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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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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1954

Summary of Free-Flight Zero-Lift Drag Results from Tests of 1/5-Scale Models of the Convair YF-102 and F-102A Airplanes and Several Related Small Equivalent Bodies at Mach Numbers from 0.70 to 1.46

One-fifth-scale rocket-propelled models of the Convair YF-102 and F-102A airplanes were tested to determine free-flight zero-lift drag coefficients through the transonic speed range at Reynolds numbers near those to be encountered by the full-scale airplane. Trim and duct characteristics were obtained along with measurements of total-, internal-, and base-drag coefficients. Additional zero-lift drag tests involved a series of small equivalent-body-of-revolution models which were launched to low supersonic speeds by means of a helium gun. The several small models tested corresponded to the following full-scale airplanes: basic, YF-102, 2-foot (full-scale) fuselage extension, F-102A, F-102A (relocated inlets), F-102A (faired nose), and F-102A (parabolic nose) . Equivalent-body models corresponding to the normal area distribution (derived for Mach number 1.0) of each of these airplane shapes were flown and, in addition, equivalent-body models designed to represent the YF-102 and F-102A airplanes at Mach number 1.2 were tested. External-drag coefficients obtained from the 115-scale tests ranged from 0.0094 to 0.0273 for the YF-102 model and from 0.0100 to 0.0255 for the F-102A model. Forebody external-pressure-drag coefficients (drag rise) at Mach number 1.05 of 0.0183 and 0.0134 were obtained from the 115-scale models of the YF-102 and F-102A, respectively, a 16-percent reduction for the F-102A model. Values of drag rise at Mach number 1.05 from the small equivalent-body tests were nearly the same for the basic, YF-102, and 2-foot-fuselage-extension airplane shapes. Equivalent-body tests of the YF-102 and F-102A shapes showed the latter to have about 25 percent less drag rise as compared with a 16-percent reduction illustrated by the 1/5-scale tests. Additional equivalent-body tests illustrating effects of modifications to the F-102A airplane shape shared that relocating the inlets on the fuselage or altering the nose shape to provide a smoother cross-sectional area progression reduced the drag rise by approximately 16 percent. Replacing a major portion of the nose of the F-102A equivalent-body model with one of parabolic shape resulted in about a 21-percent reduction in drag rise. The drag-rise data from the equivalent-body tests include base drag.

Wallskog, Harvey A.↗
DOE OSTI2020

Understanding the Impact of Lignocellulosic Biomass Variability on the Size Reduction Process: A Review

The importance of size reduction to the commercial deployment of biomass utilization technologies cannot be overemphasized. Size reduction is necessary to create good flowing, easily digestible lignocellulosic biomass. However, inefficiencies and inconsistencies have not been well addressed for the process of size reduction. This has motivated quite a few research studies, some of which have reported the influence of process variables and pretreatment on the size reduction performance as well as the development of novel size reduction equipment and empirical mathematical models. In this Perspective, we present a systematic and critical evaluation of the state of lignocellulosic biomass size reduction research to provide insights for engineers and scientists for future development and investigation. We first briefly discuss the structural biology and failure mode of lignocellulosic biomass. Then, we present a comprehensive, data-driven picture of the interactions among lignocellulosic biomass attributes, size reduction process variables, pretreatment processes, and size reduction process performance (as defined by product characteristics and size reduction energy consumption). The sizing equipment tool wear issues are also summarized. Finally, we highlight some existing gaps and future research opportunities for lignocellulosic biomass size reduction to inform the development of newer technologies that could effectively produce high-value lignocellulosic biomass particles.

09 BIOMASS FUELS↗
DOE OSTI2023

Laboratory Experiments Examining the Effect of Thermal and Mechanical Processes on Hydraulic Transmissivity Evolution

Using laboratory slide-hold-slide experiments, at temperatures from 22 to 200 degrees C, to examine effects of fracture reactivation and quasi-static loading on the evolution of fluid transport properties of simulated fractures in Westerly granite. At all temperatures, the in-plane hydraulic transmissivity consistently decays during hold periods resulting in an overall reduction in transmissivity. During the first three to fifteen hours of an experiment, transmissivity decreases rapidly due to the generation of wear products, development of a sliding surface, and compaction of the resulting gouge. Once the sliding surface has developed, the long-term transmissivity decay rate at 22 and 100 degrees C is significantly lower than the transmissivity decay rate during the initial 3-15 hours of the experiment. However, at 200 degrees C, the decay of hydraulic transmissivity remains high throughout the experiment. The long-term decay of hydraulic transmissivity can be fitted with a power law model with more rapid reduction of hydraulic transmissivity at higher temperature. Periods of sliding on the fracture surface result in transient increases in the transmissivity, due to shear dilation, as is expected for Coulomb materials. These transients are superimposed on the long-term decay. When sliding ceases and a new hold period commences, there is a rapid reduction in transmissivity and return to the long-term rate of transmissivity decay. The rate of decay of the transmissivity transients is inversely correlated with temperature, in contrast to the long-term decay and the expected behavior for processes like subcritical crack growth and indentation creep. The higher decay rates that are observed during the initial 3-15 hours of the tests and following sliding, are associated with times that the porosity of the gouge is expected to be high. The difference in decay rates suggests that when the gouge is driven far from equilibrium by active shearing, densification may be dominated by a different mechanism from long-term compaction.

15 GEOTHERMAL ENERGY↗
NASA NTRS1990

Energy management analysis of lunar oxygen production

Energy load models in the process of hydrogen reduction of ilmenite for lunar oxygen production are being developed. The load models will be used as a first step to ultimately determine the optimal energy system needed to supply the power requirements for the process. The goal is to determine the energy requirements in the process of hydrogen reduction of ilmenite to produce oxygen. The general approach is shown, and the objectives are to determine the energy loads of the processes in the system. Subsequent energy management studies will be made to minimize the system losses (irreversibilities) and to design optimal energy system power requirements. A number of processes are being proposed as possible candidates for lunar application and some detailed experimental efforts are being conducted within this project at the University of Arizona. Priorities are directed toward developing the energy models for each of the proposed processes being considered. The immediate goals are to identify the variables that would impact energy requirements and energy sources of supply.

Fazzolari, R.↗
DOE OSTI2015

Application of Nonlinear Seismic Soil-Structure Interaction Analysis for Identification of Seismic Margins at Nuclear Power Plants

Seismic probabilistic risk assessment (SPRA) methods and approaches at nuclear power plants (NPP) were first developed in the 1970s and aspects of them have matured over time as they were applied and incrementally improved. SPRA provides information on risk and risk insights and allows for some accounting for uncertainty and variability. As a result, SPRA is now used as an important basis for risk-informed decision making for both new and operating NPPs in the US and in an increasing number of countries globally. SPRAs are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in some instances the current SPRA approach contains large uncertainties, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility). INL has an advanced SPRA research and development (R&D) activity that will identify areas in the calculation process that contain significant uncertainties. One current area of focus is the use of nonlinear soil-structure interaction (NLSSI) analysis methods to accurately capture: 1) nonlinear soil behavior and 2) gapping and sliding between the NPP and soil. The goal of this study is to compare numerical NLSSI analysis results with recorded earthquake ground motions at Fukushima Daichii (Great Tohuku Earthquake) and evaluate the sources of nonlinearity contributing to the observed reduction in peak acceleration. Comparisons are made using recorded data in the free-field (soil column with no structural influence) and recorded data on the NPP basemat (in-structure response). Results presented in this study should identify areas of focus for future R&D activities with the goal of minimizing uncertainty in SPRA calculations. This is not a validation activity since there are too many sources of uncertainty that a numerical analysis would need to consider (variability in soil material properties, structural material properties, etc.). Rather the report will determine if the NLSSI calculations are following similar trends observed in the recorded data (i.e. reductions in maximum acceleration between the free-field and basemat) Numerical NLSSI results presented show maximum accelerations between the free field and basemat were reduced the EW and NS directions. The maximum acceleration in the UD direction increased slightly. The largest reduction in maximum accelerations between the modeled free-field and the NPP basemat resulted in nearly 50% reduction. The observation in reduction of numerical maximum accelerations in the EW and NS directions follows the observed trend in the recorded data. The maximum reductions observed in these NLSSI studies were due to soil nonlinearities, not gapping and sliding (although additional R&D is needed to develop an appropriate approach to model gapping and sliding). This exploratory study highlights the need for additional R&D on developing: (i) improved modeling of soil nonlinearities (soil constitutive models that appropriately capture cyclic soil behavior), (ii) improved modeling of gapping and sliding at the soil-structure interface (to appropriately capture the dissipation of energy at this interface), and (iii) experimental laboratory test data to calibrate the items (i) and (ii).

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS2017

A Comparative Study of Simulated and Measured Main Landing Gear Noise for Large Civil Transports

Computational results for the NASA 26%-scale model of a six-wheel main landing gear with and without a toboggan-shaped noise reduction fairing are presented. The model is a high-fidelity representation of a Boeing 777-200 aircraft main landing gear. A lattice Boltzmann method was used to simulate the unsteady flow around the model in isolation. The computations were conducted in free-air at a Mach number of 0.17, matching a recent acoustic test of the same gear model in the Virginia Tech Stability Wind Tunnel in its anechoic configuration. Results obtained on a set of grids with successively finer spatial resolution demonstrate the challenge in resolving/capturing the flow field for the smaller components of the gear and their associated interactions, and the resulting effects on the high-frequency segment of the farfield noise spectrum. Farfield noise spectra were computed based on an FWH integral approach, with simulated pressures on the model solid surfaces or flow-field data extracted on a set of permeable surfaces enclosing the model as input. Comparison of these spectra with microphone array measurements obtained in the tunnel indicated that, for the present complex gear model, the permeable surfaces provide a more accurate representation of farfield noise, suggesting that volumetric effects are not negligible. The present study also demonstrates that good agreement between simulated and measured farfield noise can be achieved if consistent post-processing is applied to both physical and synthetic pressure records at array microphone locations.

Konig, Benedikt↗
DOE OSTI2025

FPGA-accelerated SpeckleNN with SNL for real-time X-ray single-particle imaging

We present the implementation of a specialized version of our previously published unified embedding model, SpeckleNN, for real-time speckle pattern classification in X-ray Single-Particle Imaging (SPI), using the SLAC Neural Network Library (SNL) on an FPGA platform. This hardware realization transitions SpeckleNN from a prototypic model into a practical edge solution, optimized for running inference near the detector in high-throughput X-ray free-electron laser (XFEL) facilities, such as those found at the Linac Coherent Light Source (LCLS). To address the resource constraints inherent in FPGAs, we developed a more specialized version of SpeckleNN. The original model, which was designed for broader classification across multiple biological samples, comprised ~5.6 million parameters. The new implementation, while reducing the parameter count to 64.6K (a 98.8% reduction), focuses on maintaining the model's essential functionality for real-time operation, achieving an accuracy of 90%. Furthermore, we compressed the latent space from 128 to 50 dimensions. This implementation was demonstrated on the KCU1500 FPGA board, utilizing 71% of available DSPs, 75% of LUTs, and 48% of FFs, with an average power consumption of 9.4W according to the Vivado post-implementation report. The FPGA performed inference on a single image with a latency of 45.015 microseconds at a 200 MHz clock rate. In comparison, running the same inference on an NVIDIA A100 GPU resulted in an average power consumption of ~73W and an image processing latency of around 400 microseconds. Our FPGA-accelerated version of SpeckleNN demonstrated significant improvements, achieving an 8.9 × speedup and a 7.8 × reduction in power consumption compared to the GPU implementation. Key advancements include model specialization and dynamic weight loading through SNL, which eliminates the need for time-consuming FPGA design re-synthesis, allowing fast and continuous deployment of models (re)trained online. These innovations enable real-time adaptive classification and efficient vetoing of speckle patterns, making SpeckleNN more suited for deployment in XFEL facilities. This implementation has the potential to significantly accelerate SPI experiments and enhance adaptability to evolving experimental conditions.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Process Improvements to Biomass Pretreatment of Fuels and Chemicals

MBI, a 501c(3) company focusing on de-risking and scaling up bio-based technologies, has teamed with Michigan State University and the Idaho National Laboratory to develop and demonstrate process improvements to the ammonia fiber expansion (AFEX) pretreatment process. The logistical hurdles of biomass handling are well known, and the regional depot concept - in which small, distributed bioprocessing operations collect, preprocess, and densify biomass before shipping to a centralized refinery - is a promising alternative to centralized collection. AFEXTM (AFEX is a trademark of MBI) has unique features among pretreatments that would make it desirable as a pretreatment prior to densification at the depot scale. MBI has developed a novel design, using a packed bed reactor for the AFEX process that can be scaled down economically to the depot scale at a lower capital cost as compared to the traditional design (Pandia type reactor). Thus, the purpose of this project was to develop, scale-up, demonstrate, and improve this novel design The key challenges are the recovery of ammonia, consistent and complete pretreatment performance, and the overall throughput of the reactor. In this project an engineering scale packed bed AFEX system with 1-ton per day capacity was installed at MBI’s building. The system has been operational since mid-2013. During that time, MBI has demonstrated the robustness, reliability, and consistency of the process. To date, nearly 500 runs have been performed in the reactors. There have been no incidences of plugging (i.e., inability to remove ammonia from biomass after the treatment), nor has there been any instance of a major ammonia release into the atmosphere. Likewise, the sugar released via enzyme hydrolysis has remained consistent throughout these runs. Our economic model shows a 46% reduction in AFEX capital cost at the 100 ton/day scale compared to the traditional design of AFEX (Pandia type reactor). The key performance factors were demonstrated; >94% ammonia recovery, >75% sugar yields at high solid loading, and complete utilization of the sugars for ethanol production at the 2500 liter scale. Fermentation tests were performed using Zymomonas mobilis 8b and densified AFEX-treated corn stover at >20% solid loading. The obtained titer (~60g/l), productivity (2.5 g/L-h), and yield (330 L/tonne of biomass) exceeded the performance targets set out by NREL. The key findings from these efforts are: no contamination was observed, no cleanup of the sugar stream was required, and no major nutrient addition was required. Our economic model shows that using a packed bed design for the AFEX process and pelleted AFEX-treated biomass reduces the ethanol production cost by 24% when compared to using the traditional AFEX design.

09 BIOMASS FUELS↗
NASA NTRS2022

Automatic variable selection in ecological niche modeling: A case study using Cassin’s Sparrow (Peucaea cassinii)

MERRA/Max provides a feature selection approach to dimensionality reduction that enables direct use of global climate model outputs in ecological niche modeling. The system accomplishes this reduction through a Monte Carlo optimization in which many independent MaxEnt runs, operating on a species occurrence file and a small set of randomly selected variables in a large collection of variables, converge on an estimate of the top contributing predictors in the larger collection. These top predictors can be viewed as potential candidates in the variable selection step of the ecological niche modeling process. MERRA/Max’s Monte Carlo algorithm operates on files stored in the underlying filesystem, making it scalable to large data sets. Its software components can run as parallel processes in a high-performance cloud computing environment to yield near real-time performance. In tests using Cassin’s Sparrow (Peucaea cassinii) as the target species, MERRA/Max selected a set of predictors from Worldclim’s Bioclim collection of 19 environmental variables that have been shown to be important determinants of the species’ bioclimatic niche. It also selected biologically and ecologically plausible predictors from a more diverse set of 86 environmental variables derived from NASA’s Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) reanalysis, an output product of the Goddard Earth Observing System Version 5 (GEOS-5) modeling system. We believe these results point to a technological approach that could expand the use global climate model outputs in ecological niche modeling, foster exploratory experimentation with otherwise difficult-to-use climate data sets, streamline the modeling process, and, eventually, enable automated bioclimatic modeling as a practical, readily accessible, low-cost, commercial cloud service.

John L. Schnase↗
DOE OSTI2018

Dissimilatory Sulfate Reduction Under High Pressure by Desulfovibrio alaskensis G20

Biosouring results from production of H2S by sulfate-reducing microorganisms (SRMs) in oil reservoirs. H2S is toxic, corrosive, and explosive, and as such, represents a significant threat to personnel, production facilities, and transportation pipelines. Since typical oil reservoir pressures can range from 10 to 50 MPa, understanding the role that pressure plays in SRM metabolism is important to improving souring containment strategies. To explore the impact of pressure, we grew an oil-field SRM isolate, Desulfovibrio alaskensis G20, under a range of pressures (0.1–14 MPa) at 30°C. The observed microbial growth rate was an inverse function of pressure with an associated slight reduction in sulfate and lactate consumption rate. Competitive fitness experiments with randomly bar-coded transposon mutant library sequencing (RB-TnSeq) identified several genes associated with flagellar biosynthesis and assembly that were important at high pressure. The fitness impact of specific genes was confirmed using individual transposon mutants. Confocal microscopy revealed that enhanced cell aggregation occurs at later stages of growth under pressure. We also assessed the effect of pressure on SRM inhibitor potency. Dose-response experiments showed a twofold decrease in the sensitivity of D. alaskensis to the antibiotic chloramphenicol at 14 MPa. Fortuitously, pressure had no significant influence on the inhibitory potency of the common souring controlling agent nitrate, or the emerging SRM inhibitors perchlorate, monofluorophosphate, or zinc pyrithione. Our findings improve the conceptual model of microbial sulfate reduction in high-pressure environments and the influence of pressure on souring inhibitor efficacy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Updates to the Regional Seismic Travel Time (RSTT) Model: 1. Tomography

Abstract A function of global monitoring of nuclear explosions is the development of Earth models for predicting seismic travel times for more accurate calculation of event locations. Most monitoring agencies rely on fast, distance-dependent one-dimensional (1D) Earth models to calculate seismic event locations quickly and in near real-time. RSTT (Regional Seismic Travel Time) is a seismic velocity model and computer software package that captures the major effects of three-dimensional crust and upper mantle structure on regional seismic travel times, while still allowing for fast prediction speed (milliseconds). We describe updates to the RSTT model using a refined data set of regional phases (i.e., Pn, Pg, Sn, Lg) using the Bayesloc relative relocation algorithm. The tomographic inversion shown here acts to refine the previous RSTT public model ( rstt201404um ) and displays significant features related to areas of global tectonic complexity as well as further reduction in arrival residual values. Validation of the updated RSTT model demonstrates significant reduction in median epicenter mislocation (15.3 km) using all regional phases compared to the iasp91 1D model (22.1 km) as well as to the current station correction approach used at the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (18.9 km).

58 GEOSCIENCES↗
DOE OSTI2014

Radiosynthesis and biological evaluation of a novel enoyl-ACP reductase inhibitor for Staphylococcus aureus

Here we evaluated the pharmacokinetics (PK) and pharmacodynamics (PD) of PT119, a potent Staphylococcus aureus enoyl-ACP reductase (saFabI) inhibitor with a K i value of 0.01 nM and a residence time of 750 min on the enzyme target in mice. PT119 was found to have promising antibacterial activity in two different S. aureus infection models: it caused a 3 log reduction in the CFU’s in a mouse thigh muscle infection model and increased the survival rate from 0% to 50% in a mouse systemic infection model. PT119 was then radiolabeled with carbon-11 to evaluate its biodistribution and PK in both healthy and S. aureus infected mice using positron emission tomography (PET). The biodistribution of [ 11 C]PT119 and/or its labeled metabolites did not differ significantly between the healthy group and the infected group, and PT119 was found to distribute equally between serum and tissue during the ~1 h of analysis permitted by the carbon-11 half life. This approach provides important data for PK/PD modeling and is the first step in identifying radiotracers that can non-invasively image bacterial infection in vivo.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

A mononuclear nonheme {FeNO} 6 complex: synthesis and structural and spectroscopic characterization

While the synthesis and characterization of {FeNO} 7,8,9 complexes have been well documented in heme and nonheme iron models, {FeNO} 6 complexes have been less clearly understood. Herein, we report the synthesis and structural and spectroscopic characterization of mononuclear nonheme {FeNO} 6 and iron(III)–nitrito complexes bearing a tetraamido macrocyclic ligand (TAML), such as [(TAML)Fe III (NO)] - and [(TAML)Fe III (NO 2 )] 2- , respectively. First, direct addition of NO (g) to [Fe III (TAML)] - results in the formation of [(TAML)Fe III (NO)] - , which is sensitive to moisture and air. The spectroscopic data of [(TAML)Fe III (NO)] - , such as 1 H nuclear magnetic resonance and X-ray absorption spectroscopies, combined with computational study suggest the neutral nature of nitric oxide with a diamagnetic Fe center (S = 0). We also provide alternative pathways for the generation of [(TAML)Fe III (NO)] - , such as the iron–nitrite reduction triggered by protonation in the presence of ferrocene, which acts as an electron donor, and the photochemical iron–nitrite reduction. To the best of our knowledge, the present study reports the first photochemical nitrite reduction in nonheme iron models.

36 MATERIALS SCIENCE↗
NASA NTRS2000

Microwave Driven Actuators Power Allocation and Distribution

Design, fabrication and test of a power allocation and distribution (PAD) network for microwave driven actuators is presented in this paper. Development of a circuit that would collect power from a rectenna array amplify and distribute the power to actuators was designed and fabricated for space application in an actuator array driven by a microwave. A P-SPICE model was constructed initially for data reduction purposes, and was followed by a working real-world model. A voltage up - converter (VUC) is used to amplify the voltage from the individual rectenna. The testing yielded a 26:1 voltage amplification ratio with input voltage at 9 volts and a measured output voltage 230VDC. Future work includes the miniaturization of the circuitry, the use of microwave remote control, and voltage amplification technology for each voltage source. The objective of this work is to develop a model system that will collect DC voltage from an array of rectenna and propagate the voltage to an array of actuators.

Forbes, Timothy↗
NASA NTRS1972

Prediction of electron concentration reductions in re-entry flow fields due to electrophilic liquid and water injection.

Discussion of an analytical model which leads to predictions of reductions in electron concentrations in reentry flow fields due to the injection of electrophilic liquids and water. The processes incorporated into the model are: penetration and breakup of the liquid jet, droplet acceleration and vaporization, expansion of the liquid spray due to droplet vaporization, electrophilic vapor diffusion, heterogeneous and homogeneous charged species recombination kinetics and homogeneous electron attachment kinetics. Spray boundary calculations are shown to be in good agreement with photographic observations of water and Freon E-3 sprays in wind tunnel tests of a scale model RAM C-III flight vehicle. Fixed-bias electrostatic probe data taken during the RAM C-III flight are interpreted in terms of effective jet penetration distances - which are shown to be consistent with calculations using the present model.

Pergament, H. S.↗
NASA NTRS2024

Aera-Mip: Emission Pathways, Remaining Budgets, and Carbon Cycle Dynamics Compatible With 1.5 and 2 °C Global Warming Stabilization

While international climate policies now focus on limiting global warming to well below 2 °C or pursuing a 1.5 °C level of global warming, the climate modelling community has not provided an experimental design in which all Earth system models (ESMs) converge and stabilize at the same prescribed global warming levels. This gap hampers accurate estimations based on comprehensive ESMs of the carbon emission pathways and budgets needed to meet such agreed warming levels and of the associated climate impacts under temperature stabilization. Here, we apply the Adaptive Emission Reduction Approach (AERA) with ESMs to provide such simulations in which all models converge at 1.5 and 2.0 °C warming levels by adjusting their emissions over time. These emission-driven simulations provide a wide range of emission pathways and resulting atmospheric CO 2 projections for a given warming level, uncovering uncertainty ranges that were previously missing in the traditional Coupled Model Intercomparison Project (CMIP) scenarios with prescribed greenhouse gas concentration pathways. Meeting the 1.5 °C warming level requires a 40 % (full model range: 7 % to 76 %) reduction in multi-model mean CO 2 -forcing-equivalent (CO 2 -fe) emissions from 2025 to 2030, a 98 % (57 % to 127 %) reduction from 2025 to 2050, and a stabilization at 1.0 (−1.7 to 2.9) PgC yr−1 from 2100 onward after the 1.5 °C global warming level is reached. Meeting the 2.0 °C warming level requires a 47 % (8 % to 92 %) reduction in multi-model mean CO 2 -fe emissions until 2050 and a stabilization at 1.7 (−1.5 to 2.7) PgC yr−1 from 2100 onward. The on-average positive emissions under stabilized global temperatures are the result of a decreasing transient climate response to cumulative CO 2 -fe emissions over time under stabilized global warming. This evolution is consistent with a slightly negative zero emissions commitment – initially assumed to be zero – and leads to an increase in the post-2025 CO 2 -fe emission budget by a factor of 2.2 (−0.8 to 6.9) by 2150 for the 1.5 °C warming level and a factor of 1.4 (0.9 to 2.4) for the 2.0 °C warming level compared to its first estimate in 2025. The median CO 2 -only carbon budget by 2150, relative to 2020, is 800 GtCO 2 for the 1.5 °C warming level and 2250 GtCO 2 for the 2.0 °C warming level. These median values exceed the median IPCC AR6 estimates by 60 % for the 1.5 °C warming level and 67 % for 2.0 °C. Some of the differences may be explained by the choice of the mitigation scenario for non-CO 2 radiative agents. Our simulations highlight shifts in carbon uptake dynamics under stabilized temperature, such as a cessation of the carbon sinks in the North Atlantic and in tropical forests. On the other hand, the Southern Ocean remains a carbon sink centuries after temperatures stabilize. Overall, this new type of warming-level-based emission-driven simulation offers a more coherent assessment across climate models and opens up a wide range of possibilities for studying both the carbon cycle and climate impacts, such as extreme events, under climate stabilization.

Adaptive Emission Reduction Approach↗
NASA NTRSDate not supplied

Electrochemical Recycling of CO2

Carbon dioxide (CO2) is a molecule that plays multiple roles in our universe. Currently, its impact on global warming has rightfully given CO2 a label as a harmful waste product that must be amply handled. Nonetheless, under other circumstances, and from other perspectives, CO2 could be regarded as a valuable resource. As example, in nature CO2 is an essential building block in photosynthesis ultimately yielding molecules and materials that we harvest for numerous applications ranging from energy storage and construction to medicines and food. In a similar manner, there is a growing interest to utilize atmospheric CO2 to generate renewable fuels and platform chemicals through artificial processes. These processes can replace fossil based industrial processes on earth alleviating climate impact, but they can also find uses far away from our planet. In space, CO2 is an important source of precious oxygen, however, it can also serve as feedstock for carbon-based molecules and materials that are needed to sustain societies at distant planets such as Mars. In this presentation, I will discuss the contemporary understanding of electrochemical reduction of CO2 for selective production of desired molecules. We will zoom in to the very atomic scale to gain mechanistic understanding of how the structure and composition of the cathode electrode affects product distributions. This information is used as guide in the design of new materials that convert CO2 more efficiently and more selectively. On this basis, opportunities for recycling CO2 under different conditions will be discussed, as will remaining challenges for the ultimate application towards the sustainable human living on earth and in space.

electrochemistry↗
NASA NTRS2007

Model Checker for Java Programs

Java Pathfinder (JPF) is a verification and testing environment for Java that integrates model checking, program analysis, and testing. JPF consists of a custom-made Java Virtual Machine (JVM) that interprets bytecode, combined with a search interface to allow the complete behavior of a Java program to be analyzed, including interleavings of concurrent programs. JPF is implemented in Java, and its architecture is highly modular to support rapid prototyping of new features. JPF is an explicit-state model checker, because it enumerates all visited states and, therefore, suffers from the state-explosion problem inherent in analyzing large programs. It is suited to analyzing programs less than 10kLOC, but has been successfully applied to finding errors in concurrent programs up to 100kLOC. When an error is found, a trace from the initial state to the error is produced to guide the debugging. JPF works at the bytecode level, meaning that all of Java can be model-checked. By default, the software checks for all runtime errors (uncaught exceptions), assertions violations (supports Java s assert), and deadlocks. JPF uses garbage collection and symmetry reductions of the heap during model checking to reduce state-explosion, as well as dynamic partial order reductions to lower the number of interleavings analyzed. JPF is capable of symbolic execution of Java programs, including symbolic execution of complex data such as linked lists and trees. JPF is extensible as it allows for the creation of listeners that can subscribe to events during searches. The creation of dedicated code to be executed in place of regular classes is supported and allows users to easily handle native calls and to improve the efficiency of the analysis.

Visser, Willem↗