The high controllability and high resolution control of linear ultrasonic motors depend on effective control of driving signals.For a good control characteristic,step control which the driver output turned off and on ...The high controllability and high resolution control of linear ultrasonic motors depend on effective control of driving signals.For a good control characteristic,step control which the driver output turned off and on was used.Therefore,a novel dual PWM topology structure ultrasonic motor driver was designed and analyzed.According to the characteristics of the circuits,two kinds of hardware turned off methods named methods A and B were discussed.The differences of the voltage applied on motor by different methods were figured out.Finally,a series of experiments were carried out in the clean room to study the influence of step characteristic by different turn off methods.The experimental results show that the steplength was 230 nm by method A and 125 nm by method B,while cycles of driving signals were 6.The method B has a smaller steplength when cycles are 6.The average steplength varies in non-linear while driving cycles changing.The steplength varies approximately in linear while voltage amplitude changing.Therefore,method B is better to implement step control,because it gets a better control in positioning system.展开更多
Located along the border between Zhejiang and Fujian provinces, Taishun has exuberant vegetation and rich timber resources because the Xianxialing Mountain range runs across it. About 500 years ago during the Ming Dyn...Located along the border between Zhejiang and Fujian provinces, Taishun has exuberant vegetation and rich timber resources because the Xianxialing Mountain range runs across it. About 500 years ago during the Ming Dynasty, the local people began to use the abundant timber to make various types展开更多
This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the ange...This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the angel of perforation, on the fluid flow and heat transfer. The numerical results appeared in good agreement with previous experimental data under the same operating conditions. The results indicated that large size and positive angle of perforation changed the fluid flow pattern and the local Nusselt-number distribution fundamentally. It is noteworthy that a more uniform distribution of Nusselt-number was achieved by increasing the diameter of perforation.展开更多
The 15th ITMF Corona-Survey shows that the business situation plunged into negative territory in July 2022.The business situation is worse in Asia than in the rest of the world.Textile machinery is the only segment st...The 15th ITMF Corona-Survey shows that the business situation plunged into negative territory in July 2022.The business situation is worse in Asia than in the rest of the world.Textile machinery is the only segment still in positive territory.Business expectations have also turned negative for the first time since the start of survey in May 2021.South-East Asia and South America are relatively more optimistic,downstream segments as well.展开更多
Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved sur...Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved surface roughness of polycrystalline materials.However,it is difficult to establish a purely theoretical model for surface roughness with consideration of the grain boundary effect using conventional analytical methods.In this work,a theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials is proposed.The kinematic–dynamic roughness component in relation to the tool profile duplication effect,work material plastic side flow,relative vibration between the diamond tool and workpiece,etc,is theoretically calculated.The material-defect roughness component is modeled with a cascade forward neural network.In the neural network,the ratio of maximum undeformed chip thickness to cutting edge radius RT S,work material properties(misorientation angle θ_(g) and grain size d_(g)),and spindle rotation speed n s are configured as input variables.The material-defect roughness component is set as the output variable.To validate the developed model,polycrystalline copper with a gradient distribution of grains prepared by friction stir processing is machined with various processing parameters and different diamond tools.Compared with the previously developed model,obvious improvement in the prediction accuracy is observed with this hybrid prediction model.Based on this model,the influences of different factors on the surface roughness of polycrystalline materials are discussed.The influencing mechanism of the misorientation angle and grain size is quantitatively analyzed.Two fracture modes,including transcrystalline and intercrystalline fractures at different RTS values,are observed.Meanwhile,optimal processing parameters are obtained with a simulated annealing algorithm.Cutting experiments are performed with the optimal parameters,and a flat surface finish with Sa 1.314 nm is finally achieved.The developed model and corresponding new findings in this work are beneficial for accurately predicting the surface roughness of polycrystalline materials and understanding the impacting mechanism of material defects in diamond turning.展开更多
White layers in hard turned surfaces were identified and measured as a function ot turning parameters based on the Taguchi method. It reveals that white layers generate on the machine surface in the absence of tool fl...White layers in hard turned surfaces were identified and measured as a function ot turning parameters based on the Taguchi method. It reveals that white layers generate on the machine surface in the absence of tool flank wear, and white layer depth varies with the different combinations of hard turning parameters. Turning speed has the most important impact on white layer depth, feed rate follows, and cutting depth at last. The white layer generation consequently suggests a strong couple relation to the heat generation and thermal process of hard turning operation. White layer disappears under an optimal combination of turning parameters by Taguchi method. It suggests that a superior surface integrity without white layer is feasible under some selected combinations of turning parameters by a sharp CBN cutting tool.展开更多
Present work highlights application of utility theory combined with Principal Component Analysis (PCA) and Taguchi’s robust design for simultaneous optimization of correlated multiple surface quality characteristics ...Present work highlights application of utility theory combined with Principal Component Analysis (PCA) and Taguchi’s robust design for simultaneous optimization of correlated multiple surface quality characteristics of mild steel machined product prepared by straight turning operation. The study aims at evaluating the most favorable process environment followed by an optimal parametric combination for achieving high surface quality. Traditional Taguchi based hybrid optimization approaches rely on the assumption that quality indices are uncorrelated or independent. But it is felt that, in practice, there may be some correlation among various quality indices (responses) under consideration. To overcome this limitation of Taguchi approach, the present study proposes application of PCA to convert correlated responses into uncorrelated quality indices called principal components. Finally based on utility theory, Taguchi method has been applied to solve this optimization problem. The study demonstrates detailed methodology and concludes robustness and flexibility of the proposed optimization technique and validates its effectiveness through a case study in which correlated multiple response characteristics of turning operation have been optimized.展开更多
Zhang Fuqing, a war hero, has kept a low profi le, devoting himself to serving the people for more than seven decades. The following is an edited excerpt of a Xinhua News Agency report on him:Zhang Fuqing, 95, wears a...Zhang Fuqing, a war hero, has kept a low profi le, devoting himself to serving the people for more than seven decades. The following is an edited excerpt of a Xinhua News Agency report on him:Zhang Fuqing, 95, wears a hat almost every day, not to keep himself warm,but to ease the aftereffect of head injuries he suffered in a fi erce battle over 70 years ago.展开更多
Beijing has turned several ancient buildings into muse-ums in a drive to restore and preserve historical relics in thecity.The city government has invested 4.4 million yuan (760,000)to reconstruct the ancient building...Beijing has turned several ancient buildings into muse-ums in a drive to restore and preserve historical relics in thecity.The city government has invested 4.4 million yuan (760,000)to reconstruct the ancient buildings and stockedthem with relics and antiques.The city is expanding a several-hundred-year-oldtemple into a stone carving museum in Xicheng District.展开更多
CHINA, a once-mysterious oriental land, has nowbecome part of the international family of nations. Yetfew people realize what humiliation China once sufferedor what a suffocating life the ordinary Chinese once lived.E...CHINA, a once-mysterious oriental land, has nowbecome part of the international family of nations. Yetfew people realize what humiliation China once sufferedor what a suffocating life the ordinary Chinese once lived.Even those who experienced that part of history seemreluctant to recall the painful period.展开更多
With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynami...With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynamic behavior of the machine tool. Spatial domain frequency analyses based on fast Fourier transform were used to analyze the tool behavior. Wavelet reconstruction was used for profile filtering. The results show that machine vibration remarkably affects the surface topography at small feed rates, but has negligible effect at high feed rates. The analyses also show how to control the surface quality during hard turning.展开更多
The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and ...The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.展开更多
洛普替尼(repotrectinib)是由Turning Point Therapeutics公司研发,于2023年11月15日经美国食品药品监督管理局(FDA)批准上市,商品名为Augtyro。洛普替尼是一种多靶点激酶抑制剂,可以靶向ROS1、TRK和ALK,适用于治疗局部晚期或转移性ROS...洛普替尼(repotrectinib)是由Turning Point Therapeutics公司研发,于2023年11月15日经美国食品药品监督管理局(FDA)批准上市,商品名为Augtyro。洛普替尼是一种多靶点激酶抑制剂,可以靶向ROS1、TRK和ALK,适用于治疗局部晚期或转移性ROS1阳性非小细胞肺癌(non-small cell lung cancer,NSCLC)成人患者[1]。展开更多
Animals can differ in their individual movement behaviors during their daily displacements.Studies of animal movement patterns often disregard the need to understand individual variation in these patterns and the role...Animals can differ in their individual movement behaviors during their daily displacements.Studies of animal movement patterns often disregard the need to understand individual variation in these patterns and the role of this variation in shaping population distributions of movements.To assess the link between individual movements and population distributions,we radio-tracked 13 Fowler's Toads Anaxyrus fowleri in Long Point,Ontario,Canada,after their breeding season.We recorded individual coordinates every 30 min,from the moment they emerged from their burrows around dusk until they burrowed in the morning,and obtained a total of 157 movements.We used the resulting series of step lengths and turning angles in a Hidden Markov Model to estimate movement type as"directed"or"non-directed"We also assigned to each encounter one of 3 space-dependent movement states:"foraging""in transit'or"searching"and found that movement type and state switched within individuals irrespective of time during a single night.We find that switching between movement types varied throughout the night,leading to stochastic within-individual variation in movements,and the distribution of movement distances differed significantly among individuals.Movement states,however,were time-dependent,suggesting displacement routines were similar across individuals.Variation in movement behavior within individuals scales up to result in variation among individuals which,in turn,was found to shape the distribution of the sampled population.Our findings therefore underline the importance of a multi-scale approach in the study of movement.展开更多
【重点词汇】1.work on doing sth.致力于做某事2.once upon a time从前3.continue to do sth.继续做某事4.keep doing sth.坚持做某事5.give up放弃6.instead of代替;反而7.turn...into变成8.get married结婚。
In Shandong,the special folk activity of blowing sugar figures during the Spring Festival has a long history.It is said that this skill can be traced back to the Tang Dynasty.At that time,as sugar-making technology im...In Shandong,the special folk activity of blowing sugar figures during the Spring Festival has a long history.It is said that this skill can be traced back to the Tang Dynasty.At that time,as sugar-making technology improved a lot,smart folk craftsmen(工匠)began to use sugar to create various small items.Once heated,sugar turns soft and malleable(可塑的).展开更多
Boosting Birth Rates,Generous childcare subsidies have been reported across China as part of the country’s holistic efforts to boost birth rates,making news headlines and sparking discussions.The latest news came fro...Boosting Birth Rates,Generous childcare subsidies have been reported across China as part of the country’s holistic efforts to boost birth rates,making news headlines and sparking discussions.The latest news came from Hohhot,capital of north China’s Inner Mongolia Autonomous Region.The city announced this week that it will offer a one-time subsidy of 10,000 yuan($1,394)to couples having their first child.A second child will receive 10,000 yuan per year until he/she reaches five years old.For the third child or more,the annual subsidy is 10,000 yuan until the child turns 10.展开更多
The year 2024 is also a turning point in the outdoor gear industry's commitment to sustainability,This shift towards eco-friendly products is not just a trend but a response to a growing awareness of environmental...The year 2024 is also a turning point in the outdoor gear industry's commitment to sustainability,This shift towards eco-friendly products is not just a trend but a response to a growing awareness of environmental conservation.Manufacturers are increasingly focusing on reducing the ecological footprint of their products,utilizing recycled materials,and adopting sustainable manufacturing processes.This transformation is driven by a combination of consumer demand,environmental responsibility,and technological advancements.展开更多
基金supported by the National Science Foundation of China(No.51275235)
文摘The high controllability and high resolution control of linear ultrasonic motors depend on effective control of driving signals.For a good control characteristic,step control which the driver output turned off and on was used.Therefore,a novel dual PWM topology structure ultrasonic motor driver was designed and analyzed.According to the characteristics of the circuits,two kinds of hardware turned off methods named methods A and B were discussed.The differences of the voltage applied on motor by different methods were figured out.Finally,a series of experiments were carried out in the clean room to study the influence of step characteristic by different turn off methods.The experimental results show that the steplength was 230 nm by method A and 125 nm by method B,while cycles of driving signals were 6.The method B has a smaller steplength when cycles are 6.The average steplength varies in non-linear while driving cycles changing.The steplength varies approximately in linear while voltage amplitude changing.Therefore,method B is better to implement step control,because it gets a better control in positioning system.
文摘Located along the border between Zhejiang and Fujian provinces, Taishun has exuberant vegetation and rich timber resources because the Xianxialing Mountain range runs across it. About 500 years ago during the Ming Dynasty, the local people began to use the abundant timber to make various types
文摘This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the angel of perforation, on the fluid flow and heat transfer. The numerical results appeared in good agreement with previous experimental data under the same operating conditions. The results indicated that large size and positive angle of perforation changed the fluid flow pattern and the local Nusselt-number distribution fundamentally. It is noteworthy that a more uniform distribution of Nusselt-number was achieved by increasing the diameter of perforation.
文摘The 15th ITMF Corona-Survey shows that the business situation plunged into negative territory in July 2022.The business situation is worse in Asia than in the rest of the world.Textile machinery is the only segment still in positive territory.Business expectations have also turned negative for the first time since the start of survey in May 2021.South-East Asia and South America are relatively more optimistic,downstream segments as well.
基金National Natural Science Foundation of China(Nos.52175430,51935008 and 52105478)China National Postdoctoral Program for Innovative Talents(BX20200234)Open Fund of Tianjin Key Laboratory of Equipment Design and Manufacturing Technology(EDMT)for the support of this work。
文摘Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved surface roughness of polycrystalline materials.However,it is difficult to establish a purely theoretical model for surface roughness with consideration of the grain boundary effect using conventional analytical methods.In this work,a theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials is proposed.The kinematic–dynamic roughness component in relation to the tool profile duplication effect,work material plastic side flow,relative vibration between the diamond tool and workpiece,etc,is theoretically calculated.The material-defect roughness component is modeled with a cascade forward neural network.In the neural network,the ratio of maximum undeformed chip thickness to cutting edge radius RT S,work material properties(misorientation angle θ_(g) and grain size d_(g)),and spindle rotation speed n s are configured as input variables.The material-defect roughness component is set as the output variable.To validate the developed model,polycrystalline copper with a gradient distribution of grains prepared by friction stir processing is machined with various processing parameters and different diamond tools.Compared with the previously developed model,obvious improvement in the prediction accuracy is observed with this hybrid prediction model.Based on this model,the influences of different factors on the surface roughness of polycrystalline materials are discussed.The influencing mechanism of the misorientation angle and grain size is quantitatively analyzed.Two fracture modes,including transcrystalline and intercrystalline fractures at different RTS values,are observed.Meanwhile,optimal processing parameters are obtained with a simulated annealing algorithm.Cutting experiments are performed with the optimal parameters,and a flat surface finish with Sa 1.314 nm is finally achieved.The developed model and corresponding new findings in this work are beneficial for accurately predicting the surface roughness of polycrystalline materials and understanding the impacting mechanism of material defects in diamond turning.
基金The Ministry of Education of China"985"of International cooperation project"Clean Manufactur-ing Technology"
文摘White layers in hard turned surfaces were identified and measured as a function ot turning parameters based on the Taguchi method. It reveals that white layers generate on the machine surface in the absence of tool flank wear, and white layer depth varies with the different combinations of hard turning parameters. Turning speed has the most important impact on white layer depth, feed rate follows, and cutting depth at last. The white layer generation consequently suggests a strong couple relation to the heat generation and thermal process of hard turning operation. White layer disappears under an optimal combination of turning parameters by Taguchi method. It suggests that a superior surface integrity without white layer is feasible under some selected combinations of turning parameters by a sharp CBN cutting tool.
文摘Present work highlights application of utility theory combined with Principal Component Analysis (PCA) and Taguchi’s robust design for simultaneous optimization of correlated multiple surface quality characteristics of mild steel machined product prepared by straight turning operation. The study aims at evaluating the most favorable process environment followed by an optimal parametric combination for achieving high surface quality. Traditional Taguchi based hybrid optimization approaches rely on the assumption that quality indices are uncorrelated or independent. But it is felt that, in practice, there may be some correlation among various quality indices (responses) under consideration. To overcome this limitation of Taguchi approach, the present study proposes application of PCA to convert correlated responses into uncorrelated quality indices called principal components. Finally based on utility theory, Taguchi method has been applied to solve this optimization problem. The study demonstrates detailed methodology and concludes robustness and flexibility of the proposed optimization technique and validates its effectiveness through a case study in which correlated multiple response characteristics of turning operation have been optimized.
文摘Zhang Fuqing, a war hero, has kept a low profi le, devoting himself to serving the people for more than seven decades. The following is an edited excerpt of a Xinhua News Agency report on him:Zhang Fuqing, 95, wears a hat almost every day, not to keep himself warm,but to ease the aftereffect of head injuries he suffered in a fi erce battle over 70 years ago.
文摘Beijing has turned several ancient buildings into muse-ums in a drive to restore and preserve historical relics in thecity.The city government has invested 4.4 million yuan (760,000)to reconstruct the ancient buildings and stockedthem with relics and antiques.The city is expanding a several-hundred-year-oldtemple into a stone carving museum in Xicheng District.
文摘CHINA, a once-mysterious oriental land, has nowbecome part of the international family of nations. Yetfew people realize what humiliation China once sufferedor what a suffocating life the ordinary Chinese once lived.Even those who experienced that part of history seemreluctant to recall the painful period.
基金Supported by the DAAD (German Academic Exchange Service)
文摘With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynamic behavior of the machine tool. Spatial domain frequency analyses based on fast Fourier transform were used to analyze the tool behavior. Wavelet reconstruction was used for profile filtering. The results show that machine vibration remarkably affects the surface topography at small feed rates, but has negligible effect at high feed rates. The analyses also show how to control the surface quality during hard turning.
基金supported by the National Natural Science Foundation of China(Nos.U20A2069,62376234 and 123B2037)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.
基金funded by grants from the Fonds de Recherche du Quebec-Nature et Technologies(FRQNT)to NJthe Ontario Ministry of Natural Resources and Forestrythe Ontario Ministry of Environment,Conservation and Parks,and the Natural Sciences and Engineering Research Council(NSERC)of Canada to DMG.
文摘Animals can differ in their individual movement behaviors during their daily displacements.Studies of animal movement patterns often disregard the need to understand individual variation in these patterns and the role of this variation in shaping population distributions of movements.To assess the link between individual movements and population distributions,we radio-tracked 13 Fowler's Toads Anaxyrus fowleri in Long Point,Ontario,Canada,after their breeding season.We recorded individual coordinates every 30 min,from the moment they emerged from their burrows around dusk until they burrowed in the morning,and obtained a total of 157 movements.We used the resulting series of step lengths and turning angles in a Hidden Markov Model to estimate movement type as"directed"or"non-directed"We also assigned to each encounter one of 3 space-dependent movement states:"foraging""in transit'or"searching"and found that movement type and state switched within individuals irrespective of time during a single night.We find that switching between movement types varied throughout the night,leading to stochastic within-individual variation in movements,and the distribution of movement distances differed significantly among individuals.Movement states,however,were time-dependent,suggesting displacement routines were similar across individuals.Variation in movement behavior within individuals scales up to result in variation among individuals which,in turn,was found to shape the distribution of the sampled population.Our findings therefore underline the importance of a multi-scale approach in the study of movement.
文摘【重点词汇】1.work on doing sth.致力于做某事2.once upon a time从前3.continue to do sth.继续做某事4.keep doing sth.坚持做某事5.give up放弃6.instead of代替;反而7.turn...into变成8.get married结婚。
文摘In Shandong,the special folk activity of blowing sugar figures during the Spring Festival has a long history.It is said that this skill can be traced back to the Tang Dynasty.At that time,as sugar-making technology improved a lot,smart folk craftsmen(工匠)began to use sugar to create various small items.Once heated,sugar turns soft and malleable(可塑的).
文摘Boosting Birth Rates,Generous childcare subsidies have been reported across China as part of the country’s holistic efforts to boost birth rates,making news headlines and sparking discussions.The latest news came from Hohhot,capital of north China’s Inner Mongolia Autonomous Region.The city announced this week that it will offer a one-time subsidy of 10,000 yuan($1,394)to couples having their first child.A second child will receive 10,000 yuan per year until he/she reaches five years old.For the third child or more,the annual subsidy is 10,000 yuan until the child turns 10.
文摘The year 2024 is also a turning point in the outdoor gear industry's commitment to sustainability,This shift towards eco-friendly products is not just a trend but a response to a growing awareness of environmental conservation.Manufacturers are increasingly focusing on reducing the ecological footprint of their products,utilizing recycled materials,and adopting sustainable manufacturing processes.This transformation is driven by a combination of consumer demand,environmental responsibility,and technological advancements.
