Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “design pattern”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Printing versus coating - What will be the future production technology for printed electronics?

The market of Large Area Organic Printed Electronics is developing rapidly to increase efficiency and quality as well as to lower costs further. Applications for OPV, OLED, RFID and compact Printed Electronic systems are increasing. In order to make the final products more affordable, but at the same time highly accurate, Roll to Roll (R2R) production on flexible transparent polymer substrates is the way forward. There are numerous printing and coating technologies suitable depending on the design, the product application and the chemical process technology. Mainly the product design (size, pattern, repeatability) defines the application technology.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Electrically tunable graded index planar lens based on graphene

The realization of electrically tunable beam focusing using a properly designed conductivity pattern along a strip on a background single graphene flake with operation in the terahertz regime is proposed and numerically investigated. The strip is illuminated with a guided surface plasmon polaritons (SPP) plane wave and the physical origin of the design procedure is evaluated from the phase of effective mode index of propagating SPP wave on graphene. Upon tuning a gate voltage between the graphene sheet and the substrate, the focus tuning is achieved. Finite- difference time-domain numerical technique is employed to explore the propagation characteristic of SPP wave and the performance parameters of the lens include the focal length, full-width half-maximum, and focusing efficiency. Such a one atom thick planar lens with the capability of electrical focus tuning besides the compatibility with current planar optoelectronic systems can find valuable potential applications in the field of transformational plasmon optics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Self-supervised learning of spatiotemporal thermal signatures in additive manufacturing using reduced order physics models and transformers

Microstructure control via additive manufacturing has enormous potential as manufacturers, materials scientists, and designers alike seek to exploit novel fabrication technologies to improve component performance. Recent works have demonstrated the feasibility of producing materials with controlled microstructures across various length scales. However, the experimental approach towards exploring the process-structure space can be laborious and costly. This is particularly true if also considering scan pattern optimization which is well suited for processes such as powder bed fusion electron beam melting. In this work we propose an approach for encoding additive manufacturing layer-wise thermal response signatures using self-supervised representation learning. Thermal simulations from a reduced order model are utilized to estimate the spatiotemporal response during printing. A machine learning framework, using video-transformers, is utilized to efficiently distill spatiotemporal patterns into a compact latent space representation. This latent state representation encodes the relevant physics which is then utilized to establish a data-driven process-structure model for an additively manufactured Ni-based superalloy. In conclusion, the proposed methodology could potentially be used towards in-situ process monitoring, scan pattern experimental design, and component qualification.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Design Studies for a TPC Readout Plane Using Zigzag Patterns With Multistage GEM Detectors

Here, new design studies have been carried out for a readout plane for gas electron multiplier detectors using zigzag patterns that can significantly reduce the readout channel count while preserving excellent spatial resolution for tracking detectors. While zigzag patterns have been used in a number of applications, these studies were designed to investigate the fundamental limits of charge sharing between the electrodes to optimize the spatial resolution and minimize the nonuniformities across the readout plane, while exploring the limits of manufacturing capabilities for producing the readout board. Simulation studies were carried out to optimize the readout electrode structure, and readout boards were produced with similar zigzag designs that were tested in the laboratory using a scanning X-ray source. These studies were aimed at developing a readout board for the new time projection chamber for the sPHENIX experiment at relativistic heavy ion collider, but can readily be used in other applications, including various micropattern gas detectors, such as Micromegas.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Pattern recognition with composite correlation filters designed with multi-object combinatorial optimization

Composite correlation filters are used for solving a wide variety of pattern recognition problems. These filters are given by a combination of several training templates chosen by a designer in an ad hoc manner. In this work, we present a new approach for the design of composite filters based on multi-objective combinatorial optimization. Given a vast search space of training templates, an iterative algorithm is used to synthesize a filter with an optimized performance in terms of several competing criteria. Furthermore, by employing a suggested binary-search procedure a filter bank with a minimum number of filters can be constructed, for a prespecified trade-off of performance metrics. Computer simulation results obtained with the proposed method in recognizing geometrically distorted versions of a target in cluttered and noisy scenes are discussed and compared in terms of recognition performance and complexity with existing state-of-the-art filters.

42 ENGINEERING↗
DOE OSTI2016

Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a unique opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained beta-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer brushes, or the most effective molecular release kinetics for drug delivery applications, for example.

Pacalin, Naomi M.↗
DOE OSTI2024

Designing multicomponent hydrides with potential high T c superconductivity

While hydrogen-rich materials have been demonstrated to exhibit high T c superconductivity at high pressures, there is an ongoing search for ternary, quaternary, and more chemically complex hydrides that achieve such high critical temperatures at much lower pressures. First-principles searches are impeded by the computational complexity of solving the Eliashberg equations for large, complex crystal structures. Here, we adopt a simplified approach using electronic indicators previously established to be correlated with superconductivity in hydrides. This is used to study complex hydride structures, which are predicted to exhibit promisingly high critical temperatures for superconductivity. In particular, we propose three classes of hydrides inspired by the Fm$\overline{3}$ m RH 3 structures that exhibit strong hydrogen network connectivity, as defined through the electron localization function. The first class [RH 11 X 3 Y] is based on a Pm$\overline{3}$m structure showing moderately high T c , where the T c estimate from electronic properties is compared with direct Eliashberg calculations and found to be surprisingly accurate. The second class of structures [(RH 11 ) 2 X 6 YZ] improves on this with promisingly high density of states with dominant hydrogen character at the Fermi energy, typically enhancing T c . The third class [(R 1 H 11 )(R 2 H 11 )X 6 YZ] improves the strong hydrogen network connectivity by introducing anisotropy in the hydrogen network through a specific doping pattern. These design principles and associated model structures provide flexibility to optimize both T c and the structural stability of complex hydrides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Designing Low Tortuosity Electrodes through Pattern Optimization for Fast-Charging

The development of fast-charging technologies is crucial for expediting the progress and promotion of electric vehicles. In addition to innovative material exploration, reduction in the tortuosity of electrodes is a favored strategy to enhance the fast-charging capability of lithium-ion batteries by optimizing the ion-transfer kinetics. To realize the industrialization of low-tortuosity electrodes, a facile, cost-effective, highly controlled, and high-output continuous additive manufacturing roll-to-roll screen printing technology is proposed to render customized vertical channels within electrodes. Extremely precise vertical channels are fabricated by applying the as-developed inks, using LiNi 0.6 Mn 0.2 Co 0.2 O 2 as the cathode material. Additionally, the relationship between the electrochemical properties and architecture of the channels, including the pattern, channel diameter, and edge distance between channels, is revealed. The optimized screen-printed electrode exhibited a seven-fold higher charge capacity (72 mAh g -1 ) at a current rate of 6 C and superior stability compared with that of the conventional bar-coated electrode (10 mAh g -1 , 6 C) at a mass loading of 10 mg cm -2 . Finally, this roll-to-roll additive manufacturing can potentially be applied to various active materials printing to reduce electrode tortuosity and enable fast charging in battery manufacturing.

42 ENGINEERING↗
DOE OSTI2015

WE-EF-303-03: A New Aperture-Based Imaging System for Prompt-Gamma Range Verification of Proton Beam Therapy

Purpose: To develop and characterize a novel aperture-based imaging system for high-energy gamma-rays. This collimated system will provide 2-dimensional imaging capability for verification of proton beam range and Bragg peak dose via prompt-gamma detection. Methods: A multi-knife-edge slit collimator has been designed, constructed, and characterized via simulations and experimental measurements. The 20×20×7.5 cm{sup 3} tungsten collimator and accompanying LSO scintillation detector were simulated using the TOPAS Geant4 -based Monte Carlo package. Iterative reconstruction methods were combined with point response functions to characterize the imaging performance of the system. The response of the system has begun to be characterized experimentally as well, using 2.6 MeV gamma-rays from Th-228. Results: Both simulation and experimental results indicate that this collimated system provides 2-D imaging capability in the energy range of interest for prompt-gamma dose verification. In the current configuration, with collimator to source distance of 13 cm, image reconstruction of point sources resulted in spatial resolution (FWHM) of approximately 4 mm in both x-and y-directions in the imaging plane. The accuracy of positioning the point sources is less than 1 mm. Conclusion: This work has characterized, via simulation and measurements, a novel multi-knife-edge slit collimator in front of a more conventional position-sensitive LSO scintillator detector. The multi-slit pattern is designed to increase detection efficiency and provide spatial information in 2-dimensions -- an improvement over a single-slit collimator design. The thickness and density of the collimator will allow this detection system to perform well in an environment with high gamma flux, while ultimately providing peak determination accuracy on the order of 1 mm. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number: DE-NA0000979 through the Nuclear Science and Security Consortium.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Expert Consensus Contouring Guidelines for Intensity Modulated Radiation Therapy in Esophageal and Gastroesophageal Junction Cancer

Purpose/Objective(s): Current guidelines for esophageal cancer contouring are derived from traditional 2-dimensional fields based on bony landmarks, and they do not provide sufficient anatomic detail to ensure consistent contouring for more conformal radiation therapy techniques such as intensity modulated radiation therapy (IMRT). Therefore, we convened an expert panel with the specific aim to derive contouring guidelines and generate an atlas for the clinical target volume (CTV) in esophageal or gastroesophageal junction (GEJ) cancer. Methods and Materials: Eight expert academically based gastrointestinal radiation oncologists participated. Three sample cases were chosen: a GEJ cancer, a distal esophageal cancer, and a mid-upper esophageal cancer. Uniform computed tomographic (CT) simulation datasets and accompanying diagnostic positron emission tomographic/CT images were distributed to each expert, and the expert was instructed to generate gross tumor volume (GTV) and CTV contours for each case. All contours were aggregated and subjected to quantitative analysis to assess the degree of concordance between experts and to generate draft consensus contours. The panel then refined these contours to generate the contouring atlas. Results: The κ statistics indicated substantial agreement between panelists for each of the 3 test cases. A consensus CTV atlas was generated for the 3 test cases, each representing common anatomic presentations of esophageal cancer. The panel agreed on guidelines and principles to facilitate the generalizability of the atlas to individual cases. Conclusions: This expert panel successfully reached agreement on contouring guidelines for esophageal and GEJ IMRT and generated a reference CTV atlas. This atlas will serve as a reference for IMRT contours for clinical practice and prospective trial design. Subsequent patterns of failure analyses of clinical datasets using these guidelines may require modification in the future.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Structure Activity Relationship Approach toward the Improved Separation of Rare-Earth Elements Using Diglycolamides

The separation of adjacent lanthanides continues to be a challenge worldwide because of the similar physical and chemical properties of these elements and a necessity to advance the use of clean-energy applications. In this paper, a systematic structure–performance relationship approach toward understanding the effect of N-alkyl group characteristics in diglycolamides (DGAs) on the separation of lanthanides(III) from a hydrochloric acid medium is presented. In addition to the three most extensively studied DGA complexants [N,N,N',N'-tetra(n-octyl)diglycolamide, TODGA; N,N,N',N'-tetra(2-ethylhexyl)diglycolamide, TEHDGA; N,N'-dimethyl-N,N'-di(n-octyl)diglycolamide, DMDODGA], 12 new extracting agents with varying substitution patterns were designed to study the interplay of steric and electronic effects that control rare-earth element extraction. Subtle changes in the structure around diglycolamide carbonyl oxygen atoms result in dramatic shifts in the lanthanide extraction strength and selectivity. The effects of the chain length and branching position of N-alkyl substituents in DGAs are elaborated on with the use of experimental, computational, and solution-structure characterization techniques.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Programmable nanowrinkle-induced room-temperature exciton localization in monolayer WSe2

Abstract Localized states in two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been the subject of intense study, driven by potential applications in quantum information science. Despite the rapidly growing knowledge surrounding these emitters, their microscopic nature is still not fully understood, limiting their production and application. Motivated by this challenge, and by recent theoretical and experimental evidence showing that nanowrinkles generate strain-localized room-temperature emitters, we demonstrate a method to intentionally induce wrinkles with collections of stressors, showing that long-range wrinkle direction and position are controllable with patterned array design. Nano-photoluminescence (nano-PL) imaging combined with detailed strain modeling based on measured wrinkle topography establishes a correlation between wrinkle properties, particularly shear strain, and localized exciton emission. Beyond the array-induced wrinkles, nano-PL spatial maps further reveal that the strain environment around individual stressors is heterogeneous due to the presence of fine wrinkles that are less deterministic. At cryogenic temperatures, antibunched emission is observed, confirming that the nanocone-induced strain is sufficiently large for the formation of quantum emitters. At 300 K, detailed nanoscale hyperspectral images uncover a wide range of low-energy emission peaks originating from the fine wrinkles, and show that the states can be tightly confined to regions <10 nm, even in ambient conditions. These results establish a promising potential route towards realizing room temperature quantum emission in 2D TMDC systems.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Enhancement of phonon backscattering due to confinement of ballistic phonon pathways in silicon as studied with a microfabricated phonon spectrometer

In this work, the mechanism for enhanced phonon backscattering in silicon is investigated. An understanding of phonon propagation through substrates has implications for engineering heat flow at the nanoscale, for understanding sources of decoherence in quantum systems, and for realizing efficient phonon-mediated particle detectors. In these systems, phonons that backscatter from the bottom of substrates, within the crystal or from interfaces, often contribute to the overall detector signal. We utilize a microscale phonon spectrometer, comprising superconducting tunnel junction emitters and detectors, to specifically probe phonon backscattering in silicon substrates (∼500 μm thick). By etching phonon “enhancers” or deep trenches (∼90 μm) around the detectors, we show that the backscattered signal level increases by a factor of ∼2 for two enhancers versus one enhancer. Using a geometric analysis of the phonon pathways, we show that the mechanism of the backscattered phonon enhancement is due to confinement of the ballistic phonon pathways and increased scattering off the enhancer walls. Our result is applicable to the geometric design and patterning of substrates that are employed in phonon-mediated detection devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Anderson localization of graphene by helium ion irradiation

Irradiation of a single-layer graphene (SLG) with accelerated helium ions (He{sup +}) controllably generates defect distributions, which create a charge carrier scattering source within the SLG. We report direct experimental observation of metal-insulator transition in SLG on SiO{sub 2}/Si substrates induced by Anderson localization. This transition was investigated using scanning capacitance microscopy by monitoring the He{sup +} dose conditions on the SLG. The experimental data show that a defect density of more than ∼1.2% induced Anderson localization. We also investigated the localization length by determining patterned placement of the defects and estimated the length to be several dozen nanometers. These findings provide valuable insight for patterning and designing graphene-based nanostructures using helium ion microscopy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

An interaction scenario of the galaxy pair NGC 3893/96 (KPG 302): A single passage?

Using the data obtained previously from Fabry-Perot interferometry, we study the orbital characteristics of the interacting pair of galaxies KPG 302 with the aim to estimate a possible interaction history, the conditions necessary for the spiral arm formation, and initial satellite mass. We found by performing N-body/smoothed particle hydrodynamics simulations of the interaction that a single passage can produce a grand design spiral pattern in less than 1 Gyr. Although we reproduce most of the features with the single passage, the required satellite to host mass ratio should be ∼1:5, which is not confirmed by the dynamical mass estimate made from the measured rotation curve. We conclude that a more realistic interaction scenario would require several passages in order to explain the mass ratio discrepancy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Direct fabrication of high aspect-ratio metal oxide nanopatterns via sequential infiltration synthesis in lithographically defined SU-8 templates

Nanopatterning high aspect-ratio metal oxide structures remains challenging for conventional nanofabrication methods based on reactive ion etching due to marginal etch selectivity between target oxides and typical mask materials. Here, the authors report the application of sequential infiltration synthesis (SIS) on lithographically defined SU-8 polymer templates for patterning arbitrarily designed, high aspect-ratio metal oxide nanostructures with sub-50 nm linewidths, smooth vertical profiles, and three-dimensional (3D) morphologies difficult to achieve by the conventional fabrication methods. As examples, various AlOx nanostructures with ∼40 nm linewidths and up to 16 aspect ratios were demonstrated, along with TiOx in-plane nanowire arrays of controlled positional registrations. Detailed scanning and transmission electron microscopy studies revealed nanocrystalline and amorphous internal structures of respective AlOx and TiOx, as well as the swelling and contraction behaviors of polymer templates during the SIS process, which allowed the facile fabrication of high aspect-ratio, sub-50 nm-featured oxide nanopatterns with 3D morphologies. These results confirm the potential of vapor-phase material infiltration in directly nanopatterning complexly structured metal oxides.

Nam, Chang-Yong↗
DOE OSTI2013

Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries

Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT MLC sequences. For all phantoms and plans, time-resolved (10 Hz) ion chamber dose was collected. In addition, coronal (XY) films were exposed in the cube phantom to a VMAT beam with two different starting phases, and compared to the reconstructed motion-perturbed dose planes. Results: For the X or Y motions with the moving strip and geometrical phantoms, the maximum difference between perturbation-reconstructed and ion chamber doses did not exceed 1.9%, and the average for any motion pattern/starting phase did not exceed 1.3%. For the VMAT plans on the cubic and thoracic phantoms, one point exhibited a 3.5% error, while the remaining five were all within 1.1%. Across all the measurements (N = 22), the average disagreement was 0.5 {+-} 1.3% (1 SD). The films exhibited {gamma}(3%/3 mm) passing rates {>=}90%. Conclusions: The dose to an arbitrary moving voxel in a patient can be estimated with acceptable accuracy for a VMAT delivery, by performing a single QA measurement with a cylindrical phantom and applying two consecutive perturbations to the TPS-calculated patient dose. The first one accounts for the differences between the planned and delivered static doses, while the second one corrects for the motion.

60 APPLIED LIFE SCIENCES↗