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Wu T, Wang C, Li K. Quantitative analysis and stochastic modeling of osteophyte formation and growth process on human vertebrae based on radiographs: a follow-up study. Sci Rep 2024; 14:9393. [PMID: 38658644 PMCID: PMC11043460 DOI: 10.1038/s41598-024-60212-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 04/19/2024] [Indexed: 04/26/2024] Open
Abstract
Osteophytes are frequently observed in elderly people and most commonly appear at the anterior edge of the cervical and lumbar vertebrae body. The anterior osteophytes keep developing and will lead to neck/back pain over time. In clinical practice, the accurate measurement of the anterior osteophyte length and the understanding of the temporal progression of anterior osteophyte growth are of vital importance to clinicians for effective treatment planning. This study proposes a new measuring method using the osteophyte ratio index to quantify anterior osteophyte length based on lateral radiographs. Moreover, we develop a continuous stochastic degradation model with time-related functions to characterize the anterior osteophyte formation and growth process on cervical and lumbar vertebrae over time. Follow-up data of anterior osteophytes up to 9 years are obtained for measurement and model validation. The agreement test indicates excellent reproducibility for our measuring method. The proposed model accurately fits the osteophyte growth paths. The model predicts the mean time to onset of pain and obtained survival function of the degenerative vertebrae. This research opens the door to future quantification and mathematical modeling of the anterior osteophyte growth on human cervical and lumbar vertebrae. The measured follow-up data is shared for future studies.
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Affiliation(s)
- Tong Wu
- West China Biomedical Big Data Center, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Changxi Wang
- West China Biomedical Big Data Center, West China Hospital, Sichuan University, Chengdu, 610041, China.
- Sichuan University - Pittsburgh Institute, Sichuan University, Chengdu, 610207, China.
| | - Kang Li
- West China Biomedical Big Data Center, West China Hospital, Sichuan University, Chengdu, 610041, China.
- Orthopedics Department of West China Hospital, Sichuan University, Chengdu, 610041, China.
- Sichuan University - Pittsburgh Institute, Sichuan University, Chengdu, 610207, China.
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Harsanyi G, Poppe A, Hegedüs J, Hantos G, Bojta P, Kovacs R. Climatically Accelerated Material Processes Determining the Long-Term Reliability of Light-Emitting Diodes. MATERIALS (BASEL, SWITZERLAND) 2024; 17:1643. [PMID: 38612158 PMCID: PMC11012988 DOI: 10.3390/ma17071643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Revised: 03/28/2024] [Accepted: 03/31/2024] [Indexed: 04/14/2024]
Abstract
LEDs (Light-Emitting Diodes) are widely applied not only in decorative illumination but also in everyday lighting in buildings, flats, public areas, and automotive fields. These application areas often mean harsh environments, for example, regarding the humidity content of the surrounding air: besides outdoor and automotive illumination, even the household use cases (kitchen, bathroom, cellar) may represent extreme temperature and humidity variations (often reaching relative humidity levels close to 100%) for these devices; thus, their reliability behaviour in such circumstances should be better understood. Thermally activated processes were studied in several previous publications, but less information is available regarding high-humidity environmental tests. Moisture and temperature ageing tests with appropriate environmental parameter settings were performed as accelerated lifetime tests to investigate not only the effect of temperature but also that of humidity on the ageing and reliability of LED packages containing RGB (red green blue) chips and phosphor-converted white (pcW) LEDs. The ageing was followed not only through monitoring optical/electrical/spectral parameters but also with material analysis. Moisture-material interaction models were proposed and set up. It was found that humidity-accelerated ageing processes are more severe than expected from previous assumptions. RGB and pcW LEDs showed strongly different behaviour.
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Affiliation(s)
- Gabor Harsanyi
- Department of Electronics Technolgy, Budapest University of Technology and Economics, 3. Műegyetem rkp., 1111 Budapest, Hungary
| | - Andras Poppe
- Department of Electron Devices, Budapest University of Technology and Economics, 3. Műegyetem rkp., 1111 Budapest, Hungary; (A.P.); (J.H.); (G.H.)
| | - Janos Hegedüs
- Department of Electron Devices, Budapest University of Technology and Economics, 3. Műegyetem rkp., 1111 Budapest, Hungary; (A.P.); (J.H.); (G.H.)
| | - Gusztav Hantos
- Department of Electron Devices, Budapest University of Technology and Economics, 3. Műegyetem rkp., 1111 Budapest, Hungary; (A.P.); (J.H.); (G.H.)
| | - Peter Bojta
- Department of Electronics Technolgy, Budapest University of Technology and Economics, 3. Műegyetem rkp., 1111 Budapest, Hungary
| | - Robert Kovacs
- EFI-Labs Electronic Failure Analysis Ltd., 18. Egry J. u., 1111 Budapest, Hungary
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Ruiz-Arenas S, Rusák Z, Mejía-Gutiérrez R, Horváth I. Implementation of System Operation Modes for Health Management and Failure Prognosis in Cyber-Physical Systems. SENSORS 2020; 20:s20082429. [PMID: 32344705 PMCID: PMC7219508 DOI: 10.3390/s20082429] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 04/08/2020] [Accepted: 04/22/2020] [Indexed: 11/16/2022]
Abstract
Cyber-physical systems (CPSs) have sophisticated control mechanisms that help achieve optimal system operations and services. These mechanisms, imply considering multiple signal inputs in parallel, to timely respond to varying working conditions. Despite the advantages that control mechanisms convey, they bring new challenges in terms of failure prevention. The compensatory action the control exerts cause a fault masking effect, hampering fault diagnosis. Likewise, the multiple information inputs CPSs have to process can affect the timely system response to faults. This article proposes a failure prognosis method, which combines time series-based forecasting methods with statistically based classification techniques in order to investigate system degradation and failure forming on system levels. This method utilizes a new approach based on the concept of the system operation mode (SOM) that offers a novel perspective for health management that allows monitoring the system behavior, through the frequency and duration of SOMs. Validation of this method was conducted by systematically injecting faults in a cyber-physical greenhouse testbed. The obtained results demonstrate that the degradation and fault forming process can be monitored by analyzing the changes of the frequency and duration of SOMs. These indicators made possible to estimate the time to failure caused by various failures in the conducted experiments.
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Affiliation(s)
- Santiago Ruiz-Arenas
- Faculty of Industrial Design Engineering, Delft University of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands; (Z.R.); (I.H.)
- Design Engineering Research Group (GRID), Universidad EAFIT, Carrera 49 N° 7 Sur-50, Medellín 050001, Colombia;
- Correspondence: or
| | - Zoltán Rusák
- Faculty of Industrial Design Engineering, Delft University of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands; (Z.R.); (I.H.)
| | - Ricardo Mejía-Gutiérrez
- Design Engineering Research Group (GRID), Universidad EAFIT, Carrera 49 N° 7 Sur-50, Medellín 050001, Colombia;
| | - Imre Horváth
- Faculty of Industrial Design Engineering, Delft University of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands; (Z.R.); (I.H.)
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Yazdan Mehr M, van Driel W, De Buyl F, Zhang K. Study on the Degradation of Optical Silicone Exposed to Harsh Environments. MATERIALS 2018; 11:ma11081305. [PMID: 30060563 PMCID: PMC6117682 DOI: 10.3390/ma11081305] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 07/25/2018] [Accepted: 07/26/2018] [Indexed: 11/30/2022]
Abstract
Degradation mechanisms of silicone plates under harsh environment conditions are studied in this investigation. Environmental degradation of silicone free form, used as secondary optics in Light Emitting Diode LED lighting lamps and luminaires or any other applications requiring high quality optics being used, has negative implications for the optical performance. Degradation of silicone plates in harsh environment conditions was studied in salt bath and swimming water environments, using different light radiation and temperatures. Samples were exposed to harsh environment conditions for up to 4 months. Optical and chemical characteristics of exposed plates were studied using an Fourier transform infrared- attenuated total reflection FTIR-ATR spectrometer, an integrated sphere, and a Lambda 950 Ultraviolet-Visible UV-VIS spectrophotometer. Results show that 100 °C salt bath exposure had the most severe degrading effect on the optical characteristic of silicone plates. Increasing exposure time in the salt bath at that high temperature is associated with a significant deterioration of both optical (i.e., light transmission and relative radiant power value) and mechanical properties of silicone samples. On the contrary, silicone plates showed a great degree of stability against light exposure (UV at 360 nm and blue light at 450 nm).
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Affiliation(s)
- Maryam Yazdan Mehr
- EEMCS Faculty, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherland.
| | - Willem van Driel
- EEMCS Faculty, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherland.
- Department of Signify, High Tech Campus, 5600 JW, Eindhoven, The Netherlands.
| | - Francois De Buyl
- Dow Silicones Belgium sprl, Industrial zone C, 7180 Seneffe, Belgium.
| | - Kouchi Zhang
- EEMCS Faculty, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherland.
- State Key Laboratory of Solid State Lighting, Changzhou 100083, China.
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Yang X, Sun B, Wang Z, Qian C, Ren Y, Yang D, Feng Q. An Alternative Lifetime Model for White Light Emitting Diodes under Thermal⁻Electrical Stresses. MATERIALS 2018; 11:ma11050817. [PMID: 29772726 PMCID: PMC5978194 DOI: 10.3390/ma11050817] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 12/04/2022]
Abstract
The lifetime prediction using accelerated degradation test (ADT) method has become a main issue for white light emitting diodes applications. This paper proposes a novel lifetime model for light emitting diodes (LEDs) under thermal and electrical stresses, where the junction temperature and driving current are deemed the input parameters for lifetime prediction. The features of LEDs’ lifetime and the law of lumen depreciation under dual stresses are combined to build the lifetime model. The adoption of thermal and electrical stresses overcomes the limitation of single stress, and junction temperature in accelerated degradation test as thermal stress is more reliable than ambient temperature in conventional ADT. Furthermore, verifying applications and cases studies are discussed to prove the practicability and generality of the proposed lifetime model. In addition, the lifetime model reveals that electrical stress is equally significant to the thermal stress in the degradation of LEDs, and therefore should not be ignored in the investigation on lumen decay of LEDs products.
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Affiliation(s)
- Xi Yang
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Bo Sun
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Zili Wang
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Cheng Qian
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Yi Ren
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Dezhen Yang
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
| | - Qiang Feng
- School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China.
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Photometric and Colorimetric Assessment of LED Chip Scale Packages by Using a Step-Stress Accelerated Degradation Test (SSADT) Method. MATERIALS 2017; 10:ma10101181. [PMID: 29035300 PMCID: PMC5666987 DOI: 10.3390/ma10101181] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 10/08/2017] [Accepted: 10/10/2017] [Indexed: 11/18/2022]
Abstract
By solving the problem of very long test time on reliability qualification for Light-emitting Diode (LED) products, the accelerated degradation test with a thermal overstress at a proper range is regarded as a promising and effective approach. For a comprehensive survey of the application of step-stress accelerated degradation test (SSADT) in LEDs, the thermal, photometric, and colorimetric properties of two types of LED chip scale packages (CSPs), i.e., 4000 °K and 5000 °K samples each of which was driven by two different levels of currents (i.e., 120 mA and 350 mA, respectively), were investigated under an increasing temperature from 55 °C to 150 °C and a systemic study of driving current effect on the SSADT results were also reported in this paper. During SSADT, junction temperatures of the test samples have a positive relationship with their driving currents. However, the temperature-voltage curve, which represents the thermal resistance property of the test samples, does not show significant variance as long as the driving current is no more than the sample’s rated current. But when the test sample is tested under an overdrive current, its temperature-voltage curve is observed as obviously shifted to the left when compared to that before SSADT. Similar overdrive current affected the degradation scenario is also found in the attenuation of Spectral Power Distributions (SPDs) of the test samples. As used in the reliability qualification, SSADT provides explicit scenes on color shift and correlated color temperature (CCT) depreciation of the test samples, but not on lumen maintenance depreciation. It is also proved that the varying rates of the color shift and CCT depreciation failures can be effectively accelerated with an increase of the driving current, for instance, from 120 mA to 350 mA. For these reasons, SSADT is considered as a suitable accelerated test method for qualifying these two failure modes of LED CSPs.
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Wang Y, Jing L, Ke HL, Hao J, Gao Q, Wang XX, Sun Q, Xu ZJ. Disparity between online and offline tests in accelerated aging tests of LED lamps under electric stress. APPLIED OPTICS 2016; 55:7511-7516. [PMID: 27661576 DOI: 10.1364/ao.55.007511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The accelerated aging tests under electric stress for one type of LED lamp are conducted, and the differences between online and offline tests of the degradation of luminous flux are studied in this paper. The transformation of the two test modes is achieved with an adjustable AC voltage stabilized power source. Experimental results show that the exponential fitting of the luminous flux degradation in online tests possesses a higher fitting degree for most lamps, and the degradation rate of the luminous flux by online tests is always lower than that by offline tests. Bayes estimation and Weibull distribution are used to calculate the failure probabilities under the accelerated voltages, and then the reliability of the lamps under rated voltage of 220 V is estimated by use of the inverse power law model. Results show that the relative error of the lifetime estimation by offline tests increases as the failure probability decreases, and it cannot be neglected when the failure probability is less than 1%. The relative errors of lifetime estimation are 7.9%, 5.8%, 4.2%, and 3.5%, at the failure probabilities of 0.1%, 1%, 5%, and 10%, respectively.
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