Sound localization problems are usually tackled by the acquisition of data from phased microphone arrays and the application of acoustic holography or beamforming algorithms. However, the number of sensors required to achieve reliable results is often prohibitive, particularly if the frequency range of interest is wide. It is shown that the number of sensors required can be reduced dramatically providing the sound field is time stationary. The use of scanning techniques such as “Scan & Paint” allows for the gathering of data across a sound field in a fast and efficient way, using a single sensor and webcam only. It is also possible to characterize the relative phase field by including an additional static microphone during the acquisition process. This paper presents the theoretical and experimental basis of the proposed method to localise sound sources using only one fixed microphone and one moving acoustic sensor. The accuracy and resolution of the method have been proven to be comparable to large microphone arrays, thus constituting the so called “virtual phased arrays”.
The article describes mine survey works during opening old St. Anthony of Padua water adit in Horní Město (Czech Republic) to make it accessible to visitors. The works cover the connecting survey and orientation measurement, traverse measurement of the first opened part, setting-out projection of the end of opened part to the surface to make shaft from the surface, new connecting survey and orientation measurement by shaft and traverse measurement of the rest of water adit. Non-standard aids and techniques were used during surveying. One of the tools is a suspended prism holder developed at Institute of geodesy and mine surveying, VSB – Technical university of Ostrava, registered as a utility patent.
The present contribution reports on the rheological investigations concerning influence of high hydrostatic pressure on the molecular structure of gelatin gels. For the purpose of the study, a torsional shear wave rheometer for in-situ investigations of viscoelastic substances under high pressure was developed. Small amplitude vibrations generated by piezoelectric elements are used to determine the storage modulus of the investigated medium. The system is able to stand pressures up to 300 MPa. The experiments have been carried out with household gelatin (0.1 w/w aqueous solution). The gelification curves revealed similar time course. However, the values of G0 obtained for the gels curing 300 minutes under 100 MPa and 200 MPa were observed to be respectively 2.1 and 4 times higher than at ambient conditions. The increased number of triple helix junction zones is hypothesised to be the cause of this phenomenon as a result of reinforcement of the hydrogen bonds due to pressure. An attempt to cognize the characteristic dimensions of the molecular structure based on the theory of rubber elasticity is made.
Modern space measurement techniques like SLR, DORIS, VLBI and GNSS are used to study the tectonic plates. The determination of plate motion parameters (Φ, Λ, ω) from various geodetic measurements is outlined. This paper is the third part of our studies on estimating geodetic and geodynamic parameters; it regards an accuracy analysis of the determined Φ, Λ, ω parameters which describe motions of the tectonic plates using Very Long Base Interferometry (VLBI) technique. Prior to this, SLR and DORIS space measurement techniques were examined by authors. The study is based on the velocities of station positions, as included in a realization of the International Terrestrial Reference System– ITRF2008 forVLBI technique, published by the International Earth Rotation and Reference Systems Service (IERS). This model is made subject to an analysis in association with the APKIM2005 model. Six big plates, namely: Eurasian (EUAS), African (AFR), Australian (AUS), North American (NOAM), Pacific (PACF) and Antarctic (ANTC) were analysed. The results obtained in this analysis were compared with our previous estimations based on DORIS and SLR techniques and estimated according to the APKIM2005 model. Generally, all our three solutions based on SLR, DORIS and VLBI measurement techniques were found to be consistent.
Robotic total stations are a group of surveying instruments that can be used to measure moving prisms. These devices can generate significant errors during kinematic surveys. This is due to the different speeds of the total station’s measurement subsystems, which results in the observations of the point location being performed in different places of the space. Total stations which are several years old may generate errors of up to a few dozen centimeters. More modern designs, with much lower delays of the mechanical and electronic subsystems, theoretically allow to significantly reduce the values of the errors. This study involved the performance of kinematic tests on the modern robotic total station Leica MS50 in order to determine the values of measurement errors, and also to define the possibility of using them for the above-mentioned applications.