In the process of composite prepreg tape winding,the compaction force could influence the quality of winding products.According to the analysis and experiments,during the winding process of a rocket motor nozzle aft e...In the process of composite prepreg tape winding,the compaction force could influence the quality of winding products.According to the analysis and experiments,during the winding process of a rocket motor nozzle aft exit cone with a winding angle,there would be an error between the deposition speed of tape layers and the feeding speed of the compaction roller,which could influence the compaction force.Both a lack of compaction and overcompaction related to the feeding of the compaction roller could result in defects of winding nozzles.Thus,a flexible winding system has been developed for rocket motor nozzle winding.In the system,feeding of the compaction roller could be adjusted in real time to achieve an invariable compaction force.According to experiments,the force deformation model of the winding tape is a time-varying system.Thus,a forgetting factor recursive least square based parameter estimation proportional-integral-differential（PID）controller has been developed,which could estimate the time-varying parameter and control the compaction force by adjusting the feeding of the compaction roller during the winding process.According to the experimental results,a winding nozzle with fewer voids and a smooth surface could be wounded by the invariable compaction force in the flexible winding system.展开更多
In offshore engineering design, it is considerably significant to have an adequately accurate estimation of marine environmental parameters, in particular, the extreme wind speed of tropical cyclone （TC） with differ...In offshore engineering design, it is considerably significant to have an adequately accurate estimation of marine environmental parameters, in particular, the extreme wind speed of tropical cyclone （TC） with different return periods to guarantee the safety in projected operating life period. Based on the 71-year （1945-2015） TC data in the Northwest Pacific （NWP） by the Joint Typhoon Warning Center （JTWC） of US, a notable growth of the TC intensity is observed in the context of climate change. The fact implies that the traditional stationary model might be incapable of predicting parameters in the extreme events. Therefore, a non-stationary model is proposed in this study to estimate extreme wind speed in the South China Sea （SCS） and NWP. We find that the extreme wind speeds of different return periods exhibit an evident enhancement trend, for instance, the extreme wind speeds with different return periods by non- stationary model are 4.1%-4.4% higher than stationary ones in SCS. Also, the spatial distribution of extreme wind speed in NWP has been examined with the same methodology by dividing the west sea areas of the NWP 0°-45°N, 105°E-130°E into 45 subareas of 5° × 5°, where oil and gas resources are abundant. Similarly, remarkable spacial in-homogeneity in the extreme wind speed is seen in this area： the extreme wind speed with 50-year return period in the subarea （15°N-20°N, 115°E-120°E） of Zhongsha and Dongsha Islands is 73.8 m/s, while that in the subarea of Yellow Sea （30°N-35°N, 120°E-125°E） is only 47.1 m/s. As a result, the present study demonstrates that non-stationary and in-homogeneous effects should be taken into consideration in the estimation of extreme wind speed.展开更多
In this paper further mathematical analysis on 'correlation transfer technique' by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In c...In this paper further mathematical analysis on 'correlation transfer technique' by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In consideration of the influence of skewness of the sea surface elevation on spectral shape, a 'quasi-correlation transfer techique' is developed by the modification of the simulated target spectrum. Meanwhile, the numerical simulation of the non-Gaussian process of wind waves is carried out in view of the two conditions of the surface elevation probability distribution and the spectrum. By using its simulated results, the influence of skewness of the sea surface elevation on two parameters in the distribution of wave heights (which had been fitted by using the Weibull distribution) is analysed. The 'quasi- correlation tranfer technique' is verified and compared with the selection wave data observed in the Jiaozhou Bay in the period of 1980 to 1981. Results make clear (hat, as far as the statistical distribution of the wave heights and the distribution of the maximum (minimum) values of the sea surface elevation are concerned, the said method is obviously superior to the conventional mothed of the linear wave superposition, and that the simulated results are closer to the observation data.展开更多
Using data from more than 40 rivers in the middle Yellow River basin,a study has been made of the influence of coupled wind-water processes on hyperconcentrated flows.A simple“vehicle”model has been proposed to desc...Using data from more than 40 rivers in the middle Yellow River basin,a study has been made of the influence of coupled wind-water processes on hyperconcentrated flows.A simple“vehicle”model has been proposed to describe hyperconcentrated flows.The liquid phase of two-phase flows is a“vehicle”,in which coarse sediment particles are carried as solid-phase.The formation and characteristics of hyperconcentrated flows are closely related with the forma-tion and characteristics of this liquid-phase and solid-phase.Surface materials and geomorphic agents of the middle Yellow River basin form some patterns of combination,which have deep influence on the formation and characteristics of liquid-and solid-phases of hyperconcentrated flows.The combination of high percentages of relatively coarse material with low percentages of fine material appears in the area predominated by the wind process,where the supply of rela-tively coarse sediment is sufficient,but the supply of relatively coarse sediment is not.The com-bination of low percentages of relatively coarse material with high percentages of fine material appears in the area predominated by the water process,where the supply of fine sediment is sufficient,but the supply of fine sediment is not.In the area predominated by coupled wind-water processes appears the combination of medium percentages of coarse and fine materials,and thus both coarse and fine sediments are in relatively sufficient supply.The manner in which the mean annual sediment concentrations of liquid-and solid-phases vary with total suspended sediment concentration is different.With the increased total suspended sediment concentration,mean annual sediment concentration of liquid-phase increased to a limit and then remained constant;however,mean annual sediment concentrations of solid-phase in-creased continuously.Thus,the magnitude of total suspended sediment concentration depends on the supply conditions of relatively coarse sediment and the ability of the flow to carry these relatively coarse sediment particles.In the area predominated by wind process,both the liquid-and the solid-phases cannot develop well,and their concentrations are low.In the area pre-dominated by the water process,the mean annual sediment concentrations of liquid-and solid-phases are also low.Only in the area predominated by coupled wind-water processes,can the conditions most favor the development of both the liquid-and solid-phases,and then the peaks of mean annual sediment concentrations of liquid-and solid-phases appear.Low values of suspended sediment concentrations appear in the areas predominated by the wind process or by the water process,a fact indicating that the predominating wind process or water process does not favor the development of hyperconcentrated flows.Peak values appear in the area where the coupled wind-water processes are predominated,indicating that the cou-pled wind-water processes most favor the development of hyperconcentrated flows.展开更多
This study deals with the neuro-fuzzy (NF) modelling of a real industrial winding process in which the acquired NF model can be exploited to improve control performance and achieve a robust fault-tolerant system. A ne...This study deals with the neuro-fuzzy (NF) modelling of a real industrial winding process in which the acquired NF model can be exploited to improve control performance and achieve a robust fault-tolerant system. A new simulator model is proposed for a winding process using non-linear identification based on a recurrent local linear neuro-fuzzy (RLLNF) network trained by local linear model tree (LOLIMOT), which is an incremental tree-based learning algorithm. The proposed NF models are compared with other known intelligent identifiers, namely multilayer perceptron (MLP) and radial basis function (RBF). Comparison of our proposed non-linear models and associated models obtained through the least square error (LSE) technique (the optimal modelling method for linear systems) confirms that the winding process is a non-linear system. Experimental results show the effectiveness of our proposed NF modelling approach.展开更多
In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the win...In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.展开更多
基金supported by the National Natural Science Foundation of China(No.51375394)
文摘In the process of composite prepreg tape winding,the compaction force could influence the quality of winding products.According to the analysis and experiments,during the winding process of a rocket motor nozzle aft exit cone with a winding angle,there would be an error between the deposition speed of tape layers and the feeding speed of the compaction roller,which could influence the compaction force.Both a lack of compaction and overcompaction related to the feeding of the compaction roller could result in defects of winding nozzles.Thus,a flexible winding system has been developed for rocket motor nozzle winding.In the system,feeding of the compaction roller could be adjusted in real time to achieve an invariable compaction force.According to experiments,the force deformation model of the winding tape is a time-varying system.Thus,a forgetting factor recursive least square based parameter estimation proportional-integral-differential（PID）controller has been developed,which could estimate the time-varying parameter and control the compaction force by adjusting the feeding of the compaction roller during the winding process.According to the experimental results,a winding nozzle with fewer voids and a smooth surface could be wounded by the invariable compaction force in the flexible winding system.
基金financially supported by the Ministry of Science and Technology(863 program)(2006AA09A103-4)the National Natural Science Foundation of China(11232012)the Chinese Academy of Sciences(CAS)knowledge innovation program(KJCXYW-L02)
文摘In offshore engineering design, it is considerably significant to have an adequately accurate estimation of marine environmental parameters, in particular, the extreme wind speed of tropical cyclone （TC） with different return periods to guarantee the safety in projected operating life period. Based on the 71-year （1945-2015） TC data in the Northwest Pacific （NWP） by the Joint Typhoon Warning Center （JTWC） of US, a notable growth of the TC intensity is observed in the context of climate change. The fact implies that the traditional stationary model might be incapable of predicting parameters in the extreme events. Therefore, a non-stationary model is proposed in this study to estimate extreme wind speed in the South China Sea （SCS） and NWP. We find that the extreme wind speeds of different return periods exhibit an evident enhancement trend, for instance, the extreme wind speeds with different return periods by non- stationary model are 4.1%-4.4% higher than stationary ones in SCS. Also, the spatial distribution of extreme wind speed in NWP has been examined with the same methodology by dividing the west sea areas of the NWP 0°-45°N, 105°E-130°E into 45 subareas of 5° × 5°, where oil and gas resources are abundant. Similarly, remarkable spacial in-homogeneity in the extreme wind speed is seen in this area： the extreme wind speed with 50-year return period in the subarea （15°N-20°N, 115°E-120°E） of Zhongsha and Dongsha Islands is 73.8 m/s, while that in the subarea of Yellow Sea （30°N-35°N, 120°E-125°E） is only 47.1 m/s. As a result, the present study demonstrates that non-stationary and in-homogeneous effects should be taken into consideration in the estimation of extreme wind speed.
文摘In this paper further mathematical analysis on 'correlation transfer technique' by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In consideration of the influence of skewness of the sea surface elevation on spectral shape, a 'quasi-correlation transfer techique' is developed by the modification of the simulated target spectrum. Meanwhile, the numerical simulation of the non-Gaussian process of wind waves is carried out in view of the two conditions of the surface elevation probability distribution and the spectrum. By using its simulated results, the influence of skewness of the sea surface elevation on two parameters in the distribution of wave heights (which had been fitted by using the Weibull distribution) is analysed. The 'quasi- correlation tranfer technique' is verified and compared with the selection wave data observed in the Jiaozhou Bay in the period of 1980 to 1981. Results make clear (hat, as far as the statistical distribution of the wave heights and the distribution of the maximum (minimum) values of the sea surface elevation are concerned, the said method is obviously superior to the conventional mothed of the linear wave superposition, and that the simulated results are closer to the observation data.
基金This study was supported by the National Natural Science Foundation of Chinathe Yellow River Water Conservancy Commission(Grant Nos.40271019 and 50239080).
文摘Using data from more than 40 rivers in the middle Yellow River basin,a study has been made of the influence of coupled wind-water processes on hyperconcentrated flows.A simple“vehicle”model has been proposed to describe hyperconcentrated flows.The liquid phase of two-phase flows is a“vehicle”,in which coarse sediment particles are carried as solid-phase.The formation and characteristics of hyperconcentrated flows are closely related with the forma-tion and characteristics of this liquid-phase and solid-phase.Surface materials and geomorphic agents of the middle Yellow River basin form some patterns of combination,which have deep influence on the formation and characteristics of liquid-and solid-phases of hyperconcentrated flows.The combination of high percentages of relatively coarse material with low percentages of fine material appears in the area predominated by the wind process,where the supply of rela-tively coarse sediment is sufficient,but the supply of relatively coarse sediment is not.The com-bination of low percentages of relatively coarse material with high percentages of fine material appears in the area predominated by the water process,where the supply of fine sediment is sufficient,but the supply of fine sediment is not.In the area predominated by coupled wind-water processes appears the combination of medium percentages of coarse and fine materials,and thus both coarse and fine sediments are in relatively sufficient supply.The manner in which the mean annual sediment concentrations of liquid-and solid-phases vary with total suspended sediment concentration is different.With the increased total suspended sediment concentration,mean annual sediment concentration of liquid-phase increased to a limit and then remained constant;however,mean annual sediment concentrations of solid-phase in-creased continuously.Thus,the magnitude of total suspended sediment concentration depends on the supply conditions of relatively coarse sediment and the ability of the flow to carry these relatively coarse sediment particles.In the area predominated by wind process,both the liquid-and the solid-phases cannot develop well,and their concentrations are low.In the area pre-dominated by the water process,the mean annual sediment concentrations of liquid-and solid-phases are also low.Only in the area predominated by coupled wind-water processes,can the conditions most favor the development of both the liquid-and solid-phases,and then the peaks of mean annual sediment concentrations of liquid-and solid-phases appear.Low values of suspended sediment concentrations appear in the areas predominated by the wind process or by the water process,a fact indicating that the predominating wind process or water process does not favor the development of hyperconcentrated flows.Peak values appear in the area where the coupled wind-water processes are predominated,indicating that the cou-pled wind-water processes most favor the development of hyperconcentrated flows.
文摘This study deals with the neuro-fuzzy (NF) modelling of a real industrial winding process in which the acquired NF model can be exploited to improve control performance and achieve a robust fault-tolerant system. A new simulator model is proposed for a winding process using non-linear identification based on a recurrent local linear neuro-fuzzy (RLLNF) network trained by local linear model tree (LOLIMOT), which is an incremental tree-based learning algorithm. The proposed NF models are compared with other known intelligent identifiers, namely multilayer perceptron (MLP) and radial basis function (RBF). Comparison of our proposed non-linear models and associated models obtained through the least square error (LSE) technique (the optimal modelling method for linear systems) confirms that the winding process is a non-linear system. Experimental results show the effectiveness of our proposed NF modelling approach.
文摘In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.
