865 resultados para Zero reflection controller


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This work deals with an hybrid PID+fuzzy logic controller applied to control the machine tool biaxial table motions. The non-linear model includes backlash and the axis elasticity. Two PID controllers do the primary table control. A third PID+fuzzy controller has a cross coupled structure whose function is to minimise the trajectory contour errors. Once with the three PID controllers tuned, the system is simulated with and without the third controller. The responses results are plotted and compared to analyse the effectiveness of this hybrid controller over the system. They show that the proposed methodology reduces the contour error in a proportion of 70:1.

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This article deals with a contour error controller (CEC) applied in a high speed biaxial table. It works simultaneously with the table axes controllers, helping them. In the early stages of the investigation, it was observed that its main problem is imprecision when tracking non-linear contours at high speeds. The objectives of this work are to show that this problem is caused by the lack of exactness of the contour error mathematical model and to propose modifications in it. An additional term is included, resulting in a more accurate value of the contour error, enabling the use of this type of motion controller at higher feedrate. The response results from simulated and experimental tests are compared with those of common PID and non-corrected CEC in order to analyse the effectiveness of this controller over the system. The main conclusions are that the proposed contour error mathematical model is simple, accurate, almost insensible to the feedrate and that a 20:1 reduction of the integral absolute contour error is possible.

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julkaisumaa: 372 IE IRL Irlanti

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Sementes recalcitrantes são intolerantes à dessecação e a baixas temperaturas, que são as principais formas de conservação de sementes e, portanto, são de difícil armazenamento. Inga vera subsp. affinis produz sementes denominadas recalcitrantes, uma vez que não toleram redução do teor de água para valores inferiores a 35%. Neste trabalho é demonstrada a tolerância desses embriões a temperatura de -2 ºC. Embriões de I. vera de diferentes estádios de maturação foram armazenados por até 45 dias nas temperaturas de 8 ºC a -18 ºC, com ou sem secagens prévias até -4,0 e -6,0 MPa. Os resultados permitiram observar que, embora nenhum tratamento tenha proporcionado resistância à temperatura de -18 ºC, a secagem dos embriões maduros a -4 MPa proporcionou maior tolerância à redução de temperatura até níveis de congelamento da água (-2 ºC).

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This thesis presents point-contact measurements between superconductors (Nb, Ta, Sn,Al, Zn) and ferromagnets (Co, Fe, Ni) as well as non-magnetic metals (Ag, Au, Cu, Pt).The point contacts were fabricated using the shear method. The differential resistanceof the contacts was measured either in liquid He at 4.2 K or in vacuum in a dilutionrefrigerator at varying temperature down to 0.1 K. The contact properties were investigatedas function of size and temperature. The measured Andreev-reflection spectrawere analysed in the framework of the BTK model – a three parameter model that describescurrent transport across a superconductor - normal conductor interface. Theoriginal BTK model was modified to include the effects of spin polarization or finitelifetime of the Cooper pairs. Our polarization values for the ferromagnets at 4.2 K agree with the literature data, but the analysis was ambiguous because the experimental spectra both with ferromagnets and non-magnets could be described equally well either with spin polarization or finite lifetime effects in the BTK model. With the polarization model the Z parametervaries from almost 0 to 0.8 while the lifetime model produces Z values close to 0.5. Measurements at lower temperatures partly lift this ambiguity because the magnitude of thermal broadening is small enough to separate lifetime broadening from the polarization. The reduced magnitude of the superconducting anomalies for Zn-Fe contacts required an additional modification of the BTK model which was implemented as a scaling factor. Adding this parameter led to reduced polarization values. However, reliable data is difficult to obtain because different parameter sets produce almost identical spectra.

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Tässä työssä tutkittiin kahden suomalaisen yrityksen omistamaa yhteisyritystä Venäjällä. Tavoitteena oli kehittää tasapainotettu mittaristo suorituskyvyn mittaukseen johtamisen tueksi. Lisäksi oli tarve parantaa materiaalinhallintaa kehittämällä controllerin työtä helpottava työkalu, sekä kehittää materiaalinhallinnan prosessia läpinäkyvämmäksi ja suoraviivaisemmaksi. Työ koostuu teoreettisesta ja empiirisestä osuudesta. Teoria koostuu raportoinnista, suorituskyvyn mittauksesta ja materiaalinhallinnan seurannasta. Työssä käytettiin laadullisia menetelmiä ja tutkimustyypiksi valikoitui toimintatutkimus. Teoreettinen aineisto on peräisin julkaisuista ja alan kirjallisuudesta. Empiirinen aineisto kerättiin pääosin haastatteluista, benchmarkkauksesta ja dokumenteista. Työn tuloksena saavutettiin päätavoite, eli kehitettiin Excel – pohjaiset työkalut suorituskyvyn mittaukseen ja materiaalinhallinnan seurantaan. Lisäksi kehitettiin kirjallinen ohjeistus näiden työkalujen käyttöön ja materiaalinhallintaprosessien suoraviivaistamiseksi. Diplomityö helpottaa yrityksen johtamista ja kontrollointia sekä sisäisesti että ulkoisesti omistajanäkökulmasta katsottuna. Venäjällä toimivan ulkomaalaisomisteisen yrityksen seuranta on haastavaa, jossa prosessien toimivuus ja läpinäkyvyys ovat olennaisessa roolissa.

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The aim of this paper is to evaluate the relationship between fiscal deficits and interest rate in Brazil. An adaptation of Taylor’s Rule is tested and the data confirmed this relationship. Furthermore, evidence from a loanable funds model shows that a lower deficit can bring interest rate down. However, policy coordination is a key feature in this process.

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This is a study of one participant's reflective practice as she worked to develop online communities in a face-to-face science course. Her process of reflective practice was examined in order to address factors that influenced her learning path, and the benefits and challenges of collaborative action research. These research goals were pursued using a collaborative action research methodology, initially chosen for its close match with Schon's (1983) model of reflective practice. The participant's learning fit vnth Mezirow's (1991) model of transformative learning. She began with beliefs that matched her goals, and she demonstrated significant learning in three areas. First, she demonstrated instrumental learning around the constraints of workload and time, and achieving online learning community indicators. Second, she demonstrated communicative learning that helped her to see her own needs for feedback and communication more clearly, and how other process partners had been a support to her. Third, her emancipatory learning saw her revisiting and questioning her goals. It was through the reflective conversation during the planned meetings and the researcher's reframing and interrogation of that reflection that the participant was able to clarify and extend her thinking, and in so doing, critically reflect on her practice as she worked to develop online learning communities. In this way, the collaborative action research methodology was an embodiment of co-constructivism through collaborative reflective practice. Schon's (1983) model of reflective practice positions a lone practitioners moving through cycles ofplan-act-observe-reflect. The results fi"om this study suggest that collaboration is an important piece of the reflective practice model.

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Visual stimuli and socialization influence exploratory behaviour in crayfish. The predominant components of spontaneous exploratory behaviour were determined by observing the activity of solitary adult crayfish (Procambarus clarkii) in a glass aquarium containing fresh water and no objects. Five distinct behaviours were observed: rearing up (climbing on the wall), turning around, cornering (facing the comer), backward walking, and crossing (crossing the midline of the aquarium). The frequency of rearing up, cornering and turning around decreased when reflection from the glass wall was blocked with black cardboard, black paint or non-reflective transparent plastic. In a tank containing mirrors on one side and non-reflective plastic on the other, crayfish cornered, reared up, and turned around more in front of the mirrors. Socialization was necessary for crayfish to respond to the reflection. Crayfish that were housed in pairs for two weeks exhibited more rearing up, turning around and cornering in front of the mirrors than in the non-reflective side. Crayfish isolated for two weeks did not show these differences. Socialized crayfish also exhibited more rearing up, turning around and cornering than did isolated crayfish. Thus, crayfish respond to visual stimuli provided by a glass tank, but the responds depends on socialization.

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The purpose ofthis study was to explore various types ofreflection and to explore reflection on action, reflection as a practice, and reflection as a process. In doing this, the intent was to discover the perceived benefits of reflection in the classroom and to provide guidelines for future use at the undergraduate and graduate level. The qualitative components in this study included the data collection strategy of semistructured interviews with 2 undergraduate students, 2 graduate students, 1 undergraduate studies professor, and 1 graduate studies professor. The data analysis strategies included a within-case analysis and a cross-case analysis. Through the interviews participants discussed their experiences with the use ofreflection in the classroom. Through the completion ofthis analysis the researcher expected to discover the benefits ofreflection at this level of education, as well as provide suggestions for future use. Both undergraduate and graduate students and professors were found to benefit from the use of reflection in the classroom. The use ofreflection in the undergraduate and graduate classroom was found to improve student/teacher and student/peer relationships, foster critical thinking, allow for connections between learned theory and life experience, and improve students' writing abilities. Based on the results ofthe study the implications ofreflection for the undergraduate and graduate classroom and for further research are provided.

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This study attempted to determine whether or not dialogue journal writing encouraged critical reflection in the adult ESL (English as a Second Language) learner. According to research in adult education and anecdotal evidence, the process ofdialogue journal writing can facilitate critical reflection in the adult learner. However, little research has been conducted to examine whether or not journal writing can facilitate critical reflection in the second language learner. As a result, ten low-intermediate level adult ESL students from Brock University's Intensive English Language Programme participated in a dialogue journal writing programme in their writing class. The participants wrote journal entries over a 10-week period, and were interviewed once throughout the process to determine their perceptions ofthe journal writing experience. They also were observed by the researcher throughout the journal writing sessions to establish whether any behaviours or intrusions might affect the participants' writing processes. After the content ofthe journals and the interviews, and the observations made by the researcher were analysed, it was confirmed that, for these participants, dialogue journal writing did not necessarily encourage critical reflection. Moreover, the participants' perceptions ofjournal writing were that it helped them to practise the syntax, vocabulary, and rhetorical patterns ofEnglish; nevertheless, it did not foster critical reflection or thinking.