In this issue:

Issue 92, October 2008

*Hot Topics
*Reliability Basics
*Tool Tips
*Latest Software Updates
*Hot News
*Contribute to HotWire

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Hot Topics

Can the Likelihood Value be Greater Than 0?
ReliaSoft's Weibull++ and ALTA software packages provide the option to use the Maximum Likelihood Estimation (MLE) parameter estimation method. With this method, the set of values that maximize the likelihood function is used as the estimated parameters for the distribution. Many reliability engineers have the impression that the natural logarithm of the likelihood function (Ln-likelihood) is always negative, or in other words, that the likelihood value should always be less than 0. However, this is not true. In this article, we will explain the reason why the Ln-likelihood function can be greater than 0.

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Reliability Basics

Derating for Electronic Components
Derating is a technique usually employed in electrical power and electronic devices, wherein the devices are operated at less than their rated maximum power dissipation, taking into account the case/body temperature, the ambient temperature and the type of cooling mechanism used. In this article, we will briefly explain the theoretical background of derating and how it is applied.

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Tool Tips
  • Can I change my experiment design in DOE++ after I have created it?
  • How can I add items from another BlockSim project to the project I'm currently working on?

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Latest Software Updates
New service releases are now available for Weibull++ (SR 7.5.5), ALTA (SR 7.5.5), DOE++ (SR 1.0.2), BlockSim (SR 7.0.6) and MPC 3 (SR 3.0.16). To determine the compile revision of the application on your computer, select About from the Help menu. More Software Downloads...


Application Date Created Version
Weibull++ 7 8/6/08 7.5.5
ALTA 7 8/6/08 7.5.5
DOE++ 8/6/08 1.0.2
BlockSim 7 9/25/08 7.0.6
MPC 3 9/12/08 3.0.16
Hot News
* Wanted: Your Ideas! - We know many of you have great ideas that could morph into compelling presentations for the 2009 International Applied Reliability Symposium, North America, which will be held in San Diego, California from June 9 - 12, 2009. Step one is to submit your presentation proposal to the ARS committee by the December 5, 2008 deadline. Complete details, including the required proposal submission form, are available at Keep in mind, too, that selected presenters will receive complimentary registration to the event, along with an event shirt, a small gift and a chance to win one of the Excellent Presentation Awards. Don't miss out on this great opportunity!
* Public FRACAS Seminar - For the first time ever, ReliaSoft is offering RS 475 FRACAS Principles and Applications in a public format, November 18 - 19, 2008 in Tucson, Arizona. This two-day course provides an overview of the fundamentals of Failure Reporting, Analysis and Corrective Action Systems (FRACAS). Emphasis is placed on configuring and using ReliaSoft's XFRACAS software for incident reporting, failure analysis, problem resolution and other related analyses. For a detailed course outline, please visit To register online, simply visit or contact our sales team in the USA at +1-520886-0410.
* MIL-HDBK-217 Revision - MIL-HDBK-217, which is used for reliability prediction of electronic equipment, is being revised and updated. The Defense Standardization Program Office (DSPO), a division of the U.S. Department of Defense, has tasked the Crane Division of the Naval Surface Warfare Center (NSWC) with executing this revision. To this end, NSWC Crane is soliciting test and field part data from the reliability community. For more information, please visit
Upcoming Public Training Event Calendar
October 2008
October 13 - 17, 2008: RS 540 Reliability and Maintainability Analysis for Repairable Systems in Paphos, Cyprus
October 20 - 21, 2008: RS 470 Failure Modes, Effects and Criticality Analysis in Singapore
October 22 - 24, 2008: International Applied Reliability Symposium in Singapore
October 27 - 31, 2008: MSMT Foundations in Tucson, Arizona
November 2008
November 10 - 14, 2008: MSMT Foundations in Melbourne, Australia
November 10 - 11, 2008: RS 401(C) Reliability and Life Data Analysis (Condensed) in New Delhi, India
November 17 - 21, 2008: MSMT Foundations in Bordeaux, France
November 18 - 19, 2008: RS 475 FRACAS Principles and Applications in Tucson, Arizona
November 20 - 21, 2008: RS 490 Standards Based Reliability Prediction in Tucson, Arizona
December 2008
December 3 - 5, 2008: RS 511 Application of Reliability Growth Models in Developmental Testing and Fielded Systems in Tucson, Arizona
December 3 - 5, 2008: RS 521 Advanced Accelerated Life Testing Analysis in Tucson, Arizona
December 3 - 5, 2008: RS 560 Fundamentals of Design for Reliability in Singapore
December 10 - 12, 2008: RS 588 DOE: Experiment Design and Analysis in Tucson, Arizona
December 15 - 19, 2008: RS 540 Reliability and Maintainability Analysis for Repairable Systems in Chennai, India
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.

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