Tetragonal Tungsten Bronze Niobate, K0.2Sr0.4NbO3: A New Material for Capacitors with Flat Dielectric Curves

A new ceramic for capacitors, which exhibits flat dielectric curves with relative permittivity values (ɛ) as high as 3000 (Y7R or X7R class), has been synthesized. Use of a niobate, K_0.2Sr_0.4NbO₃ (KSN), with a tetragonal tungsten bronze structure (TTB), as a major phase for the fabrication of such ceramics is shown for the first time. Nevertheless, the addition of perovskites as minor agents—PbMg_1/3Nb_2/3O₃ (PMN)—is necessary to obtain stable temperature. Moreover, the use of lithium salts as sintering agents has been shown to be important for the fabrication of these ceramics.     

An efficient algorithm for the global modeling of RF and microwave circuits using a reduced nonlinear lumped network (RNL/sup 2/N)-FDTD approach

In this letter, we present an efficient and simple reduced nonlinear lumped network (RNL/sup 2/N)-FDTD method for the global modeling of RF and microwave circuits. This method is a simplified version of the original nonlinear lumped network (NL/sup 2/N)-FDTD approach, which does not require a complicated precalculation and a huge back-storage compared to the former version.     

Convection behavior analysis of CMOS MEMS thermal accelerometers using FEM and Hardee’s model

This paper presents convection behavior investigation of CMOS MEMS convective accelerometers using both analytical and FEM techniques. In a first part, a newly developed accelerometer 3D model is used in FEM simulations to model convection behavior as a function of design geometry and temperature. Using various sizes of two different cover shapes, sensitivity reading and its maximum position in cavity are found to be largely affected by both cover size and shape. In addition, a sensor with cavity width of 600 μm produces sensitivity saturation starting at a cavity depth of 200 μm, for both cover shapes. Using FEM data and curve fitting, differential temperature is claimed to be linearly linked to the effective heater temperature to the power of 1.7. Using the same cavity design and from computed heating efficiency values, we found that a 60 μm width heater offers the best efficiency. This cavity and heater designs give an optimal detector position of 120 μm from heater center along the sensitive axis. Moreover, dual axis accelerometers are found to be more power efficient than single axis ones. In the second part, we present Hardee’s spherical model and investigate its possible application on convective accelerometers. It is shown that inner and outer isotherms deformation, caused by accelerometer design and convection process, should be modeled by including sensor geometry parameters in the derived governing equations. Moreover, Hardee’s biasing temperature relation has to be revised if it is to be used for convective accelerometers.     

Sneddon syndrome: a case report

Doxorubicin is cardiotoxic and its use must be monitored carefully. Incidence of refractory cardiac failure is shown to increase once the cumulative dose exceeds 450 mg/m2. However, significant decline of ejection fraction (EF) may occur even at lower dose levels. EF was monitored using Multigated Radionuclide Angiography (MUGA) scan of all consecutive lung cancer patients, treated with Doxorubicin based regimens. Thirteen of 82 patients showed a significant (more than 15%) decline of left ventricular EF. The dose of doxorubicin producing this decline ranged between 91-180 mg/m2. Actual decline in EF ranged between 16-45%. Only 5 of 13 patients developed symptoms attributable to the cardiac disease. Doxorubicin can alter EF significantly in lung cancer patients at levels well below which are considered 'safe'. The reason for massive decline in ejection fraction in these patients has been hypothesized.     

Dynamic modelling of consecutive reactions: Application to the acrylonitrile amination

When dealing with optimal control problems to maximize the selectivity of reactions for fine chemical synthesis, representative kinetic and thermodynamic models should be available. While literature appears to be very extensive on theoretical approaches to solve the problem, examples presenting complete models of chemical transformations are scarce. This paper presents the identification of consecutive reactions carried out in a batch reactor. Material and energy balances, satisfying dynamical state evolutions in the temperature range 20-60°C are deduced, for concentrations of acrylonitrile ranging up to 1.6 kmol·m^?3. The stoichiometric network is simplified into two reactions, one reversible and one irreversible. Reaction enthalpies are measured from isothermal runs conducted in the RC1 heat-flow calorimeter from Mettler Toledo.     

A striking observation on the fluorescence of a twisted intramolecular charge transfer (TICT) molecule used to probe polymer dynamics in the bulk state

An anomalous effect on the twisted intramolecular charge transfer (TICT) phenomenon of 4-(N,N-dimethylamino) benzonitrile (DMABN) dissolved in elastomers such as poly(propylene oxide), poly(ethylene oxide) has been observed. Under irradiation, the normal fluorescence of DMABN in these matrices has been found to increase strongly while the emission arising from the TICT state decreases slightly.     

Photodegradation of acid dyes in nylon films

The photodegradation of three representative acid dyes commonly used to colour nylon was studied in nylon films. It was observed that irreversible photodegradation of the dyes occurs only at wavlengths shorter than 350nm and that the quantum yield increases as the photolysis wavelength decreases. It was also found that u.v. photolysis of the dyes is partially reversible and that photodegradation is inhibited by oxygen. Evidence is presented that photodegradation occurs by a reduction process, involving hydrogen transfer from the nylon polymer to the excited dye.     

Modeling the rate of corrosion of carbon steel using activated diethanolamine solutions for CO2 absorption

A mechanistic model is developed to investigate the influence of an activator on the corrosion rate of carbon steel in the absorption processes of carbon dioxide (CO₂). Piperazine (PZ) is used as the activator in diethanolamine (DEA) aqueous solutions. The developed model for corrosion takes into consideration the effect of fluid flow, transfer of charge and diffusion of oxidizing agents and operating parameters like temperature, activator concentration, CO₂ loading and pH. The study consists of two major models: Vapor-liquid Equilibrium (VLE) model and electrochemical corrosion model. The electrolyte-NRTL equilibrium model was used for determination of concentration of chemical species in the bulk solution. The results of speciation were subsequently used for producing polarization curves and predicting the rate of corrosion occurring at the surface of metal. An increase in concentration of activator, increases the rate of corrosion of carbon steel in mixtures of activated DEA.