Study of Control Methods of a High-Frequency Cycloconverter for Domestic Induction Heating Appliances

A high-frequency cyclonverter acts as a direct ac-to-ac power converter circuit that does not require a diode bidge rectifier. Bridgeless topology makes it possible to remove forward voltage drop losses that are present in a diode bridge. In addition, the on-state losses can be reduced to 1.5 times the on-state resistance of switches in half-bridge operation of the cycloconverter. A high-frequency cycloconverter is reviewed and the charging effect of the dc-capacitors in ``back-to-back'' or synchronous mode operation operation is analyzed. In addition, a control method is introduced for regulating dc-voltage of the ac-side capacitors in synchronous operation mode. The controller regulates the dc-capacitors and prevents switches from reaching overvoltage level. This can be accomplished by variating phase-shift between the upper and the lower gate signals. By adding phase-shift between the gate signal pairs, the charge stored in the energy storage capacitors can be discharged through the resonant load and substantially, the output resonant current amplitude can be improved. The above goals are analyzed and illustrated with simulation. Theory is supported with practical measurements where the proposed control method is implemented in an FPGA device and tested with a high-frequency cycloconverter using super-junction power MOSFETs as switching devices.

Socially shared metacognitive regulation during collaborative learning processes in student dyads and small groups

Traditionally metacognition has been theorised, methodologically studied and empirically tested from the standpoint mainly of individuals and their learning contexts. In this dissertation the emergence of metacognition is analysed more broadly. The aim of the dissertation was to explore socially shared metacognitive regulation (SSMR) as part of collaborative learning processes taking place in student dyads and small learning groups. The specific aims were to extend the concept of individual metacognition to SSMR, to develop methods to capture and analyse SSMR and to validate the usefulness of the concept of SSMR in two different learning contexts; in face-to-face student dyads solving mathematical word problems and also in small groups taking part in inquiry-based science learning in an asynchronous computer-supported collaborative learning (CSCL) environment. This dissertation is comprised of four studies. In Study I, the main aim was to explore if and how metacognition emerges during problem solving in student dyads and then to develop a method for analysing the social level of awareness, monitoring, and regulatory processes emerging during the problem solving. Two dyads comprised of 10-year-old students who were high-achieving especially in mathematical word problem solving and reading comprehension were involved in the study. An in-depth case analysis was conducted. Data consisted of over 16 (30–45 minutes) videotaped and transcribed face-to-face sessions. The dyads solved altogether 151 mathematical word problems of different difficulty levels in a game-format learning environment. The interaction flowchart was used in the analysis to uncover socially shared metacognition. Interviews (also stimulated recall interviews) were conducted in order to obtain further information about socially shared metacognition. The findings showed the emergence of metacognition in a collaborative learning context in a way that cannot solely be explained by individual conception. The concept of socially-shared metacognition (SSMR) was proposed. The results highlighted the emergence of socially shared metacognition specifically in problems where dyads encountered challenges. Small verbal and nonverbal signals between students also triggered the emergence of socially shared metacognition. Additionally, one dyad implemented a system whereby they shared metacognitive regulation based on their strengths in learning. Overall, the findings suggested that in order to discover patterns of socially shared metacognition, it is important to investigate metacognition over time. However, it was concluded that more research on socially shared metacognition, from larger data sets, is needed. These findings formed the basis of the second study. In Study II, the specific aim was to investigate whether socially shared metacognition can be reliably identified from a large dataset of collaborative face-to-face mathematical word problem solving sessions by student dyads. We specifically examined different difficulty levels of tasks as well as the function and focus of socially shared metacognition. Furthermore, the presence of observable metacognitive experiences at the beginning of socially shared metacognition was explored. Four dyads participated in the study. Each dyad was comprised of high-achieving 10-year-old students, ranked in the top 11% of their fourth grade peers (n=393). Dyads were from the same data set as in Study I. The dyads worked face-to-face in a computer-supported, game-format learning environment. Problem-solving processes for 251 tasks at three difficulty levels taking place during 56 (30–45 minutes) lessons were video-taped and analysed. Baseline data for this study were 14 675 turns of transcribed verbal and nonverbal behaviours observed in four study dyads. The micro-level analysis illustrated how participants moved between different channels of communication (individual and interpersonal). The unit of analysis was a set of turns, referred to as an ‘episode’. The results indicated that socially shared metacognition and its function and focus, as well as the appearance of metacognitive experiences can be defined in a reliable way from a larger data set by independent coders. A comparison of the different difficulty levels of the problems suggested that in order to trigger socially shared metacognition in small groups, the problems should be more difficult, as opposed to moderately difficult or easy. Although socially shared metacognition was found in collaborative face-to-face problem solving among high-achieving student dyads, more research is needed in different contexts. This consideration created the basis of the research on socially shared metacognition in Studies III and IV. In Study III, the aim was to expand the research on SSMR from face-to-face mathematical problem solving in student dyads to inquiry-based science learning among small groups in an asynchronous computer-supported collaborative learning (CSCL) environment. The specific aims were to investigate SSMR’s evolvement and functions in a CSCL environment and to explore how SSMR emerges at different phases of the inquiry process. Finally, individual student participation in SSMR during the process was studied. An in-depth explanatory case study of one small group of four girls aged 12 years was carried out. The girls attended a class that has an entrance examination and conducts a language-enriched curriculum. The small group solved complex science problems in an asynchronous CSCL environment, participating in research-like processes of inquiry during 22 lessons (á 45–minute). Students’ network discussion were recorded in written notes (N=640) which were used as study data. A set of notes, referred to here as a ‘thread’, was used as the unit of analysis. The inter-coder agreement was regarded as substantial. The results indicated that SSMR emerges in a small group’s asynchronous CSCL inquiry process in the science domain. Hence, the results of Study III were in line with the previous Study I and Study II and revealed that metacognition cannot be reduced to the individual level alone. The findings also confirm that SSMR should be examined as a process, since SSMR can evolve during different phases and that different SSMR threads overlapped and intertwined. Although the classification of SSMR’s functions was applicable in the context of CSCL in a small group, the dominant function was different in the asynchronous CSCL inquiry in the small group in a science activity than in mathematical word problem solving among student dyads (Study II). Further, the use of different analytical methods provided complementary findings about students’ participation in SSMR. The findings suggest that it is not enough to code just a single written note or simply to examine who has the largest number of notes in the SSMR thread but also to examine the connections between the notes. As the findings of the present study are based on an in-depth analysis of a single small group, further cases were examined in Study IV, as well as looking at the SSMR’s focus, which was also studied in a face-to-face context. In Study IV, the general aim was to investigate the emergence of SSMR with a larger data set from an asynchronous CSCL inquiry process in small student groups carrying out science activities. The specific aims were to study the emergence of SSMR in the different phases of the process, students’ participation in SSMR, and the relation of SSMR’s focus to the quality of outcomes, which was not explored in previous studies. The participants were 12-year-old students from the same class as in Study III. Five small groups consisting of four students and one of five students (N=25) were involved in the study. The small groups solved ill-defined science problems in an asynchronous CSCL environment, participating in research-like processes of inquiry over a total period of 22 hours. Written notes (N=4088) detailed the network discussions of the small groups and these constituted the study data. With these notes, SSMR threads were explored. As in Study III, the thread was used as the unit of analysis. In total, 332 notes were classified as forming 41 SSMR threads. Inter-coder agreement was assessed by three coders in the different phases of the analysis and found to be reliable. Multiple methods of analysis were used. Results showed that SSMR emerged in all the asynchronous CSCL inquiry processes in the small groups. However, the findings did not reveal any significantly changing trend in the emergence of SSMR during the process. As a main trend, the number of notes included in SSMR threads differed significantly in different phases of the process and small groups differed from each other. Although student participation was seen as highly dispersed between the students, there were differences between students and small groups. Furthermore, the findings indicated that the amount of SSMR during the process or participation structure did not explain the differences in the quality of outcomes for the groups. Rather, when SSMRs were focused on understanding and procedural matters, it was associated with achieving high quality learning outcomes. In turn, when SSMRs were focused on incidental and procedural matters, it was associated with low level learning outcomes. Hence, the findings imply that the focus of any emerging SSMR is crucial to the quality of the learning outcomes. Moreover, the findings encourage the use of multiple research methods for studying SSMR. In total, the four studies convincingly indicate that a phenomenon of socially shared metacognitive regulation also exists. This means that it was possible to define the concept of SSMR theoretically, to investigate it methodologically and to validate it empirically in two different learning contexts across dyads and small groups. In-depth micro-level case analysis in Studies I and III showed the possibility to capture and analyse in detail SSMR during the collaborative process, while in Studies II and IV, the analysis validated the emergence of SSMR in larger data sets. Hence, validation was tested both between two environments and within the same environments with further cases. As a part of this dissertation, SSMR’s detailed functions and foci were revealed. Moreover, the findings showed the important role of observable metacognitive experiences as the starting point of SSMRs. It was apparent that problems dealt with by the groups should be rather difficult if SSMR is to be made clearly visible. Further, individual students’ participation was found to differ between students and groups. The multiple research methods employed revealed supplementary findings regarding SSMR. Finally, when SSMR was focused on understanding and procedural matters, this was seen to lead to higher quality learning outcomes. Socially shared metacognition regulation should therefore be taken into consideration in students’ collaborative learning at school similarly to how an individual’s metacognition is taken into account in individual learning.

Methods of Telecommunication Technology Forecasting

This master's thesis coversthe concepts of knowledge discovery, data mining and technology forecasting methods in telecommunications. It covers the various aspects of knowledge discoveryin data bases and discusses in detail the methods of data mining and technologyforecasting methods that are used in telecommunications. Main concern in the overall process of this thesis is to emphasize the methods that are being used in technology forecasting for telecommunications and data mining. It tries to answer to some extent to the question of do forecasts create a future? It also describes few difficulties that arise in technology forecasting. This thesis was done as part of my master's studies in Lappeenranta University of Technology.

Methods of Design and Testing of Real Time Systems

Teollusuussovelluksissa vaaditaan nykyisin yhä useammin reaaliaikaista tiedon käsittelyä. Luotettavuus on yksi tärkeimmistä reaaliaikaiseen tiedonkäsittelyyn kykenevän järjestelmän ominaisuuksista. Sen saavuttamiseksi on sekä laitteisto, että ohjelmisto testattava. Tämän työn päätavoitteena on laitteiston testaaminen ja laitteiston testattavuus, koska luotettava laitteistoalusta on perusta tulevaisuuden reaaliaikajärjestelmille. Diplomityössä esitetään digitaaliseen signaalinkäsittelyyn soveltuvan prosessorikortin suunnittelu. Prosessorikortti on tarkoitettu sähkökoneiden ennakoivaa kunnonvalvontaa varten. Uusimmat DFT (Desing for Testability) menetelmät esitellään ja niitä sovelletaan prosessorikortin sunnittelussa yhdessä vanhempien menetelmien kanssa. Kokemukset ja huomiot menetelmien soveltuvuudesta raportoidaan työn lopussa. Työn tavoitteena on kehittää osakomponentti web -pohjaiseen valvontajärjestelmään, jota on kehitetty Sähkötekniikan osastolla Lappeenrannan teknillisellä korkeakoululla.

Intercultural business communication between Arabs of the United Arab Emirates and Finns

Kun kauppaa käydään eri maanosien välillä, törmätään vieraisiin kulttuureihin ja erilaisiin kaupankäyntitapoihin. Tämä tutkimus keskittyy suomalaisten liikemiesten ja - naisten työhön Yhdistyneissä Arabiemiraateissa kulttuurierojen näkökulmasta. Tavoitteena on kuvata kulttuurierojen vaikutuksia kaupankäyntiprosessiin ja löytää niitä ongelmia, joita tämän prosessin aikana kohdataan. Tavoitteena on tuottaa tietoa, jonka avulla kulttuurieroista johtuvia ongelmia voidaan vähentää tulevaisuudessa. Tutkimuksen teoreettinen tausta perustuu Hofsteden kulttuurista vaihtelua kuvaaviin dimensioihin ja Ting Toomeyn kulttuurisen identiteetin neuvotteluprosessin malliin. Näihin malleihin perustuen luotiin tähän tutkimukseen oma kulttuurien välisen kohtaamisen malli. Tutkimusongelmia ovat: 1) Miten suomalaiset liikemiehet kuvailevat arabien kaupantekokulttuuria? Kuinka vastapuoli kuvailee omaa kaupantekokulttuuriaan? 2) Minkälainen on suomalaisten ja arabien välinen kaupankäyntiprosessi? 3) Minkälaisia ongelmia kohdataan tehtäessä kauppaa suomalaisten ja arabien kesken? Tutkimus on etnografinen, laadullinen haastattelututkimus (n=12). Haastattelut tehtiin suurimmaksi osaksi Yhdistyneissä Arabiemiraateissa, osin Suomessa. Erilainen kulttuuritausta näkyy kaupankäynnissä. Kollektivistinen, maskuliininen, islamilaisen uskontoon ja vain vähäisessä määrin suoraan kielelliseen koodistoon perustuva kulttuuri heijastuu kaupankäyntiprosessiin. Ystävyyden ja sukulaisten sekä muiden verkostojen merkitys korostuu. Ruumiin kieleen, ilmeisiin ja eleisiin liittyvä kommunikaatio on erilaista ja voi aiheuttaa väärinkäsityksiä. Myös aikakäsitys ja sopimuskäytäntö poikkeavat suomalaisesta. Kaikki nämä voivat aiheuttaa ongelmia kaupankäyntiprosessissa. Tärkeimmiksi tekijöiksi ongelmien kohtaamisessa nousivat ammattitaidon lisäksi kärsivällisyys ja joustavuus. Ongelmia voidaan vähentää huolellisella valmistautumisella ennen ulkomaille lähtöä. Toinen tapa on jatkuviin työkokemuksiin perustuen oppia paikallista kulttuuria ja sen piirteitä.

The Methods of Possible Joint Treatment of Manure and Sewage Sludge in the Leningrad Region

The nutrient load to the Gulf of Finland has started to increase as a result of the strong economic recovery in agriculture and livestock farming in the Leningrad region. Also sludge produced from municipal wastewater treatment plant of the Leningrad region causes the great impact on the environment, but still the main options for its treatment is disposal on the sludge beds or Landfills. The aim of this study was to evaluate the implementation of possible joint treatment methods of manure form livestock and poultry enterprises and sewage sludge produced from municipal wastewater treatment plants in the Leningrad region. The study is based on published data. The most attention was put on the anaerobic digestion and incineration methods. The manure and sewage sludge generation for the whole Leningrad region and energy potential produced from their treatment were estimated. The calculations showed that total amount of sewage sludge generation is 1 348 000 t/a calculated on wet matter and manure generation is 3 445 000 t/a calculated on wet matter. The potential heat release from anaerobic digestion process and incineration process is 4 880 000 GJ/a and 5 950 000 GJ/a, respectively. Furthermore, the work gives the overview of the general Russian and Finnish legislation concerning manure and sewage sludge treatment. In the Gatchina district it was chosen the WWTP and livestock and poultry enterprises for evaluation of the centralized treatment plant implementation based on anaerobic digestion and incineration methods. The electricity and heat power of plant based on biogas combustion process is 4.3 MW and 7.8 MW, respectively. The electricity and heat power of plant based on manure and sewage sludge incineration process is 3.0 MW and 6.1 MW, respectively.

Eurooppalainen näkökulma suomalaiseen kulttuurijohtamiseen ja suomalaiseen yhteiskuntaan sopeutuminen

Tässä tutkielmassa korostuu Euroopan sisäinen kulttuurillinen erilaisuus ja sen vaatimukset Suomessa toimiville monikansallisille organisaatioille. Eurooppalaista johtamista on tutkittu jo vuosikymmenten ajan, mutta erityisesti suomalaisesta, Suomessa työskentelevien eurooppalaisten näkökulmasta ei vastaavaa tutkimusta tiettävästi ole aiemmin tehty. Tutkimuksen tavoitteena on selvittää suomalaisen kulttuurin ja johtajuuden arvoeroja muiden Euroopan Unionin maiden kansalaisten näkökulmasta. Pohjois-Euroopan maista tutkimuksessa on mukana edustajia Ruotsista, Tanskasta ja Hollannista. Keski-Euroopan maista edustusta löytyy Saksasta ja Itävallasta, kun Etelä-Eurooppaa edustavat ranskalaiset ja italialaiset henkilöt. Itäisestä Euroopasta mukana on latvialaisia henkilöitä ja anglo-Euroopasta britannialaisia. Tutkimus kartoittaa tutkimukseen mukaan otettujen maiden yhteisö- ja johtamiskulttuurillisia törmäyskohtia suomalaisen kulttuurin kanssa, jotta Suomessa toimivat monikansalliset työyhteisöt löytäisivät yhä parempia strategioita eurooppalaisen ihmispääoman, eurooppalaisten työntekijöiden ja näiden osaamisen, johtamiseksi ja monikansallisen yhteisön toimivuuden ymmärtämiseksi ja parantamiseksi. Näitä törmäyskohtia tarkastellaan empiirisesti Hofsteden (1984) kulttuuridimensioiden, Housen ym. (1999) GLOBE-tutkimuksen ja Koopmanin ym. (1999) johtajuusulottuvuuksien avulla. Tutkimusaineisto koostuu Internet-pohjaisesta kyselystä, joka suoritettiin keväällä 2010. Siihen osallistui 75 Suomessa työskentelevää Euroopan Unionin kansalaista. Analysointimenetelmänä tutkimuksessa käytetään klusterointia, keskiarvoistuksia, Kruskall Wallisin testiä ja sisällönanalyysiä tukemaan määrällisen analyysin tuloksia ja tuomaan esiin siitä poikkeavia havaintoja. Tutkimuksen ytimessä on johtamiskulttuurilliset erot, joista tehdään laajempaa analyysiä edellä mainituin keinoin. Yhteisökulttuurillisia eroja havainnoidaan tutkimuskyselyyn perustuvien väittämien perusteella tehtyjen histogrammien avulla. Tutkimuksen tulokset osoittavat, että maantieteellinen, uskonnollinen tai poliittinen läheisyys eivät määritä kulttuurillista läheisyyttä tai johda kulttuurilliseen sopeutumiseen. Poliittinen raja kahden naapurin välillä saattaa johtaa saman asian kokemiseen kahdella täysin eri tavalla. Lisäksi tuloksista käy ilmi, että yhteisökulttuurilliset ja johtamiskulttuurilliset arvot eivät välttämättä kulje käsikkäin Suomessa työskentelevien eurooppalaisten näkökulmasta. Yleisinä kulttuurillisina kipukohtina tutkimuksessa nousee esiin suomalaisen kulttuurin sosiaalisuuden ja kommunikaation puutteellisuus, toisaalta suomalaiseen kulttuuriin sopeutumista helpottaa suomalainen rehellisyys ja suoruus. Johtamiskulttuurillisina haasteina eurooppalaiset kokevat suomalaisen tyyppijohtajan kyvyttömyyden riskien ottamiseen ja kannustusmenetelmien puutteet. Tämän lisäksi tutkimuksessa tulee ilmi useita tiettyihin kansallisuuksiin liittyviä törmäyskohtia. Tutkimus on nähtävä tämän hetken kuvauksena. Kulttuuritutkimus sisältää monia tekijöitä, jotka ovat jatkuvassa muutoksessa ja lisäksi hyvin subjektiivisia. Kulttuurijohtajuus merkitsee kuitenkin nyt ja tulevaisuudessa kykyä olla innovatiivinen, joustava ja herkkä sosiaalisille merkityksille.

Comparison and Evaluation of Eddy Current Sensors

In the work eddy current sensors are described and evaluated. Theoretical part includes physical basics of the eddy currents, overview of available commercial products and technologies. Industrial sensors operation was assessed based on several working modes. Apart from this, the model was created in Matlab Simulink with Xilinx Blockset and then translated into a Xilinx ISE Design Suite compatible project. The performance of the resulting implementation was compared to the existing implementation in the Xilinx Spartan 3 FPGA board with the custom made sensor. Additionally, an introduction to FPGAs and VHDL is presented.