Total Volume Flow Research Articles

Continuous slug flow crystallization: Impact of design and operating parameters on product quality

A slug flow crystallizer for cooling crystallization with focus on enhanced product quality control in terms of narrow particle size distribution (PSD) was designed and characterized. Emphasis was put on slug flow stability while maintaining a convex shape of slugs to make use of the advantage of a narrow residence time distribution. Measurements of the latter one showed plug-flow-like behavior for the liquid and solid phase independent of the operating conditions within the range investigated. A tube-in-tube temperature concept led to smooth cooling from 50 to 31°C avoiding supersaturation peaks. Seeded cooling crystallization of aqueous l-alanine solution successfully led to reproducible product PSDs avoiding secondary nucleation. Thereby the crystals’ median diameter was increased by 240μm. Within a residence time of 10.5min only, a relative process yield of approximately 83% was achieved. To identify optimized operating conditions for narrow PSD and reduced agglomeration, the effect of total volume flow rate, slug length, and cooling rate on the PSD and agglomeration degree was quantified. A high flow rate (40mLmin−1) and a high cooling rate (3.6Kmin−1) reduced agglomeration to its minimum and shifted the size distribution of single crystals without its broadening by in average 90μm.

The Relationship Between Posterior Communicating Artery Formation and Vertebral Artery Flow Parameters

Objectives: It is important to know the range of normal vertebral artery (VA) flow volume. Diminished VA flow volume is associated with vertebrobasilar insufficiency. The study aim was to investigate the relationship between the posterior communicating artery (PCoA) calibration and the VA flow parameters, in patients with no underlying cerebrovascular disease, below 50 years of age. Materials and Methods: The study population consisted of 102 cases below 50 years of age. The basilar artery (BA), internal carotid artery (ICA), and the PCoA calibrations were measured with magnetic resonance angiography. The VA flow parameters (maximum systolic velocity, end-diastolic velocity, mean velocity, VA flow volume, and VA calibration) were measured with duplex sonography. Results: There was no statistically significant difference between these two imaging groups, in terms of VA Vmax, VA flow volumes, VA calibrations, and BA calibrations. However, the mean right ICA and mean left ICA calibrations were significantly higher in group 2 than group 1 ( P < .01). There was no significant correlation between mean PCoA calibration and mean Vmax, mean calibration, and the total flow volume of vertebral arteries. Conclusion: The findings indicate that the VA flow rate may be relatively maintained, regardless of PCoA measurements in this study.

The proportion of jet flow and on-wall flow and its effects on soil loss and plunge pool morphology during gully headcut erosion

Gully headcut erosion is recognized as the primary process of gully erosion and is the main contributor to sediment yield of gully erosion. However, the proportion of jet flow and on-wall flow induced by headcut and its effects on soil loss and plunge pool morphology are still unclear. A simulated flow-scouring experiment was conducted to explore the proportion of jet flow and on-wall flow and their contributions to soil loss and the effect of on-wall flow erosion on plunge pool morphology under different flow discharge (q0 = 3.0–7.2 m3 h−1) and headwall height (H0 = 0.3–1.2 m) conditions. Our results showed that jet flow and on-wall flow accounted 15.7% − 22.6% and 77.4% − 84.3% of total flow volume upstream headcut, respectively. Jet flow, on-wall flow and their interaction contributed 53.5%, 34.9% and 11.6% of total soil loss amount, respectively. Furthermore, H0 exhibited greater effect on soil loss caused by jet flow and its interaction with on-wall flow, but the soil loss caused by on-wall was mainly controlled by q0. The width and depth of plunge pool logarithmically increased with scouring time, and the q0 and H0 significantly affected the development of plunge pool morphology. On-wall flow reduced plunge pool depth by 27.8%–71.4%, and it weakened plunge pool width by 24.3%−57.3% only under H0 of 0.3–0.9 m, but for H0 of 1.2 m and q0 of >4.8 m3 h−1, it improved the plunge pool width by 7.5%. The energy consumption of jet flow showed the closest relationship with plunge pool morphology. The concentrated flow upstream gully head exhibited the stronger effect on plunge pool morphology than H0. This study is helpful to deepen the understanding of gully erosion mechanism and provide scientific reference for the design of gully erosion prevention and control measures.

Pedal Musculovenous Pump Activation Effectively Counteracts Negative Impact of Knee Flexion on Human Popliteal Venous Flow.

Knee scooters are commonly used for mobility instead of other devices. However, passive popliteal venous flow impedance has been observed with knee scooter usage ostensibly as a result of deep knee flexion. This study aimed to characterize the magnitude of impact knee flexion has on popliteal venous flow in relation to the degree of knee flexion when walking boot immobilized. Furthermore, the countervailing effect of standardized pedal musculovenous pump (PMP) activation was observed. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography in 24 healthy individuals. Straight leg, crutch, and knee scooter positioning while wearing a walking boot and non-weight-bearing were compared. Flow was assessed with muscles at rest and with PMP activation. Of 24 participants, 16 (67%) were female. Twelve limbs (50%) were right sided. The mean age was 21.9 (SD = 3.0) years, and the mean body mass index was 21.9 (SD 1.9) kg/m2. Observer consistencies were excellent (intraclass correlation range = 0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred (all P > .01). Corresponding knee flexion effect sizes were small (range = -0.04 to -0.26). A significant decrease (-24%) in active median time-averaged peak velocity occurred between upright and crutch positions (20.89 vs 15.92 cm/s; P < .001) with a medium effect size (-0.51). PMP activation increased all flow parameters (all P < .001), and effect sizes were comparatively larger (>0.6) across all knee flexion positions.Clinical Significance: Knee flexion has a small to medium impact on popliteal venous return in healthy patients. Active toe motion effectively counters the negative effects of gravity and knee flexion when the ankle is immobilized.Levels of Evidence: Therapeutic, Level IV.

Impact of sedimentation by check dam on the hydrodynamics in the channel on the Loess Plateau of China

The sedimentation by check dam in the channel affects hydrological process. In this study, the effects of the sedimentation on the dynamic process of runoff and erosion power were investigated by dynamic coupling models (MIKE SHE model and MIKE 11 model). The study area was located in Wangmaogou watershed in the Loess Plateau of China. Four scenarios including no check dam and check dam with siltation depths of 0, 4 and 8 m were designed to study the reduction effectiveness of check dam on the hydrodynamic processes. The research showed that the silt dam not only reduced the total volume flow rate of floods but also increased the flood duration and delayed the occurrence of flood peaks. The siltation depths of the dam influenced the flow velocity and runoff shear stress. With deposition, the channel was longer in 8 m siltation compared with 0 and 4 m siltation. The shear force and unit runoff power were remarkably reduced in the scenario of 8 m siltation, followed by 4 m, and lastly by 0 m. The dam system can still vastly reduce the flow velocity along the channel in the full state and decrease the maximum flow velocity along the channel by more than 50%. The decrease in flow velocity was the main reason for the decrease in the sediment-carrying capacity of the runoff, which directly reduced the runoff erosion intensity. This study provides the scientific basis for understanding the regulation of check dam and sedimentation on hydrological process.

Estimation of discharges of water flows and debris floods in a small watershed

AbstractFloods in small mountainous watersheds cover a wide spectrum of flow. They can range from clear water flows and hyperconcentrated flows to debris floods and debris flows, and calculation of the peak discharge is crucial for predicting and mitigating such hazards. To determine the optimal approach for discharge estimation, this study compared water flow monitoring hydrographs to investigate the performance of five hydrological models that incorporate different runoff yields and influx calculation methods. Two of the models performed well in simulating the peak discharge, peak time, and total flow volume of the water flood. The ratio (γ) of the monitored debris flood discharge (Qd) to the simulated water flow discharge (Qw) was investigated. Qualitatively, γ initially increased with Qw but then decreased when Qw exceeded a certain threshold, which corresponded to rainfall of 95 and 120 mm in a 6‐ and 24‐h event with a normal distribution of precipitation, respectively. The decrease might be attributable to a threshold of sediment availability being reached, beyond which increased flow rate is not matched by increased sediment input in the large watershed. Uncertainty of hydrological calculation was evaluated by dividing the catchment into sub‐basins and adopting different rainfall time steps as input. The efficiency of using a distributed simulation exhibited marginal improvement potential compared with a lumped simulation. Conversely, the rainfall time step input significantly affected the simulation results by delaying the peak time and decreasing the peak discharge. This research demonstrates the applicability of a discharge estimation method that combines a hydrological water flow simulation and an estimation of γ. The results were verified on the basis of monitored flow densities and videos obtained in two watersheds with areas of 2.34 and 32.4 km2.

Jet sweeping angle control by fluidic oscillators with master-slave designs

The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts. However, the traditional fluidic oscillator has an inherent limitation, that is, the spreading angle cannot be controlled independently, rather by the jet volume flow rate and internal geometry. Accordingly, two types of fluidic oscillators based on the master-slave design are developed in current study to decouple this correlation. In both designs, the master layer inherits the similar oscillation mechanisms of a sweeping jet, and the slave layer resembles a steady jet channel. The difference between the two designs is that Design A has a short diverging exit in the slave layer, but Design B adds a long interaction chamber in the exit channel to intensify flow instability. The external flow fields and governing oscillation properties of these two designs are experimentally explored with time-resolved Particle Image Velocimetry (PIV), while the internal flow dynamics and driving oscillation mechanisms are numerically investigated. By fixing the total volume flow rate, the jet spreading angle of Design A can be increased smoothly from 0° to above 100° by increasing the proportion of master layer's flow rate from 0 to 100%. For Design B, the control authority of the master layer is significantly enhanced by adding the interaction chamber in the slave layer. In addition, the added chamber causes notable jet oscillation even when the master layer has none input.

UNSTEADY FLOW OF DUSTY VISCO- ELASTIC LIQUID BETWEEN TWO PARALLEL PLATES (KUVSHINISKI TYPE)

The unsteady flow of dusty visco-elastic liquid (Kuvshiniski type ) between two parallel plates when the lower plate is rest and the upper one begins oscillating harmonically in its plane is considered in view of its growing importance in various technical problems. In the present paper, consider the unsteady laminar flow of visco-elastic (Kuvshiniski type) liquid containing uniformly small solid particles between two infinitely extended parallel plates when the lower plate is at rest and the upper one begins oscillating harmonically in its own plane. The analytical expressions for velocity fields of liquid and dust particles are obtained which are in elegant forms. The effects of elastic elements in the liquid, the mass concentration, and the relaxation time of dust particles on the velocity profiles are studied. The skin friction at the lower plate wall and the total volume flow in between the plates are also obtained.

Determination of local flow ratios and velocities in a femoral venous cannula with computational fluid dynamics and 4D flow-sensitive magnetic resonance imaging: A method validation.

Cannulas with multi-staged side holes are the method of choice for femoral cannulation in extracorporeal therapies today. A variety of differently designed products is available on the market. While the preferred tool for the performance assessment of such cannulas are pressure-flow curves, little is known about the flow and velocity distribution. Within this work flow and velocity patterns of a femoral venous cannula with multi-staged side holes were investigated. A mock circulation loop for cannula performance evaluation was built and reproduced using a computer-aided design system. With computational fluid dynamics, volume flows and fluid velocities were determined quantitatively and visually with hole-based precision. In order to ensure the correctness of the flow simulation, the results were subsequently validated by determining the same parameters with four-dimensional flow-sensitive magnetic resonance imaging. Measurement data and numerical solution differed 7% on average throughout the data set for the examined parameters. The highest inflow and velocity were detected at the most proximal holes, where half of the total volume flow enters the cannula. At every hole stage a Y-shaped inflow profile was detected, forming a centered stream in the middle of the cannula. Simultaneously, flow separation creates zones with significant lower flow velocities. Numerical simulation, validated with four-dimensional flow-sensitive magnetic resonance imaging, is a valuable tool to examine flow and velocity distributions of femoral venous cannulas with hole-based accuracy. Flow and velocity distribution in such cannulas are not ideal. Based on this work future cannulas can be effectively optimized.

An improved cubic law for shale fracture considering the effect of loading path

Massive multi-stage hydraulic fracturing to form one large-scale stimulated reservoir volume (SRV) with a complex fracture network is a key technique in shale gas development. A natural fracture system may contribute significantly to gas production. Fracture apertures are the key parameter for determining flow characteristics of jointed rock media and changes due to loading and unloading behaviour. In this study, a hydraulic aperture model was proposed to describe aperture variation in a complex loading path with a parabolic function. A numerical study of the hydro-mechanical model was conducted to determine the influences of loading path and nonlinear effects on fluid flow at field scale. In this specific simulation, the total flow volume considering the influence of loading path only decreased by 14%, and considering the influence of loading path decreased by 28%, meanwhile influence of two factors resulted in a 39% reduction of the total flow volume. [Received: July 25, 2018; Accepted: July 3, 2019]

Data assimilation of satellite-based terrestrial water storage changes into a hydrology land-surface model

Accurate estimation of snow mass or snow water equivalent (SWE) over space and time is required for global and regional predictions of the effects of climate change. This work investigates whether integration of remotely sensed terrestrial water storage (TWS) information, which is derived from the Gravity Recovery and Climate Experiment (GRACE), can improve SWE and streamflow simulations within a semi-distributed hydrology land surface model. A data assimilation (DA) framework was developed to combine TWS observations with the MESH (Modélisation Environnementale Communautaire – Surface Hydrology) model using an ensemble Kalman smoother (EnKS). The snow-dominated Liard Basin was selected as a case study. The proposed assimilation methodology reduced bias of monthly SWE simulations at the basin scale by 17.5% and improved unbiased root-mean-square difference (ubRMSD) by 23%. At the grid scale, the DA method improved ubRMSD values and correlation coefficients for 85% and 97% of the grid cells, respectively. Effects of GRACE DA on streamflow simulations were evaluated against observations from three river gauges, where it effectively improved the simulation of high flows during snowmelt season from April to June. The influence of GRACE DA on the total flow volume and low flows was found to be variable. In general, the use of GRACE observations in the assimilation framework not only improved the simulation of SWE, but also effectively influenced streamflow simulations.

The association between anogenital distance and benign prostatic hyperplasia related lower urinary tract symptoms in Chinese aging men.

We conducted the study to investigate the relationship between anogenital distance (AGD) and benign prostatic hyperplasia (BPH) related lower urinary tract symptoms (LUTS). From May 2018 to January 2020, 220 subjects: 110 men with BPH-related LUTS (BPH-LUTS group) and 110 men without any urination complaints (control group) were selected. Clinical questionnaires, detailed physical examinations, including AGDas (distance between the anus and posterior base of the scrotum) and AGDap (distance between the anus and upper penis) measurements, and blood tests were all assessed. The two groups were similar in terms of basic features (P > 0.05). The AGDap and AGDas in the control group were significantly shorter than the BPH-LUTS group (P < 0.001). Adjusted multivariate analyses showed that AGDas was significantly related to International Prostate Symptom Score (IPSS), post-voiding residual volume (PVR), total prostate volume (TPV) and maximum urine flow rate (Qmax) (P = 0.002, P = 0.009, P = 0.001, P = 0.028, respectively). However, the associations between AGDap and IPSS score, PVR, TPV, Qmax and total testosterone (TT) were all negligible (P > 0.05 for all). The associations between TT and BPH-LUTS related evaluations were also negligible (P > 0.05 for all). Furthermore, the study revealed that the AGDas cut-off values for mild, moderate, and severe symptom (based on IPSS score) in BPH-LUTS cases were 27.4mm and 46.8mm [area under curve (AUC): 0.802 and AUC: 0.779, respectively], respectively. Longer AGDas was related to more severe BPH related symptoms. It may be useful to consider AGD as a marker for BPH-LUTS. Further well-designed studies are remained to be done to explore the intriguing problem.

The Effect of Knee Flexion on Active and Passive Popliteal Venous Flow When Using Crutches or Knee Scooter While Immobilized

Category:Trauma; OtherIntroduction/Purpose:Knee flexion has been demonstrated to impede popliteal venous return with large effect size among patients lying supine for surgery. Passive popliteal flow impedance has also been suggested to occur with knee scooter usage due to knee flexion. This study compared the effect of knee flexion angles on popliteal venous return between upright, crutch and knee scooter positioning when immobilized. Further, the countervailing effect of standardized hallux musculovenous pump activation was observed.Methods:This was an IRB approved study of young, healthy volunteers. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography and compared between straight leg, crutch, and knee scooter positioning while wearing a walking boot and nonweightbearing. Flow was assessed with muscles at rest and with hallux musculovenous pump activation via active oscillation between hallux metatarsophalangeal joint extension and flexion at one motion per second (0.5 Hz) as paced by a metronome. Observer consistency was assessed. Paired-sample Student’s t-test and the Wilcoxon signed rank tests were used to assess within-subject differences for diameter and venous flow parameters, respectively. Knee flexion and musculovenous pump activation effects sizes were calculated. A priori sample size indicated 24 subjects were needed to achieve 80% power to detect a significant ( p < 0.006 ) difference in medial flow for any of 8 comparisons, assuming large effect sizes.Results:16 of 24 (67%) subjects were female. Twelve limbs (50%) were right sided. The mean age was 21.9 years (SD 3.0 years) and the mean body mass index was 21.9 (SD 1.9). Observer consistencies were excellent (0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred. Corresponding knee flexion effect sizes were small (range -0.04 to -0.26). A significant decrease (-24%) in active median time-averaged peak velocity (TAPV) occurred between upright and crutch position (20.89 cm/s vs. 15.92 cm/s, p < 0.001) with a medium effect size (-0.51). Hallux musculovenous pump increased all flow parameters (all p< 0.001) and effect sizes were comparatively larger (>0.6) across all knee flexion positions.Conclusion:Compared to values reported for supine individuals, upright passive popliteal venous return was observed to be markedly diminished at all knee flexion angles. Knee flexion had minimal effect on diameter, a small effect in further diminishing TAMV and TVF and a medium effect on diminishing TAPV. Hallux musculovenous pump activiation had a large effect on increasing flow at all knee flexion angles. Patients may well be counseled to use toe motion to counter the negative effects of gravity, and to a lesser extent knee flexion, when using crutches and knee scooters while their ankle is immobilized.

Reduced parenchymal cerebral blood flow is associated with greater progression of brain atrophy: The SMART-MR study

Global cerebral hypoperfusion may be involved in the aetiology of brain atrophy; however, long-term longitudinal studies on this relationship are lacking. We examined whether reduced cerebral blood flow was associated with greater progression of brain atrophy. Data of 1165 patients (61 ± 10 years) from the SMART-MR study, a prospective cohort study of patients with arterial disease, were used of whom 689 participated after 4 years and 297 again after 12 years. Attrition was substantial. Total brain volume and total cerebral blood flow were obtained from magnetic resonance imaging scans and expressed as brain parenchymal fraction (BPF) and parenchymal cerebral blood flow (pCBF). Mean decrease in BPF per year was 0.22% total intracranial volume (95% CI: –0.23 to –0.21). Mean decrease in pCBF per year was 0.24 ml/min per 100 ml brain volume (95% CI: –0.29 to –0.20). Using linear mixed models, lower pCBF at baseline was associated with a greater decrease in BPF over time (p = 0.01). Lower baseline BPF, however, was not associated with a greater decrease in pCBF (p = 0.43). These findings indicate that reduced cerebral blood flow is associated with greater progression of brain atrophy and provide further support for a role of cerebral blood flow in the process of neurodegeneration.

Differences in Blood Flow Between Superior and Inferior Retinal Hemispheres.

PurposeTo determine whether the blood flow in the superior retina is significantly different from that in the inferior retina, and to determine whether the posture affects the blood flow in the superior and inferior retina.MethodsThe blood flow in the vessels around the optic nerve head was measured by laser speckle flowgraphy in the sitting position in 68 healthy subjects. The blood flow in the superior peripapillary retina was compared with that in the inferior peripapillary retina. The measurements of the blood flow were performed in the sitting position, and the effect of switching to a supine position was determined at 2, 4, 6, 8, 10, and 30 minutes after the switch.ResultsThe total relative flow volume (RFV)-all, RFV-artery, and RFV-vein were significantly greater in the superior retina than in the inferior retina (all P < 0.001). The mean diameter-all and mean diameter-artery in the superior retina were significantly larger than that in the inferior retina (all P < 0.05). The mean blur rate (MBR)-all, MBR-artery, and MBR-vein in the superior retina were also greater than that in the inferior retina (P < 0.001, P < 0.01, and P < 0.001, respectively). Although the ocular perfusion pressure was significantly changed with the postural alteration, the total RFV-all remained greater in the superior retina than in the inferior retina after the postural change.ConclusionsClinicians need to be aware of the differences in the blood flow between the superior and inferior retinal peripapillary area when considering the mechanisms of retinochoroidal diseases.

Validating Dynamically Downscaled Climate Projections for Mountainous Watersheds Using Historical Runoff Data Coupled with the Distributed Hydrologic Soil Vegetation Model (DHSVM)

The performance of dynamically downscaled climate fields with respect to observed historical stream runoff has been assessed at basin scale using a physically distributed hydrologic model (DHSVM). The dynamically downscaled climate fields were generated by running the Weather Research &amp; Forecasting (WRF) model at 4-km horizontal resolution with boundary conditions derived from the Climate Forecast System Reanalysis. Six hydrologic models were developed using DHSVM for six mountainous tributary watersheds of the Jordan River basin at hourly time steps and 30-m spatial resolution. The size of the watersheds varies from 19 km2 to 130 km2. The models were calibrated for a 6-year period from water year (WY) 1999–2004, using the observed meteorological data from the nearby Snow Telemetry (SNOTEL) sites of the Natural Resources Conservation Services (NRCS). Calibration results showed a very good fit between simulated and observed streamflow with an average Nash-Sutcliffe Efficiency (NSE) greater than 0.77, and good to very good fits in terms of other statistical parameters like percent bias (PBIAS) and coefficient of determination (R2). A 9-year period (WY 2001–2009) was selected as the historical baseline, and stream discharges for this period were simulated using dynamically downscaled climate fields as input to the calibrated hydrologic models. Historical baseline results showed a satisfactory fit of simulated and observed streamflow with an average NSE greater than 0.45 and a coefficient of determination above 0.50. Using volumetric analysis, it has been found that the total volume of water simulated using downscaled climate projections for the entire historical baseline period for all six watersheds is 4% less than the observed amount representing a very good estimation in terms of percent error volume (PEV). However, in the case of individual watersheds, analysis of total annual water volumes showed that estimated total annual water volumes were higher than the observed for Big Cottonwood, City Creek, Millcreek and lower than the observed total annual volume of water for Little Cottonwood, Red Butte Creek, and Parleys Littledell, demonstrating similar characteristics obtained from the calibration results. Seasonal analysis showed that the models can capture the flow volume observed for Big Cottonwood, City Creek and Red Butte Creek during the peak season, and the models can capture the flow volume observed for all the watershed satisfactorily except Big Cottonwood during the dry season. Study results indicated that the dynamically downscaled climate projections used in this study performed satisfactorily in terms of stream runoff, total flow volume, and seasonal flow analyses based on different statistical tests, and can satisfactorily capture flow patterns and flow volume for most of the watersheds considering the uncertainties associated with the study.

Impact of turbulent blood flow in the aortic root on de novo aortic insufficiency during continuous-flow left ventricular-assist device support.

Severe aortic insufficiency (AI) after implantation of continuous-flow left ventricular-assist device (LVAD) affects device performance and outcomes. However, the mechanism for the occurrence and progression of AI has not been elucidated. We investigated the impact of nonphysiological retrograde blood flow in the aortic root on AI after LVAD implantation. Blood flow pattern was analyzed in patients with and without AI (n = 3 each) who underwent LVAD implantation, by computational fluid dynamics with patient-specific geometries, which were reproduced using electrocardiogram-gated 320-slice computed tomographic images. The total volume of retrograde blood flow during one cardiac cycle (716±88 mL) was higher and the volume of slow blood flow (<0.1 cm/s) (0.16 ± 0.04cm3 ) was lower in patients with AI than in those without AI (360 ± 111 mL, P =.0495, and0.49 ±0.08 cm3 , P =.0495, respectively). No significant difference in wall shear stress on the aortic valve was observed between the groups. Patients with AI had a perpendicular anastomosis at the distal ascending aorta and the simulation in the modified anastomosis model of patients with AI showed that the retrograde blood flow pattern depended on the angle and position of anastomosis. Computational fluid dynamics revealed strong retrograde blood flow in the ascending aorta and aortic root in patients with AI after LVAD implantation. The angle and position of LVAD outflow anastomosis might impact retrograde blood flow and de novo AI after LVAD implantation.

Multiscale complexity analysis on airport air traffic flow volume time series

Exploring the complexity of airport air traffic flow volume time series helps gain insights into the evolution mechanism of the air traffic system. To obtain more reliable and stable entropy values, we introduce multiple coarse-graining procedures into the multivariate multiscale permutation entropy (MMPE) method to propose an improved MMPE (IMMPE) method to explore multivariate time series. By introducing similar multiple coarse-graining procedures, we also improve the contingency to investigate the inhomogeneity level between ordinal pattern distributions in multivariate time series. With the improved multiscale permutation entropy (IMPE) method, firstly, we investigate the complexity of the departure and the arrival air traffic flow volume time series of the top ten busiest airports in China from a univariate time series perspective. Then, with IMPE and IMMPE, we investigate the complexity of the total air traffic flow volume time series of the ten airports from a univariate and a multivariate time series perspective, respectively. Results show that the complexity is dependent on the time scale, and thus it is necessary to conduct multiscale analysis on the complexity. Benefiting from the improvement in IMPE and IMMPE, on the reliable and stable entropy curves, we can exactly explore and locate sharp decreasing points of the entropy values to reveal severe fluctuations of the multiscale complexity of the time series. Gaps between IMPE and IMMPE curves of the total air traffic flow volume time series indicate the necessity of analyzing the time series from the multivariate time series perspective. Moreover, spikes on the improved contingency curves reveal that the inhomogeneity level between fluctuations of the departure and the arrival air traffic flows is also scale-dependent, and the maxima are all located on the scale 72 (6 hours).

Event selection and two-stage approach for calibrating models of green urban drainage systems

Abstract. The calibration of urban drainage models is typically performed based on a limited number of observed rainfall–runoff events, which may be selected from a larger dataset in different ways. In this study, 14 single- and two-stage strategies for selecting the calibration events were tested in calibration of a high- and low-resolution Storm Water Management Model (SWMM) of a predominantly green urban area. The two-stage strategies used events with runoff only from impervious areas to calibrate the associated parameters, prior to using larger events to calibrate the parameters relating to green areas. Even though all 14 strategies resulted in successful model calibration (Nash–Sutcliffe efficiency; NSE &gt;0.5), the difference between the best and worst strategies reached 0.2 in the NSE, and the calibrated parameter values notably varied. The various calibration strategies satisfactorily predicted 7 to 13 out of 19 validation events. The two-stage strategies reproduced more validation events poorly (NSE &lt;0) than the single-stage strategies, but they also reproduced more events well (NSE &gt;0.5) and performed better than the single-stage strategies in terms of total runoff volume and peak flow rates, particularly when using a low spatial model resolution. The results show that various strategies for selecting calibration events may lead in some cases to different results in the validation phase and that calibrating impervious and green-area parameters in two separate steps in two-stage strategies may increase the effectiveness of model calibration and validation by reducing the computational demand in the calibration phase and improving model performance in the validation phase.

Particle volume flow rate measurement by combination of dual electrical capacitance tomography sensor and plug flow shape model

Particle volume flow rate QPLUG· in plug flow through a cross section of horizontal pipe has been accurately measured by a combination of dual electrical capacitance tomography sensor and plug flow shape model (dECT-PFSM). The plug flow shape model divides the trapezoidal shape of the plug flow into three flow regions which are Tip, Filling, and Tail regions. The plug flow volume VPLUG is estimated by velocity and length which are measured in each region by the normalized permittivity signal changes obtained from the dECT images under the plug flow in the trapezoidal shape. The path time difference of the plug flow ΔtPLUG is also measured. The total volume flow rate of the plug flow is subsequently obtained from the sum of the plug flow volume of the three regions divided by ΔtPLUG. Consequently, the volume flow rate of the plug flow obtained by dECT-PFSM QECT, PFSM· is compared with that of high-speed camera (HSC) as reference and conventional cross-correlation (CC) method. The absolute error Eabs of the proposed method is less than that of the CC method. The dECT-PFSM method is, therefore an affordable noninvasive technique for accurate determination of the volume flow rate of the plug flow.