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Real-time Transition from Continuous PWM to Discontinuous PWM Technique
No full textThis paper introduces the prospect of transition from continuous pulse width modulation (PWM) technique to discontinuous PWM technique in real-time. The discontinuous PWM technique mitigates switching loss by incorporating the dead band in train of switching pulses, and total harmonic distortion (THD) of discontinuous PWM is comparable to the continuous PWM technique, particularly at high amplitude modulation ratio (ma). Consequently, implementing real-time transition to discontinuous PWM can significantly reduce switching losses while maintaining acceptable THD performance, particularly in scenarios involving high ma. This transition offers improved efficiency and better overall system operation. This paper discusses space vector PWM (SVPWM) and discontinuous space vector PWM techniques (DSVPWM); Comparison of these techniques is validated experimentally. Performance metrics for experimental implementation involve voltage THD, current THD, linearity, and fundamental output voltage. The algorithm of transitioning from SVPWM to DSVPWM in real-time is given. The proposed transition is validated by simulation on MATLAB2021a-Simulink � 2024 Elsevier B.V., All rights reserved
Mapping the hierarchical environmental transformations of nanoscale UiO-66 metal-organic framework
No full textMetal–organic frameworks (MOFs) hold immense potential for applications from separations to catalysis, yet their long-term behaviour across real-world environments remains unclear. Here we introduce a hierarchical exposure framework that tracks the structural and chemical transformations in the archetypal zirconium MOF UiO-66 across sequential compartments - atmospheric gases, air, aqueous media and a biological host – and resolves how prior exposures condition or prime subsequent transformations. Using synchrotron-based spectroscopy, we find that oxidative gases leave the Zr-carboxylate nodes essentially intact, whereas exposure to environmentally relevant aqueous media initiates partial shifts in local Zr coordination and introduces oxygen into the pores – with transformation extent governed by the chemistry of the environmental matrices. Strikingly, acute exposure (24 h) to the water flea Daphnia magna drives profound framework degradation and re-speciation to a homogeneous biotic Zr species. Microfocus XRF maps show that Zr is highly localized in the animal’s digestive tract, and region-specific XANES confirms uniform speciation across its tissues. Our findings establish a cross-compartment transformation hierarchy in which biological processes can dominate the fate of stable MOFs even when abiotic exposures appear benign. Thus, organism-level biotransformation should be performed as a necessary part of environmental safety assessments and materials design
Green computing for improving the sustainability of data centers: Optimized VM allocation with decentralized peer-to-peer nodes
No full textThe amplified concern in cloud and fog computing calls for a stimulus in the demands on the strategies that allocate virtual machines to amplify energy efficiency to alleviate high energy utilization and the environmental impacts that arise from it. This research presents a green computing approach that employs decentralized, peer-to-peer fog nodes in dynamic VM allocation within the fog and cloud ecosystems. Unlike traditional central allocation schemes, the proposed model allows for autonomous management, distribution, and sharing of workload at the level of a fog node, depending upon local capacity, real-time demands, and determined energy efficiency. P2P collaboration at geographically distributed fog nodes evokes optimal resource usage, minimal latency, energy costs, and carbon footprint. An energy-aware allocation algorithm is developed that integrates real-time workload prediction, power consumption metrics, and renewable energy availability across the boundaries of fog and cloud environments to enhance sustainability. Experimental results demonstrate that the decentralized P2P framework not only diminishes power utilization but also improves the response times for services and minimizes the overall environmental footprint of fog/cloud operations
Improving urban sustainability through microscale configuration of green infrastructure
No full textWith rapid urbanization and population expansion, the urban microclimate is becoming one of the most important determinants of urban sustainability. Uncontrolled urban growth often leads to land use and land cover changes, intensifying urban heat, altering wind patterns, and causing seasonal microclimatic variations. These changes reduce human comfort, increase cooling loads and elevate energy consumption, thus making cities major contributors to climate change. To address these challenges, the adoption of sustainable practices is essential. Green Infrastructure (GI) is one such potential strategy. However, its efficacy is highly dependent on spatial distribution, coverage ratio, seasonality and building configuration, which makes it necessary to consider at the neighbourhood scale. This study employs Computational Fluid Dynamics to assess the year-round impact of GI on microclimate regulations in a prototypical urban neighbourhood in hot-arid climatic conditions of Ahmedabad, India. It also involves investigating the effects of GI on annual energy consumption and carbon dioxide emissions. The study also introduced the comfort energy performance index (CEPI) to holistically assess performance to determine the influence of different spatial distributions and coverage ratios on an urban domain. The results reported that implementing GI led to variations in air temperature, energy consumption, and carbon dioxide emissions, ranging from approximately -4 to +1 C, -30 to +4 %, and -25 to +5 %, respectively. These findings emphasize the importance of strategic GI placement, as improper configuration of GI can lead to limited or even adverse effects. Ultimately, the insights from this study can inform urban planners and policymakers, providing a pathway to mitigate urban heat, lower energy consumption, and address climate change through GI interventions
Underestimation of Historical Terrestrial Water Storage Droughts in Global Water Models
No full textEnhanced drought modeling is crucial for realistic prediction and effective management of water resources, especially with climate change anticipated to exacerbate drought frequency and severity. Global water models (GWMs) simulate historical and future terrestrial water storage (TWS) with continuous spatial and temporal coverage. However, a global evaluation of TWS simulations by GWMs focused on drought is lacking. Here we evaluate, for the first time, GWMs' capability to represent TWS droughts by comparing simulations with Gravity Recovery and Climate Experiment satellite data. We find notable underestimation of drought severity and coverage by GWMs, across diverse regions, including North America, South America, Africa, and Northern Asia. When examined without trend removal, the underestimation of TWS droughts is more pronounced in recent years (2016–2019) compared to 2002–2015, especially in northern latitudes. This underrepresentation highlights the necessity to improve GWMs to simulate TWS droughts. Our results imply that previously reported future TWS projections could have underestimated droughts
A Novel Method for Completeness Period in Seismic Hazard Assessment: Overcoming Drawbacks of Stepp’s Method and Validation Using Regional Catalogue
No full textA crucial aspect of seismic hazard assessment involves evaluating the completeness of the available seismic data. Numerous researchers have introduced different methods for analysing the completeness of event records, with Stepp’s method being one of the most widely utilized approaches. This method relies on calculating the standard deviation of the mean annual occurrence rate of events, which is then plotted on a log-log scale. The completeness period for the seismic event record is determined by identifying the stable slope of the standard deviation in relation to the − 1/2 slope line. Standard deviation is expected to decrease with time, and it will also reduce if events are missing. Hence, it is not very sensitive if events are missing. Again, the position of − 1/2 slope line is decided by eye estimation only, which is highly subjective and not very accurate in finding the completeness period. The primary aim of this study is to evaluate the sensitivity of Stepp’s method and to introduce an alternative approach for estimating the completeness period. This new method is utilizing a moving average approach for the annual frequency of earthquake occurrences, which is anticipated to remain statistically stable over time. Hence, any slight change in the rate can be easily detected if events are missing. In this study, sensitivity of the moving average method is compared with Stepp’s method using a hypothetical catalogue and found to be more sensitive for the missing events. Results from completeness analysis of a regional catalogue by both the methods are also compared, and it is concluded that the moving average method is more sensitive and accurate as compared to the Stepp’s method
Reduction of the channel junction scour using a bed sill: a 3D numerical study
No full textOpen-channel junctions are distinguished by prominent scour zones, where bed scouring modifies river morphology, potentially affecting hydraulic structures and undermining the stability of channel banks and beds. Despite investigations into the causes of channel junction scour, studies on mitigation measures remain limited. This study aims to assess the effectiveness of a bed sill in mitigating scour at a right-angled open-channel junction, utilizing three-dimensional (3D) computational fluid dynamics (CFD) modeling and simulating sediment transport in both bed-load and suspended-load forms. The predictive accuracy of the model is validated through comparison with laboratory data reported in the literature. To address junction scour, a bed sill is installed at various downstream locations from the junction. Comparative analyses indicate that the efficacy of scour reduction is heavily dependent on the bed sill’s placement. Specifically, placing the bed sill downstream of the flow contraction region significantly reduces the near-bed secondary currents from the channel centerline towards the outer bank, leading to decreased bed shear stress and consequently less scouring. Conversely, positioning the bed sill within the flow contraction region proves ineffective in reducing scour. These findings contribute to a better understanding of junction scour mitigation strategies
A functional 2D MXene-DNA hybrid hydrogel for portable detection of blood disorder biomarker thrombin in human plasma
No full textDelaminated MXenes (2D MXenes) and DNA hydrogels have created enormous opportunities due to their versatility and ability to be tailored for specific applications. 2D MXenes offer high aspect ratio morphology and electrical conductivity, while DNA provides stimuli responsiveness and specificity in binding to ligands or complementary sequences. This synergy makes DNA an ideal actuator when combined with 2D MXenes. The present work makes the first effort to integrate and exploit them for detecting the thrombin levels, a crucial proteolytic enzyme that plays a pivotal role in regulating blood clotting by cleaving fibrinogen into fibrin and plays a critical role in bleeding disorders such as haemophilia and Von Willebrand disease. This study introduces a novel hybrid DNA hydrogel by leveraging the properties of 2D MXenes with a thiol-modified thrombin-binding aptamer (TBA) as a crosslinking agent. The TBA and its complementary DNA oligos are immobilized on 2D MXene sheets, forming a packed hydrogel. Upon thrombin binding, the TBA releases its complementary DNA, resulting in a loosened hydrogel and a change in resistance, which is used as a read-out for thrombin detection. The fabricated sensor demonstrated a high sensitivity of 0.021 [MΩ (mg L−1)]−1 cm−2, with a low limit of detection (LOD) of 0.1698 mg L−1, a resolution of 6.51 mg L−1 and also a wider linear detection range (LDR) of 10-200 mg L−1 with a correlation coefficient (R2) of 0.98, indicating excellent linearity and reliability across the tested range. The concept was successfully demonstrated, achieving a relative standard deviation (RSD) of 8-10% for thrombin detection in artificial samples, indicating excellent performance. This robust technique holds promise for biomedical sensing devices, allowing customization for detecting various target molecules using specific aptamers