On the use of time-resolved three-dimensional diagnostics to characterize firebrand showers in the WUI

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

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Impact of an Aortic Nitinol Stent Graft on Flow Measurements by Time-resolved Three-dimensional Velocity-encoded MRI

Academic Radiology ◽

10.1016/j.acra.2011.10.025 ◽

2012 ◽

Vol 19 (3) ◽

pp. 274-280 ◽

Cited By ~ 3

Author(s):

Fabian Rengier ◽

Michael Delles ◽

Roland Unterhinninghofen ◽

Sebastian Ley ◽

Sasan Partovi ◽

...

Keyword(s):

Stent Graft ◽

Three Dimensional ◽

Flow Measurements ◽

Time Resolved ◽

Nitinol Stent

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Determination of Carbon Content in Steel Using Laser-Induced Breakdown Spectroscopy

Applied Spectroscopy ◽

10.1366/0003702924123692 ◽

1992 ◽

Vol 46 (9) ◽

pp. 1382-1387 ◽

Cited By ~ 73

Author(s):

J. A. Aguilera ◽

C. Aragón ◽

J. Campos

Keyword(s):

Carbon Content ◽

Matrix Effects ◽

Sample Surface ◽

Nitrogen Atmosphere ◽

Laser Induced Breakdown Spectroscopy ◽

Time Resolved ◽

Breakdown Spectroscopy ◽

Use Of Time ◽

Laser Induced Breakdown

Laser-induced breakdown spectroscopy has been used to determine carbon content in steel. The plasma was formed by focusing a Nd:YAG laser on the sample surface. With the use of time-resolved spectroscopy and generation of the plasma in nitrogen atmosphere, a precision of 1.6% and a detection limit of 65 ppm have been obtained. These values are similar to those of other accurate conventional techniques. Matrix effects for the studied steels are reduced to a small slope difference between the calibration curves for stainless and nonstainless steels.

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Effects of Downstream Vane Bowing and Asymmetry on Unsteadiness in a Transonic Turbine

Volume 2A: Turbomachinery ◽

10.1115/gt2018-76735 ◽

2018 ◽

Author(s):

John P. Clark ◽

Richard J. Anthony ◽

Michael K. Ooten ◽

John M. Finnegan ◽

P. Dean Johnson ◽

...

Keyword(s):

Turbine Blades ◽

Three Dimensional ◽

Navier Stokes ◽

Time Resolved ◽

Turbine Engine ◽

Shock Interactions ◽

Design Changes ◽

Post Test ◽

Measured Time ◽

Transonic Turbine

Accurate predictions of unsteady forcing on turbine blades are essential for the avoidance of high-cycle-fatigue issues during turbine engine development. Further, if one can demonstrate that predictions of unsteady interaction in a turbine are accurate, then it becomes possible to anticipate resonant-stress problems and mitigate them through aerodynamic design changes during the development cycle. A successful reduction in unsteady forcing for a transonic turbine with significant shock interactions due to downstream components is presented here. A pair of methods to reduce the unsteadiness was considered and rigorously analyzed using a three-dimensional, time resolved Reynolds-Averaged Navier Stokes (RANS) solver. The first method relied on the physics of shock reflections itself and involved altering the stacking of downstream components to achieve a bowed airfoil. The second method considered was circumferentially-asymmetric vane spacing which is well known to spread the unsteadiness due to vane-blade interaction over a range of frequencies. Both methods of forcing reduction were analyzed separately and predicted to reduce unsteady pressures on the blade as intended. Then, both design changes were implemented together in a transonic turbine experiment and successfully shown to manipulate the blade unsteadiness in keeping with the design-level predictions. This demonstration was accomplished through comparisons of measured time-resolved pressures on the turbine blade to others obtained in a baseline experiment that included neither asymmetric spacing nor bowing of the downstream vane. The measured data were further compared to rigorous post-test simulations of the complete turbine annulus including a bowed downstream vane of non-uniform pitch.

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Blade-Row Interactions in an LP Turbine at Design and Strong Off-Design Operation

Volume 2C: Turbomachinery ◽

10.1115/gt2014-25343 ◽

2014 ◽

Author(s):

Martin Lipfert ◽

Jan Habermann ◽

Martin G. Rose ◽

Stephan Staudacher ◽

Yavuz Guendogdu

Keyword(s):

Experimental Data ◽

Flow Field ◽

Three Dimensional ◽

Suction Side ◽

Test Facility ◽

Time Resolved ◽

Joint Project ◽

Multi Stage ◽

Blade Row ◽

Wake Interactions

In a joint project between the Institute of Aircraft Propulsion Systems (ILA) and MTU Aero Engines a two-stage low pressure turbine is tested at design and strong off-design conditions. The experimental data taken in the altitude test-facility aims to study the effect of positive and negative incidence of the second stator vane. A detailed insight and understanding of the blade row interactions at these regimes is sought. Steady and time-resolved pressure measurements on the airfoil as well as inlet and outlet hot-film traverses at identical Reynolds number are performed for the midspan streamline. The results are compared with unsteady multi-stage CFD predictions. Simulations agree well with the experimental data and allow detailed insights in the time-resolved flow-field. Airfoil pressure field responses are found to increase with positve incidence whereas at negative incidence the magnitude remains unchanged. Different pressure to suction side phasing is observed for the studied regimes. The assessment of unsteady blade forces reveals that changes in unsteady lift are minor compared to changes in axial force components. These increase with increasing positive incidence. The wake-interactions are predominating the blade responses in all regimes. For the positive incidence conditions vane 1 passage vortex fluid is involved in the midspan passage interaction leading to a more distorted three-dimensional flow field.

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Three Dimensional Clocking Effects in a One and a Half Stage Transonic Turbine

Journal of Turbomachinery ◽

10.1115/1.3072715 ◽

2009 ◽

Vol 132 (1) ◽

Cited By ~ 7

Author(s):

O. Schennach ◽

J. Woisetschläger ◽

B. Paradiso ◽

G. Persico ◽

P. Gaetani

Keyword(s):

Flow Field ◽

Three Dimensional ◽

Fast Response ◽

Secondary Flows ◽

Pressure Probe ◽

Time Resolved ◽

Flow Angle ◽

Aerodynamic Pressure ◽

Velocity Flow ◽

Transonic Turbine

This paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three-dimensional aerodynamics of the second vane for different clocking positions. To give an overview of the time-averaged flow field, five-hole probe measurements were performed upstream and downstream of the second stator. Furthermore in these planes additional unsteady measurements were carried out with laser Doppler velocimetry in order to record rotor phase-resolved velocity, flow angle, and turbulence distributions at two different clocking positions. In the planes upstream of the second vane, the time-resolved pressure field has been measured by means of a fast response aerodynamic pressure probe. This paper shows that the secondary flows of the second vane are significantly modified by the different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out, and a 0.6% variation in the second vane loss coefficient has been recorded among the different clocking positions.

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The biochemical resolving power of fluorescence lifetime imaging

10.1101/2021.02.03.429635 ◽

2021 ◽

Author(s):

Andrew L. Trinh ◽

Alessandro Esposito

Keyword(s):

Fluorescence Lifetime ◽

Resolving Power ◽

Fluorescence Lifetime Imaging ◽

Time Resolved ◽

Instrument Response Function ◽

Lifetime Imaging ◽

Use Of Time ◽

Single Living Cells ◽

Microscopy Techniques

AbstractA deeper understanding of spatial resolution in microscopy fostered a technological revolution that is now permitting us to investigate the structure of the cell with nanometer resolution. Although fluorescence microscopy techniques enable scientists to investigate both the structure and biochemistry of the cell, the biochemical resolving power of a microscope is a physical quantity that is not well-defined or studied. To overcome this limitation, we carried out a theoretical investigation of the biochemical resolving power in fluorescence lifetime imaging microscopy, one of the most effective tools to investigate biochemistry in single living cells. With the theoretical analysis of information theory and Monte Carlo simulations, we describe how the ‘biochemical resolving power’ in time-resolved sensing depends on instrument specifications. We unravel common misunderstandings on the role of the instrument response function and provide theoretical insights that have significant practical implications in the design and use of time-resolved instrumentation.

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