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In the oil and gas industry, safety and operational efficiency at production sites are of paramount importance. A reliable non-destructive testing technology for non-metallic pipes has a high potential financial impact, since it may facilitate the replacement of metallic pipes with non-metallic ones. This article features a perspective and future trends in the field of terahertz sensing technology. Importantly, several numerical simulations that illustrate many exciting potential applications for this emerging technology are described. These range from underground detection of spilt liquids and the content of pipes to the detection of cracks in plastic pipes using both frequency-domain and time-domain finite-element simulations. [ABSTRACT FROM AUTHOR]

Reports on measurements of the millimeter wave surface resistance of grain-aligned YBa[sub2]Cu[sub3]O[subx] bulk material grown by a liquid phase process. Effect of microstructure on surface resistance; Fabrication of grain-aligned polycrystalline samples of YBa[sub2]Cu[sub3]O[subx]; Determination of surface resistance.

Examines thermally activated flux creep of oriented grained and single-crystalline YBa[sub2]Cu[sub3]O[subx]. Preparation of the samples; Results.

Presents a study which developed a seeded directional solidification method which allows the fabrication of long lengths of single-domained yttrium barium[sub2]copper[sub3]oxygen[subx] superconductor with large cross-sectional areas and predetermined grain alignment. Requirement to maximize the current carrying capability of the superconductors; Factors that limit the practical application of the melt-textured superconductors; Process of the seeded directional solidification.

Provides information on a study which detailed the measurement of magnetic levitation and stiffness in several systems composed of a permanent magnet elastically suspended above a stationary melt-textured sample of Y-Ba-Cu-O. Calculation of the levitation force and vertical stiffness; Prediction in the force and magnetization measurements; Areas in which high-temperature superconductors are used.

We show that graphene-percolated polymer composites exhibit fractional capacitance response in the frequency range of 50 kHz-2 MHz. In addition, it is shown that by varying the loading of graphene within the matrix from 2.5% to 12%, the phase can be controllably tuned from -67° to -31°, respectively. The electrostatic fractional capacitors proposed herein are easy to fabricate and offer integration capability on electronic printed circuit boards. [ABSTRACT FROM AUTHOR]

In this paper, a method to find the maximum power transfer conditions in bimorph piezoelectric-based harvesters is proposed. Explicitly, we derive a closed form expression that relates the load resistance to the mechanical parameters describing the bimorph based on the electromechanical, single degree of freedom, analogy. Further, by taking into account the intrinsic capacitance of the piezoelectric harvester, a more descriptive expression of the resonant frequency in piezoelectric bimorphs was derived. In interest of impartiality, we apply the proposed philosophy on previously published experimental results and compare it with other reported hypotheses. It was found that the proposed method was able to predict the actual optimum load resistance more accurately than other methods reported in the literature. [ABSTRACT FROM AUTHOR]

Iron-clad MgB[SUB2] superconducting tapes with a MgB[SUB2] core cross-section area of 1.07 × 10[SUP-3] cm[SUP2] were fabricated using the standard powder-in-tube method. The starting precursor was ultrafine Mg and B mixture powder prepared by high-energy ball milling. Very good grain connections as well as grain refinement were obtained in tapes annealed at 850 °C. Under a 1.5-T external magnetic field, J[SUBc] is 1.07 × 10[SUP5] and 6.54 × 10[SUP3] A/cm[SUP2] at 20 and 30 K, respectively. An extrapolation to zero field at 20 K gives a J[SUBc] of 3.0 × 10[SUP5]A/cm[SUP2]. [ABSTRACT FROM AUTHOR]

Investigates melt texturing of Nd[sub 1-x]Ba[sub 2+x]Cu[sub 3]O[sub 7-sigma] type semiconductors. Crystallization of Re-123 compounds with neodymium; Preparation of calcined Nd-123 precursor powder by solid state reaction; Determination of the temperature in melt processed bars from Re-123 compounds.

Presents measurements of the direct current transport critical current of oriented-grained YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO) superconductors. Production of high quality current contacts using thick silver pads; Formation of silver pads by sputter etching the YBCO surface; Details of the contact fabrication method.

The intergrain transport current density and its anisotropy have been studied in oriented grained bulk YBa2Cu3Ox superconductors fabricated by the liquid phase processing method. Current density measurements were performed on oriented grained samples with the transport current aligned at different angles to the a-b plane. In these measurements, the transport current passed through several oriented grain boundaries. The results indicate that the critical current density drops rapidly when the transport current flows at small angles to the a-b plane and then decreases slowly at larger angles. At 77 K and zero magnetic field, an anisotropy ratio of about 25 is observed between Jc along a-b plane and that perpendicular to the plane. Further, the critical current density in these samples is found to depend weakly on magnetic field even though the current crosses grain boundaries. These results support the notion that grain boundaries of these superconductors are different in nature from those of solid-state sintered samples. [ABSTRACT FROM AUTHOR]

A liquid phase processing method for the fabrication of bulk YBa2Cu3Ox superconductors with large current carrying capacity has been developed. Slow cooling through the peritectic transformation (1030–980 °C) has been shown to control the microstructure of these superconductors. A cooling rate of 1 °C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area. Current density up to 18 500 A/cm2 has been obtained by continuous direct current measurements and in excess of 62 000 A/cm2 with pulse current of 10 ms duration and 75 000 A/cm2 using 1 ms pulse. The strong magnetic field dependence observed in sintered bulk 1-2-3 superconductors is also minimized to a large extent where a current density in excess of 37 000 A/cm2 is obtained in a field of 6000 G. [ABSTRACT FROM AUTHOR]

A study of field trapping by the incomplete Meissner effect was performed on YBa2Cu3O7-x at 77 K on both sintered and oriented grain samples. Fields of up to BT=1280 G have been trapped in small, oriented grain, planar samples. Circulating persistent current densities of up to 4800 A/cm2 are calculated. Based on these values hollow cylinders of 2 cm i.d. will trap fields of 6000 G. Initial creep is about 10%/week for both types of samples. Creep rate varies as (BT/BT,max)2. BT, due to an external field B0, is BT∝(1-e-cB0/BT,max). Lamination and mosaic assembly steps for producing practical magnets have been performed. [ABSTRACT FROM AUTHOR]

The critical current of grain aligned YBa2 Cu3Ox bulk material was investigated by inductive flux profile and ac susceptibility measurements. The induced current was directed perpendicular to the a-b plane oriented grains where high values of the transport current, have been previously reported. In spite of the unfavorable geometry of the investigated shielding current, no features of granularity were observed. The results yield a uniform bulk critical current density jc of 3×104 A/cm2 at zero field and 77 K. Field and temperature dependences of this jc are discussed and compared with those in a granular Y-Ba-Cu-O material. [ABSTRACT FROM AUTHOR]

The effects of strain range on the ultrasonic fatigue lifetime have been investigated in brass and aluminum. The fatigue of resonant dumbell specimens was carried out by means of a piezoelectrically driven exponential horn vibrating at a frequency of 20 kHz, and a displacement amplitude ranging between 10-4 and 10-6 meters. These specimens consisted of a gauge length with an arc of circular profile, flanked by a constant cross-sectional area shoulder. The stress distribution along the gauge length was calculated by considering a hyperbolic cosine function to represent the arc of the circle. Four different sized specimens were used such that the calculated stresses predict their failure to occur over a range between 104 and 109 cycles. All the fatigue tests were performed at a controlled temperature of 0 °C. The results obtained experimentally showed that the number of cycles to failure reasonably agree with Manson's fatigue life predictions in the elastic strain range. This seems to indicate that low-frequency fatigue life in brass and aluminum can be predicted from ultrasonic fatigue tests. [ABSTRACT FROM AUTHOR]