scholarly journals Design and fabrication of a vigorous “cavitation-on-a-chip” device with a multiple microchannel configuration

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Farzad Rokhsar Talabazar ◽  
Mohammad Jafarpour ◽  
Merve Zuvin ◽  
Hongjian Chen ◽  
Moein Talebian Gevari ◽  
...  
Keyword(s):  
High Speed ◽  
Microelectromechanical Systems ◽  
Hydrodynamic Cavitation ◽  
Poly Vinyl Alcohol ◽  
Cavitation Inception ◽  
New Device ◽  
Upstream Pressure ◽  
Sudden Decrease ◽  
Single Flow ◽  
New Generation

AbstractHydrodynamic cavitation is one of the major phase change phenomena and occurs with a sudden decrease in the local static pressure within a fluid. With the emergence of microelectromechanical systems (MEMS), high-speed microfluidic devices have attracted considerable attention and been implemented in many fields, including cavitation applications. In this study, a new generation of ‘cavitation-on-a-chip’ devices with eight parallel structured microchannels is proposed. This new device is designed with the motivation of decreasing the upstream pressure (input energy) required for facile hydrodynamic cavitation inception. Water and a poly(vinyl alcohol) (PVA) microbubble (MB) suspension are used as the working fluids. The results show that the cavitation inception upstream pressure can be reduced with the proposed device in comparison with previous studies with a single flow restrictive element. Furthermore, using PVA MBs further results in a reduction in the upstream pressure required for cavitation inception. In this new device, different cavitating flow patterns with various intensities can be observed at a constant cavitation number and fixed upstream pressure within the same device. Moreover, cavitating flows intensify faster in the proposed device for both water and the water–PVA MB suspension in comparison to previous studies. Due to these features, this next-generation ‘cavitation-on-a-chip’ device has a high potential for implementation in applications involving microfluidic/organ-on-a-chip devices, such as integrated drug release and tissue engineering.

Materials for bullet core

2020 ◽  
Vol 2020 (10) ◽  
pp. 8-21
Author(s):  
A. G. Kolmakov ◽  
◽  
I. O. Bannykh ◽  
V. I. Antipov ◽  
L. V. Vinogradov ◽  
...  
Keyword(s):  
High Speed ◽  
Bending Strength ◽  
Low Alloy Steels ◽  
Hard Alloys ◽  
Small Arms ◽  
Alloy Steels ◽  
Materials Used ◽  
Basic Ideas ◽  
New Generation ◽  
Natural Composite

he basic ideas about the process of introducing cores into protective barriers and the most common core patterns and their location in conventional and sub-caliber small arms bullets are discussed. The materials used for manufacture of cores are analyzed. It is concluded that for mass bullets of increased armor penetration the most rational choice can be considered the use of high-carbon low-alloy steels of a new generation with a natural composite structure and hardness of up to 70 HRC. For specialized armor-piercing bullets, cores made from promising economically-alloyed high-speed steels characterized by a high complex of «hardness—bending strength» are better alternative than ones made of hard alloys or tungsten alloys.

scholarly journals 2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hitesh Agarwal ◽  
Bernat Terrés ◽  
Lorenzo Orsini ◽  
Alberto Montanaro ◽  
Vito Sorianello ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hafnium Oxide ◽  
High Speed ◽  
Hexagonal Boron Nitride ◽  
Temperature Stability ◽  
Cost Effective ◽  
Fold Increase ◽  
Building Blocks ◽  
High Quality ◽  
New Device

AbstractElectro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon (Si) devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. In this work, we overcome this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. We integrated hafnium oxide (HfO2) and two-dimensional hexagonal boron nitride (hBN) within the insulating section of a double-layer (DL) graphene EA modulator. This combination of materials allows for a high-quality modulator device with high performances: a ~39 GHz bandwidth (BW) with a three-fold increase in modulation efficiency compared to previously reported high-speed modulators. This 2D-3D dielectric integration paves the way to a plethora of electronic and opto-electronic devices with enhanced performance and stability, while expanding the freedom for new device designs.

High-Speed Imaging to Study an Auto-Oscillating Vocal Fold Replica for Different Initial Conditions

2017 ◽  
Vol 09 (05) ◽  
pp. 1750064 ◽  
Author(s):  
A. Van Hirtum ◽  
X. Pelorson
Keyword(s):  
Vocal Fold ◽  
High Speed ◽  
Initial Conditions ◽  
Vocal Folds ◽  
High Speed Imaging ◽  
Human Voice ◽  
Manual Intervention ◽  
Geometrical Features ◽  
Upstream Pressure

Experiments on mechanical deformable vocal folds replicas are important in physical studies of human voice production to understand the underlying fluid–structure interaction. At current date, most experiments are performed for constant initial conditions with respect to structural as well as geometrical features. Varying those conditions requires manual intervention, which might affect reproducibility and hence the quality of experimental results. In this work, a setup is described which allows setting elastic and geometrical initial conditions in an automated way for a deformable vocal fold replica. High-speed imaging is integrated in the setup in order to decorrelate elastic and geometrical features. This way, reproducible, accurate and systematic measurements can be performed for prescribed initial conditions of glottal area, mean upstream pressure and vocal fold elasticity. Moreover, quantification of geometrical features during auto-oscillation is shown to contribute to the experimental characterization and understanding.

Behavior of Unsteady Turbulent Starting Round Jets

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Neerav Abani ◽  
Jaal B. Ghandhi
Keyword(s):  
High Speed ◽  
Penetration Rate ◽  
Injection Rate ◽  
Injection Velocity ◽  
Time Varying ◽  
Velocity Change ◽  
Rate Of Penetration ◽  
Round Jets ◽  
The Difference ◽  
Sudden Decrease

Turbulent starting jets with time-varying injection velocities were investigated using high-speed schlieren imaging. Two solenoid-controlled injectors fed a common plenum upstream of an orifice; using different upstream pressures and actuation times, injection-rate profiles with a step increase or decrease in injection velocity were tested. The behavior of the jet was found to be different depending on the direction of the injection-velocity change. A step increase in injection velocity resulted in an increased rate of penetration relative to the steady-injection case, and a larger increase in injection velocity resulted in an earlier change in the tip-penetration rate. The step-increase data were found to be collapsed by scaling the time by a convective time scale based on the tip location at the time of the injection-velocity change and the difference in the injection velocities. A sudden decrease in injection velocity to zero was found to cause a deviation from the corresponding steady-pressure case at a time that was independent of the initial jet velocity, i.e., it was independent of the magnitude of the injection-velocity change. Two models for unsteady injection from the literature were tested and some deficiencies in the models were identified.

Synthesis and Analysis of a Combined Magnetic and Gas Dynamic Suspension for a Model Range of New-Generation High-Speed Micro Gas Turbine Power Units

2021 ◽  
pp. 5-17
Author(s):  
Sergey A. GANDZHA ◽  
◽  
Nikolay I. NEUSTROEV ◽  
Pavel A. TARANENKO ◽  
◽  
...  
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Turbine Unit ◽  
Electrical Machine ◽  
Gas Turbine Unit ◽  
Micro Gas Turbine ◽  
Gas Dynamic ◽  
Study Results ◽  
Generator Design ◽  
New Generation

The modern power industry is characterized by intense development of distributed generation, with which numerous sources of different capacities are connected into a single network. This makes it possible to improve the reliability of the entire system, since the probability of several sources to fail simultaneously is quite low. Electric generation based on high-speed gas turbine units accounts for a significant share in the overall balance, due to which scientific research and new engineering solutions in this area are important and relevant. An innovative design of a high-speed gas turbine unit based on a switched axial generator is proposed. This electrical machine has a diamagnetic armature, which eliminates magnetic losses, due to which better efficiency of the power unit is achieved and its design is simplified. The high speed of rotation and the presence of critical resonant rotor speeds generated the need to adopt appropriate engineering decisions in regard of its supports. A combined suspension involving the use of magnetic and gas-dynamic bearings is proposed. The magnetic bearings support the gas turbine unit operation at low speeds during its acceleration, and the gas-dynamic bearings support its operation at high nominal speed. The generator design and the combined suspension layout are shown. The numerical analyses of magnetic and gas-dynamic bearings for a gas turbine unit for a capacity of 100 kW and rotation speed of 70 000 rpm are given. The study results can be used for a series of gas turbine units with capacities ranging from 10 to 500 kW. In our opinion, this concept is competitive with modern analogs with a radial generator design.

A New Device for High-Speed Biaxial Tissue Testing: Application to Traumatic Rupture of the Aorta

2005 ◽  
Author(s):  
Matthew J. Mason ◽  
Chirag S. Shah ◽  
Muralikrishna Maddali ◽  
King H. Yang ◽  
Warren N. Hardy ◽  
...  
Keyword(s):  
High Speed ◽  
Traumatic Rupture ◽  
New Device

Characterization and comparison of properties of cryogenic conditioned CNT reinforced thermoset (epoxy) and thermoplastic (poly vinyl alcohol) composite yarns

2021 ◽  
pp. 002199832110417
Author(s):  
Wei Chen ◽  
Yifan Wang ◽  
Kun Zhang ◽  
Fujun Xu
Keyword(s):  
Tensile Strength ◽  
Vinyl Alcohol ◽  
Thermoplastic Composite ◽  
Advanced Materials ◽  
Poly Vinyl Alcohol ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Composite Yarn ◽  
Thermoset Epoxy ◽  
New Generation

Carbon nanotube (CNT) fiber/yarn reinforced composites are considered as a new generation of advanced materials for applications in aerospace and space industry. In this study, two types of CNT composite yarns were produced by twisting CNT films and infiltrating with thermoset epoxy (EP) and thermoplastic poly vinyl alcohol (PVA) resins. The tensile strength of CNT/PVA and CNT/EP composite yarn was 409.91 MPa and 206.87 MPa, much higher than that of pure CNT yarn (129.94 MPa). After mono-cryogenic condition, the mechanical and electrical properties of CNT/EP and CNT/PVA composite yarns were both enhanced due to the structure reorder of the CNT bundles and improvement of interfacial bonding. However, after 60 times cyclic-cryogenic conditions, CNT/EP composite yarn showed a ∼10% degradation of tensile strength; while CNT/PVA composite yarn exhibited 6% increment. This study provides fundamental data of the CNT reinforced thermoset and thermoplastic composite yarns for their practical applications in cryogenic environment.

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