The radiation balance of the earth-atmosphere system from Nimbus 3 radiation measurements

The radiation balance of the earth-atmosphere system and its components was computed from global measurements of radiation reflected and emitted from the earth to space. These measurements were made from the meteorological satellite Nimbus 3 during the periods from April 16 to August 15, 1969; October 3 to 17, 1969; and January 21 to February 3, 1970. Primarily the method of evaluation, its inherent assumptions, and possible error sources were discussed. Results are presented by various methods: (1) global, hemispherical, and zonal averages obtained from measurements in all semimonthly periods and (2) global maps of the absorbed solar radiation, the albedo, the outgoing longwave radiation, and the radiation balance obtained from measurements during semimonthly periods in each season (May 1 to 15, July 16 to 31, and October 3 to 17, 1969, and January 21 to February 3, 1970). Annual global averages of the albedo and of the outgoing longwave radiation were determined. These values balance to within 1 percent the annual global energy input by solar radiation that was computed for a solar constant

Conditions of brittle fracture initiation in solids containing thin elastic inclusions

Досліджено три основні механізми зародження руйнування в тілах із тонкими концентраторами напружень: безпосередньо в тілі, на межі поділу матеріалів та у самому включенні. При дослідженні руйнування тіла поблизу включення проаналізовано застосування критеріїв на основі силових функцій, J-інтеграла, густини енергії деформації. Також побудовано співвідношення, що оцінюють сумарну енергію деформації в зоні інтенсивності напружень поблизу вістря дефекту. При дослідженні руйнування межі включення–тіло побудовано залежності, що пов’язують узагальнені коефіцієнти інтенсивності напружень із максимальними значеннями контактних напружень у вершині заокругленого тонкого дефекту. Руйнування включення пов’язане із досягненням напруженнями чи деформаціями у ньому своїх критичних значень. Усі випадки проілюстровано числовими розрахунками конкретних прикладів.This paper studies three main fracture initiation mechanisms in solids with thin stress concentrators: directly in the solid; on the solid-inclusion interface and inside the inclusion. For studying of fracture of solid near inclusion it provides the analysis of fracture criterions based on the force functions, J-integral, strain energy density. Also the equation, which accounts the total strain energy in the stress intensity zone near the defect’s tip, is received. For studying of fracture of inclusion-matrix interface the relations of stress concentration and generalized stress intensity factors are obtained. Inclusion’s fracture is related with the critical values of its internal strain or stress. The numerical analysis of certain problems is provided

Integral equations of plane magnetoelectroelasticity for a half-space with cracks and thin inclusions

На основі формалізму Стро та методів теорії функції комплексної змінної побудовано інтегральні рівняння для магнітоелектропружного півпростору з отворами, тріщинами і тонкими включеннями. У цих рівняннях поряд з існуючими додатково враховано задане на межі півпростору навантаження. На основі отриманих інтегральних співвідношень побудовано схему методу граничних елементів для вивчення магнітоелектропружних півпросторів із тонкими неоднорідностями. Ефективність та достовірність числового алгоритму підтверджено зіставленням розв’язків конкретних задач із відомими в літературі. Отримано розв’язки нових задач для тріщин і тонких включень у магнітоелектропружному півпросторі.This paper presents a novel approach for obtaining the boundary integral equations of magnetoelectroelasticity for a half-space. This approach is based on the complex variable technique and the Stroh formalism. There are two fundamental relations used: the Cauchy integral formula and the Stroh orthogonality relations. The Cauchy integral formula is applied to the Stroh complex functions, which define the solution of 2D magnetoelectroelasticity. The boundary conditions at the boundary of the half-space are accounted for to obtain the integral formula for the Stroh complex functions inside the half-space. The Stroh orthogonality relations allow obtaining a useful identity, relating the vector of the Stroh complex functions with the displacement, electric and magnetic potentials and tractions, electric displacement and magnetic induction. This relation is applied to the integral formulae obtained and the Somigliana type identities are derived for a magnetoelectroelastic half-space. Using the Sokhotski–Plemelj formula the dual boundary integral equations are obtained. Derived boundary integral equations have several advantages in comparison with the existing ones: (1) these equations are obtained straightforward using a solid elegant complex variable approach; (2) the kernels are derived in transparent and easy way without any preliminary assumptions; (3) the integral formulae obtained account for the load set at the boundary of a half-space; (4) there are explicit closed-form expressions for all kernels of the dual boundary integral equations, which contain only the constants of the Stroh formalism. Obtained boundary integral equations along with the previously developed model of a thin magnetoelectroelastic inclusion are incorporated into the boundary element method. The approach is verified by comparison of the obtained results of particular problems with those referenced in literature. New results are presented for cracks and thin inclusions in the magnetoelectroelastic half-space. It is shown that even under the only mechanical load the significant intensity of electric and magnetic fields is present at the tips of inhomogeneity, which is close to the boundary of the half-space

Four simplified gradient elasticity models for the simulation of dispersive wave propagation

Gradient elasticity theories can be used to simulate dispersive wave propagation as it occurs in heterogeneous materials. Compared to the second-order partial differential equations of classical elasticity, in its most general format gradient elasticity also contains fourth-order spatial, temporal as well as mixed spatial temporal derivatives. The inclusion of the various higher-order terms has been motivated through arguments of causality and asymptotic accuracy, but for numerical implementations it is also important that standard discretization tools can be used for the interpolation in space and the integration in time. In this paper, we will formulate four different simplifications of the general gradient elasticity theory. We will study the dispersive properties of the models, their causality according to Einstein and their behavior in simple initial/boundary value problems

Regular arrays of thin inhomogeneities in the anisotropic solid

Побудовано крайові інтегральні рівняння та відповідну схему методу граничних елементів для розв’язування плоских задач теорії пружності тіл із подвійно періодичними системами тріщин і тонких неоднорідностей. Отримано інтегральні подання для середніх напружень та деформацій, що дають можливість визначати ефективні механічні характеристики тіл із подвійно періодичними системами тонких включень. Наведено числові приклади аналізу узагальнених коефіцієнтів інтенсивності напружень та ефективних характеристик композитних матеріалів із тонкими пружними включеннями.This paper develops boundary integral equations and the boundary element method for a solution of 2D problems of anisotropic elasticity for doubly periodic arrays of cracks or thin inhomogeneities. The integral representations of mean stress and strain are obtained, which allow determination of effective properties of solids with doubly periodic arrays of thin inhomogeneities. The numerical examples are presented for generalized stress intensity factors and effective properties of composite materials with thin elastic inclusions

Plane problem of elasticity for an anisotropic solid containing a thin branched elastic inclusion

Запропоновано підхід для моделювання тонких гіллястих включень за допомогою методу граничних елементів. Записано умови контакту нерозгалужених ланок для випадків жорсткого та шарнірного їх поєднання. Числово розглянуто випадки хрестоподібного та двотаврового включень в ізотропному та анізотропному середовищах. Обчислено коефіцієнти інтенсивності напружень поблизу кінців включень та внутрішні зусилля в характерних точках неоднорідностей.This paper presents a novel approach for modeling of thin branched inclusions based on the boundary element method. Contact conditions are developed for rigid or hinge joints of the chains of inclusions. The numerical analysis is provided for a cross-like and I-beam profile inclusions. The stress intensity factors along with the internal forces at the characteristic points of the inhomogeneities are evaluated

Assembly, trafficking and function of gamma-secretase

gamma-Secretase catalyzes the final cleavage of the beta-amyloid precursor protein to generate amyloid-beta peptide, the principal component of amyloid plaques in the brains of patients suffering from Alzheimer's disease. Here, we review the identification of gamma-secretase as a protease complex and its assembly and trafficking to its site(s) of cellular function. In reconstitution experiments, gamma-secretase was found to be composed of four integral membrane proteins, presenilin (PS), nicastrin (NCT), PEN-2 and APH-1 that are essential and sufficient for gamma-secretase activity. PS, which serves as a catalytic subunit of gamma-secretase, was identified as a prototypic member of novel aspartyl proteases of the GxGD type. In human cells, gamma-secretase could be further defined as a heterogeneous activity consisting of distinct complexes that are composed of PS1 or PS2 and APH-1a or APH-1b homologues together with NCT and PEN-2. Using green fluorescent protein as a reporter we localized PS and gamma-secretase activity at the plasma membrane and endosomes. Investigation of gamma-secretase complex assembly in knockdown and knockout cells of the individual subunits allowed us to develop a model of complex assembly in which NCT and APH-1 first stabilize PS before PEN-2 assembles as the last component. Furthermore, we could map domains in PS and PEN-2 that govern assembly and trafficking of the complex. Finally, Rer1 was identified as a PEN-2-binding protein that serves a role as an auxiliary factor for gamma-secretase complex assembly. Copyright (c) 2006 S. Karger AG, Basel

Mechanisms Of Fracturing In Structures Built From Topologically Interlocked Blocks

Failure of materials is in many cases associated with initiation and subsequent propagation of macroscopic fractures. Consequently, in order to increase the strength, one needs to inhibit either crack initiation or propagation. The principle of topological interlocking provides a unique opportunity to construct materials and structures in which both routes of the strength increase can be realised. Materials and structures built on the basis of this principle consist of many elements which are hold together by the special geometry of their shape, together with an external constrain. The absence of the binder phase between the elements allows the interfaces to arrest macroscopic crack propagation. In addition, with sufficiently small size of the elements an increase in local strength and, possibly, in the stress for crack initiation can be achieved by capitalising on the size effect. Furthermore, the ability of some interlocking structures to tolerate missing elements can serve to prevent the avalanche-type failure initiated by failure of one of the elements. In this paper, experimental results and a theoretical analysis with regard to this possibility are presented

Boundary element analysis of anisotropic thermoelastic half-space containing thin deformable inclusions

За допомогою розширеного формалізму Стро й теорії функції комплексної змінної побудовано інтегральні рівняння типу Сомільяни плоскої задачі термопружності для анізотропного півпростору, що містить отвори, тріщини та тонкі жорсткі та деформівні включення. Ядра записаних інтегральних подань враховують усі можливі комбінації однорідних механічних і теплових крайових умов на межі півпростору. Отримані інтегральні рівняння введено у схему модифікованого методу граничних елементів. Здійснено числовий аналіз впливу межі півпростору на інтенсивність напружень в околі торців тонких неоднорідностей.The paper studies the influence of boundary effects on the stress intensity factors at the tips of thin inclusions in an anisotropic thermoelastic half-space. It utilizes the extended Stroh formalism, which allows writing the general solution of thermoelastic problems in terms of certain analytic functions. Applying the complex variable calculus, in particular, Cauchy integral formula and Sokhotski-Plemelj formula the Somigliana type identities and boundary integral equations are derived for a thermoelastic anisotropic half-space. For modeling of solids with thin inhomogeneities, a coupling principle for continua of different dimension and the method of averaging of the physical and mechanical parameters over the thickness of the inclusion are used. Derived dual integral equations along with the models of thin thermoelastic inclusions, which are written as certain functional dependences of discontinuity functions, allow solving problems of a plane thermoelasticity for anisotropic half-space with holes, cracks and thin inclusions. The absence of the integrals over infinite path in the obtained integral relations allows to apply the boundary element method for solving of the derived integral equations of the plane problem of thermoelasticity for a half-space with thin deformable inhomogeneities. Despite the fact that the boundary conditions on the boundary of a half-space in general have both mechanical and thermal components (the surface of a half-space with zero displacements, traction-free half-space, the surface of half-space maintained at zero temperature or thermally insulated half-space), the paper presents the kernels of integral equations in a closed form for each of the four abovementioned boundary value problems. All obtained integral equations are introduced into the modified boundary element method procedure. Based on the numerical calculations held the influence of boundary effects in the half-space on the stress intensity at the tips of the inclusion is studied