•We review the existing models for the critical properties (Tc, Pc) of gas in nano-size conduits.•We use the tree-like pore model to predict the critical properties of shale gas at the core ...scale.•The critical properties are determined by accounting for the pore structure and connectivity of shale formations in the United States.
The transport properties of gas deviate from the nominal values, reported without confinements, when it is confined inside a nano-size conduit. This is because the interactions between the gas molecules and the conduit become more important than do those of the gas molecules with each other. The deviation is relevant to shale gas because of the ultra-narrow pore size in the matrix. With this in mind, we determine the critical temperature (Tc) and critical pressure (Pc) for shale formations in North America at the core scale. The shale formations are the Bakken, Barnett, Eagle Ford, Haynesville, Marcellus, Monterey, New Albany, Niobrara, Utica, Wolfcamp, and Woodford. The present study uses the acyclic pore model to account for the effective connectivity of shale samples at the core scale. It also differentiates between the pore-throat and pore-body size distributions. The former is used to derive the critical properties relevant to the fluid flow (displacement), and the latter is used to determine the effective properties relevant to the storage. Our study shows that the displacement-critical properties change significantly, whereas the storage-critical properties do not require modifications. Quantitative corrections of the critical properties for various formations are presented. The results have major applications in developing a realistic reservoir model for shale formations.
Most of the viscoplastic models used to describe the constitutive behavior of squeezing grounds assume isotropic deformation. However, it is commonly observed that squeezing behavior is characterized ...not only by large time-dependent but also often by anisotropic deformations. This study uses a semi-empirical approach based on the analysis of convergence measurements and a numerical model that takes into account the time-dependent and the anisotropic response of the rock mass to investigate the squeezing behavior of the Saint-Martin-la-Porte access gallery, excavated within the Lyon–Turin railway project. We first show how the semi-empirical convergence law of Sulem et al. (Int J Rock Mech Min Sci Geomech Abstr 24(3):155–164,
1987a
; Int J Rock Mech Min Sci Geomech Abstr 24(3):145–154,
1987b
) can be extended to anisotropic tunnel closure by considering an elliptical deformation of the rock mass and by fitting the convergence data along the principal axes of deformation. A new anisotropic time-dependent constitutive model is then proposed. This model includes ubiquitous joints of specific orientation embedded in an isotropic viscoplastic medium. This model is implemented in FLAC3D and numerical simulations are performed to back-analyze the anisotropic closure of the Saint-Martin-la-Porte access gallery. An efficient two-step procedure for calibrating the model parameters is proposed: the parameters of the isotropic solid matrix are first estimated by performing axisymmetric numerical simulations. The parameters of the ubiquitous joints are then calibrated by performing 3D computations. It is shown that the numerical results reproduce very well the convergence measurements of the studied sections of Saint-Martin-la-Porte gallery.
Data-driven analysis of resilience in airline networks Wong, Allen; Tan, Sijian; Chandramouleeswaran, Keshav Ram ...
Transportation research. Part E, Logistics and transportation review,
November 2020, 2020-11-00, Letnik:
143
Journal Article
Recenzirano
•Statistical methods can support quantification of delay abnormalities in airline networks.•Network metrics can supplement, but not replace data-driven methods.•Hybrid data-driven network metrics can ...identify impacts of major events.•Individual airline resilience is important to analyze, in addition to the overall system.
Network theory has provided key insights into the overall resilience of air transportation systems. We expand upon these insights by using Mahalanobis distance to quantify delay abnormalities, complex network metrics for high-level insights, and a hybrid method that combines data-driven and network approaches. We apply these methods to public data and discuss trends in resilience among four US airlines. We find that our data-driven methods enable more detailed insights into airline resilience than traditional network methods. We also find that simultaneously considering all three approaches provides a more comprehensive understanding of resilience than the consideration of any one in isolation.
Foundational to Vygotsky's Zone of Proximal Development (ZPD) was the influence of Marx's theory of historical materialism. Vygotsky's work radically rejected the traditional approaches of ...developmental psychology. The ZPD centralized the importance of potential development not only by measuring or testing what a child could perform, but a tool to observe developmental change as a dialectical product of society and material life. In other words, social structures and the dynamic material world play a significant role in shaping the child's development. It follows then that contemporary uptakes of Vygotsky's ZPD likewise would be remiss to neglect the importance of historical materialism and take account of the dynamism of modern capital. This paper offers for further engagement the Zone of Proximal Privilege-a contemporary uptake of Vygotsky's work that explores the ways that the excesses of capital have created vast educational privileges for some while constricting access and development for many others.
Viscosity of shale gas Tran, Huy; Sakhaee-Pour, A.
Fuel (Guildford),
03/2017, Letnik:
191
Journal Article
Recenzirano
•Effective gas viscosity of a shale using a physically representative pore model.•Effects of a pressure change on the effective gas viscosity.•Practical implications of permeability measurements for ...shale gas viscosity.•Practical applications of the effective gas viscosity for a reservoir model.
Nanofluidics, which analyzes fluid transport through sub 100-nm conduits, has fascinated engineers in different fields and we petroleum engineers are no exception. This field gained a significant interest in petroleum engineering only when hydrocarbon production from shales became economically feasible. The basic transport properties of the fluid change for this range of conduit size. With this in mind, we analyze the effective gas viscosity of a shale at different pore pressures. Our objective is not to derive detailed information about the gas transport at a pore or a sub-pore scale, but rather to discuss the implications of pore-scale simulations on the effective gas viscosity at the core scale. We use an acyclic pore model to account for the effective connectivity of the pore space at the core scale. The acyclic model is physically representative because it can capture capillary pressure measurements of the drainage obtained from mercury intrusion experiments. We present the effective gas viscosity with respect to the nominal value, under unconfined conditions. Our analysis shows that the reported permeability in a pressure-driven flow has to be considered an effective transport property if nominal viscosity and density are used for interpretation. That is, we have to modify viscosity and permeability simultaneously in our reservoir model. Our study has major implications for building a realistic reservoir model for shales based on petrophysical measurements.
A highly accurate indoor positioning under the effect of multipath reflections has been a prominent challenge for recent research. This paper proposes a novel indoor visible light communication (VLC) ...positioning model by connecting k-nearest neighbors (kNN) and random forest (RF) algorithms for reflective environments, namely, kNN-RF. In this fingerprint-based model, we first adopt kNN as a powerful solution to expand the number of input features for RF. Next, the importance rate of these features is ranked and the least effective one(s) may be removed to reduce the computation effort. Next, the training process using the RF algorithm is conducted. Finally, the estimation process is utilized to discover the final estimated position. Our simulation results show that this new approach improved the positioning accuracy, making it nearly five times better than other popular kNN algorithms.
This paper shows an effective method to significantly enhance the isolation of a closely spaced two-port patch antenna, which can be deployed for full-duplex transceivers as well as ...multiple-input-multiple-output (MIMO) systems. Two rectangular microstrip patches are arranged in the E-plane configuration. To achieve high isolation, a grounded stub is positioned between the radiating patches. For validation of the proposed concept, an antenna prototype is fabricated for measurements. The measured data demonstrates that the port-to-port mutual coupling can be suppressed to -50 dB, which is useful in self-interference cancellation for full-duplex communication systems. Compared with the coupled design, the isolation is significantly enhanced by 43 dB with an inter-element spacing of 0.034lambda.sub.c, where lambda.sub.c is a free-space wavelength at the center operating frequency. Regarding MIMO metrics, the antenna also shows good MIMO diversity performance based on an envelope correlation coefficient and a diversity gain.
Chronic inflammation is the underlying pathological condition that results in fibrotic diseases. More recently, many forms of cancer have also been linked to chronic tissue inflammation. While ...stromal immune cells and myofibroblasts have been recognized as major contributors of cytokines and growth factors that foster the formation of fibrotic tissue, the endothelium has traditionally been regarded as a passive player in the pathogenic process, or even as a barrier since it provides a physical divide between the circulating immune cells and the inflamed tissues. Recent findings, however, have indicated that endothelial cells in fact play a crucial role in the inflammatory response. Endothelial cells can be activated by cytokine signaling and express inflammatory markers, which can sustain or exacerbate the inflammatory process. For example, the activated endothelium can recruit and activate leukocytes, thus perpetuating tissue inflammation, while sustained stimulation of endothelial cells may lead to endothelial-to-mesenchymal transition that contributes to fibrosis. Since chronic inflammation has now been recognized as a significant contributing factor to tumorigenesis, it has also emerged that activation of endothelium also occurs in the tumor microenvironment. This review summarizes recent findings characterizing the molecular and cellular changes in the vascular endothelium that contribute to tissue fibrosis, and potentially to cancer formation.
This study introduces a brand-new swarm-inspired algorithm dubbed dholes hunting-based optimization (DhoH) based on an animal hunting strategy to solve global optimization problems. The technique is ...a brilliant idea for simultaneously finding many local minima. The dhole's hunting strategy is coordinated by members of a swarm, clustering and chasing prey. A clustering approach and finding an optimal global algorithm describe primarily based on gradient approximation. We use four benchmark function datasets to evaluate the DhoH's performance. We compare the achieved results with several previous research from various well-known algorithms. The comparisons demonstrate that DhoH is better than other meta-heuristic algorithms in most cases and determines high-quality solutions with fewer control parameters. Besides, we also explore the application of DhoH in optimizing the decentralized level of Meta-heuristic Proof of Criteria consensus protocol (MPoC) in Blockchain Network to further demonstrate its potential in multi-dimensional problems. The results show the superior effectiveness of DhoH in terms of computational burden and solution precision compared with the existing optimization techniques in the literature.
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