scholarly journals Механизм влияния дисперсных наночастиц на параметры мартенситных переходов в сплавах с эффектом памяти формы

2019 ◽  
Vol 61 (11) ◽  
pp. 2110
Author(s):  
Г.А. Малыгин
Keyword(s):  
Particle Concentration ◽  
Volume Concentration ◽  
Kinetic Equations ◽  
Martensitic Transformations ◽  
Transition Theory ◽  
Tini Alloy ◽  
Martensitic Transition ◽  
Particle Sizes ◽  
Coherent Coupling ◽  
Disperse Nanoparticles

AbstractWithin the diffuse martensitic transition theory based on the thermodynamic and kinetic equations and relations, the mechanism of influence of disperse nanoparticles on the parameters of martensitic transitions in alloys with the shape memory effect (SME) is analyzed. The objects of the analysis are the TiNi alloy with the varied sizes of Ti_3Ni_4 particle at their constant volume concentration, and the NiMnGaTb alloy with Tb precipitate particles with constant sizes and variation of volume concentration of the precipitates. Information about these alloys is available in the literature. The analysis has shown that, due to the coherent coupling of the Ti_3Ni_4 particles with the substrate, the temperature width of the transition R – B 19' depends on the particle sizes, which confirms the earlier established regularity of the local interior strain influence on this parameter. Concerning the NiMnGaTb alloy, the analysis has shown that, due to the presence of interior local strains associated with the Tb particles, the temperature width of the martensitic transformations increases linearly alongside the growth of the particle concentration in the alloy. The existence of the critical value of the particle concentration, above which the temperature width of the transition becomes indefinitely large, and the martensitic transformation in the alloy is blocked, is shown.

scholarly journals Dynamics of sheared droplets filled with non-Brownian particles

2020 ◽  
Vol 59 (12) ◽  
pp. 935-949
Author(s):  
Helene Van Ammel ◽  
Paula Moldenaers ◽  
Ruth Cardinaels
Keyword(s):  
Bulk Viscosity ◽  
Particle Concentration ◽  
Viscosity Ratio ◽  
Viscous Medium ◽  
Particle Sizes ◽  
Droplet Dynamics ◽  
Brownian Particles ◽  
Homogenous Medium ◽  
Single Droplets ◽  
Good Agreement

AbstractThe dynamics of single droplets containing non-Brownian particles are studied. The particle over droplet size ratio (r/R) is changed by using different particle sizes (r/R = 0.02–0.4). Additionally, the effect of particle concentration (5–20 vol%) is investigated. The dynamics of droplets with r/R = 0.02 show good agreement with the corresponding particle-free reference system which has a comparable viscosity ratio. Hence, this droplet phase can be considered as a homogenous medium characterized by its bulk viscosity which is governed by the particle concentration. However, droplets with r/R ≥ 0.1 show a more suppressed deformation and slower transient dynamics and, therefore, behave as a slightly more viscous medium than expected based on their bulk viscosity. These effects become more pronounced at higher particle concentrations and higher r/R. Moreover, local particle effects like asymmetric droplet shapes, oscillating droplet shapes, and tip streaming start to influence the droplet dynamics at particle concentrations around 15 vol%.

scholarly journals Interrelation of microstructure and thermodynamic parameters in TiNi alloy during multiple martensitic transformations

2019 ◽  
Vol 298 ◽  
pp. 00002
Author(s):  
Anna Churakova
Keyword(s):  
Thermodynamic Parameters ◽  
Rapid Heating ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Thermal Cycles ◽  
Fast Heating ◽  
Heating And Cooling ◽  
Coarse Grained State ◽  
Consistent Increase

The effect of multiple martensitic transformations on the microstructure and thermodynamic parameters of the alloy of the TiNi system was investigated. It was shown that in the Ti50Ni50 alloy, with an increase in the number of thermal cycles with rapid heating and cooling up to n = 100, a consistent increase in the dislocation density occurs, and a decrease in the width of martensitic plates is observed. And also, that in TCs with fast heating and cooling of the Ti50Ni50 alloy in a coarse-grained state, a change in the trend in the temperatures of martensitic transformations is observed — with an increase in the number of thermal cycles to n = 50, they decrease, and at n> 50 the temperatures increase.

Thermal-Hydraulic Performance of SiC-Water and Al2O3-Water Nanofluids in the Minichannel

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Ji Zhang ◽  
Yanhua Diao ◽  
Yaohua Zhao ◽  
Yanni Zhang
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Volume Concentration ◽  
Working Fluid ◽  
Al2o3 Nanoparticles ◽  
Particle Sizes ◽  
Enhance Heat Transfer ◽  
Flow And Heat Transfer ◽  
Effective Particle Size ◽  
Effective Particle

The single-phase flow and heat transfer behaviors of SiC and Al2O3 nanoparticles dispersed in water were studied experimentally in a multiport minichannel flat tube (MMFT). The volume concentrations of the two nanofluids ranged from 0.001% to 1%. Their effective particle sizes, thermal conductivities, and viscosities were also measured. Results indicated that these nanofluids as a working fluid could enhance heat transfer but increase pressure drop and the Nusselt number by up to 85%. The two nanofluids exhibited a common optimal volume concentration of 0.01% for heat transfer. Effective particle size was also found to have a significant effect on heat transfer.

Effect of Severe Plastic Deformation by Torsion on Structure and Properties of Ni54Mn21Ga25 and Ni54Mn20Fe1Ga25

2010 ◽  
Vol 168-169 ◽  
pp. 553-556
Author(s):  
N.I. Kourov ◽  
Vladimir Pushin ◽  
A.V. Korolev ◽  
V. Marchenkov ◽  
E. Marchenkova ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Physical Properties ◽  
Room Temperature ◽  
Martensitic Transformations ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Bridgman Anvil ◽  
Disordered Alloys ◽  
Cast Alloys

We report on the effect of severe plastic deformation by torsion under the Bridgman anvil pressure (SPDT) on structure and physical properties of the Ni54Mn21Ga25 and Ni54Mn20Fe1Ga25 alloys. Two types of samples were studied: ordered (cast) samples and nanocrystalline samples disordered by SPDT. The thermal expansion, thermo EMF, electro- and magnetoresistivity, Hall effect, and magnetization were measured from 4.2 to 800 K and in magnetic fields of up to 15T. We show that the deviation from the stoichiometric Ni50Mn25Ga25 composition shifts the temperatures of the martensitic transition TM and the magnetic (Curie) transition TC to room temperature. Large changes in the physical properties near TM and TC were discovered. The alloys become amorphous and nanocrystalline after the SPDT treatment. This process is accompanied by the disappearance of the martensitic transformations and of the nanocrystalline modulated substructures and, consequently, by the suppression of the magnetic shape-memory effect. The physical properties of the disordered alloys are also strongly changed. Subsequent annealing at Т ≥ 700 K leads to a practically full restoration of the structure and all properties characteristic of the initial cast alloys.

scholarly journals Size- and Time-Dependent Aerosol Removal from a Protective Box during Simulated Intubation and Extubation Procedures

COVID ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 315-324
Author(s):  
Luka Pirker ◽  
Metod Čebašek ◽  
Matej Serdinšek ◽  
Maja Remškar
Keyword(s):  
Particle Size ◽  
Particle Concentration ◽  
Time Frame ◽  
Time Dependent ◽  
Medical Professionals ◽  
Particle Sizes ◽  
Background Levels ◽  
Aerosol Generator ◽  
Plastic Bag ◽  
Measured Particle

Because the SARS-CoV-2 virus primarily spreads through droplets and aerosols, a protective box could provide adequate protection by shielding medical professionals during the intubation and extubation procedures from generated droplets and aerosols. In this study, size- and time-dependent aerosol concentrations were measured inside and outside the protective box in the particle size ranging from 14 nm to 20 μm during simulated intubation and extubation procedures. An improved protective box with active ventilation was designed based on a plastic bag with armholes covered with latex sheets that utilizes a supportive frame. Coughing during the intubation and extubation procedure was simulated using an aerosol generator which dispersed the aerosol powder into the protective box. During the intubation and extubation procedure, the concentration of particles increased inside the protective box but, due to the high negative airflow, quickly dropped to background levels. The particle concentration of all measured particle sizes decreased within the same time frame. No leakage of particles was observed through the armhole openings. The presented protective box design provides excellent protection against generated droplets and aerosols. The decrease in concentration does not depend on the particle size. Outside the box, particle concentration did not change with time.

scholarly journals Mechanical behavior and fractographic analysis of a TiNi alloy with various thermomechanical treatment

2019 ◽  
Vol 298 ◽  
pp. 00019 ◽  
Author(s):  
Anna Churakova ◽  
Anna Yudahina ◽  
Elina Kayumova ◽  
Nikita Tolstov
Keyword(s):  
Dislocation Density ◽  
Thermal Cycling ◽  
Thermomechanical Treatment ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Phase Hardening ◽  
Cold Upsetting ◽  
Cycling Treatment ◽  
Ultrafine Grained

Influence of thermomechanical treatment (deformation, thermal cycling treatment in the temperature range of martensitic transformations B2-B19’) on the TiNi alloys’ mechanical behaviour and fracture was studied. Different states were considered, they are initial coarse-grained (CG), ultrafine-grained (UFG) after ECAP (with a grain size of 200 nm), the state after ECAP and cold upsetting by 30% - UFG state with high dislocation density. It was shown that thermal cycling causes some increase in dislocation density, strength and microhardness in all the states. Thermal cycling of UFG alloys allows forming the states with non-equilibrium grain boundaries, with additional dislocations of “phase hardening”. The nature of the fracture was analysed in the TiNi alloy in various states.

Feeding of Copepodite and Adult Stages of Eudiaptomus Gracilis (G.O. Sars, 1863) (Copepoda, Calanoida) On Mixed Plastic Beads

Crustaceana ◽  
1994 ◽  
Vol 66 (1) ◽  
pp. 90-109 ◽  
Author(s):  
Nóra P. Zánkai
Keyword(s):  
Clearance Rate ◽  
Particle Concentration ◽  
Dry Weight ◽  
Size Spectrum ◽  
Particle Sizes ◽  
Lake Balaton ◽  
Clearance Rates ◽  
Experimental Animals ◽  
Feeding Experiments ◽  
Selection Of

AbstractSize selection of Eudiaptomus gracilis copepodites (CI-CV) and adults was studied in feeding experiments with beads of 1-84 μm diameter. Concentration of particles ranged between 1.3-2.1 x 107 beads ml-1, i.e. it was similar to the natural particle concentration. Animals were collected in Lake Balaton and acclimated to laboratory conditions for a few days before the experiments. On average, 91% of the experimental animals ingested beads. Almost each of the bead-ingesting animals took in 1 μm beads. Young copepodites had a narrow size spectrum (1-12 μm), whereas old copepodites and adults had broader spectra (1-39 μm). The number of ingested beads varied widely in each stage and among the individuals of the same stages. Diameter of the largest ingested bead, average number of beads in the guts, and clearance rate increased linearly with dry weight of the different stages (p < 0.001). Clearance rates were different for various particle sizes. Relatively high clearance rates were obtained for 6 μm and 10-12 μm beads in each stage. Moreover, older copepodites had higher clearance rates for beads of 20 and 25 μm diameter, and clearance rates of adults increased for larger than 30 μm particles. CI copepodites selected for particles of 4-12 μm diameter, and their selectivity increased with the increasing bead size within this range. Older stages selected only for beads larger than 12 μm, whereas adults did only for beads larger than 22 μm.

Computational Fluid Dynamics Simulation of Flow of Exhaled Particles From Powered-Air Purifying Respirators

2019 ◽  
Author(s):  
Susan S. Xu ◽  
Zhipeng Lei ◽  
Ziqing Zhuang ◽  
Michael Bergman
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Size ◽  
Simulation Study ◽  
Particle Concentration ◽  
Air Flow ◽  
Dynamics Simulation ◽  
Cfd Modeling ◽  
Particle Sizes ◽  
Flow Rates

Abstract In surgical settings, infectious particulate wound contamination is a recognized cause of post-operative infections. Powered air-purifying respirators (PAPRs) are widely used by healthcare workers personal protection against infectious aerosols. Healthcare infection preventionists have expressed concern about the possibility that infectious particles expelled from PAPR exhalation channels could lead to healthcare associated infections, especially in operative settings where sterile procedural technique is emphasized. This study used computational fluid dynamics (CFD) modeling to simulate and visualize the distribution of particles exhaled by the PAPR wearer. In CFD simulations, the outward release of the exhaled particles, i.e., ratio of exhaled particle concentration outside the PAPR to that of inside the PAPR, was determined. This study also evaluated the effect of particle sizes, supplied air flow rates, and breathing work rates on outward leakage. This simulation study for the headform and loose-fitting PAPR system included the following four main steps: (1) preprocessing (establishing a geometrical model of a headform wearing a loose-fitting PAPR by capturing a 3D image), (2) defining a mathematical model for the headform and PAPR system, and (3) running a total 24 simulations with four particle sizes, three breathing workloads and two supplied-air flow rates (4 × 3 × 2 = 24) applied on the digital model of the headform and PAPR system, and (4) post-processing the simulation results to visually display the distribution of exhaled particles inside the PAPR and determine the particle concentration of outside the PAPR compared with the concentration inside. We assume that there was no ambient particle, and only exhaled particles existed. The results showed that the ratio of the exhaled particle concentration outside to inside the PAPR were influenced by exhaled particle sizes, breathing workloads, and supplied-air flow rates. We found that outward concentration leakage from PAPR wearers was approximately 9% with a particle size of 0.1 and 1 μm at the light breathing and 205 L/min supplied-air flow rates, which is similar to the respiratory physiology of a health care worker in operative settings, The range of the ratio of exhaled particle concentration leaking outside the PAPR to the exhaled particle concentration inside the PAPR is from 7.6% to 49. We found that supplied air flow rates and work rates have significant impact on outward leakage, the outward concentration leakage increased as particle size decreased, breathing workload increased, and supplied-air flow rate decreased. The results of our simulation study should help provide a foundation for future clinical studies.

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