Multiple Boundaries Research Articles

The Impact of Fracture Geometries on Heterogeneity and Accuracy of Upscaled Equivalent Fracture Models

Abstract Fractures are widely distributed in the upper crust, which is important to transport processes in groundwater, geothermal, and hydrocarbon reservoirs. Little attention has been paid to the heterogeneity and accuracy of upscaled equivalent fracture models (EFMs) regarding the complex fracture geometries during numerical reservoir simulation. This paper investigates how fracture geometric properties affect the accuracy of highly heterogeneous EFMs. An ensemble of synthetic fractured porous rocks is generated stochastically with varied fracture length, fracture density, and aperture-length correlation. Each realization is upscaled to EFM with the recently developed multiple boundary method. Flow problems are solved for EFMs and discrete fracture models (DFMs) simultaneously, and their flow rates are compared. The results demonstrate that the heterogeneity of EFMs decreases with the number and length of fractures and increases with the aperture-length correlation component. The flow rates calculated by EFMs fit well with those by DFMs with a slope around 1.08 and R2 coefficient above 0.98. The accuracy of the upscaled EFM decreases when the aperture-length correlation changes from sublinear to linear. The uncertainty of upscaling accuracy decreases with dimensionless fracture density. The findings of this study can help for a better understanding of the effect of the discrete fracture geometries on the performance of upscaled EFMs and choosing the appropriate models for different kinds of fractured reservoirs.

Stick Motions and Grazing Flows in a Double Belt Friction Oscillator

This paper is concerned with the dynamics of a double belt friction oscillator which is subjected to periodic excitation, linear spring-loading, damping force and two friction forces using the flow switchability theory of the discontinuous dynamical systems. Different domains and boundaries for such system are defined according to the friction discontinuity, which exhibits multiple discontinuous boundaries in the phase space. Based on the above domains and boundaries, the analytical conditions of the stick motions and grazing motions are obtained mathematically. There are more theories about such friction oscillators to be discussed in future.

Microfluidics-Assisted Synthesis of Hierarchical Cu2 O Nanocrystal as C2 -Selective CO2 Reduction Electrocatalyst.

Copper-based catalysts have attracted enormous attention due to their high selectivity for C2+ products during the electrochemical reduction of CO2 (CO2 RR). In particular, grain boundaries on the catalysts contribute to the generation of various Cu coordination environments, which have been found essential for C-C coupling. However, smooth-surfaced Cu2 O nanocrystals generally lack the ability for the surface reorganization to form multiple grain boundaries and desired Cu undercoordination sites. Flow chemistry armed with the unparalleled ability to mix reaction mixture can achieve a very high concentration of unstable reaction intermediates, which in turn are used up rapidly to lead to kinetics-driven nanocrystal growth. Herein, the synthesis of a unique hierarchical structure of Cu2 O with numerous steps (h-Cu2 O ONS) via flow chemistry-assisted modulation of nanocrystal growth kinetics is reported. The surface of h-Cu2 O ONS underwent rapid surface reconstruction under CO2 RR conditions to exhibit multiple heterointerfaces between Cu2 O and Cu phases, setting the preferable condition to facilitate C-C bond formation. Notably, the h-Cu2 O ONS obtained the increased C2 H4 Faradaic efficiency from 31.9% to 43.5% during electrocatalysis concurrent with the morphological reorganization, showing the role of the stepped surface. Also, the h-Cu2 O ONS demonstrated a 3.8-fold higher ethylene production rate as compared to the Cu2 O nanocube.

Evolution of eastern segment of the Central India Tectonic Zone: an insight from a magnetotelluric study

SUMMARYThe collision process between the South Indian Block (SIB) and North Indian Block (NIB) resulted in the development of the complex crustal nature of the Central India Tectonic Zone (CITZ). The evolutionary past of CITZ covers a long geological time (∼1000 Ma), which corresponds to the assembly and spreading of Columbia and Rodinia supercontinents. Despite several studies in the western and central parts of the CITZ, the location of the suture zone between the SIB and NIB is still under debate. In addition to that, the crustal structure in the eastern segment of CITZ is yet to be resolved. Therefore, for the first time, a dense station coverage magnetotelluric (MT) study is carried out along a 275 km transect in the eastern segment of CITZ from Pandaria to Rewa. The complexity of the Central Indian Shear (CIS) and Tan Shear Zone (TSZ) are reflected as anomalous phases (beyond 90°) in the MT data. A deep crustal resistivity model derived from 2-D and 3-D inversion of the MT data brought out a high-to-moderate conductivity structure (10–100 Ω-m) in the middle of the surface expressions of CIS and TSZ. The conductive structure could be related to a deformation zone formed by tectonic interaction of the CIS and TSZ or multiple tectonic boundaries in the middle of the CIS and TSZ. The conductive structure observed in the southern limit of the CITZ also may indicate the tectonic boundary between the SIB and NIB. The high conductivity in the deformation zone may be explained by the collision-related metallic rich sediments and/or mylonite associated with interconnected fluids. Moderately conductive vertical features delineated from the MT model correlate with the intrabasinal faults which might have acted as the pathways for Deccan volcanism. This study suggests that the CITZ could have been developed under the transition of oceanic subduction to continental collision processes at multiple geological times.

Dynamics of multiple slip boundaries effect on MHD Casson-Williamson double-diffusive nanofluid flow past an inclined magnetic stretching sheet

The present research paper highlights the effect of multiple slips and inclined magnetic fields on chemically reacting Casson-Williamson with Buongiorno modeled nanofluid flow past a permeable stretching surface. Considered physical factors associated with heat transfer are viscous dissipation, Joule's heating, radiation, and double diffusion effects. The ordinary differential equations (ODEs) are formulated from governing system of highly nonlinear Partial differential equations (PDEs) by a suitable implementation of similarity invariants. The numerical results are obtained by programming the resulting equations in MATLAB software via Runge-Kutta (R-K) fourth-order technique along with the shooting scheme. The graphical illustration provides the behavior of velocity, temperature, and concentration on different non-dimensional parameters. It is worth to notice the slip parameters are greatly analogs with various physical properties of the flow field. The effect of a magnetic parameter ([Formula: see text]), Casson parameter ([Formula: see text]), Williamson parameter ([Formula: see text]), velocity slip effect ([Formula: see text]), and the inclination ([Formula: see text]) on axial velocity are shown graphically. The outstanding agreement is observed after a comparison of numerical outcomes with previously published work. The applied magnetic field and thermal radiation insert more energy into the system which improves the thermal boundary layer.

Electrical conductivity measurements and the nonhomogeneous settling behavior of aqueous suspensions of barite

AbstractUsing electrical conductivity measurements to monitor the local concentration of solids indirectly in settling tests is a practice already explored in the literature. However, since suspended particles may comprise a mixture of solids, a new suspension preparation methodology and calibration procedure were proposed to eliminate the influence of soluble materials on conductivity measurements. This article investigates water‐barite suspensions of 10%, 15%, and 20% v/v in solids. Their settling dynamics resulted in particle Reynolds numbers and Peclet numbers always smaller than 0.0012 and larger than 2100, respectively. Particle agglomeration, multiple boundaries (layers of different maximum local concentrations), channeling (formation of flow paths or channels), and particulate stratification were some phenomena inferred from the results. Hence, this article illustrates that settling behaviors typically seen in solid–liquid mixtures of non‐Newtonian continuous phase can also occur in aqueous suspensions, indicating there are still considerable challenges to understanding the process of gravitational settling.

The body of law: boundaries, extensions, and the human right to physical integrity in the biotechnical age.

The body is precondition of human existence and reference point of many legal norms. But the law only rarely asks what the body is more precisely. Answers might appear evident, but commonsensical conceptions of the body have been cast into doubt by feminists, artists, and disability theorists. Drawing on polyphonic arguments, they suggest social or post-human reconceptualizations with potential legal implications. Civil rights activists call for better protection of cyborg bodies; some legal scholars suggest redefining or even dismissing the right to bodily integrity because of its uncertain foundations. Of particular importance is the question of the boundaries of the body because the legal treatment of prostheses and assistive devices depends on whether they are part of it. This paper analyzes these boundaries with a focus on the right to bodily integrity, in light of the jurisprudence of the European Court of Human Rights and the foundational legal distinction between persons and things. It argues that bodies indeed have multiple boundaries, but none of them qualifies for legal purposes. The law must thus draw normative boundaries. Against the temper of times, it should resort to a naturalistic conception because it accommodates interests of stakeholders in the best way.

Toward an optimized design of the LNG production process: Measurement and modeling of the solubility limits of p-xylene in methane and methane + ethane mixtures at low temperature

Accurate knowledge of the solubility limits of impurities in LNG allows an optimized design of the purification units installed upstream of the liquefaction train and the prevention of solid formation in the main cryogenic heat exchanger that would reduce the performance of the heat exchanger, increase maintenance operations and cause potential safety problems. The solubility of p-xylene in methane and in methane + ethane (5 and 10% mole fraction of ethane) has been measured at p = 5 MPa from T = 183 down to T = 123 K. The experimental results have been obtained by a static-analytic method with analysis of the fluid phase samples by gas chromatography. Solubility of p-xylene in methane and methane + ethane mixtures has been measured for the first time in this temperature range. The obtained data have been modelled by the Soave-Redlich-Kwong (SRK) cubic Equations of State (EoS), tuning pure component parameters, alpha functions, and binary interaction parameters, considering thermodynamic constraints. A robust multi-phase flash algorithm was established for vapor-liquid-liquid-solid (VLLSE) equilibrium by applying phase stability analysis. The revamped thermodynamic methods and data allow accurate prediction of the multiple phase boundaries that can be present when cooling a typical natural gas mixture.

Design of multi-frequency electrical impedance tomography system based on multisine excitation and integer-period sampling

Starting from the principle that the integer-period sampling (IPS) of periodic signals is free of spectrum leakage, in this paper we propose the multisine-IPS theory, deduce theoretically the sampling rate setting formula of multisine-IPS condition for the first time, and build its realization method based on field-programmable gate array (FPGA) plus digital-to-analog converter (DAC) plus analog-to-digital converter (ADC). A new multi-frequency electrical impedance tomography (mfEIT) system based on multisine excitation and its IPS theory is developed, and a dual-target imaging model including a carrot stick and a cucumber stick is designed. The experiments of multi-frequency time-difference imaging and frequency-difference imaging are carried out on the mfEIT system. The experimental results show that the newly-designed mfEIT system can achieve full-band impedance measurements on multiple objective tissue boundary at 20 frequency points (2–997 kHz) within one fundamental period (1 ms), and the structure and position of biological tissues with different electrical properties can also be distinguished from the resulting images. The proposed multisine-IPS theory and its implementation method can complete a full-band impedance measurement within one multisine fundamental period, which lays a theoretical and technical foundation for developing high-speed mfEIT system.

Distributed State Estimation in Digital Distribution Networks Based on Proximal Atomic Coordination

With the emerging digitalization technologies represented by edge computing, distribution networks are gradually transforming into digital distribution networks (DDNs). The realization of edge computing drives the distributed operation of DDNs, where multiple areas exchange boundary information through edge computing devices. Benefitting from the data acquisition and computing capacity of edge computing devices, it is feasible to perform accurate and real-time state estimation on the edge side. Aiming at the state perception with edge computing devices in DDNs, this paper proposes a distributed state estimation (DSE) method based on the proximal atomic coordination (PAC) algorithm. Firstly, based on convex relaxation optimization, the state estimation model is converted into a positive semidefinite programming model to solve the nonconvexity caused by nonlinear measurements, which ensures the accuracy and convergence of state estimation. Then, a DSE method based on the PAC algorithm is proposed to exchange information of each area, which reduces the computation time and realizes the efficient state estimation on the edge side. The model and the effectiveness of the proposed method are numerically demonstrated on the modified PG&E 69-node system and the test case from a practical pilot in Guangzhou, China.

A Mechanics Model in Design of Flexible Nozzle with Multiple Movable Hinge Boundaries

A Mechanics Model in Design of Flexible Nozzle with Multiple Movable Hinge Boundaries

Remembering Pokémania: Memory, Cognitive Assemblages, and Augmented Reality

Introduced in July 2016, Pokémon GO is widely considered the killer app for contemporary augmented reality. Popular attention to the game has waned in recent years, but Pokémon GO remains enormously successful in terms of both player base and revenue generation. Whether individuals experienced the game for a short time or remain dedicated hardcore players, Pokémon GO exists as memories of time and place, imbuing familiar sites and routes with new meaning and temporal connection. Attending to these complex interrelationships of place, space, mobility, humans, technologies, infrastructures, environments, and memory, we situate Pokémon GO as what Hayles (2016) calls a cognitive assemblage—sociotechnical systems of interconnectivity in which cognition is an exteriorized process occurring across multiple levels, sites, and boundaries. In turn, we conceptualize cognition (and specifically memory) not as confined within a delimited hominid body, but instead operating through contextual relations, at multiple sites, and in a constant state of becoming. By reflecting on our own experiences as part of the distributed memory of Pokémon GO, we situate memory as momentary convergence of signals made possible by infrastructures, inscribed on servers and silicon, and made part of algorithmic suggestion and learning AI. Additionally, our own memories and experiences serve to highlight the experiential complexity of cognitive assemblages in relation to structures of feeling, as well as new temporal and spatial relations.

‘Who Is My Research for?’: Researcher Perceptions of the Research–Practice Relationship

AbstractThis study investigated second language (L2) researchers’ perceptions of the research–practice relationship. While research use (or lack thereof) in the classroom has been debated by researchers for decades, researchers have rarely investigated themselves as stakeholders in the relationship. However, it is vital to know researchers’ approaches to the issue so that collaborative researcher-practitioner relationships may be fostered. Hence, the current survey study explored: (a) L2 researchers’ identities; (b) their perceptions of the research–practice relationship; and (c) predictors of their perceptions. Participants were 217 researchers from 25 countries with 31 different first-language backgrounds. The results showed that L2 researchers’ identities often crossed multiple boundaries, as L2 learners, teachers, as well as researchers. A factor analysis showed that researchers held distinct beliefs for their own research (individual self) and for researchers in general (collective self). The regression models revealed that L2 teaching experience, pre-service teacher training experience, and institutional rewards positively predicted researchers’ perceptions of L2 practice. We argue that it is largely researchers’ responsibility to facilitate the research–practice dialogue.

Impact of Joule heating and multiple slips on a Maxwell nanofluid flow past a slendering surface

This manuscript presents a study of three-dimensional magnetohydrodynamic Maxwell nanofluid flow across a slendering stretched surface with Joule heating. The impact of binary chemical reactions, heat generation, thermal radiation, and thermophoretic effect is also taken into consideration. The multiple slip boundary conditions are utilized at the boundary of the surface. The appropriate similarity variable is used to transfer the flow modeled equations into ODEs, which are numerically solved by the utilization of the MATLAB bvp4c algorithm. The involved parameter’s impact on the concentration, velocity, and temperature distribution are scrutinized with graphs. The transport rates (mass, heat) are also investigated using the same variables, with the results reported in tabulated form. It is seen that the fluid relaxation, magnetic, and wall thickness characteristics diminish the velocities of fluid. Further, the velocity, concentration, and temperature slip parameters reduce the velocities of fluid, temperature, and concentration distribution. The results are compared to existing studies and shown to be in dependable agreement.

Influence of the induced magnetic field on second-grade nanofluid flow with multiple slip boundary conditions

The present research focuses on the MHD second-grade nanofluid flow with induced magnetic field and viscous dissipation over an exponentially stretching surface. The solutal and thermal energy equations are analyzed in the presence of thermophoretic effect and variable thermal conductivity. The solutal and thermal slip boundary conditions are imposed on the surface of the sheet. In the mathematical modeling, the Brownian motion, and thermophoresis consequences are also discussed. The physical appearance of the induced magnetic field on the second-grade nanofluid is the central aim of this investigation. The mathematical flow model which is in the form of nonlinear PDEs is transformed into the system of couple ODEs by the usage of suitable similarity variables. These couple equations are tackled numerically with the help Bvp4c Matlab approach. The illustration of parameters on the flow model is discussed via graphs and tables. It is noted that the induced magnetic field profile and velocity of fluid intensify for the stronger values of second-grade parameter. Further, the numerical result shows that skin friction rate boosts via greater estimation of second-grade parameter and it reduces for magnetic Prandtl number.

Differential Quadrature Method for Partial Differential Dynamic Equations of Beam–Ring Structure

The partial differential equations of a circular truss beam–ring structure with antenna extended and locked are studied. The differential quadrature method is used to discretize the differential equations and boundary conditions in a spatial domain. The method of equation substitution and the method of boundary conditions are directly substituted into the internal discrete equations and are used to deal with the boundary conditions. The natural frequency of the beam–ring structure is calculated and verified by the natural frequency obtained by Galerkin’s method in paper (Wu et al., “Vibration Frequency Analysis of Beam–Ring Structure for Circular Deployable Truss Antenna,” International Journal of Structural Stability and Dynamics, Vol. 19, No. 2, 2019, Paper 1950012). To solve the problem when there are multiple mixed boundary conditions at a point, the method of replacing the internal discrete equation with boundary conditions is not unique and the solution accuracy is low, so the differential algebraic equations are used to replace the boundary conditions directly into the internal discrete equation, and the iterative scheme is established. Finally, the fourth-order-Runge–Kutta method is used to solve the problem. Based on the numerical results, the two methods are compared by using a 200s time history diagram, 10,000s displacement constraint diagram, 10,000s velocity constraint diagram, etc. The results show that the mixed boundary conditions can be solved more accurately by using differential algebraic equations, and the stability of constraints can be maintained under long-time simulation.

Boundary-spanning coordination: Insights into lateral collaboration and lateral alignment in multinational enterprises

Interorganizational boundary spanning between multinational enterprises requires substantive internal “lateral collaboration” and “lateral alignment.” However, how actors coordinate laterally between multiple nodes and across multiple boundaries for interorganizational boundary spanning is unclear. This qualitative study of a large multinational demonstrates how actors collectively build and maintain interorganizational relationships through collective boundary spanning. To coordinate this activity, actors strategize and map contributors for collective action and then synchronize their communication and problem-solving to ensure lateral collaboration and alignment. This article contributes to the extant literature by a providing a framework depicting how boundary-spanning coordination leads to lateral collaboration and lateral alignment.

Microstructural Evolution, Hardness, and Strengthening Mechanisms in SLM AlSi10Mg Alloy Subjected to Equal-Channel Angular Pressing (ECAP).

The AlSi10Mg alloy is characterized by a high strength-to-weight ratio, good formability, and satisfying corrosion resistance; thus, it is very often used in automotive and aerospace applications. However, the main limitation of using this alloy is its low yield strength and ductility. The equal-channel angular pressing is a processing tool that allows one to obtain ultrafine-grained or nanomaterials, with exceptional mechanical and physical properties. The purpose of the paper was to analyze the influence of the ECAP process on the structure and hardness of the AlSi10Mg alloy, obtained by the selective laser melting process. Four types of samples were examined: as-fabricated, heat-treated, and subjected to one and two ECAP passes. The microstructure analysis was performed using light and electron microscope systems (scanning electron microscope and transmission electron microscope). To evaluate the effect of ECAP on the mechanical properties, hardness measurements were performed. We found that the samples that underwent the ECAP process were characterized by a higher hardness than the heat-treated sample. It was also found that the ECAP processing promoted the formation of structures with semicircular patterns and multiple melt pool boundaries with a mean grain size of 0.24 μm.

Alternating current losses in superconducting circular/stacked coils used in energy storage systems

Large transient currents and magnetic intensities are generally encountered by the superconducting magnetic energy storage systems thereby resulting in AC losses that occur during the charging/discharging durations thus, estimation of such heat loads must be known before the actual designing of cooling arrangements. Various analytical methods are accessible to approximate such losses however, not adequate to predict the same accurately. In this work, an extensive numerical model has been established to estimate AC losses among the stacked/circular coils used in superconducting magnetic energy storage applications under various transport currents (150 A to 225 A) and strong fields (1e5 A/m to 4e5 A/m). A homogenization method has been incorporated into the model stacks of high-temperature superconducting tapes (Ic=330 A @ 0 T self-field) instead of an actual multi-turned coil. The modeling has been done to achieve an anisotropic bulk equivalent for the stack keeping the overall electromagnetic identity of the model the same as that of the original multi-turned stacked geometry such that it eliminates the multiple boundaries among the geometrical layout consisting of metallic, insulating, superconducting, and substrate layers. In the present numerical model, E-J power law has been used which has considered the overcritical current densities. The results showed that transport currents affect AC losses significantly and as it approaches critical current, the AC losses increased abruptly. The novelty of the work is in the consideration of external fields which are present beforehand the actual current transportation through the coils using the homogenization approach. It has been concluded that perpendicular fields have a significant effect on AC losses compared to parallel fields. Considering the fact of high computational speed, this model can further be extended to solve more complex transient characteristics of HTS motors or generators. It has been concluded that the homogenized model can estimate average AC loss two orders faster than the original stacked model.

Atomistic Simulations of Twin Boundary Effect on the Crack Growth Behaviour in BCC Fe

In this paper, the effect of twin boundaries on the crack growth behaviour of single crystal BCC Fe has been investigated using molecular dynamics simulations. The growth of an atomically sharp crack with an orientation of (111)$<$110$>$ (crack plane/crack front) has been studied under mode-I loading at constant strain rate. In order to study the influence of twin boundaries on the crack growth behaviour, single and multiple twin boundaries were introduced perpendicular to crack growth direction. The results indicate that the (111)$<$110$>$ crack in single crystal BCC Fe grows in brittle manner. However, following the introduction of twin boundaries, a noticeable plastic deformation has been observed at the crack tip. Further, increasing the number of twin boundaries increased the amount of plastic deformation leading to better crack resistance and high failure strains. Finally, an interesting relationship has been observed between the crack growth rate and flow stress.