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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Optimizing Traffic Signal Control to Enhance Transportation Efficiency and Maximize Pedestrian Benefits in the Road Network

Increasing urban mobility requirements demand efficient transportation system strategies for both vehicular and pedestrian movement. This study enhances the Decentralized Graph-based Multi-Agent Reinforcement Learning (DGMARL) approach, originally tailored for vehicular traffic signal timing, to incorporate pedestrian traffic dynamics. The improved algorithm considers crucial metrics such as Eco_PI, assesses vehicle fuel consumption by factoring in stops and delays, and addresses pedestrian waiting time, crucial for system efficiency while acknowledging driver waiting time impact. Utilizing Digital Twin simulation along the MLK Smart Corridor in Chattanooga, Tennessee, the algorithm's performance is compared for various pedestrian control scenarios. To evaluate the effectiveness of DGMARL, this study compared DGMARL-enabled signal management with automated pedestrian traffic detection and an actuated signal management system (real-word baseline) with pedestrian recall, which predetermingly enforces a pedestrian phase every cycle. Findings indicate substantial improvements with DGMARL, showing a 28.29% enhancement in vehicle Eco_PI, a 60.55 % reduction in pedestrian waiting time, and a 55.74% decrease in driver stop delay, on average, compared to the baseline actuated signal timing plan.

Kumarasamy, Vijayalakshmi K [The University of Ten↗
NASA NTRS1972

Maximal Oxygen Uptake, Sweating and Tolerance to Exercise in the Heat

The physiological mechanisms that facilitate acute acclimation to heat have not been fully elucidated, but the result is the establishment of a more efficient cardiovascular system to increase heat dissipation via increased sweating that allows the acclimated man to function with a cooler internal environment and to extend his performance. Men in good physical condition with high maximal oxygen uptakes generally acclimate to heat more rapidly and retain it longer than men in poorer condition. Also, upon first exposure trained men tolerate exercise in the heat better than untrained men. Both resting in heat and physical training in a cool environment confer only partial acclimation when first exposed to work in the heat. These observations suggest separate additive stimuli of metabolic heat from exercise and environmental heat to increase sweating during the acclimation process. However, the necessity of utilizing physical exercise during acclimation has been questioned. Bradbury et al. (1964) have concluded exercise has no effect on the course of heat acclimation since increased sweating can be induced by merely heating resting subjects. Preliminary evidence suggests there is a direct relationship between the maximal oxygen uptake and the capacity to maintain thermal regulation, particularly through the control of sweating. Since increased sweating is an important mechanism for the development of heat acclimation, and fit men have high sweat rates, it follows that upon initial exposure to exercise in the heat, men with high maximal oxygen uptakes should exhibit less strain than men with lower maximal oxygen uptakes. The purpose of this study was: (1) to determine if men with higher maximal oxygen uptakes exhibit greater tolerance than men with lower oxygen uptakes during early exposure to exercise in the heat, and (2) to investigate further the mechanism of the relationship between sweating and maximal work capacity.

Greenleaf, J. E.↗
NASA NTRS2003

Evidence for altered alpha-adrenoreceptor responsiveness after a single bout of maximal exercise

We studied hemodynamic responses to alpha- and beta-receptor agonists in eight men to test the hypothesis that adrenoreceptor responsiveness is altered within 24 h of the performance of maximal exercise. Adrenoreceptor responsiveness was tested under two experimental conditions (with and without maximal exercise). Adrenoreceptor tests were performed 24 h after each subject performed graded upright cycle ergometry to volitional exhaustion. The 2 test days (experimental conditions) were separated by at least 1 wk, and the order of exercise and no-exercise conditions was counterbalanced. Steady-state graded infusions of phenylephrine (PE) and isoproterenol (Iso) were used to assess alpha- and beta-adrenoreceptor responsiveness, respectively. Slopes calculated from linear regressions between Iso and PE doses and changes in heart rate, blood pressure, and leg vascular resistance for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. The slope of the relationship between heart rate and Iso with maximal exercise was 1773 +/- 164 beats x microm-1x kg-1x min-1 compared with 1987 +/- 142 beats x microg-1x kg-1x min-1 without exercise (P = 0.158), whereas the slopes of the relationship between vascular resistance to Iso were -438 +/- 123 peripheral resistance units (PRU) x microg-1x kg-1x min-1 with maximal exercise and -429 +/- 105 x microg-1x kg-1 x min-1 without exercise (P = 0.904). Maximal exercise was associated with greater (P < 0.05) vascular resistance (15.1 +/- 2.8 PRU x microg-1 kg-1x min-1) and mean arterial blood pressure (15.8 +/- 2.1 mmHg. microg-1x kg-1x min-1) responses to PE infusion compared with no exercise (9.0 +/- 2.0 PRU x microg-1 kg-1 x min-1 and 10.9 +/- 2.0 mmHg. microg-1x kg-1x min-1, respectively). These results provide evidence that a single bout of maximal exercise increases alpha1-adrenoreceptor responsiveness within 24 h without affecting beta-cardiac and vascular adrenoreceptor responses.

Non-NASA Center↗
NASA NTRS1997

Cardiovascular consequences of bed rest: effect on maximal oxygen uptake

Maximal oxygen uptake (VO2max) is reduced in healthy individuals confined to bed rest, suggesting it is independent of any disease state. The magnitude of reduction in VO2max is dependent on duration of bed rest and the initial level of aerobic fitness (VO2max), but it appears to be independent of age or gender. Bed rest induces an elevated maximal heart rate which, in turn, is associated with decreased cardiac vagal tone, increased sympathetic catecholamine secretion, and greater cardiac beta-receptor sensitivity. Despite the elevation in heart rate, VO2max is reduced primarily from decreased maximal stroke volume and cardiac output. An elevated ejection fraction during exercise following bed rest suggests that the lower stroke volume is not caused by ventricular dysfunction but is primarily the result of decreased venous return associated with lower circulating blood volume, reduced central venous pressure, and higher venous compliance in the lower extremities. VO2max, stroke volume, and cardiac output are further compromised by exercise in the upright posture. The contribution of hypovolemia to reduced cardiac output during exercise following bed rest is supported by the close relationship between the relative magnitude (% delta) and time course of change in blood volume and VO2max during bed rest, and also by the fact that retention of plasma volume is associated with maintenance of VO2max after bed rest. Arteriovenous oxygen difference during maximal exercise is not altered by bed rest, suggesting that peripheral mechanisms may not contribute significantly to the decreased VO2max. However reduction in baseline and maximal muscle blood flow, red blood cell volume, and capillarization in working muscles represent peripheral mechanisms that may contribute to limited oxygen delivery and, subsequently, lowered VO2max. Thus, alterations in cardiac and vascular functions induced by prolonged confinement to bed rest contribute to diminution of maximal oxygen uptake and reserve capacity to perform physical work.

Non-NASA Center↗
NASA NTRS1992

Relationship between body and leg VO2 during maximal cycle ergometry

It is not known whether the asymptotic behavior of whole body O2 consumption (VO2) at maximal work rates (WR) is explained by similar behavior of VO2 in the exercising legs. To resolve this question, simultaneous measurements of body and leg VO2 were made at submaximal and maximal levels of effort breathing normoxic and hypoxic gases in seven trained male cyclists (maximal VO2, 64.7 +/- 2.7 ml O2.min-1.kg-1), each of whom demonstrated a reproducible VO2-WR asymptote during fatiguing incremental cycle ergometry. Left leg blood flow was measured by constant-infusion thermodilution, and total leg VO2 was calculated as the product of twice leg flow and radial arterial-femoral venous O2 concentration difference. The VO2-WR relationships determined at submaximal WR's were extrapolated to maximal WR as a basis for assessing the body and leg VO2 responses. The differences between measured and extrapolated maximal VO2 were 235 +/- 45 (body) and 203 +/- 70 (leg) ml O2/min (not significantly different). Plateauing of leg VO2 was associated with, and explained by, plateauing of both leg blood flow and O2 extraction and hence of leg VO2. We conclude that the asymptotic behavior of whole body VO2 at maximal WRs is a direct reflection of the VO2 profile at the exercising legs.

NASA Discipline Cardiopulmonary↗
NASA NTRS2009

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

Maximal power output occurs when subjects perform ballistic exercises using loads of ~30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of load on power output was: 30% > 40% > 50% = 60%. CONCLUSION: Loads of 40% and 30% of MIF elicit maximal power output during dynamic leg presses and bench presses, respectively. These findings are similar to those obtained when loading is based on 1-RM.

Spiering, Barry A.↗
DOE OSTI2025

Entanglement maximization and mirror symmetry in two-Higgs-doublet models

We consider 2-to-2 scatterings of Higgs bosons in a CP-conserving two-Higgs-doublet model (2HDM) and study the implication of maximizing the entanglement in the flavor space, where the two doublets Φ a , a = 1, 2, can be viewed as a qubit: Φ 1 = |0⟩ and Φ 2 = |1⟩. More specifically, we compute the scattering amplitudes for Φ a Φ b → Φ c Φ d and require the outgoing flavor entanglement to be maximal for a full product basis such as the computational basis, which consists of {|00⟩, |01⟩, |10⟩, |11⟩}. In the unbroken phase and turning off the gauge interactions, entanglement maximization results in the appearance of an U(2) × U(2) global symmetry among the quartic couplings, which in general is broken softly by the mass terms. Interestingly, once the Higgs bosons acquire vacuum expectation values, maximal entanglement enforces an exact U(2) × U(2) symmetry, which is spontaneously broken to U(1) × U(1). As a byproduct, this gives rise to Higgs alignment as well as to the existence of 6 massless Nambu-Goldstone bosons. The U(2) × U(2) symmetry can be gauged to lift the massless Goldstones, while maintaining maximal entanglement demands the presence of a discrete Z 2 symmetry interchanging the two gauge sectors. The model is custodially invariant in the scalar sector, and the inclusion of fermions requires a mirror dark sector, related to the standard one by the Z 2 symmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1978

Fluid-electrolyte shifts and maximal oxygen uptake in man at simulated altitude /2,287 m/

Experiments were conducted on six trained distance runners (21-23 yr) subjected to an eight-day dietary control at sea level, followed by an eight-day stay in an altitude chamber (2287-m altitude) and a four-day recovery at sea level. Fluid and electrolyte shifts during exercise at altitude were evaluated to gain insight into the mechanism of reduction in working capacity. The results are discussed in terms of resting fluid volumes and blood constituents, maximal exercise variables, and maximal exercise fluid-electrolyte shifts. Since there are no significant changes in fluid balance or resting plasma volume (PV) at altitude, it is concluded that neither these nor the excessive PV shifts with exercise contribute to the reduction in maximal oxygen uptake at altitude. During altitude exposure the percent loss in PV is found to follow the percent reduction in maximal oxygen uptake; however, on the first day of recovery the percent change in PV remains depressed while maximal oxygen uptake returns to control levels.

Greenleaf, J. E.↗
NASA NTRS1987

Influence of simulated weightlessness on maximal oxygen uptake of untrained rats

The purpose of this study was to determine the effect of hindlimb suspension on maximal oxygen uptake of rodents. Male Sprague-Dawley rats were assigned to head-down (HD) suspension, horizontal (HOZ) suspension, or cage (C) control for 6-9 days. Rats were tested for maximal oxygen uptake before and after surgical instrumentation (Doppler flow probes, carotid and jugular cannulae), and after suspension. Body weight was significantly decreased after suspension in both HD and HOZ groups, but was significantly increased in the C group. Absolute maximal O2 uptake (ml/min) was not different in the C group. However, because of their increased weight, relative maximal O2 uptake (ml/min per kg) was significantly reduced. In contrast, both relative and absolute maximal O2 uptake were significantly lower, following suspension, for the HD and HOZ groups. These preliminary results support the use of hindlimb suspension as an effective model to study the mechanism(s) of cardiovascular deconditioning.

Overton, J. Michael↗
NASA NTRS1998

Three-dimensional echocardiographic planimetry of maximal regurgitant orifice area in myxomatous mitral regurgitation: intraoperative comparison with proximal flow convergence

OBJECTIVES: We sought to validate direct planimetry of mitral regurgitant orifice area from three-dimensional echocardiographic reconstructions. BACKGROUND: Regurgitant orifice area (ROA) is an important measure of the severity of mitral regurgitation (MR) that up to now has been calculated from hemodynamic data rather than measured directly. We hypothesized that improved spatial resolution of the mitral valve (MV) with three-dimensional (3D) echo might allow accurate planimetry of ROA. METHODS: We reconstructed the MV using 3D echo with 3 degrees rotational acquisitions (TomTec) using a transesophageal (TEE) multiplane probe in 15 patients undergoing MV repair (age 59 +/- 11 years). One observer reconstructed the prolapsing mitral leaflet in a left atrial plane parallel to the ROA and planimetered the two-dimensional (2D) projection of the maximal ROA. A second observer, blinded to the results of the first, calculated maximal ROA using the proximal convergence method defined as maximal flow rate (2pi(r2)va, where r is the radius of a color alias contour with velocity va) divided by regurgitant peak velocity (obtained by continuous wave [CW] Doppler) and corrected as necessary for proximal flow constraint. RESULTS: Maximal ROA was 0.79 +/- 0.39 (mean +/- SD) cm2 by 3D and 0.86 +/- 0.42 cm2 by proximal convergence (p = NS). Maximal ROA by 3D echo (y) was highly correlated with the corresponding flow measurement (x) (y = 0.87x + 0.03, r = 0.95, p < 0.001) with close agreement seen (AROA (y - x) = 0.07 +/- 0.12 cm2). CONCLUSIONS: 3D echo imaging of the MV allows direct visualization and planimetry of the ROA in patients with severe MR with good agreement to flow-based proximal convergence measurements.

NASA Discipline Cardiopulmonary↗
NASA NTRS1987

Potential benefits of maximal exercise just prior to return from weightlessness

The purpose of this study was to determine whether performance of a single maximal bout of exercise during weightlessness within hours of return to earth would enhance recovery of aerobic fitness and physical work capacities under a 1G environment. Ten healthy men were subjected to a 10-d bedrest period in the 6-deg headdown position. A graded maximal supine cycle ergometer test was performed before and at the end of bedrest to simulate exercise during weightlessness. Following 3 h of resumption of the upright posture, a second maximal exercise test was performed on a treadmill to measure work capacity under conditions of 1G. Compared to before bedrest, peak oxygen consumption, V(O2), decreased by 8.7 percent and peak heart rate (HR) increased by 5.6 percent in the supine cycle test at the end of bedrest. However, there were no significant changes in peak V(O2) and peak HR in the upright treadmill test following bedrest. These data suggest that one bout of maximal leg exercise prior to return from 10 d of weightlessness may be adequate to restore preflight aerobic fitness and physical work capacity.

Convertino, Victor A.↗
NASA NTRS1993

Influence of simulated microgravity on the maximal oxygen consumption of nontrained and trained rats

The effects of microgravity and endurance training (TR) on maximal O2 consumption was investigated in trained and nontrained (NT) rats subjected to head-down suspension (HDS) by comparing maximal O2 consumption, treadmill run time (RT), and mechanical efficiency (ME) of treadmill running in HDS rats, both NT and TR, and in respective cage controls. It was found that HDS for 28 days was associated with significant reduction in absolute maximal O2 consumption in both TR and NT rats. Relative maximal O2 consumption, however, was significantly reduced in TR but not NT rats. Reductions in RT and ME occurring in both TR and NT rats after 28 days of HDS were similar. The TR rats exhibited greater diuretic, natriuretic, and kaliuretic responses to HDS than the NT rats.

Woodman, Christopher R.↗
NASA NTRS2004

Formation Control for the Maxim Mission.

Over the next twenty years, a wave of change is occurring in the spacebased scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today's technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. The Stellar Imager mission requirements are on the same order of those for MAXIM. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; (2) the formation control architecture devised for such missions; (3) the design of the formation control laws to maintain very high precision relative positions; and (4) the levels of fuel usage required in the duration of these missions. Specific preliminary results are presented for two spacecraft within the MAXIM mission.

Luquette, Richard J.↗
NASA NTRS2003

Prolonged head-down tilt exposure reduces maximal cutaneous vasodilator and sweating capacity in humans

Cutaneous vasodilation and sweat rate are reduced during a thermal challenge after simulated and actual microgravity exposure. The effects of microgravity exposure on cutaneous vasodilator capacity and on sweat gland function are unknown. The purpose of this study was to test the hypothesis that simulated microgravity exposure, using the 6 degrees head-down tilt (HDT) bed rest model, reduces maximal forearm cutaneous vascular conductance (FVC) and sweat gland function and that exercise during HDT preserves these responses. To test these hypotheses, 20 subjects were exposed to 14 days of strict HDT bed rest. Twelve of those subjects exercised (supine cycle ergometry) at 75% of pre-bed rest heart rate maximum for 90 min/day throughout HDT bed rest. Before and after HDT bed rest, maximal FVC was measured, via plethysmography, by heating the entire forearm to 42 degrees C for 45 min. Sweat gland function was assessed by administering 1 x 10(-6) to 2 M acetylcholine (9 doses) via intradermal microdialysis while simultaneously monitoring sweat rate over the microdialysis membranes. In the nonexercise group, maximal FVC and maximal stimulated sweat rate were significantly reduced after HDT bed rest. In contrast, these responses were unchanged in the exercise group. These data suggest that 14 days of simulated microgravity exposure, using the HDT bed rest model, reduces cutaneous vasodilator and sweating capacity, whereas aerobic exercise training during HDT bed rest preserves these responses.

Clinical Trial↗
NASA NTRS1992

Glucose transporters and maximal transport are increased in endurance-trained rat soleus

Voluntary wheel running induces an increase in the concentration of the regulatable glucose transporter (GLUT4) in rat plantaris muscle but not in soleus muscle (K. J. Rodnick, J. O. Holloszy, C. E. Mondon, and D. E. James. Diabetes 39: 1425-1429, 1990). Wheel running also causes hypertrophy of the soleus in rats. This study was undertaken to ascertain whether endurance training that induces enzymatic adaptations but no hypertrophy results in an increase in the concentration of GLUT4 protein in rat soleus (slow-twitch red) muscle and, if it does, to determine whether there is a concomitant increase in maximal glucose transport activity. Female rats were trained by treadmill running at 25 m/min up a 15% grade, 90 min/day, 6 days/wk for 3 wk. This training program induced increases of 52% in citrate synthase activity, 66% in hexokinase activity, and 47% in immunoreactive GLUT4 protein concentration in soleus muscles without causing hypertrophy. Glucose transport activity stimulated maximally with insulin plus contractile activity was increased to roughly the same extent (44%) as GLUT4 protein content in soleus muscle by the treadmill exercise training. In a second set of experiments, we examined whether a swim-training program increases glucose transport activity in the soleus in the presence of a maximally effective concentration of insulin. The swimming program induced a 44% increase in immunoreactive GLUT4 protein concentration. Glucose transport activity maximally stimulated with insulin was 62% greater in soleus muscle of the swimmers than in untrained controls. Training did not alter the basal rate of 2-deoxyglucose uptake.(ABSTRACT TRUNCATED AT 250 WORDS).

Non-NASA Center↗
DOE OSTI2026

Locally purified maximally mixed states at scale: Entanglement pruning and symmetries

Locally Purified Density Operators (LPDOs) are state-of-the-art tensor network ansatze candidates that efficiently represent mixed quantum states at scale. However, given their non-uniqueness, their representational complexity is generally sub-optimal in practical computations. Here, in this work we perform a comprehensive numerical and analytical analysis and resolve this issue in the experimentally relevant limit where noise depolarizes the density operator into a maximally mixed state. To resolve the sub-optimality issue, we analyze two numerical tools, one analytic method, and detail the relations between them. The numerical tools used are fidelity-preserving truncations and isometric gauge transformations leveraging Riemannian optimizations over entropic objective functions. In addition, by invoking the injectivity and symmetry constraints of the maximally mixed LPDO, we also present analytical closed-form expressions for the disentangler and discuss their relation to numerical optimizers. Further, away from the maximally mixed state, our simulations highlight how the truncation threshold smoothly interpolate, as a function of depolarization, between established matrix product results and our new results. Our work shows how, by minimizing the resources required to represent key states of practical interest in experiment, the efficiency of tensor network algorithms can be substantially increased. This paves the path for uncovering tensor network’s fundamental scalability limits and latent potential in representing the wide locus of mixed quantum states that are accessible on near-term quantum devices.

Gangapuram, Amit Jamadagni [Oak Ridge National Lab↗
DOE OSTI2024

Inertia-induced mixing and reaction maximization in laminar porous media flows

Solute transport and biogeochemical reactions in porous and fractured media flows are controlled by mixing, as are subsurface engineering operations such as contaminant remediation, geothermal energy production, and carbon sequestration. Porous media flows are generally regarded as slow, so the effects of fluid inertia on mixing and reaction are typically ignored. Here, we demonstrate through microfluidic experiments and numerical simulations of mixing-induced reaction that inertial recirculating flows readily emerge in laminar porous media flows and dramatically alter mixing and reaction dynamics. An optimal Reynolds number that maximizes the reaction rate is observed for individual pore throats of different sizes. This reaction maximization is attributed to the effects of recirculation flows on reactant availability, mixing, and reaction completion, which depend on the topology of recirculation relative to the boundary of the reactants or mixing interface. Recirculation enhances mixing and reactant availability, but a further increase in flow velocity reduces the residence time in recirculation, leading to a decrease in reaction rate. The reaction maximization is also confirmed in a flow channel with grain inclusions and randomized porous media. Interestingly, the domain-wide reaction rate shows a dramatic increase with increasing Re in the randomized porous media case. This is because fluid inertia induces complex three-dimensional flows in randomized porous media, which significantly increases transverse spreading and mixing. This study shows how inertial flows control reaction dynamics at the pore scale and beyond, thus having major implications for a wide range of environmental systems.

Chen, Michael A. (ORCID:0000000294614710)↗
DOE OSTI2026

Offline Maximizing Minimally Invasive Proper Orthogonal Decomposition for Reduced-Order Modeling of S n Radiation Transport

Deterministic solutions to the Sn radiation transport equation can be computationally expensive to calculate. Reduced-order modeling enables efficient approximation of the full-order model (FOM) solution. We propose a novel method for constructing reduced-order models (ROMs) of the S n radiation transport equation, offline maximizing minimally invasive (OMMI) proper orthogonal decomposition (POD). POD uses the method of snapshots to create a reduced-order basis for constructing an ROM. Minimally invasive POD leverages the sweep infrastructure existing in deterministic transport codes to create a POD-based ROM, even when infeasible by traditional methods. Offline maximizing minimally invasive proper orthogonal decomposition (OMMI-POD) extends minimally invasive POD by performing sweeps offline, therefore maximizing the potential speedup. OMMI-POD does so by creating a library of reduced systems from a training set. This library of reduced systems is then interpolated to provide a rapid approximate solution of the S n radiation transport equation. The model is evaluated on a set of test problems, achieving a low error with a 466 times speedup over the FOM. Also presented is a study of the effect of sampling method on the performance of OMMI-POD, specifically comparing naive uniform sampling to the more accurate and computationally expensive greedy sampling.

97 MATHEMATICS AND COMPUTING↗