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- 2017
- spectral reconstruction
- interference
- polarization
- transform
- imaging spectrometer
- Optoelectronic Information Science and Engineering
- BITTT
- Zhejiang University
- Guilin University of Aerospace Technology
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A Modified Photoactivation Protocol Using Two Simultaneous Light-Curing Units for Bonding Brackets to Enamel
摘要： This study investigated the effect of a modified photoactivation protocol using two simultaneous light-curing units on the shear bond strength (SBS) of brackets to enamel. Metal brackets were bonded to bovine incisors using the resin-based orthodontic cement Transbond XT (3M Unitek). Four photoactivation protocols of the orthodontic cement were tested (n=15): Control: photoactivation for 10 s on each proximal face of the bracket at a time; Simultaneous: photoactivation for 10 s on both proximal faces of the bracket at the same time; One side-20s: photoactivation for 20 s at one proximal face of the bracket only; and One side-10s: photoactivation for 10 s only at one proximal face of the bracket. SBS was tested immediately or after 1000 thermal cycles. Adhesive remnant index (ARI) was classified. Data were subjected to two-way ANOVA and Student-Newman-Keuls’ test (α=0.05). Pooled means ± standard deviations for SBS to enamel (MPa) were: 10.2±4.2 (Control), 9.7±4.5 (Simultaneous), 5.6±3.1 (One side-20s), and 4.6±1.9 (One side-10s). Pooled SBS data for immediate and thermal cycled groups were 6.3±2.6 and 8.8±5.2. A predominance of ARI scores 1-2 and 0-1 was observed for the immediate and thermally cycled groups, respectively. In conclusion, simultaneous photoactivation of the orthodontic cement using two light-curing units, one positioned at each proximal face of the bracket, yielded similar bonding ability compared to the conventional light-curing method. Photoactivation of the orthodontic cement at one proximal face of the bracket only is not recommended, irrespective of the light-curing time used.
关键词： composite,polymerization,aging,Orthodontics,shear bond strength
更新于2025-09-04 15:30:14
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Moisture absorption and hydrothermal aging of phenylethynyl-terminated pyromellitic dianhydride-type asymmetric polyimide and composites
摘要： The effects of moisture on a polymerized monomeric reactant (PMR)-type polyimide (TriA X) and associated composites were investigated. Water uptake tests were performed on the polyimide at various temperatures and relative humidity levels to investigate moisture absorption behavior. Two-stage moisture absorption was observed, in which the first stage was diffusion controlled, whereas the second stage was moisture plasticization controlled. As exposure temperature increased, the equilibrium moisture content of the polyimide decreased, indicating an exothermic absorption process. The Arrhenius temperature dependence and moisture saturation as functions of temperature and humidity in the neat polymer were determined using curve fitting based on the published mathematical models. Long-term hydrothermal aging at 95°C was conducted on the neat polyimide and associated carbon fiber composites. Reversible hydrolytic reactions and a trace of irreversible hydrolysis were observed in the long-term exposure. The tensile ductility of the neat polyimide and the short-beam shear strength of the composites decreased with increasing aging time, while the tensile strength and modulus and thermal properties of the polyimide exhibited little change after 2000-h aging, demonstrating hydrothermal stability. The decrease in the ductility of the neat polymer after long-term moisture exposure was attributed to the network structure change, driven by hydrolysis and moisture plasticization.
关键词： β-relaxation,hydrothermal aging,moisture absorption,thermal properties,hydrolysis,Polyimide,composite,mechanical properties,plasticization
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Investigation of Performance Degradation in Enhancement-Mode GaN HEMTs under Accelerated Aging
摘要： In this paper, the performance degradation of enhancement-mode (E-mode) GaN HEMFs under accelerated aging is presented in detail. A real-time degradation monitoring tool is essential to prevent costly shutdowns and minimize safety concerns. Specifically, a DC power cycling setup is first designed which operates within the safe operating area (SOA) of the device to mimic the field operation and accelerate the aging process. The E-mode GaN devices are mounted on a custom designed PCB adaptor to accommodate the curve tracer where all the parasitics are carefully controlled to minimize the measurement errors. Using the curve tracer, the parameter shifts are periodically monitored at certain aging cycles. From the experimental results, it is observed that the on-state resistance and the threshold voltage are gradually increasing over the aging cycles, which makes potential failure precursors. Meanwhile, a variation in the transfer characteristics is observed, and the transconductance decreases as the device is aged. Finally, a detailed theoretical analysis is provided to explain this parameter shift in experiments.
关键词： Power cycling,Cascode GaN device,Failure model,Aging precursor
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Industry Applications Society Annual Meeting (IAS) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Industry Applications Society Annual Meeting (IAS) - Effect of thermal and electrical stress on photometric, radiometric, and colorimetric characteristics of large area white organic light emitting diodes
摘要： The aim of this paper is to identify the photometric, radiometric, and colorimetric signatures of degradations of large area white organic light emitting diodes (Philips GL55, 41cm2 active area), subjected to various stress conditions. Nine devices have been stressed at a constant current density of 11.25mA/cm2, 13mA/cm2 and 15mA/cm2 at 23°C (room temperature), 40°C and 60°C. We have also stocked three devices under purely thermal stress at the same temperatures. Thus, we can make comparison between electrical-thermal stress and purely thermal stress. Over aging time, an increase of both the correlated color temperature and the general rendering index was observed. The degradation rate of the blue emitter is more significant than the other emitters, which induced a color shift toward a green-yellow.
关键词： OLED,thermal stress,colorimetric characterization,electrical stress,degradation signature,aging
更新于2025-09-04 15:30:14
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Framework for predicting the photodegradation of adhesion of silicone encapsulants
摘要： We developed a framework to predict and model the photodegradation of adhesion and cohesion of a silicone encapsulant for concentrator photovoltaic applications. Silicone encapsulant specimens were artificially weathered under narrow band UV filters to determine the effects of individual wavelengths within the UV spectrum on the photodegradation of the cohesion of encapsulant material and its adhesion with adjacent interfaces. The threshold wavelength, signifying the upper bound of the damaging action spectrum for the silicone, was identified from the results. In addition, specimens were artificially weathered with different relative humidities to understand the effects of moisture on the rate of photodegradation. The adhesion energy was measured using a fracture mechanics approach. The complementary delaminated surfaces were characterized to determine the failure pathway and chemistry changes resulting from photodegradation. A previously developed model was modified to account for the effects of damaging wavelengths in the terrestrial solar spectrum and reciprocity law failure due to varying UV intensity during weathering. With these modifications, the model showed good agreement with the behavior of the silicone encapsulant exposed in an outdoor solar concentrator simulating concentrator photovoltaics operating conditions. Similar studies can be adopted to develop models that can have high predictive accuracies based on accelerated aging studies.
关键词： Accelerated aging,Concentrator photovoltaics,Photodegradation,Encapsulant,Lifetime prediction,Silicone
更新于2025-09-04 15:30:14
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[IEEE 48th European Solid-State Device Research Conference (ESSDERC 2018) - Dresden (2018.9.3-2018.9.6)] 2018 48th European Solid-State Device Research Conference (ESSDERC) - Novel IC Sub-Threshold IDDQ Signature And Its Relationship To Aging During High Voltage Stress
摘要： A sub-threshold quiescent current (IDDQ) signature is observed for the first time. 14 nm SOI Ring Oscillators (ROs) are used to study a characteristic knee/peak for different device types and threshold voltages undergoing different stress conditions. The relationship of the sub-threshold IDDQ characteristics to process variability and aging are explained with detailed circuit level simulations. This novel signature has potential applications for reliability analysis and aged/used chip detection.
关键词： sub-threshold current,IDDQ,circuit aging,aged/used chip detection,elevated voltage stress
更新于2025-09-04 15:30:14
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Detection of abnormality occurring over the whole cable length by frequency domain reflectometry
摘要： In previous papers, the authors reported that a combination of frequency domain reflectometry and inverse fast Fourier transform can locate the position of occurrence of degradation or abnormality in a polymer-insulated electric cable. This paper demonstrates that this method is also applicable even if the degradation or abnormality occurs uniformly over the entire cable length.
关键词： frequency domain reflectometry,broadband impedance spectroscopy,fault location,characteristic impedance,aging
更新于2025-09-04 15:30:14
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Reliability of High-Power Mechatronic Systems 1 || Simulation of Degradation Phenomena in Semiconductor Components in order to Ensure the Reliability of Integrated Circuits
摘要： The design cycle until now only guaranteed the electrical performance of integrated circuits (ICs) before aging. Performances throughout product lifetimes are, in general, assured by taking design margins and accelerated aging tests that come in a second complementary phase to guarantee the circuit reliability. In case of degradation, a reactive design correction will necessarily mean a delay in placing the product on the market. The design cycle subject to delay has not yet passed control. This study proposes guaranteeing the level of reliability of an integrated circuit during the design phase. This new design methodology requires a simulation tool for the aging of components. In this phase of the study, reliability tests on manufactured circuits will consolidate the results of reliability simulation up to the point of refining these individualized models by component. Once the components of a technology are properly modeled, the number of reliability incidents must tend towards 0. Marketing is advanced and the design cycle is gaining control. This makes it possible to hope that this technology will be available on the market as soon as the first silicon is available, without having to wait for any accelerated qualification tests. The circuits are guaranteed to be conceptually reliable.
关键词： simulation,design methodology,reliability,integrated circuits,aging
更新于2025-09-04 15:30:14
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Diagnostic Performance of Peripapillary Retinal Nerve Fiber Layer Thickness for Detection of Glaucoma in an Elderly Population: The ALIENOR Study
摘要： PURPOSE. To assess diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) to discriminate glaucoma and control subjects in an elderly population. METHODS. The antioxidants, essential lipids, nutrition and ocular maladies study (ALIENOR: ‘‘Antioxydants, Lipides Essentiels, Nutrition et Maladies Oculaires’’) is a population-based study. From 2009 to 2010, a total of 624 subjects, aged 74 years or older underwent a complete eye examination, including optic disc color photography and SD-OCT examination of the macula and the optic nerve head. Glaucoma diagnosis was made using retinophotography of the optic nerve head and International Society for Epidemiologic and Geographical Ophthalmology criteria. Average and sectorial peripapillary retinal nerve ?ber layer thicknesses (RNFLT) were compared between glaucoma and control subjects using area under the receiver operating characteristic curves (AUC), positive and negative likelihood ratios (LRt/LR(cid:2)), and diagnostic odds ratios (DOR). RESULTS. A total of 532 subjects had complete data, 492 were classi?ed as controls and 40 were classi?ed as glaucoma. Mean age was 82.1 6 4.2 years and average RNFLT was signi?cantly different between both groups (controls: 88.7 6 12.2 lm, glaucoma: 65.4 6 14.4 lm, P < 0.001). Highest AUC values were observed for average (0.895), temporal-inferior (0.874), and temporal-superior (0.868) RNFLT. Temporal-superior RNFLT had the highest DOR (25.31; LRt, 4.65; LR(cid:2), 0.18), followed by average RNFLT (DOR: 24.80; LRt, 6.36; LR(cid:2), 0.26). When using the normative database provided by the machine, DOR increased to 31.03 (LRt, 1.75; LR(cid:2), 0.06) if at least one parameter was considered abnormal (at P < 0.05). CONCLUSIONS. Parameters of SD-OCT RNFL may provide valuable information in a screening strategy to improve glaucoma detection in a general population of elderly people.
关键词： spectral-domain OCT,OCT,optical coherence tomography,glaucoma screening,likelihood ratios,aging
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Ageing Mitigation Control Method for Power Devices in Multilevel Inverters in Standalone PV Systems
摘要： Multilevel inverters (MIs) have become widely used in photovoltaic (PV) systems for their high efficiency, reduced leakage currents, and reduced EMI levels. Although MIs suffer from unequal thermal stresses in power devices that lead to aging of power device with their continuous operation. Therefore, this paper proposes a new aging mitigation control (AMC) method to enhance the reliability of MIs against the aging effects in power devices. The operation of the proposed AMC method has three operating modes that are adapted according to the level and type of aging. In small and medium aging levels, the proposed method preserves the full output power ratings of the inverter with maximum energy extraction from PV modules. Whereas, in high aging level region and multiple devices failures, the proposed method reduces the output power so as to maintain continuous operation of the inverter without harmful consequences. The simulation and experimental results with comparisons to conventional methods show effective performance of the proposed AMC method.
关键词： lifetime,multilevel inverters (MIs),pulse width modulation (PWM),reliability,photovoltaic (PV),aging
更新于2025-09-04 15:30:14