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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

What is data assimilation really solving, and how is the calculation actually done?

Data assimilation is a procedure in which observations are combined with models. The observations correct model errors on the one hand, and the models extrapolate the data information in space, time, and among different properties on the other. The result of assimilation is generally a more complete and more accurate description of the state of the modeled system than those obtained by either observations or model simulations alone. However, data assimilation is not a panacea for correcting every model error or for compensating all deficiencies of observations.

smoother↗
NASA NTRS1991

Correction of magnetooptic device phase errors in optical correlators through filter design modifications

We address the problem of optical phase errors in an optical correlator introduced by the input and filter plane spatial light modulators. Specifically, we study a laboratory correlator with magnetooptic spatial light modulator (MOSLM) devices. We measure and characterize the phase errors, analyze their effects on the correlation process, and discuss a means of correction through a design modification of the binary phase-only optical filter function. The phase correction technique is found to produce correlation results close to those of an error-free correlator.

Downie, John D.↗
NASA NTRS2010

Self-Nulling Beam Combiner Using No External Phase Inverter

A self-nulling beam combiner is proposed that completely eliminates the phase inversion subsystem from the nulling interferometer, and instead uses the intrinsic phase shifts in the beam splitters. Simplifying the flight instrument in this way will be a valuable enhancement of mission reliability. The tighter tolerances on R = T (R being reflection and T being transmission coefficients) required by the self-nulling configuration actually impose no new constraints on the architecture, as two adaptive nullers must be situated between beam splitters to correct small errors in the coatings. The new feature is exploiting the natural phase shifts in beam combiners to achieve the 180 phase inversion necessary for nulling. The advantage over prior art is that an entire subsystem, the field-flipping optics, can be eliminated. For ultimate simplicity in the flight instrument, one might fabricate coatings to very high tolerances and dispense with the adaptive nullers altogether, with all their moving parts, along with the field flipper subsystem. A single adaptive nuller upstream of the beam combiner may be required to correct beam train errors (systematic noise), but in some circumstances phase chopping reduces these errors substantially, and there may be ways to further reduce the chop residuals. Though such coatings are beyond the current state of the art, the mechanical simplicity and robustness of a flight system without field flipper or adaptive nullers would perhaps justify considerable effort on coating fabrication.

Bloemhof, Eric E.↗
DOE OSTI2024

Rephasing spectral diffusion in time-bin spin-spin entanglement protocols

Generating high-fidelity spin-spin entanglement is an essential task of quantum repeater networks for the distribution of quantum information across long distances. Solid-state-based spin-photon interfaces are promising candidates to realize nodes of a quantum network, but are often limited by spectral diffusion of the optical transition, which results in phase errors on the entangled states. Here, we introduce a method to correct phase errors from quasi-static frequency fluctuations after the entangled state is generated, by shelving the emitters in the excited state to refocus the unknown phase. For quasi-static frequency fluctuations, the fidelity is determined only by the lifetime of the excited state used for shelving, making it particularly suitable for systems with a long-lived shelving state with correlated spectral diffusion. Such a shelving state may be found in Kramers doublet systems such as rare-earth emitters and color centers in Si or SiC interfaced with nanophotonic cavities with a strongly frequency-dependent Purcell enhancement. Furthermore, the protocol can be used to generate high-fidelity entangled spin pairs without reducing the rate of entanglement generation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Checking Questionable Entry of Personally Identifiable Information Encrypted by One-Way Hash Transformation

Background: As one of the several effective solutions for personal privacy protection, a global unique identifier (GUID) is linked with hash codes that are generated from combinations of personally identifiable information (PII) by a one-way hash algorithm. On the GUID server, no PII is permitted to be stored, and only GUID and hash codes are allowed. The quality of PII entry is critical to the GUID system. Objective: The goal of our study was to explore a method of checking questionable entry of PII in this context without using or sending any portion of PII while registering a subject. Methods: According to the principle of GUID system, all possible combination patterns of PII fields were analyzed and used to generate hash codes, which were stored on the GUID server. Based on the matching rules of the GUID system, an error-checking algorithm was developed using set theory to check PII entry errors. We selected 200,000 simulated individuals with randomly-planted errors to evaluate the proposed algorithm. These errors were placed in the required PII fields or optional PII fields. The performance of the proposed algorithm was also tested in the registering system of study subjects. Results: There are 127,700 error-planted subjects, of which 114,464 (89.64%) can still be identified as the previous one and remaining 13,236 (10.36%, 13,236/127,700) are discriminated as new subjects. As expected, 100% of nonidentified subjects had errors within the required PII fields. The possibility that a subject is identified is related to the count and the type of incorrect PII field. For all identified subjects, their errors can be found by the proposed algorithm. The scope of questionable PII fields is also associated with the count and the type of the incorrect PII field. The best situation is to precisely find the exact incorrect PII fields, and the worst situation is to shrink the questionable scope only to a set of 13 PII fields. In the application, the proposed algorithm can give a hint of questionable PII entry and perform as an effective tool. Conclusions: The GUID system has high error tolerance and may correctly identify and associate a subject even with few PII field errors. Correct data entry, especially required PII fields, is critical to avoiding false splits. In the context of one-way hash transformation, the questionable input of PII may be identified by applying set theory operators based on the hash codes. The count and the type of incorrect PII fields play an important role in identifying a subject and locating questionable PII fields.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1979

Optimizing multislot feeds for reflecting antennas

Multislot feed corrects phase errors in reflecting antennas. Variables are reduced by considering symmetry and corrective effect of each phase mode. Overall computation concerning calculation of correct phase angles while optimizing main beam efficiency is simplified by analysis used parabolic torus reflector aboard Space Shuttle.

Waineo, D. K.↗
DOE OSTI2018

Publisher's Note: “Differential voltage amplification from ferroelectric negative capacitance” [Appl. Phys. Lett. 111, 253501 (2017)]

This article was originally published online on 18 December 2017. Due to a production error, the initially-published version contained several typographical errors not corrected during proof revisions, none of which affected the substance of the article. AIP Publishing apologizes for this error. All online versions of the article were corrected on 21 December 2017, and it now appears correctly in print.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2020

Sources of Conservatism in Making Corrective Action Decisions at the NNSS - 20477

During the course of closing nuclear testing release sites at the Nevada National Security Site (NNSS) under the Federal Facility Agreement and Consent Order (FFACO) using the Risk-Based Corrective Action (RBCA) evaluation process, conservative assumptions and estimates were used in many phases of the work. These assumptions and estimates were agreed to during Data Quality Objective (DQO) meetings and published in the FFACO documents. However, the potential cumulative effect of these multiple sources of conservatism was not evaluated. The RBCA process ensures that corrective action decisions minimize the risk of making Type I errors (not applying corrective action to areas that exceed action levels) at the expense of making Type II errors (applying corrective action to areas that do not exceed action levels). Rather than fully characterizing the spatial distribution of contaminants throughout each site, the RBCA process uses a bounding methodology that conservatively estimates spatial boundaries beyond which contamination is not present that exceed corrective action levels. This process accepts that these boundaries may encompass areas that do not exceed corrective action levels and, therefore, may be somewhat larger than for fully characterized sites. This is justified at sites where the reduction in investigation costs are more than any potential increase in corrective action costs. To minimize the risk of making Type I errors, conservatism was used throughout the process. This study documents the many sources of conservatism used in the RBCA process. Conservatism was used in the RBCA process in determining potential receptors, determining action levels, collecting samples, converting sample results into receptor dose, and accounting for uncertainty. This provides decision-makers with a high level of confidence that unacceptable risk to receptors will not result from exposure to residual contamination outside the corrective action boundaries. However, it does not provide an estimate of the actual extent of areas exceeding action levels. This study provides an evaluation of the effects of compounding conservatism on RBCA process decisions. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1971

Optimum impulsive midcourse guidance with control dependent errors.

The problem of determining the optimum guidance policy for an interplanetary spacecraft is treated as a stochastic optimal control problem. An algorithm for computing the optimum velocity correction and the optimum execution time (with allowance for correction-dependent errors) is derived in the case of a single midcourse correction. The performance index was chosen to be an upper bound for the probability that the mission fails, and it is defined as a function of the maximum allowable velocity correction and the maximum allowable deviation of the terminal state. Numerical results obtained for a Jupiter fly-by mission indicate that the execution errors have a significant influence on the performance index, but an acceptably small upper bound on the probability of mission failure can be obtained for sufficiently small execution errors.

Tapley, B. D.↗
NASA NTRS2015

Preliminary Analysis of Effect of Random Segment Errors on Coronagraph Performance

Are we alone in the Universe is probably the most compelling science question of our generation. To answer it requires a large aperture telescope with extreme wavefront stability. To image and characterize Earth-like planets requires the ability to block 10(exp 10) of the host stars light with a 10(exp -11) stability. For an internal coronagraph, this requires correcting wavefront errors and keeping that correction stable to a few picometers rms for the duration of the science observation. This requirement places severe specifications upon the performance of the observatory, telescope and primary mirror. A key task of the AMTD project (initiated in FY12) is to define telescope level specifications traceable to science requirements and flow those specifications to the primary mirror. From a systems perspective, probably the most important question is: What is the telescope wavefront stability specification? Previously, we suggested this specification should be 10 picometers per 10 minutes; considered issues of how this specification relates to architecture, i.e. monolithic or segmented primary mirror; and asked whether it was better to have few or many segmented. This paper reviews the 10 picometers per 10 minutes specification; provides analysis related to the application of this specification to segmented apertures; and suggests that a 3 or 4 ring segmented aperture is more sensitive to segment rigid body motion that an aperture with fewer or more segments.

Stahl, Mark T.↗
NASA NTRS1988

Optimal location of actuators for correcting distortions due to manufacturing errors in large truss structures

A continuum approximation to the calculation of the statistical properties of the corrected shape of a beam truss is presented, and results of a comparison with the exact statistical analysis were found to be very good. In addition, the position of the actuators was optimized to minimize the weighted rms of the distortion using the continuum analysis. The optimal design is shown to be 13.6 percent better than a uniform design for a parabolic weighting function. It was also found that actuators located on the beam face elements were more effective than actuators located on the diagonal elements.

Burdisso, R.↗
DOE OSTI2014

On readout of vibrational qubits using quantum beats

Readout of the final states of qubits is a crucial step towards implementing quantum computation in experiment. Although not scalable to large numbers of qubits per molecule, computational studies show that molecular vibrations could provide a significant (factor 2–5 in the literature) increase in the number of qubits compared to two-level systems. In this theoretical work, we explore the process of readout from vibrational qubits in thiophosgene molecule, SCCl{sub 2}, using quantum beat oscillations. The quantum beats are measured by first exciting the superposition of the qubit-encoding vibrational states to the electronically excited readout state with variable time-delay pulses. The resulting oscillation of population of the readout state is then detected as a function of time delay. In principle, fitting the quantum beat signal by an analytical expression should allow extracting the values of probability amplitudes and the relative phases of the vibrational qubit states. However, we found that if this procedure is implemented using the standard analytic expression for quantum beats, a non-negligible phase error is obtained. We discuss the origin and properties of this phase error, and propose a new analytical expression to correct the phase error. The corrected expression fits the quantum beat signal very accurately, which may permit reading out the final state of vibrational qubits in experiments by combining the analytic fitting expression with numerical modelling of the readout process. The new expression is also useful as a simple model for fitting any quantum beat experiments where more accurate phase information is desired.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

SU-E-J-235: Varian Portal Dosimetry Accuracy at Detecting Simulated Delivery Errors

Purpose: To use receiver operating characteristic (ROC) analysis to quantify the Varian Portal Dosimetry (VPD) application's ability to detect delivery errors in IMRT fields. Methods: EPID and VPD were calibrated/commissioned using vendor-recommended procedures. Five clinical plans comprising 56 modulated fields were analyzed using VPD. Treatment sites were: pelvis, prostate, brain, orbit, and base of tongue. Delivery was on a Varian Trilogy linear accelerator at 6MV using a Millenium120 multi-leaf collimator. Image pairs (VPD-predicted and measured) were exported in dicom format. Each detection test imported an image pair into Matlab, optionally inserted a simulated error (rectangular region with intensity raised or lowered) into the measured image, performed 3%/3mm gamma analysis, and saved the gamma distribution. For a given error, 56 negative tests (without error) were performed, one per 56 image pairs. Also, 560 positive tests (with error) with randomly selected image pairs and randomly selected in-field error location. Images were classified as errored (or error-free) if percent pixels with γ<κ was < (or ≥) τ. (Conventionally, κ=1 and τ=90%.) A ROC curve was generated from the 616 tests by varying τ. For a range of κ and τ, true/false positive/negative rates were calculated. This procedure was repeated for inserted errors of different sizes. VPD was considered to reliably detect an error if images were correctly classified as errored or error-free at least 95% of the time, for some κ+τ combination. Results: 20mm{sup 2} errors with intensity altered by ≥20% could be reliably detected, as could 10mm{sup 2} errors with intensity was altered by ≥50%. Errors with smaller size or intensity change could not be reliably detected. Conclusion: Varian Portal Dosimetry using 3%/3mm gamma analysis is capable of reliably detecting only those fluence errors that exceed the stated sizes. Images containing smaller errors can pass mathematical analysis, though may be detected by visual inspection. This work was not funded by Varian Oncology Systems. Some authors have other work partly funded by Varian Oncology Systems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks

Purpose: Radiotherapy treatment is specified by radiation dose prescriptions, but biological DNA damage actually controls treatment effectiveness. It is impractical to directly measure dose in the clinic, so we measure quantities, such as collected charge, and calculate the relationship to dose. At small fields, such as those in stereotactic radiosurgery (SRS), charged-particle equilibrium (CPE) breaks down and the accuracy of the measurement for delivered dose decreases. By measuring DNA double-strand breaks (DSB) directly, we believe treatment accuracy could improve by providing a more meaningful measurement. Methods: A DNA dosimeter, consisting of magnetic streptavidin beads attached to 4 kilobase pair DNA strands labeled with biotin and fluorescein amidite (FAM) on opposing ends, was suspended in phosphate-buffered saline (PBS). Twenty µL samples were placed in plastic micro-capillary tubes inside a water tank setup and irradiated with 10 cm, 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm radiation field sizes, where the three smallest sizes were cones. After irradiation, the dosimeters were mechanically separated into beads (intact DNA) and supernatant (broken DNA/FAM) using a magnet. The fluorescence was read and the probability of DSB was calculated. This was used to calculate the output factor for an SRS beam and compared to that measured using a diode detector. Results: The output factors relative to a 10 cm field were 0.89±0.07, 0.76±0.08, 0.59±0.04, and 0.78±0.12 for the field sizes of 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm, respectively. Some of the diode measurements do not fall within these uncertainties. Conclusion: This was the first attempt to measure output factors in a water tank with the DNA dosimeter. Although differences compared to the diode were observed, the uncertainty analysis ignored systematic errors. For future work, we will repeat this experiment to quantify and correct systematic errors, such as those caused by positional alignment and sample contamination. This work was funded in part by CPRIT (RP140105).

60 APPLIED LIFE SCIENCES↗
NASA NTRS1973

Effect of photogrammetric reading error on slope-frequency distributions

The effect of reading error on two hypothetical slope frequency distributions and two slope frequency distributions from actual lunar data in order to ensure that these errors do not cause excessive overestimates of algebraic standard deviations for the slope frequency distributions. The errors introduced are insignificant when the reading error is small and the slope length is large. A method for correcting the errors in slope frequency distributions is presented and applied to 11 distributions obtained from Apollo 15, 16, and 17 panoramic camera photographs and Apollo 16 metric camera photographs.

Moore, H. J.↗
NASA NTRS1983

A new calibration method for time delay standard and its application

A method which is used to measure time delay accurately by using a Type 900-LB slotted line is described. The accuracy for calibrating time delay of a precision coaxial air line Type 900-L is about + or - (0.4 to 0.6)ps, and for coaxial cables with VSWR less than 1.5 and time delay t less than 50ns is about + or - (3 to 5)ps. Theoretical analysis and mathematical derivation of microwave networks in cascade are given. Methods to eliminate the errors which are caused by the discontinuities and the error analysis of the measuring system are presented. Skin effect analysis of the transient characteristic of coaxial transmission line are discussed in detail. Methods to eliminate the errors which result from using the calibrated time delay standard to calibrate time interval measurement instruments are presented. The estimation of errors and formulae for correction of those errors are described.

Su, B. W.↗
NASA NTRS1984

An adaptive interpolator algorithm for area-array fine guiance sensors

The present paper provides a description of recent and continuing work related to the development of tracking systems possessing artificial intelligence. It is pointed out that artificial intelligence is being used to provide trackers with the abilities to sense environmental changes which can affect tracker performance, to optimize tracker performance in a changing environment, and to report on the accuracy and stability of the pointing data. The implementation of artificial intelligence in tracking systems is based on the use of adaptive algorithms which correct for tracking errors by applying polynomial corrections to raw tracking output data. The basic operation of a centroid tracking system is discussed, taking into account the limitations on accuracy and stability which exist in the absence of intelligence. Attention is given to the correction method and the implementation of artificial intelligence to improve tracking.

Glavich, T. A.↗
NASA NTRS1991

Nonlinear Dynamic Compensation For Feedback Control

Nonlinear dynamic compensation scheme enhances stability of feedback control system in which feedback signal includes quantization noise. Compensator slows response of control system at low error signals to diminish effect of quantization noise but provides faster response at large error signals to speed correction of large errors.

Lin, Yu-Hwan↗