No description available.

The static relaxation program DEVIL has been updated to use N-body Finnis-Sinclair potentials. Initial calculations of self-interstitial and monovacancy formation energies confirm that the modified program is working correctly. An extra repulsive pair potential (constructed to leave the original fitting unaltered) overcomes some deficiencies in the published Finnis-Sinclair potentials. The modified potentials are used to calculate interstitial energies and relaxations in the b.c.c. transition metals vanadium, niobium, tantalum, molybdenum and tungsten. Further adaptation enables DEVIL to model dislocations running parallel to any lattice vector. Periodic boundary conditions are applied in the direction of the dislocation line, giving an infinite straight dislocation. The energies per unit length of two different dislocations are compared with experiment. A study of migration of point defects in the perfect lattice provides information on the mobility of interstitials and vacancies. The possible reorientation of split dumbbell interstitials in a migration step comes under scrutiny. The total energy needed to form and migrate an interstitial is compared with that required for a vacancy. The interaction between point defects and dislocations is studied in detail. Binding energies for both sclf-intcrstitials and monovacancies at edge dislocations are calculated for the five metals mentioned above. Formation energies of the point defects in the neighbourhood of the edge dislocation are calculated for niobium, and the extent of the regions from which the defects are spontaneously absorbed are found. For split dumbbell interstilials, the size and shape of the absorption region depends on the orientation of the dumbbell. Migration of both interstitials and vacancies into the absorption zone is studied; the presence of the dislocation has a particularly dramatic effect on vacancy migration. The results on absorption zones are related to the dislocation sink strengths vital in radiation damage theory.

When speakers of different language varieties come into contact with each other, one variety often becomes dominant (based on relative social, economic, and/or political prestige), even to the point where it totally supersedes the other variety. This is what has occurred in Green Point, Pennsylvania, a small rural mountain community whose members once spoke Pennsylvania Dutch (a German dialect). This language was superseded by English several decades ago, and for at least two generations residents have spoken their own variety of the language, Pennsylvania Dutchified English (PDE); today even that variety is threatened by the overpowering influences of the standard variety of English spoken in the region. In addition to briefly describing the some linguistic features of PDE, this study examines the forces behind the Pennsylvania Dutch--Pennsylvania Dutchified English--regional standard of English language shift that has taken place in this community, in two ways--first by looking carefully at the historical and economic factors that have played a role in residents' language choices in the past, and then by investigating the influence of certain social variables that may be linked to residents' choices between PDE and the regional standard today. The paper concludes with a discussion of the prospects for the survival of PDE in this area and offers some suggestions for actions that PDE speakers can take to preserve their dialect, if they choose to do so. / Department of English

A point-set embedding of a planar graph G with n vertices on a set S of n points is a planar straight-line drawing of G, where each vertex of G is mapped to a distinct point of S. We prove that the point-set embeddability problem is NP-complete for 3-connected planar graphs, answering a question of Cabello [20]. We give an O(nlog^3n)-time algorithm for testing point-set embeddability of plane 3-trees, improving the algorithm of Moosa and Rahman [60]. We prove that no set of 24 points can support all planar 3-trees with 24 vertices, partially answering a question of Kobourov [55]. We compute 2-bend point-set embeddings of plane 3-trees in O(W^2) area, where W is the length of longest edge of the bounding box of S. Finally, we design algorithms for testing convex point-set embeddability of klee graphs and arbitrary planar graphs.

No description available.

Using the multidimensional logarithmic residue we show a simple formula for the difference between the number of integer points in a bounded domain of R^n and the volume of this domain. The difference proves to be the integral of an explicit differential form over the boundary of the domain.

轉換點(change point)問題出現在許多的統計領域，包括了有母數、無母數、迴歸、時間序列、序貫、貝式等模型，本研究主要是針對簡單迴歸模型的估計單一轉換點之問題作探討，若我們均勻分布解釋變數並採用最小平方法來估計轉換點，模擬結果告訴我們估計值會有雙峰的現象，此現象造成了變異數的增大。我們嘗試利用二階段設計來改善之前的估計，藉由第一階段所得到轉換點的可能範圍來估計第二階段的實驗，模擬結果顯示此兩階段估計的確降低了估計值的差異。 / The change point problem can be involved in many models such as parametric, nonparametric, regression, time series, sequential, Bayesian, and so on. This thesis focuses on estimating the location of the change point in a simple regression model. We first show that the computational simulation demonstrates a bimodal phenomenon which could increase the variation of the estimator badly when the independent variables are allocated uniformly over the explanatory interval and the least square method is used to determine the estimator of the change point. In the second part,we implement a two-stage design that tries to shrink the possible location of the change point via first stage and then design the second stage accordingly. Simulation result gives a positive response in reducing the variation caused by the bimodal phenomenon.

The wood’s Point dyke swarm, Victoria, consists of a set of abundant subparallel narrow dykes with occasional elliptical expansions (“bulges”) intruded into strongly folded Lower Palaeozoic sediments. The swarm represents a hisly differentiated calc-alkaline rock series derived by fractional crystallization of a single parent magma, possibly of periodotitic composition. The rock types present include both high and low Cr-Ni periodotites, pyroxenite, hornblendite, hornblende diorite and monzonite, biotite leucodiorite, and minor residual granophyre. Apart from this hornblende-bearing rock series, a few hornblende-free basaltic dykes of related chemical composition but intruded later, are petrographically and mineralogically distinct, displaying tholeiitic tendencies. The latter dykes appear to be genetically related to volcanics underlying the Upper Devonian Acheron and Cerberean cauldron subsidences. / Fractional crystallization, flowage differentiation, crystal accumulation and chilling were important factors in the development of the members of the dyke swarm, whilst assimilation in situ was not. The dykes are zonod, ultramafic types having more basic interiors (“cores”) whereas basic to intermediate composition bulges have more basic margins (“rims”). / Magmalic copper-nickel sulphides rich in precious metals (Pt, Pd, Au) occur in dyke bulges of all compositions, especially close to margins where they accumulated by gravitational settling or were trapped by chilling. The sulphides have high Cu/Ni (and Co/Ni) ratios indicative of a highly evolved magma and, along with Au, Pd and Ir are fractionated between dykes of different silicate compositions. The base metal contents of silicates and sulphides vary sympathetically. / The dykes have undergone pervasive hydrothermal alteration during which sulphides were largely recrystallised and Au was leached from some copper-nickel sulphides. A zonal arrangement of increasing intensity of alteration inwards was observed in one ultramefic dyke bulge. Later the dykes were deformed and the basic to intermediate composition dykes were fractured and veined, and major gold deposits formed. The veins have associated wall rock alteration which may be mineralogically subdivided into inner and out zones. / Dyke bulges, ultramafic rocks, copper nickel sulphides and Au mineralization are all concentrated along two main lineations paralleling the fold axes of the sedimentary trough. The eastern and more important trend (at the centre of the trough) marks the eastern limit of the dyke swarm except at its northern end. These lineations may represent deep-seated fractures which controlled the later upward migration of Au-bearing hydrothermal solutions from depth. The source of the Au could have been various rock types present at depth, including copper-nickel sulphides and Lower Palaeozoic sediments.

Thesis (M.A.)--University of New Hampshire, 1947 / Introd. dated: 28 November, 1947. Includes bibliographical references (p. [63]-65). Also issued in print and microfiche.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 253-257). Also available on the Internet.