Wet electrostatic scrubbing for high efficiency submicron particle capture

Exposure to fine particulate matter has been associated with serious health effects, including respiratory and cardiovascular disease, and mortality. Very fine inhalable particles can remain suspended in the atmosphere for a long time, travel long distances from the emitting sources and, once inhaled, they can reach the deepest regions of the lungs and even enter in the circulatory system. Therefore, the smaller the particle size, the higher its toxicity. In typical combustion units used in process industry, the end-of-pipe technologies include trains of consecutive abatements devices. Nevertheless, the traditional particle abatement devices are mainly designed and optimized to treat particles with sizes above or around 1µm, and they are far less effective towards the submicron dimensions. Among the end-of-pipe technologies, the Wet Scrubbers (WS) are widely utilized in industry due to their capacity to capture simultaneously gaseous pollutants and particles. The main particle collection mechanisms involved in WS are those related to directional interception and inertial impact, which allow high particle abatement efficiency for particles in micrometric range. Both the mechanisms are instead ineffective in the submicron range, thus resulting in low collection efficiencies. It the past 40 years, it was demonstrated that the presence of electric charge of opposite polarities on the particles and the sprayed droplets can increase the capture efficiency due to Coulomb forces between the two phases. The presence of this additional contribution in a scrubber is an upgrade of the traditional wet scrubbing and the new process is commonly referred as Wet Electrostatic Scrubbing (WES). Experimental investigation of the pertinent literature confirmed the ability of WES to increase the particle capture efficiency respect to the classic wet scrubber, but submicron range is generally not directly investigated so that the best operating conditions to increase submicron particle abatement efficiency is still an unsolved problem. This optimization problem is mainly related to the difficulties to model wet electrostatic scrubbing process due to the high number of the variables involved, resulting in a complex experimental evaluation of the main collection mechanisms that are responsible of the particle capture. Above all, a significant hindrance to the assessment of a proper description of wet electrostatic scrubbing is the complexity of the electro-hydrodynamics of the charged water spray. In this work, a new experimental methodology was adopted to perform experiments in controlled conditions in order to allow an easier investigation of the effects of the main physical variables on the abatement of submicron particles emission. This experimental approach is based on the use of a lab scale batch reactor, in which charged particles produced by combustion are inserted. In the reactor, a train of uniform droplet size and charge is used to remove the suspended particles. This approach has the main advantages to make possible to investigate specific parameters (like the effect of droplet charge or its size) under well-defined conditions and therefore model the particle abatement process. Therefore, the objective of this work is the experimental analysis and the modeling of wet electrostatic scrubbing process for submicron particles with the new methodology developed and the evaluation of the influence of the main physical variables on the capture of submicron particles. The results obtained confirm that the particle abatement is significantly enhanced by charging both particles and droplets, and that the particle abatement rate is directly proportional to the particles and droplet charges and droplet concentration. Furthermore, tests with uncharged particles and charged droplets do not show any relevant increase in the scrubbing efficiency with respect to common wet scrubbing in the investigated conditions. The experimental results obtained were compared with the predictions of classical particle scavenging models valid for ambient temperature and humidity conditions. These models were rarely applied to submicron particles and found a reliable experimental support from the performed experiments. On the other hand, this comparison also confirm the reliability of the experimental methodology in the study of wet electrostatic scrubbing and encourage the development of further tests in experimental conditions more similar to that of industrial scrubbers

Constraining Scalar-Tensor gravity models by S2 star orbits around the Galactic Center

The aim of our investigation is to derive a particular theory among the class of scalar-tensor(ST) theories of gravity, and then to test it by studying kinematics and dynamics of S-stars around supermassive black hole (BH) at Galactic Center (GC). We also discuss the Newtonian limit of this class of ST theories of gravity, as well as its parameters. We compare the observed orbit of S2 star with our simulated orbit which we obtained theoretically with the derived ST potential and constrained the parameters. Using the obtained best fit parameters we calculated orbital precession of S2 star in ST gravity,and found that it has the same direction as in General Relativity (GR), but causes much larger pericenter shift.Comment: 13 pages, 1 table, 6 figures. Accepted for publication in Facta Universitatis: Series Phys. Chem. Tech. (Invited lecture at Balkan Workshop 2018

Accurate Modeling and Analysis of Isolation Performance in Multiport Amplifiers

A Multiport Amplifier (MPA) is an implementation of the satellite power amplification section that allows sharing the payload RF power among several beams/ports and guarantees a highly efficient exploitation of the available DC satellite power. This feature is of paramount importance in multiple beam satellite systems where the use of MPAs allows reconfiguring the RF output power among the different service beams in order to handle unexpected traffic unbalances and traffic variations over time. This paper presents Monte Carlo simulations carried out by means of an ESA in-house simulator developed in Matlab environment. The objective of the simulations is to analyse how the MPA performance, in particular in terms of isolation at the MPA output ports, is affected by the amplitude and phase tracking errors of the high power amplifiers within the MPA

Assessing Unemployment Traps in Belgium Using Panel Data Sample Selection Models

In this paper we investigate whether unemployment traps exist and are significant in the transition from unemployment into employment in Belgium. In order to assess them, we use panel data sample selection models. Specifically, we estimate a parametric random effects models composed by a wage equation and a selection equation by maximum likelihood techniques. The income ratios have been computed for every individual in the sample by using the predicted wages obtained from the estimation of the wage equation corrected for sample selectivity. The empirical analyses has exploited the data extracted from the waves 1993-1997 of the Panel Study of Belgian Household and has been led separately on (unbalanced) samples of men and women. The estimation results suggest significant differences in the behaviour of these two groups. The experience of long periods of unemployment in the past is particularly important: long-term unemployed people have difficulties in re-integrating the labour market and they obtain low salaries when they succeed in finding employment. Long unemployment spells are likely to have a ?scarring? effect on subsequent earnings. Moreover, the computation of income ratios for all individuals highlights the importance of unemployment traps for the women present in the sample. Indeed, their expected wage is often lower than their income while being unemployed. A significant proportion of the available samples (men and women) is shown to enter employment although this transition is accompanied by a substantial loss in their disposable income

rotordynamic analysis of a centrifugal pump for automotive applications

Abstract A proper design of a high speed rotating machinery cannot be performed without a deep understanding of the rotor-dynamic aspects involved. The main purpose of the present work is to show how different methodologies can be adopted and integrated, in both preliminary and detailed design phases. The study focused on the dynamic analysis of a centrifugal pump for automotive applications, called purge pump, whose role is to take the air and gasoline vapor mix from the canister to the intake manifold of combustion chambers, in order to reduce emissions. It is quite small and rotates at a constant relatively high speed. The dynamic models were developed using commercial software widely used in companies and in the academic environment. First, an analytical model was devised with all the components assumed as rigid, except the supports. Then a 1-D Finite Element model of the shaft was created with lumped masses and finally a full flexible multibody model for transient analysis, which requires much more computational time with respect to all the other approaches but provides more information, was developed,. In addition to unbalance, localized defects in the pump ball bearings as source of vibration for the pump were investigated. In particular, a detailed 3-D model of faulty ball bearing was set up using a rigid multibody commercial code in order to simulate a localized defect and to evaluate the dynamic load produced. The presented set of methodologies can be a useful tool to understand the critical aspects of the design, as well as to predict the dynamic response and to suggest suitable modifications for a better rotor-dynamic behavior of the whole system reducing vibrations and consequently acoustic noise and improving structural reliability

All-optical modulation in a CMOS-compatible amorphous silicon-based device

Active silicon photonic devices, which dynamically control the flow of light, have received significant attention for their use in on-chip optical networks. High-speed active silicon photonic modulators and switches rely on the plasma dispersion effect, where a change in carrier concentration causes a variation in the refractive index. The necessary electron and hole concentration change can be introduced either by optical pumping, or by direct electrical injection and depletion. We demonstrate a fast photoinduced absorption effect in low loss hydrogenated amorphous silicon (a-Si:H) waveguides deposited at a temperature as low as 190°C. Significant modulation (M% ~90%) occurs with a 1 mm-long device. We attribute the enhanced modulation to the significantly larger free-carrier absorption effect of a-Si:H. The complementary metal-oxide semiconductor (CMOS) compatible technology of a-Si:H could be considered as a promising candidate to enable an easy back-end integration with standard microelectronics processes

Echocardiographic evaluation of left ventricular outflow tract obstruction in complete transposition of the great arteries

Subpulmonic stenosis in complete d-transposition of the great arteries (d-TGA) is a frequently associated malformation, the precise diagnosis of which is essential for optimal medical and surgical treatment. Sixteen patients with d-TGA and subpulmonic stenosis have been studied by M-mode and two-dimensional (2DE) echocardiography and cardiac catheterization. Dynamic obstruction was found in six patients and fixed stenosis in 10. Systolic anterior motion of the mitral valve without fixed obstruction of the left ventricular outflow tract (LVOT) was present in patients with dynamic stenosis. Measurements of left ventricular end-diastolic posterior wall thickness to minor semiaxis ratio correlated well (p < 0.001) with the pressure gradient across the LVOT. Various types of anatomic fixed obstruction are described. M-mode echocardiography provides assessment of dynamic obstruction but does not allow quantitative evaluation of the length of the narrowed segment. The latter can be achieved by 2DE, which offers improved definition of different anatomic types

Field chemical immobilization of free-ranging crested porcupines with zoletil®: A reviewed dosage

The tiletamine-zolazepam mixture is a widely used anesthetic for chemical immobilization of wild mammals due to its short induction time, good muscle relaxation, smooth recovery with low convulsions occurrence, and minimal effect on respiration. An injection dose of 7–8 mg/kg of tiletamine-zolazepam has been proven to be an effective and safe immobilizing mixture for crested porcupines under field conditions. However, the occurrence of long immobilization and recovery times, with high excitement and convulsion during awakening, were recorded. In order to reduce such side effects after recovery, the effectiveness of a lower dosage (4–6 mg/kg) of tiletamine-zolazepam (Zoletil® ) was tested. The results obtained confirm that the use of tiletamine-zolazepam in crested porcupine immobilization provides a quick induction, wide safety margin, and predictable awakening under field conditions. A smaller injection dosage of 5 mg/kg has been proven to be sufficient to ensure a short induction time (average: 7.1 min), with good muscle relaxation and little excitement of the animals during awakening. The lower dosage of tiletamine-zolazepam, while providing a shorter recovery time (average: 53.6 min), proves to be adequate for standard handling procedures. Furthermore, the smaller amount of tiletamine-zolazepam also ensures safe immobilization for pregnant individuals and porcupettes

Ana María Domínguez Ferro y María Isabel González-Fernández, Estudios de literatura medieval italiana. Homenaje in memoriam Ana M. Domínguez

Review of Ana María Domínguez Ferro y María Isabel González-Fernández, Estudios de literatura medieval italiana. Homenaje in memoriam Ana M. Domínguez.Reseña de Ana María Domínguez Ferro y María Isabel González-Fernández, Estudios de literatura medieval italiana. Homenaje in memoriam Ana M. Domínguez