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1

Synchronization and stability of an elastically coupled tri-rotor vibration system

Hou Y., Du M., Fang P., Zhang L.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 1

227--240

EN

A new mechanism, an elastically coupled tri-rotor system, is proposed to implement synchronization. It is composed of a rigid body, three induction motors, coupling unit and springs. According to the Lagrange equation, the model of the system is established. The average method of small parameters is applied to study the synchronization characteristics of the system, therefore, the balance equation and stability criterion of the system can be obtained. Obviously, many parameters affect the synchronous state of the rotors, especially the spring stiffness, the stiffness of the coupling unit and the installation location of the system. Finally, computer simulations are used to verify the correctness of theoretical analysis.

2

The dynamics modeling and simulation for coupled double-rotor spindle system of high speed grynder

Hou Y., Wang S., Han Z.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 1b

25--28

EN

This study was focused on the theoretical modeling and numerical simulation about the dynamic characteristics of coupled double-rotor spindle system of high speed grinder. The critical speeds of first three orders, the modes of variation and other dynamic characteristic parameters of the spindle system were analyzed and calculated. The results showed that the critical speeds of coupled double-rotor system were arranged in a similar increasing order as to those of each single rotor. It was thus indicated that the critical speeds of each order for coupled double-rotor system corresponded to those of single rotor. Furthermore, the main vibration modes of double-rotor system at each order were analyzed. The results indicated that vibration mode of each order of double rotors was the superimposition of the vibration mode of each single rotor. At variable critical speeds, the vibration mode of each single rotor in the system varied in its extent. If the critical speed of double-rotor system was close to that of a single rotor, then the superimposition of vibration modes of single rotors would become more significant under coupling state.

PL

W pracy położono nacisk na modelowanie teoretyczne i symulację numeryczną charakterystyk dynamicznych systemu wrzeciona ze sprzężonym podwójnym rotorem w wiertarce dużej szybkości, Przeanalizowano i obliczono szybkości krytyczne trzech pierwszych rzędów, typy wibracji i inne parametry charakterystyk dynamicznych systemu wrzeciona. Wykazano, że szybkości krytyczne systemu z rotorem podwójnym odpowiadają szybkości krytycznej odpowiednika z rotorem pojedynczym. Natomiast typy wibracji każdego rzędu rotora podwójnego są superpozycją typów wibracji pojedynczych rotorów. Jeśli szybkość krytyczna systemu z podwójnym rotorem jest bliska tej, jaką ma pojedynczy rotor, typy wibracji pojedynczych rotorów stają się bardziej znaczące pod wpływem stanu sprzężenia.

3

Mixture model and Markov random field-based remote sensing image unsupervised clustering method

Hou Y., Yang Y., Rao N., Lun X., Lan J.

Opto-Electronics Review

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2011

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Vol. 19, No. 1

83-88

EN

In this paper, a novel method for remote sensing image clustering based on mixture model and Markov random field (MRF) is proposed. A remote sensing image can be considered as Gaussian mixture model. The image clustering result corresponding to the image label field is a MRF. So, the image clustering procedure is transformed to a maximum a posterior (MAP) problem by Bayesian theorem. The intensity difference and the spatial distance between the two pixels in the same clique are introduced into the traditional MRF potential function. The iterative conditional model (ICM) is employed to find the solution of MAP. We use the max entropy criterion to choose the optimal clustering number. In the experiments, the method is compared with the traditional MRF clustering method using ICM and simulated annealing (SA). The results show that this method is better than the traditional MRF model both in noise filtering and miss-classification ratio.

4

Effects of elevated CO2 and temperature on growth and morphology of fir (Abies faxoniana Rehd. et Wils.) and native herbs in a treeline ecotone : an experimental approach

Hou Y., Luo Z., Kaiyun W., Jenerette G., Qiao Y.

Polish Journal of Ecology

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2010

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Vol. 58, nr 2

311-322

EN

Determining how changes in atmospheric CO2 concentrations and climate affects growth of species is helpful for understanding plant community species shift in response to future environmental changes. In the present study, fir (Abies faxoniana) and native herbs from treeline ecotone of east Qinghai-Tibetan Plateau (altitude: 3230-3300 m) were exposed to ambient CO2 or ambient +350 [mu]mol.mol[^-1] CO2 concentration in combination with ambient or ambient +2[degrees]C air temperature for two years in enclosedtop chambers. The results showed that elevated CO2, elevated temperature and the combination of elevated CO2 and temperature increased biomass, height and diameter of fir compared to the control. Elevated CO2 decreased biomass of Deyeuxia scabrescens, but increased for Fragaria orientalis and Cardamine tangutorum. Except for Fragaria orientalis, herbaceous biomass decreased by elevated temperature. The combination stimulated growth of Fragaria orientalis and Cardamine tangutorum, but suppressed for Deyeuxia scabrescens and Carex kansuensis. The results also demonstrated that elevated CO2 and temperature increased the crown size and altered the morphology of fir, with benefits for resource capture, and did not affect growth of herbs. Larger root to shoot ratio of fir contributed the enhancement of biomass, while negatively influencing the growth of some herbs. This indicates morphological changes of trees may modify their growth responses and species around them to environmental changes. The different effects of elevated CO2 and temperature on the growth of species in treeline ecotone suggest that climate change may alter community composition and structure.

5

Crystal Structure and Ab Initio Studies on (p-Methoxyphenyl)thiosemicarbazide

Zhao P., Jian F., Hou Y.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 10

1945-1951

EN

(p-Methoxyphenyl)thiosemicarbazide [CH3OC6H4NHNHCSNH2] has been prepared and characterized by elemental analysis, IR, electronic absorption spectra and X-ray single crystal diffraction. In the crystal lattice, there exist some intermolecular hydrogen bonds, _-_ stacking interactions and C-Hźźź_ supramolecule interactions, which stabilize the crystal structure. Ab initio calculations at HF/6-31G* level of the structure, charges distribution, electronic spectra, natural population analysis and thermodynamic properties at different temperatures have been performed. The calculated results show that the sulfur atom and nitrogen atoms have bigger negative charges, which result in they are the potential sites to react with the metallic ions. The electronic transitions associated with the electronic absorption spectra are mainly derived from the contribution of bands pi-pi*.