Wideband dielectric characterization using a dielectric filledcavity adapted to the end of a transmission line

The concept, analysis, and testing of a technique for characterizing dielectric materials over a wide band of frequencies are presented. The technique utilizes a cylindrical cavity completely filled with a sample of the dielectric material under test and adapted to the end of the precision air line. The complex permittivity of the filling dielectric is derived from the measured reflection coefficient. This technique offers great advantages over conventional methods where the sample is placed in a resonant cavity or inserted in a transmission line     

Prediction of concrete initial setting time in field conditions through multivariate regression analysis

Construction of large concrete structures usually requires pouring multiple batches of concrete mixes along 1 day, which creates setting irregularities that increase the potential of crack development within pours. For the case of bridge decks, it is recommended that the initial concrete material should stay plastic over the entire casting operation of a poured bridge segment. Uniform setting of multiple batches is possible if setting times could be predicted and controlled in field conditions. In this study, more than 70 different Class K concrete mixes were manufactured and cast in field conditions, which provided material characteristics along with environmental data that were used to predict concrete initial setting times through multivariate regression analysis. Two prediction models were achieved, corresponding to the addition of set retarding and set accelerating admixtures, respectively. Validating field tests demonstrated that good predictions of concrete initial setting times can be accomplished with 2% error, when accurate field weather forecasts are available. This work also demonstrates the use of the prediction relations, with the objective of achieving uniform thermo-mechanical properties of a pouring sequence in the field.     

Effect of hydrogen-related shallow donor on the physical and chemical properties of Ag-doped ZnO nanostructures

Journal of Materials Science: Materials in Electronics - Silver-doped zinc oxide nanostructures (Ag/ZnO NSs) with Ag content of 0 wt%, 5 wt%, 10 wt%, and 20 wt% were synthesized using a...     

Creep analysis of bolted flange joints

In the petrochemical and nuclear industries, the difficulty in assessing the effect of creep on the tightening load of bolted flanged connections is recognized. Under high temperatures, the leak tightness of bolted joints is compromised due to the loss of the bolt load as a result of creep of not only the gasket and bolt materials but also the flange material. Apart from acknowledgment of this effect, there exists no established design calculation procedure that accounts for creep. This is because the relaxation of the bolt load and the corresponding loss of the gasket contact stress are not easy to assess analytically. The main objective of the work is the development of a simple analytical solution to the creep-relaxation problem encountered in bolted flange connections of the float type. Particular emphasis is put towards relaxation caused by the flange and bolt material creep.     

Enhanced uptake of CI Direct Red 79 by cotton in the presence of certain amino acids

Pretreatment of cotton fibres with solutions of alanine, valine, ß-phenylalanine or histidine in aqueous acetic acid increases the rate of dyeing with CI Direct Red 79 and improves the wet-fastness properties of the dyed cotton.     

Energy resource allocation using multi-objective goal programming: the case of Lebanon

The traditional energy-resources allocation problem is concerned with the allocation of limited resources among the end-uses such that the overall return is maximized. In the past, several techniques have been used to deal with such a problem. In this paper, the energy allocation process is looked at from two points of view: economy and environment. The economic objectives include costs, efficiency, energy conservation, and employment generation. The environmental objectives consider environmental friendliness factors. The objective functions are first quantified and then transformed into mathematical language to obtain a multi-objective allocation model based upon pre-emptive goal programming techniques. The proposed method allows decision-makers to encourage or discourage specific energy resources for the various household end-uses. The case of Lebanon is examined to illustrate the usefulness of the proposed technique.     

Improving the stiffness of commingled thermoplastics

One of the limitations of commingled recycled plastics is their low flexural modulus, resulting from both the linear nature of thermoplastics and the incompatibility of the polymer phases. The goal of this study was to increase the flexural modulus of commingled recycled plastics by the addition of small amounts of polyester that acted both as a compatibilizer and a crosslinking agent. It was found that the increase in flexural modulus was caused by the unsaturated polyester acting as a filler, the improvement in compatibility of the phases, and the crosslinking of the commingled plastics. The increase was offset somewhat by a decrease in crystallinity of the phases.     

Growth, structure, and properties of BiFeO3/-BiCrO3 films obtained by dual cross beam PLD

The properties of epitaxial Bi(2)FeCrO(6) thin films, recently synthesized by pulsed laser deposition, have partially confirmed the theoretical predictions (i.e., a magnetic moment of 2 micro(B) per formula unit and a polarization of approximately 80 microC/cm(2) at 0 K). The existence of magnetic ordering at room temperature for this material is an unexpected, but very promising, result that needs to be further investigated. Because magnetism is assumed to arise from the exchange interaction between the Fe and Cr cations, the magnetic behavior is strongly dependent on both their ordering and the distance between them. We present here the successful synthesis of epitaxial Bi(2)Fe(x)CryO(6) (BFCO x/y) films grown on SrTiO3 substrates using dual crossed-beam, pulsed-laser deposition. The crystal structure of the films has different types of (111)-oriented superstructures, depending on the deposition conditions. The multiferroic character of BFCO (x/y) films is proven by the presence of both ferroelectric and magnetic hysteresis at room temperature. The oxidation state of Fe and Cr ions in the films is shown to be 3+ only, and the difference in macroscopic magnetization with Fe/Cr ratio composition could only be due to ordering of the Cr(3+) and Fe(3+) cations to the modification of the exchange interaction between them.     

Electrical and Optical Properties of Transparent Conducting p‐Type SrTiO3 Thin Films

We report a systematic study of the electrical and optical properties of epitaxial perovskite p‐type In‐doped SrTiO₃ thin films (SrIn_xTi_1?xO₃, 0 ≤ x ≤ 0.15) grown on single‐crystal (100)‐oriented LaAlO₃ substrates using a hybrid method which combines pulsed laser deposition and molecular beam epitaxy in a range of deposition conditions. X‐ray diffraction analysis confirms the epitaxial growth of high crystal quality films. Four‐point probe and Hall Effect measurements demonstrate that the films are p‐type semiconductors with a low resistivity of ~10^?2 Ω·cm and a high carrier concentration of ~10¹⁹ cm^?3. The optical transmittance spectra reveal that the films are highly transparent (?70%) in the visible region.     

Multiferroic nanoscale Bi(2)FeCrO(6) material for spintronic-related applications

We report the control of the growth mode of Bi(2)FeCrO(6) thin and ultrathin films by either tuning the pulsed laser deposition parameters or by using a buffer layer. The films are epitaxial and the heterostructures exhibit very smooth interfaces, thus eliminating the main obstacle in the realization of tunnel junctions. By characterizing the functional properties of thin films we find that Bi(2)FeCrO(6) retains its room temperature multiferroic character even at the nanoscale. The coexistence of these properties in ultra-thin Bi(2)FeCrO(6) films will pave the way to design multifunctional devices for applications in spintronics and electronics, such as ferroelectric tunnel junctions or magnetic tunnel junctions with ferroelectric barriers.