Functionalized and Postfunctionalizable Porous Polymeric Films through Evaporation-Induced Phase Separation Using Mixed Solvents

Condensation of water droplets during rapid evaporation of a polymer solution, under humid conditions, has been known to generate uniformly porous polymer films. Similar porous films are also formed when a solution of the polymer in THF containing small amounts of water, is allowed to evaporate rapidly under air flow; this suggests that water droplets may be formed during the final stages of film formation. In the presence of added surfactants, the interface of water droplets could become lined with the surfactants and consequently the internal walls of the pores generated, upon removal of the water, could become decorated with the hydrophilic head groups of the surfactant molecules. In a series of carefully designed experiments, we have examined the effect of added surfactants, both anionic and cationic, on the formation of porous PMMA films; the films were prepared by evaporating a solution of the polymer in THF containing controlled amounts of aqueous surfactant solutions. We observed that the average size of the pores decreases with increasing surfactant concentration, while it increases with increasing amounts of added water. The size of the pores and their distribution were examined using AFM and IR imaging methods. Although IR imaging possessed inadequate resolution to confirm the presence of surfactants at the pore surface, exchange of the inorganic counterion, such as the sodium-ion of SDS, with suitable ionic organic dyes permitted the unequivocal demonstration of the presence of the surfactants at the interface by the use of confocal fluorescence microscopy.

Mixed ionic and electronic conduction in zirconia and its applications in metallurgy

Mixed ionic and electronic conduction in Zr02-based solid electrolytes was studied.The effect of impurities and second-phase particles on the mixed conduction parameter, P,, was measured for different types of ZrOZ electrolytes. The performance of solid-state sensors incorporating ZrOZ electrolytes is sometimes limited by electronic conduction in ZrOZ, especially at temperatures >I800 K. Methods for eliminating or minimizing errors in measured emf due to electronically driven transport of oxygen anions are discussed. Examples include probes for monitoring oxygen content in liquid steel as well as the newly developed sulfur sensor based on a ZrOz(Ca0) + CaS electrolyte. The use of mixed conducting ZrOZ as a semipermeable membrane or chemically selective sieve for oxygen at high temperatures is discussed. Oxygen transport from liquid iron to CO + C& gas mixtures through a ZrOZ membrane driven by a chemical potential gradient, in the absence of electrical leads or imposed potentials, was experimentally observed.

Physical chemistry of mixed conducting zirconia ceramics

Suivant la pression partielle d'oxygène, la zircone peut être conducteur ionique ou électronique. Mise au point de méthodes de mesures de f.é.m. permettant de s'affranchir des sources d'erreur introduites par ces propriétés.

Towards formal verification of analog mixed signal designs using SPICE circuit simulation traces

An extension to a formal verification approach of hybrid systems is proposed to verify analog and mixed signal (AMS) designs. AMS designs can be formally modeled as hybrid systems and therefore lend themselves to the formal analysis and verification techniques applied to hybrid systems. The proposed approach employs simulation traces obtained from an actual design implementation of AMS circuit blocks (for example, in the form of SPICE netlists) to carry out formal analysis and verification. This enables the same platform used for formally validating an abstract model of an AMS design, to be also used for validating its different refinements and design implementation; thereby, providing a simple route to formal verification at different levels of implementation. The feasibility of the proposed approach is demonstrated with a case study based on a tunnel diode oscillator. Since the device characteristic of a tunnel diode is highly non-linear with a negative resistance region, dynamic behavior of circuits in which it is employed as an element is difficult to model, analyze and verify within a general hybrid system formal verification tool. In the case study presented the formal model and the proposed computational techniques have been incorporated into CheckMate, a formal verification tool based on MATLAB and Simulink-Stateflow Framework from MathWorks.

Photocatalytic Activity of Combustion Synthesized ZrO(2) and ZrO(2)-TiO(2) Mixed Oxides

Tetragonal ZrO(2), synthesized by solution combustion technique, was found to be photocatalytically active for the degradation of anionic dyes. The compound was characterized by FT-Raman spectroscopy, X-ray photoelectron spectroscopy, FT-infrared spectroscopy, UV-vis spectroscopy, BET surface area analysis, and zero point charge pH measurement. A high concentration of surface hydroxyl groups was observed over the catalyst, as confirmed by XPS and FUR. The photocatalytic degradation of orange G, amido black, remazol brilliant blue R, and alizarin cyanine green (ACG) was carried out with this material. The effect of pH, inorganic. salts, and H(2)O(2) on the activity of the catalyst was also studied, and it was found that the catalyst maintained its activity at a wide range of pH and in the presence of inorganic salts. Having established that ZrO(2) was photocatalytically active, mixed oxide catalysts of TiO(2)-ZrO(2) were also tested for the photocatalytic degradation of ACG, and the 50% ZrO(2)-TiO(2) mixed oxides showed activity that was comparable to the activity of TiO(2).

Current‐limiting action of mixed‐phase BaTiO3 ceramic semiconductors

Stable and highly reproducible current‐limiting characteristics are observed for polycrystalline ceramics prepared by sintering mixtures of coarse‐grained, donor‐doped BaTiO3 (tetragonal) as the major phase and ultrafine, undoped cubic perovskite such as BaSnO3, BaZrO 3, SrTiO3, or BaTiO3 (cubic). The linear current‐voltage (I‐V) relation changes over to current limiting as the field strength increases, when thermal equilibrium is attained. The grain‐boundary layers with low donor and high Sn, Zr, or Sr have depleted charge carrier density as compared to that in the grain bulk. The voltage drop at the grain‐boundary layers diminishes the temperature gradient between the interior and surface regions.

Optimum Load Shedding Through Programming Techniques

This paper obtains a new accurate model for sensitivity in power systems and uses it in conjunction with linear programming for the solution of load-shedding problems with a minimum loss of loads. For cases where the error in the sensitivity model increases, other linear programming and quadratic programming models have been developed, assuming currents at load buses as variables and not load powers. A weighted error criterion has been used to take priority schedule into account; it can be either a linear or a quadratic function of the errors, and depending upon the function appropriate programming techniques are to be employed.

A note on magnetization of high temperature superconductors (YBCO, BSCCO) in mixed state

We present a critical study of the temperature and field dependence magnetization of high temperature superconductors (HTSCs). The controversial field dependence of dM/dInB for YBa(2)Cu(3)O(7) (YBCO) and Bi(2)Sr(2)CaCu(2)O(8) (BSCCO) is discussed using different models. Moreover, for both the systems the magnetization (M(H)) dependence is compared with field (H) dependence. (C) 2011 Elsevier B.V. All rights reserved.

Vlbi observations of a mixed selection of extra-galactic objects

VLBI observations at 6 cm reported of several weak radio cores of normal and Seyfert galaxies, of radio sources which have jets or a head tail morphology as well as some stronger cores of flat spectrum galaxies from the NRAO-Bonn "S 4", survey. Nearly all sources were detected at an angular resolution of approximately 15 milli arc s. Some of the sources are resolved at this level.

Impact-Angle-Constrained Suboptimal Model Predictive Static Programming Guidance of Air-to-Ground Missiles

A nonlinear suboptimal guidance law is presented in this paper for successful interception of ground targets by air-launched missiles and guided munitions. The main feature of this guidance law is that it accurately satisfies terminal impact angle constraints in both azimuth as well as elevation simultaneously. In addition, it is capable of hitting the target with high accuracy as well as minimizing the lateral acceleration demand. The guidance law is synthesized using recently developed model predictive static programming (MPSP). Performance of the proposed MPSP guidance is demonstrated using three-dimensional (3-D) nonlinear engagement dynamics by considering stationary, moving, and maneuvering targets. Effectiveness of the proposed guidance has also been verified by considering first. order autopilot lag as well as assuming inaccurate information about target maneuvers. Multiple munitions engagement results are presented as well. Moreover, comparison studies with respect to an augmented proportional navigation guidance (which does not impose impact angle constraints) as well as an explicit linear optimal guidance (which imposes the same impact angle constraints in 3-D) lead to the conclusion that the proposed MPSP guidance is superior to both. A large number of randomized simulation studies show that it also has a larger capture region.

Null Dereference Verification via Over-approximated Weakest Pre-conditions Analysis

Null dereferences are a bane of programming in languages such as Java. In this paper we propose a sound, demand-driven, inter-procedurally context-sensitive dataflow analysis technique to verify a given dereference as safe or potentially unsafe. Our analysis uses an abstract lattice of formulas to find a pre-condition at the entry of the program such that a null-dereference can occur only if the initial state of the program satisfies this pre-condition. We use a simplified domain of formulas, abstracting out integer arithmetic, as well as unbounded access paths due to recursive data structures. For the sake of precision we model aliasing relationships explicitly in our abstract lattice, enable strong updates, and use a limited notion of path sensitivity. For the sake of scalability we prune formulas continually as they get propagated, reducing to true conjuncts that are less likely to be useful in validating or invalidating the formula. We have implemented our approach, and present an evaluation of it on a set of ten real Java programs. Our results show that the set of design features we have incorporated enable the analysis to (a) explore long, inter-procedural paths to verify each dereference, with (b) reasonable accuracy, and (c) very quick response time per dereference, making it suitable for use in desktop development environments.

Continuous phase transition in mixed-valent manganite Nd0.6Pb0.4MnO3

The critical behaviour has been investigated in single crystalline Nd0.6Pb0.4MnO3 near the paramagnetic to ferromagnetic transition temperature (TC) by static magnetic measurements. The values of TC and the critical exponents β, γ and δ are estimated by analysing the data in the critical region. The exponent values are very close to those expected for 3D Heisenberg ferromagnets with short-range interactions. Specific heat measurements show a broad cusp at TC (i.e., exponent α<0) being consistent with Heisenberg-like behaviour.