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A new algorithm for computing the convex hull of a planar point set

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第8期8卷 1210-1217页

作者： liu guang-hui CHEN Chuan-bo College of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China

When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster.

关键词： Computational geometry Convex hull Extreme points Ordered convex hull point sequence

In situ observation and modeling of austenite grain growth in a Nb-Ti-bearing high carbon steel

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Journal of Iron and Steel Research International 2019年第3期26卷 292-300页

作者： guang Ji Xiu-hua Gao Zhen-guang liu Ke Zhang State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina Jiangsu Shagang Group Huaigang Special Steel Co. Ltd.Huaian 223002JiangsuChina School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212003JiangsuChina Institute of Research of Iron and Steel ShasteelZhangjiagang 215625JiangsuChina

In situ measurements of austenite grain growth were made at various temperatures in the range of 1273-1473 K with subsequent isothermal holding time of 3600 s for the Nb-Ti-bearing and Nb-Ti-free high carb on steel by using a confocal laser scanning *** solid solute behavior of Nb-Ti carbides during austenitizing process was *** experimental results indicate that the austenite grains of both steels grow up gradually with increasing the heating temperature and holding time;the size and growth rate of austenite grain of Nb-Ti-bearing high carbon steel are much lower than those of Nb-Ti-free high carbon steel.A large amount of(Nb,Ti)(C,N)nanoparticles are observed in Nb-Tibearing steel,which retain the strong pinning effect on austenite grain *** kinetics model of austenite grain growth of Nb-Ti-bearing steel during isothermal heat treatment is obtained and the predicted values calculated by using the model meet the experimental values very well.

关键词： Con focal laser scanning microscope Nb-Ti microalloying High carb on steel Grain growth Nanoparticle Grain growth model

Dual-steering mode based on direct yaw moment control for multi-wheel hub motor driven vehicles:Theoretical design and experimental assessment

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Defence Technology（防务技术） 2022年第1期18卷 49-61页

作者： Zheng Zhang Xiao-jun Ma Chun-guang liu Shu-guang Wei Department of Weapons and Control Engineering Army Academy of Armored ForcesBeijing100072China

One of the main challenges for multi-wheel hub motor driven vehicles is the coordination of individual drivetrains to improve mobility and stability in the steering *** paper proposes a dual-steering mode based on direct yaw moment control for enhancing vehicle steering ability in complex environ *** control system is designed as a hierarchical structure,with a yaw moment decision layer and a driving force distribution *** the higher-level layer,the objective optimization function is con-structed to obtain the slip steering ratio,which represents the degree of vehicle slip steering in the dual-steering *** moment controller using active disturbance rejection control theory is designed for continuous yaw rate *** the actual yaw rate of the vehicle deviates from the reference yaw rate obtained by the vehicle reference model and the slip steering ratio,the yaw moment controller isactuated to determine the yaw moment demand for vehicle *** the lower-level layer,there is a torque distribution controller based on distribution rules,which meets the requirement of yaw moment demand without affecting the total longitudinal driving force of the *** verifying the validity and feasibility of the dual-steering mode,simulations were conducted on the hardware-in-loop real-time simulation ***,corresponding real vehicle tests were carried out on an eight-wheel prototype *** results were generally consistent with the simulation results,thereby demon-strating that the proposed dual-steering mode reduces steering radius and enhances the steering per-formance of the vehicle.

关键词： Multi-wheel hub motor driven vehide Dual-steering mode Direct ya w moment control Real-time simulation

Numerical Investigation of the Effects of ITD Length on Low Pressure Nozzle

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Journal of Thermal Science 2017年第3期26卷 199-207页

作者： liu guang liu Jun liu Hongrui Wang Pei DU Qiang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The advantage of high efficiency, low SFC(Specific Fuel Consumption), ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine. The intermediate turbine duct(ITD), which connects high pressure turbine(HPT) with low pressure turbine(LPT), has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss. Therefore, it becomes more and more urgent to master the technique of designing aggressive, even super-aggressive ITD. Much more concerns have been concentrated on the duct. However, in order to further improve turbine, LPT nozzle is arranged into ITD to shorten low pressure axle. With such design concept, it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure, but receives much less interests on the contrary. In this paper, numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle. Nine models with the same swirl and nozzle blades, while the length of ITD is the only parameter to be changed, will be discussed. Finally, several conclusions and advices for designers are summarized. After changing axial length of ducts, inlet and outlet flow field of nozzle differs, correspondingly. On the other hand, the shearing stress on nozzle blade(suction and pressure) surface presents individual feature under various inlet flow. In addition to that, "Clocking-like effect" is described in this paper, which will contribute much to the pressure loss and should be paid enough attention.

关键词： Intermediate Turbine Duct Length Nozzle Pressure Loss

Chlamydomonas WDR92 in association with R2TP-like complex and multiple DNAAFs to regulate ciliary dynein preassembly

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Journal of Molecular Cell Biology 2019年第9期11卷 770-780页

作者： guang liu Limei Wang Junmin Pan MOE Key Laboratory of Protein Sciences Tsinghua-Peking Center for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing 100084China Laboratory for Marine Biology and Biotechnology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266200China

The motility of cilia or eukaryotic flagella is powered by the axonemal dyneins,which are preassembled in the cytoplasm by proteins termed dynein arm assembly factors(DNAAFs)before being transported to and assembled on the ciliary ***,we characterize the function of WDR92 in *** of WDR92,a cytoplasmic protein,in a mutant wdr92 generated by DNA insertional mutagenesis resulted in aflagellate cells or cells with stumpy or short flagella,disappearance of axonemal dynein arms,and diminishment of dynein arm heavy chains in the cytoplasm,suggesting that WDR92 is a *** of WDR92 followed by mass spectrometry identified inner dynein arm heavy chains and multiple DNAAFs including RuvBLl,RPAP3,MOT48,ODA7,and *** PIH1 domain-containing protein MOT48 formed a R2TP-like complex with RuvBLl/2 and RPAP3,while PF13,another PIH1 domain-containing protein with function in dynein preassembly,did ***,the third PIH1 domain-containing protein TWI1 was not related to flagellar ***92 physically interacted with the R2TP-like complex and the other identified *** data suggest that WDR92 functions in association with the HSP90 co-chaperone R2TP-like complex as well as linking other DNAAFs in dynein preassembly.

关键词： cilia motility dynein arm assembly factors R2TP complex WDR92 Chlamydomonas

Effects of Nozzle-Strut Integrated Design Concepton on the Subsonic Turbine Stage Flowfield

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Journal of Thermal Science 2014年第5期23卷 494-504页

作者： liu Jun DU Qiang liu guang WANG Pei ZHU Junqiang Institute of Engineering Thermophysics Chinese Academy of Sciences

In order to shorten aero-engine axial length,substituting the traditional long chord thick strut design accompanied with the traditional low pressure(LP) stage nozzle,LP turbine is integrated with intermediate turbine duct(ITD).In the current paper,five vanes of the first stage LP turbine nozzle is replaced with loaded struts for supporting the engine shaft,and providing oil pipes circumferentially which fulfilled the areo-engine structure ***,their bulky geometric size represents a more effective obstacle to flow from high pressure(HP) turbine *** five struts give obvious influence for not only the LP turbine nozzle but also the flowfield within the ITD,and hence cause higher *** investigation has been undertaken to observe the influence of the Nozzle-Strut integrated design concept on the flowfield within the ITD and the nearby nozzle *** to the computational results,three main conclusions are finally ***,a noticeable low speed area is formed near the strut's leading edge,which is no doubt caused by the potential flow ***,more severe radial migration of boundary layer flow adjacent to the strut's pressure side have been found near the nozzle's trailing *** boundary layer migration is obvious,especially close to the shroud ***,radial pressure gradient aggravates this ***,velocity distribution along the strut's pressure side on nozzle's suction surface differs,which means loading variation of the *** it will no doubt cause nonuniform flowfield faced by the downstream rotor blade.

关键词： Intermediate Turbine Duct Integrated Design Concept Flowfield Analysis Total Pressure Loss Analysis

Numerical investigation of radial inflow in the impeller rear cavity with and without baffle

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Science China(Technological Sciences) 2016年第3期59卷 456-467页

作者： liu guang DU Qiang liu Jun WANG Pei ZHU JunQiang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

In typical small engines, the cooling air for high pressure turbine （HPT） in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot com- ponents. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are can＇ied out with axisymmetric and 3-D sector models for various inlet swirl ratio ,80 （0-0.6）, turbulent flow parameter 2-r （0.028-0,280） with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in re- ducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.

关键词： impeller rear cavity de-swirling device baffle Batchelor's Model Vortex Model

De novo domestication towards new crops

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National Science Review 2021年第4期8卷 40-41页

作者： Xianrong Xie Yao-guang liu State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources South China Agricultural University guangdong Laboratory for Lingnan Modern Agriculture College of Life Sciences South China Agricultural University

Long-term natural and human selections have domesticated crops from their wild progenitors for millennia, leading to the fixation of a large number of agronomically beneficial alleles and traits in cultivated crops. However, this process has been extremely time-consuming, accompanied with negative consequences, such as genetic erosion,

关键词： scanning tunneling microscopy phenyl-based molecular film electronic correlation electron-vibration coupling Kondo effect

Hydrogen-Bonding Crosslinked Supramolecular Polymer Materials:From Design Evolution of Side-Chain Hydrogen-Bonding to Applications

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Chinese Journal of Polymer Science 2024年第11期42卷 1619-1641,I0006页

作者： Qian Zhang Zi-Yang Xu Wen-guang liu School of Materials Science and Engineering Tianjin Key Laboratory of Composite and Functional MaterialsTianjin UniversityTianjin300350China

Hydrogen bonds(H-bonds)are the most essential non-covalent interactions in nature,playing a crucial role in stabilizing the secondary structures of *** inspiration from nature,researchers have developed several multiple H-bonds crosslinked supramolecular polymer materials through the incorporation of H-bond side-chain units into the polymer chains.N-acryloyl glycinamide(NAGA)is a monomer with dual amides in the side group,which facilitates the formation of multiple dense intermolecular H-bonds within poly(N-acryloyl glycinamide)(PNAGA),thereby exhibiting diverse properties dependent on concentration and meeting various requirements across different ***,numerous attempts have been undertaken to synthesize diverse NAGA-derived units through meticulous chemical structure regulation and fabricate corresponding H-bonding crosslinked supramolecular polymer *** this,the systematic clarification of the impact of chemical structures of side moieties on intermolecular associations and material performances remains *** present review will focus on the design principle for synthesizing NAGA-derived H-bond side-chain units and provide an overview of the recent advancements in multiple H-bonds crosslinked PNAGA-derived supramolecular polymer materials,which can be categorized into three groups based on the chemical structure of H-bonds units:(1)monomers with solely cooperative H-bonds;(2)monomers with synergistic H-bonds and other physical interactions;and(3)diol chain extenders with cooperative *** significance of subtle structural variations in these NAGA-derived units,enabling the fabrication of hydrogen-bonded supramolecular polymer materials with significantly diverse performances,will be ***,the extensive applications of multiple H-bonds crosslinked supramolecular polymer materials will be elucidated.

关键词： Hydrogen bonds High strength Side chain Supramolecular polymer materials