The smart grid significantly improves the reliability, efficiency, security, and sustainability of electricity services. It plays an important role in modern energy infrastructure. A drawback of this ...new technique, however, is that the fine-grained metering data may leak private customer information. Thus, various public-key based data aggregation protocols for privacy protection have been proposed. However, the National Institute of Standards and Technology has recommended not using public-key based cryptography in the smart grid, since maintaining the public-key infrastructure is a heavy cost. In this paper, we propose an identity-based data aggregation protocol for the smart grid, which cannot only prevent unauthorized reading and fine-grained analyzing but can also protect against unintentional errors and maliciously altered messages. The basic building block of our protocol is an identity-based encryption and signature scheme in which an identity-based encryption scheme is combined with an identity-based signature scheme. They share the same private/public parameters, which greatly reduces the complexity of the protocol in the smart grid. Security analysis demonstrates the effectiveness of our protocol in the context of six typical attacks against the smart grid. A prototype implementation based on the Intel Edison platform shows that our protocol is efficient enough for physically constrained smart grid operators, such as smart meters.
The amount of plastics disposed from modern lifestyles have increased sharply in recent years. Solid biomass is an abundant energy resource that exists worldwide. Transformation of these waste ...plastics and solid biomass feedstock mixtures via co-pyrolysis can provide synergistic product enhancement for fuels and value-added products. The produced products can be used as chemicals and pollutant sorbents to foster eco-friendly pathways for waste management and sustainability. Progress into this avenue of waste disposal and energy production is the focus of this review. Properties of characteristic solid feedstock mixtures are discussed with focus on elemental composition, proximate analysis, and heating value. Effective H to C ratio of the different feedstocks is evaluated for asserting the quality of petrochemical equivalent products produced from co-pyrolysis of plastic wastes and biomass. The characteristics of polyethylene terephthalate (PET), high density and low-density polyethylene (HDPE & LDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS) and other major plastic waste components are discussed with focus on synergistic effects attainable by co-pyrolyzing them with biomass. State-of-the-art experimental methods for co-pyrolysis investigation are reviewed in detail using TGA, pyrolyzer, fixed bed reactor, fluidized bed reactor, microwave, and multi-step reactors using GC, MS, and FTIR diagnostics. In addition, different catalytic co-pyrolysis reactors are compared and discussed at different ratios of feedstock to catalyst, reactor temperature, and other operational parameters along with an in-depth understanding of several catalytic processing (ZSM-5 based catalyst, transition metal-based catalyst, multipurpose catalysts and ex-situ catalyst) for favorable products yield. Co-pyrolysis of waste plastic and solid biomass mixtures are reviewed for insights into liquid products for fuels and chemicals, as well as yield and composition of gases and solid residues evolved along with surface characteristics of the solid residues obtained from the selected configurations. The challenges and opportunities envisioned for the development in co-pyrolysis of several solid organic waste and plastic feedstock mixtures are also discussed. The goal was to provide favorable feasible pathways for clean and efficient disposal of plastic wastes with the incorporation of waste biomass for enhanced synergistic effects in waste disposal along with the recovery of energy and value-added products.
•Recent advances in artificial intelligence for predicting fouling are presented.•Working principles of AI technologies for membrane fouling prediction are discussed.•Comparisons of the inputs, ...outputs, and accuracy of AI approaches are conducted.•Future research efforts are highlighted for AI technologies in predicting membrane fouling.
Membrane fouling is one of major obstacles in the application of membrane technologies. Accurately predicting or simulating membrane fouling behaviours is of great significance to elucidate the fouling mechanisms and develop effective measures to control fouling. Although mechanistic/mathematical models have been widely used for predicting membrane fouling, they still suffer from low accuracy and poor sensitivity. To overcome the limitations of conventional mathematical models, artificial intelligence (AI)-based techniques have been proposed as powerful approaches to predict membrane filtration performance and fouling behaviour. This work aims to present a state-of-the-art review on the advances in AI algorithms (e.g., artificial neural networks, fuzzy logic, genetic programming, support vector machines and search algorithms) for prediction of membrane fouling. The working principles of different AI techniques and their applications for prediction of membrane fouling in different membrane-based processes are discussed in detail. Furthermore, comparisons of the inputs, outputs, and accuracy of different AI approaches for membrane fouling prediction have been conducted based on the literature database. Future research efforts are further highlighted for AI-based techniques aiming for a more accurate prediction of membrane fouling and the optimization of the operation in membrane-based processes.
Display omitted
Display omitted
•Key principle problems for hindering anaerobic digestion efficiency are analyzed.•Two perspectives on enhancing anaerobic digestion efficiency are proposed.•The available strategies ...for enhancing anaerobic sludge digestion are reviewed.•Main knowledge gaps in enhancing anaerobic sludge digestion are identified.•Sludge’s structure and property responsible for poor biodegradability is emphasized.
Anaerobic digestion (AD) of waste activated sludge (WAS) is an important bio-energy strategy that has been hindered by low conversion efficiency. This paper presents a comprehensive review of research on the sludge’s property and enhancing AD of WAS, and proposes two perspectives of material structure and microbial activity on improving AD efficiency. In the first part of this review, the key principle problems for hindering AD efficiency are identified based on the concept of AD. Then, the possibility that the complex microstructure and composition of WAS are responsible for poor biodegradability is considered and main methods for enhancing AD are summarized. In the third part, according to the published works, the main knowledge gaps in research are recognized as the identification and specific activity adjustment of functional microbes, the understanding of key constituents of WAS and their interactions, the deciphering of complex structure of sludge organic substance, and the revealing of relationships between complex nature of WAS and biodegradability. Further discussions reveal that to enhance AD more studies should be centered on the sludge’s structure and properties in future. However, this review is expected to provide the clear and accurate research directions for enhancing AD efficiency of WAS.
To improve our understanding of the characteristics of nanopores and their influence on liquid hydrocarbon occurrences in lacustrine shale, we carried out fractal analysis on 21 lacustrine shale ...cores from the Upper Cretaceous Qingshankou Formation (K2qn) in the Songliao Basin, NE (northeast) China, using TOC (total organic carbon) and Rock-Eval analysis, XRD (X-ray diffraction), low-pressure nitrogen adsorption experiments, and the FHH (Frenkel-Halsey-Hill) method. The relationships between composition of lacustrine shale (TOC, minerals, oil content), the pore structure parameters (BET surface area, pore volume, pore average diameter), and the fractal dimensions were investigated.
Two fractal dimensions D1 and D2 (at relative pressures of 0.5–1 and 0–0.5, respectively) were obtained, with D1 ranging from 2.5055 to 2.8888, and D2 between 2.1026 and 2.733. D1 is greater than D2, indicating that small pores are more homogeneous than larger pores. Both D1 and D2 increase with increasing BET surface areas and total pore volumes, and increase with decreasing average pore diameters. The fractal dimensions of lacustrine shale are negatively correlated with the clay content, but show no obvious relationship with the quartz content. The relationship between fractal dimensions (both D1 and D2) and TOC content is a U-shaped curve, with minimum D values at 2.5–3 wt.% TOC. Fractal dimension D1 can be used to characterize the shale oil content, and lacustrine shale samples with a lower fractal dimension have greater free oil. Therefore, considering the influence of TOC content on fractal dimension, and the relationship between oil content and fractal dimension, we conclude that lacustrine shale in the oil generation stage with 2.5–3.0 wt.% TOC is probably the preferred shale oil exploration target in the Songliao Basin. The results indicate that fractal analysis leads to a better understanding of the pore structure and oil storage capacity of lacustrine shale.
•Fractal dimensions of twenty-one lacustrine shale core samples were investigated.•Fractal dimension increases with increasing BET surface area and total pore volume, and with decreasing average pore diameter.•The relationship between fractal dimensions and TOC content is characterized by a ‘U-shaped’ curve.•Lacustrine shale samples with a lower fractal dimension (D1) have greater free oil content.
•Anaerobic dynamic membrane bioreactor was used for landfill leachate treatment.•62.2% of COD removal efficiency was achieved at the influent COD 13,000mg/L.•Average methane yield was 0.34L/g ...CODremoved at OLR 4.87kg COD/(m3d).•Archaeal community was stable while changes occurred in the bacterial community.•Genus Methanosarcina was identified as the dominant methanogen in the system.
In this study, a pilot-scale anaerobic dynamic membrane bioreactor was operated for 142days for treating landfill leachate. Under stable operation, average COD removal efficiency of 62.2% was achieved when the reactor was fed with the raw leachate containing total ammonium concentration above 3000mg/L and COD above 13,000mg/L. The methane content in the biogas was in the range of 70–90%, and the average methane yield was 0.34L/g CODremoved at the organic loading rate of 4.87kg COD/(m3d). Pyrosequencing analyses indicated that during the operation the archaeal community was relatively stable while obvious changes took place in the bacterial community. Alkaliphilus, Petrimonas, Fastidiosipila and vadinBC27 were the abundant fermentation bacteria in bacterial communities. Moreover, phylum TM6 gradually became the most dominant bacterial community and reached the highest relative abundance of 32.9% as the operation elapsed. In archaeal communities, genus Methanosarcina was identified as the dominant methanogen.
The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data ...sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the permafrost distribution on the TP. We generated a new permafrost map based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated this map using various ground-based data sets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and soil properties (moisture content and bulk density). The temperature at the top of permafrost (TTOP) model was applied to simulate the permafrost distribution. Permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06 × 106 km2 (0.97–1.15 × 106 km2, 90 % confidence interval) (40 %), 1.46 × 106 (56 %), and 0.03 × 106 km2 (1 %), respectively, excluding glaciers and lakes. Ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) were used to validate the model. Validation results showed that the kappa coefficient varied from 0.38 to 0.78 with a mean of 0.57 for the five IRs and 0.62 to 0.74 with a mean of 0.68 within the three transects. Compared with earlier studies, the TTOP modelling results show greater accuracy. The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.
Sensing of cadmium (Cd) and lead (Pb) in environmental samples is crucial for identifying potential health risks associated with exposure to these heavy metals as well as understanding the extent of ...heavy metal contamination in different environments and its impact on the ecosystem. The present study elucidates the development of a novel electrochemical sensor that can detect Cd (II) and Pb (II) ions simultaneously. This sensor is fabricated using reduced graphene oxide (rGO) and cobalt oxide nanocrystals (Co3O4 nanocrystals/rGO). The characterization of Co3O4 nanocrystals/rGO was done by using various analytical techniques. The incorporation of cobalt oxide nanocrystals with intense absorption properties results in an amplification of the electrochemical current generated on the surface of the sensor by heavy metals. This, when coupled with the unique properties of the GO layer, enables the identification of trace levels of Cd (II) and Pb (II) in the surrounding environment. The electrochemical testing parameters were meticulously optimized to obtain high sensitivity and selectivity. The Co3O4 nanocrystals/rGO sensor exhibited exceptional performance in detecting Cd (II) and Pb (II) within a concentration range of 0.1–450 ppb. Notably, the limits of detection (LOD) for Pb (II) and Cd (II) were found to be highly impressive at 0.034 ppb and 0.062 ppb, respectively. The Co3O4 nanocrystals/rGO sensor integrated with the SWASV method displayed notable resistance to interference and exhibited consistent reproducibility and stability. Therefore, the suggested sensor has the potential to serve as a technique for detecting both ions in aqueous samples using SWASV analysis.
Display omitted
•The Co3O4 nanocrystals/rGO composite have been synthesized with simple manner.•The Co3O4 nanocrystals/rGO/GCE presented high sensitivity for Cd(II) and Pb(II) detection.•The proposed sensor showed low LODs and wide leaner ranges for both ions by SWASV.•The electrode application was studied by Cd(II) and Pb(II) sensing in water samples.
For an integer 𝑛 > 1, let 𝑃(𝑛) be the largest prime factor of 𝑛. We prove that, for 𝑥 → ∞, there exists a positive proportion of consecutive integers 𝑛 and 𝑛 + 1 such that 𝑃(𝑛) < 𝑃(𝑛 + 1) ...in short intervals (𝑥, 𝑥 + 𝑦 with 𝑥⁷/¹² < 𝑦 ⩽ 𝑥. In particular, we have
|
{
n
⩽
x
:
P
(
n
)
<
P
(
n
+
1
)
}
|
≥
0.1063
x
.
This improves a previous result of La Bretèche, Pomerance and Tenenbaum.
Recent droughts have severely threatened water security in many regions worldwide. Reservoirs, designed to combat droughts and secure water supply partially, are reported failing to fill up to the ...total capacity due to severe droughts. How bad is climate affecting reservoir filling up on a global scale? This issue has not been studied. We present a big picture of reservoirs in crisis using satellite altimetry. Thanks to the unique characteristics of CryoSat‐2, 525 reservoirs worldwide were investigated during 2010–2022. Results show that most reservoirs (93%) are found not fully filled up at least once. About 21% of reservoirs, which are mainly located in the Southern Hemisphere, show a significant decline in water levels. Moreover, about 20% of reservoirs with larger level fluctuations (>3 m) are located in less developed economies, indicating informed operation rules are needed. Further analyses indicate reservoirs are largely affected by extreme climate events, such as ENSO.
Plain Language Summary
A reservoir is an artificial lake where water is collected and stored for various purposes, such as flood control, irrigation, hydropower generation, industrial use, etc. In a changing climate, drought events can cause a decline in the natural flow of streams and rivers to the reservoirs. Consequently, many of the functions provided by the reservoir might be halted if the drought continues, just like the cases of Lake Powell and Lake Mead. The past decade saw several record‐breaking global annual temperatures. How have global reservoirs been affected in terms of the filling up? Leveraging more than a decade of CryoSat‐2 altimetry observations, we provided a global picture of this issue. We found that 93% of studied reservoirs have not been fully filled up at least once during 2010–2022. Our analyses revealed that droughts are the most probable culprits. About 86% of the 398 reservoirs with accessible SPEI data exhibited significant susceptibility to drought, while 43% of the 525 reservoirs demonstrated notable sensitivity to ENSO events. These findings have important implications for future reservoir operations to cope with more intensive drought events. It also means the benefits and costs of both existing and planned reservoirs need to be re‐assessed to take adaptation strategies.
Key Points
Water levels of reservoirs in the southern hemisphere show a declining trend
About 93% of the 525 studied reservoirs have not been fully filled up at least once in the past 12 years
Less developed economies need to develop informed reservoir operation rules to cope with climate change
PDF
