In Situ Plasma Characterization of Laser-Ablated BaxSr1-xTiO3

1997 ◽  
Vol 502 ◽  
Author(s):  
D. T. Venizelos ◽  
S. Sengupta ◽  
R. C. Sausa
Keyword(s):  
Electron Density ◽  
Emission Spectroscopy ◽  
High Speed ◽  
Substrate Surface ◽  
Leading Edge ◽  
Wave Theory ◽  
Oxide Material ◽  
Stark Broadening ◽  
High Speed Imaging ◽  
Time Resolved

ABSTRACTHigh speed imaging and emission spectroscopy are used to characterize the plumes generated from the ablation of bulk barium strontium titanium oxide material in vacuum and 30–60 mTorr of O2 using a pulsed 248-nm laser with fluences ranging from 5–8 J/cm2. High speed imaging reveals that in vacuum the leading edge of the plume expands normal to the substrate surface with a velocity of 19.7 km/sec. The ratio of distance traveled to the plume's radius is ˜ 2 at the early stages of the expansion and 3.2 at the later stages near the substrate. Similar observations are observed when the plume expands in 30 mTorr of O2 for times less than 2.0 μsec. However, at times greater than 2.0 μsec the plume's expansion is retarded due to collisional momentum transfer and reactions with the background gas. This effect is more pronounced when the plume expands in 60 mTorr of O2. Blast wave theory is used to model these results. Time-resolved emission spectroscopy of Ba(I) lines in the 735–770 nm region reveals that the plume' electron temperatures, Te, in a vacuum expansion range from 18000±2000 K at 0.1 μsec to 15000±1500 K at 2.0 /μsec. In contrast, in 30 mTorr of O2 the values of Te range from 17000±2000 K at 0.1 μsec to 4000±500 K at 8.0 μsec. At 0.1 μsec the plume's electron density is estimated as 1.7±0.4 × 1017 cm−3 in both vacuum and 30 mTorr of O2. We also determine the Stark broadening of the Ba(I) line at 746 nm to be 0.5±0.1 Åat an electron temperature of 1 eV and an electron density of 1017 cm−3.

Fuel Influence on Targeted Gas Turbine Combustion Properties: Part I — Detailed Diagnostics

2014 ◽  
Author(s):  
Thomas Mosbach ◽  
Victor Burger ◽  
Barani Gunasekaran
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Leading Edge ◽  
Operating Conditions ◽  
Optical Measurements ◽  
Test Facility ◽  
Research Centre ◽  
High Speed Imaging ◽  
Combustion Properties ◽  
First Results

The threshold combustion performance of different fuel formulations under simulated altitude relight conditions were investigated in the altitude relight test facility located at the Rolls-Royce plc. Strategic Research Centre in Derby, UK. The combustor employed was a twin-sector representation of an RQL gas turbine combustor. Eight fuels including conventional crude-derived Jet A-1 kerosene, synthetic paraffinic kerosenes (SPKs), linear paraffinic solvents, aromatic solvents and pure compounds were tested. The combustor was operated at sub-atmospheric air pressure of 41 kPa and air temperature of 265 K. The temperature of all fuels was regulated to 288 K. The combustor operating conditions corresponded to a low stratospheric flight altitude near 9 kilometres. The experimental work at the Rolls-Royce (RR) test-rig consisted of classical relight envelope ignition and extinction tests, and ancillary optical measurements: Simultaneous high-speed imaging of the OH* chemiluminescence and of the soot luminosity was used to visualize both the transient combustion phenomena and the combustion behaviour of the steady burning flames. Flame luminosity spectra were also simultaneously recorded with a spectrometer to obtain information about the different combustion intermediates and about the thermal soot radiation curve. This paper presents first results from the analysis of the weak extinction measurements. Further detailed test fuel results are the subject of a separate complementary paper [1]. It was found in general that the determined weak extinction parameters were not strongly dependent on the fuels investigated, however at the leading edge of the OH* chemiluminescence intensity development in the pre-flame region fuel-related differences were observed.

Visualizations of Flow Structures in the Rotor Passage of an Axial Compressor at the Onset of Stall

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Huang Chen ◽  
Yuanchao Li ◽  
David Tan ◽  
Joseph Katz
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Incidence Angle ◽  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Stereoscopic Particle Image Velocimetry ◽  
High Speed Imaging ◽  
Vortical Structures ◽  
Flow Phenomena

Experiments preformed in the JHU refractive index matched facility examine flow phenomena developing in the rotor passage of an axial compressor at the onset of stall. High-speed imaging of cavitation performed at low pressures qualitatively visualizes vortical structures. Stereoscopic particle image velocimetry (SPIV) measurements provide detailed snapshots and ensemble statistics of the flow in a series of meridional planes. At prestall condition, the tip leakage vortex (TLV) breaks up into widely distributed intermittent vortical structures shortly after rollup. The most prominent instability involves periodic formation of large-scale backflow vortices (BFVs) that extend diagonally upstream, from the suction side (SS) of one blade at midchord to the pressure side (PS) near the leading edge of the next blade. The 3D vorticity distributions obtained from data recorded in closely spaced planes show that the BFVs originate form at the transition between the high circumferential velocity region below the TLV center and the main passage flow radially inward from it. When the BFVs penetrate to the next passage across the tip gap or by circumventing the leading edge, they trigger a similar phenomenon there, sustaining the process. Further reduction in flow rate into the stall range increases the number and size of the backflow vortices, and they regularly propagate upstream of the leading edge of the next blade, where they increase the incidence angle in the tip corner. As this process proliferates circumferentially, the BFVs rotate with the blades, indicating that there is very little through flow across the tip region.

Ceramide-1-Phosphate a Novel Mediator for Phagocytosis.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2383-2383
Author(s):  
Vania Tz Hinkovska-Galcheva ◽  
Jmes A. Shayman ◽  
Andrei L. Kindzelskii ◽  
Miki Hiraoka ◽  
Akira Abe ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Lipid Rafts ◽  
High Speed ◽  
Liquid Crystalline ◽  
Leading Edge ◽  
Fold Increase ◽  
High Speed Imaging ◽  
Transfected Cells ◽  
Ceramide Kinase ◽  
Ceramide 1

Abstract We identified the generation of ceramide-1-phosphate (C1P) through activation of a ceramide kinase in neutrophils. Our previous studies indicated that C1P enhanced calcium-dependent fusion of liposomes. We hypothesized that human ceramide kinase (hCERK) activity and C1P synthesis leads to enhanced phagocytosis through a mechanism involving modulating membrane fluidity and Ca2+ generation. hCERK was stably transfected into COS-1 cells bearing FcγRIIA. hCERK activity was 2.3 times higher in cells transfected with hCERK than in the FcγRIIA cells or cells transfected with pc-vector. Stably transfected cells showed a 3-fold increase in phagocytosis. Besides increasing phagocytosis, the percentage of ingesting COS-1 cells increased from 43+ 11 in control cells and 50 + 11 in pc-vector control to 70 + 9 (p<0.0001, n=6) in pc-hCERK transfected cells. Cells labeled with [3H]-D-erythro-sphingosine and challenged with particles increased both phagocytosis by three fold and C1P levels by two times compared to resting controls. FcγRIIA, pc-vector and pc-hCERK transfected cells were subjected to cellular fractionation. Utilizing an antibody to c-Myc we confirmed that c-Myc tagged pc-hCERK was localized in the raft fraction, which was identified by a caveolin-1 marker. To assess plasma membrane fluidity we labeled COS–1 cells with 2-dimethylamino-6-lauroylnaphthalene (Laurdan). Cells transfected with pc-hCERK showed higher liquid crystalline order than control and vector transfected cells, a condition favorable to promote membrane fusion. Such ordered structures are reported to be the site of Ca2+ waves ignition. High speed imaging revealed that cells bearing pc-hCERK showed two Ca2+ waves beginning at the leading edge of the cell that propagated in both directions. When the two waves reached the vicinity of the phagosome, a secondary waves split off from each of them, then propagated about the perimeter of the phagosome. That was inhibitable by employing a store-operated Ca2+ channel (SOC) inhibitor. This behavior is unique to the FcγRIIA/pc-hCERK transfected cells. In conclusion transfected COS-1 cells were able to increase their C1P levels during phagocytosis. This changed the structural order parameter of the lipid rafts where hCERK is localized and likely contributed to phagocytosis by promoting phagosome development. Lipid rafts were enriched in Ca2+ signaling machinery and in turn pc-hCERK transfection resulted in a novel means to markedly enhance phagocytosis by generating Ca2+ movement from SOC.

scholarly journals Three-dimensional flow and lift characteristics of a hovering ruby-throated hummingbird

2014 ◽  
Vol 11 (98) ◽  
pp. 20140541 ◽  
Author(s):  
Jialei Song ◽  
Haoxiang Luo ◽  
Tyson L. Hedrick
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Leading Edge ◽  
Dynamics Simulation ◽  
Vertical Force ◽  
Imaging Data ◽  
High Speed Imaging ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Wake Interaction

A three-dimensional computational fluid dynamics simulation is performed for a ruby-throated hummingbird ( Archilochus colubris ) in hovering flight. Realistic wing kinematics are adopted in the numerical model by reconstructing the wing motion from high-speed imaging data of the bird. Lift history and the three-dimensional flow pattern around the wing in full stroke cycles are captured in the simulation. Significant asymmetry is observed for lift production within a stroke cycle. In particular, the downstroke generates about 2.5 times as much vertical force as the upstroke, a result that confirms the estimate based on the measurement of the circulation in a previous experimental study. Associated with lift production is the similar power imbalance between the two half strokes. Further analysis shows that in addition to the angle of attack, wing velocity and surface area, drag-based force and wing–wake interaction also contribute significantly to the lift asymmetry. Though the wing–wake interaction could be beneficial for lift enhancement, the isolated stroke simulation shows that this benefit is buried by other opposing effects, e.g. presence of downwash. The leading-edge vortex is stable during the downstroke but may shed during the upstroke. Finally, the full-body simulation result shows that the effects of wing–wing interaction and wing–body interaction are small.

Optical imaging techniques for hypersonic impulse facilities

2007 ◽  
Vol 111 (1115) ◽  
pp. 1-16 ◽  
Author(s):  
T. J. McIntyre ◽  
H. Kleine ◽  
A. F. P. Houwing
Keyword(s):  
Optical Imaging ◽  
High Speed ◽  
Imaging Techniques ◽  
Flow Visualisation ◽  
Complex Flows ◽  
High Speed Imaging ◽  
Time Resolved ◽  
Flow Parameters ◽  
Planar Laser ◽  
Recent Developments

Abstract The application of optical imaging techniques to hypersonic facilities is discussed and examples of experimental measurements are provided. Traditional Schlieren and shadowgraph techniques still remain as inexpensive and easy to use flow visualisation techniques. With the advent of faster cameras, these methods are becoming increasingly important for time-resolved high-speed imaging. Interferometry’s quantitative nature is regularly used to obtain density information about hypersonic flows. Recent developments have seen an extension of the types of flows that can be imaged and the measurement of other flow parameters such as ionisation level. Planar laser induced fluorescence has been used to visualise complex flows and to measure such quantities as temperature and velocity. Future directions for optical imaging are discussed.

Experimental Investigation Into the Spatter Particle Behaviour of Maraging Steel During Selective Laser Melting

2020 ◽  
Author(s):  
Tatsuaki Furumoto ◽  
Kyota Egashira ◽  
Kazushi Oishi ◽  
Satoshi Abe ◽  
Yohei Hashimoto ◽  
...  
Keyword(s):  
Metal Powder ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
High Speed ◽  
Substrate Surface ◽  
Laser Melting ◽  
High Speed Imaging ◽  
Melt Pool ◽  
Particle Behaviour

Abstract The quality of built parts by selective laser melting (SLM) relies on the comprehension of the phenomena that takes place during the melting and solidification of the metal powder. The scattering of spatter particle as liquid metal during SLM process affects the layer consolidation of powder bed in addition to the surface quality of built part. The present study is focused on the spatter particle behaviour of maraging steel during SLM to achieve a thorough understanding of the phenomena that occur during the melting and fusing of the metal powder. The spatter particles are tracked using high speed imaging, and the effects of the process parameters on the spatter particle behaviour are investigated. The spatter particles ejected from the melt pool are also physically and chemically evaluated. The results showed that the spatter particles were classified as being spherical or satellite types, according to their scattered volumes; some spatter particles were larger than the particles in the initial metal powder. Most spatter particles were ejected from the droplet formed around the melt pool and from the melted powder in front of the melt pool; the number of spatter particles ejected from the melt pool was relatively low. The surface roughness affected the generation locations and tracks of the spatter particles, and the substrate surface wettability was the principal factor affecting the spatter particle behaviour.

Sign in / Sign up

Export Citation Format

Share Document