Plane Configuration Research Articles

Möbius-Kantor configurations in the affine plane of order 7

We partition the affine plane of order 7 into a set of Mobius-Kantor configurations 83 plus a set consisting only of one point.

On the K2of degenerations of surfaces and the multiple point formula

In this paper we study some properties of reducible surfaces, in particular of unions of planes. When the surface is the central fibre of an embedded flat degeneration of surfaces in a projective space, we deduce some properties of the smooth surface which is the general fibre of the degeneration from some combinatorial properties of the central fibre. In particular, we show that there are strong constraints on the invariants of a smooth surface which degenerates to configurations of planes with global normal crossings or other mild singularities. Our interest in these problems has been raised by a series of interesting articles by Guido Zappa in the 1950’s.

Study of ground plane of dual‐band patch antenna on SAR

AbstractThis paper investigates the effects of different ground plane configurations of a typical GSM900/1800 dual‐band internal planar inverted‐F patch antenna (PIFA) on specific absorption rate (SAR) and corresponding antenna performance. The effect of the length and width of the ground plane and the addition of vertical sidewall on the ground plane are presented. Results have shown that when the length and width of the antenna ground plane is increased, the SAR value could be reduced while radiation efficiency is not significantly affected, the antenna gain is reduced by 3.5 dB at 930 MHz, and the envelope of far‐field antenna pattern is mainly affected in the human head direction. The addition of vertical sidewall at four sides of the ground plane with a height of 7 mm could provide a SAR reduction at 1.75 GHz by 63% without significantly affecting the performance of the PIFA antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 949–953, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22316

Novel low-field magnetoresistive devices based on manganites

We present novel low-field magnetoresistive devices based on the ferromagnetic manganite La 0.7Sr 0.3MnO 3 operating in the current in plane (CIP) configuration. In these planar spin-valve devices, a focused Ga + beam is used to create pinning centers for magnetic domain walls. The spin-dependent scattering of polarized electrons at the domain walls (DW) is responsible for the magnetoresistance observed in the patterned tracks. The magneto-transport properties of these devices are interpreted within a model for DW magnetoresistance. Applications such as magnetic data storage can be envisaged for the structures we investigated.

Reconstruction of small cavities in an elastic layer

Reconstruction of the shape of a cavity with small characteristic dimensions in an elastic orthotropic layer is considered in the antiplane and plane configurations. The proposed approach is based on the information on the field of displacements that is measured at the layer boundary. The displacement field was calculated via three methods: the Born approximation, the asymptotic approach, and the boundary-element method. Results obtained via these methods are compared on the basis of numerical experiments.

Magnetoresistance switch effect in a multiferroic Fe3O4∕BaTiO3 bilayer

Multiferroic bilayers composed of a magnetite (Fe3O4) and a BaTiO3 layer show nonlinear current-voltage characteristics in current perpendicular to plane configuration. The magnetoresistance of the bilayers is strongly bias dependent and can be switched from negative at low bias to positive at large bias. It is shown that these effects do not arise from charge-carrier modulation in the magnetite layer by an electric field effect. Therefore both the nonlinear transport characteristics and the switchable magnetoresistance are attributed to interfacial transport phenomena.

Radial and ulnar bursae of the wrist: cadaveric investigation of regional anatomy with ultrasonographic-guided tenography and MR imaging

To demonstrate the anatomy of the radial and ulnar bursae of the wrist using MR and US images. Ultrasonographic-guided tenography of the tendon sheath of flexor pollicis longus (FPL) and the common tendon sheath of the flexor digitorum of the fifth digit (FD5) of ten cadaveric hands was performed, followed by magnetic resonance imaging and gross anatomic correlation. Patterns of communication were observed between these tendon sheaths and the radial and ulnar bursae of the wrist. The tendon sheath of the FPL communicated with the radial bursa in 100% (10/10) of cases, and the tendon sheath of the FD5 communicated with the ulnar bursa in 80% (8/10). Communication of the radial and ulnar bursae was evident in 100% (10/10), and presented an "hourglass" configuration in the longitudinal plane. The ulnar and radial bursae often communicate. The radial bursa communicates with the FPL tendon sheath, and the ulnar bursa may communicate with the FD5 tendon sheath.

Development of scanning micromirror with discrete steering angles

This paper describes the development of a new MEMS-based optical mirror, which can perform optical switching (or scanning) function with discrete reflection angles in an outof- plane configuration. The device is fabricated through the Deep Reactive Ion Etching (DRIE) process on silicon-on-insulator (SOI) wafer, followed by wafer dicing and assembly with two metalised glass dies. The MEMS mirror can be tilted under electrostatic force between the opposite electrodes embedded on SOI and glass structures. The most outstanding feature of this MEMS mirror is the discrete and therefore, reliable tilting angles, which generated by its unique mechanical structural design and electrostatic-driven mechanism. In this paper, the concept of the new scanning mirror is presented, followed by the introduction of device design, mechanical simulation, microfabrication process, assembly solution, and some testing results. The potential applications of this new MEMS mirror include optical scanning, optical sensing (or detection), and optical switching.

Crystal structure, vibrational spectra and optical properties of praseodymium cyclotriphosphate PrP3O9·3H2O

Single crystals of the trihydrated praseodymium cyclotriphosphate PrP3O9·3H2O were grown for the first time, using a classical method of aqueous chemistry and characterized by single crystal X-ray diffraction. PrP3O9·3H2O is isostructural with LnP3O9·3H2O (Ln=La, Ce and Nd). It crystallizes in the hexagonal system with space group P6¯(C3h1), with lattice parameters: a=6.7677(4)Å, b=6.7677(4)Å, c=6.0501(4)Å, V=239.98(3)Å3, Z=1 and Dx=2.988gcm−3. The crystal structure is resolved for the first time, with final R(F2)=0.0175 and Rw(F2)=0.0417 for 396 independent reflections (F02≥2σ(F02)). The P3O93− cyclic anions have a plane configuration with C3h symmetry. The nearest neighbours of the rare earth ion are six oxygen atoms belonging to the P3O93− anions. Pr3+ ions occupy sites with C3h symmetry. The energies of the crystal vibrational modes are obtained from infrared (IR) and Raman spectra. Optical absorption measurements and emission spectra under selective excitation in the Pr3+ (4f2) 3PJ (J=0, 1, 2) levels, at room and liquid-helium temperatures, are reported. The observed fluorescence originates mainly from 3P0 with a decay time on the order of 10ns, regardless of temperature.

Simulated performance of dedicated Ge-strip Compton telescopes as γ-lens focal plane instrumentation

With focusing of gamma rays in the nuclear-line energy regime starting to establish itself as a feasible and very promising approach for high-sensitivity γ-ray (line) studies of individual sources, optimizing the focal plane instrumentation for γ-ray lens telescopes is a prime concern. Germanium detectors offer the best energy resolution available at ∼2 keV FWHM at 1MeV and thus constitute the detector of choice for a spectroscopy mission in the MeV energy range. Using a Compton detector focal plane has three advantages over monolithic detectors: additional knowledge about (Compton) events enhances background rejection capabilities, the inherently finely pixellated detector naturally allows the selection of events according to the focal spot size and position, and Compton detectors are inherently sensitive to γ-ray polarization. We use the extensive simulation and analysis package assembled for the ACT vision mission study to explore achievable sensitivities for different Ge Compton focal plane configurations as a first step towards determining an optimum configuration.

Study of a positive corona discharge in argon at different pressures

The corona discharge in argon at atmospheric pressure has been studied by means of a 2D model. The reduced characteristic derived from the experimental data has been described by linear regressions for the different pressures and the two studied inter-electrode distances thus confirming the validity of Townsend's approximation also in case of point to plane configuration and argon as process gas. The model validated this hypothesis which has been attributed to the minor influence of space charge in the ionization zone. Its effect is, on the other hand, more significant in the drift zone where the electric field is greatly enhanced, leading, for higher currents, to the formation of a spark gap. Electron and ion distributions allow the influence of structural (electrode configurations and distance) and operative (pressure and discharge current) parameters to be evaluated including the current loss due to diffusion through different confining boundaries.

CPP transport properties of polycrystalline Fe3O4 thin films sputtered on Cu underlayers

Transport properties of sputtered Fe3O4 thin films have been studied with the current perpendicular to plane (CPP) configuration. Fabricated polycrystalline Fe3O4 films exhibit superior CPP conductivity of 12kΩ−1∙m−1. In addition to the Verwey transition (VT), observed at 114 K, another type of drastic conductivity change [field induced transition (FT)] was observed at lower temperature (T<70K) and higher bias voltage (Vb>0.18V) regime. The conductivity change at FT is discontinuous and several orders in magnitude. The transition temperature for FT presents considerable Vb dependence, contrarily no distinguished dependence for VT.

Mechanism of biochemical action of substituted 4-methylcoumarins. Part 11: Comparison of the specificities of acetoxy derivatives of 4-methylcoumarin and 4-phenylcoumarin to acetoxycoumarins: protein transacetylase

Our earlier observations led to the identification of a microsomal enzyme termed as acetoxy drug: protein transacetylase (TAase) catalyzing the transfer of acetyl groups from acetylated polyphenols to the receptor proteins. TAase was conveniently assayed by the irreversible inhibition of cytosolic glutathione S-transferase (GST) by the model acetoxycoumarin, 7,8-diacetoxy-4-methylcoumarin ( 1). The specificities of the acetoxy group on the benzenoid ring and position of the pyran carbonyl group of the coumarin with respect to oxygen heteroatom for the catalytic activity of TAase were also reported earlier. In this communication, we have demonstrated that the acetoxy coumarins and acetoxy dihydrocoumarins having a methyl group instead of a phenyl ring at the C-4, when used as the substrates, resulted in enhancement of TAase activity, while the saturation of double bond at C-3 and C-4 position had no effect on TAase activity. A comparison of the optimized structures of 1 and 7,8-diacetoxy-4-phenylcoumarin ( 2) suggested that the observed influence may be due to out of plane configuration of the phenyl ring at C-4. Further, the TAase-catalyzed activation of NADPH cytochrome c reductase and inhibition of aflatoxin B 1 (AFB 1)–DNA binding by acetoxy 4-phenylcoumarins and dihydrocoumarins were significantly lower as compared to those caused by acetoxy 4-methylcoumarins.

Balanced Configurations of 2n + 1 Plane Vectors

A plane configuration {v_1,...,v_m} of vectors in {\mathbb R}^2 is said to be balanced if for any index i, the set of the det(v_i,v_j) for j\neq i is symmetric around the origin. A plane configuration is said to be uniform if every pair of vectors is linearly independent. E. Cattani and A. Dickenstein conjectured that any uniform balanced configuration is GL_2({\mathbb R})-equivalent to a regular (2n+1)-gon. In this note, we prove this conjecture.

Entry of magnetic flux into a magnetically shielded type-II superconductor filament

In the framework of the London approximation the magnetic flux penetration into a type-II superconductor filament surrounded by a soft-magnet sheath and exposed to a transverse external magnetic field is studied. The lower transverse critical field as well as the critical field and the critical current of the first vortex nucleation at the superconductor/magnet interface are calculated on the basis of an exact solution for a vortex of arbitrary plane configuration. The Bean-Livingston barrier against the vortex nucleation is shown to strongly depend on the magnet sheath parameters.

The cone of curves associated to a plane configuration

The cone of curves associated to a plane configuration

Kinematics of charged nanometric particles in silent discharges

We use 1 mm plane to plane configurations, with or without dielectric barriers, on metallic electrodes to investigate the ac electric precipitation of charged submicronic particles of controlled electrical mobility injected in a laminar flow. The collection efficiency is calculated from concentration measurements for different voltages. Below the air ionization threshold, experimental and theoretical collection efficiencies are consistent. Above the air ionization threshold, the current and collection efficiency increase with frequency and voltage related to the number of microdischarges per second and per unit surface area. This study intends to study the influence of surface polarization due to the development of microdischarges on the collection of charged particles. Comparison between the theory of collection in a homogeneous ac field without microdischarge, on the one hand, and measured collection efficiency with microdischarges, on the other hand, proves that surface polarization by microdischarges does not improve the collection efficiency, but enables either an increase of charge by ion repulsion from the surface, whatever the frequency is, or an improved mixing at 60 kHz.

High-resolution TEM characterization of MOVPE-grown (1 1 1)-BP layer on hexagonal 6H (0 0 0 1)-SiC

A BP layer was grown on the (0 0 0 1)-surface of 6H-type hexagonal SiC substrate by atmospheric-pressure metalorganic VPE, and crystallographic feature of the resultant BP/SiC hetero-structure was evaluated by transmission electron microscopy (TEM) and transmission electron diffraction (TED). Analysis of the TED patterns from the hetero-structure gave the following epitaxial relationship: (0 0 0 1), <a-axes>-SiC // (1 1 1), <1 1 0>-BP. Extra diffraction spots in the TED pattern indicated the presence of {1 1 1}-twins in the (1 1 1)-BP layer. High-resolution TEM observation also revealed the presence of random texture which involved irregular configuration of atomic planes in the (1 1 1)-BP layer at the hetero-interface with the (0 0 0 1)-SiC. The MOCVD-grown (1 1 1)-BP layer was deduced to develop on the (0 0 0 1)-SiC, accompanying the formation of the (1 1 1)-twins and of the random texture at the interface with the (0 0 0 1)-SiC.

Influences of degree of curing and presence of inorganic fillers on the ultimate electrical properties of epoxy-based composites: experiment and simulation

This paper describes both an experimental study and a numerical investigation of the breakdown field in particle reinforced thermosets. The experimental study revealed that the increase of the conversion degree (α) of the epoxy matrix improved the breakdown voltages both in divergent and quasi-homogeneous fields. It was also observed that the presence of the second phase (mineral filler) dispersed within the polymeric host led to apparently contradictory results depending on the nature of the electric field. The neat matrix exhibited a higher field to breakdown than that of the composite in a quasi-homogeneous field configuration whereas the opposite behaviour was evidenced in a point–plane configuration. It thus appeared that the filler can either increase or decrease the breakdown voltage, depending on the nature of the electrode configuration. To further understand this behaviour, a deterministic numerical simulation of the dielectric breakdown that accounts for the organization within real composites was developed. This numerical method, based on the resistor–short breakdown model was improved to directly account for the real phase arrangement within the samples through scanning electron micrographs. The simulation furnished the explanation for the apparent disagreement, showing that the inorganic particles protect the composite in divergent fields through a mechanism similar in nature to the so-called barrier effect, whereas the same fillers were responsible for a local intensification of the electric field and thereby a reduction of the dielectric strength in a quasi-homogeneous field.

Fundamental Domains for Finite Subgroups in U(2) and Configurations of Lagrangians

We show that every finite subgroup of U(2) is contained with index two in a group generated by involutions fixing Lagrangian planes. We describe fundamental domains for their action on \({\mathbb C}^{2}\) related to the configuration of these Lagrangian planes.