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1
Deshpande, Pranav K. "Wear Resistance and Electrical Property of Infrared Processed Copper/Tungsten Carbide Composites." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1147536455.
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2
He, Mengwei. "Microstructure-Property Relationships in CoCrNi-Based High Entropy Alloys: From the Atomic-Scale." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29466.
Повний текст джерелаАнотація:
High entropy alloys (HEAs) have attracted enormous research interest world-wide because of their intriguing compositional make-up, and because of their potential as structural materials in extreme environments such as extremes of temperature, neutron fluence, mechanical wear, and cyclic deformation A key challenge in the study of HEAs remains the desire to measure the detail of the atomic neighbourhoods. This thesis proposes a new framework for the quantification of short range order (SRO) and reveals processing-SRO-mechanical property relationships in a CoCrNi-based ternary HEA.
Having established the optimal APT operating parameters, a workflow for accurately assessing the SRO in the HEAs using APT is proposed. The influence of detector efficiency and spatial resolution on the SRO was carefully evaluated. It is suggested that this new procedure has potential to significantly enhance the ability of the atom probe to precisely study atomic coordination in HEAs and other materials. On the basis of this method, the potential for relationships between thermo-mechanical processing and SRO was investigated. The results indicate that different heat treatments do indeed change the SRO in CoCrNi alloys. Then, the new approach to measuring SRO in HEAs was applied to samples at various stages of tensile deformation via interrupted tensile tests. After different plastic strain levels, the SRO and other microstructural attributes such as the defect distributions were studied, and evidence presented that the SRO is sensitive to the amount of prior plastic deformation.
Finally, retaining a focus on the mechanical properties of the HEAs, but shifting the emphasis to wear, a new series of HEAs was designed and prepared. The results demonstrate the significant potential of combining the substitutional Sc and interstitial C elements to achieve high values for hardness, wear resistance and fracture toughness.
3
Tu, Wei-Lun. "Processing, Structure, and Tribological Property Interrelationships in Sputtered Nanocrystalline ZnO Coatings." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12207/.
Повний текст джерелаАнотація:
Solid lubricant coatings with controlled microstructures are good candidates in providing lubricity in moving mechanical assembly applications, such as orthopedics and bearing steels. Nanocrystalline ZnO coatings with a layered wurtzite crystal structure have the potential to function as a lubricious material by its defective structure which is controlled by sputter deposition. The interrelationships between sputtered ZnO, its nanocrystalline structure and its lubricity will be discussed in this thesis. The nanocrystalline ZnO coatings were deposited on silicon substrates and Ti alloys by RF magnetron sputtering with different substrate adhesion layers, direct current biases, and temperatures. X-ray diffraction identified that the ZnO (0002) preferred orientation was necessary to achieve low sliding friction and wear along with substrate biasing. In addition, other analyses such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were utilized to study the solid lubrication mechanisms responsible for low friction and wear.
4
Greenhalgh, Paul. "Grease to the wheel or a spanner in the works? : an investigation of office and industrial occupier displacement and property market filtering generated by public sector assisted property developments : a case study of Tyne and Wear." Thesis, Northumbria University, 2006. http://nrl.northumbria.ac.uk/2668/.
Повний текст джерелаАнотація:
The thesis is a study of property occupier displacement generated by the supply of new office and industrial accommodation that has been promoted or assisted by property-led regeneration policies. A review of literature revealed that there had been little in-depth investigation of the phenomenon of occupier displacement and the filtering effect associated with it. A flow model was developed to illustrate the incidence of occupier displacement and the process of property market filtering. There are two main strands to the research (see Figure 1.1), firstly an exploration of the property chains generated by the displacement of office and industrial occupiers in response the supply of new accommodation, and secondly, an investigation of the reasons why office and industrial occupiers relocate and how they determine where to move to. Three phases of research were employed to record the displacement generated by twenty public sector assisted office and industrial developments in the Tyne and Wear conurbation. Occupiers of twenty developments were identified by site inspections and a total population questionnaire survey was undertaken, complemented by a telephone survey, to record the status and origin of over 500 property occupiers and allow the property chains to be pursued. The chaining exercise revealed the scale of displacement or relocation and the outcome of the resulting chains. The origin of first move occupiers and chain-ends was plotted to reveal their spatial distribution. The research recorded that over half of all occupiers had relocated and over a third of chains generated by such moves, resulted in vacant property elsewhere in the conurbation. Structured interviews with 29 office and industrial occupiers were undertaken to investigate their locational decisions and the factors that influenced their outcome, the results of which were triangulated with the earlier research phases to reveal ten key themes that fundamentally determine such decisions. The originality of the research is the scale and rigour of the chaining survey, the mapping of the spatial distribution of the origin of occupiers and the chain-ends, and the pursuit of understanding of how occupiers respond to the availability of new accommodation. The scale occupier displacement, generated by new office and industrial accommodation, is significant, but by stimulating property market excitation and vacancy a filtering effect is set-up that can generate positive benefits to a local economy by allowing occupiers to expand.
5
Tang, Fei. "The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835313-syGDu9/webviewable/.
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6
Favacchio, Giuseppe. "Cohen-Macaulayness of tower sets and Betti Weak Lefschetz Property." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1550.
Повний текст джерелаАнотація:
We deal with the Cohen-Macaulay property for monomial squarefree ideals. We characterize the Cohen-Macaulay squarefree monomial ideals of codimension two just looking at their minimal prime ideals.
We introduce the notion of tower sets and other configurations which preserve the Cohen-Macaulayness.
We study the Hilbert function and the graded Betti numbers for generic linear quotients of Artinian standard graded algebras, especially in the case of Weak Lefschetz algebras. Moreover, we investigate a particular property of Weak Lefschetz algebras, the Betti Weak Lefschetz Property, which makes possible to completely determinate the graded Betti numbers of a generic linear quotient of such algebras.
7
Abouda, Emna. "Étude de revêtements durs pour la tenue à l’usure par rechargement laser dans la robinetterie nucléaire sur des fonctions de guidage et d’étanchéité." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0007.
Повний текст джерелаАнотація:
Le remplacement des alliages durs à base cobalt par des alliages à base fer suscite un intérêt croissant pour la protection anti-usure des pièces métalliques fonctionnant dans le circuit primaire d’une centrale nucléaire. Dans le cadre de cette thèse, une étude métallurgique détaillée a été effectuée sur des dépôts épais en Norem 02™ élaborés par le procédé de projection laser.Un affinement significatif de la microstructure du Norem 02™ a été obtenu après optimisation des paramètres du procédé (puissance laser, vitesse de balayage et débit de poudre), par rapport à un procédé concurrent par Plasma à Arc Transféré. Les essais tribologiques montrent que l’amélioration de la microstructure n’empêche cependant pas l’apparition du grippage à 300°C.La deuxième partie de cette étude a été consacrée à l’amélioration du Norem 02™ avec ajout de différents éléments chimiques. Le choix de ces ajouts adéquats a été validé grâce aux tests de frottement réalisés sur des échantillons en Norem 02™ modifié, sous haute contrainte mécanique (1 GPa) et à haute température (300°C). Parmi une dizaine d’éléments d’ajouts testés, l’ajout de titane a permis une transformation complète de la microstructure du Norem 02™. Cette transformation métallurgique a amélioré son comportement tribologique avec un faible coefficient de frottement (<0.3) à 300°C.L’origine de cette amélioration du comportement mécanique du Norem 02-Ti a été étudiée et expliquée par différentes analyses microstructurales (MO, MEB, EDS, EBSD) ainsi que des essais de traction sur des éprouvettes extraites des revêtements épaisThis study aims to substitute the cobalt-based hardfacing alloys with iron-based hardfacing alloys to protect mechanical parts operating in the primary circuit of a pressurized water reactor (PWR)Firstly, a detailed metallurgical study was carried out to characterize a thick deposit on Norem 02™ produced by the laser process (Direct Metal Deposition - DMD). Compared with a classical PTA process, a microstructure refinement was achieved after an optimization of process parameters (laser power, scanning speed and powder flow-rate). However, wear tests show that the improvement of the microstructure does not prevent the occurrence of galling at 300 ° C.The second part of this study is dedicated to Norem 02™ improvement with the addition of various chemical elements. The appropriate additions to this application have been validated by wear tests under high mechanical stress (1 GPa) and at high temperature (300°C). Among a dozen samples of modified Norem 02 ™, the addition of titanium was shown to provide a complete transformation of the initial Norem 02™’s microstructure. This metallurgical transformation improved its tribological behavior with a low friction coefficient (<0.3) obtained at 300 °C.Last, the origin of the mechanical behavior improvement of Norem 02-Ti was studied and explained by microstructural analysis (MO, MEB, EDS, EBSD) and tensile tests on specimens extracted from thick coatings
8
Borozan, Valentin. "Proper and weak-proper trees in edges-colored graphs and multigraphs." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00738959.
Повний текст джерелаАнотація:
Dans la présente thèse nous étudions l'extraction d'arbres dans des graphes arêtes-coloriés.Nous nous concentrons sur la recherche d'arbres couvrants proprement arête-coloriés et faiblement arête-coloriés, notée PST et WST. Nous montrons que les versions d'optimisation de ces problèmes sont NP-Complete dans le cas général des graphes arêtes-coloriés, et nous proposons des algorithmes pour trouver ces arbres dans le cas des graphes arêtes-coloriés sans cycles proprement arêtes-coloriés.Nous donnons également quelques limites de nonapproximabilité. Nous proposons des conditions suffisantes pour l'existence de la PST dans des graphes arêtes-coloriés (pas forcément propre), en fonction de différents paramètres de graphes, tels que : nombre total de couleurs, la connectivité et le nombre d'arêtes incidentes dedifférentes couleurs pour un sommet. Nous nous intéressons aux chemins hamiltoniens proprement arêtes-coloriés dans le casdes multigraphes arêtes-coloriés. Ils présentent de l'intérêt pour notre étude, car ce sontégalement des arbres couvrants proprement arêtes-coloriés. Nous établissons des conditions suffisantes pour qu'un multigraphe contienne un chemin hamiltonien proprement arêtes-coloriés, en fonction de plusieurs paramètres tels que le nombre d'arêtes, le degré d'arêtes, etc. Puisque l'une des conditions suffisantes pour l'existence des arbres couvrants proprement arêtes-coloriés est la connectivité, nous prouvons plusieurs bornes supérieures pour le plus petit nombre de couleurs nécessaires pour la k-connectivité-propre. Nous énonçons plusieurs conjectures pour les graphes généraux et bipartis, et on arrive à les prouver pour k = 1.
9
Zucca, Fabio, and Andreas Cap@esi ac at. "The Mean Value Property for Harmonic Functions on Graphs and Trees." ESI preprints, 2001. ftp://ftp.esi.ac.at/pub/Preprints/esi1002.ps.
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10
Braga, Bruno. "On the Borel complexity of some classes of Banach spaces." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1377115201.
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11
Dreyling, Justus [Verfasser]. "Regulatory Reform under Conditions of Regime Complexity : Weak Actors and Institutional Opportunity Structures in the Global Governance of Intellectual Property / Justus Dreyling." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1214641369/34.
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12
Altafi, Nasrin. "Lefschetz Properties of Monomial Ideals." Licentiate thesis, KTH, Matematik (Inst.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223373.
Повний текст джерелаАнотація:
This thesis concerns the study of the Lefschetz properties of artinian monomial algebras. An artinian algebra is said to satisfy the strong Lefschetz property if multiplication by all powers of a general linear form has maximal rank in every degree. If it holds for the first power it is said to have the weak Lefschetz property (WLP). In the first paper, we study the Lefschetz properties of monomial algebras by studying their minimal free resolutions. In particular, we give an afirmative answer to an specific case of a conjecture by Eisenbud, Huneke and Ulrich for algebras having almost linear resolutions. Since many algebras are expected to have the Lefschetz properties, studying algebras failing the Lefschetz properties is of a great interest. In the second paper, we provide sharp lower bounds for the number of generators of monomial ideals failing the WLP extending a result by Mezzetti and Miró-Roig which provides upper bounds for such ideals. In the second paper, we also study the WLP of ideals generated by forms of a certain degree invariant under an action of a cyclic group. We give a complete classication of such ideals satisfying the WLP in terms of the representation of the group generalizing a result by Mezzetti and Miró-Roig.QC 20180220
13
Culp, Laura. "An Isomorphism Theorem for Graphs." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1952.
Повний текст джерелаАнотація:
In the 1970’s, L. Lovász proved that two graphs G and H are isomorphic if and only if for every graph X , the number of homomorphisms from X → G equals the number of homomorphisms from X → H . He used this result to deduce cancellation properties of the direct product of graphs. We develop a result analogous to Lovász’s theorem, but in the class of graphs without loops and with weak homomorphisms. We apply it prove a general cancellation property for the strong product of graphs.
14
Andreja, Tepavčević. "Specijalni elementi mreže i primene." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 1993. http://dx.doi.org/10.2298/NS19930629TEPAVCEVIC.
Повний текст джерелаАнотація:
Data je karakterizacija raznih tipova specijalnih elemenata mreže, kao što su kodistributivni, neutralni, skrativi, standardni, izuzetni, neprekidni, beskonačno distributivni i drugi i ti rezultati su primenjeni u strukturnim ispitivanjima algebri, posebno u mrežama kongruencija, podalgebri i slabih kongruencija algebri. Specijalni elementi su posebno proučavani i u bipolumrežama i dobijene su nove teoreme reprezentacije za bipolumreže. Ispitana je kolekcija svih mreža sa istim skupom i-nerazloživih elemenata, pokazano je da je ta kolekcija i sama mreža u odnosu na inkluziju i daju se karakterizacije te mreže. Rešavan je problem prenošenja mrežnih identiteta sa mreže podalgebri i kongruencija na mrežu slabih kongruencija. Proučavane su osobine svojstva preseka kongruencija i svojstva proširenja kongruencija i neke varijante tih svojstava u vezi sa mrežama slabih kongruencija. Date su karakterizacije mreže slabih kongruencija nekih posebnih klasa algebri i varijeteta, kao što su unarne algebra, mreže, grupe, Hamiltonove algebra i druge.A characterization of various types of special elements in lattices: codistributive, neutral, cancellable, standard, exceptional, continuous, infinitely distributive and others are given, and the results are applied in structural investigations in algebras, in particular in lattices of subalgebras, congruences and weak congruences. Special elements are investigated also in bi-semilattices and new representation theorems for bisemilattices are obtained. The collection of all lattices with the same poset of meet-irreducible elements is studied and it is proved that this collection is a lattice under inclusion and characterizations of this lattice is given. A problem of transferability of lattice identities from lattices of subalgebras and congruences to lattices of weak congruencse of algebras is solved. The congruence intersection property and the congruence extension property as well as various alternations of these properties are investigated in connection with weak congruence lattices. Characterizations of weak congruence lattices of special classes of algebras and varieties, as unary algebras, lattices, groups, Hamiltonian algebras and others are given.
15
Leguil, Martin. "Cocycle dynamics and problems of ergodicity." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC159/document.
Повний текст джерелаАнотація:
Le travail qui suit comporte quatre chapitres : le premier est centré autour de la propriété de mélange faible pour les échanges d'intervalles et flots de translation. On y présente des résultats obtenus avec Artur Avila qui renforcent des résultats précédents dus à Artur Avila et Giovanni Forni. Le deuxième chapitre est consacré à un travail en commun avec Zhiyuan Zhang et concerne les propriétés d'ergodicité et d'accessibilité stables pour des systèmes partiellement hyperboliques de dimension centrale au moins égale à deux. On montre que sous des hypothèses de cohérence dynamique, center bunching et pincement fort, la propriété d'accessibilité stable est dense en topologie C^r, r>1, et même prévalente au sens de Kolmogorov. Dans le troisième chapitre, on expose les résultats d'un travail réalisé en collaboration avec Julie Déserti, consacré à l'étude d'une famille à un paramètre d'automorphismes polynomiaux de C^3 ; on montre que de nouveaux phénomènes apparaissent par rapport à ce qui était connu dans le cas de la dimension deux. En particulier, on étudie les vitesses d'échappement à l'infini, en montrant qu'une transition s'opère pour une certaine valeur du paramètre. Le dernier chapitre est issu d'un travail en collaboration avec Jiangong You, Zhiyan Zhao et Qi Zhou ; on s'intéresse à des estimées asymptotiques sur la taille des trous spectraux des opérateurs de Schrödinger quasi-périodiques dans le cadre analytique. On obtient des bornes supérieures exponentielles dans le régime sous-critique, ce qui renforce un résultat précédent de Sana Ben Hadj Amor. Dans le cas particulier des opérateurs presque Mathieu, on montre également des bornes inférieures exponentielles, qui donnent des estimées quantitatives en lien avec le problème dit "des dix Martinis". Comme conséquences de nos résultats, on présente des applications à l'homogénéité du spectre de tels opérateurs ainsi qu'à la conjecture de DeiftThe following work contains four chapters: the first one is centered around the weak mixing property for interval exchange transformations and translation flows. It is based on the results obtained together with Artur Avila which strengthen previous results due to Artur Avila and Giovanni Forni. The second chapter is dedicated to a joint work with Zhiyuan Zhang, in which we study the properties of stable ergodicity and accessibility for partially hyperbolic systems with center dimension at least two. We show that for dynamically coherent partially hyperbolic diffeomorphisms and under certain assumptions of center bunching and strong pinching, the property of stable accessibility is dense in C^r topology, r>1, and even prevalent in the sense of Kolmogorov. In the third chapter, we explain the results obtained together with Julie Déserti on the properties of a one-parameter family of polynomial automorphisms of C^3; we show that new behaviours can be observed in comparison with the two-dimensional case. In particular, we study the escape speed of points to infinity and show that a transition exists for a certain value of the parameter. The last chapter is based on a joint work with Jiangong You, Zhiyan Zhao and Qi Zhou; we get asymptotic estimates on the size of spectral gaps for quasi-periodic Schrödinger operators in the analytic case. We obtain exponential upper bounds in the subcritical regime, which strengthens a previous result due to Sana Ben Hadj Amor. In the particular case of almost Mathieu operators, we also show exponential lower bounds, which provides quantitative estimates in connection with the so-called "Dry ten Martinis problem". As consequences of our results, we show applications to the homogeneity of the spectrum of such operators, and to Deift's conjecture
16
Bot, Radu Ioan. "Duality and optimality in multiobjective optimization." Doctoral thesis, Universitätsbibliothek Chemnitz, 2003. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200300842.
Повний текст джерелаАнотація:
The aim of this work is to make some investigations concerning duality for multiobjective optimization problems. In order to do this we study first the duality for scalar optimization problems by using the conjugacy approach. This allows us to attach three different dual problems to a primal one. We examine the relations between the optimal objective values of the duals and verify, under some appropriate assumptions, the existence of strong duality. Closely related to the strong duality we derive the optimality conditions for each of these three duals. By means of these considerations, we study the duality for two vector optimization problems, namely, a convex multiobjective problem with cone inequality constraints and a special fractional programming problem with linear inequality constraints. To each of these vector problems we associate a scalar primal and study the duality for it. The structure of both scalar duals give us an idea about how to construct a multiobjective dual. The existence of weak and strong duality is also shown. We conclude our investigations by making an analysis over different duality concepts in multiobjective optimization. To a general multiobjective problem with cone inequality constraints we introduce other six different duals for which we prove weak as well as strong duality assertions. Afterwards, we derive some inclusion results for the image sets and, respectively, for the maximal elements sets of the image sets of these problems. Moreover, we show under which conditions they become identical. A general scheme containing the relations between the six multiobjective duals and some other duals mentioned in the literature is derivedDas Ziel dieser Arbeit ist die Durchführung einiger Untersuchungen bezüglich der Dualität für Mehrzieloptimierungsaufgaben. Zu diesem Zweck wird als erstes mit Hilfe des so genannten konjugierten Verfahrens die Dualität für skalare Optimierungsaufgaben untersucht. Das erlaubt uns zu einer primalen Aufgabe drei unterschiedliche duale Aufgaben zuzuordnen. Wir betrachten die Beziehungen zwischen den optimalen Zielfunktionswerten der drei Dualaufgaben und untersuchen die Existenz der starken Dualität unter naheliegenden Annahmen. Im Zusammenhang mit der starken Dualität leiten wir für jede dieser Dualaufgaben die Optimalitätsbedingungen her. Die obengenannten Ergebnisse werden beim Studium der Dualität für zwei Vektoroptimierungsaufgaben angewandt, und zwar für die konvexe Mehrzieloptimierungsaufgabe mit Kegel-Ungleichungen als Nebenbedingungen und für eine spezielle Quotientenoptimierungsaufgabe mit linearen Ungleichungen als Nebenbedingungen. Wir assoziieren zu jeder dieser vektoriellen Aufgaben eine skalare Aufgabe für welche die Dualität betrachtet wird. Die Formulierung der beiden skalaren Dualaufgaben führt uns zu der Konstruktion der Mehrzieloptimierungsaufgabe. Die Existenz von schwacher und starker Dualität wird bewiesen. Wir schliessen unsere Untersuchungen ab, indem wir eine Analyse von verschiedenen Dualitätskonzepten in der Mehrzieloptimierung durchführen. Zu einer allgemeinen Mehrzieloptimierungsaufgabe mit Kegel-Ungleichungen als Nebenbedingungen werden sechs verschiedene Dualaufgaben eingeführt, für die sowohl schwache als auch starke Dualitätsaussagen gezeigt werden. Danach leiten wir verschiedene Beziehungen zwischen den Bildmengen, bzw., zwischen den Mengen der maximalen Elemente dieser Bildmengen der sechs Dualaufgaben her. Dazu zeigen wir unter welchen Bedingungen werden diese Mengen identisch. Ein allgemeines Schema das die Beziehungen zwischen den sechs dualen Mehrzieloptimierungsaufgaben und andere Dualaufgaben aus der Literatur enthält, wird dargestellt
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Mendy, Gervais. "Chaînes alternées dans les graphes arête-coloriés : k-linkage et arbres couvrants." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00769929.
Повний текст джерелаАнотація:
Un graphe arête-colorié Gc est un graphe dont les arêtes sont coloriées par un ensemble de couleurs données. Un sous-graphe de Gc est dit proprement colorié s'il ne contient pas d'arêtes adjacentes de même couleur. Un graphe ou multigraphe c-arête-colorié Gc, est dit k-lié (respectivement k-arête-lié) si et seulement si quelque soient 2k sommets distincts de V(Gc), notés, x1 y1 , x2 y2 , ..., xk yk , il existe k chaînes élémentaires sommet-disjointes (respectivement arête-disjointes) proprement arête-coloriées, reliant x1 à y1 , x2 à y2 , ... , xk à yk .Un arbre couvrant propre d'un graphe Gc est un sous-graphe de Gc qui est un arbre couvrant proprement colorié.Un arbre couvrant faiblement colorié est une arborescence telle qu'il existe une chaîne proprement coloriée entre la racine et chaque sommet du graphe.Dans la première partie de cette thèse, nous donnons des conditions suffisantes pour qu'un graphe arête-colorié soit k-lié. C'est un problème classique en théorie des graphes, avec des applications multiples. Ainsi, nous avons établi entre autres les résultats suivants.A) Tout multigraphe 2-arête-colorié d'ordre n ≥ 242k tel que dc(Gc) ≥ n/2+k -1, est k-lié. B) Tout multigraphe c-arête-colorié d'ordre n ≥ 2k et de taille m≥ cn(n-1)/2 - c(n-2k +1)+1 est k-lié.C) Tout multigraphe c-arête-colorié d'ordre n ≥ 2k tel que dc(x) ≥ n/2 pour tout sommet x, est k-arête-lié.D) Tout multigraphe 2-arête-colorié d'ordre n ≥ 2k ≥ 10 et de taille m ≥ n2 -5n + 11 tel que dc(x) ≥ 1 pour tout sommet x, est k-arête-lié.Dans la seconde partie de cette thèse, deux autres problèmes classiques en théorie des graphes sont traités dans la version arête-coloriée. Il s'agit des arbres couvrants et des chaînes hamiltoniennes. Nous donnons ci-dessous quelques résultats.E) Tout graphe simple c-arête-colorié k-connexe d'ordre n ≥ C²k+1 + k + 2 avec c ≥ C²n-k-1 + k +1, a un arbre couvrant propre.F) Tout graphe Gc connexe c-arête-colorié de degré rainbow rd(Gc)=k et d'ordre n ≥ C²k+1 + k + 2 avec c ≥ C²n-k-1 + k +1, possède un arbre couvrant propre.G) Tout graphe simple c-arête-colorié k-connexe d'ordre n ≥ ((k + j)2 + 3(k + j) - 2)/2 avec c ≥ ((n - k - j)(n - k - j - 1))/2 + 2 , où j(j -1)=k , possède un arbre couvrant faiblement colorié.H) Tout multigraphe Gc d'ordre n ≥ 14 et de taille m ≥ (n - 3)(n - 4) + 3n - 2 tel que rd(Gc) = 2, possède une chaîne hamiltonienne propre. I) Tout multigraphe c-arête-colorié d'ordre n ≠ 5, 7 et de taille m ≥ n2 - 3n + 4, possède une chaîne hamiltonienne propre.La plupart des résultats exposés, sont les meilleurs possibles relativement aux propriétés sur les conditions suffisantes.
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Martins, Rodrigues Ana Candida. "Synthèse et propriétés électriques de verres oxydes conducteurs par ion lithium." Grenoble INPG, 1988. http://www.theses.fr/1988INPG0010.
Повний текст джерелаАнотація:
L'etude porte sur la variation de la conductivite electrique des systemes borotellurates et borophosphates suivants : lio::(2)-b::(2)o::(3)-te::(2)o::(4) et li::(2)o-b::(2)o::(3)-p::(2)o::(6)-lix (x=f, cl, br). L'effet de formateur mixte pour le premier systeme et l'effet de sel dopant dans le second systeme ont ete interpretes a l'aide de la theorie de l'electrolyte faible et d'un modele de solutions regulieres
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Chen, Huyuan. "Fully linear elliptic equations and semilinear fractionnal elliptic equations." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4001/document.
Повний текст джерелаАнотація:
Cette thèse est divisée en six parties. La première partie est consacrée à l'étude de propriétés de Hadamard et à l'obtention de théorèmes de Liouville pour des solutions de viscosité d'équations aux dérivées partielles elliptiques complètement non-linéaires avec des termes de gradient,This thesis is divided into six parts. The first part is devoted to prove Hadamard properties and Liouville type theorems for viscosity solutions of fully nonlinear elliptic partial differential equations with gradient term
20
Kumar, Avinash, and Satyajeet Singh. "Wear Property of Metal Matrix Composite." Thesis, 2011. http://ethesis.nitrkl.ac.in/2318/1/avinash_final_thesis.pdf.
Повний текст джерелаАнотація:
The purpose of this paper was to study the wear property of Cu-SiC composite manufactured by powder metallurgy route with varying compositions and sintering temperatures. 12 different samples (SiC compositions 0, 5, 10 and 15 Vol.%) of the composite were made by mixing, cold pressing and sintering at three different temperatures (700, 775 and 850 oC). The change in densities and hardness values were noted and studied. Then XRD and SEM analysis of the samples were done to study the phases present and their distributions along with idea of composition. Hardness and wear studies were carried out to judge the surface mechanical properties of the composites prepared. Wear mechanism was also studied using the scanning electron microscope.
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Jha, Aman Kumar. "Structure-property correlation of wear plates." Thesis, 2018. http://ethesis.nitrkl.ac.in/9501/1/2018_MT_216MM2443_AKJha_Structure.pdf.
Повний текст джерелаАнотація:
Wear is the biggest factor that controls the performance and life of any machine part. The interaction between functional surfaces in their relative motion causes adverse effects in the surface layers, leading to their deterioration. Most worn parts do not fail from a single mode of wear but from a combination of modes, such as abrasion, erosion, etc. Hardfacing is the best method for overcoming wear problems of machine parts as it increases the life of machine part and also protects from damage. In this investigation, seven commercial hardfacing steel plates with varying Cr content and other carbide forming elements were examined. This project contributes to the understanding of the effect of carbide forming elements (Mo, V, W, Nb, and Ti) on the microstructure and abrasive wear resistance. Microstructural characterization was done by using optical and scanning electron microscopes. Energy and wavelength dispersive spectroscopy were carried out to study the carbide type and distribution in the hardfaced deposit. Abrasive wear tests were conducted by using pin-on-disc tribometer in accordance with the ASTM G99.
It was observed that wear resistance increases with increasing Cr content with other carbide forming elements in the alloy. Along with hardness, morphology and type of carbide are also important factors to decide the wear resistance. An attempt was made to co-relate the chemical
composition, carbide morphology, microstructural features with wear properties of hard facing alloys.
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Hsu, Hsiang-En, and 徐祥恩. "Study on the Wear Property of PE Composite." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/91017151683995081635.
Повний текст джерела
23
Wang, Sheng-Hau, and 王聲豪. "Study on Wear Resistance Property of High-Cr Cast Iron." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/35595063431557605705.
Повний текст джерелаАнотація:
碩士臺灣大學
機械工程學研究所
98
High-Cr white cast irons have been used extensively in industries with both abrasive and erosive environments, such as mining and mineral processing (hammers, crushers, ball mills, pulverized rolls, etc.) and steel rolling process (rolling rolls) which require high wear resistance property. In this study, both erosion and pin-on-disc tests were performed to evaluate the effects of chemical composition and heat treatment condition on wear resistance property of high-Cr white cast irons. Microstructure observations show that alloys in quenched state consist of eutectic M7C3 carbides, martensite, M23C6 secondary carbides and a substantial amount of retained austenite. On the other hand, alloys in quenched and tempered state consist of eutectic M7C3 carbides, tempered martensite, M23C6 secondary carbides dispersed in tempered martensite and a small amount of retained austenite (depending upon tempering temperature). Erosion test results indicate that varying chemical composition (C, Cr and Mo contents), but maintaining at similar heat treatment conditions, exerts little influence on erosion property in terms of erosion rate and depth, although the microstructures were changed somewhat. Furthermore, erosion testing on selected alloys with different tempering temperatures concludes that the erosion property correlated positively with alloy hardness, that is, the resistance to erosion decreases with increasing alloy hardness. However, reverse results were obtained in the pin-on-disc testing. This can be explained by that facts the material removal is the main cause of crack growth when erosion, but when pin-on-disk test the main cause of material removal is cutting.
24
Huang, Ying-Chia, and 黃盈嘉. "Friction and wear property of ceramic seals against materials in water." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/97392475467074932218.
Повний текст джерелаАнотація:
碩士國立高雄應用科技大學
機械與精密工程研究所
96
The purpose of the present study is to find out the optimal mating pairs of seal materials from the wear and friction performance of the mating pairs. From the combinations between various ceramic materials (e.g. SiC, graphite, WC, Al2O3、ZrO2 and Si3N4), they are tested on the Model Tester under conditions of dry and water lubrication to discuss the wear and friction performance of the mating pairs. In addition, pin-on-disk (POD) tribological test and the optical microscope and surface roughness apparatus are utilized to generate tribological data, to analysis of the experimental data, respectively. The correlations of POD and Model Tester are discussed. The first part is to simulate the realistic mating conditions in Model Tester which was designed by SCENIC. SiC, graphite and WC ceramic materials are used to match against impregnation resin graphite and impregnation antimony graphite.The Model Tester is modified to realize on-line monitoring the temperature.From the measured temperature and surface roughness, and investigates the lubricant states for various material on seal using experimental results. Furthermore, the anatomic and function are analyzed using OM and surface roughness apparatus. As the results, both the impregnation resin graphite A and impregnation antimony graphite A are the optimal material for heating behavior, The impregnation antimony graphite A have steady heating behavior. Temperature rises 14℃ that experiment initial 10 minutes. And temperature rises 1℃ that experiment final 10 minutes. the temperature as time reduces and the controllability is stable, hence, the impregnation antimony graphite disk are matched with ball of Al2O3, ZrO2, Si3N4, steel. Experiment second part for use POD and AD/DA system to record friction coefficient.Discuss different load condition of Si3N4、Al2O3、ZrO2、Stainless steel materials of friction and wear property in the dry and water lubrication. According to the data to drew the friction coefficient and analyse，the purpose is compare that different mating pairs material.The anatomic and function are analyzed using OM and surface roughness apparatus. Experimental result display that friction coefficient will be reduced in water lubricating. Such as the Al2O3, the friction coefficient is 0.329 in dry lubricate higher than 0.047 in water. In load 30N,water lubrication,After experiment about 15 hours (slip distance 30000m),The friction coefficient can faster through the running-in, then to make the friction coefficient reach steadily. And we find the ceramic／graphite than the metal／graphite have more quality wear property. About wear rate, No matter the dry or water lubricated. Impregnation resin graphite of wear rate higher than impregnation antimony graphite. Such as Impregnation resin graphite disk／Al2O3 ball of wear rate（1.2169％） higher than impregnation antimony graphite disk／Al2O3（0.3549％）.
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Hsueh, Hsiao-Tze, and 薛曉澤. "Study on Wear Resistance Property of Multi-Component White Cast Irons." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/30671649455165388867.
Повний текст джерелаАнотація:
碩士國立臺灣大學
機械工程學研究所
100
Multi-component white cast irons have been used extensively in the fields that require high wear resistance property, such as rolls for steel rolling process, and crushing rolls, hammers, digging teeth in crushing equipments. In this study, a base alloy composition of Fe-2%C-5%Cr-5%Mo-5%V-5%Co-X%W was selected and the effect of W content (2% and 5%), together with the influence of heat treatment condition (austenitization temperature, tempering temperature and time), on the microstructure and wear resistance property were evaluated. The as-cast microstructures of both alloy A (2.1%C-5%W) and alloy B (2.1%C-2%W) contain eutectic carbides of MC and M2C in an austenitic matrix. The eutectic carbides remain unchanged during the subsequent austenitization, quenching and tempering treatments, except that secondary carbides in M3C form were precipitated in the matrix. On the other hand, the as-cast austenitic matrix was transformed to martensite after quenching, which in turn was transformed to tempered martensite after tempering. The macro-hardnesses of both alloys increase first, reach a peak, then decreases as the tempering temperature increases, with the peak hardness occurring at 525oC for alloy A and 450oC for alloy B. Regarding the erosion wear resistance, alloy A exhibits the best resistance at the tempering temperature of 525oC, while 570oC for alloy B. On the other hand, the best abrasion wear resistance took place at 450oC for alloy A and 570oC for alloy B. The results indicate that no clear correlation between alloy hardness and wear resistance property was obtained. In addition, alloy B (2%W) exhibits better wear resistance property (both erosion and abrasion) than alloy A (5%W) in the tempered state, indicating that a reduced W content can achieve an increased resistance to both erosive and abrasive wear. And, the corresponding optimal heat treatment conditions are：Austenitization 1100oC-70min/Oil quench/Tempering 570oC-2hr.
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Chuang, Jia-Lang, and 莊家朗. "Tensile and Wear Property of Various Diameter Carbon Nanotubes Reinforced Aluminum Composites." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/82952645256015762342.
Повний текст джерелаАнотація:
碩士國立臺灣大學
材料科學與工程學研究所
92
The essential purpose of this research is to investigate the effects of diameters of carbon nanotubes on the mechanical and the wear properties of Metal Matrix Composites (MMCs). 6061 Al alloy powder (74μm) is used as metal matrix, and 1 wt% of carbon nanotubes with various diameters are added as strengthen phase. All MMC samples are prepared by powder metallurgy. The hydrocarbon content in the Al alloy is decreased from 1.1 wt% to 0.045 wt% through de-waxing. After 48 hours of planetary ball milling, the length of carbon nanotubes is cut down to less than 5 μm, and the particle size of Al alloy powder decreased from 74μm to 29μm, respectively. Wet mixing of the Al alloy powder and carbon nanotubes is adopted to avoid agglomeration of carbon nanotubes. After cold isotropic pressing, sintering and hot extrusion, composites with a density close to 100% of the theoretical density is obtained. MMCs with the addition of 1wt% ball-milled carbon nanotubes of diameters 10~20nm is observed to have the largest tensile strength due to good dispersion of carbon nanotubes in the metal matrix. Those contain carbon nanotubes without ball milling have lower tensile strength, the fracture surface is observed to take place around inclusions. Large amount of carbon nanotubes were found in the fracture surface, suggesting that the agglomeration of carbon nanotubes provided sites for crack initiation. The addition of 1wt% ball-milled carbon nanotubes of diameters 10~20nm gives MMCs the lowest wear rate. The wear rate is influenced by the aging condition. Lowest wear rate is obtained at the peak aged condition. This is in relation to the size of the precipitates during aging as well as the morphology of the interface between the precipitates and the Al alloy. As the diameter of carbon nanotubes increases, wear rates also increases, even higher than the Al alloy. This is related to the structures of the carbon nanotubes. Non-uniform axial deformations inside the multiwalled nanotubes may exist.
27
Chen, Ching-An, and 陳慶安. "Study on Wear Resistance Property of Low-Alloy Chilled Ductile Cast Iron." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/33759453574688372475.
Повний текст джерелаАнотація:
碩士臺灣大學
機械工程學研究所
98
The primary purpose of this research is study the effects of C and Si contents, solidification cooling rate (with and without chilling), and late inoculation on microstructure, hardness and wear resistance of ductile cast irons under fixed alloy compositions of 2.5%Ni-1.0%Cr-0.5%Mo-0.4%Mn. The experimental results show that, at a fixed CE of about 4.13%, increasing Si content (from 1.15% to 1.68%) increases graphite nodule count, but reduces both carbide and bainite contents. In addition, the employment of late inoculation (0.1% Fe-Si inoculant) increases nodule count, while slightly reduces carbide content. On the other hand, at a fixed Si content of some 1.46%, increasing C content (from 3.44% to 3.81%) increases both graphite nodule count and bainite content, but reduces carbide content. Late inoculation promotes bainite formation. Furthermore, when the alloy solidification cooling rate was increased by chilling, the microstructure exhibits increased graphite nodular count and carbide content, and also the carbides formed are more refined. As a result, the hardness is higher with a higher solidification cooling rate. Regarding the pin-on-disc tests (Al2O3 as dics material), the results show that the chilled specimens exhibit higher wear loss compared with non-chilled specimens. By means of multiple linear regression analysis, wear loss is functions of nodule count and bainite content, with the nodule count being a positive effect, while the bainite content a negative effect. However, a reversed results on wear loss were obtained for pin-on-flat tests (S45C as stationary counter material). In summary, alloys with moderate nodule count and with a merely bainitic matrix can attain the best wear resistance. In addition, the wear resistance is affected more by varying Si content than by C content.
28
Yu, Pi-Chun, and 游弼鈞. "Casting Process Development of the Bimetal Hammer and Its Abrasive Wear Resistance Property." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/80315009228749185367.
Повний текст джерелаАнотація:
碩士國立臺灣大學
機械工程學研究所
95
This study intended to develop the casting method for the production of bimetal hammers which consist of Cr-Ni steel shank and high Cr cast iron head, to establish the optimal heat treatment conditions for achieving the desired microstructures, hardness and wear resistant property, and to analyze the characterizations of carbides precipitated and the interface between the aforementioned two alloys by using SEM and EDAX. The aim of this study is to attain a bimetal hammer which has a tough alloyed steel shank and a high wear resistant head, which can replace the traditional single alloy (high Mn steel) hammer with substantially increased service life. A double-pour technique was employed to cast the bimetal hammer. A bottom-pour gating system with an overflow located at the intended interface between two alloys, together with a top open riser have been designed for this particular casting. Also, the optimal heat treatment conditions have been found to be (900~1000)°C/2hr/ FAC/500°C/2hr. The as-cast microstructures of the hammer head consist of proeutectic austenite dendrites and eutectic phases of M7C3 carbide and austenite. After heat treatment, most of the austenite transformed to martensite after quenching, which subsquently transformed to temper martensite after tempering. In addition, numerous small secondary carbides, which have been identified as M7C3, can also be observed within the original austenite domain. The as-cast microstructure of the hammer shank is martensite, which transformed to temper martensite after heat treatment. Furthermore, the analyses of the interface region reveal that not only a sound fusion between two alloys was achieved, but also little porosity and oxides were observed. The developed bimetal hammer exhibits good combined properties of a tough shank, 21 J/cm2, and a hard head, over 50HRC, which has much better wear resistance than the traditional high Mn steel hammer.
29
Lin, Chi-En, and 林琪恩. "Wear behavior and property of Nylon6/Clay nanocomposites in HDD load/unload technology." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/23686c.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
有機高分子研究所
96
In this paper, we studied the property and wear behavior of Nylon6/clay nanocomposite applying in Ramp component on HDD L/UL technology. Ramp plays an important role in HDD components, especially for the load/unload technology. Wear durability is determined as a function of working temperature, Load/Unload cycles, the disk rotation speed, and air bearing design. In Load/Unload (L/UL) wear study, polymer-clay nanocomposite wear performance is improved after modification . We also discover that γ-form crystals of nylon 6/clay nanocomposites exhibited predominant effect for wear duration. It was found that intercalated and partially exfoliated structures were generated by the in-situ polymerization method. Effects of the material composition on the crystalline morphology and thermal properties of nylon6/clay nanocomposites, were also studied by differential scanning calorimeter (DSC) and thermogravimetric analyses (TGA).
30
Chen, Yi-Je, and 陳奕哲. "Effect of Electroless Nickel on Erosion Wear and Mechanical Property of 7075-T6 Al-Alloy." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/18932797515782640190.
Повний текст джерелаАнотація:
碩士大同大學
材料工程學系(所)
92
7075-T6 Al-alloy is widely applied in structural and air material because of its high weight rate. Solid particle erosion is a serious and costly problem in many aeronautical applications.。Surface treatment would contribute to the promotion of 7075 Al-alloy. Electroless nickel (ENi) plating is widely applied in aeronautical、motor and chemical industry owing to their excellent corrosion and wear resistance and high hardness.。Thus, this present study directed at 7075-T6 Al-alloys to impose different P content of electroless nickel coatings. Applying erosion、wear and tension test to explore mechanical property of 7075-T6 without and with ENi coating conditions. The experiment result shows that the Hi-P specimen is more wear resistances than Me-P specimen and, we can increase the coating thickness to protect substrate. Besides, the tensile strength of the Me-P specimen is higher than the Hi-P specimen. The erosion resistance of the ENi coating is not well for the solid particles erosion. Finding thatcoatings are broken when starting test. Discussion of the erosion rate that will decrease as the incident angle increased from lower incident angle(15o) to highest incident angle(90o) for 7075-T6 Al-alloy.And the primary mechanism is cutting at low angles(15o), and indentical craters at high angles(90o). Besides, it’s because that combine of cracks, indentical craters, cutting and so on happened at 45o,resulting in maximum depth of erosion.
31
Xu, Lieh feng, and 徐列鋒. "Research on Wear Resistance Property of Superior Zinc-Aluminum Alloys by Hot Chamber Die Casting." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/68859373433649255448.
Повний текст джерелаАнотація:
碩士大葉大學
機械工程研究所碩士班
95
The zinc-aluminum metal alloy owns the very excellent machine property and wear resistance behavior, its strength in addition to highly in the casting aluminum metal alloy and general iron casting, the degree of hardness is also good.It is cheap to compare the aluminum metal alloy, the magnesium metal alloy and the titanium metal alloy , again it has the aluminum metal alloy of compare,the iron casting or the bearings bronze metal alloy alters the characteristic of the foundry. This research is to aim at three kinds of researches that the zinc-aluminum metal alloy of different and high aluminum content carries on the wear resistance, wearing the way is adopt the pin-on-disc(POD), carries on with three kinds of zinc aluminum metal alloy ZA-8,ZA-12 and the ZA-27 to the wear test, more each one wears the distance to descend the differences of the wearing quantities.Use of the section and the surface of wear variety that the OM and the SEM observation wears to descend by understanding the different foundry parameter the ZA metal alloy to the wear trend. Study the result manifestation, under the die-casting or the gravity casting condition , the ZA-27 zinc-aluminum metal alloy casting compares the ZA-12 and the ZA-8 zinc-aluminum alloy to own to more goodly wear resistance.Compared with the manufacturing process parameter of the casting temperature,the molding temperature and the casting pressure relatively, show the liquid mutually limits temperature -10℃ are the best casting temperature for three kinds of zinc-aluminum metal alloys, but the casting temperature is not obviously to wear resistance influence degree to compare of the ZA-8 metal alloys .Secondly in molding temperature of the 150℃, three kinds of ZA zinc-aluminum metal alloys all have the lowerly wear rate.In the casting pressure of 100 kg/cm2, the ZA-8, ZA-12 and the ZA-27 zinc-aluminum metal alloys own the lower wear rate.At the gravity casting condition, sprinkle the influence of the casting temperature also show the trend of the likeness to die-casting.In small degree of hardness test, the wear surface of the surface hardening layer obviously high in the metal alloy base matrix , in the fluxion layer of subsurface then because the crystal a haulage transforms to cause soften, its degree of hardness value is lowest.
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KUMAR, SANDEEP. "FRICTION STIR PROCESSING OF ALUMINUM ALLOY AND EFFECT OF NUMBER OF PASSES." Thesis, 2014. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15474.
Повний текст джерелаАнотація:
Friction stir processing is a newly developed solid state processing technique in which a rotating tool is inserted in a work piece for localized micro-structural modification for specific property enhancement. Alloys like aluminium, magnesium, copper etc. are most suitable for friction stir processing. Friction stir processing increases the super plasticity of material. It modifies the microstructure, increases micro-hardness and tribological properties like tensile strength, wear behavior etc. are improved. The aluminium alloy (grade 1050 have major alloying elements as iron and silicon. In this study we obtain optimum traverse and rotational speeds are 25 m/min and 1600rpm after a number of trails. The square pin profiled tool produced defect free FSP region compare to other pin profiles and obtain defect free micro and macrostructure in friction stir processing region at D/d ratio 3. These are fixed based on the literature review. In this study we processed the aluminium alloy (AA1050) with square pin profile of H-13 tool material at 1600rpm rotational speed and 25mm/min traverse speed by friction stir processing. Final results shows 9 percent increase in tensile strength compare to base alloy and hardness of processed sample increase compare to base material sample and tensile elongation decrease as number of passes increase. Wear loss of processed specimen also reduced due to increase in hardness of processed sample.
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Wang, Yi-Feng, and 王逸豐. "Investigation of Wear Property of As-cast Mg-(2,5,8)wt.%Sn Alloys after Different Heat Treatment Processes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/95h3fn.
Повний текст джерелаАнотація:
碩士國立交通大學
材料科學與工程學系所
105
The microstructure of (a)as-cast (b)300oC,1hr homogenization (c)520oC,15hrs annealing (d)520oC,15hrs solution heat treatment(SHT) (e)solution treatment and aging (1~3days,at 250oC),were investigated by using scanning electron microscopy (SEM) and X-ray diffraction meter (XRD).Following, these samples were tested with Pin-on-disc wear tester. From SEM observation of as-cast Mg-(2,5,8)wt.%Sn, the segregation phenomenon and primary Mg dendrite were found. Besides, Mg2Sn precipitation mainly distributed along the grain boundary. After the homogenization heat treatment (300oC,1hr),the solid-solute Sn atom around the grain-boundary precipitated more Mg2Sn at grain boundary .Thus, the degree of segregation decreased and Mg2Sn amount increased after making homogenization heat treatment. Because the 520oC temperature was high enough to attain the single-Mg phase region in Mg-Sn phase diagram, the Sn atom distributed uniformly in Mg matrix after 520oC 15hrs annealing heat treatment. Because of the furnace-cooling, there was a little amount of Mg2Sn observed. After solution heat treatment, not only Sn atom distributed uniformly in Mg matrix, but also Mg2Sn precipitation completely disappeared. After solution treatment and aging, the precipitation size & amount increase with aging time increase from 1 day to 3 days. The discussion followed the order of wear rate from low to high. Sn atoms uniformly distributed in Mg matrix, provided the compressive stress which could prohibit from forming and propagating of crack. Besides, the elimination of Mg2Sn decreased the initiation of crack & occurred-probability of abrasive wear. Therefore, 520 oC 15hrs, solution heat treatment Mg-(2,5,8)wt.%Sn alloys had the lowest wear rate. Annealing at 520oC 15hrs Mg-(2,5,8)wt.%Sn had second lower wear rate. Sn atoms uniformly distributed in Mg matrix, provided the compressive stress which could prohibit from forming and propagating of crack. Because of furnace-cooling method, there were a little amount of Mg2Sn observed at grain boundary, those precipitates increased the initiation of crack & occurred-probability of abrasive wear. The as-cast Mg-(2,5,8)wt.%Sn alloys had the third lower wear rate since the existence of soft primary dendrite increased the adhesive wear occurred-probability and there were many Mg2Sn precipitates which increased the delamination wear occurred-probability. After homogenization treatment, the solute amount of Sn atom in Mg matrix decreased and more Mg2Sn precipitated at grain boundary. The two phenomenon mentioned above increased the delamination wear occurred-probability. The wear rate of solution and aging treatment Mg-8wt.%Sn increased with aging time. The more Mg2Sn precipitated, the more nuclei-site of crack was. Besides, the excess amount of Mg2Sn was found to abrade the sample surface, resulted in increasing wear rate. In addition, the wear rate decreased with increasing hardness in all conditions except the aging condition. The wear rate increased with increasing hardness in aging treatment, because there was excess amount of precipitates which was found to abrade the surface.
34
Huang, Chun-Kai, and 黃俊凱. "Study of wear property of spray-forming,semi-solid electromagnetic stirring and casting hypereutectic Al-Si alloys." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/nrnh3c.
Повний текст джерелаАнотація:
碩士國立成功大學
材料科學及工程學系碩博士班
90
The wear properties of hypereutectic Al-Si alloys were investigated in the pass decade. The hypereutectic Al-Si alloys of SFP(spray-forming process) offer fine microstructure. Changing Si content with SFP,we study the effect of Si content in wear property. Then using the semi-solid electromagnetic stirring process and casting process that offer another two primary Si dimension, and we could evaluate primary Si particle effect in wear property. In our study, the Si weight percentage and primary Si dimension were material parameter; load and speed were testing parameter. For the result, for lower load the wear rate were not elevated with speed increasing due to the temperature increased at higher speed then soft Al-Si alloys, that made adhesion wear increase but temperature also made IDE(iron) wear surface oxidized rate increased, that made adhesion wear decreased. And wear rate increasing with load increasing. The Si content and the primary Si increasing the wear rate increasing. Si content increasing due to brittle crack and testing Al-Si alloys could not bear severe deformation. Primary Si particle dimension increasing due to crack surround Si that wear loss by delaminaiton, wear rate increasing. But the result was abrupted at Al-25Si with 80~90μm primary Si particle, the reason for the material is the subsurface mixed layer have high density Si distribution.
35
Lai, Yi-Chen, and 賴易辰. "Effects of Centrifuging Force and Melt Treatment on the Microstructure and Wear Resistance Property of A390 hyper-eutectic Al-Si Alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/97310857793545271218.
Повний текст джерелаАнотація:
碩士國立臺灣大學
機械工程學研究所
104
While casting the A390 hypereutectic alloy, primary Si particles tend to float to the upper part of the casting due to the difference in specific weight between primary Si particles and the aluminum bulk liquid, the so-called gravity segregation. As a result, the microstructures and the mechanical properties in different parts of the casting vary. This research utilized the above-mentioned phenomenon of the primary Si gravity segregation, and further to enhance this segregation nature by employing centrifuging casting process to achieve better wear resistance in specific area of the castings. A centrifuging casting apparatus was constructed which allows the casting to be solidified under the centrifugal force. Under the centrifuging casting condition, the primary Si particles which have low specific gravity and high hardness tend to move toward the rotational axis and aggregate at the inner portion of the castings, and thus to enhance the wear resistance of the A390 alloy. In addition, P refinement (for primary Si), Sr modification (for eutectic Si) and P + Cr refinement (for primary Si) of A390 alloy were performed to examine the effects of these different melt treatments on the microstructures and wear resistance property of the centrifuging castings at the rotational speed of 150 rpm (~10G). Further, the relationship between the microstructure features obtained and the wear resistance property was evaluated. The microstructure of the A390 alloy without any treatments exhibits somewhat large primary Si particles with an average size of around 96μm, and acicular type eutectic Si of class 1. When the alloy was refined with an appropriate amount of P, i.e., 0.02%P, the size of the primary Si was substantially reduced to around 43μm, while the eutectic Si remained more or less unchanged. In addition, when the alloy was refined with various combinations of P and Cr, no beneficial effect in reducing the size of the primary Si particle was found. Instead, a slight increase in primary Si size was obtained, with the average size being increased to around 65μm. On the other hand, when the alloy was modified by 0.02%Sr, even though the eutectic Si was improved to class 4-5, the primary Si was coarsened significantly to around 250μm. Furthermore, the effects of the microstructure features on the wear resistance property of A390 alloy was studied, and regression analyses were performed by looking into the correlations between the four main dependent variables, namely, the area ratio of the primary Si (X, %), the average primary Si size (Y, μm), degree of eutectic Si modification (Z, class), and the % porosity (C, %), and the wear rate (W, mm3/m). The obtained regression equation is: W = 0.029245 – 0.00098X + 0.000045Y – 0.00347Z + 0.001448C. The analysis results indicate that the wear rate can be reduced by increasing area ratio of the primary Si, decreasing primary Si size, increasing degree (class) of eutectic Si modification, and reducing % porosity.
36
Lin, Hung-wen, and 林鴻文. "The Effect of the Surface Property of Cylinder Wall and the Geometrical Shape of Piston Ring on Engine Wear Resistance and Performance." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/15244685163805869472.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
機械工程系
88
Weather the lubrication of engine can be effected by the surface property of cylinder wall and the geometrical shape of piston ring or not has been researched in this study. Here, we try different alternated surface property of cylinder wall combining the geometrical shape of piston ring in order to improve wearing resistance, reduce oil consumption and lower loss rate by blowing. Experiments design by Taguchi parameter method. Firstly, we change the contour of piston ring and the surface roughness of cylinder wall to find out the factors effecting on oil consumption rate and blowing loss rate, furthermore, construct a standard for following experiments. We not only use engine bench testers and motorcycles to assess each above factors, but also exam their surface roughness by canning electronic microscope (SEM) and EDS to find out the main wear mechanism of worn surface respectively Furthermore, we estimate the relationship between the thickness of oil membrane and the geometrical shape of piston ring. By doing so, we hope to be able to enhance the lubrication of engine and decrease power loss from roughness and improve the wear resistance. The result reveals that shrinking geometrical size of piston ring will make the tolerance gap between piston ring and piston bigger, so that further influence their flatter and resulting in the rapidly alteration of oil consumption. Using Taguchi parameter design method to analyze results can determine the main reason effecting on oil consumption is oil ring angle, while the roughness of cylinder wall and the geometrical shape of compress ring remain only the Top two cause. In conclusion, for the geometrical shape of piston ring, barrel face is the best choice, which can not only reduce the losing rate of leaking, but alsolower wearing rate. For the surface property of the cylinder wall, both over rough or too smooth won''t reduce oil consumption. Besides, diminishing cross-angle will stimulate the forming of squeeze oil, and result in better lubrication and less wearing.
37
Chang, Wei-Shin, and 張維鑫. "Study on the Optimal Heat Treatment Conditions and Wear Resistance Property of High-Cr Cast Iron and Multi-component White Cast Iron." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/87423143535439886309.
Повний текст джерелаАнотація:
碩士國立臺灣大學
機械工程學研究所
96
The objective of this study is to obtain the optimal heat treatment conditions (tempering treatment in specific) for achieving the required wear resistant property for both high-Cr (~15%Cr) cast iron used in the outer shell of bi-metal rolls and multi-component white cast iron used in hot milling rolls. The experimental results indicate that the quenched and tempered microstructures consist of temper martensite (contains numerous fine global secondary M7C3 carbides), eutectic M7C3 carbides, and retained austenite. The amount of retained austenite decreases with increasing tempering temperature, and the amount is reduced to below 3% as the tempering temperature exceeds 500oC. In addition, the hardness value increases first with increasing tempering temperature, reaches peak hardness at around 500oC, and then decreases with further increase in tempering temperature. Furthermore, the change in wear resistance of the treated alloys as affected by tempering temperature shows a reverse trend as that of hardness. Finally, the optimal heat treatment condition has been obtained to be: Destabilization: (1000~1050)oC-2hr/ Quench: forced air cooling/ Tempering: 500oC-6hr. For multi-component white cast irons, minor modifications of C and W contents from the base alloy composition of Fe-2%C-5%Cr-5%Mo-6%V-2%Co-2%W were made to evaluate their effects on the response of heat treatment and wear resistance property. The results show that the peak tempered hardness (HTmax) was achieved when tempered within 525~545oC with minor variations in different alloys. In addition, the occurrence of the minimum wear rate (Rw) coincides with the HTmax and nil retained austenite (Vγ) in the tempered state. Furthermore, an improved wear resistance was obtained by increasing austenitizing temperature, or by reducing the W content, or by increasing the C content. Finally, the optimal heat treatment condition has been obtained to be: Austenitization: 1100oC-70min/ Quench: forced air cooling/ Tempering: 525~545oC-3hr.
38
Yin-HsiangMao and 毛胤翔. "Titanium Addition of Niobium Nitride Single and Multilayer Coating on Wear Property, Corrosion Resistance and Applications on High Speed Drills after Acetylene Introduction." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2vvdbb.
Повний текст джерелаАнотація:
碩士國立成功大學
機械工程學系
107
This study was composed of three stages. In first stage, NbNxA coatings were prepared by DC magnetron sputtering. In second stage, NbTi-NX and NbN/TiNxmin coatings were prepared using RF magnetron sputtering. In third stage, acetylene was introduced to prepare NbTi-NX-CH coating. Considering wear property and corrosion resistance, NbTi-N12-CH coating was the optimal parameter for preparation in this research. Applied the NbTi-N12-CH coating to a high-speed drill and tested it by drilling 2000, 4000, and 6000 holes. The results revealed that applying this coating to the drill could increase its drill life to 4000 holes, which is two times longer than that of an uncoated drill.
39
Lin, Youth-Tyng, and 林玉婷. "Nonmetrizable Spaces in which Weak Blumberg Property Holds." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/46904941670391201092.
Повний текст джерелаАнотація:
碩士淡江大學
數學系
82
In this work, we investigate the correlation between the Blumberg property and nonmetrizable Baire spaces. In the Chapter 2 of this thesis, we modify Blumberg's idea by using densely approach to analyze the structures of real valued functions defined on a nonmetrizable space. Also, we give a new property which is near to the Blumberg property and is called weak Blumberg property. We show that every separable Hausdorff Baire space has this property.Furthermore, we give a nonmetrizable space which has weak Blumberg property. In Chapter 3, we use coordinate functions to define densely approach, exhaustibly approach and inexhaustibly approach of multivalued functions. Then, we extend the whole structure to multivalued functions.
40
Epand, Michael, and 潘啟明. "INTERNATIONAL JOINT VENTURES IN LIGHT OF WEAK INTELLECTUAL PROPERTY RIGHT LAW ENFORCEMENT IN THE PEOPLE’S REPUBLIC OF CHINA." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/07148950492140743005.
Повний текст джерелаАнотація:
碩士淡江大學
國際企業學系碩士班
100
International joint venture (IJV) is a mode of investment chosen by many firms, seeking to operate in foreign markets. It is chosen because it offers substantially lower costs of entry, and other government incentives. However, in countries with poor intellectual property right (IPR) protection regimes, JVs are a secondary choice as a mode of foreign direct investment (FDI). Due to a high risk of IPR infringement, firms prefer wholly foreign owned enterprises (WFOEs) which offer granular control over the entire venture and most important the use and dispersion of its intellectual property. This study has two main goals. The first is to understand why IJVs are risker than WFOEs thus leading most foreign investors to abandon the IJV as a mode of FDI in China. This is examined from the angle of technology spillover and then from that of the various elements that make technology spillover more likely to occur in IJVs. Due to the riskier nature of IJVs and the poor IPR protection regime in China, the second goal, is to offer country specific IPR protection methods that can be used by foreign firms in order to avoid IPR infringement. This study reviews the literature pertaining to technology spillover that results from IJV. Based on this review, we conclude that of the two modes of FDI, IJVs are more likely to result in technology spillover, and consequently a higher risk of IPR infringement. This occurs because of the closer contact firms in IJVs have with their partners as well as upstream industries that supply the JV. The proximity with foreign partners, gives local firms an opportunity to learn from the experience of being in a joint operation. This learning experience, in turn, allows firms to advance their knowledge and capabilities and raise their stature to international levels. However, this knowledge may later be used to compete with the foreign firm, and can be especially harmful if this knowledge includes the foreign partner’s intellectual property. For these reasons, IJVs are riskier than WFOEs as a mode of FDI. To address the risky nature of IJV, this study synthesizes IPR protection recommendations from the literature for firms that want invest via IJV in China. In this study we offer five IPR protection methods that do not rely on IPR law and law enforcement system in China. These protection methods are separated into two groups. The first is aimed at making it more difficult for other firms to recognize the source of a company’s competitive advantage, with particular emphasis on the company’s technology. These methods include: keeping key elements of a technology secret; purposely making the technology more complex or specialized; and lastly, educating customers in ways that they find it more beneficial to purchase original products. The second group includes the creation and maintenance of internal and external guanxi. That is, crafting relationships based on trust and friendship with stakeholders within as well as without of the JV, thus creating social barriers to reduce the chances of IPR infringement.
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Leger, Olivier A. ""Mistake of law": The taxpayer's ultimate answer to S. 152(4)(a)(i) of the Income Tax Act. If the shoe fits, wear it ... properly!" 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=452870&T=F.
Повний текст джерела
42
Stejskalová, Šárka. "Stromová vlastnost kardinálů." Master's thesis, 2014. http://www.nusl.cz/ntk/nusl-339999.
Повний текст джерелаАнотація:
In this thesis we study the Aronszajn and special Aronszajn trees, their existence and nonexistence. We introduce the most common definition of special Aronszajn tree and some of its generalizations and we examine the relations between them. Next we study the notions of the tree property and the weak tree property at a given regular cardinal κ. The tree property means that there are no Aronszajn trees at κ and the weak tree property means that there are no special Aronszajn trees at κ. We define and compare two forcings, the Mitchell forcing and the Grigorieff forcing, and we use them to obtain a model in which the (weak) tree property holds at a given cardinal. At the end, we show how to use the Mitchell forcing to construct a model in which the (weak) tree property holds at more than one cardinal. 1
43
Möller, Christian. "Charakterisierungen schwacher Kompaktheit in Dualräumen." Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003091515.
Повний текст джерелаАнотація:
In this thesis we present an extensive characterization of weak* sequentially precompact subsets of the dual of a sequentially order complete M-space with an order unit. This central part of the thesis generalizes results due to H.H. Schaefer and X.D. Zhang showing that small weak* compact subsets of the dual of a space of bounded measurable real-valued functions (continuous real-valued functions on a compact quasi-Stonian space) are weakly compact. Moreover, while the proofs of Schaefer and Zhang use measure theoretical arguments, the arguments presented here are purely elementary and are based on the well-known result, that the space l1 has the Schur property. Finally some applications are given. For example, we investigate compact or sequentially precompact subsets, which consist of order-weakly compact operators, in the space of continuous linear operators defined on a sequentially order complete Riesz space with values in a Banach space provided with the strong operator topology: as an immediate consequence of the results, we can easily deduce extended versions of the Vitali-Hahn-Saks theorem for vector measures. For this we need a generalization of the Yosida-Hewitt decomposition theorem, which is proved here with other techniques like the factorization of an order-weakly compact operator through a Banach lattice with order continuous norm.
44
Nasehpour, Peyman. "Content Algebras and Zero-Divisors." Doctoral thesis, 2011. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-201102107989.
Повний текст джерелаАнотація:
This thesis concerns two topics. The first topic, that is related to the Dedekind-Mertens Lemma, the notion of the so-called content algebra, is discussed in chapter 2. Let $R$ be a commutative ring with identity and $M$ be a unitary $R$-module and $c$ the function from $M$ to the ideals of $R$ defined by $c(x) = \cap \lbrace I \colon I \text{~is an ideal of~} R \text{~and~} x \in IM \rbrace $. $M$ is said to be a \textit{content} $R$-module if $x \in c(x)M $, for all $x \in M$. The $R$-algebra $B$ is called a \textit{content} $R$-algebra, if it is a faithfully flat and content $R$-module and it satisfies the Dedekind-Mertens content formula. In chapter 2, it is proved that in content extensions, minimal primes extend to minimal primes, and zero-divisors of a content algebra over a ring which has Property (A) or whose set of zero-divisors is a finite union of prime ideals are discussed. The preservation of diameter of zero-divisor graph under content extensions is also examined. Gaussian and Armendariz algebras and localization of content algebras at the multiplicatively closed set $S^ \prime = \lbrace f \in B \colon c(f) = R \rbrace$ are considered as well.
In chapter 3, the second topic of the thesis, that is about the grade of the zero-divisor modules, is discussed. Let $R$ be a commutative ring, $I$ a finitely generated ideal of $R$, and $M$ a zero-divisor $R$-module. It is shown that the $M$-grade of $I$ defined by the Koszul complex is consistent with the definition of $M$-grade of $I$ defined by the length of maximal $M$-sequences in I$.
Chapter 1 is a preliminarily chapter and dedicated to the introduction of content modules and also locally Nakayama modules.