A method to forecast the over-excavation of underground opening by using the Bayes discriminant analysis(BDA)theory was presented.The Bayes discriminant analysis theory was introduced.Based on an engineering example,t...A method to forecast the over-excavation of underground opening by using the Bayes discriminant analysis(BDA)theory was presented.The Bayes discriminant analysis theory was introduced.Based on an engineering example,the factors influencing the over-excavation of underground opening were taken into account to build a forecast BDA model,and the prior information about over-excavation of underground opening was also taken into consideration.Five parameters influencing the over-excavation of opening,including 2 groups of joints,1 group of layer surface,extension and space between structure faces were selected as geometric parameters.Engineering data in an underground opening were used as the training samples.The cross-validation method was introduced to verify the stability of BDA model and the ratio of mistake-discrimination was equal to zero after the BDA model was trained.Data in an underground engineering were used to test the discriminant ability of BDA model.The results show that five forecast results are identical with the actual situation and BDA can be used in practical engineering.展开更多
The paper analyzes the characteristics and causes of formation of slotting allowances in China on the base of literature review on slotting allowances. The author believes that the government should take measures to m...The paper analyzes the characteristics and causes of formation of slotting allowances in China on the base of literature review on slotting allowances. The author believes that the government should take measures to make slotting allowances more reasonable and not to interfere necessary competition.展开更多
Aero-engine fan blades of ten use a cavity structure to improve the thrust-to-weight ratio of the aircraft.However,the use of the cavity structure brings a series of difficulties to the manufacturing and processing of...Aero-engine fan blades of ten use a cavity structure to improve the thrust-to-weight ratio of the aircraft.However,the use of the cavity structure brings a series of difficulties to the manufacturing and processing of the blades.Due to the limitation of blade manufacturing technology,it is difficult for the internal cavity structure to achieve the designed contour shape,so the blade has uneven wall thickness and poor consistency,which affects the fatigue performance and airflow dynamic performance of the blade.In order to reduce the influence of uneven wall thickness,this paper proposes a grinding allowance extraction method considering the double dimension constraints(DDC)of the inner and outer contours of the hollow blade.Constrain the two dimensions of the inner and outer contours of the hollow blade.On the premise of satisfying the outer contour constraints,the machining model of the blade is modified according to the distribution of the inwall contour to obtain a more reasonable distribution of the grinding allowance.On the premise of satisfying the contour constraints,according to the distribution of the inwall contour,the machining model of the blade is modified to obtain a more reasonable distribution of the grinding allowance.Through the grinding experiment of the hollow blade,the surface roughness is below Ra0.4μm,and the contour accuracy is between-0.05~0.14 mm,which meets the processing requirements.Compared with the allowance extraction method that only considers the contour,the problem of poor wall thickness consistency can be effectively improved.It can be used to extract the allowance of aero-engine blades with hollow features,which lays a foundation for the study of hollow blade grinding methods with high service performance.展开更多
As the largest source of carbon emissions in China,the thermal power industry is the only emission-controlled industry in the first national carbon market compliance cycle.Its conversion to clean-energy generation tec...As the largest source of carbon emissions in China,the thermal power industry is the only emission-controlled industry in the first national carbon market compliance cycle.Its conversion to clean-energy generation technologies is also an important means of reducing CO_(2)emissions and achieving the carbon peak and carbon neutral commitments.This study used fractional Brownian motion to describe the energy-switching cost and constructed a stochastic optimization model on carbon allowance(CA)trading volume and emission-reduction strategy during compliance period with the Hurst exponent and volatility coefficient in the model estimated.We defined the optimal compliance cost of thermal power enterprises as the form of the unique solution of the Hamilton–Jacobi–Bellman equation by combining the dynamic optimization principle and the fractional It?’s formula.In this manner,we obtained the models for optimal emission reduction and equilibrium CA price.Our numerical analysis revealed that,within a compliance period of 2021–2030,the optimal reductions and desired equilibrium prices of CAs changed concurrently,with an increasing trend annually in different peak-year scenarios.Furthermore,sensitivity analysis revealed that the energy price indirectly affected the equilibrium CA price by influencing the Hurst exponent,the depreciation rate positively impacted the CA price,and increasing the initial CA reduced the optimal reduction and the CA price.Our findings can be used to develop optimal emission-reduction strategies for thermal power enterprises and carbon pricing in the carbon market.展开更多
基金Project(50490274)supported by the National Natural Science Foundation of China
文摘A method to forecast the over-excavation of underground opening by using the Bayes discriminant analysis(BDA)theory was presented.The Bayes discriminant analysis theory was introduced.Based on an engineering example,the factors influencing the over-excavation of underground opening were taken into account to build a forecast BDA model,and the prior information about over-excavation of underground opening was also taken into consideration.Five parameters influencing the over-excavation of opening,including 2 groups of joints,1 group of layer surface,extension and space between structure faces were selected as geometric parameters.Engineering data in an underground opening were used as the training samples.The cross-validation method was introduced to verify the stability of BDA model and the ratio of mistake-discrimination was equal to zero after the BDA model was trained.Data in an underground engineering were used to test the discriminant ability of BDA model.The results show that five forecast results are identical with the actual situation and BDA can be used in practical engineering.
文摘The paper analyzes the characteristics and causes of formation of slotting allowances in China on the base of literature review on slotting allowances. The author believes that the government should take measures to make slotting allowances more reasonable and not to interfere necessary competition.
基金Supported by National Natural Science Foundation of China(Grant No.U1908232)National Science and Technology Major Project(Grant No.2017-VII-0002-0095).
文摘Aero-engine fan blades of ten use a cavity structure to improve the thrust-to-weight ratio of the aircraft.However,the use of the cavity structure brings a series of difficulties to the manufacturing and processing of the blades.Due to the limitation of blade manufacturing technology,it is difficult for the internal cavity structure to achieve the designed contour shape,so the blade has uneven wall thickness and poor consistency,which affects the fatigue performance and airflow dynamic performance of the blade.In order to reduce the influence of uneven wall thickness,this paper proposes a grinding allowance extraction method considering the double dimension constraints(DDC)of the inner and outer contours of the hollow blade.Constrain the two dimensions of the inner and outer contours of the hollow blade.On the premise of satisfying the outer contour constraints,the machining model of the blade is modified according to the distribution of the inwall contour to obtain a more reasonable distribution of the grinding allowance.On the premise of satisfying the contour constraints,according to the distribution of the inwall contour,the machining model of the blade is modified to obtain a more reasonable distribution of the grinding allowance.Through the grinding experiment of the hollow blade,the surface roughness is below Ra0.4μm,and the contour accuracy is between-0.05~0.14 mm,which meets the processing requirements.Compared with the allowance extraction method that only considers the contour,the problem of poor wall thickness consistency can be effectively improved.It can be used to extract the allowance of aero-engine blades with hollow features,which lays a foundation for the study of hollow blade grinding methods with high service performance.
基金like to thank Major Program of National Philosophy and Social Science Foundation of China(Grant No.21ZDA086)National Natural Science Foundation of China(Grant No.71974188),and Jiangsu Soft Science Fund(Grant No.BR2022007).
文摘As the largest source of carbon emissions in China,the thermal power industry is the only emission-controlled industry in the first national carbon market compliance cycle.Its conversion to clean-energy generation technologies is also an important means of reducing CO_(2)emissions and achieving the carbon peak and carbon neutral commitments.This study used fractional Brownian motion to describe the energy-switching cost and constructed a stochastic optimization model on carbon allowance(CA)trading volume and emission-reduction strategy during compliance period with the Hurst exponent and volatility coefficient in the model estimated.We defined the optimal compliance cost of thermal power enterprises as the form of the unique solution of the Hamilton–Jacobi–Bellman equation by combining the dynamic optimization principle and the fractional It?’s formula.In this manner,we obtained the models for optimal emission reduction and equilibrium CA price.Our numerical analysis revealed that,within a compliance period of 2021–2030,the optimal reductions and desired equilibrium prices of CAs changed concurrently,with an increasing trend annually in different peak-year scenarios.Furthermore,sensitivity analysis revealed that the energy price indirectly affected the equilibrium CA price by influencing the Hurst exponent,the depreciation rate positively impacted the CA price,and increasing the initial CA reduced the optimal reduction and the CA price.Our findings can be used to develop optimal emission-reduction strategies for thermal power enterprises and carbon pricing in the carbon market.
