23,102 research outputs found
Dark solitons, modulation instability and breathers in a chain of weakly non-linear oscillators with cyclic symmetry
In the aerospace industry the trend for light-weight structures and the
resulting complex dynamic behaviours currently challenge vibration engineers.
In many cases, these light-weight structures deviate from linear behaviour, and
complex nonlinear phenomena can be expected. We consider a cyclically symmetric
system of coupled weakly nonlinear undamped oscillators that could be
considered a minimal model for different cyclic and symmetric aerospace
structures experiencing large deformations. The focus is on localised
vibrations that arise from wave envelope modulation of travelling waves. For
the defocussing parameter range of the approximative nonlinear evolution
equation, we show the possible existence of dark solitons and discuss their
characteristics. For the focussing parameter range, we characterise modulation
instability and illustrate corresponding nonlinear breather dynamics.
Furthermore, we show that for stronger nonlinearity or randomness in initial
conditions, transient breather-type dynamics and decay into bright solitons
appear. The findings suggest that significant vibration localisation may arise
due to mechanisms of nonlinear modulation dynamics
TIR-based dynamic liquid-level and flow-rate sensing and its application on centrifugal microfluidic platforms
For the first time we present a technique for the spatio-temporally resolved localization of liquid-gas interfaces on centrifugal microfluidic platforms based on total internal reflection (TIR) at the channel wall. The simple setup consists of a line laser and a linear image sensor array mounted in a stationary instrument. Apart from identifying the presence of (usually unwanted) gas bubbles, the here described online meniscus detection allows to measure liquid volumes with a high precision of 1.9%. Additionally, flow rates and viscosities (range: 1-10.7 mPa s) can be sensed even during rotation at frequencies up to 30 Hz with a precision of 4.7% and 4.3%, respectively
Sol-Gel Derived Ferroelectric Nanoparticles Investigated by Piezoresponse Force Microscopy
Piezoresponse force microscopy (PFM) was used to investigate the
ferroelectric properties of sol-gel derived LiNbO nanoparticles. To
determine the degree of ferroelectricity we took large-area images and
performed statistical image-analysis. The ferroelectric behavior of single
nanoparticles was verified by poling experiments using the PFM tip. Finally we
carried out simultaneous measurements of the in-plane and the out-of-plane
piezoresponse of the nanoparticles, followed by measurements of the same area
after rotation of the sample by 90 and 180. Such
measurements basically allow to determine the direction of polarization of
every single particle
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