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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Continuous Positive Airway Pressure for Motion Management in Stereotactic Body Radiation Therapy to the Lung: A Controlled Pilot Study

Objective: To determine the effect of continuous positive airway pressure (CPAP) on tumor motion, lung volume, and dose to critical organs in patients receiving stereotactic body radiation therapy (SBRT) for lung tumors. Methods and Materials: After institutional review board approval in December 2013, patients with primary or secondary lung tumors referred for SBRT underwent 4-dimensional computed tomographic simulation twice: with free breathing and with CPAP. Tumor excursion was calculated by subtracting the vector of the greatest dimension of the gross tumor volume (GTV) from the internal target volume (ITV). Volumetric and dosimetric determinations were compared with the Wilcoxon signed-rank test. CPAP was used during treatment if judged beneficial. Results: CPAP was tolerated well in 10 of the 11 patients enrolled. Ten patients with 18 lesions were evaluated. The use of CPAP decreased tumor excursion by 0.5 ± 0.8 cm, 0.4 ± 0.7 cm, and 0.6 ± 0.8 cm in the superior–inferior, right–left, and anterior–posterior planes, respectively (P≤.02). Relative to free breathing, the mean ITV reduction was 27% (95% confidence interval [CI] 16%-39%, P<.001). CPAP significantly augmented lung volume, with a mean absolute increase of 915 ± 432 cm{sup 3} and a relative increase of 32% (95% CI 21%-42%, P=.003), contributing to a 22% relative reduction (95% CI 13%-32%, P=.001) in mean lung dose. The use of CPAP was also associated with a relative reduction in mean heart dose by 29% (95% CI 23%-36%, P=.001). Conclusion: In this pilot study, CPAP significantly reduced lung tumor motion compared with free breathing. The smaller ITV, the planning target volume (PTV), and the increase in total lung volume associated with CPAP contributed to a reduction in lung and heart dose. CPAP was well tolerated, reproducible, and simple to implement in the treatment room and should be evaluated further as a novel strategy for motion management in radiation therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Continuous recovery of high-purity Kraft lignin from black liquor via simultaneous, liquid-phase acidification and purification

Here, a key advantage of the Sequential Liquid-Lignin Recovery and Purification (SLRP) process for the recovery of lignin from Kraft black liquor is the precipitation of a solvated, “liquid-lignin” phase (vs. the typical solid) during the CO 2 acidification step. Here, we have discovered that this lignin can also be maintained in a solvated state during the H 2 SO 4 acidification step if aqueous acetic acid from the Aqueous Lignin Purification with Hot Agents (ALPHA) process is incorporated into the H 2 SO 4 solution. As the liquid-lignin is converted from its salt form at pH = 9.5 to its acid form at pH = 2.5, the lignin initially solvated with water becomes solvated and thus liquefied with the organic–water solution. Maintaining the lignin in a solvated liquid state has two advantages: (1) the entire SLRP + ALPHA process, from starting black liquor to final lignin product, can be operated continuously; and (2) mass transfer of metals impurities out of the liquid-lignin phase is significantly enhanced, resulting in both a cleaner Kraft lignin product (~2000 ppm Na and 0.5-1.0 % ash) and reduced water washing.

09 BIOMASS FUELS↗
DOE OSTI2020

Phase stabilization and oxidation of a continuous composition spread multi-principal element (AlFeNiTiVZr) 1-x Cr x alloy

Multi-Principal Element Alloys (MPEA) have been hypothesized to maintain a stable single alloy phase and resist corrosion at high temperatures, which are desirable in various functional applications, including material of turbine blades. However, studies into oxidation resistant alloys have been constrained to individual MPEA systems or a limited selection of compositions within those systems. Here, High-Throughput Experimental (HTE) techniques were utilized to rapidly assess phase stability and resistance to oxidation of an (AlFeNiTiVZr) 1-x Cr x continuous composition spread (CCS) thin-film alloy system. High-throughput synchrotron diffraction and Raman spectroscopy were used to identify phases, especially high symmetry structures and oxides, as a function of annealing time and composition. The formation of two distinct phase regions, R 1 and R 2 , across the CCS was observed. One of these phase regions, R 2 , exhibited a stable high symmetry BCC-like phase at Cr concentrations greater than 25.4 at%, and grew a passivating mixed metal surface oxide; whereas, the R 1 phase region, decomposed on oxidation to multiple oxides and reacted with the substrate to form silicides. The passivating mixed metal oxide layer appears to prevent destabilization of the (AlFeNiTiVZr) 1-x Cr x MPEA BCC solid solution. Furthermore, at longer annealing times the passivating phase was seen only above 29.2 at% Cr. High Cr-doped (AlFeNiTiVZr) 1-x Cr x appear to be a good candidate for high temperature, oxidation-resistant structural alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Continuous-time probabilistic models for longitudinal electronic health records

Analysis of longitudinal Electronic Health Record (EHR) data is an important goal for precision medicine. Difficulty in applying Machine Learning (ML) methods, either predictive or unsupervised, stems in part from the heterogeneity and irregular sampling of EHR data. Here, we present an unsupervised probabilistic model that captures nonlinear relationships between variables over continuous-time. This method works with arbitrary sampling patterns and captures the joint probability distribution between variable measurements and the time intervals between them. Inference algorithms are derived that can be used to evaluate the likelihood of future using under a trained model. As an example, we consider data from the United States Veterans Health Administration (VHA) in the areas of diabetes and depression. Likelihood ratio maps are produced showing the likelihood of risk for moderate-severe vs minimal depression as measured by the Patient Health Questionnaire-9 (PHQ-9).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Continuous partial oxidation of methane to methanol over Cu-SSZ-39 catalysts

Here, the direct conversion of methane to methanol using molecular oxygen as the oxidant is a grand challenge in the chemical sciences. Here we describe our efforts in using copper-exchanged SSZ-39 for this chemistry and show it is a promising material for this reaction. Testing in a continuous flow reactor at 225 °C, Cu-SSZ-39 showed superior activity for methane partial oxidation compared to Cu-SSZ-13 (site time yields of 26.9 ± 0.8 mol CH3OH ·mol Cu -1 ·h -1 *10 -3 versus 13.2 mol CH3OH ·mol Cu -1 ·h -1 *10 -3 respectively). A clear maximum in methanol productivity, both in terms of a mass catalyst basis and copper atom basis is observed for Cu-SSZ-39 at a Cu/Al ~ 0.2. Running this reaction in the absence of oxygen over samples with a Cu/Al > 0.1 the reactivity is markedly lower than that in the presence of oxygen unlike what is observed in SSZ-13.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Yearlong semi-continuous operation of thermophilic two-stage anaerobic digesters amended with biochar for enhanced biomethane production

This study aimed to scale up an integrated waste-to-energy system for producing pipelinequality biomethane from shake flasks experiments to two-stage digester systems with semicontinuous operation. The yearlong operation was successfully conducted to compare the performance of thermophilic anaerobic digestion (AD) of sewage sludge amended with corn stover biochar (CSBC) and pine biochar (PBC) to the control under various conditions. Both CSBC and PBC promoted the substrate utilization, methane productivity, and process stability of AD, while CSBC showed superior potential. CSBC enhanced methane content in biogas (CH 4 %) and methane production rate (P CH$_4$ ) by up to 25% and 37% respectively in comparison to the control, with maximum CH 4 % of 95% and CH 4 yield of 0.34 L/g volatile solid (VS)-added being achieved at steady state. The biochar supplementation also led to a substantial increase of the macro- and micro-nutrients (P, K, Ca, Mg, Fe) by up to 33 times in the digestate, increasing its fertilizer value. Finally, microbial community structure and dynamics were also investigated and compared, and in particular, CSBC promoted the abundance of Clostridia and Methanosarcina. Collectively, this study proves that pyro-biochar as an effective additive material enhances AD performance with continuous operation and that CSBC shows greater potential.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Continuous condensed-phase ethanol conversion to higher alcohols: Experimental results and techno-economic analysis

The conversion of ethanol to n-butanol and higher alcohols is carried out in a continuous fixed bed reactor over a Ni/La 2 O 3 /γ-Al 2 O 3 catalyst at 210–250 °C and 100 bar. At these conditions, the reaction mixture is a condensed, near-critical phase that facilitates higher reaction rates than corresponding vapor phase reactions. Combined selectivity to n-butanol and C 6 + higher alcohols reached 74% at 41% ethanol conversion. A process concept is presented in which n-butanol and mixed C 6 + alcohols are produced as saleable products; ethanol is recycled to achieve nearly 100% overall conversion and minor byproducts are burned to provide process energy. A process design is conducted using Aspen Plus V8.4 process simulation software, and economic analyses are carried out for several cases of ethanol conversion and alcohol selectivities. Several additional cases involving permutations of the base process configuration are also examined in attempts to improve process economics. At n-butanol selectivities achieved experimentally, a facility producing 75 million kg n-butanol per year has a total capital cost of 38.1 million with a required n-butanol selling price of 1.55/kg to 1.60/kg for typical values of expected return on investment.

09 BIOMASS FUELS↗
DOE OSTI2014

Smoothed Particle Hydrodynamics Continuous Boundary Force method for Navier-Stokes equations subject to Robin boundary condition

Robin boundary condition for the Navier-Stokes equations is used to model slip conditions at the fluid-solid boundaries. A novel Continuous Boundary Force (CBF) method is proposed for solving the Navier-Stokes equations subject to Robin boundary condition. In the CBF method, the Robin boundary condition at boundary is replaced by the homogeneous Neumann boundary condition at the boundary and a volumetric force term added to the momentum conservation equation. Smoothed Particle Hydrodynamics (SPH) method is used to solve the resulting Navier-Stokes equations. We present solutions for two-dimensional and three-dimensional flows in domains bounded by flat and curved boundaries subject to various forms of the Robin boundary condition. The numerical accuracy and convergence are examined through comparison of the SPH-CBF results with the solutions of finite difference or finite element method. Taken the no-slip boundary condition as a special case of slip boundary condition, we demonstrate that the SPH-CBF method describes accurately both no-slip and slip conditions.

Pan, Wenxiao↗
DOE OSTI2017

Continuation of probability density functions using a generalized Lyapunov approach

Techniques from numerical bifurcation theory are very useful to study transitions between steady fluid flow patterns and the instabilities involved. Here, we provide computational methodology to use parameter continuation in determining probability density functions of systems of stochastic partial differential equations near fixed points, under a small noise approximation. Key innovation is the efficient solution of a generalized Lyapunov equation using an iterative method involving low-rank approximations. We apply and illustrate the capabilities of the method using a problem in physical oceanography, i.e. the occurrence of multiple steady states of the Atlantic Ocean circulation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Sequential limiting in continuous and discontinuous Galerkin methods for the Euler equations

We present a new predictor-corrector approach to enforcing local maximum principles in piecewise-linear finite element schemes for the compressible Euler equations. The new element-based limiting strategy is suitable for continuous and discontinuous Galerkin methods alike. In contrast to synchronized limiting techniques for systems of conservation laws, we constrain the density, momentum, and total energy in a sequential manner which guarantees positivity preservation for the pressure and internal energy. After the density limiting step, the total energy and momentum gradients are adjusted to incorporate the irreversible effect of density changes. Antidiffusive corrections to bounds-compatible low-order approximations are limited to satisfy inequality constraints for the specific total and kinetic energy. An accuracy-preserving smoothness indicator is introduced to gradually adjust lower bounds for the element-based correction factors. The employed smoothness criterion is based on a Hessian determinant test for the density. Finally, a numerical study is performed for test problems with smooth and discontinuous solutions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

A note on higher-order and nonlinear limiting approaches for continuously bounds-preserving discontinuous Galerkin methods

In Dzanic (2024), a limiting approach for high-order discontinuous Galerkin schemes was introduced which allowed for imposing constraints on the solution continuously (i.e., everywhere within the element). While exact for linear constraint functionals, this approach only imposed a sufficient (but not the minimum necessary) amount of limiting for nonlinear constraint functionals. This short note shows how this limiting approach can be extended to allow exactness for general nonlinear quasiconcave constraint functionals through a nonlinear limiting procedure, reducing unnecessary numerical dissipation. Finally, some examples are shown for nonlinear pressure and entropy constraints in the compressible gas dynamics equations, where both analytic and iterative approaches are used.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Effects of residue removal and tillage on greenhouse gas emissions in continuous corn systems as simulated with RZWQM2

Agricultural production is a major source of carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) globally. The effects of conservation practices on soil CO 2 and N 2 O emissions remain a high degree of uncertainty. In this study, soil CO 2 and N 2 O emissions under different residue and tillage practices in an irrigated, continuous corn system, were investigated using the Root Zone Water Quality Model (RZWQM2). Combinations of no/high stover removal (NR and HR, respectively) and no-till/conventional tillage (NT and CT, respectively) field experiments were tested over the four crop-years (Apr. 2011–Apr. 2015). The model was calibrated using the NRCT, and validated with other treatments. The simulation results showed that soil volumetric water content (VWC) in the NR treatments (i.e., NRCT and NRNT) was 1.3%–1.9% higher than that in the HR treatments (i.e., HRCT and HRNT) averaged across the four years. A higher amount of CO 2 and N 2 O emissions were simulated in the NRCT across the four years (annual average: 7034 kg C/ha/yr for CO 2 and 3.8 kg N/ha/yr for N 2 O), and lower emissions were in the HRNT (annual average: 6329 kg C/ha/yr and 3.7 kg N/ha/yr for N 2 O). A long-term simulation (2001–2015) suggested that the CO 2 and N 2 O emissions were closely correlated with the stover removal degree (SRD), tillage, VWC, soil temperature (ST), years in management (Y), and fertilizer application. Stover and tillage practices had cumulative effects on CO 2 emissions. The simulated annual CO 2 emissions in 1st year from NRCT, NRNT, and HRCT were 7.8%, 0.0%, and 7.7% higher than that from HRNT, respectively; then the emissions in 15th year were 63.6%, 47.7%, and 29.1% higher, respectively. Meanwhile, there were no cumulative effects on N 2 O emissions. Furthermore, the results also demonstrated that the RZWQM2 is a promising tool for evaluating the long-term effects of CO 2 and N 2 O emissions on different conservation practices.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Environmental application of chlorine-doped graphitic carbon nitride: Continuous solar-driven photocatalytic production of hydrogen peroxide

Solar-driven photocatalytic generation of H 2 O 2 over metal-free catalysts is a sustainable approach for value-added chemical production. Here, we synthesized chlorine-doped graphitic carbon nitride (Cl-doped g-C 3 N 4 ) through a solvothermal method to effectively produce H 2 O 2 with a rate of 1.19 ± 0.06 µM min –1 under visible light irradiation, which was improved by 104 times compared to pristine g-C 3 N 4 . Continuous net production of H 2 O 2 was realized at a rate of 2.78 ± 0.10 µM min –1 up to 54 h with isopropanol as the hole scavenger, whereas H 2 O 2 production was only sustained for ~ 6 h without scavengers. Both molecular simulations and advanced spectroscopic characterizations elucidated that the Cl dopant increased the charge transfer rate, decreased the bandgap, and reduced the activation energy of the rate-limiting step of O 2 reduction, all of which favored H 2 O 2 production. Furthermore, this work implemented a novel metal-free photocatalyst for sustainable H 2 O 2 production and elucidated the mechanism for promoting H 2 O 2 production that can guide future photoreactive nanomaterial design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Prostate Cancer Patients' Preferences for Intermittent vs. Continuous Androgen Deprivation—A Pilot Institutional Study

With locally advanced, recurrent, and metastatic prostate cancer patients, patient preference between intermittent (IAD) and continuous (CAD) androgen deprivation therapy has not been investigated. The goal of the study was to determine patients' preference for IAD vs. CAD therapy. The secondary aim was to elucidate demographic or treatment variables that may affect a patient's preference for one type of hormonal treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2026

Extended continuous cooling transformation diagram for 410 stainless steel encompassing δ → γ and γ → αʹ transformations determined by dilatometry

In this study, we use dilatometry to construct an extended Continuous Cooling Transformation (CCT) diagram for 410 stainless steel, capturing both δ → γ and γ → αʹ transformations specifically for directed energy deposition (DED) additive manufacturing (AM) applications. To ensure that the findings are representative of AM specific microstructures and compositions, dilatometry coupons were extracted from a wire arc DED wall, thereby preserving the inherent microstructural and compositional variability within the material. The on-heating phase transformations, including A c1 , A c3 , and γ → δ, were found to be essentially location independent, despite the typical heterogeneity associated with AM. Conversely, increasing cooling rates were observed to shift the start and finish temperatures of both δ → γ and γ → αʹ transformations to lower values. The resulting extended CCT diagram offers a more complete depiction of phase transformation behavior in the system, enabling accurate microstructure evolution modeling and residual stress predictions specifically for directed energy deposition additive manufacturing applications.

Additive manufacturing↗
DOE OSTI2024

Phase field-volumetric lattice Boltzmann model of ion uptake in porous nuclear waste form materials under continuous flow

The flow field within the mesopores of sorbent particles plays a crucial role in radionuclide diffusion and ion uptake kinetics, thus, impacting the overall performance of porous nuclear waste form materials. To fundamentally understand the influence of microstructures and material properties on the radionuclide absorption and retention processes requires a coupled multi-physics model that considers the advection and diffusion within the flow field, the reaction at liquid-solid interfaces, and finally, the solid-state diffusion within a complex nanoporous medium. Here, this study employs the volumetric lattice Boltzmann method (VLBM) to accurately and efficiently calculate the steady state velocity field inside the mesopores of sorbent particles. The obtained velocity field is then utilized to calculate the advection of ions in the steady flow. A phase field (PF) model of ion uptake is used to describe the reaction occurring at the solid-liquid interface and diffusion inside the porous medium. The integrated PF-VLBM model is verified in terms of the mass conservation and numerical efficiency and validated qualitatively with experimental observation data. Then, it is applied to study the influence of thermodynamic and kinetic properties, as well as flow field conditions on the ion uptake kinetics. The numerical results demonstrate that the ion uptake kinetics in porous particles has three distinct stages, which is in agreement with the observations in continuous flow experiments. In the first stage, the kinetics is predominantly controlled by the flow field and ion diffusivity in the liquid phase. The kinetics in the second stage is primarily governed by ion diffusivity in the solid phase. In the third stage the system reaches a dynamic equilibrium with a net zero uptake flux at the interface. It is also found that porous structures significantly affect the efficiency and capacity of ion uptake. The simulation results can help to understand the physics behind the observed ion uptake kinetics in experiments and to facilitate the development of constitutive equations that can account for heterogeneous microstructures in engineering performance codes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Rate analysis of sorption of Ce 3+ , Sm 3+ , and Yb 3+ ions from aqueous solution using Dowex 50W-X8 as a sorbent in a continuous flow reactor

Kinetic analysis of removal of three rare earth elements metals, Ce 3+ , Sm 3+ , and Yb 3+ ions from aqueous solutions in a continuous flow fixed bed reactor using Dowex 50W-X8 ion-exchange resin was conducted here. The performance of the fixed bed sorption was evaluated using the concept of the sorption breakthrough process. Parameters characteristic of a fixed bed sorption such as breakthrough times, saturation times, critical reactor lengths, and lengths of mass transfer zone were inferred from the metal ion concentration breakthrough curves. The sorption capacity of Dowex 50W-X8 ion-exchange resin for Ce 3+ , Sm 3+ , and Yb 3+ are 191, 252, and 294 mg/g, respectively. The sorption kinetics were evaluated using a zero-order, first-order and second-order reaction models. The kinetics of the sorption process follows a zero-order model which has not been reported before. The rate constants of sorption using the zero-order kinetic model are obtained. Two different analysis were conducted to identify whether the diffusion is intraparticle or film diffusion. Finally, both analysis confirms that the film diffusion is the controlling mechanism in reactor bed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗