Feng Gao

Jilin University, Yung-chi, Jilin Sheng, China

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Publications (161)223.88 Total impact


  • No preview · Article · Feb 2016 · Optics Express

  • No preview · Article · Feb 2016 · Optics Letters
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    Full-text · Article · Jan 2016 · Remote Sensing
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    Chenkun Qi · Feng Gao · Xianchao Zhao · Yi Yue
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    ABSTRACT: The flexible manipulator is a spatially distributed mechanical system. An accurate model of the flexible manipulator is essential for the positioning control of the end effector. In this study, a greybox distributed parameter modeling approach is proposed for the flexible manipulator with unknown nonlinear dynamics. First, a nominal Euler-Bernoulli beam model is derived to describe the linear dynamics. To compensate unknown nonlinear dynamics, a nonlinear term is added in the nominal model.The Galerkin method is used to reduce the infinite-dimensional partial differential equation (PDE) model into a finite-dimensional ordinary differential equation (ODE) model. A neural network is designed to estimate the unknown nonlinearities from the input-output data. The effectiveness of the proposed greybox distributed parameter modeling approach is verified by the simulations on a flexible manipulator.
    Preview · Article · Dec 2015
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    ABSTRACT: Actuator failure is a serious problem for legged robots working in remote or complicated environments. Having a fault-tolerant gait is essential to keep the robot walking when actuator failures occur. This paper proposes an algorithm for the fault-tolerant gait to overcome the failure of more than one actuator. The idea is that the degrees of freedom (DOFs) of the robot body are divided into two parts: the major DOFs which are critical to maintain walking and the secondary DOFs. By finding an appropriate kinematic resolution of the motions of the secondary DOFs the motions of the major DOFs can be realized. In this process, a repeatable control problem is also solved by minimizing the actuator displacement function. This method can make full use of the remaining actuators of the robot. The performance of the fault-tolerant gait is demonstrated through a series of simulations and experiments on a hydraulic quadruped robot.
    No preview · Article · Dec 2015 · Mechanism and Machine Theory
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    ABSTRACT: The morphology of two freshwater urostylid species, Neourostylopsis flava spec. nov. and Pseudourostyla subtropicaChen et al., 2014, isolated from freshwater ponds in northern and southern China, respectively, was investigated following examination of specimens in vivo and following protargol staining. Neourostylopsis flava spec. nov. is distinguished from its congeners by the following characteristics: body size 150-220×50-75μm in vivo; yellow in colour; bright yellow to yellow-brownish spherical cortical granules densely arranged along marginal cirral rows and in irregular short rows on dorsal side; adoral zone with 40-55 membranelles; six to eight frontal, three or four buccal, two pretransverse ventral and seven to nine transverse cirri; 27-40 midventral pairs extending to about anterior 55% of cell; four or five left and four right marginal rows; freshwater habitat. A redescription of a freshwater population of P. subtropica is also provided. Phylogenetic analyses based on small subunit ribosomal DNA sequences shows that P. subtropica and N. flava spec. nov. group with their congeners and both Neourostylopsis and Pseudourostyla are monophyletic.
    No preview · Article · Nov 2015 · European Journal of Protistology
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    ABSTRACT: The characteristics of whispering gallery modes (WGM) in silver-coated inverted-wedge silica microdisks are theoretically investigated by using finite element method. Dielectric TE mode always exists in silver-coated inverted-wedge resonators; dielectric TM mode tends to couple with SPP modes; only pure interior surface plasmonic polariton (SPP) mode but not pure exterior SPP mode is observed in contrast to the metal-coated cylindrical and toroidal resonators. The dependence of quality factor of different kinds of WGMs on the radius of the resonator and the thickness of the coated silver layer are systematically analyzed. We find that the quality factors of the hybrid WGMs associated with SPP mode can reach 104. The maximum light intensity enhancement in ambient for a hybrid mode consisting of a dielectric TM mode and an exterior SPP mode can be obtained when a silver film of thickness ~40 nm is deposited. The silver-coated inverted-wedge silica resonators may be widely applied in sensing and surface enhanced Raman scattering. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg.
    Full-text · Article · Nov 2015 · Science China: Physics, Mechanics and Astronomy
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    ABSTRACT: Lithium niobate (LN) microdisk resonators on a LN-silica-LN chip were fabricated using only conventional semiconductor fabrication processes. The quality factor of the LN resonator with a 39.6-μm radius and a 0.5-μm thickness is up to 1.19 × 10<sup>6</sup>, which doubles the record of the quality factor 4.84 × 10<sup>5</sup> of LN resonators produced by microfabrication methods allowing batch production. Electro-optic modulation with an effective resonance-frequency tuning rate of 3.0 GHz/V was demonstrated in the fabricated LN microdisk resonator.
    Full-text · Article · Sep 2015 · Optics Express
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    ABSTRACT: The modeling of the piezoelectric actuator is very important for the fast and accurate nano-positioning control. However, the complex creep, vibration and hysteresis dynamics make the modeling very difficult. Because there are often model uncertainties in the first-principle model, the model identification from the experimental data is very necessary. Most identification approaches only consider partial dynamics of the creep, vibration and hysteresis. Though they can be combined together after they are individually identified from different experiments, it is difficult to design the completely decoupled experiment. In this study, an incremental Hammerstein-like modeling approach is proposed to identify the creep, vibration and hysteresis dynamics from one experiment. The model is called nonlinear–linear–linear-Hammerstein-like model, where one dynamic nonlinear system is used to model the hysteresis and two dynamic linear systems are used to model the creep and vibration. The creep and vibration are assumed to be decoupled, and there is a known upper bound on the order of the creep model. A two-stage incremental modeling approach is proposed to reduce the modeling complexity, where the slow dynamics of the hysteresis and creep are estimated first and then the residual of this model is used to estimate the fast dynamics of the vibration. In each stage, the model structure and order are determined by a locally regularized orthogonal least-squares-based model term selection algorithm and the parameters are estimated using a regularized least-squares method. The effectiveness of the proposed modeling approach is verified by the simulations and experiments on typical piezoelectric actuators.
    No preview · Article · Aug 2015 · Nonlinear Dynamics
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    Full-text · Dataset · Jul 2015
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    Full-text · Dataset · Jul 2015
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    ABSTRACT: An all-fiber optical heterodyne detection configuration was proposed based on an all-fiber acousto-optic structure, which acted as both frequency shifter and coupler at the same time. The vibration waveform within a frequency range between 1 Hz to 200 kHz of a piezoelectric mirror was measured using this optical heterodyne detection system. The minimal measurable vibration amplitude and resolution are around 6 pm and 1 pm in the region of tens to hundreds of kilohertz, respectively. The configuration has advantages of compact size, high accuracy and non-contact measurement. Moreover, it is of a dynamically adjustable signal-to-noise ratio to adapt different surface with different reflections in the measurement, which will improve the usage efficiency of the light power.
    Full-text · Article · Jun 2015 · Optics Express
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    ABSTRACT: An extended theory of the mutually modulated cross-gain modulation was developed to make it valid under considerable modulated wavenumber-interaction length product. Parametric analysis of the extended theory shows that, in the modulated probe beam out of the gain medium, the spectral sensitivity of the first harmonic wave is associated with its amplitude. The larger the sensitivity is, the smaller the amplitude will be. An effective method was provided to monitor and achieve high spectral sensitivity at a pre-selected frequency detuning in practice. The validity of the extended theory was confirmed by a sensing experiment in a piece of ∼10-km fiber with 10 kHz modulation frequency, in which a fast light propagation with a sensitivity of 0.592 mrad/kHz was achieved.
    Full-text · Article · May 2015 · Optics Express
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    ABSTRACT: The living morphology and infraciliature of seven Dysteria species isolated from the seas around China were investigated by observation of both living cells and specimens after protargol impregnation. Dysteria paraprocera sp. n. is characterized as follows: cell size 110-150×30-40μm in vivo; body elongate rectangular and slender; a yellow-brown to dark red coloured pigment spot located at anterior end of body; three right kineties, with rightmost two extending apically to dorsal margin and innermost one starting at level of cytostome; eight or nine short left kineties at equatorial area. Dysteria nabia, D. proraefrons, D. brasiliensis, D. cristata, D. derouxi and D. crassipes basically correspond well with previous studies and therefore only brief descriptions are presented. Discussions of these species are helpful, however, in understanding the circumscription of Dysteria morphotypes. After careful comparison, Dysteria procera sensu Liu et al. (2008, Acta Hydrobiol. Sin. 32 (suppl.), 84-89 (in Chinese with English abstract)) was verified as a new species, D. subtropica sp. n., mainly because the innermost right kinety starts at mid-body. Small-subunit (SSU) rRNA genes were sequenced for four species of Dysteria, namely, D. paraprocera sp. n., D. subtropica sp. n., D. proraefrons and D. nabia. Sequence comparisons and phylogenetic analyses indicate that these species are well outlined and cluster with their congeners. Copyright © 2015 Elsevier GmbH. All rights reserved.
    No preview · Article · May 2015 · European Journal of Protistology
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    ABSTRACT: The spike (S) protein of porcine hemagglutinating encephalomyelitis virus (PHEV) may mediate infection by binding to a cellular neural cell adhesion molecule (NCAM). This study aimed to identify the crucial domain of the S1 subunit of the S protein that interacts with NCAM. Three truncated segments (S1-291, S277-794 and S548-868) of the S gene of PHEV and the NCAM gene were cloned individually into the Escherichia coli expression vectors and yeast two-hybrid expression vectors. The interaction between S1-291, S277-794, S548-868 and NCAM were detected by a GST pull-down experiment and yeast two-hybrid assay. Three fusion proteins (S1-291, S277-794 and S548-868) were screened for their interactions with NCAM by protein-protein interaction assays. The results of these assays clarified that S277-794 interacted with NCAM, while S1-291 and S548-868 did not. A small fragment (258-amino-acid fragment, residues 291-548) on the PHEV S protein was posited to be the minimum number of amino acids necessary to interact with NCAM. This fragment may be the receptor-binding domain that mediates PHEV binding to NCAM. © 2015 S. Karger AG, Basel.
    No preview · Article · Apr 2015 · Intervirology
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    ABSTRACT: A new marine hypotrichous ciliate, Sterkiella subtropica sp. nov. was recently isolated from a mangrove wetland in Hong Kong. Its morphology, morphogenesis and systematic position have been investigated. The new species is diagnosed by combined features of morphology, ciliature and nuclear apparatus, while its ontogenetic events present a stable pattern: (1) the six streaks of the UM- and cirral anlagen are segmented in a 1: 3: 3: 3: 4: 4 pattern from left to right, and form three frontal, four frontoventral, one buccal, five ventral and five transverse cirri; (2) the dorsal structure is similar to most other oxytrichids: that is in a "4+2" pattern with three caudal cirri being formed. Based on the small-subunit rDNA sequence, the new species is different from its congeners by between 21 bp and 35 bp, with sequence identities from 0.978 to 0.987. All molecular trees exhibit a similar topology: the monophyly of Sterkiella species is not completely supported in our analyses and the approximately unbiased tests (both including and excluding the new species) also reject the possibility that Sterkiella is a monophyletic lineage as indicated by the morphology-based classification.
    Full-text · Article · Apr 2015 · International Journal of Systematic and Evolutionary Microbiology
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    ABSTRACT: Widespread anthropogenic land-cover change over the last five centuries has influenced the global climate system through both biogeochemical and biophysical processes. Models indicate that warming from carbon emissions associated with land-cover conversion have been partially offset by cooling from elevated albedo, but considerable uncertainty remains partly because of uncertainty in model treatments of albedo. This study incorporates a new spatially and temporally explicit, land-cover specific albedo product derived from MODIS with a historical land-use dataset (Land Use Harmonization product) to provide more precise, observationally derived estimates of albedo impacts from anthropogenic land-cover change with a complete range of dataset specific uncertainty. The mean annual global albedo increase due to land-cover change during 1700–2005 was estimated as 0.00106 ± 0.00008 (mean ± standard deviation), mainly driven by snow exposure due to land-cover transitions from natural vegetation to agriculture. This translates to a top-of-atmosphere (TOA) radiative cooling of −0.15 ± 0.1 W m−2 (mean ± standard deviation). Our estimate was in the middle of the IPCC AR5 range of −0.05 to −0.25 W m−2, and incorporates variability in albedo within land-cover classes.
    Full-text · Article · Dec 2014 · Geophysical Research Letters
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    ABSTRACT: External disturbances can greatly influence the walking and working performance of legged robots. Identification of external disturbances is the basis of legged robots’ ability to adapt to a given environment. However, there are no appropriate sensors to measure the location, direction, and magnitude of external disturbances. In this paper, an indirect method is presented to identify external disturbance forces and torques for a high-payload quadruped robot. To improve carrying capacity, the robot leg is designed as a parallel–serial mechanism. This leg design ensures that there are only mechanical parts on the lower half of the robot. To increase anti-radiation capability, no sensors are installed on the robot feet. The robot is driven by twelve hydraulic actuators. A dynamic model has been proposed to identify external disturbances using hydraulic actuation forces and robot inertia. The obtained disturbances are expressed as a 6-DOF force screw, including forces and torques. The calculation process is simple because the equations can be explicitly solved without differential calculus. Simulations were performed to test the effectiveness of the identification model. A pulling experiment was carried out to evaluate the identification error. Finally, as an application, the proposed model was used to recognize changes in additional weight during crawling gait walking.
    No preview · Article · Dec 2014 · International Journal of Mechanics and Materials in Design
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    ABSTRACT: Orf virus (ORFV) is a typical member of the genus Parapoxvirus. The parapoxvirus genome consists of highly variable terminal regions and relatively conserved central regions with a high G + C content. In our previous study, a novel ORFV strain, NA1/11, was isolated from northeastern China. To fully characterize this strain, we sequenced the entire genome of NA1/11 and conducted a comparative analysis using multiple parapoxviruses. The genomic sequence of NA1/11 was found to consist of 137,080 nucleotides with a G + C content of 63.6 %, but it did not contain the terminal hairpin sequence. Alignment of ORFs from NA1/11 with NZ2, IA82 and SA00 revealed several highly variable ORFs, while the most evident ones are ORFs 001, 103, 109-110, 116 and 132. An odd phenomenon in the region of ORFs 118-120 is that the non-coding fragments are almost as long as the coding fragments. By comparative analysis of inverted terminal repeats, we identified one repeat motif and a long conserved fragment. By comparing the ITRs of SA00 with those of three other ORFVs, more clues were obtained about the correlation between ITR sequence and host adaption. Comparison of the NA1/11 genome with the sequences of other strains of ORFV revealed highly variable regions, thus providing new insights into the genetic diversity of ORFV.
    No preview · Article · Nov 2014 · Archives of Virology
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    ABSTRACT: The present study investigates the morphologic and molecular characteristics of three Condylostoma species isolated from brackish and marine tropical habitats of China, including Condylostoma tropicum spec. nov., Condylostoma elongatum spec. nov. and Condylostoma curvum Burkovsky, 1970. The two new species have slender and elongated bodies with the posterior portion distinctly narrowed, forming long tails, thus they obviously differ from most congeners. In addition, Condylostoma tropicum spec. nov. is characterized by its small buccal cavity, single frontal cirrus, 26–33 somatic kineties, and moniliform macronucleus composed of 8–22 nodules. Condylostoma elongatum spec. nov. is distinguished by its huge body size (1000–1200 μm long in vivo), the prominent buccal cavity, 5–7 frontal cirri and 37–43 somatic kineties. Condylostoma curvum is also reinvestigated in this paper using both protargol impregnation and molecular techniques. Phylogenetic analyses based on SSU rDNA sequence data indicate that the three organisms are located within the genus Condylostoma; the genus Condylostoma fails to form a monophyletic branch in both Maximum-likelihood tree and Bayesian inference analysis. Nonetheless, the AU test shows that the monophyly of Condylostoma could not be rejected.
    Full-text · Article · Nov 2014 · European Journal of Protistology

Publication Stats

2k Citations
223.88 Total Impact Points

Institutions

  • 2012-2015
    • Jilin University
      • College of Animal Science and Veterinary Medicine
      Yung-chi, Jilin Sheng, China
    • Ocean University of China
      • Laboratory of Protozoology
      Tsingtao, Shandong Sheng, China
  • 2006-2015
    • Nankai University
      • Department of Physics
      T’ien-ching-shih, Tianjin Shi, China
    • University of Massachusetts Boston
      Boston, Massachusetts, United States
  • 2004-2015
    • Shanghai Jiao Tong University
      • • State Key Laboratory of Mechanical Systems and Vibration
      • • Department of Mechanical Engineering (ME)
      Shanghai, Shanghai Shi, China
  • 2011-2013
    • East China JiaoTong University
      Jiangxi, Gansu Sheng, China
    • Shandong University of Science and Technology
      Tsingtao, Shandong Sheng, China
    • NASA
      Вашингтон, West Virginia, United States
  • 2010
    • Shandong University of Technology
      Chang-tien-shih, Shandong Sheng, China
    • Zhejiang University
      Hang-hsien, Zhejiang Sheng, China
    • East China University of Science and Technology
      Shanghai, Shanghai Shi, China
  • 2009-2010
    • Texas A&M University
      • Department of Chemistry
      College Station, TX, United States
  • 2005-2010
    • Shanghai University
      Shanghai, Shanghai Shi, China
    • Beijing Normal University
      • Research Center for Remote Sensing and GIS
      Peping, Beijing, China
  • 2008
    • Washington University in St. Louis
      San Luis, Missouri, United States
  • 2003-2008
    • University of Wisconsin - Milwaukee
      • Department of Chemistry and Biochemistry
      Milwaukee, Wisconsin, United States
  • 1029-2004
    • Boston University
      • Center for Remote Sensing
      Boston, Massachusetts, United States
  • 2001-2003
    • University of Toledo
      Toledo, Ohio, United States
  • 2002
    • Hebei University of Technology
      Ho-pei-ts’un, Beijing, China