Modeling the Structure and Dynamics of Nanoconfined Fluids
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Greathouse, Jeffery A. [Sandia National Laboratori↗
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Results for “unit dynamics”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Quantum Enhanced Fiber Sensing for Oil and Gas Applications (Final Technical Report)
The major goal of the project was to develop a quantum sensing approach compatible with current infrastructure in the oil and gas industry that could provide a quantum enhancement, with a focus towards pipeline leak detection. The proposed approach to achieving this goal consisted of the use of quantum states of light to enhance the sensitivity of fiber optic sensors beyond the classical limit. To address the limitations of existing commercial leak detection, the project focused on the study of two technologies: distributed acoustic sensors (DAS) and fiber Bragg grating (FBG)-based sensors. The initial phase of the project centered around the identification and mitigation of dominant sources of classical noise to enable operation at the classical shot noise limit (SNL). The second phase focused on the use of quantum resources to obtain sensitivities beyond the classical SNL. The final phase sought to combine quantum noise reduction techniques with advanced dynamical classical noise cancelation approaches.
02 PETROLEUM↗
Streamlined Experimental Approach to System Identification of WEC Dynamics and Excitation Characteristics
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Gaebele, Daniel Tim [Sandia National Laboratories ↗
Autonomous Radiation Cartographer (ARC) System Training Manual
This training manual is designed to provide end users with a comprehensive knowledge base for the safe and effective use of the Autonomous Radiation Cartographer (ARC) System. The ARC is a fully autonomous radiation detection robot based on the Spot Robot platform manufactured by Boston Dynamics.
42 ENGINEERING↗
Topography and functional traits shape the distribution of key shrub plant functional types in low-Arctic tundra
The expansion of shrubs in the Arctic tundra fundamentally modifies land-atmosphere interactions. However, it remains unclear how shrub distribution and expansion differ across key species due to challenges with discriminating tundra plant species at regional scales. Here, we combined multi-scale, multi-platform remote sensing and in situ trait measurements to elucidate the distribution patterns and primary controls of two representative deciduous-tall-shrub (DTS) genera, Alnus and Salix, in low-Arctic tundra. We show that topographic features were a key control on DTSs, creating heterogeneous, but predictable distributions of Alnus and Salix fractional cover (fCover). Alnus was more tolerant of elevation and slope and was found on hilly uplands (slope >10°) within a specific elevational band (200–400 m above sea level [MSL]). In contrast, Salix occurred at lower elevations (50–300 m MSL) on gentler slopes (3-10°) and required adequate soil moisture associated with its profligate water use. We also show that niche differentiation between Alnus and Salix changed with patch size, where larger patches were more specialized in resource requirements than individual plants of Alnus and Salix. To understand what constrains the growth of DTSs at locations with low fCover, we developed environmental limiting factor models, which showed that topography limits the upper bound of Alnus and Salix fCover in 69.2% and 48.7% of the landscape, respectively. These findings highlight a critical need to better understand and represent topography-controlled processes and functional traits in regulating shrub distribution, as well as a need for more detailed species classification to predict shrubification in the Arctic.
alder↗
Passive Acoustic Monitoring Provides Insights into Avian Use of Energycane Cropping Systems in Southern Florida
Birds are important indicators of ecosystem health and provide a range of benefits to society. It is important, therefore, to understand the impacts of agricultural land use changes on bird populations. The cultivation of energycane (EC)—a sugarcane hybrid—for biofuel production represents one form of agricultural land use change in southern Florida. We used passive acoustic monitoring (PAM) to examine bird community use of experimental EC fields and other agricultural land uses at two study sites in southern Florida. We deployed 16 acoustic recorders in different study plots and used the automatic species identifier BirdNET to identify 40 focal bird species. We found seasonal differences in daily avian species diversity and richness between EC experimental plots and reference agricultural fields (corn fields, orchards, pastureland), and between time periods (pre-planting, post-planting). Daily avian species diversity and richness were lower in the EC experimental plots during Fall and Winter months when plants reached maximum height (>400 cm in some areas). Despite seasonal differences in daily measures of species diversity and richness, we found no differences in cumulative species richness, suggesting that there may be little overall (season-long) effects of EC production. These findings could provide insight to avian seasonal habitat preferences and underscore the potential limitations of PAM in areas experiencing dynamic vegetation changes. More research is needed to better understand if utilization of EC cropping systems results in positive or negative effects on avian populations (e.g., foraging habitat quality, predator–prey dynamics, nest success).
BirdNET↗
Effects of Dark Matter Self-interactions on Sagittarius and its Stream
This work explores how assumptions regarding the particle-physics nature of dark matter can alter the evolution of the Sagittarius (Sgr) dwarf spheroidal galaxy and its expansive stellar stream. We run a large suite of N-body simulations to model the infall of a spherically symmetric Sgr-like dwarf, exploring how the presence of dark matter self-interactions impacts its evolution. For a scattering cross section of σ/m χ = 30 cm 2 g −1 (at orbital velocity scales), these interactions result in significantly less stellar mass and little to no dark matter bound to the progenitor at the present day. To isolate the cause of this mass loss, we introduce a novel technique for controlling which pairs of dark matter simulation particles can interact. This enables us to identify ram-pressure evaporation—the scattering of satellite and host dark matter particles—as the primary source of the enhanced mass loss. The rapid disintegration of the Sgr progenitor when self-interactions are allowed alters some key properties of the resulting stellar stream, most dramatically suppressing the presence of a “spur” on the apocenter of the trailing stream arm that correlates with the mass of the satellite at last pericenter. We demonstrate how the effects on the Sgr system scale with the particular choice of self-interaction cross section, which affects the degree of ram-pressure evaporation. These findings generalize beyond the Sgr system, underscoring that dwarf stellar streams and dwarf galaxies with close passages may serve as sensitive probes for dark matter self-interactions.
Milky Way dark matter halo↗
Dynamic microphones M-87/AIC and M-101/AIC and earphone H-143/AIC
The electrical characteristics of the M-87/AIC and M-101/AIC dynamic microphone and H-143 earphones were tested for the purpose of establishing the relative performance levels of units supplied by four vendors. The microphones and earphones were tested for frequency response, sensitivity, linearity, impedance and noise cancellation. Test results are presented and discussed.
Reiff, F. H.↗
The 25 kWe solar thermal Stirling hydraulic engine system: Conceptual design
The conceptual design and analysis of a solar thermal free-piston Stirling hydraulic engine system designed to deliver 25 kWe when coupled to a 11 meter test bed concentrator is documented. A manufacturing cost assessment for 10,000 units per year was made. The design meets all program objectives including a 60,000 hr design life, dynamic balancing, fully automated control, more than 33.3 percent overall system efficiency, properly conditioned power, maximum utilization of annualized insolation, and projected production costs. The system incorporates a simple, rugged, reliable pool boiler reflux heat pipe to transfer heat from the solar receiver to the Stirling engine. The free-piston engine produces high pressure hydraulic flow which powers a commercial hydraulic motor that, in turn, drives a commercial rotary induction generator. The Stirling hydraulic engine uses hermetic bellows seals to separate helium working gas from hydraulic fluid which provides hydrodynamic lubrication to all moving parts. Maximum utilization of highly refined, field proven commercial components for electric power generation minimizes development cost and risk.
White, Maurice↗
Static Wind-Tunnel and Radio-Controlled Flight Test Investigation of a Remotely Piloted Vehicle Having a Delta Wing Planform
At the request of the United States Marine Corps, an exploratory wind-tunnel and flight test investigation was conducted by the Flight Dynamics Branch at the NASA Langley Research Center to improve the stability, controllability, and general flight characteristics of the Marine Corps Exdrone RPV (Remotely Piloted Vehicle) configuration. Static wind tunnel tests were conducted in the Langley 12 foot Low Speed Wind Tunnel to identify and improve the stability and control characteristics of the vehicle. The wind tunnel test resulted in several configuration modifications which included increased elevator size, increased vertical tail size and tail moment arm, increased rudder size and aileron size, the addition of vertical wing tip fins, and the addition of leading-edge droops on the outboard wing panel to improve stall departure resistance. Flight tests of the modified configuration were conducted at the NASA Plum Tree Test Site to provide a qualitative evaluation of the flight characteristics of the modified configuration.
Yip, Long P.↗
Design review and analysis for a Pratt and Whitney fluid-film bearing and seal testing rig
A design review has been completed for a Pratt and Whitney (P&W)-designed fluid-film bearing and annular-seal test rig to be manufactured and installed at George C. Marshall Space Flight Center (MSFC). Issues covered in this study include: (1) the capacity requirements of the drive unit; (2) the capacity and configuration of the static loading system; (3) the capacity and configuration of the dynamic excitation system; (4) the capacity, configuration, and rotordynamic stability of a test bearing, support bearings, and shaft; and (5) the characteristics and configuration of the measurement transducers and data channels.
Childs, Dara W.↗
Low-Pressure, Field-Ionizing Mass Spectrometer
A small mass spectrometer utilizing a miniature field ionization source is now undergoing development. It is designed for use in a variety of applications in which there are requirements for a lightweight, low-power-consumption instrument that can analyze the masses of a wide variety of molecules and ions. The device can operate without need for a high-vacuum, carrier-gas feed radioactive ionizing source, or thermal ionizer. This mass spectrometer can operate either in the natural vacuum of outer space or on Earth at any ambient pressure below 50 torr (below about 6.7 kPa) - a partial vacuum that can easily be reached by use of a small sampling pump. This mass spectrometer also has a large dynamic range - from singly charged small gas ions to deoxyribonucleic acid (DNA) fragments larger than 104 atomic mass units - with sensitivity adequate for detecting some molecules and ions at relative abundances of less than one part per billion. This instrument (see figure) includes a field ionizer integrated with a rotating-field mass spectrometer (RFMS). The field ionizer effects ionization of a type characterized as "soft" in the art because it does not fragment molecules or initiate avalanche arcing. What makes the "soft" ionization mode possible is that the distance between the ionizing electrodes is less than mean free path for ions at the maximum anticipated operating pressure, so that the ionizer always operates on the non-breakdown side of the applicable Paschen curve (a standard plot of breakdown potential on the ordinate and pressure electrode separation on the abscissa). The field ionizer in this instrument is fabricated by micromachining a submicron-thick membrane out of an electrically nonconductive substrate, coating the membrane on both sides to form electrodes, then micromachining small holes through the electrodes and membrane. Because of the submicron electrode separation, even a potential of only 1 V applied between the electrodes gives rise to an electric field with a strength of in excess of a megavolt per meter strong enough to ionize any gas molecules passing through the holes. An accelerator grid and an electrostatic deflector focus the ions from the field ionizer into the rotating-field cell of the RFMS. The potentials applied to the electrodes of the cell to generate the rotating electric field typically range from 1 to 13 V. The ions travel in well-defined helices within this cell, after which they are collected in a Faraday cup. The mass of most of the molecules reaching the Faraday cup decreases with increasing frequency of rotation of the electric field in the cell. Therefore, the frequency of rotation of the electric field is made to vary in order to scan through a desired range of ion masses: For example, lightweight gas molecules are scanned at frequencies in the megahertz range, while DNA and other large organic molecules are scanned at kilohertz frequencies.
Hartley, Frank↗
Electromagnetic and Light Scattering by Nonspherical Particles XV: Celebrating 150 Years of Maxwell's Electromagnetics
The 15th Electromagnetic and Light Scattering Conference (ELS-XV) was held in Leipzig, Germany from 21 to 26 of June 2015. This conference built on the great success of the previous meetings held in Amsterdam (1995), Helsinki(1997) [2], New York City(1998) [3], Vigo (1999),Halifax (2000), Gainesville (2002), Bremen (2003), Salobreña (2005), St. Petersburg (2006), Bodrum (2007), Hatfield (2008), Helsinki (2010), Taormina (2011), and Lille as well as the workshops held in Bremen (1996,1998) and Moscow (1997). As usual, the main objective of this conference was to bring together scientists, engineers, and PhD students studying various aspects of electromagnetic scattering and to provide a relaxed atmosphere for in-depth discussion of theory, measurements, and applications. Furthermore, ELS-XV supported the United Nations "Year of Light" and celebrated the150th anniversary of Maxwell's electromagnetics. Maxwell's paper on "A Dynamical Theory of the Electromagnetic Field" was published in1865 and has widely been acknowledged as one of the supreme achievements in the history of science. The conference was attended by136 scientists from 22 countries. The scientific program included two plenary lectures, 16 invited reviews, 88 contributed oral talks, and 70 poster presentations. The program and the abstracts of conference presentations are available at the conference website http://www.els-xv-2015.net/home.html. Following the well-established ELS practice and with Elsevier's encouragement, we solicited full-size papers for a topical issue of the Journal of Quantitative Spectroscopy and Radiative Transfer (JQSRT). The result of this collective effort is now in the reader's hands. As always, every invited review and regular paper included in this topical issue has undergone the same rigorous peer review process as any other manuscript published in the JQSRT.
light scattering↗
A Vacuum-Compatible, Spectrally Tunable, Flat Panel Uniform Source for Testing Large Aperture Earth Observation Systems
Labsphere, Inc. in conjunction with NASA GSFC and Genesis Engineering Solutions Inc., has developed an innovative, vacuum compatible, calibration spectro-radiometric illumination source with a highly uniform large-area rectangular flat panel active area. This device features a uniquely shaped diffuse integration geometry to achieve high uniformity over a large active output area while maintaining a smaller and more robust overall form-factor when compared to previous designs or integrating spheres. A new liquid-cooled hybrid quartz-tungsten (QT) and light emitting diode (LED) source module has been engineered to provide direct-in-vacuum reference illumination over the full dynamic range and spectrum of the VIIRS instrument’s optical bands during pre-launch testing. The first unit has been demonstrated to meet its requirements using ambient technology and a fully-vacuum-compatible second unit is planned to allow testing in thermal vacuum (TVAC) campaigns. This technology is flexible and capable of meeting the needs of many other instruments/missions requiring this type of test/calibration capability.
Jeffrey Holt↗
Scroll-type machine
A scroll-type displacement machine, e.g. scroll compressor, has fixed and orbiting scrolls and an Oldham ring to prevent relative rotation between scrolls. A drive module positioned between the orbiting scroll and drive shaft incorporates an eccentric drive system and first and second counterweights for dynamic balancing. The motor, motor bearings, and motor shaft (i.e., drive shaft) are packaged as a separate, modular unit (e.g. “off-the-shelf” motor) that attaches to the compressor frame. The machine is configured as a high-side machine with a low-pressure port at a radial outer portion of the fixed scroll and a high-pressure port or discharge port located in the floor of the orbiting scroll at its axis, with high pressure flow passing over and around the eccentric drive bearing and drive mechanism. The Oldham ring is distributed on a lateral or radial plane of the scroll pair with a portion surrounding a portion of the fixed scroll and another portion surrounding a portion of the orbiting scroll. The ring may be formed as four arcuate members arranged on two levels, to occupy otherwise unused space in the scroll-type machine.
42 ENGINEERING↗
A Method for Obtaining Liquid–Solid Adsorption Rates from Molecular Dynamics Simulations: Applied to Methanol on Pt(111) in H 2 O
Adsorption is an important step in heterogeneous catalysis as it predetermines how many reactant molecules can participate in a surface reaction per unit time. While the rate of adsorption processes is well studied in gas–solid adsorption in both theory and experiment, such rates are still not well studied for liquid–solid adsorption. This is partly because the ever-changing configurations of liquid-phase solvent molecules impede the ability to study a molecule approaching a surface from a liquid phase by either experiment or theory. In this work, we develop a method using molecular dynamics (MD) simulations to study the rate of adsorption in liquid–solid adsorption processes. Specifically, we use MD to model the diffusion of a methanol molecule in aqueous solvent and its adsorption to a Pt(111) surface. We find that by approximating the solute motion as following the same displacement rates as a random walk model, the adsorbed and non-adsorbed states of the methanol molecule near the Pt(111) surface can be discerned and quantified. In particular, this methodology enables extracting a sticking coefficient and a macroscopically relatable adsorption rate. This method can be applied to arbitrary types of reactants and surfaces, as well as different liquid environments, thus providing a general tool for predicting quantitative adsorption rates of liquid–solid adsorption systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Dynamic P-Q Capability and Abnormal Operation Analysis of a Wind Turbine with Doubly-Fed Induction Generator
After several accidents occurred in wind farms in the United States and around the world, the subsynchronous oscillation (SSO) issues in grid-connected wind farms have gained serious attention. Particularly, these issues have caused significant challenges to wind turbines with a doubly fed induction generator (DFIG) because it is connected to the grid via both its stator and rotor paths. Traditionally, a P-Q capability chart is utilized to assure the safe operation boundary for a synchronous generator. But the energy conversion characteristics of a DFIG wind turbine are completely different. A critical factor to affect the reliable operation of a DFIG wind turbine is the rated current and pulse-width modulation (PWM) saturation constraints of its power converters. These constraint conditions can be affected by the wind turbine rotating speed and grid conditions. However, a detailed study of DFIG P-Q capability from these perspectives has not been conducted, which has hindered adequate understanding of many abnormal wind turbine operations reported in the literature and the development of advanced control technologies to overcome the challenges. The proposed study in this paper considers vector control implementation to DFIG power electronic converters in the dq reference frame, and the models and algorithms developed for the P-Q capability study have addressed specific DFIG power converter constraints that are different from those of a traditional synchronous generator. The paper especially focuses on exploring the dynamic natures of DFIG P-Q capability under uncertain and variable conditions to explore the root causes of many abnormal operations of DFIG wind turbines reported in the literature. The proposed study is validated through an electromagnetic transient simulation model of a grid-connected DFIG wind turbine. The proposed study has the potential to lead to the development of new DFIG control technologies that can help overcome the challenges for many abnormal operations of DFIG wind turbines.
17 WIND ENERGY↗
Advances in solid-state NMR for the studies of mesoporous solids: fast magic spinning and dynamic nuclear polarization
Here, this review provides an up-to-date account of the development of two solid-state (SS)NMR methods for enhancing resolution and sensitivity, fast magic angle spinning (MAS) and dynamic nuclear polarization (DNP), and the resulting progress in surface science. We demonstrate the high resolution and efficiency that can be achieved by using two-dimensional homo- and heteronuclear correlation experiments with small rotors capable of MAS at rates exceeding 100 kHz. DNP has offered significant enhancements in signal sensitivity and allowed access to nuclei and experiments that are beyond the limits of conventional SSNMR. The continuing progress in fast MAS and DNP methodologies in recent years generated an unprecedented shift in SSNMR’s capabilities in the studies of surface and interface regions of solids, especially mesoporous supports and catalysts. We give numerous examples of recent applications and discuss the prospects for further improvements of both methods.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗