Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, m...Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multi-field coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simul-(ation) model was checked by the parameters measured in an operating boiler, (DG130-9.8/540.) The maximum of relative error is less than 12% and the absolute error is less than 120℃, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.展开更多
A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditiona...A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.展开更多
AIM:To investigate the role of anal cushions in hemorrhoidectomy and its effect on anal continence of the patients.METHODS:Seventy-six consecutive patients(33 men and 43 women) with a mean age of 44 years were include...AIM:To investigate the role of anal cushions in hemorrhoidectomy and its effect on anal continence of the patients.METHODS:Seventy-six consecutive patients(33 men and 43 women) with a mean age of 44 years were included.They underwent Milligan-Morgan hemorrhoidectomy because of symptomatic third-and fourth-degree hemorrhoids and failure in conservative treatment for years.Wexner score was recorded and liquid continence test was performed for each patient before and two months after operation using the techniques described in our previous work.The speed-constant rectal lavage apparatus was prepared in our laboratory.The device could output a pulsed and speed-constant saline stream with a high pressure,which is capable of overcoming any rectal resistance change.The patients were divided into three groups,group A(< 900 mL),group B(900-1200 mL) and group C(> 1200 mL) according to the results of the preoperative liquid continence test.RESULTS:All the patients completed the study.The average number of hemorrhoidal masses excised was 2.4.Most patients presented with hemorrhoidal symptoms for more than one year,including a mean duration of incontinence of 5.2 years.The most common symptoms before surgery were anal bleeding(n = 55),prolapsed lesion(n = 34),anal pain(n = 12) and constipation(n = 17).There were grade Ⅲ hemorrhoids in 39(51.3%) patients,and grade Ⅳ in 37(48.7%) patients according to Goligher classification.Five patients had experienced hemorrhoid surgery at least once.Compared with postoperative results,the retained volume in the preoperative liquid continence test was higher in 40 patients,lower in 27 patients,and similar in the other 9 patients.The overall preoperative retained volume in the liquid continence test was 1130.61 ± 78.35 mL,and postoperative volume was slightly decreased(991.27 ± 42.77 mL),but there was no significant difference(P = 0.057).Difference was significant in the test value before and after hemorrhoidectomy in group A(858.24 ± 32.01 mL vs 574.18 ± 60.28 mL,P = 0.011),but no obvious difference was noted in group B or group C.There was no significant difference in Wexner score before and after operation(1.68 ± 0.13 vs 2.10 ± 0.17,P = 0.064).By further stratified analysis,there was significant difference before and 2 months after operation in group A(2.71 ± 0.30 vs 3.58 ± 0.40,P = 0.003).In contrast,there were no significant differences in group B or group C(1.89 ± 0.15 vs 2.11 ± 0.19,P = 0.179;0.98 ± 0.11 vs 1.34 ± 0.19,P = 0.123).CONCLUSION:There is no difference in the continence status of patients before and after Milligan-Morgan hemorrhoidectomy.However,patients with preoperative compromised continence may have further deterioration of their continence,hence Milligan-Morgan hemorrhoidectomy should be avoided in such patients.展开更多
The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the typ...The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.展开更多
This paper presented an individual recognition algorithm for human iris using fractal dimension of grayscale extremums for feature extraction.Firstly,iris region was localized from an eye image with modified circle de...This paper presented an individual recognition algorithm for human iris using fractal dimension of grayscale extremums for feature extraction.Firstly,iris region was localized from an eye image with modified circle detector stemmed from Daugman’s integro-differential operator.Then,segmentation was used to extract the iris and to exclude occlusion from eyelids and eyelashes.The extracted iris was normalized and mapped to polar coordinates for matching.In feature encoding,a new approach based on fractal dimension of grayscale extremums was designed to extract textural features of iris.Finally,a normalized correlation classifier was employed to determine the agreement of two iris feature templates,and the feature template was rotated left and right to avoid the interference from rotation of eyes and tilting of head.The experimental results show that fractal dimension of grayscale extremums can extract textural features from iris image effectively,and the proposed recognition algorithm is accurate and efficient.The proposed algorithm was tested on CASIA-IrisV3-Interval iris database and the performance was evaluated based on the analysis of both False Accept Rate(FAR)and False Reject Rate(FRR)curves.Experimental results show that the proposed iris recognition algorithm is effective and efficient.展开更多
Let φ be a normal function on [0,1) and A'(φ)(1<P<∞) Bergman space on the unit disk, weighted with φ~P(|·|)/(1-|·|~2).A sufficient condition for interpolation by functions in A^P(φ) is obtaine...Let φ be a normal function on [0,1) and A'(φ)(1<P<∞) Bergman space on the unit disk, weighted with φ~P(|·|)/(1-|·|~2).A sufficient condition for interpolation by functions in A^P(φ) is obtained by controlling norms of linear operators.展开更多
Convection-dispersion of fluids flowing through porous media is an important phenomenon in immiscible and miscible displacement in hydrocarbon reservoirs. Exact calculation of this problem leads to perform more robust...Convection-dispersion of fluids flowing through porous media is an important phenomenon in immiscible and miscible displacement in hydrocarbon reservoirs. Exact calculation of this problem leads to perform more robust reservoir simulation and reliable prediction. There are various techniques that have been proposed to solve convection-dispersion equation. To check the validity of these techniques, the convection-dispersion equation was solved numerically using a series of well known numerical techniques. Such techniques that employed in this study include method of line, explicit, implicit, Crank-Nicolson and Barakat-Clark. Several cases were considered as input, and convection-dispersion equation was solved using the aforementioned techniques. Moreover the error analysis was also carried out based on the comparison of numerical and analytical results. Finally it was observed that method of line and explicit methods are not capable of simulating the convection-dispersion equation for wide range of input parameters. The Barakat-Clark method was also failed to predict accurate results and in some cases it had large deviation from analytical solution. On the other hand, the simulation results of implicit and Crank-Nicolson have more qualitative and quantitative agreement with those obtained by the analytical solutions.展开更多
When applying fiat belts, correct tracking of the belt through the installation has to be assured. Since flat belts are commonly used for conveying and transmission purposes, tracking systems have been well developed,...When applying fiat belts, correct tracking of the belt through the installation has to be assured. Since flat belts are commonly used for conveying and transmission purposes, tracking systems have been well developed, but the ultimate tracking behaviour of the belt can be greatly enhanced by taking special care in the creation of an adequate tracking mechanism. To obtain long-life operation and full value from the equipment, the correct tracking technique plays an important role. This paper deals with two tracking techniques： The skewed and the angled pulley axis. Numerical simulation results are compared with both measurements and an analytical approach. The advantages of numerical simulation compared to experimental tests are ease, convenience and the absence of any safety risk. Compared to analytical approaches the simulation is used for systems for which simple closed form analytic solutions are not possible.展开更多
We give a definition and some primary properties of group-valued measure with a second countable complete Boolean algebra domain, and with a subset of a first countable complete Abelian po-group codomain.
Consumption of clean energy has been increasing in China.Forecasting gas consumption is important to adjusting the energy consumption structure in the future.Based on historical data of gas consumption from 1980 to 20...Consumption of clean energy has been increasing in China.Forecasting gas consumption is important to adjusting the energy consumption structure in the future.Based on historical data of gas consumption from 1980 to 2017,this paper presents a weight method of the inverse deviation of fitted value,and a combined forecast based on a residual auto-regression model and Kalman filtering algorithm is used to forecast gas consumption.Our results show that:(1)The combination forecast is of higher precision:the relative errors of the residual auto-regressive model,the Kalman filtering algorithm and the combination model are within the range(–0.08,0.09),(–0.09,0.32)and(–0.03,0.11),respectively.(2)The combination forecast is of greater stability:the variance of relative error of the residual auto-regressive model,the Kalman filtering algorithm and the combination model are 0.002,0.007 and 0.001,respectively.(3)Provided that other conditions are invariant,the predicted value of gas consumption in 2018 is 241.81×10~9 m^3.Compared to other time-series forecasting methods,this combined model is less restrictive,performs well and the result is more credible.展开更多
In order to examine and analyze the effects of integration of land surface models with TOPMODEL and different approaches for the integration on the model simulation of water and energy balances,the coupled models have...In order to examine and analyze the effects of integration of land surface models with TOPMODEL and different approaches for the integration on the model simulation of water and energy balances,the coupled models have been developed,which incorporate TOPMODEL into the Simplified Biosphere Model(SSiB) with different approaches(one divides a basin into a number of zones according to the distribution of topographic index,and the other only divides the basin into saturated and unsaturated zones).The coupled models are able to(but SSiB is not able to) take into account the impacts of topography variation and vertical heterogeneity of soil saturated hydraulic conductivity on horizontal distribution of soil moisture and in turn on water and energy balances within the basin(or a grid cell).By using the coupled models and SSiB model itself,the daily hydrological components such as runoffs are simulated and final results are analyzed carefully.Simulated daily results of hydrological components produced by both SSiB and coupled models show that(i) There is significant difference between results of soil wetness,its vertical distribution and seasonal variation,water and energy balance,and daily runoff in the basin predicted by SSiB and by the coupled models.The land surface model currently used such as SSiB is likely to misrepresent real feature of water and energy balances in the basin.(ii) Compared with the results for the basin predicted by SSiB,the coupled models predict more strong vertical and seasonal changes in soil wetness,higher evaporation and lower runoff,and improve the base flow simulation obviously.(iii) Comparing the results for the basin predicted by two coupled models with different integration approach and SSiB one by one,the results of daily runoffs and soil wetness predicted by the two coupled models are quite similar.It means,for the coupled models,the approach by dividing a region being considered into more subzones may have limited effects on improving runoff simulation results.The scheme only to divide the region into saturated and unsaturated zones may be a convenient and effective scheme.But then,if the results from the two coupled models for the basin are carefully compared,the simulated results by the coupled model with dividing the basin into more subzones will show higher evaporation and surface runoff but lower subsurface flow,lower total runoff,and lower ground water level averaged for five years.展开更多
文摘Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multi-field coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simul-(ation) model was checked by the parameters measured in an operating boiler, (DG130-9.8/540.) The maximum of relative error is less than 12% and the absolute error is less than 120℃, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.
基金Project(Z110803)supported by the State Key Laboratory of Geomechanics and Geotechnical Engineering,ChinaProject(2008AA062303)supported by the National High Technology Research and Development Program of China
文摘A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.
文摘AIM:To investigate the role of anal cushions in hemorrhoidectomy and its effect on anal continence of the patients.METHODS:Seventy-six consecutive patients(33 men and 43 women) with a mean age of 44 years were included.They underwent Milligan-Morgan hemorrhoidectomy because of symptomatic third-and fourth-degree hemorrhoids and failure in conservative treatment for years.Wexner score was recorded and liquid continence test was performed for each patient before and two months after operation using the techniques described in our previous work.The speed-constant rectal lavage apparatus was prepared in our laboratory.The device could output a pulsed and speed-constant saline stream with a high pressure,which is capable of overcoming any rectal resistance change.The patients were divided into three groups,group A(< 900 mL),group B(900-1200 mL) and group C(> 1200 mL) according to the results of the preoperative liquid continence test.RESULTS:All the patients completed the study.The average number of hemorrhoidal masses excised was 2.4.Most patients presented with hemorrhoidal symptoms for more than one year,including a mean duration of incontinence of 5.2 years.The most common symptoms before surgery were anal bleeding(n = 55),prolapsed lesion(n = 34),anal pain(n = 12) and constipation(n = 17).There were grade Ⅲ hemorrhoids in 39(51.3%) patients,and grade Ⅳ in 37(48.7%) patients according to Goligher classification.Five patients had experienced hemorrhoid surgery at least once.Compared with postoperative results,the retained volume in the preoperative liquid continence test was higher in 40 patients,lower in 27 patients,and similar in the other 9 patients.The overall preoperative retained volume in the liquid continence test was 1130.61 ± 78.35 mL,and postoperative volume was slightly decreased(991.27 ± 42.77 mL),but there was no significant difference(P = 0.057).Difference was significant in the test value before and after hemorrhoidectomy in group A(858.24 ± 32.01 mL vs 574.18 ± 60.28 mL,P = 0.011),but no obvious difference was noted in group B or group C.There was no significant difference in Wexner score before and after operation(1.68 ± 0.13 vs 2.10 ± 0.17,P = 0.064).By further stratified analysis,there was significant difference before and 2 months after operation in group A(2.71 ± 0.30 vs 3.58 ± 0.40,P = 0.003).In contrast,there were no significant differences in group B or group C(1.89 ± 0.15 vs 2.11 ± 0.19,P = 0.179;0.98 ± 0.11 vs 1.34 ± 0.19,P = 0.123).CONCLUSION:There is no difference in the continence status of patients before and after Milligan-Morgan hemorrhoidectomy.However,patients with preoperative compromised continence may have further deterioration of their continence,hence Milligan-Morgan hemorrhoidectomy should be avoided in such patients.
文摘The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.
基金supported by the Independent Innovation Foundation of Shandong University(No.2009JC004)the Program of Development of Science and Technology of Shandong(No.2010GSF10243)
文摘This paper presented an individual recognition algorithm for human iris using fractal dimension of grayscale extremums for feature extraction.Firstly,iris region was localized from an eye image with modified circle detector stemmed from Daugman’s integro-differential operator.Then,segmentation was used to extract the iris and to exclude occlusion from eyelids and eyelashes.The extracted iris was normalized and mapped to polar coordinates for matching.In feature encoding,a new approach based on fractal dimension of grayscale extremums was designed to extract textural features of iris.Finally,a normalized correlation classifier was employed to determine the agreement of two iris feature templates,and the feature template was rotated left and right to avoid the interference from rotation of eyes and tilting of head.The experimental results show that fractal dimension of grayscale extremums can extract textural features from iris image effectively,and the proposed recognition algorithm is accurate and efficient.The proposed algorithm was tested on CASIA-IrisV3-Interval iris database and the performance was evaluated based on the analysis of both False Accept Rate(FAR)and False Reject Rate(FRR)curves.Experimental results show that the proposed iris recognition algorithm is effective and efficient.
基金Supported by the Doctoral Program Foundation of Institute of Higher Education.
文摘Let φ be a normal function on [0,1) and A'(φ)(1<P<∞) Bergman space on the unit disk, weighted with φ~P(|·|)/(1-|·|~2).A sufficient condition for interpolation by functions in A^P(φ) is obtained by controlling norms of linear operators.
文摘Convection-dispersion of fluids flowing through porous media is an important phenomenon in immiscible and miscible displacement in hydrocarbon reservoirs. Exact calculation of this problem leads to perform more robust reservoir simulation and reliable prediction. There are various techniques that have been proposed to solve convection-dispersion equation. To check the validity of these techniques, the convection-dispersion equation was solved numerically using a series of well known numerical techniques. Such techniques that employed in this study include method of line, explicit, implicit, Crank-Nicolson and Barakat-Clark. Several cases were considered as input, and convection-dispersion equation was solved using the aforementioned techniques. Moreover the error analysis was also carried out based on the comparison of numerical and analytical results. Finally it was observed that method of line and explicit methods are not capable of simulating the convection-dispersion equation for wide range of input parameters. The Barakat-Clark method was also failed to predict accurate results and in some cases it had large deviation from analytical solution. On the other hand, the simulation results of implicit and Crank-Nicolson have more qualitative and quantitative agreement with those obtained by the analytical solutions.
文摘When applying fiat belts, correct tracking of the belt through the installation has to be assured. Since flat belts are commonly used for conveying and transmission purposes, tracking systems have been well developed, but the ultimate tracking behaviour of the belt can be greatly enhanced by taking special care in the creation of an adequate tracking mechanism. To obtain long-life operation and full value from the equipment, the correct tracking technique plays an important role. This paper deals with two tracking techniques： The skewed and the angled pulley axis. Numerical simulation results are compared with both measurements and an analytical approach. The advantages of numerical simulation compared to experimental tests are ease, convenience and the absence of any safety risk. Compared to analytical approaches the simulation is used for systems for which simple closed form analytic solutions are not possible.
文摘We give a definition and some primary properties of group-valued measure with a second countable complete Boolean algebra domain, and with a subset of a first countable complete Abelian po-group codomain.
基金Soft Science Research Project in Shanxi Province of China(2017041030-5)Science Fund Projects in North University of China(XJJ2016037)
文摘Consumption of clean energy has been increasing in China.Forecasting gas consumption is important to adjusting the energy consumption structure in the future.Based on historical data of gas consumption from 1980 to 2017,this paper presents a weight method of the inverse deviation of fitted value,and a combined forecast based on a residual auto-regression model and Kalman filtering algorithm is used to forecast gas consumption.Our results show that:(1)The combination forecast is of higher precision:the relative errors of the residual auto-regressive model,the Kalman filtering algorithm and the combination model are within the range(–0.08,0.09),(–0.09,0.32)and(–0.03,0.11),respectively.(2)The combination forecast is of greater stability:the variance of relative error of the residual auto-regressive model,the Kalman filtering algorithm and the combination model are 0.002,0.007 and 0.001,respectively.(3)Provided that other conditions are invariant,the predicted value of gas consumption in 2018 is 241.81×10~9 m^3.Compared to other time-series forecasting methods,this combined model is less restrictive,performs well and the result is more credible.
基金supported by National Natural Science Foundation of China(Grant Nos.41075060 and 41030106)
文摘In order to examine and analyze the effects of integration of land surface models with TOPMODEL and different approaches for the integration on the model simulation of water and energy balances,the coupled models have been developed,which incorporate TOPMODEL into the Simplified Biosphere Model(SSiB) with different approaches(one divides a basin into a number of zones according to the distribution of topographic index,and the other only divides the basin into saturated and unsaturated zones).The coupled models are able to(but SSiB is not able to) take into account the impacts of topography variation and vertical heterogeneity of soil saturated hydraulic conductivity on horizontal distribution of soil moisture and in turn on water and energy balances within the basin(or a grid cell).By using the coupled models and SSiB model itself,the daily hydrological components such as runoffs are simulated and final results are analyzed carefully.Simulated daily results of hydrological components produced by both SSiB and coupled models show that(i) There is significant difference between results of soil wetness,its vertical distribution and seasonal variation,water and energy balance,and daily runoff in the basin predicted by SSiB and by the coupled models.The land surface model currently used such as SSiB is likely to misrepresent real feature of water and energy balances in the basin.(ii) Compared with the results for the basin predicted by SSiB,the coupled models predict more strong vertical and seasonal changes in soil wetness,higher evaporation and lower runoff,and improve the base flow simulation obviously.(iii) Comparing the results for the basin predicted by two coupled models with different integration approach and SSiB one by one,the results of daily runoffs and soil wetness predicted by the two coupled models are quite similar.It means,for the coupled models,the approach by dividing a region being considered into more subzones may have limited effects on improving runoff simulation results.The scheme only to divide the region into saturated and unsaturated zones may be a convenient and effective scheme.But then,if the results from the two coupled models for the basin are carefully compared,the simulated results by the coupled model with dividing the basin into more subzones will show higher evaporation and surface runoff but lower subsurface flow,lower total runoff,and lower ground water level averaged for five years.
