Product Of Currents Research Articles

Table-Based Direct Power Control for Three-Phase AC/DC Converters Under Unbalanced Grid Voltages

This paper proposes a simple but effective direct power control (DPC) strategy for three-phase ac/dc converters operating under unbalanced grid voltage conditions. An extended instantaneous power theory is adapted and applied in the proposed DPC, where the reactive power is expressed in the form of dot product of grid currents and delayed grid voltages. Neither complicated positive/negative sequence extraction of grid voltage/current nor power compensation is required. The switching table suitable to control both active power and reactive power is constructed by analyzing the influence of each converter voltage vector on power slopes. Compared to conventional table-based DPC using original pq theory, the proposed DPC achieves constant active power and reactive power as well as sinusoidal grid currents, while maintaining the simplicity and robustness as much as possible. The presented simulation and experimental results confirm the theoretical study and the effectiveness of the proposed method.

Hölder Singular Metrics on Big Line Bundles and Equidistribution

We show that normalized currents of integration along the common zeros of random $m$-tuples of sections of powers of $m$ singular Hermitian big line bundles on a compact K\"ahler manifold distribute asymptotically to the wedge product of the curvature currents of the metrics. If the Hermitian metrics are H\"older with singularities we also estimate the speed of convergence.

Reservoir geology of the Paleocene Forties Sandstone Member in the Fram discovery, UK Central North Sea

Abstract The Fram discovery, located in the UK Central North Sea, comprises the Paleocene-aged Forties Sandstone Member with an oil rim and primary gas-cap trapped within a four-way dip closure around a pierced salt diapir. The Forties Sandstone Member reservoir at Fram is characterized by very-fine- to fine-grained sandstones interbedded with shales with post-depositional small-scale slumping and sand injection, interpreted to be the product of high-density turbidity currents and debris flows. Deposition was in an overall distal and marginal, basin-floor lobe environment. The Forties reservoir interval is considered to comprise a series of offset-stacked, turbidite lobes characterized by a systematic variation from axial amalgamated sandstone facies to more distal, marginal and thinner-bedded heterolithic sandstone facies, producing an overall sheet-like reservoir architecture. The Forties reservoir at Fram is thinner and poorer when compared with more proximal parts of the Forties submarine fan system, and reservoir quality is strongly controlled by sedimentary facies. The architecture of the reservoir is expected to result in poorer vertical, but greater lateral, stratigraphic continuity when compared with more channelized Forties reservoirs such as the Nelson and Forties fields further to the north. A key step in understanding and characterizing the Fram reservoir was the appraisal drilling in 2009, which included coring, comprehensive wireline logging, formation pressure data acquisition and a drill stem production test. This paper provides an overview of the Fram reservoir geology and demonstrates how integration of data acquired in the 2009 29/3c-8,8z appraisal wells with 3D seismic datasets, existing E&A wells and analogues has helped to improve reservoir characterization and identify the major subsurface uncertainties needing to be addressed during the field-development planning.

Higher spin currents in Wolf space for generic N

We obtain the 16 higher spin currents with spins (1,3/2,3/2,2),(3/2, 2,2, 5/2), (3/2,2,2, 5/2) and (2,5/2,5/2,3) in the N=4 superconformal Wolf space coset SU(N+2)/[SU(N) x SU(2) x U(1)]. The antisymmetric second rank tensor occurs in the quadratic spin-1/2 Kac-Moody currents of the higher spin-1 current. Each higher spin-3/2 current contains the above antisymmetric second rank tensor and three symmetric (and traceless) second rank tensors (i.e. three antisymmetric almost complex structures contracted by the above antisymmetric tensor) in the product of spin-1/2 and spin-1 Kac-Moody currents respectively. Moreover, the remaining higher spin currents of spins 2, 5/2, 3 contain the combinations of the (symmetric) metric, the three almost complex structures, the antisymmetric tensor or the three symmetric tensors in the multiple product of the above Kac-Moody currents as well as the composite currents from the large N=4 nonlinear superconformal algebra.

Stability of Monge–Ampère Energy Classes

We show that the non-pluripolar product of positive currents is a bimeromorphic invariant. Under some natural assumptions, we show that the (weighted) energy associated with big cohomology classes are also bimeromorphic invariants. We compare the weighted energy functionals of currents with respect to different cohomology classes and establish quantitative estimates between big capacities.

Mechanotransduction in the muscle spindle.

The focus of this review is on the principal sensory ending of the mammalian muscle spindle, known as the primary ending. The process of mechanosensory transduction in the primary ending is examined under five headings: (i) action potential responses to defined mechanical stimuli—representing the ending's input–output properties; (ii) the receptor potential—including the currents giving rise to it; (iii) sensory-terminal deformation—measurable changes in the shape of the primary-ending terminals correlated with intrafusal sarcomere length, and what may cause them; (iv) putative stretch-sensitive channels—pharmacological and immunocytochemical clues to their identity; and (v) synaptic-like vesicles—the physiology and pharmacology of an intrinsic glutamatergic system in the primary and other mechanosensory endings, with some thoughts on the possible role of the system. Thus, the review highlights spindle stretch-evoked output is the product of multi-ionic receptor currents plus complex and sophisticated regulatory gain controls, both positive and negative in nature, as befits its status as the most complex sensory organ after the special senses.Electronic supplementary materialThe online version of this article (doi:10.1007/s00424-014-1536-9) contains supplementary material, which is available to authorized users.

Processes and products of turbidity currents entering soft muddy substrates

New laboratory experiments reveal that cohesionless turbidity currents are able to enter cohesive soft muddy substrates without losing their shape. These intrabed currents are driven by bed shear stress exceeding bed cohesive strength, and by flow density exceeding bed den - sity. The flows produce unique turbidites with internal mud layers, mixed cohesive-nonco - hesive sediment layers, and flame and load structures. A depositional model for intrabed (I) turbidites is proposed, comprising, from base to top: I1�sand-bearing mud, with a scoured base, dispersed mud, and mud clasts; I2�muddy sand from the intrabed portion of the tur - bidity current; I3�sandy mud with a speckled appearance; and I4�mud-poor sand from the suprabed portion of the flow. Complete I1�I4 turbidites are inferred to dominate loca - tions in nature where the currents mix with the bed and deep erosional scours form, filled with deformed or chaotic sand-mud mixtures. Further downflow, base-missing I2�I4 and I4 sequences signify gradual deceleration, loss of erosivity, and termination of intrabed flow

Redheffer Products and Numerical Approximation of Currents in One-Dimensional Semiconductor Kinetic Models

When numerically simulating a kinetic model of an $n^+nn^+$ semiconductor device, obtaining a constant macroscopic current at steady state is still a challenging task. Part of the difficulty comes from the multiscale, discontinuous nature of both $p|n$ junctions, which create spikes in the electric field and enclose a channel where corresponding depletion layers glue together. The kinetic formalism furnishes a model holding inside the whole domain, but at the price of strongly varying parameters. By concentrating both the electric acceleration and the linear collision terms at each interface of a Cartesian computational grid, we can treat them by means of a Godunov scheme involving two types of scattering matrices. Combining both these mechanisms into a global S-matrix can be achieved thanks to “Redheffer's star-product.” Assuming that the resulting S-matrix is stochastic permits us to prove maximum principles under a mild CFL restriction. Numerical illustrations of collisional Landau damping and various $n^+nn^+$ devices are provided on coarse grids.

The inductive wedge product of positive currents

We define the wedge product of positive currents. Our main issue is about studying the convergence of ddcgj∧T where gj is a given sequence of plurisubharmonic functions and T is a positive current.

Endovascular Catheter for Magnetic Navigation under MR Imaging Guidance: Evaluation of Safety In Vivo at 1.5T

Endovascular navigation under MR imaging guidance can be facilitated by a catheter with steerable microcoils on the tip. Not only do microcoils create visible artifacts allowing catheter tracking, but also they create a small magnetic moment permitting remote-controlled catheter tip deflection. A side product of catheter tip electrical currents, however, is the heat that might damage blood vessels. We sought to determine the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter system. Alumina tubes with solenoid copper coils were attached to neurovascular microcatheters with heat shrink-wrap. Catheters were tested in carotid arteries of 8 pigs. The catheters were advanced under x-ray fluoroscopy and MR imaging. Currents from 0 mA to 700 mA were applied to test heating and potential vascular damage. Postmortem histologic analysis was the primary endpoint. Several heat-mitigation strategies demonstrated negligible vascular damage compared with control arteries. Coil currents ≤300 mA resulted in no damage (0/58 samples) compared with 9 (25%) of 36 samples for > 300-mA activations (P = .0001). Tip coil activation ≤1 minute and a proximal carotid guide catheter saline drip > 2 mL/minute also had a nonsignificantly lower likelihood of vascular damage. For catheter tip coil activations ≤300 mA for ≤1 minute in normal carotid flow, 0 of 43 samples had tissue damage. Activations of copper coils at the tip of microcatheters at low currents in 1.5T MR scanners can be achieved without significant damage to blood vessel walls in a controlled experimental setting. Further optimization of catheter design and procedure protocols is necessary for safe remote control magnetic catheter guidance.

Comprehensive constraints on a spin-3/2 singlet particle as a dark matter candidate

We consider the proposal that dark matter (DM) is composed of aspin-3/2 Dirac-type particle that is a singlet of the standard model(SM). Its leading effective interactions with ordinary matterinvolve a pair of their fields and a pair of SM fermions, in theform of products of chiral currents. We make a comprehensiveanalysis on possible phenomenological effects of the interactions invarious experiments and observations. These include collidersearches for monojet plus missing transverse energy events, directdetections of DM scattering off nuclei, possible impacts on thegamma rays and antiproton-to-proton flux ratio in cosmic rays, andthe observed relic density. The current data already set strongconstraints on the effective interactions in a complementary manner.The constraint from collider searches is most effective at arelatively low mass of DM, and the antiproton-to-proton flux ratiooffers the best bound for a heavy DM, while the spin-independentdirect detection is the best in between. Putting all constraintstogether, a DM mass less than ∼ 1TeV has been excluded,leaving behind a small window for a heavy DM particle of spin-3/2.

Modeling of Vias Sharing the Same Antipad in Planar Waveguide With Boundary Integral Equation and Group T-Matrix Method

We consider multiple scattering among different groups of vias with each group of vias sharing one antipad in planar waveguide. A transformation is used that converts the 2-D discretization and 2-D surface integration of the product of Green's functions and magnetic surface currents into 1-D discretization and 1-D integration of surface charges on the vias and on the ground plane. This is used to calculate the incident fields onto the vias. Based on the incident fields, the Foldy-Lax equations can be solved to calculate the circuit parameters for the problem. We show that the results are superior to the previously used finite difference method. In addition, the group T-matrix method is used to represent a group of vias to account for the scattering among different groups of vias. Results are illustrated for various cases of multiple vias up to 20 GHz. Results show the accuracy of the method even to very closely spaced vias when they are separated by merely 1 mil. Numerical results are in excellent agreement with ANSOFT HFSS.

Various approaches to products of residue currents

We describe various approaches to Coleff–Herrera products of residue currents Rj (of Cauchy–Fantappiè–Leray type) associated to holomorphic mappings fj. More precisely, we study to which extent (exterior) products of natural regularizations of the individual currents Rj yield regularizations of the corresponding Coleff–Herrera products. Our results hold globally on an arbitrary pure-dimensional complex space.

A deep subaqueous fan depositional model for the Palaeoarchaean (3.46 Ga) Marble Bar Cherts, Warrawoona Group, Western Australia

AbstractThe 3.46 Ga Marble Bar Chert Member of the East Pilbara Craton, Western Australia, is one of the earliest and best-preserved sedimentary successions on Earth. Here, we interpret the finely laminated thin-bedded cherts, mixed conglomeratic beds, chert breccia beds and chert folded beds of the Marble Bar Chert Member as the product of low-density turbidity currents, high-density turbidity currents, mass transport complexes and slumps, respectively. Integrated into a channel-levee depositional model, the Marble Bar Chert Member constitutes the oldest documented deep-sea fan on Earth, with thin-bedded cherts, breccia beds and slumps composing the outer levee facies tracts, and scours and conglomeratic beds representing the channel systems.

Structures and systems and bodies and things: historical research on primary schooling and its professional relevance

Recalling its origins as a research journal addressing educationists this article seeks to understand historical research published in History of Education as aimed at a professional audience. Primary schooling provides a significant focus as the study of education history was fostered especially in the training of elementary teachers.1 In that context a traditional strand of research on structures and systems is recognised for its past achievements and continuing importance. At the same time this account identifies and welcomes continuing innovations in research focus and research method, but asks about potential audiences in the field and argues the importance of reaching a wider professional readership. Over the lifetime of the journal History of Education, political, cultural and institutional contexts have changed along with changing research methodologies. These parallel shifts suggest that the character of research in our field is not simply the product of autonomous intellectual currents but part of a larger pattern of change that embraces schooling. Recognition of this fact should remind educationists of the value of applying their historical research to elucidating current issues. A marked trend in the lifetime of History of Education has been its increasingly international scope, and examples of research on elementary and primary education from Paedagogica Historica are referred to for comparison. 1‘Primary’ here refers to the contemporary context, ‘elementary’ to the historical. These two contrasting terms are often found interchangeably in the literature, with regard to historical time and to geographical location, in some cases varying as descriptors of ‘education’ on the one hand or ‘schools’ on the other. Various usages in the course of this article reflect terms used by authors whose works are referred to, or their application at different times and in different countries. ‘Elementary’ was succeeded by ‘primary’ as a statutory definition in the UK in 1944, but remains the preferred term in the USA, Japan and France, ‘Grundschule’ or ‘grundskola’ in Germany and Sweden, with ‘primary’ prevailing in Spain, Portugal and Italy.

The weight function for the quantum affine algebra [formula omitted

In this article, we give an explicit formula for the universal weight function of the quantum twisted affine algebra U q ( A 2 ( 2 ) ) . The calculations use the technique of projecting products of Drinfeld currents onto the intersection of Borel subalgebras of different types.

Varved clay paleomagnetism: Sedimentogenesis and secular variation record

The genesis, varve, and paleomagnetic informativeness of glaciolacustrine sediments are considered based on paleomagnetic and lithological studies. The magnetic properties of varved clays from periglacial basins have been considered using the sedimentological model of formation of varved clays as products of glacial turbidity currents, which explains the differences in the magnetic characteristics and degree of paleomagnetic informativeness of these clays. The distal zone sediments (formed due to precipitation from glacial turbidity currents, suspension, and sometimes along the periphery of the proximal zone) are most successfully used to study secular variations. The possible errors of the secular variation records in varved clays and such errors in estimating annual bedding of these clays have been analyzed. It has been indicated that information about the composition, concentration, and magnetic fraction size should be completed with detailed lithological studies, which make it possible to reconstruct the character of clastic material income into a basin and to decipher a paleomagnetic record. An analysis of the magnetic susceptibility anisotropy parameters and the magnetization formation in a sediment makes it possible to take into account disturbances caused by the sedimentation process and, thereby, to detect a pure geomagnetic signal

Pattern of sedimentation during the Late Paleozoic, Gondwanaland glaciation: An example from the Talchir Formation, Satpura Gondwana basin, central India

The Talchir Formation of Permian age is the lowermost lithostratigraphic unit of the Indian Gondwana successions preserving a record of the Late Paleozoic glaciation that affected the whole Gondwanaland. The formation unconformably overlies the Precambrian basement in all the Gondwana basins of India, and marks initiation of sedimentation after a long hiatus since the Proterozoic. The Talchir Formation of the Satpura Gondwana basin of central India shows features diagnostic of deposition under glacial regime such as the presence of diamictites, boulder pavements, bedding plane striation, faceted/striated gravels, bullet-shaped clasts, dropstone, cryoturbation, etc. The Talchir strata of the Satpura basin, in addition to tidal signatures, contain marine bivalve and trace fossils. A proglacial marine environment is thus inferred for their deposition. The dominant lithologies are conglomerate, pebbly sandstone, sandstone and shale with little limestone, which can be classified into the following major facies: • matrix-supported conglomerate, • clast-supported conglomerate, • cross-stratified, channel form pebbly sandstone, • hummocky, swaley or low-angle cross-stratified pebbly and non-pebbly sandstone, • turbidite/tempestite sheet sandstone, • massive to fissile, green to black claystone with carbonate layers and nodules. The conglomerates are interpreted as deposits of a spectrum of sub-aqueous sediment gravity flows including debris flow, hyperconcentrated/concentrated density flow and grain flow. The crossstratified pebbly sandstone bodies, on the other hand, represent braidplain delta deposits of glacial outwash origin. Hummocky, swaley, low-angle cross-stratified sediment bodies were deposited by storm-generated combined flows in a shoreface setting. In contrast, the sheet sandstone bodies are products of turbidity currents and storm-induced density currents in an inner shelf setting below fair weather wave base. The claystone facies is interpreted as a product of suspension fallout from hypopycnal sediment plumes in the outer shelf domain below storm wave base. All the lithofacies described above occur repetitively in the succession. Three facies-associations have been recognized in the Talchir Formation, representing ice-contact fandelta, outwash braidplain delta and a virtually ice-free, non-deltaic open marine realm. The different marine facies of the Talchir Formation define a number of shallowing-upward packages, which are arranged in the succession with a retrogradational trend to result in an overall fining- and deepening-upward succession. The overlying coal-bearing Barakar Formation has been interpreted to have formed in a tide-wave influenced

The SOS model partition function and the elliptic weight functions**This work is dedicated to the memory of Alexei Zamolodchikov.

We generalized a recent observation (Khoroshkin and Pakuliak 2005 Theor. Math. Phys. 145 1373) that the partition function of the six-vertex model with domain wall boundary conditions can be obtained from a calculation of projections of the product of total currents in the quantum affine algebra in its current realization. A generalization is done for the elliptic current algebra (Enriquez and Felder 1998 Commun. Math. Phys. 195 651, Enriquez and Rubtsov 1997 Ann. Sci. Ecole Norm. Sup. 30 821). The projections of the product of total currents in this case are calculated explicitly and are presented as integral transforms of a product of the total currents. It is proved that the integral kernel of this transform is proportional to the partition function of the SOS model with domain wall boundary conditions.

Global surface currents: a high-resolution product for investigating ocean dynamics

A global 1/4° resolution product of surface currents has been developed by the Centre de Topographie des Oceans et de l’Hydrosphere. The surface current is calculated from a combination of Ekman currents derived from wind estimates from QuikSCAT satellite, geostrophic current anomalies derived from altimetry, and a mean geostrophic current derived from climatology. In the equatorial band, the currents are adjusted following the methodology proposed by Lagerloef et al. (J Geophys Res, 104(C10):22313–22326, 1999). These satellite-derived currents have been compared to different types of in situ current observations. A global validation is performed using Lagrangian surface drifting buoys and acoustic Doppler current profiler current observations along ship tracks. The comparison shows a very good agreement in the subtropical and mid-latitude bands. The correlation between the satellite-derived currents and the drifter currents in zonal mean bands is around 0.7 for most of the world oceans, both for the zonal and the meridional components. This correlation rises up to 0.8 in the regions of strong boundary currents. In the equatorial band, the correlation with the surface drifting buoys is reduced. A direct comparison with the TOGA/TAO moored current meter data at the equator shows that the low frequency currents are captured by the satellite current product, but there is a substantial high-frequency signal (<20 days), which is not reproduced. This is especially the case for the meridional component and is mainly related to the tropical instability waves. We also show that using daily QuikSCAT wind forcing improves the satellite current product, particularly in the high-latitude westerly wind belt and in the tropical Indian Ocean.