50 resultados para thread rolling


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This thesis discusses the basic problem of the modern portfolio theory about how to optimise the perfect allocation for an investment portfolio. The theory provides a solution for an efficient portfolio, which minimises the risk of the portfolio with respect to the expected return. A central feature for all the portfolios on the efficient frontier is that the investor needs to provide the expected return for each asset. Market anomalies are persistent patterns seen in the financial markets, which cannot be explained with the current asset pricing theory. The goal of this thesis is to study whether these anomalies can be observed among different asset classes. Finally, if persistent patterns are found, it is investigated whether the anomalies hold valuable information for determining the expected returns used in the portfolio optimization Market anomalies and investment strategies based on them are studied with a rolling estimation window, where the return for the following period is always based on historical information. This is also crucial when rebalancing the portfolio. The anomalies investigated within this thesis are value, momentum, reversal, and idiosyncratic volatility. The research data includes price series of country level stock indices, government bonds, currencies, and commodities. The modern portfolio theory and the views given by the anomalies are combined by utilising the Black-Litterman model. This makes it possible to optimise the portfolio so that investor’s views are taken into account. When constructing the portfolios, the goal is to maximise the Sharpe ratio. Significance of the results is studied by assessing if the strategy yields excess returns in a relation to those explained by the threefactormodel. The most outstanding finding is that anomaly based factors include valuable information to enhance efficient portfolio diversification. When the highest Sharpe ratios for each asset class are picked from the test factors and applied to the Black−Litterman model, the final portfolio results in superior riskreturn combination. The highest Sharpe ratios are provided by momentum strategy for stocks and long-term reversal for the rest of the asset classes. Additionally, a strategy based on the value effect was highly appealing, and it basically performs as well as the previously mentioned Sharpe strategy. When studying the anomalies, it is found, that 12-month momentum is the strongest effect, especially for stock indices. In addition, a high idiosyncratic volatility seems to be positively correlated with country indices on stocks.

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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.

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Global energy consumption has been increasing yearly and a big portion of it is used in rotating electrical machineries. It is clear that in these machines energy should be used efficiently. In this dissertation the aim is to improve the design process of high-speed electrical machines especially from the mechanical engineering perspective in order to achieve more reliable and efficient machines. The design process of high-speed machines is challenging due to high demands and several interactions between different engineering disciplines such as mechanical, electrical and energy engineering. A multidisciplinary design flow chart for a specific type of high-speed machine in which computer simulation is utilized is proposed. In addition to utilizing simulation parallel with the design process, two simulation studies are presented. The first is used to find the limits of two ball bearing models. The second is used to study the improvement of machine load capacity in a compressor application to exceed the limits of current machinery. The proposed flow chart and simulation studies show clearly that improvements in the high-speed machinery design process can be achieved. Engineers designing in high-speed machines can utilize the flow chart and simulation results as a guideline during the design phase to achieve more reliable and efficient machines that use energy efficiently in required different operation conditions.

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Tutkimuksen tavoitteena oli selvittää, mitä suorituskyvyn osa-alueita ETO (Engineer To Order) – tyyppinen tuotekehitysprojekti pitää sisällään, ja mitkä niistä ovat projektin onnistumisen kannalta tärkeimpiä, eli niin sanottuja menestystekijöitä. Edelleen näiden tunnistettujen menestystekijöiden pohjalta oli tavoitteena kehittää suorituskyvyn mittausmalli, jonka avulla voisi arvioida ja ohjata projektin ja projektinhallinnan suorituskykyä. Tärkeimmät suorituskyvyn näkökulmat tässä mallissa olivat projektin kannattavuuden -, asiakastyytyväisyyden - ja projektinhallinnan näkökulmat. Malli tehtiin rautatieliikenne toimialalla toimivalle yritykselle, joka asetti omat vaatimuksensa mallille. Tutkimus tehtiin kolmivaiheisesti. Ensimmäisessä vaiheessa tutustuttiin aiempiin tutkimuksiin, joiden pohjalta pyrittiin löytämään projektin menestystekijät, sekä näiden suorituskyvyn analysointiin toimiviksi todetut mittausmenetelmät. Ensimmäisessä vaiheessa tutustuttiin myös alaa ohjaaviin standardeihin, ja niiden asettamiin erityisvaatimuksiin projektien suorituskyvyn mittaukselle. Tutkimuksen toinen vaihe oli tapaustutkimus kohdeyrityksen sisäiselle projektiorganisaatiolle, joka toteutettiin survey-kyselynä. Kyselyn avulla pyrittiin löytämään ne menestystekijät, jotka projektiorganisaation itsensä mielestä olivat kaikkein tärkeimpiä projektin onnistumisen kannalta. Kyselyllä pyrittiin myös selvittämään sidosryhmien välisiä näkemyseroja projektin menestystekijöistä. Kysymykset muodostettiin synteesinä tutkimuksen ensimmäisessä vaiheessa löydetyistä menestystekijöistä ja standardien vaatimista pakollisista mitattavista tekijöistä. Tärkeimmäksi menestystekijäksi kyselyssä nousi projektipäällikön kompetenssi. Kyselyssä vastaajilta kysyttiin myös sitä, minkä menestystekijöiden suorituskykyä heidän mielestään tulisi mitata. Tärkeimmäksi mitattavaksi osa-alueeksi nousi aikataulun tarkka seuranta. Kolmannessa vaiheessa näiden kohdeyrityksen menestystekijöiden pohjalta luotiin mittausmalli, joka pyrkii mittaamaan projektin ja projektinhallinnan suorituskykyä tasapainoisesti valituista näkökulmista. Malli ottaa huomioon erityisesti projektinhallinnan suorituskyvyn vaikutuksen projektin lopputuotteena syntyvien hyödykkeiden laatuun. Kohdeyrityksen kokonaissuorituskyvyn kannalta on erittäin tärkeää parantaa projektien suorituskykyä, johon projektien suorituskyvyn mittaaminen on ratkaisu. Standardien asettamat vaatimukset antavat hyvät lähtökohdat kokonaisvaltaisen mittausjärjestelmän luomiselle.

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Valssi on valssauslaitteiston keskeinen komponentti. Valssauksessa aihiota muokataan kuljettamalla sitä kahden valssin muodostaman raon välistä. Valssit altistuvat valssausprosessissa korkealle lämpötilalle ja pintapaineelle. Valsseille asetettavat vaatimukset tiukkenevat tuottavuuden vaatimusten kiristyessä. Valssit, yhtenä valssauslaitteiston komponenteista, muodostavat suuren osan valssauksen kustannuksista, joten valssien käyttöiän pidentämisen avulla voidaan parantaa valssauksen tuottavuutta ja kustannustehokkuutta. Tässä tutkimuksessa tarkasteltiin valssien käytettävyyttä ja kunnossapitoa, sillä näitä asioita kehittämällä on mahdollista saavuttaa valsseille pidempi kestoikä. Tutkimus toteutettiin kirjallisuusselvityksenä, jota täydennettiin valssausta tekevien yritysten haastatteluilla. Tavoitteena oli kerätä saatavissa oleva kirjallinen ja hiljainen tieto yksiin kansiin ja tutkia mahdollisia syy-seuraussuhteita valssien käytettävyyteen vaikuttavien ilmiöiden sekä valssien kulumisen ja vaurioitumisen välillä. Tutkimuksessa havaittiin, että vauriotyypit ovat riippuvaisia valssausprosessista, jolla tarkoitetaan, että kuuma- ja kylmävalssauksessa esiintyy erilaisia vauriotyyppejä. Kuuma- ja kylmävalssauksessa myös valssien kulumiseen vaikuttavat erilaiset ilmiöt. Valssien kulumista ja vaurioita on mahdollista ehkäistä erilaisilla pintakäsittely- ja pinnoitusmenetelmillä. Valssien kunnossapidon toteutusta tutkittaessa havaittiin, että kuluneiden valssien vaihto kunnostettuihin pyritään suorittamaan mahdollisimman nopeasti ja tätä varten on saatavilla kyseiseen tarkoitukseen kehitettyjä laitteistoja. Kuluneet valssit sorvataan ja hiotaan, jotta niiden pinnasta saadaan tasainen ja saavutetaan haluttu halkaisija. Tämän jälkeen pinnoitusmenetelmiä on mahdollista suorittaa uudelleen. Kunnossapitotoimenpiteet tehdään joko yrityksen omalla korjaamolla tai alihankintana toisen yrityksen tiloissa.