Percolation System Research Articles

A multistage biogas slurry reflux and spray anaerobic digestion reactor for high solid anaerobic digestion: Performance and application evaluation

In this study, a new vertical plug-flow continuous dry anaerobic digestion reactor equipped with a spray percolation system was designed for rice straw and cow manure in dry AD. The findings indicated that the methane yield was 290.63 ± 19.16 mL/g VS when the optimal spray time (9 times/d) was used in batch AD. In addition, the results of continuous experiments under optimal spray time conditions showed that the volumetric methane production rate of the system was 1.55 L/(L·d) when the organic loading rate was 20 g VS/(L·d). In addition, hydrolysis and acidification steps were enhanced. This study demonstrated the potential of the new reactor for stable operation of high OLR dry AD. Digestate is already used as a substitute for synthetic fertilizers precisely because of the environmental benefits associated with its agronomic use.

Role of Coulomb Blockade in Nonlinear Transport of Conducting Polymers.

Nonlinear I-V characteristics associated with Coulomb blockade (CB) in conducting polymers were systematically investigated. At low temperatures, a crossover from Ohmic to nonlinear behavior was observed, along with drastically enhanced noise in differential conductance right from the crossover. The fluctuation can be well explained by the Coulombic oscillation in the collective percolation system, where the charge transport is related to the Coulombic charging energy between crystalline domains. Furthermore, a distinct quantum conductance, the fingerprint of CB caused by the individual tunneling between crystalline grains, was observed in sub-100 nm devices, confirming a strong association between nonlinear I-V characteristics and Coulomb blockade effect.&#xD.

PREDICTION AND RISK MANAGEMENT OF SPREADING FOREST PEST INFESTATIONS USING SATELLITE DATA

The article is devoted to predicting the risk of occurrence of large foci of infection in a pine forest with bark beetles, pathogenic fungi, and nematodes. The areas of disease observed on satellite images have a spotted, clustered structure of drying forest. An important statistical characteristic of the infestation structure is the power law of distribution of infestation clusters in size. Large, catastrophic events have a significant probability in processes with power laws of distributions. The given methods of computer identification and analysis of cluster distributions make it possible to form a statistical percolation model of prediction an d risk management of forest infestation based on information captured (read out) from space images. The only effective means of combating the bark beetle is sanitary felling of the forest. The sanitary cuttings area is considered a control parameter in the model. The model uses forest observation on a lattice of satellite image pixels, similar to the lattice of a percolation system. The universality of the theory is explained by the fact that it considers the interaction of elements of infection clusters, which, near the critical state of a forest ecosystem, obey a power-law distribution. The value of the power-law indicator indicates the formation of large clusters and is used in the model for the risk prediction of infestation development. In the model, risk prediction is understood as a statistical assessment of risk in the future, taking into account changes in the conditions for its manifestation. Changes are determined based on the results of satellite imagery, and the effectiveness of sanitary tree cuttings is considered. An example of a prediction of the development of forest infestations (drying) using images from the Sent inel-2 satellites is presented. Model identification methods are c onsidered, and a test verification of the model is performed. Using scale-invariant indicators of power-law distributions made it possible to abandon expensive high-precision images and replace them with images of average spatial resolution. The approach to synthesizing a prediction and risk management model from space images discussed in the article is based on the theory of self-organized criticality. The model is quite universal and can be used in space geoinformation technologies to orga- nize effective environmental management.

Effect of shape anisotropy on percolation of aligned and overlapping objects on lattices.

We investigate the percolation transition of aligned, overlapping, anisotropic shapes on lattices. Using the recently proposed lattice version of excluded volume theory, we show that shape-anisotropy leads to some intriguing consequences regarding the percolation behavior of anisotropic shapes. We consider a prototypical anisotropic shape-rectangle-on a square lattice and show that, for rectangles of width unity (sticks), the percolation threshold is a monotonically decreasing function of the stick length, whereas, for rectangles of width greater than two, it is a monotonically increasing function. Interestingly, for rectangles of width two, the percolation threshold is independent of its length. We show that this independence of threshold on the length of a side holds for d-dimensional hypercubiods as well as for specific integer values for the lengths of the remaining sides. The limiting case of the length of the rectangles going to infinity shows that the limiting threshold value is finite and depends upon the width of the rectangle. This "continuum" limit with the lattice spacing tending to zero only along a subset of the possible directions in d dimensions results in a "semicontinuum" percolation system. We show that similar results hold for other anisotropic shapes and lattices in different dimensions. The critical properties of the aligned and overlapping rectangles are evaluated using Monte Carlo simulations. We find that the threshold values given by the lattice-excluded volume theory are in good agreement with the simulation results, especially for larger rectangles. We verify the isotropy of the percolation threshold and also compare our results with models where rectangles of mixed orientation are allowed. Our simulation results show that alignment increases the percolation threshold. The calculation of critical exponents places the model in the standard percolation universality class. Our results show that shape anisotropy of the aligned, overlapping percolating units has a marked influence on the percolation properties, especially when a subset of the dimensions of the percolation units is made to diverge.

Experimental Study on Removal of Pollutants by Microbial Community in Multi-Soil-Layering System

By analyzing the microbial diversity of the fillers in the multi-layer percolation system and using high-throughput sequencing technology, this paper conducted a detailed analysis of the microbial community structure of the multi-layer percolation system, revealing its role in pollutant removal. It was found that the microorganisms of specific bacterophyla played a key role in the pollutant removal process. It provides the microbiological basis for further optimization of multilayer percolation system.

Critical properties of the optical field localization in a three-dimensional percolating system: Theory and experiment

We systematically study the optical field localization in an active three-dimensional (3D) disordered percolating system with light nanoemitters incorporated in percolating clusters. An essential feature of such a hybrid medium is that the clusters are combined into a fractal radiation pattern, in which light is simultaneously emitted and scattered by the disordered structures. Theoretical considerations, based on systematic 3D simulations, reveal nontrivial dynamics in the form of propagation of localized field bunches in the percolating material. We obtain the length of the field localization and dynamical properties of such states as functions of the occupation probability of the disordered clusters. A transition between the dynamical states and narrow point-like fields pinned to the emitters is found. The theoretical analysis of the fractal field properties is followed by an experimental study of the light generation by nanoemitters incorporated in the percolating clusters. The experimental results corroborate theoretical predictions.

Green Campus Audit Procedures and Implementation to Educational Institutions and Industries

Nature provides a free lunch, but only if we control our appetites. As we are in the twenty-first century, modernization and industrialization are the two important outputs that have made human life more luxurious and comfortable. Simultaneously, they are responsible for several uses of exploitation of forests, natural resources, and wildlife, polluting the scarce, producing massive solid waste and sacred water resources, and finally making our planet Earth ugly and inhospitable. Today, people are getting more familiar with global issues like global warming, the greenhouse effect, ozone depletion, climate change, etc. Now, it is considered a final call by Mother Earth to walk on the path of sustainable development. The time has come to wake up, unite and combat together for a sustainable environment. The present study focuses on the concept of green audit and its importance with respect to the conservation of nature for future generations. Every organization should have its own green campus and environment policy with respect to nature conservation and environmental protection and should maintain a sizable amount of green cover area after building construction along with natural and planted vegetation. A maximum number of more oxygen-producing and carbon-di-oxide-absorbing plants should be maintained to provide a pure atmosphere to the stakeholders. The installation of a rainwater harvesting system, percolation, ponds, check dam, and drip irrigation system to conserve rainwater and groundwater should be noteworthy on the campus.

Simultaneous degradation of sulfadiazine and dissolved organic matter based on low‐impact development facilities

Sulfadiazine (SD) is a common antibiotic administered to treat bacterial infections in livestock, and its fate and migration are greatly affected by dissolved organic matter (DOM). The soil infiltration system [a typical low-impact development (LID) facility] can significantly alter DOM properties during runoff pollution, thus affecting the complexation of SD with DOM. Here, the binding characteristics of different DOM components and SD in the soil infiltration system were explored using spectroscopic techniques (excitation–emission matrices, parallel factor analysis, and synchronous fluorescence spectroscopy). Combined with the weakening of DOM fluorescence intensity and 78.63% reduction in mean SD concentration following treatment, synchronous degradation may have occurred. The binding sequence of SD and DOM fluorophores was further explored using two-dimensional correlation spectroscopy. Effluent DOM showed greater sensitivity to SD and more binding sites than influent DOM. Moreover, hydrophobic protein-like substances exhibited higher log KM values than other fluorescent components, indicating that protein-like components play significant roles in SD complexation. The soil percolation system improved the complexation stability and binding sequence of fulvic-like substances. Thus, SD–DOM can be intercepted and degraded using LID facilities to reduce the risk of SD in aquatic environments.

Universal fluctuations and ergodicity of generalized diffusivity on critical percolation clusters

Despite a long history and a clear overall understanding of properties of random walks on an incipient infinite cluster in percolation, some important information on it seems to be missing in the literature. In the present work, we revisit the problem by performing massive numerical simulations for (sub)diffusion of particles on such clusters. Thus, we discuss the shape of the probability density function of particles’ displacements, and the way it converges to its long-time limiting scaling form. Moreover, we discuss the properties of the mean squared displacement (MSD) of a particle diffusing on the infinite cluster at criticality. This one is known not to be self-averaging. We show that the fluctuations of the MSD in different realizations of the cluster are universal, and discuss the properties of the distribution of these fluctuations. These strong fluctuations coexist with the ergodicity of subdiffusive behavior in the time domain. The dependence of the relative strength of fluctuations in time-averaged MSD on the total trajectory length (total simulation time) is characteristic for diffusion in a percolation system and can be used as an additional test to distinguish this process with disorder-induced memory from processes with otherwise similar behavior, like fractional Brownian motion with the same value of the Hurst exponent.

Computer and experimental study of field-induced conductivity modulation in liquid crystal–carbon nanotubes system

In this study, the possibility of percolation system conductivity control by the applied electric field has been researched based on computer simulation and experimental measurements of electrical characteristics of liquid crystal–carbon nanotubes nanocomposite. It was found that electrical resistance of obtained nanocomposites decreases with increasing nanotube concentration. It is shown that the applied voltage reduces the resistance of the nanocomposite, which is likely associated with the change in the spatial orientation of nanotubes. Nanocomposites with 2–4% nanotube content show the maximum field-controlled relative change in resistance. The effect of concentration and orientation of the nanotubes on the percolation processes in the carbon nanotube system has been studied by computer simulations. The change in the percolation probability was revealed when limiting nanotube orientation angles that are controlled by the electrical field.

Dielectric micro-capacitance for enhancing piezoelectricity via aligning MXene sheets in composites

Piezoelectric polymers have attracted a great deal of attention for flexible electromechanical applications but still suffer from low piezoelectric coefficients (∼−24 pC/N) in commercial films. Here, we propose a dielectric micro-capacitance strategy to enhance piezoelectricity via texturing well-aligned MXene (Ti3C2Tx) sheets into a poly(vinylidene fluoride) (PVDF) matrix using a scalable blade-coating technique. This aligned MXene/PVDF composite presents a piezoelectric coefficient of −63.3 pC/N due to its improved permittivity. More importantly, a modified model of the piezo-composite is put forward to further understand the interfacial polarization and dielectric relaxation effect in this percolation system for designing piezo-composites with better performances. Notably, this work might motivate new design principles and approaches to regulate electric behavior and promote piezoelectricity in electroactive polymers.

The temporal fluctuation of the inverse participation ratio for localized field modes in three-dimensional percolation system

We investigate the structure of the optical field radiated by the disordered optical nano-emitters randomly incorporated in three-dimensional cluster of a percolation material. Our numerical studies shown that the temporal variations of the inverse participation ratio (IPR) allow analyzing the extended and localized field structures over a long time range. The properties of IPR and the dynamics of the lasing emitters allow to find the characteristic time scales when the localization of the field in a general three-dimensional disordered system occurs. The studied effect opens new perspectives to control the optical fields localization in modern optical nano-technologies.

Simple holistic solution to Archie's-law puzzle in porous media.

In this paper, we account for the many critical exponents derived from the studies of the electrical conductivity in porous media by applying analysis of the well-known relation known as Archie's law. In spite of its seeming simplicity this law is considered to be "poorly understood," and the question that was and still is debated in the literature is whether there is some "hidden physics" in this law, or if it is "strictly a parametrization use for curve fitting with a priori no physical meaning." Our solution to the corresponding long-debated 78 years old puzzle is based on the classical percolation theory, but it also involves a principle that is based on continuum percolation. This principle is that the electrical properties of a percolation system are determined by the interplay between the connectivity of the conducting objects in that system, and the connectivity of the intersections between pairs of them. We thus propose a general concept that we call an electrically affected connectivity, and we predict the corresponding evolvement of the conductivity critical exponent with the increase of the content of the electrically conducting phase. Then, we show that the zerolike threshold that characterizes Archie's law is what enables the observation of this evolution. Combining the above principle and the latter feature, we provide a holistic, yet simple, solution to the longstanding controversy surrounding this law and its practical applications. In contrast with many previous claims that Archie's law lacks a physical basis, and the commonly suggested experiential explanations for it, we provide a solution that is physically based and thus elucidates Archie's law by showing clearly that it represents a bona fide phase transition phenomenon. This conclusion and its generality are strongly supported by the fact that it also explains the behavior of the electrical conductivity exponents in nonporous systems such as composite materials. The predicted ability to extract the long sought microgeometrical information from Archie's-law data, within the framework of the percolation phase transition, is expected to open a new direction in the understanding and the applications of this law.

Multiscale entropy and asynchronies of percolation-based price model and Chinese stock market

In recent years, the concept of entropy is widely used to measure the degree of uncertainty or complexity of dynamics system. In our work, we utilize the composite multiscale entropy (CMSE) and the composite multiscale cross-sample entropy (CMSCE) which are two modified algorithms of SampEn and Cross-SampEn by considering multiscale factors, to, respectively, investigate the multiscale complexities and asynchronies (correlations) in the Chinese stock market (SSZ, SZSE and HSI) as well as in our established financial stock price model. The price model is given based on a greatly important statistical physics system, the two-dimensional continuum percolation system. In the model, the fluctuations of stock price changes are assumed to be attributed to the market information interactions among the traders, and the percolation cluster is taken to represent the traders holding the same investment attitude. The empirical CMSE and CMSCE results display and meanwhile make comparisons of abundant complexities and correlations properties about Chinese stock indices and simulation data on both overall and the upwards, downwards trend of their returns.

Influence of 80-mesh Traditional Chinese Medicine Particle Stack Thickness on Percolation Performance

In order to research the influence of 80-mesh traditional Chinese medicine particle characteristics and particle stack thickness on percolation performance, wire screen was used to carry out filtration by the vibratory action of oscillator, screen No. and screen pore size were recorded and weight of screen residue was measured, so as to calculate average distribution density of particles, distribution function of particle size, form factor and specific surface area of particles. Percolation pressure drop was utilized as the index to evaluate percolation performance. Ethanol solution at 20°C with volumetric concentration of 47% was selected as percolation solution to measure and calculate the percolation pressure drop when ethanol solution flowed through 100mm, 150mm, 180mm, 250mm and 300mm 80-mesh particle layer. The results showed that percolation pressure drop is proportional to particle stack thickness, and it is high relatively due to the small size of 80-mesh particle, which shall result in high energy consumption of percolation system.

Critical Behavior of Electrical Conductivity for Reduced Graphene Oxide/Epoxy Resin Composites

Abstract: In this paper, we analyze the dc and ac electrical conductivities, in the 240 to 400 K temperature range and 102 to 106 Hz frequency range, of a percolating system synthesized by mixing reduced graphene oxide (rGO) particles in insulating epoxy resin matrix, diglycidyl ether of bisphenol A (DGEBA). We found that the dc electrical conductivity of the samples is strongly related to the rGO content, indicating a percolating behavior with percolation threshold ≈ 4 %. The critical behavior of the dc electrical conductivity as a function of the temperature indicates a strong positive temperature coefficient and a negative temperature coefficient of resistivity below and above the transition temperature Tg, respectively. Moreover, the results showed that the dc conductivity obeys the Arrhenius law and the ac electrical conductivity is both frequency and temperature dependent and follows the Jonscher’s power law. Keywords: Composites, Dielectric properties, Fillers, Glass transition, Graphene.

Extraordinary optical transmission in nano-bridged plasmonic arrays mimicking a stable weakly-connected percolation threshold.

Ultrasensitive sensors of various physical properties can be based on percolation systems, e.g., insulating media filled with nearly touching conducting particles. Such a system at its percolation threshold featuring the critical particle concentration, changes drastically its response (electrical conduction, light transmission, etc.) when subjected to an external stimulus. Due to the critical nature of this threshold, a given state at the threshold is typically very unstable. However, stability can be restored without significantly sacrificing the structure sensitivity by forming weak connections between the conducting particles. In this work, we employed nano-bridged nanosphere lithography to produce such a weakly connected percolation system. It consists of two coupled quasi-Babinet complementary arrays, one with weakly connected, and the other with disconnected metallic islands. We demonstrate via experiment and simulation that the physics of this plasmonic system is non-trivial, and leads to the extraordinary optical transmission at narrowly defined peaks sensitive to system parameters, with surface plasmons mediating this process. Thus, our system is a potential candidate for percolation effect based sensor applications. Promising detection schemes could be based on these effects.

Applications of a neural network to detect the percolating transitions in a system with variable radius of defects.

We systematically study the percolation phase transition at the change of concentration of the chaotic defects (pores) in an extended system where the disordered defects additionally have a variable random radius, using the methods of a neural network (NN). Two important parameters appear in such a material: the average value and the variance of the random pore radius, which leads to significant change in the properties of the phase transition compared with conventional percolation. To train a network, we use the spatial structure of a disordered environment (feature class), and the output (label class) indicates the state of the percolation transition. We found high accuracy of the transition prediction (except the narrow threshold area) by the trained network already in the two-dimensional case. We have also employed such a technique for the extended three-dimensional (3D) percolation system. Our simulations showed the high accuracy of prediction in the percolation transition in 3D case too. The considered approach opens up interesting perspectives for using NN to identify the phase transitions in real percolating nanomaterials with a complex cluster structure.

Electrically conductive poly(methyl methacrylate)-reduced graphene oxide/poly(styrene-co-acrylonitrile) composite with double percolative architecture

Abstract A poly(methyl methacrylate) (PMMA)-reduced graphene oxide (rGO)/poly(styrene-co-acrylonitrile) (SAN) composite was fabricated, and its electrical conductivity was improved with a double percolation system. Powdery PMMA nanoparticles were coated on rGO sheets using miniemulsion polymerization. The rGO sheets were uniformly distributed in the PMMA nanoparticles, which prevented the aggregation of rGO sheets. Therefore, PMMA-rGO is rendered capable of dispersing in ethanol and then mixed with SAN powder. The PMMA-rGO/SAN composite was hot-pressed to segregate the rGO sheets in the PMMA phase. The co-continuous architecture of the rGO in the PMMA phase forms an effective conductive network that allows high electrical conductivity. The ratio of PMMA to SAN was set as 5:5 to optimize the continuous structure in the composite. The fabricated PMMA-rGO/SAN (5:5) composite exhibited a high electrical conductivity of 2.38–5 S cm−1, which is significantly higher than that of a neat polymer. Moreover, it showed an appropriate electrical percolation threshold for low rGO content. These results provide a simple and an effective approach to fabricate selective localized rGO sheets for a continuous conductive network.

Optimization of Dust-Containing Rain Water Percolation System for Traffic Roads in Coastal Ecological Sponge Cities

Li, S.L.; Liu, R.R., and Wang, P., 2020. Optimization of dust-containing rain water percolation system for traffic roads in coastal ecological sponge cities. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 62–66. Coconut Creek (Florida), ISSN 0749-0208.The traditional method of rain water percolation control model using probability analysis method failed to solve the quantitative relationship between the dusty rain water seepage and runoff and the statistical characteristic of rainfall in the traffic road of sponge city, and the modeling effect was not good. Based on sensor fusion tracking filter, a dust-containing rain water percolation control model for urban traffic in coastal ecological sponge cities is presented in this paper. The idea of fusion tracking filter is adopted to make the control function of rain water percolation control more close to the posterior probability density of water storage energy, which can effectively reflect rain water seepage quantity and planned runoff coefficient of traffic road in sponge city. The control function of rain water percolation control function is closer to the posterior probability density of water storage energy. The fuzzy fusion tracking filter is used to ensure the positive characterization of the covariance matrix of the traffic road dusty rain water percolation planning state and to realize the optimization design of the dusty rain water percolation system for the traffic roads in coastal ecological sponge cities. The simulation results show that the model can realize the maximum rationalization of the utilization of the dusty rain water in the traffic road of the coastal ecological sponge cities by using the model to utilize the dusty rain water and the planning control of the traffic roads in the coastal ecological sponge cities. It can provide theoretical basis and practical application reference for decision-making department to carry out urban planning and rain water utilization.