Topology optimization of heterogeneous structures can find significant use in a wide range of applications,and its fabrication has been made possible by recent advances in additive manufacturing.However,the optimizati...Topology optimization of heterogeneous structures can find significant use in a wide range of applications,and its fabrication has been made possible by recent advances in additive manufacturing.However,the optimization procedure is computationally expensive,as each structural update requires the re-evaluation of the properties.The computational time is the major limiting factor in large-scale and complex structural optimization.In this study,a convolutional neural network(CNN)model for predicting effective thermal conductivity inspired by the VGG networks is proposed.Trained using 130,000 unique binary images,the model achieves high predictive accuracy.Specifically,it shows a mean absolute percent error(MAPE)of 0.35%in testing when the thermal conductivity of the solid is ten times larger than the fluid,and when the thermal conductivities assigned are that of aluminum and water,the MAPE is 2.35%.The prediction time is 15 ms for a single image with 128×128 pixels,which is 3 to 5 orders of magnitude faster than a finite volume simulation.When employed in topology optimization,the CNN retains a MAPE between 0.67%and 11.8%for different cases.The CNN model correctly predicts trends in effective thermal conductivity and improves the structure to close proximity of a theoretical maximum in all cases.展开更多
WITH the rapid development of aerospace, industrial robots, numerical control machine tool and other high-end equipment, electrical machine system, as the core power source, requires a higher torque performance. High ...WITH the rapid development of aerospace, industrial robots, numerical control machine tool and other high-end equipment, electrical machine system, as the core power source, requires a higher torque performance. High torque density means that the machine has a smaller size and weight, which is critical in aerospace, electric vehicles and other applications where machine volume and mass requirements are stringent. In industrial robots and numerical control machine tools, low torque pulsation has an important effect on positioning accuracy and running smoothness. In this context, high torque performance machine system has gradually become an important research and development branch in the field.展开更多
Ultra-high nickel material is considered to be a promising cathode material.However,with the increase of nickel content,the interfacial side reactions between the cathode and electrolyte become increasingly serious.He...Ultra-high nickel material is considered to be a promising cathode material.However,with the increase of nickel content,the interfacial side reactions between the cathode and electrolyte become increasingly serious.Herein,an atomically controllable ionic conductor Li_(3)PO_(4)(LPO)coating is deposited on the LiNi_(0.90)Co_(0.06)Mn_(0.04)O_(2)(NCM9064)based electrode by the atomic layer deposition method.The results shows that the LPO coating is uniformly and densely covered on the surface of secondary particles of NCM9064,helping to prevent the direct contact between the electrolyte and cathode during the chargingdischarging process.In addition,the coating layer is electrochemically stable.As a result,the interfacial side reactions during the long cycle are effectively suppressed,and the solid electrolyte interphase layer at the interface is stabilized.The electrode with 20 layers of LPO deposition(ALD-LPO-20)exhibits an excellent capacity retention of 81%after 200 cycles in 2.8-4.3 V at 25℃,which is 18%higher than the unmodified material(ALD-LPO-0).Besides,the moderate LPO coating improves the rate capability and high temperature cycling performance of NCM9064.This study provides a method for the modification of ultra-high nickel cathode materials and corresponding electrodes.展开更多
The development of an ideal cathode for Li-O_(2)battery(LOB)has been a great challenge in achieving high discharge capacity,enhanced stability,and longevity.The formation of undesired and irreversible discharge produc...The development of an ideal cathode for Li-O_(2)battery(LOB)has been a great challenge in achieving high discharge capacity,enhanced stability,and longevity.The formation of undesired and irreversible discharge products on the surface of current cathode materials limit the life span of the LOB.In this study,we report the systematic electrochemical study to compare the performance of LOB employing a unique graphitic nanostructured carbon architecture,i.e.,vertically aligned carbon nanofiber(VACNF)arrays,as the cathode materials.Transition metal(Ni)and noble metal alloy(PtRu)are further deposited on the VACNF array as electrocatalysts to improve the discharge/charge processes at the cathode.The structure of as-prepared electrodes was examined with the field emission scanning electron microscopy,high-resolution transmission electron microscopy,and X-ray photoelectron spectroscopy(XPS).The LOB with VACNF-Ni electrode delivered the highest specific and areal discharge capacities(14.92 Ah·g^(−1),4.32 mAh·cm^(−2))at 0.1 mA·cm^(−2)current density as compared with VACNF-PtRu(9.07 Ah·g^(−1),2.62 mAh·cm^(−2)),bare VACNF(5.55 Ah·g^(−1),1.60 mAh·cm^(−2))and commercial Vulcan XC(3.83 Ah·g^(−1),1.91 mAh·cm^(−2)).Cycling stability tests revealed the superior performance of VACNF-PtRu with 27 cycles as compared with VACNF-Ni(13 cycles),VACNF(8 cycles),and Vulcan XC(3 cycles).The superior cycling stability of VACNF-PtRu can be attributed to its ability to suppress the formation of Li2CO3 during the discharge cycle,as elucidated by XPS analysis of discharged samples.We also investigated the impact of carbon cloth and carbon fiber as cathode electrode substrate on the performance of LOB.展开更多
Permanent magnet synchronous motors(PMSMs)are widely used because of their high power/torque density and high efficiency,particularly in applications with strict requirements for arrangement space or weight,such as in...Permanent magnet synchronous motors(PMSMs)are widely used because of their high power/torque density and high efficiency,particularly in applications with strict requirements for arrangement space or weight,such as in the electric vehicle(EV)and aerospace fields.Recently,the PMSM torque ripple problem has received increasing interest because PMSM drive requirements continuously improve.For applications with complex transmission and a wide speed range,torque ripple can easily cause system resonance,which deteriorates the driving performance.The research status and latest progress in the minimization of PMSM torque ripple based on harmonic injection are discussed.First,the causes of PMSM torque ripple are analyzed.Subsequently,the research status of the PMSM analytical model is introduced,and multiple current harmonic control and optimization methods are described in detail.Finally,future development trends in this field are analyzed.展开更多
A pot experiment was conducted in a greenhouse with three alfalfa(Medicago sativa) cultivars,Aohan, Zhongmu No.1 and Sanditi, to examine the morphological and physiological responses of alfalfa to water stress. The re...A pot experiment was conducted in a greenhouse with three alfalfa(Medicago sativa) cultivars,Aohan, Zhongmu No.1 and Sanditi, to examine the morphological and physiological responses of alfalfa to water stress. The response of alfalfa to water stress at different growth stages was generally similar, but varied among cultivars. At the branching, flowering and podding stages, the shoot biomasses of Aohan and Zhongmu No.1 were greatly affected by, and responded quickly to, water stress. The shoot biomass of Sanditi was not affected by mild water stress, but had a slight response to moderate and severe water stress. The root/shoot ratios in Aohan and Zhongmu No.1 were more sensitive to water stress than in Sanditi, with the root/shoot ratio in Aohan increasing most significantly. At flowering, the root/shoot ratio was the highest and the effect of water stress the greatest. The abscisic acid(ABA) concentration in the roots of Aohan and Zhongmu No.1 increased under water stress, while in Sanditi there was only a slight or delayed response of ABA concentration.展开更多
文摘Topology optimization of heterogeneous structures can find significant use in a wide range of applications,and its fabrication has been made possible by recent advances in additive manufacturing.However,the optimization procedure is computationally expensive,as each structural update requires the re-evaluation of the properties.The computational time is the major limiting factor in large-scale and complex structural optimization.In this study,a convolutional neural network(CNN)model for predicting effective thermal conductivity inspired by the VGG networks is proposed.Trained using 130,000 unique binary images,the model achieves high predictive accuracy.Specifically,it shows a mean absolute percent error(MAPE)of 0.35%in testing when the thermal conductivity of the solid is ten times larger than the fluid,and when the thermal conductivities assigned are that of aluminum and water,the MAPE is 2.35%.The prediction time is 15 ms for a single image with 128×128 pixels,which is 3 to 5 orders of magnitude faster than a finite volume simulation.When employed in topology optimization,the CNN retains a MAPE between 0.67%and 11.8%for different cases.The CNN model correctly predicts trends in effective thermal conductivity and improves the structure to close proximity of a theoretical maximum in all cases.
文摘WITH the rapid development of aerospace, industrial robots, numerical control machine tool and other high-end equipment, electrical machine system, as the core power source, requires a higher torque performance. High torque density means that the machine has a smaller size and weight, which is critical in aerospace, electric vehicles and other applications where machine volume and mass requirements are stringent. In industrial robots and numerical control machine tools, low torque pulsation has an important effect on positioning accuracy and running smoothness. In this context, high torque performance machine system has gradually become an important research and development branch in the field.
基金supported by the National Natural Science Foundation of China(No.52174285)the Science and Technology Innovation Program of Hunan Province(No.2022RC3048)+1 种基金the Key Research and Development Program of Yunnan Province(No.202103AA080019)the Research Foundation of Education Bureau of Hunan Province(No.18B477).
文摘Ultra-high nickel material is considered to be a promising cathode material.However,with the increase of nickel content,the interfacial side reactions between the cathode and electrolyte become increasingly serious.Herein,an atomically controllable ionic conductor Li_(3)PO_(4)(LPO)coating is deposited on the LiNi_(0.90)Co_(0.06)Mn_(0.04)O_(2)(NCM9064)based electrode by the atomic layer deposition method.The results shows that the LPO coating is uniformly and densely covered on the surface of secondary particles of NCM9064,helping to prevent the direct contact between the electrolyte and cathode during the chargingdischarging process.In addition,the coating layer is electrochemically stable.As a result,the interfacial side reactions during the long cycle are effectively suppressed,and the solid electrolyte interphase layer at the interface is stabilized.The electrode with 20 layers of LPO deposition(ALD-LPO-20)exhibits an excellent capacity retention of 81%after 200 cycles in 2.8-4.3 V at 25℃,which is 18%higher than the unmodified material(ALD-LPO-0).Besides,the moderate LPO coating improves the rate capability and high temperature cycling performance of NCM9064.This study provides a method for the modification of ultra-high nickel cathode materials and corresponding electrodes.
基金S.S.H.Z.and X.L.L.highly appreciate the support from the National Science Foundation(Nos.1833048 and 1941083)The work by J.L.’s group is partially supported by the National Science Foundation under grant(No.CBET-2054754).
文摘The development of an ideal cathode for Li-O_(2)battery(LOB)has been a great challenge in achieving high discharge capacity,enhanced stability,and longevity.The formation of undesired and irreversible discharge products on the surface of current cathode materials limit the life span of the LOB.In this study,we report the systematic electrochemical study to compare the performance of LOB employing a unique graphitic nanostructured carbon architecture,i.e.,vertically aligned carbon nanofiber(VACNF)arrays,as the cathode materials.Transition metal(Ni)and noble metal alloy(PtRu)are further deposited on the VACNF array as electrocatalysts to improve the discharge/charge processes at the cathode.The structure of as-prepared electrodes was examined with the field emission scanning electron microscopy,high-resolution transmission electron microscopy,and X-ray photoelectron spectroscopy(XPS).The LOB with VACNF-Ni electrode delivered the highest specific and areal discharge capacities(14.92 Ah·g^(−1),4.32 mAh·cm^(−2))at 0.1 mA·cm^(−2)current density as compared with VACNF-PtRu(9.07 Ah·g^(−1),2.62 mAh·cm^(−2)),bare VACNF(5.55 Ah·g^(−1),1.60 mAh·cm^(−2))and commercial Vulcan XC(3.83 Ah·g^(−1),1.91 mAh·cm^(−2)).Cycling stability tests revealed the superior performance of VACNF-PtRu with 27 cycles as compared with VACNF-Ni(13 cycles),VACNF(8 cycles),and Vulcan XC(3 cycles).The superior cycling stability of VACNF-PtRu can be attributed to its ability to suppress the formation of Li2CO3 during the discharge cycle,as elucidated by XPS analysis of discharged samples.We also investigated the impact of carbon cloth and carbon fiber as cathode electrode substrate on the performance of LOB.
基金National Natural Science Foundation of China(52107052)in part by the Natural Science Foundation of Shandong Province(ZR2021QE222 and ZR2021YQ33).
文摘Permanent magnet synchronous motors(PMSMs)are widely used because of their high power/torque density and high efficiency,particularly in applications with strict requirements for arrangement space or weight,such as in the electric vehicle(EV)and aerospace fields.Recently,the PMSM torque ripple problem has received increasing interest because PMSM drive requirements continuously improve.For applications with complex transmission and a wide speed range,torque ripple can easily cause system resonance,which deteriorates the driving performance.The research status and latest progress in the minimization of PMSM torque ripple based on harmonic injection are discussed.First,the causes of PMSM torque ripple are analyzed.Subsequently,the research status of the PMSM analytical model is introduced,and multiple current harmonic control and optimization methods are described in detail.Finally,future development trends in this field are analyzed.
基金funded by the Agricultural Research System (CARS-34)the National Major Research and Development (2016YFC0500608)the National Natural Science Foundation of China (31372370)
文摘A pot experiment was conducted in a greenhouse with three alfalfa(Medicago sativa) cultivars,Aohan, Zhongmu No.1 and Sanditi, to examine the morphological and physiological responses of alfalfa to water stress. The response of alfalfa to water stress at different growth stages was generally similar, but varied among cultivars. At the branching, flowering and podding stages, the shoot biomasses of Aohan and Zhongmu No.1 were greatly affected by, and responded quickly to, water stress. The shoot biomass of Sanditi was not affected by mild water stress, but had a slight response to moderate and severe water stress. The root/shoot ratios in Aohan and Zhongmu No.1 were more sensitive to water stress than in Sanditi, with the root/shoot ratio in Aohan increasing most significantly. At flowering, the root/shoot ratio was the highest and the effect of water stress the greatest. The abscisic acid(ABA) concentration in the roots of Aohan and Zhongmu No.1 increased under water stress, while in Sanditi there was only a slight or delayed response of ABA concentration.
