Receiver function provides the signature of sharp seismic discontinuities and the information about the shear wave (S−wave) velocity distribution beneath the seismic station. This information is very valuable in areas where any or few reflection and/or refraction studies are available and global and/or regional models give only rough information about the seismic velocities. The data recorded by broadband seismic stations have been analysed to investigate the crustal and upper mantle structure of the Svalbard Archipelago. Svalbard Archipelago is a group of islands located in Arctic, at the north−western part of the Barents Sea continental platform, which is bordered to the west and to the north by passive continental margins. The new procedure of parameterization and selection of receiver functions (RFs) has been proposed. The back−azimuthal sections of RF show a strong variation for the HSPB and KBS stations. Significant amplitudes of transversal component of RF (T−RF) for the HSPB station indicate a shallow dipping layer towards the southwest. The structure of the crust beneath the SPITS array seems to be less heterogeneous, with very low amplitudes of converted phase comparing to the KBS and HSPB stations. Forward modelling by trial−and−error method shows a division of the crust into 3–4 layers beneath all stations and layering of the uppermost mantle beneath the SPITS array and the HSPB stations. The thickness of the mantle transition zone is larger for western part of archipelago and smaller for eastern part comparing to iasp91 model.
This paper presents an enhanced internal model control (EIMC) scheme for a time-delayed second order unstable process, which is subjected to exogenous disturbance and model variations. Even though the conventional internal model control (IMC) can provide an asymptotic tracking response with desired stability margins, the major limitation of conventional IMC is that it cannot be applied for an unstable system because a small exogenous disturbance can trigger the control signal to grow unbounded. Hence, modify- ing the conventional IMC structure to guarantee the internal stability, we present an EIMC scheme which can offer better trade-off between setpoint tracking and disturbance rejec- tion characteristics. To improve the load disturbance rejection characteristics and attenuate the effect of sensor noise, we solve the selection of controller gains as an H¥ optimization problem. One of the key aspects of the EIMC scheme is that the robustness of the closed loop system can be tuned via a single tuning parameter. The performance of the EIMC scheme is experimentally assessed on a magnetic levitation plant for reference tracking application. Experimental results substantiate that the EIMC scheme can effectively coun- teract the inherent time delay in the model and offer precise tracking, even in the presence of exogenous disturbance. Moreover, by comparing the trajectory tracking performance of EIMC with that of the proportional integral velocity (PIV) controller through cumulative power spectral density (CPSD) of the tracking error, we show that the EIMC can offer better low frequency servo response with minimal vibrations.
Due to an increasing amount of music being made available in digital form in the Internet, an automatic organization of music is sought. The paper presents an approach to graphical representation of mood of songs based on Self-Organizing Maps. Parameters describing mood of music are proposed and calculated and then analyzed employing correlation with mood dimensions based on the Multidimensional Scaling. A map is created in which music excerpts with similar mood are organized next to each other on the two-dimensional display.