为了提高导引头稳定平台抗扰性及速度稳态跟踪性能,提出了一种基于扩张状态观测器(Extended State Observer,ESO)的双积分滑模控制器(Double Integral Sliding Mode Controller,DISMC)。首先,采用二阶扩张状态观测器对系统的未知扰动进...为了提高导引头稳定平台抗扰性及速度稳态跟踪性能,提出了一种基于扩张状态观测器(Extended State Observer,ESO)的双积分滑模控制器(Double Integral Sliding Mode Controller,DISMC)。首先,采用二阶扩张状态观测器对系统的未知扰动进行估计;然后,采用了双积分滑模控制器实现了系统的低稳态误差跟踪,同时采用了改进的幂次趋近律来削弱控制系统的抖振影响;最后,采用导引头稳定平台进行目标跟踪实验和隔离度性能测试。实验结果表明,与传统基于扰动观测器(Disturbance Observer,DOB)的PI控制方法相比,跟踪3(°)/s的梯形波时,在提出的控制器作用下速度跟踪快速性提高了48 ms,跟踪误差标准差提高了0.0131(°)/s。同时用转台模拟弹体扰动分别为sin(πt)°、3sin(5πt)°、7sin(2πt)°时,系统的隔离度分别提高了2.91%、0.45%、0.7%,表明基于扩张状态观测器的双积分滑模控制器对导引头稳定平台具有较强的抗扰性和较好的跟踪性能。展开更多
The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway reg...The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway regularity of two stages 6： 00--7：00 and 7： 00--9：00 is comparatively analyzed, and it is found that both the traffic conditions and the passenger demand affect headway regularity. A bus arrival model, which assumes that the dwell time of a bus is linear in headway, is built to probe the effect of scheduled headway, and the model is simulated by Matlab. The simulation results reveal that the departure intervals and fluctuations affect headway regularity. Longer intervals and less fluctuation mean higher regularity of headway. And, the fluctuation has a more obvious influence on headway regularity than the interval. Controlling the fluctuations of scheduled headway can effectively raise the regularity of headway and improve the level of public transport service.展开更多
\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid sta...\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.展开更多
The structural stabilities and electronic structures of Ga atomic chains are studied by the first-principles plane wave pseudopotential method based on the density functional theory. The present calculations show that...The structural stabilities and electronic structures of Ga atomic chains are studied by the first-principles plane wave pseudopotential method based on the density functional theory. The present calculations show that gallium can form planar chains in linear-, zigzag- and ladder-form one-dimensional structures. The most stable one among the studied structures is the zigzag chain with a unit cell rather close to equilateral triangles with four nearest neighbors, and all the other structures are metastable. The relative structural stability, the energy bands and the charge densities are discussed based on the ab initio calculations and the Jahn-Teller effect.展开更多
A simply method to measure the thermal focal length of a LD end-pumped Nd.GdVO4 solid state laser with a stable resonator is presented. By scanning a slit across the field with expression of multi-mode Gaussian distri...A simply method to measure the thermal focal length of a LD end-pumped Nd.GdVO4 solid state laser with a stable resonator is presented. By scanning a slit across the field with expression of multi-mode Gaussian distribution behind the output mirror of lasers, the radius and the M^2 factor describing the quality of beam can be measured. The waists of the multi-mode field and the TEM00 mode can be deduced according to the law of multi-mode Gassian beam propagation. Based on the ABOD matrix theory of a stable resonator,the thermal focal length of the active medium can be easily obtained. The thermal focal length of a LD end-pumped Nd. GdVO~ laser has been measured and the experimental results agree with the theoretically analyzed values.展开更多
With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. F...With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. FEM strength reduction method is used in analyzing slope stability of a wharf in Chongqing, and its accuracy is verified by comparing the acquired results with the computation of traditional limit equilibrium method. On this basis, the influences of reservoir water level variation, overload and backfill material behind the retaining wall, and soil share strength of wharf slope on slippery stratum are analyzed. Analysis shows that, there＇ s a most adverse water level in wharf slope, and the engineering proposals with a certain practical significance such as improve the drainage behind retaining wall, controll overload and improve the strength of backfill soil and subsoil are suggested.展开更多
Firstly,the common design principles for diversion tunnel plug are generalized,and two kinds of numerical analysis methods are discussed.Then the strength reduction FEM is introduced in numerical model analysis and th...Firstly,the common design principles for diversion tunnel plug are generalized,and two kinds of numerical analysis methods are discussed.Then the strength reduction FEM is introduced in numerical model analysis and the design steps of the plug's length are illustrated.During the progress to determine the plug's length,the equivalent plastic strain on the potential slip surface is assumed as the flag to tell the failure against sliding,and the plug stability is overall estimated from the plastic zone range and connectivity.展开更多
One of ways of intensification of process of manufacture of heterogeneous tinned products of fruits and vegetables is the use of sated water steam （Patent of USSR No. 500792）. This process at application as consumer...One of ways of intensification of process of manufacture of heterogeneous tinned products of fruits and vegetables is the use of sated water steam （Patent of USSR No. 500792）. This process at application as consumer glass container for such products is especially effective. However, there are some questions which are connected with thermal influence on glass container at realization of such heating. The given research is devoted as the decision of practical questions arising at process engineers.展开更多
Abstract： Because of the complex topography in southwest region of China, the water level of the inland river has a large amplitude of variation which causes a frequent diversification of water content in the river s...Abstract： Because of the complex topography in southwest region of China, the water level of the inland river has a large amplitude of variation which causes a frequent diversification of water content in the river slope. The flow caused by the infiltration of the terminal slope stability will induce a great impact on the slope stability of wharf.. This paper uses an ideal elastic-plastic model and the Moore Coulomb yield criterion for numerical simulation. Through the b an k slop e stability of the overhead-type terminal s under the changes of water, we obtained the impact of all factors on the bank slope in the course of water lowering. It was found out that the impact from the cohesion of the geo-materials of the bank slope on the slope stability is greater than that from the internal friction angle.展开更多
Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines,in particular Francis turbines.A method of cavitation calculations was proposed to predict the pressure fluctuations ...Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines,in particular Francis turbines.A method of cavitation calculations was proposed to predict the pressure fluctuations induced by draft tube vortices in a model Francis turbine,by solving RANS equations with RNG k-turbulence model and ZGB cavitation model,with modified turbulence viscosity.Three cases with different flow rates at high head were studied.In the study case of part load,two modes of revolutions with the same rotating direction,revolution around the axis of the draft tube cone,and revolution around the core of the vortex rope,can be recognized.The elliptical shaped vortex rope causes anisotropic characteristics of pressure fluctuations around the centerline of the draft tube cone.By analyzing the phase angles of the pressure fluctuations,the role of the vortex rope as an exciter in the oscillating case can be recognized.An analysis of Batchelor instability,i.e.instability in q-vortex like flow structure,has been carried out on the draft tube vortices in these three cases.It can be concluded that the trajectory for study case with part load lies in the region of absolute instability(AI),and it lies in the region of convective instability(CI)for study case with design flow rate.Trajectory for study case with over load lies in the AI region at the inlet of the draft tube,and enters CI region near the end of the elbow.展开更多
The paper refers to the behavior of a vaneless diffuser of a radial flow pump in partial flow operating conditions. Some experimental data have been obtained using 2D/2C PIV and unsteady pressure measurements within t...The paper refers to the behavior of a vaneless diffuser of a radial flow pump in partial flow operating conditions. Some experimental data have been obtained using 2D/2C PIV and unsteady pressure measurements within the diffuser, in various operating conditions. The experimental results at the lower flow rate are compared with two-dimensional numerical calculations.展开更多
Objective： To introduce bipolar hemiarthroplasty with a two-step osteotomy technique and observe its clinical result for unstable intertrochanteric frac- tures in senile patients. Methods： Fifteen consecutive patie...Objective： To introduce bipolar hemiarthroplasty with a two-step osteotomy technique and observe its clinical result for unstable intertrochanteric frac- tures in senile patients. Methods： Fifteen consecutive patients with unstable intertrochanteric fractures aged from 81 to 92 years with a mean of 85 years were treated in our hospital from August 2006 to October 2011 （Evans type III in 4 cases, Evans type IV in 11 cases）, who received bipolar hemiarthroplasty with a two-step osteotomy technique performed by a senior or- thopedic surgeon through posterior approach under general anesthesia. All cases were evaluated by Zuckerman func- tional recovery score （FRS） and operative risk assessment software 1, based on the patients＇ physical and laboratory examinations preoperatively. The duration and blood loss have been recorded. There were 4 male cases （4 hips） and 11 female cases （11 hips）. All prostheses consisted of Link SP II femoral stem and bipolar femoral head. All patients were followed up for more than 1 year. Results： The average preoperative FRS, predictive value of operative morbidity and mortality were 83.7 （81.7- 85.9）, 9.3% （7.3%- 15.0%） and 3.5% （2.3%-4.2%）, respectively. The average operation time was 50 minutes with a mean intraoperative blood loss of 310 ml. There were no operative or anesthetic complications or deaths within 30 days after operation. Sitting up was permitted 3 to 4 days, and partial weight beating was allowed 5 to 7 days after operation. The average FRS was 79.3 at 30 days and 84.9 at 1 year postoperatively. Three patients died of unrelated causes （one due to myocardial infarction and the others due to cerebral hemorrhage during at least one-year follow-up）. Conclusion： Bipolar hemiarthroplasty with a two-step osteotomy technique for unstable intertrochanteric fractures in the senile patients is a good choice for early ambulation and good hip function.展开更多
文摘为了提高导引头稳定平台抗扰性及速度稳态跟踪性能,提出了一种基于扩张状态观测器(Extended State Observer,ESO)的双积分滑模控制器(Double Integral Sliding Mode Controller,DISMC)。首先,采用二阶扩张状态观测器对系统的未知扰动进行估计;然后,采用了双积分滑模控制器实现了系统的低稳态误差跟踪,同时采用了改进的幂次趋近律来削弱控制系统的抖振影响;最后,采用导引头稳定平台进行目标跟踪实验和隔离度性能测试。实验结果表明,与传统基于扰动观测器(Disturbance Observer,DOB)的PI控制方法相比,跟踪3(°)/s的梯形波时,在提出的控制器作用下速度跟踪快速性提高了48 ms,跟踪误差标准差提高了0.0131(°)/s。同时用转台模拟弹体扰动分别为sin(πt)°、3sin(5πt)°、7sin(2πt)°时,系统的隔离度分别提高了2.91%、0.45%、0.7%,表明基于扩张状态观测器的双积分滑模控制器对导引头稳定平台具有较强的抗扰性和较好的跟踪性能。
基金The National Basic Research Program of China(973 Program)(No.2012CB725402)the National Natural Science Foundation of China(No.50978057)Program of Scientific Innovation Research of College Graduate in Jiangsu Province(No.CXLX12_0108)
文摘The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway regularity of two stages 6： 00--7：00 and 7： 00--9：00 is comparatively analyzed, and it is found that both the traffic conditions and the passenger demand affect headway regularity. A bus arrival model, which assumes that the dwell time of a bus is linear in headway, is built to probe the effect of scheduled headway, and the model is simulated by Matlab. The simulation results reveal that the departure intervals and fluctuations affect headway regularity. Longer intervals and less fluctuation mean higher regularity of headway. And, the fluctuation has a more obvious influence on headway regularity than the interval. Controlling the fluctuations of scheduled headway can effectively raise the regularity of headway and improve the level of public transport service.
文摘\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.
基金ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China （No.10374076） and the Natural Science Foundation of Fujian Province （No.E0320001）.
文摘The structural stabilities and electronic structures of Ga atomic chains are studied by the first-principles plane wave pseudopotential method based on the density functional theory. The present calculations show that gallium can form planar chains in linear-, zigzag- and ladder-form one-dimensional structures. The most stable one among the studied structures is the zigzag chain with a unit cell rather close to equilateral triangles with four nearest neighbors, and all the other structures are metastable. The relative structural stability, the energy bands and the charge densities are discussed based on the ab initio calculations and the Jahn-Teller effect.
基金Supported by the National Natural Science Foundation of China(No.60478036)
文摘A simply method to measure the thermal focal length of a LD end-pumped Nd.GdVO4 solid state laser with a stable resonator is presented. By scanning a slit across the field with expression of multi-mode Gaussian distribution behind the output mirror of lasers, the radius and the M^2 factor describing the quality of beam can be measured. The waists of the multi-mode field and the TEM00 mode can be deduced according to the law of multi-mode Gassian beam propagation. Based on the ABOD matrix theory of a stable resonator,the thermal focal length of the active medium can be easily obtained. The thermal focal length of a LD end-pumped Nd. GdVO~ laser has been measured and the experimental results agree with the theoretically analyzed values.
文摘With the growing tension of port shoreline resource in Three Gorges Reservoir area, many wharfs can only be constructed on slippery stratum with poor geological condition, which means buckling failure occurs easily. FEM strength reduction method is used in analyzing slope stability of a wharf in Chongqing, and its accuracy is verified by comparing the acquired results with the computation of traditional limit equilibrium method. On this basis, the influences of reservoir water level variation, overload and backfill material behind the retaining wall, and soil share strength of wharf slope on slippery stratum are analyzed. Analysis shows that, there＇ s a most adverse water level in wharf slope, and the engineering proposals with a certain practical significance such as improve the drainage behind retaining wall, controll overload and improve the strength of backfill soil and subsoil are suggested.
基金National Natural Science Foundation of China(No.50809051)
文摘Firstly,the common design principles for diversion tunnel plug are generalized,and two kinds of numerical analysis methods are discussed.Then the strength reduction FEM is introduced in numerical model analysis and the design steps of the plug's length are illustrated.During the progress to determine the plug's length,the equivalent plastic strain on the potential slip surface is assumed as the flag to tell the failure against sliding,and the plug stability is overall estimated from the plastic zone range and connectivity.
文摘One of ways of intensification of process of manufacture of heterogeneous tinned products of fruits and vegetables is the use of sated water steam （Patent of USSR No. 500792）. This process at application as consumer glass container for such products is especially effective. However, there are some questions which are connected with thermal influence on glass container at realization of such heating. The given research is devoted as the decision of practical questions arising at process engineers.
文摘Abstract： Because of the complex topography in southwest region of China, the water level of the inland river has a large amplitude of variation which causes a frequent diversification of water content in the river slope. The flow caused by the infiltration of the terminal slope stability will induce a great impact on the slope stability of wharf.. This paper uses an ideal elastic-plastic model and the Moore Coulomb yield criterion for numerical simulation. Through the b an k slop e stability of the overhead-type terminal s under the changes of water, we obtained the impact of all factors on the bank slope in the course of water lowering. It was found out that the impact from the cohesion of the geo-materials of the bank slope on the slope stability is greater than that from the internal friction angle.
基金supported by the National Natural Science Foundation of China(Grant No.51076077)National Key Technology R&D Program of China(Grant No.2008BAC48B02)
文摘Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines,in particular Francis turbines.A method of cavitation calculations was proposed to predict the pressure fluctuations induced by draft tube vortices in a model Francis turbine,by solving RANS equations with RNG k-turbulence model and ZGB cavitation model,with modified turbulence viscosity.Three cases with different flow rates at high head were studied.In the study case of part load,two modes of revolutions with the same rotating direction,revolution around the axis of the draft tube cone,and revolution around the core of the vortex rope,can be recognized.The elliptical shaped vortex rope causes anisotropic characteristics of pressure fluctuations around the centerline of the draft tube cone.By analyzing the phase angles of the pressure fluctuations,the role of the vortex rope as an exciter in the oscillating case can be recognized.An analysis of Batchelor instability,i.e.instability in q-vortex like flow structure,has been carried out on the draft tube vortices in these three cases.It can be concluded that the trajectory for study case with part load lies in the region of absolute instability(AI),and it lies in the region of convective instability(CI)for study case with design flow rate.Trajectory for study case with over load lies in the AI region at the inlet of the draft tube,and enters CI region near the end of the elbow.
文摘The paper refers to the behavior of a vaneless diffuser of a radial flow pump in partial flow operating conditions. Some experimental data have been obtained using 2D/2C PIV and unsteady pressure measurements within the diffuser, in various operating conditions. The experimental results at the lower flow rate are compared with two-dimensional numerical calculations.
文摘Objective： To introduce bipolar hemiarthroplasty with a two-step osteotomy technique and observe its clinical result for unstable intertrochanteric frac- tures in senile patients. Methods： Fifteen consecutive patients with unstable intertrochanteric fractures aged from 81 to 92 years with a mean of 85 years were treated in our hospital from August 2006 to October 2011 （Evans type III in 4 cases, Evans type IV in 11 cases）, who received bipolar hemiarthroplasty with a two-step osteotomy technique performed by a senior or- thopedic surgeon through posterior approach under general anesthesia. All cases were evaluated by Zuckerman func- tional recovery score （FRS） and operative risk assessment software 1, based on the patients＇ physical and laboratory examinations preoperatively. The duration and blood loss have been recorded. There were 4 male cases （4 hips） and 11 female cases （11 hips）. All prostheses consisted of Link SP II femoral stem and bipolar femoral head. All patients were followed up for more than 1 year. Results： The average preoperative FRS, predictive value of operative morbidity and mortality were 83.7 （81.7- 85.9）, 9.3% （7.3%- 15.0%） and 3.5% （2.3%-4.2%）, respectively. The average operation time was 50 minutes with a mean intraoperative blood loss of 310 ml. There were no operative or anesthetic complications or deaths within 30 days after operation. Sitting up was permitted 3 to 4 days, and partial weight beating was allowed 5 to 7 days after operation. The average FRS was 79.3 at 30 days and 84.9 at 1 year postoperatively. Three patients died of unrelated causes （one due to myocardial infarction and the others due to cerebral hemorrhage during at least one-year follow-up）. Conclusion： Bipolar hemiarthroplasty with a two-step osteotomy technique for unstable intertrochanteric fractures in the senile patients is a good choice for early ambulation and good hip function.
