Identification and monitoring of toxic gaseous pollutants by means of laser photoacoustic spectroscopy

U ovom se članku navode neki osnovni principi laserske foto-akustične spektroskopije u plinskoj fazi, kao i primjene te metode u proučavanjima problema općenite onečišćenosti zraka. Tehnološki razvoj na polju lasera i elektronike dosegao je razinu koja omogućuje realizaciju jednog praktičnog, ekonomičnog aparata (monitor-analizator) visoke osjetljivosti čije se funkcioniranje zasniva na fotoakustičnom principu. Svrha ovog članka je da zainteresiranim čitaocima pomogne pri dobivanju osnovnih uvida u korisnost upotrebe fotoakustične spektroskopije. Pritom smo se ograničili na osnovne fizičke principe i samo neke od rezultata zabilježenih u radu s plinskim komponentama.The paper deals with a few basic concepts of laser photoacoustic spectroscopy and its application for identification and monitoring of gaseous pollutants. The method has been steadily becoming more popular as a valuable analytical tool hi the study of environmental and indoor pollution problems. Technological development has currently reached the point at which the realisation of a versatile, highly sensitive, relatively inexpensive and practical monitoring-analysing equipment based on the photoacoustic principle may be anticipated

Higher-order discontinuous modeling of fracturing in concrete using the numerical manifold method

This paper presents an overview of the numerical manifold method (NMM) as a unifying framework for modeling fracturing phenomena in quasi-brittle materials, and particularly in concrete. NMM is attractive due to its potential to provide an efficient framework for modeling the entire transition between continuum to discontinuum, from a continuum point of view, without remeshing. To achieve this, the following characteristics are employed: (1) discontinuities are introduced in a discrete manner, without remeshing; (2) the approximation is improved locally, for any arbitrary level, without remeshing. Furthermore, essential boundary conditions are enforced using projection matrices and higher-order boundary issues are identified