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Mobile sampling cart automatically swabs surfaces for the recovery of microorganisms. Unit operates without human involvement and provides for control of swabbing speed, rotation of cotton swab, and the pressure and angle applied to swab. Capability of reverse direction is also available. Sampling cart use is limited to flat surfaces.
Direct numerical simulation of acoustic radiation from a turbulent boundary layer in a cylindrical domain will be conducted under the flow conditions corresponding to those at the nozzle exit of the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) operated under noisy-flow conditions with a total pressure p(sub t) of 225 kPa and a total temperature of T(sub t) equal to 430 K. Simulations of acoustic radiation from a turbulent boundary layer over a flat surface are used as a reference configuration to illustrate the effects of the cylindrical enclosure. A detailed analysis of acoustic freestream disturbances in the cylindrical domain will be reported in the final paper along with a discussion pertaining to the significance of the flat-plate acoustic simulations and guidelines concerning the modeling of the effects of an axisymmetric tunnel wall on the noise field.
A concept for mitigating the adverse effects of jet vorticity and liftoff at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This "anti-vortex" film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30deg angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.
The investigation of the electronic structures on perovskite oxides using surface-sensitive spectroscopy techniques is often hindered by their “uncleavable” nature, typically requiring expensive and complex in situ experimental setups that integrate the capabilities of sample synthesis and spectroscopy measurement under ultrahigh vacuum condition. Here, we address this challenge by developing an ozone-annealing process that yields atomically flat surfaces on perovskite oxide thin films, making them suitable for high-resolution angle-resolved photoemission spectroscopy measurements. Using this method, we present a three-dimensional electronic structure study of Nd 1−𝑥 Sr 𝑥 NiO 3 (𝑥=0 and 0.175) thin films with unprecedented accuracy. The experimentally determined low-energy fermiology exhibits quantitative agreements with two-band tight-binding simulations, which is further validated by first-principles calculations considering the material's actual crystal structure. This work provides an accessible approach for ex situ ARPES measurements on perovskite oxides and other strongly correlated oxides, including the recently discovered high-𝑇 c nickelates.
Several improvements have recently been made in the thermal analysis methods for leading edges of a hypersonic vehicle. The leading edges of this vehicle undergo exceptionally high heat loads that incorporate extreme spatial gradients as well as severe transients. Due to the varying flight conditions, complex geometry, and need for thermal loads at many points along the trajectory, full computational fluid dynamics (CFD) analysis of the aeroheating; loads is not feasible. Thus, engineering methods must be used to determine the aeroheating on the vehicle surfaces, and that must be utilized in the thermal analysis. Over the last year, the thermal analysis of a hypersonic vehicle has been enhanced in several ways. Two different engineering codes are used to predict aeroheating loads: one over the curve near the stagnation point, and the other on flat surfaces downstream of the leading edge. These two are matched together at the intersection point using a method that allows closer approximation of CFD results. User-developed FORTRAN, which is part of the thermal solver PATRAN Thermal, is used to accomplish this. The customizable FORTRAN code also allows use of many different time- and space-dependent factors, interpolation of the heat load in time and space, and inclusion of both highly swept and unswept grid structures. This FORTRAN is available to other PATRAN users who may want to accomplish a similar objective in analysis. Flux, rather than convective coefficient, is used to define heat loads, which allows more accurate analysis as well as better application of margins. Improvements have also been made in more efficient utilization of imported CAD geometry, by creating faces on solids to facilitate load application.
Pulsed sources of hyper-thermal O-atoms are now being extensively used to simulate low-earth orbit (LEO) surface exposure environments. The peak flux of these sources is many orders of magnitude larger than the corresponding LEO flux. Although it is desirable to accelerate the test by using higher fluxes than found in LEO, even commonly used fluxes are large enough to produce multi-collision effects by causing a build-up of gas at the sample surface. In this paper we characterize the physical consequences to the experiment using the direct simulation Monte Carlo (DSMC) method, DSMC allows us to extract the distributions of energy and impact angle for the O-atoms that reach the surface, and to record how strongly the gas build-up at the target assembly deflects flux from downstream instrumentation. By considering a range of source fluxes, we determine the onset conditions and severity of these multi-collision effects. We find that even at common experimental fluxes with a normally incident beam string a flat surface sample, the energy distribution of incident O-atoms broadens and develops a significant low-energy tail. The angular distributions also broaden significantly. The number of O-atoms that reach downstream instrumentation is decreased by approximately 50%. These simulations will aid in the calibration of ground-based O-atom measurements,a nd provide a model for the energy and angular distributions of O-atoms that actually impinge on surface samples.
Pulsed sources of hyper-thermal O-atoms are now being extensively used to simulate low-earth orbit (LEO) surface exposure environments. The peak flux of these sources is many orders of magnitude larger than the corresponding LEO flux. Although it is desirable to accelerate the test by using higher fluxes than found in LEO, even commonly used fluxes are large enough to produce multi-collision effects by causing a build-up of gas at the sample surface. In this paper we characterize the physical consequences to the experiment using the direct simulation Monte Carlo (DSMC) method. DSMC allows us to extract the distributions of energy and impact angle for the O-atoms that reach the surface, and to record how strongly the gas build-up at the target assembly deflects flux from downstream instrumentation. By considering a range of source fluxes, we determine the onset conditions and severity of these multi-collision effects. We find that even at common experimental fluxes with a normally incident beam striking a flat surface sample, the energy distribution of incident O-atoms broadens and develops a significant low-energy tail. The angular distributions also broaden significantly. The number of O-atoms that reach downstream instrumentation is decreased by approximately 50%. These simulations will aid in the calibration of ground-based O-atom measurements, and provide a model for the energy and angular distributions of O-atoms that actually impinge on surface samples.
ICESat-2 carries NASA's next-generation laser altimeter, ATLAS, (Advanced Topographic Laser Altimeter System), designed to measure changes in ice sheet height, sea ice freeboard, and vegetation canopy height. ATLAS contains a photon-counting lidar which transmits green (532-nm) pulses at 10kHz. Each pulse is split into 3 pairs of beams (one strong and one weak). Approximately 1014 photons per pulse travel from ATLAS through the atmosphere to reflect off the Earth's surface. Some return back into the ATLAS telescope where they are recorded. Photons from sunlight and instrument noise at the same wavelength are also recorded. The flight software time tags all photons within a 500m to 6 km range window and generates histograms. Using the histograms, it selects a telemetry window which varies from 20m over flat surfaces to hundreds of meters over rougher terrain. ATL03 contains the time, height (relative to the WGS-84 ellipsoid), latitude and longitude of every photon within the telemetry window. The basic challenge is to determine which of these photons were reflected off the surface. We have developed an algorithm that identifies these signal photons and assigns a confidence level (low, medium, or high) to each signal photon based on the signal to noise ratio. We present an overview of the signal identification algorithm and show the results on actual ICESat-2 data over ice sheet, sea ice, vegetated, and water surfaces. Higher level ATLAS products work with aggregations of the photons in order to determine the ellipsoidal height of the Earth, canopy height and structure, and other quantities of geophysical interest.
No tactile sensor array developed to date fills all, nor even most, of the requirements of: (1) many sensor elements to minimize tactile imaging time, (2) close spacing of small sensing elements for fine spatial discrimination, (3) ability to be molded to a convex fingertip surface for taction on concave surfaces, (4) ability to sense both force and temperature in order to fully mimic biological touch, (5) tolerance to overscale forces without damage, and (6) graceful failure in use, i.e., functional survival of most of the array when part of it is damaged, well. Several investigators have recently developed tactile sensing arrays suitable for imaging shapes on hard flat surfaces, but not well suited for taction on curved surfaces. Others have developed single tactile sensors suitable for incorporation into arrays, which will probably prove uneconomical when large numbers of sensors are needed. Still others have developed flexible capacitive arrays suitable for use on curved surfaces but incapable of obtaining temperature or proximity data. A technology is being developed herein suitable to the achievement of all of the above goals, and to incrementally demonstrate useful steps toward those goals.
Recent advances in Artificial Intelligence (AI) are changing the World. Novel approaches to training AI systems have led to dramatic reductions in the amount of time required. Training an AI system could take years and teams of people using traditional methods, but with the advancements of Deep Learning (DL) models this training can now be accomplished by an individual in a matter of minutes. The development of “fast AI” libraries has delivered AI to essentially everyone. Democratization of AI power has inspired many to revisit past problems that will benefit from DL approaches. For example, the application of AI has improved detection of breast cancer by 20% compared to traditional detection methods. Computer vision and machine learning are being used to identify soil deficiencies and provide planting recommendations to farmers. Success stories like these and many others have provided inspiration to see if AI can help improve one of our needed capabilities – that of visually identifying micrometeoroid and orbital debris (MMOD) impact damage to spacecraft from images of the spacecraft exterior. The need to visually locate and characterize spacecraft MMOD impact damage has been present since the early days of space travel. This is often done by either having a crew member take photographs of the spacecraft through a window using a hand-held camera or ground personnel directing externally-mounted cameras. The photographs are then transmitted back to Earth for visual analysis. This method of MMOD damage inspection works well and has been used on various spacecraft including the Space Shuttle and the International Space Station (ISS). One of the issues with the current method that we believe AI could improve is the speed and possibly the accuracy in identifying MMOD impacts. Note that detecting MMOD impacts in images can be very difficult. The visual appearance of an MMOD impact can change dramatically with lighting conditions, size of impact, depth of penetration, material types, surface waviness, fabric coverings, camera & lens, distance to surface, spacecraft orientation, analyst experience, and many other factors. Currently, this takes a team of highly-experienced specialists in both the fields of Image Analysis and MMOD impacts. This paper documents our initial research in training an AI DL model using the fast-AI library to identify actual and simulated MMOD impacts and perforations into exposed flat surfaces. While we recognize that this initial goal seems modest, it must be noted that what we have done would have taken teams of individuals and years of training just ten years ago. Our long-term goal is to add complexity and use-cases to the DL model being trained to expand the capabilities of this model so that it can be used to identify MMOD impacts on all types of spacecraft surfaces.
Multiple element continuity gage measures plane stress crack growth plus surface crack growth under plane strain conditions. The gage measures flat and curved surfaces and operates at cryogenic temperatures.
In FY2020, KSC’s Applied Physics Lab created a computer based image processing system to allow inspection of the new visors being developed for the Artemis Program. This system was based on an ASTM standard where the distortion of an image is used to determine the optical aberrations in a visor, but this approach is restricted to small fields-of-view (small areas of the visor) and is limited in its ability to reliably detect and measure distortion. From our experience with flat surface inspection, we know that other optical techniques can offer higher sensitivity and accuracy. [1] This memorandum describes a method to model and measure the distortion in curved optical surfaces using moir´e interferometry. We were able to apply this process to examine samples of the xEMU Artemis astronaut helmets. Design details are provided along with examples to illustrate performance.
The behavior at large times of the curvature of material elements in turbulence is investigated using Lagrangian velocity-gradient time series obtained from direct numerical simulations of isotropic turbulence. The main objectives are: to study the asymptotic behavior of the pdf curvature as a function of initial curvature and shape; and to establish whether the curvature of an initially plane material element goes to a stationary probability distribution. The evidence available in the literature about the asymptotic curvature-pdf of initially flat surfaces is ambiguous, and the conjecture is that it is quasi-stationary. In this work several material-element ensembles of different initial curvatures and shapes are studied. It is found that, at long times the moments of the logarithm of curvature are independent of the initial pdf of curvature. This, it is argued, supports the view that the curvature attains a stationary distribution at long times. It is also shown that, irrespective of initial shape or curvature, the shape of any material element at long times is cylindrical with a high probability.
In this article, the phenomena of the upward component in the case of flat surfaces will be referred to as the "Lilienthal effect." The Lilienthal effect will be distinguished from the Knoller-Betz effect which is explained by means of vertical wind oscillations, at the basis of which, however, there lie air motions which the Lilienthal effect could not produce. It will be shown that the same cause, which can produce the Lilienthal effect on flat airfoils, considerably strengthens the thrust due to the Knoller-Betz effect.
Previous studies have shown that spray cooling heat flux enhancement may be attained using enhanced surfaces. However, most enhanced surface spray cooling studies have been limited to extended and/or embedded surface structures. This study investigates the effect of foam on spray cooling heat flux. The foam used was graphite Poco Foam. The foam piece was attached to a copper block with a cross-sectional area of 2.0 cm(sup 2) using high thermal conductivity epoxy as the thermal interface material (TIM). Measurements were also obtained on a heater block with a flat surface for purposes of baseline comparison. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed conditions (chamber pressure of 41.4 kPa). Results show that the highest heat flux (CHF) attained was 113 W/cm(sup 2) using the graphite Poco Foam.
There is increased interest in many different processes based upon interactions between a charged solid surface and a liquid electrolyte. Energy storage in capacitive porous materials, ionic membranes, capacitive deionization (CDI) for water desalination, capacitive energy generation, removal of heavy ions from wastewater streams, and geophysical applications are some examples of these processes. Process development is driven by the production of porous materials with increasing surface area. Understanding of the physical phenomena occurring at the charged solid-electrolyte interface will significantly improve the design and development of more effective applied processes. The goal of this work is to critically review the current knowledge in the field. The focus is on concepts behind different models. We start by briefly presenting the classical electrical double layer (EDL) models in flat surfaces. Then, we discuss models for porous materials containing macro-, meso-, and micro-pores. Some of the current models for systems comprising two different pore sizes are also included. Finally, we discuss the concepts behind the most common models used for ionic transport and Faradaic processes in porous media. The latter models are used for simulation of electrosorption processes in porous media.
The Mars Orbiter Laser Altimeter (MOLA) has been successfully mapping the shape and topography of Mars on an intermittent basis since the Mars Global Surveyor (MGS) spacecraft arrived at Mars in Sept. 1997. In early April, MGS reached it's mapping orbit and began the mapping phase of the mission. Since that time MOLA has been operating continuously. MOLA is a laser altimeter with a pulse rate of 10 Hz and a precision of about 30 to 40 cm over flat surfaces. The laser pulses are approximately 330 meters apart on the surface of Mars and each pulse illuminates an area approximately 150 meters in diameter. The orbital accuracy of MGS is a few meters in the radial direction enabling the topography to be interpreted at the few meter accuracy level. The initial data have provided a new geodetic description of the size and shape of Mars, including accurate estimates for the equatorial and polar radii, and the planetary flattening. The data have revealed the northern hemisphere to be very low in elevation, very flat, and almost devoid of craters. The north polar icecap lies in a basin about 5 km below the average altitude and reaches to a height of 3 km. The heavily cratered southern hemisphere is high and the terrain is rough. The south polar icecap is about 5 km above the average planetary altitude and 2 km above the surrounding terrain. The MOLA profile data show the gradual but steady increase in altitude of the surface of Mars from the north pole to the south pole. This is a consistent feature for all north-south profiles and reflects the 3 km separation of the center of figure for Mars from the center of mass along the rotation axis.
The growth of high-quality epitaxial gallium nitride (GaN) thin films is achieved by using a baking and plasma pretreatment of the substrate prior to the GaN plasma-enhanced atomic layer deposition (PE-ALD). In this work, it is found that such pretreatment makes the GaN films grow coherently on sapphire substrates, following a layer-by-layer growth mechanism. The deposited GaN film shows high crystalline quality, a sharp GaN/sapphire interface, and a flat surface. The possibility of growing high-quality GaN epilayers in this way broadens the range of applications for PE-ALD in GaN-based devices.