1,721,163 research outputs found
Dynamic analysis and control of an active engine mount system
No full textDynamic characteristics of a prototype active engine mount (AEM), designed on the basis of a hydraulic engine mount, have been investigated and an adaptive controller for the AEM has been designed. An equivalent mass-spring-damper AEM model is proposed, and the transfer function that describes the dynamic characteristics of the AEM is deduced from mathematical analysis of the model. The damping coefficient of the model is derived by considering the non-linear flow effect in the inertia track. Experiments confirmed that the model precisely describes the dynamic characteristics of the AEM. An adaptive controller using the filtered-X LMS algorithm is designed to cancel the force transmitted through the AEM. The stability of the LMS algorithm is guaranteed by using the secondary path transfer function derived on the basis of the dynamic model of the AEM. The performance test in the laboratory shows that the AEM system is capable of significantly reducing the force transmitted through the AEM
Design of null lenses for testing of elliptical surfaces
No full textNull lenses are designed for testing the oblate elliptical surface that is the third mirror of the off-axis three-mirror anastigmatic camera used for remote sensing. Modifying the conventional autostigmatic and autocollimation types of null lenses yields a mixed-type design that has a small annular flat mirror and high sensitivity. Detailed analyses of the sensitivity of the mixed-type null lens system with changes in each surface parameter are described. (C) 2001 Optical Society of America
OPTIMIZATION OF 2-STAGE CONTINUOUS-CULTURE SYSTEM FOR PRODUCTION OF POLY-BETA-HYDROXYBUTYRATE
No full textThe optimization of poly-beta-hydroxybutyrate (PHB) fermentation process is essential to obtain a high PHB productivity. An optimization of two-stage continuous culture system by complex method for PHB production is presented. PHB production rate of the system obtained in the present study was chosen as the objective function. The PHB production rate of the system was higher than that of the phasewise optimization method which maximizes the growth rate of residual biomass in the first stage and the PHB production rate in the second stage. When the inlet glucose concentration in the first stage increased, PHB content and yield also increased. When the fermenter volume ratio (V-2/V-1) was 0.5, maximum PHB productivity in the second stage was 2.86 g/L . h, which is highest compared with the reported value on PHB
Comparative study of null lens for hyperbolic surface test
No full textBoth the autostigmatic and the mixed type of null lenses are designed for testing the hyperbolic surface of the primary mirror of the off-axis three mirror anastigmat camera for remote sensing. Through comparison of the sensitivity with respect to the change of lens surface parameters, a more suitable type of null lens for testing the hyperbolic surface is presented
Spin-Disorder and Non-Degenerate Energy States in Geometrically Frustrated Materials
No full textWe have studied chalcogenide Ni1-xFexGa2S4, showing geometrical frustration effect. M-H curves at 4.2 K reveal that the disordered spins cannot be rotated completely along the direction of high external field of 5 T, since these spins are strongly constrained in the triangular lattice. H-C increases with increasing Fe concentration, being consistent with the enhanced antiferromagnetic (AFM) spin-spin interactions and the suppressed spin-fluctuation due to the increase in freezing temperature T-f. The specific heat (C-p/T) measurement do not show any phase transformation between 2 and 160 K and there is no clear indication of gap in the temperature dependent C-p curve between 0 and 7 T, because the atomic short-range ordering of the strained spin in the geometrically frustrated triangular lattice exists at low temperature. Though typical geometrically frustrated magnet shows degeneracy, Mossbauer analysis at 4.2 K shows that 5D of 3d orbit in the samples studied here is splitted into T-5(2g) and E-5(2g), and T-5(2g) is further splitted into singlet and doublet by large electric quadrupole splitting. This suggests that Fe2+ ionic state has no absolute degenerate energy states in all samples due to Jahn-Teller effect.X1144sciescopu
Non-destructive surface profile measurement of a thin film deposited on a patterned sample
No full text2003 International Conference on Characterization and Metrology for ULSI TechnologyRedistibution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpsr.js
Correlation of the vapor-liquid equilibria of CFC, HCFC and FC mixtures: Critical evaluation of mixing rules
No full textThe vapor-liquid equilibrium data of the binary CFC, HCFC, and FC mixtures were correlated with the Soave-Redlich-Kwong equation of state incorporated with some types of mixing rules; the conventional one fluid, Panagiotopoulos-Reid and modified Huron-Vidal second order mixing rules. The Panagiotopoulos-Reid mixing rule showed the superiority to the other models in predicting the VLE of freon mixtures with low errors. The modified Huron-Vidal second order model showed good convergence ability, which was due to its robustness to parameter variation.The authors gratefully acknowledge that this paper was support-ed by the fund of Korea Institute of Science and Engineering Foundation
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