Desulphurization of damped battery paste by sodium carbonate and sodium hydroxide

The paper treats investigation of the desulphurization process of damped Pb-paste by Na₂CO₃ or NaOH. There is determined the effect of Na₂CO₃ (NaOH) concentration and the liquid–solid phase ratio on the process parameters (degree of desulphurization and degree of Na₂CO₃ (NaOH) utilization in function of the temperature and process duration). The optimum conditions for carrying out desulphurization of Pb-pastes by Na₂CO₃ or NaOH are determined in dependence of the used reactors (common reactor with laboratory agitator and rotary reactor of drum type). The content of inclusions in the solutions is examined with the purpose of producing sufficiently pure crystalline Na₂SO₄ for the industry.     

Rigorous modeling of high-speed semiconductor devices

We present a review of industrial heterostructure devices based on SiGe/Si and III–V compound semiconductors analyzed by means of numerical simulation. A comparison of device simulators and current transport models is given and critical modeling issues are addressed. Results from two-dimensional hydrodynamic analyses of heterojunction bipolar transistors (HBTs) are presented in good agreement with measured data. The examples are chosen to demonstrate technologically relevant issues which can be addressed by device simulation.     

Principles in the Evolutionary Design of Digital Circuits—Part I

An evolutionary algorithm is used as an engine for discovering new designs of digital circuits, particularly arithmetic functions. These designs are often radically different from those produced by top-down, human, rule-based approaches. It is argued that by studying evolved designs of gradually increasing scale, one might be able to discern new, efficient, and generalizable principles of design. The ripple-carry adder principle is one such principle that can be inferred from evolved designs for one and two-bit adders. Novel evolved designs for three-bit binary multipliers are given that are 20% more efficient (in terms of number of two-input gates used) than the most efficient known conventional design.     

In vivo quantification of endotoxin-induced nitric oxide production in pigs from Na15NO3-infusion

1. In this investigation the NO production rate is quantified in the pig during normotensive endotoxin-induced shock with increased cardiac output and during subsequent treatment with the NO synthase inhibitor N omega-monomethy-L-arginine (L-NMMA). NO production rate was derived from the plasma isotope-enrichment of 15N-labelled nitrate (15NO3-). 2. Three groups of animals (control, n = 5; endotoxin, n = 6; endotoxin + L-NMMA, n = 6) were anaesthetized and instrumented for the measurement of systemic and pulmonary haemodynamics. Each animal received a primed-continuous infusion of stable, non-radioactively labelled Na15 NO3 (bolus 30 mg, infusion rate 2.1 mg h-1). Arterial blood samples were taken 5, 10, 15, 30, 60 and 90 min later and every 90 minutes until the end of the experiment. 3. Continuous i.v. infusion of endotoxin was incrementally adjusted until mean pulmonary artery pressure (PAP) reached 50 mmHg and subsequently titrated to keep mean PAP approximately 35 mmHg. Hydroxyethylstarch was administered as required to maintain mean arterial pressure (MAP) > 60 mmHg. Six hours after the start of the endotoxin continuous i.v. L-NMMA (1 mg kg-1 h-1) was administered to the endotoxin + L-NMMA group. Haemodynamic data were measured before as well as 9 h after the start of the endotoxin. 4. After conversion of NO3- to nitro-trimethoxybenzene and gas chromatography-mass spectrometry analysis the total NO3- pool, basal NO3- production rate and the increase per unit time in NO3- production rate were calculated from the time-course of the 15NO3- plasma isotope-enrichment. A two compartment model was assumed for the NO3- kinetics, one being an active pool in which newly generated NO3- appears and from which it is eliminated, the other being an inactive volume of distribution in which only passive exchange takes place with the active compartment. 5. Although MAP did not change during endotoxin infusion alone, cardiac output (CO) increased by 42 +/- 40% (P < 0.05 versus baseline) by the end of the experiment due to a significant (P < 0.05 versus baseline) fall in systemic vascular resistance (SVR) to 65 +/- 25% of the baseline value. L-NMMA given with endotoxin did not change MAP, and both CO and SVR were maintained close to the pre-shock levels. 6. Baseline plasma NO3- concentrations were 43 +/- 13 and 40 +/- 10 mumol l-1 in the control and endotoxin animals, respectively, and did not differ at the end of the experiment (39 +/- 8 and 44 +/- 15 mumol l-1, respectively). The mean NO3- pool and basal NO3- production rate were 1155 +/- 294 mumol and 140 +/- 32 mumol h-1, respectively, without any intergroup difference. Endotoxin significantly increased NO3- production rate (23 +/- 10 mumol h-2, P < 0.05 versus control (6 +/- 7 mumol h-2) and endotoxin + L-NMMA groups). L-NMMA given with endotoxin (-1 +/- 2 mumol h-2, P < 0.05 versus control and endotoxin groups) had no effect. 7. Analysis of the time course of the 15NO3- plasma isotope enrichment during primed-continuous infusion of Na15NO3 allowed us to quantify the endotoxin-induced increase in NO3- production rate independently of total NO3- plasma concentrations. Low-dose L-NMMA blunted the increase in NO3- production rate while maintaining basal NO3- formation.     

Self-ignition and mechanisms of interaction of coal with oxygen at low temperatures. 3. Changes in the composition of coal heated in air at 60 °C

The gradual changes in weight, in elementary composition, in content of oxygen functional groups and in spin concentration have been established for samples of black coal, brown coal and lignite heated in air for a maximum of 1200 h. An intensive oxidative dehydrogenation was found to occur after more than 300 h oxidation. The process was preceded by a decrease in weight and in oxygen content; its start was found to coincide with a sharp increase in the alcoholic content and in coal ability to exchange hydrogen with calcium acetate, and its rate was found to diminish simultaneously with this ability. The acidity ascribed to phenols decreases gradually but it was found to increase at the end of the experiment. A decrease in ignition temperature was established for oxidized black coal, as well as a change in the composition of low-molecular-weight hydrocarbons evolved during the subsequent gradual heating in air. Some of the changes in the composition during coal oxidation may be explained by acid catalysis.     

Nonlinear Analysis of Structural Frame Systems by the State-Space Approach

This article presents the formulation and solution of the equations of motion for distributed parameter nonlinear structural systems in state space. The essence of the state-space approach (SSA) is to formulate the behavior of nonlinear structural elements by differential equations involving a set of variables that describe the state of each element and to solve them in time simultaneously with the global equations of motion. The global second-order differential equations of dynamic equilibrium are reduced to first-order systems by using the generalized displacements and velocities of nodal degrees of freedom as global state variables. In this framework, the existence of a global stiffness matrix and its update in nonlinear behavior, a cornerstone of the conventional analysis procedures, become unnecessary as means of representing the nodal restoring forces. The proposed formulation overcomes the limitations on the use of state-space models for both static and dynamic systems with quasi-static degrees of freedom. The differential algebraic equations (DAE) of the system are integrated by special methods that have become available in recent years. The nonlinear behavior of structural elements is formulated using a flexibility-based beam macro element with spread plasticity developed in the framework of state-space solutions. The macro-element formulation is based on force-interpolation functions and an intrinsic time constitutive macro model. The integrated system including multiple elements is assembled, and a numerical example is used to illustrate the response of a simple structure subjected to quasi-static and dynamic-type excitations. The results offer convincing evidence of the potential of performing nonlinear frame analyses using the state-space approach as an alternative to conventional methods.     

Complexes of poly(2-N,N-dimethylaminoethyl) methacrylate with heavy metals I. Preparation and properties

The present paper studies the synthesis of complexes of poly(2-N,N-dimethylaminoethyl) methacrylate with aqueous solutions of of salts of FeSO₄.2H₂O; CoCl₂.6H₂O; CuCl₂.2H₂O; VOSO₄.5H₂O; Na₂MoO₄.2H₂O and Na₂WO₄.2H₂O. The introduction of metal ions depends on the content of crosslinking agent and was in the range from 1.18 to 59.63 mg metal ion/g polymer carrier. The study of polymer complexes by IR and Moesbauer spectroscopy, as well as EPR, provides possibilities to suggest the probable co-ordination structure of the compounds.     

Low cost catalytic sorbents for NOx reduction. 2. Tests with no reduction reactives

Coal, char and activated char doped with model vanadium compounds (V₂O₅ and NH₄VO₃) and petroleum coke ash, PCA, (main metal components: V, Fe and Ni) have been tested as catalytic sorbents for NO reduction without the addition of a reduction reactive. The sorbents prepared have shown to be active for NO reduction at temperatures higher than 350 °C. The most efficient sorbents are those obtained from unactivated chars and doping with model vanadium compounds or PCA does not upgrade significantly their behaviour. On the other hand, for the samples prepared from activated char, an improvement of the reduction efficiency is observed after impregnation with model vanadium compounds or PCA.SSA of the samples does not play a relevant role on the NO reduction efficiency while surface chemistry significantly affect the samples’ behaviour: higher the CO₂/CO ratio determined by TPD, higher the NO reduction efficiency of the sample.Slightly higher NO conversions are observed for the samples loaded with pure compounds but PCA is perspective for producing catalyst doped activated carbons.