Search NASA⌕ Search

SEARCH · Search NASA

Results for “problem reporting”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Forced response of mistuned bladed disks

Small mistuning can cause large, catastrophic changes in blade vibrational response whereby the amplitudes of vibration of some blades may increase by several hundred percent. This can produce 'rogue' blades and HCF failure. The free and forced responses may be highly sensitive to mistuning, and the tuned system predictions may be qualitatively in error and grossly underestimate blade forced response and overestimate fatigue life. Manufacturing tolerances, material non-uniformities, nonidentical root fixtures, and in-service degradation result in blade-to-blade differences that destroy cyclic symmetry in bladed discs. Therefore, a credible forced response prediction system for turbomachinery vibration must take mistuning into account. This report addresses these problems, states several objectives, and introduces NASA research program thrusts concerning this problem. This report was given during the NASA LeRC Workshop on Forced Response in Turbomachinery in August of 1993.

Pierre, Christophe↗
NASA NTRS2005

DORIS weekly solutions: status report and open problems

Since the official start of the International DORIS Service (IDS) in 2003, several Analysis Centers have submitted time series of station coordinates in SINEX format. We discuss here the different DORIS weekly solutions available for ITRF 2004 and for the IERS Combinationa Campaign Project.

DORIS↗
NASA NTRS1980

NASA Aviation Safety Reporting System

Problems in briefing of relief by air traffic controllers are discussed, including problems that arise when duty positions are changed by controllers. Altimeter reading and setting errors as factors in aviation safety are discussed, including problems associated with altitude-including instruments. A sample of reports from pilots and controllers is included, covering the topics of ATIS broadcasts an clearance readback problems. A selection of Alert Bulletins, with their responses, is included.

Source record↗
NASA NTRS1928

Propeller problems

This report tries to give a comprehensive survey of the most important propeller problems such as the shape of propellers and the effect of atmospheric conditions on propeller performance.

PROPELLER SLIPSTREAM↗
NASA NTRS1931

An extended theory of thin airfoils and its application to the biplane problem

The report presents a new treatment, due essentially to von Karman, of the problem of the thin airfoil. The standard formulae for the angle of zero lift and zero moment are first developed and the analysis is then extended to give the effect of disturbing or interference velocities, corresponding to an arbitrary potential flow, which are superimposed on a normal rectilinear flow over the airfoil. An approximate method is presented for obtaining the velocities induced by a 2-dimensional airfoil at a point some distance away. In certain cases this method has considerable advantage over the simple "lifting line" procedure usually adopted. The interference effects for a 2-dimensional biplane are considered in the light of the previous analysis. The results of the earlier sections are then applied to the general problem of the interference effects for a 3-dimensional biplane, and formulae and charts are given which permit the characteristics of the individual wings of an arbitrary biplane without sweepback or dihedral to be calculated. In the final section the conclusions drawn from the application of the theory to a considerable number of special cases are discussed, and curves are given illustrating certain of these conclusions and serving as examples to indicate the nature of the agreement between the theory and experiment.

Millikan, Clark B↗
NASA NTRS2020

Formal Verification of a Solution to the n-Queens Problem

This report describes a formal verification of a concise algorithm that computes a solution to the n-Queens problem for all natural numbers n, such that n > 3. The formal proof of the algorithm is completed in the Prototype Verification System (PVS) theorem prover. This verification effort serves two purposes. First, it is presented as a pedagogical example for learning a theorem prover, such as PVS, and second, as a candidate benchmark for comparing other formal methods tools to PVS.

Mahyar R Malekpour↗
NASA NTRS2011

An Investigation Into HPLC Data Quality Problems

This report summarizes the analyses and results produced by a five-member investigative team of Government, university, and industry experts, established by NASA HQ. The team examined data quality problems associated with high performance liquid chromatography (HPLC) analyses of pigment concentrations in seawater samples produced by the San Diego State University (SDSU) Center for Hydro-Optics and Remote Sensing (CHORS). This report shows CHORS did not validate the methods used before placing them into service to analyze field samples for NASA principal investigators (PIs), even though the HPLC literature contained easily accessible method validation procedures, and the importance of implementing them, more than a decade ago. In addition, there were so many sources of significant variance in the CHORS methodologies, that the HPLC system rarely operated within performance criteria capable of producing the requisite data quality. It is the recommendation of the investigative team to a) not correct the data, b) make all the data that was temporarily sequestered available for scientific use, and c) label the affected data with an appropriate warning, e.g., "These data are not validated and should not be used as the sole basis for a scientific result, conclusion, or hypothesis--independent corroborating evidence is required."

Hooker, Stanford B.↗
NASA NTRS1923

Aeronautic instruments. Section VIII : recent developments and outstanding problems

This report is section VIII of a series of reports on aeronautic instruments. The preceding reports in this series have discussed in detail the various types of aeronautic instruments which have reached a state of practical development such that they have already found extensive use. It is the purpose of this paper to discuss briefly some of the more recent developments in the field of aeronautic instrument design and to suggest some of the outstanding problems awaiting solution.

Hunt, F L↗