In this paper, the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied. By introducing the average method of modified small parameters, we deduced ...In this paper, the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied. By introducing the average method of modified small parameters, we deduced dimensionless coupling equation of three exciters, which converted the problem of synchronization into that of the existence and stability of zero solutions for the average differential equations of the small parameters. Based on the dimensionless coupling torques and characteristics of the cor- responding limited functions, the synchronization criterion for three exciters was derived as the absolute value of dimensionless residual torque difference between arbitrary two motors being less than the maximum of their dimensionless coupling torques. The stability criterion of its synchronous state lies in the double-condition that the inertia coupling matrix is positive definite and all its elements are positive as well. The synchronization determinants are the coefficients of synchronization ability, also called as the general dynamical symmetry coefficients. The double-equilibrium state of the vibrating system is manifested by numeric method, and the numeric and simulation results derived thereof indicate the indispensable and crucial role the structural parameters of the vibrating system play in the stability criterion of synchronous operation. Besides, by adjusting its structural parameters, the elliptical motion of the vibrating system successfully met the requirements in engineering applications.展开更多
The evolution of oxide inclusions during isothermal heating of 18Cr–8Ni stainless steel with yttrium addition at temperatures of 1273 to 1573 K was investigated systematically.Homogeneous spherical Al–Y–Si(–Mn–Cr...The evolution of oxide inclusions during isothermal heating of 18Cr–8Ni stainless steel with yttrium addition at temperatures of 1273 to 1573 K was investigated systematically.Homogeneous spherical Al–Y–Si(–Mn–Cr)oxide inclusions were observed in as-cast steel.After heating,most of the homogeneous inclusions were transformed into heterogeneous inclusions with Y-rich and Al-rich parts,even though some homogeneous oxide particles were still observed at 1273 and 1573 K.With the increase in heating temperature,more large-sized inclusions were formed.The shape of the inclusions also changed from spherical to irregular.The maximum transformation temperature of inclusions was determined to be 1373 K.The evolution mechanism of inclusions during heating was proposed to be the combined effect of the(i)internal transformation of inclusions due to the crystallization of glassy oxide and(ii)interfacial reaction between inclusions and steel matrix.Meanwhile,the internal transformation of inclusions was considered to be the main factor at heating temperatures less than 1473 K.展开更多
Objective:To forecast the visceral leishmaniasis cases using autoregress integrated moving average(ARIMA)and hybrid ARIMAEGARCH model,which offers a scientific basis to control visceral leishmaniasis spread in Kashgar...Objective:To forecast the visceral leishmaniasis cases using autoregress integrated moving average(ARIMA)and hybrid ARIMAEGARCH model,which offers a scientific basis to control visceral leishmaniasis spread in Kashgar Prefecture of Xinjiang,China.Methods:The data used in this paper are monthly visceral leishmaniasis cases in the Kashgar Prefecture of Xinjiang from 2004 to 2016.The sample data between 2004 and 2015 were used for the estimation to choose the best model and the sample data in 2016 were used for the forecast.Time series of visceral leishmaniasis started on 1 January 2004 and ended on 31 December 2016,consisting of 1790 observations reported in Kashgar Prefecture.Results:For Xinjiang,the total number of reported cases were 2187,the male-to-female ratio of cases was 1:1.42.Patients aged between 0 and 10 years accounted for 82.72%of all reported cases and the largest percentage of visceral leishmaniasis cases was detected among scattered children who accounted for 68.82%.The monthly incidences fitted by ARIMA(2,1,2)(1,1,1)12 model were consistent with the real data collected from 2004 to 2015.However,the predicted cases failed to comply with the observed case number;we then attempted to establish a hybrid ARIMA-EGARCH model to fit visceral leishmaniasis.Finally,the ARIMA(2,1,2)(1,1,1)12-EGARCH(1,1)model showed a good estimation when dealing with volatility clustering in the data series.Conclusions:The combined model has been determined as the best prediction model with the root-mean-square error(RMSE)of 7.23%in the validation phase,which means that this model has high validity and rationality and can be used for short-term prediction of visceral leishmaniasis and could be applied to the prevention and control of the disease.展开更多
The stability of the subsea oil and gas production system is heavily influenced by slug flow. One successful method of managing slug flow is to use top valve control based on subsea pipeline pressure. However, the com...The stability of the subsea oil and gas production system is heavily influenced by slug flow. One successful method of managing slug flow is to use top valve control based on subsea pipeline pressure. However, the complexity of production makes it difficult to measure the pressure of subsea pipelines, and measured values are not always accessible in real-time. The research introduces a technique for integrating Unscented Kalman Filter (UKF) and Wavelet Neural Network (WNN) to estimate the state of subsea pipeline pressure using historical data and a state model. The proposed method treats multiphase flow transport as a nonlinear model, with a dynamic WNN serving as the state observer. To achieve real-time state estimation, the WNN is included into the UKF algorithm to create a WNN-based UKF state equation. Integrate WNN and UKF in a novel way to predict system state accurately. The simulated results show that the approach can efficiently predict the inlet pressure and manage the slug flow in real-time using the riser's top pressure, outlet flow and valve opening. This method of estimate can significantly increase the control effect.展开更多
Methanol-to-olefins(MTO)process is one of the most critical pathways to produce low carbon olefins.Typically,the reaction is driven by thermal catalysis,which inevitably needs to consume large amounts of fossil fuel.D...Methanol-to-olefins(MTO)process is one of the most critical pathways to produce low carbon olefins.Typically,the reaction is driven by thermal catalysis,which inevitably needs to consume large amounts of fossil fuel.Developing a new technique to substitute for the fuel burning is urgent for MTO process to improve the industry prospects and sustainability.Herein,we report a novel W_(18)O_(49)/Au/SAPO-34(W/Au/S),a multifunctional photothermal catalyst for the MTO reaction.A high methanol conversion was achieved under xenonum(Xe)lamp irradiation,yielding methyl ether(ME)and ethylene as the main products.The optimized W/Au/S catalysts showed ethylene yield as high as 250μmol in 60 min,which was 2.5 times higher than that of Au/SAPO-34.The physiochemical characterization revealed that the SAPO-34 molecular sieves were surrounded by Au and W_(18)O_(49)nanoparticles,which exhibited a strong localized surface plasmon resonance excitation around 540 nm and light absorption beyond 500 nm.The multifunctional catalysts showed a strong photothermal effect,arising from the broadened light absorption of Au and W_(18)O_(49)nanoparticles,leading to a temperature as high as 250℃on the surface of the catalysts.Mechanism study showed that the superior ethylene selectivity of W/Au/S catalysts was attributed to the moderating acidic sites of W_(18)O_(49)for methanol dehydration to ethylene.This research may provide new insight for designing heterostructures to improve photo-to-chemical conversion performance and is expected to accelerate progress toward the excellent multifunctional photothermal catalysts with broad light absorption for methanol activation and C-C bond formation.展开更多
An improved diffusion couple method was used to simulate the dynamic process of the solid-state reaction at the interface between oxide inclusions and a steel matrix deoxidized by Si and Mn during heat treatment at 14...An improved diffusion couple method was used to simulate the dynamic process of the solid-state reaction at the interface between oxide inclusions and a steel matrix deoxidized by Si and Mn during heat treatment at 1473 K. Experimental results indicated that good contact between the oxide and steel matrix was attained after pre-treatment at 1673 K. In addition, the reaction between the oxide and steel matrix at 1673 K was suppressed, and the effect of this reaction on the diffusion couple experiments at 1473 K was minimized. In the diffusion couple experiments, the diffusion of oxygen from the oxide to the steel matrix resulted in the precipitation of fine oxide particles and a decrease in the Mn content in the steel matrix near the interface after heat treatment at 1473 K. With increasing heat treatment time, the widths of the particle precipitation zone （PPZ） and Mn-depleted zone （MDZ） gradually increased. In addition, the solid-state reaction at the interface between the oxide and steel matrix was intense, and the widths of the PPZ and MDZ increased rapidly during the 0-20 h stage of heat treatment, especially during the 0-5 h stage. The interfacial reaction was retarded, and the rates of width expansion of PPZ and MDZ decreased with increasing heat treatment time.展开更多
基金supported by the National Key Technology R&D Program (2009BAG12A01-F01-3)the National Natural Science Foundation of China (51075063)
文摘In this paper, the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied. By introducing the average method of modified small parameters, we deduced dimensionless coupling equation of three exciters, which converted the problem of synchronization into that of the existence and stability of zero solutions for the average differential equations of the small parameters. Based on the dimensionless coupling torques and characteristics of the cor- responding limited functions, the synchronization criterion for three exciters was derived as the absolute value of dimensionless residual torque difference between arbitrary two motors being less than the maximum of their dimensionless coupling torques. The stability criterion of its synchronous state lies in the double-condition that the inertia coupling matrix is positive definite and all its elements are positive as well. The synchronization determinants are the coefficients of synchronization ability, also called as the general dynamical symmetry coefficients. The double-equilibrium state of the vibrating system is manifested by numeric method, and the numeric and simulation results derived thereof indicate the indispensable and crucial role the structural parameters of the vibrating system play in the stability criterion of synchronous operation. Besides, by adjusting its structural parameters, the elliptical motion of the vibrating system successfully met the requirements in engineering applications.
基金the National Natural Science Foundation of China(Nos.51574190 and51734003)the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-18-009C1)the China Scholarship Council(No.201806460049)。
文摘The evolution of oxide inclusions during isothermal heating of 18Cr–8Ni stainless steel with yttrium addition at temperatures of 1273 to 1573 K was investigated systematically.Homogeneous spherical Al–Y–Si(–Mn–Cr)oxide inclusions were observed in as-cast steel.After heating,most of the homogeneous inclusions were transformed into heterogeneous inclusions with Y-rich and Al-rich parts,even though some homogeneous oxide particles were still observed at 1273 and 1573 K.With the increase in heating temperature,more large-sized inclusions were formed.The shape of the inclusions also changed from spherical to irregular.The maximum transformation temperature of inclusions was determined to be 1373 K.The evolution mechanism of inclusions during heating was proposed to be the combined effect of the(i)internal transformation of inclusions due to the crystallization of glassy oxide and(ii)interfacial reaction between inclusions and steel matrix.Meanwhile,the internal transformation of inclusions was considered to be the main factor at heating temperatures less than 1473 K.
基金supported by the National Natural Science Foundation of China(11961071,61672013,and 81660333)Huaian Key Laboratory for Infectious Diseases Control and Prevention(HAP201704).
文摘Objective:To forecast the visceral leishmaniasis cases using autoregress integrated moving average(ARIMA)and hybrid ARIMAEGARCH model,which offers a scientific basis to control visceral leishmaniasis spread in Kashgar Prefecture of Xinjiang,China.Methods:The data used in this paper are monthly visceral leishmaniasis cases in the Kashgar Prefecture of Xinjiang from 2004 to 2016.The sample data between 2004 and 2015 were used for the estimation to choose the best model and the sample data in 2016 were used for the forecast.Time series of visceral leishmaniasis started on 1 January 2004 and ended on 31 December 2016,consisting of 1790 observations reported in Kashgar Prefecture.Results:For Xinjiang,the total number of reported cases were 2187,the male-to-female ratio of cases was 1:1.42.Patients aged between 0 and 10 years accounted for 82.72%of all reported cases and the largest percentage of visceral leishmaniasis cases was detected among scattered children who accounted for 68.82%.The monthly incidences fitted by ARIMA(2,1,2)(1,1,1)12 model were consistent with the real data collected from 2004 to 2015.However,the predicted cases failed to comply with the observed case number;we then attempted to establish a hybrid ARIMA-EGARCH model to fit visceral leishmaniasis.Finally,the ARIMA(2,1,2)(1,1,1)12-EGARCH(1,1)model showed a good estimation when dealing with volatility clustering in the data series.Conclusions:The combined model has been determined as the best prediction model with the root-mean-square error(RMSE)of 7.23%in the validation phase,which means that this model has high validity and rationality and can be used for short-term prediction of visceral leishmaniasis and could be applied to the prevention and control of the disease.
基金supported by Development Project in Key Technical Field of Sichuan Province(2019ZDZX0030)International Science and Technology Innovation Cooperation Program of Sichuan Province(2021YFH0115)+1 种基金Nanchong-SWPU Science and Technology Strategic Cooperation Project(SXHZ057)Key and Core Technology Breakthrough Project of CNPC(2021ZG08).
文摘The stability of the subsea oil and gas production system is heavily influenced by slug flow. One successful method of managing slug flow is to use top valve control based on subsea pipeline pressure. However, the complexity of production makes it difficult to measure the pressure of subsea pipelines, and measured values are not always accessible in real-time. The research introduces a technique for integrating Unscented Kalman Filter (UKF) and Wavelet Neural Network (WNN) to estimate the state of subsea pipeline pressure using historical data and a state model. The proposed method treats multiphase flow transport as a nonlinear model, with a dynamic WNN serving as the state observer. To achieve real-time state estimation, the WNN is included into the UKF algorithm to create a WNN-based UKF state equation. Integrate WNN and UKF in a novel way to predict system state accurately. The simulated results show that the approach can efficiently predict the inlet pressure and manage the slug flow in real-time using the riser's top pressure, outlet flow and valve opening. This method of estimate can significantly increase the control effect.
基金financially supported by the High-level Innovative Talent Cultivation Project of Guizhou Province(No.GZSQCC2019003)the Natural Science Research Project of Guizhou Provincial Department of Education(No.QJHKY Zi[2021]257)the Academic New Seedling Cultivation and Innovation Exploration Project of Guizhou Institute of Technology(No.GZLGXM-08)。
文摘Methanol-to-olefins(MTO)process is one of the most critical pathways to produce low carbon olefins.Typically,the reaction is driven by thermal catalysis,which inevitably needs to consume large amounts of fossil fuel.Developing a new technique to substitute for the fuel burning is urgent for MTO process to improve the industry prospects and sustainability.Herein,we report a novel W_(18)O_(49)/Au/SAPO-34(W/Au/S),a multifunctional photothermal catalyst for the MTO reaction.A high methanol conversion was achieved under xenonum(Xe)lamp irradiation,yielding methyl ether(ME)and ethylene as the main products.The optimized W/Au/S catalysts showed ethylene yield as high as 250μmol in 60 min,which was 2.5 times higher than that of Au/SAPO-34.The physiochemical characterization revealed that the SAPO-34 molecular sieves were surrounded by Au and W_(18)O_(49)nanoparticles,which exhibited a strong localized surface plasmon resonance excitation around 540 nm and light absorption beyond 500 nm.The multifunctional catalysts showed a strong photothermal effect,arising from the broadened light absorption of Au and W_(18)O_(49)nanoparticles,leading to a temperature as high as 250℃on the surface of the catalysts.Mechanism study showed that the superior ethylene selectivity of W/Au/S catalysts was attributed to the moderating acidic sites of W_(18)O_(49)for methanol dehydration to ethylene.This research may provide new insight for designing heterostructures to improve photo-to-chemical conversion performance and is expected to accelerate progress toward the excellent multifunctional photothermal catalysts with broad light absorption for methanol activation and C-C bond formation.
基金Acknowledgements The authors are grateful to the financial sup- port from the National Natural Science Foundation of China （Nos. 51574020, 51674023, and 51604201 ）.
文摘An improved diffusion couple method was used to simulate the dynamic process of the solid-state reaction at the interface between oxide inclusions and a steel matrix deoxidized by Si and Mn during heat treatment at 1473 K. Experimental results indicated that good contact between the oxide and steel matrix was attained after pre-treatment at 1673 K. In addition, the reaction between the oxide and steel matrix at 1673 K was suppressed, and the effect of this reaction on the diffusion couple experiments at 1473 K was minimized. In the diffusion couple experiments, the diffusion of oxygen from the oxide to the steel matrix resulted in the precipitation of fine oxide particles and a decrease in the Mn content in the steel matrix near the interface after heat treatment at 1473 K. With increasing heat treatment time, the widths of the particle precipitation zone （PPZ） and Mn-depleted zone （MDZ） gradually increased. In addition, the solid-state reaction at the interface between the oxide and steel matrix was intense, and the widths of the PPZ and MDZ increased rapidly during the 0-20 h stage of heat treatment, especially during the 0-5 h stage. The interfacial reaction was retarded, and the rates of width expansion of PPZ and MDZ decreased with increasing heat treatment time.
