Dyke swarms frequently act as natural barriers,obstructing or deflecting stream courses.Streams tend to flow along the outcrop ridges of dykes,resulting in acute junction angles.Dykes serve as structural controls by i...Dyke swarms frequently act as natural barriers,obstructing or deflecting stream courses.Streams tend to flow along the outcrop ridges of dykes,resulting in acute junction angles.Dykes serve as structural controls by influencing the orientation of streams.The relationship between stream junction angles and dyke orientation is a significant factor in stream confluences.Terrain plays a crucial role in directing the river’s flow path and shaping its characteristics.This research paper investigates the impact of dyke orientation on stream junction angles through stream hierarchy analysis.The Rangavali River,a left-bank tributary of the Tapi River,flows for a distance of 45.65 km,crossing 21 East-West(E-W)trending dykes within a 215.95 km2 basin,which forms part of the Deccan Traps.To examine the relationship between dyke orientation and stream junction angles,inputs from Google Earth imagery,LISS III im ages,SOI topographical maps,quadrangle maps,and Cartosat DEM were used to delineate the Rangavali basin and extract dyke features.The Rangavali River basin is a sixth-order drainage system that exhibits a superimposed drainage pattern within the Tapi dyke swarm zone.The prominent linear dyke ridges are predominantly aligned in an East-West direction(average angle N81˚),with a dyke density of 0.51 km/km2.The average junction angle of streams within 100 m upstream and downstream of the dyke ridges is 81˚,compared to an av-erage of 78˚in non-dyke areas.The trend of acute junction angles is attributed to the orientation of the dykes and the distance of streams from the parallel-aligned dyke ridges.This study demonstrates that dyke ridges not only redirect stream flow but also control drainage density and network development.The findings have broader implications for watershed management,flood risk as sessment,infrastructure planning,and groundwater exploration in basaltic terrains and contribute significantly to the understanding of fluvial-structural in teractions in volcanic landscapes.展开更多
The restenosis after coronary artery bypass graft(CABG) is attributed to the formation of intimal hyperplasia(IH) at the anastomosis,which is closely related to hemodynamic depend on the geometric model. In order to g...The restenosis after coronary artery bypass graft(CABG) is attributed to the formation of intimal hyperplasia(IH) at the anastomosis,which is closely related to hemodynamic depend on the geometric model. In order to give a reasonable assessment of the surgery effect and judge the long-term patency rate,the hemodynamic of CABG surgery program is compared with that of surgery design of the junction angle changed.Based on in-vivo CT coronary angiography datasets,the individual geometric model of CABG reconstructed instead of idealized geometric models are applied to simulate the real physiological blood flow utilizing pulsatile flow boundary waveforms in the present study. The simulation results show that the maximum wall shear rate(WSS) value is at the bottom of anastomosis. Moreover,the stagnation zone growing gradually with the greater angle downstream the anastomosis is prone to form the IH,which is consistent with clinical observation. It is proved that the surgery being better suited to maintain graft patency is successful.展开更多
Background:Vesicoureteral reflux is the most common urinary congenital anomaly in children.Given the risk associated with radiation exposure there has been an increasing need for radiation-free method in the diagnosis...Background:Vesicoureteral reflux is the most common urinary congenital anomaly in children.Given the risk associated with radiation exposure there has been an increasing need for radiation-free method in the diagnosis and follow-up of the vesicoureteral reflux.The aim of our study is to compare conventional urosonography without contrast enhancement and x-ray voiding cystourethrography.Patients and Methods:Children with recurrent urinary tract infection with suspected vesicoureteral reflux were included to the study.Vesicoureteral reflux is demonstrated and graded by x-ray voiding cystourethrography.DMSA is used for the evaluation of renal scar.Conventional sonographic procedure was performed in all patients.Ureterovesical junction insertion angle was evaluated.The diameter and length of the ureterovesical junction were also measured.Results:268 children enrolled to the study.Vesicoureteral reflux was demonstrated in 62 children by x-ray voiding cystourethrography.Ureterovesical junction insertion angle measurement had a statistically significant relation for right and left vesicoureteral reflux presence(right:r:.646,p:.01 and left:r:.446,p:.01).Diagnosis sensitivity of vesicoureteral reflux with conventional ultrasonography is 95.10%and specificity is 81%(Youden’s index 76.1%)for the cutoff value of the ureterovesical junction insertion angle is 28.6 degrees.Positive predictive value is 87.2%,negative predictive value is 94.73%and diagnostic accuracy is 86.29%with conventional ultrasonography.Conclusions:Measurement of ureterovesical junction insertion angle,length and diameter by conventional urosonography is an easy accessible and cheap technique with high sensitivity and specificity for the diagnosis and followup of the vesicoureteral reflux without exposure to ionizing radiation.展开更多
The flow pattern in the confluent meander bend channel under the conditions of different discharge ratios and junction angles is numerically simulated by means of the large eddy simulation（LES）, and the characterist...The flow pattern in the confluent meander bend channel under the conditions of different discharge ratios and junction angles is numerically simulated by means of the large eddy simulation（LES）, and the characteristics of the flow separation zone are analyzed. Numerical results are well validated by experimental data with a good agreement. Analysis of the vertical confinement shows that the turbulence within the separation zone can be characterized as quasi-2-D. Details of the separation zone characteristics are revealed as shown by mean velocity isolines. According to the analysis of numerical results, the length and the width of the separation zone generally increase with the increase of the discharge ratio and the junction angle. However, the width of the separation zone keeps substantially constant when the junction angle increases from 60 o to90o. The dimensionless shape of the separation zone is nearly the same for three discharge ratios and three junction angles. The formulas of the relative width and the relative length of the separation zone are obtained by means of the polynomial fit method.展开更多
文摘Dyke swarms frequently act as natural barriers,obstructing or deflecting stream courses.Streams tend to flow along the outcrop ridges of dykes,resulting in acute junction angles.Dykes serve as structural controls by influencing the orientation of streams.The relationship between stream junction angles and dyke orientation is a significant factor in stream confluences.Terrain plays a crucial role in directing the river’s flow path and shaping its characteristics.This research paper investigates the impact of dyke orientation on stream junction angles through stream hierarchy analysis.The Rangavali River,a left-bank tributary of the Tapi River,flows for a distance of 45.65 km,crossing 21 East-West(E-W)trending dykes within a 215.95 km2 basin,which forms part of the Deccan Traps.To examine the relationship between dyke orientation and stream junction angles,inputs from Google Earth imagery,LISS III im ages,SOI topographical maps,quadrangle maps,and Cartosat DEM were used to delineate the Rangavali basin and extract dyke features.The Rangavali River basin is a sixth-order drainage system that exhibits a superimposed drainage pattern within the Tapi dyke swarm zone.The prominent linear dyke ridges are predominantly aligned in an East-West direction(average angle N81˚),with a dyke density of 0.51 km/km2.The average junction angle of streams within 100 m upstream and downstream of the dyke ridges is 81˚,compared to an av-erage of 78˚in non-dyke areas.The trend of acute junction angles is attributed to the orientation of the dykes and the distance of streams from the parallel-aligned dyke ridges.This study demonstrates that dyke ridges not only redirect stream flow but also control drainage density and network development.The findings have broader implications for watershed management,flood risk as sessment,infrastructure planning,and groundwater exploration in basaltic terrains and contribute significantly to the understanding of fluvial-structural in teractions in volcanic landscapes.
文摘The restenosis after coronary artery bypass graft(CABG) is attributed to the formation of intimal hyperplasia(IH) at the anastomosis,which is closely related to hemodynamic depend on the geometric model. In order to give a reasonable assessment of the surgery effect and judge the long-term patency rate,the hemodynamic of CABG surgery program is compared with that of surgery design of the junction angle changed.Based on in-vivo CT coronary angiography datasets,the individual geometric model of CABG reconstructed instead of idealized geometric models are applied to simulate the real physiological blood flow utilizing pulsatile flow boundary waveforms in the present study. The simulation results show that the maximum wall shear rate(WSS) value is at the bottom of anastomosis. Moreover,the stagnation zone growing gradually with the greater angle downstream the anastomosis is prone to form the IH,which is consistent with clinical observation. It is proved that the surgery being better suited to maintain graft patency is successful.
文摘Background:Vesicoureteral reflux is the most common urinary congenital anomaly in children.Given the risk associated with radiation exposure there has been an increasing need for radiation-free method in the diagnosis and follow-up of the vesicoureteral reflux.The aim of our study is to compare conventional urosonography without contrast enhancement and x-ray voiding cystourethrography.Patients and Methods:Children with recurrent urinary tract infection with suspected vesicoureteral reflux were included to the study.Vesicoureteral reflux is demonstrated and graded by x-ray voiding cystourethrography.DMSA is used for the evaluation of renal scar.Conventional sonographic procedure was performed in all patients.Ureterovesical junction insertion angle was evaluated.The diameter and length of the ureterovesical junction were also measured.Results:268 children enrolled to the study.Vesicoureteral reflux was demonstrated in 62 children by x-ray voiding cystourethrography.Ureterovesical junction insertion angle measurement had a statistically significant relation for right and left vesicoureteral reflux presence(right:r:.646,p:.01 and left:r:.446,p:.01).Diagnosis sensitivity of vesicoureteral reflux with conventional ultrasonography is 95.10%and specificity is 81%(Youden’s index 76.1%)for the cutoff value of the ureterovesical junction insertion angle is 28.6 degrees.Positive predictive value is 87.2%,negative predictive value is 94.73%and diagnostic accuracy is 86.29%with conventional ultrasonography.Conclusions:Measurement of ureterovesical junction insertion angle,length and diameter by conventional urosonography is an easy accessible and cheap technique with high sensitivity and specificity for the diagnosis and followup of the vesicoureteral reflux without exposure to ionizing radiation.
基金Project supported by the Key Program of National Natural Science Foundation of China(Grant No.51439007)
文摘The flow pattern in the confluent meander bend channel under the conditions of different discharge ratios and junction angles is numerically simulated by means of the large eddy simulation（LES）, and the characteristics of the flow separation zone are analyzed. Numerical results are well validated by experimental data with a good agreement. Analysis of the vertical confinement shows that the turbulence within the separation zone can be characterized as quasi-2-D. Details of the separation zone characteristics are revealed as shown by mean velocity isolines. According to the analysis of numerical results, the length and the width of the separation zone generally increase with the increase of the discharge ratio and the junction angle. However, the width of the separation zone keeps substantially constant when the junction angle increases from 60 o to90o. The dimensionless shape of the separation zone is nearly the same for three discharge ratios and three junction angles. The formulas of the relative width and the relative length of the separation zone are obtained by means of the polynomial fit method.
