In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to im...In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties,and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved.The Lyapunov techniques and the La Salle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.展开更多
A new species of Rosaceae from Central China, Prunus sunhangii D. G. Zhang & T. Deng, sp. nov., is described and illustrated. The new species is placed in Prunus subgenus Cerasus by flower and fruit characteristic...A new species of Rosaceae from Central China, Prunus sunhangii D. G. Zhang & T. Deng, sp. nov., is described and illustrated. The new species is placed in Prunus subgenus Cerasus by flower and fruit characteristics. It is most similar to Prunus cerasoides, but differs by having longitudinally 2-lobed apical petals, an acuminate leaf apex, 17—25 stamens, white petals, dark black drupes, brown hypanthium, and different phenology. The phylogenetic placement of this species was assessed based on morphological and molecular data. Molecular analysis(cp DNA + ITS) corroborated its placement in subgenus Cerasus,specifically Prunus section Serrula.展开更多
Owing to its outstanding mechanical properties,γ-TiAl is desirable materials for crossgeneration aero-engines.Nearly 70 years of exploration have made it into the initial application.However,the intrinsic brittleness...Owing to its outstanding mechanical properties,γ-TiAl is desirable materials for crossgeneration aero-engines.Nearly 70 years of exploration have made it into the initial application.However,the intrinsic brittleness ofγ-TiAl is still a critical obstacle to its large-scale applications.In this context,researchers have made many attempts to study the machinability ofγ-TiAl.At present,existing relevant reviews have mostly discussed the processing methods ofγ-TiAl.Hence,there is still a lack of a perspective on material properties to analyze the cutting mechanism.Herein,this paper provides the systematic review of such perspectives.Above all,the developmental process,phase transformation,and microstructural evolution ofγ-TiAl are discussed,as well as its deformation mechanism at quasi-static.These topics can provide a materials science foundation for the machining ofγ-TiAl.And then,the review focuses on the cutting mechanism and surface integrity ofγ-TiAl.Moreover,special attention is paid to the microscope deformation mechanism and surface defects evolution ofγ-TiAl during cutting.Finally,the review indicates that the highperformance machining technology ofγ-TiAl faces challenges and proposes potential future research directions.Solving the difficulties during machiningγ-TiAl aero-engine components will accelerate the development of new aero-engines.展开更多
叶片养分重吸收对土壤养分的变化很敏感。然而,我们尚不清楚氮沉降如何影响植物大量元素重吸收率。杨树(Populus deltoids)是世界上栽培最广泛的阔叶树种之一。本文研究了在氮添加条件下,杨树重吸收率及其化学计量比的规律和主要驱动因...叶片养分重吸收对土壤养分的变化很敏感。然而,我们尚不清楚氮沉降如何影响植物大量元素重吸收率。杨树(Populus deltoids)是世界上栽培最广泛的阔叶树种之一。本文研究了在氮添加条件下,杨树重吸收率及其化学计量比的规律和主要驱动因素。通过一个4年的氮添加实验,我们探究中国东部沿海两个林分(8和12年)杨树人工林重吸收率及其化学计量比对氮添加的响应。我们测定了在一系列氮添加浓度水平(0、50、100、150、300 kg N ha^(−1) yr^(−1))下,土壤和叶片(包括绿叶和落叶)中氮、磷、钾、钙、镁的浓度。研究结果表明,除钙元素重吸收率和钙、镁元素重吸收率化学计量比外,氮添加对两个林分大量元素重吸收率及其化学计量比都没有显著影响。氮、磷重吸收率尺度斜率在不同氮添加水平下均小于1,表明氮添加条件下,氮、磷元素重吸收率解耦。养分重吸收率与绿叶中养分含量显著正相关,表明重吸收主要受到绿叶养分调控。我们的研究结果为中国东部沿海地区12年生杨树人工林的生长受氮限制提供了直接证据。展开更多
We demonstrate the fabrication of ultrahigh quality(Q) factor silica microdisk resonators on a silicon chip by inductively coupled plasma(ICP) etching. We achieve a dry-etched optical microresonator with an intrinsic ...We demonstrate the fabrication of ultrahigh quality(Q) factor silica microdisk resonators on a silicon chip by inductively coupled plasma(ICP) etching. We achieve a dry-etched optical microresonator with an intrinsic Q factor as high as 1.94×10^(8) from a 1-mm-diameter silica microdisk with a thickness of 4 μm. Our work provides a chip-based microresonator platform operating in the ultrahigh-Q region that will be useful in nonlinear photonics such as Brillouin lasers and Kerr microcombs.展开更多
基金supported in part by the National High Technology Research and Development Program of China(863 Program)(2015AA042307)Shandong Provincial Scientific and Technological Development Foundation(2014GGX103038)+3 种基金Shandong Provincial Independent Innovation and Achievement Transformation Special Foundation(2015ZDXX0101E01)National Natural Science Fundation of China(NSFC)Joint Fund of Shandong Province(U1706228)the Fundamental Research Funds of Shandong University(2015JC027)
文摘In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties,and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved.The Lyapunov techniques and the La Salle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.
基金supported by the Major Program of the National Natural Science Foundation of China (31590823)the National Natural Science Foundation of China (31700165)+4 种基金the National Key R & D Program of China (2017YFC0505200)the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20050203)the Fund for Reserve Talents of Young and Middle-aged Academic and Technical Leaders of Yunnan Province (2014HB027)the CAS "Light of West China" Program, the Comprehensive Scientific Investigation of Biodiversity from the Wuling Mountains (2014FY110100)the survey on baseline resources of Wufeng Houhe National Nature Reserve in Hubei Province
文摘A new species of Rosaceae from Central China, Prunus sunhangii D. G. Zhang & T. Deng, sp. nov., is described and illustrated. The new species is placed in Prunus subgenus Cerasus by flower and fruit characteristics. It is most similar to Prunus cerasoides, but differs by having longitudinally 2-lobed apical petals, an acuminate leaf apex, 17—25 stamens, white petals, dark black drupes, brown hypanthium, and different phenology. The phylogenetic placement of this species was assessed based on morphological and molecular data. Molecular analysis(cp DNA + ITS) corroborated its placement in subgenus Cerasus,specifically Prunus section Serrula.
基金supported by the National Natural Science Foundation of China(22105186)the National Natural Science Joint Safety Foundation(U2030202)the support of National Natural Science Foundation of China(21875232)for the thermal and kinetic analysis。
基金co-supported by the Science Center for Gas Turbine Project,China(No.P2022-A-IV-001-002)the National Natural Science Foundation of China(Nos.51875473 and 91960203).
文摘Owing to its outstanding mechanical properties,γ-TiAl is desirable materials for crossgeneration aero-engines.Nearly 70 years of exploration have made it into the initial application.However,the intrinsic brittleness ofγ-TiAl is still a critical obstacle to its large-scale applications.In this context,researchers have made many attempts to study the machinability ofγ-TiAl.At present,existing relevant reviews have mostly discussed the processing methods ofγ-TiAl.Hence,there is still a lack of a perspective on material properties to analyze the cutting mechanism.Herein,this paper provides the systematic review of such perspectives.Above all,the developmental process,phase transformation,and microstructural evolution ofγ-TiAl are discussed,as well as its deformation mechanism at quasi-static.These topics can provide a materials science foundation for the machining ofγ-TiAl.And then,the review focuses on the cutting mechanism and surface integrity ofγ-TiAl.Moreover,special attention is paid to the microscope deformation mechanism and surface defects evolution ofγ-TiAl during cutting.Finally,the review indicates that the highperformance machining technology ofγ-TiAl faces challenges and proposes potential future research directions.Solving the difficulties during machiningγ-TiAl aero-engine components will accelerate the development of new aero-engines.
基金This study is financially supported by the Natural Science Key Fund for Colleges and Universities of Jiangsu Province of China(17KJA180006)the Six Talent Peaks Program of Jiangsu Province(JY-041 and TD-XYDXX-006)+1 种基金the'5151'Talent Program of Nanjing Forestry University,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),the Doctorate Fellowship Foundation of Nanjing Forestry University,the Research Innovation Program for College Graduates of Jiangsu Province(KYLX16_0833)the Scientific and Technological Innovation Program for College Students of Nanjing Forestry University(DXSKC-201617).
文摘叶片养分重吸收对土壤养分的变化很敏感。然而,我们尚不清楚氮沉降如何影响植物大量元素重吸收率。杨树(Populus deltoids)是世界上栽培最广泛的阔叶树种之一。本文研究了在氮添加条件下,杨树重吸收率及其化学计量比的规律和主要驱动因素。通过一个4年的氮添加实验,我们探究中国东部沿海两个林分(8和12年)杨树人工林重吸收率及其化学计量比对氮添加的响应。我们测定了在一系列氮添加浓度水平(0、50、100、150、300 kg N ha^(−1) yr^(−1))下,土壤和叶片(包括绿叶和落叶)中氮、磷、钾、钙、镁的浓度。研究结果表明,除钙元素重吸收率和钙、镁元素重吸收率化学计量比外,氮添加对两个林分大量元素重吸收率及其化学计量比都没有显著影响。氮、磷重吸收率尺度斜率在不同氮添加水平下均小于1,表明氮添加条件下,氮、磷元素重吸收率解耦。养分重吸收率与绿叶中养分含量显著正相关,表明重吸收主要受到绿叶养分调控。我们的研究结果为中国东部沿海地区12年生杨树人工林的生长受氮限制提供了直接证据。
基金National Key Research and Development Program of China(2016YFA0302500,2017YFA0303703)National Natural Science Foundation of China(NFSC)(61922040,11621091)Fundamental Research Funds for the Central Universities(021314380149)。
文摘We demonstrate the fabrication of ultrahigh quality(Q) factor silica microdisk resonators on a silicon chip by inductively coupled plasma(ICP) etching. We achieve a dry-etched optical microresonator with an intrinsic Q factor as high as 1.94×10^(8) from a 1-mm-diameter silica microdisk with a thickness of 4 μm. Our work provides a chip-based microresonator platform operating in the ultrahigh-Q region that will be useful in nonlinear photonics such as Brillouin lasers and Kerr microcombs.
