Parallel Components Research Articles

Nematic liquid crystals blended ferroelectric nanoparticles (BaTiO3): A perspective way for improving the response time and photoluminescence for electro-optical devices

We represent a detailed study of a dilute suspension of ferroelectric barium titanate nanoparticles (BaTiO3 NPs) in a nematic matrix by probing dielectric, electro-optical, and optical properties. The strong local surface electric field (order of ∼1010 Vm−1) of BaTiO3 produces pseudonematic domains within the matrix, which renders an enhancement in both the perpendicular and parallel components of dielectric permittivity that increases with increasing NP concentrations. Due to changes in molecular ordering, the dielectric anisotropy of pristine nematic increases by 10.7%, 24.6%, and 33.3% after the addition of 0.1, 0.3, and 0.5 wt. % BaTiO3 NPs with subsequent lowering in threshold voltage. Interestingly, the nematic-BaTiO3 blended cells showed 23.2%, 49.3% and 67.6% faster electro-optic response for 0.1, 0.3, and 0.5 wt. % of NPs, respectively. In the nematic matrix, BaTiO3 NPs act like chromophores resulting in a bathochromic shift in fluorescence spectra due to an enhanced degree of conjugation. This investigation reveals that the ferroelectric BaTiO3 NPs-nematic composites will be suitable for superior fluorescent electro-optical devices.

The incompressible energy cascade rate in anisotropic solar wind turbulence

Context. The presence of a magnetic guide field induces several types of anisotropy in solar wind turbulence. The energy cascade rate between scales in the inertial range depends strongly on the direction of this magnetic guide field, splitting the energy cascade according to the parallel and perpendicular directions with respect to magnetic guide field. Aims. Using more than two years of Parker Solar Probe (PSP) observations, the isotropy and anisotropy energy cascade rates are investigated. The variance and normalized fluctuation ratios, the kinetic and magnetic energies, and the normalized cross-helicity and residual energy are studied. The connection between the heliocentric distance, the local temperature of the plasma, and the energy cascade components is made. Methods. Using exact relations for fully developed incompressible magnetohydrodynamic (MHD) turbulence, the incompressible energy cascade rate is computed. In particular, using the isotropy and 2D and slab assumptions, the isotropic, perpendicular, and parallel energy cascade rate components are estimated. Results. The variance anisotropy ratios, for both velocity and magnetic fields, do not exhibit a dependence with respect to the heliocentric distance r between 0.2 and 0.8 au. While the velocity normalized fluctuation ratio shows a dependence with r, the magnetic normalized fluctuation ratio does not. A strong correlation between the isotropic and anisotropic energy cascade rates and the temperature is found. A clear dominance of the perpendicular cascades over the parallel cascades as PSP approaches the Sun is observed. A dominant 2D cascade and/or geometry over the slab component in slow solar wind turbulence in the largest MHD scales is observed.

An adapted social communication intervention at home and education to promote social communication change in children with severe autism: the PACT-G RCT

Background Prior evidence suggests that behaviours closely related to the intervention delivered for autism are amenable to change, but it becomes more difficult when generalising treatment effects beyond that immediate context. Objectives The objectives were (1) to test an early autism social communication intervention designed to promote child social communication change in the naturalistic contexts of both home and education, with an additive effect on overall child symptom outcomes, and (2) to conduct a mechanistic study investigating the transmission of treatment effects within and across contexts to an overall treatment effect. Design The trial was a three-site, parallel-group, randomised controlled trial of the experimental treatment plus treatment as usual and treatment as usual alone. The primary intention-to-treat analysis used analysis of covariance. The mechanism analysis used regression models to test mediation of the primary outcome by parent–child and education staff (learning support assistant)–child social interactions. Setting The study took place in three urban/semiurban regions in Manchester, Newcastle upon Tyne and London. Participants Children aged 2–11 years who met the criteria for severe autism. Interventions The Preschool Autism Communication Trial was adapted to parallel components within home and educational settings using in-person and remote delivery. Treatment as usual was the control condition. Main outcome measures The primary outcome was autism symptoms on the Autism Diagnostic Observation schedule-2. The secondary outcomes were Brief Observation of Social Communication Change, dyadic social interaction between child and parent or learning support assistant, reported language, functional outcome and reduction in child disruptive behaviour. Outcomes were measured at baseline and at the 12-month end point in all settings; interim mechanism measurements were taken at 7 months. Results Participants (n = 249; 122 in the PACT-G group and 127 in the treatment-as-usual group; 51 were female and 197 were male) received a median of 10 (interquartile range 8–12) sessions at home and 8 (interquartile range 5–10) sessions in an educational setting. We found no significant treatment effects on the end-point Autism Diagnostic Observation Schedule-2 primary outcome (–0.04, 95% confidence interval –0.26 to 0.18; p = 0.734), on the end-point Brief Observation of Social Communication Change secondary outcome (–0.03, 95% confidence interval –0.31 to 0.25; p = 0.85) or on language, repetitive behaviour, adaptive behaviour and child well-being. We did find significant treatment effects on dyadic interactions (increased parent synchronous response 0.54, 95% confidence interval 0.39 to 0.69; p = 0.001); child initiations with a parent (0.27, 95% confidence interval 0.12 to 0.41; p = 0.001); learning support assistant synchronous response (0.32, 95% confidence interval 0.14 to 0.49; p = 0.001); child initiations with a learning support assistant (0.21, 95% confidence interval 0.06 to 0.36; p = 0.005); and unblinded measures of improved parental well-being and child disruptive behaviour across home and educational settings. Adult (parent/learning support assistant) synchronous responsiveness in a home/education setting improved child dyadic social initiation. The child dyadic social initiation was also associated with child symptoms on researcher Brief Observation of Social Communication Change. Limitations The delivered sessional dosage was 83% of that planned in the home setting and 67% in the educational setting, with 5.5% of home sessions and 5% of educational sessions deemed ‘unacceptable’, particularly for remote delivery. A change of therapy learning support assistant was experienced by over one-third of children by the mid-point of the trial, by another third by the end point, and by one-fifth at both points. Conclusions The multicomponent Paediatric Autism Communication Trial – Generalised (PACT-G) treatment for a child in a home or educational setting did not produce the hypothesised improvement in child autism symptomatology or adaptive behaviour, but did produce significant improvements in proximal adult–child reciprocal dyadic communication. Future work Future work will involve building on these results towards a further understanding of delivery options, dosage and multicomponent extension of social communication interventions for young children with autism in naturalistic settings. Trial registration Current Controlled Trials ISRCTN25378536. Funding This project was funded by the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health and Care Research (NIHR) partnership. This was also part funded by the NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London. This will be published in full in Efficacy and Mechanism Evaluation; Vol. 9, No. 3. See the NIHR Journals Library website for further project information.

Effects of Pressure Anisotropy on the Geometry of Magnetic Flux Rope

This paper aims to examine the effects of pressure anisotropy on the geometry of magnetic flux rope using the newly developed two-dimensional magnetohydrostatic reconstruction associated with pressure anisotropy. A small-scale magnetic flux rope observed by the Magnetospheric Multiscale mission, in the magnetosheath reconnection outflow during an outbound magnetopause crossing, is demonstrated. At the center of the flux rope, the magnetic field strength was enhanced with decreasing plasma pressure. The entire flux rope was mostly occupied by the pressure anisotropy of p ⊥ > p ∥, where the subscripts ∥ and ⊥ denote the components parallel and perpendicular to the local magnetic field, respectively. The estimated aspect ratio of the width to the length of the flux rope from reconstruction was ∼0.326 for p ⊥ > p ∥ and ∼0.389 for isotropic pressure. By comparing the magnetic field map from the isotropic Grad–Shafranov reconstruction, the results show for p ⊥ > p ∥ that (1) the width of the flux rope is reduced, leading to a small aspect ratio of the flux rope, and (2) the circular field line of the flux rope is contracted. Moreover, an experiment is conducted for p ∥ > p ⊥ by exchanging p ⊥ and p ∥ of the flux rope, for which the isotropic pressure is less affected. The experimental results indicate that the effects of p ∥ > p ⊥ on the geometry of the flux rope are opposite to that of p ⊥ > p ∥. The overall finding may provide new insight into charged particle acceleration within magnetic flux ropes/islands in anisotropic plasmas.

DC and optical signatures of the reconstructed Fermi surface for electrons with parabolic band

We study the main intra-band and inter-band transport properties at zero temperature of free electron-like system undergoing a topological reconstruction of the Fermi surface for the two-dimensional and three-dimensional case. The calculated intra-band properties include the single-particle density of states, the total and the effective concentrations of electrons and the thermopower. As for the inter-band case, the real part of the conductivity has been calculated within the vanishing inter-band relaxation approximation as a function of the incident photon energy. Within this approach, it is shown that the optical conductivity has a nonvanishing component parallel to the reconstruction wave vector and the shape which depends on the value of the Fermi energy. Each dimensionality has its particular features in the transport quantities presented in the paper, which are discussed and compared with those in the free electron scenario. Finally, we identify the signature of the topological reconstruction of the Fermi surface in the intra-band and inter-band transport functions.

Lower‐Hybrid Wave Structures and Interactions With Electrons Observed in Magnetotail Reconnection Diffusion Regions

AbstractWe investigate waves close to the lower‐hybrid frequency in 12 magnetotail reconnection electron diffusion region (EDR) events with guide field levels of near‐zero to 30%. In about half of the events, the wave vector has a small component along the current sheet normal, consistent with known lower‐hybrid drift wave properties, but the perpendicular magnetic field fluctuations can be comparable or greater than the parallel component, a feature unique to the waves inside and adjacent to EDRs. Another new wave property is that the wave vector has a significant component along the current sheet normal in some events and completely along the normal for one event. In 1/4 of the events, the term has a significant contribution to the wave electric field, possibly a feature of lower‐hybrid waves more likely to exist in the diffusion region than further away from the X‐line. Electron temperature variations are correlated with the wave potential, due to wave electric field acceleration and crossings at the corrugated separatrix region with different amounts of mixing between reconnection inflowing and outflowing populations. The latter also leads to the anti‐correlation between parallel and perpendicular temperature components. Using four‐spacecraft measurements, the magnetic field line twisting is demonstrated by the correlated fluctuations in and . The lower‐hybrid wave in the EDR of weak guide field reconnection may be generated near separatrices and penetrate to the mid‐plane or locally generated, and the latter possibility is beyond the prediction of previous reconnection simulations.

P 11 Motor adaptation learning and the effects of reinforcement in the acute phase post-stroke

Introduction: Motor recovery after stroke relies on reorganization processes that mainly occur within the critical period , a time-limited window of heightened neuronal plasticity in the first few weeks after stroke 1 . These processes are assumed to partly depend on training-dependent motor learning, which may assist in establishing new motor control policies. While chronic stroke patients have been shown to exhibit motor adaptation in response to perturbations in a reinforcement-dependent fashion 2 , it remains unclear if this is also true early after stroke. Therefore, we probed whether acute stroke patients can perform motor adaptation and if motor adaptation can be enhanced by monetary reinforcement. Patients & Methods: Hospitalized patients within the first two weeks after ischemic stroke suffering from hemiparesis and an age-matched healthy control group performed a joystick-based visuomotor adaptation task. Using a crossover design, subjects received neutral or performance-based reinforcement feedback in the form of monetary reward and punishment during adaptation learning. Results: Acute stroke patients exhibited motor adaptation with their paretic hand ( p <.01) and retained the novel learned motor control policies. Patients showed increased learning rates after offline consolidation in the retention period ( p <.05), whereas control subjects featured earlier improvements in learning rates during the learning period ( p <.05). While monetary reward and punishment feedback amplified motor adaptation compared to the neutral condition ( p <.05), reward seemed to be a more suitable framework to support visuomotor learning. Conclusion: We demonstrate for the first time that acute stroke patients can perform motor adaptation by rapidly adjusting motor control policies. From a mechanistic perspective, motor adaptation is often conceptualized as a dual-rate model 3 , including two parallel learning components acting on different timescales. Patients seem to rely on a slower learning component more heavily, while learning of controls aligns stronger with the fast component. The former is associated with slower unlearning, which may benefit effective motor rehabilitation as newly adapted motor control policies can be retained over a prolonged period and thus integrated into daily life. While both reward and punishment enhanced motor adaptation compared to neutral feedback, reward seemed to elicit the most beneficial effects on motor learning early after stroke. In summary, our findings suggest that motor adaptation may enhance relearning of motor control policies and might thus amplify recovery in a reinforcement-dependent fashion. These findings may impact future treatment protocols aiming at improving motor function in the critical period after stroke. References 1 Krakauer, 2015. Oxford Textbook of Neurorehabilitation, 55–64. 2 Quattrocchi et al., 2017. J Neurol Neurosurg Psychiatry, 88(9), 730–736. 3 Smith et al., 2006. PLoS Biol, 4(6), e179.

The current state of the theory of Pc1 range ULF pulsations in magnetospheric plasma with heavy ions: A review

The review considers the current state of the theory of short-period ULF waves in plasma with admixture of heavy ions (ions whose mass significantly exceeds the mass of protons). The presence of heavy ions influences the spectrum and propagation characteristics of waves in Pc1 range. We examine elements of the theory of quasi-parallel and quasi-perpendicular short-period ULF waves. It is usually suggested that quasi-parallel ion-cyclotron waves have a left circular polarization. Quasi-perpendicular ion-ion hybrid waves have linear polarization and can be poloidal and toroidal. We discuss the theory of an equatorial resonator for Pc1 waves and determine its size from the density of heavy ions. In the radial direction, the waves can be locked in the vicinity of the plasmapause or in the region of a local minimum in the density of heavy ions. The equatorial resonator for arbitrary values of the wave vector components is considered. We note that ion-ion hybrid waves, in contrast to Alfvén waves, have a large parallel component of the magnetic field.

Современное соcтояние теории УНЧ-пульсаций диапазона Рс1 в плазме магнитосферы с тяжелыми ионами: обзор

The review considers the current state of the theory of short-period ULF waves in plasma with admixture of heavy ions (ions whose mass significantly exceeds the mass of protons). The presence of heavy ions influences the spectrum and propagation characteristics of waves in Pc1 range. We examine elements of the theory of quasi-parallel and quasi-perpendicular short-period ULF waves. It is usually suggested that quasi-parallel ion-cyclotron waves have a left circular polarization. Quasi-perpendicular ion-ion hybrid waves have linear polarization and can be poloidal and toroidal. We discuss the theory of an equatorial resonator for Pc1 waves and determine its size from the density of heavy ions. In the radial direction, the waves can be locked in the vicinity of the plasmapause or in the region of a local minimum in the density of heavy ions. The equatorial resonator for arbitrary values of the wave vector components is considered. We note that ion-ion hybrid waves, in contrast to Alfvén waves, have a large parallel component of the magnetic field.

Predicting vacant parking space availability zone-wisely: a hybrid deep learning approach

Precise prediction on vacant parking space (VPS) information plays a vital role in intelligent transportation systems for it helps drivers to find the parking space quickly to reduce unnecessary waste of time and excessive environmental pollution. By analyzing the historical zone-wise VPS data, we find that for the number of VPSs, there is not only a solid temporal correlation within each parking lot, but also an obvious spatial correlation among different parking lots. Given this, this paper proposes a hybrid deep learning framework, known as the dConvLSTM-DCN (dual Convolutional Long Short-Term Memory with Dense Convolutional Network), to make short-term (within 30 min) and long-term (over 30 min) predictions on the VPS availability zone-wisely. Specifically, the temporal correlations of different time scales, namely the 5-min and daily-wise temporal correlations of each parking lot, and the spatial correlations among different parking lots can be effectively captured by the two parallel ConvLSTM components, and meanwhile, the dense convolutional network is leveraged to further improve the propagation and reuse of features in the prediction process. Besides, a two-layer linear network is used to extract the meta-info features to promote the prediction accuracy. For long-term predictions, two methods, namely the direct and iterative prediction methods, are developed. The performance of the prediction model is extensively evaluated with practical data collected from nine public parking lots in Santa Monica. The results show that the dConvLSTM-DCN framework can achieve considerably high accuracy in both short-term and long-term predictions.

UWB Fastly–Tunable 0.5–50 GHz RF Transmitter Based on Integrated Photonics

Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e., on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5–50 GHz without any parallelization of narrower-band components and with fast tuning (<200 μs). This first implementation represents a breakthrough in microwave photonics.

Evolution of Vibrational Spectra in the Manganese-Silicon Clusters Mn2Sin, n = 10, 12, and 13, and Cationic [Mn2Si13

A comparison of DFT-computed and measured infrared spectra reveals the ground state structures of a series of gas-phase silicon clusters containing a common Mn2 unit. Mn2Si12 and [Mn2Si13]+ are both axially symmetric, allowing for a clean separation of the vibrational modes into parallel (a1) and perpendicular (e1) components. Information about the Mn–Mn and Mn–Si bonding can be extracted by tracing the evolution of these modes as the cluster increases in size. In [Mn2Si13]+, where the antiprismatic core is capped on both hexagonal faces, a relatively simple spectrum emerges that reflects a pseudo-D6d geometry. In cases where the cluster is more polar, either because there is no capping atom in the lower face (Mn2Si12) or the capping atom is present but displaced off the principal axis (Mn2Si13), the spectra include additional features derived from vibrational modes that are forbidden in the parent antiprism.

Stochastic Comparisons of Parallel and Series Systems Comprising Multiple-Outlier Scale Components

Stochastic Comparisons of Parallel and Series Systems Comprising Multiple-Outlier Scale Components

Impacts of Coastal Terrain on Warm-Sector Heavy-Rain-Producing MCSs in Southern China

Abstract Warm-sector heavy rainfall in southern China refers to the heavy rainfall that occurs within a weakly forced synoptic environment under the influence of monsoonal airflows. It is usually located near the southern coast and is characterized by poor predictability and a close relationship with coastal terrain. This study investigates the impacts of coastal terrain on the initiation, organization, and heavy rainfall potential of MCSs in warm-sector heavy rainfall over southern China using quasi-idealized WRF simulations and terrain-modification experiments. Typical warm-sector heavy rainfall events were selected to produce composite environments that forced the simulations. MCSs in these events all initiated in the early morning and developed into quasi-linear convective systems along the coast with a prominent back-building process. When the small coastal terrain is removed, the maximum 12-h rainfall accumulation decreases by ∼46%. The convection initiation is advanced ∼2 h with the help of orographic lifting associated with flow interaction with the coastal hills in the control experiment. Moreover, the coastal terrain weakens near-surface winds and thus decreases the deep-layer vertical wind shear component perpendicular to the coast and increases the component parallel to the coast; the coastal terrain also concentrates the moisture and instability over the coastal region by weakening the boundary layer jet. These modifications lead to faster upscale growth of convection and eventually a well-organized MCS. The coastal terrain is beneficial for back-building convection and thus persistent rainfall by providing orographic lifting for new cells on the western end of the MCS, and by facilitating a stronger and more stagnant cold pool, which stimulates new cells near its rear edge.

The Effect of Current on Magnetic Null Topology during Turbulent Reconnection

Abstract Using data from the Cluster mission and the First-Order Taylor Expansion method, we investigate the spiral magnetic nulls nested in the diffusion region of turbulent reconnection in the magnetotail. We particularly focus on the relation between the magnetic null topologies and currents, which can be decomposed into a component perpendicular to spine (j ⊥) and a component parallel to spine (j ∥). We find that (1) the currents surrounding the spiral nulls are mainly contributed by j ∥; (2) the null with large (j ⊥) and small spine-fan angle (θ), which are predicted by traditional linear theory, does not exist in the turbulent diffusion region; (3) the background current j b plays an important role in determining the direction of the currents around spiral nulls and consequently the orientation of the magnetic null structures; and (4) the spiral nulls with strong current (large magnitude j ) tend to degenerate into 2D configurations, whereas the nulls with weak currents retain the 3D features. Since the spiral magnetic nulls are crucial for the energy dissipation during the turbulent reconnection process, all of these results can provide important information for better understanding 3D turbulent reconnection.

Oscillating magnetized hybrid stars under the magnifying glass of multimessenger observations

ABSTRACTWe model neutron stars as magnetized hybrid stars with an abrupt hadron–quark phase transition in their cores, taking into account current constraints from nuclear experiments and multimessenger observations. We include magnetic field effects considering the Landau level quantization of charged particles and the anomalous magnetic moment of neutral particles. We construct the magnetized hybrid equation of state, and we compute the particle population, the matter magnetization and the transverse and parallel pressure components. We integrate the stable stellar models, considering the dynamical stability for rapid or slow hadron–quark phase conversion. Finally, we calculate the frequencies and damping times of the fundamental and g non-radial oscillation modes. The latter, a key mode to learn about phase transitions in compact objects, is only obtained for stars with slow conversions. For low magnetic fields, we find that one of the objects of the GW170817 binary system might be a hybrid star belonging to the slow extended stability branch. For magnetars, we find that a stronger magnetic field always softens the hadronic equation of state. Besides, only for some parameter combinations a stronger magnetic field implies a higher hybrid star maximum mass. Contrary to previous results, the incorporation of anomalous magnetic moment does not affect the studied astrophysical quantities. We discuss possible imprints of the microphysics of the equation of state that could be tested observationally in the future, and that might help infer the nature of dense matter and hybrid stars.

Genetic-algorithm retrieval of the molecular alignment distribution with high-order harmonics generated from transiently aligned CO2 molecules

Using genetic algorithm, we propose a method to retrieve the alignment distribution of transiently aligned ${\mathrm{CO}}_{2}$ molecules from the high-order harmonic generation (HHG) spectra. The retrieval method is based on the quantitative rescattering (QRS) model where averaged photorecombination transition dipole can be factored out from the parallel (or perpendicular) harmonic spectra after the propagation of the harmonic fields in the gas medium. We examine how the retrieved alignment distributions are affected by uncertainty in alignment-dependent ionization probability and on multiple orbital contribution to the HHG. We further confirm that alignment distribution is more accurately retrieved by using the minima in the HHG spectra driven by a long-wavelength laser. In addition, we show that earlier experimental data on the ratios between the perpendicular and the parallel HHG components of aligned ${\mathrm{CO}}_{2}$ molecules are in better agreement with the QRS model if the macroscopic propagation and multiple orbital interference are included in the theoretical calculation.

Optimal Precursors Identification for North Atlantic Oscillation Using the Parallel Intelligence Algorithm

The North Atlantic Oscillation (NAO) with abnormal sea level pressure (SLP) differences influence the westerly wind strength and storm tracks in the North Atlantic, which further affects the winter climate in the northern hemisphere. The predictability of NAO has become an important area of climate research in recent years. The identification of optimal precursors (OPRs) would help to investigate the dynamics of atmospheric and oceanic motions, as well as the nonlinear characteristic. The conditional nonlinear optimal perturbation (CNOP) method has been widely used in research on the OPR of the climatic event to explore which kind of initial perturbation is most likely to trigger climate events. However, the previous works on NAO’s OPR are based on a simple ideal model, which cannot describe the evolution process of NAO. Moreover, the commonly used algorithms that rely on the adjoint model are not suitable for the large complicated numerical models that do not have corresponding adjoint models, like Community Earth System Model (CESM). To break through the limitation, this paper proposes the parallel principal component analysis (PCA)-based particle swarm optimization (PSO) and genetic algorithm (GA) hybrid algorithm (PGAPSO) algorithm to identify the OPR of NAO using CESM. For different initial conditions, OPRs identified by the proposed method can always make the basic state develop into NAO events with corresponding phases. Compared with other adjoint-free approaches, the proposed method has relatively better fitness values and more mature patterns. The results also reveal that the proposed method can avoid falling into a local optimum and has strong robustness. In terms of performance, the proposed method searches in feature space with a much lower number of dimensions, thus improving efficiency. In addition, the proposed method is accelerated with multiple parallel frameworks to enhance performance, and it achieves the speedup ratio of 40.2.

Performance Prediction of Refractured Wells Based on Embedded Discrete-Fracture Modeling Method

In unconventional reservoirs, the production rate of the initially fractured well will decrease rapidly as the development proceeds. In order to maintain economic well productivity of the initial fracture, the industries can create refractures to prevent the well production rate from decreasing. However, the production of the initial fracture can induce the stress field to reorientate, which will cause the refracture to propagate along a different direction from the initial fracture. Thus, the refracturing treatment can result in a complex fracture system which raises a stringent challenge for one to evaluate the performance of the refractured well. In this paper, the authors utilize the embedded discrete fracture model (EDFM) to characterize the performance of the refractured wells. The calculated results in this paper show that, for the same equivalent matrix permeability, a larger permeability component parallel to the initial fracture can lead to a higher increase ratio of the refracturing treatment but lower cumulative production. If the reoriented section of the refracture is orthogonal to the initial fracture, the productivity of the refracture system can be the highest. The length of the reoriented section plays a more important role than the length of the initially oriented section in influencing the refracturing treatment. The refracturing treatment can lead to a higher increase of cumulative production if the initial fracture has a lower permeability.

Coexistence of Flexo- and Ferro-Electric Effects in an Ordered Assembly of BaTiO3 Nanocubes.

It has been reported that the flexoelectric effect could be dominant in the nanoscale. The discrepancy between theory and experiments on the frequency dependence of the dielectric constant of an ordered assembly of BaTiO3 nanocubes is nearly resolved by assuming the coexistence of flexo- and ferro-electric effects. Although flexoelectric polarizations perpendicular to the applied alternating electric field contribute to the dielectric constant, those parallel to the electric field do not contribute because the magnitude of the flexoelectric polarization does not change due to the mismatch of strain at the interface of the nanocubes. On the other hand, some dielectric response is possible for the ferroelectric component of the polarization parallel to the electric field.