Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Growth efficiency”

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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Long-term integrated soil-crop management improves soil microbial community structure to reduce GHG emission and increase yield

Integrated soil-crop management (ISCM) has been shown as an effective strategy to increase efficiency and yield while its soil microbial community structure and function remain unclear. We evaluated changes in soil physicochemical factors, bacterial community structure responses, and the contributions of soil properties and bacterial communities to summer maize-winter wheat yield and GHG emissions through an ISCM experiment [T1 (local smallholder farmers practice system), T2 (improved management system), T3 (high–yield production system), and T4 (optimized management system)], which could provide scientific guidance for sustainable development of soil in summer maize-winter wheat rotation system. The results showed that the optimized ISCM could improve the soil quality, which significantly changed the soil bacterial community structure to reduce GHG emissions and increase yield. The co-occurrence network density of T3 was increased significantly. The Acidobacteria (class) and OM190 (class) were enriched in T2 and T4. The Frankiales (order) and Gaiellales (order) were enriched in T3. However, the changes in different crop growth stages were different. At the wheat jointing stage and maize mature stage, T4 could enhance carbon-related functional groups, such as aromatic hydrocarbon degradation and hydrocarbon degradation, to increase the soil organic carbon content. And at the maize tasseling stage, T4 could enhance nitrogen-related functional groups. And soil bacteria structure and function indirectly affected annual yield and GHG emission. T2 and T4 exhibited a similar soil microbial community. However, the yield and nitrogen use efficiency of T2 were reduced compared to those of T4. The yield of T3 was the highest, but the GHG emission increased and soil pH and nitrogen use efficiency decreased significantly. Therefore, T4 was a suitable management system to improve soil quality and soil bacterial community structure and function to decrease GHG emissions and increase the yield of the summer maize-winter wheat rotation system.

Yu, Ningning↗
DOE OSTI2022

Covalent Organic Framework as an Efficient Protection Layer for a Stable Lithium-Metal Anode

We report Lithium (Li) metal shows great potential for achieving high-energy-density rechargeable batteries. However, the practical applications of Li-metal batteries are still challenged by the formation of Li dendrites and unstable solid-electrolyte interphase (SEI) on metallic Li. Herein, a thin covalent organic framework layer is in situ fabricated on Li (COF-Li) to suppress Li dendrite growth and mitigate the side reaction on the Li anode. The COF has a periodic and uniform porosity, allowing for selectively sieving Li ions and guiding a uniform Li deposition. As a result, the COF-Li exhibits a non-dendrite morphology during repeated Li plating/stripping and demonstrates a remarkable cycle life over 13 200 h with an extremely low overpotential of only 16 mV at a high current density of 10 mA cm -2 and a high areal capacity of 10 mAh cm -2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Shift in Peaks of PAH-Associated Health Risks From East Asia to South Asia and Africa in the Future

Lung cancer risk from exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is expected to change significantly by 2050 compared to 2008 due to changes in climate and emissions. Integrating a global atmospheric chemistry model, a lung cancer risk model, and plausible future emissions trajectories of PAHs, we assess how global PAHs and their associated lung cancer risk will likely change in the future. Benzo(a)pyrene (BaP) is used as an indicator of cancer risk from PAH mixtures. From 2008 to 2050, the population-weighted global average BaP concentrations under all RCPs consistently exceeded the WHO-recommended limits, primarily attributed to residential biofuel use. Peaks in PAH-associated incremental lifetime cancer risk shift from East Asia (4 × 10 –5 ) in 2008 to South Asia (mostly India, 2–4 × 10 –5 ) and Africa (1–2 × 10 –5 ) by 2050. In the developing regions of Africa and South Asia, PAH-associated lung cancer risk increased by 30–64% from 2008 to 2050, due to increasing residential energy demand in households for cooking, heating, and lighting, the continued use of traditional biomass use, increases in agricultural waste burning, and forest fires, accompanied by rapid population growth in these regions. Due to more stringent air quality policies in developed countries, their PAH lung cancer risk substantially decreased by ~80% from 2008 to 2050. Climate change is likely to have minor effects on PAH lung cancer risk compared to the impact of emissions. Future policies, therefore, need to consider efficient combustion technologies that reduce air pollutant emissions, including incomplete combustion products such as PAH.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Directed evolution of phosphite dehydrogenase to cycle noncanonical redox cofactors via universal growth selection platform

Abstract Noncanonical redox cofactors are attractive low-cost alternatives to nicotinamide adenine dinucleotide (phosphate) (NAD(P) + ) in biotransformation. However, engineering enzymes to utilize them is challenging. Here, we present a high-throughput directed evolution platform which couples cell growth to the in vivo cycling of a noncanonical cofactor, nicotinamide mononucleotide (NMN + ). We achieve this by engineering the life-essential glutathione reductase in Escherichia coli to exclusively rely on the reduced NMN + (NMNH). Using this system, we develop a phosphite dehydrogenase (PTDH) to cycle NMN + with ~147-fold improved catalytic efficiency, which translates to an industrially viable total turnover number of ~45,000 in cell-free biotransformation without requiring high cofactor concentrations. Moreover, the PTDH variants also exhibit improved activity with another structurally deviant noncanonical cofactor, 1-benzylnicotinamide (BNA + ), showcasing their broad applications. Structural modeling prediction reveals a general design principle where the mutations and the smaller, noncanonical cofactors together mimic the steric interactions of the larger, natural cofactors NAD(P) + .

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Solution processed high aspect ratio ultra-long vertically well-aligned ZnO nano scintillators for potential X-ray imaging applications

We report the photon (PL), electron (CL) and X-ray (XEL) induced luminescence characteristics of high aspect ratio ultra-long (~ 50 µm) ZnO nanorods (NRs) and discuss the potential for fast X-ray detection based on the consistent and efficient visible emission (~ 580 nm) from ZnO NRs. Nanostructured ZnO scintillators were rearranged to form a vertically well-aligned NR design in order to help light absorption and coupling resulting in luminescent and fast scintillation properties. The design of the nanorod array combines the key advantages of a low-cost growth technique together with environmentally friendly and widely available materials. A low temperature hydrothermal method was adopted to grow ZnO NRs in one cycle growth and their structural, optical and X-ray scintillation properties were investigated. The relatively short (~ 10 µm) ZnO NRs emitting in the near-band-edge region were found to be almost insensitive to X-rays. On the other hand, the higher XEL response of long ZnO NRs, which is a key parameter for evaluation of materials to be used as scintillators for high quality X-ray detection and imaging, along with a decay time response in the order of ns confirmed promising scintillation properties for fast and high-resolution X-ray detector applications.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Laser wavelength dependence of laser imprint

In laser direct-drive inertial confinement fusion, laser imprint is one of the major causes of degradation in target performance through its seeding of hydrodynamic instabilities. Early experiments and simulations have shown that laser imprint could be mitigated with a longer laser wavelength because of its lower critical density and longer conduction zone. Building upon this work, we explore a scenario where the laser wavelength during the picket pulse differs from that of the main pulse in order to gain the benefit of reduced imprint, while avoiding losses in drive coupling efficiency or an increase in laser-plasma instabilities. A series of 2D radiation-hydrodynamic simulations, which test three different laser wavelengths for the picket pulse, has been performed, where the intensity of the picket pulse is adjusted in order to maintain the same implosion adiabat. A detailed analysis of the growth of the mass density modulations at the ablation front over a large range of mode numbers confirms that the laser imprint can be mitigated with a picket pulse operating at a longer wavelength than the main pulse because of the longer conduction zone and enhanced thermal smoothing. The amplitude of the ablation front modulations is found to be lower for all mode numbers, which reduces the seeding of the Rayleigh–Taylor instability without affecting the mode growth rates.

Fourier analysis↗
DOE OSTI2025

Adaptive Computing for Scale-Up Problems

Adaptive Computing is an application-agnostic outer loop framework to strategically deploy simulations and experiments to guide decision making for scale-up analysis. Resources are allocated over successive batches, which makes the allocation adaptive to some objective such as optimization or model training. The framework enables the characterization and management of uncertainties associated with predictive models of complex systems when scale-up questions lead to significant model extrapolation. A key advancement of this framework is its integration of multi-fidelity surrogate modeling, uncertainty management, and automated orchestration of various computing and experimentation resources into a single integrated software package. This enables efficient multi-fidelity modeling across multiple computing resources by incorporating real-world constraints such as relative queue times and throughput on individual machines into the multi-fidelity sampling decision. We discuss applications of this framework to problems in the renewable energy space, including biofuels production, material synthesis, perovskite crystal growth, and building electrical loads.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Measurement-induced entanglement phase transitions in variational quantum circuits

Variational quantum algorithms (VQAs), which classically optimize a parametrized quantum circuit to solve a computational task, promise to advance our understanding of quantum many-body systems and improve machine learning algorithms using near-term quantum computers. Prominent challenges associated with this family of quantum-classical hybrid algorithms are the control of quantum entanglement and quantum gradients linked to their classical optimization. Known as the barren plateau phenomenon, these quantum gradients may rapidly vanish in the presence of volume-law entanglement growth, which poses a serious obstacle to the practical utility of VQAs. Inspired by recent studies of measurement-induced entanglement transition in random circuits, we investigate the entanglement transition in variational quantum circuits endowed with intermediate projective measurements. Considering the Hamiltonian Variational Ansatz (HVA) for the XXZ model and the Hardware Efficient Ansatz (HEA), we observe a measurement-induced entanglement transition from volume-law to area-law with increasing measurement rate. Moreover, we provide evidence that the transition belongs to the same universality class of random unitary circuits. Importantly, the transition coincides with a “landscape transition” from severe to mild/no barren plateaus in the classical optimization. Our work may provide an avenue for improving the trainability of quantum circuits by incorporating intermediate measurement protocols in currently available quantum hardware.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1981

Trends and pacing items in computational aerodynamics

A perspective is presented of trends in computational aerodynamics, and of important technology development items that pace future advanced applications. From a survey of AIAA Journal papers published during the past two decades, the growth trends and the progressively increasing emphasis on code development for viscous, compressible, turbulent flow are illustrated. These trends are reflected in the chronology of introduction by the aerospace industry of new computational methods in aircraft design. Key pacing items outlined are: automatic grid generation for nonlinear inviscid computations; advanced computers, improved efficiency of numerical methods, and improved turbulence models for Reynolds-averaged Navier-Stokes computations; advanced computers, time-dependent three-dimensional law-of-the-wall, code development, improved efficiency of numerical methods, and improved subgrid-scale turbulence modeling for large eddy simulations.

Chapman, D. R.↗
NASA NTRS1981

Epitaxial thin film GaAs solar cells using OM-CVD techniques

A new approach has been initiated at JPL to fabricate thin-film, high efficiency GaAs solar cells on low-cost, single-crystal Si substrates having a thin CVD interlayer of Ge to minimize the lattice and thermal expansion mismatch. For initial experiments, n(+)/p GaAs cells were grown by OM-CVD on single-crystal GaAs and Ge wafers. Details of the growths and performance results will be presented. Subsequently, a combined epitaxial structure of OM-CVD GaAs on a strongly adherent Ge interlayer on (100) Si was grown. This is the first report of the successful growth of this composite structure. Low module costs projected by JPL SAMICS methodology calculations and the potential for 400-600W/kg space solar arrays will be discussed.

Stirn, R. J.↗
NASA NTRS1995

Plasma Enhanced Microwave Joining

A new method for plasma enhanced microwave joining of high purity (99.8%) alumina has been developed. The controlled application of a plasma between the adjoining surfaces of two rods initially heats the microwave-low-absorbing alumina rods to temperatures high enough for them to absorb microwave energy efficiently. With this technology, the adjacent surfaces of alumina rods can be melted and welded together in less than three minutes using approximately 400 watts of microwave energy. Four point bending tests measured fracture strengths of up to 130 MPa at the joined interface. Optical and SEM micrographs indicated that exaggerated grain growth prevailed for all joints studied.

Yiin, T.↗
NASA NTRS2003

METAShield: Hot Metallic Aeroshell Concept for RLV/SOV

An innovative fuselage design approach that combines many desirable operational features with a simple and efficient structural approach is being developed by NASA. The approach, named METAShield for MEtallic TransAtmospheric Shield, utilizes lightly loaded, hot aeroshell structures surrounding integral propellant tanks that carry the primary structural loads. The aeroshells are designed to withstand the local pressure loads, transmitting them to the tanks with minimal restraint of thermal growth. No additional thermal protection system protects the METAShield, and a fibrous or multilayer insulation blanket, located in the space between the aeroshell and the tanks, serves as both high temperature and cryogenic insulation for the tanks. The concept is described in detail, and the performance and operational features are highlighted. Initial design results and analyses of the structural, thermal, and thermal-structural performance are described. Computational results evaluating resistance to hypervelocity impact damage, as well as some supporting aerothermal wind tunnel results. are also presented. Future development needs are summarized.

Scotti, Stephen J.↗
NASA NTRS2017

Adaptive Management Using Remote Sensing and Ecosystem Modeling in Response to Climate Variability and Invasive Aquatic Plants for the California Sacramento-San Joaquin Delta Water Resource

The California Sacramento-San Joaquin River Delta is the hub for California's water supply and supports important ecosystem services, agriculture, and communities in Northern to Southern California. Expansion of invasive aquatic plants in the Delta coupled with impacts of changing climate and long-term drought is detrimental to the San Francisco Bay/California Delta complex. NASA Ames Research Center and the USDA-ARS partnered with the State of California to develop science-based, adaptive-management strategies for invasive aquatic plant in the Sacramento-San Joaquin Delta. Specific mapping tools developed utilizing satellite and airborne platforms provide regular assessments of population dynamics on a landscape scale and support both strategic planning and operational decision making for resource managers. San Joaquin and Sacramento River watersheds water quality input to the Delta is modeled using the Soil-Water Assessment Tool (SWAT) and a modified SWAT tool has been customized to account for unique landscape and management of agricultural water supply and drainage within the Delta. Environmental response models for growth of invasive aquatic weeds are being parameterized and coupled with spatial distribution/biomass density mapping and water quality to study ecosystem response to climate and aquatic plant management practices. On the water validation and operational utilization of these tools by management agencies and how they are improving decision making, management effectiveness and efficiency will be discussed. The project combines science, operations, and economics related to integrated management scenarios for aquatic weeds to help land and water resource managers make science-informed decisions regarding management and outcomes.

Adaptive↗
NASA NTRS2021

Breakdown in Tantalum Capacitors

Failures in tantalum capacitors can be considered as a time-dependent-breakdown and reliability of all types of capacitors, including wet, MnO2 and polymer cathode parts, depends on the efficiency of self-healing that can mend parts after breakdown. A mechanism of self-healing in MnO2 capacitors is associated with oxygen reduction in the cathode layer and isolation of the breakdown site with high-resistive Mn2O3/Mn3O4 compositions. Although this mechanism is commonly accepted, details of self-healing have not been analyzed sufficiently yet, and the effects of scintillations on behavior of the parts has not been fully understood. There is a lack of data on the self-healing efficiency in different lots of capacitors. Even less is known about self-healing in polymer tantalum capacitors. In this work, different types of polymer and MnO2 capacitors have been tested for scintillation breakdown using a constant current stress (CCS) technique modified to allow detection of the amplitudes and durations of current spikes during breakdown. Characteristics of the parts and in particular leakage currents were measured to assess the efficiency of self-healing and improve screening processes for tantalum capacitors. Damaged sites were localized using infrared camera and their appearance analyzed after deprocessing and crosssectioning. Thermal effects during scintillations have been modeled, self-healing processes in polymer and MnO2 cathode capacitors discussed, and mechanisms of breakdown based on the growth of conductive filaments in the dielectric suggested.

tantalum polymer capacitors↗
DOE OSTI2024

Miscanthus: An Environmental Choice for Marginal Lands

Miscanthus x giganteus, or Giant Miscanthus, is a tall, perennial grass originally from Asia. It is considered a sterile hybrid that has been bred to not produce viable seeds. Instead, rhizomes are planted to establish the crop. Here, the rhizome is an underground modified stem mass that puts out shoots and roots supporting new growth each year. This perennial crop takes two to three years to reach maturity, but established stands can reach upwards of 12 ft. tall with a very thick canopy (Pyter, 2007). Miscanthus has shown potential for high dry matter yields compared to other biomass crops, which could in turn lead to more efficient land use especially when applied to a bioenergy and bioproduct supply chain. In one study, switchgrass (Panicum virgatum) yielded 10.3 Mg/ha of biomass on average, while miscanthus yielded 22.4 Mg/ha (Heaton et al., 2004). Additionally, miscanthus production has been associated with many environmental benefits, including benefits to water quality, nutrient load removal, soil stabilization, and soil health (Bhardwaj et al., 2011; Hussain et al., 2019). Many of the possible practical and environmental benefits that are associated with miscanthus production may be attractive to stakeholders who are interested in alternative land use options, particularly in areas considered to be marginal in productivity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Floatable Protective Layers: a Strategy to Minimize Solid Electrolyte Interphase Growth and Maximize the Lithium Utilization

Abstract Maximizing lithium (Li) utilization is crucial for enhancing the long‐term stability of Li‐based batteries. In anode‐free Li batteries (AFLBs), although the initial formation of solid electrolyte interphase (SEI) is beneficial on limiting further reaction between Li and electrolyte, large volume change of Li metal anode (LMA) during cycling often leads to continuous breakdown and re‐formation of SEI and formation of inactive Li, hindering its efficiency. In this study, a novel strategy is presented to protect Li metal by applying a floatable protection layer (FPL) on a copper substrate, enabling large Li particles to be primarily deposited below FPL, but SEI to be primarily formed above FPL. This approach effectively minimizes the direct contact between electrolyte and freshly deposited Li, therefore mitigating the continuous side reactions and early failure of AFLBs. As a result, Li consumption is minimized, and the overall stability of the battery is significantly enhanced. Further development of this approach can also be used to improve the performance of other Li‐based batteries for large‐scale applications.

Lim, Hyung‐Seok [Energy and Environment Directorat↗
DOE OSTI2021

PLEKHA7 signaling is necessary for the growth of mutant KRAS driven colorectal cancer

Plekha7 (Pleckstrin homology [PH] domain containing, family A member 7) regulates the assembly of proteins of the cytoplasmic apical zonula adherens junction (AJ), thus ensuring cell-cell adhesion and tight-junction barrier integrity. Little is known of Plekha7 function in cancer. In colorectal cancer (CRC) Plekha7 expression is elevated compared to adjacent normal tissue levels, increasing with clinical stage. Plekha7 was present at plasma membrane AJ with wild-type KRas (wt-KRas) but was dispersed in cells expressing mutant KRas (mut-KRas). Fluorescence lifetime imaging microscopy (FLIM) indicated a direct Plekha7 interaction with wt-KRas but scantily with mut-KRas. Inhibiting Plekha7 specifically decreased mut-KRas cell signaling, proliferation, attachment, migration, and retarded mut-KRAS CRC tumor growth. Binding of diC8-phosphoinositides (PI) to the PH domain of Plekha7 was relatively low affinity. This may be because a D175 amino acid residue plays a “sentry” role preventing PI(3,4)P{sub 2} and PI(3,4,5)P{sub 3} binding. Molecular or pharmacological inhibition of the Plekha7 PH domain prevented the growth of mut-KRas but not wt-KRas cells. Taken together the studies suggest that Plekha7, in addition to maintaining AJ structure plays a role in mut-KRas signaling and phenotype through interaction of its PH domain with membrane mut-KRas, but not wt-KRas, to increase the efficiency of mut-KRas downstream signaling.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Surface SiO 2 Thickness Controls Uniform-to-Localized Transition in Lithiation of Silicon Anodes for Lithium-Ion Batteries

Silicon is a promising anode material for lithium-ion batteries because of its high capacity, but its widespread adoption has been hampered by a low cycle life arising from mechanical failure and the absence of a stable solid–electrolyte interphase (SEI). Understanding SEI formation and its impact on cycle life is made more complex by the oxidation of silicon materials in air or during synthesis, which leads to SiO x coatings of varying thicknesses that form the true surface of the electrode. Here, the lithiation of SiO 2 -coated Si is studied in a controlled manner using SiO 2 coatings of different thicknesses grown on Si wafers via thermal oxidation. SiO 2 thickness has a profound effect on lithiation: below 2 nm, SEI formation followed by uniform lithiation occurs at positive voltages versus Li/Li + . Si lithiation is reversible, and SiO 2 lithiation is largely irreversible. Above 2 nm SiO 2 , voltammetric currents decrease exponentially with SiO 2 thickness. For 2–3 nm SiO 2 , SEI formation above 0.1 V is suppressed, but a hold at low or negative voltages can initiate charge transfer whereupon SEI formation and uniform lithiation occur. Cycling of Si anodes with an SiO 2 coating thinner than 3 nm occurs at high Coulombic efficiency (CE). If an SiO 2 coating is thicker than 3–4 nm, the behavior is totally different: lithiation at positive voltages is strongly inhibited, and lithiation occurs at poor CE and is highly localized at pinholes which grow over time. As they grow, lithiation becomes more facile and the CE increases. Pinhole growth is proposed to occur via rapid transport of Li along the SiO 2 /Si interface radially outward from an existing pinhole, followed by the lithiation of SiO 2 from the interface outward.

25 ENERGY STORAGE↗