Abstract:
calcium aluminate cement (cac) bonded alumina-magnesia refractory castables present great advantages for steel ladle applications as a result of in-situ expansive formation of spinel and ca<6, which leads to high basic slag and thermal shock resistance. the cac content in those castables strongly influences its expansive behavior mainly due to ca6 formation. in the present work, the effects of the cac content in magnesia-alumina castables were analyzed. the results showed that calcium aluminate cement affects the volumetric stability of mgo-spinel system: the lower the cac content, the lower the shrinkage. these effects on the sintering and in the mechanical properties after sintering at high temperatures are also presented and discussed.

Abstract:
considering that developments on refractories performance are of utmost importance to the steel industry advances, thermo-mechanical properties and the corrosion and slag penetration resistance of the lining material are constantly being improved to extend steel ladle working life. these benefits could be attained in high alumina refractory castable by adding pre-formed spinel or magnesia, in order to result in the latter condition in in-situ spinel during the first use of the lining. the objective of the present work was to compare between high alumina castables with pre-formed or in situ spinel in order to verify their main properties differences. in addition, pre-formed spinel was used as aggregate replacing tabular alumina in alumina-magnesia compositions to analyze the effect of coarse particles in the expansion behavior of this type of castable. the results showed higher expansion and better mechanical performance for castables with in-situ spinel after firing at 1500 oc. also, the use of different aggregates in the same composition resulted in distinct expansion values.

Abstract:
the expansive behavior of alumina-magnesia refractory castable, attributed to the in-situ spinel formation, is affected by the magnesia source and its grain size. in the present work, increasing mgo grain size induced cracking, and, consequently, reduced the mechanical properties as a result of a large expansion. scanning electron microscopy evaluations after firing at 1500 oc showed distinct microstructures for castables containing different grain sizes (< 45 μm and < 100 μm). for the composition with finer magnesia, phases commonly detected in the literature were observed: spinel and ca6. nevertheless, besides those two phases, the castable with the coarse magnesia also presented forsterite and monticellite around the magnesia remaining grains. hence, the objective of this work is to analyze how the refractory castable properties could be considerably affected even by changing a single parameter: the magnesia grain size.

Abstract:
the usual binder of alumina-magnesia castables is the calcium aluminate cement. due to in-situ spinel (mgal2o4) formation at high temperatures, these materials present an expansive behavior. when bonded with cement, further reactions (ca2 and ca6 formation) also contribute to the overall expansion. changing the most common cement used (~ 30 wt.% cao) for other containing less calcia (~ 20 wt.% cao) or for hydratable alumina are suitable alternatives for controlling the castables' volumetric stability. nevertheless, the binder replacement may affect castables properties, such as cold mechanical strength, mgo hydration degree and properties during and after sintering. therefore, the objective of the present paper is to analyze the effects of these binders on the alumina-magnesia castables processing. as a result, the binder systems can be used as a tool for designing the alumina-magnesia castables expansion, increasing the flexibility on the selection of steel ladles linings.

Abstract:
We present the whole class of Gaussian coordinate systems for the Kerr metric. This is achieved through the uses of the relationship between Gaussian observers and the relativistic Hamilton-Jacobi equation. We analyze the completeness of this coordinate system. In the appendix we present the equivalent JEK formulation of General Relativity -- the so-called quasi-Maxwellian equations -- which acquires a simpler form in the Gaussian coordinate system. We show how this set of equations can be used to obtain the internal metric of the Schwazschild solution, as a simple example. We suggest that this path can be followed to the search of the internal Kerr metric.

Abstract:
With the eminent confirmation or disproof of the existence of Higgs boson by experiments on the LHC it is time to analyze in a non-dogmatic way the suggestions to understand the origin of the mass. Here we analyze the recent proposal according to which gravity is what is really responsible for the generation of mass of all bodies. The great novelty of such mechanism is that the gravitational field acts merely as a catalyst, once the final expression of the mass does not depend either on the intensity or on the particular characteristics of the gravitational field.

Abstract:
We investigate a new form of contribution for the anomalous magnetic moment of all particles. This common origin is displayed in the framework of a recent treatment of electrodynamics that is based in the introduction of an electromagnetic metric which has no gravitational character. This effective metric constitutes a universal pure electromagnetic process perceived by all bodies, charged or not charged. As a consequence it yields a complementary explanation for the existence of anomalous magnetic moment for charged particles and even for non-charged particles like neutrino.

Abstract:
We show that the path of any accelerated body in an arbitrary space-time geometry $g_{\mu\nu}$ can be described as geodesics in a dragged metric $\hat{q}_{\mu\nu}$ that depends only on the background metric and on the motion of the body. Such procedure allows the interpretation of all kind of non-gravitational forces as modifications of the metric of space-time. This method of effective elimination of the forces by a change of the metric of the substratum can be understood as a generalization of the d'Alembert principle applied to all relativistic processes.

Abstract:
The purpose of this paper is to present a unified description of mass generation mechanisms that have been investigated so far and that are called the Mach and Higgs proposals. In our mechanism, gravity acts merely as a catalyst and the final expression of the mass depends neither on the intensity nor on the particular properties of the gravitational field. We shall see that these two strategies to provide mass for all bodies that operate independently and competitively can be combined into a single unified theoretical framework. As a consequence of this new formulation we are able to present an answer to the question: what is the origin of the mass of the Higgs boson?

Abstract:
We show that Gordon metric belongs to a larger class of geometries, which are responsible to describe the paths of accelerated bodies in moving dielectrics as geodesics in a metric $\hat q_{\mu\nu}$ different from the background one. This map depends only on the background metric and on the motion of the bodies under consideration. As a consequence, this method describes a more general property that concerns the elimination of any kind of force acting on bodies by a suitable change of the substratum metric.