Ravninski simetričan nehomogen volumno viskozan domenski zid u Lyrinoj geometriji

Some bulk viscous general solutions are found for domain walls in Lyra geometry in the plane symmetric inhomogeneous spacetime. Expressions for the energy density and pressure of domain walls are derived in both cases of uniform and time varying displacement field β. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Some physical consequences of the models are also given. Finally, the geodesic equations and acceleration of the test particle are discussed.Našli smo neka opća rješenja za domenske zidove u Lyrinoj geometriji za volumno viskozan nehomogen prostor-vrijeme i ravninsku simetriju. Izveli smo izraze za gustoću energije i tlak domenskih zidova za stalno i za vremenski promjenljivo posmačno polje β. Pretpostavljamo da je koeficijent viskoznosti volumne viskozne tekućine dan s potencijom gustoće mase. Opisujemo neke izvode modela. Na kraju, raspravljamo geodetske jednadžbe i ubrzanje ispitne čestice

Nova vrsta viskoznog tekućeg svemira Bianchijevog tipa i s vremenski-promjenljivim kozmološkim članom

A new class of Bianchi type I viscous-fluid cosmological models with a variable cosmological constant are investigated in which the expansion is considered only in two directions, i.e. one of the Hubble parameter (H1 = A4/A) is zero. We have considered four cases: (i) coefficients of bulk (ξ) and shear (η) viscosity are taken as constant, (ii) ξ and η are considered to be inversely dependent on time, (iii) Λ is taken as inverse square of t and (iv) ξ and η are considered as proportional to scale of expansion in the model. The cosmological constant Λ is found to be positive and is a decreasing function of time which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.Istražujemo novu vrstu kozmoloških modela viskoznog tekućeg svemira Bianchijevog tipa I s promjenljivom kozmološkom konstantom, u kojima se širenje razmatra samo u dva smjera, tj., jedan od Hubbleovih parametara, H1 = A4/A, jednak je nula. Razmatramo četiri slučaja: (i) volumni i viskozno-smični koeficijenti, (ξ) i (η), su stalni, (ii) (ξ) i (η) su inverzno razmjerni vremenu, (iii) Λ je razmjeran inverznom kvadratu vremena i (iv) ξ i η razmjerni su ljestvici širenja svemira u modelu. Nalazimo da je kozmološka konstanta pozitivna i opadajuća funkcija vremena, što je u skladu s nedavnim ishodima opažanja supernova Ia. Raspravljaju se također neka fizikalna i geometrijska svojstva tih modela

Sweet home Pennsylvania and selected stories

Please note: this work is permanently embargoed in OpenBU. No public access is forecasted for this item. To request private access, please click on the locked Download file link and fill out the appropriate web form.Two stories and a novel excerpt.2999-01-01T00:00:00

Validity, Verifiability, and Confirmability: A Critique of Multiphase Packed Bed Modeling

The pseudocontinuum models of reactions in packed beds are complicated, and an assessment of the reliability of the predictability of their numerical solution is difficult. The predictability reliability depends on validity and verifiability, whereas the numerical solutions of models of reactions in packed beds cannot be validated or verified. Scientific acceptability cannot commence by metaphysics alone, and the truth of the speculative justifications of the results of the numerical models without robust empirical confirmation is a matter of chance occurrence. Adherence to the principles of noncontradiction and mathematical consistency seems to be the minimal criterion if a pseudocontinuum model is to demonstrate a degree of reliability in prediction, simulation, and design. This article is an exposition of the verifiability, validity, and confirmability characteristics of multiphase multidimensional models of reactions in packed beds. It addresses the difficulties of validation and the complexities of construction of models of reactions in packed beds by modeling kinetic data directly to show that often the claims of validity, verifiability, or confirmability of the results of multidimensional or even one-dimensional models of chemical reactions in packed beds, in spite of robust statistical tools, should be viewed with some degree of skepticism