1,720,975 research outputs found
Aircraft Wing Flutter Characteristics Considering Control Surface and Actuator Nonlinearity in Subsonic and Supersonic Regions
Full text linkThis research was supported by the Agency for Defense Development (ADD) and
Flight Vehicle Research Center(FVRC) in the Republic of Korea. This support is gratefully
acknowledged
Development of a Laparoscopic Surgical System and Coordinates Relationship Between a Laparoscopic View and a Slave Manipulator
No full text
Aeroelastic characteristics of cylindrical hybrid composite panels with viscoelastic damping treatments
No full textSupersonic flutter analysis of cylindrical composite panels with structural damping treatments has been performed using the finite element method based on the zig-zag layerwise shell theory. The natural frequencies and loss factors of cylindrical viscoelastic composites are computed considering the effects of transverse shear deformation. And Kumhaar's modified piston theory is applied for the calculation of aerodynamic forces. The flutter of cylindrical composite panels is analyzed considering structural damping effect. With respect to aeroelastic stabilities, various damping characteristics of unconstrained layer, constrained layer, and symmetrically co-cured sandwich laminates are compared with those of an original base panel. (c) 2006 Elsevier Ltd. All rights reserved
Effects of actuator nonlinearity on aeroelastic characteristics of a control fin
No full textThe influences of actuator nonlinearities on actuator dynamics and the aeroelastic characteristics of a control fin were investigated by using iterative V-g methods in subsonic flows; in addition, the doublet-hybrid method (DHM) was used to calculate unsteady aerodynamic forces. The changes of actuator dynamics induced by nonlinearities, such as backlash or freeplay, and the variations of flutter boundaries due to the changes of actuator dynamics were observed. Results show that the aeroelastic characteristics can be significantly dependent on actuator dynamics. Thus, the actuator nonlinearities may play an important role in the nonlinear aeroelastic characteristics of an aeroelastic system. The present results also indicate that it is necessary to seriously consider the influence of actuator dynamics on the flutter characteristics at the design stage of actuators to prevent aeroelastic instabilities of aircraft or missiles. (C) 2007 Elsevier Ltd. All rights reserved.This research was supported by the Agency for Defense Development (ADD) in the Republic of Korea. This support is gratefully acknowledged
Nonlinear aeroelastic analysis for a control fin with an actuator
No full textNonlinear aeroelastic characteristics of a control fin with an actuator were investigated, including the structural nonlinearity, by using the iterative v-g method. System identification of an actuator was performed with a sine sweep test, and the doublet-hybrid method was used to calculate unsteady aerodynamic forces. Structural nonlinearity located in the load links of the actuator was considered and assumed to be the freeplay. Nonlinear aeroelastic analyses were performed in both the frequency and time domains, and the nonlinear flutter analyses showed that the flutter characteristics significantly depend on the structural nonlinearity as well as the effects of the actuator. The results also indicate that it is necessary to consider seriously the effects of the poles and zeros of the actuator on the flutter characteristics to predict flutter behavior accurately when designing the actuators of missiles or aircraft.The authors gratefully acknowledge the support of the Agency for Defense Development (ADD), Republic of Korea
Influence of Lithiation on Nanomechanical Properties of Silicon Nanowires Probed with Atomic Force Microscopy
No full textThe nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value for lithiated silicon nanowire and a higher value for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value than that of the Si nanowire substrate by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The Young's modulus obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively higher value than lithiated silicon nanowire due to the elastically soft amorphous structures. The frictional forces acting on the tip sliding on the surface of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
