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Search Results: 1 - 10 of 24474 matches for " X. Cao "
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An ARX-Based PID-Sliding Mode Control on Velocity Tracking Control of a Stick-Slip Pi-ezoelectric-Driven Actuator  [PDF]
Y. Cao, X. B. Chen
Modern Mechanical Engineering (MME) , 2015, DOI: 10.4236/mme.2015.51002
Abstract: Piezoelectric-driven stick slip actuators have been drawn more and more attention in the nano- positioning application due to the high accuracy and theoretical unlimited displacement. However, the hysteresis of piezoelectric actuator (PEA) and the nonlinear friction force between the end- effector and the stage make control of piezoelectric-driven stick slip actuator challenge. This paper presents the development of an autoregressive exogenous (ARX)-based proportional-integral-derive (PID)-sliding mode control (SMC) for the velocity tracking control of the piezoelectric-driven stick slip actuator. Stability is guaranteed by rigorously choosing the appropriate PID parameters and the zero steady state error is achieved. To verify the effectiveness of the proposed method, experiments were carried out on a commercially-available piezoelectric-driven stick slip actuator. The tracking errors were compared with the traditional PID controller, illustrating that in spite of existing of modeling error, the ARX-based PID-SMC is able to better improve the velocity tracking performance of piezoelectric-driven stick slip actuator, compared with the traditional PID controller.
Aspects of red soil properties and water management in China
Cao Z.,Zhu X.
International Agrophysics , 1999,
Abstract: This paper is a brief reviev of studies on red soil water properties and its management in the tropics and subtropics of China. Although annual precipitation is more than evaporation, there is still seasonal draught in the area because of the uneven distribution of both rainfall and evaporation. Red soil structure is another reason for the seasonal draught. Several measures for alleviating this da-mage are also discussed in the paper.
Statistics of random lasing modes and amplified spontaneous emission spikes in weakly scattering systems
X. Wu,H. Cao
Physics , 2007,
Abstract: We have measured the spectral correlations and intensity statistics of random lasing modes in weakly scattering systems, and compared them to those of the amplified spontaneous emission spikes. Their dramatic differences revealed the distinct physical mechanisms. We find that local excitation of a weakly scattering system may greatly reduce the number of lasing modes even without absorption outside the pumped region. The lasing modes can be very different from the quasimodes of the passive system due to selective amplification of the feedback from the scatterers within the local gain region.
Adsorption, Segregation and Magnetization of a Single Mn Adatom on the GaAs (110) Surface
J. X. Cao,X. G. Gong,R. Q. Wu
Physics , 2005, DOI: 10.1103/PhysRevB.72.153410
Abstract: Density functional calculations with a large unit cell have been conducted to investigate adsorption, segregation and magnetization of Mn monomer on GaAs(110). The Mn adatom is rather mobile along the trench on GaAs(110), with an energy barrier of 0.56 eV. The energy barrier for segregation across the trenches is nevertheless very high, 1.67 eV. The plots of density of states display a wide gap in the majority spin channel, but show plenty of metal-induced gap states in the minority spin channel. The Mn atoms might be invisibl in scanning tunneling microscope (STM) images taken with small biases, due to the directional p-d hybridization. For example, one will more likely see two bright spots on Mn/GaAs(110), despite the fact that there is only one Mn adatom in the system.
Proton beams with controlled divergence and concentrated energy in TNSA regime by USUI laser pulse interaction with a tailored hole-target
Huan Wang,Lihua Cao,X. T. He
Physics , 2015,
Abstract: An improved acceleration scheme to produce protons with controlled divergence and concentrated energy density is studied using ultrashort ultraintense (USUI) laser pulse interaction with a tailored hole-target in target normal sheath acceleration (TNSA) regime. Two-dimension-in-space and three-dimension-in-velocity (2D3V) particle-in-cell (PIC) simulations show that the tailored hole-target helps to reshape the sheath electric field and generate a transverse quasistatic electric field of $TV/m$ along the inner wall of the hole. The transverse electric field suppresses the transverse expansion of the proton beam effectively, as it tends to force the produced protons to focus inwards to the central axis, resulting in controlled divergence and concentrated energy density compared with that of a single plain target. The dependence of proton beam divergence and energy feature on depth of the hole is investigated in detail. A rough estimation of the hole depth ranges depending on $a_{0}$ of the incident laser is also given.
Photonic band structure of ZnO photonic crystal slab laser
A. Yamilov,X. Wu,H. Cao
Physics , 2005, DOI: 10.1063/1.2134880
Abstract: We recently reported on the first realization of ultraviolet photonic crystal laser based on zinc oxide [Appl. Phys. Lett. {\bf 85}, 3657 (2004)]. Here we present the details of structural design and its optimization. We develop a computational super-cell technique, that allows a straightforward calculation of the photonic band structure of ZnO photonic crystal slab on sapphire substrate. We find that despite of small index contrast between the substrate and the photonic layer, the low order eigenmodes have predominantly transverse-electric (TE) or transverse-magnetic (TM) polarization. Because emission from ZnO thin film shows strong TE preference, we are able to limit our consideration to TE bands, spectrum of which can possess a complete photonic band gap with an appropriate choice of structure parameters. We demonstrate that the geometry of the system may be optimized so that a sizable band gap is achieved.
Effect of Chloride on the Atmospheric Corrosion of Simulated Artifact Iron in Nitrogenous
EFFECT OF CHLORIDE ON THE ATMOSPHERIC CORROSION OF SIMULATED ARTIFACT IRON IN NO3-BEARING POLLUTANT ENVIRONMENT

X Cao,CC Xu,
X.
,Cao,C.C.,Xu

金属学报(英文版) , 2006,
Abstract: The effect of chloride in nitrogen-bearing pollutant on the atmospheric corrosion of cast iron was investigated by using periodic wet-dry test, electrochemical experiment and surface tension test.Scanning electron microscopy (SEM) with energy disperse atomic X-ray (EDAX) was used to identify the corrosion processes and products. The results of the weight loss measurement showed that the whole corrosion kinetics can be approximately described by: AW=AtB. With the addition of NaC1, B increases. The result presented that Cl- accelerated the corrosion rate obviously during the whole corrosion process. The initial corrosion process was investigated from the viewpoint of surface tension. At the initial corrosion period, the corrosion rate was proportion to the adsorption of anions contained the solutions. And as corrosion went on, the penetration effect of anions and different characteristics of the corrosion products began to dominant the corrosion process, which led to the accelerated effect.
A dwarf wheat mutant is associated with increased drought resistance and altered responses to gravity
X Zhang, X Chen, Z Wu, X Zhang, C Huang, M Cao
African Journal of Biotechnology , 2005,
Abstract: Drought resistance is an important trait for crops. Here we report a new wheat mutant with increased drought resistance and altered gravitropism. During the bombardment transformation of Chinese wheat cultivar ‘Jingdong 6’, a recessive remarkably dwarf wheat mutant named ‘s-dwarf’ (super dwarf wheat) was created. It was severely dwarf and gibberellic acid insensitive. The relative water loss ratio of the detached leaf and the transpiration rate of s-dwarf seedlings were remarkably lower than Jingdong 6 while the photosynthetic rate of s-dwarf seedlings was significantly higher than Jingdong 6. Most of the s-dwarf seedlings survived in recovering experiement after water loss. The stalk of s-dwarf seedling also showed reduced gravitropism. This is the first report about a new dwarf wheat mutant associated with increased drought resistance and altered stalk gravitropism.
Variation of photosynthetic tolerance of rice cultivars (Oryza sativaL.) to chilling temperature in the light
X Li, K Cao, C Wang, Z Sun
African Journal of Biotechnology , 2010,
Abstract: Forty-two genotypes from the rice germplasm (Oryza sativa L.) were identified under chilling temperature in the light at bud, seedling and booting stages and divided into three basic types; cultivars tolerant to chilling in the light such as japonica, cultivars sensitive to chilling in the light such as indica and cultivars that have intermediate tolerance to chilling in the light such as hybrid rice cultivar. Photosynthetic characteristics of two cultivars tolerant (c.v. Taipei309 and Wuyujing3), two cultivars sensitive (c.v.CA212 and Pusa) and two intermediated tolerant (c.v. Liangyoupeijiu and Shanyou63) to the chilling treatment in the light were compared. The results showed that, compared to the rice varieties chilling tolerant rice, the sensitive ones indica exhibited a significant inhibition of maximum photosynthetic rate (Pm) and a decrease in the photochemical efficiency of photo-system 2 (PS2)(Fv/Fm), which led to the accumulation of AOS and decrease of Chl content. Interestingly, the ratios of ASA/DHA and GSH/GSSG showed similar changes as those with the performance of chilling tolerance, which indicated that ASA/DHA cycle might be an important protecting strategy in chilling tolerance, especially for the middle tolerant ones. We describe a simple and effective screening method and physiological basis for breeding crops for enhanced tolerance to chilling temperature in the light.
Recruitment of bloom-forming cyanobacteria and its driving factors
X Tan, F Kong, H Cao, Y Yu, M Zhang
African Journal of Biotechnology , 2008,
Abstract: Based on most of the literature, this paper reviewed the progress made in following aspects: cognition to cyanobacteria recruitment, various traps for studying cyanobacteria recruitment in lakes, recruitment patterns of some species of cyanobacteria, and the driving factors for recruitment. Additionally, perspective studies of cyanobacteria recruitment in lakes were pointed out. In light of the existing knowledge, cyanobacteria recruitment could be regarded as a process that benthic overwintering cyanobacteria migrated to the pelagic phase after germination and growth renewal under suitable conditions. This process was divided into three consecutive phases: germination, a potential growth phase, and migration to the pelagic phase. Previous studies mostly focused on the migration from sediments to water. To date, several kinds of traps had been designed to investigate cyanobacteria recruitment. Some studies showed that amounts of cyanobacteria recruitment were higher in shallow regions than deep regions of lakes, and the recruitment rates mostly peaked in a given time of year before blooms onset. Temperature, resuspension and bioturbation had been recognized to be the most important factors for driving cyanobacteria recruitment. Other factors (such as light, nutrients, anoxia, etc.) also played a role.
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