Showing papers by "National Institute of Standards and Technology published in 2023"

Characterizing light engine uniformity and its influence on liquid crystal display based vat photopolymerization printing

Abstract: Vat photopolymerization (VP) is a rapidly growing category of additive manufacturing. As VP methods mature the expectation is that the quality of printed parts will be highly reproducible. At present, detailed characterization of the light engines used in liquid crystal display (LCD)-based VP systems is lacking and so it is unclear if they are built to sufficiently tight tolerances to meet the current and/or future needs of additive manufacturing. Herein, we map the irradiance, spectral characteristics, and optical divergence of a nominally 405 nm LCD-based VP light engine. We find that there is notable variation in all of these properties as a function of position on the light engine that cause changes in extent of polymerization and surface texture. We further demonstrate through a derived photon absorption figure of merit and through printed test parts that the spatial heterogeneity observed in the light engine is significant enough to affect part fidelity. These findings help to explain several possible causes of variable part quality and also highlight the need for improved optical performance on LCD-based VP printers.

ASCE/SEI 41 assessment of reinforced concrete buildings: Benchmarking nonlinear dynamic procedures with empirical damage observations

Abstract: ASCE/SEI 41 is the consensus US standard for the seismic evaluation and retrofit of existing buildings. Although the performance-based engineering standard is based on decades of research and has been significantly vetted by ASCE and other committees, it is unclear how well the evaluations capture the seismic response of real building systems. This article examines six, primarily nonductile, reinforced concrete buildings, including four damaged in earthquakes and two experimental structures tested and damaged on shake tables, to compare the measured response and observed damage to simulated outcomes produced following ASCE/SEI 41 nonlinear dynamic procedure. The results show that the simulations are generally able to capture the story mechanism and peak transient story drift demands at the critical story (predicted values are typically within ±20% of the measured values). However, drifts at non-critical stories and floor accelerations at all stories show greater error relative to the measured responses. At the component level, the simulations, in most cases, correctly identify the location(s) of the critical component(s) and the failure mode (e.g. flexure vs shear). However, the extent of the damage is overestimated in some cases. These results form the basis for recommendations for column, beam, and wall modeling procedures that can be used to improve ASCE/SEI 41.

2022 Optical Interference Coatings Conference: Manufacturing Problem Contest [Invited]

Abstract: Participants in the 2022 Manufacturing Problem Contest were challenged to fabricate an optical filter with a specified stepped transmittance spanning three orders of magnitude from 400 to 1100 nm. The problem required that contestants be versed in the design, deposition, and measurement of optical filters to achieve good results. Nine samples from five institutions were submitted with total thicknesses between 5.9 and 53.5 µm with between 68 and 1743 layers. The filter spectra were measured by three independent laboratories. The results were presented in June 2022 at the Optical Interference Coatings Conference in Whistler, B.C., Canada.

Thick gate oxide extrinsic breakdown – The potential role of neutral hydrogen atom

Abstract: Power electronics is currently a hot topic due to its important role in fighting climate change. Gate oxide breakdown is the Achilles heel of power devices, and it is well known that extrinsic breakdown is the chief concern. However, the root cause of extrinsic breakdown is poorly understood. Recently, a "lucky defect" model was introduced to explain extrinsic breakdown beyond the traditional "local thinning" model. In this work, the "lucky defect" model is further developed to allow it to examine the responsible defect's energy distribution. It is found that only defects with energy 1.5 eV ± 0.3 eV above the substrate conduction band can produce the breakdown distributions commonly reported. Few studied defects can satisfy this requirement. An exception is the neutral hydrogen atom, and its known properties are consistent with experimental results in the literature. If confirmed, this has important implication on how to remedy extrinsic breakdown.

VECSEL systems for quantum information processing with trapped beryllium ions

Abstract: We demonstrate two systems based on vertical-external-cavity surface-emitting lasers (VECSELs) for producing ultraviolet laser light at wavelengths of 235 and 313 nm. The systems are suitable for quantum information processing with trapped beryllium ions. Each system consists of a compact, single-frequency, continuous-wave VECSEL producing high-power near-infrared light, tunable over tens of nanometers. One system generates 2.4 W at 940 nm, using a gain mirror based on GaInAs/GaAs quantum wells, which is converted to 54 mW of 235 nm light for photoionization of neutral beryllium atoms. The other system uses a gain mirror based on GaInNAs/GaAs quantum wells, enabling wavelength extension above 1200 nm with manageable strain in the GaAs lattice. This system generates 1.6 W at 1252 nm, which is converted to 41 mW of 313 nm light that is used to laser cool trapped 9 Be + ions and quantum state preparation and detection. The 313 nm system is also suitable for implementing high-fidelity quantum gates.

V-Ramp test and gate oxide screening under the “lucky” defect model

Abstract: The persistent (after exhaustive wafer cleaning) extrinsic breakdown distribution of thick gate oxides requires an early breakdown mechanism that goes beyond the popular local thinning model to explain. The success of the “Lucky” defect model in fulfilling this role deserves a further exploration of its implications. This work examines the implications of using the V-Ramp and the high-voltage screening methods to identify early failures. In this study, it is shown that the V-Ramp method fails to produce useful information about the oxide quality at operation voltages and that the high-field screening method fails to screen out early failures.

Optimizing Product Life Cycle Systems for Manufacturing in a Circular Economy

Abstract: Abstract Global population growth and increasing resource scarcity are necessitating sustainable manufacturing and circular economy (CE) practices. These practices require the decisions made at each product life cycle (PLC) stage consider sustainability and circularity implications. We propose PLC system level optimization to identify the most favorable choices, instead of siloed individual PLC stage-specific optimizations. This should yield better circularity by permitting manufacturers to take a more holistic view and identify the areas of highest impact across the PLC. This paper presents initial work towards building a PLC system optimization framework. From an initial review of current circularity metrics, we identify metrics that are suitable for forming the optimization objectives. Second, we identify decision variables available to manufacturers across the PLC that are useful in optimizing the entire system’s circularity and sustainability. Finally, we identify limitations of current metrics, and discuss major challenges and potential solutions to PLC system optimization problems.

Towards Incorporating a Possibility of Zero-day Attacks Into Security Risk Metrics: Work in Progress

Abstract: This paper reports on work in progress on incorporating a possibility of zero-day attacks into security risk metrics. System security is modelled by Attack Graph (AG), where attack paths may include a combination of known and zero-day exploits. While set of feasible zero-day exploits and composition of each attack path are known, only estimates of likelihoods of known exploits are available. We propose addressing uncertain likelihoods of zero-day exploits within framework of robust risk metrics. Assuming some base likelihoods of zero-day exploits, robust risk metrics assume worst-case Probabilistic or Bayesian AG scenario allowing for a controlled deviation of actual likelihoods of zero-day exploits from their base values. The corresponding worst-case scenario is defined with respect to the system losses due to a zero-day attack. These robust risk metrics interpolate between the corresponding probabilistic or Bayesian AG model on the one hand and purely antagonistic game-theoretic model on the other hand. Popular k-zero day security metric is a particular case of the proposed metric.

Classifying Multi-generational Products for the Circular Economy

Abstract: Abstract Manufacturers are increasingly interested in the circular economy (CE) and potential of circular productions. To fully utilize CE, better guidance at the design stage is needed to establish closed-loop flows and prioritize higher value retaining end-of-use (EoU) practices such as reuse and remanufacture (i.e., parts harvesting). Intergenerational commonality (IC) is a method to increase EoU parts harvesting. However, closed-loop parts harvesting potential depends on the compatible timing between design generations' production and EoU returns curves. Therefore, in this paper, we explore an approach to make an initial assessment on where IC as a closed-loop CE strategy can produce most benefit, where such closed-loops may fall short, and what favorable design decisions can be made. The proposed indicator (based on the ratio between product's average usable lifetime and time between generation introductions, u avg /t intro ) provides a basis for developing an objective design-support tool. Using a hypothetical example, we discuss the approach and effectiveness of this indicator. The insights gained suggest that overall production's sustainability performance show substantial improvement when u avg /t intro < 1.25, and the IC benefits are highest when 0.25 < u avg /t intro < 2.0. We also highlight a few managerial insights gained from the indicator useful to strategize EoU recovery and IC.

Design Approaches to Expand the Toolkit for Building Cotranscriptionally Encoded RNA Strand Displacement Circuits

Abstract: Cotranscriptionally encoded RNA strand displacement (ctRSD) circuits are an emerging tool for programmable molecular computation, with potential applications spanning in vitro diagnostics to continuous computation inside living cells. In ctRSD circuits, RNA strand displacement components are continuously produced together via transcription. These RNA components can be rationally programmed through base pairing interactions to execute logic and signaling cascades. However, the small number of ctRSD components characterized to date limits circuit size and capabilities. Here, we characterize over 200 ctRSD gate sequences, exploring different input, output, and toehold sequences and changes to other design parameters, including domain lengths, ribozyme sequences, and the order in which gate strands are transcribed. This characterization provides a library of sequence domains for engineering ctRSD components, i.e., a toolkit, enabling circuits with up to 4-fold more inputs than previously possible. We also identify specific failure modes and systematically develop design approaches that reduce the likelihood of failure across different gate sequences. Lastly, we show the ctRSD gate design is robust to changes in transcriptional encoding, opening a broad design space for applications in more complex environments. Together, these results deliver an expanded toolkit and design approaches for building ctRSD circuits that will dramatically extend capabilities and potential applications.

Reply on RC2

Abstract: Abstract. We present an open-path mid-infrared dual-comb spectrometer (DCS) capable of precise measurement of the stable water isotopologues H₂¹⁶O and HD¹⁶O. This system ran in a remote configuration at a rural test site for 3.75 months with 60 % uptime and achieved a precision of <2 ‰ on the normalized ratio of H₂¹⁶O and HD¹⁶O (δD) in 1000 seconds. Here, we compare the δD values from the DCS to those from the National Ecological Observatory Network (NEON) isotopologue point sensor network. Over the multi-month campaign, the mean difference between the DCS δD values and the NEON δD values from a similar ecosystem is <2 ‰ with a standard deviation of 18 ‰, which demonstrates the inherent accuracy of DCS measurements over a variety of atmospheric conditions. We observe time-varying diurnal profiles and seasonal trends that are mostly correlated between the sites on daily time scales. This observation motivates the development of denser ecological monitoring networks aimed at understanding regional and synoptic scale water transport. Precise and accurate open-path measurements using DCS provide new capabilities for such networks.

Precision engineering of biological function with large-scale measurements and machine learning

Abstract: As synthetic biology expands and accelerates into real-world applications, methods for quantitatively and precisely engineering biological function become increasingly relevant. This is particularly true for applications that require programmed sensing to dynamically regulate gene expression in response to stimuli. However, few methods have been described that can engineer biological sensing with any level of quantitative precision. Here, we present two complementary methods for precision engineering of genetic sensors: in silico selection and machine-learning-enabled forward engineering. Both methods use a large-scale genotype-phenotype dataset to identify DNA sequences that encode sensors with quantitatively specified dose response. First, we show that in silico selection can be used to engineer sensors with a wide range of dose-response curves. To demonstrate in silico selection for precise, multi-objective engineering, we simultaneously tune a genetic sensor’s sensitivity ( EC 50 ) and saturating output to meet quantitative specifications. In addition, we engineer sensors with inverted dose-response and specified EC 50 . Second, we demonstrate a machine-learning-enabled approach to predictively engineer genetic sensors with mutation combinations that are not present in the large-scale dataset. We show that the interpretable machine learning results can be combined with a biophysical model to engineer sensors with improved inverted dose-response curves.

Methodologies and Implementation of Laser Powder-Bed Fusion Process Control

Abstract: Abstract Part quality in additive manufacturing (AM) is highly dependent on process control, but there is a lack of adequate AM control methods and standards. Laser powder-bed fusion (L-PBF) is one of the most-used metal AM techniques. This article focuses on the following laser control parameters: laser focus, laser power, laser position, and laser power-position synchronization. It then provides a discussion on laser scan strategies. The article also provides an overview of the AM control framework, the two major sections of which are software and hardware.

Analysis of E3 Transitions in Ag-like High-Z Ions Observed with the NIST EBIT

Abstract: We report measurements and identification of the E3 4f7/2,5/2-5s1/2 transitions and E1 allowed transitions in Ag-like W (Z = 74), Re (Z = 75), and Ir (Z = 77). The spectra were recorded at the NIST EBIT using a grazing-incidence EUV spectrometer. The present measured wavelengths and theoretical predictions using GRASP2K calculations confirm previous observations of the same E3 transitions in Ag-like W. Our collisional–radiative model using the NOMAD code offers an insight into the population kinematics for Ag-like ions of heavy elements. We discuss the observed spectra and comparisons of the measured and simulated spectral lines.

"Measurements and models of GHGs and short-lived pollutants in the Baltimore/Washington area: Emissions and environmental justice"

Abstract: Abstract: Greenhouse gases and associated pollutants (CO, NOx, VOCs, aerosols) are measured from a small airplane, mobile laboratory, and towers.&#160; Through mass balance calculations and comparison to numerical models such as CMAQ-GHG&#160; we estimate the total flux from the cities of Baltimore, MD and Washington, DC.&#160; Emissions inventories were found to underestimate methane emissions substantially and have been improved.&#160; Major sources include leakage in the natural gas delivery system and biogenic processes including landfills.&#160; Measurements with high spatial and temporal resolution reveal hot spots of high concentrations often associated with pollutants such as black carbon (BC) and NO2 that pose a health hazard in disadvantaged communities.&#160;

Standards and Conformity Assessment

Abstract: Standards and conformity assessment are important to strengthening the science and quality of forensic science. Standards provide a foundation for consistency between processes related to testing, accreditation, management systems, and personnel certification. This article provides an overview of U.S. and international documentary standards and conformity assessment concepts as they relate to forensic science service providers (FSSPs) and discusses the current state of standards development and associated challenges for implementation.

Towards Security Metrics Combining Risks of Known and Zero-day Attacks: Work in Progress

Abstract: This paper reports on work in progress on security metrics combining risks of known and zero-day attacks. We assume that system security is modelled by Attack Graph (AG), where attack paths may include a combination of known and zeroday exploits and impact of successful attacks is quantified by system loss function. While set of feasible zero-day exploits and composition of each attack path are known, only estimates of likelihoods of known exploits are available. After averaging the system loss function over likelihoods of known exploits, we propose addressing uncertain likelihoods of zero-day exploits within framework of robust risk metrics. Assuming some prior likelihoods of zero-day exploits, robust risk metrics are identified with the worst-case Bayesian AG scenario subject to a controlled deviation of actual likelihoods of zero-day exploits from their priors. The corresponding worst-case scenario is defined with respect to the system losses due to a zero-day attack. We argue that the proposed risk metric quantifies potential benefits of system configuration diversification, such as Moving Target Defense, for mitigation of the system/attacker information asymmetry.

Letter to the Editor Concerning “Simultaneous, Single-Particle Measurements of Size and Loading Give Insights into the Structure of Drug-Delivery Nanoparticles”

Abstract: ADVERTISEMENT RETURN TO ISSUELetter to the EditorNEXTLetter to the Editor Concerning “Simultaneous, Single-Particle Measurements of Size and Loading Give Insights into the Structure of Drug-Delivery Nanoparticles”Andrew C. MadisonAndrew C. MadisonMicrosystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United StatesMore by Andrew C. Madisonhttps://orcid.org/0000-0002-9456-2754, Adam L. PintarAdam L. PintarStatistical Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United StatesMore by Adam L. Pintarhttps://orcid.org/0000-0002-5021-2576, Craig R. CopelandCraig R. CopelandMicrosystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United StatesMore by Craig R. Copelandhttps://orcid.org/0000-0002-3340-0006, Natalia FarkasNatalia FarkasMicrosystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United StatesTheiss Research, La Jolla, California 92037, United StatesBuilding and Fire Sciences, United States Forest Service, Forest Products Laboratory, Madison, Wisconsin 53726, United StatesMore by Natalia Farkashttps://orcid.org/0000-0002-7102-7345, and Samuel M. Stavis*Samuel M. StavisMicrosystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States*Email: [email protected]More by Samuel M. Stavishttps://orcid.org/0000-0002-7108-1405Cite this: ACS Nano 2023, 17, 10, 8837–8842Publication Date (Web):May 23, 2023Publication History Published online23 May 2023Published inissue 23 May 2023https://doi.org/10.1021/acsnano.2c04894Copyright © Published 2023 by American Chemical SocietyRIGHTS & PERMISSIONSArticle Views797Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Diffusion,Hydrodynamics,Lipids,Nanoparticles,Transport properties Get e-Alerts

On Potential Risks of “Natural” Hybrid Load Balancing in Large-Scale Clouds: Work in Progress

Abstract: Realization of economic, reliability, and low latency benefits of the Cloud computing model will probably require flexible hybrid static/dynamic load balancing which combine good queuing performance under stable exogenous conditions with timely response to varying/uncertain exogenous conditions. This paper reports on work in progress on potential risks/benefits of natural two-tier hybrid load balancing strategies. At the “slow” time scale, this strategy employs quasi static load balancing which adjusts to the expected/normal exogenous conditions. Once divergence between the actual and expected exogenous conditions is indicated by grows of the real-time queues, a “natural” dynamic load balancing is employed. Our main, and somewhat unexpected, finding is that while this “natural” hybrid strategy inherits benefits of static load balancing, it also inherits local instability risk of dynamic load balancing.

Ground-to-UAV, laser-based, multi-species emissions quantification at long standoff distances

Abstract: Abstract. Determination of trace gas emissions from sources is critical for understanding and regulating air quality and climate change. Here, we demonstrate a method for rapid quantification of the emission rate of multiple gases from simple and complex sources using a mass-balance approach with a spatially scannable open-path sensor – in this case, an open-path dual-comb spectrometer. The open-path spectrometer measures the total column density of gases between the spectrometer and a retroreflector mounted on an unmanned aerial vehicle (UAV). By measuring slant columns at multiple UAV altitudes downwind of a source (or sink), the total emission rate can be rapidly determined without the need for an atmospheric dispersion model. Here, we demonstrate this technique using controlled releases of CH4 and C2H2. We show an emission rate determination to within 50 % of the known flux with a single 10-minute flight and within 10 % of the known flux after 10 flights. Furthermore, we estimate a detection limit for CH4 emissions to be 0.03 g CH4/s. This detection limit is approximately the same as the emissions from 25 head of beef cattle and is less than the average emissions from a small oil field pneumatic controller. Other gases including CO2, NH3, HDO, ethane, formaldehyde (HCHO), CO, and N2O can be measured by simply changing the dual-comb spectrometer.

Fabrication error detection in diffraction gratings with high dynamic range Fourier plane imaging and spatial filtering

Abstract: We summarize our development of a low-cost instrument for the detection of fabrication errors in diffraction gratings. Our instrument applies a low-cost digital camera and high dynamic range (HDR) imaging in the focal plane of a lens to analyze light reflected by a diffraction grating. A dynamic range close to 1010 is achieved for a spatial frequency range that is relevant for types of errors that occur in the lithographic fabrication of gratings. We also describe a modification of the instrument in which a spatial filter is used to block the large fraction of light that does not carry information on fabrication errors. This “coronagraph” modification reduces measurement times by about an order of magnitude. A unique pseudologarithmic transformation is described for the visualization of wide range data that include zero or negative values, such as HDR images.

The Quantum Reform of the International System of Units

Abstract: On 20 May 2019, Le Système internationale d’unités (SI) or the International System of Units underwent a historic change to become defined in terms of assigned values of constants of nature. This chapter provides a brief historical overview of units and describes the changes that occurred in the redefinition. We dedicate this chapter to the memory of Prof. Ian Mills, OBE, FRS (1930–2022), who played a significant role in the redefinition.