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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SU-E-J-199: A Software Tool for Quality Assurance of Online Replanning with MR-Linac

Purpose: To develop a quality assurance software tool, ArtQA, capable of automatically checking radiation treatment plan parameters, verifying plan data transfer from treatment planning system (TPS) to record and verify (R&V) system, performing a secondary MU calculation considering the effect of magnetic field from MR-Linac, and verifying the delivery and plan consistency, for online replanning. Methods: ArtQA was developed by creating interfaces to TPS (e.g., Monaco, Elekta), R&V system (Mosaiq, Elekta), and secondary MU calculation system. The tool obtains plan parameters from the TPS via direct file reading, and retrieves plan data both transferred from TPS and recorded during the actual delivery in the R&V system database via open database connectivity and structured query language. By comparing beam/plan datasets in different systems, ArtQA detects and outputs discrepancies between TPS, R&V system and secondary MU calculation system, and delivery. To consider the effect of 1.5T transverse magnetic field from MR-Linac in the secondary MU calculation, a method based on modified Clarkson integration algorithm was developed and tested for a series of clinical situations. Results: ArtQA is capable of automatically checking plan integrity and logic consistency, detecting plan data transfer errors, performing secondary MU calculations with or without a transverse magnetic field, and verifying treatment delivery. The tool is efficient and effective for pre- and post-treatment QA checks of all available treatment parameters that may be impractical with the commonly-used visual inspection. Conclusion: The software tool ArtQA can be used for quick and automatic pre- and post-treatment QA check, eliminating human error associated with visual inspection. While this tool is developed for online replanning to be used on MR-Linac, where the QA needs to be performed rapidly as the patient is lying on the table waiting for the treatment, ArtQA can be used as a general QA tool in radiation oncology practice. This work is partially supported by Elekta Inc.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-251: Developing a Daily Proton Beam Monitoring System

Purpose: To develop a daily monitoring system for proton beam output check and beam uniformity check. Methods: Designed for continuously irradiated photon and electron beams with a field size of 20 cm x 20 cm, the daily output checker (Sun Nuclear, Inc.) is not suitable for monitoring proton beams with inter-pulse beam-off and a field size smaller than 14–16 cm in diameter. To allow such proton beam monitoring, the following tests were performed. 1. Absolute dose and array calibrations which accept continuous irradiation only, were performed using photon beams. 2. Five ion chambers within the central area of 8 cm x 8 cm were utilized to check constancy of output at the center of beam modulation and at distal edge and to check beam symmetry and flatness. 3. To simplify our evaluation, the array calibration was manually modified, such that all five chambers report equal values in spite of their differences in build-up thicknesses. 4. The chamber at the lower-right corner is placed under a buildup thickness that can offer dose measurement at the distal edge. This buildup thickness was determined by proton beam range measurements, which established buildup thickness for beam output measurement at the central chamber and range measurement at the corner chamber. 5. The beam-off delay which allows receipt of pulsed irradiation was activated and optimal delay times were determined for each proton beam at 149.6, 185.6, and 249.5 MeV. Results: The above system was tested by miss-steering proton beams and altering phantom thickness by 1 mm at a time. The system reliably monitored the beam with: 3% tolerance for beam flatness, symmetry and output. The range difference of 0.5 mm could be detected at all energies by setting a tolerance of 20%. Conclusion: A quick daily proton beam monitoring system was feasible.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

SU-E-T-636: ProteusONE Machine QA Procedure and Stabiity Study: Half Year Clinical Operation

Purpose: The objective of this study is to evaluate the stability of ProteusOne, the 1st commercial PBS proton system, throughout the daily QA and monthly over 6 month clinical operation. Method: Daily QA test includes IGRT position/repositioning, output in the middle of SOBP, beam flatness, symmetry, inplane and crossplane dimensions as well as energy range check. Daily range shifter QA consist of output, symmetry and field size checks to make sure its integrity. In 30 mins Daily QA test, all the measurements are performed using the MatriXXPT (IBA dosimetry). The data from these measurement was collected and compare over the first 6 month of clinical operation. In addition to the items check in daily QA, the summary also includes the monthly QA gantry star shots, absolute position check using a novel device, XRV-100. Results: Average machine output at the center of the spread out bragg peak was 197.5±.8 cGy and was within 1%of the baseline at 198.4 cGy. Beam flatness was within 1% cross plane with an average of 0.67±0.12% and 2% in-plane with an average of 1.08±0.17% compared to baseline measurements of 0.6 and 1.03, respectively. In all cases the radiation isocenter shift was less than or equal to 1mm. Output for the range shifter was within 2% for each individual measurement and averaged 34.4±.2cGy compare to a baseline reading of 34.5cGy. The average range shifter in and cross plane field size measurements were 19.8±0.5cm and 20.5±0.4cm compared with baseline values of 20.19cm and 20.79cm, respectively. Range shifter field symmetry had an average of less 1% for both in-plane and cross plane measurements. Conclusion: All machine metrics over the past 6 months have proved to be stable. Although, some averages are outside the baseline measurement they are within 1% tolerance and the deviation across all measurements is minimal.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

SU-E-T-649: Quality Assurances for Proton Therapy Delivery Equipment

Purpose: The number of proton therapy centers has increased dramatically over the past decade. Currently, there is no comprehensive set of guidelines that addresses quality assurance (QA) procedures for the different technologies used for proton therapy. The AAPM has charged task group 224 (TG-224) to provide recommendations for QA required for accurate and safe dose delivery, using existing and next generation proton therapy delivery equipment. Methods: A database comprised of QA procedures and tolerance limits was generated from many existing proton therapy centers in and outside of the US. These consist of proton therapy centers that possessed double scattering, uniform scanning, and pencil beams delivery systems. The diversity in beam delivery systems as well as the existing devices to perform QA checks for different beam parameters is the main subject of TG-224. Based on current practice at the clinically active proton centers participating in this task group, consensus QA recommendations were developed. The methodologies and requirements of the parameters that must be verified for consistency of the performance of the proton beam delivery systems are discussed. Results: TG-224 provides procedures and QA checks for mechanical, imaging, safety and dosimetry requirements for different proton equipment. These procedures are categorized based on their importance and their required frequencies in order to deliver a safe and consistent dose. The task group provides daily, weekly, monthly, and annual QA check procedures with their tolerance limits. Conclusions: The procedures outlined in this protocol provide sufficient information to qualified medical physicists to perform QA checks for any proton delivery system. Execution of these procedures should provide confidence that proton therapy equipment is functioning as commissioned for patient treatment and delivers dose safely and accurately within the established tolerance limits. The report will be published in late 2015.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

TU-G-BRD-01: Quantifying the Effectiveness of the Physics Pre-Treatment Plan Review for Detecting Errors in Radiation Therapy

Purpose: Physics pre-treatment plan review is crucial to safe radiation oncology treatments. Studies show that most errors originate in treatment planning, which underscores the importance of physics plan review. As a QA measure the physics review is of fundamental importance and is central to the profession of medical physics. However, little is known about its effectiveness. More hard data are needed. The purpose of this study was to quantify the effectiveness of physics review with the goal of improving it. Methods: This study analyzed 315 “potentially serious” near-miss incidents within an institutional incident learning system collected over a two-year period. 139 of these originated prior to physics review and were found at the review or after. Incidents were classified as events that: 1)were detected by physics review, 2)could have been detected (but were not), and 3)could not have been detected. Category 1 and 2 events were classified by which specific check (within physics review) detected or could have detected the event. Results: Of the 139 analyzed events, 73/139 (53%) were detected or could have been detected by the physics review; although, 42/73 (58%) were not actually detected. 45/73 (62%) errors originated in treatment planning, making physics review the first step in the workflow that could detect the error. Two specific physics checks were particularly effective (combined effectiveness of >20%): verifying DRRs (8/73) and verifying isocenter (7/73). Software-based plan checking systems were evaluated and found to have potential effectiveness of 40%. Given current data structures, software implementations of some tests such as isocenter verification check would be challenging. Conclusion: Physics plan review is a key safety measure and can detect majority of reported events. However, a majority of events that potentially could have been detected were NOT detected in this study, indicating the need to improve the performance of physics review.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-251: The Quality Assurance for the Heavy Patient Load Department in the Developing Country: The Primary Experience of An Entire Workflow QA Process Management in Radiotherapy

Purpose: To implement an entire workflow quality assurance (QA) process in the radiotherapy department and to reduce the error rates of radiotherapy based on the entire workflow management in the developing country. Methods: The entire workflow QA process management starts from patient registration to the end of last treatment including all steps through the entire radiotherapy process. Error rate of chartcheck is used to evaluate the the entire workflow QA process. Two to three qualified senior medical physicists checked the documents before the first treatment fraction of every patient. Random check of the treatment history during treatment was also performed. A total of around 6000 patients treatment data before and after implementing the entire workflow QA process were compared from May, 2014 to December, 2015. Results: A systemic checklist was established. It mainly includes patient’s registration, treatment plan QA, information exporting to OIS(Oncology Information System), documents of treatment QAand QA of the treatment history. The error rate derived from the chart check decreases from 1.7% to 0.9% after our the entire workflow QA process. All checked errors before the first treatment fraction were corrected as soon as oncologist re-confirmed them and reinforce staff training was accordingly followed to prevent those errors. Conclusion: The entire workflow QA process improved the safety, quality of radiotherapy in our department and we consider that our QA experience can be applicable for the heavily-loaded radiotherapy departments in developing country.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-458: Tracking Trends of TG-142 Parameters Via Analysis of Data Recorded by 2D Chamber Array

Purpose: With increasing QA demands of medical physicists in clinical radiation oncology, the need for an effective method of tracking clinical data has become paramount. A tool was produced which scans through data automatically recorded by a 2D chamber array and extracts relevant information recommended by TG-142. Using this extracted information a timely and comprehensive analysis of QA parameters can be easily performed enabling efficient monthly checks on multiple linear accelerators simultaneously. Methods: A PTW STARCHECK chamber array was used to record several months of beam outputs from two Varian 2100 series linear accelerators and a Varian NovalisTx−. In conjunction with the chamber array, a beam quality phantom was used to simultaneously to determine beam quality. A minimalist GUI was created in MatLab that allows a user to set the file path of the data for each modality to be analyzed. These file paths are recorded to a MatLab structure and then subsequently accessed by a script written in Python (version 3.5.1) which then extracts values required to perform monthly checks as outlined by recommendations from TG-142. The script incorporates calculations to determine if the values recorded by the chamber array fall within an acceptable threshold. Results: Values obtained by the script are written to a spreadsheet where results can be easily viewed and annotated with a “pass” or “fail” and saved for further analysis. In addition to creating a new scheme for reviewing monthly checks, this application allows for able to succinctly store data for follow up analysis. Conclusion: By utilizing this tool, parameters recommended by TG-142 for multiple linear accelerators can be rapidly obtained and analyzed which can be used for evaluation of monthly checks.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

SU-G-TeP4-08: Automating the Verification of Patient Treatment Parameters

Purpose: To automate the daily verification of each patient’s treatment by utilizing the trajectory log files (TLs) written by the Varian TrueBeam linear accelerator while reducing the number of false positives including jaw and gantry positioning errors, that are displayed in the Treatment History tab of Varian’s Chart QA module. Methods: Small deviations in treatment parameters are difficult to detect in weekly chart checks, but may be significant in reducing delivery errors, and would be critical if detected daily. Software was developed in house to read TLs. Multiple functions were implemented within the software that allow it to operate via a GUI to analyze TLs, or as a script to run on a regular basis. In order to determine tolerance levels for the scripted analysis, 15,241 TLs from seven TrueBeams were analyzed. The maximum error of each axis for each TL was written to a CSV file and statistically analyzed to determine the tolerance for each axis accessible in the TLs to flag for manual review. The software/scripts developed were tested by varying the tolerance values to ensure veracity. After tolerances were determined, multiple weeks of manual chart checks were performed simultaneously with the automated analysis to ensure validity. Results: The tolerance values for the major axis were determined to be, 0.025 degrees for the collimator, 1.0 degree for the gantry, 0.002cm for the y-jaws, 0.01cm for the x-jaws, and 0.5MU for the MU. The automated verification of treatment parameters has been in clinical use for 4 months. During that time, no errors in machine delivery of the patient treatments were found. Conclusion: The process detailed here is a viable and effective alternative to manually checking treatment parameters during weekly chart checks.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TU-D-201-02: Medical Physics Practices for Plan and Chart Review: Results of AAPM Task Group 275 Survey

Purpose: AAPM Task Group (TG) 275 is charged with developing riskbased guidelines for plan and chart review clinical processes. As part of this work an AAPM-wide survey was conducted to gauge current practices. Methods: The survey consisted of 103 multiple-choice questions covering the following review processes for external beam including protons: 1) Initial Plan Check, 2) On-Treatment and 3) End-of-Treatment Chart Check. The survey was designed and validated by TG members with the goal of providing an efficient and easy response process. The survey, developed and deployed with the support of AAPM headquarters, was released to all AAPM members who have self-reported as working in the radiation oncology field and it was kept open for 7 weeks. Results: There are an estimated 4700 eligible participants. At the time of writing, 962 completed surveys have been collected with an average completion time of 24 minutes. Participants are mainly from community hospitals (40%), academicaffiliated hospitals (31%) and free-standing clinics (18%). Among many other metrics covered on the survey, results so far indicate that manual review is an important component on the plan and chart review process (>90%) and that written procedures and checklists are widely used (>60%). However, the details of what is reviewed or checked are fairly heterogeneous among the sampled medical physics community. Conclusion: The data gathered from the survey gauging current practices will be used by TG 275 to develop benchmarks and recommendations for the type and extent of checks to perform effective physics plan and chart review processes.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

TU-FG-201-03: Automatic Pre-Delivery Verification Using Statistical Analysis of Consistencies in Treatment Plan Parameters by the Treatment Site and Modality

Purpose: A novel computer software system, namely APDV (Automatic Pre-Delivery Verification), has been developed for verifying patient treatment plan parameters right prior to treatment deliveries in order to automatically detect and prevent catastrophic errors. Methods: APDV is designed to continuously monitor new DICOM plan files on the TMS computer at the treatment console. When new plans to be delivered are detected, APDV checks the consistencies of plan parameters and high-level plan statistics using underlying rules and statistical properties based on given treatment site, technique and modality. These rules were quantitatively derived by retrospectively analyzing all the EBRT treatment plans of the past 8 years at authors’ institution. Therapists and physicists will be notified with a warning message displayed on the TMS computer if any critical errors are detected, and check results, confirmation, together with dismissal actions will be saved into database for further review. Results: APDV was implemented as a stand-alone program using C# to ensure required real time performance. Mean values and standard deviations were quantitatively derived for various plan parameters including MLC usage, MU/cGy radio, beam SSD, beam weighting, and the beam gantry angles (only for lateral targets) per treatment site, technique and modality. 2D-based rules of combined MU/cGy ratio and averaged SSD values were also derived using joint probabilities of confidence error ellipses. The statistics of these major treatment plan parameters quantitatively evaluate the consistency of any treatment plans which facilitates automatic APDV checking procedures. Conclusion: APDV could be useful in detecting and preventing catastrophic errors immediately before treatment deliveries. Future plan including automatic patient identify and patient setup checks after patient daily images are acquired by the machine and become available on the TMS computer. This project is supported by the Agency for Healthcare Research and Quality (AHRQ) under award 1R01HS0222888. The senior author received research grants from ViewRay Inc. and Varian Medical System.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Technical basis for inner container leak detection sensitivity goals in 3013 DE surveillance

Helium leak checking of 3013 inner container lids is under consideration for addition to DE Surveillance tasks as an improved means to detect any through-wall flaws that may have formed during storage. This white paper evaluates whether leak checking at DE could replace and improve upon the current method of comparing gas compositions and pressures within the inner and outer containers. We have used viscous and molecular flow equations in ANSI N14.5 to calculate what the measured standard helium leak rate would be for hypothetical leaks of three different sizes. For comparison, we have also calculated the effects on gas composition and pressure differences as a function of pre-DE storage time for the same three leak sizes, using molecular and viscous flow equations as well as diffusion equations to predict the relevant gas transport. For a hypothetical leak that would be measured at 1x10 -7 std cc/sec, likely an achievable sensitivity using helium leak checking at DE, the calculations predict no measurable effect on pressure difference or gas composition as measured by DE gas analysis. We also calculate that it would take over 200 years for water vapor to diffuse through a 10 -7 std cc/sec leak enough to raise the RH outer container to half the RH value in the inner container. A leak 100 times larger, which would be measured at 1x10 -5 std cc/sec, the same water vapor diffusion would take at least 14 years. Our conclusion is that helium leak checking will be useful even at a sensitivity of 1x10 -5 std cc/sec, and a significant improvement over current DE methods at a sensitivity of 1x10 -7 std cc/sec.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Sierra/SolidMechanics Verification Report

This document presents the Sierra/SolidMechanics (Sierra/SM) verification plan. This plan centers on the tests in the Sierra/SM verification test suite, a subset of which are documented in the Sierra/SM Verification Tests Manual. Most of these tests are run nightly with the Sierra/SM code suite, and the results of the tests are checked against analytic solutions. For each of the tests presented in the Verification Tests Manual, the test setup, a description of the analytic solution, and comparison of the Sierra/SM code results to the analytic solution is provided. Mesh convergence is also checked on a nightly basis for several of these tests. This verification plan discusses these various types of tests and what they mean for Sierra/SM verification. Many other activities also contribute to Sierra/SM quality. These address code and solution quality and range from low-level unit tests, run nightly, up to full-fidelity acceptance tests, used to verify release stability. This acceptance test suite checks that new versions of Sierra/SM continue to yield the same answers for high-resolution analyst problems. Further code quality measures include an extensive suite of intermediate-size regression tests and automated nightly code quality checks. While these additional activities do not fall under a strict definition of verification, they greatly add to the quality, stability, and reliability of Sierra/SM, and are discussed here as well.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

A Comparison of Cosmological Parameters Determined from CMB Temperature Power Spectra from the South Pole Telescope and the Planck Satellite

The Planck cosmic microwave background temperature data are best fit with a Lambda CDM model that mildly contradicts constraints from other cosmological probes. The South Pole Telescope (SPT) 2540 deg(2) SPT-SZ survey offers measurements on sub-degree angular scales (multipoles 650 <= l <= 2500) with sufficient precision to use as an independent check of the Planck data. Here we build on the recent joint analysis of the SPT-SZ and Planck data in Hou et al. by comparing Lambda CDM parameter estimates using the temperature power spectrum from both data sets in the SPT-SZ survey region. We also restrict the multipole range used in parameter fitting to focus on modes measured well by both SPT and Planck, thereby greatly reducing sample variance as a driver of parameter differences and creating a stringent test for systematic errors. We find no evidence of systematic errors from these tests. When we expand the maximum multipole of SPT data used, we see low-significance shifts in the angular scale of the sound horizon and the physical baryon and cold dark matter densities, with a resulting trend to higher Hubble constant. When we compare SPT and Planck data on the SPT-SZ sky patch to Planck full-sky data but keep the multipole range restricted, we find differences in the parameters n(s) and A(s)e(-2 tau). We perform further checks, investigating instrumental effects and modeling assumptions, and we find no evidence that the effects investigated are responsible for any of the parameter shifts. Taken together, these tests reveal no evidence for systematic errors in SPT or Planck data in the overlapping sky coverage and multipole range and at most weak evidence for a breakdown of Lambda CDM or systematic errors influencing either the Planck data outside the SPT-SZ survey area or the SPT data at l > 2000.

Aylor, K.↗
NASA NTRS1988

Solutions to time variant problems of real-time expert systems

Real-time expert systems for monitoring and control are driven by input data which changes with time. One of the subtle problems of this field is the propagation of time variant problems from rule to rule. This propagation problem is even complicated under a multiprogramming environment where the expert system may issue test commands to the system to get data and to access time consuming devices to retrieve data for concurrent reasoning. Two approaches are used to handle the flood of input data. Snapshots can be taken to freeze the system from time to time. The expert system treats the system as a stationary one and traces changes by comparing consecutive snapshots. In the other approach, when an input is available, the rules associated with it are evaluated. For both approaches, if the premise condition of a fired rule is changed to being false, the downstream rules should be deactivated. If the status change is due to disappearance of a transient problem, actions taken by the fired downstream rules which are no longer true may need to be undone. If a downstream rule is being evaluated, it should not be fired. Three mechanisms for solving this problem are discussed: tracing, backward checking, and censor setting. In the forward tracing mechanism, when the premise conditions of a fired rule become false, the premise conditions of downstream rules which have been fired or are being evaluated due to the firing of that rule are reevaluated. A tree with its root at the rule being deactivated is traversed. In the backward checking mechanism, when a rule is being fired, the expert system checks back on the premise conditions of the upstream rules that result in evaluation of the rule to see whether it should be fired. The root of the tree being traversed is the rule being fired. In the censor setting mechanism, when a rule is to be evaluated, a censor is constructed based on the premise conditions of the upstream rules and the censor is evaluated just before the rule is fired. Unlike the backward checking mechanism, this one does not search the upstream rules. This paper explores the details of implementation of the three mechanisms.

Yeh, Show-Way↗
NASA NTRS1988

Development of an expert planning system for OSSA

This paper presents concepts related to preliminary work for the development of an expert planning system for NASA's Office for Space Science and Applications (OSSA). The expert system will function as a planner's decision aid in preparing mission plans encompassing sets of proposed OSSA space science initiatives. These plans in turn will be checked against budgetary and technical constraints and tested for constraint violations. Appropriate advice will be generated by the system for making modifications to the plans to bring them in line with the constraints. The OSSA Planning Expert System (OPES) has been designed to function as an integral part of the OSSA mission planning process. It will be able to suggest a best plan, be able to accept and check a user-suggested strawman plan, and should provide a quick response to user request and actions. OPES will be written in the C programming language and have a transparent user interface running under Windows 386 on a Compaq 386/20 machine. The system's sorted knowledge and inference procedures will model the expertise of human planners familiar with the OSSA planning domain. Given mission priorities and budget guidelines, the system first sets the launch dates for each mission. It will check to make sure that planetary launch windows and precursor mission relationships are not violated. Additional levels of constraints will then be considered, checking such things as the availability of a suitable launch vehicle, total mission launch mass required vs. the identified launch mass capability, and the total power required by the payload at its destination vs. the actual power available. System output will be in the form of Gantt charts, spreadsheet hardcopy, and other presentation quality materials detailing the resulting OSSA mission plan.

Groundwater, B.↗
NASA NTRS1989

Liquid Rocket Booster (LRB) for the Space Transportation System (STS) systems study. Appendix E: Pressure-fed booster test bed for the liquid rocket booster study

The stress analysis/structural design of the Pressure-Fed Booster Engine Test Bed using the existing F-1 Test Facility Test Stand at Huntsville, Alabama is described. The analysis has been coded and set up for solution on NASTRAN. A separate stress program was established to take the NASTRAN output and perform stress checks on the members. Joint checks and other necessary additional checks were performed by hand. The notes include a brief description of other programs which assist in reproducing and reviewing the NASTRAN results. The redesign of the test stand members and the stress analysis was performed per the A.I.S.C. Code. Loads on the stand consist of the loaded run tanks; wind loads; seismic loads; live loads consisting of snow and ice: live and dead loads of steel; and loaded pressurant bottle. In combining loads, wind loads and seismic loads were each combined with full live loads. Wind and seismic loads were not combined. No one third increase in allowables was taken for the environmental loads except at decks 147 and 214, where the increase was used when considering the stay rods, brackets and stay beams. Wind and seismic loads were considered from each of the four coordinate directions (i.e. N,S,E,W) to give eight basic conditions. The analysis was run with the pressurant tank mounted at level 125. One seismic condition was also run with the tank mounted at levels 169 and 214. No failures were noted with mounting at level 169, but extensive deck failure with mounting at level 214 (the loadsets used are included on the tape, but no detailed results are included in the package). Decking support beams at levels 147 and 214 are not included in the model. The stress program thus does not reduce strut lengths to the length between support beams (the struts are attached to the beams at intersection points) and gives stress ratios larger than one for some of the struts. The affected members were therefore checked by hand.

Source record↗
NASA NTRS1990

Hypercubes for critical spacecraft command verification

Interplanetary spacecraft are controlled with sets of onboard commands called 'sequences' that control the spacecraft for hours, days, or weeks depending upon the craft and its current activity phase. The sequence-checking problem, with some examples from practical experience, and the technical challenges of implementing sequence checking on a parallel computer are presented. Hypercube applications including computational-physics problems, 'optimistic' and 'conservative' categories are discussed. Finally, future development and prototype ways of balancing the checking network across the hypercube nodes, handling time dependencies among the checks, and minimizing communication are described.

Horvath, Joan C.↗
NASA NTRS1995

ANSYS duplicate finite-element checker routine

An ANSYS finite-element code routine to check for duplicated elements within the volume of a three-dimensional (3D) finite-element mesh was developed. The routine developed is used for checking floating elements within a mesh, identically duplicated elements, and intersecting elements with a common face. A space shuttle main engine alternate turbopump development high pressure oxidizer turbopump finite-element model check using the developed subroutine is discussed. Finally, recommendations are provided for duplicate element checking of 3D finite-element models.

Ortega, R.↗