ABSTRACT The ceramic ball bearing has been used to exact machine for its good properties such as heat-resistant, corrosion-resisting, and wear-resisting. Now, the produced expense of ceramic ball is hundred of steel ball because the grinding process must spend much time and money. This study research the effects of eccentricity (e: the distance is between the center of the ball circulation and the center of the spindle), spindle speed, and load on grinding characteristics of ball by using eccentric ultra-precision ball grinding machine which developed by our lab, under saving cost and time, search the optimum operating conditions of this machine, it¡¦s good for industrial circles in the future. Experimental results show that the converged rate of the saturated value for the sphericity is increased with increasing eccentricity. Saturated value of sphericity is sphericity reduced to a steady state. The saturated value of the sphericity is not fully proportional to eccentricity. The relation between eccentricity and saturated value of sphericity are divided two region by one rb, the first region is that sphericity is proportional to eccentricity when eccentricity is 0~rb, and the second region is that sphericity is inverse proportional to eccentricity when eccentricity is rb~2rb. The converged rate of surface roughness (Ra) are negative with increasing eccentricity and the saturated value of the surface roughness (Ra) is higher. The volume removal rate is increased with increasing eccentricity. The converged rate of the saturated value for the sphericity and surface roughness (Ra) are increased with increasing spindle speed and load, and the saturated value are higher. The volume removal rate is also increased with increasing spindle speed and load.

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L'excentricité, comprise généralement au sens littéral (terme emprunté à l'astronomie et à la géométrie) qu'au sens symbolique (l'excentricité comme catégorie esthétique), représente une notion clé qui dynamise et définit l'acte de l'écriture de Gérard de Nerval, sa pensée et son âme, non seulement dans Les Illuminés, mais aussi dans son oeuvre entière. En gros, elle est constitutive de l'acte de la création littéraire de Nerval~ elle détermine et active la pensée de l'auteur, ses gestes et comportements, sa raison et folie, ses doutes, certitudes, credos, ainsi que ses aspirations.L'excentricité abordée en tant que métaphore est dans l'écriture de Nerval un catalyseur de thèmes, d'idées profondes et de mouvements, compte tenu que la métaphore n'est pas une simple figure rhétorique, mais le moteur de la génération et de la régénération du sens. De même, notre apport consiste dans le propos d'une nouvelle dimension de recherche sur l'excentricité, à savoir l'analyse de cette notion en tant qu'instrument d'étude. Le but n'est pas, bien entendu, de se proposer une approche exhaustive de l'excentricité, respectivement de l'excentrique, et cela parce que ces notions débordent le cadre linguistique. Au lieu de conceptualiser les termes, nous nous penchons plutôt sur le mécanisme de fonctionnement de ces notions, renvoyant simultanément à la notion de centre et à la sortie du centre.Les notions d'"excentricité", respectivement d'"excentrique" ne peuvent pas être conçues d'une façon absolue, comme des objets constitués une fois pour toutes, c'est pourquoi l'analyse de leurs sens ou significations demande d'ouvrir un champ plus vaste de recherche qui nepeut pas délaisser les contenus idéologique, historique, philosophique, religieux et littéraire du XIXe siècle, dans lesquels ces notions naissent et s'enrichissent. / The eccentricity generally understood both in the literal sense (a term borrowed from astronomy and geometry) and in the symbolic meaning (the eccentricity as aesthetic category), is a key concept that energizes and defines the Gerard de Nerval's act of writing, his mind and soul, not only in Les Illuminés, but also in his entire work. Basically, it is constitutive of the act of literary creation of Nerval, and it determinates and activates the author's mind, his actions and behaviors, reasons and madness, doubts and certainties, creeds and aspirations. The eccentricity as metaphor in Nerval 's writing catalyses themes, profound ideas and movements, given that the metaphor is not simply rhetorical, but the engine of the generation and meaning regeneration. Therefore, our contribution is the proposal of a new dimension of eccentricity research, namelv the analvsis of this concept as a tool for studv. The goal is not, of course, to nrovide a comprehensive approach to the eccentricity, respectively, the eccentric, and that because these notions overcomes the linguistic field. Instead of conceptualizing terms, we focus instead on the operating mechanism of these notions, referring simultaneously to the notion of center and outside the center. The notions of eccentricity, respectively of eccentric cannot be conceived in an absolute way, as objects made once and for all, which is why the analysis oftheir meanings require to open a wider field of research that cannot abandon the ideological content, historical, philosophical,religious and literary of the nineteenth century, in which these concepts are born and grow rich.

For a vertex x of G, the eccentricity e (x) is the distance between x and a vertex farthest from x. Then x is a contour vertex if there is no neighbor of x with its eccentricity greater than e (x). The x-y path of length d (x,y) is called a x-y geodesic. The geodetic interval I [x,y] of a graph G is the set of vertices of all x-y geodesics in G. For S ⊆ V , the geodetic closure I [S] of S is the union of all geodetic intervals I [x,y] over all pairs x,y ∈S. A vertex set S is a geodetic set for G if I [S] = V (G). In this thesis, we study the contour sets of product graphs and discuss these sets are geodetic sets for some conditions.

It is generally assumed that the temperature in the inner part of the primordial nebula was too high to form and agglomerate ice bodies. Yet, water is present in most of the terrestrial planets of our solar system. To investigate the reason for this we concentrate on comets as a potential water deliverer to the inner planets. The data for this work is taken from 3D simulations of comet trajectories inside a gas-dust disk with embedded planet embryos. We have developed a MATLAB code that could read data files from these simulations containing orbital elements of the comets and planetary embryos. Comets experience inward migration due to friction with the remains of the disk. We study comets of four different sizes.      We find that smaller comets migrate faster and therefore spend less time in the inner solar system. Smaller comets are numerous and are therefore destroyed in greater numbers than the larger comets. Larger comets on the other hand slow their migration and spending much more time among inner planets they are more massive and produce more massive collisions with the inner planets than the smaller comets. Therefore are larger comets a more promising source of water delivery to the inner planets. In Studying individual collisions we observe that a typical interaction involves regular close encounters with the same embryo during periods of 100000 years or more before the two orbits intersect. This also tells us that with a large number of comets expected at this stage of solar system evolution the collective effect of comets on low-mass planetary embryos may be significant.

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The study presented in this thesis is an attempt towards a better understanding of the coupled lateral-torsional response of buildings subject to seismic ground motion. Some of the problems identified in the past studies are thoroughly investigated and some new areas of study are explored. Some of these problems encountered in the literature include (a) the existence of several definitions of uncoupled torsional to lateral frequency ratio (b) an arbitrary selection of structural parameters in a parametric analysis resulting in a physically inadmissible structure and (c) the effect of nonlinearity. Because of the simplified models with either eccentricity in one direction or the ground motion applied in only one direction, the effects of a bi-directional loading have not been investigated in detail. These effects may include the relative differences in the amplitude or phase components of the individual accelerograms and their orientation with respect to the building. The phase properties of accelerograms are of particular interest and these have not received much attention in the past. Using analytical methods such as Chasle's[16] and Gerschgorin's[39] theorems, the equation of motion of a bi-eccentric system is derived and all of the existing problems regarding the definition of structural parameters and their bounds are studied in depth. To facilitate nonlinear parametric study, a paraboloid non-linear elastic stiffness model is proposed. Fourier spectral methods are used to study the frequency domain characteristics of the accelerogram pair. The difference in phase and amplitude of the component frequencies in each direction are studied for their effects on the response. For phase difference, cross-correlation function is used as a comparative statistical indicator. USA earthquake records obtained from US National Geophysical Data Centre are grouped into four soil types and the analysis is performed for each group in order to explore the soil-dependency of the aforementioned effects on the response. Computer programs are written in FORTRAN for both parametric and numerical model analyses. The latter can handle any number and orientation of columns with the assumed nonlinear stiffness properties. Newmark's and Runge-Kutta methods of numerical integration with adaptive step size control have been used to calculate parametric and the hysteretic responses of the system. The response to harmonic ground acceleration is used as a preliminary investigation into the response to actual accelerogram frequency components. The study has developed relationships for different definitions of the uncoupled torsional to lateral frequency ratio. Detailed derivation of the Equation of Motion has clarified the confusion that produced different definitions in the past studies. Graphical descriptions of the admissibility bounds on system parameters are produced. The variation in the response quantities is studied for a range of amplitude and phase contents of the applied ground acceleration. The difference in phase and amplitude in x and y ground accelerations have been found to affect the response quite significantly. More generally, the relationship of these differences to the torsional mode amplification has been observed. The effects of structural frequency and eccentricity parameters are also studied. Graphs showing the relationship between, the angle of incidence of the accelerogram with respect to the principal axis of the building, and the phase difference in the accelerogram pair, have been produced. The proposed analysis involving the bi-directional ground acceleration on a bi-eccentric system is an improvement on the current methods employed in design practice. Further work is, however, required before simplified design recommendations can be made and some proposals for future research are given at the end of this thesis.

The distance d(u,v) from vertex u to vertex v in a digraph G is the length of the shortest directed path from u to v. The eccentricity e(v) of vertex v is the maximum distance of v to any other vertex of G. A vertex u is an eccentric vertex of vertex v if the distance from v to u is equal to the eccentricity of v. The eccentric digraph ED(G) of a digraph G is the digraph that has the same vertex set as G and the arc set defined by: there is an arc from u to v iff v is an eccentric vertex of u. The idea of the eccentric digraph of a graph was introduced by Buckley (Congr. Numer. 149 (2001) 65) and the idea of the eccentric digraph of a digraph by Boland and Miller (Proceedings of AWOCA'01, July 2001, p. 66). In this paper, we examine eccentric digraphs of digraphs for various families of digraphs and we consider the behaviour of an iterated sequence of eccentric digraphs of a digraph. The paper concludes with several open problems.

No / We used biased random-dot dynamic test stimuli to measure the strength of the motion aftereffect (MAE) to evaluate the usefulness of this technique as a measure of motion adaptation strength. The stimuli consisted of noise dots whose individual directions were random and of signal dots moving in a unique direction. All dots moved at the same speed. For each condition, the nulling percentage (percentage of signal dots needed to perceptually null the MAE) was scaled with respect to the coherence threshold (percentage needed to perceive the coherent motion of signal dots without prior adaptation). The increase of these scaled values with the density of dots in the test stimulus suggests that MAE strength is underestimated when measured with low densities. We show that previous reports of high nulling percentages at slow speeds do not reflect strong MAEs, but are actually due to spatio-temporal aliasing, which dramatically increases coherence thresholds. We further show that MAE strength at slow speed increases with eccentricity. These findings are consistent with the idea that using this dynamic test stimulus preferentially reveals the adaptation of a population of high-speed motion units whose activity is independent of adapted low-speed motion units.

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