Rectangular Tapes Research Articles

Polarimetric linear absolute position encoder

Abstract Optical encoders based on measurement of the axis-angle of linear polarizers offer high resolution and moderate accuracy, but are usually restricted to rotary measurement. We show that annular polymer sheet polarizer materials can be sheared into rectangular tapes, with a polarizing axis that varies linearly along the tape. This makes possible the construction of polarimetric linear absolute position encoders. We demonstrate also sheared polymer birefringent retarders, which function similarly, potentially with cost and size-flexibility advantages.

Design and Construction of Large Amyloid Fibers

Mixtures of “template” and “adder” proteins self-assemble into large amyloid fibers of varying morphology and modulus. Fibers range from low modulus, rectangular cross-sectioned tapes to high modulus, circular cross-sectioned cylinders. Varying the proteins in the mixture can elicit “in-between” morphologies, such as elliptical cross-sectioned fibers and twisted tapes, both of which have moduli in-between rectangular tapes and cylindrical fibers. Experiments on mixtures of proteins of known amino acid sequence show that control of the large amyloid fiber morphology is dependent on the amount of glutamine repeats or “Q-blocks” relative to hydrophobic side chained amino acids such as alanine, isoleucine, leucine, and valine in the adder protein. Adder proteins with only hydrophobic groups form low modulus rectangular cross-sections and increasing the Q-block content allows excess hydrogen bonding on amide groups that results in twist and higher modulus. The experimental results show that large amyloid fibers of specific shape and modulus can be designed and controlled at the molecular level.

Reconfigurable Microstrip Patch Antenna for Frequency Diversity Using RF MEMS

A novel reconfigurable patch antenna for frequency diversity is proposed by reconfiguring its geometry using tree rectangular tapes that are connected to the patch via six RF MEMS switches. So switching between the different frequency bands is achieved by using capacitive series RF-MEMS switches. The antenna was designed to operate at 2.6 GHz, 3.1 GHz, 3.5 GHz and 5 GHz.

Influence of locally varying Jc distribution on AC transport losses for superconductor wires and tapes with various cross sections

The influence of locally varying J c value on AC transport losses in self-fields is investigated on superconductor wires and tapes with various cross sections through numerical calculations. For round wires, the loss values depend on the J c variation along a radial direction in their cross sections. The distribution that J c increases in going from the center to the edge along a radial direction lowers the loss value, below the theoretical prediction for an elliptic superconductor without any J c variation. For tapes, the loss values are mainly influenced by the J c variation along a width direction. The rectangular tapes with high aspect ratio and also with nearly uniform J c value behave as a thin strip superconductor. The distribution that J c decreases in going from the center to the edge along a width direction raises the loss value, and the loss value approaches the theoretical prediction for an elliptic superconductor as the J c variation becomes significant.

Effects of overpressure processing on porosity in Ag-sheathed Bi-2212 multifilamentary tapes with various geometries

In long lengths of Bi-2212 tapes and wires, gases such as CO/sub 2/ and H/sub 2/O can cause bubbling of the Ag-sheath and porosity in the superconducting core. Applying a pre-processing step, which consists of vacuum annealing and annealing at 835/spl deg/C in 100% O/sub 2/ (VA+835), eliminates H/sub 2/O and reduces CO/sub 2/ that evolves during heating. To also counteract porosity, an overpressure heat treatment was utilized. Air was compressed to 5 atm total pressure (P/sub total/) while keeping pO/sub 2/ fixed at 1 atm. Thickness variations were measured for a number of variables: with and without VA+835; P/sub total/ 1 or 5 atm; and sample geometry such as round wires and rectangular tapes with different silver wall thickness. Light micrographs and SEM images show thin-walled monocore and multifilamentary tapes bubble unless they are pre-processed. The size and shape of pores in thick and thin multifilaments changes with overpressure processing. Microstructures with smaller and more uniformly distributed pores correlate with higher critical current values.

Field-free core, current distribution, and alternating current losses in self fields for rectangular superconductor tapes

A method is proposed to calculate the shape of field-free core, the current distribution, and accordingly the alternating current (ac) losses in self fields as a parameter of current amplitude I0 for straight superconductor tapes with the arbitrary sectional geometry. The validity for this is justified by showing that magnetic fields inside the field-free core are negligibly small and by checking that calculation results of ac losses for elliptic tapes agree with the prediction by the theory of Norris. The ac losses for rectangular tapes behave as a thin strip superconductor in high I0 values near critical current, while showing a gradual deviation from this behavior as I0 is lowered. A decrease in the aspect ratio of width to thickness in the rectangular tape makes the deviation more remarkable.

数値計算による高温超電導テープの交流通電損失の解析

A new method is proposed to carry out numerical calculations on the shape of field-free core, current distribution, and AC transport losses in self-fields as a function of current amplitude I0 for high-Tc superconducting tapes with arbitrary cross-sectional geometry. Its validity can be confirmed by verifying that calculated results of AC losses for elliptic tapes agree with the prediction advanced by the theory of Norris. An application to rectangular tapes leads to the finding that the AC losses for them behave as a thin-strip superconductor in high I0 values near critical current Ic, but gradually deviate from this behavior with decreasing I0. A decrease in the aspect ratio of width to thickness for rectangles makes the deviation more remarkable. By using this method, the AC transport losses for two kinds of the 7-filamentary tapes with different filament arrangements are calculated, and the results are compared with the experimental behaviors of losses for tapes fabricated by a powder-in-tube method using the Ag sheath. The measured losses can be explained neither by the prediction for an elliptic tape nor by that for a thin strip based on the theory of Norris. Furthermore, the loss values depend on the filament arrangement, which is explained by the calculated results of loss-density distribution. The influence of filament arrangement on the loss behaviors is suppressed as the number of filaments increases to 37, from 7.

Nonclosure Properties of Two-Dimensional One-Marker Automata

Several nonclosure properties of each class of sets accepted by two-dimensional alternating one-marker automata, alternating one-marker automata with only universal states, nondeterministic one-marker automata, deterministic one-marker automata, alternating finite automata, and alternating finite automata with only universal states are shown. To do this, we first establish the upper bounds of the working space used by "three-way" alternating Turing machines with only universal states to simulate those "four-way" non-storage machines. These bounds provide us a simplified and unified proof method for the whole variants of one-marker and/or alternating finite state machine, without directly analyzing the complex behavior of the individual four-way machine on two-dimensional rectangular input tapes. We also summarize the known closure properties including Boolean closures for all the variants of two-dimensional alternating one-marker automata.

Preface

Several nonclosure properties of each class of sets accepted by two-dimensional alternating one-marker automata, alternating one-marker automata with only universal states, nondeterministic one-marker automata, deterministic one-marker automata, alternating finite automata, and alternating finite automata with only universal states are shown. To do this, we first establish the upper bounds of the working space used by "three-way" alternating Turing machines with only universal states to simulate those "four-way" non-storage machines. These bounds provide us a simplified and unified proof method for the whole variants of one-marker and/or alternating finite state machine, without directly analyzing the complex behavior of the individual four-way machine on two-dimensional rectangular input tapes. We also summarize the known closure properties including Boolean closures for all the variants of two-dimensional alternating one-marker automata.

CONSTANT LEAF-SIZE HIERARCHY OF TWO-DIMENSIONAL ALTERNATING TURING MACHINES

“Leaf-size” (or “branching”) is the minimum number of leaves of some accepting computation trees of alternating devices. For example, one leaf corresponds to nondeterministic computation. In this paper, we investigate the effect of constant leaves of two-dimensional alternating Turing machines, and show the following facts: (1) For any function L(m, n), k leaf- and L(m, n) space-bounded two-dimensional alternating Turing machines which have only universal states are equivalent to the same space bounded deterministic Turing machines for any integer k≥1, where m (n) is the number of rows (columns) of the rectangular input tapes. (2) For square input tapes, k+1 leaf- and o(log m) space-bounded two-dimensional alternating Turing machines are more powerful than k leaf-bounded ones for each k≥1. (3) The necessary and sufficient space for three-way deterministic Turing machines to simulate k leaf-bounded two-dimensional alternating finite automata is nk+1, where we restrict the space function of three-way deterministic Turing machines to depend only on the number of columns of the given input tapes.

(001) grain boundaries in Ag-clad Bi2Sr2Ca1Cu2O8+y (BSCCO) tapes

Recently, Ag-clad tapes of Bi-cuprate superconductors have shown great promise for application as conductors in very high magnetic fields at temperature 4-20 K. High critical current densities (Jc) with weak field dependence indicate that the powder-in-tube process can drastically reduce the effect of grain boundary weak links at 4-20 K. It is thus of great interest to study the grain boundaries in the Ag-clad BSCCO tapes to understand their effect on the Jc.BSCCO Ag-clad wires with 2:2:1:2 starting composition were drawn and rolled to rectangular tapes (0.1 x 3 mm) with BSCCO core thickness of 45μm. The sample was heated at 920°C for 15 minutes, cooled to 840°C at 10°C/h, then annealed at 840°C for 70 h. The measured Jc values exceed 2x104 A/cm2 (5T, 4.2K) and do not exhibit obvious weak link behaviour. In order to investigate the (001) grain boundaries, samples were made by bonding several tapes together along their broad face. Thin longitudinal slices were cut and then ion milled at 4.5 kV in liquid nitrogen. TEM was carried out by using a JEOL 200CX-II at 200 kV.

THE SIMULATION OF TWO-DIMENSIONAL ONE-MARKER AUTOMATA BY THREE-WAY TURING MACHINES

We denote a two-dimensional deterministic (nondeterministic) one-marker automaton by 2-DM1 (2-NM1), and a three-way two-dimensional deterministic (nondeterministic) Turing machine by TR2-DTM (TR2-NTM). In this paper, we show that the necessary and sufficient space for TR2-NTMs to simulate 2-DM1s (2-NM1s) is n log n (n2), and the necessary and sufficient space for TR2-DTMs to simulate 2-DM1s (2-NM1s) is 2O(n log n) (2 O(n2)), where n is the number of columns of rectangular input tapes.