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Made available in DSpace on 2020-12-12T02:16:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Surrogate-based optimization is employed to maximize the thermo-hydraulic performance of a solar air heater duct with non-periodic rows of rectangular winglet pairs mounted in the absorber plate. The present optimization study encompasses the variation of Reynolds number (5000 and 10,000) and of three geometric parameters for each row of rectangular winglets such as chord of the winglets ranging from 8 mm to 40 mm; height of winglets from 8 mm to 21 mm; and angles of attack from 15° to 45° (Flow-Up) and from −45° to −15° (Flow-Down). The Pareto frontiers show that periodic configurations are suboptimal solutions, i.e., the thermo-hydraulic performance of a solar air heater with rectangular winglet pairs not periodically arranged along the channel outperform the periodic arrangements. The aspect ratios and angles of attack for non-periodic and periodic optimized designs are completely different from each other. Moreover, the optimized solutions for Flow-Down arrangement present higher performance than Flow-Up, and this behavior is independent of the Reynolds number. Complex flow patterns and heat transfer mechanisms of the non-periodic optimized solutions are observed, especially the interactions of corner and main vortices along the duct. The first row of winglet pair play the most important role on pressure penalty and heat transfer enhancement when compared to the other rows of rectangular winglet pairs, mainly on Flow-Up arrangement at Re = 10,000. In general, Flow-Up arrangements create a vortex structure more intense than Flow-Down arrangement. Federal University of ABC (UFABC) – The Engineering Modeling and Applied Social Sciences Center (CECS), Santo André Department of Mechanical Engineering São Paulo State University (UNESP), Ilha Solteira Department of Mechanical Engineering São Paulo State University (UNESP), Ilha Solteira FAPESP: 2017/06978-3

Made available in DSpace on 2019-10-04T12:37:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present work aims to perform a parametric study of heat transfer enhancement and the associated pressure loss applied to louvered fins with rectangular winglet vortex generators (RWL). The contributions of a set of design variables on heat transfer and pressure drop are evaluated for two geometry types, L1 and L2. The procedure to investigate the relative importance of the geometrical design variables on thermal-hydraulic performance is enabled by a Design of Simulations (DOS) method called Latin Hypercube Sampling (LHS) in association with a modern non-parametric statistical method (Smoothing Spline ANOVA method) and Computational Fluid Dynamics. Outcomes from the screening analyses turned out that the louver angle is the unique contributor to friction factor for both geometry types and this behaviour is independent of Reynolds number. With respect to heat transfer, the contributions of the input variables are different for both geometry types and Reynolds numbers. For Re-Dh = 120, no important two-factor interaction effects were observed for both L1 and L2, in the same way as occurred in terms of friction factor. Conversely, for Re-Dh = 240 one relevant interaction effect was observed. Fed Univ ABC, Energy Engn, Santo Andre, SP, Brazil Univ Sao Paulo, Polytech Sch, Dept Mech Engn, Sao Paulo, SP, Brazil Univ Munich, Angew Mech, Munich, Germany Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, SP, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, SP, Brazil FAPESP: 2017/06978-3 FAPESP: 2016/14620-9 CNPq: 307421/2014-7

Objectives Stenotrophomonas maltophilia is an opportunistic pathogen that has high intrinsic and acquired antimicrobial resistance, with great genetic diversity. The aim of this study was to characterise four S. maltophilia clinical isolates displaying different susceptibility profiles using whole-genome sequencing. Methods The whole genomes of four clinical isolates of S. maltophilia from three patients were sequenced using Ion Torrent™ PGM technology. The isolates presented different susceptibilities to trimethoprim/sulfamethoxazole (SXT) and levofloxacin. Results Three new multilocus sequence typing (MLST) profiles were identified (ST144, ST172 and ST173), differing in virulence and resistance genes. The ST172 isolate had more genes related to toxins than related to motility or adhesion and had different types of efflux pumps than the other isolates. The SXT-resistant strains belonged to ST172 or ST144 and did not harbour the sul1, sul2 or dfrA resistance genes. Strains I and II, from the same patient and belonging to the same ST but differing in resistance to SXT, had all of the resistance genes searched for in common, except for the SmeABC efflux pump complex genes that were only found in the SXT-resistant strain. All strains, including the strain susceptible to levofloxacin, harboured the qnrB gene, which may question the importance of this gene in determining levofloxacin resistance in S. maltophilia. Conclusion Here we describe three new MLST profiles. Resistance to SXT in these strains appears to be associated with efflux pumps.

Summary Background Several cases of Mycobacterium chimaera infection have recently been reported in cardiosurgical patients. So-called heater–cooler units (HCUs) used in cardiosurgical procedures are suspected to be the reservoir for pathogen growth and dissemination. Aim To assess the contamination status of HCUs at our facility. Methods Air sampling for mycobacteria was conducted at different distances from the machines and in the area around the operating table. Air sampling was also conducted for non-fermenters as a surrogate parameter for water-associated pathogens. Findings Mycobacterium chimaera was detected in the water tanks of the HCUs. When the devices were operating, M. chimaera was also found in their exhaust air, as well as in the area around the operating table. Non-fermenters were identified at different distances from the running HCU and the area around the operating table. Cultures remained negative when the devices were switched off. Conclusions Exhaust air from HCUs may be a pathway of pathogen transmission to patients undergoing open chest heart surgery. Although, for technical reasons, relocation of HCUs is difficult to achieve, only strict separation of the HCU from the operating room appears to enhance patient safety. Using non-fermenters as a surrogate parameter may be considered a viable option for a timely risk assessment. The design of HCUs should be modified to keep susceptibility to contamination at a minimum.

Surrogate-based optimization procedure is used to maximize the heat transfer of multilouvered fin compact heat exchangers with delta-winglet vortex generators (DWL). Five input parameters, such as louver angle and DWL angles of attack and positions, were chosen. The heat transfer enhancement performance of two distinct geometries, GEO1 and GEO2, with two rows of delta-winglets were considered on this research. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The surrogate-based optimization procedure uses the NSGA-II (Non-Dominated Sorting Genetic Algorithm) combined with artificial neural networks. Compared with the respective baseline geometry (louvered fin without DWLs), the results showed that GEO1 optimized solutions increased the heat transfer by 21.27% and 23.52% with associated pressure loss increase of 24.66% and 36.67% for the lower and the higher Reynolds numbers, respectively. For GEO2 optimized solutions, the heat transfer was increased by 13.48% and 15.67% with an increase of the pressure drop by 20.33% and 23.70%, for the lower and the higher Reynolds numbers, respectively. The optimized solutions showed that heat transfer behind the second row of delta-winglets are as high as that behind the first row, for both Reynolds numbers. The flow patterns and heat transfer characteristics from optimized solutions presented some particular behavior, differently from the findings when louvered fin and DWLs are applied separately.

The study evaluated impact of sulfamethoxazole on acetate utilization kinetics and microbial community structure using respirometric analysis and pyrosequencing. A fill and draw reactor fed with acetate was sustained at a sludge age of 10 days. Acute impact was assessed by modeling of respirometric data in batch reactors started with sulfamethoxazole doses in the range of 25-200 mg/L. Fill and draw operation resumed with continuous sulfamethoxazole dosing of 50 mg/L and the chronic impact was evaluated with acclimated biomass after 20 days. Acute impact revealed higher maintenance energy requirements, activity reduction and slight substrate binding. Chronic impact resulted in retardation of substrate storage. A fraction of acetate was utilized at a much lower rate with partial biodegradation of sulfamethoxazole by the acclimated biomass. Pyrosequencing indicated that Amaricoccus sp. and an unclassified Bacteroidetes sp., possibly with the ability to co-metabolize sulfamethoxazole, dominated the community.

Optimization is now recognized as essential in the design of modern compact heat exchanger since the augmentation of heat transfer applying longitudinal vortex generator depends on different interacting parameters, such as its streamwise and spanwise locations, and attack and roll angles and shape. For this work, an optimization procedure based on the SIMPLEX method was conducted through a fluid–solid conjugated heat transfer modeling considering a fin-tube compact heat exchanger with two rows of tubes in staggered and inline arrangements, in order to find an optimum configuration of the vortex generators for two objective functions related to Colburn factor (j) and Friction factor (f). Two Reynolds numbers (250 and 650), performing as a function of fin-pitch, were evaluated. Moreover, a simple approach based on trigonometric decomposition to treat the constraints is presented, which allows great flexibility to vortex generators to cover the design space solution. Seven independent input parameters for each vortex generator in optimization procedure were considered, totaling fourteen independent variables. The results indicate that this work-optimized configuration for the vortex generators achieved higher heat transfer augmentation than those in previous works in the open literature, for both objective functions, Reynolds number and tube arrangements, and it is more pronounced for staggered tube arrangement than for inline tube arrangement. Moreover, suitable vortex generator shapes to maximize the objective functions are more similar to rectangular-winglet type than delta-winglet type, and the optimum ratio between the vortex generator height and fin-pitch is 0.6. Although several trends could be defined for the optimum points, optimized configurations of the vortex generators were found to be different for each Reynolds number, tube arrangement and objective functions, indicating strong asymmetry between the vortex generators to achieve higher heat transfer augmentation.

The demand for LNG (liquefied natural gas) increases each year, and relevant studies have been developed in order to reduce both power consumption and greenhouse gas emissions of LNG plants. Multistream plate-fin heat exchangers (MPFHE) are widely used in these plants due to their large heat transfer surface area per unit volume for multi-phase flows. The thermal-hydraulic performance of heat exchangers also impacts on compressor shaft work of liquefaction plants. In this study, an automated optimization procedure is performed for commonly used MPFHE in a three-stage propane pre-cooling cycle to maximize the coefficient of performance (COP) of liquefaction plants. Four geometric input parameters (fin type, fin height, fin thickness, and fin frequency) have been selected for the optimization. The optimal heat exchangers and operating conditions of the entire refrigeration cycle and their feasibility are taken into account. The optimal fin designs of the heat exchangers affect the cycle operating conditions, which results in COP improvements of 18.9%, 2.5%, and 9.4%, and ranging from 7% to 32% of mitigation in CO2 emission when compared to the literature cases. Compared with the baseline case, the COP is improved by 9.4%, compressor shaft power is reduced by 7.1% (about 11.2 MW), heat transfer is augmented by 1.5% (3.8 MW), and CO2 emission is reduced by 6.3 t/h, which result in more efficient and sustainable LNG production.

This current research is focused on sensitivity analysis and surrogate-based optimization of solar air heater channel-types with three rows delta winglet pairs arranged in both Common-Flow-Down and Common-Flow-Up orientations at Reynolds numbers of 5,000 and 10,000. The performance of the channel is investigated by considering the variation of nine input parameters related to chord, height and angle of attack of each row of delta winglet pairs, in which the rows of the vortex generators are independent from each other. Sensitivity analysis is carried out by means of Morris, FAST and PAWN indices. From sensitivity analysis, it is highlighted that the friction factor is much more sensitive to the design variables than Nusselt number. The optimization procedure consists on the combination of the Anisotropic Kriging model and Non-dominated Sorting Genetic Algorithm (NSGA-II). The optimized solutions indicated the highest performances of the channel are achieved when the vortex generators are not periodically distributed along the channel. With regard to net power ratio, Common-Flow-Up array performs better than Common-Flow-Down arrays, and further enhancement of this parameter is noted when the Reynolds number is increased. The main vortices generated by delta winglet pairs at Re = 10,000 propagate downstream closer to the absorber plate, and the corner vortices are weak and rapidly dissipated along the main flow direction, for both Common-Flow-Up and Common-Flow-Down arrangements.

The combination of multi-louvered fins and delta-winglet vortex generators is a promising strategy to enhance heat transfer in flat-tube compact heat exchangers. This paper focuses on screening analysis and, pressure drop and heat transfer characteristics of some parameters of multi-louvered heat exchangers combined with delta-winglets. Two rows of delta-winglets were considered for this research. The thermal-hydraulic performance of two distinct geometries, GEO1 and GEO2, were evaluated. The main differences between those two geometries are the louver height and delta-winglet frontal area. The contribution of the input parameters such as louver angle, angle of attack of the delta-winglet and streamwise position of the delta-winglet are also investigated in order to understand which of these parameters strongly influences heat transfer and pressure drop. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The Smoothing Spline ANOVA model was used to investigate main and interaction effects among the input parameters. The randomly sample generation is performed by the Latin Hypercubes Sampling (LHS) method. The results indicate that the louver angle is the main contributor to increase the Friction factor for GEO1 and GEO2 for both Reynolds numbers. At the lower Reynolds number, the most important heat transfer parameter was the louver angle for both geometries, while at the higher Reynolds number, the angles of attack of the first row of delta-winglets mostly contributed to GEO1, and the angle of attack of the first row of delta-winglets was as important as the louver angle for GEO2. Although those specific geometries can be considered a kind of compound enhancement technique, relevant interactions were not verified between louvers and delta-winglet vortex generators parameters, i.e., the main effects were predominant in heat transfer and pressure drop.

Augmentation of heat transfer has been an important research topic for many years. Although many heat transfer enhancement techniques have been proposed over the years, few researches deal with thermal optimization considering vortex generators (VG). This work is related to optimization of VG position and angles in a fin-tube compact heat exchanger using the Genetic Algorithm (GA). Two approaches were evaluated: Response Surface Methodology (RSM) applying Neural Networking method, and Direct Optimization (DO). Numerical analyses based on the finite-volume methodology was performed to analyze heat transfer and pressure drop of a fin-tube heat exchanger with two row of tubes in staggered tube arrangement applying two delta winglet type longitudinal vortex generators with aspect ratio 2. Turbulent flow simulation was performed for Reynolds number 1400 (based on fin pitch). Four vortex generator parameters which impact heat exchanger performance were analyzed: longitudinal vortex generator position in x–y directions, attack angle (θ) and roll angle (φ). The present work is the first to study the influence of VG roll angle on heat transfer enhancement. Therefore, eight independent input parameters were considered, four VG parameters for each tube. Four performance evaluation criteria (PEC) based on Colburn factor (j) and Friction factor (f) were chosen as objective function. The optimized VG configurations led to heat transfer enhancement rates higher than reported in the literature. Direct Optimization reported better results than Response Surface Methodology for all objective functions. Important flow interactions were found between vortices generated by VG1 and VG2, which influenced the results of Colburn factor (j) and Friction factor (f). The best results for each objective functions were achieved when VG1 was not symmetrical to VG2. Regarding global pressure drop, VG1 does not contribute to its mitigation, whereas VG2 is very important to flow separation delay in tube 2. The main contribution of VG1 is to increase the heat transfer rate, whereas VG2 increases the heat transfer rate and decreases the pressure drop. Roll angle has a strong influence on friction factor (f), especially for VG1.

Stakeholder behavior and stakeholder management are key success factors within project portfolio management (PPM). This empirical study of 197 project portfolios investigates the effect of the intensity of engagement (IoE) of portfolio-internal stakeholders on project portfolio success. We show that the effect of stakeholders is phase-specific and that role clarity as a measure of PPM maturity affects the nature of the relationship between the IoE of stakeholders and portfolio success. The effects of the IoE of senior managers on success are not clearly positive with regard to strategic portfolio structuring and are even negative in operative portfolio steering in established PPM systems. In immature PPM systems, line managers tend to take advantage of their position in resource management. Surprisingly, the influence of portfolio managers in portfolio steering is insignificant. Altogether, this paper shows the diverse effect of the IoE of stakeholders on portfolio success. This study enriches project research by applying stakeholder theory to the project portfolio context and offers practical guidance for further professionalizing PPM.

The study focused on variable kinetics for substrate utilization, primarily addressing the following issue: Is variable process kinetics observed under different operating conditions and culture history (sludge ages), the result of changes inflicted on the metabolic machinery of the same microbial culture? Or, is this the result of a different microbial population selected under different operating conditions? For this purpose, the study mainly emphasized to assess the microbial population composition sustained at different sludge ages. It explored the relationship between observed process kinetics and microbial population structure using respirometric modeling and high-throughput sequencing of 16S rRNA gene. Experimental results indicated a significant change in the composition of the microbial community fed with the same organic substrate, when the culture history was changed, lower sludge age selecting a different and faster growing microbial community. (C) 2012 Elsevier Ltd. All rights reserved.

The genus Stenotrophomonas is genetically and phenotypically heterogeneous. Of the nine species now accepted, only S. maltophilia is of clinical importance. Based on DNA-sequences of seven house keeping genes, it encompasses genogroups of DNA-similarity below 97% that predominantly comprise strains of environmental origin. Therefore, in order to unravel the uneven distribution of environmental isolates within genogroups and reveal genetic relationships within the genus, there is need for an easy and reliable approach for the identification and delineation of Stenotrophomonas spp. In this first study, a multi-locus sequence analysis (MLSA) with seven housekeeping genes (atpD, gapA, guaA, mutM, nuoD, ppsA and recA) was applied for analysis of 21 S. maltophilia of environmental origin, Stenotrophomonas spp. and related genera. The genotypic findings were compared with the results of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analyses. Our MLSA provided reliable inter- and intra-species discrimination of all tested isolates that correlated with the MALDI-TOF mass spectrometry data. One distantly related genogroup of environmental S. maltophilia strains needs to be reclassified as S. rhizophila. However, there are still remaining delineated S. maltophilia genogroups of predominantly environmental origin. Our data provide further evidence that ‘Pseudomonas’ beteli is a heterotypic synonym of S. maltophilia. Based on MLSA and MALDI-TOF data, Stenotrophomonas sp. (DSM 2408) belongs to S. koreensis.

Introduction Enterococci, particulary Enterococcus faecalis, are still a primary concern in endodontic infections. To date, enterococci have been considered to be only transiently present in the oral cavity. The aim of this study was to examine whether different enterococci from food are able to reside in oral biofilm. Methods Six healthy volunteers wore dental splints loaded with enamel slabs. After 3 days, the volunteers consumed cheese containing enterococci. The fate of the enterococci was analyzed by culture technique and 16S rRNA gene sequencing. All isolates were characterized genotypically by macrorestriction analysis ( Sma I) and pulsed-field gel electrophoresis. E. faecalis was also analyzed by using fluorescent in situ hybridization (FISH). Results E. faecalis , E. faecium , E. avium, and E. durans were detected in the initial biofilm after 2 hours, as well as in the 5-day-old oral biofilm. E. faecalis , E. faecium, and E. avium isolated from the initial biofilm and from the 5-day-old biofilm, as well as those isolated from cheese, showed genetic homogeneity. E. faecium and E. avium had integrated into a pre-existing 3-day-old biofilm. No genetic similarity between E. durans strains isolated from cheese and those from the initial and 5-day-old oral biofilm was detected. E. faecalis was also detected in the oral biofilm by using FISH. Conclusions Food-borne enterococci, particularly E. faecalis, might not only be transient but could also survive in the oral biofilm and become a source for endodontic infections. Moreover, genotypic analysis is required to study the source of oral enterococci.

Conservative testing revealed a stable antibiotic resistance situation for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Enterobacter cloacae in 32 German intensive care units (ICUs) actively participating in the SARI (surveillance of antimicrobial use and antimicrobial resistance in ICUs) project over a three-year period (2001--2003). No significant changes were shown for methicillin-resistant S. aureus (MRSA) (P=0.501; the MRSA rate increased in 18 ICUs and decreased in 14 ICUs). The only exception was an increase in ciprofloxacin-resistant E. coli.

Bacteria of the genus Klebsiella are opportunistic pathogens responsible for an increasing number of multiresistant infections in hospitals. The two clinically and epidemiologically most important species, Klebsiella pneumoniae and K. oxytoca, have recently been shown to be subdivided into three and two phylogenetic groups, respectively. The aim of this study was an in depth evaluation of the amplified fragment length polymorphism (AFLP) genetic characterization method for epidemiological and phylogenic analyzes of Klebsiella isolates. First, we investigated the variability of AFLP patterns for Klebsiella strains within and between different outbreaks. Second, by use of carefully characterized phylogenetically representative strains, we examined whether different Klebsiella species and phylogenetic groups can be discriminated using AFLP. Twenty-four strains originating from seven presumed outbreaks and 31 non-associated strains were investigated. The AFLP fingerprints of all epidemiologically associated strains showed three or fewer fragment differences, whereas unrelated strains differed by at least four fragments. Cluster analysis of the AFLP data revealed a very high concordance with the phylogenetic assignation of strains based on the gyrA sequence and ribotyping data. The species K. pneumoniae, K. oxytoca, K. terrigena and the possibly synonymous pair K. planticola/K. ornithinolytica each formed a separate cluster. Similarly, strains of the phylogenetic groups of K. pneumoniae and K. oxytoca fell into their corresponding clusters, with only two exceptions. This study provides a preliminary cut-off value for distinguishing epidemiologically non-related Klebsiella isolates based on AFLP data; it confirms the sharp delineation of the recently identified phylogenetic groups, and demonstrates that AFLP is suitable for identification of Klebsiella species and phylogenetic groups.

In some clinical settings, herbal tea is used in patient care (eg, for oral hygiene). Teabags containing herbal tea were therefore tested with regard to the presence of microbial contamination before and after brewing. In addition, pathogen growth in intentionally contaminated brewed tea was investigated over time. Teabags and brewed tea were highly contaminated (maximum mean values of 1.9 x 10(8) CFU/g raw tea), and it was found that the pathogen load of intentionally contaminated tea increased significantly (by a maximum of 10(5) colony-forming units/mL brewed tea) over time, suggesting a possible risk of patients developing a nosocomial infection when used in patient care.