ABSTRACT
In this paper, an effective strategy for fault detection of nitrogen sensors in alternated active sludge treatment plants is proposed and tested on a simulated set-up. It is based on two predictive neural networks, which are trained using a historical set of data collected during fault-free operation of a wastewater treatment plant and their ability to predict reduced (ammonium) and oxidized (nitrates and nitrites) nitrogen is tested. The neural networks are also characterized by good generalization ability and robustness with respect to the influent variability with time and weather conditions. Then, simulations have been carried out imposing different kinds of fault on both sensors, as isolated spikes, abrupt bias and increased noise. Processing of residuals, based on the difference between measured concentration values and neural networks predictions, allows a quick revealing of the fault as well as the isolation of the corrupted sensor.
Subject(s)
Neural Networks, Computer , Nitrogen/chemistry , Sewage/chemistry , Automation , Models, Theoretical , Waste Disposal, Fluid , Waste ManagementABSTRACT
Waveguides in LiNbO3 are realized by a soft proton exchange (SPE) process with use of a melt of stearic acid highly diluted by lithium stearate. No phase transitions are formed when alpha-phase waveguides are obtained by SPE. The alpha-phase presents the same crystalline structure as that of pure LiNbO3 crystal, and it maintains the excellent nonlinear and electro-optical properties of the bulk material. The kinetics of the SPE method is studied by the use of secondary-ion mass spectrometry and prism-coupling techniques. The hydrogen effective diffusion coefficient as well as the self-diffusion coefficients of H+ and Li+ ions are determined as a function of the proton-exchange temperature for X-cut LiNbO3.
ABSTRACT
BACKGROUND: The authors report their experience in recent-onset atrial fibrillation treated with intravenous flecainide and propafenone, in comparison with the placebo group. METHODS: We randomized 352 (138 in the flecainide group, 164 in the propafenone group and 50 in the control group) consecutive patients (167 males, 185 females, mean age 59 +/- 12 years) with recent-onset atrial fibrillation. The electrocardiogram of all patients was monitored for at least 24 hours. RESULTS: The restoration of sinus rhythm occurred in 72.5, 80.4, 86.2 and 89.8% of patients in the flecainide group; in 54.3, 68.3, 75 and 92.1% in the propafenone group; in 22.2, 27.8, 35.2 and 46.3% in the control group, at 1, 3, 6 and 24 hours respectively. The occurrence of side effects was the same in all treatment groups, and occurred in about 10% of patients in the flecainide and propafenone groups, and in 4% in the control group. In our study population the treatment of recent-onset atrial fibrillation with flecainide was faster in converting the arrhythmia to sinus rhythm (p < 0.005 at 1 hour, p < 0.05 at 3 hours, p = 0.05 at 6 hours). However within 24 hours the efficacy of either flecainide or propafenone was the same (p = NS at 24 hours). CONCLUSIONS: Side effects were similar in both treatment groups. In particular malignant arrhythmias did not occur in the treatment groups and in the control group.
Subject(s)
Anti-Arrhythmia Agents/therapeutic use , Atrial Fibrillation/drug therapy , Flecainide/therapeutic use , Propafenone/therapeutic use , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Time FactorsABSTRACT
Magnesium diffusion can be used to optimize the characteristics and performance of a Ti:LiNbO(3) Mach-Zehnder modulator. Suitable use of titanium/magnesium double diffusion reduces fiber-waveguide coupling loss, minimizes the modulator size by increasing the bend radius of curvature without increasing bend losses, and decreases separation of the modulator arms. The proposed method also makes it possible to reduce the modulating voltage by improvement of guided-wave lateral confinement. Secondary ion mass spectrometry and 771-line techniques are used to characterize Ti/Mg:LiNbO(3) waveguides. A numerical optimization procedure based on the full vectorial beam-propagation method is presented.
