The short-range applications of Terahertz (THz) synthetic aperture radar (SAR) can be found in material characterization, hyper-accuracy localization at sub-mm or even better level, scattering analysis of rough surfaces. THz SAR can also be used for material defect detection and it is an active research area. Recent experiments have shown that defects inside material can be observed by a synthetic aperture radar (SAR) operating at THz frequencies. In this paper, the experimental results of material defect detection under various circumstances are presented, for example, defects are inside a standalone material, at the back-end surface, the material with defects is conterminous to different materials. The materials considered in the experiments include electrical insulator, semiconductor, and perfect electric conductor. The electrical insulator is damaged, causing defects in the order of millimeter and submillimeter. An SAR testbed based on a vector network analyzer operating in the frequency range 220-330 GHz is used to measure the electrical insulator with damages in the form of SAR with a two-dimensional (2D) aperture. The experimental results show that damage inside the electrical insulator can be observed under various circumstances. This supports material defect detection, which enhances the monitoring of industrial production processes and the control of product quality. 

The resolution of a synthetic aperture radar (SAR) system depends not only on the operating frequency range of a radar but also on the geometry. A radar system operating at MHz frequencies facilitates SAR resolution to the meter (m) level with a linear aperture. With the same radar system, the realization of the circular aperture can further enhance the SAR resolutions to the submeter level. For GHz SAR systems, the realization of circular apertures helps to reduce the resolution from the centimeter (cm) level to the millimeter (mm) level. In this paper, a resolution equation for SAR systems synthesizing circular aperture (CSAR) is introduced. The equation is derived from the backprojection integral for CSAR, its Fourier transform, and the method of stationary phase. The accuracy of the derived equation is enhanced with a correcting factor that is numerically calculated with a cubic interpolation. Therefore, the equation can provide a more accurate, analytical, and practical estimate of the spatial resolution that can be reached with a CSAR system than the ones available in the literature. The resolution equation introduced in this paper is verified with simulations of a MHz SAR system and a GHz SAR system. The equation is further verified by an experiment with a THz inverse SAR (ISAR) system. The radar utilized in the ISAR experiment is a D-band radar system mounted on an antenna positioner that supports circular movement.

The emerge of Terahertz (THz) radar systems allows the short-range applications such as material characterization, hyper accuracy localization at cm or even better level, scattering analysis of rough surfaces, and material defect detection. The paper presents the experimental results about material defect detection based on synthetic aperture radar (SAR) operating at THz frequencies. For the experiments, an electrical insulator is damaged causing the defects in the orders of mm and sub-mm. A SAR testbed at THz frequencies built with a vector network analyzer and a frequency extender in the frequency range 325-500 GHz is used to measure the electrical insulator in the form of SAR with a two-dimensional (2D) aperture. The damaged parts inside the electrical insulator can be observed clearly in the three-dimensional (3D) SAR image. This supports the material defect detection that enhances monitoring industrial production processes and controlling product quality. 

The activity of a surface is determined by the local electronic structure. When nano particles are adsorbed, the catalytic properties will change. Surfaces with adsorbed nano particles often show a significantly higher chemical reactivity than the clean counterpart. Gold, for instance, shows an extra high activity towards many reactions, such as low-temperature catalytic combustion, partial oxidation of hydrocarbons and CO oxidation when dispersed as ultra-fine particles on metal oxide surfaces. In the case of CO oxidation, the activity has been observed to depend critically on the nano particle size, the nature of the support and the detailed synthetic procedure. Since it has been observed experimentally that the chemical reactivity of a nanoparticulated surface tend to depend on the size of the adatom structures, suggesting a quantum size effect, we find it well motivated to perform a theoretical investigation with focus on the cluster-size dependence. We have chosen to model CO interaction with sodium nano particles with focus on small particles, containing only a few atoms, since we expect the eventual quantum effects to be most pronounced for these. Further, we limit our investigation to unsupported nano particles because our previous investigations [1] have shown that it is predominately states localized to the nano particle region that contribute to the local electronic structure above the particle itself. The calculations have been performed in the context of density functional theory applying the MIKA real-space program package [2], using norm-conserving pseudo-potentials for the molecule. The nano particle has been modeled as a cylindrically symmetric quantum dot. For further details, see [3,4]. Our results show that the charge transfer between the nano particle and the CO molecule depends critically on the nano particle size, and that this dependence is intimately connected to the local electronic structure at the point where the molecule approaches the particle. The key factor for charge transfer turns out to be the presence of states with the symmetry of the chemically active molecular orbital at the Fermi level. [1] T. Torsti, V. Lindberg, M. J. Puska ,and B. Hellsing, Phys. Rev. B 66, 235420 (2002). [2] M. Heiskanen, T. Torsti, M. J. Puska, and R. M. Nieminen, Phys. Rev. B 63, 245106 (2001). [3] V. Lindberg and B. Hellsing, J. Phys. Condens. Matter 17, S1075 (2005). [4] V. Lindberg, T. Petersson, and B. Hellsing, Surf. Sci. 600, 6 (2006).

En ytas aktivitet bestäms av den lokala elektronstrukturen. När nanopartiklar adsorberas på en metallyta, ändras den lokala elektronstrukturen och därmed också de kemiska egenskaperna. Man har sett att den kemiska reaktiviteten ofta blir större för ytor med adsorberade nanopartiklar, än vad den är för rena ytor. Här studeras hur den kemiska reaktiviteten beror på storleken av de adsorberade nanopartiklarna. Idetta fall CO reaktivitet på en Na-yta. Vi visar att det finns ett tydligt storleksberoende, som kan hänvisas tillbaka på kvantmekaniska effekter.l

Engineering education in Sweden as in the rest of the world is experiencing a decline in student interest. There are concerns about the ways in which students think about engineering education, why they join an academic programme in engineering, and why they persist in their studies. In this context the aims of the Nationellt ämnesdidaktiskt Centrum för Teknikutbildning i Studenternas Sammanhang project (CeTUSS) is to investigate the student experience and to identify and support a continuing network of interested researchers, as well as in building capacity for disciplinary pedagogic investigation. The Stepping Stones project brings together these interests in a multi-researcher, multi-institutional study that investigates how students and academic staff perceive engineering in Sweden and in Swedish education. The first results of that project are reported here. As this study is situated uniquely in Swedish education, it allows for exploration of a Swedish perspective on conceptions of engineering. The Stepping Stones project was based on a model of research capacity-building previously instantiated in the USA and Australia (Fincher & Tenenberg, 2006).