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Understanding the factors and drivers of user satisfaction with public transportation (PT) systems has been a subject of research for decades, as it provides insight into influencing ridership increases. This research addresses user satisfaction using SEM-MIMIC models to analyze three PT bus subsystems in the same city (Bogotá Colombia): A Bus Rapid Transit, a formalized bus subsystem, and a semi-formalized one that operates simultaneously. After developing three independent models, we found the same three latent variables (LVs), namely subsystems "condition", "service", and "safety/security", in each one. However, the strength and significance of the direct and indirect effects among the three LVs vary from one subsystem to another. In general, satisfaction is initially based on a person's perception of the subsystem's condition and ends with his/her perception of the service, with safety and service being the mediating variables to explain satisfaction. Unlike previous studies, we were able to identify relationships among these three independent variables for each subsystem, allowing us to assess the direct and indirect effects on overall subsystem satisfaction. This research provides decision-makers with a broader understanding of how infrastructure, vehicles, operational attributes, and regulation processes influence user satisfaction through perceptions and how they can help improve the PT service for its users. [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]

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]

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]

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]

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]

• 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]

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]