171 research outputs found
On some aspects of the geometry of differential equations in physics
In this review paper, we consider three kinds of systems of differential
equations, which are relevant in physics, control theory and other applications
in engineering and applied mathematics; namely: Hamilton equations, singular
differential equations, and partial differential equations in field theories.
The geometric structures underlying these systems are presented and commented.
The main results concerning these structures are stated and discussed, as well
as their influence on the study of the differential equations with which they
are related. Furthermore, research to be developed in these areas is also
commented.Comment: 21 page
Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control
This paper presents a new hybrid active & semi-active control method
for vibration suppression in flexible structures. The method uses a combination of a
semi-active device and an active control actuator situated elsewhere in the structure
to suppress vibrations. The key novelty is to use the hybrid controller to enable
the magneto-rheological damper to achieve a performance as close to a fully active
device as possible. This is achieved by ensuring that the active actuator can assist
the magneto-rheological damper in the regions where energy is required. In addition,
the hybrid active & semi-active controller is designed to minimize the switching of the
semi-active controller. The control framework used is the immersion and invariance
control technique in combination with sliding mode control. A two degree-of-freedom
system with lightly damped resonances is used as an example system. Both numerical
and experimental results are generated for this system, and then compared as part
of a validation study. The experimental system uses hardware-in-the-loop to simulate
the effect of both the degrees-of-freedom. The results show that the concept is viable
both numerically and experimentally, and improved vibration suppression results can
be obtained for the magneto-rheological damper that approach the performance of an
active device
Modification of cell surface properties of Pseudomonas alcaligenes S22 during hydrocarbon biodegradation
Biodegradation of water insoluble hydrocarbons can be significantly increased by the addition of natural surfactants one. Very promising option is the use of saponins. The obtained results indicated that in this system, after 21 days, 92% biodegradation of diesel oil could be achieved using Pseudomonas alcaligenes. No positive effect on the biodegradation process was observed using synthetic surfactant Triton X-100. The kind of carbon source influences the cell surface properties of microorganisms. Modification of the surface cell could be observed by control of the sedimentation profile. This analytical method is a new approach in microbiological analysis
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