•A single ranking method will not yield best performance for all varieties of network.•It is a difficult task to measure the percentage completeness of a network structure.•We propose a new ranking ...method “Weighted kshell degree neighborhood method”.•The proposed method is applicable to different varieties and large-scale networks.
Due to the fast and worldwide growth of the social network, it has become a potent platform for broadcasting any information. Through the network, people can easily reach to a mass, can easily propagate a piece of information within a short time. Considering the advantages, especially to accelerate the information spreading or controlling the spreading, the organizations want to exploit the social network to its best. However, as we know, the network is formed by connecting one node (i.e., user) to another node, and it is not that all the nodes will be effective equally in spreading. Because it depends on many factors and one of them is their topological position in the network. Automatically finding the effective nodes (the influential spreaders) from a network is a real challenge. In the literature, kshell decomposition and degree centrality are the two popular measures for identifying the influential spreaders from a network. Moreover, it is more challenging in identifying the influential spreaders when network connectivity structure varies from network to network. It has been found that the kshell decomposition method works better in the complete global network connectivity structures and neighbors’ degree method in the incomplete global network connectivity structures. But the degree of completeness of the network connectivity structures also vary. Under this circumstance, only the kshell method or only the neighbors’ degree method will not be able to obtain the best influential spreaders. To overcome this problem, this article proposes an indexing method weighted kshell degree neighborhood which is a composition of kshell and degree through tunable parameters. We have evaluated the effectiveness of the proposed method using different real networks and the Susceptible-Infected-Recovered (SIR) spreading epidemic model. The results show that the proposed method can significantly obtain the best spreading dynamics from different varieties of network connectivity structures and outperforms the other existing indexing methods.
Influential spreaders are the key players in maximizing or controlling the spreading in a complex network. Identifying the influential spreaders using kshell decomposition method has become very ...popular in the recent time. In the literature, the core nodes i.e. with the largest kshell index of a network are considered as the most influential spreaders. We have studied the kshell method and spreading dynamics of nodes using Susceptible–Infected–Recovered (SIR) epidemic model to understand the behavior of influential spreaders in terms of its topological location in the network. From the study, we have found that every node in the core area is not the most influential spreader. Even a strategically placed lower shell node can also be a most influential spreader. Moreover, the core area can also be situated at the periphery of the network. The existing indexing methods are only designed to identify the most influential spreaders from core nodes and not from lower shells. In this work, we propose a kshell hybrid method to identify highly influential spreaders not only from the core but also from lower shells. The proposed method comprises the parameters such as kshell power, node’s degree, contact distance, and many levels of neighbors’ influence potential. The proposed method is evaluated using nine real world network datasets. In terms of the spreading dynamics, the experimental results show the superiority of the proposed method over the other existing indexing methods such as the kshell method, the neighborhood coreness centrality, the mixed degree decomposition, etc. Furthermore, the proposed method can also be applied to large-scale networks by considering the three levels of neighbors’ influence potential.
•Every core node in kshell decomposition method is not the most influential spreader.•Even a strategically placed lower shell node can also be the most influential spreader.•We propose an indexing method using node’s kshell, degree, contact distance, neighbors’ influence potential and so on.•The proposed method outperforms other measures in the large scale network.
The influential spreaders play a significant role in maximizing or controlling any spreading process in a network. In the literature, many methods have been proposed to identify influential ...spreaders. In this article, we classify all the methods mainly into four categories, such as local centrality, global centrality, semi-global centrality and hybrid centrality. Among them, we have found semi-global centrality based methods have immense potential in identifying the influential spreaders from various types of network structures. However, we have observed that the existing semi-global centrality methods can identify the spreaders from the periphery of a network, where the nodes in the periphery are loosely coupled and the collective influence in the peripheral region of a spreading process will be nominal. We propose a new indexing method “semi-global triangular centrality”, which does not consider the best spreaders from the periphery. The proposed method maximizes the total collective influence of a spreading process by selecting the best spreaders from the dense part of a network. We have examined the performance of the proposed method using the Susceptible–Infected–Recovered epidemic model and applied to nine real-networks. The experimental result reveals that the proposed method performs better than the other centrality methods in terms of spreading dynamics.
•Proposes a semi-global triangular centrality based on triangle pattern of a network.•The proposed method identifies the best spreaders from dense part of a network.•The proposed method yields a significant spreading performance.•The method is applicable in different scales and varieties of networks.
In this article, supercritical water gasification of biocrude at different conditions was performed and compared to each other. Three scenarios were considered while treating biocrude originating ...from cattle manure (CM) and corn husk (CH), namely, uncatalyzed feedstock, catalyzed with 10% Ni–0.08% Ru/Al2O3 and finally catalyzed with 10% Ni–0.08% Ru/Al2O3–ZrO2. It was found that 10% Ni–0.08% Ru/Al2O3–ZrO2 has performed significantly better than the other two scenarios over the 5 hour run time with a 193 and 187% higher hydrogen yield compared to the uncatalyzed and 10% Ni–0.08% Ru/Al2O3 catalyzed scenarios, respectively. Compared to CM gasification in the presence of a 10% Ni–0.08% Ru/Al2O3–ZrO2 catalyst, the catalyst got deactivated because of the high phenol and furan content in the corn husk biocrude, therefore hydrogen yield performance fell significantly. It was observed that the carbon gasification efficiency of the biocrude was independent of temperature. In terms of carbon conversion, the equilibrium conditions for the biocrude considered were attained at lower temperature. A mechanistic model based on the Eley–Rideal method was devised and tested against the obtained data. The dissociation of adsorbed oxygenated hydrocarbon is found to be the rate-determining step with an average absolute deviation of 3.55%.
•Densification characterization of the raw and pretreated miscanthus is proposed.•HTC pretreated miscanthus shows improved grindability and reduced ash yield.•Energy density and O/C–H/C ratios of ...HTC-260°C pellets are comparable to lignite.•HTC pellets show improved hydrophobicity and resistance against water immersion.•Torrefied pellets show low mass density and durability even compare to raw pellets.
Lignocellulosic biomass has the potential to produce sustainable clean-green energy and other bio-based materials. However, due to the inferior physicochemical properties compared to coal, biomass is not regarded as an ideal feedstock for industrial applications. The work presented in this study evaluates the feasibility of two different thermal pre-treatments, torrefaction and hydrothermal carbonization (HTC), followed by densification. The densified and pretreated samples obtained from miscanthus feedstock were characterized in terms of the strength, storage, and combustion properties for energy applications. The results showed that both the thermal pre-treatments are promising methods for upgrading biomass. However, the HTC pellets showed considerably superior physicochemical properties when compared to the raw and torrefied pellets. The mass density (mass per unit volume) and volumetric energy density (HHV per unit volume) of the pellets produced via HTC at 260°C was significantly higher (1036kg/m3, 26.9GJ/m3) compared to raw pellets (834kg/m3, 15.7GJ/m3) and torrefied pellets (820kg/m3, 16.7GJ/m3). Moreover, the HTC pellets showed improved hydrophobicity, reduction in ash content, reduction in alkali and alkaline earth metal content, and a considerable increase in the carbon content. Based on these results, the HTC pellets have potential for the heat and power applications, including replacing coal in the existing coal-fired power plants without any significant modifications.
Corn wet distillers’ fiber (corn fiber) is a byproduct of the corn-ethanol production process, with high potential as a precursor for activated carbon due to its moderate nitrogen content and ...availability. However, there has been limited investigation into activated carbons from the corn fiber. In this work, we produce activated carbons from the corn fiber using three procedures, including direct KOH activation, hydrothermal carbonization (HTC) followed by KOH activation, and FeCl3-catalyzed HTC followed by KOH activation. Catalytic HTC with FeCl3 was found to slightly increase the degree of carbonization relative to uncatalyzed HTC while also removing the nitrogen content at increasing concentrations and slightly increasing the porosity. The resulting activated carbon samples are then characterized by thermal gravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen analysis. The two-step process resulted in activated carbon with substantially higher surface areas than the one-step process (1220 vs 789 m2/g), as well as much higher thermal stability and nitrogen content (up to 1.20%). The results show that the corn fiber has potential for activated carbon production, with the two-step HTC followed by the activation process producing more favorable material properties than direct activation.
In this paper, a nano-PCM filled enclosure, which is a representative geometry of a thermal energy storage (TES) system, is investigated using scale analysis, numerical simulation, and experimental ...analysis. The enclosure is assumed to be square in shape. It is also assumed that one vertical wall of the enclosure is actively participating in absorbing energy from a source while the remaining walls are insulated. The thermal boundary condition at the active wall is treated as ‘constant heat flux boundary condition’ in this paper. The energy absorbing material, i.e., the nano-PCM, is CuO nanoparticles dispersed in coconut oil PCM. The influence of the volume fraction of nanoparticles (0≤φ≤5%) is investigated on the flow and thermal fields, heat transfer rate, energy stored and liquid fraction during the melting process of nano-PCM at different values of Rayleigh number based on base PCM (104≤Raφ=0%≤108). The Rayleigh number is adjusted by adjusting the size of the enclosure (i.e., higher Ra represents the larger enclosure). In addition to the isothermal lines and velocity vectors, heatlines are utilized to exhibit the energy flow patterns inside the enclosure during the melting process. Besides the numerical calculations, scale analysis is presented to demonstrate the different stages of melting process of nano-PCM. The detailed scale analysis assists to identify relationship of Nusselt number and solid-liquid interface location as a function of well established dimensionless numbers: Stefan number (Ste), Fourier number (Fo), and Rayleigh number (Raφ=0%). Finally, an experimental setup is developed to visualize the melting process of nano-PCM inside a prototype enclosure. Experiments are conducted to illustrate the impact of adding nanoparticles into PCM on the melting process. The numerical and experimental results show the significant improvement of the melting process by adding nanoparticles to PCM.
This study presents a numerical investigation of steam gasification of hydrochar derived from fruit wastes. Four fruit wastes, apple chip pomace, grape pomace, rotten apple, and apple juice pomace, ...were used as feedstocks. Aspen Plus was used to simulate the gasification process. The syngas composition, hydrogen to CO ratio (H2/CO), CO to CO2 ratio (CO/CO2), and heating value (HHV) of the resulting syngas were analyzed. Results show that hydrothermal carbonization (HTC) increases the CO and reduces the CO2 content of the syngas after gasification. Accordingly, H2/CO reduces, and CO/CO2 increases after HTC treatment. Hydrothermal treatment also improves the HHV of the syngas. The obtained HHV of syngas from hydrochar gasification ranged from 10.1 to 15.3 MJ/Nm3 depending on the process parameters. Additionally, effects of process parameters were studied. Increasing the steam to biomass ratio (SBR) leads to a higher H2/CO, enriching the syngas with hydrogen (up to 64.7 vol%). Higher SBR also lowers the CO/CO2 ratio due to the consumption of CO and a rise in CO2. HHV increases with increasing pressure, and hydrochars exhibit more changes in HHV than raw feedstocks. The reaction temperature contributes to an increase in the fraction of CO in the syngas (up to 39.6 vol%). Although hydrogen increased initially with temperature, a slight reduction was observed for the gas at elevated temperatures, reducing the H2/CO ratio and increasing the CO/CO2 ratio.
•A numerical study of steam gasification of hydrochar from fruit wastes is performed.•Aspen Plus equilibrium-based model is used to simulate the gasification process.•Effect of hydrothermal carbonization temperature on syngas composition is studied.•The composition, H2/CO, CO/CO2, and the heating value of product gas are computed.•Effects of steam to biomass ratio, temperature and pressure are investigated.
Hydrothermal carbonization (HTC) is a promising method to process high moisture biomass into biofuel/biomaterial. The environmental benefits of biomass depend on the processing methods and its ...end-use. Although life cycle assessment (LCA) of HTC of wet biomass has been conducted, co-processing of peat moss with agricultural biomass (miscanthus) is yet to be reported. This study evaluates the environmental performance of hydrothermally carbonized biomass (peat moss, miscanthus, and a blend of the two) used for energy (S3, S5, S7) or soil amendment (S2, S4, S6, S8) and compared with untreated biomass (peat moss left on-site: S1; peat moss used for soil amendment: S2) to determine the most viable pathway of biomass. Hydrochar produced from miscanthus had a lower global warming potential (GWP) compared with the hydrochar from peat moss or their blend; however, other impact categories were observed to be greater. The environmental impacts from the life cycle of biomass depend on their life cycle pathways. The highest GWP was observed in the case of peat moss used for horticulture application (S2) followed by S3, S5, S4, S6, S7, S8 and S1. Hydrochar used in soil amendment was more environmentally benign than the energy application, but the benefits were dependent on the decomposition rate of biomass. Additionally, HTC process required a considerable amount of water even it can process high moisture biomass. Renewable energy and agricultural policy may be needed to encourage hydrochar use/production/integration into soil amendment and energy application in rural communities.
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•Life cycle of hydrothermally carbonized and untreated biomass has been evaluated.•Peat moss, miscanthus, their blend are used for energy or horticulture application.•Hydrochar from miscanthus has a lower GWP than the hydrochar from peat moss.•Hydrochar horticulture application is environmentally benign than energy application.
Biomass steam gasification could be an attractive option for sustainable hydrogen production. Biomass, regarded as carbon neutral emitter, could be claimed as carbon negative emitter if carbon ...dioxide produced is captured and not allowed to emit to the environment during the process. Thus here an experimental study is carried out to find out the potential of hydrogen production from steam gasification of biomass in presence of sorbent CaO and effect of different operating parameters (steam to biomass ratio, temperature, and CaO/biomass ratio). Product gas with hydrogen concentration up to 54.43% is obtained at steam/biomass
=
0.83, CaO/biomass
=
2 and
T
=
670
°C. A drop of 93.33% in carbon dioxide concentration was found at CaO/biomass
=
2 as compared to the gasification without CaO. Mathematical model based on Gibbs free energy minimization has been developed and is compared with the experimental results.
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