Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Thin film & Vortex. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

Quantization of Pseudo-differential Operators on the Torus

Abstract: Pseudo-differential and Fourier series operators on the torus ${{\mathbb{T}}^{n}}=(\Bbb{R}/2\pi\Bbb{Z})^{n}$ are analyzed by using global representations by Fourier series instead of local representations in coordinate charts. Toroidal symbols are investigated and the correspondence between toroidal and Euclidean symbols of pseudo-differential operators is established. Periodization of operators and hyperbolic partial differential equations is discussed. Fourier series operators, which are analogues of Fourier integral operators on the torus, are introduced, and formulae for their compositions with pseudo-differential operators are derived. It is shown that pseudo-differential and Fourier series operators are bounded on L 2 under certain conditions on their phases and amplitudes.

Particle size effects for carbon nanofiber supported platinum and ruthenium catalysts for the selective hydrogenation of cinnamaldehyde

Abstract: The selective hydrogenation of cinnamaldehyde was studied over carbon nanofibers (CNF) supported platinum and ruthenium catalysts. The catalysts differed independently in their metal particle sizes and amount of acidic oxygen groups on the CNF surface. For the catalysts with oxygen on the CNF surface, the larger metal particles (∼3.5 nm) displayed the highest selectivity towards cinnamyl alcohol. Surprisingly, when the oxygen groups were removed from the catalyst surface, the smaller particles (∼2.0 nm) exhibited the highest selectivity to cinnamyl alcohol. Also the hydrogenation activity increased for all catalysts after oxygen removal. A model is proposed to account for the role of the metal particle size and oxygen surface groups in the hydrogenation of cinnamaldehyde.

An Insider's Experiences with Environmental Entrepreneurship

Abstract: Most entrepreneurial principles apply to environmental ventures as well.Ecopreneurship (i.e., environmental entrepreneurship) is outlined from a practical and an academic perspective, based on previous research.Environmental businesses are classified in four categories:nature-oriented enterprises, producers of environmental technology, providers of environmental management services, and producers of environmentally friendly products. Each classification is discussed in terms of the drivers (geographical influences, reason for market emergence, degree of enforcement) that influence their existence.Three major barriers to ecopreneurship--the challenge of market creation, financing barriers, and ethics-based decision making--are described, and implications are discussed.A typology of ecopreneurs is created based on a desire to change the world and a desire to make money.Concluding remarks provide an overview of these drivers and barriers and explain how they contribute to the market-creation difficulties experienced by environmental businesses as compared to non-environmental businesses. (AKP)

The multiwavelength variability of 3C 273

Abstract: Aims. We present an update of the 3C 273’s database hosted by the ISDC, completed with data from radio to gamma-ray observations over the last 10 years. We use this large data set to study the multiwavelength properties of this quasar, especially focussing on its variability behaviour. Methods. We study the amplitude of the variations and the maximum variability time scales across the broad-band spectrum and correlate the light curves in different bands, specifically with the X-rays, to search for possible connections between the emission at different energies. Results. 3C 273 shows variability at all frequencies, with amplitudes and time scales strongly depending on the energy and being the signatures of the different emission mechanisms. The variability properties of the X-ray band imply the presence of either two separate components (possibly a Seyfert-like and a blazar-like) or at least two parameters with distinct timing properties to account for the X-ray emission below and above ∼20 keV. The dominant hard X-ray emission is most probably not due to electrons accelerated by the shock waves in the jet as their variability does not correlate with the flaring millimeter emission, but seems to be associated to long-timescale variations in the optical. This optical component is consistent with being optically thin synchrotron radiation from the base of the jet and the hard X-rays would be produced through inverse Compton processes (SSC and/or EC) by the same electron population. We show evidence that this synchrotron component extends from the optical to the near-infrared domain, where it is blended by emission of heated dust that we find to be located within about 1 light-year from the ultraviolet source.

Contextual patterns in mobile service usage

Abstract: Mobile services differ from other services because of their temporal and spatial attributes. Mobile services additionally differ from each other in their value-added to the end-user. Some services--such as emailing and voice--are more business oriented. On the other hand, various free-time oriented services are provided in new smartphones, such as imaging and music playback. The present paper studies how mobile services are used in different contexts. For this, the paper develops a specialized algorithm that can be used with handset-based usage data acquired straight from end-users in an established panel study process. Educated guesses can be drawn on the user context based on the developed algorithm. In the present exercise usage contexts were divided into home, office and "on the move". The algorithm is used with exemplary data from Finland and the UK covering 324 consumers in 2006. More than 70% of contextual use cases are correctly classified based on raw data. According to exemplary results particularly multimedia services are used "on the move", whereas legacy mobile services experience more evenly distributed usage across all contexts. The algorithm that identifies context based on raw data provides a new angle to mobile end-user research. In the future, the accuracy of the algorithm will be improved with the integration of seamless cell-id logging and GPS data.