Recent studies have recognized the importance of non-pharmacological factors such as setting to induce or promote mystical experiences or challenging experiences among ayahuasca users. This study ...aimed to evaluate the association between the setting in which ayahuasca is consumed and the intensity of mystical and challenging experiences considering three ayahuasca using traditions (União do Vegetal, Santo Daime and neo-shamanic groups). A cross-sectional analysis was performed on survey data collected online from 2,751 participants. The Setting Questionnaire for the Ayahuasca Experience (SQAE) was used to evaluate six dimensions of the setting characteristics. The Mystical Experience Questionnaire (MEQ) and the Challenging Experience Questionnaire (CEQ) were used to quantify the psychedelic experience. Ratings on every SQAE setting dimension were negatively correlated with ratings of the CEQ (
r
values between 0.21 and 0.36) for all ayahuasca using traditions. Regression analysis revealed that ratings on four SQAE dimensions (Social, Comfort, Infrastructure and Decoration) explained 41% of the variance in CEQ ratings. Associations between SQAE and MEQ ratings were relatively weak and confined to the dimensions Leadership and Comfort, explaining 14% of the variance in MEQ ratings. Ratings of Social context were higher among members of União do Vegetal compared to Santo Daime and neo-shamanic members. Ratings of Infrastructure, Comfort and Decoration were more consistently correlated with MEQ in the neoshamanic tradition compared to the other traditions. This study shows that the setting is an important moderator of a challenging experience under ayahuasca. Maximizing the quality of the setting in which ayahuasca is taken will reduce the chance of a challenging experience while contributing positively to a mystical experience. The present findings can be considered when designing rituals and the (social) environment of ayahuasca ceremonies, and indicate that the SQAE questionnaire can be employed to monitor the influence of ceremonial settings on the ayahuasca experience.
High-voltage direct current (HVdc) circuit breakers based on power electronic technology usually require a large number of insulated-gate bipolar transistors (IGBTs) to achieve large-capacity ...breaking. The insufficient current capacity is an important reason for the excessive cost of dc circuit breakers. However, the single switching condition in the circuit breaker makes it possible for IGBTs to control the current of several times rated value in a short time. This article proposed an effective current boosting method for IGBT. By applying an unconventionally ultrahigh driving-voltage (UDV) to the gate of devices, the instantaneous current capability of IGBTs can be significantly improved. The possible failure modes and lifetime issues caused by UDV are also discussed in detail. Through comprehensive theoretical calculations and experimental analysis, a proper UDV selection principle for IGBTs in HVdc circuit breakers is proposed. The single device is verified to have the ability to control 31.2 kA current in milliseconds by using UDV. This conclusion can greatly increase the allowable working area of IGBTs, thereby significantly reducing the cost of HVdc circuit breakers.
In piping systems, the flow through a bend is typically undeveloped, unsteady, and complicated. In this study, we proposed a novel method to accurately predict downstream flow in bent pipes based on ...radial basis function neural network (RBFNN) and ultrasound Doppler velocimetry (UDV). An improved UDV method was developed for the measurement of complex flow in bent pipes. The downstream flow characteristics of three different bend configurations were investigated using computational fluid dynamics (CFD). The proposed RBFNN models established the relationships between the velocity profile along the symmetric axis and the velocity distribution over the pipe cross-section. Numerical data were used for model training and validation, whereas the combined datasets with UDV data as inputs and the corresponding CFD data as outputs were used for model modification. The model prediction performance was then evaluated with new UDV inputs by comparing the predicted velocities with the associated CFD results. The results indicated that the velocity profiles obtained using modified UDV agreed well with the present numerical simulation. Finally, the trained model exhibited satisfactory flow reconstruction performance and high flowrate prediction accuracy, with a maximum error of approximately 3%. This work contributes to the application of the UDV method in complex flow measurements and further demonstrates that artificial neural networks (ANNs) are promising for modeling fluid mechanics.
•An improved ultrasound Doppler velocimetry (UDV) was developed for bend pipe flow.•Radial basis function neural network (RBFNN) was employed for flow reconstruction.•Three types of in-plane piping configurations were considered.•Flowrate prediction error by the proposed model was less than 3%.
In this work, we study the effect on the electric potential difference (EPD) of a liquid metal (LM) flow confined in a cuboid vessel. The interaction between a magnetic field (MF) and an electric ...current density (j0) along the ascending axial direction generates a Lorentz force that stirs the LM producing an MHD flow. The MF is produced by either a single or a pair of NdFeB dipolar permanent magnets. j0 is in the range of 384 to 1153 A m-2. Experimental characterization is done by measuring velocity components using the ultrasound Doppler velocimetry (UDV) technique and measurements of the EPD in terminals of the vessel. Additionally, an MHD model is solved using the COMSOL Multiphysics software. A good agreement between measurements and simulations for the magnetic and velocity fields is obtained. Furthermore, an order of magnitude analysis for the characteristic velocity of the flow and EPD is presented. Comparing with a configuration without magnets, the EPD when one magnet is used reaches 16.8% higher values. In contrast, for a pair of magnets values are 22.9% smaller. This increasing/decreasing behavior for the EPD with the flow patterns could be of interest to applications such as liquid metal batteries.
•A Lorentz force stirs the GaInSn alloy confined in a cuboid vessel.•NdFeB magnets and currents in the range of 384 to 1153 A m-2 are considered.•Velocity profiles are measured with the UDV technique.•Numerical simulations with COMSOL Multiphysics are performed.•The electric potential difference depends on the flow behavior.
Population growth and global industrialization cause a dramatic increase in the amount of sewage sludge produced annually worldwide from Municipal and Industrial Wastewater treatment. The efficient ...measurement of sewage, which is a typical solid-liquid two-phase flow, has become an important issue that requires to be urgently addressed. In this study, an improved Ultrasonic Doppler Velocimetry (UDV) is proposed to optimize the probe design and hardware design, which reduces the influence of working frequency and echo reverberation on accuracy and improves the stability of the system. A Doppler peak extraction and superposition method is also put forward to correct the offset of Doppler peak frequency. In this paper, Particle Image Velocimetry (PIV) is used to calibrate the UDV system to modify the measurement model of ultrasonic Doppler liquid-solid two-phase flow, and dynamic experiments are carried out in a vertical steel pipe with inner diameter of 50 mm at different flow conditions. The results show that the accuracy and stability of UDV measurement system are greatly improved, with a maximum relative error of 1.49%.
•In this study, ultrasonic Doppler velocimetry (UDV) was used to achieve high-efficiency measurement of solids velocity in sewage.•The PIV flow rate measurement system has high accuracy and can realize online calibration for UDV.•The dual-modality UDV-PIV system proposed in this paper has a significant sewage treatment effect, achieving a maximum relative error of 1.49%.•The proposed dual modality system can have a great potential for measuring industrial solid-liquid flow with excellent precision.
Flow behavior in the slab mold by optimized swirling flow generation in the submerged entry nozzle (SEN) is investigated. Therefore, hydromechanical model experiment was carried out to simulate this ...metallurgical process, the effect of turning around the nozzle with swirling and different bottom shape of nozzle is especially analyzed. The flow behavior in the mold was recorded by dye tracer and camera; The two dimension average velocity distribution in the slab mold was measured by the Ultrasound Doppler Velocimetry (UDV). The velocity distribution agrees well with flow pattern recorded by camera. The swirling flow in SEN can reduce the impinging to the narrow face and slag entrapment is inhibited by swirling. Furthermore, the flow in the mold was optimized with swirling in SEN as well as turning around the nozzle outlet in reverse, which avoids the impinging to both the wide and narrow faces of the mold at the same time. It is a potential technology for continuous casting.
The article is devoted to the study of the influence of geometric parameters of sound-conducting walls on the quality of measurement of liquid metal flow velocities by ultrasonic Doppler velocimetry. ...It was shown that the thickness and radius of a sound-conducting wall (waveguide) have a notable effect on the resulting velocity profiles. The flow in a round pipe, the length of which is much larger than its diameter, is considered as a reference flow. The positive effect of a stepwise waveguides with a diameter smaller than the diameter of the piezoelectric element of an ultrasonic transducer on the quality of velocity measurements was verified experimentally. It was found that the accuracy of the resulting velocity profiles largely depends on the length and the material of the waveguides, as well as the velocity of the incoming flow of liquid metal.
•Waveguide allows to focus ultrasonic beam.•Ultrasound focusing increase depth and quality of measurement.•Geometrical parameters of waveguide is received for commercial UDV devices.•Comparison of velocity profiles received for set of waveguides.
Computational fluid dynamics (CFD) is an increasingly used method for investigation of hemodynamic parameters and their alterations under pathological conditions, which are important indicators for ...diagnosis of cardiovascular disease. In hemodynamic simulation models, the employment of appropriate boundary conditions (BCs) determines the computational accuracy of the CFD simulation in comparison with pressure and velocity measurements. In this study, we have first assessed the influence of inlet boundary conditions on hemodynamic CFD simulations. We selected two typical patients suspected of carotid artery disease, with mild stenosis and severe stenosis. Both patients underwent digital subtraction angiography (DSA), magnetic resonance angiography, and the invasive pressure guide wire measured pressure profile. We have performed computational experiments to (1) study the hemodynamic simulation outcomes of distributions of wall shear stress, pressure, pressure gradient and (2) determine the differences in hemodynamic performances caused by inlet BCs derived from DSA and Womersley analytical solution. Our study has found that the difference is related to the severity of the stenosis; the greater the stenosis, the more the difference ensues. Further, in our study, the two typical subjects with invasively measured pressure profile and thirty subjects with ultrasound Doppler velocimeter (UDV) measurement served as the criteria to evaluate the hemodynamic outcomes of wall shear stress, pressure, pressure gradient and velocity due to different outlet BCs based on the Windkessel model, structured-tree model, and fully developed flow model. According to the pressure profiles, the fully developed model appeared to have more fluctuations compared with the other two models. The Windkessel model had more singularities before convergence. The three outlet BCs models also showed good correlation with the UDV measurement, while the Windkessel model appeared to be slightly better (
R
2
=
0.942
). The structured-tree model was seen to have the best performance in terms of available computational cost and accuracy. The results of our numerical simulation and the good correlation with the computed pressure and velocity with their measurements have highlighted the effectiveness of CFD simulation in patient-specific human carotid artery with suspected stenosis.
► Viscous fluids displacing yield stress fluids at high Bingham number. ► Two flow regimes (central and slump) separated by Re/Fr. ► Residual layers of yield stress fluid. ► Experimental ...visualization and supporting computations.
We present results of a primarily experimental study of buoyant miscible displacement flows of a yield stress fluid by a higher density Newtonian fluid along a long pipe, inclined at angles close to horizontal. We focus on the industrially interesting case where the yield stress is significantly larger than a typical viscous stress in the displacing fluid, but where buoyancy forces may be significant. We identify two distinct flow regimes: a central-type displacement regime and a slump-type regime for higher density ratios. In the central-type displacement flows, we find non-uniform static residual layers all around the pipe wall with long-wave variation along the pipe. In the slump-type displacement we generally detect two propagating displacement fronts. A fast front propagates in a thin layer near the bottom of the pipe. A much slower second front follows, displacing a thicker layer of the pipe but sometimes stopping altogether when buoyancy effects are reduced by spreading of the front. In the thin lower layer the flow rate is focused which results in large effective Reynolds numbers, moving into transitional regimes. These flows are frequently unsteady and the displacing fluid can channel through the yield stress fluid in an erratic fashion. We show that the two regimes are delineated by the value of the Archimedes numbers (equivalently, the Reynolds number divided by the densimetric Froude number), a parameter which is independent of the imposed flow rate. We present the phenomenology of the two flow regimes. In simplified configurations, we compare computational and analytical predictions of the flow behaviour (e.g. static layer thickness, axial velocity) with our experimental observations.
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