| In this issue: |
Issue 109,
March 2010 |
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Reliability HotWire is a service of
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Hot Topics |
Crow Extended Fleet Analysis
RGA offers two data types that have been designed to analyze data from systems operating in the field: Repairable and Fleet. This example illustrates the use of the Fleet data type. This type of data is intended to be used for analyzing randomly selected systems from the field. The results are returned in terms of total number of fleet failures vs. total fleet operation time (as opposed to the Repairable data type, which returns results in terms of individual system time). The main advantage of the Fleet data type is the ability to apply the Crow Extended model to data obtained from in-service systems that are being used in the field. With this analysis, you can evaluate the improvement (i.e. the "jump" in the MTBF) that could be achieved by rolling out a fix (or set of fixes) for all units operating in the field. In this article we will illustrate this application.
To read more, see
http://www.weibull.com/hotwire/issue109/hottopics109.htm
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Reliability Basics |
Unbiasing Parameters in Weibull++
Commonly used methods for parameter estimation, such as the maximum likelihood estimation (MLE) and the least squares estimation (LSE) or rank regression (RR), are known to be biased. This is particularly true with small sample sizes and censored data. Bias correction methods have been studied in the literature. A well known example is the standard deviation obtained using MLE for which it can be shown that an unbiased estimator may be obtained.
Weibull++ makes it possible to calculate unbiased parameters for the standard deviation in the Normal distribution, and for beta in the 2-parameter Weibull distribution. In this article, we will discuss the method used in
Weibull++ to calculate the unbiased beta estimator for MLE, for both complete and censored data. Unlike the case of the Normal distribution, this is an empirical method obtained via simulation.To read more, see
http://www.weibull.com/hotwire/issue109/relbasics109.htm
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Tool Tips |
- How can I assign factors to specific columns of a Taguchi orthogonal array in
DOE++?
- What tools are available to help me design a reliability demonstration test?
To read more, see
http://www.weibull.com/hotwire/issue109/tooltips109.htm
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Hot News |
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Sneak Preview
- With new major version releases of Xfmea
and
RCM++
on the horizon, we thought you would
enjoy a brief glimpse into our plans for Version 5. Although we have
included many new features and enhancements,
much of our focus has been on
improving usability in order to make
the power and flexibility of this software
more accessible to all users, regardless of experience. The
redesigned interfaces are more user-friendly
due to better organization of menus, tools,
settings and controls, as well as the inclusion
of popular features such as drag-and-drop
functionality. We've also made it easier
to customize reports and FMEA spreadsheets,
while providing more visibility for related analyses such as
DRBFMs, DVP&Rs and Control Plans. New
features
include a custom Risk Ranking Utility and
Risk Discovery Analysis and an Import Utility
that allows you to query and record type up to 3
search terms. More
detailed information will appear on
ReliaSoft.com once
Xfmea 5 and RCM++ 5 are
officially released. Please e-mail us at Sales@ReliaSoft.com
if you would like to be added to our
notification list. |
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U.S. Military
Directives Update - As many of you
know, weibull.com is the most
comprehensive Web site
devoted entirely to the topic of reliability
engineering. You may not know, however, that we
included a section specifically for U.S. Military
directives, handbooks and standards related to
reliability practices at
http://www.weibull.com/knowledge/milhdbk.htm.
For your convenience, we post periodic updates
such as the
November 2009 memorandum from the Director
to DOT&E Staff regarding "Test and Evaluation
(T&E) Initiatives." This particular memorandum
stresses that Test and Evaluation Strategies (TES) and
Test and Evaluation Master Plans (TEMP) for new or
restructured programs will not be approved if
they lack a reliability growth curve or software
failure profile. If you are actively involved
with the U.S. Military as an engineer or a
supplier, the
full memorandum may be of interest
to you. |
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Upcoming Public Training Event Calendar |
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March 2010 |
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March 15 - 19, 2010:
MSMT Foundations
in
Kuala Lumpur, Malaysia |
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March 16 - 18, 2010:
RS 522 Advanced System Reliability / Maintainability Analysis
in
Tucson, Arizona |
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March 22 - 23, 2010:
RS 490 Standards Based Reliability Prediction
in
Singapore |
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March 24 - 26, 2010:
RS 522 Advanced System Reliability / Maintainability Analysis
in
Singapore |
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April 2010 |
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April 5 - 9, 2010:
RS 540 Reliability and Maintainability Analysis for Repairable Systems
in
Jakarta, Indonesia |
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April 7 - 9, 2010:
International Applied Reliability Symposium
in
Berlin, Germany |
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April 19 - 23, 2010:
MSMT Foundations
in
Stockport, United Kingdom |
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April 19 - 23, 2010:
MSMT Foundations
in
Tucson, Arizona |
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April 19 - 21, 2010:
RS 521 Advanced Accelerated Life Testing Analysis
in
Bangalore, India |
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May 2010 |
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May 10 - 14, 2010:
MSMT Foundations
in
Singapore |
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May 10 - 12, 2010:
RS 588 DOE: Experiment Design and Analysis
in
Warsaw, Poland |
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May 11 - 13, 2010:
RS 511 Application of Reliability Growth Models in Developmental Testing and Fielded Systems
in
Tucson, Arizona |
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May 11 - 13, 2010:
RS 521 Advanced Accelerated Life Testing Analysis
in
Tucson, Arizona |
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Contribute to HotWire |
Contributions Welcomed
As always, your feedback
and contributions are appreciated. ReliaSoft is able to
provide the most user-friendly reliability software packages
and support because we listen to our customers. This applies
to our newsletters and publications as well. We welcome
any suggestions or contributions you may have for Reliability
HotWire. If you have a topic or article that you think
would be useful to the readers of Reliability HotWire,
feel free to contact us. We can be reached by e-mail at
HotWire@ReliaSoft.com,
or by standard mail at 1450 S. Eastside Loop, Tucson, AZ
85710-6703, USA. |
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Corporation, ALL RIGHTS RESERVED. |
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