Prolonged exposure of concrete to high temperatures, as in fire occurrences, can cause physio-chemical changes that reduce strength and durability, as well as degradation to the microstructure. Geopolymer has emerged as an alternative binder for concrete that is fire-resistant due to its inorganic base and ceramic-like properties. Notwithstanding the high fire resistance of geopolymer concrete, its application in buildings has to consider potential deficiencies during fire occurrences. The present study evaluates the residual compressive strength and microstructural properties of fly-ash-based geopolymer concrete with exposure to fire at burning temperatures of 500 and 1200 °C relative to OPC-based concrete. Increment in mechanical strength for geopolymer concrete were observed during the exposure to fire at 500 °C due to further geopolymerization but eventually reduced in strength at 1200 °C. The matrix of the geopolymer concrete is denser, hence indicating a higher structural integrity relative to OPC-based concrete, as well a higher thermal stability.
This article is particularly interested in the numerical modeling of water hammer in a hydraulic circuit, taking into account the prevailing water temperature. The study concerns the propagation velocity of the wave and the amplitude of unsteady phenomena encountered in the circuit, as well as the severity and collapse of cavitations that are also considered as major risks. To conjecture the consequences of these phenomena, we were led to simulate a single-phase and two-phase transient flows in a hydraulic copper pipe system in a temperature range of 4–95 °C. To do this, we have developed a solver for the dynamic and continuity equations’ resolution. The method of characteristics is chosen for its capacities to solve these equations. Its application shows that it is robust and adapted to the problem studied. Two cavitations’ models and column separation have been incorporated; in this case, the Discrete Vapor Cavity Model (DVCM) and the Discrete Gas Cavity Model (DGCM). Moreover, in addition to the classic models of quasi-stable friction, of which the models of unsteady friction have been included, like the one based on the instantaneous acceleration proposed by Brunone and the one proposed by Vardy & Brown based on the convolution integral. Although single-phase and two-phase water hammers do not behave in the same way, the results obtained with these models show that the temperature produces a great effect on the hammer.
Selective Laser Sintering (SLS) is a 3D printing process on a powder bed that presents a real revolution for many industrial sectors, it allows to produce layer by layer precise prototypes, fast, with high dimensional accuracy and with remarkable mechanical characteristics. This technology uses a laser to fuse polymer micro particles, following the geometry of digitally cut CAD models. However, the external surfaces of the parts produced by this process are characterized by a high degree of roughness due mainly to the properties of the powder, the orientation in the build-up tray and the manufacturing parameters. In this study selective laser sintering experiments were performed with PA12 powders, in order to analyze the optimal process parameters for the realization of parts with minimal roughness. The process parameters chosen for the study were carefully selected and which are laser power, scanning speed, layer thickness and scanning space. The samples were printed in different orientations 0°, 45° and 90°. The Taguchi method was used to study the parameters. Regression equations for each of the orientations were established, these developed a linear relationship between the roughness and the parameters studied.
The direct proportionality between the flow rate and the pressure gradient of creeping flows was experimentally discovered by H. Darcy in the 19th century and theoretically justified a couple of decades ago using upscaling methods such as volume averaging or homogenization. X-ray computed micro-tomography (CMT) and pore-scale numerical simulations are increasingly used to estimate the permeability of porous media. However, the most general case of non-periodic anisotropic porous media still needs to be completely numerically defined. Pore-scale numerical methods can be split into two families. The first family is based on a direct resolution of the flow solving the Navier–Stokes equations under the assumption of creeping flow. The second one relies on the resolution of an indirect problem—such as the closure problem derived from the volume averaging theory. They are known to provide the same results in the case of periodic isotropic media or when dealing with representative element volumes. To address the most general case of non-periodic anisotropic porous media, we have identified four possible numerical approaches for the first family and two for the second. We have compared and analyzed them on three-dimensional generated geometries of increasing complexity, based on sphere and cylinder arrangements. Only one, belonging to the first family, has been proved to remain rigorously correct in the most general case. This has been successfully applied to a high-resolution 3D CMT of Carcarb, a carbon fiber preform used in the thermal protection systems of space vehicles. The study concludes with a detailed analysis of the flow behavior (streamlines and vorticity). A quantitative technique based on a vorticity criterion to determine the characteristic length of the material is proposed. Once the characterized length is known, the critical Reynolds number can be estimated and the physical limit of the creeping regime identified.
Geopolymer concrete possesses superior fire resistance compared to ordinary Portland cement (OPC)-based concrete; however, there are concerns regarding its vulnerability when exposed to real fire events. In the present study, the fire resistance of fly-ash-based geopolymer concrete was evaluated relative to that of OPC-based concrete. Concrete specimens of standard strength grades of 20, 40, and 60 MPa were exposed to fire at 500 and 1200 °C for 2 h to simulate real fire events. Visual observation was performed, mass loss and residual compressive strength were measured, and scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted. OPC-based concrete suffered major cracks accompanied with spalling for the high-strength specimen, while geopolymer concrete experienced minor cracks with no spalling. Mass losses of the geopolymer concrete—of 1.69% and 4%, after the exposure to fire at 500 and 1200 °C, respectively—were lower than those of the OPC-based concrete. More than 50% of the residual compressive strength for low- and medium-strength geopolymer concrete, after the exposure to fire at 1200 °C, was maintained. After the exposure to fire at 500 °C, the residual compressive strength of the geopolymer concrete increased from 13 to 45%, while the OPC-based concrete was not able to sustain its compressive strength. SEM images showed that the matrix of the geopolymer concrete, after the exposure to fire, was denser than that of the OPC-based concrete, while the FTIR spectra of the geopolymer concrete showed a minor shift in wavelength. Hence, our findings indicate that fly-ash-based geopolymer concrete has an excellent fire resistance as compared to OPC-based concrete.
Robotization is increasingly used in the agriculture since the last few decades. It is progressively replacing the human workforce that is deserting the agricultural sector, partly because of the harshness of its activities and health risks they may present. Moreover, robotization aims to improve efficiency and competitiveness of the agricultural sector. However, it leads to several research and development challenges regarding robots supervision, control and optimization. This paper presents a simulation and optimization approach for the optimization of robotized treatment tasks using type-c ultraviolet radiation in horticulture. The optimization of tasks scheduling problem is formalized and a heuristic and a genetic algorithms are proposed to solve it. These algorithms are evaluated compared to an exact method using a multiagent-based simulation approach. The simulator takes into account the evolution of the disease during time and simulates the execution of treatment tasks by the robot.
In the present study, both experimental and numerical were conducted on a free surface flow over an obstacle. Numerical simulations were performed using the Renormalization Group (RNG-k-ɛ) based Reynolds-Averaged Navier–Stokes (RANS) turbulence model coupled with the Volume OF Fluid (VOF) method in FLUENT Software to investigate the effect of the channel slope on the flow pattern upstream, above and downstream the obstacle. Respectively, 5%, 7%, 8%, 10%, 20% and 50% channel slopes were considered. Numerical simulation has showed a good agreement compared against experimental results. Effect of the slope on the flow is observed particularly upstream of the obstacle where the flow takes the vertical direction after hitting the upstream wall. The more the slope becomes steeper, the higher the level of the water is. Recirculation zones in the case of a horizontal channel are elongated downstream the weir, whereas in the case of a sloped channel, they are localized just at the foot of the downstream wall.
The adoption of electric vehicles (EVs) is increasing worldwide as it may help reduce reliance on fossil fuels and greenhouse gas emissions. However, the large-scale use of charging stations for electric vehicles poses some challenges to the power grid and public infrastructure. To overcome the problem of extended charging time, the simple solution of increasing the charging station and increasing the charging capacity does not work due to the load and space limitation of the power grid. Therefore, researchers focused on developing intelligent planning algorithms to manage the demand for public charging based on predicting the charging time of electric vehicles. As a result, this paper proposes a deep learning approach for predicting the duration of charging sessions. These approaches are validated using a real-world dataset of charging processes collected at public charging stations in Morocco. Numerical results show that the gated recurrent units (GRU) regression method slightly outperforms the other methods in predicting the charging sessions duration. Accurate prediction of electric vehicles charging duration has many potential applications for utilities and charging operators, including grid reliability, scheduling, and smart grid integration. In the case of Morocco, the massive deployment of EVs can cause a variety of problems to the electrical system due to the considerable charging power and stochastic charging behaviors of electric vehicle drivers. Thanks to this study's results, we can assess the expected impact of additional EVs on the grid, considering specific characteristics of the Moroccan power system.
Statement of problem Dental implant geometry affects the mechanical performance and fatigue behavior of butt-joint implant-supported restorations. However, failure of the implant component has been generally studied by ignoring the prosthetic screw, which is frequently the critical restoration component. Purpose The purpose of this in vitro study was to evaluate the effect of 3 main implant geometric parameters: the implant body diameter, the platform diameter, and the implant-abutment connection type (external versus internal butt-joint) on the fatigue life of the prosthetic screw. The experimental values were further compared with the theoretical ones obtained by using a previously published methodology. Material and methods Four different designs of direct-to-implant dental restorations from the manufacturer BTI were tested. Forty-eight fatigue tests were performed in an axial fatigue testing machine according to the International Organization for Standardization (ISO) 14801. Linear regression models, 95% interval confidence bands for the linear regression, and 95% prediction intervals of the fatigue load-life (F-N) results were obtained and compared through an analysis of covariance (ANCOVA) to determine the influence of the 3 parameters under study on the fatigue behavior (α=.05). Results Linear regression models showed a statistical difference (P<.001) when the implant body diameter was increased by 1 mm; an average 3.5-fold increase in fatigue life was observed. Increasing the implant abutment connection diameter by 1.4 mm also showed a significant difference (P<.001), leading to 7-fold longer fatigue life on average. No significant statistical evidence was found to demonstrate a difference in fatigue life between internal and external implant-abutment connection types. Conclusions Increasing the implant platform and body diameter significantly improved (P<.001) the fatigue life of the prosthetic screw, whereas external and internal connections provided similar results. In addition, experimental results proved the accuracy of the fatigue life prediction methodology.
Turbulent flows are characterized by the presence of "scales of fluctuations", or "structures" of varying magnitudes, the effects in which the mixing, transfer and dissipation of energy are preponderant. Most importantly, dissipation determines the depth profile of the flow. This contribution aims to implement a model able to predict unsteady turbulent flows generated by the presence of obstacles in a channel with complex geometry and to report, where the complexity of the phenomena are observed, such as: the separation of the boundary layer, the succession of vortices, local heat transfers, and the recirculation zones in the wake of obstacles and the oscillatory regime of the hydraulic jump for which this research is of exclusive interest. The current work therefore, presents the numerical simulation in unsteady turbulent regime based on the resolution of balance equations, using the RANS (Reynolds-Averaged Navier–Stokes) approach with an RNG k−ε closure model. To solve the incompressible Navier–Stokes equations governing these flows, we appealed to the motivated finite volume method, and its ability to process complex geometries. The simulation software FLUENT we used is based on the finite volume method. It allows to explore, the velocity and pressure fields in the digital channel of the studied flows.
In the Oil and Gas industry, installing pipe loops is a well-known hydraulic practice to increase oil pipeline capacities. Nevertheless, pipe loops could promote an unfavorable phenomenon known as fouling. That means that in a heavy oil-water mixture gathering system with low flow velocities, an oil-water stratified flow pattern will appear. In consequence, due to high viscosity, the oil stick on the pipe, causing a reduction of the effective diameter, reducing handled fluids production, and increasing energy consumption. As jet pumps increase total handled flow, increase the fluid velocities, and promote the homogenous mixture of oil and water, this type of pump could result attractive compared to other multiphase pump systems in reactivating heavy crude oil transport lines. Jet pumps are highly reliable, robust equipment with modest maintenance, ideal for many applications, mainly in the oil and gas industry. Nevertheless, their design method and performance analysis are rarely known in the literature and keep a high experimental component similar to most pumping equipment. This paper proposes a numerical study and the optimization of a booster multiphase jet pump system installed in a heavy oil conventional loop of a gathering system. First, the optimization of a traditionally designed jet pump, combining CFD simulation and optimization algorithms using commercials software (ANSYS CFX® and PIPEIT® tool), has been carried out. This method allowed evaluating the effect of multiple geometrical and operational variables that influence the global performance of the pump to run more than 400 geometries automatically in a reduced time frame. The optimized pump offers a substantial improvement over the original concerning total flow capacity (+17%), energy, and flow distribution. Then, the effect of the three jet pump plugin configurations in a heavy oil conventional trunkline loop was analyzed. Simulations were carried out for different driving fluid pressures and compared against a traditional pipeline loop’s performance. Optimum plugin connection increases fluid production by 30%. Finally, a new eccentric jet pump geometry has been proposed to improve exit velocities and pressure fields. This eccentric jet pump with the best connection was analyzed over the same conditions as the concentric optimized one. An improvement of 2% on handled fluid was achieved consistently with the observed uniform velocity field at the exit of the pump. A better total fluid distribution between the main and the loop line is obtained, handling around half of the complete fluid each.
IntroductionGlobal alignment analysis is of upmost importance in adult spinal deformity patients (ASD). Numerous parameters exist in the literature to measure global alignment based upon C7 or T1. One common limitation of these parameters is that they neglect the cervical segment which is essential in spinal compensatory mechanisms and in horizontal gaze preservation. A recent stereoradiography analysis of asymptomatic subjects introduced a new 3D parameter (ODHA), defined as the angle between the vertical reference line and the line joining the odontoid tip (OD) to hip axis center (HA). Thus, the goal of this study was to analyze 3D global alignment of ASD patients using the new parameter odontoid hip axis angle and its relationship to other spinal parameters.Methods In this prospective study, 90 adult patients with lumbar scoliosis (Cobb > 20°) were included. All subjects underwent low dose biplanar X-rays with 3D spinal reconstructions. Based on published normative values of ODHA, we defined abnormally high value as mean ODHA of asymptomatic subject + 2SD (i.e., ODHA > 6.1°). Values of 3D radiographic parameters and ODI were compared between patients with ODHA > 6.1° and < 6.1°.ResultsMean ODHA was 5+/− 3.6° (0.4° to 18.6°). 22 patients had abnormally high ODHA. They were older than the 68 other patients (68+/− 9y vs 53+/− 14y, p = 0.001), without any significant difference in terms of sex, BMI and rate of rotatory subluxation (54% vs 62%, p = 0.06). However, coronal and sagittal deformity was more important in patients with abnormal ODHA (larger Cobb angle, coronal malalignment, pelvic tilt and lower lumbar lordosis). Patients with abnormal ODHA had significantly worst ODI (50+/− 23 vs 30+/− 18, p = 0.0005).Conclusion Extreme values of ODHA are observed in significantly older patients with significant functional impairment. In addition, in these patients with sagittal malalignment with loss of lumbar lordosis, who recruit compensatory mechanisms such as pelvic retroversion, the cervical area is also involved with a posture in cervical hyperlordosis to maintain the head over the pelvis. Thus, ODHA is an interesting parameter allowing a more comprehensive alignment measurement taking into account the mechanisms of compensation of the cervical spine to the pelvis.
Objective To identify the different apex and transitional vertebra according to the shape of the pelvis of individuals despite their difference in sagittal alignment using our measurement system.Methods Full-spine X-rays using EOS in standard stand-position of 99 volunteers were selected (47 women, 52 men, mean age 31 years old). Validated 3D reconstruction technique allows extraction of spinopelvic parameters, and position and rotation of each vertebra and lumbar disks. Subjects were divided into three groups: low PI (lowPI, n = 37), moderate PI (midPI, n = 52), high PI (highPI, n = 10), with, respectively, a PI below 45°, between 45° and 60° and above 60°. Occurrence of specific position and rotation values of apex and transitional vertebra were assessed in each group.ResultsFrequency curves tend to move cranially when the incidence increases except in cervicothoracic where T1 is a constant for all shapes of spine with occurrence approaching 90%. Angulation value of relevant vertebra and lumbar lordosis are significantly positively correlated for the whole population.Conclusions Our study allowed the assessment of the distribution of spine curvatures according to the pelvic incidence. It describes the occurrence of localization of the apex and transitional vertebrae according to pelvic incidence. These results should be taken into account during the analysis of the sagittal balance, especially when planning deformity surgery in adults.
With the rapid development of digital technologies, products connectivity is increasing as well as the data produced and collected. Forecasts on product development predict that this trend will keep on growing. In this context, new design solutions based on data are emerging. Those data-driven design approaches are common for identifying the customers' need when developing a new product. However, few studies cover data-driven design in the other early stages of product design. Thus, the research question addressed in this paper is: what are the challenges of data-driven design research in the early phases of the product development process? Through a literature review and a workshop proposed at the conference DESIGN 2020, this paper offers a first glimpse of future research leads. A list of 5 challenges for data-driven design in the early stages of product design is proposed and ranked from short term to long term.
cheese using the packaging evaluation method and to propose suggestions to improve the efficiency of packaging logistics that would impact the efficiency of the entire supply chain. We engage all supply chain actors for evaluating the packaging features. The first packaging is not convenient as its weight and cost are quite high for cheese, the secondary packaging is deemed less efficient, whilst the tertiary packaging is not optimal in terms of traceability. Speaking of cost, environmental impacts, especially impact on other features in the supply chain, we propose solutions to replace the circular wooden box of the cheese with a cardboard box with a round shape. Then, only the cardboard trays will be used as secondary packaging all along the supply chain. These combined solutions reduce the handling work, the packaging material cost and provide more convenience for all actors.
The development of composites based on plant fibres has considerably grown in last decades; however, their high sensitivity to moisture limits their use in structural applications. The objective of this study is to determine and understand the impact of moisture variations during one-year cyclic hygrothermal ageing i.e. 52 cycles on the transverse properties of a unidirectional epoxy flax composite. A cycle consists of 3.5 days at 90% RH followed by 3.5 days at 40% RH. Compared to the studies usually carried out to determine the impact of ageing on the longitudinal properties of unidirectional composites, the determination of the transverse mechanical properties during this type of ageing allowed to focus on the contribution of the matrix and the interface on the evolution of the composite properties. The multi-scale analyzes provided identification of the phases responsible for the evolution of transverse mechanical properties induced by ageing. The transverse ultimate tensile strength drops by about 20% after the first week of ageing and slightly decreases up to 2 months. This evolution seems to be induced by the creation of flaws, in particular the phenomena of fibre-fibre and matrix-fibre debonding and the creation of cracks in the fibres initiated at the lumen level, revealed by SEM. The transverse modulus also strongly drops after the first week by about 18% to reach about 45% loss after one year of ageing. These evolutions are mainly linked to the physical plasticization of the epoxy matrix demonstrated by the reversible change of its glass transition temperature, but analyses showed that water does not lead to chemical degradation of the matrix.
Book Series Editorial Board John Michopoulos, Naval Research Laboratory David Rosen, Georgia Institute of Technology Chris Paredis, Georgia Institute of Technology Judy Vance, Iowa State University This is the second volume in this book series that aims to capture advances in computers and information in engineering research, especially by researchers and members of ASME’s Computers & Information in Engineering (CIE) Division. The series is focusing on advances in computational methods, algorithms, tools, and processes on the cutting edge of research and development as they have evolved and/or have been reported during the last three to five annual CIE conferences. The series will provide a resource for enhancing engineering practice by enabling the understanding and the application of evolving and emerging technologies that impact critical engineering issues related to the topics and themes under CIE’s technical committees areas of interest, but not limited to: Advanced Modeling and Simulation; Computer-Aided Product and Process Development; Systems Engineering, Information and Knowledge Management; Virtual Environments and Systems.
PurposeSpinal muscles are a major component of posture in spinal pathologies and changes to the spine with aging. Specifically, spinopelvic muscles may compensate for underlying anomalies such as pelvic retroversion, knee flexion, and cervical or thoracic spinal balance abnormalities. To increase understanding between muscular characteristics and compensatory mechanisms, this study aimed to compare the volume of spinopelvic muscles in adults with a spinal deformity (ASD) to a control group of well-aligned adult subjects.Methods Twenty-eight lumbar ASD patients [Cobb angle > 20°, > 40 years old (yo)] were prospectively included and compared to 35 normal subjects divided into 2 different groups: one group of young (Y) subjects (n = 23, < 20 yo) and one group of old (O) subjects (n = 12, > 40 yo). All subjects had a fat/water separation MRI (from C7 to the knees). Volumetric 3D reconstructions of 30 spinopelvic muscles were performed and muscles volumes were compared.ResultsMean age was 60 ± 16 yo, without significant differences between the ASD and O groups (57 ± 11 yo). Age and BMI were smaller in the young group. Mean Cobb angle of the ASD group was 45 ± 11°. Comparing the ASD and O groups, total muscular volume was similar; however, erector spinae (0.24 ± 0.06 vs 0.68 ± 0.08 dm3, p = 0.001), iliopsoas (0.49 ± 0.09 vs 0.60 ± 0.09 dm3, p = 0.001) and obliquus (0.42 ± 0.08 vs 0.50 ± 0.08 dm3, p = 0.02) were significantly smaller in the ASD group. Comparing the Y and the ASD groups, total muscular volume was higher in the Y group than the ASD group (+ 3.3 dm3, p = 0.003) and erector spinae (0.24 ± 0.06 vs 0.74 ± 0.08, p = 0.0001), gluteus medius (0.51 ± 0.07 vs 0.62 ± 0.13, p = 0.01) and vastus lateralis (1.33 ± 0.21 vs 2.08 ± 0.29, p = 0.001) were significantly bigger in the Y group.Conclusion This is the first study to compare volume of spinopelvic muscles between ASD patients and a control group without spinal deformity. Our results demonstrate that muscular degeneration has a double origin: aging and deformity. Erector spinae, iliopsoas, and obliquus are the muscles most affected by degeneration.
We report nonlinear vibration localisation in a system of two symmetric weakly coupled nonlinear oscillators. A two degree-of-freedom model with piecewise linear stiffness shows bifurcations to localised solutions. An experimental investigation employing two weakly coupled beams touching against stoppers for large vibration amplitudes confirms the nonlinear localisation.
The work presented in this article underlines the embodiment design phase aiming at the determination of different possible architecture of a system according to the energy vision combined with the graph theory. Indeed, the embodiment design phase presents the difficulty of organizing the design alternatives. This difficulty is due to the fact that the various components of the system are not yet fully defined, and there are many arrangement possibilities. In this context, we seek to structure a methodology for the preliminary definition of the technical system architecture, while respecting the TRIZ law of completeness of the system parts. We consider the availability of the transmission elements of the principal energy flow (functional flow). The modeling of the system will concern the flow ensuring the positioning of the system principal component called (contact flow). The modeling of an optimal system composed of the main elements (converter, transmitter, operator, and reference) with a graph ensures the possibility to propose various architectures based on the combinations of these components. The proposed approach consists of three principal phases: appropriate graph-system model association, inappropriate solutions elimination, full system definition, and decision making. An illustration of the methodology is carried out on a wind system example.
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