Hardware Design of a 13.8-kV/3-MVA PV Plus Storage Solid-State Transformer (PVS-SST)
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Engineering↗
SEARCH · Engineering Papers
Results for “Ordering transformation”
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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ROM-Based Surrogate Systems Modeling of EBR-II
We report the System Analysis Module (SAM), developed and maintained by Argonne National Laboratory, is designed to provide whole-plant transient safety analysis capabilities for a number of advanced non-light water reactors, including sodium-cooled fast reactor (SFR), lead-cooled fast reactor (LFR), and molten salt reactor (MSR)/fluoride-salt-cooled high-temperature reactor (FHR) designs. SAM is primarily constructed as a systems-level analysis tool, with the potential to incorporate reduced order models from three-dimensional computational fluid dynamics (CFD) simulations to improve characterization of complex, multidimensional physics. It is recognized that the computational expense associated with CFD can be intractable for various engineering analyses, such as uncertainty quantification, inference, and design optimization. This paper explores the reducibility of a SAM model using recent advances in randomized linear algebra techniques, which attempt to find recurring patterns in the various realizations generated by a model after randomly perturbing all its input parameters. The reduction is described in terms of fewer degrees of freedom (DOFs), referred to as the active DOFs, for the model variables such as input model parameters and model responses. The results indicate that there is significant room for additional reduction that may be leveraged for additional computational gains when employing SAM for engineering-intensive analyses that require repeated model executions. Different from physics-based reduction approaches, the proposed approach allows one to estimate upper bounds on the reduction errors, which are rigorously developed in this work. Finally, different methods for surrogate model construction, such as regression and neural network-based training, are employed to correlate the input and output active DOFs, which are related back to the original variables using matrix-based linear transformations.
42 ENGINEERING↗
Effect of Cd on the Nucleation and Transformation of Amorphous Calcium Carbonate
Qualitative measurements observations and field observations measurements indicate mineral coatings are one of the most abundant ways earth materials form, including in sedimentary deposits and certain biominerals. Formation of amorphous carbonates and other metastable intermediates in such these mixed cation systems is poorly understood, however. Using in situ PDF and SAXS, along with ICP-MS and SEM, results from this study 1) determines identify a novel short-range ordered Cd-ACC phase and 2) finds determine amorphous carbonate is stabilized by Cd2+, and 3) support formation of Cd-substituted vaterite, a polymorph of Ca that is not natively formed by Cd CO3. Results are highly dependent on ACC supersaturation, suggesting Cd-induced stability of Cd-ACC are is dependent primarily very sensitive on amorphous phase kinetics rather than thermodynamics to the rate of Cd-ACC nucleation and transformation. Findings provide a quantitative understanding of precursor intermediate phase structure and stability in mixed cation carbonate systems and aggregation that impact and suggest alternate pathways to forming the chemical heterogeneities frequently observed in natural mineral coatings.
Mergelsberg, Sebastian T.↗
A Voltage Injection-Based Current Harmonics Suppression Strategy for Six-Phase PMSM With Nonsinusoidal Back EMF
This article presents a voltage injection-based current harmonic minimization method for wide bandgap device-based six-phase permanent magnet synchronous machine (PMSM) drives. The presence of low-order harmonics is common in the back EMF of PMSMs with low slot and high pole numbers. The back EMF harmonics generate low-order harmonic currents that increase torque ripples. Furthermore, zero-sequence current (ZSC) is also observed if all six phases are connected to a common neutral point. ZSC does not affect the torque ripple but reduces the system efficiency. A special technique is required to reduce ZSC for variable speed drives as direct ac component to synchronous reference frame (SRF) dc transformation is not possible for ZSC. In this article, a voltage injection-based current harmonics reduction method is proposed. The injected harmonic voltage coefficients are calculated from the harmonic estimations of back EMF and updated using closed-loop harmonic compensators to improve steady-state performance. For ZSC reduction, third harmonics power controller, and for 6n ± 1 (n = 1, 2,...) order harmonic current reduction, SRF current controllers are presented in this article. Furthermore, the current harmonics minimization method is experimentally verified using a GaN-based three-level active neutral point clamped inverter-driven six-phase PMSM.
42 ENGINEERING↗
Gradient flow based phase-field modeling using separable neural networks
Allen–Cahn equation is a reaction–diffusion equation and is widely used for modeling phase separation. Machine learning methods for solving the Allen–Cahn equation in its strong form suffer from inaccuracies in collocation techniques, errors in computing higher-order spatial derivatives, and the large system size required by the space–time approach. To overcome these challenges, we propose solving the gradient flow of the Ginzburg–Landau free energy functional, which is equivalent to the Allen–Cahn equation, thereby avoiding the second-order spatial derivatives associated with the Allen–Cahn equation. A minimizing movement scheme is employed to solve the gradient flow problem, eliminating the complexities of a space–time approach. We utilize a separable neural network that efficiently represents the phase field through low-rank tensor decomposition. As we use the minimizing movement scheme to numerically solve the gradient flow problem, we thus, refer to the proposed method as the Separable Deep Minimizing Movement (SDMM) method. The evaluation of the functional in the minimizing movement scheme using the Gauss quadrature technique bypasses the inaccuracies associated with collocation techniques traditionally used to solve partial differential equations. A hyperbolic tangent transformation is introduced on the phase field prior to the evaluation of the functional to ensure that it remains strictly bounded within the values of the two phases. For this transformation, theoretical guarantee for energy stability of the minimizing movement scheme is established. Our results suggest that this transformation helps to improve the accuracy and efficiency significantly. The proposed method resolves the challenges faced by state-of-the-art machine learning techniques, outperforming them in both accuracy and efficiency. It is also the first machine learning method to achieve an order of magnitude speed improvement over the finite element method. In addition to its formulation and computational implementation, several case studies illustrate the applicability of the proposed method.
42 ENGINEERING↗
Faster fourier transformation: The algorithm of S. Winograd
The new DFT algorithm of S. Winograd is developed and presented in detail. This is an algorithm which uses about 1/5 of the number of multiplications used by the Cooley-Tukey algorithm and is applicable to any order which is a product of relatively prime factors from the following list: 2,3,4,5,7,8,9,16. The algorithm is presented in terms of a series of tableaus which are convenient, compact, graphical representations of the sequence of arithmetic operations in the corresponding parts of the algorithm. Using these in conjunction with included Tables makes it relatively easy to apply the algorithm and evaluate its performance.
Zohar, S.↗
Adaptive model reduction for continuous systems via recursive rational interpolation
A method for adaptive identification of reduced-order models for continuous stable SISO and MIMO plants is presented. The method recursively finds a model whose transfer function (matrix) matches that of the plant on a set of frequencies chosen by the designer. The algorithm utilizes the Moving Discrete Fourier Transform (MDFT) to continuously monitor the frequency-domain profile of the system input and output signals. The MDFT is an efficient method of monitoring discrete points in the frequency domain of an evolving function of time. The model parameters are estimated from MDFT data using standard recursive parameter estimation techniques. The algorithm has been shown in simulations to be quite robust to additive noise in the inputs and outputs. A significant advantage of the method is that it enables a type of on-line model validation. This is accomplished by simultaneously identifying a number of models and comparing each with the plant in the frequency domain. Simulations of the method applied to an 8th-order SISO plant and a 10-state 2-input 2-output plant are presented. An example of on-line model validation applied to the SISO plant is also presented.
Lilly, John H.↗
3D Temperature-Controlled Interchangeable Pattern for Size-Selective Nanoparticle Capture
Patterned surfaces with distinct regularity and structured arrangements have attracted great interest due to their extensive promising applications. Although colloidal patterning has conventionally been used to create such surfaces, herein, we introduce a novel 3D patterned poly(N-isopropylacrylamide) (PNIPAM) surface, synthesized by using a combination of colloidal templating and surface-initiated photoinduced electron transfer-reversible addition–fragmentation chain transfer (SI-PET-RAFT) polymerization. In order to investigate the temperature-driven 3D morphological variations at a lower critical solution temperature (LCST) of ~32 °C, multifaceted characterization techniques were employed. Atomic force microscopy confirmed the morphological transformations at 20 and 40 °C, while water contact angle measurements, upon heating, revealed distinct trends, offering insights into the correlation between surface wettability and topography adaptations. Moreover, quartz crystal microbalance with dissipation monitoring and electrochemical measurements were employed to detect the topographical adjustments of the unique hollow capsule structure within the LCST. Tests using different sizes of PSNPs shed light on the size-selective capture–release potential of the patterned PNIPAM, accentuating its biomimetic open–close behavior. Notably, our approach negates the necessity for expensive proteins, harnessing temperature adjustments to facilitate the noninvasive and efficient reversible capture and release of nanostructures. Finally, this advancement hopes to pave the way for future innovative cellular analysis platforms.
36 MATERIALS SCIENCE↗
Metastability and Ostwald step rule in the crystallisation of diamond and graphite from molten carbon
Abstract Experimental challenges in determining the phase diagram of carbon at temperatures and pressures near the graphite-diamond-liquid triple point are often related to the persistence of metastable crystalline or glassy phases, superheated crystals, or supercooled liquids. A deeper understanding of the crystallisation kinetics of diamond and graphite is crucial for effectively interpreting the outcomes of these experiments. Here, we reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon through molecular simulations with first-principles machine learning potentials. Our simulations accurately reproduce the experimental phase diagram of carbon near the triple point and show that liquid carbon crystallises spontaneously upon cooling. Metastable graphite crystallises in the domain of diamond thermodynamic stability at pressures above the triple point. Furthermore, whereas diamond crystallises through a classical nucleation pathway, graphite follows a two-step process in which low-density fluctuations forego ordering. Calculations of the nucleation rates of the two competing phases confirm this result and reveal a manifestation of Ostwald’s step rule, where the strong metastability of graphite hinders the transformation to the stable diamond phase. Our results provide a key to interpreting melting and recrystallisation experiments and shed light on nucleation kinetics in polymorphic materials with deep metastable states.
Science & Technology - Other Topics↗
Travelling wave‐based fault detection and location in a real low‐voltage DC microgrid
Abstract This paper discusses a device‐level implementation of a travelling wave (TW) protection device (PD) designed for a real low‐voltage DC microgrid. The TWPD fault detection and location algorithm is executed on a commercial digital signal processor (DSP) board, involving signal sampling at 1 MHz via the DSP board's analog‐to‐digital converter (ADC). The analogue input card measures positive pole, negative pole and pole‐to‐pole voltages at the TWPD location. Upon a successful fault detection using a second‐order high‐pass filter, the voltage data is normalised and multi‐resolution analysis (MRA) is performed on a 128‐sample buffer around the TW arrival time. MRA employs the discrete wavelet transform (DWT) to capture high‐frequency voltage patterns, and then the Parseval's energy theorem quantifies these TW characteristics by computing the energy of reconstructed wavelet coefficients. These energy values per decomposed frequency band are the basis for training a random forest classifier that predicts fault location and type. The TWPD is fully implemented and connected to a real DC microgrid in Albuquerque, NM, USA, for validation, and results are shown for field tests verifying the performance under faults.
Paruthiyil, Sajay Krishnan [Department of Electric↗
Vibrational Cooper minima used to verify the dissociation pathway induced by a short intense laser pulse
Vibrational Cooper minima due to weak dipole coupling were previously observed in strong-field dissociation of H 2 + as minima in the kinetic-energy-release (KER) spectrum [McKenna et al., Phys. Rev. Lett. 103, 103006 (2009)]. We demonstrate in two independent experiments that these vibrational Cooper minima occur more generally and can be used as “fingerprints” to identify the final electronic state in the dissociation pathway. In the first experiment, we show the wavelength dependence of the vibrational Cooper minima observed in the KER spectrum of O 2 + dissociation induced by 396- and 264-nm photons. These minima appear at the locations predicted by our first-order perturbation-theory calculations. In the second experiment, a delay-dependent KER spectrum is obtained from O 2 using an ionizing pump and a dissociating probe, then Fourier-transformed to generate a spin-rotation quantum beat spectrum of O 2 + . As a result, this spectrum shows vibrational Cooper minima at the expected locations, confirming their presence in another observable. In this case, these minima are used to identify the dissociation pathway.
Molecular dissociation↗
Memcomputing the Spectrum of Correlated Quantum Systems
The goals and objectives of the grant DE‐SC0020892 were to apply a new computing paradigm, MemComputing, to efficiently simulate properties of correlated quantum systems. The method has been applied to a wide set of problems ranging from quantum state tomography to finding the ground state of correlated systems. In all cases, substantial advantages compared to state-of-the-art approaches have been obtained. The project has also led to the suggestion of the transformer architecture (used nowadays in large-language models) as an efficient quantum state representation, and a better understanding of the role of memory in the generation of long-range order in neural networks. This grant has supported the work of a PhD student, inspired a new class on unconventional computing taught at the University of California, San Diego and has generated several peer-reviewed papers.
97 MATHEMATICS AND COMPUTING↗
The Preservation of Super-Earths and the Emergence of Gas Giants after Their Progenitor Cores Have Entered the Pebble-isolation Phase
The omnipresence of super-Earths suggests that they are able to be retained in natal disks around low-mass stars, whereas exoplanets' mass distributions indicate that some cores have transformed into gas giants through runaway gas accretion at ≳1 au from solar-type stars. In this paper, we show that transition to runaway gas accretion by cores may be self-impeded by an increase of the grain opacity in their envelope after they have acquired sufficient mass (typically ~ 10M ⊕ ) to enter a pebble-isolation phase. The accumulation of approximately millimeter- to meter-sized pebbles in their migration barriers enhances their local fragmentation rates. The freshly produced submillimeter grains pass through the barrier, elevate the effective dust opacity, and reduce the radiative flux in the core's envelope. These effects alone are adequate to suppress the transition to runaway accretion and preserve super-Earths in the stellar proximity (~0.1 au), albeit entropy advection between the envelope and the disk can further reduce the accretion rate. At an intermediate distance (~1 au) from their host stars, the escalation in the dust opacity dominates over entropy advection in stalling the transition to runaway accretion for marginally pebble-isolated cores. Beyond a few astronomical unit, the transformation of more-massive cores to gas giants is reachable before severe depletion of disk gas. This requirement can be satisfied either in extended disks with large scale height via orderly accretion of migrating pebbles or through the mergers of oligarchic protoplanetary embryos, and can account for the correlated occurrence of long-period gas giants and close-in super-Earths.
79 ASTRONOMY AND ASTROPHYSICS↗
Advanced Intra-Cycle Detection of Pre-Ignition Events through Phase-Space Transforms of Cylinder Pressure Data
The widespread adoption of boosted, downsized SI engines has brought pre-ignition phenomena into greater focus, as the knock events resulting from pre-ignitions can cause significant hardware damage. Much attention has been given to understanding the causes of pre-ignition and identify lubricant or fuel properties and engine design and calibration considerations that impact its frequency. This helps to shift the pre-ignition limit to higher specific loads and allow further downsizing but does not fundamentally eliminate the problem. Real-time detection and mitigation of pre-ignition would thus be desirable to allow safe engine operation in pre-ignition-prone conditions. This study focuses on advancing the time of detection of pre-ignition in an engine cycle where it occurs. Furthermore, phase space transforms through time-delay embedding of cylinder pressure and principal component analysis were applied to same-cycle detection of pre-ignition and shown to enable detection on the order of a crank degree earlier than deviation in cylinder pressure can be identified through direct statistical observation of the pressure data. Additionally, it appears that the deviation of the trajectory in phase space may offer the opportunity to extend this method to further extend the detection window and allow more time for mitigation actions to occur.
42 ENGINEERING↗
Regoliths on small bodies in the solar system
A regolith is defined as a layer or mantle of loose, incoherent, rocky material of whatever origin, that nearly everywhere forms the surface of the land and rests on coherent bedrock. The regoliths on many planetary bodies are the result of continual impacts, which transform coherent surfaces into fragmental debris. The present investigation is concerned with the special case of regolith formation and evolution on small objects, such as asteroids and meteorite parent bodies. First order models of regolith evolution on asteroidal surfaces are constructed on the basis of data provided by studies of lunar samples and meteorites. It appears that regolith formation proceeds by deposition of discrete layers of the widely spread ejecta primarily from the larger impacts. Moderate-size (100-300 km diameter) asteroids are covered by modest regoliths of the order of one km in depth. Small rocky asteroids develop negligible regoliths.
Housen, K. R.↗
Predicted electrothermal deicing of aircraft blades
A finite difference method is presented for the transient two-dimensional simulation of an electrothermal de-icer pad of an aircraft wing or blade. The irregular geometry of the composite ice laden blade is handled by use of a body fitted coordinate transformation. By this approach the various blade layers are mapped into a set of stacked rectangular strips in which the numerical solution takes place. Several heat conduction examples are presented in order to demonstrate the accuracy of the numerical procedure. Ice melting time predictions are made and compared to earlier predictions where possible. Finally, a new graphical presentation of thermal results is shown.
Keith, T. G., Jr.↗
Spectroscopic planetary detection
The Sun-as-a-star was monitored using the McMath Fourier transform spectometer (FTS) on Kitt Peak in 1983. In 1985 the first measurement was made using the laser heterodyne technique. The FTS measurements now extend for three years, with errors of order 3 meters/sec at a given epoch. Over this 3 year period, a 33 meter/sec change was measured in the apparent velocity of integrated sunlight. The sense of the effect is that a greater blueshift is seen near solar minimum, which is consistent with expectations based on considering the changing morphology of solar granular convection. Presuming this effect is solar-cycle-related, it will mimic the Doppler reflex produced by a planetary companion of approximately two Jupiter masses, with an 11 year orbital period. Thus, Jupiter itself is below the threshold for detection by spectroscopic means, without an additional technique for discrimination. However, for planetary companions in shorter period orbits (P approx. 3 years) the threshold for unambiguous detection is well below one Jupiter mass.
Deming, D.↗
Some Results from Studies on Relationships Between the Optical-meteorological Parameters and Solar Activity. Part 2: Development of the Problem of Solar Forcing
A set of complex spectral, actinometric and meteorological data obtained in the periods of heightened solar activity (1981 and 1988) has been considered in order to reveal the atmospheric component affected by solar emissions in the troposphere and lower stratosphere. For the first time, it has been found out that water vapor molecules can be transformed, under the impact of corpuscular and microwave solar emissions, from the free state to the bound one (association into clusters), and vice versa. The transition of water vapor molecules into the bound state results in a decrease of spectral optical thickness in the visible, near IR and IR spectral regions, and an appearance and deepening of the cluster absorption bands at wavelengths 330 to 340, 365, 380 to 390, and 480 nm.
Kondratyev, K. Y.↗