Selected developments in computational electromagnetics for radio engineering

This thesis deals with the development and application of two simulation methods commonly used in radio engineering, namely the Finite-Difference Time-Domain method (FDTD) and the Finite Element Method (FEM). The main emphasis of this thesis is in FDTD. FDTD has become probably the most popular computational technique in radio engineering. It is a well established, fairly accurate and easy-to-implement method. Being a time-domain method, it can provide wide-band information in a single simulation. It simulates physical wave propagation in the computational volume, and is thus especially useful for educational purposes and for gaining engineering insight into complicated wave interaction and coupling phenomena. In this thesis, numerical dispersion taking place in the FDTD algorithm is analyzed, and a novel dispersion reduction procedure is described, based on artificial anisotropy. As a result, larger cells can be used to obtain the same accuracy in terms of dispersion error. Simulation experiments suggest that typically the dispersion reduction allows roughly doubling the cell size in each coordinate direction, without sacrificing the accuracy. The obtainable advantage is, however, dependent on the problem. In the open literature, a few other procedures are also presented to reduce the dispersion error. However, the rather dominating effect of unequal grid resolution along different coordinate directions has been neglected in previous studies. The so-called Perfectly Matched Layer (PML) has proven to be a very useful absorbing boundary condition (ABC) in FDTD simulations. It is reliable, works well in wide frequency band and is easy to implement. The most notable deficiency of PML is that it enlarges the computational volume - in open 3-D structures easily by a factor of two. However, due to its advantages, PML has become a standard ABC. In this thesis, the operation of PML in FDTD has been studied theoretically, and some interesting properties of it not known before are uncovered. For example, it is shown that, surprisingly, PML can absorb perfectly (i.e. with zero reflection) plane waves propagating towards almost arbitrary given direction at given frequency. Optimizing the conductivity profile allows reduction of the PML thickness. A typical application of the FDTD method is the design of a mobile handset antenna. An improved coaxial probe model has been developed for antenna simulations. The well-known resistive voltage source (RVS) model has also been discussed. A reference plane transformation is proposed to correct the simulated input impedance. A popular thin-wire model in 2-D FDTD is discussed, and it is shown to be based on erroneous reasoning. The error has been corrected by a simple procedure, and the corrected model has been demonstrated to simulate infinite long thin wires much better than the commonly used model. A novel way to implement singular basis functions in FEM is discussed. It is shown theoretically and demonstrated by examples that if a waveguide propagation mode contains field singularities, then explicit inclusion of singularities in finite element analysis is crucial in order to obtain accurate cut-off wavenumbers.reviewe

Evaluation of the effect of donor weight on adipose stromal/stem cell characteristics by using weight-discordant monozygotic twin pairs

Background Adipose stromal/stem cells (ASCs) are promising candidates for future clinical applications. ASCs have regenerative capacity, low immunogenicity, and immunomodulatory ability. The success of future cell-based therapies depends on the appropriate selection of donors. Several factors, including age, sex, and body mass index (BMI), may influence ASC characteristics. Our aim was to investigate the effect of acquired weight on ASC characteristics under the same genetic background using ASCs derived from monozygotic (MZ) twin pairs. Methods ASCs were isolated from subcutaneous adipose tissue from five weight-discordant (WD, within-pair difference in BMI > 3 kg/m(2)) MZ twin pairs, with measured BMI and metabolic status. The ASC immunophenotype, proliferation and osteogenic and adipogenic differentiation capacity were studied. ASC immunogenicity, immunosuppression capacity and the expression of inflammation markers were investigated. ASC angiogenic potential was assessed in cocultures with endothelial cells. Results ASCs showed low immunogenicity, proliferation, and osteogenic differentiation capacity independent of weight among all donors. ASCs showed a mesenchymal stem cell-like immunophenotype; however, the expression of CD146 was significantly higher in leaner WD twins than in heavier cotwins. ASCs from heavier twins from WD pairs showed significantly greater adipogenic differentiation capacity and higher expression of TNF and lower angiogenic potential compared with their leaner cotwins. ASCs showed immunosuppressive capacity in direct cocultures; however, heavier WD twins showed stronger immunosuppressive capacity than leaner cotwins. Conclusions Our genetically matched data suggest that a higher weight of the donor may have some effect on ASC characteristics, especially on angiogenic and adipogenic potential, which should be considered when ASCs are used clinically.Peer reviewe

Hedge-rahastostrategiat, niiden tuotto ja osuus optimaalisessa sijoitusportfoliossa

Siirretty Doriast

Käytönjohtajapalveluiden kehittäminen

Tämän opinnäytetyön tarkoituksena oli tutkia ja kehittää Oulun Energia Urakointi Oy:n käytönjohtajapalveluiden nykyistä toimintaa yhdessä käytön johtajien kanssa. Työn aikana löydettiin useita raportointiin liittyviä ongelmia. Työn tavoitteena oli saada käy-tönjohtajapalveluista yhtenäiset ja selvittää, miten käytönjohtajapalvelut toimivat tällä hetkellä ja miten niitä tulisi käytön johtajien mielestä kehittää. Teoriaosuudessa on käsitelty käytön johtajan ja sähkölaitteiston haltijan tehtäviä ja toi-menpiteitä, jotka perustuvat sähköturvallisuuslain ja valtioneuvoston asetuksen 1435/2016 asettamiin vaatimuksiin. Teoriaosuudessa on myös käyty läpi käytönjohta-japalveluiden nykyistä toimintaa. Työ aloitettiin tutustumalla käytönjohtajuuskohteisiin ja samalla nykyisiin käytönjohta-japalveluihin. Ongelmien ratkaisemiseksi tehtiin uusia lomakkeita ja tarkastuspöytäkir-joja. Uudet lomakepohjat ja tarkastuspöytäkirjat on tarkoitus tulevaisuudessa liittää sähköiseen kunnossapitojärjestelmään. Työn tuloksena saatiin Oulun Energia Urakointi Oy:n käytönjohtajapalveluihin useita uudistettuja lomake- ja pöytäkirjapohjia sekä luetteloita ylläpitämään järjestystä muun-tamoiden laitteista, varusteita ja vuosihuolloista. Uudistetuilla lomake- ja pöytäkirjapoh-jilla pystytään yhtenäistämään käytönjohtajapalveluita Oulun Energia Urakointi Oy:ssä.The objective of this thesis was to examine and develop Oulun Energia Urakointi Oy’s current operations of the supervisor services together with the supervisors. Several problems have already been recognized in the reporting of the supervisor services and many more were found during the process. The aim of this thesis was to study how the supervisor services work at the moment and how the supervisors want to develop their services. The theoretical part of this thesis covers the tasks and duties of the supervisor and the holder of the electrical equipment. These tasks and duties are based on Electrical Safety Act and Government Decree on Electrical Work and Operational Work of Electri-cal Installations. In addition, this thesis goes through current activities of Oulun Ener-gia Urakointi Oy’s supervisor services. Thesis began by exploring the units under supervision and current supervisor ser-vices. I discussed with many supervisors about the development of supervisor services and their suggestions were taken into account while making the new documents. As a result of this thesis several forms and inspection records were made to solve the existing problems of Oulun Energia Urakointi Oy’s supervisor services. Also, many lists were made to maintain the order of the devices, equipment’s and the annual services of transformer substations. New forms and inspection records will be integrated into the electrical maintenance system in the future