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Investigation on the stall types in impellers with different blade numbers

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Journal of Hydrodynamics 2023年第2期35卷 299-313页

作者： xiao-dong liu Yao-jun Li Zhu-qing liu Wei Yang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing100083China

Stall is a complex flow phenomenon and its existence usually shows significant differences in different impeller *** this paper,the flow field characteristics and mechanism of stall types in impellers with different blade numbers were studied through the combination of experiment and numerical simulation at stall inception *** the experiments,it was observed that the five-blade impeller entered the rotating stall stage from a relatively stable flow field within a small flow rate *** the six-blade impeller,the root cause that stall vortices appeared in channels alternately rather than each one evenly was also reasonably *** validated numerical simulation method was utilized to reveal the three-dimensional flow field in impeller *** results indicate the swirling vortex near the impeller shroud was periodically sucked in and escaped from region near the blade suction side,which was the fundamental driving force of rotating *** sudden change of flow field caused by the fusion of the separation vortex at the channel inlet and the vortex induced by the swirling vortex near shroud is the essential reason for the formation of alternating ***’s more,the stall inception flow field is clearly defined in impellers,which is of great significance for the further analysis of stall *** on the distribution characteristics of vortex structure near impeller shroud with different blade numbers at different flow rate conditions,this paper deeply investigated the formation mechanism of different stall types in impellers.

关键词： Numerical simulation high-frequency particle image velocimetry(PIV) impellers swirling vortex stall type

Inverse Fluid-solid Interaction Scattering Problem Using Phased and Phaseless Far Field Data

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Acta Mathematicae Applicatae Sinica 2020年第1期36卷 74-94页

作者： Xia JI Yun-fei JIA xiao-dong liu LSEC Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100190China

We consider the inverse fluid-solid interaction scattering of incident plane wave from the knowledge of the phased and phaseless far field *** the phased data,one direct sampling method for location and shape reconstruction is *** inner product is involved in the computation,which makes it very simple and fast to be *** the help of the factorization of the far field operator,we give a lower bound of the proposed indicator functional for the sampling points inside the elastic *** for the sampling points outside,we show that the indicator functional decays like the Bessel function as the points go away from the boundaries of the elastic *** also show that the proposed indicator functional continuously dependents on the far field patterns,which further implies that the novel sampling method is extremely stable with respect to data *** the phaseless data,to overcome the translation invariance,we consider the scattering of point sources *** adding a reference sound-soft obstacle into the scattering system,we show some uniqueness results with phaseless far field ***,we introduce a phase retrieval algorithm to retrieve the phased data without the additional *** novel phase retrieval algorithm can also be combined with the sampling method for phased *** also design two novel direct sampling methods using the phaseless data ***,some numerical simulations in two dimensions are conducted with noisy data,and the results further verify the effectiveness and robustness of the proposed numerical methods.

关键词： fluid-solid interaction scattering direct sampling method far field pattern phaseless phase retrieval

Motion planning for redundant prismatic-jointed manipulators in the free-floating mode

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Acta Mechanica Sinica 2012年第5期28卷 1449-1456页

作者： xiao-dong liu He-Xi Baoyin Xing-Rui Ma School of Aerospace Tsinghua University

This paper investigates the motion planning of redundant free-floating manipulators with seven prismatic joints. On the earth, prismatic-jointed manipulators could only position their end-effectors in a desired way. However, in space, the end-effectors of free-floating manipulators can achieve both the desired orientation and desired position due to the dynamical coupling between manipulator and satellite movement, which is formally expressed by linear and angular momentum conservation laws. In this study, a tractable algorithm particle swarm optimization combined with differential evolution （PSODE） is provided to deal with the motion planning of redundant free-floating prismatic-jointed manipulators, which could avoid the pseudo inverse of the Jacobian matrix. The polynomial functions, as argument in sine functions are used to specify the joint paths. The co- efficients of the polynomials are optimized to achieve the desired end-effector orientation and position, and simulta- neously minimize the unit-mass-kinetic energy using the redundancy. Relevant simulations prove that this method pro- vides satisfactory smooth paths for redundant free-floating prismatic-jointed manipulators. This study could help to recognize the advantages of redundant prismatic-jointed space manipulators.

关键词： Motion planning - Prismatic joints - Space manipulators Redundant manipulators Free-floating robots ~Nonholonomic planning

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World Journal of Clinical Cases 2021年第11期9卷 2611-2618页

作者： Cen Wu xiao-Ming Zhou xiao-dong liu Department of Respiratory and Critical Care Medicine Shengjing Hospital of China Medical UniversityShenyang 110004Liaoning ProvinceChina Department of Pharmacy Shengjing Hospital of China Medical UniversityShenyang 110004Liaoning ProvinceChina

BACKGROUND Eltrombopag is an orally administered thrombopoietin receptor agonist linked to a heightened risk of treatment-related *** venous and arterial thromboses have been documented in the medical *** SUMMARY In the absence of nephropathy,a 48-year-old patient receiving eltrombopag for immune thrombocytopenia(ITP)developed renal vein thrombosis and pulmonary *** renal vein thrombus spontaneously resolved during subsequent anticoagulant treatment,restoring venous *** A rapid upsurge in platelets,rather than their absolute number,may trigger thrombotic events in this *** patients at high thrombotic risk,individualized eltrombopag dosing and vigilance in platelet monitoring are perhaps needed during treatment of ITP.

关键词： Eltrombopag Immune thrombocytopenic purpura Thrombopoietin receptor agonist Renal vein thrombosis Case report

Periodic orbits around areostationary points in the Martian gravity field

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Research in Astronomy and Astrophysics 2012年第5期12卷 551-562页

作者： xiao-dong liu Hexi Baoyin Xing-Rui Ma School of Aerospace Tsinghua University 100084 Beijing China

This study investigates the problem of areostationary orbits around Mars in three-dimensional space. Areostationary orbits are expected to be used to establish a future telecommunication network for the exploration of Mars. However, no artificial satellites have been placed in these orbits thus far. The characteristics of the Martian gravity field are presented, and areostationary points and their linear stability are cal- culated. By taking linearized solutions in the planar case as the initial guesses and utilizing the Levenberg-Marquardt method, families of periodic orbits around areo- stationary points are shown to exist. Short-period orbits and long-period orbits are found around linearly stable areostationary points, but only short-period orbits are found around unstable areostationary points. Vertical periodic orbits around both lin- early stable and unstable areostationary points are also examined. Satellites in these periodic orbits could depart from areostationary points by a few degrees in longitude, which would facilitate observation of the Martian topography. Based on the eigenval- ues of the monodromy matrix, the evolution of the stability index of periodic orbits is determined. Finally, heteroclinic orbits connecting the two unstable areostationary points are found, providing the possibility for orbital transfer with minimal energy consumption.

关键词： planets and satellites: Mars -martian gravity field -- periodic orbit -- areostationary orbits

Power optimization for maximum channel capacity in MIMO relay system

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The Journal of China Universities of Posts and Telecommunications 2007年第3期14卷 10-15页

作者： WANG Ying SHEN xiao-dong WU Tong liu Bao-ling Key Laboratory of Ubiquitous Wireless Communication Ministry ofEducation Beijing University of Posts and TelecommunicationsBeijing 100876 China

Introducing multiple-input multiple-output（MIMO） relay channel could offer significant capacity gain. And it is of great importance to develop effective power allocation strategies to achieve power efficiency and improve channel capacity in amplify-and-forward relay system. This article investigates a two-hop MIMO relay system with multiple antennas in relay node （RN） and receiver （RX）. Maximizing capacity with antenna selection（MCAS） and maximizing capacity with eigen-decomposition （MCED） schemes are proposed to efficiently allocate power among antennas in RN under first and second hop limited scenarios. The analysis and simulation results show that both MCED and MCAS can improve the channel capacity compared with uniform power allocation （UPA） scheme in most of the studied areas. The MCAS bears comparison with MCED with an acceptable capacity loss, but lowers the complexity by saving channel state information （CSI） feedback to the transmitter （TX）. Moreover, when the RN is close to RX, the performance of UPA is also close to the upper bound as the performance of first hop is limited.

关键词： MIMO-relay MCAS MCED UPA maximum channel capacity

Two Faces of One Seed： Hormonal Regulation of Dormancy and Germination

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Molecular Plant 2016年第1期9卷 34-45页

作者： Kai Shu xiao-dong liu Qi Xie Zu-hua He State Key Laboratory of Plant Genomics Institute of Genetics and Developmental Biology Chinese Academy of Sciences Beijing 100101 China National Key Laboratory of Plant Molecular Genetics Institute of Plant Physiology and Ecology Chinese Academy of Sciences Shanghai 200032 China Key Laboratory of Crop Ecophysiology and Farming System in Southwest China Institute of Ecological Agriculture Sichuan Agricultural UniversityChengdu 611130 China College of Agronomy Xinjiang Agricultural University Urumqi 830052 Xinjiang China These authors contributed equally to this article

Seed plants have evolved to maintain the dormancy of freshly matured seeds until the appropriate time for germination. Seed dormancy and germination are distinct physiological processes, and the transition from dormancy to germination is not only a critical developmental step in the life cycle of plants but is also impor- tant for agricultural production. These processes are precisely regulated by diverse endogenous hormones and environmental cues. Although ABA （abscisic acid） and GAs （gibberellins） are known to be the primary phytohormones that antagonistically regulate seed dormancy, recent findings demonstrate that another phytohormone, auxin, is also critical for inducing and maintaining seed dormancy, and therefore might act as a key protector of seed dormancy. In this review, we summarize our current understanding of the sophisticated molecular networks involving the critical roles of phytohormones in regulating seed dormancy and germination, in which AP2-domain-containing transcription factors play key roles. We also discuss the interactions （crosstalk） of diverse hormonal signals in seed dormancy and germination, focusing on the ABA/GA balance that constitutes the central node.

关键词： seed dormancy germination ABA GA auxin crosstalk

Cu/chiral phosphoric acid-catalyzed radical-initiated asymmetric aminosilylation of alkene with hydrosilane

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Science China Chemistry 2019年第11期62卷 1529-1536页

作者： Yang Zeng xiao-dong liu Xian-Qi Guo Qiang-Shuai Gu Zhong-Liang Li xiao-Yong Chang Xin-Yuan liu Shenzhen Grubbs Institute Southern University of Science and TechnologyShenzhen 518055China Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China Department of Chemistry Southern University of Science and TechnologyShenzhen 518055Chin

The catalytic radical-initiated asymmetric 1,2-aminosilylation of alkene with a hydrosilane under Cu(I)/CPA cooperative catalysis has been *** method features the use of hydrosilane as the reductive radical precursor,enabling efficient access to skeletally diverse silicon-containing azaheterocycles including pyrrolidine,indoline and isoindoline bearing anα-tertiary stereocenter with high *** key to the success includes the use of Cu(I)/CPA cooperative catalyst system and theβ-silicon effect of the silyl group to stabilize the in situ generated carbocation intermediate.

关键词： asymmetric radical chemistry aminosilylation alkenes Cu/chiral phosphoric acid silyl radical

Synthesis of trifluoromethyl-/cyclopropyl-substituted 2-isoxazolines by DBU-promoted domino reaction

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Chinese Chemical Letters 2017年第8期28卷 1780-1783页

作者： xiao-dong liu Hai-Yan Ma Chun-Hui Xing Long Lu School of Chemistry and Molecular Engineering East China University of Science and Technology Key Laboratory of Organofluorine Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences

NTrifluoromethyl and cyclopropyl substituted 2-isoxazolines were synthesized via a DBU-promoted domino reaction of β-trifluoromethyl-/β-cyclopropyl-substituted enones with hydroxylamine. The domino reaction consists of a Michael addition and the followed cyclization. A wide range of 3-substituted 5-cyclopropyl-5-trifluoromethyl-2-isoxazolines were obtained in good to excellent yields under mild reaction conditions. The method could also apply to other trifluoromethyl-substituted enones.

关键词： Isoxazoline Enone Michael addition Cyclization Domino reaction