PRACTICAL ASPECTS OF SHAKER MEASUREMENTS FOR MODAL TESTING
Shaker testing is commonly used as a method for measuring forced input in experimental modal analysis. The setup of conventional shakers, stingers and transducers is often the source of test difficulties and avoidable measurement errors. This paper reviews the basic design of shakers as beneficial to modal testing, and the common problems associated with setup issues and resulting measurement errors. These include shaker selection, shaker alignment, stinger selection, connections, reciprocity assumptions and other common mishaps and misunderstandings.
Advantages of Multiple-Input Multiple-Output Testing
Multiple-input, multiple-output (MIMO) measurement techniques are a well-proven and well-established method for collecting FRF (frequency response function) data sets. Despite that, the idea of using multi-references and multiple shakers can be intimidating for an inexperienced modal test engineer. MIMO methods offer some distinct advantages for measuring and extracting basic modal parameters especially while testing larger structures. Compared to single-input, single-output (SISO) techniques, MIMO allows for more uniformly distributed energy across the structure, force levels can be kept lower, modal test data can be taken in one single shot, while nonlinearities are less likely to be excited. Experimental data were taken using single and multiple shakers on an aeronautical structure and results were compared to illustrate the basic principles behind the MIMO technique. Practical aspects of shaker setup, reciprocity checks and the capability of MIMO to resolve closely spaced modes and repeated roots are highlighted throughout the example.
Implementation of Tourism Satellite Account: Assessing the Contribution of Tourism to the Croatian Economy
Compiling the indicators of tourism consumption and the output of tourism industries, Tourism Satellite Account (TSA) provides a framework for internationally harmonized measurements of direct macroeconomic contribution of tourism. Ivandic and Marusic provide a detailed methodological approach for the transfer of TSA theoretical concepts to the assessment of tourism economic contribution on the case of the Croatia. Giving that the TSA compilation is still characterized by a surprisingly wide range of ‘styles’ used, the chapter contributes to a better understanding of the issues related to measurement of direct tourism impacts. It also gives a set of baseline criteria for resource allocation within tourism policy and the further evaluation of its effectiveness.