Reflux Length Research Articles

Optimized Design and Experiment of a Self-Covering Furrow Opener for an Automatic Sweet Potato Seedling Transplanting Machine

The yield and quality of sweet potatoes are significantly influenced by the transplantation posture of sweet potato seedlings. The performance of the sweet potato seedling transplanting opener directly affects the transplantation posture of sweet potato seedlings. In order to improve the yield and quality of sweet potatoes, this study proposes a joint simulation method based on discrete element and flexible multi body dynamics (DEM-FMBD), which optimizes the structure of a self-covering soil opener. By exploring the influence of self-covering soil trenchers on the planting depth and posture of sweet potato seedlings during horizontal transplantation, it was determined that the influencing factors of the experiment were wing spacing, soil reflux height, and soil reflux length. Based on the DEM-FMBD coupling simulation platform, single factor, and quadratic rotation orthogonal experiments were carried out. According to the results of the simulation test, the effect of the interaction of test factors on planting depth and planting attitude was analyzed by the response surface method. Finally, the optimal structural parameter combination was obtained by a multi-objective optimization method: the spacing of the wings was 58 mm, the height of the soil backflow port was 71 mm, and the length of the soil backflow port was 163 mm; thus, the quality of transplanting is improved effectively. This study provides the method and theory reference for the study of sweet potato transplanting.

A novel angiographic method to estimate arterial blood flow rates using contrast reflux: Effect of injection parameters.

Contrast reflux, which is the retrograde movement of contrast against flow direction, is commonly observed during angiography. Despite a vast body of literature on angiography, the hemodynamic factors affecting contrast reflux have not been studied. Numerous methods have been developed to extract flow from angiography, but the reliability of these methods is not yet sufficient to be of routine clinical use. To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length. Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico-cerebral vasculature. A total of 194 high-speed angiograms were acquired under varying "blood" flow rates and injection conditions (catheter size, injection rate, and injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter-tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit-time method and compared to measured flow rates. Contrast reflux lengths were significantly affected by contrast injection rate (p < 0.0001), baseline blood flow rate (p= 0.0004), and catheter size (p= 0.04), but not by contrast injection time (p= 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R2 = 0.6-0.99). When considering the entire dataset in unison, flow estimation errors with the reflux-length method (39% ± 33%) were significantly higher (p= 0.003) than the transit-time method (33% ± 36%). However, when subgrouped by catheter, the error with the reflux-length method was substantially reduced and was significantly lower (14% ± 14%, p < 0.0001) than the transit-time method. Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux.

Influence of mechanical smoke exhaust on smoke spread in underground tunnel

The model of a tunnel in Beijing is established, and the smoke reflux, the smoke reflux length and the influence of longitudinal wind speed on temperature distribution of the tunnel vault are studied using numerical simulation method. The length of the tunnel is 150 m, the cross section is circular, the height of the tunnel is 6.3 m and the width is 6 m. The simulation results show that the smoke reflux length of the subway tunnel fire decreases with the increase of the longitudinal positive pressure wind speed, and the reflux length decreases linearly with the increase of wind speed when the reflux length is more than 10 m. The gradient of the reflux length decreases with the increase of the wind speed when the distance from the fire source decreases. The temperature curve of tunnel vault is consistent. Under the same fire source heat release rate, the flue gas temperature decreases with the increase of ventilation wind speed, and the distance between the highest temperature of the ceiling and the fire source decreased with the increase of the longitudinal ventilation wind speed.

N-butyl cyanoacrylate embolization using a detachable tip microcatheter: initial experience

IntroductionEndovascular embolization of intracranial vascular malformations with N-butyl cyanoacrylate (nBCA) using a detachable tip microcatheter allows prolonged injection and decreases the risk of catheter retention.MethodsBetween March and December 2013, the...

The Flow Field Analysis and Flow Calculation of Ultrasonic Flowmeter Based on the Fluent Software

We can build the three-dimensional structure model based on the Gambit software and achieve the distribution of flow field in the pipe and reflux flow condition at the position of transducer in regard to the real position of transducer according to the Fluent software. Under the framework, define the reflux length based on the distance of reflux along the channel and evaluate the effect of reflux on flow field. Then we can correct the power factor with the transmission speed difference method in the ideal condition and obtain the matching expression of power correction factor according to the practice model. In the end, analyze the simulation experience and produce the sample table based on the proposed model. The comparative analysis of test results and simulation results demonstrates the validity and feasibility of the proposed simulation method. The research in this paper will lay a foundation for further study on the optimization of ultrasonic flowmeter, enhance the measurement precision, and extend the application of engineering.

Comment to: Great saphenous vein diameter at the saphenofemoral junction and proximal thigh as parameters of venous disease class, by Mendoza E, Blättler W, Amsler F. Eur J Vasc Endovasc Surg 2013;45:76-83.

The aim of this study was to investigate a possible correlation of GSV diameters measured at the SFJ and the proximal thigh (PT) with the importance of the venous disorder. Between October and December 2009. 844 legs were screened and 182 legs included in the survey (CEAP C1-C5). The criterion for patient inclusion was the presence of a GSV reflux beginning at the terminal or the preterminal valve and escaping through a mid-thigh branch vein (above knee reflux, -51 legs- group II) or escaping through a lower leg branch vein (above and below knee reflux-71 legs-, group III). Legs with varices but no GSV were recruited as controls (-60 legs- group I). Vein diameters were measured holding the probe transversely with no pressure at the SFJ distal to the terminal valve and 15 cm below the junction. Measurement of GSV vein diameter at the SFJ is challenging for the curvature of the inguinal GSV, the presence of epigastric, pudendal and accessory veins and eventual aneurysmatic dilatations. The PT site 15 cm below the SFJ, chosen by CHIVA Group members, is located in the truncal portion of GSV where the vein is cylindrical and largely devoid of joining branches, so well accessible, and diameter measurements can be taken reliably. GSV diameters in all groups, measured at both sites, were not related with patients&rsquo; age and sex or calf muscle-pump function. Modest correlations were found with body weight and BMI but not with height. GSV diameters in controls (group I) measured 7.5 mm (&plusmn;1.8) at the SFJ and 3.7 mm (&plusmn;0.9) at the PT. In patients with GSV reflux (groups II and III), they measured 10.9 mm (&plusmn;3.9) at the SFJ and 6.3 mm (&plusmn;1.9) at the PT, respectively. Vein diameters were larger in the presence of reflux, compared with its absence, by an average of 3.4 mm at the SFJ and 2.6 mm at the PT. No difference in diameters was found between group II and group III. Thus, the degree of vein dilatation was independent of the length of reflux above knee only versus above and below knee. A GSV diameter above the 2 SD margin of group I legs was found in 2% in group I at either point of measurement. In groups II and III, a significantly different prevalence was observed when measurements made at the SFJ and PT, respectively. The 2 SD margin was exceeded by 43% of patients when measured at the SFJ and by 62% when measured at the PT. A mathematical formula was developed to mutually convert measurements taken at the SFJ and the PT, used to revise published data. Conversion PT to SFJ (95% CI 1.698&ndash;1.836): diameter SFJ (mm) = 1.767 &times; diameter PT (mm) Conversion SFJ to PT (95% CI 0.544&ndash;0.548): diameter PT (mm) = 0.566 &times; diameter SFJ (mm) Measurement at the PT as compared to measurement at the SFJ demonstrated higher accuracy and both higher sensitivity and specificity for venous disease class as well as for prediction of reflux. GSV diameter, venous hemodynamic (PPG refilling times) and clinical disease class did not differ whether reflux was above knee only or above and below knee. Diameter assessment at the PT seems suitable for stratification of patients allocated to future interventional trials as well as for outcome evaluation.