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Title: An efficiency-decay model for Lumen maintenance

Abstract

Proposed is a multicomponent model for the estimation of light-emitting diode (LED) lumen maintenance using test data that were acquired in accordance with the test standards of the Illumination Engineering Society of North America, i.e., LM-80-08. Lumen maintenance data acquired with this test do not always follow exponential decay, particularly data collected in the first 1000 h or under low-stress (e.g., low temperature) conditions. This deviation from true exponential behavior makes it difficult to use the full data set in models for the estimation of lumen maintenance decay coefficient. As a result, critical information that is relevant to the early life or low-stress operation of LED light sources may be missed. We present an efficiency-decay model approach, where all lumen maintenance data can be used to provide an alternative estimate of the decay rate constant. The approach considers a combined model wherein one part describes an initial “break-in” period and another part describes the decay in lumen maintenance. During the break-in period, several mechanisms within the LED can act to produce a small (typically <; 10%) increase in luminous flux. The effect of the break-in period and its longevity is more likely to be present at low-ambient temperatures and currents,more » where the discrepancy between a standard TM-21 approach and our proposed model is the largest. For high temperatures and currents, the difference between the estimates becomes nonsubstantial. Finally, our approach makes use of all the collected data and avoids producing unrealistic estimates of the decay coefficient.« less

Authors:
 [1];  [1];  [1];  [1]
  1. RTI International, Triangle Park, NC (United States)
Publication Date:
Research Org.:
RTI International, Triangle Park, NC (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1318789
Grant/Contract Number:
EE0005124
Resource Type:
Journal Article: Published Article
Journal Name:
IEEE Transactions on Device and Materials Reliability
Additional Journal Information:
Journal Volume: 16; Journal Issue: 3; Journal ID: ISSN 1530-4388
Publisher:
IEEE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 97 MATHEMATICS AND COMPUTING; light-emitting diodes (LEDs); lumen maintenance; efficiency-decay model

Citation Formats

Bobashev, Georgiy, Baldasaro, Nicholas G., Mills, Karmann C., and Davis, J. Lynn. An efficiency-decay model for Lumen maintenance. United States: N. p., 2016. Web. doi:10.1109/TDMR.2016.2584926.
Bobashev, Georgiy, Baldasaro, Nicholas G., Mills, Karmann C., & Davis, J. Lynn. An efficiency-decay model for Lumen maintenance. United States. doi:10.1109/TDMR.2016.2584926.
Bobashev, Georgiy, Baldasaro, Nicholas G., Mills, Karmann C., and Davis, J. Lynn. 2016. "An efficiency-decay model for Lumen maintenance". United States. doi:10.1109/TDMR.2016.2584926.
@article{osti_1318789,
title = {An efficiency-decay model for Lumen maintenance},
author = {Bobashev, Georgiy and Baldasaro, Nicholas G. and Mills, Karmann C. and Davis, J. Lynn},
abstractNote = {Proposed is a multicomponent model for the estimation of light-emitting diode (LED) lumen maintenance using test data that were acquired in accordance with the test standards of the Illumination Engineering Society of North America, i.e., LM-80-08. Lumen maintenance data acquired with this test do not always follow exponential decay, particularly data collected in the first 1000 h or under low-stress (e.g., low temperature) conditions. This deviation from true exponential behavior makes it difficult to use the full data set in models for the estimation of lumen maintenance decay coefficient. As a result, critical information that is relevant to the early life or low-stress operation of LED light sources may be missed. We present an efficiency-decay model approach, where all lumen maintenance data can be used to provide an alternative estimate of the decay rate constant. The approach considers a combined model wherein one part describes an initial “break-in” period and another part describes the decay in lumen maintenance. During the break-in period, several mechanisms within the LED can act to produce a small (typically <; 10%) increase in luminous flux. The effect of the break-in period and its longevity is more likely to be present at low-ambient temperatures and currents, where the discrepancy between a standard TM-21 approach and our proposed model is the largest. For high temperatures and currents, the difference between the estimates becomes nonsubstantial. Finally, our approach makes use of all the collected data and avoids producing unrealistic estimates of the decay coefficient.},
doi = {10.1109/TDMR.2016.2584926},
journal = {IEEE Transactions on Device and Materials Reliability},
number = 3,
volume = 16,
place = {United States},
year = 2016,
month = 8
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1109/TDMR.2016.2584926

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  • Proposed is a multicomponent model for the estimation of light-emitting diode (LED) lumen maintenance using test data that were acquired in accordance with the test standards of the Illumination Engineering Society of North America, i.e., LM-80-08. Lumen maintenance data acquired with this test do not always follow exponential decay, particularly data collected in the first 1000 h or under low-stress (e.g., low temperature) conditions. This deviation from true exponential behavior makes it difficult to use the full data set in models for the estimation of lumen maintenance decay coefficient. As a result, critical information that is relevant to the earlymore » life or low-stress operation of LED light sources may be missed. We present an efficiency-decay model approach, where all lumen maintenance data can be used to provide an alternative estimate of the decay rate constant. The approach considers a combined model wherein one part describes an initial “break-in” period and another part describes the decay in lumen maintenance. During the break-in period, several mechanisms within the LED can act to produce a small (typically <; 10%) increase in luminous flux. The effect of the break-in period and its longevity is more likely to be present at low-ambient temperatures and currents, where the discrepancy between a standard TM-21 approach and our proposed model is the largest. For high temperatures and currents, the difference between the estimates becomes nonsubstantial. Finally, our approach makes use of all the collected data and avoids producing unrealistic estimates of the decay coefficient.« less
  • Two cells lines--Madin-Darby canine kidney (MDCK) and normal murine mammary gland (NMuMG)--growing as monolayers on collagen gels were overlaid with another collagen gel. The cells responded to the overlay by undergoing reorganization resulting in the creation of lumina. MDCK cells formed lumina that coalesced to form large cavities comparable in size with a tubule. NMuMG cells formed clusters surrounding small lumina, which appeared similar to acini of glandular tissue. The characteristic arrangements, described here by light and electron microscopy, resembled the morphology of the tissues of cell line origin. MDCK cells, grown in the presence of serum, formed lumina whethermore » or not serum was removed at the time of overlay, whereas NMuMG cells required either a nondialyzable component of serum or hormonal supplements in serum-free defined media. Lumen formation was delayed by MDCK cells in the presence of the glutamine analog 6-diazo-5-oxo-L-norleucine, but this compound did not affect NMuMG lumen formation. In both cell lines, lumen formation was unaffected by the absence of sulfate, the presence of an inhibitor of sulfate glycosaminoglycan synthesis, or an inhibitor of collagen synthesis. DNA synthesis accompanied lumen formation but was not required.« less
  • In our objective, we descibe how dynamic contrast-enhanced MRI (DCE-MRI) has become a standard component of multiparametric protocols for MRI examination of the prostate, and its use is incorporated into current guidelines for prostate MRI examination. Analysis of DCE-MRI data for the prostate is usually based on the distribution of gadolinium-based agents, such as gadodiamide, into two well-mixed compartments, and it assumes that gadodiamide does not enter into the glandular lumen. However, this assumption has not been directly tested. The purpose of this study was to use x-ray fluorescence microscopy (XFM) imaging in situ to measure the concentration of gadodiamidemore » in the epithelia and lumens of the prostate of healthy mice after IV injection of the contrast agent. For our materials and methods, six C57Bl6 male mice (age, 28 weeks) were sacrificed 10 minutes after IV injection of gadodiamide (0.13 mmol/kg), and three mice were sacrificed after saline injection. Prostate tissue samples obtained from each mouse were harvested and frozen; 7-μm-thick slices were sectioned for XFM imaging, and adjacent 5-μm-thick slices were sectioned for H and E staining. Elemental concentrations were determined from XFM images. Our results show mean (± SD) baseline concentration of gadolinium of 0.01 ± 0.01 mM was determined from XFM measurements of prostatic tissue samples when no gadodiamide was administered, and it was used to determine the measurement error. When gadodiamide was added, the mean concentrations of gadolinium in the epithelia and lumens in 32 prostatic glands from six mice were 1.00 ± 0.13 and 0.36 ± 0.09 mM, respectively. In conclusion, our data suggest that IV administration of gadodiamide results in uptake of contrast agent by the glandular lumens of the mouse prostate. We were able to quantitatively determine gadodiamide distributions in mouse prostatic epithelia and lumens.« less
  • A new kinetic model provides a theoretical framework to describe how coke formation, adsorption, and desorption can lead to catalyst activity maintenance or decay in reaction mixtures. The system consists of the reactions of 1-hexene, its product isomers, and hexene oligomers on a Pt/[gamma]-Al[sub 2]O[sub 3] catalyst in sub or supercritical reaction mixtures. The formation of coke compounds on the catalyst proceeds via the production of hexene oligomers in the bulk fluid phase, followed by their transformation to mobile polynuclear aromatic coke compounds on the catalyst. A kinetic scheme is presented for describing the formation of these coke compounds followedmore » by their reversible adsorption/desorption between the catalyst phase and the fluid phase. Based on this kinetic scheme a mathematical model is developed to describe catalyst activity dynamics when Pt/[gamma]-Al[sub 2]O[sub 3] catalyzed 1-hexene isomerization occurs in a continuous stirred tank reactor. The model predictions relating to temporal conversion and activity profiles, activity maintenance or decay, and the formation of oligomers and coke compounds are consistent with reported experimental observations. In spite of increased coke formation at supercritical pressures, activity maintenance is predicted due to enhanced desorption of coke-forming compounds in the dense supercritical reaction mixture.« less