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At least 613 records · Page 34

Wind Turbine Drivetrain Reliability Research - Gearbox Bearing Axial Cracking Failure Mode Example

The U.S. Department of Energy's National Renewable Energy Laboratory and Argonne National Laboratory have been conducting wind turbine drivetrain (formerly gearbox) reliability research for many years. Although the drivetrain focus has not changed, detailed projects are adjusted every few years based on dynamic needs seen in the field across the wind industry. This webinar will walk through the research methodology by using wind turbine gearbox bearing axial cracking failure mode as an example. The detailed steps include: 1) top failure mode identification based on actual failure data collected from project partners, 2) bench-top testing to identify possible contributing factors and formulate a damage metric, 3) physics domain modeling and validation through testing, 4) reliability assessment and prognosis based on the physics domain model and data domain inputs, and further enhancement through machine learning algorithms, using actual wind plant operational and failure event data. Hopefully, the presented work is of interest to the IISE community, and some members can apply their expertise to wind turbine and plant applications, helping enhance wind power generation technology advancement and its broader deployment.

axial cracking↗

A Mo-anode-based in-house source for small-angle X-ray scattering measurements of biological macromolecules

We demonstrate the use of a molybdenum-anode-based in-house small-angle X-ray scattering (SAXS) setup to study biological macromolecules in solution. Our system consists of a microfocus X-ray tube delivering a highly collimated flux of 2.5 × 10{sup 6} photons/s at a beam size of 1.2 × 1.2 mm{sup 2} at the collimation path exit and a maximum beam divergence of 0.16 mrad. The resulting observable scattering vectors q are in the range of 0.38 Å{sup −1} down to 0.009 Å{sup −1} in SAXS configuration and of 0.26 Å{sup −1} up to 5.7 Å{sup −1} in wide-angle X-ray scattering (WAXS) mode. To determine the capabilities of the instrument, we collected SAXS data on weakly scattering biological macromolecules including proteins and a nucleic acid sample with molecular weights varying from ∼12 to 69 kDa and concentrations of 1.5–24 mg/ml. The measured scattering data display a high signal-to-noise ratio up to q-values of ∼0.2 Å{sup −1} allowing for an accurate structural characterization of the samples. Moreover, the in-house source data are of sufficient quality to perform ab initio 3D structure reconstructions that are in excellent agreement with the available crystallographic structures. In addition, measurements for the detergent decyl-maltoside show that the setup can be used to determine the size, shape, and interactions (as characterized by the second virial coefficient) of detergent micelles. This demonstrates that the use of a Mo-anode based in-house source is sufficient to determine basic geometric parameters and 3D shapes of biomolecules and presents a viable alternative to valuable beam time at third generation synchrotron sources.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Unexpected structural/motional mode of water intercalated into an α-crystalline zirconium phosphate deduced by 31 P and 2 H solid-state MAS NMR spectra

Here, in developing the approach to understanding dynamics of intercalates in layered materials, crystalline-layered zirconium phosphate Zr (HPO 4 ) 2 ·0.35D2O has been prepared and characterized by the 1 H, 31 P, and 2 H solid-state MAS NMR spectra, including 31 P and 2 H T 1 measurements. At temperatures >253 K, the intercalated water shows two spectrally-distinguished deuterons unprecedentedly with different DQCC's and 2 H T 1 times, one of which is hydrogen bonded. The collected data allowed to identify an unexpected bonding/dynamic mode of water molecules, which experience fast rotation around the hydrogen bond, formed with a zirconium-coordinated oxygen. The low-temperature 2 H MAS NMR experiments have demonstrated the presence of additional hydrogen bond P—(H)O˙˙˙ DO, population of which grows on cooling to 195 K corresponding to the doubly hydrogen-bonded immobile water molecule.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Mode Meter for Mitigating Forced Oscillations on the Grid

Increased renewable energy sources connected to the power grid leads to forced power oscillations that result in costly outages and an unstable grid. Forecasting and predicting fluctuations is difficult for grid operators. PNNL, Montana Tech and the University of Wyoming developed Mode Meter, a power tool that detects and reports grid instabilities. Using three advanced algorithms, Mode Meter detects, analyzes, and helps localize power swings that are growing unstable. Mode Meter uses precise, time-synchronized data collected from thousands of advanced sensors placed on powerlines and other transmission devices. Information is reported in an easy-to-read visual tool. The patented innovation is available for commercialization. Contact Commercialization Manager Peter Christensen at peter.christensen@pnnl.gov

24 POWER TRANSMISSION AND DISTRIBUTION↗

Mesoscopic two-point collective dynamics of glass-forming liquids

The collective density–density and hydrostatic pressure–pressure correlations of glass-forming liquids are spatiotemporally mapped out using molecular dynamics simulations. It is shown that the sharp rise of structural relaxation time below the Arrhenius temperature coincides with the emergence of slow, nonhydrodynamic collective dynamics on mesoscopic scales. The observed long-range, nonhydrodynamic mode is independent of wave numbers and closely coupled to the local structural dynamics. Below the Arrhenius temperature, it dominates the slow collective dynamics on length scales immediately beyond the first structural peak in contrast to the well-known behavior at high temperatures. Furthermore, these results highlight a key connection between the qualitative change in mesoscopic two-point collective dynamics and the dynamic crossover phenomenon.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Ion-Flow-Induced Excitation of Electrostatic Cyclotron Mode in Magnetized Dusty Plasma

The stability of electrostatic cyclotron mode is investigated in a flowing magnetized dusty plasma in the presence of strong ion–neutral collisions. In the high magnetic field limit, when the dust magnetization becomes important, it is expected that the collective behavior of magnetized dust grains suspended in the near-sheath region substantially influences the dispersion properties of electrostatic modes. The growth/damping of the collective excitation is significantly controlled by such parameters as the ion–neutral collision frequency, Mach number, and magnetic field strength. In our case, the explicit dependence of the Mach number on the magnetic field and collision frequency has been taken into account and possible implications on the stability of the mode is analyzed. Streaming instability of cyclotron modes may be important to understand issues related to the interaction mechanism between dust grains and other associated phenomena like Coulomb crystallization, phase behavior, transport properties, etc., in the relatively strong magnetic field limit, which is currently accessible in the DPD (Kiel University) and MDPX (PSL, Auburn University) experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Orientational Pair Correlations in a Dipolar Molecular Liquid: Time-Resolved Resonant and Nonresonant Pump–Probe Spectroscopies

Orientational pair correlations (OPCs), when they are sufficiently strong in a liquid, contain information on the interplay between structure and dynamics that arise from intermolecular interactions. Consequently, the quantification of OPCs remains a subject of substantial interest in current experimental and theoretical work. In the case of benzonitrile, the importance of OPCs remains ambiguous owing to the use of model-dependent analyses or reliance on a single spectroscopic technique. In this work, IR polarization selective pump-probe (PSPP) and optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments were used to quantify OPCs in benzonitrile. These methods measure single molecule and collective relaxation, respectively. Comparison of the orientational correlation function (PSPP) of the naturally abundant 13CN stretching mode and the polarizability anisotropy relaxation (OHD-OKE) of the liquid revealed that collective reorientation was a factor of 1.56 ± 0.08 slower than the single molecule reorientation time. The two types of measurements on dilute benzonitrile in carbon tetrachloride were the same within experimental error. These results support the proposition that OPCs exist and arise from the formation of parallel-aligned intermolecular structures in the neat liquid.

14 SOLAR ENERGY↗

Determination of plate wave velocities and diffuse field decay rates with braod-band acousto-ultrasonic signals

Lowest symmetric and lowest antisymmetric plate wave modes were excited and identified in broad-band acousto-ultrasonic (AU) signals collected from various high temperature composite materials. Group velocities have been determined for these nearly nondispersive modes. An algorithm has been developed and applied to determine phase velocities and hence dispersion curves for the frequency ranges of the broad-band pulses. It is demonstrated that these data are sensitive to changes in the various stiffness moduli of the materials, in agreement by analogy, with the theoretical and experimental results of Tang and Henneke on fiber reinforced polymers. Diffuse field decay rates have been determined in the same specimen geometries and AU configuration as for the plate wave measurements. These decay rates are of value in assessing degradation such as matrix cracking in ceramic matrix composites. In addition, we verify that diffuse field decay rates respond to fiber/matrix interfacial shear strength and density in ceramic matrix composites. This work shows that velocity/stiffness and decay rate measurements can be obtained in the same set of AU experiments for characterizing materials and in specimens with geometries useful for mechanical measurements.

Kautz, Harold E.↗

Cross-Calibration of GNC and OLA LIDAR Systems Onboard OSIRIS-REx

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission carried two distinct light detection and ranging (LIDAR) systems: A scanning LIDAR called OSIRIS-REx Laser Altimeter (OLA) as part of the science payload, and a flash LIDAR system has part of the Guidance, Navigation, & Control (GNC) subsystem to serve as a navigation sensor during TAG. This presents a unique opportunity to compare the performance of the two LIDAR systems in close proximity to a small asteroid body. During the Orbital B mission phase, between June to August 2019, the OSIRIS-REx spacecraft orbited Bennu in a near-circular terminator orbit during which the altitude above the surface varied between 645 m to 740 m. Over five-week period observations were recorded with the OLA instrument that were subsequently used to construct a global digital terrain map (DTM) with a resolution of 5 cm and accuracy of ±20 cm. This model provides an excellent reference for assessing the performance of the GNC LIDAR system. Two different GNC LIDAR checkout activities were also conducted during the Orbital B phase: A limb-crossing check-out featured a series of slews to collect GNC LIDAR data across varying ranges and phase angles and operate the automatic gain control modes of the device; An OLA-GNC LIDAR cross calibration was designed to collect data from both the OLA and GNC LIDAR devices with overlapping footprints while the spacecraft was pointed nadir. This paper compares the on-orbit performance observed during the cross-calibration activity. The OLA-based global DTM and point clouds are used to evaluate the GNC LIDAR not available during previous analysis. The GNC LIDAR measurements were found to be well within accuracy and precision specified for the instrument, but much noisier than the measurements from OLA within this operating regime.

Jason M Leonard↗

NASA's Orbital Debris Optical and IR Ground-Based Observing Program Utilizing the MCAT, UKIRT, and Magellan Telescopes

Characterizing debris in Earth-orbit has become increasingly important as the population growth rises steadily, posing greater and greater threats to active satellites with each passing year. Currently, the Joint Space Operations is tracking over 23,000 pieces of debris, ranging in size from 1-meter and larger in geosychronous orbits (GEO) to 10-cm and larger at low-Earth orbits (LEO). Model estimates suggest that there may be more than 500,000 pieces of spacecraft debris larger than 1 cm currently in orbit around the Earth. With such a small fraction of the total population being tracked, and new break-ups occurring in LEO, GEO, and Geo Transfer Orbits, new assets, techniques, and approaches for characterizing this debris are needed. With this in mind, NASA's Orbital Debris Program Office has actively tasked a suite of telescopes around the world. In 2015, the newly-built 1.3m optical Meter Class Autonomous Telescope (MCAT) came on-line on Ascension Island in the South Atlantic Ocean and is currently in its commissioning phase. MCAT is designed to track Earth-orbiting objects above 200km, conduct surveys at GEO, and work in tandem with a newly-installed Raven-class commercial-off-the-shelf system, a 0.4-meter telescope co-located on Ascension with a field-of-view similar to MCAT's and research-grade instrumentation designed to complement MCAT for observations taken either simultaneously or in tandem. The 3.8m infrared UKIRT telescope on Mauna Kea, Hawaii, has been heavily tasked throughout 2015 and into 2016, collecting data on individual targets as well as in survey modes to study both the general GEO population as well as an individual break-up event of a BRIZ-M Rocket body that occurred in January 2016. Data collected include photometry and spectroscopy in the near-Infrared (0.85-2.5 m) and the mid-infrared (8-16 m). Finally, the 6.5-m Baade Magellan telescope at Las Campanas Observatory in Chile was used to collect optical photometric survey data in October 2015 of two GEO Titan breakups, focusing on locations of possible debris concentrations as indicated by the NASA standard break-up model.

Lederer, Susan↗

The features of a quantum description of radiation in an optically dense medium

This paper is devoted to the theory of quantum electromagnetic field in an optically dense medium. Self-consistent equations describing interaction between a quantum field and a quantum dielectric medium are obtained from the first principles, i.e., outside a phenomenological description. Using these equations, we found a transformation (of the Bogoliubov transformation type) that converts the operators of the “vacuum” field into operators of collective perturbations of the field and an ensemble of atoms, that is, photons in the medium. Transformation parameter is the refractive index of the wave mode considered. It is shown that besides the energy of the collective electromagnetic field, the energy of photons in the medium includes the energy of the internal degrees of freedom of the substance and the energy of near-field dipole interaction between atoms in the polarized medium. The concept of negative energy photons is introduced on the basis of self-consistent equations. - Highlights: • Quantum equations of field–medium interaction are obtained from the first principles. • Transformation of field operators from vacuum to medium is of Bogoliubov type. • The concept of negative energy photons is introduced.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Deciphering between enhanced light emission and absorption in multi-mode porphyrin cavity polariton samples

Abstract It remains unclear how the collective strong coupling of cavity-confined photons to the electronic transitions of molecular chromophore leverages the distinct properties of the polaritonic constituents for future technologies. In this study, we design, fabricate, and characterize multiple types of Fabry-Pérot (FP) mirco-resonators containing copper(II) tetraphenyl porphyrin (CuTPP) to show how cavity polariton formation affects radiative relaxation processes in the presence of substantial non-Condon vibronic coupling between two of this molecule’s excited electronic states. Unlike the prototypical enhancement of Q state radiative relaxation of CuTPP in a FP resonator incapable of forming polaritons, we find the light emission processes in multimode cavity polariton samples become enhanced for cavity-exciton energy differences near those of vibrations known to mediate non-Condon vibronic coupling. We propose the value of this detuning is consistent with radiative relaxation of Herzberg-Teller polaritons into collective molecular states coupled to the cavity photon coherently. We contrast the feature stemming from light emission from the HT polariton state with those that occur due to polariton-enhanced light absorption. Our results demonstrate the landscape of molecular and photonic interactions enabled by cavity polariton formation using complex chromophores and how researchers can design resonators to leverage these interactions to characterize and control polaritonic properties.

Odewale, Elizabeth O.↗

The tilt rotor research aircraft (XV-15) program

The tilt rotor concept is introduced and the performance capabilities and noise characteristics of the XV-15 aircraft are discussed. In hover, the aircraft is lifted by the two wing tip mounted rotors with the nacelles in the vertical position. In this flight mode, the vehicle is a twin rotor helicopter and is controlled by rotor cyclic and collective controls. The aircraft can fly as a helicopter or tilt the nacelle to the propeller mode and operate as a fixed-wing twin turboprop airplane. It is also possible to stop the conversion at any intermediate angle and fly continuously or reconvert. The rotors are powered by two modified T-53 engines and the power train includes a cross shaft located in the wing, to allow for the engine failure case and still retain power to both rotors.

Magee, J. P.↗

Aeroelastic Stability for Straight and Swept-Tip Rotor Blades in Hover and Forward Flight

Two isolated, hingeless rotors with identical fiber-reinforced composite root flexures were tested in hover and forward flight at realistic tip speeds. The rotors differed in blade planform and structure. The first blade set was of rectangular planform. The second set had blades of stiffer construction with swept-tips. The purpose of these tests was to measure the isolated rotor aeroelastic stability of bending/torsion coupled rotor blades over a range of flight conditions. The two soft inplane rotor systems were designed with low first torsion frequency to emphasize the effects of torsion. Regressing lag mode damping is shown in hover with precone and collective pitch variations and in forward flight with airspeed, shaft angle, precone and collective pitch variations. Correlation with comprehensive analysis for a number of test conditions is shown. Agreement in hover is excellent and forward flight correlation is reasonably good.

REGRESSING LAG MODE DAMPING↗

Climate sensitive size-dependent survival in tropical trees

Survival rates of large trees determine forest biomass dynamics. Survival rates of small trees are linked to mechanisms that maintain biodiversity across tropical forests. How species survival rates change with size offers insight into the links between biodiversity and ecosystem function across tropical forests. We tested patterns of size-dependent tree survival across the tropics using data from 1781 species and over two million individuals to assess whether tropical forests can be characterized by size-dependent life-history survival strategies. We found species were classifiable into four “survival modes” that explain life-history variation that shapes carbon-cycling and the relative abundances within forests. Frequently collected functional traits, such as wood density, leaf mass per area, and seed mass, were not generally predictive of species’ survival modes. Mean annual temperature and cumulative water deficit predicted the proportion of biomass of survival modes, indicating important links between evolutionary strategies, climate, and carbon cycling. The application of survival modes in demographic simulations predicted biomass change across forest sites. Our results reveal globally identifiable size-dependent survival strategies that differ across diverse systems in a consistent way. The abundance of survival modes and interaction with climate ultimately determine forest structure, carbon storage in biomass, and future forest trajectories.

Johnson, Daniel J.↗

Investigating the interconnectedness of active transportation and public transit usage as a primer for Mobility-as-a-Service adoption and deployment

With the advent of Mobility-as-a-Service packages to reduce car usage and (by extension) greenhouse gas emissions, it is crucial that researchers and practitioners consider mutual determinants and outcomes that link the adoption of multiple alternative modes. This study therefore investigates the joint usage of active travel (walking, cycling, bike-sharing) and public transit (bus, rail) modes with respect to personal and situational contexts. Online survey data (n = 826) were collected across six Midwestern U.S. states using Amazon MTurk. Respondents indicated their average weekly usage of eight travel modes across three trip purposes so that multimodality could be assessed. Several psychological constructs were extracted via (a) the stages of change framework, used to indicate willingness to adopt new behavior, and (b) confirmatory factor analysis conducted on Likert scales rooted in theories of community, identity, norms, personality, and well-being. A multiple-indicators multiple-causes structural equation model is then employed to investigate the process of adopting a modality style that incorporates active and transit modes. The model confirms that compatible physical and social contexts, as well as navigational skills and openness to learning, are key primers of multimodalism. However, a path juncture stemming from neighborhood support for mobility innovation illustrates a potential polarity in outcomes between individuals and communities. In addition, the stage of active mobility adoption is linked to identity and norm activation, offering further guidance on what influences readiness for change. The seamless integration of mobility services is critical to matching the convenience and comfort of the private vehicle; understanding potential pathways to sustainable mobility, though, requires analyses and interventions that are driven by well-being outcomes and grounded in rigorous psychological frameworks. Here, the research findings offer practical guidance for identifying intervention opportunities to be linked with MaaS enrollment while demonstrating the need to illuminate how mobility might relate to social cohesion, identity expression, and various sources of satisfaction.

42 ENGINEERING↗

An Overview of Technologies for Individual Trip History Collection: Mobility Decision Science Pillar SMART Mobility Consortium

WholeTraveler is a project of the Department of Energy's Smart Mobility consortium that explores how an individual's attitudes and lifestyle characteristics are embodied in transportation behaviors throughout one's life trajectory. As a study at the nexus of decision science and urban systems analysis, fine-grained location data (FGLD), or records of an individual's location collected at a resolution sufficient to determine both the unique destinations a traveler visits each day and the modes used to travel between them, underlie high quality results. Moreover, the methods for collecting FGLD and the means through which they are associated with a traveler's personal attributes have significant implications for the burden on research participants, the cost and complexity of the study, as well as the confidence with which hypotheses can be validated. This paper provides a broad overview of existing technologies for FGLD collection and is intended to provide a literature review for researcher exploring similar domain areas. Technologies are categorized as either network or onboard approaches. An onboard system, such as smartphone or GPS device, sends signals to external networks to capture its own location. Conversely, network systems, such as cell towers, are comprised of sensing nodes with known locations that record when individually identifiable assets come within their range of detection. Our analysis indicates that the most sensible approach to FGLD collection, for the purposes of WholeTraveler, is to leverage onboard devices, and in particular the existing Moves or Google Maps applications for Android and iOS smartphones. Dedicated GPS devices have been widely implemented by the transportation research community and pose an alternatively acceptable form of FGLD collection. Independently developing a custom smartphone application is not recommended because of the notable challenges in establishing minimal viable functionality, as well as in ensuring compatibility across an ever-growing combination of hardware devices and software versions. No matter the technical means of data collection, the secure handling of FGLD is of critical importance.

33 ADVANCED PROPULSION SYSTEMS↗

Augmented Adaptive Control of a Wind Turbine in the Presence of Structural Modes

Wind turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, potentially causing component fatigue and failure. Two key technology drivers for turbine manufacturers are increasing turbine up time and reducing maintenance costs. Since the trend in wind turbine design is towards larger, more flexible turbines with lower frequency structural modes, manufacturers will want to develop methods to operate in the presence of these modes. Accurate models of the dynamic characteristics of new wind turbines are often not available due to the complexity and expense of the modeling task, making wind turbines ideally suited to adaptive control. In this paper, we develop theory for adaptive control with rejection of disturbances in the presence of modes that inhibit the controller. We use this method to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the interference of certain structural modes in feedback. The control objective is accomplished by collectively pitching the turbine blades. The adaptive pitch controller for Region 3 is compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller.

Frost, Susan A.↗