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Digitale Medien

Study of age dependent half-life of iodine in man: A reinforcement-depletion urn model (1985)

Bowman, K. O. ; Shenton, L. R. ; Bernard, S. R.

Springer

Bulletin of mathematical biology 47 (1985), S. 205-213

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ISSN: 1522-9602

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Mathematik

Notizen: Abstract An urn contains balls ofs different colors. The problem of the reinforcement of a specified color and random depletion of balls has been considered by Shenton (1981, 1983). In this paper, the theory is applied to the biological age dependent half-life of radioactive iodine in man; the data of Cook and Snyder (1965) is used. The intake of radioactive iodine and its retention subsequently is studied.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02460031

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Digitale Medien

Structural optimization of lifting surfaces with divergence and control reversal constraints (1989)

Bowman, K. B. ; Grandhi, R. V. ; Eastep, F. E.

Springer

Structural and multidisciplinary optimization 1 (1989), S. 153-161

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ISSN: 1615-1488

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract In this paper, the static aeroplastic characteristics, divergence velocity, control effectiveness and lift effectiveness are considered in obtaining an optimum weight structure. Swept wing structures are used with upper and lower skins, spar and rib thicknesses, and spar cap and vertical post cross-sectional areas as the design parameters. The aerodynamic strip theory is used to derive the constraint formulations and aerodynamic load matrices. A Sequential Unconstrained Minimization Technique (SUMT) algorithm is used to optimize the wing structure to meet the desired aeroelastic constraints.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01637335

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Some exact expressions for the mean and higher moments of functions of sample moments (1992)

Bowman, K. O. ; Shenton, L. R.

Springer

Annals of the Institute of Statistical Mathematics 44 (1992), S. 781-798

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ISSN: 1572-9052

Schlagwort(e): Coefficient of variation ; Frullani integrals ; moment series ; sample variance ; symbolic characteristic function

Quelle: Springer Online Journal Archives 1860-2000

Thema: Mathematik

Notizen: Abstract Examples of exact expressions for the moments (mainly of the mean) of functions of sample moments are given. These provide checks on alternative developments such as asymptotic series for n→∞, and simulation processes. Exact expressions are given for the mean of the square of the sample coefficient of variation, particularly in uniform sampling; Frullani integrals studied by G. H. Hardy arise. It should be kept in mind that exact results for (joint) moment generating functions (mgfs) are of interest as they produce a means of obtaining exact results for (cross) moments—including moments with negative indices. Thus an exact expression for the joint mgf of the 1st two noncentral moments can be used to obtain the mean of the (c.v.)2 (but not for the mean of the c.υ.). A general expression is given for the moment generating function of the sample variance. The limitations of Fisher's symbolic formula for the characteristic function of sample moments (or more general statistics) are noted.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00053406

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Moment solution to an urn model (1996)

Shenton, L. R. ; Bowman, K. O.

Springer

Annals of the Institute of Statistical Mathematics 48 (1996), S. 169-184

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ISSN: 1572-9052

Schlagwort(e): Bernard's urn ; beta integral transforms ; finite difference calculus ; generating function ; hypergeometric distributions ; hypergeometric functions ; moments ; replenishment-depletion urn

Quelle: Springer Online Journal Archives 1860-2000

Thema: Mathematik

Notizen: Abstract A subset of Bernard's RD-model (replenishment-depletion) is considered from the viewpoint of the calculus of finite differences. The most general case is considered and includes an urn with balls of many colors, each color being replenished either deterministically or stochastically. Factorial moment generating functions (fmgfs) are employed to define probability generating functions. A new result is given for the two color case defining the fmgf and probability generating function (with probabilities) when the replenishments are positive valued random variables with given factorial moments. This result involves beta integral transforms defining a manifold of discrete distributions. Particular cases relate to hypergeometric discrete distributions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00049297

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Texture development in Si3N4/BN fibrous monolithic ceramics (2000)

Lienard, S. Y. ; Kovar, D. ; Moon, R. J. ; [weitere]

Springer

Journal of materials science 35 (2000), S. 3365-3371

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Preferred orientation was measured in Si3N4/BN fibrous monolithic ceramics using x-ray diffraction. The materials were manufactured by co-extrusion of polymer binder/ceramic blends which were subsequently pyrolized and then hot-pressed to produced a fully dense ceramic composite. A very strong modified wire texture was present in the BN with the basal planes aligned parallel to the axis of extrusion due to shear-induced reorientation of the platelet-shaped BN particles during co-extrusion. Texture was also observed in the Si3N4 and was attributed to a combination of co-extrusion and hot-pressing. After hot pressing, the basal planes of the rod-shaped β-Si3N4 were observed to be preferentially aligned perpendicular to the extrusion direction. Measurements prior to hot-pressing revealed that a small amount (≈5%) of β-Si3N4 was present in the α-Si3N4 starting powder. Although texturing of the predominant α-Si3N4 did not occur during co-extrusion, significant texturing of the β-Si3N4 was observed. During subsequent hot-pressing, the pre-existing textured β-Si3N4 particles appeared to act as seeds for transformation and preferred growth of rod-shaped β grains parallel to the axis of extrusion.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1004880901978

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