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Search Results: 1 - 10 of 126973 matches for " Zhengcai Li "
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Robust Adaptive Fuzzy Control for Planetary Rovers While Climbing up Deformable Slopes with Longitudinal Slip
Li Zhengcai,Wang Yang
Advances in Aerospace Engineering , 2014, DOI: 10.1155/2014/620890
Abstract: Mobility control is one of the most essential parts of planetary rovers’ research and development. The goal of this research is to let the planetary rovers be able to achieve demand of motion from upper level with satisfied control performance under the rough and deformable planetary terrain that often lead to longitudinal slip. The longitudinal slip influences the mobility efficiency obviously, especially on the major deformable slopes. Compared with the past works on normal stiff terrains, properties of soil and interaction between wheels and soil should be considered additionally. Therefore, to achieve the final goal, in this paper, wheel-soil dynamic model for six-wheel planetary rovers while climbing up deformable slopes with longitudinal slip is first built and control based in order to account for slip phenomena. These latter effects are then taken into account within terramechanics theory, relying upon nonlinear control techniques; finally, a robust adaptive fuzzy control strategy with longitudinal slip compensation is developed to reduce the effects induced by slip phenomena and modeling error. Capabilities of this control scheme are demonstrated via full scale simulations carried out with a six-wheel robot moving on sloped deformable terrain, whose real time was computed relying uniquely upon RoSTDyn, a dynamic software. 1. Introduction In the field of special mobile robots environment, including planetary exploration missions, caravan survey, polar expedition, and wild fire spreading, rovers may need to traverse on deformable terrains, and the interaction between rigid wheels and soft soil has become a meaningful research topic because of longitudinal slip influence mobility control obviously [1]. In the past works on normal stiff terrains, for example, Kanayama et al. [2] proposed a stable control scheme for an autonomous mobile robot under the assumption of perfect velocity tracking. Kim and Oh [3] proposed a modified input-output linearization method to solve the problem of a decoupling matrix using a generalized inverse that provided a least-squares solution to the tracking control of two-wheeled mobile robots. Raibert et al. [4] proposed a PID controller to solve the path tracking problem of a mobile robot using a simple linearized model of the mobile robot, which was composed of an integrator and a delay. Colombano et al. [5] proposed an output-feedback controller that allowed a unicycle mobile robot to track a predefined path. However, all of these control methods based on normal stiff terrains hypothesis of nonholonomic mobile robot
Negative Pressure Wound Therapy Decreases Mortality in a Murine Model of Burn-Wound Sepsis Involving Pseudomonas aeruginosa Infection
Yang Liu, Qin Zhou, Yunchuan Wang, Zhengcai Liu, Maolong Dong, Yaojun Wang, Xiao Li, Dahai Hu
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090494
Abstract: Background The colonization of burn wounds by Pseudomonas aeruginosa can lead to septic shock, organ injuries, and high mortality rates. We hypothesized that negative pressure wound therapy (NPWT) would decrease invasion and proliferation of P. aeruginosa within the burn wound and reduce mortality. Methods Thermal injuries were induced in anesthetized mice, and P. aeruginosa was applied to the wound surface for 24 h. After removing the burn eschar and debridement, the animals were subjected to either NPWT or wet-to-dry (WTD) treatment protocols. The bacterial loads on the wound surface were assessed during 7 d of treatment, as were the concentrations of inflammatory cytokines in the peripheral blood samples. Survival was monitored daily for 14 d after burn induction. Finally, samples of wounded skin, lung, liver, and kidney were collected and subjected to histopathological examination. Results Applying P. aeruginosa to the burn wound surface led to sepsis. During early stages of treatment, NPWT reduced the mortality of the septic animals and levels of P. aeruginosa within the burn wound compared with WTD-treated animals. Circulating levels of cytokines and cytoarchitectural abnormalities were also significantly reduced via NPWT. Conclusions Our data indicate that NPWT inhibits the invasion and proliferation of P. aeruginosa in burn-wounded tissue and decreases early mortality in a murine model of burn-wound sepsis. These therapeutic benefits likely result from the ability of NPWT to decrease bacterial proliferation on the wound surface, reduce cytokine serum concentrations, and prevent damage to internal organs.
Floating-zone growth and property characterizations of high-quality La2-xSrxCuO4 single crystals
Xiaoli Shen,Zhengcai Li,Caixia Shen,Wei Lu,Xiaoli Dong,Fang Zhou*,Zhongxian Zhao
Physics , 2009,
Abstract: We have grown underdoped (x = 0.11, 0.12) and optimally doped (x = 0.16) La2-xSrxCuO4 (LSCO) crystals by traveling-solvent floating-zone (TSFZ) technique. In order to obtain LSCO single crystals of high quality, we have made much effort to optimize the preparation procedures. For example, we have adopted sol-gel route to prepare highly fine and homogeneous LSCO precursor powder, and used quite slow growth rate. The sizable grown crystal ingots are typically about 6.6 mm in diameter and 100 mm in length, and no impurity phases were detected. The high quality of grown crystals has been verified by double-crystal x-ray rocking curves, with full-width-at-half-maximum (FWHM) being only 113 ~ 150 arcseconds (or 0.03 deg - 0.04 deg), which are the best data reported so far for LSCO crystals. The superconducting critical temperatures (TC's) of the cuprate crystals are 30 K for x = 0.11, 31 K for x = 0.12 and 38.5 K for x = 0.16 samples according to magnetic measurements.
Anti-Atherosclerotic Effects Mediated by the Combination of Probucol and Amygdalin in Apolipoprotein E-Knockout Mice Fed with a High Fat Diet
Deng Jiagang,Hailian Wang,Yuande Liu,Chunyang Li,Erwei Hao,Zhengcai Du,Chuanhong Bao,Jianzhen Lv,Yi Wang
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2012.20.25
Abstract: To ameliorate atherosclerosis progression, researchers studied the combined therapy of amygdalin and probucol, a cholesterol-lowering drug in ApoE knockout mice. About 8 weeks old male ApoE knockout mice were fed on a High Fat Diet (HFD) and received amgydalin treatment alone, probucol treatment alone or combined therapy in the present study. Triglyceride (TG), Total Cholesterol (TC) and Low Density Lipoprotein (LDL) cholesterol levels were measure at the end of treatment. Aortic lesion area, plaque area and plaque coverage percentage of aortic sinus were also quantified. Meanwhile, inflammation related proteins as Matrix Metalloproteinase-2 (MMP-2) and Matrix Metalloproteinase-9 (MMP-9) were analyzed. Studies on blood lipid revealed that combined therapy significantly decreased both total cholesterol and LDL cholesterol levels. Moreover, significantly decreased blood lipids levels were accompanied with reduced plaque areas and plaque coverage percentages indicating the anti-atherosclerotic function of combined therapy is through reduction of cholesterol levels. Furthermore, observations on the mRNA levels and expression of MMP-2 and -9 suggested that combined therapy induces decreased expression of MMP-2 and -9 in aortic lesions. The studies indicated that the combination of amygdalin and probucol was more effective in retarding atherosclerotic lesion progression than the administration of each drug alone.
Resonance as a probe of the electron superconducting gap in BaFe1.9Ni0.1As2
Jun Zhao,Louis-Pierre Regnault,Chenglin Zhang,Miaoying Wang,Zhengcai Li,Fang Zhou,Zhongxian Zhao,Pengcheng Dai
Physics , 2009, DOI: 10.1103/PhysRevB.81.180505
Abstract: The discovery of high-transition temperature (high-Tc) superconductivity near antiferromagnetism in iron arsenides raised the possibility of an unconventional superconducting mechansim1-8. The observation of clear Fermi surfaces and nodeless superconducting gaps by angle resolved photoemission9-12 suggests that electron pairing in these materials may be mediated by quasiparticle excitations between sign reversed hole and electron Fermi pockets5-8. Although the presence of a 'resonance' in the spin excitation spectrum found by inelastic neutron scattering13-17 is consistent with this picture18-20, there has been no direct evidence connecting the resonance to the superconducting gap energy. Here we show that for the optimally electron doped BaFe1.9Ni0.1As2 (Tc =20 K, Fig. 1c) iron arsenide superconductor, application of a magnetic field that suppresses the superconductivity and superconducting gap energy also reduces the intensity and energy of the resonance. These results suggest that the energy of the resonance is proportional to the electron pairing energy, and thus indicate that spin fluctuations are intimately related to the mechanism of superconductivity in iron arsenides.
Effect of electron-doping on spin excitations of underdoped BaFe$_{1.96}$Ni$_{0.04}$As$_{2}$
Leland W. Harriger,Astrid Schneidewind,Shiliang Li,Jun Zhao,Zhengcai Li,Wei Lu,Xiaoli Dong,Fang Zhou,Zhongxian Zhao,Jiangping Hu,Pengcheng Dai
Physics , 2009,
Abstract: We use neutron scattering to study magnetic order and spin excitations in BaFe$_{1.96}$Ni$_{0.04}$As$_{2}$. On cooling, the system first changes the lattice symmetry from tetragonal to orthoromhbic near $\sim$97 K, and then orders antiferromagnetically at $T_N=91$ K before developing weak superconductivity below $\sim$15 K. Although superconductivity appears to co-exist with static antiferromagnetic order from transport and neutron diffraction measurement, inelastic neutron scattering experiments reveal that magnetic excitations do not respond to superconductivity. Instead, the effect of electron-doping is to reduce the c-axis exchange coupling in BaFe$_2$As$_2$ and induce quasi two-dimensional spin excitations. These results suggest that transition from three-dimensional spin waves to two-dimensional spin excitations by electron-doping is important for the separated structural/magnetic phase transitions and high-temperature superconductivity in iron arsenides.
Unconventional Superconductivity Revealed by Peculiar Angular Dependence of the Upper Critical Field in K2Cr3As3
Huakun Zuo,Jin-Ke Bao,Yi Liu,Jinhua Wang,Zhao Jin,Zhengcai Xia,Liang Li,Zhuan Xu,Zengwei Zhu,Guang-Han Cao
Physics , 2015,
Abstract: The upper critical magnetic field $H_{\mathrm{c2}}$ of a superconductor measures the strength of superconductivity in response to external magnetic fields, which gives clues to the superconducting Cooper pairing. In this paper, we report measurements of $H_{\mathrm{c2}}$ as functions of temperature $T$, polar angle $\theta$ and azimuthal angle $\phi$ of the applied magnetic field direction, for a newly discovered superconductor K$_{2}$Cr$_{3}$As$_{3}$ with a quasi-one-dimensional and non-centrosymmetric crystal structure. We demonstrate that the anisotropy reversal in $H_{\mathrm{c2}}(T)$ reported previously comes from a fully anisotropic Pauli-limiting effect. The $H_{\mathrm{c2}}(\theta)$ data reveal an intrinsic uniaxially effective-mass anisotropy ($m_{\bot}/m_{\parallel}\sim$ 2.0) with an extrapolated orbitally limited field of 510.5 kOe at zero temperature. More interestingly, the in-plane $H_{\mathrm{c2}}(\phi)$ profile shows a unique threefold modulation, which breaks the time-reversal symmetry. The $H_{\mathrm{c2}}(\theta, \phi, T)$ behaviours strongly suggest unconventional superconductivity characterized by a dominant triplet Cooper pairing with odd parity in K$_{2}$Cr$_{3}$As$_{3}$.
High temperature superconducting FeSe films on SrTiO3 substrates
Yi Sun,Wenhao Zhang,Ying Xing,Fangsen Li,Yanfei Zhao,Zhengcai Xia,Lili Wang,Xucun Ma,Qi-Kun Xue,Jian Wang
Physics , 2014, DOI: 10.1038/srep06040
Abstract: Interface enhanced superconductivity at two dimensional limit has become one of most intriguing research directions in condensed matter physics. Here, we report the superconducting properties of ultra-thin FeSe films with the thickness of one unit cell (1-UC) grown on conductive and insulating SrTiO3 (STO) substrates. For the 1-UC FeSe on conductive STO substrate (Nb-STO), the magnetization versus temperature (M-T) measurement shows a diamagnetic signal at 85 K, suggesting the possibility of superconductivity appears at this high temperature. For the FeSe films on insulating STO substrate, systematic transport measurements were carried out and the sheet resistance of FeSe films exhibits Arrhenius TAFF behavior with a crossover from a single-vortex pinning region to a collective creep region. More intriguing, sign reversal of Hall resistance with temperature is observed, demonstrating a crossover from hole conduction to electron conduction above Tc in 1-UC FeSe films.
A STUDY OF SCORE EQUATING IN THE COLLEGE ENGLISH TEST:A NEW APPROACH BASED ON "ANCHOR ITEMS" AND TWO-PARAMETER IRT MODEL
大学英语四、六级考试分数等值研究

Zhu Zhengcai,
朱正才

心理学报 , 2005,
Abstract: In China's College English Test (CET), Rasch model has been used in the score equating procedure for 15 years and lots of score equating data have been accumulated. This paper discusses in detail some demerits of the score equating method based on Rasch model, and introduces a new score equating approach based on "anchor items" and two-parameters IRT model (the Item Response Theory model). It is assumed that for the old score equating method based on Rasch model: 1)The students in the control group give equal attention to both the formal and the control papers. 2)There has been no leakage of the items in either paper. 3) All items have the same Discrimination Index. A failure in assumption 1) would usually occur because the students feel that the control paper test is an extra burden to them and they often do not give it the same importance as the formal paper. In this case their marks on the control paper would be lower than their true performance. If the two papers were, in fact, equally easy or difficult they would score lower marks on the control paper, thus making it appear harder. This would have the effect of making the formal paper seem to be relatively easier and in the process of equating the students' marks would be reduced. If assumption 2) is not true and the control paper has not truly been kept confidential, the effects would be in the opposite direction. The candidates would do better than they should on the control paper, causing their marks on that paper to be relatively high in comparison with the formal test. The latter test would therefore appear to the equating algorithm to be harder than it really is and all the students' marks would be increased. Note that this would be true even if only a few items were leaked. For example, if just one Reading passage were leaked, together with the associated items, those five items would be scored correct for students who might otherwise have failed at least in some of them. Since reading items have double weight, this could falsely increase the score of weaker students by up to 10 marks! Of course, the effect on the mean score would be smaller since many students would have scored on these items anyway. It might also be argued that, since there is evidence that the items do not all have the same Discrimination Index, the two/three-parameter IRT model should be used. It has to be accepted that any equating step will increase the standard error of measurement (SEM) of the final score because the parameters that need to be used for equating will be estimated with some standard error of their own. However, this increase will usually be small (given the sample size of several hundred used to do the model fitting) and should be more than compensated for by the reduction in the "between-forms" bias, which the equating procedure is designed to correct. In this paper, a pilot study with real CET test data is reported with satisfactory score equating results.
RESEARCH ON SECONDARY EMISSION PROPERTIES OF IMPREGNATED BARIUM SCANDATE DISPENSER CATHODE UNDER BOMBARDMENT OF POWERFUL ELECTRON BEAM
强流电子束轰击下浸渍钪酸盐钡钨阴极的次级发射特性

Xie Zhengcai,
偰正才

电子与信息学报 , 1989,
Abstract: Secondary emission properties of impregnated barium scandate dispenser cathode has been studied under the bombardment of pulse powerful electron beam (electron energy-2300eV and electronic density-10A/cm2).
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