Long life has been billed as a key advantage of LEDs, but understanding and communicating how LED products fail and how long they last can be challenging. While LED-based products hold the potential to achieve lifetimes that meet or exceed their traditional counterparts, manufacturer claims can be misconstrued by users who do not fully understand LED product failure mechanisms or the difference...

A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are conside...

The structure signature of a system made up of n components having continuous and i.i.d. lifetimes was defined in the eighties by Samaniego as the n-tuple whose k-th coordinate is the probability that the k-th component failure causes the system to fail. More recently, a bivariate version of this concept was considered as follows. The joint structure signature of a pair of systems built on a co...

Preventive maintenance is required to keep critical systems available at reasonable costs. Instead of applying the traditional experience-based approach of statistical analysis of failure data, the present paper proposes to adopt a predictive maintenance policy that relies on detailed knowledge of the physical failure mechanisms. A structured scheme for this approach is presented. Then three ca...

We describe a simulator for modeling complex control dynamics in optical line systems involving the interaction of multiple transmission, control, and monitoring elements in response to channel changes, component failure, and recovery events.

Purpose Orbital myositis is characterized by pain with eye movements, gaze restriction, diplopia, and enlargement of extraocular muscles on imaging. Varicella zoster virus (VZV) is an extremely rare cause of the disease in the elderly and has never been reported in a patient younger than forty-five years old such as the adolescent described herein. We present this case to raise awareness of an ...