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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Constructing realistic Szekeres models from initial and final data

The Szekeres family of inhomogeneous solutions, which are defined by six arbitrary metric functions, offers a wide range of possibilities for modelling cosmic structure. Here we present a model construction procedure for the quasispherical case using given data at initial and final times. Of the six arbitrary metric functions, the three which are common to both Szekeres and Lemaître-Tolman models are determined by the model construction procedure of Krasinski and Hellaby. For the remaining three functions, which are unique to Szekeres models, we derive exact analytic expressions in terms of more physically intuitive quantities — density profiles and dipole orientation angles. Using MATLAB, we implement the model construction procedure and simulate the time evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1980

An interactive modular design for computerized photometry in spectrochemical analysis

A general functional description of totally automatic photometry of emission spectra is not available for an operating environment in which the sample compositions and analysis procedures are low-volume and non-routine. The advantages of using an interactive approach to computer control in such an operating environment are demonstrated. This approach includes modular subroutines selected at multiple-option, menu-style decision points. This style of programming is used to trace elemental determinations, including the automated reading of spectrographic plates produced by a 3.4 m Ebert mount spectrograph using a dc-arc in an argon atmosphere. The simplified control logic and modular subroutine approach facilitates innovative research and program development, yet is easily adapted to routine tasks. Operator confidence and control are increased by the built-in options including degree of automation, amount of intermediate data printed out, amount of user prompting, and multidirectional decision points.

Bair, V. L.↗
NASA NTRS1986

NASA Task Load Index (TLX): Computerized Version - Volume 1.0

This booklet and the accompanying diskette contain the materials necessary to collect subjective workload assessments with the NASA Task Load Index on IBM PC compatible microcomputers. This procedure for collecting workload ratings was developed by the Human Performance Group at NASA Ames Research Center during a three year research effort that involved more than 40 laboratory, simulation, and inflight experiments Although the technique is still undergoing evaluation, this package is being distributed to allow other researchers to use it in their own experiments Comments or suggestions about the procedure would be greatly appreciated This package is intended to fill a "nuts and bolts" function of describing the procedure. A bibliography provides background information about previous empirical findings and the logic that supports the procedure.

Hart, Sandra G.↗
NASA NTRS2002

Design and Stress Analysis of Low-Noise Adjusted Bearing Contact Spiral Bevel Gears

An integrated computerized approach for design and stress analysis of low-noise spiral bevel gear drives with adjusted bearing contact is proposed. The procedure of computations is an iterative process that requires four separate procedures and provide: (a) a parabolic function of transmission errors that is able to reduce the effect of errors of alignment on noise and vibration, and (b) reduction of the shift of bearing contact caused by misalignment. Application of finite element analysis enables us to determine the contact and bending stresses and investigate the formation of the bearing contact. The design of finite element models and boundary conditions is automated and does not require intermediate CAD computer programs for application of general purpose computer program for finite element analysis.

Fuentes, A.↗
DOE OSTI2017

Economic consequences of aviation system disruptions: A reduced-form computable general equilibrium analysis

The state of the art approach to economic consequence analysis (ECA) is computable general equilibrium (CGE) modeling. However, such models contain thousands of equations and cannot readily be incorporated into computerized systems used by policy analysts to yield estimates of economic impacts of various types of transportation system failures due to natural hazards, human related attacks or technological accidents. This paper presents a reduced-form approach to simplify the analytical content of CGE models to make them more transparent and enhance their utilization potential. The reduced-form CGE analysis is conducted by first running simulations one hundred times, varying key parameters, such as magnitude of the initial shock, duration, location, remediation, and resilience, according to a Latin Hypercube sampling procedure. Statistical analysis is then applied to the “synthetic data” results in the form of both ordinary least squares and quantile regression. The analysis yields linear equations that are incorporated into a computerized system and utilized along with Monte Carlo simulation methods for propagating uncertainties in economic consequences. Although our demonstration and discussion focuses on aviation system disruptions caused by terrorist attacks, the approach can be applied to a broad range of threat scenarios.

Aviation System Disruptions↗
DOE OSTI2019

Onyx Embolization for Occlusion of the Proximal Internal Iliac Artery During EVAR in Patients with Unsuitable Landing Zones in the Common Iliac Artery

Background: Twenty percent of the patients with AAA have an aneurysm involving the common iliac arteries. Large common iliac diameter can be treated with an iliac branched device or extension of the stent graft to the external iliac artery with occlusion of the ipsilateral internal iliac artery (IIA) to prevent type 2 endoleaks. This study describes and evaluates a embolization technique using Onyx in conjunction with EVAR in aneurysms with poor landing zones in the common iliac arteries. Methods: Patients with Onyx IIA embolization during EVAR, identified from the hospital operating code database, constitute the study population. Onyx embolization was performed by injection at the IIA origin. Peri- and postoperative complications were collected from the medical records. Thin-sliced CT scan was performed 1 month and 1 year after the procedure. Results: Thirty-six patients with complex iliac anatomy and insufficient landing zones (without sealing possibility for standard stent grafts) were identified out of 243 consecutive EVAR treatments during a 13-year period. In seventeen patients (7%), the IIA was embolized with Onyx. Technical success was obtained in all 17 patients, without adverse event or procedural complication. No complication related to the embolization procedure was noted during follow-up. Conclusions: During EVAR treatment of patients with aneurysm involving the common iliac artery, Onyx embolization of IIA is a feasible option without need of selective catheterization of the IIA orifice, potentially preserving important branches of the IIA and simplifying emergency procedures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Jose Cabrera dismantling and decommissioning project

The Jose Cabrera Nuclear Power Plant (NPP) was the first commercial power reactor (Westinghouse 1 loop PWR 510 MWth, 160 MWe) commissioned in Spain and provided the base for future development and training. The reactor construction started in 1963 and it was officially on-line by 1969. The NPP operated from 1969 until 2006 when it became the first reactor to be shut down after completing its operational period. The containment is reinforced concrete with a stainless steel head. In 2010 responsibility for D and D was transferred to Enresa to achieve IAEA level 3 (a green field site available for unrestricted re-uses) by 2017. Of the total of more than 104,000 tons of materials that will be generated during dismantling, it is estimated that only ∼4,000 tons will be radioactive waste, some of which, 40 t are considered as intermediate level long-lived wastes and the rest (3,960 t) will be categorized as VLLW and ILLW. The Project is divided into five phases: Phase 0 - Removal of fuel and preliminary work.. Phase 1 - Preparatory Activities for D and D. complete. Phase 2 - Dismantling of Major Components. Phase 3 - Removal of Auxiliary Installations, Decontamination and Demolition. Phase 4 - Environmental Restoration. Phase 2, is currently ongoing (50% completed). To manage the diverse aspects of decommissioning operations, Enresa uses an internally developed computerized project management tool. The tool, based on knowledge gathered from other Enresa projects, can process operations management, maintenance operations, materials, waste, storage areas, procedures, work permits, operator dose management and records. Enresa considers that communication is important for both internal and external stakeholder relations and can be used to inform, to neutralize negative opinions and attitudes, to remove false expectations and for training. Enresa has created a new multi-purpose area (exhibition/visitor centre) and encourages visits from the public, local schools, local and national politicians and technical groups. Greenfield is the final end state objective. The total cost of this project, including a 20% contingency as estimated in 2003 is 135 Meuros. This figure does not include the management of the plant spent fuel, which has constituted an independent project that has been completed in 2009 (35 Meuros). Enresa, with 15 staff on site are managing a team of ∼250 workers, 40 of whom belong to the previous operator. The spent fuel is On-Site prior to the final destination in the future Spain Centralized Spent Fuel Installation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

MO-DE-207A-10: One-Step CT Reconstruction for Metal Artifact Reduction by a Modification of Penalized Weighted Least-Squares (PWLS)

Purpose: Metal objects create severe artifacts in kilo-voltage (kV) CT image reconstructions due to the high attenuation coefficients of high atomic number objects. Most of the techniques devised to reduce this artifact utilize a two-step approach, which do not reliably yield the qualified reconstructed images. Thus, for accuracy and simplicity, this work presents a one-step reconstruction method based on a modified penalized weighted least-squares (PWLS) technique. Methods: Existing techniques for metal artifact reduction mostly adopt a two-step approach, which conduct additional reconstruction with the modified projection data from the initial reconstruction. This procedure does not consistently perform well due to the uncertainties in manipulating the metal-contaminated projection data by thresholding and linear interpolation. This study proposes a one-step reconstruction process using a new PWLS operation with total-variation (TV) minimization, while not manipulating the projection. The PWLS for CT reconstruction has been investigated using a pre-defined weight, based on the variance of the projection datum at each detector bin. It works well when reconstructing CT images from metal-free projection data, which does not appropriately penalize metal-contaminated projection data. The proposed work defines the weight at each projection element under the assumption of a Poisson random variable. This small modification using element-wise penalization has a large impact in reducing metal artifacts. For evaluation, the proposed technique was assessed with two noisy, metal-contaminated digital phantoms, against the existing PWLS with TV minimization and the two-step approach. Result: The proposed PWLS with TV minimization greatly improved the metal artifact reduction, relative to the other techniques, by watching the results. Numerically, the new approach lowered the normalized root-mean-square error about 30 and 60% for the two cases, respectively, compared to the two-step method. Conclusion: A new PWLS operation shows promise for improving metal artifact reduction in CT imaging, as well as simplifying the reconstructing procedure.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

An Easy Algorithm to Generate Colored Noise Sequences

The need for accurate and efficient simulation of the noise background arises in statistical significance tests for periodic signals buried in colored noise. This paper discusses techniques for generating colored-noise sequences which simulate processes with a given spectral density. Matlab routines based on the fast fractional difference algorithm are presented. These routines can create various stochastic models (e.g., first-order autoregressive (AR(1)), power law (PL), autoregressive fractionally integrated moving average ((1, d, 0)), and generalized Gauss Markov (GGM)) that serve as possible candidate null hypotheses to test against in various scenarios. Allan variance and power spectral density (PSD) show that our algorithms are accurate and efficient, and can be easily implemented for stationary noise models and non-stationary PLs with spectral indices up to 2. Our algorithms can also be extended to produce a non-stationary PL with a range-limited steeper PSD (spectral indices up to about 4) using a GGM approximation with a proper break frequency. The red-noise leakage effect on the periodogram is further discussed. The result shows that our GGM approximation has a potential for alleviating the red-noise leakage in the PSD estimates. The Timmer and Koenig procedure is also included for comparison.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Design and Stress Analysis of Low-Noise Adjusted Bearing Contact Spiral Bevel Gears

An integrated computerized approach for design and stress analysis of low-noise spiral bevel gear drives with adjusted bearing contact has been developed. The computation procedure is an iterative process, requiring four separate steps that provide: (a) a parabolic function of transmission errors that is able to reduce the effect of errors of alignment, and (b) reduction of the shift of bearing contact caused by misalignment. Application of finite element analysis permits the contact and bending stresses to be determined and investigate the formation of the bearing contact. The design of finite element models and boundary conditions is automated and does not require an intermediate CAD computer program. A commercially available finite element analysis computer program with contact capability was used to conduct the stress analysis. The theory developed is illustrated with numerical examples.

Litvin, Faydor L.↗
DOE OSTI2018

An Investigation of Chaotic Diffusion in a Family of Hamiltonian Mappings Whose Angles Diverge in the Limit of Vanishingly Action

The chaotic diffusion for a family of Hamiltonian mappings whose angles diverge in the limit of vanishingly action is investigated by using the solution of the diffusion equation. The system is described by a two-dimensional mapping for the variables action, I, and angle, θ and controlled by two control parameters: (i) ϵ, controlling the nonlinearity of the system, particularly a transition from integrable for ϵ=0 to non-integrable for ϵ≠0 and; (ii) γ denoting the power of the action in the equation defining the angle. For ϵ≠0 the phase space is mixed and chaos is present in the system leading to a finite diffusion in the action characterized by the solution of the diffusion equation. The analytical solution is then compared to the numerical simulations showing a remarkable agreement between the two procedures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

The method of convergence to calculate particles fluxes in X rays spectrometry techniques. Application in nuclear compounds

A method to calculate particle fluxes applicable in most of the spectroscopy techniques is described. Flux intensities of backscattered or absorbed electrons and emitted photons are calculated using a method of convergence to solve the invariant embedding equations that are used to describe the particle trajectories inside a solid sample. Our results are found to be helpful to carry out a procedure for quantitative characterization using instruments such as electron probe microanalyser or other probes. Examples of application to calculate the composition of ternary alloys are given and are compared with the same calculations using another procedure.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Robotic Left Hepatectomy and Roux-en-Y Hepaticojejunostomy After Bile Duct Injury

Background: Bile duct injuries after cholecystectomy remain a major concern because their incidence has not changed through the years despite technical advances. This video presents a robotic left hepatectomy and Roux-en-Y hepaticojejunostomy as a treatment for a complex bile duct injury after laparoscopic cholecystectomy. Methods: A 52-year-old man underwent laparoscopic cholecystectomy at another institution 8 years previously, which resulted in a bile duct injury. His postoperative period was complicated by jaundice and cholangitis. He was treated with endoscopic retrograde cholangiopancreatography and multiple endoprostheses for 3 years, after which the endoprostheses were removed, and he was sent to the authors’ institution. Computed tomography showed that the left liver had signs of disturbed perfusion and dilation of the left intrahepatic bile duct. The patient was asymptomatic and refused any further attempt at surgical correction of the lesion. He was accompanied for 5 years. Magnetic resonance imaging showed progressive atrophy of the left liver. Finally, 3 months before this writing, he presented with intermittent episodes of cholangitis. A multidisciplinary team decided to perform left hepatectomy with Roux-en-Y hepatojejunostomy via a robotic approach. The left liver was atrophied, and left hepatectomy was performed. Fluorescence imaging was used to identify the right bile duct. At opening of the right bile duct, small stones were found and removed. Antecolic Roux-en-Y hepaticojejunostomy then was performed. Results: The operative time was 335 min. Recovery was uneventful, and the patient was discharged on postoperative day 4. Conclusions: Robotic repair of bile duct injuries is feasible and safe, even when liver resection is necessary. This video may help oncologic surgeons to perform this complex procedure.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1977

A computerized traffic control algorithm to determine optimal traffic signal settings

An algorithm was developed to optimally control the traffic signals at each intersection using a discrete time traffic model applicable to heavy or peak traffic. Off line optimization procedures were applied to compute the cycle splits required to minimize the lengths of the vehicle queues and delay at each intersection. The method was applied to an extensive traffic network in Toledo, Ohio. Results obtained with the derived optimal settings are compared with the control settings presently in use.

Seldner, K.↗
DOE OSTI2018

Clinical Experience with Real-Time 3-D Guidance Based on C-Arm-Acquired Cone-Beam CT (CBCT) in Transjugular Intrahepatic Portosystemic Stent Shunt (TIPSS) Placement

PurposeThe aim of this study was to evaluate the feasibility of cone-beam computed tomography (CBCT)-based real-time 3-D guidance of TIPSS placement and its positioning compared to standard guiding methods.Materials and MethodsIn a prospective, randomized, consecutive study design from 2015 to 2017, we included 21 patients in the CBCT guided group and 15 patients in the ultrasound (US) guided group. The prospective groups were compared in terms of success rate of intervention, portal vein puncture/procedure time, number of puncture attempts and applied dose. We furthermore retrospectively analyzed the last 23 consecutive cases with fluoroscopic guided portal vein puncture in terms of success rate, procedure time and applied dose, as it has been the standard method before US guidance.ResultsThe median number of puncture attempts (CBCT: n = 2, US: n = 4, p = 0.249) and the mean puncture time (CBCT: 32 ± 45 min, US: 36 ± 45 min, p = 0.515) were not significantly different. There were furthermore no significant differences in the mean time needed for the total TIPSS procedure (CBCT: 115 ± 52 min, US: 112 ± 41 min, fluoroscopy: 110 ± 33 min, p = 0.996). The mean applied dose of the complete procedure also showed no statistically significant differences (CBCT: 563 ± 289 Gy·cm{sup 2}, US: 322 ± 186 Gy·cm{sup 2}, fluoroscopy: 469 ± 352 Gy·cm{sup 2}, p = 0.069). There were no image guidance related complications.ConclusionReal-time 3-D needle guidance based on CBCT is feasible for TIPSS placement. In terms of puncture attempts, duration and dose, CBCT guidance was not inferior to the control groups and may be a valuable support for interventionists in TIPSS procedures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

A Simplified Procedure to Determine Post-necking True Stress–Strain Curve from Uniaxial Tensile Test of Round Metallic Specimen Using DIC

Triaxial state of stress is usually generated in the necked zone because of neck geometry, and as a consequence proper correction of true tensile stress–strain curve after necking is mandatory. Various correction factors like Bridgman, Davidenkov and Spiridonova, Siebel and Schwaigere are available in the published literature to calculate true stress from mean axial stress. Similarly true strains can be calculated from the minimum diameters of the round specimen in the necked region for various true stress levels. But experimental determination of correction factors and minimum diameters of the round specimen in the necked region is a cumbersome task. This investigation shows a simplified procedure to determine true strains and the correction factors from digital image correlation-based local strain measurement in the necked region. The present procedure is validated by experimental results of rail steel.

36 MATERIALS SCIENCE↗
DOE OSTI2014

How accurately can the peak skin dose in fluoroscopy be determined using indirect dose metrics?

Purpose: Skin dosimetry is important for fluoroscopically-guided interventions, as peak skin doses (PSD) that result in skin reactions can be reached during these procedures. There is no consensus as to whether or not indirect skin dosimetry is sufficiently accurate for fluoroscopically-guided interventions. However, measuring PSD with film is difficult and the decision to do so must be madea priori. The purpose of this study was to assess the accuracy of different types of indirect dose estimates and to determine if PSD can be calculated within ±50% using indirect dose metrics for embolization procedures. Methods: PSD were measured directly using radiochromic film for 41 consecutive embolization procedures at two sites. Indirect dose metrics from the procedures were collected, including reference air kerma. Four different estimates of PSD were calculated from the indirect dose metrics and compared along with reference air kerma to the measured PSD for each case. The four indirect estimates included a standard calculation method, the use of detailed information from the radiation dose structured report, and two simplified calculation methods based on the standard method. Indirect dosimetry results were compared with direct measurements, including an analysis of uncertainty associated with film dosimetry. Factors affecting the accuracy of the different indirect estimates were examined. Results: When using the standard calculation method, calculated PSD were within ±35% for all 41 procedures studied. Calculated PSD were within ±50% for a simplified method using a single source-to-patient distance for all calculations. Reference air kerma was within ±50% for all but one procedure. Cases for which reference air kerma or calculated PSD exhibited large (±35%) differences from the measured PSD were analyzed, and two main causative factors were identified: unusually small or large source-to-patient distances and large contributions to reference air kerma from cone beam computed tomography or acquisition runs acquired at large primary gantry angles. When calculated uncertainty limits [−12.8%, 10%] were applied to directly measured PSD, most indirect PSD estimates remained within ±50% of the measured PSD. Conclusions: Using indirect dose metrics, PSD can be determined within ±35% for embolization procedures. Reference air kerma can be used without modification to set notification limits and substantial radiation dose levels, provided the displayed reference air kerma is accurate. These results can reasonably be extended to similar procedures, including vascular and interventional oncology. Considering these results, film dosimetry is likely an unnecessary effort for these types of procedures when indirect dose metrics are available.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-420: Failure Effects Mode Analysis for Trigeminal Neuralgia Frameless Radiosurgery

Purpose: Functional radiosurgery has been used successfully in the treatment of trigeminal neuralgia but presents significant challenges to ensuring the high prescription dose is delivered accurately. A review of existing practice should help direct the focus of quality improvement for this treatment regime. Method: Failure modes and effects analysis was used to identify the processes in preparing radiosurgery treatment for TN. The map was developed by a multidisciplinary team including: neurosurgeon, radiation oncology, physicist and therapist. Potential failure modes were identified for each step in the process map as well as potential causes and end effect. A risk priority number was assigned to each cause. Results: The process map identified 66 individual steps (see attached supporting document). Corrective actions were developed for areas of high risk priority number. Wrong site treatment is at higher risk for trigeminal neuralgia treatment due to the lack of site specific pathologic imaging on MR and CT – additional site specific checks were implemented to minimize the risk of wrong site treatment. Failed collision checks resulted from an insufficient collision model in the treatment planning system and a plan template was developed to address this problem. Conclusion: Failure modes and effects analysis is an effective tool for developing quality improvement in high risk radiotherapy procedures such as functional radiosurgery.

60 APPLIED LIFE SCIENCES↗