The dissymmetric flow phenomenon exists in a symmetric multistrand tundish. It was studied by the physical simulation experiment. The fundamental flow characteristic of dissymmetry was analyzed. The asymmetry of the f...The dissymmetric flow phenomenon exists in a symmetric multistrand tundish. It was studied by the physical simulation experiment. The fundamental flow characteristic of dissymmetry was analyzed. The asymmetry of the flow field, the temperature field, and the inclusions distribution without flow-control devices （FCDs） were compared with those with FCDs. It is proved that the asymmetry of the flow and temperature field along the outlets at the long range is more obvious. The symmetric FCDs installation has a slight effect on the dissymmetric temperature field, simultaneously, the symmetry of the average residence time and the fluid flow pattern has improved, and the fluid flow in the tundish has been more reasonable. In case of a symmetric multistrand tundish having a large volume, the influence of the dissymmetric phenomenon should be considered and the flow behaviors in the whole tundish should be studied completely.展开更多
Background Coronary slow flow phenomenon （CSFP） is an important, angiographic clinical entity but is lacking non-invasive detecting techniques. This study aimed to elucidate the value of transthoracic Doppler echoca...Background Coronary slow flow phenomenon （CSFP） is an important, angiographic clinical entity but is lacking non-invasive detecting techniques. This study aimed to elucidate the value of transthoracic Doppler echocardiography （TTDE） in the diagnosis and monitoring of coronary slow flow in left anterior descending （LAD） coronary artery.Methods We consecutively enrolled 27 patients with CSFP in LAD detected by coronary arteriography from August 2009 to April 2010. Thirty-eight patients with angiographically normal coronary flow served as control. Corrected thrombolysis in myocardial infarction （TIMI） frame count （CTFC） was used to document coronary flow velocities. All subjects underwent TTDE within 24 hours after coronary angiography. LAD flow was detected and the coronary diastolic peak velocities （DPV） and diastolic mean velocities （DMV） were calculated.Results Sixty of 65 （92.3%） subjects successfully underwent TTDE. Baseline clinical characteristics were similar between the two groups. Coronary DPV and DMV of LAD were significantly lower in the CSFP group than in the control group （（0.228±0.029） m/s vs. （0.302±0.065） m/s, P=0.000; （0.176±0.028） m/s vs. （0.226±0.052） m/s, P=0.000,respectively）. There was a high inverse correlation between CTFC and coronary DPV and DMV （r=-0.727, P=0.000;r=-0.671, P=0.000, respectively）. Receiver operating characteristic （ROC） curve showed that the area under the curve （AUC） was less than one half for coronary DPV （AUC=0.104） and DMV （AUC=0.204）, respectively.Conclusions In patients with CSFP, there is a high inverse correlation between CTFC and coronary diastolic flow velocities in the LAD coronary artery, as measured by TTDE. The value of TTDE in the monitoring and evaluation of coronary flow in patients with CSFP deserves further investigation.展开更多
In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angio...In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angiograms and in 16 patients with normal angiographic coronary flow (NF). A 3.5 F, 20 MHz ultrasound catheter (Boston Scientific) was used for ICUS and a 0.014 inch FloWire (Cardiometrics) was used for ICD. Coronary flow velocity including average peak velocity (APV), maximal peak velocity (MPV) at rest and at hyperemia as well as coronary flow reserve (CFR) were compared in both groups in comparison to the presence or absence of plaque formation based on ICUS. CFR in the SF group (4.2±1.1) was even higher than that of the NF group (3.1±0.6, P<0.001). Department of Cardiology, University GHS Essen, Germany (Ge JB, Simon H, Jeremias A, Liu FQ, Grge G, Haude M, Baumgart D and Erbel R) Significant differences were also found concerning the APV and MPV among both groups (both P <0.001). Plaque formation was found in 7/13 patients with a lumen reduction of 21%±24% in SF group and in 7/16 of the NF group with a lumen reduction of 19%±17%. Comparison of APV, MPV and CFR in SF and NF grups. Comparison of APV, MPV and CFR in SF and NF groups[BHDFG1*2,WK8ZQ1,WK11DW,WK11DWW] SF group NF groupAPV (cm/s) Rest 7.7±2.0 21.1±5.0 * Peak31.7±14.961.3±14.2 *MPV (cm/s) Rest17.4±4.637.0±11.4 * Peak56.8±14.981.8±17.7 *CFR4.2±1.13.1±0.6 # * P<0.001, #P=0.002. Coronary slow flow phenomenon in angiography indicates reduced resting flow velocity without reduction of coronary flow reserve.展开更多
The effects of packing configurations on the phase transition of straight granular chute flow with two bottlenecks axe studied. The granular flow shows a dilute- to-dense flow transition when the channel width is vari...The effects of packing configurations on the phase transition of straight granular chute flow with two bottlenecks axe studied. The granular flow shows a dilute- to-dense flow transition when the channel width is varied, accompanied with a peculiar bistable phenomenon. The bistable phenomenon is induced by the initial packing config- uration of particles. When the packing is dense, the initial flux is small and will induce a dense flow. When the packing is loose, the initial flux is large and will induce a di- lute flow. The fabric network of granulax packing is analyzed from a complex network perspective. The degree distribution shows quantitatively different characteristics for the configurations. A two-dimensional （2D） packing clustering coefficient is defined to better quantify the fabric network.展开更多
Slow coronary flow phenomenon(SCFP) is an angiographic observation characterized by delayed distal vessel opacifi-cation in the absence of significant epicardial coronary disease. Only limited studies have been focuse...Slow coronary flow phenomenon(SCFP) is an angiographic observation characterized by delayed distal vessel opacifi-cation in the absence of significant epicardial coronary disease. Only limited studies have been focused on the etiologies,clinical manifestations and treatment of this unique angiographic phenomenon. In our case report,we described an 85-year-old man who came with significant ST segment elevation in leads V1-V4 and V3R-V5R without increase in myocardial enzyme. The patient also developed respiratory failure requiring intubation and mechanical ventilation. Coronary angiography revealed only mild atherosclerosis without spasm or thromboembolic occlusion. Slow flow was seen in all coronary arteries,especially in the left anterior descending and right coronary arteries. This case speculated that transmural myocardial ischemia with ST segment elevation might be resulted from slow coronary flow. Transmural myocardial ischemia can occur owing to abnormalities of the coronary microcirculation.展开更多
A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow.Existing observed field and experimental data in the literature have bee...A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow.Existing observed field and experimental data in the literature have been examined and a valuable database has been developed.Different conditions,including the river water depth,flow velocity,river bank slope,Froude number,wave height,wave period,and wave obliquity have been considered.Results from an empirical equation (Bhowmik,1978) that only considers the maximum wave height and river bank slope have been compared with the results calculated by the newly developed equation.Calculated results have also been verified against field data.Results show that not only the maximum wave height and river bank slope but also the water depth,flow velocity,wave length,wave obliquity,and wave period are important parameters for predicting the mean diameter of the armor units,highlighting the multivariate behavior of protecting the river bank in the presence of ship-induced waves and river flow velocity.展开更多
The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a po...The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.展开更多
Moist flow over a bell-shaped mountain is investigated using the advanced regional prediction system (ARPS). Three closely related issues are addressed: the upslope precipitation mechanism, periodic evolution of preci...Moist flow over a bell-shaped mountain is investigated using the advanced regional prediction system (ARPS). Three closely related issues are addressed: the upslope precipitation mechanism, periodic evolution of precipitation associated with mountain waves, and lee precipitation induced by reversal flow. The results show that precipitation is strongly the moist distribution and terrain scale dependent. Beginning with the case of uniformly stratified flow over mountain, upslope precipitation and lee wave precipitation pattern are obtained. Most importantly, lee precipitation induced by reversal flow can be caused by layered flow over mountain, wherein lee reversal flow exerts a significant influence on the orographic precipitation.展开更多
文摘The dissymmetric flow phenomenon exists in a symmetric multistrand tundish. It was studied by the physical simulation experiment. The fundamental flow characteristic of dissymmetry was analyzed. The asymmetry of the flow field, the temperature field, and the inclusions distribution without flow-control devices （FCDs） were compared with those with FCDs. It is proved that the asymmetry of the flow and temperature field along the outlets at the long range is more obvious. The symmetric FCDs installation has a slight effect on the dissymmetric temperature field, simultaneously, the symmetry of the average residence time and the fluid flow pattern has improved, and the fluid flow in the tundish has been more reasonable. In case of a symmetric multistrand tundish having a large volume, the influence of the dissymmetric phenomenon should be considered and the flow behaviors in the whole tundish should be studied completely.
基金This study was supported by grants from National Natural Science Foundation of China （No. 81070166） and Scientific Research Common Program of Beijing Municipal Commission of Education （No. KM201010025020）.Acknowledgement： We are grateful to all staff members of the Department of Cardiology and Catheterization Laboratory, Beijing Anzhen Hospital, Capital Medical University.
文摘Background Coronary slow flow phenomenon （CSFP） is an important, angiographic clinical entity but is lacking non-invasive detecting techniques. This study aimed to elucidate the value of transthoracic Doppler echocardiography （TTDE） in the diagnosis and monitoring of coronary slow flow in left anterior descending （LAD） coronary artery.Methods We consecutively enrolled 27 patients with CSFP in LAD detected by coronary arteriography from August 2009 to April 2010. Thirty-eight patients with angiographically normal coronary flow served as control. Corrected thrombolysis in myocardial infarction （TIMI） frame count （CTFC） was used to document coronary flow velocities. All subjects underwent TTDE within 24 hours after coronary angiography. LAD flow was detected and the coronary diastolic peak velocities （DPV） and diastolic mean velocities （DMV） were calculated.Results Sixty of 65 （92.3%） subjects successfully underwent TTDE. Baseline clinical characteristics were similar between the two groups. Coronary DPV and DMV of LAD were significantly lower in the CSFP group than in the control group （（0.228±0.029） m/s vs. （0.302±0.065） m/s, P=0.000; （0.176±0.028） m/s vs. （0.226±0.052） m/s, P=0.000,respectively）. There was a high inverse correlation between CTFC and coronary DPV and DMV （r=-0.727, P=0.000;r=-0.671, P=0.000, respectively）. Receiver operating characteristic （ROC） curve showed that the area under the curve （AUC） was less than one half for coronary DPV （AUC=0.104） and DMV （AUC=0.204）, respectively.Conclusions In patients with CSFP, there is a high inverse correlation between CTFC and coronary diastolic flow velocities in the LAD coronary artery, as measured by TTDE. The value of TTDE in the monitoring and evaluation of coronary flow in patients with CSFP deserves further investigation.
文摘In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angiograms and in 16 patients with normal angiographic coronary flow (NF). A 3.5 F, 20 MHz ultrasound catheter (Boston Scientific) was used for ICUS and a 0.014 inch FloWire (Cardiometrics) was used for ICD. Coronary flow velocity including average peak velocity (APV), maximal peak velocity (MPV) at rest and at hyperemia as well as coronary flow reserve (CFR) were compared in both groups in comparison to the presence or absence of plaque formation based on ICUS. CFR in the SF group (4.2±1.1) was even higher than that of the NF group (3.1±0.6, P<0.001). Department of Cardiology, University GHS Essen, Germany (Ge JB, Simon H, Jeremias A, Liu FQ, Grge G, Haude M, Baumgart D and Erbel R) Significant differences were also found concerning the APV and MPV among both groups (both P <0.001). Plaque formation was found in 7/13 patients with a lumen reduction of 21%±24% in SF group and in 7/16 of the NF group with a lumen reduction of 19%±17%. Comparison of APV, MPV and CFR in SF and NF grups. Comparison of APV, MPV and CFR in SF and NF groups[BHDFG1*2,WK8ZQ1,WK11DW,WK11DWW] SF group NF groupAPV (cm/s) Rest 7.7±2.0 21.1±5.0 * Peak31.7±14.961.3±14.2 *MPV (cm/s) Rest17.4±4.637.0±11.4 * Peak56.8±14.981.8±17.7 *CFR4.2±1.13.1±0.6 # * P<0.001, #P=0.002. Coronary slow flow phenomenon in angiography indicates reduced resting flow velocity without reduction of coronary flow reserve.
基金Project supported by the National Natural Science Foundation of China(Nos.11034010 and 71171185)
文摘The effects of packing configurations on the phase transition of straight granular chute flow with two bottlenecks axe studied. The granular flow shows a dilute- to-dense flow transition when the channel width is varied, accompanied with a peculiar bistable phenomenon. The bistable phenomenon is induced by the initial packing config- uration of particles. When the packing is dense, the initial flux is small and will induce a dense flow. When the packing is loose, the initial flux is large and will induce a di- lute flow. The fabric network of granulax packing is analyzed from a complex network perspective. The degree distribution shows quantitatively different characteristics for the configurations. A two-dimensional （2D） packing clustering coefficient is defined to better quantify the fabric network.
文摘Slow coronary flow phenomenon(SCFP) is an angiographic observation characterized by delayed distal vessel opacifi-cation in the absence of significant epicardial coronary disease. Only limited studies have been focused on the etiologies,clinical manifestations and treatment of this unique angiographic phenomenon. In our case report,we described an 85-year-old man who came with significant ST segment elevation in leads V1-V4 and V3R-V5R without increase in myocardial enzyme. The patient also developed respiratory failure requiring intubation and mechanical ventilation. Coronary angiography revealed only mild atherosclerosis without spasm or thromboembolic occlusion. Slow flow was seen in all coronary arteries,especially in the left anterior descending and right coronary arteries. This case speculated that transmural myocardial ischemia with ST segment elevation might be resulted from slow coronary flow. Transmural myocardial ischemia can occur owing to abnormalities of the coronary microcirculation.
文摘A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow.Existing observed field and experimental data in the literature have been examined and a valuable database has been developed.Different conditions,including the river water depth,flow velocity,river bank slope,Froude number,wave height,wave period,and wave obliquity have been considered.Results from an empirical equation (Bhowmik,1978) that only considers the maximum wave height and river bank slope have been compared with the results calculated by the newly developed equation.Calculated results have also been verified against field data.Results show that not only the maximum wave height and river bank slope but also the water depth,flow velocity,wave length,wave obliquity,and wave period are important parameters for predicting the mean diameter of the armor units,highlighting the multivariate behavior of protecting the river bank in the presence of ship-induced waves and river flow velocity.
基金supported by the Major Program of National Natural Science Foundation of China(Nos.11632016 and 91634103)
文摘The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.
文摘Moist flow over a bell-shaped mountain is investigated using the advanced regional prediction system (ARPS). Three closely related issues are addressed: the upslope precipitation mechanism, periodic evolution of precipitation associated with mountain waves, and lee precipitation induced by reversal flow. The results show that precipitation is strongly the moist distribution and terrain scale dependent. Beginning with the case of uniformly stratified flow over mountain, upslope precipitation and lee wave precipitation pattern are obtained. Most importantly, lee precipitation induced by reversal flow can be caused by layered flow over mountain, wherein lee reversal flow exerts a significant influence on the orographic precipitation.
