Landscape pattern is a widely used concept for the demonstration of landscape characteristic features. The integral spatial distribution trend of landscape elements is interested point in the landscape ecological rese...Landscape pattern is a widely used concept for the demonstration of landscape characteristic features. The integral spatial distribution trend of landscape elements is interested point in the landscape ecological research, especially in those of complex secondary forest regions with confusing mosaics of land cover. Trend surface analysis which used in community and population ecological researches was introduced to reveal the landscape pattern. A reasonable and reliable approach for application of trend surface analysis was provided in detail. As key steps of the approach, uniform grid point sampling method was developed. The efforts were also concentrated at an example of Guandishan forested landscape. Some basic rules of spatial distribution of landscape elements were exclaimed. These will be benefit to the further study in the area to enhance the forest sustainable management and landscape planning.展开更多
Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensi...Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensive model is established for evaluating the e ect of magnetic frequency mixing.A polynomial is selected as the regression function to express explicitly the correlation between the excitation parameters and the frequency-mixing e ect.The excitation parameters were then optimized using genetic algorithm.Magnetic frequency mixing experiments were conducted to measure the surface hardness of some ferromagnetic materials.Frequency mixing is further enhanced under the optimal settings,resulting in an improvement in the measurement sensitivity.The results of this study support the application of the magnetic frequency mixing technique in non-destructive testing.展开更多
To examine the influence of the structural parameters and working parameters of a double-drum regeneration mixing station on its mixing uniformity,the influence of the discrete element method and response surface meth...To examine the influence of the structural parameters and working parameters of a double-drum regeneration mixing station on its mixing uniformity,the influence of the discrete element method and response surface method on the uniformity of the aggregate mixing when the interaction between two different factors was analyzed.A mathematical model of the influence of various factors and interactions on the coefficient of variation of the aggregates was established.The matching of each parameter was optimized with the goal of minimizing the coefficient of variation.The results show that when the aggregate particle size is different,the significance of each parameter affecting its mixing uniformity is also different.Moreover,increasing the speed and reducing the axial installation angle of the blade can reduce the coefficient of variation of the three aggregates.To obtain a good mixing uniformity,the mixing-arm phase angle when the drum inclination angle is large should be smaller than the phase angle when the drum inclination angle is small,and the mixing of large particles should not be arranged with a large mixing-arm phase angle.With a blade radial installation angle of 38°,a blade axial installation angle of 35°,a drum inclination angle of 6°,a drum rotation speed of 10 r/min,and a mixing-arm phase angle of 32°,the aggregate as a whole can exhibit the best mixing uniformity.展开更多
Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliabilit...Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliability for guiding economic dispatch and reducing the risks.Current methods cannot meet the requirement for the operational timeliness of reliability evaluations due to the high computa-tional complexity of the optimal power flow(OPF)calculations of massive contingencies.This paper pro-poses a fully analytical approach to construct fast-to-run analytical functions of reliability indices and avoid reassessments when the load and RES change.The approach consists of uniform design(UD)-based contingency screening and a modified stochastic response surface method(mSRSM).The contin-gency screening method is used to select critical contingencies while considering the uncertainties.The mSRSM is used to construct the analytical functions of the load shedding to the load and RES gener-ation for the selected contingencies.An analytical function of a smooth virtual variable that maps to the load shedding is established in such a way that,when the load and RES vary,the reliability can be assessed within a very short time rather than using laborious OPF calculations.Case studies illustrate the excellent performance of the proposed method for real-time reliability evaluation.展开更多
文摘Landscape pattern is a widely used concept for the demonstration of landscape characteristic features. The integral spatial distribution trend of landscape elements is interested point in the landscape ecological research, especially in those of complex secondary forest regions with confusing mosaics of land cover. Trend surface analysis which used in community and population ecological researches was introduced to reveal the landscape pattern. A reasonable and reliable approach for application of trend surface analysis was provided in detail. As key steps of the approach, uniform grid point sampling method was developed. The efforts were also concentrated at an example of Guandishan forested landscape. Some basic rules of spatial distribution of landscape elements were exclaimed. These will be benefit to the further study in the area to enhance the forest sustainable management and landscape planning.
基金Supported by National Key Research and Development Program of China(Grant No.2017YFF0209703)National Natural Science Foundation of China(Grant Nos.11972053,11527801).
文摘Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensive model is established for evaluating the e ect of magnetic frequency mixing.A polynomial is selected as the regression function to express explicitly the correlation between the excitation parameters and the frequency-mixing e ect.The excitation parameters were then optimized using genetic algorithm.Magnetic frequency mixing experiments were conducted to measure the surface hardness of some ferromagnetic materials.Frequency mixing is further enhanced under the optimal settings,resulting in an improvement in the measurement sensitivity.The results of this study support the application of the magnetic frequency mixing technique in non-destructive testing.
基金The Natural Science Basic Research Plan in Shaanxi Province(No.2017JM5077)the Fundamental Research Funds for the Central Universities under Grant(No.300102259109).
文摘To examine the influence of the structural parameters and working parameters of a double-drum regeneration mixing station on its mixing uniformity,the influence of the discrete element method and response surface method on the uniformity of the aggregate mixing when the interaction between two different factors was analyzed.A mathematical model of the influence of various factors and interactions on the coefficient of variation of the aggregates was established.The matching of each parameter was optimized with the goal of minimizing the coefficient of variation.The results show that when the aggregate particle size is different,the significance of each parameter affecting its mixing uniformity is also different.Moreover,increasing the speed and reducing the axial installation angle of the blade can reduce the coefficient of variation of the three aggregates.To obtain a good mixing uniformity,the mixing-arm phase angle when the drum inclination angle is large should be smaller than the phase angle when the drum inclination angle is small,and the mixing of large particles should not be arranged with a large mixing-arm phase angle.With a blade radial installation angle of 38°,a blade axial installation angle of 35°,a drum inclination angle of 6°,a drum rotation speed of 10 r/min,and a mixing-arm phase angle of 32°,the aggregate as a whole can exhibit the best mixing uniformity.
基金supported by the Joint Research Fund in Smart Grid under cooperative agreement between the National Natural Science Foundation of China(NSFC)and the State Grid Cooperation of China(SGCC,U1966601)the Fundamental Research Funds for the Central Universities of China(2023CDJYXTD-004).
文摘Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliability for guiding economic dispatch and reducing the risks.Current methods cannot meet the requirement for the operational timeliness of reliability evaluations due to the high computa-tional complexity of the optimal power flow(OPF)calculations of massive contingencies.This paper pro-poses a fully analytical approach to construct fast-to-run analytical functions of reliability indices and avoid reassessments when the load and RES change.The approach consists of uniform design(UD)-based contingency screening and a modified stochastic response surface method(mSRSM).The contin-gency screening method is used to select critical contingencies while considering the uncertainties.The mSRSM is used to construct the analytical functions of the load shedding to the load and RES gener-ation for the selected contingencies.An analytical function of a smooth virtual variable that maps to the load shedding is established in such a way that,when the load and RES vary,the reliability can be assessed within a very short time rather than using laborious OPF calculations.Case studies illustrate the excellent performance of the proposed method for real-time reliability evaluation.
