Electrical characterization of carbon nanotube Y-junctions: a foundation for new nanoelectronics

A review on the syntheses and electrical characterization of Y-shaped multi-walled carbon nanotube morphologies is presented. Modified thermal CVD processes, using Ti precursors, are used to grow Y-junctions of different geometries and distribution of catalyst particles. It has been established that novel electrical switching behavior is feasible, where any one of the three branches of the Y-junction can be used for modulating the electrical current flow through the other two branches. Current blocking behavior, leading to perfect rectification, is seen which could be related to the interplay of the carrier lifetime and the transit time. The overall goal is to investigate the possibility of obtaining novel functionality at the nanoscale, which can lead to new device paradigms.     

Effect of pH on the Crystallization of Homogeneously Precipitated Nanosized PZT Powder

Nanosized lead zirconate titanate (PZT) powder with Zr:Ti ratio in the morphotropic phase boundary region was synthesized by homogeneous precipitation of metal ions. The powder precipitated at 90°C and at pH 6.7 resulted single-phase perovskite lead zirconate titanate powder when calcined at 550°C and above for 4 hours in air. The solution pH and the precipitation temperature strongly affect the composition of the calcined powder. The results obtained by structural characterization of homogeneously precipitated powder were compared with that obtained from the conventional precipitation method using ammonia in terms of crystallization, homogeneity, and microstructure. The homogeneously precipitated powder showed smaller particle size, minimum agglomeration and uniform shape on calcination and annealing. Powdered samples that precipitated by homogeneous precipitation crystallized directly to perovskite PZT, without any intermediate pyrochlore phase formation. In contrast, the NH₃ precipitated powder converted to perovskite PZT via metastable pyrochlore and it showed phase segregation upon annealing at higher temperatures. The reaction kinetics has been studied by X-ray diffraction, differential thermal analysis, and differential scanning calorimetry.     

On the notion of control signals in digital designs

The concept of control signals is fundamental to digital design. It evokes the notion of one or more signals that influence computation on other signals in a system, and regulate the behavior of the system. A formal definition of control signals is presented. It is argued that knowledge of the control signals in a complex design such as a microprocessor or a computer is crucial to the comprehension and specification of the design and that knowledge of the control signals of a design leads to a more efficient hardware implementation. The identification of control signals in two microprocessors are presented as examples     

Conductivity study of polyethylene oxide (PEO) complexed with sodium bicarbonate

Ion conducting thin film polymer electrolytes based on polyethylene oxide (PEO) complexed with NaHCO₃ salt has been prepared using solution-cast technique. The complexation of NaHCO₃ salt with PEO is confirmed by XRD and IR studies. DC conductivity in the temperature range 303–368 K has been evaluated. The conductivity is found to increase in the PEO complex with the NaHCO₃ salt and also with an increase in temperature. Using this polymer electrolyte, an electrochemical cell with the configuration Na/(PEO + NaHCO₃)/(I₂ + C + electrolyte) has been fabricated and its discharge characteristics studied. Open Circuit Voltage (OCV) and Short Circuit Current (SCC) are found to be 2.69 V and 1.28 mA, respectively. Other parameters associated with the cell are evaluated and presented in this paper.     

Pressure drop for single and two‐phase flow of non‐newtonian liquids in helical coils

New experimental results on pressure loss for the single and two‐phase gas‐liquid flow with non‐Newtonian liquids in helical coils are reported. For a constant value of the curvature ratio, the value of the helix angle of the coils is varied from 2.56° to 9.37°. For single phase flow, the effect of helix angle on pressure loss is found to be negligible in laminar flow regime but pressure loss increases with the increasing value of helix angle in turbulent flow conditions. On the other hand, for the two‐phase flow, the well‐known Lockhart‐Martinelli method correlates the present results for all values of helix angle (2.56‐9.37°) satisfactorily under turbulent/laminar and turbulent/turbulent conditions over the following ranges of variables as: 0.57 ≤ n′ ≤ 1; Re′ < 4000; Re_l < 4000; Re_g < 8000; 8 ≤ x ≤ 1000 and 0.2 ≤ De′ ≤ 1000.     

Membrane degumming of crude rice bran oil: Pilot plant study

The procedure for the classical chemical refining of vegetable oils consists of degumming, alkali neutralization, bleaching, and deodorization. Conventional refining of rice bran oil using alkali gives oil of acceptable quality, but the refining losses are very high. A critical work has been carried out to study the application of membrane technology in the pretreatment of crude rice bran oil. Oils intended for physical refining should have a low phosphorus content, and this is not readily achievable by the conventional acid/water degumming process. The application of membrane technology for the pretreatment of rice bran oil has been investigated. The process has already been successfully applied to other vegetable oils. Ceramic membranes, which are important from the commercial point of view, were examined for this purpose. The results showed that the membrane‐filtered oils met the requirements of physical refining, with a substantial reduction in color. It was observed that most of the waxy material was also rejected. Experiments were carried out to establish the relationship between permeate flux and rejection with membrane pore size, trans‐membrane pressure and micellar solute concentration.     

Negation as Failure as Resolution

Providing a clean procedural semantics of the Negation As Failure rule in Logic Programming has been an open problem for some time now. This rule has been treated as a technique in nonmonotonic reasoning, not as a rule in classical logic. This paper contains a demonstration of the negation as failure rule as a resolution procedure in first-order logic. We present a sound and complete resolution scheme for negation as failure rule for the larger class of constraint logic programs. The approach is to consider a canonical partition of the completion of a definite (constraint) program into the IF and the FI programs. We show that a negated goal, provable from the completed definite program is provable from just the FI part. The clauses in this program have a structure dual to that of definite Horn clauses. We describe a sound and complete linear resolution rule for this fragment, and show that a resolution proof of the negated goal from the FI part corresponds to a finite failure tree resulting from classical linear resolution applied to the goal on the If part of the original definite program. Our work shows that negation as failure rule can be computationally efficient in the sense that the SLD-resolution on the If part of a definite program along with the negation as failure rule is more efficient than a direct resolution procedure on the completion of that program.     

Copper extraction into emulsion liquid membranes using LIX 984N-C®

The extraction of copper from aqueous sulfate media into ELMs using the extractant LIX 984N-C was studied. Appropriately characterized emulsions on the basis of viscosity and internal drop sizes were used to study the effect of different parameters on extraction. The effects of stirring speed, surfactant concentration, pH of the external continuous phase, carrier concentration, internal phase stripping acid concentration and initial copper concentration are reported. These results show that LIX 984N-C efficiently extracts copper at low pH values typical of leach solutions. It was found that LIX 984N-C could extract up to 80% copper from aqueous solutions at pH value of 1. Performance of LIX 984N-C was also compared with LIX 84 and LIX 84-I at different pH values. Results indicate that LIX 984N-C could open up new avenues for extraction of copper into ELMs, not only from dilute solutions, but also from sulfuric acid leach solutions.     

Chimie douce hydrogen production from Hg contaminated water,with desirable throughput,and simultaneous Hg-removal

Hydrogen's widespread use is fraught with many difficulties. The challenges currently are to do with safety concerns in gas storage and transportation, and low rate of production leading to non-viability of technologies at the point-of-use. Another global concern of immediate relevance involves heavy-metal ion pollution. Viable processes which can simultaneously remove and result in beneficiation of the contaminants are hitherto rarely reported. In this context we report a single-step, in situ co-reduction approach which has the dual advantage of (i) Hg contaminant removal, and (ii) room temperature hydrogen production. Hydrogen is produced via galvanic corrosion of in situ synthesized nanoaluminium amalgam. The production rate (720 mL/min for 0.5 g-Al salt) is far superior to what would be expected from the use of pure hydrides, and/or using bulk amalgams at room temperature. The method is simple, chimie douce (i.e soft chemical), hence potentially affordable, and capable of providing a means of beneficiating Hg contaminated water present in effluents from certain industries (for example, industries which uses chlor-alkali process). The in situ co-reduction approach helps in bypassing the usual rate limiting step which involves formation of an alumina passivation layer on hydrolytic material surface. Given the potential that exists in scale down and up, this approach offers a method to address the long standing challenge of point-of-use hydrogen availability.     

Estimation of sharma constant and thermoacoustic properties of fatty acids

From the volume expansivity α, a number of thermoacoustic parameters, including the Sharma constant,S ₀, are estimated for four fatty acids as a function of temperature. The Sharma constant, which was established to be a constant with the characteristic value 1.11 ± 0.01 over a number of systems investigated by earlier investigators, is also found to be a constant with the same value for all fatty acids under investigation. Further, the Sharma constant,S ₀, is independent of temperature and dependent only on α. All other parameters estimated are discussed and compared with the values reported in the literature by earlier workers for different systems.