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Performance analyses of Gas Generator cycle Air Turbo Ramjet (GG-ATR) engine are conducted to investigate the feasibility of ethanol fuel, as comparing Liquefied Hydrogen (LH2), Liquefied Natural Gas (LNG), and n-C12H26. Liquefied Oxygen (LOX) is considered as an oxidizer. Gas generator combustion temperature and compressor pressure ratio are selected as the analytical parameters, which are varied from 900 to 1700 K and from 2.0 to 4.0, respectively. In general, specific impulses of light molecule weight fuels, such as LH2 and LNG, are higher than those of large molecule weight fuel. For storable fuel, Isp of ethanol is larger than that of n-C12H26 when gas generator temperature is less than 1300 K, although specific heat release of ethanol is only two thirds of n-C12H26 heat release. The main chemical species of n-C12H26 gas generator (GG) combustion gas are CH4 and CO. On the other hand, ethanol GG combustion gas is mainly composed of H2 and CO, resulting in smaller molecular weight than n-C12H26. These characteristics contribute to larger Isp of ethanol than n-C12H26 and indicate the feasibility of ethanol for GG-ATR engine fuel., 本アーカイブに掲載したPDFは校正前の原稿である。

Fluidic thrust vectoring (FTV), an ability of air vehicles to manipulate the nozzle flow deflect their longitudinal axis, can satisfy the modern aircraft requirements dramatically. Numerical and experimental studies of FTV are performed with a nozzle pressure ratio (NPR) of 4–10, a secondary pressure ratio (SPR) of 1, 2 or 3, and two different secondary jet locations. Numerical simulations of the nozzle flow are done with solving the Navier-Stokes equations, and the input parameters are set to match the experimental conditions. The thrust pitching moment and the thrust pitching angle are determined to evaluate the FTV performance., 特集 : Special Section for the Papers Presented at the Symposium on Mechanical Engineering, Industrial Engineering, and Robotics held at Noboribetsu, Hokkaido, Japan on 11 - 12 January 2012

Dissertação (mestrado) - Pontifícia Universidade Católica de Minas Gerais, Programa de Pós-Graduação em Ensino de Ciências e Matemática. Bibliografia: f. 54-57 Resumo: A presente pesquisa apresenta um Produto Educacional para ser aplicado aos alunos do ensino médio, por meio de um roteiro de atividades experimentais, sobre o estudo da indução eletromagnética. A abordagem teórica-pedagógica deste estudo está fundamentada na teoria sociointeracionista de Vygotsky (1998). Para tanto, no desenvolvimento dos experimentos privilegiou-se a interação do sujeito com o meio escolar e a discussão dialógica, importante para o processo ensino-aprendizagem. Os Três Momentos Pedagógicos, sistematizados por Delizoicov; Angotti (1994) foram aplicados nas atividades experimentais desenvolvidas no laboratório. Esta pesquisa aplicada no IFNMG, Montes Claros, teve como sujeitos participantes os alunos do terceiro ano do ensino médio Integrado de Química. Na aplicação do produto foi realizada uma coleta de dados com os sujeitos participantes da pesquisa sobre os experimentos desenvolvidos. Essa coleta contemplou os momentos da problematização inicial e da aplicação do conhecimento. A análise dos dados foi feita a partir da Análise de Conteúdo, proposta por Bardin (2011). Dessa forma, constatou-se que a metodologia adotada corroborou as proposições de Vygotsky (2001). Também, ao se contemplar os Três Momentos Pedagógicos no desenvolvimento e aplicação do estudo da indução eletromagnética, verificou-se que a maioria dos alunos foi capaz de associar a pergunta inicial ao desenvolvimento dos experimentos, bem como à aplicação do conhecimento. Palavras-chave: Ensino de Física. Indução Eletromagnética. Teoria Sociointeracionista. Três Momentos Pedagógicos. Abstract: This research presents an Educational Product to be applied to high school students through a roadmap of experimental activities about the study of electromagnetic induction. The theoretical and pedagogical approach of this study is based on the Vygotsky's sociointeractionist theory (1998). For this, the development of experiments favored the interaction of the subject with the school and the dialogic discussion, and this is important for the teaching-learning process. Three Pedagogic Moments systematized by Delizoicov; Angotti (1994) were applied in experimental activities in the lab. This applied research in IFNMG, Montes Claros, had as subjects participating third year students of Integrated Chemistry high school. In application of the product, a collection of data on the developed experiments was carried out with the students participating. This collection included the initial moments of questioning and application of knowledge. Data analysis was made from the content analysis proposed by Bardin (2011). In this way, it was found that the adopted methodology supports the Vygotsky's proposals (2001). Also, when contemplating the three pedagogical moments in the development and application of electromagnetic induction study, it was found that most students were able to associate the initial inquiry to the development of the experiments as well as the application of knowledge. Keywords: Physics Teaching. Electromagnetic induction. Sociointeractionist theory. Three Pedagogic Moments.

平成21年度 プレ共同研究成果

平成18年度研究論文

Dissertação (Mestrado) - Pontifícia Universidade Católica de Minas Gerais, Programa de Pós-Graduação em Ensino de Ciência e Matemática. Bibliografia: f. 104-109 O objetivo deste trabalho é desenvolver e aplicar uma sequência didáticasobre a geração, transmissão e recepção das Ondas Eletromagnéticas no contextoda história da Bobina de Tesla. O produto educacional é composto por um conjuntode atividades experimentais que permitem aos alunos explorar, testar e discutir osfenômenos físicos relacionados ao eletromagnetismo. O referencial teóricopedagógicoé o conceito sócio-histórico de Vigotski, valorizando-se, assim, a relaçãoprofessor-aluno, colocando este como mediador do processo de aprendizagem. Umteste preliminar da sequência foi aplicado ao alunos do terceiro período deEngenharia Civil, na disciplina Física II; a aplicação efetiva foi realizada com osalunos na disciplina Eletromagnetismo do quinto período de Engenharia Elétrica. Aavaliação dos alunos foi feita por meio da análise de dados coletados através deobservações, um questionário e um texto produzido pelos próprios alunos. Osresultados mostram que os alunos foram capazes de desenvolver conceitoscientíficos. Acreditamos que esta proposta é adequada para ensinar tópicos deondas eletromagnéticas, auxiliando professores de física a preparar aulascontextualizadas. Palavras-chave: Eletromagnetismo, Conceitos Científicos, Bobina de Tesla, Ensino de Física, Vigotski. The aim of this work is to develop and apply a didactic sequence about thegeneration, transmission and reception of electromagnetic waves in the context of thehistory of the Tesla coil. The educational product consists of a set of experimentalactivities that allow the students to explore, test and discuss the physical phenomenarelated to electromagnetism. The theoretical-pedagogical frame is Vigotski's socialhistoricalconcept, thereby enhancing the teacher-student relationship, andemphasizing the teacher as the mediator of the learning process. A preliminary testof the product was performed with civil engineering students, in the course Physics II;it was subsequently put into effect in an electromagnetism course for electricalengineering students. The students' performance was evaluated through the analysisof the data collected from observations, a questionnaire and a text composed by thestudents. The results show that the students were able to develop scientific concepts.We believe that this proposal is appropriate for teaching about electromagneticwaves, helping physics teachers to prepare contextualized classes. Keywords: Electromagnetism, scientific concepts, Tesla coil, physics education, Vigotski.

Τα τελευταία χρόνια υπάρχει εκτεταμένη πειραματική και θεωρητική μελέτη στην περιοχή των νανοσωματιδίων διότι βρίσκουν εφαρμογές σαν μέσα μαγνητικής εγγραφής και αποθήκευσης πληροφοριών και πιο πρόσφατα στην ιατρική. Στόχος των ερευνών είναι να κατασκευαστούν όσο το δυνατό μικρότερα σε μέγεθος νανοσωματίδια, στα οποία όμως οι μαγνητικές ιδιότητες να είναι σταθερές σε θερμοκρασία δωματίου, δηλαδή με μεγάλη ανισοτροπία. Τα σύνθετα νανοσωματίδια με μορφολογία σιδηρομαγνητικού πυρήνα/αντισιδηρομαγνητικού φλοιού εμφανίζουν μία επιπλέον ανισοτροπία την ανισοτροπία ανταλλαγής η οποία τα καθιστά θερμικά σταθερά σε μικρό μέγεθος. Στην παρούσα εργασία χρησιμοποιήθηκε η τεχνική Μetropolis Monte Carlo για την μελέτη της μαγνητικής συμπεριφοράς νανοσωματιδίων με μορφολογία πυρήνα/φλοιού τα οποία εμφανίζουν την ανισοτροπία ανταλλαγής. Η τεχνική αυτή έχει το πλεονέκτημα ότι μπορεί να περιλάβει στους υπολογισμούς τις λεπτομέρειες της μικροδομής του συστήματος και την θερμοκρασία. Στόχος της εργασίας μας ήταν με την ανάπτυξη κατάλληλου θεωρητικού μοντέλου να μελετηθεί ο μηχανισμός που προκαλεί την εμφάνιση της ανισοτροπίας ανταλλαγής και οι παράγοντες που επηρεάζουν τόσο την εμφάνιση της όσο και την ισχύ της. Βρήκαμε ότι η ανισοτροπία ανταλλαγής η οποία επάγεται από την αλληλεπίδραση ανταλλαγής κατά μήκος της σιδηρομαγνητική/αντισιδηρομαγνητική διεπιφάνειας οφείλεται στην ύπαρξη μη αντισταθμισμένων μαγνητικών ροπών στην διεπιφάνεια μεταξύ σιδηρομαγνητικού πυρήνα του νανοσωματιδίου και αντισιδηρομαγνητικού φλοιού και οι παράγοντες που επηρεάζουν το μέγεθος της είναι α)το πάχος του φλοιού, έχουμε εμφάνιση της μετά το δεύτερο στρώμα αντισιδηρομαγνητικού φλοιού β)το μέγεθος της σταθεράς ανταλλαγής στην διεπιφάνεια και λιγότερο στον φλοιό που ενισχύουν το φαινόμενο, γ)το και το είδος της ανισοτροπίας στον φλοιό, είναι πιο έντονη για ανισοτροπία z-άξονα στο φλοιό και δ)από το μέγεθος της ανισοτροπίας της διεπιφάνειας. Ένα άλλο φαινόμενο που συνδέεται με την εμφάνιση της ανισοτροπίας ανταλλαγής είναι η κάθετη μετατόπιση. Δηλαδή η ασσυμετρία του βρόχου υστέρησης των σύνθετων νανοσωματιδίων με μορφολογία πυρήνα φλοιού στον κάθετο άξονα της μαγνήτισης. Οι υπολογισμοί μας έδειξαν ότι σε αντίθεση με την ανισοτροπία ανταλλαγής η κάθετη μετατόπιση οφείλεται στην ύπαρξη του συνολικού αριθμού των μη αντισταθμισμένων μαγνητικών ροπών του φλοιού και όχι μόνο της διεπιφάνειας. Οι υπολογισμοί μας συγκρίθηκαν με πρόσφατα πειραματικά αποτελέσματα, και βρέθηκαν σε πολύ καλή συμφωνία. Επιβεβαιώνοντας ότι οι ανταγωνιστικές αλληλεπιδράσεις που οφείλονται στην ύπαρξη ανταγωνιστικών αλληλεπιδράσεων ανταλλαγής σε σύνθετα νανοσωματίδια με μορφολογία σιδηρομαγνητικού πυρήνα/αντισιδηρομαγνητικού φλοιού είναι υπεύθυνες για τη μεταβολή των μαγνητικών τους ιδιοτήτων σε σχέση με αυτές των σιδηρομαγνητικών νανοσωματιδίων. The magnetic properties of nanoparticles have been subject of continuously growing interest, driven by fundamental research and technological interest especially in the magnetic recording industry and more recently in medicine. The small size of the nanoparticles and the reduced symmetry at their surface result in high coercivity. More recently, the requirement for stable magnetic behavior of the nanoparticles at room temperature led to the development of complex spin nanostructures with core/shell morphology that results to enhanced magnetic anisotropy. Composite nanoparticles with ferromagnetic core/ antiferromagnetic shell morphology have an extra anisotropy, the exchange anisotropy which makes them thermally stable in room temperature even in the case of very small size. In the current work we use the Metropolis Monte Carlo method to study the magnetic behaviour of nanoparticles with core/shell morphology which exhibit exchange anisotropy. The advantages of this method is that the microstructure of the nanoparticles is explicitly included and the temperature. The main goal of this thesis was to develop an appropriate theoretical model for the study of the origin of the exchange anisotropy and the parameters which affect its appearance and its magnitude. We find that the exchange anisotropy which is induced by the exchange interaction between ferromagnetic core and antiferromagnetic shell in the interface can is due to the existence of uncompensated bonds along the interface. The size of the exchange anisotropy depends on a) the shell thickness, at least two antiferromagnetic shell layers are necessary for the appearance of the effect, b) the magnitude of exchange interaction at the interface and at the shell influence the strength of the exchange anisotropy also c) the type of anisotropy in the antiferromagnetic shell, it is bigger for z-axis shell anisotropy and d) the magnitude of anisotropy at the interface. Another phenomenon which is related with exchange anisotropy is the vertical shift i.e. the asymmetry of the hysterisis loop on the vertical axis. Our calculations show that this shift depends on the total number of the uncompensated spins in the antiferromagnetic shell and not only from the interface. Our calculations are in good agreement with recent experimental results. This confirms that exchange interaction between ferromagnetic core and antiferromagnetic shell is responsible for the exchange anisotropy effect in these composite nanoparticles with ferromagnetic core/antiferromagnetic shell morphology that results to magnetic behaviour different from that of pure ferromagnetic nanoparticles.

Dissertação (mestrado) - Pontifícia Universidade Católica de Minas Gerais, Programa de Pós-Graduação em Engenharia Eletrica. Bibliografia: f. 90-96. Resumo: Esta dissertação faz parte de um projeto de pesquisa envolvendo PUC Minas, UnB, CEFET-MG, UFMG, FIAT Automóveis e financiamento do CNPq. Esse projeto teve como o objetivo avaliar a viabilidade do uso de uma câmara semianecóica de dimensões reduzida para a condução de testes de imunidade eletromagnética em alternativa ao que é proposto pela (ISO 11451-2, 2001), com o uso de câmara semianecóica de grandes dimensões. A configuração de testes de imunidade eletromagnética proposta pelo projeto de pesquisa consiste em utilizar somente a parte frontal do veículo. A justificativa dessa configuração baseia-se no fato de que a maior parte da eletrônica embarcada está concentrada na parte frontal do veículo. Com isso espera-se poder criar uma proposta de metodologia de testes capaz de atender preliminarmente aos requisitos normativos com uma estrutura laboratorial menos onerosa. Nesse contexto o presente trabalho concentra-se no uso de metodologias numéricas de cálculo de campo eletromagnético como ferramenta para reproduzir e validar no ambiente computacional os experimentos propostos no projeto de pesquisa. É abordada ainda a utilização de modelos simplificados como forma de compreensão dos fenômenos eletromagnéticos, penetração de campo em aberturas e cavidades ressonantes eletromagnéticas, presentes em uma estrutura veicular complexa. Abstract: This dissertation is part of a research project involving PUC Minas, UnB, CEFET-MG, UFMG, FIAT Automóveis financed by CNPq. The project objective is to evaluate the viability of the use of a semi-anechoic chamber with reduced dimensions for the conduction of electromagnetic immunity test as an alternative to what it is established by (ISO 11451-2, the 2001), where is applied semi-anechoic chamber with large dimensions. The configuration of tests of electromagnetic immunity proposed by the project consists of using only the frontal part of the vehicle in the test. This is justified by the fact that most of the embedded electronics is concentrated in this part of the vehicle. It is the project expectancy the creation of an alternative proposal for preliminary vehicle radiated electromagnetic immunity test, applying cheaper laboratory structures. In this context the present work concentrates in the development of computational simulations of the tests configurations in order to evaluate the research project proposal. Simplified models are used as form of understanding the electromagnetic phenomena, field penetration in apertures and electromagnetic resonance cavity, in a complex vehicular structure. The results had demonstrated hopeful and satisfactory in comparison to the degree of difficulty for electromagnetic numerical simulations in large structures as automotive vehicle. O CD-ROM encontra-se no Setor de Coleções Especiais

平成20年度共同研究プロジェクト成果

従来の宇宙輸送システムはコストが高く，十分な信頼性が得られていないことから民間による需要が少なく，宇宙開発の発展を妨げる要因になっている。また，環境負荷の低減から，宇宙輸送システムに対しても再使用化やクリーン推進剤の使用が求められている。クリーン推進剤として，液化天然ガス（LNG）やバイオエタノール（BE）燃料が注目されている。LNG及びBEを燃料とするロケットでは，燃焼ガス中に煤の発生が少なく，ロケットの再使用化に適している。また，LNGは製造段階を含めてCO2排出量が少なく，BEはカーボンニュートラルであり，環境負荷の低減に効果がある。一方，これらの燃料を用いたロケットの性能も比較的高く，従来のケロシン（RP-1）燃料ロケットの性能と比較して遜色はない。ロケットエンジンの再使用化においては，再生冷却における冷却材の挙動が重要である。LNGやBEを冷却材として用いた場合，ロケットの高性能化（高燃焼圧化）に伴う冷却材の高温化によって再生冷却溝表面へのコーキング（熱分解に伴う煤の析出）が生じ，冷却材と再生冷却溝表面間の熱伝達率の低下や再生冷却流路の下流に位置する推進剤噴射器流路の閉塞を招く。また，再生冷却溝にサルファアタック（含有硫黄成分による腐食）が発生し，その金属材料の構造強度を低下させる。これらが原因となって再使用性（耐久性）や信頼性が低下する。本研究ではLNG及びBE燃料を用いてコーキングやサルファアタックが再生冷却に与える影響を解明することを目的としている。更に，両現象を抑制する手法を提案し，その有効性を実証した。コーキングに関する研究の結果，LNG，BE共に熱分解に伴う炭素の析出が再生冷却性能の低下と推進剤噴射器流路の閉塞に繋がる危険性を示した。再生冷却溝金属には触媒効果があるため，熱分解が生じない冷却材温度はLNGでは約600[K]，BEでは約550[K]であった。また，再生冷却溝金属表面にグラファイトコーティングしてコーキングを抑制する手法を提案し，熱分解が生じない温度を約100[K]上昇できた。サルファアタックに関する研究の結果，LNGでは腐食による再生冷却溝金属表面の組成変化と引張強度の低下が確認でき，再生冷却性能や構造強度の低下に繋がる恐れを示した。更に400[K]でも金属硫化物を確認でき，サルファアタックは低温でも進展する可能性を示した。BEでは，再生冷却溝金属表面への硫黄の付着を確認し，腐食反応への進展を示した。また，再生冷却溝壁に金メッキしてサルファアタックを抑制する手法を提案し，サルファアタックを抑制する効果を実証した。本研究成果に基づいて，コーキング，サルファアタックが影響しない冷却材最大温度に対する燃焼ガス圧力はLNG １ton級エンジンでは約36[MPaA]，BE 600kg級エンジンでは約26[MPaA]まで上昇可能と予測され，信頼性，再使用性を維持した上で高性能化が可能であることを示した。また，本研究成果はジェットエンジンや多様なパワープラントの再生冷却にも広く適用できる。