: Skurikhin A V , Kostanovsky A V
Published: March 2021

The results of estimation of three heat transfer mechanisms in porous refractory thermal insulating materials on example of exfoliated vermiculite at temperatures near 626, 773 and 910 K using experimental data by additive approach are presented.
Common features of swirling motion of two immiscible fluids in closed vortex reactors
Authors: Naumov I V , Shtern V N , Tsoy M A , Sharifullin B R
Published: March 2021

The paper analyses the typical topology of swirling flows of two immiscible fluids generated in the cylindrical container by its rotating end wall. Using the flow visualization and velocity measurements by PIV for different parameters of rotation of the upper end of the cylinder, this study reveals general features of the evolution of counter flow (bubble-like vortex breakdown, VB) which is common for vortex flows with various liquids at the interface or the solid rotated end. In both fluids, the rotation generates centrifugal meridional circulations and a local circulation cell (vortex breakdown bubble, VBB). The research shows that the scenario for the VBB appearance depends weakly on the properties of the medium that restricts the circulation of the working fluid. Patterns and formation of cellular structure appear common for flows with “liquid bottom” and “liquid rotating lid”. The VBB scenario is similar to that occurring in a single-fluid flow and in the upper or lower fluids of a two-fluid flow, but the range of the Reynolds numbers can be different depending on the volume of the upper fluid and kinematic viscosity of the lower liquid. This study can serve as the first step in the “rotating liquid lid” and “liquid lid” technology for chemical and biological processes where fine, gentle, and nonintrusive mixing is favourable.
Features of particle flows hydrodynamics in recirculating systems and pneumatic valves of CFB boilers
Authors: Ryabov G A , Folomeev O M
Published: March 2021

Circulating fluidized bed (CFB) technology is characterized by relatively high reactor velocity that exceed the transport velocity of medium-sized particles, and the presence of separators (mainly of the cyclone type) with a system for returning trapped particles to the reactor. These systems consist of downpipes equipped in the lower part with pneumatic valves for transporting material from the low (atmospheric) pressure zone in the cyclone to the high-pressure zone in the furnace. Pneumatic valves operate on the principle of fluidized valves, and the locking function of the valves is performed by a lifting section with an inclined return flow to the furnace (loop gate or J-valve) or a horizontal section connecting the drain to the furnace (L-valve). The report discusses the current state of development and methods for standpipe and pneumatic valve operation and calculating. A brief description of the test rigs and the results of our own studies of CFB returned system are given. The results of the work can be used for the design and commissioning of a circulating fluidized bed reactors, including systems with dual reactors for polygenerating systems and chemical looping.
Laboratory modeling of hydrodynamic instability and sound generation processes in the ship NPS
Authors: Sergeev D A , Kandaurov A A , Suvorov A S
Published: March 2021

This work is devoted to investigations of the self-oscillation regimes in the model of emergency stop valve chamber in the ductline of the systems of heat exchange in the ship nuclear power setup (NPS). Experiments were carried out on special aeroacoustical setup with simultaneous use of PIV methods for measuring velocity fields and measurements of sound generation characteristics. Dependency of parameters of self-oscillation regimes on the parameter of the length of the gap between the inlet and outlet ducts in the chamber was investigated. An explanation of the observed regimes was proposed.
Problem of heat transfer in compact heat exchangers using variable thermal resistance
Authors: Chichindaev A V , Dyachenko Yu V , Sidenko D E , Shakin A D
Published: March 2021

The paper presents the results of a complex of studies, analysis of the efficiency of the heat exchangers of aircraft ACS, as well as developed methods for protecting the heat transfer surface from freezing and thermal stresses. The basis of the work was the results of experimental studies of heat and mass transfer of a three-phase flow of “moist air - supercooled water aerosol” with a negative temperature in the CPFHE channels. As well as previously developed methods for modeling the processes of local heat transfer in compact heat exchangers with two-phase coolants (condenser) and in the presence of thermal stresses at high temperatures of hot air (preliminary heat exchanger). The proposed methods are based on the idea of obtaining a given surface temperature by changing the thermal resistances during the heat transfer process. The improvement of the models consists in taking into account the variable thermal resistances along the length of the hot and cold tract. In particular, the parameters of heat transfer processes defined by the geometry of the fins and flow regimes, as well as local heat and mass transfer processes during phase transitions.
Numerical simulation of the particle size distribution function evolution of an ultradispersed system in a vapor-gas medium
Authors: Ginevsky A F , Volgin Y S
Published: March 2021

To control the process of nanopowders generating in order to ensure the required characteristics, it is necessary to solve the general physical problem of vaporization and condensation of steam in a gas-phase synthesis plant. A model of the physical problem should describe besides the formation of condensed particles, the hydrodynamic features of the flow, as well as heat exchange processes with other objects inside the working chamber. The questions of interaction of particles within an ultradispersed system through coagulation were considered. A mathematical model that describes the process of coagulation of a monodisperse system inside the evaporation-condensation chamber was formulated. A variant of the optimization of a coagulation numerical model in an ultradispersed system by reducing the number of sections corresponding to particle fractions of the mass scale was proposed. The use of an reduced scale made it possible to optimize the information received, and also gave advantages in the speed of calculations, which made it possible to reduce the time spent in problems with coagulation of systems.
Experimental investigation of spray propagation under crossflow conditions with Shadowgraph and Schlieren techniques
Authors: Zueva T S , Weiss L , Wensing M , Garyaev A B
Published: March 2021

This paper is devoted to the description and analysis of the experimental results which were carried out to investigate sprays of liquid hydrocarbons under crossflow conditions. The experimental conditions corresponded to the injection conditions of gasoline sprays in a cylinder of an internal combustion engine. Two types of liquid hydrocarbons, isooctane and ethanol, were used as injected fuels. The injection pressure varied between 100 and 170 bar, the air crossflow velocity ranged from 0 till 50 ms-1 and the fuel temperature from 25 till 98 °C. Two optical methods, Shadowgraph and Schlieren, were used to visualize the spray movement over time. The boundaries of liquid and vapour spray phases as well as basic principles of spray propagation and evaporation under crossflow conditions were obtained after processing and analysing these images.
Experimental study of the shock wave influence on adiabatic wall temperature in a supersonic air-droplet flow
Authors: Popovich S S , Zditovets A G , Kiselev N A , Vinogradov Y A
Published: March 2021

The results of an experimental study of the thermal parameters of a supersonic flow around a flat wall in the presence of finely divided water droplets are presented. The relative mass flow rate of the liquid (mass concentration) varied in the range 0.05-0.5%. Liquid (distilled water) was sprayed through centrifugal nozzles into the air flow in the prechamber of the supersonic wind tunnel. Next, the adiabatic wall temperature for the given flow conditions was measured with the use of infrared thermal imager. The input flow Mach number was 2.5, the Reynolds number based on the dynamic boundary layer length from the nozzle throat was at least 2·107 at the nozzle exit section. The research was performed at the experimental facilities of the Institute of Mechanics of Lomonosov Moscow State University.
Analysis of experiments on condensation induced water hammers at KGU test facility by WAHA code
Authors: Volkov G J , Melikhov V I , Melikhov O I , Nikonov S M
Published: March 2021

Experiments at the KGU test facility, devoted to steam induced water hammers were analysed with the WAHA code. Test section of the KGU test facility is slightly inclined horizontal pipe of 3 m length and of 64 mm inner diameter. Subcooled water was supplied to the pipe inlet, pipe outlet was connected to separator vessel. Upper part of separator vessel was connected to steam source. Experiments were performed for different system pressure, different water subcooling and different mass flow rate of water supply. The WAHA code has been developed for simulation of condensation induced water hammers in pipelines. It is based on two-fluid approach, WAHA numerical scheme is based on Godunov numerical methods. Numerical simulations of the KGU tests revealed disagreement between numerical and experimental occurrences of water slug formations and water hammers events. Methodological calculations with variation of heat transfer to subcooled water showed, that this value significantly influences on water slug and water hammer formation.
Numerical simulation of the liquid film suction process through the slots of various geometry in the last stages of steam turbines
Authors: Gribin V G , Tishchenko A A , Alekseev R A , Gavrilov I Yu , Popov V V , Tishchenko V A
Published: March 2021

The liquid film suction process through the slot is considered. The stator blade row of the last stage of the steam turbine was used as an object of study. Based on the CFD modelling of two-phase flow in blades cascade the boundary conditions for slots modelling have been obtained. The numerical analyses of film removal were conducted in a domain including only a flow zone near the studied slot. The multi-phase VOF model was used to calculate the interaction between liquid and steam phases and model the interface evolution during the water removal process. Four different geometries of the slots were considered. For each of them, the unsteady calculations at two different operating regimes have been performed. The numerical results provide information about film suction details in a space of the slot. The behaviour of the film flow was analysed for each slot shape. The conditions of the film separation and its further breakup have been considered. For the studied slot designs efficiency analysis was performed. The results have shown how the way the liquid film moves in the slot effects on the removed water and steam mass flow rates.
Numerical simulation of pollutant dispersion in a test ventilated room
Authors: Ivanov N G , Podmarkova A D , Zasimova M A , Markov D
Published: March 2021

The paper presents the numerical study of 3D flow and neutrally buoyant pollutant transport in a model atrium under conditions of test experiment by Thatcher et al. (2004) with a controlled uranine dye spill. For the Reynolds number of 2160 the Reynolds-Averaged Navier-Stokes approach was applied. Analysis of CFD predictability for a steady-state fully-developed regime and a transient process was done in comparison with the experimental data on contaminant concentration fields. For various positions of the contaminant source the ventilation effectiveness was computed and discussed.