Online Identification of Horizontal Two-Phase Flow Regimes Through Gabor Transform and Neural Network Processing

The fundamental objective of this work is the development of a specialist system capable of diagnosing different configurations of horizontal two-phase flow regimes. It is important to emphasize that this knowledge is of capital importance to the efficient operation of facilities for the manipulation and transportation of multiphase fluids, and it represents one of the most important challenges in petrochemical and thermonuclear industries today. The working principle of the proposed methodology is based on the signals acquired by a rapid response pressure gradient sensor and their decomposition into Gabor coefficients, followed by processing through a previously trained artificial neural network. The implementation is accomplished in such a way that the diagnosis operation is performed online, from the acquisition of the signal to its post-processing. An experimental campaign was conducted at the facilities of the Thermal and Fluids Engineering Laboratory (NETeF) at the University of São Paulo in order to validate the proposed methodology. Experimental pressure gradient signals were obtained for all main horizontal air-water flow regimes (stratified smooth, stratified wavy, intermittent, annular, and bubbly) produced in a 12 m long test section with an internal diameter of 30 mm. Results show that the percentage of correct flow regime diagnosis in steady-state conditions is practically 100%, provided the detection level is adequately set.     

Effects of competing environmental variables and signage on route-choices in simulated everyday and emergency wayfinding situations

This study examined the relative influence of environmental variables (corridor width and brightness) and signage (directional and exit signs), when presented in competition, on participants' route-choices in two situational variables (everyday vs. emergency), during indoor wayfinding in virtual environments. A virtual reality-based methodology was used. Thus, participants attempted to find a room (everyday situation) in a virtual hotel, followed by a fire-related emergency egress (emergency situation). Different behaviours were observed. In the everyday situation, for no-signs condition, participants choose mostly the wider and brighter corridors, suggesting a heavy reliance on the environmental affordances. Conversely, for signs condition, participants mostly complied with signage, suggesting a greater reliance on the signs rather than on the environmental cues. During emergency, without signage, reliance on environmental affordances seems to be affected by the intersection type. In the sign condition, the reliance on environmental affordances that started strong decreases along the egress route.     

Aerosol composition and source apportionment in Santiago de Chile

Santiago de Chile, São Paulo and Mexico City are Latin American urban areas that suffer from heavy air pollution. In order to study air pollution in Santiago area, an aerosol source apportionment study was designed to measure ambient aerosol composition and size distribution for two downtown sampling sites in Santiago. The aerosol monitoring stations were operated in Gotuzo and Las Condes during July and August 1996. The study employed stacked filter units (SFU) for aerosol sampling, collecting fine mode aerosol (dp<2 μm) and coarse mode aerosol (210 mass of particles smaller than 10 μm) and black carbon concentration were also measured. Particle-Induced X-ray Emission (PIXE) was used to measure the concentration of 22 trace elements at levels below 0.5 ng m⁻³. Quantitative aerosol source apportionment was performed using Absolute Principal Factor Analysis (APFA). Very high aerosol concentrations were observed (up to 400 μg/m³ PM₁₀). The main aerosol particle sources in Santiago are resuspended soil dust and traffic emissions. Coarse particles account for 63% of PM₁₀ aerosol in Gotuzo and 53% in Las Condes. A major part of this component is resuspended soil dust. In the fine fraction, resuspended soil dust accounts for 15% of fine mass, and the aerosols associated with transportation activities account for a high 64% of the fine particle mass. Sulfate particle is an important component of the aerosol in Santiago, mainly originating from gas-to-particle conversion from SO₂. In the Gotuzo site, sulfates are the highest aerosol component, accounting for 64.5% of fine mass. Direct traffic emissions are generally mixed with resuspended soil dust. It is difficult to separate the two components, because the soil dust in downtown Santiago is contaminated with Pb, Br, Cl, and other heavy metals that are also tracers for traffic emissions. Residual oil combustion is observed, with the presence of V, S and Ni. An aerosol components from industrial emissions is also present, with the presence of several heavy metals such as Zn, Cu and others. A factor with molybdenum, arsenic, copper and sulfur was observed frequently, and it results from emissions of copper smelters.     

Vacuum frying of high-quality fruit and vegetable-based snacks

Sweet potato, green beans, Tommy Atkins mango, and blue potato were fried in a vacuum frying process at a temperature of 120-130 ± 1°C. Before frying, green beans and mango slices were soaked in a 50% maltodextrine 0.15% citric acid solution. The products were also fried in a traditional (atmospheric pressure) fryer at 160-165 ± 1°C for 4 min. A 30-member consumer panel rated the sensory quality of both types of fried snacks using a 1-9 hedonic scale. Compared with traditional frying, oil content of vacuum-fried sweet-potato chips and green beans was 24% and 16% lower, respectively. Blue potato and mango chips had 6% and 5% more oil, respectively, than the traditional-fried samples. Anthocyanin (mg/100 g d.b.) of vacuum-fried blue potato chips was 60% higher. Final total carotenoids (mg/g d.b.) were higher by 18% for green beans, 19% for mango chips, and by 51% for sweet-potato chips. Sensory panelists overwhelmingly preferred (p < 0.05) the vacuum-fried products for color, texture, taste, and overall quality. Most of the products retained or accentuated their original colors when fried under vacuum. The traditional-fried products showed excessive darkening and scorching. These results support the applicability of vacuum frying technology to provide high-quality fruit and vegetable snacks.     

Satellite-derived conditions and advection patterns off Iberia and NW Africa: Potential implications to sardine recruitment dynamics and population structuring

Surface velocity estimates from wind and altimeter data, together with satellite-derived sea surface temperature and chlorophyll, were used to explore the advection patterns and environmental conditions using a simple Lagrangian model. Although the model is generic (only considering the physical transport), the results are of particular interest for sardine (Sardina pilchardus) early life stages, due to the spawning dynamics of the species off Iberia and NW Africa. Particles were released on the shelf of the Iberian and northern African Atlantic coasts every five days from 1998 to 2004 and advected for 27-days. Trajectories were computed using combinations of three surface velocity constituents: Ekman velocity, geostrophic velocity derived from sea level anomaly maps and mean geostrophic velocity derived from two mean dynamic topographies. Daily time series of sea surface temperature, chlorophyll-a concentration and water depth where constructed for each particle trajectory. The results showed strong regional and seasonal dependence of the transport due to wind, with average seasonal cycles of the percentage of particles found in the shelf reflecting the anticipated effect of the seasonal north–south migration of the trade wind belt. The addition of the geostrophic transport led to the attenuation of seasonal cycles and higher mean/maximum values in the probability of retention within the shelf. This increased capacity for retention even during strong upwelling conditions seems to have been overlooked by theories aiming to describe the reproductive strategies of pelagic fish and understand recruitment dynamics based primarily on wind variability. On the other hand, the average surface chlorophyll values indicated a distribution area with higher primary production for particles that never leave the shelf, in comparison to those that return to it or are found in the open sea a month after release, which is in agreement with existing hypotheses that offshore advection is detrimental to larval survival mainly due to the higher risk of starvation. Finally, the exchange between adjacent shelf areas was generally small (less than 5%) within the study period, with the exception of the Gulf of Cadiz. In the latter area, up to 50% of particles released in the southern Iberian shelf reached the Moroccan shelf in several events, contradicting previous suggestions that the Strait of Gibraltar acts as a physical barrier that promotes genetic differentiation among neighbouring sardine populations in the Atlantic. Overall, these results provide useful insights for the study of sardine dynamics in the northeast Atlantic but the unexpectedly high sensitivity of summary metrics (namely retention probability) to the choice of surface velocity field preclude firm conclusions and indicate alternative routes for future studies.     

An experimental study of the tribological behaviour of the brass/steel pair

This paper presents a study of the behaviour of the brass/steel pair in the presence of friction and wear. A plan of experiments, based on the techniques of Taguchi, was performed on a pin-on-disc machine. The objective was to establish a correlation between load, sliding velocity and temperature in contact with the wear and coefficient of friction. These correlations were obtained by multiple linear regression. Finally, confirmation tests were performed to make a comparison between the foreseen results from the mentioned correlations and the experimental results.     

Strain-life fatigue predictions for sintered steels with nonzero mean stress

Several approximate models have been utilized for fatigue life prediction. Some of these models are available for mean stress (or strain) correction on fatigue life, when nonzero mean stress (or strain) is applied. In this paper, the most commonly used empirical strain-life models for fatigue life predictions, for materials subjected to variable amplitude loads, are described. Experimental results of fatigue tests, where the specimens of sintered steels were subjected to partial random loads, are presented and compared with those results obtained theoretically by the models. The utilization of the various models and their influence on results are discussed.     

Visible PL Phenomenon at Room Temperature in Disordered Structure of SrWO4 Powder

The SrWO₄ (SWO) powders were synthesized by the polymeric precursor method and annealed at different temperatures. The SWO structure was obtained by X-ray diffraction and the corresponding photoluminescence (PL) spectra was measured. The PL results reveal that the structural order–disorder degree in the SWO lattice influences in the PL emission intensity. Only the structurally order–disordered samples present broad and intense PL band in the visible range. To understand the origin of this phenomenon, we performed quantum-mechanical calculations with crystalline and order–disordered SWO periodic models. Their electronic structures were analyzed in terms of band structure. The appearance of localized levels in the band gap of the order–disordered structure was evidenced and is a favorable condition for the intense PL to occur.