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The properties of space charge and breakdown in epoxy/paper composites are studied in this paper. The results show that the breakdown voltage of the epoxy/paper composite is lower than that of the epoxy under AC voltage but is higher under DC voltage. In order to explain this phenomenon, the space charge behavior is investigated. In epoxy/paper composites, the space charges easily accumulate at the epoxy/paper interface at low fields, and the electric field distribution is highly deformed. However, the amount of interface charges decreases with increasing voltage, leading to a more uniform field distribution in the composites. This behavior is different from that of the pure epoxy, resulting in the different breakdown properties of pure epoxy and epoxy/paper composites. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This study shows that larger rates of change of gradient with time (dG/dt) can be achieved at the threshold for peripheral nerve stimulation by applying a uniform concomitant field varying synchronously with a transverse field gradient and that this increase may be achieved without significant reduction of the spatial extent of the region over which imaging can be carried out. Realization of similar benefits through application of a uniform, z-directed field varying synchronously with an axial gradient is also demonstrated. The design and construction of transverse and axial coil arrangements is described, along with the results of volunteer studies that were carried out on 20 subjects, with the subjects positioned with four different regions (head, heart, hips, and knees) centered in the coils. These experiments were carried out at zero-field on a prototype system in which the coils were not actively shielded. The uniform concomitant field coil was not torque balanced. The increase in the rate of change of gradient at the threshold for peripheral nerve stimulation that could be achieved by the addition of the uniform field depends on body position and was larger for the transverse coils (head = × 1.9 ± 0.6; heart = × 0.9 ± 0.3; hips = × 1.4 ± 0.4; knees = × 1.5 ± 0.4) than for the axial coils (head = × 1.5 ± 0.6; heart = × 0.8 ± 0.3; hips = × 1.3 ± 0.4; knees = × 1.1 ± 0.3). Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.

Evidence for a possible role for the peripheral retina in the control of refractive development is discussed, together with Howland's suggestion (Paper presented at the 13th International Myopia Conference, Tubingen, Germany, July 26-29, 2010) that signals to generate appropriate growth might be derived from ocular oblique astigmatism. The dependence of this, or similar peripheral mechanisms, on exposure to a uniform field of near-zero dioptric vergence is emphasized: this is required to ensure a consistent relationship between the astigmatic image fields and the retina. This condition is satisfied by typical outdoor environments. In contrast, indoor environments are likely to be unfavourable to peripherally-based emmetropization, since dioptric stimuli may vary widely across the visual field. This is particularly the case when short working distances or markedly asymmetric head postures with respect to the visual task are adopted.

SUMMARY The breakdown voltage (BDV) of compressed sulfur hexafluoride (SF6) in the pressure range of 1–5 atm at 30 kHz, the frequency used by Navy for communications with vessels, is presented. Experiments were conducted in both uniform field (plane–plane gap) and non-uniform field (rod–plane gap). The impact of pressure on the BDV is quantitatively analyzed. The pressure correction factors for calculating the BDV of SF6 at 30 kHz have been developed from knowledge of breakdown characteristics of air and from regression models. Copyright © 2010 John Wiley & Sons, Ltd.

A theoretical study of the donor-related absorption coefficient in spherical CdS quantum dots (QD) in the presence of a uniform magnetic field is performed. The wave functions and the eigenvalues of the initial and final states are obtained in the effective-mass approximation by using a variational method and a perturbation method, respectively. The results obtained show that the absorption coefficient presents essentially two peaks; one associated with on-center donors and another related to transitions involving donors at the QD edge. The dependences of the absorption coefficient on sample dimensions, the magnetic field strength and the light polarization are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Introduction: Termination of ventricular fibrillation by electric shocks is believed to be due to the direct activation of large tissue mass that may be caused by microscopic virtual electrodes formed at discontinuities in tissue structure. Here, microscopic shock-induced activation was measured optically in myocyte cultures; spatially averaged microscopic Vm measurements were compared with macroscopic measurements from left ventricular (LV) tissue. Methods and Results: Experiments were performed in linear cell strands of different width (∼0.1 and 0.8 mm) and isolated porcine LV preparations. Uniform field shocks were applied across strands or LV preparations during diastole and action potential (AP) plateau. Depending on shock strength, three different types of activation were observed in cell strands. Weakest shocks produced “delayed make” activation that started on the cathodal strand side after long latency and rapidly spread to the anodal side. Stronger shocks caused “make” activation with short latency and rapid spread across strands. Strongest shocks caused nonuniform “make-break” activation where the cathodal side was activated with a short latency but activation of the anodal side was delayed until after the shock end due to a large negative shock-induced polarization. Spatial averaging of Vm responses across 0.1-mm (but not 0.8-mm) strands resulted in AP upstrokes and plateau polarizations that closely resembled the Vm responses measured in LV myocardium. The shock strength for the transition between fast and delayed activation in 0.1-mm cell strands and LV myocardium was similar as well. Conclusion: These data provide evidence that microscopic tissue structures with dimensions of approximately hundred microns are responsible for shock-induced activation of ventricular tissue.

Multiple Acquisition with Micro-B0 Array (MAMBA) is a class of parallel imaging techniques. Its distinguishing feature is the use of auxiliary coil arrays that introduce a stepped field within the B0 field. The steps form regions of uniform field, which then can be used to encode in one or more dimensions. The steps can also be used in conjunction with sensitivity encoding (SENSE) techniques to achieve higher acceleration factors. Step fields necessarily contain high-order harmonics and require high currents to implement them. To reduce current demands, we have combined the pseudoinverse target field method with subset selection and Tikhonov regularization to derive coil array designs for some MAMBA configurations. We conclude that MAMBA will be most effective in long and narrow or thin and flat configurations. In these situations, our algorithm enables sparse designs with low current demands to be obtained. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 20B: 1–8, 2004.

We examine how the RG cardinal mechanism adapts to a shift from one spatially uniform field to another. A probe-flash paradigm allowed the response to be esti- mated at an initial adaptation state, an end adaptation state, and four intermediate time conditions. The threshold curves were higher and flatter in the intermediate conditions than at the beginning and end of adaptation. The intermediate results cannot be explained by combinations of cone or opponent-level multiplicative and subtractive gain controls, and implicate higher-order adaptation processes.© 2000

Hydrodynamic characteristics of fluidized beds of pure iron (1416 μm), copper (934 μ) and their admixture (25, 50 and 75 mass %) particles when exposed to a uniform magnetic field collinear with the gas flow are investigated. Bed pressure-drop data taken as a function of increasing and decreasing gas velocities (up to about 8 m/s) for different values of magnetic-field intensity over a wide range (0 to 17 272 A/m) are employed to determine the superficial minimum bubbling and fluidization gas velocities at ambient temperature and pressure. The minimum bubbling velocity is found to increase with an increase in the value of the magnetic-field intensity, as well as with the mass fraction of magnetizable particles in the bed. These data are correlated with an empirical relation, as well as with a semi-theoretical expression. The bed voidage data are also generated and analyzed, as also the bed quality fluidization in terms of interparticle magnetic forces. These hydrodynamic properties of magnetically stabilized fluidized-bed reactors are useful in their design and operation for a variety of chemical and biochemical applications. On a etudie les caracteristiques hydrodynamiques de lits fluidises de particules de fer pur (1416 um) et de cuivre pur (934 \im), puis de leur melange (25, 50 et 75% en masse) lorsqu'elles sont exposees a un champ magnetique uniforme colineaire avec le debit de gaz. On a employe des donnees de perte de charge de lit en fonction des vitesses de gaz croissant et decroissante (jusqu'a environ 8 m) pour une large gamme d'intensite de champ magnetique (0 a 17272 A/m) afin de determiner le bullage superficiel minimum et les vitesses de gaz de fluidisation a la temperature et a la pression ambiante. On a trouve que la vitesse de' bullage minimum augmentait avec la valeur de l'intensite du champ magnetique ainsi qu'avec la fraction de masse des particules magnetisables dans le lit. Ces donnees sont correlees a une relation empirique et a une expression semi-theorique. Les donnees de vide de lit sont egalement calculees et analysees tout comme la fluidisation de qualite de lit en termes des forces magnetiquement stabilises sont utiles dans leur conception et leur fonctionnement pour diverses applications chimiques et biochimiques.

Using the Lee-Low-Pines variational method the effective mass of a polaron in a rectangular quantum wire subject to a strong uniform external magnetic field along the wire length is studied. Taking the GaAs quantum wire as an example numerical results are given. The results show that the effective mass of the polaron is dominated mainly by the smaller dimension of the quantum wire cross section and the external magnetic field has an interesting influence on it.

A new design of a three-channel surface gradient coil (SGC) is presented. The optimal objective of this design is to minimize parasitic field gradients by modifying the wire arrangement in the individual coils. A 3D finite element (FE) model is employed to analyze the SGC's field predictions. The numerical analysis results of the new SGC design indicate improved field behaviors when compared with those of a previously reported SGC designed by Cho and Yi (J. Magn. Reson. 94, 471-485 (1991)). To confirm the predicted improvement, two Gy (Y-axis) gradient coils, based on the old and new designs, have been constructed and installed in a General Electric CSI 2 Tesla MRI system with a 15-cm bore. Based on the resulting MR images, the new gradient coil configuration provides more uniform field gradients and less parasitic field gradients, which results in higher quality images than the previously reported SGC design. This paper also demonstrates the remarkable accuracy of the 3D FE simulation model.

The field distribution of a new type of TEM cell with a cross of unequal-length arms as the inner conductor is given here. The whole field of such a cell consists of a high-field region and a uniform field region, useful in many applications.

School of Chemistry, Seoul National University, Seoul 151-747, KoreaReceived November 10, 2003Field emission of carbon nanotubes (CNTs) fabricated by disproportionation of CO has been studied. CNTsfabricated on well-ordered Co nanowire arrays formed on the porous anodic aluminum oxide templates werewell graphitized, uniform in diameter and aligned vertically with respect to the plane of the template, andshowed a good field emission property. Very uniform emissions were observed from the CNTs fabricated atrelatively low temperature, 500-600

The boundary conditions on the exposed face of a dielectric mirror are shown to be effectively the same as those for perfect electric conductors, whereas the boundary conditions on the exposed face of a chiral mirror are very different from those for either perfect electric conductors or perfect magnetic conductors. Cavities between two chiral mirrors have a relatively uniform field distribution, which is significant for spectral-hole filters and coherent light generation. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 63–64, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21082

In some microwave field problems we have to utilize the perturbing effect of o conducting body in a uniform electrostatic field as on approximate solution. Here we solve one such problem of an incomplete spherical electrode in a uniform electrostatic field.

SUMMARY NMR images of distinct sections through a three-dimensional phantom were obtained using steady magnetic fields much less uniform than those generally considered necessary for NMR imaging, but whose substantial gradient served to define the slices to be imaged. A sensitive point technique and a modified spin-echo pulse sequence were used. ABSTRACT NMR images are generally produced in highly uniform steady magnetic fields, to which switched gradients are added to achieve spatial selection. In this note we show that NMR images can be produced in a substantially non-uniform field, provided the field is shaped so that the gradient of the steady field can be used to define the slice to be imaged.

The electromagnetic response of anticline fold models in a uniform field has been studied using scale-modeling. With the increasing conductance the in-phase anomaly increases initially but then starts to decrease and finally attains a negative saturations, whilst the quadrature anomaly reaches a positive saturation. E.M. response of folds is similar to that of an interaction between two weakly coupled circuits in a dipolar field. The base of the fold is one of the characteristic parameters to determine the measured response.

In a fairly uniform field of grain approximately 60 to 80% of the straw and chaff is found below the level of the lowest heads. Straw weights decrease rapidly with higher cutting, largely because the culms decrease in thickness upward from the base to the peduncle. Three and a half times as much straw sometimes is harvested in cutting a lodged crop with a combine as in harvesting an erect crop. Straw yield data from experimental plats are of limited value unless the height of cutting is uniform.

A technique utilizing the convolution theorem is developed to obtain the time-domain electromagnetic response for a number of input pulses from the given step-function response. For illustration an idealized model of a homogeneously conducting non-permeable sphere placed in a uniform field is considered. The nature of the responses due to different types of pulses and their usefulness in estimating the constitution parameter of the sphere are discussed. To show the applicability of the suggested technique to generalized systems, calculations for a conducting permeable sphere are presented in the appendix.

The electric field distribution and current–voltage characteristic in the avalanche region is calculated for InSb crystals of both n- and p-type. It is shown that space charge effects make the field distribution highly non-uniform when the transit time is short compared to the carrier lifetime. A current controlled negative differential resistance may also be developed due to the same effects. Die elektrische Feldstarke und die Strom–Spannungscharakteristik in der Lawinenzone werden fur n- und p-leitende InSb-Kristalle berechnet. Wenn die Laufzeit der Ladungstrager im Verhaltnis zur Lebensdauer klein ist, zeigen sich auf Grund von Raumladungseffekten grose Abweichungen von der Homogenitat in der elektrischen Feldstarke. Aus dem gleichen Grund entsteht ein durch den Strom kontrollierter negativer differentieller Widerstand.

Summary A uniform field of the normal geomagnetic vertical intensity and its normal dependence on the first and second powers of latitude and longitude are derived for Europe and represented by sketches. The epochs of 1938.5, 1941.5, 1944.5, 1947.5, 1950.5, 1953.5, and 1956.5 have been chosen. It is suggested that anomalies of the vertical intensity should be given according to this field in order to obtain, in course of time, a coherent image of the magnetic effects of the European continent. Zusammenfassung Em einheitliches Normalfeld der erdmagnetischen Vertikalintensitat und seine normale Breiten- und Langenabhangigkeit erster und zweiter Ordnung werden fur Europa abgeleitet und zeichnerisch dargestellt. Als Epochen sind 1938.5, 1941.5, 1944.5, 1947.5, 1950.5 1953.5 1956.5 gewahlt worden. Es wird empfohlen, die Anomalien der Vertikalintensitat diesem Feld entsprechend anzugeben, um so im Laufe der Zeit ein zusammenhangendes Bild der magnetischen Wirkung des europaischen Kontinents zu erhalten.