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At least 1,063 records · Page 59

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SERVIR: Cross-Comparison of Carbon Emission Estimates Based on Variable Land Use Land Cover Changes within SERVIR Focus Regions

Deforestation in the tropics contributes approximately one-fifth of the annual global greenhouse gas (GHG) emissions. In an effort to reduce GHG emissions, SERVIR - a joint USAID and NASA initiative - is currently implementing the SERVIR CArbon Pilot (S-CAP) activity. By developing a comprehensive CO2 tracking system in Google Earth Engine based on both remotely sensed data and in situ observations, S-CAP aims to build capacity within the SERVIR regional hubs to improve decision making and local monitoring efforts surrounding GHG emissions. The S-CAP estimations are being completed throughout 11 pilot countries within the SERVIR regions of Asia, Africa, and the Americas to integrate partner contributions and local input into the development process. These emission estimate calculations use country-level REDD+ FREL reported values, global remotely sensed data (e.g. Global Forest Watch) and regional datasets and are completed using the IPCC Guidelines for National Greenhouse Gas Inventories. From the S-CAP activity thus far, country CO2 estimations had varied differences, ranging from 56% to 197% between their lowest and highest estimates. The results from this study show that CO2 emission estimates can differ greatly depending on the land cover data sets used as well as the biomass values, and how a comprehensive database is essential in understanding the full range of impacts that land cover change has in these regions. Using this ensemble approach, SERVIR hubs can better select the most appropriate datasets available for estimating emissions.

Carbon Emission↗

DOE OSTI2016

System and method for reducing combustion dynamics in a combustor

A system for reducing combustion dynamics in a combustor includes an end cap that extends radially across the combustor and includes an upstream surface axially separated from a downstream surface. A combustion chamber is downstream of the end cap, and tubes extend from the upstream surface through the downstream surface. Each tube provides fluid communication through the end cap to the combustion chamber. The system further includes means for reducing combustion dynamics in the combustor. A method for reducing combustion dynamics in a combustor includes flowing a working fluid through tubes that extend axially through an end cap that extends radially across the combustor and obstructing at least a portion of the working fluid flowing through a first set of the tubes.

42 ENGINEERING↗

DOE OSTI2017

Bulkhead insert for an internal combustion engine

An engine includes a cylinder block defining at least one main bearing bulkhead adjacent to a cylinder, and a crankshaft rotatably housed within the block by a main bearing. A bulkhead insert has a cap portion, and an insert portion provided within the bulkhead. The insert portion has having first and second end regions connected by first and second straps. Each strap having a flanged beam cross section. The first and second ends of the insert portion are configured to connect a main bearing cap column to a cylinder head column. Each of the first and second end regions define at least one protrusion having a surface substantially normal to engine combustion and reactive loads. The cap portion is configured to mate with the first end region at the main bearing cap column and support the main bearing.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2019

Systems and methods for miniaturized drawbar extension springs

Extension springs that can be manufactured to a small size with a precise free length are described herein. An extension spring comprises a first drawbar member and a second drawbar member that extend along a same direction. The extension spring further comprises a compression spring coil that surrounds respective portions of the draw bar members. At either end of the spring coil are positioned end caps that surround the drawbar members. The end caps provide flat surfaces on which the ends of the spring coil rest in a resting position of the extension spring. The end caps are held against bent ends of arms of the drawbar members by tension of the spring coil. When the drawbar members are drawn apart from one another, the end caps compress the spring coil. Compression of the spring coil causes forces that resist the motion of the drawbar members apart from one another.

42 ENGINEERING↗

DOE OSTI2021

Tamper-resistant fastener

A tamper-resistant threaded fastener including a circular head having a slot formed in the head transverse to the longitudinal axis, the slot having an enlarged region intermediate an apex and a base of the slot. A cap member includes a head having a drive feature formed therein, the head extending to a first shank portion, extending to an enlarged second shank portion, extending to a foot. The cap member is insertable in the slot only from a direction transverse to the longitudinal axis. During rotational installation of the fastener and cap member in a threaded counterbored opening for securing a barrier for protecting an asset, the foot shears inside the slot at a predetermined rotational drive force, the cap member being rotatable in the opening and protectively covering the fastener head.

Neidigk, Stephen↗

DOE OSTI2021

Target unit with ceramic capsule for producing cu-67 radioisotope

A target unit for producing Cu67 radioisotope is described herein, and comprises a cage body releasably coupled to a screw-on cap; and a ceramic capsule containing a solid Zn68 target ingot and having one open end and one closed end and defining an interior chamber for the target ingot. The ceramic capsule is releasably contained between the cage body and the screw-on cap with a lid disposed on the open end of the capsule and a washer positioned between the lid and the screw-on cap. The screw-on cap and the washer provide a water-tight seal between the lid and the capsule. The interior of the capsule is in intimate physical contact with the target ingot; and the Zn68 of the target ingot is free of traces of residual oxygen that interfere with contact of the Zn68 to the capsule.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2022

Shock test assembly

An assembly for shock testing a specimen, the assembly including first and second opposing brackets and opposing lower and upper caps. The opposing brackets include lower and upper angled surfaces. The lower cap includes lower angled surfaces configured to engage the lower angled surfaces of the left and right brackets. The upper cap includes upper angled surfaces configured to engage the upper angled surfaces of the left and right brackets. The first and second brackets are configured to be drawn toward each other via fasteners, thereby wedging the lower and upper caps toward each other against the specimen.

Busenitz, Clark↗

DOE OSTI2023

Shock test assembly

Busenitz, Clark↗

DOE OSTI2019

Closure Device For a Containment Vessel in a Small Gram Quantity Shipping Package

SRNL has been chartered by DOE Environmental Management (DOE-EM) to develop a new Type B shipping package for Small Gram Quantities (SGQ) of radioactive material. Design a containment vessel (CV) closure device that will reduce the operation time and improve the ease-of- use for Operations Personnel. The Containment Vessel (CV) includes a closure lid cap with spring shaft and locking tabs, multiple disc springs, and vessel with integral locking ring. The CV is assembled by aligning the tabs on the lid cap with the openings in the locking ring. Next, the lid cap is pushed down to compress the disc springs. Finally, the lid is rotated 45-degrees to locking location. When released, the tabs are secured against the locking ring. Disc springs (e.g. Belleville washers, coned-disc springs, Belleville spring, etc.) exert axial loads on the mating parts when compressed. The orientation of the disc springs can be configured to change the deflection and axial loads for specific designs. In addition to securing the lid cap to the vessel, the compressed disc springs can be used to apply a load to a containment seal (e.g. o-ring). A prototype of the CV closure was 3D printed to evaluate the locking mechanism design and functionality. A test plan will be developed to evaluate the mechanical properties (i.e. compression forces) and functionality of the CV closure design.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2025

Advanced Computational Modeling of High-Level Waste Vitrification at the Hanford Site

The U.S. Department of Energy (DOE) has selected vitrification for stabilizing legacy tank waste at the Hanford site, where radioactive waste from plutonium production was historically stored in underground tanks. This waste will be separated into low-activity waste (LAW) and high-level waste (HLW) fractions and processed at the Waste Treatment and Immobilization Plant (WTP). At WTP, glass melters are used for the vitrification of radioactive tank waste, transforming it into a stable borosilicate glass form for safe long-term storage. The melter vessel is constructed from highly durable and heat-resistant materials, where the vitrification process occurs. The main regions that are modeled are the melt pool, plenum, cold cap, riser/discharge chamber, and surrounding structure with insulation layers. Forced convection induced by air bubblers at the base of the melter ensure uniform temperature distribution and provide heat to the cold cap layer. The cold cap is a region of reacting batch feed that floats on top of the molten glass and is where the batch-to-glass reactions occur. Joule heating provided by electrodes mounted along the vertical walls of the melter and immersed directly in the glass, generates the necessary heat for the net endothermic conversion processes that occur in the cold cap. The high temperatures, radioactivity, and opaque nature of the glass prevent direct observation inside the melters. Therefore, computational models are essential for providing insight into factors that affect melter throughput. Thermocouples in the plenum provide operators with plenum temperature measurements. Operational adjustments include bubbling rate, voltage supplied to the electrodes, feed adjustments, and glass removal rate. Different computational fluid dynamics (CFD) models have been developed, each serving a specific purpose. There are CFD models of different scale melters, as well as models that capture the two-phase flow interfaces of rising bubbles in the molten glass or models with a simplified molten glass region so that the surrounding structure and plenum can be feasibly incorporated. Pilot-scale melter models have been developed to serve as validation of the methods employed in the simulation of the full-scale WTP melters. Models incorporating resolved bubbling are used to develop momentum source terms to implement into a single phase, multi-region, steady-state flow model that is being validated by measured process parameters such as glass production rate, voltage, input power, plenum temperatures, etc. The resolved bubbling model uses the multiphase volume of fluid approach to model the system with a high-resolution interface capturing scheme to maintain sharp interfaces between the molten glass and the air phase. The suite of CFD models is continually being improved to incorporate more realistic physics and achieve faster turnaround time. For example, an incremental controller is implemented to automatically adjust electrode voltage within the simulation to a molten glass set point temperature of 1150°C. Newer models feature improved meshes to ensure conformal meshes between regions and eliminate unnecessary mesh refinement in areas that are not of interest (such as boundary layers in offgas ports). Instead of explicitly modeling the structural, refractory, and insulation layers of the melter, a thermal resistance approach is used with published correlations used for boundary conditions. The development of robust and efficient CFD models will be instrumental in enabling the WTP to successfully fulfill its mission of safely stabilizing legacy nuclear waste.

12 - MGMT OF RADIOACTIVE AND NON-RADIOACTIVE WASTE↗

DOE OSTI2024

Ultrathin Magnesium-Based Coating as an Efficient Oxygen Barrier for Superconducting Circuit Materials

Scaling up superconducting quantum circuits based on transmon qubits necessitates substantial enhancements in qubit coherence time. Over recent years, tantalum (Ta) has emerged as a promising candidate for transmon qubits, surpassing conventional counterparts in terms of coherence time. However, amorphous surface Ta oxide layer may introduce dielectric loss, ultimately placing a limit on the coherence time. In this study, a novel approach for suppressing the formation of tantalum oxide using an ultrathin magnesium (Mg) capping layer is presented. Synchrotron-based X-ray photoelectron spectroscopy studies demonstrate that oxide is confined to an extremely thin region directly beneath the Mg/Ta interface. Additionally, it is demonstrated that the superconducting properties of thin Ta films are improved following the Mg capping, exhibiting sharper and higher-temperature transitions to superconductive and magnetically ordered states. Moreover, an atomic-scale mechanistic understanding of the role of the capping layer in protecting Ta from oxidation is established based on computational modeling. Further, this work provides valuable insights into the formation mechanism and functionality of surface tantalum oxide, as well as a new materials design principle with the potential to reduce dielectric loss in superconducting quantum materials. Ultimately, the findings pave the way for the realization of large-scale, high-performance quantum computing systems.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Criteria Air Pollutants and Greenhouse Gas Emissions from Hydrogen Production in U.S. Steam Methane Reforming Facilities

The global and U.S. domestic effort to develop a clean energy economy and curb environmental pollution incentivizes the use of hydrogen as a transportation fuel, owing to its zero tailpipe pollutant emissions and high fuel efficiency in fuel cell electric vehicles (FCEVs). However, the hydrogen production process is not emissions free. Conventional hydrogen production via steam methane reforming (SMR) is energy intensive, coproduces carbon dioxide, and emits air pollutants. Therefore, it is necessary to quantify the environmental impacts of SMR hydrogen production alongside the use-phase of FCEVs. This study fills the information gap, analyzing the greenhouse gas (GHG) and criteria air pollutant (CAP) emissions associated with hydrogen production in U.S. SMR facilities by compiling and matching the facility-reported GHG and CAP emissions data with facilities’ hydrogen production data. The actual amounts of hydrogen produced at U.S. SMR facilities are often confidential. Thus, we have developed four approaches to estimate the hydrogen production amounts. The resultant GHG and CAP emissions per MJ of hydrogen produced in individual facilities were aggregated to develop emission values for both a national median and a California state median. Lastly, this study also investigates the breakdown of facility emissions into combustion emissions and noncombustion emissions.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Multifunction Hydrophobic Ligand Engineered Cd(S, Se)/ZnS Quantum Dots for Stabilizing Highly Efficient Carbon‐Based Perovskite Solar Cells

The long-term operational stability of perovskite solar cells (PSCs) remains a key challenge impeding their commercialization, particularly due to ambient environments (e.g., moisture, oxygen, heat)-induced degradation. Carbon electrode-based PSCs have emerged as cost-effective and relatively stable alternatives to metal electrode-based devices due to carbon materials' hydrophobic behavior, yet they still lag in both long-term durability and power conversion efficiency (PCE). In this work, an ultrathin hydrophobic ligand-modified core–shell Cd(S,Se)/ZnS quantum dots (QDs) capping layer is introduced as a multifunctional interfacial modifier for carbon-electrode-based PSCs. This oleic acid ligand-modified QDs capping layer exhibits inherent hydrophobicity, effectively serving as a moisture barrier to retard perovskite degradation under ambient conditions. Furthermore, the strong interfacial bonding between the QDs and perovskite halide surfaces leads to efficient trap state passivation, reducing trap density and creating a more uniform electrical contact. The modified QDs/perovskite interface also features an elevated conduction band edge, promoting improved charge extraction. As a result, devices incorporating this quantum dot capping layer retain 98% of their initial PCE after 450 h of ambient aging and achieve a champion efficiency of 20.74%. As a result, this strategy highlights the potential of hydrophobic ligand-modified chalcogenide QDs as surface modifiers to enhance both the stability and performance of carbon-based PSCs, offering a promising route toward scalable fabrication of durable perovskite solar modules.

14 SOLAR ENERGY↗

DOE OSTI2020

Thermally Activated Adsorption in Metal–Organic Frameworks with a Temperature‐Tunable Diffusion Barrier Layer

Abstract Modification of the external surfaces of metal–organic frameworks offers a new level of control over their adsorption behavior. It was previously shown that capping of MOFs with ethylenediamine (EDA) can effectively retain small gaseous molecules at room temperature. Reported here is a temperature‐induced variation in the capping‐layer gate‐opening mechanism through a combination of in situ infared experiments and ab initio simulations of the capping layer. An atypical acceleration and increase in the loading of weakly adsorbed molecules upon raising the temperature above room temperature is observed. These findings show the discovery of novel temperature‐dependent kinetics that goes beyond standard kinetics and suggest a new avenue for tailoring selective adsorption by thermally tuning the surface barrier.

Tan, Kui↗

DOE OSTI2020

Thermally activated adsorption in metal–organic frameworks with a temperature–tunable diffusion barrier layer

Modification of the external surfaces of metal organic frameworks offers a new level of control over their adsorption behavior. Here, we have previously shown that capping of MOFs with ethylenediamine (EDA) can effectively retain small gaseous molecules at room temperature. Here, we report a temperature–induced variation in the capping–layer gate opening mechanism through a combination of in situ IR experiments and ab initio simulations of the capping layer. We find an atypical acceleration and increase in the loading of weakly adsorbed molecules upon raising the temperature above room temperature. Our findings show the discovery of a novel temperature–dependent kinetics that goes beyond standard kinetics and suggest a new avenue for tailoring selective adsorption by thermally tuning the surface barrier.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Design of a Short Thermally Stable α‐Helix Embedded in a Macrocycle

Abstract Although helices play key roles in peptide–protein and protein–protein interactions, the helical conformation is generally unstable for short peptides (10–15 residues) in aqueous solution in the absence of their binding partners. Thus, stabilizing the helical conformation of peptides can lead to increases in binding potency, specificity, and stability towards proteolytic degradation. Helices have been successfully stabilized by introducing side chain‐to‐side chain crosslinks within the central portion of the helix. However, this approach leaves the ends of the helix free, thus leading to fraying and exposure of the non‐hydrogen‐bonded amide groups to solvent. Here, we develop a “capped‐strapped” peptide strategy to stabilize helices by embedding the entire length of the helix within a macrocycle, which also includes a semirigid organic template as well as end‐capping interactions. We have designed a ten‐residue capped‐strapped helical peptide that behaves like a miniprotein, with a cooperative thermal unfolding transition and T m ≈70 °C, unprecedented for helical peptides of this length. The NMR structure determination confirmed the design, and X‐ray crystallography revealed a novel quaternary structure with implications for foldamer design.

Wu, Haifan↗

DOE OSTI2018

Suggestion of an Indicator to Evaluate Material Deposition in Resistance Spot Welding: Weld–Surface Interaction Index

Resistance spot welding (RSW) is still leading joining process in the automotive industry due to the simplicity and speed of the process. On the other hand, galvanized steel sheets provide improvement in corrosion resistance of the auto body. Material deposition has an influence on the corrosion resistance and weld strength; however, in the literature very little effort has been made to identify any weld–surface interaction numerically. In this study, a numerical approach called “Weld–Surface Interaction Index” (I{sub WSI}) has been introduced to investigate the effect of material deposition on the corrosion sensitivity of the welding zone and its periphery. A systematic investigation was carried out to better understand the effects of an electrode cap–galvanized steel sheet interface on the corrosion resistance of spot-welded steel. The chemical composition of DP600 steel sheet and Z-Trode electrode cap was analyzed by using a spectrometer. The specimens were then joined by using same caps up to 1200 welds. SEM–EDS analysis was also performed on the chosen specimens to determine the weight percentages (wt.%) of Fe, Zn and Cu. EDS analysis results and coefficient of variation wt.% of Fe, Zn and Cu were used to compose I{sub WSI} formula. In the proposed formula, wt.% of Zn represented resistivity of the cover to corrosion, while wt.% of Fe represents the vulnerability.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Evaluation of methods for characterizing the fine particulate matter emissions from aircraft and other diffusion flame combustion aerosol sources

The U. S. Environmental Protection Agency in collaboration with the U. S. Air Force Arnold Engineering Development Complex conducted the VAriable Response In Aircraft nvPM Testing (VARIAnT) 3 and 4 test campaigns to compare nvPM emissions measurements from a variety of diffusion flame combustion aerosol sources (DFCASs), including a Cummins diesel engine, a diesel powered generator, two gas turbine start carts, a J85-GE-5 turbojet engine burning multiple fuels, and a Mini-CAST soot generator. The VARIAnT research program has conducted four test campaigns to date with the VARIAnT 3 and 4 test campaigns focusing on BC mass instrument performance, use of gas turbine engine sources for BC mass instrument calibration, and the characterization of the aerosols produced from the combustion sources. Results from both campaigns revealed agreement of about 20% between the AVL Micro-Soot Sensor, the Cavity Attenuated Phase Shift (CAPS PMSSA) monitor and the thermal-optical reference method for elemental carbon (EC), independent of the calibration source used. For the Artium LII-300, the measured mass concentrations in VARIAnT3 fall within 18% and in VARIAnT4 fall within 32% of the reference EC mass concentration when calibrated on a combustor rig in VARIAnT3 and on a LGT-60 start cart in VARIAnT4, respectively. It was also found that the three mass instrument types (MSS, CAPS PMSSA, and LII-300) can exhibit different BC to reference EC ratios depending on the emission source that appear to correlate to particle geometric mean mobility diameter, morphology, or some other parameter associated with particle geometric mean diameter (GMD) with the LII-300 showing a slightly stronger apparent trend with GMD. Systematic differences in LII-300 measured mass concentrations have been reduced by calibrating with a turbine combustion source (combustor or turbine engine). With respect to the particle size measurements made, the sizing instruments (TSI SMPS, TSI EEPS, and Cambustion DMS 500) were found to be in general agreement in terms of size distributions and concentrations with some exceptions. Teflon filter measurements of the total aerosol mass produced by the various DFCASs differed from the reference EC, BC, and integrated particle sized distribution measured aerosol masses. The Teflon filter measured mass was 30 to 40% greater than the reference EC and 50 to 60% greater than the BC mass for the J85 in both test campaigns. The measurements of particle size distributions and single particle analysis by miniSPLAT indicated the presence of large particles (>100 nm) having more compact morphologies, higher effective density, and a composition dominated by OC and ash. This increased large particle fraction is also associated with higher values of single scattering albedo measured by the CAPS PMSSA instrument and higher OC/EC measurements. These measurements indicate gas turbine engine emissions can be a more heterogeneous mix of particle types beyond the original E31 assumption that it is mainly composed of black carbon.

33 ADVANCED PROPULSION SYSTEMS↗