Helsinki University of Technology

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

Exact image theory for the Sommerfeld half-space problem, part II: Vertical electrical dipole

Abstract: Applying the Laplace transform, the exact distributed image current function is obtained for the classical Sommerfeld half-space problem with vertical magnetic current source. The resulting field integral is well behaved when the image current is situated in complex space. Unlike previous approximate images, the present theory is valid for any distance, height of the source, frequency, and half-space parameters. It is demonstrated that the present image theory reduces to the well-known dipole image at complex depth for large dielectric parameters of the half-space. Also, the reflection-coefficient method is obtained as a farfield approximation. Calculation of fields through exact image integration is seen to be simple and accurate and require modest computer capacity and time. In an appendix, some properties of the multivalued Green's function arising from a dipole source in complex space are also studied.

PLS marker variable approach to diagnosing and controlling for method variance

Abstract: Partial least squares (PLS) path modeling has been adopted as part of the statistical toolbox of many information systems (IS) scholars, particularly when dealing with survey data. Since these data are susceptible to common method variance, several statistical approaches for diagnosing and controlling for this undesirable feature have been developed. While most of these statistical techniques are only applicable to structural equation modeling (SEM), Liang, Saraf, Hu, and Xue (2007) proposed how one of these techniques can be used with PLS analysis. Since this was the first time that a method for controlling common method variance had been made available for PLS users, the method of Liang et al. quickly gained popularity in IS journals. However, recent analysis on the Liang et all approach shows that the method does neither detect nor control for common method variance. In this paper, we propose an alternative PLS marker variable approach for analyzing data contaminated with method variance and provide simulation evidence for the validity of this new approach.

Molecular-dynamics simulation of the growth of diamondlike films by energetic carbon-atom beams

Abstract: The growth of diamondlike films and overlayers by the depsotion of energetic carbon atoms has been investigated by molecular-dynamics simulations. The interatomic many-atom potential suggested by Tersoff is used. The structurel analysis of the grown films shows that there is an energy window between 40 and 70 eV for the deposited atoms where the growth most closely results in dense diamondlike structure. This observation supports earlier experimental suggestions for optimal deposition conditions.

High-impedance surfaces having stable resonance with respect to polarization and incidence angle

Abstract: The work presented in this paper concerns a theoretical study on frequency selective surfaces (FSS) with application to artificial magnetic conductors or high-impedance surfaces (HIS). Current realizations of HIS are based on a planar FSS at the interface of a metal-backed dielectric slab either including vertical vias or not. A stable resonance was found for the case of series-resonance grids without vias in the slab. The resonance turns out to be unique in theory for all angles of incidence and both polarizations of plane waves illuminating the HIS. It was shown that vias destroy the stabilization effect and introduce a frequency shift. The analytical model was validated by HFSS simulations.

Using the focus group method in software engineering: obtaining practitioner and user experiences

Abstract: This paper reflects on three cases where the focus group method was used to obtain feedback and experiences from software engineering practitioners and application users. The focus group method and its background are presented, the method's weaknesses and strengths are discussed, and guidelines are provided for how to use the method in the software engineering context. Furthermore, the results of the three studies conducted are highlighted and the paper concludes in a discussion on the applicability of the method for this type of research. In summary, the focus group method is a cost-effective and quick empirical research approach for obtaining qualitative insights and feedback from practitioners. It can be used in several phases and types of research. However, a major limitation of the method is that it is useful only in studying concepts that can be understood by participants in a limited time. We also recommend that in the software engineering context, the method should be used with sufficient empirical rigor.