Browsing by Author "Saarinen, Tapio"

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  • Combinatory Feeding Method for Mobile Applications
    (2019-07-01) Saarinen, Tapio; Hannula, Jari-Matti; Lehtovuori, Anu; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This letter presents a method for implementing frequency reconfigurability without lumped elements. The method is based on feeding an antenna element simultaneously at different locations with differently delayed and amplified signals and dynamically manipulating the number of active feeds. To demonstrate the concept, an example design of a handset antenna that is compatible with most modern mobile phones is presented. The proposed antenna geometry is simple and practical, consisting only of a folded rectangular sheet and four feeding points. The simulated efficiency of the antenna is higher than 50% from 0.7 GHz to 7 GHz with the highest efficiency being above 90% in 2x2 MIMO operation
  • Discretized Antenna Concept
    (2020-08-04) Viikari, Ville; Hannula, Jari-Matti; Kormilainen, Riku; Kutinlahti, Veli-Pekka; Lehtovuori, Anu; Luomaniemi, Rasmus; Saarinen, Tapio
     A4 Artikkeli konferenssijulkaisussa
    All electrical properties of an antenna are determined by its current distribution. It is possible to numerically solve a current distribution producing optimal performance in some sense. However, this ideal current distribution is nearly impossible to realize in practice. We propose the discretized antenna concept, which makes it possible to realize nearly optimal current distributions in practice. The method does not necessitate manual error and trial type iteration and it can be solved with many design goals. In this paper, we describe the design steps.
  • Effect of cationic polymethacrylates on the rheology and flocculation of microfibrillated cellulose
    (2011) Karppinen, Anni; Vesterinen, Arja-Helena; Saarinen, Tapio; Pietikäinen, Pirjo; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Eight-element MIMO handset based on combinatory feeding
    (2020-02) Saarinen, Tapio; Hannula, Jari-Matti; Lehtovuori, Anu; Viikari, Ville
     A4 Artikkeli konferenssijulkaisussa
    To meet the needs of continuously increasing wireless data consumption, new antenna design schemes are needed. Combinatory feeding is a recently introduced method that utilizes a configurable multiport excitation to create simple frequency configurable antennas. This paper investigates the feasibility of implementing a combinatorially fed antenna capable of 8x8 MIMO in 1.5-6.5 GHz frequency range and 2x2 MIMO in 0.7-0.9 GHz frequency range. A prototype antenna is manufactured and measured results demonstrate, that the method is capable of producing antennas of wide bandwidth.
  • Flocculated flow of microfibrillated cellulose water suspensions: an imaging approach for characterisation of rheological behaviour
    (2012) Saarikoski, Eve; Saarinen, Tapio; Salmela, Juha; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Flocculation of microfibrillated cellulose in shear flow
    (2012) Karppinen, Anni; Saarinen, Tapio; Salmela, Juha; Laukkanen, Antti; Nuopponen, Markus; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Flocculation of microfibrillated cellulose in water suspension
    (2009) Saarikoski, Eve
     Helsinki University of Technology | Master's thesis
    The aim of the master's thesis was to characterize the aqueous suspension rheology of micro fibrillated cellulose (MFC) and cellulose fibers flocculation. Measurements were carried out using rotational rheometer. Special glass geometry was manufactured for the purpose of taking photographs during the measurements. Conclusions were drawn from comparing the photographs and data obtained from measurements. Literary part of the work defines the terms relating to the micro fibrillated cellulose fibers. The most common methods of manufacture, the main characteristics and uses of cellulose fibers are presented. Also theories of the interaction of the forces, adhesion and colloid systems are presented. Literature part also deals with different type of cellulose suspensions and their rheological properties and flocculation factors of cellulose fibers. In experimental part measurements were carried out to characterize how different types of MFC- suspensions differ from one another. To verify these difference pictures were taken of suspension during the measurements. Studied variables selected for examination of MFC- suspensions were degree of fluidization, changes in measuring systems gap, sodium chloride concentration and the effects of changing shear rate during the measurement. It was studied how flocsize changes under different conditions and during network structure decomposition. In addition, analysis of the microscope pictures and the effects of amplitude sweep were done. As a conclusion from the measurements it can be said that the flow of the micro fibrillated cellulose suspension has same type phenomena in the decomposition of the network and flocculated flow that can also be seen in macro size cellulose fibers. The investigations indicate also that flocsize is dependent on changes of geometry gap. In addition, examining the effects of sodium chloride concentration of suspension photographs explained observed phenomena's seen in measurement data. In future the research method can be further improved and the tests can also be made with many other changing factors, such as fiber concentration, mixing or pH effects.
  • Flow and recovery of anionically modified microfibrillated cellulose gels
    (2009) Wang, Miao
     Helsinki University of Technology | Master's thesis
  • Frequency Reconfigurable Multiband Handset Antenna Based on a Multichannel Transceiver
    (2017-09) Hannula, Jari Matti; Saarinen, Tapio; Holopainen, Jari; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The upcoming standards of wireless communications result in additional and more stringent requirements for antennas in mobile phones. In this paper, we present a frequencyreconfigurable antenna that could potentially be suited for future mobile devices. Frequency reconfigurability is achieved through a cluster of mutually coupled antenna elements that are excited with frequency-dependent weights using a multichannel transceiver. We report a mobile handset antenna cluster measuring 15x15x1.6 mm3; that covers the frequency bands of 1.7-2.7, 3.3-4.5, and 5.475-6.425 GHz with an antenna efficiency better than 90 %. The operation of the antenna cluster is experimentally verified by feeding all the antenna elements with proper weights using tailor-made power splitters that represent a multichannel transceiver with adjustable amplitude and phase in each branch. The results obtained with the feed networks suggest the feasibility of the reconfigurability concept, and pave way for codesign of the antenna and the transceiver.
  • Frequency-reconfigurable 8 x 8 MIMO handset utilizing combinatory feeding
    (2019-03-11) Saarinen, Tapio
     Sähkötekniikan korkeakoulu | Master's thesis
    The rapid development of smartphones during the past decade has increased the number of antennas in mobile handsets. In conjunction with large touch screens that occupy large portions of the devices, designing and fitting multiple antennas to a mobile phone has become a challenging task. This master’s thesis studies different methods for mobile handset design. In addition, this work introduces a novel method: Combinatory feeding, which can be used to implement high-efficiency antennas for mobile applications. The method relies on simultaneous excitation of a multiport antenna and does not require external matching circuitry consisting of lumped elements. To test the proposed method, an antenna prototype is designed for 0.7—6.5 GHz frequency range. The design consists of eight individual antennas and it is designed to support 2 x 2 MIMO in a low 0.7—0.9 GHz band and 8 x 8 MIMO at high bands. The designed antennas feature high efficiency at wide frequency band. According to simulations, the total efficiency of the antennas is above 50 % in 1.55—6.5 GHz frequency band. The antenna design is manufactured and experimentally verified with S-parameters and far-field patterns measurements. The obtained results match the simulated results well. However, computational results that further describe the handsets performance differ from the simulated values due to effects of measurement cables. Despite the discrepancies, the obtained results indicate that combinatory feeding method can be utilized for designing wideband mobile antennas by using simple radiating bodies.
  • Healthy Learning Mind (HLM) : Cluster Randomized Controlled Trial on A Mindfulness Intervention, Moderators and Association with Perceived Socioeconomic Status, and Comparison to Other National Data
    (2023-02) Lassander, Maarit; Saarinen, Tapio; Simonsen-Rehn, Nina; Suominen, Sakari; Vahlberg, Tero; Volanen, Salla Maarit
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Background: This paper presents the baseline characteristics and their moderators in the Healthy Learning Mind (HLM)– school-based cluster-randomized controlled trial. Objectives: The paper evaluates the state of various measures of well-being, their moderators and how these results compare to national and global norms/population studies. Methods: Data were collected from all participants prior to the intervention and further analyzed by gender, grade and perceived socioeconomic status, including standardized measures for resilience, depressive symptoms and socioemotional functioning; health-related quality of life, dispositional mindfulness, satisfaction with life, compassion/self-kindness, self-rated health and morning tiredness. Results: Participating 2793 students (1425 girls, 1368 boys), ages 12 to 15 years, filled in the questionnaires. The outcomes were in line with previous research, demonstrating gender differentiation and lower wellbeing among older children and adolescents. Conclusions: All outcomes were associated with perceived socioeconomic status, suggesting that perceived low socioeconomic status should be addressed as a serious risk factor and included as a moderator in similar trials.
  • Kahden mikroaaltotehonjakajan suunnittelu ja toteutus
    (2016-12-05) Saarinen, Tapio
     Sähkötekniikan korkeakoulu | Bachelor's thesis
  • Kalvonäppäimistöjen luotettavuus
    (1985) Saarinen, Tapio
     Helsinki University of Technology | Licentiate thesis
  • Puulevyjen ja -rakenteiden ilmaääneneristävyydestä
    (1978) Saarinen, Tapio
     Helsinki University of Technology | Master's thesis
  • Shear-Induced Crystallization of Metallocene Catalyzed Polyethylenes and Polypropylenes
    (2000) Saarinen, Tapio
     Helsinki University of Technology | Master's thesis
  • Surface functionalization of nanofibrillated cellulose using click-chemistry approach in aqueous media
    (2011) Pahimanolis, Nikolaos; Hippi, Ulla; Johansson, Leena-Sisko; Saarinen, Tapio; Houbenov, Nikolay; Ruokolainen, Janne; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Yrityksen informaatiotuotannon suunnittelu - haaste liikkeenjohdolle
    (1970) Saarinen, Tapio
     School of Business | Master's thesis