Search Results (1,028)

The thermal contact resistance between a clip-attached TO 247 package and heat sink is a very large contributor to the total thermal resistance. Therefore, it is important to investigate its reliability and lifetime behavior. The novelty of this investigation is the new, detailed lifetime behavior measurement results of thermal contact resistance between package and heat sink. We have carried out an accelerated lifetime test on 30 samples at 110 °C with acceleration factor of 35 for 18 weeks, corresponding to 12.1 years operating life in indoor environments. The samples were 7 without interlayer film, 12 with 12.5 µm thick silver film and 11 with 6 µm thick silver film. At the start of the test, the average of the thermal contact resistance of samples with 12.5 µm silver film was 20.7% lower, and with 6 µm silver film, the average of thermal contact resistance was 8.7% lower than the average of thermal contact resistance of samples without film. During the first operating month, thermal contact resistance decreased by an average of 5%. Then followed an additional 5% decrease for 12 years. All individual samples show lower thermal contact resistance after 12.1 years compared to the start. No failures were observed, not even among high outliers. By a visual inspection of heat sink surfaces, high outliers can be avoided from start. The thermal contact resistance variation is smaller for samples with silver films compared to samples without film. Samples show decreasing thermal contact resistance with increasing dissipated power. Several previously known stabilizing mechanisms can hypothetically explain the results. Not only the softness of silver, but also the high ductility and Poisson Ratio, which elongate a 12.5 µm thick film more than a 6 µm thick µm film, are hypothesized to better fill out microscopic voids. We observe silver film surface structure changes when comparing aged silver films to un-aged silver films, indicating material movements, but no exact mechanism could be proven. Therefore, the explanations studied are hypothetical. Since all measured thermal contact resistances were lower after 12.1 years, our conclusion is that stabilizing types of mechanisms are dominant during the operating lifetime for indoor environments. Full article

An experimental morphology-based information extraction methodology is presented for locating reinforcing bars and estimating their effective ultrasonic scattering diameters in reinforced concrete (RC) members using ultrasonic pitch–catch (UPC) non-destructive testing combined with synthetic aperture focusing technique (SAFT) reconstruction. Reinforced concrete slab specimens with known reinforcement layouts were constructed and tested using a commercial ultrasonic device equipped with dry point contact shear wave transducers in a pitch–catch configuration. The collected ultrasonic data were post-processed using an in-house software package to reconstruct two-dimensional (2D) SAFT images of the specimens. In the reconstructed images, embedded rebars consistently produced characteristic bipolar scattering responses composed of dominant trough–crest waveform pairs. Based on these repeatable scattering response features, an empirical morphology-based procedure was developed in which rebar depth was estimated from the midpoint of the dominant trough–crest pair, while the effective ultrasonic scattering diameter was characterized using their vertical separation. The experimental results obtained from twelve reinforced concrete slab specimens demonstrated reliable depth estimation and a strong monotonic relationship between reconstructed scattering response width and nominal rebar diameter under the investigated testing conditions. Regression analysis indicated that larger rebars generally produced broader reconstructed bipolar scattering responses due to cylindrical wave interaction, diffraction, interference, finite transducer aperture effects, and SAFT reconstruction characteristics. The proposed methodology does not attempt to reconstruct the exact physical boundary of the reinforcement or solve the full elastodynamic inverse problem. Instead, the proposed methodology provides a practical and computationally efficient morphology-based information extraction framework that transforms reconstructed ultrasonic scattering responses into quantitative morphological descriptors for embedded reinforcement characterization. By extracting repeatable scattering response features from SAFT-reconstructed images and establishing an empirical mapping between these descriptors and reinforcement characteristics, the proposed approach enables the quantitative interpretation of ultrasonic images without requiring computationally intensive full waveform inversion. Full article

Background/Objectives: Front-of-pack labelling systems such as Nutri-Score are promoted as public health tools to guide consumers towards healthier food choices. However, their capacity to accurately signal sugar content in child-targeted foods—a key determinant of dental caries risk—remains poorly characterised. This study aimed to evaluate whether Nutri-Score category reliably reflects sugar content in pre-packaged foods marketed to children, and to discuss the implications for paediatric oral health. Methods: A cross-sectional observational study analysed the nutritional labels of 100 pre-packaged foods directed at the paediatric population, all displaying a Nutri-Score label, selected from three major supermarket chains in Valencia, Spain. Products were grouped into eight predefined food categories. Sugar content (g/100 g or 100 mL), Nutri-Score category (A–E), and ordinal position of sugar in the ingredients list were recorded. Global association between Nutri-Score grade and sugar content was evaluated using Spearman’s rank correlation coefficient; category-level analyses used the Kruskal–Wallis or Mann–Whitney U test as appropriate. Results: A moderate statistically significant positive correlation was found between Nutri-Score grade and sugar content across all 100 products (ρ = 0.515, p < 0.001). In the exploratory category-level analyses, suggestive differences were observed in biscuits (H = 8.72, p = 0.033), milks and milk drinks (H = 9.02, p = 0.029), and desserts (H = 8.31, p = 0.016); none of these p-values survived Bonferroni correction for multiple comparisons (adjusted α = 0.006). Notably, some products rated A and B contained high sugar levels: one A-rated breakfast cereal reached 22.4 g/100 g, and the highest B-rated product (a flavoured milk drink) contained 22.1 g/100 g. No significant association was detected in cereals, breads, dairy products, juices, or frozen foods. Conclusions: Nutri-Score demonstrated limited discriminatory ability to identify high-sugar child-targeted foods consistently across food categories. These findings support recommending that paediatric dental practitioners advise caregivers to evaluate sugar content and ingredients lists beyond front-of-pack grading. Further regulatory refinement of the algorithm to specifically weight added sugar exposure in child-targeted products may be warranted. Full article

This study investigates the degradation mechanisms of 2835-packaged white LEDs commonly used in residential lighting scenarios under various environmental conditions and explores how standard ageing tests compare to those that better reflect real-world use cases. The samples consist of commercially available LED strips, both cool and warm white. The luminous output of each LED on a strip is spectrally measured individually before ageing, then aged under particular conditions for a certain time and measured individually again. The measurements for a given LED are then analysed from multiple aspects, including material degradation processes during ageing, for example by following changes in phosphor efficiency. Full article

To investigate the influence of substrate curvature and process deviations on the bonding quality of microchips mounted on curved surfaces, a thermo–mechanical coupled finite element model was developed in ANSYS 19.2 using a 0402 microchip as a representative component. The model was employed to evaluate the effects of substrate curvature radius, chip placement position, chip angular misalignment, and thermocompression-head angular deviation on the stress distribution and bonding behavior during conformal assembly. The simulation results were further validated through thermocompression bonding experiments. The results show that decreasing the substrate curvature radius significantly increases the stress concentration in the chip-pad region and leads to a more non-uniform stress distribution. In addition, placement errors and loading-direction deviations adversely affect bonding quality by altering the contact stress distribution and increasing the tendency for chip displacement and sliding. Quantitative analysis reveals the relative sensitivity of bonding performance to different geometric and process parameters, providing insight into the dominant thermo–mechanical mechanisms governing curved-surface assembly. Experimental results further demonstrate that excessive thermocompression tilt angles can significantly reduce bonding strength and increase chip sliding, suggesting that the tilt angle should be controlled within an appropriate range to ensure assembly reliability. The proposed thermo–mechanical modeling approach provides a quantitative tool for evaluating the influence of process variations on curved-surface microchip assembly and offers practical guidance for process parameter selection, tolerance control, and reliability-oriented design of conformal electronic packaging. Full article

Silicone gel for high-voltage power module packaging is prone to interfacial failure due to poor intrinsic adhesion, which seriously threatens the reliability of devices. This study explores ways to improve the adhesion performance of silicone gel from the two aspects of crosslink network structure and interfacial connection. The crosslink structure is regulated by adjusting the ratio of side-hydrogen-containing silicone oil to terminal-hydrogen-containing silicone oil, and interface adhesion is improved by adding three different contents of silane coupling agents (KH560, KH570, A171). The adhesion strength is evaluated by lap shear experiments. The results show that when the ratio of side-hydrogen to terminal-hydrogen is 16:24, the adhesion strength reaches a peak value of 0.0921 MPa. Among the coupling agents, KH560 shows the most significant enhancement, with the adhesion strength reaching 0.1356 MPa at 4% addition and a 47% improvement over the baseline, KH570 is only effective at low addition levels, and A171 shows the weakest effect due to vinyl interference in the crosslink network. Breakdown tests confirm that all three modification schemes do not seriously damage insulation performance. This study provides a feasible strategy and basis for the adhesion reliability design of silicone gel for power module packaging. Full article

Copper–aluminum (Cu-Al) wire-bonded devices are widely used in microelectronic packaging; however, corrosion at exposed Cu-Al bimetallic interfaces can lead to Al pad degradation, undercutting, and eventual ball-bond lift-off or open-circuit failure under humid, halide-contaminated conditions. This work presents a scalable post-wire-bond wet-chemical passivation process using octadecylphosphonic acid (ODPA) to simultaneously modify exposed Cu/Pd-coated Cu (PCC) and Al surfaces. The passivation process includes a hydroxylation pretreatment to generate reactive oxide/hydroxide surface sites, followed by ODPA treatment and solvent rinsing to remove weakly adsorbed species. Surface modification was evaluated using contact-angle measurements, reflection–absorption infrared spectroscopy (RAIRS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). ODPA treatment increased the water contact angle on Cu and Al, confirming a substantial increase in surface hydrophobicity following coating formation. RAIRS identified ODPA-associated aliphatic C-H bands, AFM showed treatment-induced nanoscale surface changes, and XPS supported metal–oxygen–phosphorus interfacial bonding. Under aggressive 100 ppm chloride-ion immersion, ODPA passivation strongly suppressed corrosion-induced ball-bond lift-off across both device platforms. Lift-off decreased from 99.0% to 0.73% for Cu-Al devices and from 23.3% to 0.42% for PCC-Al devices. Collectively, these findings establish an effective, process-compatible post-wire-bond strategy for substantially protecting corrosion-susceptible interfaces and thereby improving the reliability of wire-bonded interconnects in halide-containing environments. Full article

Understanding vegetation phenology is critical for assessing the impacts of climate change, particularly in regions vulnerable to environmental fluctuations. This study investigates the temporal trends and spatial variability of the start of photosynthetic activity (SOP) in natural vegetation across Central Asia over the past four decades (1982–2022) using satellite-derived Normalized Difference Vegetation Index (NDVI) data. The research emphasizes the critical role of vegetation phenology in understanding responses to climate change. To extract spring phenological data, various smoothing techniques were applied, including filter-based methods, asymmetrical Gaussian fitting, and three nonlinear and piecewise linear methods, ensuring accurate representation from continuous time series data. NDVI time series were smoothed using a phenological extraction package. The results indicate an average advance in SOP of 1.26 days per decade, with forest ecosystems exhibiting the greatest shift at 3.05 days per decade. A spring temperature threshold near 0 °C was identified as a reliable predictor for dormancy break. Ensemble Empirical Mode Decomposition (EEMD) was utilized to differentiate between cumulative and instantaneous trends, revealing dynamic phenological responses. A notable shift around 2005 was observed, with approximately 76.28% of pixels showing a change in SOP trend, while 23.60% displayed a stable, monotonic trend. Vegetation at elevations between 1500 and 3000 m experienced a significant SOP advance of 2.27 days per decade, whereas vegetation above 3000 m showed no significant change over the study period. Spatially, SOP trends exhibited a latitudinal gradient, with delays observed in the southern regions and advancements north of 45° N. These findings underscore the importance of developing region-specific phenological models to inform environmental management and climate adaptation strategies, particularly in arid and semi-arid ecosystems. Full article

Food safety systems are increasingly challenged by globalized supply chains, emerging contaminants, and the need for rapid decision-making before contaminated products reach consumers. Although conventional methods remain essential for confirmatory analysis, their dependence on centralized facilities, specialized personnel, and time-intensive workflows limits their suitability for real-time monitoring. Sustainable nanotechnology offers a promising approach to address these limitations by enabling rapid, sensitive, portable, and resource-efficient contaminant detection. This review critically examines recent advances in nano-enabled platforms for detecting foodborne pathogens, toxins, pesticide residues, heavy metals, allergens, and other food-related contaminants. Emphasis is placed on colorimetric, fluorescent, electrochemical, surface-enhanced Raman scattering, and biosensor-based systems employing sustainable nanomaterials, including biopolymer nanoparticles, carbon-based nanostructures, metal and metal oxide nanoparticles, quantum dots, and hybrid nanocomposites. The roles of green synthesis, low-toxicity materials, reduced solvent use, and safe-by-design strategies are evaluated in relation to environmental sustainability and practical implementation. The integration of nanosensors with smart packaging, portable devices, Internet of Things platforms, artificial intelligence, and data-driven risk assessment is also discussed. Key challenges include matrix interference, reproducibility, sensor stability, scalability, regulatory approval, environmental fate, and consumer acceptance. Continued progress will require validated, scalable, and environmentally responsible technologies capable of reliable operation under real-world food system conditions. Full article

To narrow spectral linewidth, stabilize longitudinal mode and improve output performance of a 1064 nm distributed feedback (DFB) semiconductor laser, we design and fabricate a laser module adopting fiber Bragg grating (FBG) external-cavity feedback and a butterfly packaging structure. The butterfly package effectively enhances heat dissipation and optical coupling reliability. Based on the classic Schawlow–Townes theory, we elaborate on how the narrowband filtering of FBG and the extended external cavity suppress mode hopping and reduce laser linewidth. A delayed self-heterodyne testing system is built to evaluate the photoelectric characteristics, spectral features and linewidth performance under varying driving currents and ambient temperatures. Experimental results show that the laser has a threshold current of 22.54 mA and a slope efficiency of 0.18 W/A, and its maximum output power reaches 80.8 mW at 480 mA. The side-mode suppression ratio (SMSR) reaches 58.2 dB at a temperature of 25 °C and driving current of 150 mA. Benefiting from FBG feedback, the laser linewidth is compressed from 485 kHz to 115 kHz, with lower noise and excellent wavelength stability. This compact all-fiber laser is well-suited for fiber sensing, coherent detection and LiDAR systems. Full article

Traditional methods for wine bottle packaging leakage detection often suffer from low efficiency, high false-positive rates, or an inability to detect micro-leakages. This paper proposes a near-infrared laser leakage detection system based on tunable diode laser absorption spectroscopy at 1392 nm, combined with a LightGBM machine learning model. The system detects gaseous ethanol vapor escaping from leaking bottles, addressing the spectral interference caused by ambient water vapor. A total of 1410 samples were collected, and each raw 2000-point spectral contour was compressed into a 200-dimensional feature vector through baseline correction, Z-score normalization, and uniform down-sampling. A two-stage hyperparameter optimization strategy yielded the optimal LightGBM configuration with a 5-fold cross-validation. For the binary classification task, the model achieved an AUC of 0.9949 and an inference speed of 0.0058 ms per sample on a CPU, outperforming Random Forest, PLS, and four deep learning models. For the regression task, the model achieved an R² of 0.5854 ± 0.0919. An anti-interference experiment on 422 samples under varying flow rates, temperatures, and commercial wine types confirmed the model’s robustness, achieving an overall accuracy of 0.94 and an alcohol recall of 0.99. To further validate the system under realistic conditions, a simulated micro-leakage test was conducted using a negative-pressure extraction method: 320 samples were collected from artificially damaged commercial wine bottles placed in a custom-built acrylic vacuum chamber that replicates the production line enclosure. The model achieved an accuracy of 0.95 with zero false negatives. The complete detection cycle takes no more than 5 s per bottle, enabling non-destructive, rapid, and online packaging integrity assessment. The results demonstrate that the proposed system provides a low-cost and reliable solution for wine bottle leakage detection suitable for industrial deployment. Full article

The power density of modern high-power integrated processors keeps rising rapidly. Among them, chiplet-based high-power AI accelerators exhibit local peak heat flux exceeding 1 kW/cm², which leads to concentrated hotspots, severe internal temperature gradients, device performance degradation and reliability deterioration. Conventional heat dissipation approaches are limited by the bottleneck of series interfacial thermal resistance and fail to meet the cooling demands of complex integrated architectures. Chip-level thermal management serves as a core method to suppress hotspots near heat sources and reduce overall system thermal resistance, which guarantees long-term stable operation of high-power integrated processors and plays a vital role in improving the energy efficiency and service life of computing platforms. This paper systematically reviews mainstream chip-level thermal management technologies for high-power integrated processors, covering heterogeneous integration of high-thermal-conductivity substrates, embedded microchannel liquid cooling, solid-state active heat pumps, multi-physics co-design and advanced packaging manufacturing processes. The basic working principles and state-of-the-art research progress of each cooling technology are elaborated in detail. The common engineering bottlenecks, including ultra-high heat flux endurance, packaging process compatibility, fluid leakage risks and multi-layer interfacial thermal resistance, are summarized, and the future development trends of this field are clarified. This review can provide comprehensive theoretical guidance for structural design and large-scale engineering implementation of near-junction thermal management solutions for various high-power integrated processors, especially high-computing-power AI accelerators. Full article

In this work, we implement the finite-field (FF) method for isotope shift (IS) calculations within the relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) framework of the GRASPG program package. The implementation is benchmarked using the ten lowest-lying fine-structure levels of B II by comparing FF results for the IS parameters with first-order perturbation theory (PT) results obtained using the RIS4 program. The relative deviations for the IS parameters are within 0.03%, and the computed transition isotope shifts agree with previous theoretical predictions and experimental measurements within the reported experimental uncertainties. Additional calculations for Ar XV further confirm the consistency between the FF and PT methods for heavier ions, and the resulting isotope shifts are consistent with the experimental values. This implementation therefore provides GRASPG with two equivalent and reliable approaches for isotope shift calculations. Full article

Energy poverty remains a persistent challenge in South Africa, despite relatively high levels of electricity access in urban townships. This study investigates household energy consumption patterns, energy-related challenges, and community perceptions of renewable energy in South Africa. In this study, a quantitative research design was employed, using a structured questionnaire administered to households selected from both electrified and non-electrified areas. The data were analyzed using descriptive statistics and inferential analysis with the Statistical Package for the Social Sciences (SPSS Version 30). The findings demonstrated that although electricity is widely used for basic services such as cooking and lighting, many households continue to rely on multiple fuels to meet their daily energy needs. This practice of energy stacking reflects ongoing concerns about affordability, reliability, and safety, and highlights that access to electricity alone does not guarantee energy security. Households also report significant financial pressure from energy costs, as well as health and fire risks associated with the use of unsafe alternative fuels. While awareness of renewable energy is present within the community, knowledge levels are uneven and not strongly associated with demographic factors, suggesting the need for more inclusive and targeted engagement strategies. Overall, the study demonstrates that energy poverty in urban South African townships extends beyond physical grid connection and is shaped by complex socio-economic and safety considerations. By foregrounding community perspectives, this research contributes to the international literature on multidimensional energy poverty and supports the design of integrated, people-centered interventions that advance affordable, reliable, and clean energy transitions in the Global South. Full article

Pharmaceutical cold chains operate under tightly coupled compliance, operational, and sustainability requirements, yet managers still face a practical challenge when deciding which improvement initiatives should be implemented first under limited resources and uncertain expert judgment. This study develops an integrated multi-criteria decision framework to prioritize pharmaceutical cold chain improvement initiatives by combining fuzzy DEMATEL and fuzzy TOPSIS. Thirteen evaluation criteria were derived from the literature and organized into three clusters covering risk, operational performance, and sustainability, while nine implementable initiatives were evaluated by a cross-national panel of pharmaceutical cold chain experts. Fuzzy DEMATEL was used to model causal interdependencies among the criteria and to derive structurally informed weights, and fuzzy TOPSIS was then applied to rank the initiatives. The results show that monitoring reliability, handling and process compliance, deviation management capability, and traceability event quality act as the main upstream drivers in the system. In the resulting prioritization, handling procedure redesign and targeted training, followed by formal excursion management, emerged as the highest priority initiatives. Packaging qualification, monitoring governance, and interoperable event capture formed the next tier. Sensitivity analysis showed that the leading priorities remained stable under plausible weight changes, supporting the robustness of the proposed framework. This study moves beyond method combination by linking expert perceived interdependencies among pharmaceutical cold chain risk, performance, and sustainability criteria to a sequenced portfolio of implementable initiatives. It contributes a theory-informed and operationally interpretable prioritization framework while recognizing that the inferred influence structure reflects structured expert judgement rather than externally validated operational causality. Full article