Long-term Reliability Research Articles

Impact of multi-annual renewable energy variability on the optimal sizing of off-grid systems

It remains a significant technical and economic challenge to fully power large-scale grids with intermittent renewable energy (RE). Meanwhile, due to the rapid decrease in the cost of RE power generation technologies in recent years, the number of real-world implementations and studies dedicated to the optimal capacity sizing of renewable off-grid systems has increased. However, a common approach in the literature is to rely on typical single-year meteorological and demand data. A negative effect of this assumption is that it does not consider the RE inter-annual variability, which might cause blackouts or oversizing the system and large curtailments. This study employs 43 years of hourly solar, wind, and demand data, coupled with different microgrid configurations, to evaluate the impact of diverse simulation periods on the total system cost, optimal RE mix, and system reliability. Our findings indicate that extended simulation periods considerably increased renewable energy systems (RES) reliability and that the resulting configurations can be up to 94% more robust than those obtained using a single year of data. Additionally, the optimal energy storage requirements increased when considering longer simulation periods, indicating that short simulation periods could underestimate energy storage capacities in off-grid systems. The overestimations or underestimations resulting from optimizations based on single-year data directly affect the long-term sustainability, reliability, and cost-effectiveness of the RES.

Effective phase utilization and efficiency improvement of high power interleaved DC–DC converter using modified rotating phase shedding control

The interleaved bidirectional DC–DC converters (IBC’s) have a poor efficiency profile at light load conditions because the switching and core losses are more dominant than conduction losses. A phase shedding control (PSC) approach is one of the methods for multi-phase IBC to maintain a good efficiency profile across all load circumstances. However, in a PSC of IBC, one phase remains active throughout the load change while the remaining phases only operate at the significant load change. This uneven utilization of phases causes the aging problem of over-exploited phase, which also may cause thermal instability and long-term reliability issues of the converter. This paper proposes an efficiency-based modified rotating phase-shedding control (MRPSC) algorithm for 3−ϕ IBC with an automatic phase selection to improve efficiency across all loading conditions and minimize the uneven aging effect in all phases by proper phase utilization. In addition, an auto-change inner loop-average current mode control (ACIL-ACMC) has been included in the proposed MRPSC algorithm to maintain equal current sharing and voltage regulations. The sampling and computational delay of ADC have also been considered for designing adequate inner and outer loop PI controllers of ACIL-ACMC. The proposed MRPSC algorithm has been implemented in the DSP (TMS320F28335) for 7.5kW IBC.

Degradation of GaN-Based Multiple Quantum Wells Solar Cells Under Forward Bias: Investigation Based on Optical Measurements and Steady-State Photocapacitance

Gallium nitride (GaN) multiple quantum well (MQW) solar cells proved to have very good performance in high-temperature conditions and under intense excitation. However, the long-term reliability under harsh conditions has not been investigated in the literature. The aim of this article is to fill this gap, by investigating the degradation mechanisms of GaN solar cells, submitted to forward current stress. The cells were characterized by means of dark and illuminated current–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> ) measurements, capacitance–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> ) measurements, and steady-state photocapacitance (SSPC). The current step-stress experiment showed an initial decrease in the main parameters of the devices (open-circuit voltage, external quantum efficiency (EQE), and optical-to-electrical power conversion efficiency). <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> and SSPC showed a correlation between the charge inside the active region of the device and the concentration of trap states. Also, a relation was found between the decrease in power conversion efficiency and the amount of charge in the active region of the devices. Degradation was ascribed to a redistribution of the charge in the active region, related to an increase in the density of midgap states ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}_{\textit{C}} -\text{1.6}$</tex-math> </inline-formula> eV), resulting in the lowering of the efficiency of the devices.

Understanding Multiple Stressors Which Degrade Antisoiling Coatings: Combined Effect of Rain, Abrasion, and UV Radiation

Antisoiling coatings (ASCs) are nano or microlayer coatings which reduce the settlement of dust on the surface of the PV module and are extensively investigated as a dust mitigation strategy. Since the coating is applied on the outer surface of the PV module, they are exposed to various environmental stressors, and the durability of these coatings is essential. Various studies have reported the effect of individual stressors that degrade ASCs. However, there are very few reports on the impact of the combination of stressors relevant to outdoor field conditions. In this article, we investigate the impact of the combination of the following stressors that degrade ASCs: 1) the combination of the impact of raindrops and acidic water, 2) the combination of UV radiation, the impact of raindrops, and acidic water, and 3) the combination of abrasion, UV radiation, the impact of raindrops and acidic water. The key takeaways from this study are 1) coating life reduced by 21× (average of all coatings) when exposed to the rainy season compared with those exposed to the nonrainy season. 2) All coated samples show lower coating life varying from 10× to 48× when exposed to the impact of raindrops with pH 7 water than those exposed to water immersion/water contact test with pH 7 water. This indicates that, during a rain event, the impact of raindrops hitting the coated surface causes more significant damage than water contact. This study shows that coatings A, B, C, and D are unreliable for long-term use in warm and humid climate zones, considering 25-year module lifetime. However, other chemistries of hydrophobic and hydrophilic solutions could be effective if they exhibit long-term reliability.

An advanced approach to improve the high-temperature property for Ni-based superalloys: Interface segregation manipulation

In response to the requirements for the long-term service reliability of Ni-based superalloys, the correlations between the microstructure and creep property are investigated in present work. Creep experiments were conducted on a designed Ni-based single crystal superalloy at 900 °C/330 MPa, the results indicate that the creep rupture properties deteriorated following thermal exposure at both 900 °C and 1000 °C. The γ′-phase, γ-matrix and γ/γ′ interface undergo varying degrees of degradation, including the coarsening and the decrease in the volume fraction of γ′-phase, the decrease in the γ-matrix strength, the decrease in the lattice misfit and the increase in the dislocation network spacing. When the values of the microstructural parameters (γ′-phase size and volume fraction) were numerically similar for different thermal exposure times at 900 °C and 1000 °C, taking 900 °C/10,000h and 1000 °C/2000h samples as examples. The experimental alloy exhibited better creep resistance after being exposed to 1000 °C compared to 900 °C. Through the combination of atom probe tomography and first-principles calculations, an interface strengthening mechanism driven by interface segregation is identified. Finally, a design concept for high-strength metal alloys based on the decoration of solutes interface segregation is proposed, also called “Interface Segregation Manipulation”.

Short- and long-term test-retest reliability of the English version of the 7-item DN4 questionnaire- a screening tool for neuropathic pain.

The original French version of the "Douleur Neuropathique en 4 Questions (DN4) questionnaire" is a valid screening tool for the identification of neuropathic pain (NeP). The DN4 has been translated into English, but the reliability of the English version has not yet been investigated. The aim of this study was to investigate the 7-item DN4 questionnaire in regards to short-term reliability before (T0) and immediately after (T1) the clinical examination and long-term reliability one week later (T2). A total of 222 participants (age 56.33±16 years, 56 % female) were recruited from a Pain Management Department and Neurosurgery Spinal Clinic. For T2 measurements, the 7-item DN4 was sent by post with the "Patient Global Impression of Change Scale". The scale detects possible changes of symptoms, scoring from "very much improved" (1) to "very much worse" (7). Only participants whose symptoms had not changed much (scores 3-5) were included in the T0-T2 analysis. Weighted Kappa was used to analyse the reliability of the DN4 total scores and unweighted Kappa for the DN4 classifications. Considering missing data and exclusions, data of 215 participants could be used for the T0-T1 and data of 103 participants for T0-T2 analysis. There was almost perfect agreement for the 7-item DN4 total score between T0-T1 (weighted k: 0.891, CI: 0.758-1.024) and T0-T2 (weighted k: 0.850, CI: 0.657-1.043). Classifications between neuropathic pain and no neuropathic pain showed almost perfect agreement (k: 0.835, CI: 0.755-0.915) for T0-T1 and substantial agreement (k: 0.733, CI: 0.598-0.868) for T0-T2. The English 7-item DN4 is a reliable screening tool for neuropathic pain. #RGS0000001759.

Failed Dental Implant: When Titanium Fractures.

Despite the widespread use of titanium implants in orthopedic and dental surgeries, concerns have recently emerged regarding potential deformations and fractures after osseointegration. In a recent clinical case, a titanium implant fractured after successful osseointegration. This fracture occurred despite the absence of any significant trauma or excessive external force applied to the area. The fracture was attributed to a combination of factors, including abutment design flaws, material fatigue, and biomechanical stress imposed on the implant during functional loading. This raises concerns about the long-term durability and reliability of titanium implants, particularly in high-stress areas such as the posterior region or weight-bearing bones. An image was made with scanning electron microscopy showing the fracture region near the prosthetic platform and highlighting the knowledge that despite their ductility, titanium implants can fracture.

Understanding the impact of desert stressors factors on standard PV panel performance: Case study of Algeria's desert

Compared to moderate climate conditions, hot and dry environment, as known desert, present the most difficult environment that affects negatively PV panels performance. In the present paper, the root causes that have the major contribution in PV panel performance degradation in desert climates and the direct relationship between desert climate factors and accelerate degradation mechanism are analyzed. Algeria's desert is chosen as a case to study, an overview of Algeria's desert climate has been presented. High solar irradiation accompanied by high ambient temperature has been considered as the most responsible for accelerated discoloration and initiating damage of EVA encapsulant material which can create a challenge for long-term reliability of c-Si PV panels. The declared 20–25 year PV panel lifetime is very optimistic in Algeria's desert climates. This research work can be beneficial in future studies on challenges related to the optimal performance and the expected operating lifetime of photovoltaic applications in desert climates.

Impact of Charge-Trapping Effects on Reliability Instability in AlxGa1-xN/GaN High-Electron-Mobility Transistors with Various Al Compositions.

In this study, we present a detailed analysis of trapping characteristics at the AlxGa1-xN/GaN interface of AlxGa1-xN/GaN high-electron-mobility transistors (HEMTs) with reliability assessments, demonstrating how the composition of the Al in the AlxGa1-xN barrier impacts the performance of the device. Reliability instability assessment in two different AlxGa1-xN/GaN HEMTs [x = 0.25, 0.45] using a single-pulse ID-VD characterization technique revealed higher drain-current degradation (∆ID) with pulse time for Al0.45Ga0.55N/GaN devices which correlates to the fast-transient charge-trapping in the defect sites near the interface of AlxGa1-xN/GaN. Constant voltage stress (CVS) measurement was used to analyze the charge-trapping phenomena of the channel carriers for long-term reliability testing. Al0.45Ga0.55N/GaN devices exhibited higher-threshold voltage shifting (∆VT) caused by stress electric fields, verifying the interfacial deterioration phenomenon. Defect sites near the interface of the AlGaN barrier responded to the stress electric fields and captured channel electrons-resulting in these charging effects that could be partially reversed using recovery voltages. The quantitative extraction of volume trap density (Nt) using 1/f low-frequency noise characterizations unveiled a 40% reduced Nt for the Al0.25Ga0.75N/GaN device, further verifying the higher trapping phenomena in the Al0.45Ga0.55N barrier caused by the rougher Al0.45Ga0.55N/GaN interface.

Comparative Investigation on Aging Precursor and Failure Mechanism of Commercial SiC MOSFETs Under Different Power Cycling Conduction Modes

Power cycling test (PCT) is an effective method to evaluate the SiC MOSFETs' long-term reliability, including lifetime and degradation mechanisms. Some of the aging precursors of PCT have been identified in previous literature. But when multiple failure mechanisms compete with each other, the individual precursors are nullified. Although PCT is mainly used to evaluate the package reliability, there are still unresolved problems due to the gate oxide reliability of SiC MOSFET, the repeated gate stress of the power cycling has different effects on the devices with different gate structures. This paper presents a comprehensive investigation of the aging precursors and failure mechanism of three typical commercial SiC MOSFETs with different gate structures through PCTs under two different conduction modes. Degradation-related essential precursors and possible causes behind them are discussed. The failure mechanisms and correlation with the degradation state of different devices are studied in depth. In addition, the effects of PCT under different conduction modes on failure mechanism and lifetime have been investigated.

Double Optical Fiber Temperature Compensation Method for Measurement of Interface Pressure Between Simulated Cable and Accessory at High Temperatures

Reliable interface pressure between cables and accessories is closely associated with the safe operation of a power cable system. Using an external optical fiber Bragg grating temperature-compensating curvature sensor, a new method for online measurement of the interface pressure between a cable and an accessory at high temperatures is proposed. On the basis of the sensing principle of a fiber Bragg grating, a mathematical pure bending model, and a model of a thick-walled cylinder, a fiber Bragg grating temperature-compensating curvature sensor is fabricated using Dow Corning Sylgard-184 silicone rubber. The interface pressures of 10 kV cable accessories with different expansion rates at different temperatures are measured. The results of the measurements show that the temperature-compensated deviation of wavelength measurements made by the fiber grating curvature sensor ranges from -2.59% to 5.50%. The interface pressure between the cable and the accessory gradually increases with an increase in temperature from 30 to 60 °C. The results are consistent with the results of measurements made using a traditional piezoelectric sensor. This method is expected to evaluate the long-term reliability of the interface pressure of cable accessories in actual complex-temperature environments.

Development of macroinvertebrate based multimetric index for ecological health monitoring in Lake Hawassa, Ethiopia

Little information is available on the use and applicability of biotic indices in aquatic resource conservation and management in Eastern Africa, especially in lentic ecosystems. The aim of this study was to develop a macroinvertebrate multimetric index (MMIH) to assess the ecological condition of Lake Hawassa. Sampling sites were clustered based on percentage disturbance score (PDS) and categorized into minimally (three sites), moderately (three sites) and highly disturbed (three sites). Physicochemical and invertebrate sampling was done at these clustered sites along the lakeshore area from February to November 2015 and 2016. Out of a total of 35 macroinvertebrate candidate metrics, ten core metrics were selected based on redundancy analysis, metrics response to environmental parameters, percent discriminatory efficiency (%DE) and box and whisker plots, and incorporated in the development of MMIH. The developed MMIH index performed well and showed a clear demarcation between the reference and non-reference sites and between the three-disturbance levels. The validation of the MMIH index performed well in discriminating the independent data sets taken from Lake Hawassa and L. Ziway. Besides, it also showed a strong but inverse relation with PDS (R2 = 0.91, P = 0.0003). Hence, in a lentic ecosystem, this index should be considered as a starting point in terms of lake bio-assessment in Ethiopia, but additional data in all ecoregions of the country are necessary to determine the long-term reliability and usefulness of the MMIH. In the short-term, this index will provide resource managers and aquatic environmentalists with a tool to assess the ecological condition of freshwater lakes.

Bionic Porous Design and Mechanical Response of Short Implants

Due to the material itself and the traditional geometric design, short implants have the problems of high stiffness, less osseointegrated area, and lower long-term reliability in clinical application. In this research, short implants with various porous structures were constructed and their biomechanical responses were evaluated, including biomechanical properties, compression capability, and stress distribution of surrounding bone tissue. Thus, three types of short implants were built: the diamond-like porous short implant (5.0 × 5.0 mm), the hexahedral porous short implant (5.0 × 5.0 mm), and the solid short implant (5.0 × 5.0 mm). Three implant-supported prosthetic models were built based on the above three implants, and their static mechanical properties were assessed. Besides, the average stiffness of regular cylindrical samples was calculated by compression test simulation. The result confirmed that hexahedral porous short implants showed minimum peak stress compared with the diamond-like porous and solid short implants. Similarly, the value of stress peaks in the bone-implant interface for the hexahedral porous short implant appeared lower than the other two short implants. Compression simulation indicated the average stiffness of cylinders after diamond-like and hexahedral porous design was 92.2% and 56.3% lower than the solid cylinder. Compared with the other two designs, the hexahedral porous short implant obtained better stress distribution, even avoiding bone overstress.

On-Chip Heater Design and Control Methodology for Reliability Testing Applications Requiring Over 300°C Local Temperatures

This paper presents the design details and control methodologies for on-chip heaters that can provide fast and accurate local temperature control for reliability testing applications. The on-chip heater uses the Joule heating effect of a metal or poly line to heat the surrounding devices-under-test (DUT) to a target temperature as high as 300∘C. Many generations of on-chip heaters, including different heater positions, heater areas, and heater layers, have been demonstrated in technology nodes from 350nm to 16nm. To accurately operate the heater and extend the heater’s operation lifetime for long-term reliability testing, we have also developed control methodologies for precise and reliable heater control.

Interactions between nonfullerene acceptors lead to unstable ternary organic photovoltaic cells

For organic photovoltaic (OPV) devices to achieve consistent performance and long operational lifetimes, organic semiconductors must be processed with precise control over their purity, composition, and structure. This is particularly important for high volume solar cell manufacturing where control of materials quality has a direct impact on yield and cost. Ternary-blend OPVs containing two acceptor-donor-acceptor (A-D-A)-type nonfullerene acceptors (NFAs) and a donor have proven to be an effective strategy to improve solar spectral coverage and reduce energy losses beyond that of binary-blend OPVs. Here, we show that the purity of such a ternary is compromised during blending to form a homogeneously mixed bulk heterojunction thin film. We find that the impurities originate from end-capping C=C/C=C exchange reactions of A-D-A-type NFAs, and that their presence influences both device reproducibility and long-term reliability. The end-capping exchange results in generation of up to four impurity constituents with strong dipolar character that interfere with the photoinduced charge transfer process, leading to reduced charge generation efficiency, morphological instabilities, and an increased vulnerability to photodegradation. As a consequence, the OPV efficiency falls to less than 65% of its initial value within 265 h when exposed to up to 10 suns intensity illumination. We propose potential molecular design strategies critical to enhancing the reproducibility as well as reliability of ternary OPVs by avoiding end-capping reactions.

Fatigue crack growth behavior of titanium with oxygen impurities: Experiments and modeling

The long-term reliability of structural elements in many advanced applications, such as power generation and transportation infrastructures, is paramount, especially under cyclic damage conditions. In this work, fatigue crack growth experiments were performed in commercial purity titanium with different initial oxygen contents and load ratios (R). To model fatigue crack initiation and growth, a fatigue indicator parameter (FIP) along with high-resolution crystal plasticity simulations were carried out. The crack-nucleation along with microstructurally short crack (MSC) growth models are calibrated for R = 0.1 with different oxygen contents. The resulting calibrated parameters along with the average total FIP values for R = 0.2 were used to predict nucleation and MSC growth behavior. Results indicate that this approach can predict the number of cycles required for crack nucleation and MSC behavior.

Effects of low melting point SnBi58 alloy on the properties of isotropic conductive adhesives

Adequate mechanical and electrical properties and long-term reliability are critical in conductive adhesive interconnects. In order to improve the electrical and mechanical properties of isotropic conductive adhesives (ICAs), reduce contact resistance and enhance the aging resistance of ICAs, the effects of low melting point SnBi58 alloy on the properties of ICAs were studied. The low melting point SnBi58 alloy formed metallurgical bonds between conductive fillers, as well as between the ICAs and a Cu substrate and not only improved the electrical conductivity and mechanical properties of ICAs, but also reduced the contact resistance shift of ICAs effectively. It was found that when the mass ratio of SnBi58 alloy in conductive fillers was maintained at 20 wt%, the bulk resistivity of ICAs reached 4.8 × 10−4 Ω cm, the shear strength of ICAs was 27.71 MPa, and the contact resistance shift of ICAs was 7% after aging. In addition, better bulk resistivities and higher shear strengths of ICAs were achieved after aging at 85 °C/85%RH.

Total Ionizing Dose Effects of 60Co γ-Ray Radiation on Split-Gate SiC MOSFETs

SiC power devices require resistance to both single-event effects (SEEs) and total ionizing dose effects (TIDs) in a space radiation environment. The split-gate-enhanced VDMOSFET (SGE-VDMOSFET) process can effectively enhance the radiation resistance of SiC VDMOS, but it has a certain impact on the gate oxide reliability of SiC VDMOS. This paper investigates the impact mechanism and regularity of using the SGE process to determine the radiation resistance and long-term reliability of SiC VDMOS under other identical processes and radiation conditions. Our experimental results show that after 60Co γ-ray irradiation, the degradation degrees of the static parameters of SGE-VDMOSFET and planar gate VDMOSFET (PG-VDMOSFET) are similar. The use of the new process leads to more defects in the oxide layer, reducing the long-term reliability of the device, but its stability can recover after high-temperature (HT) accelerated annealing. This research indicates that enhancing the resistance of SEEs using an SGE-VDMOSFET structure requires simultaneously considering the demand for TIDs and long-term reliability.

The Impact of Taxes on Prices and Production in Jordan

Purpose: This study aims to demonstrate the impact of taxes on prices and production in Jordan. Theoretical framework: Study problem lies in asking the following questions Does the tax system in Jordan serve the economic aspects? Does the tax in Jordan affect the economic aspect? Is the tax in Jordan fair? Is there an impact of the tax on prices in Jordan? Is there an impact of the tax on production in Jordan? What is the effect of taxes on consumer speeding on necessary versus luxury goods? What is the impact of higher taxes on personal income of consumers? The effect of Lower taxes on the economy and disposable income? What is the alternative for governments to increase their income other than direct higher tax system? What is the effect of various government entities; such as financial, administrative, and social corruption on Jordan economy? Design/methodology/approach: Researchers used standard analysis method and vector error correction model for the period (2011-2020), and used the profit margin ratio indicator as a representative indicator for production and prices. Findings: Results showed a long-term causal relationship between prices and production; from one side and direct and indirect taxes; from the other side and that relationship between short-term deviations and long-term reliability is corrected at a rate of (3%) per year. Results showed a negative significant impact of indirect taxes on price competitiveness; in the long term which was reinforced by the variance components’ analysis and response function’s test. Results also showed an insignificant impact of direct and indirect taxes on price competitiveness; in the short term. Research, Practical &amp; Social implications: Demonstrating the impact of taxes on prices and production in Jordan. As well as, discussing the governmental tax and income. Originality/value: The importance of study stems from research topic, since taxes have multiple effects on various areas in society which can be divided into scientific and practical importance.

25. Short Term Maintenance of Cadaveric Costal Cartilage Integrity in Ear Reconstruction

PURPOSE: Cartilage allografts are widely used in orthopedic and reconstructive surgery. Concerns over resorption and warping have limited their use in ear reconstruction. Newer sterilization methods forgo high dose radiation yielding high quality allografts with reliable longevity. In this study, we evaluate the use of this non/minimally irradiated cadaveric costal cartilage (NCCC) for primary ear reconstruction in congenital type III microtia. METHODS: Patients who underwent ear reconstruction using NCCC between August 2020 and August 2022 were included. Demographics, complications, and outcomes were recorded. Pre and post implantation cartilage samples from four patients stained with H&E and safranin-O were analyzed qualitatively using light microscopy. RESULTS: 12 ears were reconstructed for 11 patients (six male, five female) with congenital type III microtia. Average age was 10.7 years (range 4 - 25) and average follow up time post stage I reconstruction was 11.1 months (range 1.5-25.3). Two instances of surgical site infection were recorded as well as two instances of 1cm x 1cm construct exposure which were successfully salvaged. All patients required less than 90 minutes of anesthesia and were discharged home same day with over-the-counter analgesics for pain. Histologic analysis revealed repopulation of empty lacuna at stage II with cells and absence of lymphocytic infiltration. CONCLUSION: Ear reconstruction with NCCC shows short term maintenance of cartilage integrity with evidence of integration on histology. Advantages over current options include significantly reduced anesthesia time, reduced post operative pain, same day discharge, and reconstruction as early as 4 years old. Longer follow up times will reveal long-term reliability.