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Compact heat exchangers equipped with flat tubes have traditionally been employed in automotive cooling systems. To augment thermal performance, louvered fins have been integrated on the air side. over recent decades, the efficacy of longitudinal vortex generators (LVG) in heat exchangers has been rigorously investigated, leading to the proposal of innovative designs characterized by their aerodynamic properties. In this study, a novel LVG design sourced from extant literature was juxtaposed against the conventional louvered fins. The shear-stress transport (SST) k-? model was utilized to depict the turbulence. When the turbulent flow and heat transfer properties were assessed, distinct variations were observed between multiple rows of LVG and the louvered fins. Enhanced thermal performance, with a value reaching 1.3, was noted for configurations incorporating five rows of LVG arrangements at a Reynolds number of 8000. In contrast, the thermal performance of louvered fins was observed to wane with increasing Reynolds numbers, recording a performance measure of merely 1.08 at the aforementioned Reynolds number. [ABSTRACT FROM AUTHOR]

Longitudinal vortex generators (LVG) over the last decades have been investigated to enhance heat transfer in rectangular channels with different design to obtain high thermal performance (TEF). In this investigation, the shear-stress transport (SST) k-e model is used to model the turbulence. The turbulent flow and heat transfer, using delta wing (DW), delta winglet pair (DWP), DWP inclined (DWPI) and rectangular winglet pair curved (RWPC) was compared in a rectangular channel. The best TEF by 1.26 was obtained using DW for Reynolds number of 2800. The DW is a simple to manufacture LVG, and the TEF is only a little lower compared to other new, complex to manufacture, conic type LVG recently found in the literature. [ABSTRACT FROM AUTHOR]

Cycling is a desirable mode of transportation in urban areas due to its environmental, social, and economic benefits. Design manuals are used as standardized references and guides to provide safe, functional, and convenient bicycle infrastructure. These guidelines usually provide best practice recommendations and refer to minimum requirements for dimensions (geometry) and materials. However, these documents rarely include input from cyclists. Unlike the infrastructure service perceived by motorists, which is related to performance measurements such as speed or travel time, the quality of service (QoS) experienced by pedestrians and cyclists is strongly influenced by perceptions (e.g., safety) owing to the fact that they are directly exposed to the environment. Beyond the performance-related indicators (e.g., Level of Service), when cyclists assess QoS, their cognitive process incorporates their perceptions of the surroundings. We present a user-oriented perspective in this paper, since supply-oriented evaluation and design has been carried out for decades without giving a relevant role to user perceptions. Our objective is to uncover factors explaining QoS perceived by cyclists from users' perceptions and to analyze new contributions to existing bicycle infrastructure design practices. By means of stepwise models from cyclist perception intercept surveys in Bogotá, Colombia, we uncovered factors that explain QoS. Model testing and site visits enrich the analysis of the six statistically significant variables that explain QoS. This research raises an interesting discussion on the general approach and philosophy of the bicycle infrastructure design guidelines and evidences that cyclists' perceptions have substantial potential for future research and application. [ABSTRACT FROM AUTHOR]

Motorcycle and car ownership are rapidly growing in the Global South. However, little research has been conducted to understand the factors influencing motorcycle ownership and whether they differ from those affecting car ownership. In this paper, we explore and explain the similarities and differences between the factors that influence the decision to own both types of private vehicles in Bogotá, Colombia. Using information from the 2019 Household Travel Survey and open land-use information of Bogotá, we formulate and estimate two independent discrete choice models for car ownership and motorcycle ownership. Our results indicate that the factors influencing the decision to own a car are indeed not the same as those influencing the decision to own a motorcycle. First, we found that sociodemographic variables do not keep the same sign, magnitude, or meaning in both types of ownership models. However, the main difference between the two specifications is associated with spatial-related (geographic) variables. Mixed land uses, density, and proximity to mass transit seems to affect car ownership, while living in the periphery of the city increases the likelihood of owning a motorcycle. Our findings provide evidence about a topic that is essential in transportation demand models for mobility plans, especially in the Global South. They also highlight the need for further research focusing on motorcycle ownership. • There is limited information for understanding motorcycle ownership in Global South. • Factors for motorcycle ownership are different to those explaining car ownership. • Living in the urban periphery of the city rises the utility of owning a motorcycle. • Motorcycle ownership seems to be related with mass transit quality of service. • Further research focusing on motorcycle ownership and policies should be made. [ABSTRACT FROM AUTHOR]

Over the last decades several studies have searched for improved Fin and Tube Heat Exchanger (FTHE) designs capable of providing the best thermo-hydraulic performance. The present study aims at quantifying and comparing the thermo-hydraulic performance of different FTHE configurations. Six different designs were analyzed. The first FTHE consisted of an in-line circular tube arrangement and the last one was a FTHE with staggered oval tube with two pairs of Delta Winglet Vortex Generators (DWVG) in common flow up-common flow down (CFU-CFD) configuration. The best performance was obtained using DWVG in CFU-CFD orientation. This configuration enabled a 90% increase of the thermal performance factor when compared with the first case, using only two pairs of vortex generator's per tube. [ABSTRACT FROM AUTHOR]

Brucellosis is the most common zoonosis, particularly in developing countries. The true incidence of human brucellosis is unknown. The WHO points out that 500,000 cases of brucellosis are reported each year from around the world. In Colombia, there is currently no regular surveillance of the event in humans and its prevalence is low due a low clinical suspicion. We report a case of a 66-year-old man, an urban merchant, who had received a liver transplant 11 years ago. The patient presented to the emergency department for two months of fatigue, severe myalgia, paresis of the extremities, loss of muscle strength, and progressive deterioration of functional class. In the emergency room, he became disoriented and was transferred to the intensive-care unit. He had a white blood cell count of 18990/uL and creatine phosphokinase 10302 U/L. Routine blood cultures were positive for Brucella melitensis. The patient reported consumption of unpasteurized bovine milk. He was treated with doxycycline and ciprofloxacin. Despite antibiotic management, after one month of hospitalization and in the context of septic shock with multiorgan failure, the patient died. Brucellosis is an unsuspected and underdiagnosed disease. It can occur in people with or without risk factors. Although the mortality is low, immunocompromised patients can develop fatal infections. A presumptive diagnosis can be established through the correlation of patient history and classic laboratory findings, which include transaminitis, anemia, and leukopenia with relative lymphocytosis; however, other findings can help us to guide the diagnosis, such as rhabdomyolysis, which appears as a complication in different infections; however, it had not been described before in brucellosis. A partnership between clinical suspicion laboratory diagnostic tests and improved disease surveillance systems is necessary to fight the disease. [ABSTRACT FROM AUTHOR]

Background: Extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBL-PE) infections are frequent and highly impact cancer patients. We developed and validated a scoring system to identify cancer patients harboring ESBL-PE at the National Institute of Cancer of Colombia.Methods: We retrospectively analyzed medical records of 1695 cancer patients. Derivation phase included 710 patients admitted between 2013 to 2015, ESBL-PE positive culture (n = 265) paired by month and hospitalization ward with Non-ESBL-PE (n = 445). A crude and weighted score was developed by conditional logistic regression. The model was evaluated in a Validation cohort (n = 985) with the same eligibility criteria between 2016 to 2017.Results: The score was based on eight variables (reported with Odds Ratio and 95% confidence interval): Hospitalization ≥7 days (5.39 [2.46-11.80]), Hospitalization during the previous year (4, 87 [2.99-7.93]), immunosuppressive therapy during the previous 3 months (2.97 [1.44-6.08]), Neutropenia (1.90 [1.12-3.24]), Exposure to Betalactams during previous month (1.61 [1.06-2.42]), Invasive devices (1.51 [1.012-2.25]), Neoplasia in remission (2.78 [1.25-1.17]), No chemotherapy during the previous 3 months (1.90 [1.22-2.97]). The model demonstrated an acceptable discriminatory capacity in the Derivation phase, but poor in the Validation phase (Recipient Operating Characteristic Curve: 0.68 and 0.55 respectively).Conclusions: Cancer patients have a high prevalence of risk factors for ESBL-PE infection. The scoring system did not adequately discriminate patients with ESBL-PE. In a high-risk population, other strategies should be sought to identify patients at risk of resistant ESBL-PE infection. [ABSTRACT FROM AUTHOR]

Recent information and communication technology innovations have brought with them a broad set of new urban transportation options (e.g. ridesourcing, scooters, etc.), as well as the opportunity to improve transportation systems. The taxi industry, historically linked to communication technology, is now in the throes of a massive upheaval due to the introduction and use of internet-based mobile technologies in personal devices. Taxi e-hailing cellphone applications (apps) pair users looking to ride with available taxis. Do apps replace the radiophone? Do drivers behave differently? Is it more profitable for them to operate with apps? This paper answers these and more questions related to the effects of these technological innovations on taxi operations and taxi drivers' behavior, based on a before-after survey in Bogotá, Colombia. We applied descriptive statistics, hypothesis testing, and multivariate regression analysis based on surveys involving the city's taxi drivers, conducted in 2009 and 2016. [ABSTRACT FROM AUTHOR]

Fluid-mechanical and morphological parameters are recognized as major factors in the rupture risk of human aneurysms. On the other hand, it is well known that a lot of machine learning tools are available to study a variety of problems in many fields. In this work, fluid–structure interaction (FSI) simulations were carried out to examine a database of 60 real saccular cerebral aneurysms (30 ruptured and 30 unruptured) using reconstructions by angiography images. With the results of the simulations and geometric analyses, we studied the analysis of variance (ANOVA) statistic test in many variables and we obtained that aspect ratio (AR), bottleneck factor (BNF), maximum height of the aneurysms (MH), relative residence time (RRT), Womersley number (WN) and Von-Mises strain (VMS) are statically significant and good predictors for the models. In consequence, these ones were used in five machine learning algorithms to determine the rupture risk predictions of the aneurysms, where the adaptative boosting (AdaBoost) was calculated with the highest area under the curve (AUC) in the receiver operating characteristic (ROC) curve (AUC 0.944). [ABSTRACT FROM AUTHOR]

Background: The determinants of parasite persistence or elimination after treatment and clinical resolution of cutaneous leishmaniasis (CL) are unknown. We investigated clinical and parasitological parameters associated with the presence and viability of Leishmania after treatment and resolution of CL caused by L. Viannia. Methods: Seventy patients who were treated with meglumine antimoniate (n = 38) or miltefosine (n = 32) and cured, were included in this study. Leishmania persistence and viability were determined by detection of kDNA and 7SLRNA transcripts, respectively, before, at the end of treatment (EoT), and 13 weeks after initiation of treatment in lesions and swabs of nasal and tonsillar mucosa. Results: Sixty percent of patients (42/70) had evidence of Leishmania persistence at EoT and 30% (9/30) 13 weeks after treatment initiation. A previous episode of CL was found to be a protective factor for detectable Leishmania persistence (OR: 0.16, 95%CI: 0.03–0.92). kDNA genotyping could not discern differences between parasite populations that persisted and those isolated at diagnosis. Conclusions: Leishmania persist in skin and mucosal tissues in a high proportion of patients who achieved therapeutic cure of CL. This finding prompts assessment of the contribution of persistent infection in transmission and endemicity of CL, and in disease reactivation and protective immunity. [ABSTRACT FROM AUTHOR]

Computational Structural Dynamics (CSD) simulations, Computational Fluid Dynamics (CFD) simulation, and Fluid Structure Interaction (FSI) simulations were carried out in an anatomically realistic model of a saccular cerebral aneurysm with the objective of quantifying the effects of type of simulation on principal fluid and solid mechanics results. Eight CSD simulations, one CFD simulation, and four FSI simulations were made. The results allowed the study of the influence of the type of material elements in the solid, the aneurism’s wall thickness, and the type of simulation on the modeling of a human cerebral aneurysm. The simulations use their own wall mechanical properties of the aneurysm. The more complex simulation was the FSI simulation completely coupled with hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness. The FSI simulation coupled in one direction using hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness is the one that presents the most similar results with respect to the more complex FSI simulation, requiring one-fourth of the calculation time. [ABSTRACT FROM AUTHOR]

This study investigates the effects of different solid models on predictions of brain shift for three craniotomies. We created a generic 3D brain model based on healthy human brain and modeled the brain parenchyma as single continuum and constrained by a practically rigid skull. We have used elastic model, hyperelastic 1st, 2nd, and 3rd Ogden models, and hyperelastic Mooney-Rivlin with 2- and 5-parameter models. A pressure on the brain surface at craniotomy region was applied to load the model. The models were solved with the finite elements package ANSYS. The predictions on stress and displacements were compared for three different craniotomies. The difference between the predictions of elastic solid model and a hyperelastic Ogden solid model of maximum brain displacement and maximum effective stress is relevant. [ABSTRACT FROM AUTHOR]

A sensitivity study of the results provided by computational fluid dynamics (CFD) in models of cerebral aneurysms including fluid structure interaction (FSI) was performed. With 83 reconstructed models of cerebral aneurysms, a geometrical study was done and one case was selected for a detailed study of the computational fluid dynamics. In this model the number of carotid siphon used for the CFD simulations was varied. In the FSI study, five simulations were conducted varying the elastic modulus of the artery and the arterial wall thickness, and the effect of hypertension on the results was reported. The FSI simulations have shown that the most important parameter that affects the aneurysm wall stress state is the arterial hypertension with maximum stress of around 900 kPa. It is concluded that FSI simulations must be used to simultaneously determine the wall stress and the fluid dynamics inside cerebral aneurysm. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we solve the Falkner–Skan equation with heat transfer through an expansion in Fourier series, results are improved by incorporating an asymptotic analysis for the Fourier series coefficients. The results show that the classical expansion in Fourier series together with the incorporation of an asymptotic analysis for coefficients of the series delivers a solution with very good accuracy and rapid convergence when it is compared with other methods of solution found in the literature as finite difference and shooting method. [ABSTRACT FROM AUTHOR]

Haemodynamically induced stress plays an important role in the progression and rupture of cerebral aneurysms. The current work describes computational fluid dynamics (CFD), fluid-structure interaction (FSI) and computational structural dynamics (CSD) simulations in an anatomically realistic model of a carotid artery with two saccular cerebral aneurysms in the ophthalmic region. The model was obtained from three-dimensional (3D) rotational angiographic imaging data. CFD and FSI were studied under a physiologically representative waveform of inflow. The arterial wall was assumed elastic or hyperelastic, as a 3D solid or as a shell depending on the type of modelling used. The flow was assumed to be laminar, non-Newtonian and incompressible. The CFD, FSI and CSD models were solved with the finite elements package ADINA. Predictions of velocity field and wall shear stress (WSS) on the aneurysms made using CFD and FSI were compared. The CSD model of the aneurysms using complete geometry was compared with isolated aneurysm models. Additionally, the effects of hypertensive pressure on CSD aneurysm models are also reported. The vortex structure, WSS, effective stress, strain and displacement of the aneurysm walls showed differences, depending on the type of modelling used. [ABSTRACT FROM AUTHOR]

Abstract: Solid mechanics plays an important role in the progression and rupture of cerebral aneurysms. The hypothesis is that the mechanism that control aneurysm enlargement is the wall remodeling under the effect of time dependent arterial pressure. When the aneurysm enlarges, the characteristics of the collagen fibers change, increasing the risk of rupture. The current work describes the solid dynamics in 30 patient-specific models of cerebral aneurysms. An area based index shows important difference between unruptured and ruptured aneurysms. The effective wall stress and displacement showed large variations depending on aneurysm size and form. The effects of hypertension were reported and correlations between the maximal effective stress and displacement with geometrical indices were found. [Copyright &y& Elsevier]

Abstract: The unsteady non-Newtonian blood flow in symmetric stenotic arteries is numerically simulated considering fluid–structure interaction (FSI) using the code ADINA. A two layer hyperelastic anisotropic structural model is used for the compliant arterial wall. The pressure used as outlet boundary condition was obtained running a CFD simulation for each stenosis with a physiologically-realistic time variation of pressure at inlet for different velocities. The obtained pressure drop increases in potential form with the inlet velocity for a fixed stenosis severity. The FSI results show that the maxima velocity and WSS at throat increase in exponential form with stenosis severity. The minimum and maximum effective stress at throat for stenosis severity of S =70% ranged between 47 kPa and 96 kPa at diastole and systole, respectively. [Copyright &y& Elsevier]

Abstract: Hemodynamics plays an important role in the progression and rupture of cerebral aneurysms. The temporal and spatial variations in wall shear stress (WSS) within the aneurysmal sac are hypothesized to be correlated with the growth and rupture of the aneurysm. The current work describes the blood flow dynamics in 34 patient-specific models of saccular aneurysms located in the region of the anterior and posterior circulation of the circle of Willis. The models were obtained from three-dimensional rotational angiography image data and blood flow dynamics was studied under a physiologically representative waveform of inflow. The three-dimensional continuity and momentum equations for unsteady laminar flow were solved with commercial software using non-structured fine grid sizes. The vortex structure, the wall pressure, and the WSS showed large variations, depending on the morphology of the artery, size of the aneurysm, and form. A correlation existed between the mean WSS on the aneurysmal sac for lateral unruptured and ruptured aneurysms with an aneurysm surface index, which is defined as the ratio between the aneurysm area and the artery area at model inlet, respectively. [Copyright &y& Elsevier]

Abstract: In this work the unsteady non-Newtonian blood flow and mass transfer in symmetric and non-symmetric stenotic arteries are numerically simulated considering the fluid-structure interaction (FSI) using the code ADINA. Blood with hyperviscosity syndrome is considered and hyperelastic Mooney–Rivlin model is used for the compliant arterial wall. The inlet boundary condition of imposed velocity or pressure is critical to obtain realistic hemodynamic results in stenotic arteries. The FSI affects significantly the hemodynamics on the stenotic arteries models, the arteries are considerably dilated and compressed due the stenosis. The stenosis severity and geometry have important influence on recirculation length, and distribution of concentration of macromolecules, such as low density lipoproteins (LDL). [Copyright &y& Elsevier]

Abstract: Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture and surgical treatment of intracranial aneurysms. This paper describes the flow dynamics and arterial wall interaction in a representative model of a terminal aneurysm of the basilar artery, and compares its wall shear stress, pressure, effective stress and wall deformation with those of a healthy basilar artery. The arterial wall was assumed to be elastic or hyperelastic, isotropic, incompressible and homogeneous. The flow was assumed to be laminar, Newtonian, and incompressible. The fully coupled fluid and structure models were solved with the finite elements package ADINA. The intra-aneurysmal pulsatile flow shows single recirculation region during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations. The wall thickness, the Young’s modulus in the elastic wall model and the hyperelastic Mooney–Rivlin wall model affect the aneurysm deformation and effective stress in the wall especially at systole. [Copyright &y& Elsevier]

Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture, and surgical treatment of intracranial aneurysms. The temporal and spatial variations of wall pressure and wall shear stress in the aneurysm are hypothesized to be correlated with its continuous expansion and eventual rupture. In addition, the assessment of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils. This paper describes the flow dynamics in two representative models of a terminal aneurysm of the basilar artery under Newtonian and non-Newtonian fluid assumptions, and compares their hemodynamics with that of a healthy basilar artery. Virtual aneurysm models are investigated numerically, with geometric features defined by β=0 deg and β=23.2 deg, where β is the tilt angle of the aneurysm dome with respect to the basilar artery. The intra-aneurysmal pulsatile flow shows complex ring vortex structures for β=0 deg and single recirculation regions for β=23.2 deg during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations for both models. When compared to a non-Newtonian fluid, the symmetric aneurysm model (β=0 deg) exhibits a more unstable Newtonian flow dynamics, although with a lower peak wall shear stress than the asymmetric model (β=23.2 deg). The non-Newtonian fluid assumption yields more stable flows than a Newtonian fluid, for the same inlet flow rate. Both fluid modeling assumptions, however, lead to asymmetric oscillatory flows inside the aneurysm dome. [ABSTRACT FROM AUTHOR]

Background Cancer patients are susceptible to infections due to immunodeficiency, frequent invasive interventions-devices, chemotherapy and antibiotics exposure. Infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae increase morbidity and mortality. The objective was to identify clinical factors associated with ESBL in infected patients with cancer at the Instituto Nacional de Cancerología. Methods A case–control study was conducted from 2013 to 2015. Cases were infected patients with ESBL-producer Enterobacteriaceae. Controls (matched for date and ward) with non-ESBL-producer Enterobacteriaceae were included. Data were extracted from electronic medical records at index culture: clinical and admission data, Charlson index, immunosuppressive, radio and chemotherapy, neutropenia, invasive devices, surgical procedures and antimicrobial therapy. Microorganisms were identified by the automatized system. Conditional logistic regression and backward stepwise was used to identify predictors of ESBL isolation. Results A total of 265 patients with ESBL producer Enterobacteriaceae and 445 non-ESBL producers were identified, mean age 59, 61% male, 48% admitted as outpatients, 73% with solid tumors, 38% with Charlson index ≥4. E.coli and Klebsiella spp. represented 90% of microorganisms. Factor associated with ESBL producer Enterobacteriaceae were hospitalization ≥7 days (OR: 1,59; CI 1.11–2,29), hospitalization the previous year (OR: 4.02; CI 2,68–6,02), immunosuppressive therapy (OR: 2.07; CI 1,05–4.05), Β-lactam therapy the last month (OR: 1.54; CI 1.05–2.26), invasive devices (OR: 1.58; CI 1.10–2.27), active neoplasia (OR: 2,22; CI1.05–4.68), neutropenia (OR: 2.03; CI:1.26–3.27) and absence of chemotherapy during last 3 months (OR: 1.91; CI1.29–2.82). Discriminatory capacity was acceptable (AUC: 0.71). Conclusion The presence of ESBL-producer Enterobacteriaceae in oncologic patients is associated with health care, hospital admission and length of stay, invasive devices and exposure to antibiotics. The magnitude of associated factors are weak and do not completely allow the identification of cancer patients infected with ESBL-producer Enterobacteriaceae. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Blood flow dynamics play an important role in the pathogenesis and treatment of intracranial aneurysms. The evaluation of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils, in addition the temporal and spatial variations of wall shear stress in the aneurysm are correlated with its growth and rupture. The present numerical investigation describes the hemodynamics in two models of terminal aneurysm of the basilar artery. Aneurysm models with an aspect ratio of 1.0 and 1.67 were studied. Each model was subject to a steady, sinusoidal and physiologically representative waveform of inflow for a mean Reynolds number of 560. Symmetric and asymmetric outflow conditions in the branches were also studied. The three-dimensional continuity and the Navier-Stokes equations for incompressible, unsteady laminar flow with Newtonian properties were solved with a commercial software using non structured grids with 61334 and 65961 cells for models 1 and 2, respectively. The grids were primarily composed of tetrahedral elements. The intra-aneurysmal flow was unsteady for all input conditions and in both models, the flow always showed a complex vortex structure. The inflow and outflow zones in the aneurysm neck were determined. The wall shear stress on the aneurysm showed large temporal and spatial variations. The asymmetric outflow increased the wall shear stress in both models. [ABSTRACT FROM AUTHOR]

The flow structure and heat transfer in a plane channel with periodically placed vortex generators of different forms have been investigated in the Reynolds number range corresponding to unsteady laminar and transitional flow. Numerical results from four different configurations are reported: a pair of square bars, a rectangular bar, and two different baffle arrangements. The heat transfer and pressure drop are strongly dependent on the geometry used. A wide range of geometric parameters have been computed to cover the different possibilities. The unsteady Navier–Stokes equations and the energy equation have been solved by a finite-volume code with staggered grids combined with SIMPLEC pressure correction. The velocity and temperature fields were computed. Results for the same pumping power show heat transfer enhancement by a factor larger than 3.5 in the best cases. [Copyright &y& Elsevier]

A numerical investigation was conducted to analyze the unsteady turbulent flowfield and heat transfer characteristics in a channel with streamwise periodically mounted square bars arranged side-by-side to the approaching flow. The transverse separation distance between the bars is varied, whereas the bar height to channel height (d/H) are 0.152 and 0.2, the Reynolds number Re based on channel height is 2×104 and the periodicity length is 2H. The channel walls are subjected to a constant wall temperature. The k–ϵ turbulence model was used in conjunction with the Reynolds-averaged momentum and energy equations for the simulations. A finite volume technique is applied with a fine grid and time resolution. Complex periodic vortex shedding develops in the channel due the interaction between the two streamwise periodically mounted square bars. Results show that the unsteady flow behavior, pressure drop and heat transfer are strongly dependent of the transverse separation distance of the bars. [Copyright &y& Elsevier]

The unsteady laminar flow and heat transfer characteristics in a plane channel with two square bars mounted staggered to the approaching flow are numerically analyzed. A finite volume method is applied with a fine grid and time resolution. The longitudinal and transverse separation distances between the bars are varied, whereas the bar height to channel height d/H, and the Reynolds number based on channel height Re, are d/H=SHAPE="SOL" ALIGN="C" STYLE="S">18 and 800 respectively. Complex flow patterns develop in the channel due the interaction between the two staggered square bars. For the cases with L/d≥2 shedding of vortices with only one frequency are present in the flow, and biased flow with frequency modulation of the vortices shedding for the cases with L/d<2 are found. [Copyright &y& Elsevier]

Computations are conducted to study the heat transfer and friction in a channel with a mounted square bar of different sizes detached from the channel wall. The Reynolds number (Re) based on channel height ranges from 10 4 to 105, whereas the bar height to channel height (d H) varies from 0.15 to 0.35. The channel walls are subjected to a constant wall temperature. The standard k- epsilon turbulence model and a modified version were used in conjunction with the Reynolds-averaged momentum and energy equations for the simulations and were compared thereafter. A finite volume technique with staggered grids combined with the SIMPLEC algorithm is applied. Results show that the local and global Nusselt numbers on the channel walls are strongly modified by the unsteady vortex shedding induced by the bar. The displacement of the bar from the channel axis toward the wall did not cause an increase in the global heat transfer coefficient on the channel walls compared with the bar centered in the channel. [ABSTRACT FROM AUTHOR]

The thermal performance of a compact heat exchanger with flat tubes was numerically investigated in a laminar regime by introducing longitudinal vortex generators (LVG) in arrays comprising: 9 alternating, 18 alternating, 18 aligned, 27 alternating and 39 alternating LVG. Vortex generators, in the form of delta winglets with an angle of attack of 35o, were used. For each geometry, the local heat flux, local and global Nusselt number and the friction factor were analysed. The Reynolds number varied between 400 and 2000. [ABSTRACT FROM AUTHOR]

Since the late 1990s, Bogotá has been implementing measures and policies to promote sustainable transportation. For example, to promote cycling, the city built 232 km of segregated bicycle infrastructure between 1998 and 2000. Modal share for bicycles was around 0.58% before the massive introduction of cycling facilities; ten years later, it had increased to 6%. Does this intervention have a differential effect on bicycle ridership for people who live close to the cycling infrastructure? The objective of this paper is to determine the impact of residence proximity to linear bicycle infrastructure in Bogotá on bicycle ridership. The selected evaluation method is the difference-in-difference technique used for the georeferenced 1995 and 2011 Household Transportation Surveys, and which provides information relating to before and after the implementation of the new infrastructure. The difference in the travel behavior of people closer to the bike infrastructure, compared to the rest of the city, provide evidence of the effectiveness of the policy measure. We found that living close to cycling infrastructure in Bogotá has a positive and marginal but significant impact on the odds of an individual choosing a bicycle as his or her main mode of transportation, controlling for socio-economic and environmental characteristics. Results are discussed in the light of bicycle-related transportation policies and the econometric modeling technique applied. • Proximity to cycling infrastructure increases marginally the likelihood of using this mode of transportation. • Effects of policies such as off-street bike-path construction are more localized depending on the age and gender. • Depending on socio-economic and trip characteristics, new cycling infrastructure may encourage new cyclists to show up • In a developing country context, middle-income population appeared to be less prone to using the bicycle. [ABSTRACT FROM AUTHOR]

• The Mehrabian-Russell model can explain pedestrians' avoidance behavior. • Overarousal and submissiveness evince a negative emotional response. • A negative emotional response towards infrastructure is related with avoidance. • Given our results, non-motorized transportation can incorporate the MRM. • Approach behaviors need to be understood within the sustainable mobility paradigm. Social and environmental psychology provide a variety of models based on which to understand how built environments can elicit people's behavioral responses. The Mehrabian-Russell model (MRM), initially presented in 1974, provides a framework that explains avoid–approach behavior towards a place based on a primary emotional response (PER) and affective states elicited by the perceived stimuli from the environment. However, despite the potential applications of the MRM in travel behavior studies, traditional models (e.g., discrete choice models and integrated choice latent variable) do not incorporate this specific psychological process that converts environmental stimuli into behavioral responses. Hence, this paper aims to test the applicability of MRM to urban sidewalks. To fulfill this objective, we developed a two-level structural equation model using latent variables (LV) identified from a confirmatory factor analysis (CFA) based on 1056 in-person surveys on 30 different sidewalks in Bogotá, Colombia. We then evaluated the effect of the PER on declared avoidance as a proxy of behavioral intention. The CFA uncovered three LV equivalent to the three affective dimensions of the MRM—arousal, pleasure, and dominance—followed by a fourth LV, representing the PER, which explains the three previous LVs. This confirms the applicability of these kinds of psychological and environmental models in pedestrian behavior evaluation. We found that PER can explain the declared intention of avoidance towards the sidewalk in an urban setting. Proving that this kind of model can explain the way in which the built environment can elicit pedestrians' emotional responses and subsequent behaviors, provides information that can be used as input in travel behavior studies focusing on the promotion of active traveling and mode change. [ABSTRACT FROM AUTHOR]

• Pedestrians' interaction with their built environment affects the perceived quality of service. • Pedestrian perception of their QoS is directly improved by the perception of the sidewalk characteristics. • Pedestrian perception of their QoS decrease by the interaction with motor vehicles, bicyclists, and themselves. • New studies about pedestrian infrastructure quality of service should include pedestrians' sensory experiences. A better understanding of what walking entails is important in sustainable transportation planning. Recent research has shown that perceptions have a higher power to explain the quality of service (QoS) than objective measures have; the latter being typically used in the pedestrian level of service methodologies. Despite the existing research on perceptions and QoS in other transportation fields, very little information has been found in the literature that can explain a clear cognitive structure that defines the pedestrian QoS. In this research, we propose a cognitive map to make it possible to understand and explain pedestrian sidewalk QoS of a given infrastructure when walking, based on perceptions. We gathered the perceptions of 1056 pedestrians on-site, regarding the attributes (indicators) identified in the literature review in 30 locations in Bogotá, Colombia. Based on an Exploratory Factor Analysis, we developed a conceptual model through Structural Equation Modeling. We found that seven latent variables (LVs) (i.e., Sidewalk characteristics, Externalities, Surrounding, Discomfort, Bike hassles, Protection, and Amenities) interrelate to each other, forming a pedestrian cognitive map. QoS is directly explained by how pedestrians perceive the LVs sidewalk characteristics and surrounding and indirectly by the rest of LVs. The cognitive map shows three LVs related to the interaction between pedestrians and other transportation modes (i.e., externalities, discomfort, and bike hassles) that impact the perceived QoS negatively, and four LVs related to the interaction between pedestrians and different elements of the sidewalk (i.e., sidewalk characteristics, surrounding, amenities, and protection) that impact the perceived QoS positively. To understand pedestrian perceptions when walking and the path that these perceptions follow to develop a QoS perception provides an accurate tool by which to improve the QoS from the useŕs perspective, generating a new opportunity to provide better pedestrian facilities. [ABSTRACT FROM AUTHOR]

Accurate characterization of two phase bubbly flows is crucial in many industrial processes such as fluidized reactors, ore froth flotation, etc. The bubble size determines the rate at which components present in the gas phase are transferred to the surroundings and vice versa while bubble rate defines the appropriate bubbly flow regime occurring in the heterogeneous system. This research work employs deep neural networks (DNNs) to predict bubble size and bubble rate using data obtained from validated computational fluid dynamics (CFD) computations. Pure water and slurry (in conditions similar to those employed in mineral froth flotation) case studies are evaluated. It is found that the DNN can predict the CFD results accurately when using four hidden layers, describing discontinuities in the bubbly flow regime. The relative errors computed between the CFD data and the prediction obtained by the DNN is as low as 8.8% and 1.8% for bubble size and bubble rate, respectively. These results confirm that the DNN can be applied to sophisticated fluid dynamics systems and allow developing better control process strategies since once the DNN is trained critical variables can be computed very efficiently. The slurry case study, although restricted to the application of mineral froth flotation, can also be generalized to other industrial operations keeping the exact same procedure. [ABSTRACT FROM AUTHOR]

The aim of this research work is to propose a signal processing based technique to classify and estimate bubble sizes. Bubbles are generated by computational fluid dynamics simulations. Local measuring points for velocity and pressure are set, and the captured data are analyzed using signal processing. The signal analysis includes the generation of templates for signal measurements of different bubble sizes using the short-time Fourier transform. Euclidean distances between templates of the different bubble size classes are subsequently computed. An inter/intra-class distance based matrix methodology is proposed to assess the discriminability of the Fourier-based template representation. The results indicate that the proposed technique based on signal processing can lead to the discrimination of bubble sizes with the information of bubbles passing through a single sensor point. Moreover, the model presented in this paper suggests that the analysis window size may play a highly important role in the discriminability according to the range of target bubble sizes. [ABSTRACT FROM AUTHOR]

The problem of a hydromagnetic hot two-dimensional laminar jet issuing vertically into an otherwise quiescent fluid of a lower temperature is studied. We propose solutions to the boundary layer equations using the classical Fourier series. The method is essential to transform the boundary layer equations to a coupled set of nonlinear first- order ordinary differential equations through the Fourier series. The accuracy of the results has been tested by the comparison of the velocity distributions obtained by the Fourier series with those calculated by finite difference method. The results show that the present method, based on the Fourier series, is an efficient method, suitable to solve boundary layer equations applied to plane jet flows with high accuracy. [ABSTRACT FROM AUTHOR]

• Cyclists' interaction with their built environment affects the perceived quality of service. • Cyclists' attitudes and perceptions when riding explain infrastructure quality of service. • Pro-bike attitudes have a direct effect on perceived enjoyment. • Cycling infrastructure quality of service is influenced indirectly by pro-bike attitudes. • New studies on cycling infrastructure quality of service should include cyclists' sensory experiences. Many approaches have been developed to assess the performance or Quality of Service (QoS) rendered by cycling infrastructure. The most common methodologies (Level of Service/Level of Traffic Stress) do not consider user inputs. In other disciplines, user perceptions constitute a powerful tool that can help improve and tailor designs. This study was intended to explore the effect of cyclists' attitudes and perceptions on the perceived QoS of different cycling infrastructures using Structural Equation Modeling (SEM). The SEM model was developed using cyclist surveys applied at 16 locations comprising all typologies of cycling infrastructure in Bogotá, Colombia. We found that user attitudes and perceptions of tangible (e.g., pavement) and intangible attributes (e.g., enjoyment) can explain cyclists' QoS. The results lead to a better understanding of typical Global South cyclist perceptions when riding, and provide an accurate tool with which to improve cycling infrastructure QoS from a cyclist perspective. [ABSTRACT FROM AUTHOR]

Brain arteriovenous malformations (bAVM) are complex vascular diseases. Several models have been used to simulate endovascular treatments; thus in vitro models have not been widely employed because it has been difficult to recreate realistic phantoms of this disease.To describe the development and evaluate the preliminary experience of a novel bAVM in vitro model for endovascular embolization using millifluidic three-dimensional (3D) printing technology.We designed a bAVM phantom starting from simple to more complex designs, composed of a nidus, feeding arteries and draining vein. We recreate the design by using millifluidic technology with stereolithography 3D printing. Structural and functional tests were performed using angiographic images and computer flow dynamics. Treatment simulations with ethylene vinyl alcohol were tested using two different microcatheter position techniques. A Likert-scale questionnaire was applied to perform a qualitative evaluation of the model.We developed a realistic model of a bAVM with hollow channels. The structural evaluation showed a high precision of the 3D printing process. Embolization tests with the liquid agent gave similar sensations and material behaviour as in vivo cases. There were no significant differences between microcatheter position techniques, thus we observed a trend for better nidus filling with a deeper in-nidus position technique.We were able to create and test a novel bAVM in vitro model with stereolithography 3D printing in resin. It showed a high capacity for simulating endovascular embolization characteristics, with an excellent user experience. It could be potentially used for training and testing of bAVM embolizations. [ABSTRACT FROM AUTHOR]

Abstract: Undesirable splashing appears in copper converters when air is injected into the molten matte to trigger the conversion process. We consider here a cylindrical container horizontally placed and containing water, where gravity waves on the liquid surface are generated due to water injection through a lateral submerged nozzle. The fluid dynamics in a transversal section of the converter is modeled by a 2-D inviscid potential flow involving a gravity wave equation with local damping on the liquid surface. Once the model is established, using a finite element method, the corresponding natural frequencies and normal modes are numerically computed in the absence of injection, and the solution of the system with injection is obtained using the spectrum. If a finite number of modes is considered, this approximation leads to a system of ordinary differential equations where the input is represented by the fluid injection. The dynamics is simulated as perturbations around a constant fluid injection solution, which is the desired operating state of the system, considering that the conversion process does not have to be stopped or seriously affected by the control. The solution is naturally unstable without control and the resulting increase of amplitude of the surface waves are assimilable to the splashing inside the converter. We show numerically that a variable flow around the operating injection is able to sensibly reduce these waves. This control is obtained by a LQG feedback law by measuring the elevation of the free surface at the point corresponding to the opposite extreme to where the nozzle injection is placed. [Copyright &y& Elsevier]